Properties Of Hydrides Research Articles

Machine learning analysis of alloying element effects on hydrogen storage properties of AB2 metal hydrides

Zirconium-titanium-based AB 2 is a potential candidate for hydrogen storage alloys and NiMH battery electrodes. Machine learning (ML) has been used to discover and optimize the properties of energy-related materials, including hydrogen storage alloys. This study used ML approaches to analyze the AB 2 metal hydrides dataset. The AB 2 alloy is considered promising owing to its slightly high hydrogen density and commerciality. This study investigates the effect of the alloying elements on the hydrogen storage properties of the AB 2 alloys, i.e., the heat of formation (ΔH), phase abundance, and hydrogen capacity. ML analysis was performed on the 314 pairs collected and data curated from the literature published during 1998–2019, comprising the chemical compositions of alloys and their hydrogen storage properties. The random forest model excellently predicts all hydrogen storage properties for the dataset. Ni provided the most contribution to the change in the enthalpy of the hydride formation but reduced the hydrogen content. Other elements, such as Cr, contribute strongly to the formation of the C14-type Laves phase. Mn significantly affects the hydrogen storage capacity. This study is expected to guide further experimental work to optimize the phase structure of AB 2 and its hydrogen sorption properties. • Machine learning analysis on a newly collected data of AB 2 . • Effect Ni in the B site affect significantly to the enthalpy of formation and hydrogen capacity. • Cr contributes enormously to the microstructure and phase stability. • The maximum capacity is the sub-stoichiometry composition.

Evaluation of irradiation hardening in proton-irradiated [formula omitted]-zirconium hydride and Zr2.5Nb

A sample with a δ-zirconium hydride rim grown on a Zr2.5Nb pressure tube was proton irradiated to different damage levels and its mechanical properties were probed using nanoindentation. Irradiations were also carried out on non-hydrided Zr2.5Nb as a reference. A numerical model proposed by Dao et al. and developed by Wang et al. was used to calculate the yield strength and the work hardening exponent. The samples were subjected to 0.2, 0.4, and 0.8 displacements per atom (dpa), with the irradiation temperature kept below 100 ∘C. To account for the indentation size effect, the Nix-Gao model was used to calculate the true hardness (H0) of both materials. Both hydrided and non-hydrided samples show an increase in the true hardness and in the yield strength due to the irradiation hardening. The true hardness of the δ-zirconium hydride increased from 3 GPa at 0 dpa to 4.31 at 0.8 dpa. Similarly, the H0 of the Zr2.5Nb increased from 2.53 at 0 dpa to 3.03 at 0.8 dpa. Additionally based on the model analysis, the yield strength increased from 731 MPa to 1146 MPa for the δ-zirconium hydride, and 662 MPa to 850 MPa for the Zr2.5Nb, with the latter in good agreement with literature values for Zr2.5Nb. Lastly, evaluation of the work hardening exponent with the different dpa levels suggests the defects density evolves differently with irradiation in the two materials. These novel results demonstrate a clear change in mechanical properties of the δ-zirconium hydride with irradiation.

Tailoring the electronic, optical and mechanical properties of KMgH3 and RbCaH3 perovskite hydrides without and with Samarium

Perovskite hydrides such as KMgH3 and RbCaH3 have been proven to be an attractive candidate for good application prospects in optoelectronic devices and conversion energy. Doping these perovskites with rare earth has turned into a progressively essential way to improve luminescence and photo-conversion of devices. In this work, the ab-initio calculations have been carried out to explore the structural, electronic, optical, and mechanical properties of both KMgH3 and RbCaH3 without and with Sm based on generalized gradient approximation functional within the framework of DFT including the spin−orbit coupling. It is found that doping the perovskites with Sm depicts substantially modification in electronic behavior leading increased bandgap energy as well as the carrier effective masses with increasing Sm concentrations for the case of KMgH3, while it has been reduced for RbCaH3. In addition, the optical investigation reveals a blue-shift phenomenon from absorption coefficient spectra, which is owing to the Sm doping into KMgH3; combined with a minimum absorption in visible spectrum for pure KMgH3 perovskite. Besides, we denote a maximum absorption in the UV region of the doped RbCaH3. Furthermore, the mechanical analysis exhibits that these perovskites are hard and stiffer, especially KMgH3 hydride systems. These outcomes may conduct and give a reliable reference for experimenters to design novel perovskite hydrides toward improving optoelectronic performances.

