Ignition of Fully Dense Nanocomposite Thermite Powders by an Electric Spark

摘要

Electrostatic discharge ignition of nanocomposite thermites prepared by Arrested Reactive Milling was investigated. The powders 2Al-3CuO and 8Al-MoO_3 were placed in a sample holder and subjected to an electrostatic discharge from a discharging capacitor. Their optical emission was monitored. Two ignition modes were detected: immediate ignition of individual particles and delayed ignition of a cloud of aerosolized powder. Experiments addressed the effects of material composition and morphology, aging, energy input, layer thickness, and environment on the ignition mode and ignition delays. Prepared thermites were blended with pure metal powders to study ignition of such blends. Individual particle ignition was observed for samples prepared as monolayers in air and argon and for any samples in vacuum. For thicker samples in air and in argon, a delayed powder ignition mode was observed. The delays varied from 10 μs to several milliseconds. Powders of 2Al-3CuO had shorter ignition delays compared with 8Al-MoO_3. For both materials, delays decreased for the powders prepared using longer mliling times. For 2Al-3CuO, aged powders ignited after longer delays compared with the freshly prepared powders; however, shorter delays were observed for the aged 8Al-MoO_3. Electrostatic discharge energy and layer thickness (except for a monolayer) did not affect the ignition delay. Blending nanocomposite thermites with Al and Ti powders reduced their electrostatic discharge ignition sensitivity and caused longer ignition delays.