Effects of Al powder on the reaction process and reactivity of B/KNO3 energetic sticks

Boron/potassium nitrate (B/KNO3) is a type of critical energetic composite material (ECM). However, the inert oxide layer on the B surface of B/KNO3 hinders the contact between pure fuel and oxidant, thus limiting energy release This limitation could be eliminated by adding highly reactive Al powder. To discern the effects of Al powder size on the reaction process and reactivity of B/KNO3, this study prepared Al/B/KNO3/polyvinylidene fluoride (PVDF) energetic sticks using the direct ink writing (DIW) technology. This study characterized the macroscopic morphology and structure of the energetic sticks using a laser scanning microscope and a scanning electron microscope, examined the reaction process of the composites using a differential scanning calorimeter and a thermogravimetric analyzer, and observed the flame propagation behavior of energetic sticks and energetic architectures using a high-speed camera. Furthermore, it tested the pressure output characteristics of the energetic composites using a closed volume tank. The results show that adding Al powder can improve the combustion efficiency of B/Al composite fuels and reduce the agglomeration of the combustion products. The Al powder with various particle sizes affects various reaction stages of the composite. The combustion and pressure output tests suggest that adding Al powder with a particle size of 1 μm yielded high reactivity and that flame jump propagation appeared in energetic architectures when the channel spacing was below 10 mm. These findings provide a guide for modifying the B/KNO3 energetic composites and regulating the reactivity of energetic sticks.