THE ANNALS OF ˝DUNAREA DE JOS ˛ UNIVERSITY OF GALATI · 2016. 1. 22. · THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI. FASCICLE IX. METALLURGY AND MATERIALS SCIENCE N0.4–

MINISTRY OF NATIONAL EDUCATION

THE ANNALS OF“DUNAREA DE JOS” UNIVERSITY

OF GALATI

Fascicle IXMETALLURGY AND MATERIALS SCIENCE

YEAR XXXIII (XXXVIII)December 2015, no. 4

ISSN 1453-083X

2015GALATI UNIVERSITY PRESS

EDITORIAL BOARD

EDITOR-IN-CHIEFProf. Marian BORDEI - ’’Dunarea de Jos’’ University of Galati, Romania

EXECUTIVE EDITORLecturer Marius BODOR- ’’Dunarea de Jos’’ University of Galati, Romania

PRESIDENT OF HONOURProf. Nicolae CANANAU - ’’Dunarea de Jos’’ University of Galati, Romania

SCIENTIFIC ADVISORY COMMITTEEAssoc. Prof. Stefan BALTA - ’’Dunarea de Jos’’ University of Galati, RomaniaProf. Lidia BENEA - ’’Dunarea de Jos’’ University of Galati, RomaniaAcad. Prof. Ion BOSTAN - Technical University of Moldova, Moldova RepublicProf. Bart Van der BRUGGEN - Katholieke Universiteit Leuven, BelgiumProf. Francisco Manuel BRAZ FERNANDES - New University of Lisbon Caparica, PortugalAcad. Prof. Valeriu CANTSER - Academy of Moldova Republic, Moldova RepublicProf. Anisoara CIOCAN - ’’Dunarea de Jos’’ University of Galati, RomaniaLecturer Alina CIUBOTARIU - ’’Dunarea de Jos’’ University of Galati, RomaniaProf. Alexandru CHIRIAC - ’’Dunarea de Jos’’ University of Galati, RomaniaAssoc. Prof. Stela CONSTANTINESCU - ’’Dunarea de Jos’’ University of Galati, RomaniaAssoc. Prof. Viorel DRAGAN - ’’Dunarea de Jos’’ University of Galati, RomaniaProf. Valeriu DULGHERU - Technical University of Moldova, Moldova RepublicProf. Jean Bernard GUILLOT - École Centrale Paris, FranceAssoc. Prof. Gheorghe GURAU - ’’Dunarea de Jos’’ University of Galati, RomaniaProf. Iulian IONITA - ’’Gheorghe Asachi’’ Technical University Iasi, RomaniaProf. Philippe MARCUS - École Nationale Supérieure de Chimie de Paris, FranceProf. Vasile MARINA - Technical University of Moldova, Moldova RepublicProf. Rodrigo MARTINS - NOVA University of Lisbon, PortugalProf. Strul MOISA - Ben Gurion University of the Negev, IsraelProf. Daniel MUNTEANU - Transilvania University of Brasov, RomaniaProf. Viorica MUSAT - ’’Dunarea de Jos’’ University of Galati, RomaniaProf. Maria NICOLAE - Politehnica University Bucuresti, RomaniaProf. Petre Stelian NITA - ’’Dunarea de Jos’’ University of Galati, RomaniaProf. Florentina POTECASU - ’’Dunarea de Jos’’ University of Galati, RomaniaAssoc. Prof. Octavian POTECASU - ’’Dunarea de Jos’’ University of Galati, RomaniaProf. Cristian PREDESCU - Politehnica University Bucuresti, RomaniaProf. Iulian RIPOSAN - Politehnica University Bucuresti, RomaniaProf. Antonio de SAJA - University of Valladolid, SpainProf. Wolfgang SAND - Duisburg-Essen University Duisburg GermanyProf. Ion SANDU - ’’Al. I. Cuza’’ University of Iasi, RomaniaProf. Georgios SAVAIDIS - Aristotle University of Thessaloniki, GreeceProf. Elisabeta VASILESCU - ’’Dunarea de Jos’’ University of Galati, RomaniaProf. Ioan VIDA-SIMITI - Technical University of Cluj Napoca, RomaniaProf. Mircea Horia TIEREAN - Transilvania University of Brasov, RomaniaAssoc. Prof. Petrica VIZUREANU - ’’Gheorghe Asachi’’ Technical University Iasi, RomaniaProf. Maria VLAD - ’’Dunarea de Jos’’ University of Galati, RomaniaProf. François WENGER - École Centrale Paris, France

EDITING SECRETARYProf. Marian BORDEI - ’’Dunarea de Jos’’ University of Galati, RomaniaLecturer Marius BODOR - ’’Dunarea de Jos’’ University of Galati, Romania

THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI.FASCICLE IX. METALLURGY AND MATERIALS SCIENCE

N0. 4 – 2015, ISSN 1453 – 083X

Table of Content

1. Alina Ciubotariu, Lidia Benea, Wolfgang Sand - Surface Roughness andTopography of Ni / Micro-SiC Layers: Influence of Current Density on ElectrodepositionProcess.……………................................................................................................................. 5

2. Stela Constantinescu - Influence Physical-Chemical Factors on the Distribution ofHeavy Metals in the Delta Ecosystems.................................................................................... 11

3. Georgeta Toderaşcu, Valentin Dumitraşcu, Lidia Benea, Alexandru Chiriac -Corrosion Behaviour and Biocompatibility of 316 Stainless Steel as Biomaterial inPhysiological Environment...................................................................................................... 16

4. Mădălina Simona Bălțatu, Ramona Cimpoeșu, Petrică Vizureanu, Dragoş CristianAchiței, Mirabela Georgiana Minciună – Microstructural Characterization of TiMoZrTaalloy.......................................................................................................................................... 23

5. Nicoleta Matei (Ciobotaru), Dan Scarpete - Treatment of Ammonia Wastewater byUltrasound. Part I: The Influence of Ultrasound Energy on Ultrasound Bath Temperature... 27

6. Adrian Leopa, Diana Anghelache - Urban Pollution Issues Generated by TramsTraffic....................................................................................................................................... 32

7. Tamara Radu - Environmental Risk Assessment for Thermal Power Plants.................... 38

8. Anișoara Ciocan - Emissions of Hydrochloric Acid Vapors Generated by PicklingProcess from Cold Rolling Mill of Steel Strips........................................................................ 43

9. Dragoş Cristian Achiţei, Mirabela Georgiana Minciună, Petrică Vizureanu -Chemical and Metallurgical Analysis of Cooper Based Shape Memory Alloys..................... 48

10. Elisabeta Vasilescu, Vlad Gabriel Vasilescu, Dumitru Dima - Research onChemical Deposition of Silver with Antibacterial Role in Implantology............................... 52

11. Beatrice Tudor, Anisoara Ciocan - Noise Levels in Workplaces of Cold Rolling MillPlant………………………………………………………………………………………….. 58

12. Cătălin-Andrei Țugui, Petrică Vizureanu, Carmen Nejneru, Manuela-CristinaPerju, Mihai Axinte, Simona-Madălina Bălţatu - Deposition Technologies for Obtaining Thin Films with Special Properties.…………………………………………………….. ……. 66

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Fascicle IXMetallurgy and Materials Science

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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATIFASCICLE IX. METALLURGY AND MATERIALS SCIENCE

No. 4 – 2015, ISSN 1453 – 083X

SURFACE ROUGHNESS AND TOPOGRAPHYOF Ni / MICRO-SiC LAYERS: INFLUENCE OF CURRENT DENSITY

ON ELECTRODEPOSITION PROCESS

Alina CIUBOTARIU1,*, Lidia BENEA1, Wolfgang SAND21Dunărea de Jos University of Galati, Faculty of Engineering, Competences Center Interfaces –Tribocorrosion

and Electrochemical Systems,47 Domneasca Street, 80008, GALATI, Romania2University of Duisburg Essen, Biofilm Centre, Geibelstraße 41, 47057, Duisburg, Germany

*Corresponding authore-mail: [email protected]

ABSTRACT

The surface properties are directly responsible for the performance ofengineering materials because most of failures such as friction, wear, corrosionand fatigue often take place on the material surface. Electrodeposition technique isof great interest for industrial usage because it produces functional and protectivecoatings with low cost and easy control. The present work has the purpose toevaluate roughness and to analyze surfaces of Ni / micro-SiC composite layersobtained at different parameters for electrodeposition. The layers wereelectroplated from a Watts bath with a suspension of SiC particles (mean diametersize of particles 30 μm) by adding 5g/L of particles. Electrodeposition took place at400C and a current density of 2 A/dm2 and 4 A/dm2 for 1h. The suspension bath wasstirred by a mechanical stirrer at a constant rotational speed of about 500 rpm. Theroughness and topography of the layers were evaluated by atomic force microscopy(AFM) method.

KEYWORDS: electrodeposition, composite layers, atomic force microscopy,topography, roughness

1. Introduction

In the last years, composite layers have beendeveloped quickly because they have manyadvantages in technology with a good resistance toaggressive working environments and fast processingsystems. Embedding different particles into metalmatrix improve the material properties such assurface hardness, corrosion resistance, wearresistance, erosion – corrosion resistance etc. [1 – 3].

Layers of Ni / SiC composites have beenstudied because of their high wear resistance andgood corrosion properties provided by the ceramicparticles embedded in nickel matrix [4 - 6].

Electrodeposition is one of the most usedtechniques for obtaining metallic and non-metalliccomposite layers. Between 1950 - 1960, thedevelopment of electrodeposited composite coatingsexpended progressively [7]. During the 1970s and1980s, researches were focused on the need toproduce coatings with enhanced mechanical,corrosion and tribological properties.

The advanced physical properties of compositelayers quickly became clear and during the 1990s,new areas such as electrocatalysts andphotoelectrocatalysts were considered [8].

To obtain composite layers it can be used ametal as matrix that could embed a dispersed phasewith a good adhesion property on a substrate. Asdispersed phases to obtain a composite layers therecould be used pure metals particles, ceramic particlesor organic particles.

Surface roughness has an important role onmechanical as well as tribological properties of thecomposite layers.

The different properties such as wear, friction,corrosion, creep, fatigue failure, heat transmission,electrical conductivity, light reflection and lubricityetc. are affected by surface roughness that has animportant role for composite layers because affectsporosity of them. Due to higher porosity the corrosionresistance of the composite coating may be reduced.Hence it is very essential to carry out investigation onsurface roughness and to optimize the bath process

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parameters to reduce the surface roughness atpreferred level. Atomic force microscopy (AFM) is amethod to see a surface in its full, extremely versatiletool to investigate the three- dimensional morphologyof surfaces. The method applies to hard and softsynthetic materials as well as biological structures(tissues, cells, biomolecules), irrespective ofopaqueness or conductivity. The 3D object is notperceived in the usual way, that is, by line-of-sight,reflections or shadows. Given that the image isconstructed from height numbers, one also canmeasure peak-to-valley distances, compute standarddeviations of height, compile histograms of heights orslopes of hills. These metrics of topography can bedirectly relevant to technological performance orbiological function, whether in microelectronics(roughness of layers in multilayer depositionprocesses), tribology (friction and wear on hard diskread heads), polymer-drug coatings (surface contourarea impacting drug release), intrabody medicaldevices (shape of surface in contact with cells,tissues), cellular membranes and surface components(phospholipid bilayer, protein receptors) and muchmore [10 - 12].

The paper intends to study the surfacetopography and roughness of Ni /micro-SiCcomposite layers compared with pure nickel layers.The samples were obtained at two values ofelectrodeposition current densities because theelectrodeposition parameters influence thetopography of the surfaces. The topography of thelayers was evaluated by atomic force microscopymethod and the values of surface roughness wasevaluated by histograms of the tested layers.

2. Experimental

Nickel and Ni / micro-SiC composite layerswere electrochemically deposited from a Watts bathwith the following composition: 0.90M NiSO4x6H2O;0.21M NiCl2x6H2O; 0.48M H3BO3 and additive: SDS(sodium dodecyl sulphate) 0.4 g/L. The pH of thesolution was maintained at 4. Suspension wasprepared by adding SiC particles with a meandiameter size of 30 μm to the solution to give aconcentration of 5 g/L in the nickel platingelectrolyte. Electrodeposition took place in the bath ata temperature of 400C and a current density of 2A/dm2 and 4 A/dm2 for 60 minutes. The suspensionbath was stirred by a mechanical stirrer at a constantrotational speed of about 500 rpm.

A NanoWizardII atomic force microscope (JPKInstruments, Germany) was used for surface analysisand evaluate roughness of the surfaces.

For AFM images, silicon cantilever CSC37 A(Mikromasch, Estonia) with the following featureswas used: typical length, 250 μm; width, 35 μm;thickness, 2 μm; resonance frequency, 41 kHz; andnominal force/spring constant, 0.65 N/m. Each AFMimage consists of 512 by 512 pixels. AFM imageswere performed by contact mode in air.

3. Results and discussion

The surface topography of pure nickel layerselectrodeposited at a current density of 2A/dm2 and4A/dm2 under atomic force microscope are presentedin Figs. 1 – 2.

From the AFM images of the tested surfaces fornickel obtained at a low current density it wasobserved that the electrodeposited nickel consists ofpyramidal crystals with pronounced crystallographicpolyhedral form with equigrannular structure. Abimodal grain structure of truncated pyramidal typecan be observed. A cluster of fine grains issurrounded by relatively large grains. For nickellayers obtained at 4 A/dm2 the surface topographywas changed at it was observed a homogeneousmetallic structure with regular pyramidal shapecharacteristically for nickel crystallites [13 - 15].

(a)

(b)

Fig. 1. AFM images of pure nickel surfaceelectrodeposited at 2A/dm2:

2D (a) and 3D (b)

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(a) (b)

Fig. 2. AFM images of pure nickel surface electrodeposited at 4A/dm2:2D (a) and 3D (b)

(a) (b)Fig. 3. AFM images of Ni / micro-SiC surface layers obtained at 2A/dm2: 2D (a) and 3D (b)

(a) (b)

Fig. 4. AFM images of Ni / micro-SiC surface layers obtained at 4A/dm2: 2D (a) and 3D (b)

Figs. 3 – 4 represent the 2D and 3D AFMimages of Ni / micro-SiC composite layers obtainedat 2A/dm2 (Fig. 3) and 4 A/dm2 (Fig. 4).

From the AFM images for Ni / micro-SiCcomposite layers it could be observed that thecomposite layers are smooth surfaces and it could beobserved particles of SiC embedded into Ni matrix.

The particle size of SiC has an important role inthe entrapment of SiC in the electrodeposited nickelcoatings layers. The micro SiC particles couldadsorbe more nickel ions and the Coulombic force is

stronger than in case of nano SiC particles. On theother hand codeposition of pure nickel compared withSiC particles codeposited into nickel matrix iscomplex because a lot of factors act simultaneously.These factors include particle-particle interactionsand the mobility of particles as a function of size andcharge [16].

Comparing the topography of pure nickel layerswith composite layers it could be observed that thepure nickel layers have a rather regular surface andthe composite coatings have a nodular disturbed

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surface structure. Growing nickel crystals wasperturbed by the current density used forelectrodeposition and the incorporation of SiC macroparticles. From Fig. 3 and 4 it could be seen that themicron-sized particles are codeposited at the bordersand the edges of the nickel crystallites and theembedding mechanism can be characterized as inter-crystalline [ 17, 18]. The histograms of the scannedsurfaces of pure nickel layers and Ni / micro-SiCcomposite layers are presented in Figs. 5 – 8.

Fig. 5. Histogram of the scanned surfaces forpure nickel layers obtained at 2A/dm2

Fig. 6. Histogram of the scanned surfaces forpure nickel layers obtained at 4A/dm2

Fig. 7. Histogram of the scanned surfaces forNi / micro-SiC composite layers

obtained at 2A/dm2

Fig. 8. Histogram of the scanned surfaces forNi / micro-SiC composite layers

obtained at 4A/dm2

The histograms presented in Figs. 5 – 8 wereused to estimate the surface roughness of pure nickeland Ni / micro-SiC composite layers.

Surface roughness has an influence of how areal system interacts with the environment and isquantified by the vertical deviations of a real surfacefrom its ideal form. If these deviations are large, thesurface is rough; if they are small the surface issmooth.

The roughness can be characterized by severalparameters and functions, but the average value is byfar the most common used. The average roughness isthe area between the roughness profile and its meanline, or the integral of the absolute value of theroughness profile height over the evaluation lengthand is described in equation 1.

(1)

where Z(x) is the function that describes thesurface profile analyzed in terms of height (Z) andposition (x) of the sample over the evaluation length“L”. Thus, the Ra is the arithmetic mean of theabsolute values of the height of the surface profileZ(x) [19, 20].

Variations of the surface roughness for purenickel and Ni / micro-SiC composite layers are shownin Fig. 9.

From values of average roughness of thesurfaces presented in Fig. 9 it could be observed thatthe roughness decreases for Ni / micro-SiC compositelayers. The roughness is higher for pure nickel andcomposite layers obtained at a value of 4A/dm2 forelectrodeposition current density as compared withthe values of roughness obtained at a value ofelectrodeposition current density of 2A/dm2.

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Fig.9. Variation of roughness surfaces of purenickel and Ni / micro-SiC composite layers

obtained at different electrodeposition currentdensity

The smaller values of average roughness of thecomposite layers compared with the values of averageroughness for pure nickel layers could be determinedby the inhibition of nickel crystals growth induced bySiC micro particles.

The dispersed phase was uniformly distributedin the nickel matrix and the Ni / micro-SiC compositelayers are more smoothed surface, uniform andcompact than pure nickel surface, that is indicate bythe values of average surface roughness.

Conclusions

From the AFM images of the tested surfaces fornickel obtained at 2A/dm2 it was observed that theelectrodeposited nickel consists of pyramidal crystalswith pronounced crystallographic polyhedral formwith equigrannular structure and for nickel layersobtained at 4 A/dm2 it was observed a homogeneousmetallic structure with regular pyramidal shapecharacteristically for nickel crystallites.

From the AFM images of Ni / micro-SiCcomposite layers it could be observed that thesurfaces are smooth and it could be observed themicro SiC particles embedded into Ni matrix. Theparticle size of SiC has an important role in theentrapment of SiC in the electrodeposited nickelcoatings layers. The micro SiC particles couldadsorbed more nickel ions and the Coulombic force ishigh. Comparing the topography of pure nickel layerswith composite layers it could be observed that thepure nickel layers have a rather regular surface andthe composite coatings have a nodular disturbedsurface structure. Growing of nickel crystals was

perturbed by the current density used forelectrodeposition and the incorporation of SiC macroparticles.

From values of average roughness of thesurfaces it could be observed that the roughnessdecreases for composite layers. The roughness ishigher for pure nickel and composite layers obtainedat a value of 4A/dm2 for electrodeposition currentdensity compared with the values of roughnessobtained at a value of electrodeposition currentdensity of 2A/dm2.

The smaller values of average roughness of thecomposite layers compared with the values of averageroughness for pure nickel layers could be explainedby the inhibition of nickel crystals growth induced bymicro SiC particles.

References[1]. J.A. Calderón, J.E. Henao, M.A. Gómez, Erosion–corrosion

resistance of Ni composite coatings with embedded SiCnanoparticles, Electrochimica Acta, 124, 2014, pp. 190–198[2]. E. García-Lecina, I. García-Urrutia, J.A. Díez, M. Salvo,

F. Smeacetto, G. Gautier, R.Seddon, R. Martin, Electrochemicalpreparation and characterization of Ni/SiC compositionally gradedmultilayered coatings, Electrochimica Acta, 54, 2009, pp. 2556–2562[3]. M. Srivastava, V.K. William Grips, K.S. Rajam, Influence

of SiC, Si3N4 and Al2O3 particles on the structure and properties ofelectrodeposited Ni, Materials Letters, 62, 2008, pp.3487–3489[4]. L. Benea, P.L. Bonora, A. Borello, S. Martelli, Wear

corrosion properties of nano-structured SiC–nickel compositecoatings obtained by electroplating, Wear, 249, 2002, pp. 995–1003.[5]. Felicia Bratu, Lidia Benea, Jean-Pierre Celis,

Tribocorrosion behaviour of Ni–SiC composite coatings underlubricated conditions, Surface and Coatings Technology, 201,2007, pp. 6940-6946[6]. S. Pradeep Devaneyan, T. Senthilvelan, Electro Co-

deposition and Characterization of SiC in Nickel Metal MatrixComposite Coatings on Aluminium 7075, Procedia Engineering,97, 2014, pp. 1496-1505[7]. R.V. Williams, Electrodeposited composite coatings,

Electroplating Metal Finishing, 19, 1966, pp. 92 - 96[8]. M. Musiani, Electrodeposition of composites: an expanding

subject in electrochemical materials science, Electrochimica Acta,45, 2000, pp. 3397 - 3402[9]. Prasanna Gadharia, Prasanta Sahooa, Influence of process

parameters on multiple roughness characteristics of Ni–P–TiO2composite coatings, Procedia Engineering, 97, 2014, pp. 439 – 448[10]. Greg Haugstad, Atomic Force Microscopy: UnderstandingBasic Modes and Advanced Applications, John Wiley & Sons, Inc.Publications, 2012[11]. Camila Fernández, Chiara Pezzotta, Gijo Raj, Eric M.Gaigneaux, Patricio Ruiz, Understanding the growth of RuO2colloidal nanoparticles over a solidsupport: An atomic forcemicroscopy study, Catalysis Today, 2015, article in press[12]. Hans-Jurgen Butt, Brunero Cappella, Michael Kappl,Force measurements with the atomic force microscope: Technique,interpretation and applications, Surface Science Reports, 59, 2005,pp. 1–152[13]. Lidia Benea, Sorin-Bogdan Başa, Eliza Dănăilă, NadegeCaron, Olivier Raquet, Pierre Ponthiaux, Jean-Pierre Celis,Fretting and wear behaviors of Ni/nano-WC composite coatings indry and wet conditions, Materials and Design, 65, 2015, pp. 550–558

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[14] Mohajeri S, Dolati A, Rezagholibeiki S., Electrodepositionof Ni/WC nanocomposite in sulfate solution, Materials Chemistryand Physics, 129, 2011, pp. 746–750.[15]. P. Narasimman, Malathy Pushpavanam and V.M.Periasamy, Effect of Surfactants on the Electrodepositionof Ni-SiCComposites, Portugaliae Electrochimica Acta, 30, 2012, pp. 1-14[16]. Abouzar Sohrabi, Abolghasem Dolati, MohammadGhorbani, Aidin Monfared, Pieter Stroevec, Nanomechanicalproperties of functionally graded composite coatings:Electrodeposited nickel dispersions containing silicon micro- andnanoparticles, Materials Chemistry and Physics, 121, 2010, pp.497–505[17]. Th. Lampke, A. Leopold, D. Dietrich, G. Alisch, B.Wielage, Correlation between structure and corrosion behaviour

of nickel dispersion coatings containing ceramic particles ofdifferent sizes, Surface and Coatings Technology, 201, 2006, pp.3510 - 3517[18]. D. Thiemig, R. Lange, A. Bund, Influence of pulse platingparameters on the electrocodeposition of matrix metalnanocomposites, Electrochimica Acta, 52, 2007, pp. 7362 – 7371[19.] R.R.L. De Oliveira, D.A.C. Albuquerque, T.G.S. Cruz,F.M. Yamaji and F.L. Leite, Measurement of the NanoscaleRoughness by Atomic Force Microscopy: Basic Principles andApplications, book edited by Victor Bellitto, 2012[20]. E. S. Gadelmawla, M. M. Koura, T. M. A. Maksoud, I. M.Elewa, H. H. Soliman, Roughness Parameters, Journal ofMaterials Processing Technology,123, 2002, pp. 133-145.

