Cheng Yuan Tsai

Bio: Cheng Yuan Tsai is an academic researcher from National Chiao Tung University. The author has contributed to research in topics: Cubic zirconia & Composite material. The author has an hindex of 2, co-authored 2 publications receiving 43 citations.

Dependence of Oxidation Modes on Zirconia Content in Silicon Carbide/Zirconia/Mullite Composites

Abstract: Two basic oxidation modes of silicon carbide/zirconia/mullite (SiC/ZrO2/mullite) composites were defined based on the plotted curve of the gradient of the silica (SiO2) layer thickness (formed on individual SiC particles) versus depth. Mode I, where oxygen diffusivity was much slower in the matrix than in the SiO2 layer, exhibited a relatively large gradient and limited oxidation depth. Mode II, where oxygen diffusivity was much faster in the matrix than in the SiO2 layer, displayed a relatively small gradient and an extensive oxidation depth. When the volume fraction of ZrO2 was below a threshold limit, the composites exhibited Mode I behavior; otherwise, Mode II behavior was observed. For composites with a ZrO2 content above the threshold limit, the formation of zircon (ZrSiO4), as a result of the reaction between ZrO2 and the oxidation product (i.e., SiO2), might change the oxidation behavior from Mode II to Mode I.

Effect of zirconia content on the oxidation behavior of silicon carbide/zirconia/mullite composites

Abstract: The oxidation of hot-pressed SiC-particle (SiCp)/zirconia (ZrO2)/mullite composites with various ZrO2 contents, exposed in air isothermally at 1000° and 1200°C for up to 500 h, was investigated; an emphasis was placed on the effects of the ZrO2 content on the oxidation behavior. A clear critical volume fraction of ZrO2 existed for exposures at either 1000° or 1200°C: the oxidation rate increased dramatically at ZrO2 contents of >20 vol%. The sharp transition in the oxidation rate due to the variation of ZrO2 content could be explained by the percolation theory, when applied to the oxygen diffusivity in a randomly distributed two-phase medium. Morphologically, the composites with ZrO2 contents greater than the critical value showed a large oxidation zone, whereas the composites with ZrO2 contents less than the critical value revealed a much-thinner oxidation zone. The results also indicated that the formation of zircon (ZrSiO4) at 1200°C, through the reaction between ZrO2 and the oxide product, could reduce the oxidation rate of the composite.

Block Copolymer Modified Nanonetwork Epoxy Resin for Superior Energy Dissipation

Abstract: Herein, this work aims to fabricate well-ordered nanonetwork epoxy resin modified with poly(butyl acrylate)-b-poly(methyl methacrylate) (PBA-b-PMMA) block copolymer (BCP) for enhanced energy dissipation using a self-assembled diblock copolymer of polystyrene-b-poly(dimethylsiloxane) (PS-b-PDMS) with gyroid and diamond structures as templates. A systematic study of mechanical properties using nanoindentation of epoxy resin with gyroid- and diamond-structures after modification revealed significant enhancement in energy dissipation, with the values of 0.36 ± 0.02 nJ (gyroid) and 0.43 ± 0.03 nJ (diamond), respectively, when compared to intrinsic epoxy resin (approximately 0.02 ± 0.002 nJ) with brittle characteristics. This enhanced property is attributed to the synergic effect of the deliberate structure with well-ordered nanonetwork texture and the toughening of BCP-based modifiers at the molecular level. In addition to the deliberate structural effect from the nanonetwork texture, the BCP modifier composed of epoxy-philic hard segment and epoxy-phobic soft segment led to dispersed soft-segment domains in the nanonetwork-structured epoxy matrix with superior interfacial strength for the enhancement of applied energy dissipation.

Diamond-structured nanonetwork gold as mechanical metamaterials from bottom-up approach

Abstract: Abstract Herein, this work aims to develop a facile method for the fabrication of metallic mechanical metamaterial with a well-ordered diamond structure from a bottom-up approach using a self-assembled block copolymer for templated electrochemical deposition. By controlling the effective volume fraction of PDMS in PS- b -PDMS via solvent annealing followed by HF etching of PDMS, it is feasible to obtain nanoporous PS with diamond-structured nanochannels and used it as a template for templated electrochemical deposition. Subsequently, well-ordered nanonetwork gold (Au) can be fabricated. As evidenced by nanoindentation and micro-compression tests, the mechanical properties of the diamond-structured Au after removal of PS give the combination of lightweight and mechanically robust characteristics with an exceptionally high reduced elastic modulus of 11.9 ± 0.6 GPa and yield strength of 193 ± 11 MPa above the Hashin-Shtrikman upper bound of 72 MPa with a bending-dominated structure at equivalent density. The corresponding deformation mechanism can be elucidated by morphological observations experimentally and finite element analysis (FEA) numerically. This work demonstrates the bottom-up approach to fabricating metallic monolith with diamond structure in the nanoscale, giving a superior performance as mechanical metamaterials.

