Synthesis of Si-Al Carbonates from Kaolin and Sintering Characteristics by Reaction Bonding Si3N4

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J. Korean Ceram. Soc. > Volume 28(9); 1991 > Article

Journal of the Korean Ceramic Society 1991;28(9): 667.

카올린으로부터 Si-Al 탄화물의 합성 및 Si$_3$N$_4$ 결합 소결 특성

백용혁, 김영구, 한창, 권양호

전남대학교 무기재료공학과

Synthesis of Si-Al Carbonates from Kaolin and Sintering Characteristics by Reaction Bonding Si3N4

ABSTRACT

In this study, Kaolin was carbonized at 1300~175$0^{circ}C$ and its constituent mineral change was investigated. Carbonized kaolin at 1$650^{circ}C$ was mixed with metallic silicon, formed and nitrified at 135$0^{circ}C$ in N2-NH3 atmosphere. Properties of this product such as porosity, bulk density, MOR, nitrization rate and oxidation resistence were measured, and its mineralogical changes were investigated by XRD. The results were as follows; 1) $beta$-SiC was initially synthesized at 150$0^{circ}C$, and its amount was continuously increased with reaction temperature to 1$700^{circ}C$. 2) At 1$600^{circ}C$, mullite was rapidly decomposed and the amounts of $beta$-SiC and $alpha$-Al2O3 were increased simultaneously. 3) By adding alkali to kaolin, the decomposition temperature of mullite was dropped approximately 10$0^{circ}C$, but the amount of $alpha$-SiC was increased. 4) The highest values of their nitrization rate and MOR were obtained at the specimen of 35 wt% metallic silicon in nitrization reaction. 5) It seems that increment of $alpha$-Si3N4 and $alpha$-Al2O3 phase during nitrization was due to the decomposition of Al4SiC4 existed in carbonized kaolin. 6) Si3N4 bonded SiC-Al2O3 composite were fabricated from kaolin at relatively low temperature (135$0^{circ}C$).