The fast pyrotechnic reaction of silicon with lead oxides: Differential scanning calorimetry and hot-stage microscopy studies

Differential scanning calorimetry has been applied in the study of the fast pyrotechnic reaction of silicon with (a) PbO; and (b) Pb 3O 4 in powder form. Samples were heated up to 725 °C at heating rates from 0.3 to 160 °C min −1 under a nitrogen atmosphere. Hot-stage microscopy was used to observe phase changes up to 1000 °C at heating rates of 0.1–100 °C min −1, and X-ray analysis to identify products. The DSC studies of both compositions indicate two exothermic peaks at 548–667 °C and 667–726 °C, corresponding to surface and bulk reaction. The use of PbO with a smaller particle size results in a larger first and smaller second peak indicating enhanced surface activity. For Pb 3O 4/Si compositions, reaction is principally between Si and PbO, resulting from the decomposition of PbO. At a heating rate of 100 °C min −1 both compositions ignite above 700 °C. Hot-stage microscopy correlates phase and colour changes with temperature of occurrence of peaks in the DSC studies.