Debye Temperature and Quantum Diffusion of Hydrogen in Body-Centered Cubic Metals

Diffusion of deuterium in potassium is studied herein. Mass transfer is controlled predominantly by the mechanism of overbarrier atomic jumps at temperatures 120-260 K and by the tunneling mechanism at 90-120 K. These results together with literature data allowed us to determine conditions under which the quantum diffusion of hydrogen in metals can be observed, which is a fundamental problem. It is established that in metals with a body-centered cubic lattice tunneling can be observed only at temperatures below the Debye temperature θD solely for metals with θD < 350 K. Predictions are made for metals in which quantum diffusion of hydrogen can be experimentally registered. Metals for which such results cannot be obtained are specified as well. Among them are important engineering materials such as α-Fe, W, Mo, V, and Cr. © 2022 The Authors. Published by American Chemical Society.Ministry of Education and Science of the Russian Federation, Minobrnauka: AAAA-A19-119012990095-0The research was carried out within the state assignment of Ministry of Science and Higher Education of the Russian Federation (theme “Function” no. AAAA-A19-119012990095-0)

Hydrogen isotope exchange in proton-conducting oxides during proton and deuteron irradiation

It has been found that during accelerator beam deuteron irradiation of a proton-conducting oxide containing protium H/D isotope exchange between beam ions and dissolved ions takes place. This isotope exchange was also observed during high-energy proton irradiation of the oxide containing dissolved deuterium atoms. These results provide evidence to a new type of hydrogen isotope exchange. Any appreciable effects of conjugate diffusion of hydrogen and oxygen ions and of the interface processes on the isotope exchange rate were eliminated. In this type of exchange the rate of replacement of H+ by D+ and of D+ by H+ was determined only by the properties of the crystal. The discovered effect was used in our study to obtain experimental data characterizing the dynamic and equilibrium behavior of hydrogen isotopes in the oxide BaZr0.9Y0.1O3 - δ. © 2013 Pleiades Publishing, Ltd

Oxygen and nitrogen concentrations in the Ti-6Al-4V alloy manufactured by direct metal laser sintering (DMLS) process

Published ArticleTwo machines from two scientific centers (Russia and South Africa) were used for the manufacturing of the Ti6Al4V alloys by the direct metal laser sintering. The chemical composition of powders complies with the ASTM F-136 (grade 5), ASTM B348 (grade 23) standard for medical applications. Analysis of the oxygen and nitrogen contamination in DMLS alloys was done with Van de Graaff accelerator with two Mega Volts. It is found that structures of the samples manufactured with two different machines used the same regimes are close to each other. TEM studies found the metastable martensitic structure and silicon nitride Si3N4. It was found that the oxygen and nitrogen contents in both samples are within the normal range for medical grade titanium alloys

Effect of preliminary nanostructuring frictional treatment on the efficiency of nitriding of metastable austenitic steel in electron beam plasma

The paper studies the effect of the temperature of nitriding in electron beam plasma, ranging between 250 and 500 °, on the nitrogen concentration, phase composition and microhardness of the surface of the AISI 321 chromium-nickel austenitic steel in two initial states - quenched undeformed and after nanostructuring frictional treatment. The lowest nitriding temperature (350 °C) for the efficient hardening of the steel has been established. The application of frictional pretreatment with a sliding synthetic diamond indenter in an argon environment is shown to be highly efficient for increasing the depth of the layer nitrided at this temperature. The contribution of the formed S-phase (nitrogen-oversaturated austenite γN) to the intensive hardening of the steel nitrided at low temperatures (300 to 400 °) is noted. © 2017 Author(s).01201354598Russian Foundation for Basic Research, RFBR: 15-08-07947Ural Branch, Russian Academy of Sciences, UB RAS: 15-9-12-45, 01201463331The work was done in the framework of the Complex Program of UB RAS (project No. 15-9-12-45), within the state order on the subject “Structure” (No. 01201463331), the government assignment for IES UB RAS (theme No. 01201354598) and supported by RFBR, project No. 15-08-07947

