Effect of Y2O3 addition on the properties of reaction-bonded porous SiC ceramics

Porous SiC ceramics were fabricated without and with Y2O3 addition from SiC, Al2O3 and graphite in air by the in situ reaction bonding process. This process is based on the oxidation of SiC and the mullitization between Al2O3 and oxidation-derived SiO2. SiC particles are bonded by the mullite (3Al2O3·2SiO2) and SiO2. The pores are produced by both stacking SiC particles and burning out graphite. Comparison of phase composition, microstructure, flexural strength, open porosity and pore size distribution of reaction-bonded porous SiC ceramics without and with Y2O3 addition was conducted. Moreover, the effect of Y2O3 content was investigated. Due to the enhancement of neck formation (bonding part between SiC particles) by the addition of Y2O3, a high strength of 27.5 MPa was achieved at an open porosity of 44.4%.