The Experts below are selected from a list of 15828 Experts worldwide ranked by ideXlab platform
Feng Wang - One of the best experts on this subject based on the ideXlab platform.
-
porous sic ceramics fabricated by quick freeze casting and solid State Sintering
Progress in Natural Science: Materials International, 2017Co-Authors: Feng Wang, Jinwei Yin, Dongxu Yao, Yongfeng Xia, Kaihui Zuo, Yuping ZengAbstract:Abstract Porous SiC ceramics with uniform microstructure were fabricated by quick freezing in liquid nitrogen and solid State Sintering. Poly (vinyl alcohol) (PVA) was added as binder and pore morphology controller in this work. The microstructure and mechanical properties of porous SiC ceramics could be controlled by the composition of the aqueous slurries. Both solid content of the slurries and PVA content impacted on the pore structures and mechanical properties of the porous SiC ceramics. The solid content of slurries and PVA content varied from 60 to 67.5 wt% and 2–6 wt%, respectively. Besides, the grain morphology of ceramics was also tailored by changing the Sintering temperature from 2050 to 2150 °C. Porous SiC ceramics with an average porosity of 42.72%, flexural strength of 59.28 MPa were obtained at 2150 °C from 67.5 wt% slurries with 2 wt% PVA.
-
porous sic ceramics prepared via freeze casting and solid State Sintering
Ceramics International, 2016Co-Authors: Feng Wang, Dongxu Yao, Yongfeng Xia, Kaihui Zuo, Yuping ZengAbstract:Abstract Porous SiC ceramics were prepared by freeze-casting process. In order to enhance the mechanical properties of the porous SiC, poly(vinyl alcohol) (PVA) was added as binder and pore morphology controller in this work. The results indicated that high porosity (>60%) SiC ceramics was obtained although the Sintering temperature was over 2000 °C. The pore structure could be divided into two kinds: macropores generated by sublimation of large ice crystals, and micropores in the ceramic matrix caused by sublimating of small ice crystals, stacking of SiC particles, and burning out of PVA. With the increase of the Sintering temperature, the specimens exhibited higher density, thus resulted in higher strength. Porous SiC ceramics sintered at 2100 °C showed a good flexural strength of 11.25 MPa with an open porosity as high as 66.46%.
-
fabrication of porous sic ceramics through a modified gelcasting and solid State Sintering
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: Feng Wang, Jinwei Yin, Dongxu Yao, Yongfeng Xia, Kaihui Zuo, Yuping ZengAbstract:Abstract With starch as pore forming agent, porous silicon carbide (SiC) ceramics were successfully fabricated by gelcasting. A novel and simple gelling system of isobutylene and maleic anhydride (Isobam) can gel in air at room temperature was used. The rheological behaviors of SiC slurries were investigated as a function of starch content. The gelled SiC green bodies were sintered at 2050–2150 °C through solid State Sintering with B 4 C and carbon as Sintering additives. Porosity of the porous SiC ceramics sintered at 2100 °C was well controlled from 34.20% to 42.68% with the starch content increasing from 0 to 20 wt%. With increasing the Sintering temperature from 2050 to 2150 °C, flexural strength and porosity of porous SiC ceramics with 20 wt% starch varied from 61.0 to 128.0 MPa and 48.1% to 34.2%, respectively. The porous SiC ceramics fabricated with 20 wt% starch addition and sintered at 2100 °C were proved to possess excellent thermal shock resistance. The ceramics after water-quenching at 1500 °C showed an average flexural strength of 95.8 MPa, which was higher than the strength of samples without quenching.
Yuping Zeng - One of the best experts on this subject based on the ideXlab platform.
