E. N. Lysenko

Kinetics of phase formation in a Li2CO3-TiO2-Fe2O3 system during radiation-thermal synthesis

Kinetic changes in the concentration of source components in a Li2CO3-TiO2-Fe2O3 system during radiation-thermal (RT) synthesis are considered. The phase composition control is realized by X-ray diffraction (XRD) analysis, thermogravimetry (TG/DTG) analysis, and differential scanning calorimetry (DSC). The initial composition of reaction mixtures corresponds to the stoichiometric formula of spinel Li0.5(1 + x)Fe2.5 − 1.5xTixO4, where x = 0.2, 0.4, 0.6.

Determination of the oxygen diffusion coeficient in polycrystalline Li-Ti ferrites

Two independent methods, the isotope method based on nuclear microanalysis and the method based on measuring the electronic-conductivity activation energy, are used to determine the grain-boundary diffusion and volume diffusion of an oxygen isotope 18O in a polycrystalline lithium-titanium ferrite at the thermal annealing temperature 1073 K. A comparative analysis is conducted of the potential of the methods in studying oxygen diffusion in the material concerned. It is shown that the technique for obtaining the diffusion parameters from the electronic conductivity measurements allows a comparatively precise determination of both the volume and grain-boundary diffusion coefficients of oxygen in polycrystalline ferrites.

Microwave properties of Li-Zn ferrite ceramics

The work presents results of a study of the electromagnetic properties Li-Zn ferrite ceramics in a wide frequency range. It is shown that a homogeneous composition of such ceramics typically appear good radio-absorbing properties in the low-frequency range of microwave. The method of solid-phase radiation-thermal synthesis with preparatory mechanical activation of reagent mixture for obtain a homogeneous composition of ferrite powders is proposed.

Effect of powder compaction on radiation-thermal synthesis of lithium-titanium ferrites

Effect of powder compaction on the efficiency of thermal and radiation-thermal synthesis of lithium-substituted ferrites was investigated by X-Ray diffraction and specific magnetization analysis. It was shown that the radiation-thermal heating of compacted powder reagents mixture leads to an increase in efficiency of lithium-titanium ferrites synthesis.

Thermomagnetometric analysis of lithium ferrites

In this work, the magneto-phase transitions in pure lithium (Li0.5Fe2.5O4), lithium–zinc (Li0.4Fe2.4Zn0.2O4) and lithium–titanium (Li0.6Fe2.2Ti0.2O4) ferrites were studied by the thermogravimetric analysis in magnetic field, which is known as the thermomagnetometry method. The ferrites were prepared by the solid-state synthesis from oxides and carbonates. The Curie point of magnetic phase in ferrites and their composite mixtures was determined from the derivative thermogravimetric curve in the region of ferrite mass change associated with the ferrimagnet–paramagnet transition in the magnetic phase. The method based on the analysis of ferrite mass change at Curie temperature was developed to estimate the ferrite phase concentrations in composite magnetic materials.

Microstructure and thermal analysis of lithium ferrite pre-milled in a high-energy ball mill

AbstractIn this work, the effect of ball milling of synthesized LiFe5O8 ferrite powders on the microstructure and properties of ferrite ceramics was studied by XRD, laser diffraction and SEM analysis as well as thermal analysis. The mechanical milling of LiFe5O8 was carried out in a Fritsch Pulverisette 7 planetary mill using the zirconia or steel grinding balls. The process of ferrite sintering was investigated using dilatometric analysis. In addition, ferrite ceramics electromagnetic properties, including magnetization, Curie point and electrical resistivity, were investigated. The results showed a strong difference in the structure of ferrite ceramics obtained from ferrite powders pre-milled by zirconia or steel grinding balls. Thus, the milling results in a decrease in the particle size of the ferrite powders to ultrafine range. The ferrite ceramics, obtained from powder milled by steel balls, is characterized by high density and low porosity as well as good electromagnetic properties and the main presence of a disordered β-LiFe5O8 phase. However, the mechanical milling using zirconia balls leads to the contamination of ferrite by zirconia, resulting in the formation of β-LiFe5O8/ZrO2 composite ceramics during sintering.

Influence of reagents mixture density on the radiation-thermal synthesis of lithium-zinc ferrites

Influence of Li2CO3-ZnO-Fe2O3 powder reagents mixture density on the synthesis efficiency of lithium-zinc ferrites in the conditions of thermal heating or pulsed electron beam heating was studied by X-Ray diffraction and magnetization analysis. The results showed that the including a compaction of powder reagents mixture in ferrite synthesis leads to an increase in concentration of the spinel phase and decrease in initial components content in lithium-substituted ferrites synthesized by thermal or radiation-thermal heating.

High energy effect in Li-Ti-Zn ferrite syntesis

Lithium-zinc-titanium ferrite synthesis under the high energy action, including mechanical activation of initial reagents mixture in a planetary mill and subsequent heating of reaction mixture by a high-energy electron beam, is investigated using x-ray diffraction and thermal analyzes. The composition of initial reagents mixture corresponds to lithium substituted ferrite formation with a stoichiometric spinel formula: Li0.65Fe1.6Ti0.5Zn0.2Mn0.05O4. The synthesized ferrites were examined by saturation magnetization and Curie temperature measurements. It was shown that the mechanical activation for 60 min and radiation-thermal heating at 800°C of the initial reagents mixture significantly increase the reactivity of solid phase systems, and thereby, decrease the temperature and time of synthesis, improving the homogeneity of the end product. The obtained lithium-titanium-zinc ferrites are characterized by the high values of both the specific magnetization and Curie temperature.

Study of the dielectric polarization in Li-Zn ferrite ceramics

Paper presents the results of dielectric properties investigation in radio frequency range for lithium-zinc ferrite ceramics. Dielectric parameters of ferrite was obtained using mathematical processing (for Debye type polarization) of experimental data. It is shown that the observable ceramics composition has dielectric anomalies characterized by ferroelectric type.

Effect of ion-plasma treatment on oxidation-reduction processes in lithium-titanium-zinc ferrites

We examined the effect of nitrogen, oxygen and argon plasma on the diffusion- controlled oxidation-reduction processes in lithium-titanium-zinc ferrite ceramics by measuring the activation energy of electrical conductivity in the depth of the sample. The experimental results show that the high-temperature treatment in polycrystalline ferrites by nitrogen or argon ion plasma greatly accelerates the oxidation-reduction processes in ferrites and changes the process direction depending on the partial pressure of oxygen.