Combustion synthesis and characteristics of aluminum oxynitride ceramic foams

Aluminum oxynitride (AlON) ceramic foams were prepared by combustion synthesis using Al and Al2O3 as starting materials under high nitrogen pressure. By introducing Al(NO3)3·9H2O into reactants as active pore-forming agent, AlON ceramic foams with well-distributed pores were cost-effectively fabricated. The influences of Al(NO3)3·9H2O content on the combustion process, pore content and structure were studied systematically. The experiment results showed that porous AlON ceramics containing evenly distributed and noncontiguous pores were obtained when Al(NO3)3·9H2O content was 30%, in which the closed porosity of 80% was found by Archimedes’ method. Pore distribution measured by mercury intrusion porosimetry indicated that pores with several types of diameter were formed in the foams because of the different conditions of pore fusion and molten viscosity.