This research combines experimental testing of hydrogen sorption, krypton ion irradiation, and high-temperature steam oxidation with first-principles theoretical modeling to elucidate protective mechanisms of chromium coatings on the surface of zirconium alloy E110. Results indicate that the Cr coating reduced the hydrogen sorption rate and decreased radiation-induced defect concentration. The chromium coating deposition leads to the reduction of oxidation-induced weight gain by approximately 50% during LOCA-simulated testing. The probability of oxygen location in the Zr bulk and at the Cr/Zr interface is approximately equal based on firstprinciples calculations, indicating that the Cr/Zr interface does not impede oxygen diffusion into the bulk of zirconium. Therefore, the reduced impact of oxidation is primarily due to the barrier properties of the chromium coating: the location of the oxygen atom on the chromium surface and at the Cr/Zr interface is energetically more favorable than in the Cr bulk. Prior irradiation of the Cr-coated zirconium alloy with heavy krypton ions increases the weight gain of the alloy due to oxidation. This is because the formation of vacancies in the chromium lattice facilitates oxygen uptake due to the formation of strong O-Cr bonds within vacancies. Thus, the irradiation-induced vacancies in the Cr lattice act as oxidation initiation centers.

In the present work, a composite based on magnesium hydride with the addition of aluminum obtained by the electrical explosion of wires method was studied. The behavior of hydrogen sorption and desorption for the composite was investigated in the temperature range of 300-360 degrees C. It was found that the energy of hydrogen absorption and desorption is 45-60 % lower for the MgH2-10 wt%-nanoAl composite compared to MgH2. The enthalpy of hydrogen sorption and desorption is lower for the composite by a value of 2-11 kJ/mol as well. It is showed that EEWAl nanoparticles are uniformly distributed on the surface of MgH2 particles. These Al nano-clusters on the surface of MgH2 inhibit particle agglomeration and allow high cyclic stability to be achieved. Ab initio calculations showed that the stability of the Mg-H bond can be significantly decreased with the addition of Al atoms, as well as Al and O (AlO) atoms. This explains the decrease in the activation energy of hydrogen sorption and desorption and the shift in the hydrogen release temperature to a lower side for the composite. The results obtained on the strong catalytic effect of aluminum nanoparticles obtained by the electric explosion wire method are useful for studying materials based on magnesium hydride in order to further improve its hydrogen storage properties.

The current study presents a composite material based on magnesium hydride with the addition of aluminum, obtained by the method of electrical explosion of wires (EEW). The study demonstrated that the material has improved hydrogen interaction characteristics, which is associated with its core–shell structure, defect formation during milling, and the hydrogenation process. The combination of these factors contributes to a decrease in the activation energy of desorption from (161 ± 2) to (109 ± 1) kJ/mol, and consequently, to a reduction in operating temperatures. The data obtained are correlate with a model in which mechanochemical treatment and the formation of Mg–Al interfaces induce a developed network of vacancies, dislocations, and increased microstrains. Based on all of the above, a corresponding mechanism for low-temperature hydrogen desorption from the composite was described.

The new composite hydrogen storage material based on magnesium hydride with the addition of 20 wt% of nickel powder obtained by the electric explosion wire (EEW) method has been developed. The behavior of hydrogen desorption from the composite was investigated in the temperature range of (380-773) K. The maximum of hydrogen release for the MgH2-EEWNi composite is shifted towards lower temperatures (up to 380 K) compared to milled MgH2 powder during hydrogen desorption. Activation energy of hydrogen desorption from the composite is 42 +/- 1 kJ/mol, which is 113 kJ/mol lower than the activation energy of hydrogen desorption from magnesium hydride 155 +/- 2 kJ/mol. The hydrogen capacity decreases with the addition of EEWNi compared to magnesium hydride without additives by an average of 2-2.5 wt%, however, the hydrogen release temperature decreases significantly. The maximum amount of absorbed hydrogen at temperatures of 423, 453, 483 and 513 K for the MgH2-EEWNi composite were 5.09, 5.11, 5.31 and 5.45 wt%, respectively. About 4.1 wt% H2 can be released from MgH2-EEWNi composite in first 30 min at 453 K with Ea of 33 kJ/mol. It is showed that EEWNi nanoparticles are uniformly distributed on the surface of MgH2 particles. Ab initio calculations show that the nickel and oxygen atoms adsorbed on the surface of magnesium hydride attract the nearest hydrogen atoms and weaken Mg-H bonds, which contributes to the release of hydrogen at lower temperatures compared to pure MgH2. The results obtained on the strong catalytic effect of nickel nanoparticles obtained by the electric explosion of wire method are useful for studying materials based on magnesium hydride in order to further improve its hydrogen storage properties.

