Thermal reactivity of metastable metal-based fuel Al/Co/AP: Mutual interaction mechanisms of the components

In this paper, a group of novel intermetallic metastable composites Al/Co@AP has been designed, and three methods including ultrasonic dispersion, mechanical grinding and spray-drying have been attempted for their preparation. The latter one has demonstrated to be the most appropriate means, by which the core–shell structured Al/Co@AP with desired properties could be successfully obtained. The thermal reactivity of Al/Co/AP composites prepared differently has been investigated and compared by TG/DSC technique. It has been shown that the heat release rate of AP in DSC curve was largely increased in the presence of Al/Co when spray-drying technique was used, which may be attributed to the increased nuclear site by the intimate contact. The initial reaction temperature of AP in Al/Co@AP was decreased by 7.8 °C and the heat releases by the thermal decomposition of AP and the intermetallic reaction between Al and Co were enhanced by 52.6 % and 67.7% in comparison with that of pure AP and Al/Co. The types of major gaseous products of Al/Co@AP are almost identical to that of pure AP, which include HCl, H₂O, N₂O and NO₂. However, the concentrations of NO₂ and N₂O in gaseous products for Al/Co@AP are lower than that observed for pure AP, which may be due to the partial consumption of N element by the reaction of Al with acidic substance (HNO₃) decomposed from AP. In addition, the AP in Al/Co@AP composite decomposes in one-step with the apparent activation energy (E_a) of 98.8 kJ·cm⁻³. The decomposition process of the AP in Al/Co@AP composite follows two-dimensional nucleation and growth model(A2), whereas the pure AP follows different physical models, which are close to three-dimensional nucleation and growth, chain scission and phase boundary-controlled reaction (contracting area) models. The intermetallic reaction between Al and Co in Al/Co@AP is merged into one-step following the A2 physical model.