The oxidation of mechanically activated ultrafine iron powders was studied using X-ray powder diffractionand thermogravimetric analyzes. The powders with average particles size of 100 nm were made by the electricexplosion of wire, and were subjected to mechanical activation in planetary ball mill for 15 and 40 minutes. Itwas shown that a certain amount of FeO phase formed during mechanical activation of ultrafine iron powders.According to thermogravimetric analysis, a preliminary mechanical activation of the initial powdersconsiderably changes the nature of the iron powders oxidation, leads to increasing of the temperature ofoxidation onset and shifts the reaction to higher temperatures
