Influence of the gas atmosphere on the obtention of cobalt and iron based nanocomposites and core/shell nanoparticles by calcination in the presence of chitosan

In this work, CoFe2O4/CoFe2 nanoparticles with core/shell structure were synthesized by carbothermic reduction using chitosan beads impregnated with Fe3+ and Co2+ ions. The samples were synthesized at 400, 550, 650 and 750 degrees C, during intervals of 30, 90 and 120 min and under air, N-2 and H-2 gases. To apply the carbothermic method, chitosan was thermally decomposed in presence of N(2 )gas. The structural and magnetic properties were studied using X-ray powder diffraction, transmission electron microscopy, vibrating sample magnetometry and Mossbauer spectroscopy. The results showed that the Co-Fe impregnated chitosan beads thermally treated, firstly, in air at a given temperature and afterwards treated at 400 and 550 degrees C in H-2 for 30 and 90 min led to the formation of CoFe2O4/CoFe2 nanoparticles, the samples treated at higher temperatures were single phase of CoFe2. However, the Co-Fe chitosan beads treated in N-2 for 120 min at 550, 650 and 750 degrees C favored the formation of a core/shell (CoFe2O4/CoFe2) nanoparticles with CoFe2 concentration ranging from 75.5 to 35.0 Wt %, the amount of CoFe2 increased with the increase of temperature. The highest saturation magnetization of 227.7 emu/g was achieved for the sample treated a 550 degrees C under N-2 atmosphere.

Automated summary

In this study, core/shell structured CoFe2O4/CoFe2 nanoparticles were synthesized using carbothermic reduction method with chitosan beads impregnated with Fe3+ and Co2+ ions. The samples were synthesized under different conditions of temperature and atmosphere, and their structural and magnetic properties were investigated. The results showed the formation of CoFe2O4/CoFe2 nanoparticles or single phase CoFe2 nanoparticles depending on the treatment conditions, with the samples treated under N2 atmosphere exhibiting the highest saturation magnetization.