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Hydrogen reduction route towards the production of nano-grained alloys.- Synthesis and characterization of Fe2Mo powder.
KTH, Superseded Departments, Materials Science and Engineering.
2002 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

With a view to design processes based on gas-solid reactiontowards the production of fine-grained novel alloys andintermetallics, studies of the reduction of the mixed oxides ofFe and Mo by hydrogen towards the production of Fe-Mo alloyshave been carried out in the present work. The route offersexcellent potentials toward the bulk production of nano-grainedmaterial of tailored-composition in bulk in a green processpath. As a case study, the reduction of the mixed oxides ofiron and molybdenum were carried out from the viewpoint ofmaterials processing, chemical reaction kinetics, as well asmechanical and structural properties. The reduction kinetics ofthin layer of fine oxide particles of Fe2MoO4 was studied usingthermogravimetric technique. This technique allowed determiningreduction parameters such as temperature of reduction as wellas the activation energies for the chemical reaction as therate-controlling step. The end products were analyzed by X-raydiffraction. The reduction product was found to be reduced topure, homogeneous Fe2Mo. In order to examine the upscaling ofthe process, production of the alloy in larger amounts wascarried out in a laboratory-scale fluidized reactor and theprocess parameters were optimized. It was found that, under theconditions of the experiments, the chemical reaction was therate-controlling step. TEM, SEM and X-ray analyses of thereaction product showed the presence of a monolithicintermetallic with micro- and nanocrystalline structure. Themechanical properties of this alloy were determined.Compositions of microcrystalline Fe-Mo alloys were varied byreducing mixtures of Fe2MoO4 with MoO2 or FeO with differentFe/Mo ratios. The products after the reduction consisted of twophases, viz. intermetallic FexMoy compound and metallic Fe orMo. XRD analyses revealed that the former had microcrystallinestructure while the latter were in crystalline form. This workshows that gas-solid reaction method, together with powdermetallurgy technique is a promising process route towards theproduction of novel metallic alloys such as Fe2Mo intermetallicwith micro- and nanocrystalline grains.

Key words: nanoalloys, intermetallics, iron-molybdenumalloy, hydrogen reduction, thermogravimetry, fluidized bed,mechanical properties, structure

Place, publisher, year, edition, pages
Stockholm: Materialvetenskap , 2002. , x, 43 p.
Keyword [en]
Intermetallics, nano-graines, redcution kinetics
Identifiers
URN: urn:nbn:se:kth:diva-3404ISBN: 91-7283-356-4 (print)OAI: oai:DiVA.org:kth-3404DiVA: diva2:9200
Public defence
2002-10-04
Note
NR 20140805Available from: 2002-09-23 Created: 2002-09-23Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
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