Kinetics of thermal oxidation of silicon nitride powders

The kinetics of thermal oxidation of H.C. Starck M-11 and Ube SN-E10 Si3N4 powders was evaluated in the temperature range 650 degrees-1200 degrees C using isothermal and nonisothermal thermogravimetric analysis, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy, Between 700 degrees and 1200 degrees C, the isothermal kinetics was modeled equally well using the Ginstling-Brounshtein and Zuravlev-Lesokhin-Tempel'man equations. Despite their similar particle sizes and surface areas, the two powders exhibited different oxidation kinetics, The activation energies for oxidation of the M-11 and SN-E10 powders were determined to be 400 and 540 kJ/mol, respectively, between 1000 degrees and 1200 degrees C, and 230 and 260 kJ/mol, respectively, between 700 degrees and 1000 degrees C. The parabolic rate constants for oxidation of the two powders were comparable to those reported in the literature for monolithic, chemically-vapor-deposited Si3N4 at the higher temperatures, At lower temperatures, the oxidation kinetics of the M-11 powder was nearly linear, whereas the kinetics of the SN-E10 powder remained power-law dependent.