Mechanical Properties and Microstructures of Self-toughened Silicon Nitride Cermic Prepared by Microstructural Control

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J. Korean Ceram. Soc. > Volume 36(4); 1999 > Article

Journal of the Korean Ceramic Society 1999;36(4): 432.

미세구조 제어에 의해 제조한 자체 강인화 질화규소 세라믹의 기계적 성질과 미세조직

김완중, 이영규, 조원승¹, 최상욱

인하대학교 무기재료공학과
¹인하대학교 무기재료공학

Mechanical Properties and Microstructures of Self-toughened Silicon Nitride Cermic Prepared by Microstructural Control

ABSTRACT

The self-toughened Si3N4 ceramics where needle-like coarse ${beta}$-Si3N4 grains were dispersed within fine-grain-ed matrix were prepared via hot-prssing at 1730$^{circ}C$ for 2 h using 5 vol% ${beta}$-Si3N4 whiskers as a seed. In this study the microstructures and mechanical properties of self-toughened Si3N4 ceramics were investigated. The flexural strength of self-toughened Si3N4 ceramics was increased from 600-800 MPa of the Si3N4 monolith to 830-1025 MPa. The KIC was also increased from 4.0-5.0MPa$.$m1/2 of the Si3N4 monolith to 5.8-6.5MPa$.$m1/2$.$The needle-like coarse Si3N4 grains in self-toughened ceramics were considered to induce various toughening mechanisms including the crack deflection pull-out and bridging and to contribute to KIC improvement. In ad-dition to toughening mechanisms the KIC improvement was considered to be partially indebted also to the orien-tation of large ${beta}$-Si3N4 grains and to the promoting effect of ${beta}$-Si3N4 whiskers on the ${alpha}$ to ${beta}$ transtion.

Key words: Self-toughned silicon nitrde, Microstructure, Strength, Fracture toughness