BN-MgAlON composites were prepared by hot-pressing sintering under nitrogen atmosphere with BN-MgAlON composite powders as raw material and Y2O3 as sintering additive.Based on thermodynamic analysis,the oxidation resistance of BN-MgAlON composites was investigated and the dynamics of oxidation process was also analyzed.The oxidation process and the micro-morphology of the samples before and after oxidation were characterized by X-ray diffraction and scanning electron microscopy.The dynamics of oxidation resistance of the BN-MgAlON composites was investigated via the analysis of the constant temperature oxidation mass gain curves.The results show that the main components of the material are MgAlON,Sialon,BN and CaYAl3O7 at 1 650-1 750 ℃,and the content of CaYAl3O7 decreases as the sintering temperature increases.The BN-MgAlON composites prepared at1 750 ℃is uniform and compact with the balanced distributions of Al,Mg,O,and N.The oxidation process of BNMgAlON composites in air mainly consists of MgAlON,Sialon and BN oxidation.The section after being oxidized at1 000-1 300 ℃involves three layers,namely,the outer layer,the middle layer and the inner layer.The oxidation process follows the parabola model.The apparent activation energy of the oxidation process is 2.13×105 J/mol and the frequency factor is 4.66×106.
Ran LIUXin-yuan ZHANGXing-juan WANGYa-na QIEQing LFu GAO
