KINETICS AND MECHANISMS OF NANOCRYSTALLINE MGFE2O4/ CUFE2O4 CORE/SHELL REDUCTION IN FLOWING HYDROGEN AT 400–700 OC

Document Type : Original Article

Authors

1 Researcher, Central Metallurgical Research and Development Institute (CMRDI), Helwan, Egypt.

2 Prof. of Materials Science , Chemistry Department, Faculty of Science, Beni-Sueif University, Beni-Sueif, Egypt.

3 Faculty of Science, Beni-Sueif University, Beni-Sueif, Egypt.

Abstract

ABSTRACT:
Copper ferrite nanoparticles are coated with magnesium ferrite nanoparticles to form CuFe2O4/ MgFe2O4 core/shell structure by hydrothermal precipitation method. The final precipitate was filtered, washed thoroughly with deionized water and dried at 343K for 24 h. The resulting sample was then calcined at 1173K for 2 h giving the magnetic material CuFe2O4/MgFe2O4 core/shell. The fired powder is then pressed in form of pellets and sintered at 500 oC for 2 h. CuFe2O4/ MgFe2O4 core/shell were isothermally reduced in hydrogen flow at 400-700 oC. The reduced nano-crystalline CuFe2O4/MgFe2O4 core/ shell compacts were characterized by XRD, TEM, SEM, VSM and reflected light microscope. Microstructure of partially and completely reduced samples was studied and the activation energy values were calculated from Arrhenius equation. The activation energy of the initial stage was found to be 9.2kJ/mol, and for the final stage is found to be 23kJ/mol. The approved mathematical formulations for the gas solid reaction were applied and it was found that at the initial stages the reaction is controlled by gaseous diffusion mechanism while the final reaction stages is controlled by the combined gaseous diffusion and interfacial chemical reaction mechanisms.

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