Energy release characteristics of the nanoscale aluminum-tungsten oxide hydrate metastable intermolecular composite

Abstract

Tungsten oxides are of interest as an oxidant for metals in metastable intermolecular composites (MICs), a reactive nanoscale powder useful for such applications as electric matches and gun primers. Smaller particles typically lead to fast reaction rates in this class of energetic material, and we have synthesized nanoscale WO3∙H2O using wet chemistry. Analysis by electron microscopy and small angle x-ray scattering revealed an approximately 100-nm-wide by7-nm-thick platelet morphology. X-ray diffraction verified the orthorhombic structure and composition of the hydrate. A MIC material was formulated using 44nm Al as the fuel. Performance was measured using a pressure cell where total enthalpy change and energy release rate was measured. This report includes the thermodynamic analysis of the pressure cell (calorimetry) that allows the determination of these metrics. Accuracy of the technique is discussed. Performance of the hydrate was found to significantly exceed that of MIC formulated with dehydrated tungsten oxide for one formulation, having an energy release of approximately 1.8MJ∕kg at a rate of approximately 215GW∕m2, compared to around 1.1MJ∕kg at a rate of around 130GW∕m2 for the dehydrated formulation. The data show that the enhanced behavior of the hydrated MIC formulation resulted from the reaction of aluminum with the interstitially bound water, which had additional energy release and generated hydrogen gas.