Special features of the kinetics and mechanism of the interaction between aluminum nitride and gas media

The unique thermophysical properties of aluminum nitride and its good dielectric characteristics combined with elevated thermal and chemical stability explain the wide use of this material for high temperature engineering. However, the literature bears virtually no data on the kinetics and mechanisms of processes that occur in heating of AlN powders in the range 320-1400K in various gas media, which virtually determine in the final analysis all the further action of the gas medium and, as a consequence, affect the technology and service possibilities of materials based on AlN. The method of precision thermogravimetry is used to study the special features of the kinetics and mechanism of the process of interaction between powder AlN and nitrogen and oxygen under various partial pressures of these gases. The temperature ranges and the activation energies typical for processes that occur by various mechanisms (two-dimensional and three-dimensional diffusion due to Yander and anti-Yander, etc.) in the range 350-1400 K are established. It is supposed that AlN bears aluminum vacancies, and their ultimate number density at the temperature of melting of AlN is evaluated with the use of a modified Mott-Kroger formula.