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INFLUENCE PHYSICAL-CHEMICAL FACTORSON THE DISTRIBUTION OF HEAVY METALS

IN THE DELTA ECOSYSTEMS

Stela CONSTANTINESCUUniversity “Dunarea de Jos“ of Galati

email: [email protected]

ABSTRACT

Recognized to the influence of micropollutants, heavy metals represented onthe ecological status of surface waters, including delta ecosystems, the paper aimsto study the impact of environmental factors (temperature, pH,electroconductivitity, total salt content, dissolved oxygen content) the presence ofheavy metals in aquatic ecosystems of the Danube Delta Biosphere Reserve.

In this paper special attention is given to conservation of sampling and watersamples, sediments, plankton and plant material, specific methods for thedetermination of heavy metals and physical-chemical indicators, specific methodsfor quality assurance of chemical analysis.

I t presents a wide range of data on the concentration levels of heavy metals,both in terms of spatial distribution, and bioaccumulation in water samples,sediments, plankton and morphological parts of species that characterize Reserveaquatic ecosystems Danube Delta Biosphere, in terms of the levels and effects ofheavy metal pollution.

KEYWORDS: aquatic ecosystems, heavy metals, environmental factors,sediments

1. Introduction

Heavy metals are part of the persistentpollutants in the environment and is an additionalargument for research activities dedicatedsurveillance levels of heavy metals in the deltaecosystems and assess the effects of thesecontaminants on aquatic ecosystems areexercised.[1,2].

To assess the influence of physical-chemicalfactors on the distribution of heavy metals in aquaticecosystems were taken into account the followingphysico-chemical parameters: water temperature,water pH, electroconductivity, dissolved oxygencontent and total content of salts. The heavy metalshave selected cadmium, chromium, nickel, lead,manganese and zinc [3,4,5].

Increasing water temperature increases metalconcentrations in water and sediment. pH affects thetoxicity of heavy metal salts, at a low level (at theupside of heavy metal toxicity).

The practical value and theoretical significanceof the results and conclusions arising from the work

on the impact of environmental factors on heavymetals delta ecosystems [6,7].

Physico-chemical analyzes were performed inthe chemistry laboratory of the National Institute forResearch and Development Danube Delta, laboratoryaccredited to EN ISO / IEC 17025: 2005 by theAccreditation Association of Romania, RENAR

2. Experimental procedure

The main topic addressed in this paper is relatedto the problems and damage to ecosystems due toheavy metals and toxic pollution effects of which aredeveloped both directly and indirectly.

In an aquatic ecosystem metal toxicity can beinfluenced by variations of abiotic environmentalfactors such as oxygen, water hardness, pH andtransparency.

The temperature, in particular, is an importantfactor influencing metal toxicity, because mostaquatic organisms are poikilothermic.

Although hardness is widely recognized thataffect the aquatic toxicity of metals, pH is often thebiggest effect on metal toxicity.

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Some studies show that low levels of pH inwater reduces the toxicity of cadmium in seaweed andfish. It has also been suggested that the toxicity is lowdue to the competition between ions H + and metalcations free transport mechanism.Other factors that may play a role are: organic matter,carbon dioxide, metabolic activity, period (time) ofhalving the metal, suspended solids, total organiccarbon (TOC), the interaction between pollutants,

stage of development and changes bodiesintraspecific the susceptibility of metals. Theinfluence of these factors on the distribution ofphysical-chemical, metal, occurs either through directaction on the physiological activity of the body'smetabolic processes changing intensity or acting onthe microclimate by changing the physico-chemicalor pollutant concentration.

0.5750

0.5800

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0.60500.6100

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Diagrama de control Cadmiu 2012

Xi

LC

Xm+2S

Xm-2S

Xm+3S

Xm-3S

Fig. 1. Diagram of control indicator cadmium

Determining pollution gradient and degree ofaccumulation of inorganic pollutants on substrates(water, mineral, vegetable) and for the purposes setout in this paper, we consider the aquatic complexRazim-Sinoe, representative of the Danube DeltaBiosphere Reserve.

The types of samples are: samples of surfacewater, sediment samples, samples of plant material(Phragmites australis (reed) Typha angustifolia(rush). Water samples were collected quarterly in2012-2015. Sediment samples were collectedannually in 2012-2015. Aquatic vegetation sampleswere collected quarterly in 2012-2015.

He samples were mineralized in the microwaveAnton Paar. Step mineralization is performeddifferently depending on the type of sample, incompliance with applicable standards andrecommendations suggested by Anton Paar ovenmanufacturer.

Determination of heavy metals by atomicabsorption spectrometry . Atomic absorption may beused to determine very low concentrations of ions insolution.

This method is widely applied in biologicalsamples, metallurgical, geological or to determinepollution. Figure 1 diagrams represented cadmiumcontrol indicator. Values with concentrations in thecontrol charts are determined to be validmeasurements, respectively in Xm +/- 2 S, (mean +/-standard deviation of all measurements).

For comparative tests extraction and analysis,the same type of sample, we have established twosystems of extraction and analysis:

1. Mineralizorul Skalar and atomic absorptionspectrometer VARIAN AA100.

2. Anton Paar microwave oven and massspectrometer with inductively coupled plasma ICP-MS Elan DRC is.

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Samples of water, sediment and reed treated byboth methods were taken starting from 2014 inaquatic complex Razelm - Sinoe.

3. Result and discussions

In relation to national quality standards for lakebottom sediment, most samples investigated in the

period 2012-2015, had levels of manganese and zinclimits. Cadmium was the item that recorded thehighest percentage of exceedances of the standard forquality, as shown in Figure 2.

To assess concentrations of metals, weconsidered the mean concentrations of cadmiumdetermined in 2014 the aquatic complex Razim-Sinoe.

0.0000.2000.4000.6000.8001.0001.2001.4001.600

Complex Razim - Sinoe

P. australisT. angustifolia

ppm

Cd

subs

t. us

cata

Fig. 2. Dynamics of cadmium concentrations in samplesPhragmites australis and Typha angustifolia, aquatic complex Razim-Sinoe

Heavy metals enter into ciclulul biologicalaquatic plants through the roots and leaves. They candirectly affect plant growth, excessive intake of suchelements in plants can also be dangerous for humanand animal health. The chemical composition reflectsthe composition of the soil and plant the plant surfacecontamination indicates the presence of contaminants

harmful to the environment, in the air. In order toassess the accumulation of heavy metals in partsmorphology of the species Phragmites australis,respectively, stalk, rhizomes and leaves, aquatic plantsamples were collected at the stage of developingtheir most complex Razim-Sinoe water in the summerof 2014.

CadmiumRhizomes

43%Leaves

38%

Stalk 19%

Fig. 3. Distribution of cadmium in parts morphologicalPhragmites australis species of aquatic complex Razim-Sinoe

Analyzing the percentage values of theconcentrations of heavy metals we observed that allthe metals analyzed, namely cadmium, chromium,nickel, lead, manganese and zinc, accumulates mostlyin the rhizomes samples Phragmites australis(between 37% and 75%), figure 3.

The results show that Phragmites australisleaves have a capacity to accumulate heavy metals incomparison to the roots, the reason for this isprobably short-lived; leaves renew every year, whilerhizomes have a longer life, so rhizomes accumulate alarger amount of heavy metals than the leaves.

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Table 1. Values factors bioaccumulation of heavy metals in aquatic vegetation in Razim-SinoeNo Complex

aquaticVegetationaquatic

BCF CdL/kg

BCF CrL/kg

BCF NiL/kg

BCF PbL/kg

BCF MnL/kg

BCF ZnL/kg

P. australis 120.111 90.501 759.500 2.998 8.490 360.1601. Razim-Sinoe T.

angustifolia 123.180 101.622 692.401 5.900 9.998 390.100

To calculate bioaccumulation factors were takeninto account the average annual values ofconcentrations of heavy metals in water and helofiletwo species, Phragmites australis and Typhaangustifolia, Table 1.

Analyzing large amounts of bioaccumulationfactors obtained for these two species studiedmacrophytes in aquatic complex, we conclude thatboth species have shown great potential forbioaccumulation of heavy metals. In general, theorder growth factors bioaccumulation of heavy metalsin the two species studied helofile the pool complex isas follows:

BCF Pb <BCF Mn <BCF Cr <BCF Cd <BCFZn <BCF Ni.

Given this abundance and distribution of theseplants must be seriously taken into consideration.

In terms of accumulation of heavy metals,emerged vegetation is different from submergedvegetation in that submerged vegetation accumulatedmore metal than that emerged.

Heavy metals in the two types of vegetationaccumulates most in submerged vegetation tovegetation emerged, except cadmium and lead thataccumulates the same in both types of aquaticmacrophytes, Figure 4.

Fig. 4. Accumulation of heavy metals in vegetation submerged and emerged

In conclusion species of aquatic macrophytesselected Phragmites australis, Typha angustifolia, sotake heavy metals from water and sediment (by-rhizome root system, highly developed) in studyingaquatic complex.

Investigations on the use of aquaticmacrophytes as bioaccumulate heavy metals as wellas their ability to be used in modern techniques ofcleaning a water body could be very useful forenvironmental monitoring and health check of thewater body.

To assess the influence of physical-chemicalfactors on the distribution of heavy metals in aquaticecosystems were taken into account the followingphysico-chemical parameters: water temperature,water pH, electroconductivity, dissolved oxygen

content and total content of salts. The heavy metalshave selected cadmium, chromium, nickel, lead,manganese and zinc.Increasing water temperatureincreases metal concentrations in water and sediment.pH affects the toxicity of heavy metal salts, at a lowlevel (at the upside of heavy metal toxicity).

Analyzing correlations between concentrationsof metals in water samples and sediments and ofphysico-chemical, select, we conclude that strict rulesare not possible to give both positive and negativevalues of the indices Pearson, Table 2. This Danubedelta demonstrate that it is an open system thatcontinuously circulates water so that theconcentrations of metals in water and sediment sufferpermanent changes.

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Table 2. Pearson correlation index values determined for cadmium in aquatic complex Razim-Sinoe

Temperature(0C) pH Ec

(µs/cm)

O2disolvation(mg O2/L)

Totalsalts

(mg/L)

Cd-Water(mg/L)

Cd-Water(mg/L) 0.3500 0.1801 0.1158 0.4700 -0.3110 1

Cd-Sedim.(mg/kg) 0.5010 -0.7900 0.8051 0.7998 -0.2612 -0.1161

Pearson correlation index values which werethe basis for determining the influence of physical-chemical factors on the distribution of heavy metalsin the delta ecosystems.

4. Conclusions

Chemical analyzes were performed by standardmethods.

Aquatic macrophytes having the ability toabsorb and accumulate large amounts of heavymetals, have an important role as biofilters, bio-accumulate and bio-indicators. Similar trendsaccumulation of heavy metals in the analyzedsamples show the universal importance of theseaquatic macrophytes in environmental clean living.

Particular capacity of these two species,Phragmites australis and Typha angustifolia, toaccumulate heavy metals and that these twomacrofite produce a significant amount of organicmatter, which increases the potential foraccumulation of toxic substances in these twospecies of macrophytes , make them suitable for usein environmental monitoring of water quality wherethey live and their role biofilters aquatic ecosystems.

Analyzing the influence of physical-chemicalfactors (water temperature, water pH,electroconductivity, dissolved oxygen content andtotal content of salts) on the distribution of heavymetals (cadmium, chromium, nickel, lead,manganese and zinc) in lake complex Razim- Sinoefound that the influence of these factors acting on the

microclimate manifests itself by changing itsphysico-chemical properties.

Increase water temperature increases metalconcentrations in water and sediment, with certainexceptions; pH affects the toxicity of heavy metalsalts, at a low level (at the upside of heavy metaltoxicitye microclimate manifests itself by changingits physico-chemical properties.

Cadmium aquatic vegetation has resulted froma normal distribution.

References

[1]. P.Kotze, H.H.Du Preez, and J.H.J.Van Vuren -Bioaccumulation of copper and zinc in Oreochromis mossambicusand Clarias gariepinus from the Olifants river, Mpumalanga,South Africa. Water SA, 1999. 25(1): p. 99-110.[2]. M .Van Der Merwe,. J. H. J .Van Vuren, and et al.-Lethal copper concentration levels for Clarias gariepinus(Burchell, 1822)- a preliminary study. Koedoe, 1993. 36: p. 77-86.[3]. P.D. Abel - Water Pollution Bilogy., ed. E.H.Poblishers. 1989, Chichester. 231.[4]. L.Teodorof et al. - Heavy metals extraction andanalysis in aquatic ecosystems with automated techinques, inAdvances in Electrical and Computer Engineering, Suceava,Romania. 2009. p. 102.[5]. D.J. Pietrzyk and C. W.Frank - Chimie Analitica. 2ed. 1989, Bucuresti: Editura Tehnica. 558.[6]. A.Shehu et al. - Assessment of Heavy MetalsAccumulation by Different Spontaneous Plant Species Grownalong Lana River, Albania. Balwois 2010 - Ohrid, 2010.[7]. G.Jamnická et al. - Heavy metals content in aquaticplant species from some aquatic biotopes in Slovakia. inProceedings 36th International Conference of IAD. AustrianCommittee Danube Research/ IAD. 2006. Vienna.

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CORROSION BEHAVIOUR AND BIOCOMPATIBILITYOF 316 STAINLESS STEEL AS BIOMATERIAL IN PHYSIOLOGICAL

ENVIRONMENT

Georgeta TODERAŞCU1, Valentin DUMITRAŞCU1, Lidia BENEA1,*,Alexandru CHIRIAC2

1Research (Competences) Centre: Interfaces-Tribocorrosion and Electrochemical Systems (CC-ITES),Faculty of Materials and Environmental Engineering, Dunărea de Jos University of Galati,

47 Domnească Street, RO-800008, Galati, Romania2Faculty of Medicine and Pharmacy, Dunărea de Jos University of Galati, 47 Domnească Street,

RO-800008, Galati, Romania*Corresponding author

e-mail: [email protected]

ABSTRACT

Although stainless steel is a widely used material for biomedical applications,its surface properties for long term application are still a serious concern. 316Lstainless steel (SS 316L) is a material commonly used in dentistry for orthodonticbraces, wires and in some cases as dental crowns. The pH value of natural salivafrom oral cavity can suffer sudden modification due to food products which are richin citric acid. The electrochemical corrosion behavior of 316L stainless steel wasevaluated in two simulated body fluids solution, Fusayama-Mayer artificial salivawith pH=5 and Fusayama-Mayer artificial saliva adjusted with citric acid to apH=1.58 which simulates the environmental conditions of oral cavity. The surfaceof SS316L was investigated by optical microscope before and after corrosionassays. The electrochemical corrosion behavior was studied by open circuitpotential, potenitodynamic polarization and linear polarization. Optical microscopywas used to characterize the corrosion damage after the electrochemical assays.

KEYWORDS: biomaterials, stainless steel, corrosion, simulated body fluids

1. Introduction

Man-made materials and devices have beendeveloped to replace diseased or damaged parts(which become non-functional) in the human body inorder to prolong life, to improve and restore tissuefunction, and to improve quality of life [1], throughproduction of contact lenses, dental implants,artificial skin, heart valves, breast implants, jointprostheses or bone plates. Significant developmentshave been taking place to provide suitablebiomaterials from metals/alloys, ceramics, bioglasses,and polymers with minimal reaction and rejection bythe body [1].

It is well known that a series of interactionsoccur between the surface of biomaterials and thebiological environment after they have been

implanted into the human body. Therefore, thebiomaterials surface plays an extremely importantrole in the response of artificial medical devices to thebiological environment [2]. The current researchfocus on the biomaterials and the research communityis aimed at understanding the fundamental processesat the interface between implant surfaces andsurrounding living tissues [2].

Table 1. show the types, applications, and majorfailure mechanism of various biomaterials includingmetallic/alloys. However, each of these has somelimitations. A single material cannot offer all desiredproperties; therefore, they have been used incombination with each other in the form of coatingsand joints [1].

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Table 1. Types of biomedical materials and their applications [1]

Biomaterials Objectives Degradationmechanism

Applications

Metals/alloys: SS316L,Co-Cr alloy, Ti and Tialloys, Ni-Ti alloys

Load bearing Corrosion andmechanical

Fracture fixation plates, screws, pins,nails, joint replacements, orthodonticwires, femoral stems, cases forpacemakers, supports for heart valves,dental implants, dental crowns, bridges,fillings, and inner ear bone replacements

Ceramics: Carboncoatings, alumina, oxides,zirconia, glass, glassceramics, and hydroxyapatite (HAP)

High hardness,wear resistance,and better bonebonding

Corrosion andmechanical

Carbon in heart valves, dental implants,joint implants, coatings for dental andjoint implants, fill bone voids/cavities byHAP, tissue scaffolds, drug deliverysystems, and inner ear implants

Polymer: Ultra highmolecular weightpolyethylene, polyester,polytetraflouroethylene,PMMA, hydrogels,silicone rubber, PGA/PLA, collagen, cellulose,and chitosan

Articulatingsurfaces

Wear, swelling,leaching, chemical

Joint replacement, vascular grafts, bonecement, orthodontic devices (e.g. plates,dentures) contact and intraocular lenses,catheters, hand and toe joints, artificialtendon and ligament, reconstructivesurgery, sutures, staples, tissuescaffolds, drug delivery systems, andhemostatic bandages, pace maker leads.

Metallic materials such as Ti, Ti-alloy, Co–Cralloy and stainless steel–AISI (American Iron andSteel Institute) 316L are used as biomaterials due totheir superior tensile and fatigue strength and fracturetoughness as compared to nonmetals such aspolymeric and ceramic. However, metallic materialscorrode by aggressive biofluid and release metallicions which resulted in the reduction of theirbiocompatibility [1, 3]. The biocompatibility andcorrosion resistance of these implants are primarilydetermined by their constituent material and surfacemicro structural properties such as roughness, grainsize, etc. [3].

The stability of the surface oxide layer is one ofthe most important requirements of a biomaterial. Foruntreated 316L SS, the stability of the surface oxidelayer is not very high and the possibility of metal ionsbeing released is greater in comparison to Co-Cr andTi-6Al-4V alloys [4]. After electrolytic polishing,316L stainless steel forms very thin, of a few-nanometer, compact oxide film resistant againstcorrosion in the presence of physiological humanbody fluids environments [5].

Among the metallic materials, AISI 316Lstainless steel is most commonly employed fortemporary devices such as fracture plates, bonescrews and hip nails due to its low cost andacceptable biocompatibility [3, 6, 7]. It also has goodductility and possesses good biocompatibility [7, 8].

However, it has been often reported to sufferfrom severe crevice and galvanic corrosion, primarilydue to the presence of occluded sites and highchloride concentration in physiological fluids.

The corrosion of the stainless steel implantreleases metal ions such as Fe, Ni and Cr, whichproduce local systematic effects and thereby plays arole in prosthetic loosening [3].

In dental industry, the metallic alloys are mainlyused for crown, bridges, prostheses, supra-constructions and implants. They need to fulfillimportant requirements such as ease and reliability ofhandling and treatment, toughness appropriate to thesituation of application, good biocompatibility andaesthetic properties. These materials are confrontedwith extreme environmental conditions in the mouth,as the temperature can vary between 5 and 55oC andthe composition and the pH of the saliva variesdepending on the nutrition [9]. The interactionsbetween saliva and these foreign materials can affectthe corrosion and tribocorrosion performance of 316Lstainless steel prostheses [10].

The original artificial saliva solution wasintroduced by Takao Fusayama [10], but the chemicalcomposition of artificial saliva has changed in time.Although saliva has a neutral acidity (pH of 7), due tothe acidity of the modern western diet rich in citricacid from fruits and vegetables, saliva frequentlybecomes acidic (pH 5–6) during mastication. It is notuncommon for proteins, antibacterial agents andenzymes to be added to artificial organic solutions.

In recent years, there has been a significantincrease in the number of studies examining thecorrosion properties of 316L stainless steel used inmedical/dental applications. In some recent studiesthe corrosion mechanisms of 316L stainless steel invarious solutions, including different artificial saliva

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[10-13], have been examined. The aim of this study isto identify the occurring corrosion mechanisms where316L stainless steel is exposed to an environmentwith different pH values, which is similar to the oralcavity through electrochemical methods.


2.1 Materials

In this work it was analyzed 316L stainless steelwith the chemical composition given in Table 2.Before corrosion examinations, the 316L stainlesssteel samples were polished with SiC #600 anddiamond paste. The polish plates were degreased withalcohol and acetone and rinsed with distilled water.Afterwards the polished samples were dried with ahair dryer and inserted in corrosion holder to obtain ameasurable surface of 1.76 cm2.

2.2 Electrochemical behavior tests in bio-simulated fluid solution

In situ electrochemical measurements such asopen circuit potential (OCP), linear polarization (Rp)and potentiodynamic polarization (PD) were carriedout to access the anti-corrosive characteristics of316L stainless steel in Fusayama-Mayer artificialsaliva with two different pH. All electrochemicalassays were performed using VoltaLab PGZ100potentiostat/galvanostat and the data were recordedwith VoltaMaster software.

