The University of Tokyo · 재료과학
히데히로 요시다 교수의 연구실은 고온 내구성 세라믹스, 특히 산화알루미나 및 첨가제 도핑을 통한 고순도 산화야트륨과 스파이널의 밀도화 및 미세구조 제어를 핵심으로 합니다. 스파크 플라즈마 소결(SPS)과 플래시 소결 기술을 활용해 저온에서 고밀도 다결정 세라믹스를 제조하는 데에 초점을 맞추고 있으며, 특히 입자 경계에서의 이온 분포와 확산 메커니즘을 통해 고온에서의 피로 저항성 향상을 연구하고 있습니다. 이는 고온 구조재 및 광학 소재 응용에 기여합니다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
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
