PARTICLE COMBUSTION DYNAMICS OF METAL-BASED REACTIVE MATERIALS

Micron-sized particles of aluminum and aluminum-based reactive materials were fed into a CO 2 laser beam where they were ignited. Just prior to entering the CO 2 beam, particles were illuminated by a low-power infrared laser, and their sizes were measured in situ using the intensity of scattered light. Experiments are presented for spherical Al and nanocomposite powders prepared by mechanical milling, including Al center dot CuO, Al center dot MoO3, Al center dot I-2, Al center dot B center dot I-2, Al-wax, and Al-polyethylene. The particle emission signals were recorded and their combustion temperatures were measured optically. In addition, the intensity of molecular AlO emission was monitored. Experiments were performed in air for all materials; additional data for Al combustion in different oxidizers are also presented. For all materials, the effect of particle size on its burn time was observed to be small. No composite material demonstrated consistently higher temperatures or shorter burn times compared to Al powders. For materials with volatile additives (I-2, wax, polyethylene), particle combustion was accompanied by pronounced oscillatory patterns; especially large vapor-phase flames were observed for Al-hydrocarbon composites. Distinct surface reactions were observed for Al center dot B center dot I-2 composite particles, which also had the longest burn times compared to other materials. Al center dot CuO particles fragmented upon ignition while Al center dot MoO3 particles burned relatively slowly and without fragmentation.