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ELECTROLYTE MATERIALS DEVELOPMENT FOR INTERMEDIATE TEMPERATURE SOLID OXIDE FUEL CELLS
การพัฒนาสารอิเล็กโตรไลตของเซลลเชื้อเพลิงแบบออกไซดของแข็งสําหรับใชที่อุณหภูมิต่ํา
สุทิน คูหาเรืองรอง1 และสมุิตรา จรสโรจนกุล2
1วิศวกรรมเซรามิก สํานักวิชาวิศวกรรมศาสตร มหาวิทยาลัยเทคโนโลยีสุรนารี นครราชสีมา 30000 โทรศัพท 0-4422-4474 โทรสาร 0-4422-4220 E-mail: [email protected]
2ศูนยเทคโนโลยีโลหะและวสัดุแหงชาติ สํานักงานพัฒนาวิทยาศาสตรและเทคโนโลยีแหงชาติ ปทุมธานี 12120 โทรศัพท 0-2564-6500 ตอ 4227 โทรสาร 0-2564-6501 E-mail:
บทคัดยอ เซลลเชื้อเพลิงแบบออกไซดของแข็งเปนเทคโนโลยีที่ไดรับความสนใจเพื่อใชเปนแหลงพลังงานทดแทนในอนาคต วัสดุที่นาํมาประกอบขึ้นเปนสวนประกอบของเซลลมีความสําคัญอยางมากตอประสทิธิภาพในการผลิตกระแสไฟฟาและอณุหภูมิในการใชงาน ในการลดอุณหภูมิใชงานลง จําเปนตองพัฒนาวัสดใุหมีสมบัติทางไฟฟาควบคูกันไป ซ่ึงวสัดุที่ไดนํามาศึกษาในงานวจิัยนี้คือ สารประกอบของซีเรียมออกไซด (CeO2) ที่ใชเปนอิเล็กโตรไลตในชวงอณุหภูมิต่ํากวา 800 องศาเซลเซียส โดยทําการศกึษาเฟสและโครงสรางจุลภาคที่เกิดขึ้นภายหลังการเผาซนิเทอร รวม ทั้งการวัดคาสมัประสิทธิ์การขยายตัวทางความรอน
คําสําคัญ : เซลลเชื้อเพลิงออกไซดของแข็ง ซีเรียมออกไซด อิเล็กโตรไลต
Abstract A Solid Oxide Fuel Cell (SOFC) technology is an interesting alternative energy source in the future. The power conversion efficiency depends very much on the materials used for components in the cell and the operation temperature. Electrical properties of the materials must be optimized while the operating temperature is reduced. Phases study from XRD and microstructures from SEM of doped cerium oxide (CeO2) after sintering have been investigated in our research. Doped cerium oxide is used as an electrolyte material at below 800 degree Celsius. The coefficient of thermal expansion of these materials was also measured.
Keywords: Solid oxide fuel cell, CeO2, Electrolyte
ตีพิมพใน : The Proceedings of NSTDA Annual Conference S&T in Thailand (NAC2005), P062.
112
GELCASTING วิธีการขึ้นรูปเซรามิกสําหรับอนาคต
สุธรรม ศรีหลมสัก สาขาวิชาวิศวกรรมเซรามิก สํานักวิชาวิศวกรรมศาสตร มหาวิทยาลัยเทคโนโลยีสุรนารี
111 ถ.มหาวิทยาลยั ต.สุรนารี อ.เมือง จ.นครราชสีมา 30000
บทคัดยอ Gelcasting เปนวิธีการขึ้นรูปเซรามิกแบบใหมที่มวีิธีการคลายกับวิธีการขึ้นรูปแบบ slip casting ซ่ึงเปนวิธีการขึ้นรูปที่นักเซรามิกคุนเคย ไมตองใชเครื่องมือราคาแพงๆ และเหมาะสมกับการนําไปขึ้นรูปผลิตภัณฑทีม่ีลักษณะซับซอนไดดวย คาดวาอีกไมนานการขึ้นรูปแบบ gelcasting จะเปนวิธีขึ้นรูปผลิตภัณฑทีแ่พรหลายเชนเดียวกันกับวิธีการขึ้นรูปเซรามิกแบบอื่นๆ ตีพิมพใน : วารสารเทคโนโลยีวัสดุ ฉบับที่ 40 กรกฎาคม-กันยายน 2548 หนา 69-70.
