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Aluminum particles 15–25 μm in size are widely used in fuel propellants and underwater propulsion systems in national defense research. However, these particles are covered with an aluminum oxide film, which has a high melting point, so ignition is difficult. To improve the ignitability of high-energy aluminum powder and to understand the reaction phenomenon as a function of particle size(15–25 μm, 74–105 μm, and 2.38 mm) and oxidizer(air, CO2, and argon), the natural oxide films are chemically removed. The particles are then coated with nickel using an electro-less method. The degree of nickel deposition is confirmed qualitatively and quantitatively through surface analysis using scanning electron microscopy/energy dispersive spectroscopy. To characterize the nickel coatings, elemental analysis is also conducted by using X-ray diffraction. Thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) enable comparisons between the uncoated and coated aluminum, and the reaction process are investigated through fine structural analysis of the particle surfaces and cross sections. There are little difference in reactivity as a function of oxidant type. However, a strong exothermic reaction in the smaller nickel-coated aluminum particles near the melting point of aluminum accelerates the reaction of the smaller particles. Explanation of the reactivity of the nickel-coated aluminum depending on the particle sizes is attempted.

To improve the ignitability of high energy aluminum powder, in this study, natural oxide films (alumina, Al2O3) were chemically removed and nickel coatings were deposited using an electroless method for nickel plating. The time-dependent degree of nickel deposition was confirmed qualitatively and quantitatively through surface analysis using scanning electron microscopy/energy dispersive spectroscopy. To characterize the nickel coatings, we also conducted elemental analysis by using X-ray diffraction and weight analysis by using inductively coupled plasma optical emission spectrometry. Thermophysical studies were also conducted using thermogravimetric analysis/differential scanning calorimetry in an airoxidized environment. The results of these analyses explain the ignition enhancement mechanism observed in the nickel-coated aluminum powder. A novel plating method for creating a nickel-coated aluminum powder was established and the mechanism for the enhancement of the ignition and combustion of the powder is elucidated.