In-situ synthesis of AlON reinforcing phases in resin bonded Al2O3 composite materials

AlON reinforced Al2O3 composite materials were prepared from fused corundum, tabular alumina, active Al2O3 powders and phenolic resin through a carbothermal reduction nitridation process. The as-synthesized composite materials are characterized by X-ray diffraction, Scanning electronic microscope and Energy-dispersive X-ray spectroscopy. The results show that the major phase is Al2O3 in the composite materials synthesized at various sintering temperatures. And the in-situ formed AlON reinforcing phases show an evolution, which changes from 21R polytype (Al7O3N5), to γ-AlON (Al5O6N) and finally to φ′-AlON (Al11O15N), with the elevation in sintering temperature. Due to the fact that different AlON crystals are connecting neighboring Al2O3 matrix particles, the physical properties of the as-synthesized composite materials are improved. Based on the conducted characterizations and calculations, AlON phases are formed from the reaction between small quantities of residual carbon from phenolic resin and active Al2O3 powders.