高纯硅粉氮化和普通硅粉氮化过程具有明显差别,在相同氮化时间,高纯硅粉氮化率明显低于普通硅粉;高纯硅粉氮化具有明显阶段性特征,可分为反应形核期、快速氮化期,速率减缓期和缓慢氮化期,而普通硅粉氮化的阶段性并不明显;高纯硅粉氮化前期产物以α-Si3N4相为主,在氮化后期,前期生成的氮化硅阻隔了氮气和硅粉直接接触,氮化明显变慢,产物主要为β-Si3N4,晶粒生长主要发生在基面上,而柱面生长缓慢,晶粒呈长径比较大的细长棒状.普通硅粉氮化时氮化硅晶粒生长不仅发生在基面,同时也发生在柱面上,前期生成的氮化硅并不能阻隔氮气和硅粉直接接触,其产物始终以α-Si3N4相为主,氮化硅颗粒的形状从短柱状至长柱状都有分布,柱面和基面同时生长是氮化较快的主要原因.%The nitridation course of high-pure silicon powder is obviously different from normal silicon powder, the nitridation ratio of high pure silicon powder is far smaller than normal silicon powder during same nitridation time. The nitridation of high-pure silicon powder shows obvious periodical features, including reaction nucleation stage, rapid nitridation stage, slowing down stage of nitridation and slowing nitridation stage, the periodical feature is not obvious for normal silicon powder. At prophase, the major product of high-pure silicon powder nitridation was α-phase, at later stage, because the Si3N4formed at prophase would separate the contact between silicon powder and the nitrogen gas, the reaction slows down obviously, the product wasβ- Si3N4, the grain growth occurs on the base plane mainly, the growth on the cylinder planes was much slower, the grain is rod-like with bigger aspect ratio. For normal silicon powder, the growth of Si3N4grain not only occurs on base planes, but also on cylinder planes, so the Si3N4formed at prophase would not separate the contact between silicon powder and the nitrogen gas, the product contain much more α- Si3N4, the grain shape distributes from shot rod to long rod, and it is also the reason of nitridation more fast.
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