Peer-Reviewed Journal Details
Mandatory Fields
Venables, D. S.,Brown, M. E.;
Thermochimica Acta
Reduction of tungsten oxides with hydrogen and with hydrogen and carbon
Optional Fields
The reductions of WO3 and of WO3-graphite mixtures with hydrogen were studied in isothermal experiments in a tube furnace from 575 to 975 degrees C, using evolved gas analysis, X-ray powder diffraction, and scanning electron microscopy. The intermediate phases W20O58, W18O49, and WO2 were observed in the reductions. The final product of the reductions with hydrogen and carbon was tungsten. The reactant/product gas ratio had a considerable influence on the reactions occurring. The morphology of the sample was characterised at different stages of the reduction. Some particle growth was observed in the reduction with hydrogen and was attributed to the formation of WO2(OH)(2)(g), but the sizes and shapes of the tungsten particles produced were not greatly affected by the presence of carbon. The reactions were controlled by mass-transfer under the conditions investigated. The addition of carbon increased the rate of the reduction process, but did not affect the phases formed in the system. CO2 was evolved mainly at the start, and CO mainly at the end of the process. The reaction mechanisms were determined on the basis of the evolved gas analyses. Results are compared with results obtained in other studies of the reduction using carbon alone and carbon monoxide.
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