Photoflash and laser ignition of high-nitrogen materials
Gas-producing energetic materials that can be readily ignited with a photoflash are typically opaque sensitive primary explosives. This study explores the photoactivity of select high-nitrogen (HiN) compounds that are much less sensitive than primary explosives. These HiN materials produce large amounts of gas upon decomposition. This makes them suitable for use in actuators, igniters, or micro-thrusters. Detailed Ignition studies were conducted using similar shaped pulses at two different wavelength ranges; specifically using a xenon photoflash and a single wavelength CO2 laser. Several select HiN materials were tested for flash ignitability, and those that were found to be flash ignitable were further ignited with CO2 laser heating. By comparing ignition behavior at various laser and flash intensities, some ignition mechanisms are suggested. Thermal heating, regardless of source, appears to be the dominant mechanism responsible for ignition and photochemical effects appear to be negligible in the ignition of the materials considered in this study. Higher laser and photoflash irradiance is shown to require less energy, and is therefore more efficient. The opacity of the material is an important consideration in ignitability, but not a sufficient criteria. Opaque materials that successfully propagate well in small capillary tubes are seen to be more likely to successfully flash ignite. It is suggested that this is due to the higher burning rate of these materials and also in part to the exothermic reaction occurring at or near the burning surface, rather than further from the burning surface. Both of these characteristics better allow reaction to proceed without quenching and will lead both to more successful microchannel combustion and flash/laser ignition.
Son, Purdue University.
Chemistry|Aerospace engineering|Mechanical engineering
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