Surface Coating Strategies for Improving Boron Powder Combustion in Propellant Applications: A Review

Abstract

Boron powder is a remarkable metal fuel renowned for its high gravimetric and volumetric calorific values, making it an ideal choice for military applications, including solid propellants, high-energy explosives, and pyrotechnics. However, the formation of a liquid oxide layer on the surface of boron powder can lead to a gel layer’s creation, resulting from the reaction of hydroxyl (-OH) group in the hydroxyl-terminated polybutadiene (HTPB) binder, which hampers the propellant processing and limits the boron powder’s complete oxidation. To enhance the combustion efficiency of boron powder, researchers worldwide have explored the ignition and combustion mechanisms of boron powder and devised surface coating modification strategies. These modifications aim to optimize the surface properties, improve the reaction activity, and promote the energy release of boron powder. This review highlights recent studies on the ignition and combustion mechanisms of boron powder. Additionally, the review classifies the reported boron powder coating materials based on their chemical structure and reaction mechanism. Furthermore, the review summarizes the mechanisms and features of various coating materials, including providing mechanism diagrams of fluoride and metal oxide. Moreover, the review proposes promising directions for modification methods and outlines the potential application prospects of boron powder.