-
porous sic ceramics fabricated by quick freeze casting and solid State Sintering
Progress in Natural Science: Materials International, 2017Co-Authors: Feng Wang, Jinwei Yin, Dongxu Yao, Yongfeng Xia, Kaihui Zuo, Yuping ZengAbstract:Abstract Porous SiC ceramics with uniform microstructure were fabricated by quick freezing in liquid nitrogen and solid State Sintering. Poly (vinyl alcohol) (PVA) was added as binder and pore morphology controller in this work. The microstructure and mechanical properties of porous SiC ceramics could be controlled by the composition of the aqueous slurries. Both solid content of the slurries and PVA content impacted on the pore structures and mechanical properties of the porous SiC ceramics. The solid content of slurries and PVA content varied from 60 to 67.5 wt% and 2–6 wt%, respectively. Besides, the grain morphology of ceramics was also tailored by changing the Sintering temperature from 2050 to 2150 °C. Porous SiC ceramics with an average porosity of 42.72%, flexural strength of 59.28 MPa were obtained at 2150 °C from 67.5 wt% slurries with 2 wt% PVA.
-
porous sic ceramics prepared via freeze casting and solid State Sintering
Ceramics International, 2016Co-Authors: Feng Wang, Dongxu Yao, Yongfeng Xia, Kaihui Zuo, Yuping ZengAbstract:Abstract Porous SiC ceramics were prepared by freeze-casting process. In order to enhance the mechanical properties of the porous SiC, poly(vinyl alcohol) (PVA) was added as binder and pore morphology controller in this work. The results indicated that high porosity (>60%) SiC ceramics was obtained although the Sintering temperature was over 2000 °C. The pore structure could be divided into two kinds: macropores generated by sublimation of large ice crystals, and micropores in the ceramic matrix caused by sublimating of small ice crystals, stacking of SiC particles, and burning out of PVA. With the increase of the Sintering temperature, the specimens exhibited higher density, thus resulted in higher strength. Porous SiC ceramics sintered at 2100 °C showed a good flexural strength of 11.25 MPa with an open porosity as high as 66.46%.
-
fabrication of porous sic ceramics through a modified gelcasting and solid State Sintering
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: Feng Wang, Jinwei Yin, Dongxu Yao, Yongfeng Xia, Kaihui Zuo, Yuping ZengAbstract:Abstract With starch as pore forming agent, porous silicon carbide (SiC) ceramics were successfully fabricated by gelcasting. A novel and simple gelling system of isobutylene and maleic anhydride (Isobam) can gel in air at room temperature was used. The rheological behaviors of SiC slurries were investigated as a function of starch content. The gelled SiC green bodies were sintered at 2050–2150 °C through solid State Sintering with B 4 C and carbon as Sintering additives. Porosity of the porous SiC ceramics sintered at 2100 °C was well controlled from 34.20% to 42.68% with the starch content increasing from 0 to 20 wt%. With increasing the Sintering temperature from 2050 to 2150 °C, flexural strength and porosity of porous SiC ceramics with 20 wt% starch varied from 61.0 to 128.0 MPa and 48.1% to 34.2%, respectively. The porous SiC ceramics fabricated with 20 wt% starch addition and sintered at 2100 °C were proved to possess excellent thermal shock resistance. The ceramics after water-quenching at 1500 °C showed an average flexural strength of 95.8 MPa, which was higher than the strength of samples without quenching.
Jianqiang Wang - One of the best experts on this subject based on the ideXlab platform.
-
Fabrication of Lanthanum Strontium Manganite Ceramics via Agar Gel Casting and Solid State Sintering
Materials, 2019Co-Authors: Shiyu Zhang, Cheng Peng, Chengzhi Guan, Guoping Xiao, Jianqiang WangAbstract:Fabricating lanthanum strontium manganite (LSM) ceramics with certain shapes is important for the design and construction of high-temperature energy conversion and storage devices. Here, we describe a low-cost and environmentally friendly method for fabricating LSM ceramics via agar gel casting and high temperature Sintering. This new approach uses temperature tuning to fabricate LSM gel bodies, not only by manufacturing in the secondary process but also by remolding and recycling during the gel casting process. The effect of the Sintering temperature on the properties of LSM ceramics was investigated as well. As a result, the porosity and compressive strength of LSM ceramics sintered at 1000 °C are ~60% and 5.6 MPa, respectively. When the Sintering temperature increases to 1200 °C, the porosity decreases to ~28%, whereas the compressive strength increases to 25 MPa, which is able to meet the requirement of cathode-supported SOFCs (solid oxide fuel cells).
