Effect of ceramic bonding phases on the thermo-mechanical properties of Al 2 O 3 –C refractories

Abstract Ceramic bonding phases of non-oxide whiskers can enhance the hot strength and the thermal shock resistance of Al 2 O 3 –C refractories. In this paper, the effect of different metals on the microstructure and thermo-mechanical properties of Al 2 O 3 –C refractories has been investigated. Thermodynamic calculation of Al–Si–O–C–N systems shows that Al 4 C 3 , AlN, SiC and β-Sialon are stable at elevated temperature. AlN with the shape of short column can be generated in Al 2 O 3 –C refractories with metallic Al, which leads to high hot modulus of rupture (HMOR) and poor resistance to thermal shock. SiC whiskers formed in Al 2 O 3 –C refractories with metallic Si give rise to low HMOR and good resistance to thermal shock. When metallic Si and Al are added together in the refractories, β-Sialon ( z =2) with plane structure can be generated under the action of catalyst (nano-sized Ni). The existence of the catalyst promotes the diffusion of Al and O in Si 3 N 4 crystals and contributes to the generation of plane-shaped β-Sialon. The corresponding HMOR and residual cold modulus of rupture respectively increase to about 20 MPa and 10.3 MPa. The plane-shaped β-Sialon can significantly enhance both hot strength and thermal shock resistance of Al 2 O 3 –C refractories.