The oxidation kinetics of nickel particles with an approximate median size of 15 nm was determined by thermogravimetry. The particles had a thin initial oxide shell amounting to 36 wt of the sample. The kinetics was studied in pure oxygen in the temperature range 135-235 degreesC, giving power law behavior of each isotherm with an exponent between 0.48 and 0.58. By use of a master plot technique an apparent activation energy of 1.34 eV was determined. The power law exponent is considerably lower than the one expected for diffusion limited oxidation of a spherical particle with an initial oxide shell. The deviations from parabolic kinetics are discussed in terms of nonlinear diffusion, grain growth, and particle agglomeration. (C) 2001 American Institute of Physics. References: 79
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