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Ordem dos Engenheiros, Região Sul – dia/ mês/ 2018Ordem dos Engenheiros | Região Sul | 16 de outubro de 2018
Os Novos Desafios da Engenharia
Ciclo de Conferências
Espaço, Terra e Mar
Os Materiais Auto-Reparáveis e a Sustentabilidade
Mário Ferreira
Universidade de Aveiro
16 de Outubro, 2018
“What is a scientist after all? It is a curious man
looking through a keyhole, the keyhole of nature,
trying to know what's going on.”
Jacques Cousteau (1910-1997)
Mimicking Nature...
2
(E.D. Hutchins et al., PLOS One, DOI: 10.1371/journal.pone.0105004)
http://www.natgeocreative.com
Self-healing
3
futureprospects.wordpress.com
-superhydrophobic effect (CA>150º)
-combination of hierarchical structures at micro
and nanoscale (roughness) and chemical
compositionF. Xia, L. Jiang, Adv. Mater. 20 (2008) 2842.
Lotus effect
4
www.gettyimages.com
Smart adhesive: heriarchical structures allow
for a mechanical control of adhesion,
depending on the adequate orientation of
setae (cedras)
Autumn, K. (2006). How gecko toes stick. American Scientist
94, 124–132.
Tokay Gecko
5
Result of optical phenomena such as interference,
refraction, difraction (not due to the presence of
pigments)
F. Xia, L. Jiang, Adv. Mater. 20 (2008) 2842
http://www.webexhibits.org/
Structural coloration
6
8
Key factors for introduction of new technologies:
-economic needs;
-reduction in environmental pollution;
-improvement of performance: anti-corrosion, durability, etc.
New technologies
Self-healing materials
Materials that can heal defects leading to extended service life and
reducing degradation/failure of material
Autonomic – defects activate the healing mechanism
Non-autonomic – requires external stimulus for healing
9
• Capsule-basedEntrapment of healing agent in discrete capsules. Upon rupture by damage, healing agent is releasedinto the region of damage (singular local healing event).
• VascularEntrapment of healing agent in a network form of capillaries, hollow channels which may beinterconnected. Upon damage, release of healing agent occurs. The network may be re-filled (multiplelocal healing events).
• IntrinsicNo healing agent. Latent self-healing functionality which is triggered by damage or external action(multiple healing events).
10
Blaiszik et al., Annu Rev Mater Res 40
(2010) 179-211.
B.S.H. Cho et al., Adv. Mater. 18 (2006) 997-1000.
Encapsulated catalystpolyurethane microcapsules
(di-n-butyltin dilaurate) - yellow
Repairing agent Siloxane-based agent is not encapsulated
but phase separated – white
11
Capsule-based healing
R.S. Trask, I.P. Bond, Smart Mater. Struct. 15 (2006) 704–710.
12
FRPs
Vascular-based
healing
13
Extrapolated Corrosion Costs: $276 billion,
3.1% of GDP
State and Local
Government, 3.0%
$8.3 Billion
Transportation and
Utilities, 34.9%
$96.2 Billion
Construction, 18.1%
$50.0 Billion
Federal Government,
7.3%
$20.1 Billion
Services, 5.2%
$14.3 Billion
Manufacturing,
31.5%
$86.8 Billion
NACE, USA
Corrosion
costs
2-4 %
PIB
Service-life conditions of cars
T: +70ºC to -50ºC
DT: 10-20ºC during day
Stone chiping
High loads of salts
High UV exposure
Physical stresses (car washing)
...
No single coating can meet all the requirements.
Multilayer coating system is necessary!
14
Substrate
Surface treatmentCr(VI) free pre-treatment
Cr-loaded Primer
Top Coat
Cr(VI) Cr-free protection
Substrate
Active Pre-treatment
Cr-Free Primer
Top Coat
Past... Present...