The composite material MgH2-EEWNi-Cr (20 wt. %) with a hydrogen content of 5.2 ± 0.1 wt.% is characterized by improved hydrogen interaction properties compared to the original MgH2. The dissociation of the material occurs in three temperature ranges (86–117, 152–162, and 281–351 °C), associated with a complex of effects consisting of changes in the specific surface area of the material, alterations in the crystal lattice during ball milling, and changes in the electronic structure in the presence of a Ni–Cr catalyst, based on first-principles calculations. The decrease in desorption activation energy (Ed = 65–96 ± 1 kJ/mol, ΔEd = 59–90 kJ/mol) is due to the catalytic effect of N–Cr, leading to a faster decomposition of the hydride phase. Based on the results of ab initio calculations, Ni–Cr on the MgH2 surface leads to a significant decrease in hydrogen binding energy (ΔEb = 60%) compared to pure magnesium hydride due to the formation of Ni–H and Cr–H covalent bonds, which reduces the degree of H–Mg ionic bonding. The results obtained allow us to expand our understanding of the mechanisms of hydrogen interaction with storage materials and the possibility of using these as mobile hydrogen storage and transportation materials.

One of the most preferred candidates for hydrogen storage and purification are metal hydrides and composites based on them. In this paper, one of the high-capacity composite materials for hydrogen storage based on Mg/ MgH2 and single-walled carbon nanotubes is considered. It was confirmed that the hydrogen storage efficiency of Mg/MgH2 can be improved by doping with carbon nanotubes with Fe nanoparticles remaining in the nanotubes after their growth. Using TEM microscopy, it was shown that carbon nanotubes are uniformly distributed over the surface of Mg/MgH2 particles, and some of the nanotubes are partially embedded in the bulk of Mg/MgH2. Iron nanoparticles are deposited from the nanotubes on the surface of magnesium particles as well. These carbon nanotubes and iron nanoparticles cause defects and serve as nucleation sites for new phases that are formed in the process of hydrogenation and dehydrogenation reactions. It was found that the activation energies of Mg/ MgH2 hydrogen absorption and dehydrogenation decreased by 13 and 24 kJ/mol, respectively, using experimental hydrogen sorption-desorption data and the Kolmogorov-Johnson-Mehl-Avrami equation. In addition, the Mg/MgH2 + 5wt%SWCNT composite absorb 4.8 wt% H2 in 6000 s, while Mg/MgH2 can absorb 4.3 wt% H2 in 6000 s at a temperature of 563 K and a pressure of 3 MPa. However, Mg/MgH2 can release about 5.2 wt% H2 within 6000 s, while Mg/MgH2 + 5wt%SWCNT composite showed 4.8 wt% H2 desorbed in the same time. Cycling stability testing showed that the hydrogen storage capacity of the Mg/MgH2 + 5wt%SWCNT remained almost unchanged during 10 cycles due to the reduction in particle agglomeration by the addition of carbon nanotubes, which was confirmed by SEM images of composite. Mg/MgH2 + 5wt%SWCNT composite was characterized by in situ defect structure analysis during hydrogen sorption process using positron annihilation spectroscopy method. According to the results obtained, a scheme of the hydrogen sorption by magnesium and the Mg/MgH2 + 5wt%SWCNT composite was suggested.

In this work, the peculiarities of microstructure changes in Cr-coated Zr1%Nb alloy under high-temperature hydrogenation and Kr ion irradiation were investigated. A comprehensive analysis revealed that Cr coating reduces the thickness of the Kr+ radiation damage zone by 15%–20% and decreases the density of radiation-induced defects compared to that of uncoated Zr1%Nb alloy. Additionally, Cr-coated samples exhibit a more uniform hydrogen distribution. According to first-principles calculations and positron annihilation spectroscopy, hydrogen-free dislocations predominate in the Cr-coated Zr1%Nb alloy after hydrogenation and irradiation. These findings emphasize the protective role of Cr coatings in mitigating radiation damage and hydrogen embrittlement in zirconium alloys.