113
Gelcasting วิธีขึ้นรูปวุนเซรามิก
สุธรรม ศรีหลมสัก สาขาวิชาวิศวกรรมเซรามิก สํานักวิชาวิศวกรรมศาสตร มหาวิทยาลัยเทคโนโลยีสุรนารี
111ถ.มหาวิทยาลัย ต.สุรนารี อ.เมือง จ.นครราชสีมา 30000
Abstract Gelcasting is a forming process similar to slip casting; and can produce complex-shaped ceramic parts similar to injection molding. With high green strength, gelcast parts are strong and can be machined, if needed, before firing. Gelcasting do not involve complex and long debinding steps which are problems with injection molding. Therefore, gelcasting is promising new technology for complex shape ceramics that are either too complicated or too expensive to be manufactured by other processes. ตีพิมพใน : วารสารเซรามิกส พฤศจิกายน 48 – มกราคม 2549 หนา 72-73.
114
PREPARATION AND CHARACTERIZATION OF HAP-GLASS POROUS COMPOSITES
Charussri Lorprayoon* and Shigeki Morimoto
School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand
*Author for correspondence, e-mail: [email protected]/[email protected]
Abstract The aim of this study was to prepare a porous biocomposite material for bone defect replacement. Hydroxyapatite (HAP), a bioactive and biocompatible powder, was mixed with phase-separable borosilicate glass containing calcium oxide. Calcium carbonate was added as a foaming agent. The composite specimens were made by mixing, pressing and sintering. Phase separation of the glassy phase was controlled by heat treatment. Thereafter, the specimens were acid-leached and characterized in terms of phase, pore size and pore structure by means of x-ray diffractometry (XRD), scanning electron microscopy (SEM) and mercury porosimetry. The evaluations were performed both before and after acid leaching. The results showed that HAP-glass porous composites containing a HAP phase and a minor amount of the second phase and having an interconnected pore structure could be prepared. Keywords: hydroxyapatite-glass composite, porous biocomposite. Published in : Chiang Mai Journal of science 2005, 32(3): pp. 495-500.
115
FUEL CELL TECHNOLOGY IN THAILAND
P. Aungkavattana, S. Charojrochkul, H. Mahaudom, A. Kittiwanichawat, W. Wattana, M. Henson
National Metal and Materials Technology Center, 114 Thailand Science Park Pathumthani 12120, Thailand
S. Assabumrungrat, and S. Srichai Chulalongkorn University Patumwan Bangkok 10330, Thailand
S. Kuharuangrong Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
J. Charoensuk, W. Khan-ngern, P. Khamphakdi, and N. Nakayothin
King Mongkut’s Institute of Technology, Ladkrabang Bangkok 10520, Thailand
Abstract An overview of fuel cell research and development in Thailand is presented, with
emphasis on a solid oxide fuel cell (SOFC) project. The focus of the project is to develop technology to generate electricity from electrochemical reactions between ethanol and oxygen gas in air using solid oxide fuel cells. Research work on cell development and characterization (including performance testing) of solid oxide fuel cells, and on the development of a prototype electric generator from solid oxide fuel cells is presented. The results from this project will contribute to a better understanding and the development of technology to generate power from solid oxide fuel cells. The learning process will lead to commercialization of a clean energy source as an alternative to fossil fuels to generate electricity in Thailand in the future.
Published in: Proceedings form the International Conference on the Characterization and Control of Interfaces for High Quality Advanced Materials (ICCCI 2003), Kurashiki, Japan, 2003, Ceramic Transactions, Volume 146.
116
FORMATION, ABSORPTION AND EMISSION SPECTRA OF Cr4+ LONS IN Li2O-SiO2 SYSTEM TRANSPARENT GLASS-CERAMICS
Shigeki Morimoto
School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand
Abstract
The formation mechanism, optical absorption and emission spectra of Cr4+ ions-containing Li2O-SiO2 system transparent glass-ceramics were investigated. In the material, the main crystalline phase was Li2O-2SiO2, and the percent crystallinity and crystal size were 67-72 and 20-33 nm, respectively. The remarkable change in color and absorption spectra was observed upon crystallization. The characteristic emission of tetrahedrally coordinated Cr4+ ions was identified in the near infrared region, 1000-1600 nm. It was found that tetrahedrally coordinated Cr4+ ions exist in this transparent glass-ceramics from absorption and emission measurement. The Cr4+ ions exist in residual high SiO2 glassy phase, and their ligand field parameters are estimated to be: 10Dq = 10,610 cm-1, B = 690 cm-1 and Dq/B = 1.54. This Dq/B value is just below the crossing point of 3T2 and 1E levels (Dq/B = 1.6). The Cr4+ ions in Li2O-SiO2 system transparent glass-ceramics occupy the little stronger ligand field sites than those in aluminate glass reported previously (Dq/B = 1.2) It is considered that the Cr4+ ions can be formed by the reduction of Cr6+ ions (chromate ion [CrO4]2-) associated with decreasing the basicity of residual glassy phase during crystallization. In this process the behavior of Li+ ions plays a significant role. The [CrO4] formed is equivalent to [SiO4] and substitutes [SiO4] sites in the residual high SiO2 glassy phase. Keywords : Li2O-LiO2 system, Transparent glass-ceramics, Tetrahedrally coordinated Cr4+ ions, Emission spectra Published in : Journal of Ceramic Society of Japan, Vol. 112, 2004, pp. 486-490.