Table 2. Chemical composition of316L stainless steel

Element Composition(wt%)

C 0.02Si 0.47P <0.007S <0.03Cr 17.5Mn 1.92Cu 0.3Ni 13.3Mo 2.04Nb 0.07Fe Balance

The surfaces of SS 316L were investigated withan optical microscope type OPTIKA XDS-3METbefore and after corrosion tests in order to confirm theresults of electrochemical assays. The optical imageswere performed with software Vision Pro Plus,version 5.0 on computer connected to opticalmicroscope.

Electrochemical measurements were carried outin a conventional three electrodes cell shown in Fig.1. consisting of Platinum-Rhodium grid as counterelectrode (CE), Ag/AgCl (saturated solution of KCl,E=200 mV vs. Standard Hydrogen Electrode (SHE))as reference electrode and 316L stainless steel asworking electrode (WE).

Fig. 1. Electrochemical cell set-up for corrosion tests

The corrosion behavior of 316L stainless steelwas tested in Fusayama Mayer artificial saliva withpH=5 and respectively pH=1.58 adjusted with citricacid. Chemical compositions of these solutions areclose to the natural saliva and contain different typesof salts which are shown in Table 3.

The pH of Fusayama-Mayer artificial saliva wasadjusted to 1.58 in order to understand the corrosionbehavior of SS 316L under the worst-case conditions,although it is know that this pH value is much moreaggressive than would be normal for natural saliva.

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Table 3. Chemical composition of Fusayama-Mayer artificial saliva

Compound Fusayama-Mayerartificial saliva

NaCl 0.4 g/L-1

KCl 0.4 g/L-1

CaCl2 0.8 g/L-1

Na2HPO4 0.69 g/L-1

CH4N2O 1 g/L-1

Deionizedwater

Balance

pH 5


3.1. Open Circuit Potential

The open circuit potential was monitored withthe exposure time of 60 minutes, in order to obtain astable potential vs. Ag/AgCl (reference electrode).The potential-time measurements are one of the waysto study the corrosion behavior of 316L stainless steelin Fusayama-Mayer artificial saliva with two differentpH values and recorded data are presented in Fig. 2.From Fig. 2. it can be observed that the potential of316L stainless steel immersed in Fusayama-Mayerartificial saliva with two different pH values shift topositive values at the end of 60 minutes. In the sameFig. 2. it can be seen that the potential of sampleimmersed in Fusayama-Mayer artificial saliva withpH=5, drop down slowly in the first 2 minutes due toslow degradation of native passive layer from thesurface and after that, increase up to -90 mV at theend of studied time period. The potential of samplesimmersed in modified Fusayama-Mayer artificialsaliva with pH=1.58, the potential decreases faster inthe first 5 minutes due to rapid degradation of passivefilm and after that increases slowly up to value of -120 mV.

Fig. 2. Open circuit potential plots obtained in:(1) Fusayama-Mayer artificial saliva pH=5.0

and (2) Fusayama-Mayer artificial salivaadjusted with citric acid at pH=1.58

This increasing trend of potential has beenobserved by T. Hryniewicz [14] for 316L stainlesssteel after immersion in Ringer solution. Theincreasing trend of 316L stainless steel potentialreveals the formation of a stable passive oxide layeron the sample surface.

3.2. Evolution of polarization resistance(Rp) values during immersion time

Linear polarization method was used toevaluate the polarization resistance of 316L stainlesssteel in Fusayama-Mayer artificial saliva with twodifferent pH values. The evaluation of polarizationresistance was measured around open circuit potentialvalue with a very small potential amplitude (±40 mV)in order to preserve the steady state surface.

The polarization resistance diagrams of SS316L immersed in Fusayama-Mayer artificial salivawith pH=5 respectively 1.58 are presented in Fig. 3(a).

Fig. 3. (a) The evolution of polarization resistance (Rp) and (b) the evolution of corrosion rate valuesduring the immersion in Fusayama-Mayer artificial saliva with (1) pH=5 and (2) pH=1.58

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From Fig. 3 (a). it can be seen that thepolarization resistance value of SS 316L, immersed inFusayama-Mayer with pH=5, is equal to 130kohm•cm2. In comparison, the polarization resistancevalue of SS 316L immersed in Fusayama-Mayerartificial saliva adjusted with citric acid to a pH valueof 1.58 is equal to 80 kohm•cm2. The increasedpolarization resistance value means that the formedpassive film after immersed in Fusayama-Mayerartificial saliva with pH=5 more resistant comparedwith that formed in low pH value equal to 1.58. Adecreasing of polarization resistance value at oncewith decreasing of pH value lead to the increasing ofcorrosion current density and therefore to a highercorrosion rate, as it can be seen from Fig. 3 (b). InFig. 3 (b) are presented the corrosion rates versustime corresponding to SS 316L surfaces immersed inFusayama-Mayer artificial saliva with two differentpH values. According with the data plotted in Fig. 3(b). it can be seen that the higher corrosion ratecorrespond to SS 316L immersed in Fusayama-Mayerartificial saliva with lowest pH value (pH=1.58) incomparison with corrosion rate of SS 316L immersedFusayama-Mayer artificial saliva with pH=5. Theseresults show that the SS 316L has a lower corrosionresistance in Fusayama-Mayer artificial saliva (pH=5)and are in good agreement with the evolution of opencircuit potential values.

3.3. Potentiodynamic polarization

The potentiodynamic polarization studies wererecorded in a range of potential starting from -1.5 Vvs. Ag/AgCl to +1.5 V vs. Ag/AgCl at a scan rate of 5mV/s. Fig. 4. shows the potentiodynamic polarizationof SS 316L after immersion in Fusayama-Mayerartificial saliva with two different pH value, 5respectively 1.58.

Fig. 4. Tafel representation of potentiodynamicpolarization for SS 316L immersed in

Fusayama-Mayer with (1) pH=5 and (2)pH=1.58

Table 4. The electrochemical corrosion data extracted from the electrochemical corrosionpolarization curves

Sample/Solution

Ecorr (i=0)(mV vs. Ag/AgCl)

Rpkohm. cm2

icorrmA. cm2

ba(mV vs.

Ag/AgCl)

bc(mV vs.

Ag/AgCl)SS 316L/Fusayama-MayerpH=5

-770 3.25 11.21 241.4 -214.4

SS 316L/Fusayama-Mayerwith citric acidpH= 1.58

-472.7 1.16 52.49 380.2 -146.8

Anodic Tafel constant βa and cathodic Tafelconstant βc, as well as corrosion current density Icorr,were calculated from the intersection of the anodicand cathodic Tafel lines in the polarization curves atEcorr [15, 16].

The results are listed in Table 4.From Fig. 4. itcan be observed that the corrosion current (icorr) of SS316L immersed in Fusayama-Mayer artificial salivawith pH value equal to 1.58 is higher than thecorrosion current of SS 316L immersed in Fusayama-Mayer artificial saliva with pH value equal to 5 whichprovoked the decreasing of corrosion rate from 3.25

kohm•cm2 to 1.16 kohm•cm2 with decreasing of pHvalue.

3.4. Optical microscopy

The surfaces of SS 316L was investigatedbefore and after corrosion tests in Fusayama-Mayerartificial saliva with pH value equal to 5 andFusayama-Mayer artificial saliva adjusted with citricacid and pH value equal to 1.58 in order to estimatethe corrosive effects and are presented in Fig. 5.

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Fig. 5. Optical microscopy of SS 316L (a) before corrosion, (b) after corrosion in Fusayama-Mayerartificial saliva with pH=5 and (c) after corrosion in modified Fusayama-Mayer artificial saliva with

citric acid and pH=1.58

From Fig. 5 (a). it can be observed that the SS316L before corrosion tests has a uniform surfacewith no defects. After corrosion tests in Fusayama-Mayer artificial saliva with pH=5 (Fig. 5 (b)), the316L stainless steel suffer small diameters pits andare visible a few rust spots in comparison with the316L stainless steel surface (Fig. 5 (a)) beforecorrosion assays.

The samples of 316L stainless steel surfaceimmersed in Fusayama-Mayer artificial salivaadjusted with citric acid and pH value equal with 1.58present sever pitting damage (Fig. 5 (c)) incomparison with the samples immersed in Fusayama-Mayer artificial saliva with pH value equal with 5.The pitting damage covers a high surface of the 316Lstainless steel samples and the pits are deeper into thesubstrate.

4. Conclusion

The corrosion behavior of Stainless Steel 316Lwas investigated in simulated body fluid – Fusayama-Mayer Artificial Saliva at different pH values.

The experimental results reveal that the SS316Lpresent a better corrosion behavior in Fusayama-Mayer Saliva with pH=5 in comparison with

Fusayama-Mayer Saliva modified with Citric Acidand pH=1.58.

From the linear polarization curves it can beseen that the decreasing of pH from 5 to 1.58 producea decrease of polarization resistance (Rp) from 130kohm•cm2 to 80 kohm•cm2.

The optical microscopy images are in goodagreements with electrochemical measurements.

Acknowledgements

UEFISCDI - Ministry of Education andResearch is acknowledged for the financial support toCompetences Centre Interfaces - Tribocorrosion andElectrochemical Systems (CC-ITES) - Dunarea de JosUniversity of Galati - Research Project: HyBioElect,contract 10 /30-08-2013 (2013 - 2016) in the frame ofNational Research Programme Romania - PN II PCE.

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prevention by surface modification of biometallic materials,Journal of Materials Science: Materials in Medicine 18 (2007)725–751[2]. X. Liu, P.K. Chu, C. Ding, Surface nano-functionalization of

biomaterials, Materials Science and Engineering R 70 (2010) 275–302

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[3]. S.K. Tiwari, T. Mishra, M.K. Gunjan, A.S. Bhattacharyya,T.B. Singh, R. Sing, Development and characterization of sol–gelsilica–alumina composite coatings on AISI 316L for implantapplications, Surface & Coatings Technology 201 (2007) 7582–7588[4]. T.P. Singh, H. Singh, H. Singh, Characterization, corrosion

resistance, and cell response of high-velocity flame-sprayed HAand HA/TiO2coatings on 316L SS, Journal of Thermal SprayTechnology 21 (2012) 917–927[5]. T. Hryniewicz, R. Rokicki, K. Rokosz, Surface

characterization of AISI 316L biomaterials obtained byelectropolishing in a magnetic field, Surface & CoatingsTechnology 202 (2008) 1668–1673[6]. A. Mahapatro, Bio-functional nano-coatings on metallic

biomaterials, Materials Science and Engineering C 55 (2015) 227–251[7]. A. Parsapour, S.N. Khorasani, M.H. Fathi, Effect of surface

treatment and metallic coating on corrosion behavior andbiocompatibility of surgical 316L stainless steel implant, Journal ofMaterials Science Technology 28 (2012) 125–131[8]. J. Yang, F. Cui, I.S. Lee, X. Wang, Plasma surface

modification of magnesium alloy for biomedical application,Surface & Coatings Technology 205 (2010) S182–S187[9]. W.-D. Mueller, C. Schoepf, M.L. Nascimento, A.C.

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[10]. A. Hayes, S. Sharifi, M.M. Stack, Micro-abrasion-corrosionmaps of 316L stainless steel in artificial saliva, Journal of Bio- andTribo-Corrosion 1 (2015) 1–15[11]. K. Hajizadeh, H. Maleki-Ghaleh, A. Arabi, Y.Behnamiam, E. Aghaie, A. Farrokhi, M.G. Hosseini, M.H.Fathi, Corrosion and biological behavior of nanostructured 316Lstainless steel processed by severe plastic deformation, Surface andInterface Analysis 47 (2015) 978–985[12]. Y. Kayali, A. Buyuksagis, Y. Yalcin, Corrosion and wearbehaviors of boronized AISI 316L stainless steel, Metals andMaterials International 19 (2013) 1053–1061[13]. B. Al-Mangour, R. Mongrain, E. Irissou, S. Yue,Improving the strength and corrosion resistance of 316L stainlesssteel for biomedical applications using cold spray, Surface &Coatings Technology 216 (2013) 297–307[14]. T. Hryniewicz, R. Rokicki, K. Rokosz, Electrochemical andXPS studies of AISI 316L stainless steel after electropolishing in amagnetic field, Corrosion Science 50 (2008) 2676–2681[15]. L. Benea, E. Mardare-Danaila, M. Mardare, J.P. Celis,Preparation of titanium oxide and hydroxyapatite on Ti–6Al–4Valloy surface and electrochemical behavior in bio-simulated fluidsolution, Corrosion Science 80 (2014) 331–338[16]. K. F. Khaled, S.S. Abdel-Rehim, Electrochemicalinvestigation of corrosion and corrosion inhibition of iron inhydrochloric acid solutions, Arabian Journal of Chemistry 4 (2011)397–402

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MICROSTRUCTURAL CHARACTERIZATION OF TiMoZrTa ALLOY

Mădălina Simona BĂLȚATU1, Ramona CIMPOEȘU1,Petrică VIZUREANU1,2, Dragoş Cristian ACHIȚEI1,2,

Mirabela Georgiana MINCIUNĂ1,21Gheorghe Asachi Technical University of Iasi, Faculty of Materials Science and Engineering,

Blvd. D. Mangeron 41, 700050, Iasi, Romania2Center of Excellence Geopolymer & Green Technology (CEGeoGTech), School of Materials Engineering,

Universiti Malaysia Perlis, 01000 Kangar, Perlis, Malaysiae-mail: [email protected]

ABSTRACT

In recent years different types of titanium alloys have been investigated withthe aim of using materials in biomaterials field, and Ti–Mo system alloys are verypromising materials. Alloying titanium with biocompatible elements like Mo, Zr andTa make then possible for these alloys to be used in medical applications.Microstructures of two TiMoZrTa alloys were investigated. Obtaining of thisoriginal recipes alloys was prepared using vacuum arc re-melting methodafterwards composition of this alloys were verified by quantitative qualitativeanalysis EDX. Aim of this study is investigating aspects of microstructuresTiMoZrTa alloys using optical and scanning electron microscopes, verifying thetype of grains, that will shows us the most important properties.

KEYWORDS: Ti-based alloy, biomaterials, microstructure, XRD analysis

1. Introduction

Metallic biomaterials, like stainless steel or Co-based alloys, titanium and its alloys continue to beused extensively in different medical applications,therefore this are research and improved [1,2].

Titanium and its alloys are still widely used, forimplant materials because presents an acceptablebiocompatibility, relatively low elastic modulus, hasexcellent corrosion resistance due superficial oxidelayer and the density / resistance rapport is very good[3,4].

Representative titanium alloys used for implantmaterials are Ti-6Al-4V and commercial puretitanium. This alloys the type of α+β , in time, shownthat V and Al are toxic for human body. Therefore,researchers replaced V and Al with non-allergicelements like Mo, Nb, Ta, Sn and Zr. In recent years,the β-type titanium alloys composed of nontoxicelements was extensively investigated becauseprocessing variables can be controlled to produceselected results (e.g. Ti-15Mo, Ti-35.5Nb-5.1Ta-7.1Zr, Ti-24Nb-4Zr-8Sn and Ti-12Mo-6Zr-2Fealloys) [5-8]. The β type alloys compared to α and(α+β) type Ti have advantages like lower elastic

modulus, improved fatigue resistance and excellentresistance to wear and abrasion [9, 10].

Titanium has an allotropic transformation froma hexagonal close-packed (hcp) which referred to“alpha” phase into a body-centered cubic (bcc), called“beta” phase at 882 ºC.

Depending on phase microstructure of alloyedtitanium alloys can be classified into three mainstructural types: alpha alloys, alpha + beta alloys andbeta alloys, but these metallographic transformationscan be improved by additions of selected α or βalloying stabilizers [11-13].

The aim of this study is to characterizedmicrostructures of a new alloy with medicalapplications.


The alloy was obtained from the melting of thepure elements like Ti, Mo, Zr, Ta in an arc meltingfurnace, MRF vacuum ABJ 900.

Due to the big difference in the melting point ofelements (Ti: 1.668 ºC, Mo: 2.623 ºC, Zr: 1.855 ºC,Ta: 3.020 ºC ) and density (Ti: 4.51 g/cm3, Mo: 10.2g/cm3, Zr: 6.5 g/cm3, Ta: 16,65 g/cm3) between thefour pure metals, the alloy was followed by re-

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melting of the alloy for 6 times for refining andhomogenizing the structure in the same installation[11,14].

The alloy used in this study, after melting, wascharacterized by chemical composition, X-raydiffraction, optical microscopy. Chemicalcomposition of the alloy was analysis with EMVEGA II LSH scanning electron microscopemanufactured by the TESCAN Co., the CzechRepublic, coupled with an EDX QUANTAX QX2detector manufactured by the BRUKER/ROENTECCo., Germany.

The phases were analysis using X-raydiffraction, made on the diffractometer X'Pert PROMPD PANalytical X-ray with the followingparameters: continuous scan, 2θ - (10°-90°), Stepsize: 0,0131303, Time per step: 61,20, Scan speed:0,05471,45 KV and 40 mA using a copper anode X-ray tube.

After X-ray diffraction, alloys were prepared bya standard metallographic process, by polishing alloysin SiC waterproof papers until #2000 grit andcolloidal alumina suspension.

Metallographic structure of alloys was shownby the attack surface with a chemical solution havingthe following composition: 10 ml HF, 5 ml HNO3, 85ml H2O immersed in 5-30s [12].

The device used in microstructure analysis forTi alloy was metallographic microscope Leica5000DMI.

3. Results and discutions

3.1. Chemical composition

The chemical analyses (EDX or XRF) wereperformed in many different areas. The results andspectrum are shown in Fig. 1.

The chemical composition of the alloy (Table 1)was homogeneous and no showed differencesbetween surface and core.

Figure 1 show the spectrum and distributionmap of the chemical elements of the alloy studied.

Distribution map show that alloy studied ishomogeneously all over the surface.

Table 1. Chemical composition of alloy studied

Element (wt%)

Ti 67.65

Mo 12.84

Zr 8.8

Ta 10.71

Fig. 1. Spectrum and distribution map of the main chemical elements of the alloy studied

3.2. X-ray diffraction

The X-ray diffraction patterns for Ti-based alloyare shown in Figure 2. The patterns of alloy could beindexed in the cubic β type structure, the space groupof Im-3m [10,14].

According to Table 2, increased amount of βstabilizing elements (Mo, Ta) alloys present in thecomposition was not enough to form a single phase β.

In the structure of alloy has been identified twomain phases: β with a body-centered cubic structureand α’’ with orthorhombic structure.

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By adding pure tantalum lead to the appearanceemergence phase α’’ as β phase is confirmed and toY.L.Zhou [8]. According X.H. Min by addingzirconium in conjunction with a higher percentage of10% of Mo leads predominantly β phase appearance[15].

In alloy sample was found β phase with themajor peak at the angle 2θ = 38,8485 and α’’ with themajor peak at the angle 2θ = 37,0213.

Network unit cell parameters of the alloy aregiven in Table 2.

Fig. 2. X-ray diffractograms for Ti-based alloy

Table 2. Compound parameters

Elements Ti, Mo, Zr, Ta

Space Group Im-3mCrystal system Cubic

a(Å) 3.31b(Å) 3.31c(Å) 3.31α(º) 90β(º) 90γ(º) 90

Cell volume(106 pm3) 36.30

Its very important to know the microstructure ofa metallic biomaterial, like Ti and its alloys, becauseof a coexistance of hexagonal α Ti and bcc β Ti.

Knowing these important aspects, can controlmechanical properties and corrosion resistance,having a direct effect on their biocompatibility.

3.3. Microstructures

The microstructure of the alloy studied, as shownin the Fig. 3-4, was consistent with the XRD results.

Optical microstructure of Ti-based alloy studiedpresent acicular (dendritic) structure with irregulargrain boundaries (Fig. 3). The microstructure ofTiMoZrTa alloy is a specific beta [16,17].

Fig. 3. Optical microstructure of Ti-based alloy: a) 50X, b) 100X

For microstructure characterization of alloystudied were acquired images secondary electron (SE)

and backscatter (BSE) using detectors BSE(Backscattered Detector). Because metal sample were

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analyzed, was used the High Vacuum mode using avoltage of 20 kV.

SEM images of the alloy studied confirm theacicular (dendritic) structure.

Fig. 4. SEM image of Ti-based alloy: a) 300X, b) 500X

Electron micrographs (Fig. 4) of alloy show abiphasic structure, consisting of a high proportion ofβ solid solution, occurring a lamellar structuresintragranulation specific orthorhombic martensite α’’,as shown in Fig. 3. Orthorhombic martensite α’’occurs frequently in the case of titanium base alloyswhich are found in β-stabilized transition metalcategory, in which Ta and Zr is included [15, 18].

3. Conclusions

An alloy was developed from the melting of thepure elements like Ti, Mo, Zr, Ta in an arc meltingfurnace.

The SEM analysis revealed surfaces withoutdefects and the elements mapping showed ahomogeneous distribution for all alloys.

Molybdenum, zirconium and tantalum alloyingelements presents influence to the structure andmicrostructure of alloy, through the β- stabilizeraction. Microstructure of the alloy studied presentacicular structure with irregular grain boundaries,with β phase. The XRD results present a predominantβ phase and a α’’ secondary phase showed in theFigure 2. Finally we conclude that presented alloy ifcan be used for medical application.

References

[1]. D.M. Bombac, M. Brojan, P. Fajfar, F. Kosel, R. Turk,Review of materials in medical applications, Materials andGeoenvironment, 54(4) (2007) 471-499.[2]. M. G. Minciuna, P. Vizureanu, D. C. Achitei, N. Ghiban, A.V. Sandu, N. C. Forna, Structural Characterization of SomeCoCrMo Alloys with Medical Applications, 65(3) (2014) 335-338.[3]. M. Niinomi, M. Nakai, J. Hieda, Development of newmetallic alloys for biomedical applications, Acta Biomater, 8(2012) 3888-3903.[4]. C. Leyens, P. Manfred P. Titanium and titanium alloys:Fundamentals and Applications, John Wiley & Sons, 2003.

