Atomic-Layer-Engineered Inorganic-Organic Dual-Shell Nanocoatings for Water-Resistant Aluminum Hydride

Aluminum hydride (AlH₃) is a promising high-energy-density fuel for solid propellants, yet its sensitivity to moisture severely limits practical applications. Herein, an inorganic-organic dual-shell surface architecture is constructed to enhance the water resistance of AlH₃, comprising an atomic-layer-deposited TiO₂ inorganic inner layer and a perfluorodecyltrimethoxysilane (FAS-17) outer layer. The conformal TiO₂ interlayer (2.5 nm) acts as a robust barrier to hinder permeation and improve the thermal stability of AlH₃, while subsequent FAS-17 modification (4.6 nm) yields a superhydrophobic surface via stable interfacial Si-O-Ti bonds. As a result, the coated AlH₃ maintains an exceptional mass retention of 99.95% after exposure at 25 °C and 85% relative humidity for 15 days. Hydrothermal and acidic aging tests conducted in liquid environments at 50 °C further reveal substantially suppressed hydrogen release and better-preserved particle morphology for the coated AlH₃. These improvements are attributed to the dual-shell nanocoating, which enhances mechanical integrity and effectively blocks water penetration. This work highlights the effectiveness of atomic-layer-deposited interlayers combined with hydrophobic surface modification for stabilizing moisture-sensitive energetic materials.