117
OPTICAL ABSORPTION OF CR-CONTAINING Li2O – SiO2 SYSTEM TRANSPARENT GLASS-CERAMICS
Shigeki Morimoto
School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand
Abstract
The absorption spectra of Cr-containing Li2O-SiO2 transparent glass-ceramics was investigated. The crystalline phases precipitated in glass-ceramics are mainly Li2O-2SiO2 with a small amount of α-SiO2. The percent crystallinity and crystal sizes are 40-77 and 20-42 nm, respectively. A strong absorption band ascribed to the charge transfer of Cr6+ ion and a weak d-d absorption band ascribed to Cr3+ ion were observed in the glass. However, the new absorption bands appeared at around 600-700 nm and the absorption intensity of these bands increased significantly (about 15 times) upon crystallization. It was suggested that the tetrahedrally coordinated Cr4+ ion might exist in Li2O-SiO2 transparent glass-ceramics.
Keywords: Li2O-SiO2 system, Transparent glass-ceramics, Cr ions, Absorption spectra Published in : Journal of the Ceramic Society of Japan, Vol. 112[3] ,2004, pp. 130-132.
118
STRENGTH OF Li2O-SiO2 SYSTEM TRANSPARENT GLASS-CERAMICS
Shigeki Morimoto and Waraporn EMEM School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology,
111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand
Abstract The relationship between fracture strength and crystal size in the Li2O-SiO2-system transparent glass-ceramics was investigated. The precipitated crystal phase, percent crystallinity and crystal size were Li2O-2SiO2, 60-80% and 20-60% nm, respectively, following heat treatment below 800o C for 5-144 h. It is found that fracture strength increases linearly with increasing crystal size in the range of 20-60 nm for both non abraded and abraded specimens. Fractures strength can be expressed as a function of crystal size, d (nm), by σ = 100.5+2.32d (MPa) [Non-abraded] σ = 56.3+0.99d (MPa) [Abraded] This result shows the opposite tendency for previous result of glass-ceramics of micrometer order crystals. This indicates that very fine crystals cannot effectively interrupt crack propagation, and hence, the stress required for changing the direction of propagation might be small. It can be considered that a critical crystal size may exist for the attainment of the maximum strength. Keywords: Li2O-SiO2 system, Transparent glass-ceramics, Nanocrystals, Fracture strength Published in : Journal of Ceramic Society of Japan, Vol. 112, 2004, pp. 259-262.
119
ABSORPTION AND EMISSION SPECTRA OF Cr LON-CONTAINING TRANSPARENT CLASS-CERAMICS
Shigeki Morimoto* Waraporn Emem
School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand
Abstract
The absorption and emission spectra of Cr ion-containing transparent glass-ceramics was investigated. The Li2O-SiO2 system transparent glass-ceramics melted in air exhibits a remarkable change in color and absorption spectra by crystallization. It is confirmed that this change is due to the formation of tetrahedrally coordinated Cr4+ ions in residual high-SiO2 glassy phase. And the emission near infrared region ( 1300 nm) caused by tetrahedrally coordinated Cr≈ 4+ ions was also identified. It was found that the Cr4+ ions can be formed by the redox reaction between Cr+6+ ions and non-bridging oxygen ions during crystallization. The Cr ions-containing spinel type transparent glass-ceramics melted in air also exhibits a marked change in color and absorption spectra by crystallization. The Cr3+ ions occupy the strong octahedral sites in nano-crystallite of spine1 [(Mg, Zn)Al2O4] and emits a characteristic narrow R-line ascribed to 2E→ 4A2 transition. Keywords : Cr ion, transparent glass-ceramics, nano-crystallite, absorption and emission spectra)
Published in: The 20th International Congress on Glass, Kyoto, Japan, September 26-October 1, 2004.
120
PREPARATION OF MACHINABLE GLASS-CERAMIC BASED ON β -Ca2P2O7 CRYSTAL
Shigeki Morimoto* and Charussri Lorprayoon
School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand
E-mail : [email protected]
Abstract The new type machinable glass-ceramics based on β -Ca2P2O7 crystal can be prepared successfully by the heat treatment of Na2O-CaO-B2O3-P2O5-Al2O3-SiO2 system of glass. An isolated droplet type phase separation takes place prior to crystallization. Three kind of crystals precipitate, AIPO4(tridymite type), β -Ca3(PO4)2 and β -Ca2P2O7. The amount and size of β -Ca2P2O7 crystal increases with increase in the temperature, particularly above 750oC. The machinability of glass-ceramics was examined by conventional drilling test, and it was found that the glass-ceramics containing a large amount and a large size (> 10µ m) of β -Ca2P2O7 crystal exhibits a good machinability. Keywords: CaO-P2O5 glass, β -Ca2P2O7 crystal, machinability Published in: Smart Mat’ 04 International Conference, Chiang Mai University, 1-3 December, 2004.
