Andrey M. Lider

Positron Annihilation Spectroscopy of Defects in Commercially Pure Titanium Saturated with Hydrogen

The experimental study of the structure of commercially pure titanium after saturation with hydrogen from the gas phase by means of positron lifetime spectroscopy (PLS) and Doppler broadening spectroscopy (DBS) was carried out. In the result of penetration and accumulation of hydrogen, significant changes of annihilation characteristics occurred due to the defect structure changing. The investigated samples contained hydrogen in concentrations varying from 0 to 0.961 wt.%. Several stages of hydrogen interaction with the metal structure were revealed.

Investigation of Commercially Pure Titanium Structure during Accumulation and Release of Hydrogen by Means of Positron Lifetime and Electrical Resistivity Measurements

In this work the goal was to study the behavior of titanium-hydrogen system with hydrogen concentration of 1 wt. % at high temperature vacuum annealing by means of positron lifetime (PL) spectroscopy and electrical resistivity measurements. The range of hydrogen concentrations under investigation requires the γ phase formation. The study is related with the X-ray diffraction (XRD) and thermal desorption spectra (TDS) analysis. The registered positron lifetime spectra were analyzed by multiexponential decomposition into two components. Correlation of changes of the parameters of the PL spectrum and the electrical resistivity is revealed in this paper.

Application of Automated Complex Gas Reaction Controller for Hydrogen Storage Materials Investigation

Automated complex Gas Reaction Controller and its application for hydrogen storage materials investigation are described in this article. Pressure-composition isotherms (PCI) and kinetics measurements of LaNi5 have been obtained for validation of the apparatus. Measurements of both absorption and desorption PCI curves and kinetics measurements at different conditions have been obtained for carbon nanotubes to estimate its hydrogen storage properties.

Hydrogen Accumulation in Technically Pure Titanium Alloy at Saturation from Gas Atmosphere

This paper presents experimental results of study of hydrogen accumulation in technically pure titanium alloy at saturation from gas atmosphere. Automated complex Gas Reaction Controller has been used for hydrogen saturation from gas atmosphere. Temperatures increasing from 350 °C to 500 °C allow increase hydrogen sorption process and as a result significantly increase hydrogen concentration in technically pure titanium alloy. At hydrogen saturation from gas atmosphere at temperature 500 °C increasing of saturation time from 10 minutes to 120 minutes leads to hydrogen concentration increasing from 0.1 wt.% to 1 wt.% and increasing of hydrides volume content throughout the samples. The activation energy for hydrogen evolution has been estimated by thermal desorption spectroscopy method by equal 102 kJ/mol.

Investigation of Hydrogen Distribution from the Surface to the Depth in Technically Pure Titanium Alloy with the Help of Glow Discharge Optical Emission Spectroscopy

Optimal operating parameters for the study of titanium-hydrogen system with the help of glow discharge optical emission spectroscopy have been selected. Hydrogen distribution from the surface to the depth in technically pure titanium alloy after electrochemical hydrogen saturation has been studied.

The Evolution of Defects in Zirconium in the Process of Hydrogen Sorption and Desorption

The influence of hydrogen sorption-desorption cycles on defect structure of Zr-1Nb alloy was investigated. Specimens were hydroganated from gas atmosphere at temperature 500 °C and pressure 2 atm up to the hydrogen concentration equal to 0.05 wt.% for each cycle. The hydrogen concentration during saturation was determinate by the volumetric method. Then samples were annealed at temperature 900 °C with the heating rate of 4 °C/s. The lattice defects were studied by means of positron lifetime spectroscopy (PLS) and doppler broadening spectroscopy (DBS). New experimental data about the evolution of the average positron lifetieme τavg, as well as the relative changes in the parameters S, W depending treatment stage in Zr-1Nb alloy during thermo hydrogen proccessing was obtained.

Influence of hydrogen on the properties of Zr-1%Nb alloy modified by a pulsed electron beam

The influence of hydrogen and a pulsed electron beam on the properties of Zr-1%Nb alloy is studied. It is shown that electron beam processing results in the formation of martensite with an intricate morphology in the subsurface layer of the alloy. It is found that the amount of hydrogen penetrating into the modified alloy is twice as low as in the as-prepared material. In addition, the modified alloy is more stable against the hydrogen action.

Investigation of Defects in Hydrogen-Saturated Titanium by Means of Positron Annihilation Techniques

This paper presents the results of a defect structure investigation in commercially pure titanium alloy after hydrogen charging in a gaseous atmosphere at the temperature of 873 K up to the concentration of 5.1 at. %. Structure of samples was studied by positron lifetime, Doppler broadening and X-ray diffraction spectrometry. Several processes, corresponding to the different ranges of hydrogen concentrations were revealed. It was shown that hydrogen, penetrating in the material, expands its crystal lattice, initiates formation of vacancy-like defects of different dimensions and reacts with the last ones, forming the defect-hydrogen complexes.

Effect of Pulsed Electron Beam Treatment and Hydrogen on Properties of Zirconium Alloy

The paper presents the results of the pulsed beam effect on the structure and phase composition of zirconium alloy. Such treatment is demonstrated to lead to forming of complex morphology martensite in the surface layer of the alloy. The processes of hydrogen absorption by zirconium alloy with modified surface have been studied. Modification of the samples is found to reduce the amount of hydrogen, absorbed by the volume of zirconium alloy during hydrogenation.

Positron spectroscopy of defects in submicrocrystalline nickel after low-temperature annealing

Using the method of measuring the positron lifetime spectra and Doppler broadening annihilation line spectroscopy, the annealing of defects in submicrocrystalline nickel produced by equal channel angular pressing has been studied. In as-prepared samples, the positrons are trapped by dislocation defects and vacancy complexes inside crystallites. The size of vacancy complexes decreases with increasing annealing temperature in the interval ΔT = 20–300°C. However, at T = 360°C, the complexes start growing again. The dependence of S-parameter on W-parameter derived from the Doppler broadening spectroscopy has two parts with different inclinations to axes that correspond to different types of primary centers of positron trapping in submicrocrystalline nickel. It has been elucidated that, at recovery stage in the temperature interval ΔT = 20–180°C, the main centers of positron trapping are low-angle boundaries enriched by impurities, while at in situ recrystallization stage in the temperature interval ΔT = 180–360°C, the primary centers of positron trapping are low-angle boundaries.