Surface hydroxylation-driven polyacrylic acid coating strategy for enhanced thermal stability and nitrate esters compatibility of aluminum hydride

The oxide layer on aluminum hydride (α-AlH₃) facilitates the cleavage of the O–NO₂ bond in nitrate esters, leading to the generation of NO₂ radicals and accelerating the autodecomposition of α-AlH₃. To mitigate this effect, the oxide layer was transformed into aluminum hydroxide (Al(OH)₃), and a core–shell structure was constructed through self-assembly with polyacrylic acid (PAA). This modification enhances the compatibility between α-AlH₃ and nitrate esters by preventing mutual decomposition. The thermal stability, decomposition behavior, and compatibility of α-AlH₃ with adhesion and plasticizing systems in solid propellants were systematically investigated. The uniform Al(OH)₃/PAA double-layer shell reduces thermal conductivity and extends the diffusion path, resulting in an approximately 20 % increase in decomposition activation energy. Furthermore, the core–shell architecture physically isolates α-AlH₃ from nitrate esters. The modified α-AlH₃ exhibits improved compatibility with adhesion and plasticizing systems. Notably, in the presence of nitrate esters, the net increase in hydrogen release decreased significantly from 10.03 to 0.96 mL g⁻¹. This study demonstrates, for the first time, that modified α-AlH₃ is compatible with nitrate esters at 60 °C, providing a theoretical basis for its application in high-energy solid propellants.