Abstract
To deepen the oxidation depth and promote the exothermic reaction of aluminum nanoparticles (Al NPs), this work constructed perfluoropolyether-functionalized Al NPs by using a facile fabrication method. It was determined that perfluoropolyether (PFPE) was uniformly distributed on the surface of the Al NPs with no obvious agglomeration by micro-structure analysis. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), microcomputer automatic calorimeter (MAC), and combustion and ignition experiments were performed for varying percentages of PFPE blended with Al NPs to examine the reaction kinetics and combustion performance. It was revealed that the oxidation mechanism of PFPE-functionalized Al NPs at a slow heating rate was regulated by the reaction interface Fuel-Oxidizer ratio. Due to the enlarged Fuel-Oxidizer contact surface area, fluorine atoms could adequately decompose the inert alumina shell surrounding the Al NPs, optimizing the combustion process of Al NPs. The analytical X-ray diffraction (XRD) pattern results confirmed the existence of aluminum trifluoride in combustion products, providing insights into the oxidation mechanism of Al NPs. The obtained results indicated that PFPE participated in the oxidation of Al NPs and improved the overall reactivity of Al NPs.
Highlights
Aluminum (Al) has been considered as a reactive metal with potentially superior exothermic performance (83.8 kJ·cm−3 /31.05 kJ·g−1 ) [1] and has been widely used in the fields of propellants, explosives, and pyrotechnics [2,3,4]
TEM photos were captured to characterize the micro-structural differences between the aluminum nanoparticles (Al NPs) and PFPE-functionalized Al NPs
A clear contrast is observed in high-angle annular dark-field (HAADF) TEM images, further confirming the core–shell structure of Al NPs
Summary
Aluminum (Al) has been considered as a reactive metal with potentially superior exothermic performance (83.8 kJ·cm−3 /31.05 kJ·g−1 ) [1] and has been widely used in the fields of propellants, explosives, and pyrotechnics [2,3,4]. Its application has often been restrained due to the native dense oxide layer (Al2 O3 ) passivating on the surface, hindering the diffusion of oxygen throughout Al particles in the combustion process [5,6,7]. The combustion process of Al particles usually accompanies ignition delay, incomplete combustion, and so on [8,9,10]. The larger the size of Al particles is, the longer the path of heat conduction will be [11]. This phenomenon is a minor point, but it must not be overlooked. The above-mentioned points are the main reasons why its high theoretical enthalpy of combustion cannot be achieved in practical applications
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