Controlling the Energy Release Behavior of Aluminum Nanoparticles as Metal Fuels by Atomic Layer Deposited Copper Oxide Nanocoatings

Aluminum (Al) powder is widely employed in the aerospace and defense industries, particularly for its use in explosives and as a metal fuel. Enhancing the energy release performances of Al nanopowder is an important task. The surface properties of Al nanoparticles have a significant impact on their energy release characteristics. In this work, atomic layer deposition (ALD) technology is utilized to grow nanometer-thin films of cuprous/cupric oxide (CuOx) on the surface of Al nanopowder as an oxidizer to initiate redox reactions. Structural, morphological, and chemical properties of the Al@CuOx nanocomposites are characterized by various spectroscopic and microscopic techniques. The CuOx coating encapsulates the Al nanoparticles to form Al@CuOx core-shell nanocomposites, wherein the contact between Al and CuOx is significantly promoted; thus, the average fuel-oxidizer diffusion path is reduced. The thickness of the CuOx coating can be conveniently changed with nanometer-scale precision by varying the ALD cycle number, which enables flexible control over the structure of the nanocomposites. Oxidation, ignition, and combustion behaviors of Al@CuOx nanocomposites are investigated by differential scanning calorimetry and laser ignition experiments. Only a few nanometers of the CuOx surface modification layer can effectively enhance the energy release performances of Al powder, which is manifested specifically by significantly reduced ignition delay time, oxidation temperature, and remarkably increased reaction rate.