15
reduction in environmental pollution
Automotive industryPre-treatment: inorganic
phosphate conversion layer 1-2
mm (increase surface area and
corrosion protection)
Cathodic electrocoating: passive
corrosion protection (20-22 mm).
Primer surfacer: cover
uneveness, protection against
stone chipping and provide anti-
corrosion properties.
Colored topcoat: applied in two
steps without curing in between,
with a basecoat and a clearcoat.Car body: steel, galvanized steel, aluminum
16
http://www.nissan-global.com/
https://secure.drivers.lexus.com/
17
Self-repair coating
Minimum film thicknesses have to be used since
weight is an extremely sensitive parameter for
utilization and energy costs.
The structural components for an aircraft are
pretreated separately and in the case of
aluminum they are anodized or chromated.
The corrosion protection primer is based on an
epoxy resin which cures with amines or
isocyanates at room temperature. Chromate-
containing active pigments are still used today.
The topcoat is made with a 2-component PUR
paint and has high gloss, color fastness and
weather resistance.
Aeronautical industry
Top coat 50-200 mm
Primer 5-200 mm
Pre-treatment <60 nm
Substrates: aluminum alloys,
steel, CFRP, titanium
18
Maritime industry Surface pre-treatement: sand
blasting.
Primer: anti-corrosion protection
(250-400 mm).
Tie coat: promote adhesion
between layers.
Top coat: anti-fouling coating (>
300 mm).
The overall paint scheme can be
in the mm range.
In addition to corrosion protection
ships are also cathodically
protected by active anodes or
external current (the coating has
to withstand alkaline
environment).
Substrate: steel (carbon steel)
19
Courtesy of JOTUN AS
-hull surface becomes rough due to the growth of algae and
barnacles increasing the ship’s fuel consumption up to 40%;
-increases GHG emissions;
-adds strain on the structure and hinder maneuverability.
20
FP7-OCEAN-2013 Proposal for a Collaborative RTD project BYEFOULING Part B
4
comprising macroscopically visible algae (seaweeds) and invertebrates such as soft corals, sponges,
anemones, tunicates and hydroids (after 2 or 3 weeks of immersion), and c) “hard macrofouling”2 (e.g.
ascidians, mussels, barnacles).
It is often stated that surface colonization follows a linear ‘successional’ model3,4,5
in which bacterial biofilm
formation is followed within a week by spores of macroalgae (seaweeds), fungi and protozoa, followed in
turn, within several weeks, by larvae of invertebrates, such as barnacles. This ‘classical’ view is a
simplification as motile spores of seaweeds are capable of settling within minutes of presenting a clean
surface and larvae of some species of barnacles or bryozoans settle within a few hours of immersion2.
However this “successional model” becomes of great use when determining the action spectra for most biocide and foul-release materials, always taking into account that, while there is a relationship among
different stages, it cannot be assumed that blocking initial stages completely eliminates later ones. Therefore,
a global action against different stages is required for an antifouling material to be effective.
Figure 1-2. Diversity and size scales of a range of representative fouling organisms.2
Figure 1-3. Colonisation process of marine fouling6.
2 J. Callow, M. Callow, Trends in the development of environmentally friendly fouling-resistant marine coatings. Nat. Commun., 2011, 2, 244. 3 L. Chambers, et al., Modern approaches to marine antifouling coatings. Surf. Coat. Technol., 2006, 201, 3642–3652. 4 C. Magin, et al., Non-toxic anti-fouling strategies. Mater. Today, 2010, 13, 36–44. 5 A. Rosenhahn, et al., The role of ‘inert’ surface chemistry in marine biofouling prevention. Phys. Chem. Phys., 2010, 12, 4275–4286. 6 M. Lejars, et al., Fouling Release Coatings: A Nontoxic Alternative to Biocidal Antifouling Coatings. Chem. Rev., 2012, 112 4347–4390.