-
Fabrication of Lanthanum Strontium Manganite Ceramics via Agar Gel Casting and Solid State Sintering
MDPI AG, 2019Co-Authors: Shiyu Zhang, Cheng Peng, Chengzhi Guan, Guoping Xiao, Jianqiang WangAbstract:Fabricating lanthanum strontium manganite (LSM) ceramics with certain shapes is important for the design and construction of high-temperature energy conversion and storage devices. Here, we describe a low-cost and environmentally friendly method for fabricating LSM ceramics via agar gel casting and high temperature Sintering. This new approach uses temperature tuning to fabricate LSM gel bodies, not only by manufacturing in the secondary process but also by remolding and recycling during the gel casting process. The effect of the Sintering temperature on the properties of LSM ceramics was investigated as well. As a result, the porosity and compressive strength of LSM ceramics sintered at 1000 °C are ~60% and 5.6 MPa, respectively. When the Sintering temperature increases to 1200 °C, the porosity decreases to ~28%, whereas the compressive strength increases to 25 MPa, which is able to meet the requirement of cathode-supported SOFCs (solid oxide fuel cells)
Eugene A. Olevsky - One of the best experts on this subject based on the ideXlab platform.
-
numerical simulation of solid State Sintering
International Journal of Solids and Structures, 2005Co-Authors: Michael V Braginsky, Veena Tikare, Eugene A. OlevskyAbstract:Abstract This paper discusses in detail the development of a numerical model capable of simulating microstructural evolution and macroscopic deformation during Sintering of complex powder compacts. The model based on the kinetic Monte Carlo (Potts) approach simulates grain growth, vacancy diffusion, and pore annihilation at grain boundaries, which is responsible for densification. Results of 2D simulations for perfect close-packed and random starting configurations are presented and discussed. The microstructural evolution is used to obtain the Sintering stress––the macroscopic stress that is equivalent to the microstructural driving force for deformation.
-
Effective diffusion coefficients in solid-State Sintering
Acta Materialia, 2004Co-Authors: Andrey L. Maximenko, Eugene A. OlevskyAbstract:A numerical analysis of the Sintering neck growth rate between rigid spherical particles of the same size is carried out. The contributions of the surface, grain-boundary and volume diffusion transport into Sintering kinetics during the first and the second stages of Sintering are estimated. It is shown that the three-dimensional problem of the matter redistribution during Sintering can be reduced to a two-dimensional problem if the effective diffusion coefficients are introduced. The effective diffusion coefficients are the grain-boundary diffusion coefficients that include the contribution of volume diffusion. The effective diffusion coefficients are sensitive to the stage of Sintering: they have different form during the first and the second stages. During the second stage of Sintering, the unified effective diffusion coefficient is determined. It is demonstrated that the effective diffusion coefficients can be used also for the description of the pressure-assisted Sintering.
-
numerical simulation of solid State Sintering i Sintering of three particles
Journal of the American Ceramic Society, 2003Co-Authors: Veena Tikare, Michael V Braginsky, Eugene A. OlevskyAbstract:A kinetic, Monte Carlo model, capable of simulating microstructural evolution Sintering in a two-dimensional system of three particles, has been presented. The model can simulate several mechanisms simultaneously. It can simulate curvature-driven grain growth, pore migration and coarsening by surface diffusion, and densification by diffusion of vacancies to grain boundaries and annihilation of these vacancies. Morphologic changes and densification kinetics are used to verify the model.
Jianlin Shi - One of the best experts on this subject based on the ideXlab platform.
