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The dependence of the electrochemical characteristics of layered cathode materials LiNixMnyCozO2 (0.4 ≤ x ≤ 0.6; y = 0.2, 0.3; z = 0.2, 0.4) on the method of applying a protective layer of nanoparticles of lithium-conductive material Li1.3Al0.3Ti1.7(PO4)3 with NASICON structure onto their surface has been investigated. It is shown that the surface modification reduces the capacity fading during prolonged charge/discharge cycling (up to 15%) and improves the suitability for fast charge/discharge processes. [ABSTRACT FROM AUTHOR]

LiNi0.6Co0.2Mn0.2O2 (NMC 622) cathode material is widely used for lithium-ion batteries. The effect of the method of creating a protective layer of Li1.3Al0.3Ti1.7(PO4)3 (LATP) on the electrochemical characteristics of commercial cathode material NMC 622 was investigated. It was found that both methods of LATP coating did not affect the crystal structure and morphology of NMC 622. The prototypes of Li-ion batteries with a cathode based on modified NMC 622 are characterized by significantly higher stability of capacitive characteristics during long charge/discharge cycling, compared with prototypes of Li-ion batteries based on the pristine cathode material. In addition, the protective layer of LATP, applied by the sol–gel method, can significantly increase the capacity of the cathode material NMC 622 at the high current density and reduce the capacity drop during the continuous charge/discharge cycling. Creating a protective layer of LATP via sol–gel method is an effective way to improve the electrochemical characteristics of cathode materials such as NMC 622. [ABSTRACT FROM AUTHOR]

Temperature-dependent magnetic properties and spin echo decay behavior have been studied for an ensemble of La1−xSrxMnO3 (x = 0.23) nanoparticles (of 30 nm in diameter) synthesized by the sol–gel method. Characteristic magnetic parameters, such as blocking temperature and effective Curie temperature for the ensemble, are determined. Enhanced coercivity and its unusual temperature dependence compared to bulk counterparts are revealed, and possible reasons for this phenomenon are discussed. A conclusion about the non-negligible role of interparticle interactions in the enhancement of the coercivity in the ensembles of substituted manganites is made. [ABSTRACT FROM AUTHOR]

La0.775Sr0.225MnO3 nanoparticles were synthesized by sol-gel method with heat treatment at T = 1073 K and covered with silica shells of various thicknesses. Analysis of their experimental ferromagnetic resonance spectra was carried out in the temperature range of 77–290 K. The linewidth of absorption curves change in a nonlinear manner in coated samples in the temperature range of 230 K ≤ T ≤ 290 K. Such changes indicate the appearance of external stresses between nanoparticles due to the difference in the thermal expansion coefficients of the two materials. [ABSTRACT FROM AUTHOR]

Amplification of a dosimetric EPR signal in mineralized biological materials available in limited quantities has been demonstrated in this paper. Powders of irradiated enamel, dentin, and bone tissue were placed into silica ampoules with the outer diameter close to 1.4 mm. To amplify the signal, the dielectric insert in the form of cylinder with the outer radius 2.85 mm, the inner radius 0.75 mm, and the height 1.85 mm made of a high-κ and low-loss ceramic material BaTi4O9 + 8.5% ZnO has been used. It has been shown that maximum signal amplification (about an order of magnitude) has been achieved when the sample is completely inserted into this dielectric. It has been found that the line shape of the dosimetric signal is not distorted, if using the dielectric insert. Decomposition of the amplified EPR spectra allowed us to determine the relative contribution of two types of CO2- radicals to the dosimetric signal, which coincides with the literature data. [ABSTRACT FROM AUTHOR]

Structural aspects of powders containing magnetic nanoparticles Fe3O4/CoFe2O4 with the anticipated “core-shell” structure are considered by means of comparative analysis with individual particles of Fe3O4, CoFe2O4 in accordance of data obtained from X-ray powder diffraction and small-angle scattering of X-ray (synchrotron) radiation and neutrons. It is shown that magnetic particles in the powders under study have a strong polydispersity and form complex aggregates. Characteristic sizes of the crystallites, as well as a ratio of magnetite to cobalt-ferrite in the composition of the Fe3O4/CoFe2O4 particles were evaluated from the analysis of the diffraction peaks. Аnalyzing the data on small-angle scattering, the dimensional characteristics of particles and aggregates, as well as the volume fraction of the last ones in the powders, have been obtained. Fractal dimensions of aggregates are determined. A significant difference is observed in the scattering on Fe3O4/CoFe2O4 particles and the total scattering consisting of partial contributions to scattering on individual magnetite (Fe3O4) and cobalt-ferrite (CoFe2O4) powders, which does not exclude the formation of the “core-shell” structure. [ABSTRACT FROM AUTHOR]

Magnetostatic properties and AC magnetic heating characteristics of (La,Sr)MnO3 nanoparticles with substitutions in manganese and lanthanum sublattices have been studied. The nanoparticles with average sizes in the range 25-38 nm were synthesized via sol-gel method. Fe substitution for Mn, as well as Sm substitution for La have been used in the experiment. It is shown that the increase in substitution level (for both Fe and Sm substitutions) results in lowering the Curie temperature TC and weakening heating efficiency under the action of AC magnetic field. The results demonstrate that the action of AC field causes effective heating of nanoparticles at temperatures lower than TC, while heating efficiency becomes strongly reduced at higher temperatures. It is proved experimentally that the substitutions in Mn sublattice result in more rapid changes of magnetic properties, as compared to the substitutions in La one. Thus, complex substitutions based on suitable combinations of substituting elements may serve as an efficient tool to "softly" tune the maximal temperature achieved during the AC magnetic field induced heating of nanoparticles, which is important for application of these materials as heat mediators for self-controlled magnetic nanohyperthermia. [ABSTRACT FROM AUTHOR]