6 Nanocomposites and nanomaterials

Study of the process coprecipitation of Fe-Ni hydroxides for ferrite production

L. Frolova, O. Tsepich

Department of Technology Inorganic Materials and Ecology, 
Ukrainian State University of Chemical Technology, ave Gagarina, 8, Dnipro-49005, Ukraine.
Email: 19kozak83@gmail.com

Nickel ferrite has been the subject of research by scientists for many years. This is primarily due to the extremely wide range of its applications, covering such as high-density magnetic recording, computed tomography, magnetic resonance imaging contrast agents, targeted drug administration and hyperthermia, electronics, telecommunications and space equipment, environmental technologies, gas sensors, supercapacitors, etc.
The use of liquid-phase technologies for the production of nickel ferrites allows to change the structure, composition and, as a consequence, the functional properties of the final product. A hydrophase method is common, which includes the stage of coprecipitation of trivalent and divalent hydroxides followed by heat treatment at high temperatures. More promising is the technology based on co-precipitation of iron (II) and nickel (II) hydroxides. However, this process has not been studied enough.
In this work, Fe2+ -SO42- - H2O, Ni2+ -SO42- - H2O, Fe2+ -Ni2 + -SO42- - H2O systems were investigated using thermodynamic calculations, potentiometric titration, cyclic voltammetry (CVA), residual concentration method. The multistage mechanism of formation of hydroxocomplexes is established. Thermodynamic calculations have shown that the pH of hydroxides precipitation has similar values. Equilibrium compositions corresponding to different pH values are calculated.
The method of residual concentrations showed that the basic salts are formed first, with increasing pH the main product is polyheterohydroxides. The obtained CVA at a molar ratio of n = [OH - / [M2 +] = 1 in the system Ni2 + - Fe2 + -SO42- - H2O. The course of the cathode sections of the curves does not change for cycles 1-5, which indicates the stability of the formed intermediates.
As follows from the obtained data for n = 1, in the presence of both cations of iron (II) and nickel (II) in the solution, there are peaks that are not additive to individual solutions of Fe2 + -SO42- - H2O, Ni2 + -SO42- - H2O.