Hydrogen reduction kinetics of electrometallurgical slime

The interaction of hydrogen with the zinc-containing electrometallurgical slime of the Severstal’ metallurgical works has been studied. The sequence of transformations in the slime heated to 1100°C in hydrogen or air has been established. The experimental and calculated weight losses coincide. Some of the carbonates are shown to decompose in the temperature range 300–700°C, and most iron and zinc oxides are reduced to a metal. In the temperature range 650–850°C, zinc is almost completely sublimated. At temperatures above 800°C, complex oxides are reduced and calcium and magnesium carbonates and sulfates are likely to decompose. Experimental digital data on the zinc sublimation rate are processed by the least squares method with approximating equations used in thermal analysis. The kinetics of nonisothermal zinc sublimation is comprehensively analyzed using a unique procedure developed for taking into account the background of a peak and the effect of accompanying processes. An equation for the calculation of the zinc sublimation rate under experimental conditions (fluidized bed) is given and tested.     

Observation of superconducting transition temperature oscillations in metal-nonmetal film systems

For technetium-carbon, molybdenum-carbon, and vanadium-carbon thin-film layer structures an oscillatory dependence of the superconducting transition temperature on carbon layer thickness is found. The oscillations take place for thin metal layers (d<300 Å) and for very small thicknesses of the nonmetal film (d _C<30 Å). In addition to the oscillations ofT _c , oscillations of the normal-state electrical resistance remaining up to room temperature are found in the layered samples. A correlation is observed between critical temperature and resistance changes: Maxima in the curveT _c (d _C) correspond to minima in (d _C). The amplitude of the critical temperature oscillations is 10–15% of theT _c value and depends on the metal layer thickness, increasing with decreasingd approximately as 1/d. Also found in the thin-film layer structures are oscillations of the critical magnetic fieldsH _c andH _c correlating withT _c oscillations. A mutual influence of nonmetal layers located on opposite sides of the metal film was observed.     

Determination of the structure of subsurface layers by means of coaxial time-of-flight scattering and recoiling spectrometry (TOF-SARS)

It is demonstrated that both surface and subsurface structural information can be obtained from Si{100}-(2 × 1) and Si{100}-(1 × 1)-H by coupling coaxial time-of-flight scattering and recoiling spectrometry (TOF-SARS) with three-dimensional trajectory simulations. Experimentally, backscattering intensity versus incident angle scans at a scattering angle of 180° have been measured for 2 keV He⁺ incident on both the (2 × 1) and (1 × 1)-H surfaces. Computationally, an efficient three-dimensional version of the Monte Carlo computer code RECAD has been developed and applied to simulation of the TOF-SARS results. An R (reliability) factor has been introduced for quantitative evaluation of the agreement between experimental and simulated scans. For the case of 2 keV He⁺ scattering from Si{100}, scattering features can be observed and delineated from as many as 14 atomic layers ( 18 Å) below the surface. The intradimer spacing D is determined as 2.2 Å from the minimum in the R-factor versus D plot.     

High-temperature oxidation of titanium-hydride powders

The oxidation kinetics of titanium-hydride powders were studied in the temperature range of 298–1378 K in air at atmospheric pressure. DTA, DSC, X-ray analysis, and scanning electron microscopy were used. Oxidation was found to take place by TiH_xO_y oxyhydride phases formation. The oxidation reaction rate at temperatures above 870 K was limited by diffusion of oxygen atoms through a rutile scale formed on the surface. The activation energy and preexponential values of the Arrhenius equation for different interaction stages as well as transformation enthalpies were calculated.     

Multilevel Bipolar Memristor Model Considering Deviations of Switching Parameters in the Verilog-A Language

Russian Microelectronics - We describe a bipolar memristor in the Verilog-A language. The proposed model concepts take into account the following parameter deviations in the memristor switching...     

Pulse Train Microprocessor Programmer for NMR Relaxometers-Diffusiometers

A pulse train programmer for a spin–echo NMR relaxometer–diffusiometer is based on an AT89C51-24PC microcontroller. The programmer ensures the arbitrary generation of pulse trains with a minimum train step of 30 s and recording of up to 30000 10-bit amplitudes of spin–echo NMR signals with a minimum quantization step of 3 s. The all-in-one one-board programmer is connected to a computer serial asynchronous data port, which is compatible with NMR relaxometer–diffusiometers of almost any design.