Hydrogen storage properties of magnesium hydride catalyzed by Ni-based solid solutions

The Ni–25%X (X=Fe, Co, Cu, molar fraction) solid solutions were prepared and then doped into MgH2 through high-energy ball milling. The initial dehydrogenation temperatures of MgH2/Ni–25%X composites are all decreased by about 90 °C relative to the as-milled pristine MgH2. The Ni–25%Co solid solution exhibits the most excellent catalytic effect, and the milled MgH2/Ni–25%Co composite can release 5.19 wt.% hydrogen within 10 min at 300 °C, while the as-milled pristine MgH2 can only release 1.78 wt.% hydrogen. More importantly, the dehydrogenated MgH2/Ni–25%Co composite can absorb 5.39 wt.% hydrogen at 275 °C within 3 min. The superior hydrogen sorption kinetics of MgH2/Ni–25%Co can be ascribed to the actual catalytic effect of in-situ formed Mg2Ni(Co) compounds. First-principles calculations show that the hydrogen absorption/desorption energy barriers of Mg/MgH2 systems decrease significantly after doping with transition metal atoms, which interprets well the improved hydrogen sorption properties of MgH2 catalyzed by Ni-based solid solutions.

Hydrogen-phase naklep as a result of single isothermal hydride transformations

Hydrogen treatment of metallic materials is a promising area of controlled hydrogen action on metals and alloys in order to impart special properties to them. In this work, the changes in the mechanical properties of palladium during single hydride transformations, which are initiated in the initially non-nakleped palladium hydride, have been experimentally studied. Were investigated wire palladium samples with a purity of 99.98 %, a diameter of 0.5 mm and a length of 165 mm. Samples for research were preliminarily subjected to hydrogen treatment, and then mechanical tests were carried out. The mechanical properties of non-nakleped palladium hydride are presented. Hydrogen-phase naklep of palladium during hydrogen treatment has been studied. It is shown that palladium hydride is a plastic material with low strength characteristics. During the reverse hydride transformation, the hydrogen phase naklep of palladium develops. Experimental facts of the appearance of hydrogen-phase naklep during the interaction of hydrogen with other metals and alloys are discussed.

Influence of Chemical Substitution and Light Element Insertion on the Magnetic Properties of Nanocrystalline Pr2Co7 Compound

It is well recognized that intermetallics based on rare-earth (R) and transition metals (T) display numerous interesting magnetic properties, leading to potential applications in different fields. The latest progress regarding magnetic properties and the magnetocaloric effect (MCE) in the nanostructured Pr2Co7 compound, as well as its carbides and hydrides, is reviewed in this paper. Some of this progress reveals remarkable MCE performance, which makes it attractive in the field of magnetic refrigeration at high temperatures. With the purpose of understanding the magnetic and magnetocaloric characteristics of these compounds, the crystal structure, microstructure, and magnetism are also brought into focus. The Pr2Co7 compound has interesting magnetic properties, such as a high Curie temperature TC and uniaxial magnetocrystalline anisotropy. It crystallizes in a hexagonal structure (2:7 H) of the Ce2Ni7 type and is stable at relatively low temperatures (Ta ≤ 1023 K), or it has a rhombohedral structure (2:7 R) of the Gd2Co7 type and is stable at high temperatures (Ta ≥ 1223 K). Studies of the magnetocaloric properties of the nanocrystalline Pr2Co7 compound have shown the existence of a large reversible magnetic entropy change (ΔSM) with a second-order magnetic transition. After its substitution, we showed that nanocrystalline Pr2Co7−xFex compounds that were annealed at Ta = 973 K crystallized in the 2:7 H structure similarly to the parent compound. The extended X-ray absorption fine-structure (EXAFS) spectra adjustments showed that Fe atoms preferably occupy the 12k site for x ≤ 1. The study of the magnetic properties of nanocrystalline Pr2Co7−xFex compounds revealed an increase in TC of about 26% for x = 0.5, as well as an improvement in the coercivity, Hc (12 kOe), and the (BH)max (9 MGOe) product. On the other hand, the insertion of C atoms into the Pr2Co7 cell led to a marked improvement in the TC value of 21.6%. The best magnetic properties were found for the Pr2Co7C0.25 compound annealed at 973 K, Hc = 10.3 kOe, and (BH)max = 11.5 MGOe. We studied the microstructure, hydrogenation, and magnetic properties of nanocrystalline Pr2Co7Hx hydrides. The crystal structure of the Pr2Co7 compound transformed from a hexagonal (P63/mmc) into an orthorhombic (Pbcn) and monoclinic (C2/c) structure during hydrogenation. The absorption of H by the Pr2Co7 compound led to an increase in the TC value from 600 K at x = 0 to 691 K at x = 3.75. The Pr2Co7H0.25 hydride had optimal magnetic properties: Hc = 6.1 KOe, (BH)max = 5.8 MGOe, and TC = 607 K. We tailored the mean field theory (MFT) and random magnetic anisotropy (RMA) methods to investigate the magnetic moments, exchange interactions, and magnetic anisotropy properties. The relationship between the microstructure and magnetic properties is discussed. The obtained results provide a fundamental reference for adapting the magnetic properties of the Pr2Co7, Pr2Co6.5Fe0.5, Pr2Co7C0.25, and Pr2Co7H0.25 compounds for potential permanent nanomagnets, high-density magnetic recording, and magnetic refrigeration applications.

