Aluminum Microspheres Coated with Copper and Nickel Nanoparticles: Catalytic Activity in the Combustion of Ammonium Perchlorate

This study employed an in-situ displacement technique to eliminate the oxide layer present on the surface of micron aluminum (μAl). Utilizing the exposed metallic aluminum, we facilitated the displacement of copper and nickel nanoparticles. These nanoparticles, approximately 90 nanometers in size, were densely adhered to the surface of the μAl particles. The elemental composition and structural characteristics of the composite particles were meticulously analyzed using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDS), Vibrating Sample Magnetometry (VSM), and X-Ray Photoelectron Spectroscopy (XPS). Subsequently, thermal analysis and combustion performance assessments were conducted to elucidate the catalytic effects of the composite particles ([nCu+nNi]/μAl) on the thermal decomposition and combustion efficiency of ammonium perchlorate (AP). The results elucidate that the nanoparticles immobilized on the surface of μAl are unequivocally metallic copper (nCu) and metallic nickel (nNi). Following the application of nCu and nNi, the oxidation reaction of μAl accelerated by nearly 400 °C; furthermore, the incorporation of [nCu+nNi]/μAl raised the thermal decomposition peak temperature of AP by approximately 130 °C. Notably, the thermal decomposition activation energy of raw AP reached as high as 241.7 kJ/mol; however, upon doping with [nCu+nNi]/μAl, this activation energy significantly diminished to 161.4 kJ/mol. The findings of the combustion experiments revealed that both the raw AP and the AP modified solely with μAl were impervious to ignition via the hot wire method. In contrast, the AP doped with [nCu+nNi]/μAl demonstrated pronounced combustion characteristics, achieving an impressive peak flame temperature of 1851 °C. These results substantiate that the nCu and nNi, when deposited on the surface of μAl, not only facilitate the oxidation and combustion of μAl but also significantly enhance the thermal decomposition and combustion dynamics of ammonium perchlorate. Consequently, the [nCu+nNi]/μAl composite shows considerable promise for application in high-burn-rate hydroxyl-terminated polybutadiene (HTPB) propellants.