Preliminary Kinetic Characterization of Lithium–Aluminum Based Hydrides for Airbreathing Propulsion

Abstract

The aim of this research is to present a preliminary experimental investigation on the behavior of lithium–aluminum complex hydrides when exposed to gaseous nitrogen in the range of 20–350°C for airbreathing propulsion applications. This specific task is part of the long-term project devoted to the use of lithium–aluminum hydrides in airbreathing propulsion applications. It is known that a launch system based on the airbreathing technology, by using air as oxidizer, reduces the cost per kilogram of the launch; it is therefore much more profitable than common rocket engines (solid and liquid rockets). The effect of nitrogen gas on the thermal behavior and the kinetic parameters of lithium–aluminum hydride and trilithium–aluminum hydride has been investigated. Differential scanning calorimeter tests, performed using nitrogen gas, have shown the presence of a strong exothermic peak that, when using helium or argon gas, is barely noticeable. A nitridation reaction has been suggested to explain the increase of the sample mass after each differential scanning calorimeter test, which supports the experimental data. The activation energy and frequency factor for the samples of lithium–aluminum hydride and trilithium–aluminum hydride have been calculated using two simplified kinetic methods: the Ozawa method and the Kissinger method.