Nickel ferrite nanoparticles electro-synthesized using three electrodes

In the recent decades, research into ferrite structures has attracted great attention in a large panel of technological fields. Nickel ferrites are successfully utilized in a wide range of applications including computer memories, high density information storage, high quality filters, isolators, permanent magnets, energy storage in supercapacitor, biotechnology, magnetic fillers, magnetic resonance imaging, magnetic sensors, biomedical applications and medical diagnosis, magnetic drug carrier and hyperthermia agent in medicine, induction heating, magnetic separation, and water purification methods. Nickel ferrite nanoparticles were synthesized using electrochemical method in an electrolytic cell containing an aqueous solution of sodium sulfate, one nickel cathode and two sheets of iron and nickel as anodes. Products were grown under an applied potential difference using a direct current (DC). In order to find the better growth condition, different samples synthesized by changing the surface area of nickel anode from 0.5 cm2 to 8 cm2 keeping the applied voltage constant at 20 V. The samples were analyzed 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 depending on the experimental conditions. When the surface area of nickel anode increases, the presence of nickel ferrite in the sample goes up. Figure 1 shows a typical SEM image of the sample synthesized with 8 cm2 surface area of nickel anode by applying 20 V. From SEM images one can see that by changing the surface area of nickel anode from 0.5 cm2 to 8 cm2, the mean particle size increase from about 30 nm to ~60 nm. Also, the samples synthesized with smaller nickel anode surface area are highly agglomerated. Based on the magnetization curves of all samples we found that all samples are magnetically soft with a little hysteresis, but the magnetization depends on the growth parameters and the magnetic phase.