Oxidation mechanism of tantalum in carbon dioxide

The oxidation of tantalum plates in carbon dioxide between 700 and 880degreesC at a pressure of 100 kPa, leads to the dissolution of oxygen in the metal, the nucleation of the suboxide TaOz and the growth of a non-protective coating of betaTa(2)O(5). After an initial decelerated period, the kinetics become continuously accelerated. To correlate the curve shape with the morphological development of the oxide scale, the proposed oxidation model associates in parallel the diffusion of oxygen in the substrate and a phase boundary process in which the nucleation of TaOz constitutes a necessary step for the formation of Ta2O5. (C) 2002 Elsevier Science B.V. All rights reserved.