Aluminum Hydride as a Fuel Supplement to Nanothermites

An experimental study was conducted in which aluminum hydride (alane, AlH3) replaced nanoaluminum incrementally as a fuel in a nanocomposite thermite based on CuO, Bi2O3, and Fe2O3. Pressure cell and burn tube experiments demonstrated enhancements in absolute pressure, pressurization rate, and burning velocity when micron-scale aluminum hydride was used as a minor fuel component in a nanoaluminum-copper-oxide thermite mixture. Peak pressurization rates were found when the aluminum hydride made up about 25% of the fuel by mole. Pressurization rates increase by a factor of about two with the addition of AlH3, whereas burn tube velocities increase by about 25%. The enhancement in pressurization rate appears to primarily be a result of the increased pressure associated with the AlH3 decomposition in the nanocomposite thermite system and an enhancement in convective heat transfer. Similar experiments were conducted with micron-scale aluminum in place of the aluminum hydride, which resulted in a reduction of all the previously mentioned parameters with respect to the baseline nanoaluminum-copper-oxide thermite. The addition of any amount of alane to iron oxide based thermite resulted in a reduction in performance in pressure cell testing. The performance of Bi2O3 based thermite was largely unaffected by alane until alane became the majority fuel component. These results have been found to correlate with changes in the combustion mechanism through equilibrium calculations.