Facile Fabrication of Highly Efficient Hollow Ni/Al Bimetal Fuel with Enhanced Thermal Oxidation Behavior

Al powder has been used as a common fuel in various energetic materials because of the high enthalpy of its oxidation. The thermal oxidation behavior of Al fuel is a key issue that can determine the energetic properties of Al-based energetic materials. Paradoxically, highly active Al with a low melting point is trapped by a dense surface Al2O3 inertia layer with a high melting point, resulting in low thermal oxidation efficiency at elevated temperatures. In this work, a series of low content of hollow Ni nanoparticles are decorated on the Al surface, and the formed Ni/Al bimetal fuels are constructed through a novel and simple replacement reaction between Al and NiF2 solution. NiF2 not only ionizes F– to remove the Al2O3 inertia layer but also ionizes Ni2+ to provide a Ni source for deposition. Decorating with low-content Ni nanoparticles improves the intensity, speed, and completion of the high-temperature thermal behavior of Al powder. For instance, the high-temperature oxidation peak of the representative Ni/Al with 2% Ni content is advanced by approximately 95 °C, and the heat release is over 1.85 times than that of the raw Al. The main role of Ni decoration can destroy effectively the Al2O3 inert layer at high temperature and then enlarge the transport channels of oxygen molecules and Al ions, causing the inner molten Al to encounter external rich-oxygen environment rapidly. The as-obtained Ni/Al bimetal fuels are expected to have wide application prospects in solid energetic materials.