121
MICROSTRUCTURE AND FRACTURE TOUGHNESS OF A SPARK PLASMA SINTERED Al2O3-BASED COMPOSITE WITH BaTiO3 PARTICULATES
Sirirat Rattanachan, Yukio Miyashita, Yoshiharu Mutoh*
Department of Mechanical Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka-shi 940-2188, Japan
Abstract
Dense Al2O3- based composites with dispersed BaTiO3 particulates were fabricated by using spark plasma sintering (SPS) at sintering temperatures between 1100 and 1500oC with a heating rate of 100o C/ min. High-density of BaTiO3-Al2O3 with various compositions could be achieved by SPS at lower sintering temperatures compared to those by conventional pressure-less sintering (PLS). However, full densification was prevented by the onset of abnormal grain growth in Al2O3-BaTiO3 composites sintered by SPS. It was found that SPS process could accelerate the abnormal grain growth due to the activation and purification of particle surface. The addition of BaTiO3 in Al2O3 matrix improved fracture toughness of the composites fabricated by both SPS and PLS. The highest fracture toughness of 6.04 MPa.m1/2 was achieved in the composite sintered by SPS process with 5 mol% BaTiO3, while that of the monolithic Al2O3 was about 4.0 MPa.m1/2. Keywords: Al2O3; BaTiO3; Composites; Sintering; Toughness and toughening Published in : Journal of the European Ceramic Society 23, 2003, pp. 1269-1276.
122
EFFECT OF POLARIZATION ON FRACTURE TOUGHNESS OF BaTiO3/Al2O3 COMPOSITES
Sirirat Rattanachana Yukio Miyashitab, Yoshiharu Mutohb
aInstitute of Engineering, Suranaree University of Technology, 111 University Avenue, Nakhon Ratchasima 3000, Thailand
bDepartment of Mechanical Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka-shi 940-2811, Japan
Abstract
In this study, Al2O3 based composites dispersed with BaTiO3 particles were fabricated by a conventional sintering process. The relative density and microstructure (grain size, phase) of composites were studied. The relative density of BaTiO3/Al2O3 composites decreased with increasing BaTiO3 content, and there were reaction phased between Al2O3 matrix and dispersed BaTiO3 particles. The Indentation Fracture Method was used to evaluate the fracture toughness of the present composites before and after polarization. It was verified that an applied electric field induced distinct anisotropy in fracture toughness of BaTiO3/Al2O3 composites between parallel and perpendicular directions to the poling direction. The fracture toughness was improved with addition of BaTiO3 particles to Al2O3 matrix. The toughening mechanisms of BaTiO3/Al2O3 composites have been also discussed. Keywords: Al2O3; BaTiO3; Composites; Ferroelectric properties; Fracture toughness; Piezoelectric properties; Polarization Published in: Journal of the European Ceramic Society 24 2004: pp.775-783.
123
FABRICATION OF PIEZOELECTRIC LAMINATE FOR SMART MATERIAL AND CRACK SENSING CAPABILITY
Sirirat RattanachanaYukio Miyashitab, Yoshiharu Mutohb
aInstitute of Engineering, Suranaree University of Technology, 111 University Avenue, Nakhon Ratchasima 3000, Thailand
bDepartment of Mechanical Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka-shi 940-2811, Japan
Abstract
Piezoelectric laminate composite has been successfully fabricated as a smart material by a spark plasma sintering process. Fully or nearly fully dense BaTiO3/MgO (pre-sintered)/BaTiO3, BaTiO3/MgO with 10 vol% BaTiO3/BaTiO3 laminates were sintered at 1300oC with a holding time of 5 min under a pressure of 35 MPa. From EDS analysis, no reaction between BaTiO3 and MgO layers was observed along the interface. Effect of cycle stress and stress intensity factor on the voltage response of the proposed laminates were investigated for confirmation of a crack detecting capability. The resultant relationship between crack length and voltage response range clearly showed that the proposed laminates have a crack sensing capacity. Keyword: Smart material; Piezoelectric; Laminate; Spark plasma sintering; Fatigue; Crack sensing Published in : Science and Technology of Advanced Materials 6(2005) pp.704-711.
