Ignition of nanocomposite thermites by electric spark and shock wave

Nanocomposite 8Al MoO₃ thermite particles were prepared using arrested reactive milling and ignited using two experimental techniques. In spark ignition, a monolayer of powder was placed on a conductive substrate and heated in air by a pulsed electrostatic discharge. In shock ignition, an individual particle was targeted by a miniature, laser-driven flyer plate accelerated to a speed in the range of 0.5-2 kms^-1. In both experiments, time-dependent optical emission produced by the ignited material was monitored and recorded. The heating rates achieved in the present experiments are on the order of 10^9--10¹¹ Ks^-1. These ignition methods result in a very fast combustion with characteristic burn times reduced by 1-3 orders of magnitude compared to the burn times measured previously for the same material ignited in the CO₂ laser beam, where it was heated at a much lower rate of about 10^6--10 ⁷ Ks^-1. Ignition delays observed in both shock and spark ignition experiments are close to each other and vary in the range of 120-200 ns. The times of characteristic rapid increase in the optical emission of the ignited particles are also close to each other for the two experiments; however, these times are somewhat shorter (less than one μs) for the spark ignition tests compared to few μs observed for the shock initiated particles. Preliminary ideas enabling one to interpret the present results are discussed. This work establishes an approach for systematic studies of high rate ignition and respective combustion of nanocomposite reactive materials.