Microsized aluminum/ammonium dinitramide core-shell particles to improve the combustion performance of aluminum powders

Microcomposite particles of aluminum (Al) dotted by ammonium dinitramide (ADN) (Al@ADN) are successfully prepared by an in-situ crystallization growth method. The morphologies, structures and thermal behavior of Al@ADN are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and simultaneous thermogravimetry and differential scanning calorimetry. The compositions and morphologies of Al@ADN after heating are characterized by X-ray photoelectron spectroscopy (XPS) and SEM. A high-speed camera is used to record the combustion performances of Al@ADN in a transparent quartz tube. Furthermore, the morphologies and structures of the residues are analyzed by SEM and XRD. The results show that ADN is deposited on the surface of Al to form Al@ADN. The decomposition of ADN increases the total oxidation degree of the Al particles. Under heating, the acids decomposed by ADN corrode the surficial alumina layer and the internal aluminum react with HNO₃ to form Al(NO₃)₃, which makes the combustion of Al easier. Under an oxygen atmosphere, the pure Al could not be ignited. In contrast, Al@ADN could be ignited and Al@ADN 5:1 has a shorter ignition and burning time compared with Al@ADN 10:1. After burning, the Al@ADN composites are completely converted to α- and γ-Al₂O₃. For Al@ADN 10:1, the residues show a cube-like stacking, while a ribbon-like stacking is presented for Al@ADN 5:1.