124
KHORAT CLAYS AS RAW MATERIALS FOR LIGHTWEIGHT AGGREGATES
Sirirat Rattanachan* and Charussri Lorprayoon
Institute of Engineering, Suranaree University of Technology, 111 University Avenue, Muang, Nakhon Ratchasima, Thailand 30000
Abstract
This study assesses the possible use of Khorat clays, deposited at Suranaree University of Technology (SUT), for the production of lightweight aggregates. The SUT clays were collected and divided into 2 groups, i.e. white clay and reddish brown clay, to study their heat-treatment behavior. The SUT clay mixtures in various ratios were investigated to find the suitable compositions and heat-treatment (between 1000 and 1250oC) for the production of lightweight aggregates. After firing at 1250oC, the SUT clays expanded 21.05 and 5.70% for the white and reddish brown clays, respectively. Firing expansion was mainly dependent on the amount of SiO2, fluxing oxides and water of the raw materials. These aggregates are highly impervious to water and exhibit considerable firing expansion, low bulk density (1.2.9-1.76 g/cm3) and fair technical properties (unit weight and bending strength) for light weight concrete. These results encourage the use of these clays for the production of lightweight aggregates. Keywords: Khorat clays, SUT clays, lightweight aggregates, lightweight concrete. Published in : ScienceAsia, 2005, Vol. 31, No. 3 pp: 277-281.
125
FRACTURE TOUGHNESS OF BaTiO3 - MgO COMPOSITES SINTERED BY SPARK PLASMA SINTERING
Sirirat Rattanachana, Yukio Miyashitab and Yoshiharu Mutohb
aInstitute of Engineering, Suranaree University of Technology, 111 University Avenue, Muang, Nakhon Ratchasima, Thailand 30000
bDepartmane of Mechanical Engineering, Nagaoka University of Technology 1603-1 Kamitomioka, Nagaoka-shi 940-2188 Japan
Abstract
BaTiO3-MgO composites with various compositions were fabricated by using a Spark Plasma Sintering (SPS) method. BaTiO3-MgO composites with very high density were successfully sintered by SPS method. From the experimental results of as-sintered composites, Vickers hardness decreased and fracture toughness increased with increasing BaTiO3 content. The higher fracture toughness of BaTiO3-MgO composite with 10 vol% BaTiO3 content was achieved compared to monolithic MgO. In order to investigate the effect of piezoelectric BaTiO3 particles dispersed in MgO matrix, fracture toughness of the polarized composites was also evaluated. After polarization, fracture toughness of the BaTiO3-MgO composites was improved and higher than that of monolithic MgO, while polarization induced distinct anisotropy in fracture toughness between parallel and perpendicular directions to the poling direction. Published in: Fracture Mechanices of Ceramics, Vol. 14, White, K.W.; Bradt, R.C.; Sakai, H.; Munz, D. (Editors) 2005, XVIII, ISBN : 0-387-24134-5
126
FRACTURE TOUGHNESS OF BaTiO3 and BaTiO3 – Al2O3 COMPOSITE UNDER ELECTRIC FIELD
Sirirat Rattanachana, Yukio Miyashitab and Yoshiharu Mutohb
aInstitute of Engineering, Suranaree University of Technology, 111 University Avenue, Muang Nakhon Ratchasima, Thailand 30000
bDepartmane of Mechanical Engineering, Nagaoka University of Technology 1603-1 Kamitomioka, Nagaoka-shi 940-2188 Japan
Abstract
In order to investigate the effect of electric polarization on fracture toughness of monolithic BaTiO3 and 5 mol% BaTiO3-Al2O3 composite (5B95A), indentation fracture tests were conducted on unpoled and poled samples under various applied electric fields. From the results, it is found that applied electric fields can increase or decrease fracture toughness in both monolithic BaTiO3 and 5B95A composite depending on the direction of electric field. For unpoled and poled samples under the positive (in the same direction to the poling direction), fracture toughness parallel to the poling direction increased, while that perpendicular to the poling direction decreased. Under the negative (in the opposite direction to the poling direction), fracture toughnesses both parallel and perpendicular to the poling direction for poled monolithic BaTiO3 and 5B95A composite were decreased with increasing the applied electric field. This behavior of 5B95A composite was consistent with that of monolithic BaTiO3. It was concluded that polarization switching of piezoelectric BaTiO3 particles phase under electric fields has a significant influence on fracture toughness of the present composite.
Published in : Fracture Fracture Mechanices of Ceramics, Vol. 14, White, K.W.; Bradt, R.C.; Sakai, H.; Munz, D. (Editors) 2005, XVIII, ISBN : 0-387-24134-5.
