Rapid Chemical Vapor Infiltration of Silicon Carbide Minicomposites at Atmospheric Pressure

Abstract

The chemical vapor infiltration technique is one of the most popular for the fabrication of the matrix portion of a ceramic matrix composite. This work focuses on tailoring an atmospheric pressure deposition of silicon carbide onto carbon fiber tows using the methyltrichlorosilane (CH₃SiCl₃) and H₂ deposition system at atmospheric pressure to create minicomposites faster than low pressure systems. Adjustment of the flow rate of H₂ bubbled through CH₃SiCl₃ will improve the uniformity of the deposition as well as infiltrate the substrate more completely as the flow rate is decreased. Low pressure depositions conducted at 50 Torr deposit SiC at a rate of approximately 200 nm*h^-1, while the atmospheric pressure system presented has a deposition rate ranging from 750 nm*h^-1 to 3.88 μm*h^-1. The minicomposites fabricated in this study had approximate total porosities of 3 and 6% for 10 and 25 SCCM infiltrations, respectively.