Stage 1 Biochemical
conditioning
surface
Stage 2 Bacterial colonisation
Stage 3 Diatom and
protozoan
colonisation
Stage 4 Settlement of invertebrates
larvae and algal spores
M. Lejars et al., Chem. Rev. 112 (2012) 4347–4390.
Biofouling
M.L.Zheludkevich et al., Chem. Mater. 19 (2007) 402-411.
D.G.Shchukin et al., Adv. Mater. 18 (2006) 1672–1678.
D.G. Shchukin et al., J. Phys. Chem. C 112 (2007) 958-964.
Polyelectrolyte shells: pH-dependent
permeability for controlled release of
corrosion inhibitor
LbL (Layer-by-Layer) assembly
21
Functional self-healing of coatings
Controlled release of corrosion inhibitor
Coating recovers its function
after healing, within defects/flaws
22
Cl-
Cl-
Cl-
M.L.Zheludkevich et al., Chem. Mater. 19 (2007) 402-411
Chitosan
Chitosan - linear polysaccharide obtained from the partial deacetylation of Chitin
Chitin - second most abundant polysaccharide after cellulose
main component of exoskeleton of crustaceans and insects
Source of images: internet
O
O
HO
NH
OH
O
O
HO NH
OH
O
O
HO
NH2
OH
O
OHO NH2
OHCH3
O
CH3
O
n
12
3
4 5
6
1-DADA
Chemical structure of copolymers (chitin (DA>>1-DA) and
chitosan (1-DA>>DA)) of N-acetyl-D-glucosamine (molar
fraction=DA) and D-glucosamine units (molar fraction=1-
DA). Generally, chitin DA> 0.50 and chitosan DA<0.50
23
The new A350XWB
Composites 53%
Aluminum alloys 19%
Titanium 14%
Steel 6%
Misc. 8%
http://www.a350xwb.com/advanced/fuselage/
F. Capezzuto et al., Composite Structures 92 (2010) 1913–1919
Sensing coating for detection of
mechanical impacts
24
Effect of reinforcement corrosion on
structural behaviour
Cracking and spalling of cover concreteCorrosion products has a volume 2-4 times than that of steel, causing volume
expansion, developing tensile stresses, and cracking.
Catastrophic failure of structureReduce cross-section of steel.
Pitting can reduce the section at a point, no longer withstand the applied load.
26
Geim and Novoselov isolated graphene in
2004 at the University of Manchester.
They won the 2010 Nobel Prize in Physics
for their work with graphene
Graphene: the new hype in corrosion?
Graphene is the world’s first 2D material
-Thin layer of pure carbon
-Tightly packed layer of carbon atoms
bonded in a hexagonal honeycomb lattice
-Layers of graphene stacked on top of
each other = graphite
https://www.extremetech.com/
http://www.graphene.manchester.ac.uk/
27
Hypothesis: if graphene exhibits execellent barrier properties and is very
good electrical conductor this can be a perfect form for obtaining some sort
of noble character in active metals!
Not exactly!
ACS Nano, 7 (2013) 5763-5768
28
Is this the end of line for graphene in
Corrosion Science and Engineering?
Potential properties for coating technologies
• The 2-D structure of graphene and graphene oxide may in increase barrier
effect within polymeric matrices (increase in tortuosity for diffusion of
species);
• Graphene can also be modified to be used as nanocontainer for delivery of
inhibitors.
Challenges
• Cost effectiveness compared to other potential systems (e.g. clay materials);
• Availability of material in large amounts;
• Application technologies.
• ...
29
• Ordem dos Engenheiros pelo Convite para esta apresentação.
• Prof. João Tedim da Universidade de Aveiro por me ter permitido usar
nesta apresentação vários “slides” por ele preparados para a “3rd
International Summer School on Multifunctional Smart Coatings and
Surfaces”, que teve lugar de 16 a 20 de Julho de 2018 no Departamento
de Engª de Materiais e Cerâmica da Universidade de Aveiro.
Agradecimentos