東京大学 · 材料科学
Hidehiro Yoshida教授の研究室では、酸化物セラミックスの高致密化と高温特性の向上を目的とした粉体工学的・プロセス工学的アプローチが展開されています。特に、スパークプラズマ焼結（SPS）やフラッシュ焼結を用いた低・中温焼結技術の開発が中心であり、Y₂O₃やAl₂O₃、MgAl₂SiO₄スピンエルなどの酸化物セラミックスのナノ構造制御と界面化学の理解が進んでいます。また、ドーピングによる界面拡散の抑制と高温強度向上のメカニズム解明にも注力しています。
Figures are computed from collected data and may differ slightly.
Abstract The sintering behavior of commercially available MgAl 2 O 4 spinel was investigated under DC electric field in a range of 0 and 1000 V/cm. Flash‐sintering results in densification close to theoretical density at 1410°C under the DC field of 1000 V/cm, in comparison to the higher sintering temperature of 1650°C in case of conventional sintering. It was observed that the fields less than 750 V/cm had no significant effect on the densification behavior. An abrupt increase in power dissipat
The high-temperature creep resistance in Al2 O3 is improved greatly by ZrO doping. Zirconium ions are found to be segregated in Al O grain boundaries. The activation energies for creep in high-purity Al2 O3 and ZrO-doped Al O are - estimated to be 430 and 650 kJ mol1, respectively. The grain boundary diffusivity of Al ions is expected to be reduced by the segregation of Zr4+ in the grain boundaries.
The sinterability of high‐purity, nanocrystalline Y 2 O 3 without any additives was investigated by spark plasma sintering (SPS) for a combination of low sintering temperatures (850°–1050°C) and low heating rates (2–50°C/min). At a sintering temperature of 950°C and a heating rate of 2°C/min, the SPS yielded a polycrystalline Y 2 O 3 having a relative density of 99% and an average grain size of 190 nm. The Y 2 O 3 bodies sintered at 950° and 1050°C for 1h at the heating rate of 2°C/min exhibited
High-temperature creep resistance in polycrystalline Al2O3 with 0.05 mol% lanthanoid oxides of Y, Sm, Eu, Tm or Lu has been examined by uniaxial compression creep testing at 1250oC. The creep resistance is improved by the doping, and the dopant effect is dependent on the type of lanthanoid; the effect is in the order Sm < Tm < Eu < Y < Lu. Each dopant cation was found to segregate in grain boundaries and is likely to suppress grain-boundary diffusion. The change in chemical bonding state with do
We investigated the densification of undoped, nanocrystalline yttria (Y 2 O 3 ) powder by spark plasma sintering (SPS) at sintering temperatures between 650°C and 1050°C at a heating rate of 10°C/min and an applied stress of 83 MPa. In spite of the low sinterability of the undoped Y 2 O 3 , a remarkable densification of the powder started at about 600°C, and a theoretical density of more than 97% was achieved at a sintering temperature of 850°C with a grain size of about 500 nm. The low temperat
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