Microstructural Changes of <TEX>$SiO_2-Si$</TEX> During Liquid-Phase Sintering

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J. Korean Ceram. Soc. > Volume 31(4); 1994 > Article

Journal of the Korean Ceramic Society 1994;31(4): 443.

액상소결단계에서 $SiO_2-Si$의 미세조직 변화

강대갑, 정충환

한국원자력연구소

Microstructural Changes of $SiO_2-Si$ During Liquid-Phase Sintering

ABSTRACT

Compacts of mixed SiO2-Si powder were liquid phase sintered at 145$0^{circ}C$ for up to 60 min in a hydrogen atmosphere. In contrast to the conventional microstructures of liquid phase sintered materials, the specimens showed that the solid phase of SiO2 formed a matrix while the liquid phase of Si was the dispersed in the solid matrix. The dispersion of liquid Si pockets was attributed to the high wetting angle of liquid Si on solid SiO2. Because of relatively high solubility of SiO2 in liquid Si at 145$0^{circ}C$, SiO2 particles accommodated their shape via a solution-reprecipitation process. The liquid Si pockets grew by coalescing with their neighbour pockets. In the latter stage of the sintering, plate-shape grains appeared in the liquid Si pockets. The grains were SiO2 phase precipitated from the liquid Si which was oversaturated with oxygen during cooling to room temperature. By the formation and subsequent removal of the gaseous SiO phase due to the reaction between SiO2 and Si, the specimens became porous.