Preparation of high-temperature filter by pressure-pulsed chemical vapour infiltration of SiC into carbonized paper-fibre preforms

Abstract

SiC was partially infiltrated into three types of carbonized paper-fibre preforms using pressure-pulsed chemical vapour infiltration from SiCl4(4%)–CH4(4%)–H2 at 1100 °C (A-type preforms, source fibres of filter paper; BH- and BL-type preforms, source fibres of recycled paper). The porosity of the preforms decreased linearly with the number of pulses. After 10 000 pulses, the porosity of A-, BH- and BL-type samples was 77,78 and 85%, respectively. Average pore sizes of A-, BH- and BL-type samples after 10 000 pulses were about 5.0, 2.7 and 7.0 μm, respectively. On an A-type sample of 10 mm Φ and 5 mm long after 10 000 pulses, pressure drop along the direction of axial air flow was 10 kPa at a face velocity of 0.8 m s−1. The order of pressure drop was BH,>, A >, BL. Flexural strength of A-type sample reached 10 MPa after 15,000 pulses.