Substrate effect on the preparation of silicon carbide whiskers by chemical vapor deposition

Chemical vapor deposition of silicon carbide whiskers activated by a metal impurity was studied using a gas mixture of methyltrichlorosilane and H-2 on both Ni-coated graphite and Ni foil substrates. The as-grown whiskers were characterized by scanning electron microscopy and their nucleation and growth behaviors were determined. It is found that the melting behavior of Ni coating on a graphite substrate differs from that of a Ni foil, which in turn affects the nucleation of SiC whiskers on the respective substrates. SIC whiskers can be successfully prepared on both substrates by the VLS mechanism, but the growth behavior and the quality of whiskers prepared is determined by the way and characteristics of the metal catalyst provided. With an appropriate choice of the type of catalyst and processing parameters, the bulk form catalyst can also be effective in activating the VLS growth of SIC whiskers; therefore, the necessity for a catalyst-layering step in conventional processes can be avoided.