Positron annihilation spectroscopy of vacancy-type defects hierarchy in submicrocrystalline nickel during annealing

Positron annihilation and X-ray diffraction analysis have been used to study submicrocrystalline nickel samples prepared by equal channel angular pressing. In the as-prepared samples the positrons are trapped at dislocation-type defects and in vacancy clusters that can include up to 5 vacancies. The study has revealed that the main positron trap centers at the annealing temperature of deltaT= 20°C-180°C are low-angle boundaries enriched by impurities. At deltaT = 180°C-360°C, the trap centers are low-angle boundaries providing the grain growth due to recrystallization in-situ

Structural features of Ni-Cr-Si-B materials obtained by different technologies

This study considers the structural features of Ni-Cr-Si-B (Ni - base; 15.1 % Cr; 2 % Si; 2 % B; 0.4 % C) materials obtained by different methods. The self-fluxing coatings were deposited by plasma spraying on the tubes from low carbon steel. Bulk cylinder specimens of 20 mm diameter and 15 mm height were obtained by spark plasma sintering (SPS). The structure and phase composition of these materials were investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The major phases of coatings and sintered materials are [gamma]-Ni, Ni[3]B, CrB and Cr[7]C[3]. We demonstrate that the particle unmelted in the process of plasma spraying or SPS consist of [gamma]-Ni-NEB eutectic and also CrB and Cr[7]C[3] inclusions. The prolonged exposure of powder to high temperatures as well as slow cooling rates by SPS provide for the growth of the structural components as compared to those of plasma coatings materials. High cooling rates at the plasma spraying by melted particles contribute to the formation of supersaturated solid solution of Cr, Si and Fe in [gamma]-Ni. The structure of the melted particles in sintering material has gradient composition: the core constituted of Ni grains of 10 μm with [gamma]-Ni-Ni[3]B eutectic on the edges. The results of the experiment demonstrate that the sintering material has a smaller microhardness in comparison with plasma coatings (650 and 850 MPa, respectively), but at the same time the material has higher density (porosity less than 1 %) than plasma coatings (porosity about 2.. .3 %)

Influence of Filler Metals in Welding Wires on the Phase and Chemical Composition of Weld Metal

The influence of filler metals used in welding wires on the phase and chemical composition of the metal, which is surfaced to mining equipment exposed to abrasive wear, has been investigated. Under a laboratory environment, samples of Mo-V-B and Cr-Mn-Mo-V wires were made. The performed experiments have revealed that fillers of the Cr-Mn-Mo-V system used in powder wire show better wear resistance of the weld metal than that of the Mn-Mo-V-B system; the absence of boron, which promotes grain refinement in the Mn-Mo-V-B system, significantly reduces wear resistance; the Mn-Mo-V-B weld metal has a finer structure than the Cr-Mn-Mo-V weld metal

Application of Microsecond Voltage Pulses for Water Disinfection by Diaphragm Electric Discharge

The paper presents the dependence of copper and silver ions formation on the duration of voltage pulses of diaphragm electric discharge and on the pH of treated liquid medium. Knowing it allows one to create an automatic control system to control bactericidal agent's parameters obtained in diaphragm electric discharge reactor. The current-voltage characteristic of the reactor with a horizontal to the diaphragm membrane water flow powered from the author`s custom pulse voltage source is also presented. The results of studies of the power consumption of diaphragm electric discharge depending on temperature of the treated liquid medium are given

Plastometric Simulation of the Hot Rolling Process of Al/B4C Powder Composite

The actual problem of nuclear machine building is mastering the manufacture of Al/B4C powder composite cladded with layers of aluminum alloy in a rigid technological casing by a high-production method of rolling. Simulation tests of cylindrical samples were carried out using a uniaxial compression method on a cam plastometer with an evaluation of the influence of the strain on the density of the Al/B4C powder compact with the aim of optimizing the rolling technology. The strain rate and strain correspond to the ones for the rolling process, and the compression process of samples was divided into three stages. The temperature of deformation and strain of the powder compound of aluminum and dispersed particles of boron carbide Al/B4C were varied according to the experiment plan. The final density of the powder compound after each compression stage was accepted as an experimental variable as well as its cutting ability according to which the manufacturability of the obtained composite was evaluated. According to the simulation experiment results, the conditions of hot compaction of the Al/B4C powder composite were evaluated and recommendations for temperature–deformation regimes were formulated.The study was made within the basic part of the state job in the field of scientific activity No. 11.9538.2017/8.9 and was supported by Act 211 of the Government of the Russian Federation (agreement No. 02.A03.21.0006). The equipment of the “Plastometriya” collective use center was used in the research

Technical project of complex fast cycle heat treatment of hydrogenous coal preparation

Problems of heat-treated milled hydrogenous coal preparation site creation in leading fast cycle heat treatment complex were considered. Conditions for effective use of electrostatic methods of heat-treated milled hydrogenous coal preparation were set. Technical project of heat treatment of milled hydrogenous coal preparation site was developed including coupling of working equipment complex on fast heat treatment and experimental samples of equipment being designed for manufacturing. It was stated that methods of electrical separation are used for heat-treated milled hydrogenous coal preparation with effective ways of organic and mineral components separation. Laboratory test for determination of optimal separation size sent into separators of heat-treated milled hydrogenous coal were made

Influence of metal structural heterogeneity on corrosion of steam boiler pipes

The degree of metal structural heterogeneity and its influence on intergranular and intragranular creep and processes of general and pitting pipe corrosion of steam boilers connected with them has been estimated on the basis of the roentgenophase analysis of samples taken from pipe steel 20

Separability and entanglement of four-mode Gaussian states

The known Peres-Horodecki criterion and scaling criterion of separability are considered on examples of three-mode and four-mode Gaussian states of electromagnetic field. It is shown that the principal minors of the photon quadrature dispersion matrix are sensitive to the change of scaling parameters. An empirical observation has shown that the bigger the modulus of negative principal minors, the more entangled the state.Comment: 14 pages, 11 figure

Scaling Separability Criterion: Application To Gaussian States

We introduce examples of three- and four-mode entangled Gaussian mixed states that are not detected by the scaling and Peres-Horodecki separability criteria. The presented modification of the scaling criterion resolves this problem. Also it is shown that the new criterion reproduces the main features of the scaling pictures for different cases of entangled states, while the previous versions lead to completely different outcomes. This property of the presented scheme is evidence of its higher generality.Comment: 7 pages, 4 figure

Study of single muons with the Large Volume Detector at Gran Sasso Laboratory

The present study is based on the sample of about 3 mln single muons observed by LVD at underground Gran Sasso Laboratory during 36500 live hours from June 1992 to February 1998. We have measured the muon intensity at slant depths from 3 km w.e. to 20 km w.e. Most events are high energy downward muons produced by meson decay in the atmosphere. The analysis of these muons has revealed the power index of pion and kaon spectrum: 2.76 \pm 0.05. The reminders are horizontal muons produced by the neutrino interactions in the rock surrounding LVD. The value of this flux is obtained. The results are compared with Monte Carlo simulations and the world data.Comment: 13 pages, 2 figures, accepted for publication in "Physics of Atomic Nuclei