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The effect of helium ion irradiation on the microstructure and properties of composites based on Zr/Nb nanoscale multilayer coatings (NMCs) was studied. X-ray diffraction (XRD), transmission electron microscopy (TEM), and variable-energy Doppler broadening spectroscopy (DBS) were used for the in-depth analysis of defects in the irradiated NMCs. After irradiation of the Zr/Nb NMCs with helium ions at a 1017 ion/cm2 dose, the layered structure was generally retained, but the internal stresses in the layers were increased, which caused wave-like distortion in the ion deposition zone. The Zr/Nb NMCs with an individual layer thickness of 25 nm were characterized by the smallest microstress changes, but single blisters were formed in the near-surface region. The microstructure of the Zr/Nb NMCs with a layer thickness of 100 nm exhibited relatively smaller changes upon helium ion irradiation. The prevailing positron-trapping center was the reduced-electron-density area at the interfaces before and after irradiation of the Zr/Nb NMCs regardless of the layer thickness. However, the layer thickness affected the DBS parameter profiles depending on the positron energy, which was probably due to the different localization of implanted ions within the layers or at the interfaces.

Hydrogen saturated samples of technically pure titanium have been studied by the electron-positron annihilation method (EPA), coupled with the thermoelectric power measurements performed in these samples saturated by different amount of hydrogen. The structure of the hydrogenated samples was additionally investigated by X-ray diffraction. The complete coincidence of the moment of occurrence of a change in the structure of hydrogenated titanium depending on the amount of introduced hydrogen has been established. The intensity of positron annihilation drops with increasing hydrogen concentration in α-titanium to 0.04 wt % and then remains unchanged up to values of 0.05 wt % ($$\alpha + \delta $$) -titanium to increases afterwards. At the same time, a sharp change in the values of the thermoelectric power occurs in this range. In the region of 0.05%, the annihilation rate stabilizes and begins to increase, while the thermoelectric power begins to decrease slowly. The inflection point on the dependence of thermoelectric power on hydrogen concentration corresponds to the onset of the formation of titanium $$\delta $$-hydrides. An increase in the positron lifetime is observed in the concentration range of 0.05–0.08 wt %, then the lifetime stays stable up to concentrations of 0.08–0.12 wt %. A transition from ($$\alpha + \beta $$) to ($$\alpha + \delta $$) phase is formed in this range. Next, the positron lifetime increases, as does the number of defects, while the thermoelectric power gradually drops (to a concentration of 0.24 wt %). This is followed by a stabilization mode of all the above parameters to 0.35 wt %.

In this work, the hydrogen sorption kinetics as well as the hydrogen effect on phase transformations, structure and properties of additively manufactured Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy using electron beam melting (EBM) were studied. In situ X-ray diffraction complex was used to analyze phase transitions in the EBM Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy under hydrogenation in gas atmosphere. The EBM mode is found to affect significantly on the microstructure and the rate of hydrogen sorption by Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy during hydrogenation at a temperature of 650 °C. The measurements have shown that the highest rate of hydrogen absorption is observed in samples manufactured at the beam current of 3 mA and the scanning speed of 150 mm/s. Hydrogenation of the samples leads to redistribution of alloying elements in the titanium alloy resulted in the formation of aluminum-rich α2-Ti3Al intermetallic phase and hydrides precipitation.

In this study, a noncommercial 3D printing machine was used to fabricate Ti-6Al-4V alloy by electron-beam melting (EBM). The influence of beam current on the microstructure, phase composition and mechanical properties of electron-beam-melted Ti-6Al-4V alloy was investigated. Numerical simulation is implemented to evaluate thermal fields during electron-beam melting of Ti-6Al-4V powder. The decrease in beam current from 3.5 to 2.5 mA leads to refinement of microstructure: The average width of α plates decreases from 10 down to 6 μm. The formation of finer microstructure is attributed to higher cooling rate at lower beam current confirmed by simulation. The phase composition of EBM Ti-6Al-4V indirectly depends on the beam current. High content of β phase (7%) was achieved at the beam current of 3 mA. The produced Ti-6Al-4V samples are characterized by high microhardness (470-520 HV).

Using the methods of X-ray structural analysis and electron and positron spectroscopy, it is found out that an irradiation of the surface of a Zr – 1 wt.% Nb specimen with an electron beam in the melting mode results in the formation of lamellar α+α′-structure, an increase in the dislocation density, a dissolution of the β-Nb phase, and the formation of defects of the vacancy-impurity type. The presence of hydrogen in the alloy irradiated with an electron beam favors the formation of complex hydrogen-vacancy complexes in the surface layer along with dislocations.

