Reducing roasting of the ilmenite concentrates of deposit Tsentral’noe

The reducing roasting of the titanium-containing concentrates of deposit Tsentral’noe is studied over a wide range of operating conditions to develop a new technology of processing to exclude melting in an electric furnace. The roasting products are investigated by scanning electron microscopy and electron-probe microanalysis. The structure of the forming cinder and its phase composition are considered as functions of the reducing agent content and the roasting temperature. Optimum roasting conditions are proposed for roasting used as the main stage of the proposed technology.     

Effect of the strain rate on the properties of electrical copper

The effect of the strain rate on the texture and strength characteristics of electrical copper is analyzed using an industrial experiment on low- and high-speed wire drawing. The mechanical properties of the product are determined. The strength of the wire drawn at a high speed is found to be about 20 MPa higher than that of the wire drawn at a low speed. Metallographic analysis shows no differences in the wire structures, and texture analysis reveals differences in the behavior of dominant texture components. The directions of the dominant texture components are found to rotate near the periphery of the workpiece (i.e., at the workpiece surface). The solution of the drawing problem by the finite element method demonstrates an analogous rotation of the principal elongation directions.     

Structure-phase composition and properties of mechanically alloyed high-nitrogen powder steels

The structure and properties of the Fe-21% Cr-N and Fe-18% Cr-7% Ni-0.8% Mn-0.5% C-N powder systems mechanically alloyed in nitrogen atmosphere and steels sintered from the powders in dissociated ammonia at t = 1170°C have been investigated. The thermodynamic calculations of the phase compositions of the steels are carried on the basis of searching the Gibbs integral energy minimum for the system. In comparing the obtained experimental data with the results of thermodynamic calculations for the Fe-Cr-C-N and Fe-Cr-N systems, it is found that the equilibrium phase composition is not reached. The resulted steels contain increased nitrogen quantity (1.6 to 2.1%) distributed in austenite and/or nitrides. The steels have high strength, wear and corrosion resistance.     

Thermodynamic simulation of phase equilibria in the UO<Subscript>2</Subscript>-Gd<Subscript>2</Subscript>O<Subscript>3</Subscript> system at high temperatures

Thermodynamic models of a UO₂-based melt and cubic solid solution were developed on the basis of the most accurate measurements of the UO₂-Gd₂O₃ liquidus in a range of 0–30 mol. % of Gd₂O₃. These models enabled computing the phase diagram of this system in a temperature range of 1900–3200 K for all composition varieties.     

Ferroelastic domains and phases in ferromagnetic nanostructured FePd alloy

Polarization optical, electron microscopic, and thermomagnetic investigations of FePd single crystals undergoing an A1 → L1₀ phase transformation have been carried out. The results obtained have been analyzed proceeding from the concept of ferroelasticity and the experimental criteria of its existence. The features of phase transformations in equiatomic FePt and FePd alloys have been compared. A conclusion has been drawn that the atomic ordering in the FePd alloy is preceded by the formation of a ferroelastic lowsymmetry disordered (BCT) phase, and the A1 → L1₀ phase transformation presents a combination of different types of phase transitions such as cooperative displacement and ordering of atoms.     

Pressure-induced formation of thermal donor centers in silicon after oxygen ion bombardment

This paper discusses the generation of thermal donor centers in silicon by oxygen ion implantation in the temperature range 350 to 550 °C. These donors are distributed almost uniformly over the entire thickness of the silicon crystals and well outside the region of direct penetration of the ions. It is established that implantation of Czochralski-grown silicon with oxygen ions followed by annealing accelerates the introduction of these donors into the silicon, and that application of hydrostatic pressure further accelerates the process of donor-center formation. The data indicate that this accelerated introduction of donors is associated with diffusion of radiation-induced defects from the implanted layer into the crystal bulk, and that the diffusion coefficients of these defects are 1×10⁻⁷ cm²/s or larger. Fiz. Tekh. Poluprovodn. 33, 1153–1157 (October 1999)     

Active wireless ultrawideband networks based on chaotic radio pulses

Active wireless networks with ultrawideband chaotic pulses used as the data carrier for wireless transmission are discussed. A universal transceiver module for nodes of active networks is proposed, designed, and studied. Various types of nodes based on this module are examined. The structure of active ultrawideband wireless networks and their operation principles are investigated. Examples of experimental networks based on the universal module are given, and their parameters are presented.     

Amplitude aperture-distribution control in displaced-axistwo-reflector antennas

A design method for improving the efficiency and reduction of sidelobes in displaced-axis two-reflector antennas is presented. The method is based on an analysis of the geometrical-optics field transformation in the displaced-axis two-reflector arrangement. The principal difference of the displaced-axis antenna from the Cassegrain/Gregory two-reflector antenna is pointed out. While decreasing the level of illumination of the subreflector edge in the Cassegrain/Gregory antenna leads to decreasing the sidelobe levels, and, respectively, the efficiency of the antenna system, in the displaced-axis antenna, decreasing the level of illumination of the subreflector leads to an increased level of sidelobes and an essentially nonuniform amplitude distribution in the aperture. The aperture-amplitude-distribution dependence of the illumination level of the subreflector edge in displaced-axis antennas is much stronger than in Cassegrain/Gregory antennas     

Dirac Cone Spin Polarization of Graphene by Magnetic Insulator Proximity Effect Probed with Outermost Surface Spin Spectroscopy

The effects of the proximity contact with magnetic insulator on the spin‐dependent electronic structure of graphene are explored for the heterostructure of single‐layer graphene (SLG) and yttrium iron garnet Y₃Fe₅O₁₂ (YIG) by means of outermost surface spin spectroscopy using a spin‐polarized metastable He atom beam. In the SLG/YIG heterostructure, the Dirac cone electrons of graphene are found to be negatively spin polarized in parallel to the minority spins of YIG with a large polarization degree, without giving rise to significant changes in the π band structure. Theoretical calculations reveal the electrostatic interfacial interactions providing a strong physical adhesion and the indirect exchange interaction causing the spin polarization of SLG at the interface with YIG. The Hall device of the SLG/YIG heterostructure exhibits a nonlinear Hall resistance attributable to the anomalous Hall effect, implying the extrinsic spin–orbit interactions as another manifestation of the proximity effect.     

Continuous-wave operation of singlemode GaInAsSb lasers emittingnear 2.2 μm at Peltier temperatures

A continuous-wave regime, lasing near 2.2 μm, has been achieved for single longitudinal mode GaInAsSb double heterostructure lasers mounted on a Peltier cooler. In the pulsed regime the lasers exhibited a characteristic temperature of the threshold current as high as 132 K at heatsink temperatures up to 60°C