Development and application of oxygen permeable membrane in selective oxidation of light alkanes

Abstract: In this paper, oxygen permeable membrane used in membrane reactor for selective oxidation of alkanes will be discussed in detail. The recent developments for the membrane materials will be presented, and the strategy for the selection of the membrane materials will be outlined. The main applications of oxygen permeable membrane in selective oxidation of light alkanes will be summarized, which includes partial oxidation of methane (POM) to syngas and partial oxidation of heptane (POH) to produce H2, oxidative coupling of methane (OCM) to C2, oxidative dehydrogenation of ethane (ODE) to ethylene and oxidative dehydrogenation of propane (ODP) to propylene. Achievements for the membrane material developments and selective oxidation of light alkanes in membrane reactor in our group are highlighted.

Synthesis and structure-property relationships of a new family of layered carbides in Zr-Al(Si)-C and Hf-Al(Si)-C systems

Abstract: The layered ternary and quaternary carbides in Zr-Al(Si)-C and Hf-Al(Si)-C systems with general formulae of ( T C) n Al 3 C 2 , ( T C) n Al 4 C 3 and (TC) n [Al(Si)] 4 C 3 (where T = Zr or Hf, n = 1, 2, 3…) have attracted increasing attentions due to their fascinating properties such as high specific stiffness, high strength and fracture toughness, refractory, machinability by electrical discharge method, thermal shock resistance, as well as high-temperature and ultrahigh-temperature oxidation resistance. The combination of these properties makes them promising as structural components or coatings for high- and ultrahigh-temperature applications. In this review, the progresses on processing, and structure–property relationships of the novel layered carbides are comprehensively outlined. The crystal structure characteristics are introduced first. Then, methods for processing powders and bulk samples are summarized. The third section focuses on the multi-scale structure–property relationships. Finally, the potential applications and further trends in tailoring the properties and developing low cost processing methods are highlighted.

La-Doped BaCoO3 as a Cathode for Intermediate Temperature Solid Oxide Fuel Cells Using a LaGaO3 Base Electrolyte

Abstract: Cathodic behavior of BaCoO 3 doped with La was investigated in this study for an intermediate temperature solid oxide fuel cell (ITFC). Electrical conductivity of BaCoO 3 increased monotonically with an increasing amount of La doped for the Ba site at 1073 K po 2 = 10 5 atm. Cathodic overpotential at 1073 K decreased with increasing La content and attained a minimum at X = 0.3-0.5 in Ba 1-x La x CoO 3 . Since the cathodic overpotential of Ba 0.6 La 0.4 CoO 3 kept a small value at decreased temperature, Ba 0.6 La 0.4 CoO 3 is the optimum composition for the cathode of an ITFC among BaCoO 3 -based oxides When La 0.8 Sr 0.2 Ga 0.8 Mg 0.15 Co 0.05 O 3 was used for the electrolyte, the power density of the cell using Ba 0.6 La 0.4 CoO 3 for the cathode at 1073 K attained a value of 550 mW/cm 2 , which is slightly higher than that using Sm 0.5 Sr 0.5 CoO 3 for the cathode. In addition, a low cathodic overpotential of Ba 0.6 La 0.4 CoO 3 was also maintained in air. 18 O- 16 O exchange reaction was performed to estimate the surface activity for oxygen dissociation. It was found that BaCoO 3 exhibits high activity for the oxygen exchange reaction. Therefore, superior cathode property was assigned to the high surface activity of BaCoO 3 .

Screening of A-Substitution in the System A0.68Sr0.3Fe0.8Co0.2O3 − δ for SOFC Cathodes

Abstract: Several elements were studied as potential A-site substituents in the perovskite A 0.68 Sr 0.3 Fe 0.8 Co 0.2 O 3-δ system. The considered elements included La, Pr, Sm, Nd, Er, Eu, Gd, Dy, and Ba. The multicomponent oxides were prepared following a complexation-polymerization-pyrolysis method. The materials were characterized by X-ray diffraction, thermal dilatometry, and electrical conductivity under different oxidant atmospheres. The obtained materials were studied as solid oxide fuel cell cathodes, preparing porous films on top anode-supported cells with a yttria-stabilized zirconia electrolyte and a CGO protective layer. The complete cell was characterized by direct current voltamperometry using air and wet H 2 as fuel, whereas the porosity of the layer was studied by gas diffusion experiments after electrochemical testing. Oxygen conduction was investigated on gastight membranes prepared for La- and Pr-based materials under flow of air and helium (sweep) in the range from 650 to 1000°C. Pure perovskite structure was not obtained for the cations with the smallest ionic radii. The materials with the best electrochemical performance at 650°C contained Pr, Sm, La, and Ba. The good electrochemical performance seems to be principally related to the intrinsic electrocatalytic properties of the material (perovskite or small clusters of the single oxide) because no clear correlations of the electrochemical performance and ionic conductivity, electronic conductivity, or gas diffusivity could be found. The electrochemical performance at 650°C could be correlated with the catalytic activity for methane oxidation in a fixed bed reactor in the same temperature range. Finally, the catalytic promotion of a Pr-containing perovskite was evaluated by impregnation with Pd.

Interfacial reactions in ceramic membrane reactors for syngas production

Abstract: Ceramic membrane reactors based on Mixed Ionic and Electronic Conductors (MIEC) show great promise for the production of syngas from natural gas. Here, the principles behind this technology are briefly reviewed. By comparing these reactors to solid oxide fuel cells, for which the operating principles are nearly identical, we argue that surface reactions on the membrane frequently limit the performance of these devices. Concepts for increasing surface reaction rates and incorporating catalysts onto the surface are discussed.