Calcium-assisted reduction of cobalt ferrite nanoparticles for nanostructured iron cobalt with enhanced magnetic performance
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This paper demonstrates the potential of a calcium-assisted reduction process for synthesizing fine-grain (~100 nm) metal alloys from metal oxide nanoparticles. To demonstrate the process, an iron cobalt alloy (Fe66Co34) is obtained by hydrogen annealing 7-nm cobalt ferrite (CoFe2O4) nanoparticles in the presence of calcium granules. The calcium serves as a strong reducing agent, promoting the phase transition from cobalt ferrite to a metallic iron cobalt alloy, while maintaining high crystallinity. Magnetic measurements demonstrate the annealing temperature is the dominant factor of tuning the grain size and magnetic properties. Annealing at 700 °C for 1 h maximizes the magnetic saturation, up to 2.4 T (235 emu/g), which matches that of bulk iron cobalt.
KeywordsMagnetic nanomaterials Iron cobalt Calcium-assisted reduction High saturation Grain evolution
This work was supported in part by the US Army Research Office (W911NF-09-1-0511) and National Science Foundation (CMMI-1451993). The authors thank Stefan Kelly for assistance in the DLS measurements, Lorena Maldonado-Camargo and Dr. Carlos Rinaldi for making the FC/ZFC measurements, and the UF MAIC facility for the invaluable support in material characterization.
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Conflict of interest
The authors declare that they have no conflict of interest.
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