Alkaline steaming-assisted conversion: a new strategy for the synthesis of pure NiFe2O4 and CoFe2O4 spinel ferrite nanoparticles

Abstract

Spinel ferrites have potential applications as gas sensors, catalysts, microwave absorbers, and they can be used for information storage systems, rechargeable lithium batteries and medical diagnostics. Alkaline steaming-assisted conversion, a new strategy, was first developed for the synthesis of pure NiFe₂O₄ spinel nanoparticles, and its mechanism is discussed. Ammonia, ethylenediamine, and mixtures of both were used as steaming vapor to convert the dry powder of a stoichiometric mixture of FeCl₃·6H₂O and NiCl₂·6H₂O into NiFe₂O₄. In this system, ethylenediamine cooperates with ammonia in the alkaline steaming vapor to convert the Ni and Fe precursors into NiFe₂O₄ nanoparticles. Pure NiFe₂O₄ nanoparticles were only obtained by the combination of alkaline ammonia and ethylenediamine. The results show that the purity of the product depends on the concentration of ethylenediamine. The crystallization and the magnetization of these NiFe₂O₄ nanoparticles depend on the processing temperature and duration of the steaming process. The alkaline-steaming assisted conversion strategy was further successfully extended to the synthesis of pure CoFe₂O₄ nanoparticles, demonstrating a broad application possibility.