Том 81, № 3 (2017)

Structural and chemical modifications of tantalite and columbite surfaces, induced by treating the minerals with anolyte—a product derived via the electrolysis of aqueous solutions—and high-voltage electromagnetic pulses, are studied by means of X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy, atomic force microscopy, and electrophoretic light scattering. The mechanical properties of the surfaces are characterized via Vickers microhardness testing. Treating the minerals with anolyte removes iron-containing surface films and leads to considerable conversion of surface-confined Fe(II) species into Fe(III), increasing the differences between the physicochemical and electrical properties of these rare earth minerals. The nonthermal impact of high-voltage pulses results in effective surface softening, a reduction in microhardness, and the disintegration of mineral particles, yielding surface micro- and nanosized phases enriched with iron and oxygen.

Low-temperature magnetic and magnetoresistive properties of compacted ferromagnetic halfmetal CrO₂ powders with nanoparticle shape anisotropy are studied. Magnetic anisotropy induced by the formation of magnetic texture during compaction is revealed. It is shown that tunneling magnetoresistance anisotropy is associated with the difference between a sample’s rates of magnetization in the longitudinal and transverse fields.

Two series of nitrilotrismethylenephosphonic complexes of 3d elements, [MII(H₂O)₃{NH(CH₂PO₃H)₃}]_n (M = Cr–Zn) and Na₈[MII{N(CH₂PO₃)₃}]₂nH₂O (M = Co–Zn), are studied. A comparative analysis of their structural features showed the influence the Jahn–Teller effect has on the formation of the crystal structures, reactive capacities, and anticorrosive activities of these compounds.

The possibility of using AES data on the composition of a free surface to assess surface and grain boundary tensions, and the grain boundary strength of polycrystalline copper, is discussed. Using familiar theoretical models, it is shown that sulfur impurity segregation substantially reduces these characteristics, with the energy of grain boundary fracture lowered by 5–8%.

The kinetics of ordering in nanostructured CoPt particles is investigated. The low activation energy (58 ± 2 kJ/mol) of the ordering process indicates that the kinetics of ordering is not limited by bulk diffusion. Coercivity grows along with the degree of ordering and reaches its maximum value of 14.2 kOe upon the complete ordering of CoPt alloy with a crystallite size of no more than that of a single domain.

The magnetoresonance characteristics of granular nanocomposite magnetic systems with carbon matrices are studied. Analysis of the experimental data reveals the formation of iron/cobalt carbide nanoparticles upon synthesis that determine the magnetoresonance characteristics.

Mechanical tests are performed for Ni₃Ge alloy single crystals in the intense plastic shear deformation scheme under quasi-hydrostatic pressure at different test temperatures. Dependences of resistance to shear deformation on the Bridgman anvils’ angle of rotation are obtained. The microrelief of the surface damage of Ni₃Ge single crystals fractured by plane bending after specimens were withdrawn from the Bridgman anvils is studied. X-ray diffraction patterns of deformed Ni₃Ge single crystals are obtained.

Processes that occur upon the straining of a polycrystal are studied. Components of the internal stress tensor were determined. Changes in the bending and torsion stresses in the crystal lattice of a strained polycrystal are analyzed. A correlation between changes in the internal stress tensor components and the fraction of material with complex bending is established.

The use of X-ray magnetic circular dichroism (XMCD) spectra for determininghe t magnitude of atomic magnetic moments in compounds of rare-earth and transition elements is discussed. The standard sum rule approach often yields a magnitude of moments that is often smaller than values obtained from magnetic measurements. We attribute this to strong spin fluctuations in the surface layers in which XMCD signals form. A way of determining the values of local magnetic moments in the presence of strong fluctuations is proposed and tested.

The structure, Mössbauer effect, and dielectric characteristics of 0.95PFN-0.05BFO crystals prepared via mass crystallization are studied. It is shown that temperatures approaching those of the antiferromagnet → paramagnet and ferroelectric → paraelectric transitions are reached inside these crystals, in contrast to PFN.