-
relation between grain growth densification and surface diffusion in solid State Sintering a direct observation
Journal of Materials Science, 2005Co-Authors: Jianlin Shi, Yoichi Deguchi, Yukio SakabeAbstract:A direct observation of the grain growth and densification of BaTiO3 ceramics were made in a TEM equipped with an in-situ installed heating platform. Both real two-sphere and three-sphere models for BaTiO3 ceramics were found and parallel processes of the shrinkage between particles and the grain growth (coarsening) were observed during the heating process. Attempts of relating the grain growth and densification was made which reveals, though roughly, the close relation between the two competing process: they took place simultaneously and in parallel, therefore it is believed that the process took place via the same mass transport mechanism. Surface diffusion on the TiO2 particle surface was observed directly, which takes place with the co-motion of several lattice layers from a smaller grain onto the surface of an adjacent larger one. The surface diffusion was accompanied by the diminishing of a small grain, i.e., overall grain growth.
-
thermodynamics and densification kinetics in solid State Sintering of ceramics
Journal of Materials Research, 1999Co-Authors: Jianlin ShiAbstract:Based on the stability analysis of the closed pores in two dimensions which was determined mathematically with their particle coordination number and dihedral angle, the stability of those in three dimensions was determined with a spherical pore model. The model is set up by first excluding the effect of interface tension, so the pore was supposed to be spherical, and then the tensile stress arisen from the interface tension was supposed to act on this hypothesized spherical pore. On the basis of the spherical pore model, microstructure models based on pores, not grains, for the real powder compacts were first established. Densification kinetics were then determined from the models by the densification rate equations, which were derived by relating density to pore size to grain size ratio, for the intermediate and final stages of Sintering. The criteria for pore shrinkage were discussed quantitatively. The derived equations can be used to simulate the relation between densification rate and density during heating with a constant rate and for the explanation of the effects of pore size distribution, agglomerates, and green density on Sintering.
-
relations between coarsening and densification and mass transport path in solid State Sintering of ceramics model analysis
Journal of Materials Research, 1999Co-Authors: Jianlin ShiAbstract:The correlations between coarsening (including grain and pore growth) and densification, and the effects of mass transport on particle coarsening and densification were discussed based on the simple particle array models and for the real particle compacts. Grain boundary motion could cause particle coarsening only under a certain particle size distribution but not densification; mass transport is reasoned to contribute to both grain growth (particle coarsening) and shrinkage for one-dimensional particle arrays. Under a certain limitation for the change of the particle size aspect ratio during Sintering, very limited effects of grain grown by itself on the shrinkage of particle a rrays throughreinitiating the Sintering could be found. For a real powder compact system, mass transport between the particles, which surround a pore, contributes to the particle coarsening and densification when the pore is thermodynamically unstable and only to particle coarsening when the pore is thermodynamically stable. The mass transport mechanism for both particle coarsening and densification would be the same, which cannot exclude, at least on thermodynamics, the contribution from surface diffusion in the intermediate stage of Sintering.
-
relation between coarsening and densification in solid State Sintering of ceramics experimental test on superfine zirconia powder compacts
Journal of Materials Research, 1999Co-Authors: Jianlin ShiAbstract:Coarsening (including grain growth and pore growth) and densification behavior of superfine Y-TZP and YSZ powder compacts in the intermediate stage were investigated. It has been found that grain growth in the compacts is basically not affected by the compaction properties, and pore growth is driven by both grain growth and densification. Grain growth alone leads to size-proportional pore growth, and densification results in pore shrinkage. The relation between grain size and density is analyzed to be linear when grain growth and densification are believed to be driven by different stresses under an identical diffusion process. Both theoretical and experimental results show that compaction properties and the heating rate do not alter this linear relation between grain size and density but influence the slope of the linear relation. Larger dihedral angle, higher green density, and narrower particle and pore size distributions are found favorable for the achievement of the grain size-density trajectory with promoted densification and minimized grain growth.
