Nano-sized boron improving the ignition and combustion of micron-sized aluminum powder in water vapor

Micron-sized aluminum (Al-μm) powder is difficult to ignite or burn thoroughly in water vapor (WRV). These issues limit the application of Al powder in solid propellants. To address these issues, nano-sized boron (B-nm) powder was incorporated into Al-μm powder, and the effects of different B contents and temperatures on the ignition and combustion (IAC) performance of the B-Al mixtures in a high-temperature tube furnace were studied. The addition of B-nm powder significantly reduces both the ignition temperature and the ignition delay time (IDT) of Al-μm in WRV. When the ambient temperature is 1000 °C, the IDT of the B-Al mixtures gradually decreases with the increase of B content. Notably, the sample containing 40 wt% B-nm powder exhibits the optimal performance, which has the lowest ignition temperature (334.85 °C), the shortest IDT (2.82 s), and the highest combustion temperature (1176.53 °C). Compared with Al-μm powder, the ignition temperature and the IDT of Al with 40% B-nm addition are reduced by 62.32% and 76.69%, respectively. All these results demonstrate that adding B-nm powder can improve the IAC of Al-μm powder in WRV. In addition, the combustion mechanism of the B-Al mixtures in WRV is discussed. This study not only contributes to improving the combustion of Al but also increases the heat release of the Al/Water system in ramjet engines.