Papers by Author: Wen Cheng J. Wei

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Authors: Wen Cheng J. Wei, B.Y. Yu, J.F. Li, C.S. Chen
Abstract: SiO2 core/TiO2 shell composite particles were synthesized by four different heterogeneous coagulation techniques. The configurations of the composite particles and the microstructure of assembly were characterized by SEM and TEM. The colloidal stability of nano-particles was also computer-simulated by a discrete element method (DEM) in consideration of Brownian motion occurring on the nano-particles. The results indicated that uniform adsorption of the fine particle absolutely needed fine tuning of surface charging conditions and processing steps.
Authors: Wen Cheng J. Wei
Abstract: Solid Oxide Fuel Cell (SOFC) has several non-replaceable advantages over the others, e.g. the issues of high volumetric power density and low cost. Those advantages have been appreciated in recent developments, and implemented in several micro-SOFC devices conducted by several international projects. ONEBAT System by ETH (with 4 other groups) in Switzerland, micro-tubular SOFC by AIST in Japan, micro-honeycomb fuel cell (FC) by Professor Ishihara at Kyushu University will be reviewed in this report. Some micro-devices have been built on Si-chip, or in associated with the accessory parts, such as fuel reformer, electric power collector, or micro-turbine. Those have demonstrated important technology breakthrough and also shown the potential for commercial applications. This report will also discuss two important issues, including gas transport limitation in small gaps and glass sealing for the practical applications of Micro-SOFCs.
Authors: Ming Tsung Weng, Wen Cheng J. Wei
Abstract: The effects of different kneading sequences, chemical additives, and solid loadings to the homogeneity and rheological behavior of the Al2O3/3Y-TZP (ZTA) feedstock were investigated. The properties of the feedstock were analyzed by the torque rheometry, transmission optical microscopy (OM) and scanning and transmission electron microscopy (SEM & TEM). The optimal kneading process was determined when good homogeneity was reached. The concepts of critical solid loading and the homogeneity of two-oxide systems, and the power consumption to reach best microstructure will be introduced and quantitatively analyzed.
Authors: Ming Tsung Weng, Wen Cheng J. Wei, Chi Yuen Huang
Abstract: Al2O3 composites with different volume fractions of 3Y-TZP (3 mol% yttria-doped tetragonal zirconia polycrystalline) were prepared by using a colloidal process and pressure-casting into green specimens, then were pressureless sintered to full density at 1550oC. The resulted two-phase microstructure contained uniformly distributed and submicro- meter-sized grains. The addition of 15 vol% ZrO2 resulted in an increase in bending strength (average 656 MPa by 4 pt. test). Appreciate amount of m-ZrO2 phase was detected after fracture. The enhanced transformability results in an increase in flexural strength and toughness. The addition of 30 vol% ZrO2 resulted in best toughness (5.4 MPam0.5) and outstanding wear resistance (7.2×10-8 cm3/Nm).
Authors: Yu Ju Chen, Wen Cheng J. Wei
Abstract: Ion-beam sputtering deposition is a physical deposited method which uses accelerated ionbeam to sputter oxide or metal targets, and deposits atoms on substrate. Thin films of yttrium-stabilized zirconia (YSZ) were deposited on Si (100) wafer and NiO/YSZ plate. Scanning electron microscopy and transmission electron microscopy with EDS were employed to study the microstructural and chemically stoichiometric results of the films and the crystal growth process by various heat treatments. X-ray diffraction was also used to analysis crystalline phase of the YSZ films. The influence of different targets, substrates deposited efficiency and the properties of the film will be presented and discussed.
Authors: Wen Cheng J. Wei, Chih Lung Chen, Andreas Roosen
Abstract: La2O3-Al2O3-B2O3 (LAB) glass with Al2O3 particulates is a lead-free, non-alkali, and low-sintering temperature glass-ceramic system, which has been developed for LTCC application. The glass melting and sintering process window of the LAB systems were investigated. A systematic study on the wetting behaviors of the LAB glass on alumina plate, microstructures and crystallization in the glass-ceramics had also been conducted. The densification and crystallization temperatures of the glass-ceramics took place as low as 800oC. The interface condition of layer glass-ceramics with Ag electrode was also characterized. No obvious interfacial diffusions were observed.
Authors: Wen Cheng J. Wei
Abstract: Two oxides, Y2O3 and Nb2O5, were doped into Bi2O3-based electrolyte in a composition of (Bi 1-x-y,Nb x,Y y)2O 3, where (x+y)=0.12 to 0.2 and the x:y ratio 3:1 to 1:3. The delta-phase retention, the oxygen vacancy order-disorder transformation, the ionic and electric conductivity were investigated by various techniques. The long-term conductivity of the dense electrolytes was determined showing moderate degradation due to phase transformation possible triggered by surface evaporation of Bi-oxide. The best retention of the conductivity is about 60% after 300 hr test.
Authors: Sheng Chang Wang, Wen Cheng J. Wei, Li Tong Zhang
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