Synthesis, Structure and Electrical Properties of Li+-doped Pyrochlore Gd2Zr2O7

Received: 08.04.2020. Accepted: 20.05.2020. Published: 30.06.2020.The pyrochlore Gd1.55Li0.45Zr2O6.55 was prepared by the solution and solidstate methods. The introduction of lithium in the Gd-sublattice led to decrease in the lattice parameter a = 10.4830(8) Å in comparison with Gd2Zr2O7 (a =10.5346(2) Å). Monitoring of the lithium content in the sample during heat treatments showed a loss of lithium at temperatures above 1100 °C, so, to maintain the stoichiometry of lithium the low temperature sintering methods are required. The sample Gd1.55Li0.45Zr2O6.55 exhibited a predominant oxygen-ion transport over a wide range of temperatures. Although doping did not lead to an increase in the oxygen-ion conductivity compared to Gd2Zr2O7, it caused the suppression of the hole conductivity.The reported study was funded by RFBR and Sverdlovsk region, project number 20‑43‑660033a

Electrical Properties of Li+-Substituted Solid Solutions Based on Gd2Zr2O7

Abstract: Solid solution (Formula presented.) with a pyrochlore structure is synthesized for the first time. The cationic composition is confirmed via chemical analysis and nuclear reactions. It is found that the stoichiometry with respect to lithium is retained up to 1100°C. The lattice parameter diminishes in the homogeneity range 0 ≤ x ≤ 0.30, while the free volume of migration grows. Introducing lithium into the Gd sublattice raises oxygen–ion conductivity, due to the emergence of oxygen vacancies and enhancement of their mobility. Maximum conductivity is reached for composition with х = 0.10 (~1 × 10−3 Ω−1 cm−1, 650°C). An assumption is made about the formation of associates of the type (Formula presented.) at high contents of the dopant (x = 0.30), accompanied by an increase in the activation energy of conductivity. © 2021, The Author(s).This work was performed with a grant from the Russian Foundation for Basic Research, project no. 20-43-660033, and financial support from the State Atomic Energy Corporation ROSATOM (State Contract no. Н.4о.241.19.21.1070 of April 16, 2021; electronic identifier 07731000003210000330001)

Isotopic exchange of gaseous oxygen with mechanoactivated manganese oxides

Isotope exchange of oxygen 18O 2 with oxides Mn 2O 3 and Mn 3O 4 was investigated in the temperature range of 300-700° C. It was established that the content of the isotope O 18 in mechanically activated powders was noticeably higher than in the initial ones. Already at relatively low annealing temperatures isotope exchange leads to nearly the maximum possible under the given conditions replacement of atoms 16O to 18O. The isotope exchange parameters connected with the processes at the boundaries of the particles of mechanoactivated powder and within their volume were determined. © (2012) Trans Tech Publications

Diffusion of insoluble carbon in zirconium oxides

The diffusion coefficient of insoluble carbon in zirconium oxides has been obtained for the temperature range of 900-1000A degrees C. There are no published data on the diffusion of insoluble impurities; these data are of current interest for the diffusion theory and nuclear technologies. Tracer atoms 13C have been introduced into oxides by means of ion implantation and the kinetics of their emission from the samples in the process of annealing in air has been analyzed. The measurements have been performed using the methods of nuclear microanalysis and X-ray photoelectron spectroscopy. The diffusion activation energy is 2.7 eV and the carbon diffusion coefficient is about six orders of magnitude smaller than that for oxygen self-diffusion in the same systems. This result indicates the strong anomaly of the diffusion properties of carbon in oxides. As a result, zirconium oxides cannot be used in some nuclear technologies, in particular, as a material of sources for accelerators of short-lived carbon isotopes

Oxygen isotope exchange in nanosized powders of the Al2O3 oxide

Oxygen isotope exchange (OIE) between nanosized powders of the aluminum oxide Al2O3 and oxygen-containing gases 18O2 and C 18O2 has been studied in a temperature range of 100-500°C. The con-centration of the oxygen isotope 18O in the powders was determined by nuclear microanalysis technique (NRA). It has been shown that for this oxide the OIE exhibits a significant size effect. It has been established that the OIE of the Al2O3 nanopowder is characterized by a specific time dependence of the concentration of the 18O isotope at the surface of grains and by a low level of the content of 18O in the oxide. A linear depen-dence of the concentration of 18O in the nanopowders on the specific surface of the nanoparticles has been revealed. The experimental data are discussed in terms of several models of the process of isotope exchange. © Pleiades Publishing, Ltd., 2012