Nano-aluminum particles were produced by the electrical wire explosion method at this laboratory. The size and shape of the particles were measured using a transmission electron microscope (TEM). Aluminum wires are exploded by application of high voltage, to yield particles of size around 40 nm. The X-ray diffraction (XRD) results also confirm that the powder formed by the above process as aluminum with an average size of 42 nm. Previous studies on ultrafine-aluminum applied to solid propellants have tested a particle size not less than about 100 nm. The thermal characteristics were analyzed using thermo gravimetric and differential thermal analyses (TG-DTA). The composition of the material was characterized by energy dispersive angle X-ray (EDAX) analysis. The low pressure deflagration limit (LPDL) tests were carried out for dry-pressed pellets of the nano-aluminum or normal aluminum with ammonium perchlorate (AP). Sandwich burning tests of the nano-aluminum and normal aluminum added to the middle lamina of binder were also carried out. It showed that the addition of nano-aluminum marginally increased the burning rate at elevated pressures and higher lamina thicknesses. Composite propellant formulations were developed out with a bimodal size distribution of AP particles, with the baseline non-aluminized formulations exhibiting plateau burning rate trends. Burning rate studies of the non-aluminized, nano-aluminized, and normal aluminized propellants were carried out. It was found that the burning rate of the nano-aluminized propellants increased by 100% compared to normal aluminized propellants. In the nano-aluminized propellants, the plateau effects in the burning rate of the corresponding non-aluminized propellants in the intermediate pressure range were removed, but significantly low pressure-exponents were observed at elevated pressures. The results point out that the nearly complete combustion of nano-aluminum near the propellant burning surface actually controls the propellant burning rate. The nano-aluminum combustion is diffusion-limited at elevated pressures, and hence, results in significantly low pressure-exponents of burning rate in that pressure range.
|Journal||Data powered by TypesetCollection of Technical Papers - 45th AIAA Aerospace Sciences Meeting|
|Publisher||Data powered by TypesetAmerican Institute of Aeronautics and Astronautics|
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