The enhanced thermal stability and reduced hygroscopicity of aluminum hydride coated with vinyltrimethoxysilane

Abstract

Alpha-aluminum hydride (α-AlH₃) is an excellent high-energy additive for solid propellants because of its high hydrogen content (10.8 wt%) and energy density, low decomposition temperature, and good combustion performance. However, the application of α-AlH₃ is limited by its poor thermal stability and hygroscopicity. In this work, we present a facile method to improve the thermal stability and hygroscopicity of α-AlH₃ by coating the α-AlH₃ surface with an organic layer using vinyltrimethoxysilane (A171). The α-AlH₃@A171 composite shows enhanced performance in terms of thermal stability and hygroscopic properties. In the constant temperature experiments at 100 °C, the required time to lose 1% mass of α-AlH₃@A171 is 561.5 minutes, showing excellent stability. More importantly, the resulting α-AlH₃@A171 composite exhibits an increased activation energy of 4.32 kJ mol⁻¹ after stabilization. Furthermore, the α-AlH₃@A171 composite also shows excellent performance in resisting water erosion, and the hydrophobic angle increases from 24.23° to 96.94° after the organic layer is coated on the α-AlH₃ surface. The hygroscopic weight gain of α-AlH₃@A171 was only 0.89% when stored at 30 °C and 80% relative humidity for 30 days, which was lower than that of α-AlH₃ (23.1%). This work provides a convenient method for the safe application of α-AlH₃ in the field of solid propellants.