[5]. N. T.C. Oliveira, G. Aleixo, R. Caram, A.C.Guastaldi,Development of Ti-Mo alloys for biomedical applications:Microstructure and electrochemical characterization, MaterialsScience and Engineering A 452-453 (2007) 727-731.[6]. L.C. Zhang, D. Klemm, J. Eckert, Y.L. Hao, T.B.Sercombe, Manufacture by selective laser melting and mechanicalbehavior of a biomedical Ti-24Nb-4Zr-8Sn alloy, Scr. Mater, 65(2011) 21-24.[7]. M.G. Minciuna, P. Vizureanu, V. Geanta, I. Voiculescu,A.V. Sandu, D.C. Achitei, A.M. Vitalariu, Effect of Si on theMicrostructure and Mechanical Properties of Biomedical CoCrMoAlloy, Revista de chimie, 66(6) (2015) 891-894.[8]. Y. L. Zhou, M. Niinomi, T. Akahori, Effects of Ta content onYoung’s modulus and tensile properties of binary Ti-Ta alloys forbiomedical applications, Materials Science and Engineering A 371(2004) 283-290.[9]. S.B. Gabriel, J.V.P. Panaino, I.D. Sanros, L.S. Araujo, P.R.Mei, L.H. de Almeida, et al., Characterization of a new betatitanium alloy, Ti-12Mo-3Nb, for biomedical applications, J.Alloys Compd. 536 (Suppl.1) (2012) S208-S210.[10]. A.C. Bărbînţă, R. Chelariu, M. Benchea,C.I. Crimu, S.Iacob Strugaru, C. Munteanu, (2014), A comparative analysis ofnew Ti-Nb-Zr-Ta orthopedic alloys, Advanced Materials Research,837 (2014) 259-264.[11]. ***, ASM Handbook, Alloy Phase Diagrams, vol.3, pp. 254.[12]. ***, ASM Handbook, Metallography and Microstructure,vol.9, pp. 2157-2208.[13]. I.C.Lupu, D. Agop-Forna, I.G.Sandu, C.Mocanu,Microscopic Assessment of the Corrosion Resistance of someSuperficially Enhanced Ti-Based Dental Alloys withHidroxyapatite, Revista de Chimie, 66 (6) (2015) 808-812.[14]. Lutjering, G., Williams, J.C., (2003) Titanium, Springer-Verlag, Berlin, pp. 289.[15]. X. H. Min, S. Emura, L. Zhang, K. Tsuzaki, Effect of Feand Zr additions on ω phase formation in β-type Ti-Mo alloys,Materials Science and Engineering A 497 (2008) 74-78.[16]. Oliveira, N.T.C., Aleixo, G., Caram, R., Guastaldi, A.,Development of Ti-Mo alloys for biomedical applications:Microstructure and electrochemical characterization, MaterialsScience and Engineering A, 452-453 (2007) 727-731.[17]. D.R.N. Correa, F.B. Vicente, R.O. Araujo, et all, Effect ofsubstitution elements on the microstructure of the Ti-15Mo-Zr andTi-15Zr-Mo system alloys, J Mater Res Technol. 4(2) (2015) 180-185.[18]. S. Ehteman Haghighi, H.B. Lu, C.Y. Jian, G.H. Cao, D.Habibi, L.C. Zhang, Effect of α’’martensite on the microstructureand mechanical properties of beta-type Ti-Fe-Ta alloys, Materialsand Design 76 (2015) 47-54.

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TREATMENT OF AMMONIA WASTEWATER BY ULTRASOUND.PART I: THE INFLUENCE OF ULTRASOUND ENERGY ON

ULTRASOUND BATH TEMPERATURE

Nicoleta MATEI (CIOBOTARU)1*, Dan SCARPETE21“Dunarea de Jos” University of Galati, Faculty of Engineering and Agronomy,

Calarasi Street, 29, RO-810017, Braila, Romania2“Dunarea de Jos” University of Galati, Faculty of Engineering,

Domneasca Street, 47, RO-800008, Galati, Romania*Corresponding author


ABSTRACT

Industrial ammonia water decontamination depending on the sampletemperature is monitored by this study. The treatment was conducted by theUP100S ultrasound generator (Hielscher Ultrasound Technology, Germany),operating at 30kHz frequency and acoustic power densities of 90W/cm2 and460W/cm2 respectively. The effect of sonication both on bath temperature andammonia removal, based on treatment time, is presented in this paper. Experimentswere carried out according to different parameters, so as the sample temperaturevariation by ultrasonic treatment to be determined. Studied parameters were: theoperating mode variation (continuous or intermittent), the additional aeration andthe application of a cooling water serpentine. Based on the results, the ammoniaremoval efficiency is improved by the heating produced by the ultrasonic energy.

KEYWORDS: ultrasound, ammonia wastewater, acoustic cavitation,temperature, ammonia removal

1. Introduction

Among all the uses of power ultrasound,treatment of wastewater containing toxic and complexpollutants, both from industrial and domestic sources,appears to be the most attractive field of study [1].The advantages of this technology include potentialchemical-free and simultaneous oxidation, thermo-lysis, shear degradation, enhanced mass-transferprocesses together [2].

Enhancement in the processing rates is mainlydue to the fact that, when ultrasound is passed thoughliquid medium it can generate cavitation phenomenadue to alternate compression and rarefaction cycles[3], as shown in Figure 1 [4]. Cavitation can be asuitable technology for degradation of wastewaterstreams or at the minimum it can be used for loweringthe toxicity levels of the effluent stream so thatconventional biological oxidation can be readilyapplicable [5].

Ultrasonic cavitation concentrates the energyand with the collapse of bubbles the energy isreleased within a tiny area, which generates a veryhigh local temperature (around 5000 °C) and pressure(in excess of 500 atm), forming the so-called 'hotspots', which will open up widespread new chemicalreaction routes and abruptly accelerate the chemicalreaction rate [6].

During treatment process, an ultrasonicgenerator transforms the electrical energy into otherkinds of energies as shown in Figure 2.

Fig. 1. Compression and expansion cycle ofultrasound [4]

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Fig. 2. The energy transformation chain duringultrasonic treatment [7]

In this work, the effect of the temperature risedue to the thermal energy emitted by the probe duringsonication was assessed. The potential influence ofthe bulk phase temperature at ultrasonic treatmentapplication and the optimum temperature range fordifferent processes is discussed in many papers [8-15]. The thermal impact of continuously implodingcavitation bubbles on the surrounding liquid orsonicated matter itself depends on the physicalproperties of sonication medium such as vaporpressure or viscosity [16, 17], surface tension, gasesdissolved and bulk temperature. According to manyauthors, the temperature increase of the sonicatedliquid medium leads to an increase of the vaporpressure and a reduction of viscosity and surfacetension [18-20]. With an increase in the vaporpressure of the liquid, the vapor content of the cavityincreases thereby lowering the energy released duringthe cavitational collapse [18]. On the other hand, thereduction of viscosity and/or surface tension lowersthe threshold intensity required to produce cavitation[19] and makes the effects temperature rise to befavorable. Increasing temperature results in reductionin acoustic cavitation threshold, meaning, the liquidscavitate at lower intensities [21]. Notwithstanding,Raman et al. explaines that lower cavitationthresholds translate into ease of cavity formation,thereby making higher temperatures more favorablefor particle breakage [20].

The present study refers to ammonia waterdecontamination by sonication and it is focused onthe ultrasound influence on the heating occurring inthe treated sample. This work is further continued byPart II, referring on the effect of ultrasound onammonia removal. Considering that the separation ofthe ammonia-water mixture can be achieved byconventional distillation [22], heating appears to havea beneficial effect in ammonia removal. However, theseparation performance is subjected to thethermodynamic constraints of the system based on thevolatility (boiling point) difference of the various

substances (e.g., −33.4 °C for ammonia and 100 °Cfor water at atmospheric pressure) [22, 23].

2. Materials and methods

2.1. Wastewater Features

This research is conducted on ammonia waterdecontamination by ultrasonic treatment. Severalactivities generate high-strength ammonia wastewaterincluding human waste, agricultural waste andindustrial effluent [24].The sample utilized in the current paper is generatedin the ion exchangers chemical industry. By washingthe ammonium gas, ammonia water results as residualwater. In order to carry out experiments in normallaboratory conditions, appropriate dilutions of 1:1000were applied to the effluent. The final concentrationof the sample subjected to tests was of 72.840 mg/lammonium and 56.597 mg/l ammonia nitrogenrespectively, after dilution. The volume of the sampleto be treated was set at 300 ml.

Fig. 3. Schematic representation ofexperimental set-up

The temperature increase was measured at roomtemperature by using a thermometer, which wasimmersed and held at the half height of the sonicatedsample of ammonia water.

2.2. Experimental Set-Up

Schematic representation of ultrasonic setupdesigned for the treatment of industrial ammoniawater is shown in Figure 3, where: 1-electronicgenerator; 2-electromechanical transducer; 3-probe;4-vessel containing ammonia water sample; 5-water

ELECTRICAL ENERGY

MECHANICAL ENERGY

ACOUSTICAL ENERGY

THERMAL ENERGY

CAVITATION ENERGY

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cooling coil; 6, 7-hoses for cooling water in and out;8-thermometer; 9-aeration pump; 10-air stone.

The electric energy produced by thepiezoelectric type generator 1 is converted tomechanical energy by transducer 2, further convertedinto acoustic energy in the form of ultrasonic wavestransmitted through probe 3 to the ammonia watersample from vessel 4. This energy causes physicaland chemical effects in the liquid medium to betreated and it is finally converted into heat.

In order to highlight both the effect ofsonication and the effect of heating that occurs duringthe treatment process, the cooling water coil 5 wassunk in the vessel 4. The cooling water was takenfrom current water source by hose 6 and the usedwater was directed to a sink by the drain hose 7.Experimental tests have been carried out both withand without water cooling coil. Ammonia watertemperature is constantly monitored by thethermometer 8 immersed in the ammonia wastewatersample. To create the effect of bubbling, or theadditional oxygen diffusion into the liquid, theaeration pump 9, fitted with air stone 10 (having therole of a fine spray air bubbles) were used.

The ultrasonic processor UP100H, HielscherUltrasonics GmbH, Teltow, Germany, was utilized toconduct the experiments. The generator is working ata 30 kHz fixed frequency with the possibility toadjust the amplitude of the oscillating system. Theamplitudes used in the treatment process were themaximum amplitudes working with each of the usedprobe (70 and 180 µm, respectively). Also, to eachprobe a different acoustic power density (ultrasonicintensity) corresponds, as follows:

- Probe MS 3 (3 mm diameter): 460 W/cm2

- Probe MS 10 (10 mm diameter): 90 W/cm2

The maximum depth to which the probe wasimmersed in the tested liquid was 30 mm.


For both acoustic intensities of the ultrasonicpiezoelectric generator, various ways of temperaturevariation have been registered. In the following, thedynamics of the temperature during sonication isdiscussed depending on the working parameters (withor without additional aeration, in either continuous orintermittent operation and depending on whether thecooling water coil is applied). Temperature valueswere read every 5 to 5 minutes for 60 minutes by thethermometer immersed in the solution. It was notedthe constant value of temperature after an hour oftreatment, which is explained by the dynamic thermalequilibrium conditions of permanent transfers of heatbetween the treated ammonia water and the ambientair.

The initial temperature at which the readingsstarted can vary by experiment, due to the ambienttemperature of the laboratory, which was constantlymonitored. However, of primary interest is thedynamics of temperature rise and the registered upperlimit.

3.1. Thermal effect at higheracoustic intensity

The dynamics of temperature depending on theoperating mode (continuous or intermittent) and theadditional aeration at higher acoustic intensity isgiven in Figure 4.

Fig. 4. Dynamics of temperature at460 W/cm2 acoustic intensity

The ultrasonic power of 460 W/cm2 generatesthe temperature raise in the treated sample, up to amaximum constant at 34 °C, after 50 minutes, incontinuous operation without additional aeration.

At additional aeration, the sample temperaturereaches a maximum of 33 °C after 55 minutes, due tothe air generated to the working vessel by the aerationpump attached to the set-up designed for thetreatment of industrial ammonia water.

Fig. 5. Dynamics of temperature at 460 W/cm2

acoustic intensity by cooling water coil

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In the case of intermittent operation of 0.5seconds, the temperature of the sample reaches 28 °Cafter 45 minutes, without aeration or 27 °C after 50minutes with additional aeration.

Considering the role of maintaining the sampleof treated water at a constant temperature, theapplications where the cooling water coil was utilizedrecorded a decrease of 1°C compared to the initialtemperature of the water, according to Figure 5. Thiswater temperature evolution was recorded when usingMS 3 probe in both continuous and intermittentoperation. Additional aeration does not affect thestudied water temperature.

3.2. Thermal effect at loweracoustic intensity

When the ultrasonic treatment is conducted atacoustic power density of 90 W/cm2, the sampleheating is remarkable. The maximum constant valueof 60 °C is reached after 60 minutes of continuousmode treatment, both with and without additionalaeration. Intermittent operation of the ultrasonicirradiation generates a constant upper limit of 46 °Cafter 50 minutes without additional aeration or after55 minutes with aeration applied (Figure 6).

Fig. 6. Dynamics of temperature at 90 W/cm2

acoustic intensity

Fig. 7. Dynamics of temperature at 90W/cm2 acoustic intensity by cooling water coil

Figure 7 shows the effects on temperature whenusing the cooling water coil for the treatment withMS 10 probe. In intermittent operation, there is atemperature drop of 3 °C in the first 20 minutes ofultrasound treatment, followed by a temperaturemaintaining to the value equal to the cooling watertemperature throughout the treatment period.

In continuous mode, the temperature remainsconstant, but cooling is provided only with 1 °C, dueto much higher heating trend of the sample.

Additional aeration has no influence on thestudied water temperature.

In the second part of the study, complete resultsobtained in the treatment of ammonia water with adetailed discussion will be presented. Some of theobjectives can be summarized as follows:

- The thermal effect in ammonia removal byultrasonic technique is intended. In order to determineboth effects of ultrasonic irradiation with heating andwithout heating on elimination rate, the experimentswill be conducted by the addition of the cooling watercoil.

- The removal efficiency according to allowabledischarge limits (to natural water courses or publicsewerage networks) will be determined.

4. Conclusions

The entire study refers to the determination ofthe optimum removal of ammonia from industrialammonia wastewaters. In this part of the study, theinfluence of the acoustic power density on the liquidmedium temperature by sonication was determined.

At higher ultrasonic intensity (460 W/cm2) thetemperature rise is recording an upper limit of 34 °Cin 60 minutes of treatment. The lower studied ultraso-nic intensity (90 W/cm2) generates higher temperaturerise rates of 60 °C after 60 minutes of treatment.

The beneficial effect of heating on the elimi-nation of ammonia from liquid mediums is alreadyknown. However, to be strictly observed the effect ofultrasonic treatment without additional heating effect,a cooling water coil to maintain a constant sampletemperature, was applied to the treatment setup.

Acknowledgements

The work has been funded by the SectorialOperational Programme Human ResourcesDevelopment 2007-2013 of the Ministry of EuropeanFunds through the Financial Agreement POSDRU/159/1.5/S/132397.

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References

[1]. P.R. Gogate et al., Sonochemical reactors for waste watertreatment: comparison using formic acid degradation as a modelreaction. Advances in Environmental Research 7 (2003) 283-299.[2]. M. Matouq et al., The kinetic of dyes degradation resulted

from food industry in wastewater using high frequency ofultrasound. Separation and Purification Technology 135 (2014) 42-47.[3]. V.S. Sutkar et al., Theoretical prediction of cavitational

activity distribution in sonochemical reactors. ChemicalEngineering Journal 158 (2010) 290-295.[4]. A. Mahvi, Application of Ultrasonic Technology for Water

and Wastewater Treatment. Iranian J Publ Health, 38 (2009) 1-17.[5]. P.R. Gogate, Treatment of wastewater streams containing

phenolic compounds using hybrid techniques based on cavitation:A review of the current status and the way forward. UltrasonicsSonochemistry 15 (2008) 1-15.[6]. J. Huang et al., Low-MHz frequency effect on a sonochemical

reaction determined by an electrical method. UltrasonicsSonochemistry 2 (1995) S93-S97.[7]. Z. Kobus et al., Influence of physical properties of liquid on

acoustic power of ultrasonic processor. TEKA Kom. Mot. Energ.Roln. – OL PAN 8a (2008) 71–78.[8]. V.A. Lemos et al., Ultrasound-assisted temperature-

controlled ionic liquid microextraction for the preconcentrationand determination of cadmium content in mussel samples. FoodControl 50 (2015) 901-906.[9]. S. Rochebrochard et al., Sonochemical efficiency dependence

on liquid height and frequency in an improved sonochemicalreactor, Ultrasonics Sonochemistry 19 (2012) 280–285.[10]. M. Plesset, Temperature effects in cavitation damage. Journalof Basic Engineering 94 (1972) 559–566.[11]. S. Hattori et al., Influence of air content and vapor pressureof liquids on cavitation erosion. Trans. JSME 68 B (2002) 130–136.

[12]. S. Hattori et al., Influence of temperature on erosion by acavitating liquid jet. Wear 260 (2006) 1217–1223.[13]. B. Ondruschka et al., Ultrasound in environmental engine-ering. TUHH Reports on Sanitary Engineering, 1999, p. 139.[14]. H. Destaillats et al., Applications of ultrasound in NAPLremediation: sonochemical degradation of TCE in aqueoussurfactant solutions. Environ. Sci. Technol. 35 (2001) 3019–3024.[15]. L. Wenjun et al., Removal of Organic Matter and AmmoniaNitrogen in Azodicarbonamide Wastewater by a Combination ofPower Ultrasound Radiation and Hydrogen Peroxide. ChineseJournal of Chemical Engineering, 20 (2012) 754-759.[16]. P.V. Cherepanov et al., Up to which temperature ultrasoundcan heat the particle? Ultrasonics Sonochemistry 26 (2015) 9–14.[17]. M. Ashokkumar et al., Sonochemistry, in: Kirk-OthmerEncyclopedia of Chemical Technology, John Wiley & Sons, 2007.[18]. P.R. Gogate et al., Sonochemical reactors: Important designand scale up considerations with a special emphasis onheterogeneous systems. Chemical Engineering Journal 166 (2011)1066–1082.[19]. M. Goel et al., Sonochemical decomposition of volatile andnon-volatile organic compounds-A comparative study. WaterResearch 38 (2004) 4247–4261.[20]. V. Raman et al., Experimental investigations on ultrasoundmediated particle breakage. Ultrasonics Sonochemistry 15 (2008)55–64.[21]. T. Mason et al., Applied Sonochemistry: The Uses of PowerUltrasound in Chemistry and Processing. Wiley-VCH VerlagGmbH and Co. KGaA, 2002.[22]. X. Yang et al., A Pervaporation Study of Ammonia SolutionsUsing Molecular Sieve Silica Membranes. Membranes 4 (2014) 40-54.[23]. Y.A.Cengel et al., Thermodynamics: An EngineeringApproach. Mcgraw-Hill College: New York,, USA, 2011, ISBN-13: 978-0073398174.[24]. S.H. Mirhossaini et al., Effect of influent COD on biologicalammonia removal efficiency. International Journal of Environmen-tal, Chemical, Ecological, Geological and Geophysical Engineering4 (2010) 86-88.

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URBAN POLLUTION ISSUES GENERATEDBY TRAMS TRAFFIC

Adrian LEOPA, Diana ANGHELACHE”Dunarea de Jos” University of Galati,

Engineering and Agronomy Faculty of Brailae-mail: [email protected]

ABSTRACT

Modern society development involves new and diverse issuesconsidering urban environmental pollution. Traffic generated sound andvibration are two up-to-date urban environmental pollution causes besidesair and water pollution ones. Public transportation in metropolitan areasis a major and constant all levels environmental pollution cause. Electricengines as an alternative to internal combustion ones could reduce the airpollution caused by urban public transportation. Tram network is animportant element of this approach even if a poor condition of tramnetwork elements could be a major cause of sound and vibrationenvironmental pollution. This research paper is a study of a particularcase considering the vibration level transmitted to a building close to tramnetwork in Braila City.

KEYWORDS: urban, pollution, vibration, tram

1. Introduction

In this century of speed, the tram, as a partof public transportation, generates fewenvironmental and economic problems. Forinstance, it requires expensive runways andpower networks, low speed and a high weight.For example, the Imperio model produced by SCAstra vagoane Arad, Romania, can be purchasedfor 1.7 million Euros despite the abovementioned drawbacks as well as acoustic andvibration pollution.

Having said the low maintenance costs andhigh exploatation durability, this type of publictransportation does not pollute the environmentas much as internal combustion engines do.

Due to the increase of registered vehicles,the use of trams has become a compulsorynecessity regarding the pollution of theatmposphere.

In Romania, immediately after the earlybeginning of the 2008 financial crisis, the carpark has been keeping its increasing tendence,but in a slower rate.

As a result, between 2010 and 2014, itincreased by 777 547 vehicles.

The city of Braila had its auto parkexapanded by a number of 13079 cars, in the2010-2014 period, reported to the 180 000inhabitants. A natural consequence of theincreased number of vehicles is the pollutionemphases caused by the gases released by theinternal combustion engine [5].

Fig. 1. Evolution of the number of vehiclesin Romania

Even if some vehicles are provided withcatalysts, they start functioning at an optimumlevel after a certain time, when they reach at least400oC, which is equal to driving for nearly 10km.

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Fig. 2 Evolution of the number of vehicles inBraila City

2. The effects of the trams on buildingsand their inhabitants

Usually, when both the driving way and thetram do not have defects of intense usage oraccident, this type of transportation must notproduce polluting vibrations [9]. Otherwise, thevibrations generated by the functioning tram mayhave undesirable effects on nearby buildings,their tenants and technical equipments, aswell[10]. As for buildings placed in thepropagated vibration area, it can result in thedefacement of the construction elements, such asunequal settlements or even a reduced level ofstructure stability [1]. The same fenomenon mayinduce to the inhabitants of those buildingstiredness which lead to various pathologies ormay have bad effects on the proper functioningof electronic equipments which requires a highperformance level [1]. There are legal noticeswhich enforce maximum values to vibrationparameters for the nearby buildings, to avoidnegative effects produced by trams’ traffic.

In Romania, the laws and regulations in thefield consider the SR12025-2-94 as the standard,in which the legal limit is mentioned forvibrations generated by the road traffic andtransmitted to buildings or to certain parts ofthem [2].

2.1. Building presentation

For inhabited buildings or socio-culturalones, using them properly can be reached byproviding structural entirety and inside comfort.The assessment of these two desires can beachieved by predictive maintenance activitieswhich consists of periodic checks of the vibrationparameter values for buildings in imposed limitesby the regulations.

Through the current study, the vibrationparameters have been quantified experimentally,

which are generated by the trams' traffictransmitted to a block of flats from Brăila city,regarding the examination of these values inorder to compare them to the permitted quota.

The building which was observedthroughout this experimental study is placed onthe Indepence Boulevard in Braila, at a 9 metresdistance from the drive way of the tram of theRadu Negru-Vidin route.

