Kinetics and mechanisms of the reduction of Cu 0.5Zn 0.5Fe 2O 4 with hydrogen at 400–600 °C for the production of metallic nanoparticles

Abstract

Ferrites have continued to attract attention over years. As magnetic materials, ferrites cannot be replaced by any other magnetic material because they are relatively inexpensive, stable and have a wide range of technological applications in transformer core, high quality filters, high frequency circuits and operating devices. Nanocrystallite sizes of Cu 0.5 Zn 0.5Fe 2O 4 with 25 nm have been obtained by hydrothermal route. Cu 0.5Zn 0.5Fe 2O 4 powder was isothermally reduced in H 2 flow at 400–600 °C. The reduction behavior of the produced powder as well as the influence of reduction temperature on the structural characteristics of the products was extensively studied. Microstructure of partially and completely reduced samples was investigated and the activation energy values were calculated from Arrhenius equation. The activation energy for nanocrystallite Cu 0.5 Zn 0.5Fe 2O 4 reduced at the initial stage was found to be 37.4 kJ/mole, while that at the final stage is 14 kJ/mole. The approved mathematical formulations for the different crystallite sizes gas solid reaction were applied and it was found that at the final stages the reaction is controlled by the gaseous diffusion while the combined gaseous diffusion and interfacial chemical reaction is the rate controlling mechanisms at the initial stages. The reduction process produce nanoparticles metallic phases of iron, copper and zinc, which have ball and fibers shapes.