On Mechanism of Thermal Initiation in Fully-Dense 2Al.3CuO Nanocomposite Powder

Several composite 2Al∙3CuO thermite powders with CuO inclusions of different dimensions embedded in Al matrix were prepared by Arrested Reactive Milling.  Different milling times were used to adjust the dimensions of CuO inclusions for different powder samples.  Thermal initiation in these powders was studied using thermo-analytical techniques (DSC/TGA), ignition on an electrically heated filament, and ignition by electro-static discharge.  In ignition experiments, pressure generated by igniting powders was monitored in addition to the produced optical signatures.  Each experimental technique involves a different range of heating rates, varied from 10^-2 to 10⁷ K/s.  The results were compared to prediction of a recently developed model describing kinetics of heterogeneous Al/CuO reaction.  The model was expanded to account for oxygen release by the CuO, which is partially reduced by subsolidus reaction and decomposes upon further heating.  The effect of the oxygen release on thermal diffusivity of the composite powder was also considered while interpreting the ignition experiments.  This paper will present experimental data, comparisons with the model predictions and discuss implications of the present measurements for development of a comprehensive model describing thermal initiation in Al-CuO nanocomposite materials for a broad range of heating rates.