Oxidation behavior of AlN–Al2O3 composites

The effect of composition and microstructure on the oxidation behavior of AlN samples having different amounts of Al2O3 was investigated. Oxidation was studied by weight gain measurement in air at elevated temperatures up to 1300 °C using an analytical balance. The microstructure of sintered samples was characterized by scanning electron microscope and optical microscopy. The results showed that presence of different phases and microstructure have a great influence on the oxidation behavior of sintered AlN–Al2O3 composites. Samples having 1 wt.% alumina could not produce protective oxide layer around them and consequently the whole sample was oxidized to Al2O3. However, around the samples having 20 and 70 wt.% alumina a protective oxide layer was formed which retarded their further oxidation.