The purpose of this work is to implement the positron lifetime and Doppler broadening techniques for the study of hydrogen-induced defects in Zr–1wt% Nb (hereinafter Zr–1Nb) alloy. It was shown that spark cutting is an appropriate instrument to obtain a pair of Zr-1Nb samples with the same hydrogen content for the “sandwich” geometry and does not introduce open-volume defects in them during the cut. The ab-initio calculations were implemented to evaluate the positron annihilation characteristics for expanded crystal lattice, Zr with absorbed hydrogen, Zr-vacancy and Zr-vacancy-hydrogen complexes. The type of defects created in Zr-1Nb alloy loaded with hydrogen from the gas phase up to various hydrogen concentrations was studied. The main types of defects induced by hydrogen loading are vacancy-hydrogen complexes and dislocations. The processes of crystal lattice expansion and hydrogen dissolution in the lattice were studied.

The defect microstructure of the samples manufactured from Ti-6Al-4V powder was studied using electron beam melting (EBM) in the beam current range of 17 - 13 mA. The hybrid digital complex combined positron lifetime spectroscopy and coincidence Doppler broadening spectroscopy was used to characterize the defect structure of the materials. The microstructure and defects were also analyzed by transmission electron microscopy. It has been established that the main type of the defects in the EBM manufactured samples is dislocations. According to the conducted measurements and calculations, the dislocation density in the EBM manufactured samples exceeds by two orders the similar value for the cast Ti-6Al-4Valloy. Formation of Ti-Ti-Al nanoscale clusters has been found in the EBM manufactured samples. Keywords: Titanium alloy, Additive technology, Electron beam melting, Positron spectroscopy, Defects, Transmission electron microscopy

In this work, microstructure and defect evolution at a temperature and activation treatment of the TiCr2 intermetallic compound of Laves phase C36-type synthesized in the abnormal glow discharge plasma were investigated. The crystalline structure of the C36 TiCr2 powder crushed by hydrogenation-dehydrogenation (HD) method is characterized by the following lattice parameters: a = 4.932 A and c = 16.059 A. The dilatation of the crystal lattice under the hydrogenation at the HD crushing process leads to the formation of partial dislocations. For the first time ever the experimental value of the positron lifetime of the synthesized compound of the C36 TiCr2 Laves phase, this amounted to (141 ± 2) ps, established by the positron spectroscopy. The optimal activation parameters of the HD-crushing C36 TiCr2 powder were established: the temperature should be in the range from 450 to 500 °C, the exposure time in a hydrogen atmosphere at a pressure of (1–8) atm. must be at least 10 min.

In this work, the cyclic stability of the C36-type TiCr2 Laves phase synthesized in the abnormal glow discharge plasma was investigated. Melting of titanium-chromium metallic powders by the glow discharge plasma leads to the formation of the TiCr2 hexagonal C36 Laves phase with lattice parameters a = 4.928 A and c = 15.983 A. The hydrogenation-dehydrogenation method was used for crushing to increase the effective sorption capacity of the C36-type TiCr2 Laves phase. The stable hydride TiCr2Hx (x ≤ 0.5) phase of structural polytype C36 is formed during the first absorption/desorption cycle at the temperature of 30 °C. After 15 cycles hydride with the stoichiometric composition close to the TiCr2H0.5 phase of C36 polytype with lattice parameters: a = 4.961 A and c = 16.224 A was observed by XRD analysis. The hydrogen is localized in the crystal lattice in three main states: in a solid solution trapped by defects, open volume defects, and in the form of hydrides.

The paper deals with melting of titanium and chromium metal powders in plasma of abnormal glow discharge which results in the formation of the hexagonal С36 Laves phase compound TiCr2 with a = 4.928 A and c = 15.983 A lattice parameters. The hydrogenation–dehydrogenation process is used to prepare the powder of C36 Laves phase intermetallic compound TiCr. The hydrogenation–dehydrogenation process is performed at 100°C, 2 atm hydrogen pressure and 30 min ageing followed by vacuum cooling. The prepared metal powder is characterized by rounded lamellar and coarse particles 6 ± 2 μm and 21 ± 7 μm in size, respectively.

The possibility of obtaining hydrogen storage materials based on TiCr2 intermetallic compounds by the methods of melting in abnormal glow discharge plasma and electron beam melting is shown. The use of melting in abnormal glow discharge plasma leads to the formation of a Laves phase of the C36 structural type, while electron beam melting allows the C14-type Laves phase to be obtained. It is established that the formation of Laves phases of different structural types is associated with different cooling rates, which is caused by the specific features of the methods for synthesizing intermetallic compounds.

