The effect of applied voltage on nickel ferrite nanostructures prepared by electrooxidation

Amongst the various nanomaterials, mixed transition metal oxide received increasing technological and industrial attention due to their distinctive properties and improved overall application performance. Nickel ferrite, NiFe2O4 is known as one of the versatile, multifaceted and technologically important ferrite because of its favorable properties. Here we report a new electrooxidation technique using three electrodes which helps us to control different properties of products through the production process by tuning the experimental conditions such as applied potential. Iron/nickel oxide nanostructures were synthesized by an electrochemical method. One nickel cathode and two sheets of iron and nickel as anodes with high purity were prepared. The electrodes were mounted 2 cm apart each other in an electrolytic cell containing an aqueous solution of sodium sulfate. Products were grown under an applied potential difference using a direct current (DC). The obtained precipitates were separated from the reaction medium and washed with deionized water and dried. Due to the significant role of the applied voltage in the electrochemical cell, we have studied the effect of applied voltages ranging from 5 V to 25 V on structural and magnetic properties of the particles. The nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). Based on XRD patterns, we found that cubic structure of NiFe2O4, rhombohedral structure of hematite (α-Fe2O3), hexagonal structure of Ni(OH)2 and rhombohedral structure of Fe8.7O10 are formed in different samples depending on the experimental conditions. It is possible to improve the crystal structure of particles by increasing the applied voltage. Figure 1 shows a typical SEM image of the sample synthesized by applying 25 V. SEM images show that the samples synthesized by applying lower voltages are highly agglomerated. The particles prepared under 25 V with mean particle size of ~60 nm are more dispersed. According to VSM results all samples are magnetically soft with a little hysteresis, but the magnetization depends on the growth conditions and the magnetic phase.