Thermo-mechanical aspects of the heterogeneous ignition of metals

During the heterogeneous oxidation of metallic particles in a gaseous oxidant, a film of oxide usually separates the metal and oxidant, with the reaction rate being governed to a great extent by the protective properties of the film. A theoretical and experimental study of the influence of the failure of the protective oxide film on the metal's heterogeneous ignition has been performed. The possible reasons for the fracture are analyzed; also the critical conditions of the oxide film are estimated. Experiments conducted with aluminum and titanium powders have shown that the fracture of the protective oxide film results in a significant increase in the metal's reactivity. The assumptions of a theoretical analysis are confirmed experimentally. (C) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.