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Magnesium hydride is considered to be one of the most promising hydrogen storage materials, although it nevertheless has some problems, such as the high value of the activation energy of hydrogen desorption. To solve this problem, some scientists have proposed adding nanocarbon materials, in particular carbon nanotubes, to magnesium hydride. Currently, a detailed understanding of the mechanisms of obtaining composites based on magnesium hydride and carbon nanotubes is lacking, as is our understanding of the effect of nanocarbon additives on the activation energy and temperature of hydrogen desorption depending on the parameters of the composite synthesis. In addition, the data obtained at various values of milling parameters are very different, and in some works the effect of carbon nanomaterials on the hydrogen properties of magnesium hydride was not confirmed at all. Thus, it is important to determine the effect of nanocarbon additives on the properties of hydrogen storage of magnesium hydride under various milling parameters. This work is devoted to the study of the effect of nanocarbon additives on magnesium hydride and the determination of the dependences of the hydrogen desorption temperature and activation energy on the synthesis parameters. Composite powders containing MgH2 with 5 wt.% single-walled carbon nanotubes (SWCNT) were prepared using a planetary ball mill. The milling was carried out at various milling speeds, namely 300, 660, and 900 rpm. Results suggested that the structure of the nanotubes is preserved with prolonged grinding of magnesium hydride and SWCNT in a ball mill for 180 min at a relatively low grinding speed of 300 rpm. The composite obtained with these parameters has the lowest temperature of hydrogen desorption and an activation energy of H2 desorption of 162 ± 1 kJ/mol H2, which is 15% lower than that of the magnesium hydride MgH2 (189 ± 1 kJ/mol H2).

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.

The efficient operation of a metal hydride reactor depends on the hydrogen sorption and desorption reaction rate. In this regard, special attention is paid to heat management solutions when designing metal hydride hydrogen storage systems. One of the effective solutions for improving the heat and mass transfer effect in metal hydride beds is the use of heat exchangers. The design of modern cylindrical-shaped reactors makes it possible to optimize the number of heat exchange elements, design of fins and cooling tubes, filter arrangement and geometrical distribution of metal hydride bed elements. Thus, the development of a metal hydride reactor design with optimal weight and size characteristics, taking into account the efficiency of heat transfer and metal hydride bed design, is the relevant task. This paper discusses the influence of different configurations of heat exchangers and metal hydride bed for modern solid-state hydrogen storage systems. The main advantages and disadvantages of various configurations are considered in terms of heat transfer as well as weight and size characteristics. A comparative analysis of the heat exchangers, fins and other solutions efficiency has been performed, which makes it possible to summarize and facilitate the choice of the reactor configuration in the future.

The hydrogenation behavior of Cr-coated resistance upset welds (RUW) of E110 zirconium alloy was investigated at 360, 450 and 900 °C and a hydrogen pressure of 2 bar. The deposition of Cr coating, via magnetron sputtering, can decrease the hydrogen absorption rate of an RUW Zr alloy. The activation energy for the hydrogen absorption of Cr-coated specimens (84 kJ/mol) is higher in comparison with uncoated ones (71 kJ/mol), which indicates the deceleration of the hydriding of welded Zr alloys in the case of Cr coating deposition. A Cr coating can limit the formation of radially oriented hydrides and the hardening of RUW specimens at 360 and 450 °C. No significant difference in the hydrogen absorption rate was found at 900 °C. The application of Cr coating deposition to protect resistance-upset-welded Zr alloys in a hydrogen atmosphere is discussed.

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 MgH[sub.2]-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 Mg[sub.2]NiH[sub.0.3] and Mg[sub.2]NiH[sub.4] 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.

