ケミカルプロセッシングによるジルコニア含有ムライト複合体の調製

抄録

Chemical processing of mullite/4mol% yttria-zirconia (4Y·ZrO₂) composites was investigated with the surface modification through the hydrolysis of metal alkoxides on the surface of mullite particles.
Mullite particles were coated with yttrium-zirconium hydroxide particles formed by preferential hydrolysis of yttrium and zirconium isopropoxides on the surfaces of mullite particles, which can lead to the preparation of highly homogeneous composite particles of mullite/4Y·ZrO₂. It was clarified from the BET measurement and the TEM observation that original mullite particles were homogeneously coated with zirconia particles.
The mullite/4Y·ZrO₂ composite particles were consolidated by colloidal filtering pressing to give highly homogeneous green compacts, being sintered at 1500°C for 1hr to fully densed bodies with a homogeneous distribution of fine zirconia particles.
The fracture toughness, K_1c, and Vickers hardness, H_V, of mullite/4Y·ZrO₂ sintered bodies were remarkably improved to the values higher than 5.6MPa·m^1/2 and 13.7GPa, compared with those of sintered mullite body, 2.2MPa·m^1/2 and 9.8GPa, respectively. The crack in mullite/10 vol% 4Y·ZrO₂ sintered bodies with zirconia grains of a few micrometer was propagated by the crack deflection to give the relatively high toughness, whereas the cracks in mullite/20vol% 4Y·ZrO₂ with larger zirconia grains of-5μm traversed through several zirconia grains in mullite matrix.