Nano‐Scale Tungsten Oxides for Metastable Intermolecular Composites

Abstract

AbstractTungsten oxides are of interest as an oxidant for metals in metastable intermolecular composites, a nano‐scale powder useful for such applications as electric matches and gun primers. Smaller particles typically lead to faster reactions and we have synthesized nano‐scale WO3 using wet chemistry. Ammonium paratungstate was dissolved in acid. Tungstic acid was precipitated by addition to distilled water and the resulting powder was dried. Analysis by X‐ray diffraction, Raman spectroscopy and electron microscopy revealed hydrated WO3, having approximately 100 nm×7 nm platelet morphology. Thermal treatment in air at 200 °C or 400 °C removed water, forming cubic or monoclinic WO3, respectively. Tungsten forms other stable oxides and we accessed WO2 by reducing WO3 in dilute H2 at 650 °C. Reaction performance of these WOx‐materials, mixed with nano‐Al at various stoichiometries, is reported. Open‐tray burn velocity reached 250 m/s. Pressure cell experiments found a maximum pressure of 1.45 MPa and maximum pressurization rate of 500 GPa/s. These maximum pressures and rates occurred very near a stoichiometric mixture of the Al and WO3.