Yu. I. Tyurin

Non-equilibrium release of atomic hydrogen from metals under irradiation

The release of atomic hydrogen isotopes and positively charged ions under irradiation by electrons in pre-threshold region of metals saturated by hydrogen isotopes has been studied. The mechanisms of non-equilibrium exchange and release of atomic hydrogen as well as of positive ions from metals are discussed, which are based on the accumulative properties of internal hydrogen atmosphere of metals.

Hydrogen migration and release in metals and alloys at heating and radiation effects

Abstract Deuterium and hydrogen migration and release have been studied in stainless steel, niobium, palladium during accelerated electrons and 14N ions. It was shown that radiation stimulates the intensive release of electrolytically introduced deuterium from stainless steel, Pd and Nb. The mechanism release of deuterium from metals under the influence of radiation released with accumulative properties of internal D(H) atmosphere and influence of ionizing radiation on potential surface barrier preventing formation of D2 (H2), molecules and its desorption in gas phase.

Ionizing radiation-stimulated diffusion and desorption of hydrogen from metals

The processes of hydrogen diffusion from a sample depth activated by electrons with an energy of tens of keV are studied. The difference from the known models of electron-stimulated desorption, which consider as a rule electron energies from 0.5 to several keV, is noted. The proposed model is shown to correspond to at least two established experimental facts: the nonlinear dependence of hydrogen isotope desorption on the electron beam current density affecting the sample and the dependence of hydrogen desorption on the irradiation time of the sample.

Hydrogen permeability of protective coating formed by electron treatment of zirconium alloys

The results of studying the hydrogen permeability and physicomechanical properties of zirconium alloy irradiated with a pulse electron beam are presented. It is established that, with an increase in the beam energy, a surface layer of this material is hardened to depths of about 2.5 μμm. The depth distribution of Young’s modulus values of zirconium alloy confirms the obtained results. The study of the hydrogen permeability of this material has shown that, after hydrogen charging of samples, the hydrogen concentration in a sample treated at an energy density of 18 J/cm2 is 2.5–3 times lower than that of the initial material charged with hydrogen.

The formation of stable hydrogen impermeable TiN-based coatings on zirconium alloy Zr1%Nb

TiN coatings were deposited by DC reactive magnetron sputtering (dcMS) method on Zr1%Nb substrates with different film thickness. The influence of crystalline structure and thickness of the coatings on hydrogen permeation was investigated. The results revealed that the increase in thickness of the film reduced hydrogen permeability. 1.54 μm TiN deposited in N2/Ar gas mixture with a ratio of 3/1 reduces hydrogen permeation in more than two orders of magnitude at 350 °C. Adhesion strength decreased with increasing film thickness (0.55 to 2.04 μm) from 7.92 to 6.65 N, respectively. The Ti underlayer applied by arc ion plating (AIP) leads to the formation of stable Ti/TiN coatings on Zr1%Nb under thermocycling conditions up to 800 °C. Meanwhile, hydrogen permeation rate of Ti/TiN deposited by combination of AIP and dcMS remains at the same level with TiN deposited by dcMS.

Grinfeld instability as a mechanism of the formation of self-similar structures on aluminum single-crystal foils under cyclic tension

Based on the analysis of our results and data available in the literature, it has been shown that the formation of self-similar tweed structures on (100)[001] aluminum single-crystal foils during constrained cyclic tension occurs under conditions of the Grinfeld instability. This is confirmed by the good agreement between the theoretical estimates obtained for the period of tweed structures in terms of the Grinfeld instability model and the experimentally measured values. It has been demonstrated that the Grinfeld instability manifests itself in different boundary conditions associated with the specific features of the elasto-plastic deformation of a two-layer aluminum foil-specimen system, which is responsible for the self-similarity of tweed structures. It has been assumed that the material redistribution on the surface of foils is due to the migration of point defects that are formed during cyclic tension and exhibit a sufficient mobility at room temperature.