A Modeling and Neutron Diffraction Study of the High Temperature Properties of Sub-Stoichiometric Yttrium Hydride for Novel Moderator Applications

Low-enriched-uranium (LEU) reactor systems utilize moderators to improve neutron economy. Solid yttrium hydride is one of the primary moderator candidates for high-temperature (>700 °C) nuclear reactor applications. This is due to its ability to retain hydrogen at elevated temperatures compared to other metal hydrides. For reactor modeling purposes, both neutronic and thermos-mechanical modeling, several high-temperature properties for sub-stoichiometric yttrium hydride (YH2−x) are needed. In this paper, we present an atomistics and a neutron diffraction study of the high-temperature properties of Y and YH2−x. Specifically, we focus on the thermal lattice expansion effects in yttrium metal and yttrium hydride, which also govern bulk thermal expansion. Previously reported physical and mechanical properties for sub-stoichiometric yttrium hydride at ambient conditions are expanded using lattice dynamics to take into account high-temperature effects. Accordingly, an array of newly generated properties is presented that enables high-fidelity neutronics, and thermomechanical modeling. These properties include various elastic moduli, thermal expansion parameters for yttrium and yttrium hydride, and single-phase (YH2−x) and two-phase (Y + YH2−x) density as a function of stoichiometry and density.

Experimental Studies of Radiation-Protective Properties of a Modified Titanium Hydride

The results of experimental studies of the protective properties of titanium hydride with respect to neutron and gamma radiation in order to determine the optimal conditions for their use in the composition of the structural radiation protection of the nuclear reactor are presented. The weakening of the basic functionals in the thickness of protection, including the density of fast, intermediate and thermal neutrons, and the dose rate of gamma radiation is established. The functions of weakening the density of neutron flow and the dose rate of gamma radiation are measured in the conditions of "barrier" geometry. Determination of the protective properties of the structure was carried out when the modified titanium hydride fraction was placed in aluminum containers with a filling coefficient of a volume of container 0.63. The relaxation lengths for all neutron groups are close and on average are 9.8 cm. The functions of weakening the dose rate of gamma radiation of point sources Cs-137 and Co-60 are exponential. The weakening of radiation occurs with a constant relaxation length. For energy 0.661 MeV, the relaxation length is 7.1 cm, for energy 1.25 MeV, the relaxation length is equal to 10.1 cm. On the basis of the experimental studies, the high efficiency of the modified fraction of titanium hydride was confirmed during its use in protecting nuclear power plants.

Carbon content drives high temperature superconductivity in a carbonaceous sulfur hydride below 100 GPa.

We report a previously unobserved superconducting state of the photosynthesized carbonaceous sulfur hydride (C-S-H) system with a maximum TC of 191(1) K below 100 GPa. The properties of C-S-H are dependent on carbon content, and X-ray diffraction and simulations reveal the system remains molecular-like up to 100 GPa.

Regulation of the integrated hydrogen storage properties of magnesium hydride using 3D self-assembled amorphous carbon-embedded porous niobium pentoxide

3D self-assembled amorphous carbon-embedded porous niobium pentoxide (C-p-Nb2O5) is prepared by the wet chemical method, and C-p-Nb2O5 doped MgH2 show excellent integrated hydrogen storage properties.

Dynamic fatigue behavior of lithium hydride at elevated temperatures

The fatigue properties of lithium hydride (LiH) are crucial to its application as neutron shielding and moderating at elevated temperatures. The dynamic fatigue tests of LiH were investigated with the notched 3-point bend (3 PB) specimens over ranges of loading rates at RT up to 400 °C. At RT, the results showed that slow crack growth (SCG) occurred prior to failure as the minor deviation from linearity to nonlinearity in the load-deflection curves. In addition, the fracture strength of LiH decreased with decreasing stress rate and the SCG zone gradually became smaller with higher stress rates, indicating evident dynamic fatigue phenomenon. However, the trends were quite different at 200, 300 and 400 °C due to accumulative creep damage for low stress rates at elevated temperatures. With increasing temperature and decreasing stress rate, there existed a transition of the dominated failure mechanism, from SCG to creep rupture. Evidence of very small SCG zone could also be detected at the notch for the failure dominated by creep rupture.

