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In this work, the crystal structure of Leptothrix biosamples was studied using positron annihilation lifetime spectroscopy, MIKA modeling package and X-ray diffraction method. The structural analysis results showed that free cubic and orthorhombic phase Fe and trigonal Fe2O3 and cubic Fe3O4 phases were detected in Leptothrix biosamples. It has been determined that the concentration of cubic Fe3O4 phases in biosamples is higher than other phases. The theoretical bases of the regularity of distribution of hydrogen and oxygen atoms in the form of free and vacancies in the trigonal Fe2O3 and cubic Fe3O4 phases were calculated. On the other hand, the lifetime of vacancies in Fe, Fe2O3 and Fe3O4 structures has been determined. [ABSTRACT FROM AUTHOR]

The effect of heavy ions on the magnetic properties of Fe3O4 nanoparticles with d = 20–30 nm was studied. The magnetic properties were studied by vibrational magnetometry. It has been established that Fe3O4 nanoparticles have ferromagnetic properties under normal conditions and at room temperature. The value of the specific magnetic moment was determined: M = 33.4 emu/g. It has been established that under the influence of temperature, a decrease in the value of the specific magnetic moment in Fe3O4 nanoparticles is observed, at a temperature of TC = 655 K, a ferromagnet-paramergrite phase transition occurs, and the value M = 0 is obtained. As a result of the study, the values of the specific magnetic moment and Curie temperature in Fe3O4 nanoparticles irradiated with a stream of fast heavy 132Xe ions with an energy of 167 MeV at intensities of 4.14 × 1012 ion/cm2, 2.75 × 1013 ion/cm2 and 3.83 × 1014 ion/cm2. The mechanism of change of magnetic properties depending on radiation is determined. [ABSTRACT FROM AUTHOR]

The results of Doppler broadening of the annihilation line spectroscopy obtained using a variable energy positron beam for the pure gold samples exposed to 100 keV self-implantation and 250 keV H+ implantation are reported. The annihilation characteristics of parameter S as a function of positron energy were determined. Irradiation-induced defects were confirmed in all measured profiles. However, the S parameter distributions were not typical for the ion-implanted materials. No significant changes in the shape of defect profiles for non-defected and self-implanted samples were found. The implanted Au+ ions fill the earlier produced vacancies and decrease the overall defect concentration. In the case of 100 keV H+ implantation, the distribution does not cover the area with higher S values pointing out the presence of defects. This is caused by the localization of H+ inside the produced vacancies. The thicknesses of the damaged layers are smaller compared to those numerically predicted by the SRIM implantation ranges. The long-range effect was not observed. [ABSTRACT FROM AUTHOR]

Possibility to prepare finely dispersed Cu2ZnSnS4 by using the method of selfpropagating high-temperature synthesis has been studied in this work. Investigations of Raman scattering and IR-Fourier spectroscopy of the synthesized finely dispersed material have been carried out. The analysis of the Raman and IR-Fourier spectra showed that the synthesized material in the process of preparing is formed with a kesterite structure with the inclusion of a certain amount of secondary phases in the form of sulfides and stannites. [ABSTRACT FROM AUTHOR]

The crystal structure and atomic dynamics of Fe3O4 nanoparticles have been studied. The crystal structure of iron oxide nanoparticles was determined by X-ray diffraction. The analysis showed that the crystal structure of d ≈ 50–100 nm dimensional iron oxide corresponds to a high symmetry cubic crystal structure. Calculations have shown that there are four infrared active, five Raman active and seven hyper-Raman active modes in the space group Fd-3m with cubic symmetry. Four of these modes have been observed using Raman spectroscopy: 213, 271, 380 and 591 cm − 1 . The vibrational modes are interpreted by Gaussian function. It was found that these vibration modes correspond to the vibration of O–Fe–O bonds and iron-oxygen polyhedra. [ABSTRACT FROM AUTHOR]