127
PIEZOELECRIC LAMINATES FOR SMART MATERIALS SINTERED BY SPARK PLASMA SINTERING
Sirirat Rattanachan1, Yukio Miyashita2 and Yoshiharu Mutoh2
1Institute of Engineering, Suranaree University of Technology, Nakorn Ratchasima, 30000 Thailand 2Department of Mechanical Engineering, Nagaoka University of Technology
1603-1 Kamitomioka, Nagaoka-shi 940-2188 Japan
Abstract A rapid consolidation process, Spark Plasma Sintering (SPS), has been applied to fabricate piezoelectric laminates as a smart material. Fully or near fully dense BaTiO3/MgO (pre-shaped) and BaTiO3/MgO with 10 vol% BaTiO3 laminates were sintered at 1300oC with a holding time of 5 min under a pressure of 35 MPa. From the EDS analysis, no reaction between BaTiO3 and MgO was observed along interface. The effects of maximum applied stress and applied stress intensity factor on the responding output electric potential of present laminates with and without surface crack were investigated. The output signal was positive when tensile stress was applied while the output signal became negative when the compressive stress was applied. These results indicate that the present laminates have strain sensing capability. The fatigue test was also conducted to investigate the relationship between the crack length and the responding output signal of the poled laminates. A linear relationship between them could be successfully obtained. Keywords: Smart materials; Crack; Sensing; Piezoelectric; Laminate; Spark Plasma Sintering; Piezoelectric Laminate Published in: The 5th International Symposium on the 21st Century COE Program of Nagaoka University of Technology, Miracle Grand Convention Hotel, Bangkok, August 10-11, 2004.
128
EFFECT OF ELECTRIC FIELD ON FRACTURE TOUGHNESS OF BaTiO3-Al2O3 COMPOSITES
Sirirat Rattanachan, Yukio Miyashita and Yoshiharu Mutoh*
Department of Mechanical Engineering, Nagaoka University of Technology 1603-1 Kamitomioka, Nagaoka-shi 940-2188 Japan
Abstract
As one of novel approaches for toughening of ceramics, composites with piezoelectric secondary phase have been proposed, where energy dissipation due to piezoelectric effect and domain switching have been suggested as the main toughening mechanisms. In the present study, fracture toughness of 5 mol% BaTiO3/Al2O3 (95A5B) composite, which was sintered at 1300oC under a compacting load of 38 MPa by using Spark Plasma Sintering method, for both before and after polarization was investigated under various applied electric fields to discuss the toughening mechanisms. The generated cracks in the parallel or perpendicular direction to poling were observed in detail, and compared to those for monolithic BaTiO3. In this experiment, the cracks introduced by a Vickers indenter were perpendicular or parallel to the applied electric field. The combination of electrical and mechanical loading was achieved by applying an electrical potential across the electroded specimen during indenting. Static electric fields were applied in either the same or opposite direction to the poling direction using a high voltage power supply. Fracture toughness was evaluated by using the IF method. Fracture toughness of unpoled and poled Al2O3-based composite with 5 mol% BaTiO3 was evaluated under various applied electric fields, as compared to BaTiO3. The positive applied electric field increased the fracture toughness in the parallel direction to the poling direction an decreased it in the perpendicular to the poling direction. The negative applied electric field degraded the fracture toughness in the parallel direction and enhanced it in perpendicular direction. Improvement of fracture toughness under positive applied electric field was significant compared to that for poled sample without applied electric field. These behaviors can be explained based on the polarization switching and the stress induced domain switching. Published in : International Symposium on Advanced Materials, Nagoya, Japan, October 2-3, 2003, pp. 69-70.
129
PREPARATION OF BIOCOMPOSITES WITH MECHANICALLY COATED PARTICLES
Sukasem Kangwantrakool1, A. Takenaka2, J. Suwanprateeb3, K. Shinohara2*
1School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
2Division of Materials Science and Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
3National Metal and Materials Technology Center, Ministry of Science, Technology and Environment, Pathumthani 12120, Thailand
Abstract New preparation route for enhancing mechanical properties of high-density polyethylene
reinforced with hydroxyapatite biocomposite has been investigated. Hydroxyapatite (HA) was used as fine particles to coat each coarse particle of polyethylene (HDPE) with a elliptical-rotor-type mixer and a high-speed rotational impact blending machine. The effects of mixing conditions such as the rotor speed, the total treatment time, the number of preparation steps and the total volume fraction of HA, and the particle size of HDPE were studied. In comparison, it was found that the coating and embedment of HA fine particles onto the surface of HDPE core particle was easily achieved by rotational impact blending due to high impact energy to yield uniform dispersion of HA in the composite material and relatively high mechanical properties. However, the multi-coating steps or layers are required due to high percentage of powder loss during operation. In contrast, uniform and tight coating of core particles was performed without particle loss by elliptical-rotor-type mixing. Nevertheless, due to the slight embedment of fine particles by gentle shear and compressive stress, the molten HDPE of core particles hardly spread out or escaped through the thick and tight coating layer of HA during formation, resulting in weak bonding among coated particles to yield lower mechanical properties.
Keywords: Coated particle; Rotational impact blending; Elliptical-rotor-type mixer; Bioceramics; Composite materials Published in : Ceramic Soc Japan-Nippon Seramikkusu Kyokai, 2-22-17 Hyakunin-Cho Shinjuku-Ku, Tokyo, 169, Japan.
