6 Nanocomposites and nanomaterials

Effect of pH on the magnetic properties of magnetite obtained by the plasma method

L.A. Frolova, A. A. Pivovarov

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

Magnetic nanoparticles are studied because of their wide range of applications. Magnetite nanoparticles can be used for sewage treatment, magnetic resonance imaging, catalyst production, pigment synthesis and magnetic recording. To obtain nanodispersed magnetite, such methods as coprecipitation, microemulsion, hydrothermal, sol-gel, thermal decomposition, sonochemical synthesis are used.
Most of them are associated with annealing at high temperature and obtaining large agglomerated particles. The method of precipitation has become widespread due to its simplicity, reasonable cost, non-toxic precursors, which do not require much time and equipment.
It is known that the particle size and crystallinity can be varied by adjusting the supersaturation during the nucleation and growth processes of the crystals, which in turn can depend heavily on the concentration of the initial solutions and the deposition conditions such as temperatures and the initial pH.
A special place is occupied by methods of synthesis using a contact nonequilibrium low-temperature plasma.
Plasma-chemical synthesis is sensitive to pH, which affects the properties of the magnetite formed, the particle size and the degree of crystallinity. Consequently, pH can cause changes in the physical and chemical properties of magnetite.
In this paper, magnetite nanoparticles were synthesized in a plasma-chemical reactor at various pH (8-12) and a treatment time of 50 minutes.
The results revealed the formation of a single-phase spinel structure for all samples. Crystallinity and crystallite size increased with increasing pH. After the end of the series of experiments, it can be concluded that the magnetic properties of the precipitates obtained during the processing of the samples directly depend on the initial pH. As a result of the experiments, the maximum magnetic saturation of MS 139 emu / g was reached at pH = 11, and a maximum of Hc 80 Oe at pH = 10.