用聚碳硅烷为先驱体制备SiC/Si_3N_4纳米复相陶瓷

STUDY OF SiC/Si_3N_4 NANO COMPOSITES BY USING POLYCARBOSILANE AS PRECURSOR

采用聚碳硅烷（ＰＣＳ）为先驱体，利用原位生长法制备ＳｉＣ／Ｓｉ３Ｎ４ 纳米复相陶瓷，其室温弯曲强度和断裂韧性达到了６３７ ＭＰａ 和８．１０ ＭＰａ·ｍ １／２。研究了材料微观结构的形成及断裂机理，指出在微观结构的形成过程中，控制ＳｉＣ纳米微晶的生成和β－Ｓｉ３Ｎ４ 柱状晶的生长是关键，而增韧补强的主要原因在于形成了晶内型结构和长径比大（大于７．５）的Ｓｉ３Ｎ４ 柱状晶，从而改变了断裂机理。

A cost effective SiC/Si 3N 4 nano composite was obtained by in situ synthesis of precursor, using polycarbosilane as precursor. The results showed that the ambitious flexural strength and fracture toughness of this material had improved. The formation of this composites microstructure and the mechanism of fracture were discussed at the same time.It was important to control the formation of SiC nano crystals and the growth of rod like β Si 3N 4 grain.The formation of the intragranular structure and the rod like β Si 3N 4 grains(aspect ratio more than 7.5) was the reason for the improvement properties.