The block of flats is built on two floors,semi-basement and a storey, its structure beingmade out of brick.

Fig. 3 The building located near tram line:1- residential building; 2 - road [7]

2.2. The system of measurement devices

The assessment of the vibration leveloriginated from trams' traffic has been realisedusing the following equipments:

- acquisition and processing system withPCeight-channel acquisition boardHARMONIE Octav - Sinus MesstechnikGmbH;

- two piezoelectric accelerometers(seismic), type 393B04 - PCB;

- required connectors.

a. floor b. semibasement

Fig. 4 Accelerometer location on the firstand second floor, on the external wall,

parallel to the tram rails

Experimental measurements were carriedout with two vertically placed accelerometers, atthe same time, on different building elements, asfollows:

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- simultaneously positioning on two levels;- two floors simultaneous positioning on

the wall, parallel to the road;- two floors simultaneous positioning on

the wall, perpendicular to the road;


Fig. 5. Accelerometer location on the firstand second floor


Fig. 6. Accelerometer location on the firstand second floor, on the external wall,

perpendicular to the tram rails

In order to determine the level of vibrationabsorbed by each building element, seven sets ofsignal acceleration have been recorded andprocessed using MATLAB R14, [6], [7]. Aspectral analysis of the acquired accelerationsignals has been performed to identify thesignificant frequencies and to determine theirparameter’s levels.

10 15 20 25 30-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

X: 11.02Y: 0.0006909

Time [s]

Acc

eler

atio

n [m

/s2 ]

X: 24.03Y: -0.03036

X: 24.02Y: 0.02951

a. floor

10 15 20 25 30-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

X: 23.8Y: -0.1548

Time [s]

Acc

eler

atio

n [m

/s2 ]

X: 15.16Y: 0.001756

X: 23.8Y: 0.1528

b. semibasement

Fig. 7. Acceleration signals from exteriorwall accelerometer, parallel to the tram line

0 100 200 300 400 5000

1

2

x 10-4

X: 107.8Y: 7.855e-005

Frequency [Hz]

Acc

eler

atio

n am

plitu

de [m

/s2 ]

X: 47.63Y: 0.000125

X: 67.86Y: 0.000204

X: 17.24Y: 0.0001244

a. floor

0 100 200 300 400 5000

0.2

0.4

0.6

0.8

1

1.2x 10-3

X: 125Y: 0.0001794

Frequency [Hz]

Acc

eler

atio

n am

plitu

de [m

/s2 ]

X: 91Y: 0.0007541

X: 68.06Y: 0.001018

X: 18.91Y: 0.0001334

b. semibasement

Fig. 8. Graphic presentation of the spectralaccelerometer acceleration signals fromexterior wall, parallel to the tram line

0 5 10 15-0.08

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0.08

X: 1.982Y: 0.0003746

Time [s]

Acc

eler

atio

n [m

/s2 ]

X: 10.01Y: -0.06124

X: 10.02Y: 0.06596

a. floor

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0 5 10 15-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

X: 12.05Y: 0.01358

Time [s]

Acc

eler

atio

n [m

/s2 ]

X: 8.267Y: 0.01988

X: 9.706Y: -0.03147

X: 9.531Y: 0.03776

b. semibasement

Fig. 9. Acceleration signals consideringaccelerometer floor location

0 100 200 300 400 5000

0.2

0.4

0.6

0.8

1

1.2

1.4x 10-3

X: 125Y: 0.0002271

Frequency [Hz]

Acc

eler

atio

n am

plitu

de [m

/s2 ]

X: 15.71Y: 0.0002475

X: 79.8Y: 0.001286

a. floor

0 100 200 300 400 5000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1x 10-3

X: 106.2Y: 0.0003286

Frequency [Hz]

Acc

eler

atio

n ap

litud

e [m

/s2 ]

X: 76.24Y: 0.0004626

X: 14.84Y: 0.0009502

b. semibasement

Fig. 10. Graphic presentation of thespectral acceleration for accelerometer

location on floors

2 4 6 8 10 12 14 16-0.02

-0.015

-0.01

-0.005

0

0.005

0.01

0.015

0.02

0.025

X: 3.985Y: 0.008369

Time [s]

Acc

eler

atio

n [m

/s2 ]

X: 7.819Y: -0.01717

X: 7.177Y: 0.02084

a. floor

0 5 10 15-0.08

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0.08

X: 9.803Y: 0.02055

Time [s]

Acc

eler

atio

n [m

/s2 ]

X: 7.096Y: -0.0645

X: 7.943Y: 0.06692

b. semibasement

Fig. 11. Accelerometer accelerationsignals from exterior wall, perpendicular

to the tram line

0 100 200 300 400 5000

0.5

1

1.5

2

2.5

3

3.5

4

4.5x 10-4

X: 120.7Y: 7.106e-005

Frequncy [Hz]

Acc

eler

atio

n am

plitu

de [m

/s2 ]

X: 59.03Y: 0.0003076

X: 17.59Y: 0.0002699

a. floor

0 100 200 300 400 5000

0.5

1

1.5x 10-3

X: 137.2Y: 0.0001544

Frequency [Hz]

Acc

eler

atio

n am

plitu

de [m

/s2 ]

X: 84.9Y: 0.001438

X: 17.59Y: 0.0003413

b. semibasement

Fig. 12. Graphic presentation of thespectral acceleration signals foraccelerometers on the outer wall,

perpendicular to the tram line

3.3. Final evaluation

To assess the harmfulness of tram trafficinduced vibrations, the following parametershave been calculated: vibration intensity,acceleration level it vibration strength.

To assess the comfort of buildingoccupants, the vibration acceleration values(according to SR 12025/94) have been used forvibration levels being reported to 80 equal curve

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physiologically tolerable level (AVZ),

corresponding to residential buildings. Accordingto Table 1, some values (red) stand out. They are

located above the curve 80, especially for lowfrequencies vibration, but under the 92 curve,corresponding to commercial buildings.

Table 1. Vibration parameters on residential buildings

Acc

eler

omet

ers

posit

ione

d

Rec

ordi

ng

Leve

l

Acc

eler

atio

n pe

ak[m

/s2 ]

Freq

uenc

y [H

z]

Vib

ratio

nin

tens

ity[c

m2 /s3 ]

Acc

eler

atio

n le

vel

[dB]

Vib

ratio

n st

reng

th[v

ibra

r]

semibasement 0.016 15 0,17 84.08 2.32Recording 2

floor 0.091 81 1,02 99.18 10.09


floor 0.15 66 3,40 103.52 15.32

semibasement 0.02 14 0,28 86.02 4.55

A.Accelerometerlocation on thefirst and secondfloor, on theexternal wall,parallel to thetram rails

Recording 4floor 0.077 66 0,89 97.72 9.53

semibasement 0.065 79.8 0,52 96.25 7.23Recording 5

floor 0.038 14 1,03 91.59 10.13

semibasement 0.044 79.7 0,24 92.86 3.85

B.Accelerometer location on thefirst and secondfloor Recording 6

floor 0.03 14 0,64 89.54 8.08


floor 0.029 63 0,13 89.24 1.25

semibasement 0.02 17 0,23 86.02 3.71

C.Accelerometer location on thefirst and secondfloor, on theexternal wall,perpendicular tothe tram rails

Recording 8floor 0.066 64 0,68 96.39 8.32

In order to evaluate the effect of vibrationon the structure of the building, the vibrationstrength levels have been compared to allowablevalues recommended in the specific literature [2].One single value, which is classified as a mildtremor, exceeded the vibration strength levels forthe wall that paralleled the tram rails.

3. Conclusions and outlook

The assessment of the tram traffic vibrationlevel on residential buildings is a necessityimposed by the requirements of indoor comfortfor residents and ensures structural integrity ofthe building.

Experimental measurements have shown anexcess of vibration level that have not affectedthe residents. There was a single case of vibrationwhich can be classified as a light one. We canconsider that the vibrations are not currently amajor stress factor for inhabitants or an imminentthreat to the structural integrity of the building,due to reduced traffic (one tram at every 10 or 15minutes).

The application of predictive maintenancehas to be considered. It requires regularassessment of the level of trams traffic vibrationon buildings as a method of evaluation fornormal operation and tread.

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Several solutions can be implemented toreduce or even eliminate the effects of vibrationfrom trams traffic on nearby buildings:

- rehabilitation by replacing the treadrubber damping elements installed under tramtracks.The viscoelastic proprieties of the rubbervaries with time. After 15 years, the rubber „isgetting old”, losing its initial properties;

- replacing the old trams;- insulating the base of nearby buildings.

This is an approach for new buildings (toexpensive for old ones);

References

[1]. Bratu P, Monitorizarea în timp real a vibraţiilortransmise de sursele industriale cu efect asupra omului şi amediului construit, Simpozion AGIR, 2007.

[2]. Buzdugan Gh., Izolarea antivibratorie a mașinilor, EdAcademiei Republicii Socialiste România 1980.[3]. Buzdugan Gh., Izolarea antivibratorie , Bucureşti,

Editura Academiei Române, 1993.[4]. Bratu, P., Vibratiile sistemelor elastice, Editura Tehnică

Bucuresti, ISBN 973-31-1418-9, (1999).[5]. Debeleac C., Nastac S., On Vibration Exposure

Monitoring at Industrial Intensive Pollutant Areas, Journal ofScience and Arts, Year 2010.[6]. Ghinea, M., Fireteanu, V., Matlab - Calcul numeric,

grafica, aplicatii, Teora Publishing House, Romania, 2003[7]. Gilat, A., MATLAB: An Introduction with Applications

2nd Edition, Wiley edition, 2004.[8]. ***Harta 3D a municipiului Braila,

http://www.harta3d.ro/harta-satelit-braila.html;[9]. Leopa A., Nastac S., Debeleac C., Protection Against

Vibrations, a Desideratum of The Sustainable Development,International Multidisciplinary Scientific GeoConference :SGEM: Surveying Geology & mining EcologyManagement 5: 641-648. Sofia: Surveying Geology & miningEcology Management.[10]. Nastac S., Picu M, Evaluating methods of whole-body-vibration exposure in trains, Ann.“Dunarea de Jos” Univ.Galati, Fasc. XIV Mech. Eng, 2010.

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ENVIRONMENTAL RISK ASSESSMENT FORTHERMAL POWER PLANTS

Tamara RADU“Dunărea de Jos” University of Galati, Romania


ABSTRACT

Thermal power plants represent, still, an important source of energy inRomania but also in Europe. Risks on the environment are primarily generated bythe noxae generated from combustion of fossil fuels, namely: noxious gases (CO2,CO, NOx, SOx), particulate, heavy metals (As, Cd, Cr, Cu, Ni, Pb), CH4, polycyclicaromatic hydrocarbons (PAHs), dioxins and furans. All these pollutants plus theslag and the ash resulting from combustion of fuels have, in time, a significantenvironmental impact. The environmental hazards caused by these emissions areanalyzed in this paper depending on the gravity of the consequences and likelihoodof occurrence. It shows the risk analysis, the risk matrix and treating andmonitoring to identified risks.

KEYWORDS: hazards, risk analysis, risk matrix, management

1. Introduction

After a descendant trend for several decades, theuse of coal for energy is rising again. Coal is still animportant energy source in Europe, covering about aquarter of the electricity production [1].

Thermal Power Plants (TPP) are producingelectricity by converting thermal energy resultingfrom combustion of fossil fuels such as coal, fuel, oiland natural gas. Combustion of fossil fuel in largecombustion plants such as those for TPP generateCO2, present in variable proportions and SO2, SO3,NOX and in smaller quantities heavy metals,halogenated compounds, dioxins and furans[2]. Allthese pollutants plus the slag and the ash resulting outof fuels combustion have a significant environmentalimpact in time.

Romania, same as Germany are on second placein the top of pollution generated by thermal powerplant on coal. To reduce environmental impact, bothat European and national level, series of regulationsto limit emissions of certain pollutants from theselarge combustion installation were adopted.

The main pollutants emitted in the air by TPPsare those resulting from combustion of fuels: huila /lignite and natural gas or fuel oil [3, 4]. The pollutantsspecific of the combustion in boilers are: noxiousgases (CO2, CO, NOx, SOx), particulate matter, heavymetals (As, Cd, Cr, Cu, Ni, Pb), CH4, polycyclic

aromatic hydrocarbons (PAHs), dioxins and furans[5].

Most likely way of transfer of the pollutants tothe receptors is through air, an environmental factorthat favors a fast transport and direct contaminationby inhalation. In this manner employees are affectedby pollutants present in the atmosphere of theworkplace, from diffuse sources and in highconcentrations. Also in this way, the population andecosystems in the vicinity of the TPP come in contactwith gaseous and particulate pollutants specific to theprocesses, resulting out of controlled sources anddiffuse sources, but in smaller concentrations, afterhaving undergone a prior dilution in the atmosphere.

The main sources of air pollution are:- emissions of SO2, NOx, particulates and CO2;- coal dust originated from the deposits solid

fuel (coal), which has an action zonal;- dust arising from deposits (dumps) of ash and

slag through deflation, when these particles areshattered by the wind and entrained into theatmosphere.

The pollutants emissions (E) are influenced bythe quality of fuels (coal, fuel oil, natural gas).

The methodology for calculating the quantity ofthose emissions is based on fuel consumption (B),caloric power of the fuel (C) and emission factors (e)[2]:

E[Kg] = B x C x e (1)

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The water required for technological steamproduction in thermal circuit of the TPP and for firesextinguishing is collected and treated (softened,demineralized and deferrized).

The rainwater polluted with oil productsresulting from the site of the fuel oil deposit arecollected through the sewage system and transportedto an oil separator then discharged in the pluvial andtechnological drainage system.

The soil can be affected by deposition ofparticulates and action of heavy metals resulting outof combustion of coal. The main waste materialsderived from the combustion of fuels solid (coal) atthe TPPs are the slag (15%) and the ash (85%) [5].

The slag-ash mixture, coming from electrofiltersand water is called hydro-mixture and it is dischargedinto specially designed storage (dump).

Slag-ash dumps cause pollution of theatmosphere and soil through slag-ash drifting. Soilmonitoring is performed periodically (usuallyannually).

2. Environmental risk assessment

2.1. Analysis of the impact on theenvironment

Water pollution [6], air pollution and disposal ofwastes have a significant impact on biotic factors.The dispersion in atmosphere of CO2, SO2, ofparticulates [7] and toxic VOCs and the dissolving inwater and passing in soil of pollutants is a permanentsource of risk to living organisms.

The particulate matter resulted from the coaldeposit and into processes or the dust shattered on theslag dump may reduce the intensity of the chlorophyllassimilation by reducing light radiation. Depositionsof suspensions on leaves is causing the stomatablockage affecting photosynthesis and plant regime ofgas exchange with effects such as: reducing the rateof development, lower production and decreasedquality of production. Dusts with content of heavymetals can indirectly affect plants growth bydepositing on soil which modifies the nutrientstransformation processes of the plants.

Sulfur oxides emitted to the atmosphere come incontact with rain water resulting in acid rain (dilutesolution of sulfuric acid and sulfur dioxide) that causeadverse effects [2;5] on the environment, such as:

- vegetation damage, especially of theconiferous forests, through direct destruction ofchlorophyll;

- acidification of soils and deficiencies in plantnutrition by dissolving the salts of calcium andmagnesium in the soil;

- dissolving of the waxy protective layer of theleaves, the plants becoming less resistant to pests;

- over-fertilizing the soil resulting in prematureaccelerated of plants growth;

- acidification of lakes and damage ichtyofauna.Depending of the degree of exposure, SO2 can

lead to physiological and biochemical effects such as:reducing photosynthesis, chlorophyll degradation,changes in the metabolism of proteins, lipids andenzyme balance activity. These effects translate intonecrosis, plant growth reduction, increasedsusceptibility to various pathogens and at the severeclimatic conditions.

Sulphur oxides have negative effects on humanhealth, causing irritation or respiratory problems. [8].

Polycyclic aromatic hydrocarbons (PAHs) arecarcinogenic at long exposure time even at very lowconcentrations. Short-term exposures to PAHs maycause skin irritation and upper respiratory tract,dizziness, nausea, headaches, weakness. Very highdoses can lead to respiratory collapse and liverdamage, damage of lungs, kidneys and blood system.Long-term exposure can also lead to cancer anddamage the liver, kidneys, lungs and blood and lymphsystems. The simultaneous presence of SO2exacerbates these effects.

Nitrogen oxides it forming during the fuelscombustion and in function of combustion conditionsNO or NO2 may result. NO quickly turns into NO2 inthe atmosphere, a gas with irritating smell and strongoxidant. NO2 is a precursor to ozone forming. Byreaction with the water in the atmosphere a portion ofthe NO2 is converted to nitric acid (HNO2 andHNO3). In urban areas these acids are combined withammonia to form ammonium nitrate (NH4NO3).Ammonium nitrate is found as aerosols contributedsignificantly to pollution of urban areas withparticulate matter (having dimensions of 2.5-10 μm).

Human health is affected directly by nitrogenoxides through exposure to NOx and indirectlythrough the formation of secondary pollutants such asozone and the atmospheric aerosols contributing tophotochemical mist and particulate matter [8; 9].Nitrogen oxides (NOx) have a beneficial effect on theplants up to a certain concentrations contributing toplants growth. Over toxic thresholds NOx has a clearphytotoxic action such as reducing photosynthesisand transpiration, chlorosis and necrosis. NOx andSO2 have a synergistic effect on the plants, only thesetwo pollutants or in combination with the ozone. Theeffects of acidic rainwater containing NOx and SO2may affected plants and ecosystems situated at a greatdistance from the emission source.

Ozone (O3) is formed in the atmosphere byphotochemical reaction of NOx and solar radiation,favored by a wide spectrum of volatile organiccompounds (VOCs) into the atmosphere Both

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pollutants, NOx and VOCs, are specific of combustionprocesses, so it is expected that ozone to be present inthe atmosphere in the vicinity and inside thermalpower plants. Ozone is a strong oxidant and thereforecan react with each class of biological substances.Long-term exposure leads to chronic diseases of theupper respiratory tract and ischemic heart disease[10]. Ozone affects crop plants and trees, especiallyspecies that have a long growth / development cycle,causing alterations visible as defoliation and foliagechanges. It can have effects both on plant species andon biodiversity of ecosystems natural.

Volatile organic compounds (VOC) arepollutants commonly found in any combustionprocess, as a result of incomplete combustion. Theeffects of these compounds on human health arerelated to their presence in the atmosphere in naturalstate or transformed. These are substances with hightoxicity and potential risk of cancer.

Dioxins and furans - PCDD / F are organiccompounds unintentionally produced in very lowconcentrations into emissions or in products of someprocesses. They have very high and variable toxicitywith a potential hazard to the environment andpeople. Main emission sources is the combustionprocesses. To evaluate the toxicity of these substancesEuropean reference standards recommended the toxicequivalent (TEQ) [11; 12]. This value is used toevaluate the health risk of those exposed to theseemissions. Numerous harmful effects of dioxins andfurans on human health have been demonstrated.These are characterized as destructive substances forthe endocrine system, causing fertility problems,pregnancy problems and even infertility.

Water pollutants (phenols, ammonia, heavymetals, petroleum products) can affect the life andactivity of aquatic ecosystems, having the effect of aquantitative reduction [13].

The radioactivity. The main source ofradioactivity is coal, which may contain: U-238, Th-232 and K-40 [6]. By burning of coals the naturalradioactive substances present in their compositionare concentrating in slag and ash, and radioactivityincreases. Even if the amount of radioactive elementsis large, considering that the distribution in the slagdump is homogeneous, the effect of irradiation "insitu" is not usually higher than the allowable limits.The radiological risk should not be ignored thecumulative effects can to be adverse on biotic factors.

The noise. In relation to the frequency, duration,moment of production of the different noises andpropagation conditions (wind direction) employeesand neighboring populations may be affected. Amongfrequent manifestations due to noise exposure,hearing fatigue, hearing loss and deafnessprofessional are included.

2.2. Analysis of environmental hazardsidentified

The flammable materials used or resulted fromprocesses, the toxic or corrosive materials, handled,used or generated in processes, diffuse emissions,action cumulative and synergistic of the pollutantsand the noise of installations and of the aggregates,can create problems for personnel safety andenvironment.

In a thermal power plant, places with highpollution potential (risk) are:

- the chemical treatment station;- the boilers-steam power station;- the solid fuel station.Principal risk factors are:- chemical risk factors (CO, CO2, SO2, VOC,

dioxins and furans);- physical risk factors: noise, microclimate,

radioactivity, electric and magnetic field;- physico-chemical pollutants: particulate

diverse (coal dust, slag, ash).The usage of fuels (coal, gas, fuel oil, diesel,

coal dust) has a high potential risk of fire andexplosion, and poisoning with CO.

Potential hazards for environmental factors are:P1 - the emission, transport and dispersion of

SO2 in the air over the accepted norms;P2 - the emergence of acid rain caused by SO2,

SO3 by reaction with rainwater;P3 - CO2 emissions with major influence on

climate change;P4 - NOx emissions over the accepted norms;P5 - formation, due to NO2, of the nitric acid

and the ammonium nitrate aerosols;P6 - formation of the ozone; having as precursor

of NO2;P7 - emissions diffuse / fugitive of CO;P8 - emissions diffuse / fugitive of dioxins and

furans;P9 - soil pollution in the slag dump;P10 - Soil pollution by coal dust in the storage

of raw materials;P11 - Soil pollution by oil products;P12 - pollution of groundwater;P13 - pollution by wastewater;P14 - fly ash;P15 - slag and ash particles shattered of the air

currents;P16 - radioactive slag and ash;P17 - transfer and dispersion of pollutants in

aquatic environments;P18 - noise pollution;P19 - production of the fires;P20 – production of the explosions.

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2.3. Risk AnalysisConsidering the high impact of the pollutants

analyzed on the environment was chosen for

environmental risk assessment on a matrix of the typeshown in Table 1.

Table 1. Risk Matrix

Likelihood Low impact Medium impact High impact

Not very likely (<10%) - - risk less(P17)

Less likely (<35%) - - risk medium(P7, P8, P12, P13, P20, P19)

Can or not can happen (35%-65%) - risk medium(P5, P6, P11)

risk high(P2)

Fairly likely (>65%) risk less(P4) - risk high

(P1, P14, P15)

Very likely (>90%) risk medium/ high(P3, P9, P10, P18)

risk high(P16)

As shown in the risk matrix there are a largenumber of hazards, with medium and high risk,requiring reduction measures. The low risks will bemonitored so that they remain in this class of risk.