The assessment of reliability in non-repairable subsystems of mining electronic equipment represents a computationally challenging problem, particularly for complex and highly connected structures. This study presents a systematic comparative analysis of several deterministic approaches for reliability estimation, focusing on their computational efficiency, accuracy, and applicability. The investigated methods include classical boundary techniques (minimal paths and cuts), analytical decomposition based on the Bayes theorem, the logic–probabilistic method (LPM) employing triangle–star transformations, and the algorithmic Structure Convolution Method (SCM), which is based on matrix reduction of the system’s connectivity graph. The reliability problem is formally represented using graph theory, where each element is modeled as a binary variable with independent failures, which is a standard and practically justified assumption for power electronic subsystems operating without common-cause coupling. Numerical experiments were carried out on canonical benchmark topologies—bridge, tree, grid, and random connected graphs—representing different levels of structural complexity. The results demonstrate that the SCM achieves exact reliability values with up to six orders of magnitude acceleration compared to the LPM for systems containing more than 20 elements, while maintaining polynomial computational complexity. Qualitatively, the compared approaches differ in the nature of the output and practical applicability: boundary methods provide fast interval estimates suitable for preliminary screening, whereas decomposition may exhibit a systematic bias for highly connected (non-series–parallel) topologies. In contrast, the SCM consistently preserves exactness while remaining computationally tractable for medium and large sparse-to-moderately dense graphs, making it preferable for repeated recalculations in design and optimization workflows. The methods were implemented in Python 3.7 using NumPy and NetworkX, ensuring transparency and reproducibility. The findings confirm that the SCM is an efficient, scalable, and mathematically rigorous tool for reliability assessment and structural optimization of large-scale non-repairable systems. The presented methodology provides practical guidelines for selecting appropriate reliability evaluation techniques based on system complexity and computational resource constraints.

In this paper, room-temperature chemiresistive gas sensors for NO2 detection based on CVD-grown carbon nanofibers (CNFs) were investigated. Transmission electron microscopy, low-temperature nitrogen adsorption, and X-ray diffraction were used to investigate the carbon nanomaterials. CNFs were synthesized in a wide range of pressure (1–5 bar) by COx-free decomposition of methane over the Ni/Al2O3 catalyst. It was found that the increase in pressure during the synthesis of CNFs induced the later deactivation of the catalyst, and the yield of CNFs decreased when increasing pressure. Sensing properties were determined in a dynamic flow-through installation at NO2 concentrations ranging from 1 to 400 ppm. Ammonia detection was tested for comparison in a range of 100–500 ppm. The obtained sensors based on CNFs synthesized at 1 bar showed high responses of 1.7%, 5.0%, and 10.0% to 1 ppm, 5 ppm, and 10 ppm NO2 at 25 ± 2 °C, respectively. It was shown that the obtained non-modified carbon nanomaterials can be used successfully used for room temperature detection of nitrogen dioxide. It was found that the increase in relative humidity (RH) of air induced growth of response, and this effect was facilitated after reaching RH ~35% for CNFs synthesized at elevated pressures.

In this paper, room-temperature chemiresistive gas sensors for NO[sub.2] detection based on CVD-grown carbon nanofibers (CNFs) were investigated. Transmission electron microscopy, low-temperature nitrogen adsorption, and X-ray diffraction were used to investigate the carbon nanomaterials. CNFs were synthesized in a wide range of pressure (1–5 bar) by CO[sub.x] -free decomposition of methane over the Ni/Al[sub.2] O[sub.3] catalyst. It was found that the increase in pressure during the synthesis of CNFs induced the later deactivation of the catalyst, and the yield of CNFs decreased when increasing pressure. Sensing properties were determined in a dynamic flow-through installation at NO[sub.2] concentrations ranging from 1 to 400 ppm. Ammonia detection was tested for comparison in a range of 100–500 ppm. The obtained sensors based on CNFs synthesized at 1 bar showed high responses of 1.7%, 5.0%, and 10.0% to 1 ppm, 5 ppm, and 10 ppm NO[sub.2] at 25 ± 2 °C, respectively. It was shown that the obtained non-modified carbon nanomaterials can be used successfully used for room temperature detection of nitrogen dioxide. It was found that the increase in relative humidity (RH) of air induced growth of response, and this effect was facilitated after reaching RH ~35% for CNFs synthesized at elevated pressures.