A novel strategy for the fabrication of AlN–AlON refractories: Nitrogen gas pressure sintering of Al4O4C

A novel strategy was exploited for the fabrication of AlN–AlON refractories via nitrogen gas pressure sintering of Al4O4C. The phase transformation and microstructure evolution during the reaction at 1600–1800°C were thoroughly investigated. The results indicated that the high N2 pressure was essential for the effective nitridation. The in situ generated AlN–AlON refractories had a homogeneous local chemical composition, and the (101) plane of AlN and the (222) lattice plane of Al5O6N were bonded at their grain boundary with no amorphous phase. The as‐fabricated AlN–AlON refractories treated at 1700°C by a 20 atm nitrogen pressure exhibited an optimum bending strength of 111.10 MPa, combining an apparent porosity of 20% with a low bulk density of 1.97 g/cm3. The diffusion of the generated oxygen led to an increase in the apparent porosity and decrease in the bulk density at 1800°C. Furthermore, the fabrication mechanism of AlN–AlON refractories under the nitrogen gas‐pressure was discussed.