Directional Effect of Applied Pressure during the Sintering on the Microstructures and Fracture Toughness of Heat-treated Silicon Nitride Ceramics

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J. Korean Ceram. Soc. > Volume 32(6); 1995 > Article

Journal of the Korean Ceramic Society 1995;32(6): 653.

소결시의 가압방식이 열처리 후 질화규소의 미세조직과 파괴인성에 미치는 영향

이상훈, 박희동, 이재도

한국화학연구소 무기소재연구부

Directional Effect of Applied Pressure during the Sintering on the Microstructures and Fracture Toughness of Heat-treated Silicon Nitride Ceramics

ABSTRACT

Directional effect of applied pressure during sintering on the microstructure and fracture toughness of the heat-treated silicon nitride ceramics has been investigated. The specimens with a composition of 92Si3N4-8Y2O3(in wt%) were sintered at 172$0^{circ}C$ by a hot press (HP ) and a hot isostatic press (HIP) and heat-treated for grain growth at 1800~20$0^{circ}C$. The fracture toughness of the HP samples increased with the grain size while the fracture toughness of the HIP treated samples remained the same even though the grain growth occurred. This discrepancy was explained by a bimodal grain size distribution and large aspect ratio of the HPed samples and a monomodal grain size distributjion and samll aspect ratio of the HIP treated samples.

Key words: Silicon nitride, Fracture toughness, Directionality, Bimodal grain size distribution, Aspect ratio