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Kinetics of Reduction of NiO–WO3 Mixtures by Hydrogen
Department of Materials Science and Engineering, Royal Institute of Technology.
Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo.
Kungliga tekniska högskolan, KTH.
2010 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 1, 161-172 p.Article in journal (Refereed) Published
Abstract [en]

The kinetics of reduction of the oxide mixtures of Ni-W with different Ni/(Ni-W) molar ratios within the range of 923 K to 1173 K in flowing hydrogen gas was investigated by means of thermogravimetric analysis under isothermal conditions. The products were examined by X-ray diffraction, scanning electron microscope (SEM), and electron dispersion spectroscopy (EDS) analyses. Five different oxide mixtures apart from the pure oxides were studied in the present work. The results indicate that the reduction reaction proceeds through three consecutive steps that are as follows:NiO-WO3→Ni-WO3→Ni-WO2→Ni-WFrom the experimental results, the Arrhenius activation energies of the three steps were evaluated for all of the studied compositions. The activation energy for the first step was calculated to be approximately 18 kJ/mol. For the second and third stages, the activation energy values varied from 62 to 38 kJ/mol for the second stage and 51 to 34 kJ/mol for the third stage depending on the Ni/(Ni + W) molar ratio in the precursors; the activation energy increased with increasing ratios. SEM images showed that the grain size of the final product was dependent on the Ni/(Ni + W) molar ratio; smaller grains were formed at higher nickel contents.

Place, publisher, year, edition, pages
2010. Vol. 41, no 1, 161-172 p.
National Category
Metallurgy and Metallic Materials
Research subject
Process Metallurgy
Identifiers
URN: urn:nbn:se:ltu:diva-3192DOI: 10.1007/s11663-009-9302-7Local ID: 0fc1f20e-0257-48fd-9649-8e776dc26614OAI: oai:DiVA.org:ltu-3192DiVA: diva2:976048
Note
Upprättat; 2010; 20141022 (hesahm)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-10-19Bibliographically approved

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