纯B_4C和掺碳B_4C的烧结机制

SINTERING MECHANISM OF PURE AND CARBON-DOPED BORON CARBIDE

研究了中位粒径为 0 .42 μm的纯B4C和掺碳B4C粉末的烧结致密化过程 .根据烧结温度和保温时间对线收缩率的影响 ,得出了它们的烧结动力学方程 ;由特征指数n值对比研究了它们的烧结致密化机制 .纯B4C的烧结致密化机制为体扩散和晶界扩散 ,而掺碳B4C的烧结机制主要为晶界扩散 ,因此 ,掺碳对B4C起到了活化烧结的作用 .在 2 160℃烧结 45min ,掺碳B4C烧结后相对密度大于 90 % .掺入的碳除了固溶于B4C晶格中之外 ,其它均以游离石墨形式存在 ,不形成新相 .掺碳还导致B4C晶粒尺寸大大减小 .

Sintering densification processes of pure and carbon-doped boron carbide powders with 0.42 μm median particle size were studied. Their sintering kinetic equations were obtained according to the influence of sintering temperature and holding time on the linear shrinkage rate. The sintering mechanisms were investigated by comparing the characteristic exponent n. It is deduced that the main sintering mechanisms will be volume diffusion and grain boundary diffusion for pure boron carbide and grain boundary diffusion for carbon-doped boron carbide showing activated sintering. The relative density of the carbon-doped B4C sintered at 2160°C for 45 min is more than 90%. Apart from those dissolved in the sintered boron carbide, the rest of the added carbon is in the form of free carbon, and no new phase is formed. Carbon-doping also results in a great decrease of B4C grain size.