Pressure-pulsed chemical vapour infiltration of SiC to porous carbon from a gas system SiCl4-CH4-H2

Abstract

SiC matrix was deposited into porous carbon from a gas system SiCl4-CH4-H2 in the temperature range 900–1200 °C using pressure-pulsed chemical vapour infiltration (PCVI) process. At 1000 °C, silicon single phase, a mixed phase of (Si + SiC), and SiC single phase, were detected by X-ray diffractions for specimens obtained with the reaction time per pulse of ∼ 1, 2–3, and ∼ 5 s, respectively. At 1100 °C, SiC single phase was obtained with a reaction time of only 0.3s. Between 1050 and 1075 °C, deposition rate accelerated suddenly. The increase of SiCl4 concentration increased the deposition rate linearly up to 4%–6%. The residual porosity decreased from 29% to 6% after 2×104 pulses of CVI at 1100 °C, and the flexural strength was 110 MPa.