Study of olivines from Omolon and Seymchan meteorites using X-ray diffraction and Mössbauer spectroscopy with a high velocity resolution

Study of olivine from Omolon and Seymchan meteorites was performed using X-ray diffraction and Mössbauer spectroscopy with a high velocity resolution. X-ray diffraction patterns were measured at room temperature while Mössbauer spectra were measured at 295 and 90 K. The orthorhombic crystal lattice parameters were evaluated for olivine from Omolon and Seymchan. These parameters appeared to be different for olivines from both meteorites. Mössbauer spectral components related to 57Fe in crystallographically non-equivalent sites M1 and M2 in both olivines were determined and its Mössbauer hyperfine parameters were evaluated. Some differences in the tendencies of temperature dependence of spectral parameters and small variations of 57Fe quadrupole splitting in both M1 and M2 sites of olivines from Omolon and Seymchan were found. On the basis of Mössbauer parameters and chemical data, the temperatures of equilibrium cation distribution were evaluated for both olivines. © 2012 American Institute of Physics

Photo- and Cathodoluminescence MG-doped Alumina Ceramics

This work was financially supported by the Russian Science Foundation (RSF), project No. 1872-10082

Scattering on Spin Fluctuations in Itinerant Quantum Disordered Ferromagnets Near the Quantum Phase Transition

Taking into account the long-ranged spin interactions due to weak localization effects in disordered itinerant ferromagnets the scattering of both electrons and neutrons on critical spin fluctuations near the quantum phase transition is considered. It is shown that for the case of low electron density, when kFξ ≪ 1, where kF is the Fermi momentum and ξ is the magnetic correlation length, the transport cross section of electrons is proportional to the magnetic susceptibility as for the case of scattering by conventional critical fluctuations in absence of weak localization effects. However, the intensity of the multiple small-angle neutron scattering becomes exponentially small as compared with the intensity of the multiple scattering by conventional critical fluctuations.This work was partially supported by Russian Foundation for Basic Research (Project No. 97-02-17315)

High-rate low-temperature PVD of thick 10 μm α-alumina coatings

α-Al2O3 coatings have been deposited by evaporation of Al in an anodic arc with a growth rate of ∼ 5 μm•h-1 at 640?C under the conditions of low ionization of the Al vapors and an increased concentration of atomic oxygen, which has been achieved by the use of a hollow anode.Intensive (current density up to 15 mA•cm-2) low-energy (50 eV) ion bombardment has provided deposition of adhesive single-phase nanocrystalline (50-150 nm) α-Al2O3 coatings with a thickness of up to 10 μm with low intrinsic stresses (1.5 GPa) and low microstrains of the crystal lattice (less than 0.1%). The composition of the discharge plasma has been determined using the optical spectroscopy method. The effect of the O2 flow and the hollow anode current on the growth rate of the alumina coatings has been investigated and it has been shown that the increasing degree of O2 dissociation promotes an increase in the growth rate of coatings. © 2019 IOP Publishing Ltd. All rights reserved.Russian Science Foundation, RSF: 18-19-00567This work was supported by the Russian Science Foundation (grant No. 18-19-00567)

Influence of Rare Regions on Quantum Phase Transition in Antiferromagnets with Hidden Degrees of Freedom

The effects of rare regions on the critical properties of quantum antiferromagnets with hidden degrees of freedom within the renormalization group is discussed. It is shown that for 'constrained' systems the stability range on the phase diagram remains the same as in the mean-field theory while for 'unconstrained' systems the stability range is effectively decreased

Characterization of α-Al2O3 coatings deposited by reactive evaporation in an anodic arc under high-current ion assistance

The article presents the results of studies of the mechanical and adhesive characteristics of α-Al2O3 coatings depositeedby reactive anodic evaporation of Al in an arc discharge at low-energy (50 eV) high-current (up to 15 mA•cm-2) ion assistance at 640?C. The coatings are characterized by a strong texture (300), which contributes to an increase in adhesive strength (the critical load at which the destruction of the coating is observed reaches 2560?29 mN). It was shown that there is an optimal discharge current (20 A), at which the best adhesion, the surface quality (Ra = 13.4 nm, Rz = 44.7 nm) and the resistance of elastic deformation of coatings (H/E = 0.08) are achieved. © 2019 IOP Publishing Ltd. All rights reserved.Russian Science Foundation, RSF: 18-19-00567This work was supported by the Russian Science Foundation under grant No. 18-19-00567

Characterization of the matrix and fusion crust of the recent meteorite fall Ozerki L6

We studied the interior and the fusion crust of the recently recovered Ozerki L6 meteorite using optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy, X-ray diffraction (XRD), magnetization measurements, and Mossbauer spectroscopy. The phase composition of the interior and of the fusion crust was determined by means of SEM, XRD, and Mossbauer spectroscopy. The unit cell parameters for silicate crystals were evaluated from the X-ray diffractograms and were found the same for the interior and the fusion crust. Magnetization measurements revealed a decrease of the saturation magnetic moment in the fusion crust due to a decrease of Fe-Ni-Co alloy content. Both XRD and Mossbauer spectroscopy show the presence of magnesioferrite in the fusion crust. The temperatures of cation equilibrium distribution between the M1 and M2 sites in silicates calculated using the data obtained from XRD and Mossbauer spectroscopy appeared to be in a good consistency: 553 and 479 K for olivine and 1213 and 1202 K for orthopyroxene.Peer reviewe

THE INFLUENCE OF SYNTHESIS PARAMETERS ON MICROCRYSTAL STRUCTURE ARTIFICIAL HYDROXYAPATITES (HAP)

The phase composition and crystal structure of hydroxyapatites (HAP) obtained by chemical precipitation have been studied by X-ray phase analysis. During the experiment, samples annealed at 700 °C have a structure close to human tooth enamel and are promising for use as ionizing radiation sensors

Synthesis of α-Al2O3 coatings by reactive anodic arc evaporation under high-density low-energy ion assistance

Reactive anode evaporation of Al on metallic substrates with an isostructural sublayer at a temperature of 640 °C has allowed obtaining α-Al2O3 coating at a rate of 4.5 μm/h. It has been shown that the use of low-energy (50 eV) intense (up to 15 mA/cm2) ion assistance with a low content of metal ions ensures the formation of the Al2O3 α-phase with a low level of micro-distortions (less than 0.15%), an increased nanocrystallite size (more than 40 nm) and low internal stress (up to 2 GPa). © Published under licence by IOP Publishing Ltd.Russian Science Foundation, RSF: 18-19-00567This work was supported by the Russian Science Foundation under grant No. 18-19-00567

Determination of the Crystal Structure of WMnB2 Compound by X-ray Diffraction

The crystal structure of new compound WMnB2 was determined from the X-ray diffraction pattern. Reflection indexing were performed by several methods: DICVOL, ITO, McMaille, TREOR. The best results were obtained for the rhombic system with lattice parameters: a(A)=3.13; b(A)=8.14; c(A)=3.02