Low temperature isothermal reduction behaviour of hydrothermally precipitated CuFe2 O4/MgFe2O4 core/shell nanocrystallites

A hydrothermal precipitation method has been used to coat copper ferrite nanoparticles with magnesium ferrite nanoparticles to form core/shell magnetic structures. The final precipitate was dried at 343 K for 24 h, then calcined at 900°C for 2 h to give the CuFe 2 O 4 /MgFe 2 O 4 core/shell structur...

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Bibliographic Details
Published in:Materials technology (New York, N.Y.) N.Y.), 2008-12, Vol.23 (4), p.224-230
Main Authors: Bahgat, M., Khedr, M. H., El Rouby, W. M. A.
Format: Article
Language:English
Subjects:
CORE/SHELL MAGNETIC POWDERS
KINETICS
MAGNETIC PROPERTIES
MECHANISMS
NANOPARTICLES
REDUCTION
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Summary:A hydrothermal precipitation method has been used to coat copper ferrite nanoparticles with magnesium ferrite nanoparticles to form core/shell magnetic structures. The final precipitate was dried at 343 K for 24 h, then calcined at 900°C for 2 h to give the CuFe 2 O 4 /MgFe 2 O 4 core/shell structure. The fired powder was pressed to form pellets and sintered at 500°C for 2 h. CuFe 2 O 4 / MgFe 2 O 4 compacts were isothermally reduced in hydrogen at 400-700°C. The microstructure of partially and completely reduced samples was studied and the activation energy for reduction calculated on the basis of X-ray diffraction studies. The activation energy of the initial stage was found to be 9˙2 kJ mol −1 , and for the final stage 23 kJ mol −1 . Reaction kinetics calculations suggest that the reaction is rate controlled by gaseous diffusion in the initial stages, and by combined gaseous diffusion and interfacial chemical reaction mechanisms in the later stages.
ISSN:1066-7857
1753-5557
DOI:10.1179/175355508X330834