This work is aimed at studying the peculiarities of structural-phase transformations and defect structure evolution in samples of Zr1%Nb zirconium alloy with and without chromium coating. As a result of ex situ and in situ study of thermal and hydrogen impact processes, it was found that chromium coating on zirconium alloy Zr1%Nb contributes to the reduction of hydrogen absorption rate, which is 1.8 less compared to the material without protective coating. It is established that in the process of hydrogenation of zirconium alloy with chromium coating hydrogen diffuses into the volume of the material and is evenly distributed through the thickness of the sample which indicates the excellent protective qualities of this coating. A gradient of hydrogen distribution is observed in the volume of material without chromium coating after hydrogenation. It has been shown that the increase in hydrogen resistance of zirconium alloy with chromium coatings is in additional due to the presence of an incoherent interface and defects in its vicinity. Positron spectroscopy has shown that, in the case of chromium-coated zirconium materials after thermal treatment and hydrogenation, hydrogen is mainly localized at the Zr/Cr interface. Ex situ methods have determined that thermal and hydrogen impact results in the accumulation of dislocation-type defects in zirconium alloy due to the formation of hydrides.

A composite based on magnesium hydride and nanosized aluminum powder obtained by electric explosion of wires was synthesized. Mechanical synthesis was carried out in a planetary ball mill. The time and frequency of synthesis, the mass ratio of balls and composite, and the percentage of aluminum were constant, while the diameter of grinding balls was varied: 3, 6, and 10 mm. Scanning electron microscopy was used to determine the average particle size of the composite depending on the diameter of the grinding balls. It was found that with a decrease in diameter from 10 to 3 mm the average particle size decreased from 2.7 to 2.2 μm. Energy dispersion analysis showed that nanosized aluminum particles were distributed evenly over the surface of magnesium hydride. A “core–shell” structure was formed. X-ray phase analysis revealed β-magnesium hydride, magnesium, magnesium oxide, and aluminum in the composite. X-ray diffraction patterns of the samples made it possible to calculate the structural parameters of the obtained composites, including microstresses. The average microstress value varied in the range of 0.004–0.006. A hypothesis has been put forward about an inversely proportional relationship between microstress and desorption temperature.

This paper presents the results of the study of the composite based on magnesium hydride with the addition of nanosized nickel powder, obtained by the method of an electric explosion of wires. The obtained MgH2-EEWNi (20 wt.%) composite with the core-shell configuration demonstrated the development of a defect structure, which makes it possible to significantly reduce the hydrogen desorption temperature from 418 °C for pure magnesium hydride to 229 °C for hydride with the addition of nickel powder. In situ studies of the evolution of the defect structure using positron annihilation methods and diffraction methods made it possible to draw conclusions about the influence of the Mg2NiH0.3 and Mg2NiH4 phases on the sorption and desorption properties of the composite. The results obtained in this work can be used in the field of hydrogen energy in mobile or stationary hydrogen storage systems.

One of the main directions of modern activity of metrology researchers is to provide the real sector of the economy of the Russian Federation with reference materials that have no analogues in the country. The article discusses the research of highly efficient materials for fuel cladding (fuel elements) in the active zones of thermal reactors, the scope of which is wide. The purpose of the study is the development of samples of the composition of the zirconium alloy to establish and control the stability of the calibration curves of spectrometers when determining the mass fraction of hydrogen, provided that the metrological and technical characteristics of the reference material meet the requirements of the measurement procedure. The main methods for determining the hydrogen content in materials are analyzed. It has been established that the method of glow discharge optical emission spectroscopy has found the widest application. It has also been established that zirconium alloys are chosen as the main material in most cases.The need to create samples for constructing a calibration curve for spectrometers for measuring the hydrogen content in a zirconium alloy is noted. Samples of zirconium alloy Zr-1Nb (grade Э110) have been developed to construct a calibration curve using a glow discharge emission spectrometer for measurements with a mass fraction of hydrogen from 0.034 to 0.498 %. Calibration is carried out using the developed samples to obtain a calibration curve using the example of an emission glow discharge spectrometer of the GD Profiler2 type. The relative error of the hydrogen mass fraction obtained during calibration does not exceed ± 10 %.The practical significance of the study lies in the development of samples that can be used to calibrate spectrometers based on the method of glow discharge optical emission spectroscopy.

