Characterization of the SiC_f/SiC Composite Fabricated by the Whisker Growing Assisted CVI Process

Abstract

To obtain a dense SiCf/SiC composite by the chemical vapor infiltration (CVI) process, whisker growing before matrix filling was applied, which is called the whisker growing assisted CVI process. The whisker growing and matrix filling processes were carried out using MTS (CH3SiCl3) and H2 as source and diluent gases, respectively. Tyranno-SATM was used as a reinforced substrate. Characterizations of SiC whisker grown during the in situ whisker growing process have been investigated. The weight gain rates with the matrix filling time and the density of composites was measured. The flexural strength with the thickness of the pyrolytic carbon (PyC) interlayers has been evaluated. b-SiC whiskers with many stacking faults were grown well in the Tyranno SATM fabrics. Tyranno-SA/SiC composite with a PyC interlayer thickness of 150 nm had a flexural strength of 610 MPa and the density of 2.71 g/cm3.

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“…However, CVI leaves a typical porosity of 10-15% inside the composite, which leads in particular to a reduction in fatigue and creep-rupture strength. Dense SiC/SiC f composites with a homogeneous microstructure have been recently obtained by applying either a whisker growing process prior to the conventional CVI process [150] or reaction sintering using the sheet stacking hot pressing method [151]. In addition, it was recently demonstrated that the addition of single crystal SiC nano-wires into the SiC matrix is a very efficient reinforcement method for SiC/SiC f composites [152].…”