A plant for studying radiation and thermal desorption of gases from inorganic materials

A high-vacuum plant and methods for studying thermal and radiation-stimulated desorption from solid-state materials are described. Radiation-stimulated desorption was studied using an electron gun with a 1- to 120-keV beam energy, featuring a new technology of power supply units. Partial pressure gages with a sensitivity of up to 10−13 Pa were used to record mass spectra of residual gases. Results of studying thermal- and radiation-stimulated yields of hydrogen from submicrocrystalline samples of a BT-6 alloy are presented to demonstrate the serviceability of the created procedures.

Evolution of the Electron Structure and Excitation Spectrum in Palladium as a Result of Hydrogen Absorption

Metal‐hydrogen systems are of both practical and scientific interest and have been studied already for many decades [1, 2]. Great efforts were expended on experimental and theoretical studies of the behavior of hydrogen in the vicinity of vacancies, at dislocations, at grain boundaries, and on surfaces of bulk materials, as well as in various nanocrystal systems such as films, clusters, and multilayer structures [3]. Considerably less attention was given to investigating the effect of ionizing radiation on the properties of these systems. For example, up to now, there is no explanation of the results obtained in [4, 5], where it was shown that the action of ionizing radiation on the Pd‐H system leads to intense hydrogen liberation from the metal at both room and cryogenic temperatures. It is important that the hydrogen yield occurs from the entire sample surface even when only a small fraction of the sample was irradiated [4]. The results obtained completely exclude the possibility of using the thermal mechanism to explain the observed effect. In the present study, we make an attempt to substantiate the plasmon mechanism as that underlying the effect under discussion. This mechanism is associated with collective excitations of the electron density, which are capable of propagating over the entire crystal [6]. It is well-known that ionizing radiation releases its energy in a solid, mainly by the excitation of its electron subsystem. In this case, the lifetime of the excitations in metals is rather short and attains the order of ~10 –15 s. Here, the principal question arises: in what manner does the Pd‐H electron subsystem manage to redistribute the energy absorbed by a hydrogen atom over the entire volume of the crystal? The way to answer this question is to investigate both the evolution of the electron structure and the excitation spectrum of metals in the process of their saturation with hydrogen. In the present study, using the first-principle calculation of the electronic structure for both pure Pd and the Pd‐H solution, we investigated the effect of hydrogen on the electron properties of palladium. The calculation was performed by the full-potential linear augmented plane wave method [7] in the framework of the local approximation of the density-functional theory. For all concentrations under study, hydrogen atoms were considered to be localized in the most profitable (from the energy standpoint) octahedral interstitial sites.

Features of excitation of the hydrogen (deuterium)-metal system by an electron bunch

We report on the results of mass-spectroscopic analysis of the hydrogen yield from metals saturated with hydrogen under the action of accelerated electrons (with an energy of up to 100 keV and a current density from 3 to 30 μA). It is found that the desorption rate is determined not only by parameters of the electron bunch, but also by the structure of the oxide film. It is discovered that the electronic subsystem of hydrogen-enriched metals enhances their ability to absorb the energy of the external electromagnetic action and to preserve it for a longer time as compared to a pure metal. This facilitates nonequilibrium migration and yield of hydrogen under the action of radiation in the subthreshold range. A theoretical model is proposed and analytic dependences are derived for the intensity of hydrogen yield from metals exposed to an electron bunch. The results of this study can be used for the removal of hydrogen from metals and for obtaining submicrocrystalline materials (e.g., titanium).

Dynamics of hydrogen accumulation and radiation-stimulated release from steels

Hydrogen accumulation during electrolytic saturation of 12Kh18N10T and 12Kh12M1BFR steels, as well as during thermally and radiation-stimulated hydrogen release from the same materials, was studied. It was shown that there is a critical hydrogen concentration in the sample, which is reached in 50 h for this saturation method (1 M H2SO4 electrolyte, current density is 0.5 A/cm2). Initially, hydrogen is trapped at low-temperature (400–500°C) traps of several types in surface layers. At saturation times of 50 h and longer, hydrogen penetrates to high-temperature (800–900°C) traps in the sample bulk. Under electron irradiation of saturated samples, the hydrogen yield nonlinearly increases with electron current density and energy above 40 keV. It was concluded that electronic processes (Auger process and plasmon excitation) play a dominant role in hydrogen diffusion and desorption activation.