effect of Si–Bi₂O₃ on the ignition of the Al–CuO thermite

The ignition temperature of the Al–CuO thermite was measured using DTA at a scan rate of 50°Cmin⁻¹ in a nitrogen atmosphere. Thermite reactions are difficult to start as they require very high temperatures for ignition, e.g. for Al–CuO thermite comprising micron particles it is ca. 940°C. It was found that the ignition temperature is significantly reduced when the binary Si–Bi₂O₃ system is added as sensitizer. Further improvement is achieved when the reagents are nano-sized powders. For the composition Al+CuO+Si+Bi₂O₃ (65.3:14.7:16:4wt.%), with all components nano-sized, the observed ignition temperature is ca. 613°C and a thermal runaway reaction is observed in the DTA.