Preparation and properties of porous reaction-bonded SiC ceramic using Si3N4 as silicon source

Abstract In the traditional porous reaction-bonded silicon carbide (RBSC) ceramic, the phenomenon of residual silicon usually happens due to the usage of monatomic silicon as reactant, which greatly weakens its high-temperature properties as well as corrosion resistance. In this paper, Si3N4 was successfully utilized as silicon source for the preparation of porous RBSC ceramics. Only SiC phase in the final bulks was detected by X-ray, indicating the achievement of avoiding residual silicon. There were homogeneous and isotropous pores with 48.3% of porosity for as-acquired RBSC ceramic. Its average pore size was ∼1.6μm, while the pore throat size was less than 1μm. Compared with porous oxide-bonded SiC ceramic, porous RBSC ceramic showed superiority in N2 permeability (217 m3/(m2·h·bar)) as well as flexural strength at normal temperature (35.5±2.3 MPa) and high temperature of 1000 oC (21.2±1.7 MPa). Moreover, porous RBSC could keep intact after exposing in boiling solutions of 10wt% H2SO4 and 1wt% NaOH for 12h, indicating its chemical stability in the acid and alkaline environment.