A study on modification of aluminum powder by ammonium perchlorate and glycidyl azide polymer to improve its combustion

Aluminum powder has a high energy density, but it is easy to agglomerate during the combustion process, which can lead to a decrease in the combustion efficiency. Ammonium perchlorate (AP) and glycidyl azide polymer (GAP) are commonly used an oxidant and a binder in solid propellants. They can promote the combustion of aluminum powder to a certain extent, but their coupling mechanism is still lacking. In this study, GAP and AP were sequentially coated on the surface of nano-sized aluminum powder by a dissolution-recrystallization method, and the coupling effect of AP/GAP on the combustion of aluminum powder and the influence of the AP/GAP coating ratio on the combustion performance of aluminum-rich fuel were studied by using an ignition laser method combined with a spectrum diagnosis test. The promotion effect of AP/GAP on the combustion of aluminum powder was analyzed. The chain-like coating structure of GAP can form a steric hindrance mechanism and inhibit the agglomeration of aluminum powder. The heat of GAP decomposition at a lower temperature accelerates the decomposition of AP and makes the aluminum powder come into contact with the oxidizing atmosphere more quickly. At the same time, the heat provided by GAP combustion can quickly break the local oxide film on the surface of aluminum powder, so that the activated aluminum overflows. When the content of aluminum powder is constant, the combustion performance of the sample with AP: GAP = 3:1 is better than that of the sample with AP: GAP = 4:1. When the aluminum powder content reaches 65 wt.%, its combustion performance is the best, and the ignition delay is reduced by about 21 %. The combustion of the Al-AP/GAP system generates more nitrides. These nitrides can react with alumina and hinder the formation of alumina during the reaction, thereby suppressing combustion interruption.