Controlling the Energy\nRelease Behavior of Aluminum\nNanoparticles as Metal Fuels by Atomic Layer Deposited Copper Oxide\nNanocoatings

Aluminum (Al) powder is widely employed\nin the aerospace\nand defense\nindustries, particularly for its use in explosives and as a metal\nfuel. Enhancing the energy release performances of Al nanopowder is\nan important task. The surface properties of Al nanoparticles have\na significant impact on their energy release characteristics. In this\nwork, atomic layer deposition (ALD) technology is utilized to grow\nnanometer-thin films of cuprous/cupric oxide (CuO<sub><i>x</i></sub>) on the surface of Al nanopowder as an oxidizer to initiate\nredox reactions. Structural, morphological, and chemical properties\nof the Al@CuO<sub><i>x</i></sub> nanocomposites are characterized\nby various spectroscopic and microscopic techniques. The CuO<sub><i>x</i></sub> coating encapsulates the Al nanoparticles to form\nAl@CuO<sub><i>x</i></sub> core–shell nanocomposites,\nwherein the contact between Al and CuO<sub><i>x</i></sub> is significantly promoted; thus, the average fuel-oxidizer diffusion\npath is reduced. The thickness of the CuO<sub><i>x</i></sub> coating can be conveniently changed with nanometer-scale precision\nby varying the ALD cycle number, which enables flexible control over\nthe structure of the nanocomposites. Oxidation, ignition, and combustion\nbehaviors of Al@CuO<sub><i>x</i></sub> nanocomposites are\ninvestigated by differential scanning calorimetry and laser ignition\nexperiments. Only a few nanometers of the CuO<sub><i>x</i></sub> surface modification layer can effectively enhance the energy\nrelease performances of Al powder, which is manifested specifically\nby significantly reduced ignition delay time, oxidation temperature,\nand remarkably increased reaction rate.