Viktor N. Kudiiarov

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.

The influence of nickel layer thickness on microhardness and hydrogen sorption rate of commercially pure titanium alloy

The influence of nickel coating thickness on microhardness and hydrogen sorption rate by commercially pure titanium alloy was established in this work. Coating deposition was carried out by magnetron sputtering method with prior ion cleaning of surface. It was shown that increase of sputtering time from 10 to 50 minutes leads to increase coating thickness from 56 to 3.78 μm. It was established that increase of nickel coating thickness leads to increase of microhardness at loads less than 0.5 kg. Microhardness values for all samples are not significantly different at loads 1 kg. Hydrogen content in titanium alloy with nickel layer deposited at 10 and 20 minutes exceeds concentration in initial samples on one order of magnitude. Further increasing of deposition time of nickel coating leads to decreasing of hydrogen concentration in samples due to coating delamination in process of hydrogenation.

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.

Investigation of Hydrogen Sorption-Desorption Processes and Hydrides Formation and Dissolution in Zirconium by Using Sievert Apparatus and Short-Wave Diffraction of Synchrotron Radiation

Hydrogen sorption-desorption processes by zirconium alloy Zr-1Nb was investigated in this article. Sievert apparatus was used for investigation of hydrogen interaction with material. It was shown that hydrogenation at gas atmosphere at 350, 450 and 550 °C temperatures leads to the δ-hydride formation in all material volume. Hydrogen sorption rates were calculated on the linear parts of sorption curves and equal to 0.5·10-4 wt%/s at 350 °C, 9.5·10-4 wt%/s at 450 °C and 23.1·10-4 wt%/s at 550 °C. Short-wave diffraction of synchrotron radiation was used for investigation of hydrides dissociation during heating. Hydrides dissociation formed after hydrogenation at gas atmosphere occurs at temperature 522-540 °C. Further temperature increasing leads to β-phase appearance which indicates α to β phase transition at zirconium.

Research of Hydrogenation and Dehydrogenation Effect on the Structural and Phase State of the Titanium Alloy

Effect of hydrogen on the structural and phase state of the fine-grained and submicrocrystallinestructure of two-phase (alpha + beta) titanium Ti-6Al-4V alloy was investigated by the methods of electron microscopy and X-ray diffraction analysis. Hydrogenation is found to result in minor structural and phase changes both in fine-grained and submicrocrystalline samples.The use of electron beam exposure combined with heating for hydrogen release in the Ti-6Al-4V alloy is shown to reduce degassing time and decrease the hydrogen concentration to the values closed to the engineering standards for the Ti-6Al-4V alloys.