Enhancing the ignition and combustion performance of aluminum by surface modification: tannic acid and tea polyphenols

Aluminum has been long and widely used in propellants, thermite, and pyrotechnics. However, the commonly used micron aluminum has the problems of slow burning rate and incomplete release of chemical energy in the combustion process. Therefore, finding ways to promote the ignition and combustion of aluminum is essential to enhance the performance of aluminum-based energetic materials. Herein, environmentally friendly tannic acid (TA) and tea polyphenols (TP) were used to surface modify aluminum to improve its combustion performance, respectively. The results showed that TA and TP could be coated on the outer surface of aluminum particles effectively by solvent evaporation induced self-assembly method. Heat was released during the thermal decomposition of the composite particles, which was clearly beneficial in promoting aluminum ignition. Ignition and combustion tests showed that after modification with TA and TP, the samples showed shorter ignition delay, increased combustion time, increased combustion intensity, and reduced agglomeration compared to pure aluminum. This revealed that the modified samples possessed better ignition and combustion properties. The X-ray diffraction patterns of the condensed combustion products showed that the products of pure aluminum possessed more active aluminum and aluminum nitride, while the samples modified with TA and TP had more gamma-Al2O3 and alpha-Al2O3, suggesting that TA and TP could effectively enhance the combustion efficiency of aluminum. In addition, TP showed better modification than TA, which may be related to the higher heat release during thermal decomposition of TP. Although TA and TP can improve the ignition and combustion performance of aluminum to some extent, the enhancement effect is limited. Considering that TA and TP possess good adhesion, perhaps they can play a better role in promoting as intermediate layers in the future. It is hoped that this paper can provide a new idea for the surface modification of aluminum.