Growth of SiC Whiskers in SiC_f/SiC Composites and Its Effect on Mechanical Properties

摘要

Silicon carbide fiber-reinforced silicon carbide matrix (SiC_f/SiC) composites are considered as advanced materials for control rods and other in-core components of high-temperature gas cooled reactors . In general, two-dimensional woven SiC_f/SiC composites have a significant anisotropy in the transverse and in-plane thermo-mechanical properties. Moreover, the composites produced by the chemical vapor infiltration (CVI) technique contain large pores although the technique produces highly pure SiC matrix. The recently developed 'whisker growing-assisted process,' in which one-dimensional SiC nanostructures with high aspect ratios such as whiskers, nanowires and nanorods are introduced into the fiber preform before the matrix infiltration step, results in composites with a lower porosity and an uniform distribution of pores compared with the conventional CVI. This is expected to increase mechanical and thermal properties of the SiC_f/SiC composites. In order to utilize the full advantage of the whisker growing strategy, however, a homogeneous growth of long whiskers is required. In this study, we applied the chemical vapor deposition at an atmospheric pressure without metallic catalysts for the growth of SiC whiskers within Tyranno-SA fiber preforms. We controlled the concentration of the reactant gas for the homogeneous growth of long whiskers. Mechanical properties of the whiskerized SiC_f/SiC composites were evaluated as well.