The transition from a dipolar electron–hole liquid (EHL) to a spatially direct one in two-dimensional layers of a type II (buffer Si_1–yGe_y)/tSi/sSi_1–xGe_x/tSi/(cap Si_1–yGe_y) heterostructure is studied via photoluminescence spectroscopy at helium temperatures and high excitation levels. This transition occurs when the sSi_1–xGe_x barrier layer for electrons (a quantum well (QW) for holes), that separates electron QWs (tSi layers) gets thinner. The basic parameters of both types of EHLs and the lifetime of dipolar excitons are determined.

Anomalies induced by an external electric field in the reflection of a TE electromagnetic plane wave, incident from without on the surface of a semi-infinite ferromagnetic insulator (in Voigt geometry), are studied. The effect these anomalies have on the magnitude and sign of the Goos–Hanchen effect for a beam of plane volume electromagnetic waves with s-type polarization, reflected from the surface of a ferromagnet, is investigated. The results are generalized to a one-dimensional ferromagnet–nonmagnet photonic crystal under the action of a constant electric field.

Changes in the phase composition of 0.34С–1Cr–1Ni–1Mo–Fe steel during electrolytic plasma nitrocarburizing are studied via TEM. It is found that nitrocarburizing leads to considerable changes in the steel’s structure (phase composition, number of existing phases, and morphology).

Size effects in the local mechanical properties of multiphase materials are studied by means of micro- and nanoindentation. The numerical values of the elasticity modulus, hardness, and crack resistance of single phases and interphase boundaries in several rock samples (polycrystalline banded iron formations, granite, anthracite, sandstone, marble, and serpentine marble) are determined. The strongest and weakest intergrowth boundaries in the investigated materials are established. Thermal activation analysis is performed, and the activation and energy characteristics of local deformation in a material under an indenter are identified. The predominant micromechanisms of plasticity in single phases and inclusions in rocks under the action of high local stresses are identified.

Fourier transform infrared spectroscopy (FTIR), analytical electron and atomic force microscopy, and physicochemical examination of the structure and properties of mineral surfaces are used to study changes in the structural defects, functional and chemical compositions, and surface electrical properties and hydrophobicity of diamond surfaces exposed to nonthermal nanosecond high-voltage pulse treatment. The degradation of secondary mineral phase films, their peeling from the diamond surfaces, the growth of crystal hydrophobicity, and an increase in the number of B2 defects were observed after 50 s of treatment with electric pulses. Lengthening the period of irradiation (the dose) to 150 s resulted in oxidation of the diamond surfaces by products of water–air medium radiolytic decomposition, which led to the production of hydroxyl and/or carbonyl groups on the crystal surfaces, a further shift of the diamond electrokinetic and electrostatic potential into the region of negative values, and deterioration of the diamond’s hydrophobic properties.

The pressure dependence of electrical resistivity of highly oriented pyrolytic graphite is investigated at room temperature. The time needed to stabilize a sample’s resistance at constant pressure ranges from one hour to several days. The influence of the thickness of a sample and a current passed through it on the magnitude and pronouncedness of characteristic features in the pressure dependence of graphite resistance is found.

The effect inert additions of complex oxide Ba₂InNbO₆ have on the structure and properties of solid electrolyte Ba₂In₂O₅ is studied. It is shown that composite samples of (1 − x) Ba2In2O5 · xBa₂InNbO₆ acquire improved electrical properties, due to the stabilization of a highly conductive modification of barium indate characterized by a disordered arrangement of oxygen vacancies.

Torsion-curvature χ of a crystal lattice that occurs upon the deformation of polycrystalline Cu‒Mn and Cu–Al alloys is studied by means of transmission diffraction electron microscopy. The sources of χ are determined, the effect grain size has on the magnitude of χ is established. A linear relationship between χ and the density of the disoriented deformation boundaries is discovered.

It is found experimentally that in the Ni₃Mn and Pd₃Fe alloys with superstructure L1₂, ordered through a two-phase region A1 + L1₂, an increase in the degree of long range atomic order is accompanied by a reduction in the special and twin boundaries’ angle of deviation from the special boundaries in the CSL model, and by a change in the special boundaries’ spectrum and its average energy. The dependence of the proportion of Σ3 twin boundaries within the spectrum of special boundaries and the average energy of special boundaries on the degree of long range atomic order is determined by the dependence of these parameters on the mean square displacement and probability of antiphase grain boundaries being superimposed on the boundary planes, and on the presence of second phases on special boundaries.