Synthesis Powder Of AlON And Preparation Of Alon Ceramics By Spark Plasma Sintering

In this paper, Aluminum Oxynitride(Al ON) was synthesized by reaction sintering, carbothermal reduction and nitridation(CRN). Effect of raw materials, component and reaction parameters was studied. Al ON ceramics were prepared by Spark Plasma Sintering(SPS). Effect of parameters of sintering process on denfication, structure and mechanical properties of the samples was discussed. The oxidation resistance of Al ON ceramic was also studied.Single-phase Al ON powder was prepared by reaction sintering using α-Al2O3 and Al N as raw materials. The results show that the production of Al ON powder was more when synthesised at higher temperature during 1700℃ to 1800℃. Higher temperature(1800℃) had an advantage in synthesising Al ON powder. A longer holding time would increase the productivity of Al ON powder. Single-phase Al ON powder was synthesized from the composition containing 27mol% Al N holding 2h at 1800℃.Single-phase Al ON powder was synthesized from γ-Al2O3 and active carbon by CRN holding 2h at 1600℃ and 3h at 1800℃ respectively with 0.5MPa N2. At the first stage, the production of Al N was increased with the growth of active carbon. But the amount of Al N will not increase any more when the composite containing more than 6.0wt% active carbon. With increasing reaction temperature and ho lding time, the purity of Al ON powder will increase. Ball-milling 24 h can reduce the particle size and improve the particle size distribution and the shape of Al ON powder was also improved.Al ON ceramic can be prepared by SPS at low temperature and short sintering time. The result shows that the samples possessed better properties fabricated under vacuum than N2 atomphere. High relative density Al ON ceramic was obtained by sintering at low temperature and short time. The sintering time had a little effect on the dendity of Al ON ceramic. Larger grain, which can decreased the flexure strength and modulus of elasticity, but improve the fracture toughness, were found by increasing the sintering time.The oxidation experiment of Al ON ceramic ranging from 900℃ to 1200℃ shows that Al ON ceramic has excellent oxidation resistance below 1200℃. Weight gain and oxidation thickness of the samples increased with the oxidation temperature and time. The oxidation rate was higher at higher oxidation temperature. The oxidation product was γ-Al2O3 below 1200℃. And beyond 1200℃, the oxidation production was α-Al2O3. The oxidation process of Al ON ceramic was divided into three stages. In the earlier stage, the oxidation process was controlled by chemical reaction. The middle stage was controlled by chemical reaction and diffusion and the later stage was controlled by diffusion.