Effect of the Heating Rate on the Microstructure and Fracture Toughness of Silicon Nitride Ceramics

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J. Korean Ceram. Soc. > Volume 32(11); 1995 > Article

Journal of the Korean Ceramic Society 1995;32(11): 1227.

소결시의 승온속도가 질화규소 요업체의 미세조직과 파괴인성에 미치는 영향

이상훈, 이재도, 김도연¹

한국화학연구소 무기소재부
¹서울대학교 무기재료공학과

Effect of the Heating Rate on the Microstructure and Fracture Toughness of Silicon Nitride Ceramics

ABSTRACT

Effect of heating rate on the microstructure of the silicon nitride ceramics has been investigated. The specimens with composition of 92Si3N4-6Y2O3-2Al2O3 (in wt%) were sintered at 176$0^{circ}C$ under 127 kPa for 3h in N2 atmosphere at various heating rates from 1 to 10$0^{circ}C$/min. The grain size of larger than 2${mu}{textrm}{m}$ and less than 1${mu}{textrm}{m}$ were measured and compared for the specimens. Regardless of heating rate, grain size of all the specimens showed bimodal distributions and the fracture toughness remained in the range of 5.53~5.72 MPa.m1/2. However, the aspect ratio of the grains of diameter above 2${mu}{textrm}{m}$ increased with the heating rate while their grain size and volume fraction decreased.

Key words: Silicon nitride, Heating rate, Aspect ratio, Volume fraction, Fracture toughness