The defect structure and mechanical properties of the samples manufactured from Ti-6Al-4V powder by electron beam melting (EBM) before and after hydrogenation was studied. It has been established that hydrogenation of EBM titanium alloy to a concentration of 470 ppm leads to the formation of titanium γ-hydride, the volume content of which is 2.2%. A further increase in the concentration of hydrogen to 650 ppm is accompanied by a slight increase in the content of the hydride phase, while the proportion of the β phase of titanium increases (to 4.9%). When the hydrogen content is 900 ppm, the fraction of γ hydride decreases and the fraction of the beta phase decreases to 4.2%, and the formation of the hydride phase δ is observed. The introduction of hydrogen leads to a decrease in the wear and an increase in the hardness of EBM Ti-6Al-4V samples. This circumstance is due to the microstructure refinement under the action of hydrogen and the formation of secondary phase precipitates. The hydrogen content increases, the dislocation density and the concentration of hydrogen-vacancy complexes linearly increase, which indicates that hydrogen not only actively interacts with existing defects but also induces the formation of new defects.

Free volume is an extremely important intrinsic defect in polymers. Structurally, free volume is the randomly distributed holes in the polymer molecular chain segments. In proton exchange membrane fuel cells, free volume is also the space needed for the directional conduction of protons. Irradiation by α particles to grafting sulfonated poly(vinylidene fluoride) (PVDF) is one of the methods to produce proton exchange membrane with good proton channel rate. Positron annihilation lifetime spectroscopy was used to study the free volume size at different absorbed dose levels from 0.13 MGy to 0.65 MGy. Measurement method of positron annihilation lifetime spectroscopy for PVDF based on 44Ti positron source was developed. For low dose irradiation at 0.26 MGy, a decrease in free volume and practically unchanged crystallinity were observed. Further increase of absorbed dose range from 0.26 MGy to 0.39 MGy led to an increasing crystallinity with the same free volume level. For the absorbed dose from 0.39 MGy to 0.65 MGy, crystallinity was decreased but free volume remained almost constant.

Nanoscale multilayer coatings (NMCs) with different crystal structures are considered as capable of self-healing after radiation damage due to the recombination of vacancies and interstitials. This work is focused on a defect distribution study of NMCs based on Zr/Nb layers (25/25 nm and 100/100 nm) after proton irradiation. Coatings with a total thickness of 1.05 &plusmn, 0.05 &micro, m were irradiated by 900-keV protons using a pelletron-type electrostatic accelerator with an ion current of 2 &micro, A for durations of 60 min to 120 min. The influence of the irradiation effect was studied by X-ray diffraction analysis (XRD), glow discharge optical emission spectrometry (GD&ndash, OES), and Doppler broadening spectroscopy using a variable energy positron beam. The results obtained by these methods are compatible and indicate that defect concentration of Zr/Nb NMCs remains unchanged or slightly decreases with increasing irradiation time.

Super-resolution multi-contrast X-ray imaging performed using a Shack–Hartmann sensor for hard X-rays is presented., Different approaches of 2D lens arrays as Shack–Hartmann sensors for hard X-rays are compared. For the first time, a combination of Shack–Hartmann sensors for hard X-rays (SHSX) with a super-resolution imaging approach to perform multi-contrast imaging is demonstrated. A diamond lens is employed as a well known test object. The interleaving approach has great potential to overcome the 2D lens array limitation given by the two-photon polymerization lithography. Finally, the radiation damage induced by continuous exposure of an SHSX prototype with a white beam was studied showing a good performance of several hours. The shape modification and influence in the final image quality are presented.

We have obtained restructured zinc (high-purity zinc prepared by mechanothermal action of various intensity levels) and have analyzed its structure by the positron spectroscopy methods. Bulk vacancytype defects (vacancies and vacancy clusters), as well as the regions with an extended crystal lattice, have been discovered in the restructured samples and analyzed quantitatively. These effects are responsible for the emergence of internal microstresses in the material, which modify its properties.

To study the hydrogen distribution in Zr-1Nb alloy (Э110 alloy) GD-OES was applied in this work. Qualitative analysis needs the standard samples with hydrogen. However, the standard samples with high concentrations of hydrogen in the zirconium alloy which would meet the requirements of the shape, size are absent. In this work method of Zr + H calibration samples production was performed at the first time. Automated Complex Gas Reaction Controller was used for samples hydrogenation. To calculate the parameters of post-hydrogenation incubation of the samples in an inert gas atmosphere the diffusion equations were used. Absolute hydrogen concentrations in the samples were determined by melting in the inert gas atmosphere using RHEN602 analyzer (LECO Company). Hydrogen distribution was studied using nuclear reaction analysis (HZDR, Dresden, Germany). RF GD-OES was used for calibration. The depth of the craters was measured with the help of a Hommel-Etamic profilometer by Jenoptik, Germany.

