HIGH-TEMPERATURE (TO 1670℃) AIR OXIDATION OF AlN–Si_3N_4 AND AlN–Si_3N_4–(Ni–Cr–Al) CERAMIC MATERIALS

摘要

The kinetics and mechanism of high-temperature air oxidation of powders and compact materials with different compositions in the AlN–Si_3N_4 and AlN–Si_3N_4–(Ni–Cr–Al) systems are studied using nonisothermal (up to 1500℃) and isothermal (1350 and 1670℃) thermogravimetry, DTA, XRD, petrography, and EMPA. During heating, Al_4O_4–xNx and Si_2N_2O oxynitrides, α-Al_2O_3 and α-SiO_2 (crystobalite) oxides, and mullite-based Al_2O-3 and SiO_2 solid solution of the boundary composition form during the first oxidation stage, and 3Al2O3 and 2SiO2 mullite forms at higher temperatures (>135℃) in the upper scale layer and aluminum-nickel chromite spinel in the intermediate (barrier) scale layer. The AlN–Si_3N_4 and AlN–Si_3N_4–(Ni–Cr–Al) ceramics may be regarded as hightemperature composites (HTCs) owing to their high corrosion resistance.