E. P. Naiden

Radiation-thermal synthesis of W-type hexaferrites

The results of investigations of the phase composition, structural parameters, static and dynamic magnetic properties of BaCo0.7Zn1.3Fe16O27 hexaferrites obtained by the method of self-propagation high-temperature synthesis in combination with mechanochemical activation and radiation-thermal post-sintering are presented. The prospects of the proposed energy-saving approach for the production of ferrite ceramics with a hexagonal structure is shown.

Colony-forming activity of unipotent hemopoietic precursors under the effect of nanosized ferrites in a constant magnetic field in vitro

We studied in vitro effect of ferrimagnetic nanoparticles in a dose of 3 mg/liter (10 maximum permissible concentrations) on colony-forming capacity of bone marrow granulocytic and monocytic precursors in a constant magnetic field at magnetic field intensity of 200 Oe. We tested powders obtained by the methods of electrical explosion of conductors (magnetite and a mixture of hematite with magnetite) or mechanochemical synthesis (cobalt ferrite). According to electron microscopy, size of particles was within 6–65 nm. Specific effect of nanopowders on functional properties of hemopoietic and stromal cells were demonstrated; this effect was not related to dissolution of these powders, but had a complex nature. It depends on the size and magnetic characteristics of powder particles, the route and dose of administration, and the presence of external magnetic field. It was emphasized that in multicellular systems a reaction of committed hemopoietic precursors mediated via cells (factors) of microenvironment cannot be excluded, the state of this system varying in different individuals and under different conditions. Our data open new vistas for the creation and targeted use of nanosized materials and technologies for individual therapy in the context of personalized medicine.

Effect of conditions of the mechanochemical synthesis and heat treatment on the phase composition, structural parameters, and magnetic properties of nanodimensional powders of cobalt spinel ferrite

Nanodimensional powders of cobalt spinel ferrite are obtained from salt systems by mechanochemical synthesis. The effect of the duration (τ) of mechanochemical synthesis and the temperature (t) of subsequent thermal treatment on the phase composition, structural parameters, and main magnetic properties of cobalt spinel ferrite is investigated by means of X-ray structural analysis, transmission electron microscopy, and X-ray fluorescent analysis. It is established that its yield and the average size of nanoparticles grow while the specific surface area and internal elastic stresses diminish as τ and t increase. The magnetization saturation in this case increases while variations in the effective magnetic-anisotropy field are of a more complex character, being conditioned mainly by the reduced contribution from the magnetoelastic component to the total energy of magnetic.

Magnetic properties and microstructure of SHS-Produced co-containing hexaferrites of the Me2W system

BaCo2 − xZnxFe16O27 hexaferrite powders were prepared by mechanoactivated SHS. The ferrites were characterized by XRD and phase analyses. The values of specific saturation magnetization, field of magnetocrystalline anisotropy, spin reorientation transition, and Curie’s temperatures were derived from static and dynamic measurements of respective magnetic properties. The spectra of magnetic permeability and dielectric permittivity were measured within the microwave range.

Mechanisms of the self-propagating high-temperature synthesis, phase composition, and magnetic properties of complex oxide ferrimagnets with M structure

Mechanisms of the combustion of reagent mixtures that form complex oxide ferrimagnets (hexaferrites with M structure) are investigated. The phase composition of the end product is found, depending on technological conditions that include self-propagating high-temperature synthesis with preliminary mechanical activation and/or subsequent ferritization. The basic static and dynamic magnetic properties of an end product synthesized in the optimum mode are determined. An energy-saving technique for manufacturing hexaferrites with M structure, making it possible to lower production costs substantially, is proposed.

Mechanochemical modification of the phase diagrams of hexagonal oxide ferrimagnets

Mechanical activation and fine comminution of hexagonal oxide ferrimagnets by milling to a nanocrystalline state (ultradisperse powder), followed by sintering, leads to significant changes in the phase diagram, the temperature of synthesis, and the magnetic properties as compared to those of the materials obtained by traditional ceramic technology. The final material structure is formed through “chemical assembly”—sequential consolidation of nanodimensional particles (structure-forming blocks)—rather than through the formation of low-temperature phases and their decomposition with increasing temperature.

Effect of heat treatment on the structural parameters and magnetic properties of copper ferrite nanopowders obtained by the sol-gel combustion*

Phase composition, structure parameters and basic magnetic characteristics obtained by the sol-gel combustion nanopowders of ferrospinel CuFe2O4 are investigated. A comparison of the properties of synthesized materials: first sample - immediately after the combustion of the gel and second sample - after annealing at 1073 K for 4 hours are performed. Annealing leads to an increase in the concentration of the phase with tetragonal crystal structure. Particle sizes and the value of anisotropy field of this phase also increased.

Synthesis of fullerites in steel under action of low-pressure arc discharge with graphite anode

The chemical and thermal effects of low-pressure arc discharge with graphite anode in nitrogen on the near-surface layer of a low-carbon (St3 grade) structural steel have been studied. The elemental and phase compositions of the arc-discharge-modified surface layer have been determined by the Auger electron spectroscopy and X-ray diffraction analysis. Fullerites (C60, C70) and a considerable amount of FenC carbides have been found in addition to a high fraction of an amorphous phase with a complex elemental composition. At the same time, graphite and austenite, which are characteristic of the thermodynamic equilibrium process in the Fe-C system with high carbon content, are completely absent in arc-discharge-treated steel.