One of the important tasks of improving the properties of metal hydride reactors is the design of system with optimized heat and mass transfer. Many works are devoted to the selection of the optimal heat exchanger for metal hydride hydrogen storage systems. At the same time, it is necessary to consider the composition of the metal hydride bed, which affects thermal conductivity as well. Little attention has been paid to the study of heat transfer properties in hydrogen storage systems with a heat exchanger and a metal hydride bed based on magnesium hydride and carbon nanotubes. In this work we used numerical simulation to determine the effectiveness of carbon nanotubes addition and heat exchangers with different fin number and geometries on hightemperature magnesium-based hydrogen storage tanks performance. It was found, that increasing the number of fins from three to five makes a smaller contribution in the temperature increasing as compared to the addition of three fins to the heater. The three solid, radial and complex fins have a similar effect on the average Mg/MgH2 bed temperature at 60 min. The most optimal fin number and geometry is three radial fins in terms of the efficiency and the volume it occupies. The addition of carbon nanotubes increases the average temperature of the Mg/MgH2 bed by 67 K for a reactor equipped with a heater without fins. Hydrogen storage system with three radial fins and Mg/MgH2 bed enhanced with carbon nanotubes provides an increase in the average bed temperature of about 180 K as compared to system without fins and nanotubes. This leads to a reduction in the hydrogen absorption time to reach 90% saturation by almost 63% for the three radial fins reactor with carbon nanotubes addition to the metal hydride bed. It has been confirmed that the addition of carbon nanotubes to Mg/ MgH2 makes a significant contribution to the heat transfer in the metal hydride bed. In addition, it is shown that both an increase in the heat transfer area and the thermal conductivity coefficient leads to a significant improvement in the efficiency of the metal hydride reactor. In the future, the obtained results can be taken into account when designing hydrogen storage systems based on these materials.

This work is devoted to the study of barrier properties of graphene coating against hydrogen permeation into E110 zirconium alloy. For the first time, the kinetics of hydrogen absorption by the graphene-coated zirconium alloy with a single-layer graphene coating obtained by chemical vapour deposition (CVD) is studied in this work. It was shown that the graphene coating exhibits barrier properties and reduces hydrogen absorption rate by E110 zirconium alloy in the temperature range (350-550)degrees C. The activation energy for hydrogen absorption was reduced from 72 to 61 kJ/mol. Phase transformations in zirconium alloy during hydrogenation can result in degradation of protective properties of graphene coating.

Solid-state hydrogen storage tanks are key equipment for fuel cell vehicles and hydrogen storage. However, the low heat transfer properties of hydrogen storage tanks result in the inability to meet the hydrogen supply requirements of fuel cells. In this study, different thermal management approaches were explored through the design of LaNi5-based solid-state hydrogen storage tanks. We experimentally studied the effects of different internal heat transfer methods, that is, expanded natural graphite (ENG), copper foam, and copper fins on the hydrogen absorption and desorption performance. We also studied the effects of external cooling methods with natural convection, air cooling, and water cooling, respectively. Under the same external cooling method of natural convection, a solid hydrogen storage tank filled with 5 wt.% ENG has similar performance to a tank filled with copper foam. Compared to natural convection, air and water cooling can significantly improve the heating performance of metal hydride (MH) beds by increasing the external heat transfer coefficient. The effect of water cooling is better than that of air cooling, and in these two enhanced performance conditions, the tank filled with copper foam performs better than with ENG. In the case of water cooling, by adding copper fins to a hydrogen storage tank filled with 5 wt.% ENG, the tank was saturated with hydrogen absorption in only 29.4 min, which is 55.6 % shorter than the hydrogen uptake time in a hydrogen storage reactor without copper fins. And its stable hydrogen desorption (1 NL/min) has reached 98.1 % of the total hydrogen released. The results show that the effective thermal conductivity and heat transfer area of metal hydride bed play key roles in improving heat transfer and reaction rate. In addition, heat transfer is more important than mass transfer to improve the performance of the hydrogen storage tank.

In this work, we have investigated the defect structure of an E110 zirconium alloy after saturation with hydrogen by means of the layer-by-layer system analysis. A series of experiments were intended to create a hydride rim in zirconium alloy cladding tubes. To determine the distribution of a hydrogen gradient and the thickness of hydrides in zirconium alloy samples, a layer-by-layer positron spectroscopy system was developed. The results from the developed positron annihilation method are well consistent with the results from nanohardness indentation and glow discharge optical emission spectroscopy (GD-OES). We can draw a conclusion that the use of nickel-plating on the zirconium alloy surface increases the rate of hydrogen entering the surface, which produces a hydride rim with a thickness of about 150 µm on the outer surface of the E110 alloy. This work allowed us to develop a methodology for studying the defective structure of alloys in the field of nuclear energy.

