Synthesis of nanocrystalline Fe–W composite through hydrogen reduction of thermally synthesized iron tungstate, Fe 2WO 6

Abstract

Iron tungstate (Fe 2WO 6) powder was prepared through the ceramic route by calcination of a stoichiometric mixture of iron oxide and tungsten oxide (Fe 2O 3/WO 3) at 800 and 950 °C. The Fe 2WO 6 powder was isothermally reduced in pure hydrogen at 800–1000 °C for synthesis of a Fe–W composite. The reduced powder was sintered in a hydrogen atmosphere at 1200 °C for 2 h. Based on thermogravimetric analysis, the reduction behavior and kinetic reaction mechanism were studied. The initial tungstate powder and the various reduction products were characterized by XRD, SEM, VSM, reflected light microscope, pore size and digital nanohardness to reveal the effects of hydrogen reduction on microstructure, magnetic properties, hardness and reaction kinetics of the produced Fe–W composite. Complete reduction was achieved with synthesis of a nanocrystalline homogenous Fe–W composite. The initial reduction stages are controlled by a mixed reaction mechanism while the final stags are controlled by a solid-state reaction mechanism.