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  • The compositions of different energetic metallic particles

    2018-11-01

    The compositions of different energetic metallic particles and corresponding coatings are chosen in order to take advantage of the resulting SAR302503 reactions of alloying when the metals are combined or alloyed through heat activation. Bimetallic particles composed of a core/shell type structure of having different metals are to be properly chosen so that upon achieving the melting point (for at least one of the metals) a relatively great deal of exothermic heat of alloying is liberated. In a typical embodiment, the core metal is aluminum and the shell metal is nickel. Throughout the coating process the nickel may be deposited onto the outer surface of the aluminum particles by using an electrolysis process of a suitable metal salt solution with a reducing agent in an aqueous solution or a solvent media. The aluminum particles may be pretreated with zinc to remove any aluminum oxide present on the surface. The resulting bimetallic particles may be utilized as an enhanced blast additive by being dispersed within an explosive material [33]. The core metal can be one of aluminum, magnesium, boron, silicon, hafnium, or carbon. The outer shell metal is from nickel, zirconium, boron, titanium, sulfur, selenium, or vanadium. In the first stage of the procedure, 11 mL of zincate solution is mixed (a zinc gluconate solution having an approximately pH of 13) with 100 mL of deionized water. In the next step, the solution is stirred rapidly (with a magnetic PTFE stirbar) and the solution is brought to 65 °C. Then 0.25 g of aluminum powder composite is added (specifically, the grade H-60 aluminum powder). Then, the solution is stirred for 45 s, and vacuum filtered through a 1.2 µm PTFE membrane. Finally, the collected zinc coated aluminum particles are rinsed with deionized water. In the second stage, those pretreated aluminum particles are nickel plated. For this step, 30 mL of nickel sulfate is mixed with 90 mL of solution B (sodium hypophosphite), stirred with a PTFE coated stirbar and then heated to approximately 90–95 °C. Next, 0.29 g of the zinc treated aluminum powder is added and this temperature is maintained and the mixture is stirred until the appropriate amount of nickel is deposited. Then the solution is vacuum filtered through a 1.2 µm PTFE membrane. Finally, the collected aluminum core/nickel shell particles are rinsed with water, and then allowed to dry. The explosive material may be any type of explosive material that can mix with the bimetallic particles of the present invention as an enhanced-blast additive, e.g., octogen (HMX), hexahydrotrinitrotriazine (RDX), pentaerythritol tetranitrate (PETN), picrate salts and esters, dinitrobenzofuroxen and its salts, hexanitrohexaazaisowurtzitane (C-20), trinitrotoluene (TNT), glycidyl azide polymer (GAP), diazodinitrophenol (DDNP), lead azide and other azide salts, lead styphnate and other styphnate salts, triaminoguanidine nitrate, tetranitrodibenzole trazapentalente, diaminohexanitrophenyl, triaminotrinitrotoluene (TATB), or plastic bonded explosives (PBX) [33]. A processing technique was demonstrated by Vasylkiv et al., which was based on the synthesis of ceramic nanopowders and simultaneous impregnation with metallic nanoparticles by multiple “nano-blasts” of embedded cyclotrimethylene trinitramine (RDX) in preliminary engineered multi-component nano-reactors [62]. The “nano-blasts” of impregnated RDX deagglomerate the nanopowder due to the high energetic impacts of the blast waves, while in the decomposition of compounds, their solid-solubility is enhanced by the extremely high local temperature generated during the nano-explosions. The investigators applied this technique to produce nanosized agglomerate-free 8 mol% yttria-doped cubic zirconia aggregates with an average size of 53 nm impregnated with 10 mass% of platinum particles of 2–14 nm. The same authors also published a similar article to demonstrate a unique processing technique which was based on engineering of the multi-component ceramic nanopowders and composites with precise morphology by nano-explosive deagglomeration/calcinations [63]. As mentioned above, multiple nanoexplosions of impregnated cyclotrimethylene trinitramine (RDX) deagglomerate the nanopowder (due to the highly energetic impacts of the blast waves) while the solid-solubility of one component into the other is enhanced by the extremely high local temperature generated during the nano-explosions. They applied this technique to produce nanosize agglomerate-free ceriagadolinia solid solution powder with uniform morphology and an average aggregate size of 32 nm, and as mentioned before, 8 mol% yttria-doped zirconia aggregates with an average size of 53 nm impregnated with platinum (2–14 nm).