[en] There has been studied the effect of heat input plasma hardening steels process 0.9 C-Cr-Si, 1 C and 1.7 C-Cr-Ni-Mo on the structure, the depth of hardening and the hardness of the local area. It is shown that a graded structure is formed along the depth of the zone with regularly changing dispersion and microhardness. There have been specified the dependences, allowing to operate the structural state and performance properties of the hardening zone, ensuring their optimum ratios for different wear conditions. (paper)

[en] The structure, size and hardness of the zone of hardening of pre-annealed steels (30XHMA, 34XH1M, 35XH2Φ, 38XΓH, 40XHMA, 40XH2MA, 45) was studied after treatment with a plasma arc of direct polarity. It was shown that plasma hardening forms a thin layer of martensitic-austenitic structure with variable composition and hardness on the treated steel surface. The zone subjected to hardening was represented by marten site of different dispersion and ferrite veins. Between the quenching zone and the base metal there was a transition zone with a gradient structure of plate perlite and elements of perlite-ferrite base, the share of which was gradually increasing. The structural-phase structure of this zone provided a smooth transition of mechanical properties from the hardened layer to the base metal. Dependences for management of a structural condition, hardness and depth of a zone of hardening were determined. (paper)

[en] SrTiO₃ buffer layers have been deposited on rolled Ni substrates using metal organic deposition (MOD) for HTS-coated conductors. The MOD process is based on the formation of the SrTiO₃ layer coated on the surface of a Ni substrate using dip-coating as well as spin-coating techniques from a solution-based precursor, which is prepared by dissolving strontium acetate and titanium (IV) butoxide in acetic acid and methanol. The films were annealed at 950 deg. C for 2 h under 5% H₂-Ar gas flow. X-ray diffraction (XRD) shows that the buffer layers on the Ni tape are highly oriented. The pole figure indicates a single cube-on-cube texture in addition to SEM and AFM observations revealing a continuous, dense, smooth and crack-free microstructure for the coated buffer. These results offer the potential of further manufacturing coated conductors with high current density

[en] This paper presents an 8-band Kane model for arbitrary heterostructures with abrupt interfaces. The method of invariants for heterostructures is used to construct Γ_1-Γ_1_5 effective kp-Hamiltonian, taking into account both conductance and valence bands kp-interaction and charge carriers scattering at an interface. The Γ_6-Γ_8-Γ_7 effective kp-Hamiltonian is obtained from the Γ_1-Γ_1_5 effective kp-Hamiltonian within the assumption that spin-orbit interaction of the bands Γ_6, Γ_8 and Γ_7 with all the rest band can be neglected

[en] We present a theory for heterostructures based on diamond structured semiconductors, with an emphasis of calculating inter-valley coupling. The theory allows taking into account microscopic symmetry of heterointerface within the envelope-function approach. To find out corrections to the effective Hamiltonian we use methods of group theory. We calculated valley-orbit splitting and electron wave functions for SiO₂/Si/SiO₂ finite square quantum wells. The results are in good agreement with those obtained by other authors

[en] For the first time the composite fibers based on cellulose with additives of vinyltriethoxysilane (VTEOS) have been obtained. The choice of the additive was justified by the chemical structure of the VTEOS, namely the Si-C links content and the low C/O ratio. Composite fibers were prepared from solid phase pre-solutions of cellulose with VTEOS in N-methylmorpholine-N-oxide (NMMO). An investigation of the rheological behavior of the filled cellulose solutions with VTEOS showed a slight effect of the additive on the viscosity properties of the system. Introduction of 5% of VTEOS to cellulose does not lead to significant structural changes and, as a result, mechanical properties of the fibers. The thermal behavior of composite fibers differs from cellulose fibers. (paper)

[en] We performed numerical self-consistent solution of Schrödinger and Poisson equations for GaAs/InGaAs/AlGaAs pHEMT structures with quantum well. Based on the results we calculated optical transition matrix elements and photoluminescence spectra of such structures with the same design and different parameters (such as doping level and epitaxial layers width). In the photoluminescence spectra calculations three fitting parameters have been used. These parameters are GaAs/InGaAs valence band offset in strained quantum well, hole quasi Fermi level and inhomogeneous broadening. The PL peaks amplitudes and positions dependencies on the structure parameters were established. These dependencies can be used as the basis for pHEMT structure non-destructive diagnostics.

[en] The powder-in-tube technique, which includes wire drawing and rolling, has been widely used to fabricate superconducting tapes for possible electric power applications. In the present study the starting billet was reduced in size by groove rolling instead of by wire drawing. To optimize the deformation and thermomechanical treatment processes, BSCCO wires of various dimensions were fabricated. The wires were flat rolled to a final thickness of 250 μm. Short-length tapes were subjected to a series of thermal and deformation steps. Phase development and microstructural development during the process were monitored by XRD, SEM and TEM. Current transport properties of the tapes were determined in the temperature range of 20-77 K in self-field. Thermomechanical treatment resulted in tapes with average critical current densities of 18000 A cm^-2 at 77 K. High-resolution electron microscopy revealed better texturing and grain structure at the superconductor-silver interface. Superconducting lap- and butt-joints have been formed by a chemical etching technique. Detailed microstructural and current transport properties of the joints have also been measured. (author)

[en] Solid–state dissolution in N–methylmorpholine N–oxide was used to obtain solutions of mixtures derived from cellulose and various organosilicon additives, namely, tetraethoxysilane, vinyltriethoxysilane, and bis (trimethylsilyl)acetylene. Optical study of the phase composition and morphology of these solutions showed that they are two–phase emulsions with a rather broad size distribution of particles of the dispersed phase. The nature of the flow of the mixed systems in continuous and dynamic deformation when the rheological behavior is monotypic depends to a certain extent on the nature of the organosilicon additive. Dry wet–jet spinning was used to obtain composite fibers. The structure and morphology of these fibers were studied as well as their mechanical and thermal properties. Analysis of the x–ray patterns diffractograms of the cellulose and composite fibers showed that the introduction of organosilicon additives into the cellulose matrix leads to less structural ordering of the cellulose. The mechanical characteristics of the composite fibers show some decrease in the strength and deformation characteristics with an increase in the elastic modulus in comparison with the cellulose fibers. Heat treatment of the cellulose and composite fibers up to 1000°C revealed a significant increase in the mass of carbon residue, whose amount depends on the type of additive.

[en] The GaAs/AlGaAs superlattice grown by metal-organic chemical vapour deposition (MOCVD) was investigated by photoreflectance (PR) spectroscopy. Optical transitions over the whole band structure were measured at room temperature. Different laser pump beams (632 and 532 nm) were used to clarify the nature of the PR signal formation. Charge carriers transport over minibands was revealed by using long-wave modulation. An acceptable correlation of theoretical and experimental results was achieved for low-energy transitions. Optical transitions relating to the edges of the first and the second minibands for electrons, heavy and light holes were clearly observed experimentally. (paper)