不同粒径碳化硅粉体的复合烧结与表征

以氮化硅为烧结助剂，聚乙烯吡咯烷酮（PVP）为黏结剂，通过重结晶烧结法制备了纯碳化硅（SiC）陶瓷。采用X射线衍射、扫描电子显微镜和阿基米德定律对产物的结构、形貌和相对密度进行了表征，主要研究了SiC细粉的质量分数对SiC晶粒形貌的影响。结果表明，SiC细粉质量分数的变化对烧结样品的晶粒尺寸与形貌及其相对密度有较大影响。细粉质量分数由0%增加至60%，SiC晶粒的形貌由等轴状晶粒过渡为六方片状晶粒，晶粒尺寸非线性增加，样品的相对密度则呈先增加后降低的趋势，当细粉的质量分数为40%时，SiC陶瓷的相对密度最高。因SiC高温（2 000 ℃以上）蒸发与凝聚的烧结作用，当SiC细粉的质量分数为60%时，重结晶普遍发生，且SiC粗粉晶粒尺寸急剧增大，形成六方片状。

Composite Sintering and Characterization of SiC Powders with Different Particle Sizes

Pure silicon carbide （SiC） ceramics were prepared through recrystallization sintering by using silicon nitride as a sintering additive and polyvinyl pyrrolidone（PVP） as a binder. X-ray diffraction，scanning electron microscopy and Archimede’s law were used to characterize the structure，morphology and relative density of the SiC ceramics. The effect of the mass fraction of the fine SiC powder on the morphology of SiC grains was investigated. The results demonstrate that the mass fraction of the fine SiC powder greatly affects the sizes and morphology as well as the relative density of the final grains of SiC ceramics. With the mass fraction of the fine SiC powder increasing from 0% to 60%，the morphologies of the SiC grains change from equiaxed crystal to hexagonal plate crystal，and the grain size increases nonlinearly. The relative density of the SiC ceramics increases first and then decreases，and it reaches the highest value when the mass fraction of the fine powder is 40%. When the mass fraction of the fine SiC powder is 60%，due to the effect of evaporation and condensation of SiC at high temperatures （above 2 000 ℃），recrystallization commonly happens and the grain size increases sharply，the grains finally grow into hexagonal plate crystal.