Treatment Of Micron-Nano Aluminum/Boron And Their Application In Energetic Materials As Fuels

A key point to enhance the performance of weapon systems is to increase the energy density of the energetic materials used in the weapons. The addition of micron-sized and nano-sized boron and aluminum to energetic materials can really achieve a higher energy release and bigger burn rate in certain experiment conditions. However, when the loading of nano particles becomes higher during the preparation of castable energetic materials, the viscosity of the solution will become very large, cause the deterioration of the procedure. Besides, nanoaluminum and nanoboron are very easily to be oxidized during the production, storage and usage, the oxide layer formed on the surface of the particle caused reduce of the chemical reactivity and the effective contents. An investigation of making nanoparitcles into sub-micron fibers and micron spherical particles by electrospinning and electrospray is introduced here, trying to solve the problem of the aggregation of nano particles.The nano particles are aimed to be made to larger sized agglomerations without reducing its reactivity. The oxidation kinetics of boron was investigated by TG-DSC. The aging process of boron during natural storage was also studied by TG-DSC. For the aging boron, solvent washing and mechanically milling were taken for its purification. TG-DSC was used to study the effect of the treatment. Combustion properties of the boron delay composition were also studied with the treated boron.Electrospinning technique was used to make NC(nitrocellulose)/Al-CuO and NC/Al-Cu(NO3)2fibers with the diameter of several hurdred nanometers and a length of more than500μm. Al, CuO and Cu(NO3)2were homogenously dispersed in the fibers. High speed camera was used for the measurement of the burn rates of NC, NC/Al, NC/Al-CuO and NC/Al-Cu(NO3)2fibrous textiles in the open air. Results show that the combustion of NC, NC/Al and NC/Al-CuO fibrous textiles were completely finished. However, a lot of solid residues were generated during the combustion of NC/Al-Cu(NO3)2. The burn rate of NC was12.4cm/s, the burn rates of NC/Al were even smaller than NC. With the increase of Al in the NC/Al, the burn rate decreased. NC/Al-CuO containing50%Al-CuO had the biggest burn rate (106cm/s), which was8.5times of pure NC fibers.Micron-sized Al-CuO composites were firstly electrosprayed. The Al-CuO/NC with10%NC had the best morphology. There were vacancies between nanoparticles in the big particles. With the increase of NC, the as sprayed particles became close-grained. The nano Al and CuO particles were homogenously dispersed in the bigger particles. When the content of NC was 13%, fibers were seen between big particles. Burning pressure cell tests were taken to investigate the combustion properties of the aggregated spherical particles. Results show that AI-CuO/NC with3%NC had the biggest burn rate and optical strength. When the content of NC was bigger than3%, the combustion of Al-CuO/NC became weaker.Thermoanalytical techniques TG-DSC were introduced to investigate the oxidation kinetics of nano boron and micron boron. Results show that:(1) The oxidation of boron consisted of two steps, called fast reaction and slow reaction.(2) Ozawa equation was used to calculate the kinetics parameters of the fast reaction, and non-linear coefficient was used to get the optimum oxidation mechanism. Results show that the oxidation of boron was F1.(3) Nano boron lost6.6%of its active content during3months of natural storage, the onset temperature and the peak temperature of the reaction was30℃higher than before; while micron boron lost66.7%of its active content during10years of natural storage, the onset temperature and the peak temperature of the reaction was20℃higher than before.Solvent washing and mechanically milling were taken to purify the aging nano and micron boron, TG-DSC was used to study the effects of the treatment. Results show that there was no obvious improvement by the solvent washing for nano boron. But the active content of micron boron could increase by100%with solvent washing. Mechanically milling was taken with absolute ethanol as solvent to protect boron from being oxidized. Sodium hydroxide (NaOH) was added to the mill. Results show that mechanically milling could obviously increase the reaction ability of boron; however, it couldn’t increase the active content of boron.The combustion properties and reaction mechanism of micron boron/lead oxide (Pb3O4) and nano/micron boron/barium chromate (BaCrO4) delay composition was investigated. Optical-electrical targets device was used to test the burn rates of the delay composites. Results show:(1) burn rate of B/Pb3O4delay composites was linearly increased with the content of boron in the composite.The burn rate of treated boron delay composition was2.2times of the aging boron delay composition.(2)Burn rates of nano B/BaCrO4delay composition were bigger than that of micron boron delay composition, and burn rates of delay composition with treated boron were bigger than with aging boron.