SnSe and Sm 1 − x Ce x SnSe 2 compounds based on SnSe have been synthesized. Thermal properties of SnSe and Sm 1 − x Ce x SnSe 2 compounds within x = 0. 0 2 – 0. 5 concentration ranges of Ce atoms have been investigated using Differential Thermal Analysis (DTA). Thermodynamic parameters were calculated based on DTA spectra within 3 0 0 K ≤ T ≤ 1 2 5 0 K temperature intervals. It was determined from the relation of different rates concentrations of Sm and Ce elements on energies that Sm 1 − x Ce x SnSe 2 system compounds have their high symmetric structure in the form of Sm 0. 2 5 Ce 0. 7 5 SnSe 2 . Thermodynamic parameters were determined for each system and the changing mechanism of these parameters depending on concentration of Ce atoms was performed. [ABSTRACT FROM AUTHOR]

The aim of this study is to provide information about microstructural and thermal properties of tungsten-based composites. Phase composition and microstructural characterization of tungsten composites were performed using X-ray diffractometer (XRD), Scanning Electron Microscopy (SEM), and Raman Spectroscopy. SEM images revealed the distribution of tungsten (W), vanadium carbide (VC) and graphite (C) powders in the tungsten matrix. The Raman spectra showed two major peaks, which are recorded at 1331 (vs) cm−1, and 1583 (vs) cm−1. These bands can be attributed to disorder graphite (D) and graphite (G). Thermogravimetric analysis (TGA) measurements were performed to determine the weight loss and thermal stability of the tungsten-based composites under argon gas atmosphere and at high temperatures. TGA measurements were performed to determine weight loss and thermal stability of tungsten-based composites under argon gas atmosphere and at high temperatures. The TG curve showed a slight weight loss in this temperature range. Mass loss is thought to be due to oxidation and gas desorption of materials. [ABSTRACT FROM AUTHOR]

Bi 2 Se 3 and Bi 2 Se 0. 5 Te 2. 5 compounds were synthesized and the thermophysical properties were investigated by differential thermal analysis. It was determined that the DSC spectrum of the Bi 2 Se 3 compounds is divided into three regions. The first region was explained by the splitting of water and hydroxide groups in the compound, and the second and third regions with phase transitions. The DSC spectrum of the Bi 2 Se 0. 5 Te 2. 5 compound was somewhat simpler. The spectrum, divided into two regions, consisted of the first region observed by the decomposition of the water and hydroxide group, and the second region corresponding to the phase transition. Thermodynamic parameters of phase transitions, enthalpy and free energy, were determined. [ABSTRACT FROM AUTHOR]

The structure and thermal properties of Ba 0. 5 La 0. 5 MnO3 polycrystalline powder have been investigated using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. The structural studies have shown that Ba 0. 5 La 0. 5 MnO3 compound crystallizes in perovskite structure with Pm-3m cubic symmetry group. The lattice parameters were obtained to be a = b = c = 3.9073 Å. Mass changes have been observed from thermogravimetric (TG) and differential thermogravimetric (DTG) curves obtained in a wide temperature interval of 30–950 ∘ C. Free energy and enthalpy changes for all observed transformations were determined. Observed endo and exo effects. [ABSTRACT FROM AUTHOR]

Triple compounds with the formulas TlFeS2 and TlFeSe2 and magnetic properties are investigated via X-ray diffraction, differential-thermal, and thermogravimetric analyses. Their crystal structures are found. It is ascertained that they are described by monoclinic space group C2/m under normal conditions. The atomic coordinates and interatomic distances are determined. From differential-thermal and thermogravimetric analyses performed at temperatures of 30-900°C, it is revealed that stronger covalent bonds are implemented in TlFeS2 crystals than in TlFeSe2 compounds. The effects associated with energy exchange in the compounds under study are observed. The physical nature of the observed effects is discussed. [ABSTRACT FROM AUTHOR]