Citric acid enhances the ignition and combustion performance of aluminum: coating and etching

The combustion efficiency of Al is usually not high due to the influence of alumina film and agglomeration. Therefore, finding ways to enhance the ignition and combustion performance of Al is important. Herein, a simple one-step recrystallization method was used to prepare the Al@ citric acid (CA) sample. The results showed that the one-step recrystallization method could well coat CA on the outer surface of Al particles and could etch Al particles uniformly. After modification by CA, Al was more prone to thermal oxidation. Compared with pure Al, the addition of CA resulted in shorter ignition delay time, longer combustion time, increased combustion intensity, and weakened agglomeration degree. Condensed combustion products (CCPs) showed that Al sintered significantly during combustion, forming a large agglomerate. The CCPs of Al@CA were more dispersed and had many hollow shell particles. Furthermore, the addition of CA led to a decrease in the active Al content and an increase in the α-Al2O3 content in CCPs. The above phenomena indicated that CA could significantly improve the combustion efficiency of Al. At last, the possible mechanism of CA promoting the ignition and combustion of Al was proposed. Overall, the enhancement of Al combustion performance by CA is attributed to the etching and coating effects of CA. Hoping that this paper will provide a possible pathway for exploring ways to improve Al combustion efficiency.