Preparation Of Organic Coated Nano-aluminum Powder And Study On Its Activity Retention

Aluminum (Al) nanopowders, as a new type of metal fuel,are often used as additives in solid propellant due to their unique properties such as high energy density,low temperature oxidation performance which can evidently improve the burning rate and decrease the pressure index. Despite their large surface, small particle size and high surface energy, Al nanopowders are easy to react with oxygen to form a dense oxide film (Al2O3) when exposed to air. The Al2O3 will decrease the stability, thus limit the application of Al nanopowders in the propellant and bring a certain degree of difficulty in storage. Therefore, it is necessary to improve the surface modification of Al nanopowders in order to maintain its activity and improve its storage performance.This paper selected paraffin and perfluorotetradecanoic acid as coated material for surface, using the liquid chemical method to modify the surface of Al nanopowders.A1 nanopowders, A1 nanopowders/paraffin composite particles and Al nanopowders/perfluorotetradecanoic acid composite particles were prepared, the prepared particle size, morphology and structure were characterized through a variety of characterization methods, and compared the remaining activity of these three kinds of coating material on the Al nanopowders, the specific contents are as follows:(1) A1 nanopowders particles were prepared through liquid phase chemical method, using toluene as solvent, anhydrous AlCl3, N(Et)3 and LiAlH4 as raw materials with the protection of inert gas. The results showed that the composite particles were spherical with a particle size range of 80 nm-120 nm, and the average active aluminum content was about 75.5%. In order to further investigate the activity of Al nanopowders particles, it was stored at normal temperature and pressure for a period of time. Compared to the results of 60 days ago, the activity aluminum content decreased by 30.4%.(2) Al nanopowders/paraffin composite particles were prepared by liquid phase chemical method. Al nanopowders/paraffin composite particles which regular morphology were prepared successfully under this condition, the composite particles were spherical, the particle size range of 80 nm-120 nm. The FTIR results showed that the paraffin was coated on the surface of A1 nanopowders with physical deposition method. The active aluminum content of A1 nanopowders/paraffin composite particles was 80.8%, and the content of active aluminum content decreased by 1.7% after two month.(3) Al nanopowders/perfluorotetradecanoic acid composite particles were prepared by adding the perfluorotetradecanoic acid of anhydrous ether solution under the conditions of preparation (1). The composite particles were spherical, and the particle size range of 80 nm-100 nm, the crystal of composite particles was regular.The FTIR results showed that perfluorotetradecanoic acid was attached on the surface of A1 nanopowders by chemical bonds, the active aluminum content of Al nanopowders/ perfluorotetradecanoic acid composite particles was 80.0%, and the content of active aluminum content decreased by 3.8% after two month.The results showed that the surface coated treatment of A1 nanopowders with paraffin and perfluorotetradecanoic acid can effectively prevent the oxidation of Al nanopowders and maintain the activity of A1 nanopowders, and has better coated effective of paraffin.