シリカ-アルミナセラミックスの機械的性質に及ぼす化学組成の影響

概要

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Mechanical properties of SiO_2-Al_2O_3 ceramics were studied in relation to the chemical composition. Raw powders of the composition ranging from 60 to 78 wt% Al_2O_3 were synthesized by the spray pyrolysis method and sintered at 1650℃ for 4 h. The room temperature flexural strength and fracture toughness of the specimens showed no significant difference with the composition ranging from 66 to 78 wt% Al_2O_3. But for the SiO_2-rich specimens containing less than 66 wt% Al_2O_8, those values decreased slightly. For the Al_2O_3-rich specimens which contain no glassy phase, the high-temperature strength and fracture toughness decreased gradually with increasing temperature. In contrast, the strength and the K_<IC> of the specimens containing both mullite and a glassy phases increased with increasing silica content and increasing temperature up to 1300℃. While the flexural strength decreased drastically at 1400℃. The maximum fracture strength at high temperature depends on both chemical composition and the amount of grain boundary glassy phase. The increase in strength and fracture toughness for the SiO_2-rich specimens at high temperatures is explained in terms of stress relaxation and/or crack healing in the grain boundary glassy phase, and pull out of acicular mullite grains due to decrease in viscosity of the glassy phase, respectively.
社団法人日本セラミックス協会の論文
1988-01-01