Aggregation of experiments for estimation of hydrogen permeability parameters

The study of the hydrogen permeability of materials employs a variety of methods with their own specific features, advantages and drawbacks. The penetration method allows determining the diffusion coefficient from so-called lag time. The accuracy of the estimation depends on the degree of proximity to the DLR (diffusion limited regime) mode. The method of ‘communicating vessels’ is more sensitive to surface processes. ‘Separate’ application of these methods leads to a situation where the materials studied are in fact somewhat different (for example, due to different impacts on the surface), and significant differences in parameter estimates ensue. This paper suggests and implements a cascade experiment technique and the corresponding mathematical toolkit. The informative capacity of experimental studies and the accuracy of the estimation of hydrogen permeability parameters (diffusion, absorption, desorption) are thus enhanced.     

A High-Voltage Switching Device Based on Two High-Current Vacuum Gaps Connected in Series

A high-voltage switch that consists of two -43 triggered vacuum spark gaps connected in series has been manufactured and tested. The switch is intended for use at a voltage of up to 80 kV. The maximum current switched is 200 kA. The breakdown strength of the switch has been theoretically and experimentally investigated. Experimental and theoretical breakdown-voltage distribution functions have been obtained for the gaps and the switch. Based on the empirical breakdown-voltage distributions for both of the gaps, the breakdown-voltage distribution for the switch has been calculated and found to be in satisfactory agreement with the measurement results.     

Using Deform-2d Software to Study Heat-Insulation Materials as Protection of Air Tuyeres Against Burnout

Metallurgist - To analyze the dynamics of heating of an air tuyere by the finite-element method (axisymmetric problem), DEFORM-2D software is used. Different heat-insulation materials protecting...     

Surface Сonductivity Dynamics in PbSnTe:In Films in the Vicinity of a Band Inversion

Semiconductors - The features of transient processes under the field effect in PbSnTe:In films with a variation in the current up to a factor of 105 are studied at helium temperatures. These...     

Features of MIS Structures Based on Insulating PbSnTe:In Films with the Composition in the Vicinity of the Band Inversion Related to Their Ferroelectric Properties

Semiconductors - The characteristics of metal-insulator-semiconductor (MIS) structures based on insulating PbSnTe:In films with compositions in the vicinity of band inversion grown by...     

Optical Properties of Copper-Doped Lithium Niobate Crystals

We have studied the optical properties of copper-doped lithium niobate crystals using semiconductor light-emitting diodes and lasers emitting in the visible and ultraviolet spectral regions as excitation sources. The results demonstrate that, at an excitation frequency approaching the frequency of electronic absorption in copper ions, there is discrete resonance Raman scattering in the form of a frequency comb. The observed Raman satellites of discrete light scattering are due to polar longitudinal A₁ optical modes of the lithium niobate single crystal. Under excitation by a light-emitting diode with a wavelength of 520 nm, we observe a sharp increase in discrete light scattering intensity in comparison with the photoluminescence excited by shorter wavelength excitation sources.     

Gamma-Densitometer for Studies of High-Temperature Metal Melts

The set-up for the measurement of the density of high-temperature melts by means of penetrating gamma-radiation is described. The modern device base, which makes it possible to automatize the work, is the main difference from the earlier existing gamma-densitometers. The key characteristics of the absolute measurements with the use of very exact values of the mass attenuation coefficient for the gamma-quanta beam are described and the accuracy of measurements is estimated. The results of the density measurement of the molten aluminum, cadmium, tin, and bismuth are presented; they confirm the a priori estimate of the error.     

Resource-saving technologies of making advanced cast and deformable superalloys with allowance for processing all types of wastes

The results of thermodynamic analysis of the vacuum–melt–ceramic system and experimental investigations of using up to 100% wastes during vacuum-induction melting are presented. An important role of rare-earth and alkaline-earth metals and heat treatment is shown for effective refining of a melt from impurities and gases. As a result, a resource-saving technology of making advanced cast and deformable nickel superalloys is developed with allowance for processing all types of wastes, including off-grade wastes. The developed technology of refining wastes under vacuum makes it possible to manufacture the alloys that fully meet the requirements of alloy specifications from 100% wastes. This technology is now used for the mass production of nickel superalloys in a research complex at FGUP VIAM.     

Refining a complex ZhS32-VI nickel alloy from silicon and phosphorus by unidirectional solidification of the melt at low solidification front velocities

The possibility of decreasing the silicon and phosphorus contents in a high-temperature ZhS32-VI nickel alloy by directional movement of solidification front at a velocity V = 6 mm/h has been studied. As a result, the contents of the impurities have decreased as compared to those in the starting alloy; the decrease in the silicon and phosphorus contents is from 2 to 4 and from 14 to 20 times, respectively. Thus, nonmetallic inclusions, in particular, those containing silicon and phosphorus, are moved to the top of the ingot.