On the Oxidation and Combustion of AlH₃ a Potential Fuel for Rocket Propellants and Gas Generators

Abstract

Aluminum hydride is a promising candidate for application in energetic materials and hydrogen storages. E.g. an AP/HTPB rocket propellant filled with alane was calculated for a 100 N s kg À1 higher specific impulse compared to the same concentration of aluminum. Different investigations on a-AlH 3 polyhedra using thermoanalytical methods and X-ray diffraction were performed to receive a better understanding of dehydration at about 450 K, passivation of the remaining porous aluminum particles and further oxidation. A modeling approach to describe these conversions including diffusion processes, Avrami-Erofeev mechanism and Arrhenius type reaction steps of n-th order were introduced. Results were discussed in comparison to experimental investigations under pressure with model propellants on the base of gelled pure nitromethane and also filled with alane or pure aluminum in concentrations of 5%, 10% and 15%. Both alane and aluminum increase the burning rate on a factor of two correlated with a temperature increase up to 500 K and more. A mesa burning effect at 6 to 10 MPa was indicated by the mixtures with alane.

Photoelectron spectroscopic study of carbon aluminum hydride cluster anions

“…Due to poor thermal stability and material purity issues, AlH 3 has not been widely used as a propellant, 1,2 even though on a small scale, it performs better than hydrocarbons and elemental aluminum. [1][2][3][4] More complex aluminum hydrides, however, may offer better prospects. Gas phase studies discovered and characterized hundreds of previously unknown aluminum hydride cluster anions, Al y H z − , [5][6][7][8][9][10][11] and with them their corresponding neutral aluminum hydride cluster compositions.…”

Novel methods for synthesizing halide-free alane without the formation of adducts

“…α-AlH 3 can be easily handled and controlled using catalysts or varying particle sizes to desorb hydrogen at desirable rates for optimal fuel cell operation [3,4]. Besides its potential use in hydrogen-powered cars, alane can also be useful in portable power systems and a wide array of other applications such as reagents in chemical reactions [5] and rocket fuel [6].…”

“…Larger alane particle sizes are ideally desired for their ability to remain stable for years at ambient temperature [6]. This increase in stability is likely assisted by minor oxide layer coatings formed on these particles.…”

Combustion of alane and aluminum with water for hydrogen and thermal energy generation

“…Aluminum hydride, or alane, has been broadly used in many energetic materials due to its high hydrogen storage capacity (theoretically, 10.1% by weight) [17][18][19][20][21][22][23][24]. Alane is a covalently bonded hydride which often appears in a polymeric form (AlH 3 ) n and has at least seven known nonsolvated forms.…”