The effect of low energy plasma immersion ion implantation and deposition of titanium on microstructure, defect structure and hydrogen trapping in zirconium alloy Zr-1Nb was studied. Defect structure and distribution were analyzed by Doppler broadening using slow positron beam. The surface microstructure after modification is represented by nanostructured Ti grains with random orientation. The gradient distribution of titanium as well as vacancy type defects were analyzed. The concentration of vacancy type defects is rising with increasing bias voltage. Gas-phase hydrogenation of the Ti-modified Zr-1Nb alloy was performed at 400 °C for 60 min. The strong interaction of hydrogen with vacancy type defects was demonstrated. Two different changes in the defect structure after hydrogenation were observed: when a titanium film is formed on the surface (after deposition at 500 V) hydrogen trapping occurs with the formation of titanium hydride phases, while in the implanted layer (deposition at 1000 and 1500 V) hydrogen is trapped due to interaction with vacancy type defects. The physical basis of Ti diffusion and its influence on the evolution of defect structure after surface modification and hydrogenation were discussed.

Zirconium alloys, such as Zr-1Nb are widely used as cladding materials for nuclear fuel elements of light water reactors. Hydrogen embrittlement problem causes degradation of these parts of nuclear reactors. It is known, that hydrogen uptake causes changes in microstructure and defect structure of metals. The aim of this work is study of Zr-1Nb alloys’ defect structure after hydrogen saturation up to the concentration of 600 ppm. Saturation of hydrogen was carried out from the gas phase under high temperature and pressure. This study reveals the increase of average positron lifetime with the increase of hydrogen concentration. Value of the average positron lifetime achieves plateau when the concentration of hydrogen is about 600 ppm. Also the following effects were detected in the material after hydrogen uptake up to different concentrations: crystal lattice expansion, dislocations and vacancy-like defects formation, as well as the defect-hydrogen complexes formation.

The results of hydrogen sorption and desorption processes investigation at commercially pure titanium alloy during hydrogenation at gas atmosphere are shown in this article. Titanium alloy hydrogenation at temperatures 350, 450 и 550 °С leads to δ-hydrides formation in samples’ volume. Hydrogen sorption rates were calculated on the linear parts of sorption curves and equal to 0.15·10-4 wt%/s at 350 °C, 0.86·10-4 wt%/s at 450 °C, 1.55·10-4 wt%/s at 550 °C. Phase transition in titanium-hydrogen system during thermally stimulated hydrogen desorption investigation by the means of short-wave diffraction of synchrotron radiation shows hydrides dissociation until 520-530 °C. Then α→β transition takes place until 690-720 °C and at this temperatures the phase transformation ends and additional hydrogen desorption peak appears in thermally stimulated hydrogen desorption curve. Defect structure at different hydrogen concentration investigation by the means of electron-positron annihilation techniques shows that hydrogen penetration into titanium leads to crystal lattice expansion. It initiates vacancy-type defects formation which reacts with hydrogen and forms defect-hydrogen complexes.

Titanium and its alloys are promising materials for hydrogen storage. However, hydrogen penetration accompanies the exploitation of hydrogen storage alloys. In particular, hydrogen penetration and accumulation in titanium alloys changes their mechanical properties. Therefore, the research works of such materials are mainly focused on improving the reversibility of hydrogen absorption-liberation processes, increasing the thermodynamic characteristics of the alloys, and augmenting their hydrogen storage capacity. In the process of hydrogenation-dehydrogenation, the formed defects both significantly reduce hydrogen storage capacity and can also be used to create effective traps for hydrogen. Therefore, the investigation of hydrogen interaction with structural defects in titanium and its alloys is very important. The present work, the hydrogen-induced formation of defects in the alloys of commercially pure titanium under temperature gas-phase hydrogenation (873 K) has studied by positron lifetime spectroscopy and Doppler broadening spectroscopy. Based on the evolution of positron annihilation parameters τf, τd, their corresponding intensities If, Id and relative changes of parameters S/S0 and W/W0, the peculiarities of hydrogen interaction with titanium lattice defects were investigated in a wide range of hydrogen concentrations from 0.8at% to 32.0at%.

In this study, the effect of additional heat treatment on the microstructure and mechanical properties of the titanium Ti-6Al-4V alloy produced by the method of electron beam melting was studied. It has been established that additional heat treatment of samples allows reducing the friction coefficient and decreasing internal stresses in the material. At the same time, a decrease in microhardness, as well as the strength and plastic characteristics of EBM Ti-6Al-4V alloy, is observed. Simultaneously, heat treatment leads to a reduction in the rate of hydrogen accumulation by EBM Ti-6Al-4V alloy during saturation from a gaseous medium.

