Morphological development and oxidation mechanisms of aluminum nitride whiskers

Hexagonal aluminum nitride (AlN) whiskers have been synthesized at 1873 K under a flowing nitrogen atmosphere. The synthesized whiskers are long straight filaments with diameters between 1 and 5 μm and length in the cm range. In order to investigate its “oxidation resistance”, a series of experiments have been performed. The oxidation behavior was quite different in the experimental temperature range assigned, which can be attributed to the kinetic factor and the morphological development during oxidation process. It was chemical controlled at lower temperature while both chemical reaction and diffusion controlled at medium temperature. Further accelerating of temperature to 1473 K, AlN whiskers was peeled into smaller parts, which increased the oxidation rate and hence showed powder-like oxidation behavior. Our new kinetic theory has been applied to study the oxidation behavior of AlN whiskers. The comparison of the experimental data with the theoretical ones validates the applicability of the new model.