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

Alpha-aluminum hydride (alpha-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 alpha-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 alpha-AlH3 by coating the alpha-AlH3 surface with an organic layer using vinyltrimethoxysilane (A171). The alpha-AlH3@A171 composite shows enhanced performance in terms of thermal stability and hygroscopic properties. In the constant temperature experiments at 100 degrees C, the required time to lose 1% mass of alpha-AlH3@A171 is 561.5 minutes, showing excellent stability. More importantly, the resulting alpha-AlH3@A171 composite exhibits an increased activation energy of 4.32 kJ mol(-1) after stabilization. Furthermore, the alpha-AlH3@A171 composite also shows excellent performance in resisting water erosion, and the hydrophobic angle increases from 24.23 degrees to 96.94 degrees after the organic layer is coated on the alpha-AlH3 surface. The hygroscopic weight gain of alpha-AlH3@A171 was only 0.89% when stored at 30 degrees C and 80% relative humidity for 30 days, which was lower than that of alpha-AlH3 (23.1%). This work provides a convenient method for the safe application of alpha-AlH3 in the field of solid propellants.

Automated summary

Coating α-AlH3 surface with an organic layer using A171 can enhance its thermal stability and hygroscopic properties, leading to improved performance in resisting water erosion and maintaining stability during constant temperature experiments.