The VT1-0 titanium alloy (phase α-Ti) with various hydrogen and hydrogen-vacancy concentrations has been studied. The stability of the 32-atom Ti–nV–mH supercell (n is the number of the V vacancies, and m is the number of hydrogen atoms H) with varying numbers of vacancies and hydrogen atoms has been calculated from the first principles. The structural state of the α-Ti phase has been identified by the Rietveld method based on the calculations of the supercell stability and the data on the defect concentration obtained using positron spectroscopy. The complete structural information on the considered states of the α-Ti phase (the lattice parameters, spatial distribution of titanium and hydrogen atoms and vacancies) has been obtained.

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.

Titanium and zirconium are used in many fields such as chemical, aircraft and nuclear industries. Hydrogen penetration and accumulation in titanium and zirconium alloys leads to the hydrogen-induced embrittlement. The study of hydrogen accumulation and distribution as well as phase transitions in zirconium alloy Zr1%Nb and commercially pure titanium alloy during the gas-phase hydrogenation is motivated by looking for a way to prevent materials from embrittlement. Gas-phase hydrogenation and thermo-stimulated desorption methods were used for hydrogen sorption and accumulation processes investigation. Synchrotron XRD method was applied for in situ investigation of phase transitions during heating of hydrogen saturated materials. Measurements were performed using SR from the VEPP-3 storage ring.

In this paper the results of experimental study of microstructure changes in Zr–1Nb alloy after low energy high current pulsed electron beam surface modification and hydrogenation are discussed. Surface treatment was carried out with energy density equal from 5 to 25 J/cm 2 and impulses number equal from 1 to 5. Subsequent hydrogenation was carried out at temperature equal to 350 °C until reaching the hydrogen concentration of 0.05 wt.%. The structure was analyzed by X-ray diffraction, transmission electron microscopy and by means of electron–positron techniques.

Free volume is an extremely important intrinsic defect in polymers. Structurally, the free volume is the randomly distributed holes in the polymer molecular chain segments. From the perspective of molecular movement, it is also the space needed for the movement of molecular segments. In proton exchange membrane fuel cells, the free volume is also the space needed for the directional conduction of protons. Irradiation grafting sulfonated polyvinylidene fluoride (PVDF) is one of the methods to produce proton exchange membrane with good proton channel rate. Using the LYS-1 program, based on the linear absorption coefficient and backscatter coefficient models, the percentage of annihilated positrons in PVDF in the two-layer model and the three-layer model was studied, and comparing the two fitting results it is determined that the model closest to the positron annihilation percentage required by the PALS experiment is the two-layer model, which allows the percentage of positrons that are annihilated in PVDF films with a thickness of 100 μm to reach 46% using the high energy positron source 44Ti without using the positron moderator. Using positron annihilation lifetime spectrum (PALS) analysis methods, based on Eldrup's classical model of free volume, the influence of absorbed doses of α particles on the free volume and crystallinity of PVDF was investigated, respectively. Based on the two test results the model of cross-linking and degradation of polyvinylidene fluoride irradiated by α particles was determined. Afterwards, X-ray diffraction (XRD) methods was used to study the change of PVDF crystal area before and after irradiation. The XRD results are consistent with the results measured by PALS.

Influence of manufacturing parameters (beam current from 13 to 17 mA, speed function 98 and 85) on microstructure and hydrogen sorption behavior of electron beam melted (EBM) Ti-6Al-4V parts was investigated. Optical and scanning electron microscopies as well as X-ray diffraction were used to investigate the microstructure and phase composition of EBM Ti-6Al-4V parts. The average alpha lath width decreases with the increase of the speed function at the fixed beam current (17 mA). Finer microstructure was formed at the beam current 17 mA and speed function 98. The hydrogenation of EBM Ti-6Al-4V parts was performed at the temperatures 500 and 650 degrees C at the constant pressure of 1 atm up to 0.3 wt %. The correlation between the microstructure and hydrogen sorption kinetics by EBM Ti-6Al-4V parts was demonstrated. Lower average hydrogen sorption rate at 500 degrees C was in the sample with coarser microstructure manufactured at the beam current 17 mA and speed function 85. The difference of hydrogen sorption kinetics between the manufactured samples at 650 degrees C was insignificant. The shape of the kinetics curves of hydrogen sorption indicates the phase transition alpha(H)+beta(H)->beta(H).