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NEW MICROSTRUCTURE DESIGN FOR HARD COMPOSITE MATERIAL BY MECHANICAL COATING OF CERAMIC PARTICLES
Sukasem Kangwantrakool1, K. Shinohara2
1School of Ceramic Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
2Division of Material Science and Engineering, Hokkaido University, Sapporo 060-8628, Japan
Abstract In order to obtain ideal microstructure with highly uniform dispersion of each component
of sintered composite material, the microstructure of multi-components has been designed using ceramic coated particles prepared by high-speed rotational impact blending as a novel technique. The results revealed that the sintered sample prepared with coated particles possesses excellent morphological characteristics and uniform distributions of each component which yielded higher mechanical properties.
Published in : Symposium on Process Intensification & Miniaturization, Newcastle, UK, August 18-21, 2003, pp. 62-67.
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SINTERING BEHAVIOR OF MECHANICALLY COATED WC-Co/TiC-Al2O3 PARTICLES BY HIGH-SPEED ROTATIONAL IMPACT BLENDING
Sukasem Kangwantrakool1, Kunio Shinohara2*
1School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
2Division of Materials Science and Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
Abstract
The sintering behavior of WC-Co/TiC-Al2O3 composite has been investigated from its microstructure. The coated particles were prepared by high-speed rotational impact blending and sintered by spark plasma method (SPS) and hot press. The powder of the same composition was also mixed by means of an ordinary ball mill for comparison of their microstructural uniformities and mechanical properties. The microstructure was quantitatively measured on SEM photos by image analysis technique, and characterized by void size distribution curves. The results revealed that the sintered sample prepared with coated particles and with SPS possesses excellent morphological characteristics, such as smaller WC and Al2O3 mean grain sizes and uniform spatial distributions of hardest β phase to yield higher mechanical properties such as hardness and transverse rupture strength than the cases of the ball mill and the hot press. The superior mechanical properties were obtained at higher sintering temperature with moderate sintering time of SPS. Keywords: Sintering Behavior, Coated Particles, Spark-Plasma, Cemented Carbides,
Microstructure Published in : International Journal of Refractory Metals & Hard Materials, Vo. 21,
No. 3-4, pp. 171-182.
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HARMONIC ANALYSIS OF POLARIZATION HYSTERESIS OF AGED PZTs
Sutham Srilomsak, *,+ Walter A. Schulze,* Steven M. Pilgrim,* and Francis A. Williams Jr. School of Ceramic Engineering and Material Science,
Alfred University, Alfred, New York 14802
Abstract Many studies have been performed on aging of lead zirconate titanate (PZT), but a single model has not been universally accepted. An aim of this research was to determine whether harmonic analysis could distinguish among the models for the aging of PZTs. Doped and undoped PZT samples were prepared, and the aging behaviors of relative dielectric constant (K), planar coupling factor (kp), dielectric coefficient (d33) and polarization were analyzed by both weak-field and harmonic analysis methods at 37oC. Results indicated that aging behavior, as noted by a harmonic analysis, substantially agreed with the weak-field behavior. This finding suggests that harmonic analysis is a promising new method for studying the aging of PZTs, which may contribute to developing a better aging model for PZTs. Published in : Journal of the American Ceramic Society 88 (8): 2121-2125, 2005.
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EFFECTS OF Ni ON THE ELECTRICAL CONDUCTIVITY AND MICROSTRUCTURE OF La0.82Sr0.16MnO3
Sutin Kuharuangrong
School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand
Abstract
The effects of Ni doped into La0.82Sr0.16MnO3 (LSM) have been studied. La0.82Sr0.16Mn1-x NixO3 compositions with Ni Content up to x = 0.3 have been prepared by the solid state reaction and characterized to investigate the microstructure, thermal expansion coefficient (TEC) and electrical conductivity. A second phase detected by X-ray diffractometry has been found in all compositions after sintering at 1470oC for 2 h. The results from scanning electron microscope show that the grain sizes of LSM reduce with Ni content and its TEC is changed insignificantly by Ni. The TEC value of 11.7 x 10-6K-1 between 100 and 900oC is obtained for 0≤ x 0.3. The electrical conductivity from dc four point measurement indicates a trend of decreasing conductivity with increasing Ni content.
≤
Keywords: C. Electrical conductivity; D. Perovskites Published in : Ceramics International 30 (2004) 273-277.
