Electrodeposition of Zn–Co alloy coatingsfrom sulfate–chloride electrolytes

The composition, surface morphology and appearance of Zn–Co alloy deposits as a function of current density, electrode potential and Co2+ concentration in the electrolyte was studied. It was found that coatings of good quality with low (1%) Co content are formed at a current density of 0.2Adm–2 and with high (6.5%) Co content at 2Adm–2 from electrolytes containing 1.0M Co2+ under galvanostatic conditions. The potentiodynamic dissolution of coatings with Co content of 6.5% indicates successive deposition of Co enriched phases and a pure Zn phase. The Zn–Co alloys are more corrosion resistant than zinc but are less resistant than cobalt.     

Rheological Modeling and Fracture of Hard Oxide Ceramics Modified by Ultra-Dispersed Diamond Nanoparticles

Fracture of Al-Al 2 O 3 -diamond-containing composite coating was investigated using rheological models for principal Hertzian contact of a sphere and a plate. The crystallographic and morphologic texture was characterized and the fracture resistance was measured using fracture mechanics. A rheological model of the composite coating was proposed and confirmed by in situ experiments. Examination of the composite coating showed a hardness value of 25 GPa (about 25% higher than for an alumina-based layer) and fracture resistance (about 50% higher than for a single oxide ceramic layer) as compared to prior alumina-based coatings on a soft substrate. Experiments revealed ultimate stresses and stress-strain modes of the coating. Diamond nanoparticles improved fracture resistance of an alumina-based layer. It is also thought that the composite coatings will have higher thermal conductivity and thermal shock resistance than alumina-based layers. Such physical characteristics suggest a number of possible commercial applications for the composite coatings, particularly for wear-resistant and related applications. The higher hardness and toughness of the coatings make them very attractive as substitutes for alumina-based and other ceramic-based composite coatings in these applications. composite rheology fracture stress indentation diamonds     

基于XeF(C-A)放大器的混合(固态/气态)超高功率飞秒激光系统

提出了基于前端发生器和终端放大器,使用光泵浦XeF(C-A)激活介质的太瓦级混合激光器(THIA00)系统.前端发生器由长532 nm的连续激光泵浦的钛宝石飞秒脉冲振荡器,脉冲展宽机构,532 nm的脉冲激光泵浦的再生多通道放大器,衍射光栅压缩器和二次谐波发生器(KDP)组成.其光束输出参数为:脉冲持续时间50 fs,...     

Heap Biooxidation - Bioleachingofa Refractory Gold-Bearing Ore

Abstract

A refractory pyrite/arsenopyrite ore containing 3.7 g/ton of gold finely disseminated in the sulphide matrix was subjected to microbial leaching in a heap containing 120 tons of ore crushed to minus 15 mm. The ore was initially leached by means of acidophilic chemolithotrophic bacteria to oxidize the sulphide minerals and to liberate the gold. About 50% of the sulphide sulphur was oxidized within 90 days. Previous laboratory experiments had shown that such degree of sulphide oxidation resulted in a high gold extraction during the subsequent leaching of the pretreated ore. After the bacterial pretreatment the ore was washed with water and was treated by alkaline solutions until the pH of the heap effluents was established in the range of 9- 10. Then the leaching of the gold was started with solutions containing amino acids of microbial origin and thiosulphate as gold-complexing agents as well as some ions participating in the oxidation and/or complexation of the gold. 70.7% of the gold was leached within 12 days in this way. Silver was leached together with gold. The pregnant solutions were treated by cementation with metallic zinc to precipitate the dissolved precious metals.     

Results of the Main Phase of Ion Separation in the Process of Plasma-Optical Mass Separation

This paper presents separation results of a mixture of nitrogen, argon and krypton ions in the process of plasma-optical mass separation on the POMS-E-3 separator model. We determined the behavior of the separation with a change in the value of magnetic field induction in the azimuthator and in the degree of compensation of the spatial charge in ion flows. An analysis is performed for experimental data by correlation with the results of a theoretical study and numerical experiments. The objectives of future experiments are outlined.     

DIELECTRIC BEHAVIOUR OF A NANOGRAIN PMN POWDERS

ABSTRACT

Dielectric permittivity of 150 nm mean grain size Pb(Mn_1/3Nb_2/3)O₃ (PMN) nanopowder has been investigated by dielectric spectroscopy in the 20 Hz–1 MHz frequency range and 100 K–400 K temperature range. The broad and diffused dielectric dispersion has been observed, but the dispersion region and the maximum of the real part of dielectric permittivity is shifted to lower temperatures compare to PMN single crystal and ceramics. The mean relaxation time, obtained from fits of the frequency dependences of the dielectric permittivity with Cole-Cole formula, changes according to the Vogel-Fulcher law with the freezing temperature T ₀ = 88 K which is much lower than in bulk PMN materials.     

Anomalous acceleration of ions in a plasma accelerator with an anodic layer

In a plasma accelerator with an anodic layer(PAAL), we discovered experimentally the effect of‘super-acceleration' of the bulk of the ions to energies W exceeding the energy equivalent to the discharge voltage Vd. The E?×?B discharge was ignited in an environment of atomic argon and helium and molecular nitrogen. Singly charged argon ions were accelerated most effectively in the case of the largest discharge currents and pressure P of the working gas. Helium ions with W??eV_d(e being the electron charge) were only recorded at maximum pressures. Molecular nitrogen was not accelerated to energies W??e Vd. Anomalous acceleration is realized in the range of radial magnetic fields on the anode 2.8?×?10~(–2)≤B_(rA)≤4?×?10~(–2) T. It was also found analytically that the cathode of the accelerator can receive anomalously accelerated ions. In this case, the value of the potential in the anodic layer becomes higher than the anode potential, and the anode current exceeds some critical value. Numerical modeling in terms of the developed theory showed qualitative agreement between modeling data and measurements.     

Millimetre-wave second-harmonic Gunn-diode oscillator with magnetic tuning

A second-harmonic Gunn-diode oscillator with a rectangular waveguide resonator for the fundamental frequency has been designed and tested in the SO GHz frequency range. A longitudinally magnetized ferrite slab, placed in the resonator, makes possible a frequency decrease of 0 to 250 MHz when a static magnetic field of 0 to 220 Oe is applied.