2.4. Treatment and monitoringof the risks

In order to ensure adequate health and safetyconditions of work in the energy system and toimprove the environmental performance it isnecessary to take organizational and technologicalmeasures. Management measures will beimplemented for labor discipline and measures thatlead to exploitation of installations under appropriateconditions, especially the sealing of the equipmentspossible generating of the pollutants. Equallyimportant, will be taking some technical measures byintroducing facilities or equipment that lead toreducing emissions under a maximum admissible orthat would create the possibility of conductingactivities outside noxious environment.

To reduce the environmental impact ofidentified risks, many measures starting frommanagement ones to the technical and technologicalsolutions, such as:

•control of combustion processes that are themain generating sources of pollutants;

• improve ventilation in all indoor spaces;• modernization of the electro filters;• using of the desulphurization installations of

the latest generation;• burning fuel with low content of ash, sulfur

etc;• use of facilities for monitoring of gaseous

emissions;

• wetting the dry areas of the dumps.Monitoring emissions can be done through a

system of monitoring and measuring of the gaseouscomponents at the chimney exit to determine theconcentrations of SO2, NOx and dust. It is alsonecessary to measure the relevant process parametersof the fuel burning respectively: % O2, temperature,pressure, humidity and flue gas flow to the chimney.

3. Conclusions

Fossil fuel combustion in thermal powerplants, generates large amounts of CO2 and in varyingproportions SO2, SO3, NOx, heavy metals,halogenated compounds, dioxins and furans, slag andash, that have a significant impact on theenvironment.

Most of the identified dangers in the riskanalysis are included in medium and high risk classes.

The below have a an impact with high riskon the environment

- CO2 emissions with major influence onclimate change;

- the slag and ash particles shattered of the aircurrents from the dump and depositing them on soiland vegetation or inhaled their by humans andanimals;

- radioactive slag and ash;- formation of the nitric acid and the ammonium

nitrate aerosols due to NO2;- the emergence of acid rain caused by SO2, SO3

by reaction with rainwater;- formation of the ozone; having as precursor of

NO2; To reduce the environmental impact of the

identified risks, measures can be taken from

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managerial to technical measures and even closingthese plants through larger scale usage of renewableenergies.

References[1] Adrian Ioana Analiza impactului termocentralelor asupramediului inconjurator Revista Tehnica Instalatiilor ISSN 1582-6244 Targu Mures, ianuarie 2014.[2] Traian Vasiu, Victor Marian Bucaleţ, Aportul combustibililorsolizi utilizaţi, în termocentrala Mintia–Deva, la impactul asupramediului, Buletinul AGIR nr. 3/2006.[3] Alexander Leyzerovich, Turbine cu abur de mare putere,Editura AGIR, București 2003.[4] C. Moțoiu, Centrale termo și hidroelectrice, Editura Didacticăși Pedagogică, București, 1974[5] Victor Vaida, Calitatea cărbunelui, factor determinant laimpactul termocentralei Mintia asupra mediului înconjurător,Buletinul AGIR nr. 3/2006.[6] Balint Lucica., Minodora Rîpă, Petre Stelian Niţă, BalintSimion., Radu Tamara. Air quality monitoring in Galati. Casestudy, Analele Universităţii “ Dunărea de Jos “ din Galaţi,Fascicola IV, Frigotehnie motoare cu ardere internă cazane şi

turbine, 2005, p.299-305, ISSN 1221-4558.[7] Radu T., Ciocan A., Balint L., Distribution of accumulationparticles in the urban atmosphere, TEHNOMUS Journal, P -ISSN-1224-029X. E - ISSN-2247-6016, 2013 p.9.[8]*** Studiu de evaluare a riscului la ISPAT-SIDEX Galaţi,ICEM S.A. Bucureşti - Laborator Protecţia Mediului, 2006.[9] Radu T., Vlad M., Dragan V., Basliu V., Istrate G. G.,Occupational Risk Management in Industry, The Anals of“Dunărea de Jos” University of Galati, Fascicula IX ISSN 1453-083X, vol. 3, p.34-39, sept 2013.[10] Radu T., Ciocan A., Evaluation of the Occupational Riskassociated to Work Environment in Ferrous Metallurgy, The Analsof “Dunărea de Jos” University of Galati, Fascicula IX ISSN 1453-083X , vol. 4 , p.90-96, 2013.[11] Radu T., Ciocan A., Balint S.I., Balint L., Dioxins andfurans emissions in the primary steel sector, Proceedings of the13th International Multidisciplinary Scientific Geoconference,SGEM.2013, p. 609.[12] Ciocan Anişoara, Generarea si controlul poluantilorindustriali, Ed. GUP 2013, ISBN 978-606-8348-74-2.[13] Lucica Balint, Doru Matei, Simion Ioan Balint,Environmental Risk at Urban Wastewater treatment, The annals of“Dunarea de Jos” University of Galati, fascicle IX Metallurgy andMaterials Science, ISSN 1453 – 083X, p. 293.

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EMISSIONS OF HYDROCHLORIC ACID VAPORS GENERATEDBY PICKLING PROCESS FROM COLD ROLLING MILL

OF STEEL STRIPS

Anisoara CIOCAN“Dunărea de Jos” University of Galaţi, 111, Domnească Street, 800201, Galaţi, Romania


ABSTRACT

Most important pollutant emitted in the sector of pickling within a cold stripmill in an integrated steel mill are hydrochloric acid vapors. În this work arepresented the chemical reactions between hydrochloric acid and iron oxides layersformed on surface of the steel strip after the hot rolling process and analyzeddifferent areas of the pickling line as generators of acid vapors. Measurementvalues of hydrochloric acid vapors concentrations in the working atmosphere arecorrelated with operational regimes and with occupational exposure limit valuesaccording to national legislation. Finally are presented solutions that can beapplied to reduce emissions of hydrochloric acid vapor in the sector of analysis.

KEYWORDS: steel strip, cold rolling, pickling, hydrochloric acid, pollution

1. Introduction

Cold rolling mill within an integrated steel millis a complex technological lines which is specializedin manufacturing of low carbon steel bands or sheets.Cold-rolled sheet is hot-rolled sheet that has beenfurther processed through a pickle line, which is anacid bath that removes scaling from surface of steelstrips. Then it is successively passed through a rollingmill without reheating until the desired gauge, orthickness and other physical properties have beenachieved. Cold-rolling reduces gauge and hardens thesteel and, when further processed through anannealing furnace and a temper mill, improvesuniformity, ductility and formability [1, 2].

The main operations related to cold rolling ofsteel bands are: pre-treatment to surface preparation(pickling) for improved the quality of cold rolledbands; trimming and oiling; cold rolling for reductionin thickness of steel products; degreasing and heattreatment (annealing) to get particular metallic,chemical or mechanical performances, required bycustomers.

All of these sub-processes are sources ofpollutant emissions: hydrocarbons and decompositionproducts of lubricant oil; acid aerosols and fumes;nitrogen oxides and carbon monoxide, polycyclicaromatic hydrocarbons etc. [3, 4]. In this paper isanalysed the pickling process and acid vaporsemissions. The common pickling processes are

operated at temperatures that usually give rise to acidaerosols and fumes. Also Emissions of acid vaporsmay arise also from acid regeneration processes [5].

2. Generation of hydrochloric acid vaporsat pickling of the hot rolled steel strips

Emissions of hydrochloric acid vapors frompickling of the hot rolled steel strips of an integratedsteel mill come from multiple sources.

During the hot rolling of steel, oxygen from theatmosphere reacts with the iron in the surface of thesteel to form a iron oxides crust. There is a mixture ofiron oxides, practically disposed as three kinds ofscale which differ in the temporal and local evolution.The primary, secondary, and tertiary scale is formedon the steel band surface within the hot rollingprocess.

The share of three layers in the crust is differentfor different temperatures, oxidation times and steelcomposition (Figure 1).

The presence of oxides or scale on the surfaceof the steel is harmful when the hot rolled steel stripis subjected to cold rolling process. To remove ironoxides or scale from the surface of strip steel in orderto obtain a clean surface are required mechanicallyand chemically treatments. Firstly is applied the de-scaling of the hot strip material into scale breaker(placed downstream to pickling installation).

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Fig. 1. Cross section of the three-layer steel oxide scale formed during the hot rolling stage onsurface of the steel strip [6]

To increase the value of steel strip products it isessential to follow the second treatment. Thisinvolves the removing of oxides layers by the steelchemical pickling bath method (named pickling) [7,8]. The steel strip is dipped in a acid bath (H2SO4 orHCl solutions). Such this is pickled for the removal ofoxides and other residues from the surface. Todissolve iron oxides from the surface of a metalwithout any significant attack on the steel itself isused the HCl acid solution as pickle liquor.Hydrochloric acid pickling is widely used becausehas more advantages: high pickling efficiency; lesspickling time; lower investments required; lower riskof embrittlement (hydrogen diffusion in the material),the process taking place at low temperatures; loweracid consumption per tone of pickled strip. However,sulphuric acid has a low vapors pressure and thusrequire less intensive ventilation. This is reflected inthe cost-recycling regenerative technologies [1].

The HCl concentrations in a batch picklingprocess are 16.5 % for a fresh solution and 3.5 wt %before acid replenishment. The rate of picklingincreases with concentration of HCl and temperature.

The pickling line linked to tandem cold rollingmill is composed of several sections where take placespecific technological operations: pickling in acidtanks with different concentrations, rinsing and dryerof steel strip.

In the acid tanks the iron oxides and metalliciron react with hydrochloric acid and ferrous chloride,water, and hydrogen gas are formed according to thefollowing reactions [9]:

FeO(s) + 2HCl(aq) → FeCl2(aq)+ H2O(l)Fe3O4(s) + Fe(s) + 8HCl(aq) → 4FeCl2(aq)+ 4H2O(l)Fe2O3(s) + Fe(s) + 6HCl(aq) → 3FeCl2(aq)+ 3H2O(l)

Fe(s) + 2HCl(aq) → FeCl2(aq)+ H2(g)

Hydrochloric acid pickling is carried out inheated bath. Usually the range of temperaturerecommended is 65...85 0C. Depending on thetemperature of the pickling baths, the speed ofpassage of the strip through pickling baths is amaximum of 4 m/s. In these conditions HCl vaporsare produced and released into atmosphere during thepickling process (Figure 2).

Fig. 2. Pickling line and hot points for producing and releasing of HCl vapours emissions

The HCl volatilized, together with steam andhydrogen gas, is released as acid fumes. It is presentat the surface of the pickling tank and the pickled

material. From here it is transferred to the rinse tank.Also it is present in chemical area of pumps androutes of acid.

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In normal functioning and operation conditionsof facilities from pickling sector hydrochloric acidvapors (as venting or fugitive emissions) aregenerally collected and treated in the air pollutioncontrol system to remove HCl.

There are some situations when emissions frommany batch operations are uncontrolled released ashazardous air pollutant. Potential sources of HClvapors are the loading and unloading operations(planned for maintenance or accidental stops). In thiscase the emissions of hydrochloric acid vapors areproduced and released into atmosphere of theworking hall as acid fumes. The natural circulation ofair currents can get them up to tandem mill sector.

More emissions are released in the workingspace to the damaging of systems and equipmentsthat handled and transport acid (pipelines, storagetanks, acid pumps etc.). In this case emit acid fumeshall being moved by the natural circulation of aircurrents.

The United States Environmental ProtectionAgency (EPA) specifies that for each million tons ofsteel processed at continuous coil or pushpull coilmodel facilities, storage tank losses are estimated toamount to 0.39 tpy. For other types of picklingfacilities, storage tank losses are estimated to be about11.19 tpy of HCl per million tons of steel processed[10].

The recovery process of HCl from the wastepickling liquid in the acid regeneration process alsocan be a potential source of emitting significantamounts of hydrochloric acid vapors.

HCl emissions from processes of cleaning andacid regeneration depend on the pickling processused. A range of 1 – 145 mg/Nm³ maximum (up to 16g/t) were reported; with the range reported byindustry being 10 – < 30 mg/Nm³ (~ 0.26 g/t) [3].

3. Level of hydrochloric acid vapors inatmosphere of pickling sector

The concentration of hydrochloric acid vapors isperiodicaly controled in the hot points of pickling lineand in the area of tandem mill. Ministry of Health,Institute of Public Health and Medical SciencesAcademy Bucharest have specified procedures fordetermination of hydrogen chloride emissions fromstationary sources. A spectrophotometric method isused. Data collection frequency is once a quarter. Theconditions of data collection are: the pickling plant inoperation; the pickling plant in stationary regim; withpickling plant off (for maintenance works).

The average annual values of measuredconcentration for HCl vapors are given in Table 1.

Table 1. Average annual values of concentration of hydrochloric acid vapors for main sector of steelbands pickling lines and tandem mill, [ppm]

YearMeasuring point 2013 2014 2015Tandem mill: rolling stands 1…5 0.20 0.22 0.20

Pickling sector: at steel strip dipping in thepickling bath 0.21 0.23 0.20

Pickling sector: acid tanks; dryer 5.90 6.20 5.80Pickling sector: at steel strip extraction from

pickling bath 0.61 0.62 0.60

Occupational exposure limit values forhydrochloric acid vapours generated in areas of steel

pickling lines imposed by Annex 1 from HG1218/06.09.2006 are shown in Table 2 [11].

Table 2. Occupational exposure limit values for hydrochloric acid vapours generated by process steelpickling lines according to national legislation HG 1218/06.09.2006

Occupational exposure limit values8 hours short time duration (15 minutes)

HazardousAir

PollutantCAS EINECS

mg/m3 ppm mg/m3 ppmHCl 7647-01-0 231-595-7 8 5 15 10

The level of measured concentrations in someareas of pickling instalation presented in Table 1 arecompared with the occupational exposure limit values

prezented in Table 2. The results are given in Figure3.

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Fig. 3. Comparison between measured values and limits allowed by legislation for hydrochloric acidvapors in the working atmosphere

It is observed that the higher values of HClvapors concentration have been observed at picklingtanks area. Also these are present in the area of rinsetanks where are generated by the surface of pickledsteel band. Lower values were found at dipping and attake out of steel strip. All measured values werebelow the limits stipulated by legislation for

hazardous pollutants. This demonstrates that theconditions of safety are respected.

The emissions from pickling line are collectedand efficient treated. The cleaning of exhaust gas andthe ensuring of hydrochloric acid recuperation areimperatively used. The scrubber system to remove thehydrochloric acid vapors is shown in Figure 4.

Fig. 4. Treatment facility for HCl vapors emissions

5. Conclusions

The acid emissions to air from cold rolling mayarise from pickling and acid regeneration processes.With open pre-treatment systems, it is inevitable toeliminate the content of HCl vapors emissions in the

air around the pickling facilities, especially when thematerial is taken out of the bath.

Generally, for all types of pickling sectors theemission control measures can be taken. The bestsolution for minimization of air emissions are:optimization of temperature, composition of pickle

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solution; covering of tanks; enclose pickling bathoperations or install hoods and extraction systems;reduction of pickling emissions with gas scrubbing;pickling tank fume control [5].

To optimize operation of regeneration plant andthe pickling section is necessary to minimize the acidlosses as vapors. The measures to prevent emissionsinclude a reduction of the waste gas volume and thecontaminant load of the waste gas, which is exhaustedfrom the pickling tanks.

Acknowledgements

The author wishes to thank of the studentMonica Basoc, who has contributed to make thisstudy.

References

[1] R. Saban, C. Dumitrescu s.a., Tratat de stiinta si ingineriamaterialelor metalice. Vol.5. Tehnologii de procesare finala amaterialelor metalice., Ed.AGIR, 2012[2] *** arcelormittal - 20-f - 20080319 - company_information,http://google.brand.edgar-online.com/[3] *** Integrated Pollution Prevention and Control (IPPC)Reference Document on Best Available Techniques in the FerrousMetals Processing Industry, December 2001,http://www.anpm.ro/anpm_resources/migrated_content/files2/bref/BREF/ES_Ferrous_Metals_Processing_Industry_EN.pdf.

[4]*** Iron and steel production, EMEP/EEA emission inventoryguidebook 2013,file:///C:/Users/aciocan/Downloads/2.C.1%20Iron%20and%20steel%20production%20GB2013.pdf[5] *** EPA, Final Draft BAT Guidance Note on Best AvailableTechniques for Ferrous Metal Processing and the Pressing,Drawing and Stamping of Large Castings where the ProductionArea exceeds 500 Square Metres, September 2012,https://www.epa.ie/pubs/.[6] M. Graf, R. Kawalla, Scrap development on steel hot striprolling, La Metallurgia Italiana, No. 2/2014, pp.43-49.,http://www.aimnet.it/allpdf/pdf_pubbli/feb14/Graf.pdf.[7] R. M. Hudson, Pickling of hot rolled strip: an overview, Ironand Steelmaker (USA), 1991, 18(9), pp. 31-39.[8] D. Wolfgang and F. Kladnig, A review of steel pickling andacid regeneration: an environmental contribution, InternationalJournal of Materials and Product Technology, 2003, 19(6), 550-561.[9] Y. Jatuphaksamphan, N. Phinichka, K. Prapakorn and M.Supradist, Pickling Kinetics of Tertiary Oxide Scale Formed onHot-Rolled Steel Strip, Journal of Metals, Materials and Minerals,Vol.20 No.1 pp.33-39, 2010., http://www.material.chula.ac.th/Journal/v20-1/33-39%20JATUPHAKSAMPHAN.pdf.[10] *** EPA, EMERGENCY PLANNING AND COMMUNITYRIGHT-TO-KNOW ACT - SECTION 313 Guidance for ReportingHydrochloric Acid (acid aerosols including mists, vapors, gas, fog,and other airborne forms of any particle size),http://www2.epa.gov/sites/production/files/documents/1999hclguidance.pdf.[11] *** HG 1218/06.09.2006, Hotararea de Guvern nr. 1218 din6 septembrie 2006 privind stabilirea cerintelor minime desecuritate si sanatate in munca pentru asigurarea protectieilucratorilor impotriva riscurilor legate de prezenta agentilorchimici, http://www.iprotectiamuncii.ro/legi/hg-1218-2006.pdf.

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Chemical and Metallurgical Analysis of Cooper Based ShapeMemory Alloys

Dragoş Cristian ACHIŢEI1,2, Mirabela Georgiana MINCIUNĂ1,2,Petrică VIZUREANU1,2

1Gheorghe Asachi Technical University of Iasi, Faculty of Materials Science and Engineering,Blvd. D. Mangeron 41, 700050, Iasi, Romania

2Center of Excellence Geopolymer & Green Technology (CEGeoGTech), School of Materials Engineering,Universiti Malaysia Perlis, 01000 Kangar, Perlis, Malaysia

e-mails: [email protected], [email protected], [email protected]

ABSTRACT

The paper presents some aspects on the thermo-mechanical fatigue of shapememory alloy, a documentary synthesis of their industrial applications andchemical aspects concerning the use of these alloys on biomedical applications.

KEYWORDS: shape memory alloys; biomaterials; thermal fatigue; corrosion

1. Introduction

The fatigue of metals is the phenomenon whichprovides the cracks in different applications, in theconditions of temperature and work parametersvariations. The thermal tensions are induced when thedimensions vary for a part due to the temperaturechange [1, 2].

In the case of equipments which work at hightemperatures, the conditions to appear the cracks dueto thermal fatigue are created. The behavior ofmaterials at thermal fatigue is influenced by thestructural transformation effects and the mechanicalproperties.

The mechanism of defects accumulation due tothermal fatigue, in the crystalline network and insidethe grain lead to create the tension local zone, where acrack may appear. The cracks due to thermal cycles issometimes associated to network tension by blockingthe dislocation, which are moving inside the grainmatrix, specially, due to mechanical or thermo-mechanical tensions which appear. The cracks bythermal fatigue are initiated along the surface.Because, the cracks are initiated from exterior, thecorrosion process and oxidation along the surface ofthermal fatigue cracks, it is inversely proportionalwith the crack depth [3, 4].

For producing a crack by fatigue are necessarythree base factors:

- A maximum normal tension with a high value;- A large enough variation of applied tensions;- A large number of cycles for applied tension.

The cracking process develops slowly; thecracks propagation speed is progressively increased,reached that in moment of crack. The process takesplace so fast, like in the case of static cracks forfragile materials, without producing a visible plasticdeformation.

The cracked surface present two zones: oldcrack and new crack. The old crack have a smoothaspect and sometime shiny. The new crack ischaracterized by irregular aspects, with highgranulation, that proves a breakable character ofcracks.

2. ResultsThermo-mechanical fatigue of shape

memory alloys

In the case of metallic parts made of shapememory alloys, the possibility to appear the thermalfatigue or thermo-mechanical fatigue exist.

The mechanical fatigue involves the crackproduction in four stages: the accumulation ofdefects, the crack formation, crack propagation instationary and un-stationary regime and respectivelyfinal break.

The main method to increase the resistance ofmechanical fatigue for shape memory alloys is thegranulation finishing, which may be realized byalloying, energy quenching and powder metallurgy.

The thermal fatigue is related to the irreversibleformation of defects, which lead to a considerable

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hardening, in the case of binary brasses, bi-phase, like(Cu-40%Zn).

In the case of shape memory alloys, Cu-Zn-Altype, should be noted that the mechanical cycling

affect the critical temperatures of transformation, butmuch more reduced than thermal cycling.

In figure 1 it is present the surface of Cu-Zn-Alalloys, with fatigue cracks.

Fig.1. The aspects of cracks for a shape memory alloy, Cu-Zn-Al type, by thermo – mechanicalfatigue on different magnifications 1000X, 500X and 100X

The cracking by fatigue is the phenomenonwhich leads to break under repetitive tension orfluctuating, which are lower than elastic tensionof material.

The cracks at fatigue are progressive, withlittle cracks at beginning, which increase underthe action of fluctuating tension. The shapememory alloys are sensitive at fatigue.

Much more that the phenomenon for theclassic crystalline materials, the shape memoryalloys have some additional mechanism of linkat the change of phase which characterized them.

It is found that the type of crack observeddepend by the applying mode for mechanicalfatigue.

The improving of life duration for thesematerials imposed the decrease of level forinternal tension at grains limits and the increaseof cracking resistance.

For obtaining these results, we can realize:

- the increase of grains measurements,decrease the measurements for martensite plates;

- generation of laminated texture, whichcan reduce the differences of orientation betweenthe grains, for reduction of the incompatibilityfor deformation;

- the possibility to obtain the plasticdeformation at the level of grains limitsappropriate also by the deformation efficiency.

