Fabrication of mullite-bonded porous silicon carbide ceramics by in situ reaction bonding

摘要

An in situ reaction bonding technique was developed to fabricate mullite-bonded porous silicon carbide (SiC) ceramics in air from SiC and alpha-Al_2O_3, using graphite as the pore-former. Graphite is burned out to produce pores and the surface of SiC is oxidized to SiO_2 at high temperature. With further increasing the temperature, the amorphous SiO_2 converts into cristobalite and reacts with alpha-Al_2O_3 to form mullite (3Al_2O_3 centre dot 2SiO_2). SiC particles are bonded by the mullite and oxidation-derived SiO_2 to obtain porous SiC ceramics. The reaction bonding behavior, open porosity, pore size distribution and mechanical strength of porous SiC ceramics were investigated as a function of the sintering temperature, forming pressure and graphite content. In addition, the phase composition and microstructure were also studied.