In-situ reaction bonding to obtain porous SiC membrane supports with excellent mechanical and permeable performance

Abstract

In order to develop filter material that can be used for high-temperature gas cleaning, porous SiC ceramic membrane support was fabricated by in situ reaction bonding. Pressureless sintering was carried out in the temperature range of 1280–1480 °C in air. Green bodies were formed by uniaxially pressing coarse SiC particles (150–180 μm) as a skeleton, fine SiC particles and ρ-Al2O3 powder as bonding additives, basic magnesium carbonate as sintering aid and polyvinyl alcohol (PVA) as binder. Effects of sintering temperature and ρ-Al2O3 content on mechanical performance and physical properties of porous SiC ceramics were systematically investigated. Results revealed that interconnected pores of support were mainly formed due to the packing of SiC coarse particles. Mullite (3Al2O3·2SiO2) was formed due to in-situ reaction between cristobalite obtained by SiC surface oxidation and α-Al2O3 converted from ρ-Al2O3 at higher temperatures. SiC particles were strongly bonded by mullite and oxidation-derived SiO2, which resulted in highly porous SiC membrane support with excellent mechanical properties. Open porosity of samples decreased with an increase in sintering temperature and ρ-Al2O3 content. In addition, flexural strength initially increased up to threshold limit, followed by gradual decrease. The sample with 9 wt. % ρ-Al2O3 exhibited the highest flexural strength after sintering at 1430 °C for 3 h. As-prepared SiC support with 9 wt. % ρ-Al2O3 demonstrated flexural strength of 25.1 MPa and air permeability of 4.8 × 10−12 m2. Moreover, as-prepared support exhibited excellent resistance to cyclic thermal shock, which indicates that these supports can be used for high-temperature flue gas cleaning under normal pressure.