Medical applications for shape memoryalloys

Are known many types of shape memoryalloys, but most are expansive due to the nobleand rare metals use, also due to the complexobtaining technologies. The most interest isrepresent by the alloys like: Ni-Ti, Cu-Zn-Al andCu-Al-Ni, which may be used in medicalpractice applications [4-9].

Fig. 2. Optical microstructures for Cu-Zn-Al shape memory alloy; martensite structure (200X).

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The study of shape memory alloys hasdetermined a development of the research indifferent activity domains, in the order to findthe corresponding applications. At present, thesealloys are used in industry of aeronautics,aerospace, mechanical, electronic and medicaltechnique. These materials are obtained inlaboratory conditions, in order to certify thecharacteristics necessary in exploitation. In eachof these cases, the parts made of shape memory

alloys should be thermally treated (heating andcooling), to realize the proposed objective.Between the heat shape and cold shape anenergy difference exist. The reversibility of thechanges for the two shapes it is the base formultiple applications. In this case, a greatimportance it is the exact reproductivity of thetwo shapes. After some cycles of function, this isaffected and so are affected the properties ofshape memory.

Fig. 3. The medical applications for the shape memory alloys [14]

Porous materials made from shape memoryalloys, are also important, used in variousmedical fields to replace some bone parts.

In time, these parts will be embedded bythe human body, by the development inside thepores of organic cells characteristics to bonesystem. In this way the micro-prostheses make

common body with the body cells and it isintegrates in bone system, where adversereactions should be limited.

The porous materials used in medical fieldfor prostheses present a good biocompatibilityand elasticity, imitating the behavior of bone partwhich is substituted.

Fig. 4. Optical micrographs on porosity of materials: a and b - large pores: porosity 42% (250X);c and d - big pores: porosity 50% (100X, 500X) [15]

For the dental materials used to fabricatethe prosthetics devices, is distinguished a highdiversity of metallic alloys. The diversity wasmade in the direction to develop new materialswith superior properties, but with lower costs ofobtaining. The cooper based alloys, erepromoted like dental materials, for economicreasons, due to the increase of noble metalscosts. In some countries of Europe, the alloysbased on cooper are consider incompatible withthe qualities of biomaterials used in prosthetics

and are present like materials with allergic risksand low resistance at corrosion [10-11].

Cooper and its alloys are recognized likematerials with a good corrosion resistance andare used in many activity domains.

Their good resistance for these materials isrelated to the formation of a uniform andadherent film on surface, which protect thesubstrate to the environment.

The appearance of corrosion phenomenon itis related to the formation and stability of this

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film; if the film is not formed or it is destroyed,the metal is corroded, either the entire surface,either located.

The copper is an essentially metal for livingorganisms, but too much cooper may be harmful.From this reason, the toxic effects of cooperalloys may be confirmed when these alloys wereimplanted subcutaneously or intramuscularly.

The date’s analysis show clearly that thesematerials lead to modifications of tissues, likenecrosis and inflammation. The cooper mayhave a chemically modifying role, inducing thecarcinogen activity much more than nickel.

Chronic poisoning with cooper is acontroversial problem and frequently is relatedwith muscle pain, hypertension, various neuro-psychological phenomena or hair loss. However,World Health Organization considers the cooperlike a non-toxic metal.

3. Conclusions

The researches present the correlationbetween the technological parameters whichinfluenced the appearance of thermal fatiguephenomenon and the properties specific tometallic material with shape memory.

The shape memory alloys, copper based,may be use like biocompatible materials forhuman body, just after the corrosion tests indifferent mediums which simulated the liquidsfrom human body.

Also the manufacturing of parts from shapememory alloys must take into account that thefatigue phenomenon may appear in the

exploitation time, concretized by the degradationof shape memory effect.

These characteristics for shape memoryalloys permit their use in smart structures, micro-actuators, some advanced composites, medicalcomponents and dental implants.

References

[1]. D.C. Achiţei, M.M. Al Bakri Abdullah, A.V. Sandu, P.Vizureanu, A. Abdullah, On the Fatigue of Shape Memory Alloys,Key Engineering Materials, 594 – 595, (2014), 133-139.[2]. D.C. Achiţei, A. V. Sandu, M. M. Al Bakri Abdullah, P.Vizureanu, A.Abdullah, On the Structure of Shape MemoryAlloys, Key Engineering Materials, 594 – 595, (2014), 140-145.[3]. N. Cimpoeşu, A.D. Ursanu, S. Stanciu, R. Cimpoeşu, B.Constantin, C. Paraschiv, S.O. Gurlui, Preliminary Results ofCopper Based Shape Memory Alloys Analyze Used for MEMSApplications, Applied Mechanics and Materials, 371 (2013) 368-372.[4]. M.G. Minciuna, P. Vizureanu, D.C. Achitei, N. Ghiban,A.V. Sandu, N.C. Forna, Structural Characterization of SomeCoCrMo Alloys with Medical Application, Revista de Chimie(Bucharest), 65 (2014) 335-338.[5]. G.Ungureanu, D.Mareci, D.Aelenei, G.Nemtoi, J.MirzaRosca, The Gaudent – a biocompatible material?, Al V-leaSimpozion Naţional de Biomateriale – Biomateriale şi AplicaţiiMedico - Chirurgicale, Iaşi, (2005).[6.] Y.Setiyorini, S.Pintowantoro, Biocompatibility Improvementof NiTi Orthodontic Wire from Various Coatings, AdvancedMaterials Research, 789 (2013) 225-231, (2013).[7]. M.G. Minciună, P. Vizureanu, Cobalt alloys research used inmedical applications, Metalurgia International, Special Issue 6,pages 123-126, (2013).[8]. A.V. Traleski, S. Vurobi, O.M. Cintho, Processing of Cu-Al-Ni and Cu-Zn-Al alloys by mechanical alloying, Materials ScienceForum, 727-728, (2012), 200-205.[9]. V.Agafonov, B.Legendre, A.Kahn, G.Guénin, B.Dubois,Study of Strain-Induced Martensites Obtained in the β-Cu-Zn-AlSystem, Materials Science Forum, 56-58 (1990) 447-449.[10]. A.V. Sandu, C. Bejinariu, G. Nemtoi, I.G. Sandu, P.Vizureanu, I. Ionita, C. Baciu, New anticorrosion layers obtainedby chemical phosphatation, Revista de Chimie (Bucharest) 64, 8,(2013) 825-827.

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RESEARCH ON CHEMICAL DEPOSITION OF SILVER WITHANTIBACTERIAL ROLE IN IMPLANTOLOGY

Elisabeta VASILESCU1, Vlad Gabriel VASILESCU2,Dumitru DIMA1

1Dunărea de Jos University of Galați2Carol Davila UMF București


ABSTRACT

The paper presents a synthesis of the laboratory research on the conditions ofachieving chemical deposition of silver on oral implants made ofTi base alloy(bioalloy Ti10Zr). There were used several chemical deposition regimes in whichwere modified deposition parameters (temperature, stirring time) for two types ofimplants (different screwthread geometry). Study of the influence of depositionconditions was performed through analysis at scanning electron microscope (SEM)with EDX analyzer. The results revealed the presence of silver,microdispersedparticles with morphologies and degrees of dispersion dependent on the factors andtechnological conditions of obtaining the chemical deposition.

KEYWORDS: silver, Ti10Zr bioalloy, implant, chemical deposition, electronmicroscope SEM

1. Introduction

Properties and role of antibiotic, antioxidant anddisinfectant of silver are known in the world for manycenturies. Laboratory tests confirm todayconclusively that silver ions have a bactericidal effectand constitute an effective disinfectant by destroyingmore than 600 viruses and harmful germs [1,2].Antibacterial efficacy of different metals has beenestablished since 1893 and this property has beencalled oligodynamic effect, but later it was found thatof all metals with antimicrobial properties, silver hasthe most effective antibacterial action and is less toxicto animal cells (Guggenbichler et. al, 1999).

Although known for centuries, only recentlyhave been understood mechanisms through whichsilver antimicrobial properties inhibits bacterialgrowth.

The evolution of modern ways of investigationand analysis, such as radioactive isotopes andelectron microscopy has allowed explaining theantibacterial mechanism of silver (Modak and Fox,1974; Feng et al, 2000). One of these is based on theconsideration that silver atoms bind to thiol groups (-SH) of enzymes and subsequently determine theirinactivation. Forms of silver with S-Ag stable

compounds contain thiol in the cell membrane that isinvolved in trans membrane energy production andtransport of ions (Klueh et al., 2000).

It is also believed that silver ions can take partin catalytic oxidation reactions which have as resultthe formation of disulfide bonds (RSSR). Silver doesthis by catalysing the reaction between oxygenmolecules from the cells and the hydrogen atoms ofthe thiol groups: water is released as a product andtwo thiol groups become covalently linked togetherby a disulfide bond (Davies and Etris, 1997).

Disulfide bond formation catalyzed by silverchanges cellular enzyme form and subsequently affecttheir function. Disulfide bond formation catalyzed bysilver can lead to changes in protein structure andinactivation of key enzymes such as those requiredfor the "breath" of the cell (Daviesand Etris, 1997), ormay even lead to the death of cells (Yamanaka et al.,2005).

Another mechanism which explains theantimicrobial activity of the silver has been proposedby Klueh et al. (2000), which shows that the Ag +enters the cell and cause its disruption.

It has been demonstrated that silver ionsassociates with the DNA once they enter the cell(Foxand Modak, 1974).

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Fig.1. Treatment of cells with Ag+results in DNA condensation, cell wall damage, and silver granuleformation. (A)E. coli and (B)S. aureuscells with and without Ag+treatment were observed with

transmission electron microscopy (Fenget al., 2000).

In order to have anti-microbial properties, silverhas to be in its ionized shape (Lok et al, 2007; Rai etal., 2009).Silver in its non-ionised form is inert(Guggenbichler et al., 1999), but in contact with amoist environment leads to the release of silver ions(Radheshkumar and Munstedt, 2005).Therefore, allforms of silver or silver as compounds with anti-microbial properties are in one way or another sourceof silver ions (Ag +); these silver ions can beincorporated and released slowly. Feng et al. (2000)conducted a study to see the effects of ions of silverper gram-positive and gram-negative bacteria, such asStaphylococcus aureus and Escherichia coli.Theytreated cells with AgNO3 which is a source of Ag + inaqueous medium, and they observed structural andmorphological effects of these ions of silver on cells.Cells were exposed to AgNO3 for 4-12 hours beforebeing prepared for microscopy (TEM).There wassome deterioration of the cell wall and outer denseparticles, and in some cases within the cell (Figure3).Dense particles which have been formed inside andoutside the cell were extracted and subjected to X-raymicroanalysis for the determination of theircomposition. It was found that the particles weremade of silver and sulfur. This finding supports theidea that silver inactivate binding proteins tocompounds that contain sulfur (Klueh et al., 2000).Itwas also observed that when treated with Ag +, E.coli, a gram-negative bacterium causes moresustained structural damage than gram-positive S.aureus (Feng et al., 2000).It was also shown thattreating cells with silver leads to dehydration andcontraction of the cell (Guggenbichler et al, 1999).TEM images from Feng at. al. (2000) show that cellswhich suffered extensive damage, finally will endwith the deterioration of the cell membrane. Cells

membrane damage leads to the elimination of thecytoplasm, such as dehydrated and wrinkled cells areshown in the SEM images from Guggenbichler et al.(1999).Silver can be managed in different ways. Thevarious effective forms of silver that contribute to thethe inhibition of microbial are silver salts. One ofthese is silver nitrate (AgNO3) and is effectivebecause it can provide a large amount of silver ions atonce. It turned out that prolonged antimicrobialactivity of silver is best achieved through thecontinuous release of moderate amounts of silverions. In addition the size and shape of thenanoparticles plays also an important role in theantibacterial activity (Pal et al., 2007). Smallernanoparticles require less time for penetrating throughthe cell membrane and cell wall in relation to largernanoparticles that have a higher surface-volume ratio(Martinez-Castanon et al., 2008).This means that permassunit, smaller nanoparticles provide more silveratoms in contact with the solution than do largenanoparticles, meaning there are more silver atomsable to take part in the processes of cell destruction.Regarding the form of nanoparticles with role in theantibacterial activity, Pal et al. (2007) hadexperienced three types of silver nanoparticles(spherical in the form of rods and triangular tested onE. coli.).It was found that the order in which theantibacterial effect manifested was the triangularshape, spherical, rod-shaped. This order ofantibacterial activity is explained by the differenttypes of veneers on nanoparticles.Triangularnanoparticles have more active facets(electronsdense facets) than spherical nanoparticles.Spherical nanoparticles, which were not perfectlyspherical, have more active facets than thenanoparticles in the form of rods (Pal et al., 2007).

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2. Experimental conditions

For chemical coating with metallic silver therewere used solutions prepared with pure chemicalreagents, double distilled water and two types ofdental implants made from Ti10Zr alloy (developedat SC TEHNOMED Bucharest). The research wasconducted in the Laboratory of Chemistry of theFaculty of Science and Environment of DanubeUniversity of Galati.

Chemical staining was performed as follows:100ml of a 2% AgNO3 was treated with 50 ml of 5%NaOH, and then the resulting precipitate wasdissolved by adding 50 ml 2% NH3 solution. Theimplants (pins) were inserted in a 250 mL container

in Tollens reagent obtained according to the recipeabove. Alsoa magnetic stirrer was inserted to achievethe homogenization of the system. Under stirring at500rpm,2 ml of formaldehyde 30% were added.

The first pivot was extracted from the solutionwith tweezers after 5 minutes and the second pivotafter 10 minutes. The two pins were rinsed in doubledistilled water and placed for drying in an oven at1050C for 4 hours.

2.1.Method PrincipleChemical reactions in metallic Ag

deposition:

(Ag+ + NO3- ) + (Na+ + HO- ) = Ag (OH) (white pp.) + (Na+ + NO3-) (1)2 AgOH Ag2O (black pp.) + H2O (2)Ag2O + NH3 + H2O→ ( [ Ag (NH3)2] + HO-) (complexcolorless combination) (3)H – C= O – H + 2 ( [ Ag (NH3)2] + HO-) → 2 Ag + H- (4)

The second regime of chemical deposition usingthe same pivots, however, the solution heated at atemperature of 500C with hold for 5 min and drippingformaldehyde from 30 to 30 seconds. The regime wasrepeated in the same conditions for the temperature of700C. Experimental samples were analyzed byelectron scanning electronic microscopy (SEM) withEDX analyzer. In the next paragraphs the resultsobtained are presented, which revealed the presenceof silver, microdispersed particles having

morphologies and degrees of dispersion according tothe factors and technological conditions of obtainingthe chemical deposition.

3. Experimental results

SEM microstructural aspects and EDX analysisof pivots (dental implants made at SC TehnomedBucuresti SA from Ti10Zrbioalloy).

- Regime1 (5min maintainingin solution with stirring, without heating)

Weight % C-K O-K Al-K Si-K P-K Ti-K Ag-L

1ag(1)_pt1 2.78 26.15 8.68 0.16 2.34 59.47 0.42

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Image Name: 1ag(2)

Accelerating Voltage: 20.0 kV

Magnification: 1128

O-K Al-K P-K Ti-K Fe-K Ag-L

1ag(2)_pt1 5.52 1.60 0.89 91.19 0.81

1ag(2)_pt2 9.13 1.46 0.55 88.10 0.76

1ag(2)_pt3 11.90 3.53 1.26 82.35 0.45 0.51

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- Regime 2 (10 min maintaining in solution with stirring and heating at 500C)

Magnification:489

O-K Na-K Mg-K Al-K Si-K P-K Ti-K Fe-K Ag-L2ag(1)_pt1 0.49 99.512ag(1)_pt2 40.40 0.04 0.11 10.19 0.23 1.66 46.77 0.28 0.33

4. Conclusions

Experimental results on chemical deposition ofmetallic silver on the implant built form Ti10Zralloyconfirm the presence of particles both in regimes ofdeposition without heating but also in those whichwere made by heating the solution at500Crespectively 700C and added formaldehyde drop

by drop. It was noted however that at shortermaintenance periods (5 minutes) silver particles havesmall dimensions and a low degree of dispersion.Also heating the solution at 700C does not changesize, shape or degree of dispersion of metallic silverparticles deposited at 500C solution temperature.Electronic microscopy analysis with electronscanning(SEM) and energy dispersive spectroscopic analysis(EDX) revealed the presence of silver particles

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microdispersed having morphologies and degrees ofdispersion dependent on the technology of obtainingthe chemical deposition and enables formulating aconclusion regarding the optimum regime. Particleswith a high compactness and dispersion degree areobtained by heating the solution at temperatures ofabout 500C, maintaining about 10 minutes withshaking and additions of formaldehyde drop by drop.

References

[1]. Wikipedia: Silver[2]. http://www.ziare.com/articole/proprietati+antibacteriene+argint[3]. Feng, Q.L., Wu, J., Chen, G.Q., Cui, F.Z., Kim, T.N., Kim,J.O. "A mechanistic study of the antibacterial effect of silver ionson Escherichia coli and Staphylococcusaureus."Journal of

Biomedical Materials Research Part A. 2000. Volume 52, issue 4.p. 662-668.[4]. Kawahara, K., Tsuruda, K., Morishita, M., Uchida, M."Antibacterial effect of silver-zeolite on oral bacteria underanaerobic conditions." Dental Materials. 2000. Volume 16, issue 6.p. 452-455.[5]. Martinez-Castanon, G.A., Nino-Martinez, N., Martines-Gutierrez, F., Martinez-Mendoza, J.R., Ruiz, F. "Synthesis andantibacterial activity of silver nanoparticles with different sizes."Synthesis and antibacterial activity of silver nanoparticles withdifferent sizes. 2008. Volume 10, No. 8. p. 1343-1348.[6]. Pal, S., Tak, Y.K., Song, J.M. "Does the AntibacterialActivity of Silver Nanoparticles Depend on the Shape of theNanoparticle? A Study of the Gram-NegativeBacterium Escherichia coli." Applied and EnvironmentalMicrobiology. 2007. Volume 73, No. 6. p. 1712-1720.[7]. "The antibacterial effects of silver and its compounds." SaltLake Metals, November 2008.http://www.saltlakemetals.com/Silver_Antibacterial.htm.

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NOISE LEVELS IN WORKPLACES OF COLDROLLING MILL PLANT

Beatrice TUDOR, Anisoara CIOCAN“Dunărea de Jos” University of Galaţi, 111, Domnească Street, 800201, Galaţi, Romania


ABSTRACT

Excessive noise exposure is one of numerous physical hazards present in steelindustry. Considerable noise develops the steel strips rolling process. In this studyare presented and discussed the noise levels at different working areas of a coldrolling mill plant. The average of annual values of noise levels is given. The annualoverall values of equivalent sound levels have been calculated. These are discussedin relation with noise exposure level normalized to a normal 8hr working dayallowed by standard. The results revealed that workers at numerous roll millingplat areas are exposed to noise levels higher than 87 dB(A) 8- hour standard. As aresult at the end of the paper are proposed some specific measures to diminishnoise levels.

KEYWORDS: steel strips, cold rolling mill, working areas, occupationalnoise

1. Introduction

A typical major source of noise in the steelindustry is hot or cold rolling processes. The sub-processes related to cold rolling mill within anintegrated steel mill includes the surface preparation(pickling), trimming and oiling, cold rolling,degreasing and heating processes (annealing) [1, 2].Many of these processes are noisy and may causedisturbance to the workplaces. Consequently, thenoise is a typical environmental issue for rolling millplant and requires continuous monitoring [3].

For this reason noise pollution for workers fromsteel industry is great concern in world. The industrialnoise from steel rolling mills induces to workersdeafness and hearing impairments [4, 5]. TheEuropean Union has established a common policyaimed at controlling the risks due to the exposure ofworkers to noise. EU has introduced specificlegislation that provides the measures to minimizeand even reduce it (Directive 2002/49/EC of theEuropean Parliament and of the Council of 25 June2002 relating to the assessment and management ofenvironmental noise with successive amendments andcorrections that have been incorporated into theoriginal text, http://eur-lex.europa.eu/). Romaniannational transposition is achieved through theadoption of various legislative acts.

The limits of exposure time for continuousnoise for occupational health issues are related byInternational Standards. The terms used forOccupational Exposure Levels in the European Unionare following: daily personal noise exposure of aworker - dEPL , (noise exposure level normalized toa normal 8hr working day); weekly average of thedaily values wEPL , . If hearing damage isproportional to the acoustic energy received by theear, then an exposure to a particular noise level forone hour will result in the same damage as anexposure for two hours to a noise level which is 3 dBlower than the original level. This is referred to the 3dB(A) trading rule and is generally accepted in manyparts of the world. However, 4 dB(A) and 5 dB(A)rules exist in the USA and the purpose of this sectionis to discuss the relative merits of the various tradingrules in current use [6].

Several European countries followed limitsadopted by the ISO standard. These are known as ″the3 dB(A) rule″ [7]. USA respect the levels imposed byOccupational Safety and Health Administration –OSHA, so-called ″the 5 dB(A) rule″ [8, 9]. The OHSNoise Regulations set exposure levels commonlyreferred to as 85 dB(A)Leq for an averaged over aneight hour period and a maximum or peak noise levelof 140 dB(C) [7, 10].

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In addition to the European nations, most othernations around the world have adopted the 3-dBAER. Table 2 shows the PEL and ER used by various

nations, along with the date of their standards orregulations when available.

Table 1. Permissible exposure limits (PEL) and exchange rates used by various nations [11]Nation, date PEL (8-hour-

average) dBAExchange rate

dBALevel dBAengineering

controls

Level dBA audiotests, and otherHC practices

Argentina, 2003 85 3 85 85Australia, 2000 85 3 85 85

Brasil, 1992 85 5 85Canada, 1991 87 3 87 84Chile, 2000 85 3China, 1985 85 3 85

Colombia, 1990 85 5EU, 2003 87 3 85 85

Finland, 1982 85 3 85France, 1990 85 3 85

Germany, 1990 85 3 90 85Hungary 85 3 90

India, 1989 90Israel, 1984 85 5Italy, 1990 85 3 90 85

Mexico, 2001 85 3 90 80Netherlands, 1987 80 3 85 85

New Zealand, 1995 85 3 80Norway, 1982 85 3 80Spain, 1989 85 3 90 80

Sweden, 1992 85 3 85 85United Kingdom, 1989 85 3 90 85

United States, 1983 90 5 90 85Uruguay, 1988 85 3 85 85

Venezuela 85 3

Typical noise levels associated with individualprocess at steel plants range between 59 and 84 dBA,while the combined noise levels for entire steelcomplexes range between 90 and 92 dBA [12]. Theeffective noise level generated by hot and cold rollingmill is 95-110 dB(A) [13].

