A Reaction Engineering Study on SiC Whisker Growth Control by High Temperature Masking of Substrate Surface

为了开发低成本的碳化硅晶须的批量生产工艺，提出了一种新的工艺概念，在此基础上，总结了以往的知识并系统地应用于厚晶须的选择性生长。本工作采用了基础数据进行开发。本实验采用垂直管式反应器，安装有连续给料器、连续SiO气体散热器（1400-1600 C）和SiO晶须生长段（1400-1600 C），其中植入催化剂颗粒。考察了催化剂的组成、气体流量、SiO生成速率和生长方向与重力的关系。当SiO_2/C复合颗粒和CH_4+Ar气体分别以0.0258/min和400 ml/min的速度进料时，成功地保持了直径为50 gm的催化剂液滴。10小时后得到线状须，粗25微米，长10微米。然而，例如，将37个催化剂滴放在衬底上生长的晶须中，大多数都有缺陷和弯曲。为了解决这些问题，收集了有关操作因素的基本数据。从产品的SCM照片中得到以下信息：(1)通过催化剂滴剂的预饱和可以缩短晶须生长的诱导期，防止催化剂的蒸发损失和二次成核；(2) SiO浓度的增加和气体流速的降低提高了晶须的生长速度；(3)重力的影响不太显著。虽然控制扭结形成的因素还不清楚，但已经证实，在目前连续的情况下，饱和催化剂可以在衬底SiO辐射体系上产生厚而长的SiC晶须

For the development of a low cost mass production process of SiC whiskers a new process concept was developed, where previous knowledge was summarized and systematically applied for the selective growth of thick whiskers. In this work fundamental data were taken for the development. In the present experiment constructed was a vertical tube reactor mounted with a continuous feeder, a continuous SiO gas radiator(1400ﾟC)and a SiO whisker growth section(1400-1600ﾟC)in which the substrates with implanted catalyst particles were placed. The composition of catalysts, gas flow rate, SiO generation rate and growth direction in relation with the gravity were investigated. Successful holding of a catalyst drop of 50 gm in diameter was established when SiO_2/C Composite particles and CH_4+Ar gas were fed in a rate of 0.0258/min and 400 ml/min, respectively. After 10 hours obtained was a linear whisker of 25mum thick and lOOmum long. However, for instance, most of the whiskers grown from 37 catalysts drops placed on a substrate had defects and kinks. To cope with such problems fundamental data were collected regarding operating factors. From SCM photographs of the products the following information was obtained :(1)By the presaturation of catalyst drops the induction period of whisker growth can be shortened and both evaporation loss of catalyst and secondary nucleation can be prevented ; (2)Increased SiO concentration and decreased gas flow rate improve the whisker growth rate ; and(3)The effect of gravity is not very significant. Although the very factor that controls the kink formation has not yet made clear, it was confirmed that thick and long SiC whiskers can be raised on the substrate SiO radiation system from the presaturated catalyst with the present continuous