In this paper, a new hydrogen storage composite based on magnesium hydride and metal-organic framework MIL-101(Cr) (an acronym for Material Institute Lavoisier) has been mechanically synthesized and investigated. The hydrogen sorption and desorption behavior in the composite was investigated for the temperature and pressure ranges of (593-653) K and (0-3) MPa, respectively. According to the pressure-composition -temperature isotherms of hydrogen sorption/desorption, the MgH2-5 wt%MIL-101(Cr) composite starts to absorb hydrogen at a lower pressure at 593 K. In addition, the hydrogen release peak for composite shifts to lower temperatures by about 140 K compared to the pure milled MgH2 during temperature programmed desorption at a heating rate of 6 K/min. The activation energy of hydrogen desorption from the composite is 120 +/- 2 kJ/mol, which is 36% lower than the activation energy of hydrogen desorption from magnesium hydride (189 +/- 2 kJ/mol). The enthalpy of hydrogen absorption was found to be 73 kJ/mol H2 and 60 kJ/mol H2 for milled MgH2 and MgH2-5 wt%MIL-101(Cr) composites, respectively. It is showed that the MIL-101(Cr) MOF structures decompose during ball milling and the chromium oxide nanoparticles form a core-shell structure with MgH2 particles. Thus, composite has better sorption and desorption properties than pure magnesium/magnesium hydride due to the nanoconfinement of MgH2. The chromium oxide nanoparticles act as active sites on the surface of the magnesium particles and facilitate the dissociative chemisorption or recombinative desorption of hydrogen. The main regularities of the phase transition in the magnesium-hydrogen system for the composite and magnesium hydride during dehydrogenation have been studied for temperatures in the range of 298-750 K. The in situ analysis of the phase transitions during the dehydrogenation of MgH2 and MgH2-5 wt%MIL-101(Cr) composite indicates a pronounced catalytic effect of the addition of MIL-101(Cr) to the Mg/MgH2. Based on the experimental results and ab initio calculations, a mechanism for the sorption and desorption of hydrogen by the composite has been proposed.

A new composite with a core–shell structure based on magnesium hydride and finely dispersed aluminum powder with an aluminum oxide shell was mechanically synthesized. We used magnesium chips to produce magnesium hydride and aluminum wire after exploitation to produce nano-sized aluminum powder. The beginning of the hydrogen release from the composite occurred at the temperature of 117 °C. The maximum desorption temperature from the MgH2-EEWAl composite (10 wt.%) was 336 °C, compared to pure magnesium hydride—417 °C. The mass content of hydrogen in the composite was 5.5 wt.%. The positive effect of the aluminum powder produced by the electric explosion of wires method on reducing the activation energy of desorption was demonstrated. The composite’s desorption activation energy was found to be 109 ± 1 kJ/mol, while pure magnesium hydride had an activation energy of 161 ± 2 kJ/mol. The results obtained make it possible to expand the possibility of using magnesium and aluminum waste for hydrogen energy.

Chromium carbide (CrC) coatings were proposed as an accident-tolerant fuel complementary concept to provide enhanced protection for the inner side of nuclear fuel claddings, with preliminary results showing promising performance. To evaluate the neutronics performance of CrC coatings, a reactor physics-based analysis was performed. A single VVER-1200 fuel assembly was used as a model, and the Monte Carlo code MCNPX was used to perform the calculations. Results were compared to previous work on metallic chromium performance as inner-side coating material. Results showed that CrC coatings generally have less negative impacts on neutronics performance compared to chromium coatings. Neutron flux spectra showed slight reductions in the thermal energy region that reached up to -0.6% in a 40-& mu;m CrC internally coated fuel assembly at an energy of 0.025 eV. The analysis of CrC internally coated fuel assembly nuclide inventories showed a relative increase in the isotopic concentration of some nuclides such as Pu-239 and Pu-241, which was less than 1% for the cases considered. Comparing the calculated negative neutronics impacts, such as thermal neutron flux and fuel assembly operating time reductions, caused by CrC and Cr coating materials, the study revealed that the difference between these induced negative neutronics impacts is proportional to coating thickness. Therefore, CrC coatings will be most effective in terms of mitigating negative neutronics impacts when the specified coating thickness is large.

In this paper, Cr (8 μm)/Ta (3 μm) bilayer coatings deposited on a Zr-1Nb alloy substrate were investigated and compared with a Cr-coated alloy under high-temperature steam oxidation at 1200–1400 °C. The bilayer coatings with α- and β-Ta interlayers were obtained by magnetron sputtering. The Cr/Ta-coated samples were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), and optical microscopy (OM). The coating with an α-Ta interlayer can suppress the interdiffusion of chromium and zirconium more effectively up to 1330 °C in comparison with the coating having a β-Ta interlayer. The weight gain of the α-Ta-coated samples after oxidation at 1200 °C for 2000 s was 5–6 times lower than that of the Cr-coated Zr alloy samples. Oxidation at 1400 °C for 120 s showed no significant difference in the weight gain of the Cr- and Cr/Ta-coated Zr-1Nb alloy samples. It was shown that the effect of suppression of Zr-Cr interdiffusion by the barrier coating (α- and β-Ta) is only short-term.