Other studies give the general level of operatingnoises around 84-90dBA and peaks to 115 dBA [14].

In this study are presented and discussed thenoise levels at different working areas of a coldrolling mill plant. The average of annual values ofnoise levels is given. These are discussed in relationwith noise exposure level normalized to a normal 8hrworking day allowed by standard.

2. Experimental method

The noise levels in workplaces of cold rollingplant were measured with the noise dosimeter withmeasuring range of 20-140 dB (Cirrus Research plc).

The annual overall values of equivalent sound levelshave been calculated and compared with theregulatory limit from Romanian Noise Regulations(HG 493/12.04.2006 about occupational safety andhealth regarding the exposure of workers to the risksarising from noise). This regulation establishes theexposure limit values and exposure values whichtrigger the action of employer on safety and healthprotection in relation to daily noise exposure levelsand peak sound pressure. These values are following:

- Noise exposure limit level: L(EX, 8hr) =87dB(A) and respectively sound pressure p(peak) =200 Pa (140 dB(C) at reference sound pressure in air20 µPa);

- Maximum exposure level which triggers theaction: L(EX, 8hr) = 85 dB(A) and respectively soundpressure p(peak) = 140 Pa (137 dB(C) at referencesound pressure in air 20 µPa);

- Minimum exposure level which triggers theaction: L(EX, 8hr) = 80 dB(A) and respectively sound

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pressure p(peak) = 140 Pa (135 dB(C) at referencesound pressure in air 20 µPa).

3. Results and Discussion

In the entire rolling zone are develop noise. Theprincipal sources of noise are the gearbox of the rollsand straightening machines, the pressure waterpumps, the shears and saws, the throwing finished

products into a pit and the stopping movements of thematerial with metal plates [14].

In respect to these aspects the levels of noisefrom different working areas are presented. This iscompared with the daily permissible exposure limit -L(EX, 8hr) considered for working spaces of rollmilling plant (87dB). In addition are presented thevalues from other sectors of the cold rolling millplant. The average of annual values of noise levels forpickling sector are given in Table 2 and Figure 1.

Table 2. Annual overall values of equivalent sound level inside pickling sector

NAEC dB(A)Source of noise2013 2014 2015

areas of pickling tanks and drying tank 84.2 85 83.7Pickling linearea of steel band output 91.5 92.1 91.8

83.70

85.0084.20

91.8092.1091.50

87

78

80

82

84

86

88

90

92

94

2013 2014 2015

Noi

se le

vel,[

dB]

Noise of areas of pickling tanks and drying tankNoise of area of steel band outputDaily permissible exposure limit - L (EX, 8hr)

Fig. 1. Overall values of equivalent sound level for surface preparation sector from cold rolling mill plant

The exceedances of noise limit values arerecorded in the output of sheet strips from picklingoperation. These are observed in all years.

In the tandem rolling mill stands for allvertically stacked rolls, the average levels of noise

exposure level normalized to a normal 8hr workingday are higher as permissible exposure limit (Table 3and Figure 2). The maximum exposure level whichtriggers the action is exceeded. The steel strip thatmoving quickly over steel rollers produces noise.

.Table 3. Annual overall values of equivalent sound level for tandem mill sector


1 90.5 90.3 90.72 93.8 92.4 93.23 94.5 93.3 94.84 97.8 96.6 97.7

Stands of tandem mill

5 100.8 98.5 101.2

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90.790.390.5

93.292.4

93.894.8

93.394.5

97.796.6

97.8

101.2

98.5

100.8

87

75

80

85

90

95

100

105

2013 2014 2015

Noi

se le

vel,[

dB]

Stand 1 Stand 2 Stand 3 Stand 4 Stand 5 Daily permissible exposure limit - L (EX, 8hr)

Fig. 2. Sound level for tandem mill

In the temper pas rolling sector the noiseexceeds the permissible level developed (Table 4 andFigure 3). It has been observed that the sector of rollsmachining is not so noisy. Near to straightening

machines the noise levels were below standard limits.These were slightly above the permissible level forthe area around blast cleaning machine (Table 5,Figure 4).

Table 4. Annual overall values of equivalent sound level into area of temper pas rolling sectorNAEC dB(A)Source of noise 2013 2014 2015

open door 102.3 102.6 101.7Milling stand of temper pasrolling operation door closed 100.5 100.8 98.3

101.7102.6102.3

98.3

100.8100.5

87

75

80

85

90

95

100

105

2013 2014 2015

Noi

se le

vel,[

dB]

Open door Door closed Daily permissible exposure limit - L (EX, 8hr)

Fig. 3. Noise level inside of temper-pas rolling sector

Table 5. Annual overall values of equivalent sound level for sector of machining of rolls


area of straightening machines 76.5 75.8 76.5Machining sector ofrolls area around blast cleaning machines 87.2 87.8 87.6

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76.575.8

76.5

87.687.887.287

687072747678808284868890

2013 2014 2015

Noi

se le

vel,[

dB]

Noise of area of straightening machinesNoise of area around blast cleaning machinesDaily permissible exposure limit - L (EX, 8hr)

Fig. 4. Sound level for machining sector of rolls

Also inside the pumps room from water household the noise level has higher (Table 6 and Figure 5).

Table 6. Annual overall values of equivalent sound level for sector of pumps room from waterhousehold which serves the rolling mill plant


Pumps room 95.8 96.1 95.5

95.596.195.8

87

82

84

86

88

90

92

94

96

98

2013 2014 2015

Noi

se le

vel,[

dB]

Pumps room Daily permissible exposure limit - L (EX, 8hr)

Fig. 5. Noise level inside pumps room from water household

Also inside area from hydraulic operating sectorand from sector of oiling tandem rolls the noise level

recorded was higher with 10 and 15dB over dailypermissible exposure limit (Tabel 7 and Figure 6).

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Table 7. Annual overall values of equivalent sound level for hydraulic operating sector and oilingtandem rolls of mill

NAEC dB(A)Source of noise2013 2014 201597.8 98.2 97.598.4 98.6 98.8Hydraulic operating sector and Oiling

tandem rolls sector102.5 102.1 102.1

98,2 98,697.8 97.598.4 98.8.102.15 102.1 102.1

87

7580859095

100105

2013 2014 2015

Noi

se le

vel,

[dB

]

Hydraulic operating sector and Oiling tandem rollssectorHydraulic operating sector and Oiling tandem rollssectorHydraulic operating sector and Oiling tandem rollssectorDaily permissible exposure limit - L (EX, 8hr)Fig. 6. Noise level inside of hydraulic operating sector and in area of oiling tandem rolls

Even in the intermediate rolls deposit noiselevel was exceeded (Table 8 and Figure 7). Productmovement in stockyards, loading vehicles and vehicle

movements are sources of noises. The noise level wasslightly exceeded inside steel strips adjustment area(Table 9 and Figure 8)

Table 8. Annual overall values of equivalent sound level for intermediate rolls deposit


Intermediate rolls deposit 91.2 90.8 91.33

91.3390.8

91.2

87

84

85

86

87

88

89

90

91

92

2013 2014 2015

Noi

se le

vel,[

dB]

Intermediate rolls deposit Daily permissible exposure limit - L (EX, 8hr)

Fig. 7. Noise level inside of intermediate deposit for steel strips rolls

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Table 9. Noise level inside adjustment areaNAEC dB(A)Source of noise 2013 2014 2015

88.8 87.6 88.3Sector of steel strips adjustment

90.5 90.2 89.4

88.3

87.6

88.8

89.4

90.290.5

87

85

86

87

88

89

90

91

2013 2014 2015

Noi

se le

vel,[

dB]

Sector of steel strips adjustment Daily permissible exposure limit - L (EX, 8hr)

Fig. 8. Noise level inside adjustment area

4. Conclusions

Average noise exposure levels inside manysector of cold steel-rolling mill were significantlyhigher. The results revealed that workers at numerousroll milling plat areas are exposed to noise levelshigher than 87 dB(A) 8- hour standard. To protectworkplaces from noise the effective anti-noisemeasures can be accordingly formulated andimplemented. There is a need for employee trainingon noise exposure hazards and enforcement of the useof protective devices. The plant should be extensivelyautomated. The machines and equipment demandmaintenance and, the workers have need personalprotection. Particular attention should be paid torollers and handling, cutting and grinding activities.

Acknowledgements

The authors wish to thank the student BasocMonica who helped us in this study.

References[1]. R. Saban, C. Dumitrescu s.a., Tratat de stiinta si ingineria

materialelor metalice. Vol.5. Tehnologii de procesare finala amaterialelor metalice., Ed.AGIR, 2012

[2]. *** arcelormittal - 20-f - 20080319 - company_information,http://google.brand.edgar-online.com/[3]. *** United Nations Environment Programme (UNEP) and

Steel Institute (IISI). 1997. Steel Industry and the Environment:Technical and Management Issues. Technical Report No. 38. Parisand Brussels: UNEP and IISI.[4]. F.E. Ologe, T.M. Akande, T.G. Olajide, Occupational

noise exposure and sensorineural hearing loss amongworkers of a steel rolling mill , Otology, European Archives ofOto-Rhino-Laryngology and Head & Neck, July 2006, Volume263, Issue 7, pp 618-621.[5]. G.H. Pandya, D.M. Dharmadhikari, A Comprehensive

Investigation of Noise Exposure in and Around an Integrated Ironand Steel Works, AIHA Journal, Volume 63, Issue 2, 2002, pp.72-84.[6]. D.L. Johnson, P. Papadopoulos, N. Watfa and Dr J.

Takala, Exposure criteria, occupational exposure levels,http://www.who.int/occupational_health/publications/noise4.pdf[7]. S. Kumar Nanda, Noise Impact Assessment and Prediction in

Mines Using Soft Computing Techniques, Thesis for the award ofthe degree of Doctor of Philosophy in Engineering,http://ethesis.nitrkl.ac.in/4560/1/PhD50405001revised.pdf.[8]. *** OSHA Technical Manual (OTM), Section III: Chapter 5 -

Noise, https://www.osha.gov/dts/osta/otm/new_noise/.[9]. *** Occupational Safety and Health Administration (OSHA).

Guidelines for Identification and Control of Safety and HealthHazards in Metal Recycling, 2008, pp.4-48, www.osha.gov.[10]. *** Criteria for a recommended standard, OccupationalNoise Exposure, Revised Criteria 1998, U.S. DEPARTMENT OFHEALTH AND HUMAN SERVICES,http://www.nonoise.org/hearing/criteria/criteria.htm[11]. TK. Madison, Recommended Changes to OSHA NoiseExposure Dose Calculation, 3M JobHealth Highlights, Vol. 25.No. 8 December 2007,

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http://multimedia.3m.com/mws/media/485124O/recommended-changes-to-osha-noise-exposure-dose-calculation.pdf.[12]. S. Kerketta, P.K. Dash and L.T.P. Narayan, Work zonenoise levels at Aarti steel plant, Orissa and its attenuation in farfield, Journal of Environmental Biology, September 2009, 30(5)903-908 (2009), pp.903-908.[13]. *** Environmental Handbook: Volume II: Documentation onmonitoring and evaluating environmental impacts, Volume II,

Agriculture, mining/energy, trade/industry. by Germany.Bundesministerium für Wirtschaftliche Zusammenarbeit undEntwicklung, http://www.worldcat.org/.[14]. J. Masaitis, Enciclopaedia of Occupational Health andSafety. Chapter 73. Iron and Steel,http://www.ilocis.org/documents/chpt73e.htm

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DEPOSITION TECHNOLOGIES FOR OBTAINING THIN FILMSWITH SPECIAL PROPERTIES

Cătălin-Andrei ȚUGUI1, Petrică VIZUREANU1, Carmen NEJNERU1Manuela-Cristina PERJU1, Mihai AXINTE2,Simona-Madălina BĂLŢATU1

1Technical University “Gheorghe Asachi” of Iasi-Romania, Department of Technologies and Equipments forMaterials Processing, Blvd. Mangeron, No. 51, 700050, Iasi, Romania

2Technical University “Gheorghe Asachi” of Iasi-Romania, Materials Science,Blvd. Mangeron, No. 41, 700050, Iasi, Romania

e-mails: [email protected], [email protected]

ABSTRACT

Properties of metallic materials can be improved by deposition of materials.The coating has a tear strength, and better corrosion hydro-abrasive. The thinlayer deposition having a thickness of less than 10 micrometers.

Engineering is not just thin layers deposited layer but the whole assembly(layer / substrate), also have taken into account the degree of adherence and thecosts of making such a substrate must be much more powerful than anything in thewhole taken separately.

In this paper we presented several methods of thin film deposition. We alsohighlighted some of the advantages and disadvantages of some deposition methods.

Keywords: Deposition method, thin layers, substrate, SEM

1. Introduction

Surface is the most important part ofengineering components, most defects appear here,especially those caused by corrosion.

The surface may also have important functionalattributes, is not limited to chemical and mechanicalproperties, but also features thermal, electronic,magnetic and optical influencing the choice ofmaterial. Depositions of thin films are widely usedworldwide in various technologies. Thesetechnologies are successfully applied deposition for along time, specifically since 1400 when contemporaryrecord dates, [1].

Along with traditional technologies forobtaining thin layers, we are witness to thedevelopment, improvement and expansion ofdeposition, modern techniques of the physical andphysicochemical methods, which ensures high purityand strong adhesion through a wide variety ofprocesses for coatings, [1].

Technologies involved are based on vacuumprocesses, with a low environment impact.

Also from economic point of view thistechnologies have an increased efficiency, comparingwith the traditional methods.

Therefore, in recent years there has been adramatic increase in industrial applications are used.

2. Theoretical contributions

Thin layers can be produced by mechanical,chemical, and by condensation of the gaseous phase.The work environment is one of the basic factors ofdeposit, which strongly influences the compositionand structure of the deposited layers.

The environment necessary for the gas-phasecondensation method is vacuum or pressurecontrolled atmosphere reduced the averagedeployment submission process that ensures theachievement of reproducible layers unaffected byimpurities.

Thin films vacuum deposition methods areclassified as following: Physical vapor deposition methods (PVD) by

pulse laser deposition (PLD); Chemical vapor deposition method (CVD):

CVD deposition method at hightemperatures (HTCVD); CVD deposition method based on organmetallic compounds (MOCVD);

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CVD deposition method of plasma assisted(PACVD).

2.1. Physical vapor deposition methods(PVD)

2.1.1. Pulsed laser depositionTechnique where a high power pulsed laser

beam is focused inside a vacuum chamber for hittinga target of the material that is to be deposited, (Figure1).

This material is vaporized from the target, in aplasma plume, which deposits it as a thin film on asubstrate

Fig.1. Schematic diagram of the pulse laserdeposition [2].

Fig.2. SEM images of thin layers Cu2ZnSnS4 of coated PLD method: a) surface image for the thinlayer b) cross sections through coating and substrate layer [3]

Figure 2(a) show SEM image of annealedCu2ZnSnS4 thin films for various deposition times. Itis observed that, due to recrystallization withannealing, resultant grain size is increased, comparedto as-deposited film.

Figure 2(b) show the cross-sectional FE-SEMimage of the annealed Cu2ZnSnS4 thin films.

The thickness of film is found to vary between0.525 and 2.902 µm, which indicates that depositiontime is a vital parameter to increase the thicknessindirectly to increase the efficiency, [2].

2.2. Chemical vapor deposition method(CVD)

2.2.1. High temperature chemical vapordeposition

The thin layer deposition methods works at hightemperatures in the range of 2100-2300ºC and aschematic diagram of this method is shown in figure

3. With HTCVD crystals can produce high qualitylarge diameter SiC in a very cost, opening newmarkets and applications.

Fig.3. Schematic diagram of the method of hightemperature CVD (HTCVD)

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Fig.4. SEM images of thin layers SiC of coated HTCVD method: a) surface image for the thin layerb) cross sections through coating and substrate layer [4].

Figure 4 shows the cross-section and surfacemorphology of HTCVD coated samples. SiC coatinghas a thickness of about 30 μm and a good adhesionto C/SiC composites figure 4(a).

No obvious interlinear or impenetrate crackscan be observed.

The high magnification image figure 4(b) showsthat the surface is closely stacked by spherical grains,with grain size in a range of 10–30 μm.

The coating shows a dense surface with novisible micro cracks. The SiC layer can improve thecompactness of the coating and provide goodoxidation protection for C/SiC composites at high-temperature, [3].

High temperature, specific HTCVD process, is amajor drawback it adversely affecting the structure ofthe substrate, especially when it is steel. To eliminatethe negative effects required both prior andsubsequent heat treatment to reduce the negativeeffects of overheating, [4].

2.2.2. Metalorganic chemical vapordeposition

MOCVD method is quite simple and consists ofdissolving the organic metal compound in an organicsolvent. The diagram of the principle with thismethod shown in figure 5.

Fig. 5. Schematic diagram of MOCVDdeposition method, [5].

Fig.6. SEM images of thin layers MoSi2 of coated MOCVD method: a) surface image for the thinlayer b) cross sections through coating and substrate layer [6].

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The micrographs were obtained by a scanningelectron microscope (SEM).

The surface morphology of the specimensbefore and after the different stages of coatings are infigure 6(a) and (b).

The original surface of the substrate appearedsmooth. Several cracks on the surface of the MoSi2coating were observed from high magnification SEM.The observation was not unusual as MoSi2 filmsproduced by CVD of Si on a Mo substrate are oftencharacterized by cracks and voids [7, 8].

On further coating with silica, the surfaceadopted equiaxed grain morphology. Cross-sectionsof the coating after 3 h at 620ºC were analyzed bySEM.

As shown in figure 6(b); this micrographreveals that the coating thickness was about 7.5 µm at620ºC, [6].

An advantage of this method is replacing somedonors used metal organic metal compounds.

By this replacement with metal organiccompounds shall be greatly decreases the depositiontemperature reaching 400ºC.

2.2.3. Plasma assisted chemical vapordeposition

In this method, gas phase reactions arecatalyzed CVD process specific for the presence inthe reactor of cold plasma produced by the glowdischarge luminescence form similar to that,produced by the ion nitriding.

Fig.7. Schematic diagram of deposition method,[9].

Fig. 8. SEM images of thin layers ZnO of coated PACVD method: a) surface image for the thin layerb) cross sections through coating and substrate layer [10].

Figure 8(a) represents the cross-section of thescanning electron microscopy (SEM) image for ZnOthin film grown at 185°C.

Figure 8 (b) show the top view of SEM imagefor ZnO thin films grown at 160° C. The thickness ofZnO thin film is about 200 nm and a pillar-likestructure can be found [11] in figure 8(a).

During the deposition, atomic kinetic energy isprimarily determined by the deposition temperature.Figure 8(b) exhibit a collapsed pillar structure due tothe low kinetic energy and weak intensity.

3. ConclusionsIn this layers study, which presents methods for

obtaining thin films and some surfaces and depthmorphology we can conclude the following:

1. By PLD can obtain high quality coatingswith a wide variety of properties

2. Quality of ZnO thin layers is improved whenincreasing the sputtering power.

3. HTCVD deposition method is a method thatis not much use as high temperature affectsthe substrate.

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4. MOCVD method is a method of depositionof thin films on the deposition temperature islow so it affects the layer.

5. PACVD deposition method is an advancedand widely used method.

Therefore, the choice of method of submissionshall consider both the nature of the deposited layerand the base material.

Acknowledgements

This work was supported by the strategic grantPOSDRU/159/1.5/S/133652, co-financed by theEuropean Social Fund within the SectorialOperational Program Human Resources Development2007 – 2013.

References

[1]. G. Vermesan, E. Vermeasan, Introducere in ingineriasuprafetelor (Introduction to surface engineering), Ed. Dacia Cluj-Napoca, (1999). [2]. G. Subramanyam, M. W. Cole, N. X. Sun, T. S. Kalkur, N.M. Sbrockey, G. S. Tompa, X.Guo, C. Chen, S. P. Alpay, G. A.Rossetti Jr., K. Dayal, L.Q.Chen, and D. G. Schlom, Challengesand opportunities for multi-functional oxide thin films for voltage

tunable radio frequency/ microwave components Journal ofApplied Physics 114, 191301, (2013). [3]. A.V. Moholkar, S.S. Shinde, A.R. Babar, Kyu-Ung Sim, H.K. Lee, K.Y. Rajpure, P.S.Patil,C.H. Bhosale, J.H. Kimb,Synthesis and characterization of Cu2ZnSnS4 thin films grown byPLD: Solar cells, Journal of Alloys and Compounds 509, (2011). [4]. X.Yang, L.Wei, W. Song, Z. Bi-feng, C. Zhao-hui,Microstructures and mechanical properties of CVD-SiC coatedPIP-C/SiC composites under high temperatur, Surface & CoatingsTechnology 209 197–202, (2012). [5]. G. Subramanyam, M. W. Cole, N. X. Sun, T. S. Kalkur, N.M. Sbrockey, G. S. Tompa, X.Guo, C. Chen, S. P. Alpay, G. A.Rossetti Jr., K. Dayal, L.Q.Chen, and D. G. Schlom, Challengesand opportunities for multi-functional oxide thin films for voltagetunable radio frequency/ microwave components Journal ofApplied Physics 114, 191301, (2013). [6]. E. K. Nyutua, M. A. Kmetzc, S. L. Suiba, Formation ofMoSi2–SiO2 coatings on molybdenum substrates byCVD/MOCVD, Surface & Coatings Technology 200, 3980 – 3986,(2006). [7]. H.O. Pierson, Handbook of Chemical Deposition, Noyespublications, Park Ridge, NJ, 1999. [8]. J.-K. Yoon, J.-K. Jee, J.-Y. Byun, G.-H. Kim, Y.-H. Paik,J.S. Kim, Surf. Coat. Technol. 160 (2002). [9]. http://www.sio2med.com/technology-plasma-deposition.html.[10]. P-H Lei , H.M. Wu, C-M Hsu, Zinc oxide (ZnO) grown onflexible substrate using dual-plasma-enhanced metalorganic vapordeposition (DPEMOCVD)Surface & Coatings Technology 2063258–3263(2012).[11]. I. Volintiru, M. Creatore, B.J. Kniknie, C.I.M.A. Spee,M.C.M. van de Sanden, J., Appl. Phys. 102 043709, (2007).

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