Kinetics of the oxidation of an electroexplosion iron nanopowder during heating in air

The regularities of the oxidation of electroexplosion iron nanopowder, produced by the wire electric explosion, heated in air under conditions of linearly increasing temperature and in the isothermal mode are examined. The oxidation process under conditions of linear heating is demonstrated to occur stepwise due to the combined influence of the fractional composition of the powder, its phase composition, and the structure of the oxide layer formed on the surface of the particles. It is shown that, under isothermal conditions (250–600°C), the oxidation of the nanopowder, as opposed to micron-sized powders, obeys a linear law and proceeds in the kinetic regime with Ea = 100 ± 7 kJ/mol. The conditions of thermogravimetry analysis at which the thermal self-ignition of the nanopowder occurs are determined. Based on the numerical evaluation of the sample surface heating parameter, the experimentally measured critical temperature is verified.