Cobalt Ferrites: Formation from Nitrate Solutions under the Action of DC Discharge

A new method for obtaining ultrafine particles of cobalt ferrites is proposed. This synthesis is a two-step process: the first step is the synthesis of ultrafine particles from aqueous solutions of nitrates under the action of non-equilibrium low-temperature plasma. The second stage is high-temperature treatment of the resulting powders. The action of plasma on solutions of iron and cobalt nitrates leads to the formation of a colloidal suspension at the plasma-solution interface in the liquid anode. The kinetics of co-precipitation from solutions under the action of plasma has been studied. It is shown that the process of formation is complex, includes several stages. The rate of formation of particles directly depends on the concentration of iron nitrate in the initial mixture. An increase in the discharge current leads to an increase in the rate of particle formation. The obtained substances were studied immediately after the plasma-solution interaction, after centrifugation, and after high-temperature treatment. X-ray diffraction analysis showed that the resulting ultrafine particles are a mixture of hydroxonitrites and hydroxides of cobalt and iron. The data of thermogravimetric analysis confirm the data of X-ray diffraction analysis. The surface morphology was studied using a scanning electron microscope; the resulting powders have a well-developed surface. The resulting particles are characterized by two sizes, 92 nm and 1.46 μm. The magnetic characteristics of the particles were studied using a vibrating magnetometer at room temperature with a maximum applied field of up to 30 kOe. The coercive force of the obtained particles was 210 Oe. The saturation magnetization (MS) obtained at room temperature was found to be 65 emu/g and remanent magnetization (Mr) was 22 emu/g.