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EFFECTS OF Co AND Fe ADDITION ON THE PROPERTIES OF LANTHANUM STRONTIUM MANGANITE
S. Kuharuangronga, T. Dechakuptb, P. Aungkavattanac
aSchool of Ceramic Engineering at Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
bDepartment of Materials Science, Chulalongkorn University, Bangkok 10330, Thailand cNational Metal and Materials Technology Center, Patumthani 12120, Thailand
Abstract
The effects of Co and Fe dopants with the amount of 20 and 40 mol% on the properties of La0.84Sr0.16MnO3 were investigated. All compositions were prepared by conventional mixed oxide process and sintered at 1450oC. The structure of undoped and Co-doped compositions was found to be monoclinic. In addition, the second phase was observed in these sintered compositions. The conductivity of doped materials decreased as compared to that of La0.84Sr0.16MnO3. The SEM microstructure showed the decrease of grain size as Co content increased. The thermal expansion coefficient (TEC) tended to increase as Co content increased. In contrast, the monoclinic and orthorhombic structures were found in 20 and 40 mol% Fe-doped La0.84Sr0.16MnO3. The amount of second phase in sintered composition depends on the amount of Fe content. The conductivity at 1000oC decreased, but the grain size increased as Fe content increased. The thermal expansion coefficient slightly changed with Fe addition. Keywords: Solid oxide fuel cell; Lanthanum strontium manganite; Electrical conductivity Published in : Materials Letters ELSEVIER Vol. 58/12-13 หนา 1964-1970, 2004.
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FRACTURE TOUGHNESS AND CRACK SENSING OF MgO-BASED SMART COMPOSITES WITH PIEZOELECTRIC PHASE
Yoshiharu Mutoh*, Sirirat Rattanachan** and Yukio Miyashita*
*Nagaoka University of Technology, Nagaoka-shi 940-2188 Japan **Suranaree University of Technology, Nakhon Rachashima, Thailand
Abstract
Development of functional composites and smart materials would contribute to improve the performance and reliability of components. In the present study, ceramic matrix composite with piezoelectric phase, BaTiO3-MgO, was fabricated by using a spark plasma sintering (SPS) process. With addition of BaTiO3, fracture toughness of the composite was successfully improved compared to that of the monolithic MgO. It was found that domain switching of piezoelectric BaTiO3 phase, which is induced near crack tip region during the test and relazes the stress intensity factor at the crack tip, has a significant influence on toughening of the composite. BaTiO3/MgO/BaTiO3 and BaTiO3/MgO-based composite/BaTiO3 laminates were fabricated by SPS to investigate possibility for a self-damage sensing smart material. A good correlation between electrical output signal range and crack length was found during fatigue load cycling, which indicated the laminates could be candidates for smart materials with self-crack-detecting capability. Keywords: Piezoelectric composite, Fracture toughness, Crack sensing, Domain switching, Smart material, BaTiO3-MgO Published in : International Symposium on Frontiers in Design of Materials 2005, Institute of Technology Madras, Indian.
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FRACTURE TOUGHNESS OF BaTiO3-Al2O3 COMPOSITE UNDER APPLIED ELECTRIC FIELDS
Yoshiharu Mutho*, Sirirat Rattanachan and Yukio Miyashita Departmane of Mechanical Engineering, Nagaoka University of Technology
1603-1 Kamitomioka, Nagaoka-shi 940-2188 Japan
Abstract As one of novel approaches for toughening of ceramics, composites with piezoelectric secondary phase have been proposed, where energy dissipation due to piezoelectric effect and domain switching have been suggested as the main toughening mechanisms. The research works on toughening mechanisms and fracture toughness of ceramic composites with piezoelectric phases have been limited, while those for monolithic piezoelectric/ferroelectric materials have been widely available. In the present study, fracture toughness of 5 mol% BaTiO3/Al2O3 (95A5B) composite sintered by using Spark Plasma Sintering method, for both before and after polarization was investigated under various applied electric fields to discuss the toughening mechanisms. The generate cracks in the parallel or perpendicular direction to poling were observed in detail, and compared to those for monolithic BaTiO3. The combination of electrical and mechanical loading was achieved by applying an electrical potential across the electrodes on the specimen surface during indenting. Static electric fields were applied in either the same or opposite direction to the poling direction using a high voltage power supply. Fracture toughness was evaluated by using the IF method. From the results, it is found that applied electric fields can increase or decrease fracture toughness in both monolithic BaTiO3 and 95A5B composite depending on the direction of electric field. For unpoled and poled samples under the positive electric field (in the same direction to the poling direction), fracture toughness parallel to the poling direction increased, while that perpendicular to the poling direction decreased. Under the negative electric field (in the opposite direction), fracture toughnesses both parallel and perpendicular to the poling direction for poled monolithic BaTiO3 and 95A5B composite were decreased with increasing applied electric field. This behavior of 95A5B composite was consistent with that of monolithic BaTiO3. It was concluded that polarization switching of piezoelectric BaTiO3 particles phase under electric fields has a significant influence on fracture toughness of the present composite.
Published in : The 8th 21st Century COE International Symposium on Creation of Hybridized Materials with Super-Functions and Formation of International Research and Education Center, Park Royal Hotel, Batu Feringghi, Penang, Malaysia, August 7-10, 2005.
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