β-Si_3N_4纤维及柱晶的制取

Fabrication of β-Si_3N_4 Fibers and Columan Cystals

采用燃烧合成工艺，制取了细长的β-Si3N4纤维·纤维顶端有小球，小球中含Si，Al成分，纤维有扭曲、拧结现象．VLS机制是控制纤维生长的主要机制．晶体顶端有螺旋生长蜷线．燃烧合成的β-Si3N4为六方柱晶，表面无缺陷。柱晶主要通过VC机制生长。β-Si3N4柱晶是从微晶β-Si3N4中长出的，其生长具有晶格继承性．异相添加剂和少量杂质Al的引入有利于形成较长的柱晶和纤维。控制原始反应物中的添加剂含量，保持较高的燃烧温度，是制取β-Si3N4纤维的关键。

β-Si3N4 fibers were fabricated through combustion synthesis (CS) process.Droplets composed of Si and Al at the tip of fibers were found. It is concluded that the growth of β-Si3N4 fibers is controled mainly by VLS mechanism. Hexagonal colummna single crystal β-Si3N4 with smooth surface and without any default was also found in the conbustion process of silicon powder. VC process is the controled mechanism for the growth of colummna single crystal β-Si3N4.