In-situ synthesis mechanism of plate-shaped β-Sialon and its effect on Al2O3-C refractory properties

This study investigated the effect of the sintering temperature on the microstructural evolution and properties of Al2O3-C refractory samples, which were prepared using corundum, flake graphite, reactive alumina, Al and Si powders. The phenolic resin and nanometallic Ni were respectively applied as the binder and catalyst. The results indicate that hexagonal AlN particles, generated from the reaction of Al-N2 in Al2O3 refractories at 1000 °C, could transform into whiskers at 1200 °C. By increasing the sintering temperature to 1400 °C, a large number of plate-shaped β-Sialon could be generated. Under the action of Ni catalyst, the β-Sialon phases in refractories grew preferentially toward the crystalline facets (210) and (011) of AlN crystal and formed the plate-shape structure. When plate-shaped β-Sialon formed, the cold crushing strength (CCS) and cold modulus of rupture (CMOR) increased from 90.57 MPa to 148.67 MPa and from 22.83 MPa to 33.02 MPa, respectively. After two thermal shock cycles, the CCS of the refractories containing the plate-shaped β-Sialon had only decreased by 4.5 MPa. Thus, the in situ formation of plate-shaped β-Sialon could significantly improve the thermal shock resistance of Al2O3-C refractories.