Oxidation kinetics of small nickel particles

The oxidation kinetics of two kinds of polycrystalline nickel particles wit h an approximate median diameter of 5 mu m but with different morphology, h as been studied by thermogravimetric measurements in the temperature range 573-973 K. The oxidation was found to be thermally activated with an appare nt activation energy of about 1.5 eV. The kinetics was compared with a homo geneous field, coupled-currents theory for oxidation of spherical metal par ticles. Calculations using a median particle size or a distribution of part icle sizes do not give satisfactory fits to the experimental data. Possible explanations of the deviations in terms of space charge, grain boundary di ffusion, grain growth, and sintering are discussed. (C) 1999 American Insti tute of Physics. [S0021-8979(99)08502-3].