Nanocrystalline tungsten hydrides at high pressures

A combined experimental and theoretical study has been carried out on the synthesis and characterization of tungsten hydride at high pressures. We confirm the synthesis of tungsten monohydride at above 25 GPa and 300 K. At higher pressures, hydrogen content is found to increase and ab-initio calculations reveal the formation of overstoichiometric tungsten hydride WHn with n similar to 11/3. Synchrotron x-ray diffraction and transmission electron microscopy (TEM) measurements demonstrate the formation of a nanocrystalline microstructure upon hydrogenation. TEM micrographs show elongated grains with diameters of similar to 20 nm, a structure similar to nanocrystalline diamond.