Study On The Preparation Of Nano-Al Powder By Wet Chemical Method And Its Surface Coating

Aluminum(Al)nanopowders,as a new metal fuel additive in energetic materials,have been attracting a great deal of attention due to their unique properties such as high energy density and high heat of reaction to form Al2O3.But due to their large surface area and high surface energy,Al nanopowders are easy to be oxided with oxygen and water,which leads to the loss of active Al and greatly limits their practical application.Therefore,stabilization of Al nanopowders become extremely important to realize their potential in various application.In this work,the core-shell nanocomposite particles have been achieved by coating the surface of Al nanoparticles with hydroxyl-terminated polybutadiene(HTPB)and oxidant hexogeon(RDX)which are the main composition in a typical propellant formula.The sizes,morphologies and structures of the composite particles have been characterized and the active aluminum contents have been measured.The main works are as follows:(1)Al/Al2O3 nanocomposite particles were prepared by the wet-chemical method,in which AICl3,LiAlH4 and N(Et)3 were chosen as raw materials and toluene was served as solvent.The sizes,morphologies and structures of nanocomposite particles can be effectively controlled by manipulating reaction conditions.The optimum operation parameters were as follows:the molar ratio of AICl3 and LiAlH4 is 1:6;the adding amount of catalyst was 0.04mL and the temperature was 25?.The spherical Al/Al2O3 nanocomposite particles with the size of 80-150nm were prepared and the active Al content was about 66.0%.(2)Al/HTPB nanocomposite particles were prepared by a simply solvent evaporation method,HTPB adsorption deposited and coated on the surface of Al nanopowders in situ,which successfully inhibited the oxidization of Al nanoparticles.The optimum amount of HTPB with Al powder mass ratio is 3:10,coating thickness of HTPB was about 5nm.The result of FT-IR indicated that HTPB capped nano Al by the way of physical deposition.Compared with aluminum oxide passivated,HTPB cladding could effectively prevent nano Al from reacting with oxygen and water.Active Al content accounted for 91.1%of total Al in the Al/HTPB composite particles.(3)Al/RDX nanocomposite particles were prepared by a solvent-antisolvation method.The saturated solution of RDX was drop added to the antisolvation,the supersaturated maked RDX precipitation,they deposited and growed on the surface when meet the Al nuclears.The type and volume ratio of solvent-antisolvent and recrystallization temperature were investigate on the effects of composite particles.The best preparation parameters were:solvent-antisolvent choosen DMF/toluene,volume ratio was 2:60 and the optimum temperature to adding RDX was 25?.FESEM result showed that most of the nano A1 were coatted by RDX.FT-IR confirmed that RDX combine with Al nuclear by physical deposition.Active Al content accounted for 89.0%of total Al in the Al/RDX composite particles.The results showed that HTPB and RDX cladding can effective prevents Al nanoparticles from oxidation,the activity of nano Al have be greatly improved.