QIAO Ruiqing, BAI Xingliang, WANG Chao, XIAO Li
(School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110023, Liaoning, China)
Abstract: 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 Si3N4 formed 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 Si3N4 grain not only occurs on base planes, but also on cylinder planes, so the Si3N4 formed 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.
Key words: high-pure silicon powder, normal silicon powder, sold phase, periodical features