Research Of Combustion Synthesis Of AlON Foam Ceramics

In this paper, compact AlON ceramics were prepared successfully by Combustion Synthesis process using exothermic reactions in Al-Al₂O₃-N₂ system. Foam ceramics with 76% porosity and single phase AlON were prepared for Al(NO3)3·9H2O blister being added. The effects of AlON preparation using SHS process by processing parameters were studied using lot kinds of experiment and analysis method.The thermodynamics of Al-Al₂O₃-N₂ system were analyzed. Studied how temperature affects the free energy of reaction and did calculation of how Al₂O₃ content affects the insulation temperature. The results of calculation to insulation temperature show that: with the Al₂O₃ content gradually increasing, the insulation temperature declines. According to the calculation result and Merzhanov criterion, we draw a conclusion elementary that When the Al₂O₃ content is lower than 82wt%, the system can carry out the combustion synthesis reaction.The effects of Al₂O₃ content to product phase were studied, the results show that: in the Al-Al₂O₃-N₂ system, the combustion synthesis product is made up with AlON, free Al and AlN; with the increase of Al₂O₃ content, the AlON content in product increase gradually, and the free Al content decline, the product appearance change from graininess to lath-shaped and the product densities have a peak in 30% Al₂O₃ content.When Y₂O₃ was added, Y₂O₃ and Al₂O₃ will react and the phase Al5Y3O12 is produced in high temperature. There is liquid sintering in the SHS process which is helpful to make the high-temperature phase AlON generate. When the Al₂O₃ content is up to 60%, besides minute qualitity Al₅Y₃O₁₂, AlN and free Al, the product is almost the AlON single phase.The effects of blank initial relative density to product properties were studied, the results show that: the density of products has a peak inρ0=0.67. And the increase of blank initial porosity is helpful to the formation of AlON phase.Al(NO₃)₃·9H₂O was added to the Al-Al₂O₃-N₂ system as blister, and foam ceramics with 76% porosity, single AlON phase were prepared in the SHS...