High temperature hardness testing of [formula omitted]-zirconium hydride: Yield stress estimation by analytical and numerical models

The mechanical properties of δ-zirconium hydrides were studied using a combination of nanoindentation techniques and numerical and analytical models. Two different alloys, containing different forms of δ-zirconium hydride (blister and rim), were analyzed at room temperature and at elevated temperatures up to 300 ∘C. A reduction of hardness from RT to 300 ∘C showed an approximately linear relationship with the change in temperature. For the δ-zirconium hydride rim, the hardness reduced from 3.73GPa at RT to 1.49GPa at 300 ∘C, a reduction of 61%. For the δ-zirconium hydride blister, hardness decreased from 3.5GPa at RT to 1.91GPa at 300 ∘C, a reduction of 45%. The yield stresses were calculated using two approaches: a numerical model proposed by Johnson to calculate values at RT, and another proposed by Dao for values up to 300 ∘C. At RT, the yield stress for the δ-zirconium hydride rim obtained was 883±21MPa, 224MPa at 300 ∘C. The δ-zirconium hydride blister showed a reduction from 879.5±10.5MPa at RT to 324MPa at 300 ∘C, a reduction in 61% and 45% for the hydride rim and blister, respectively. Through this combination of experimental and modeling techniques, this study showed the variation of hardness and yield stress in complex systems, and in different environments, using nanoindentation as the main characterization technique.

Engineering the hydrogen storage properties of the perovskite hydride ZrNiH3 by uniaxial/biaxial strain

In the present work, the bonding length, electronic structure, stability, and dehydrogenation properties of the Perovskite-type ZrNiH3 hydride, under different uniaxial/biaxial strains are investigated through ab-initio calculations based on the plane-wave pseudo-potential (PW-PP) approach. The findings reveal that the uniaxial/biaxial compressive and tensile strains are responsible for the structural deformation of the ZrNiH3 crystal structure, and its lattice deformation becomes more significant with decreasing or increasing the strain magnitude. Due to the strain energy contribution, the uniaxial/biaxial strain not only lowers the stability of ZrNiH3 but also decreases considerably the dehydrogenation enthalpy and decomposition temperature. Precisely, the formation enthalpy and decomposition temperature are reduced from −67.73 kJ/mol.H2 and 521 K for non-strained ZrNiH3 up to −33.73 kJ/mol.H2 and 259.5 K under maximal biaxial compression strain of ε = −6%, and to −50.99 kJ/mol.H2 and 392.23 K for the maximal biaxial tensile strain of ε = +6%. The same phenomenon has been also observed for the uniaxial strain, where the formation enthalpy and decomposition temperature are both decreased to −39.36 kJ/mol.H2 and 302.78 K for a maximal uniaxial compressive strain of ε = - 12%, and to −51.86 kJ/mol.H2 and 399 K under the maximal uniaxial tensile strain of ε = +12%. Moreover, the densities of states analysis suggests that the strain-induced variation in the dehydrogenation and structural properties of ZrNiH3 are strongly related to the Fermi level value of total densities of states. These ab-initio calculations demonstrate insightful novel approach into the development of Zr-based intermetallic hydrides for hydrogen storage practical applications.

Structural and high-field magnetic properties of Laves phase RFe2-H hydrides

The crystal structure and magnetic properties of the multicomponent compounds (Tb1−xYx)0.8Sm0.2Fe2Hz (x = 0, 0.2, 0.4, 0.6, 0.8, 1; z = 0 and 3.7) are investigated. The compounds crystallize in the MgCu2 type of structure. While the parent compounds Tb0.8Sm0.2Fe2 and Y0.8Sm0.2Fe2 are single phase, we detect 5%–8% of a second phase with a crystal structure of the PuNi3 type (space group R3m) in the alloys with 0.2 ≤ x < 0.8. Hydrogen absorption does not change the space group of the (Tb,Y,Sm)Fe2 compounds but boosts significantly the lattice parameter a. A large volume change of ΔV/V ∼ 28% upon hydrogen absorption is observed. By applying high magnetic fields up to 58 T, we observed rotations of the magnetic sublattices and hence we were able to determine the critical transition fields, H, from the ferrimagnetic to the ferromagnetic state and the inter-sublattice exchange parameter λ. The magnetic compensation occurs at x ≈ 0.6 and 0.2 in (Tb1−xYx)0.8Sm0.2Fe2Hz at z = 0 and 3.7, respectively. While maintaining the collinear magnetic structure, the phenomenon of compensation in hydrides should be observed at x ≈ 0.4.

Phase transitions, elastic and electronic properties of hydrogen storage Na2PdH4

Hydrogen can be absorbed by some materials at specific pressures and temperatures. This is extremely important in terms of creating carbon-free and sustainable society. In this work hydrides are good candidates to fulfill these aims. Electronic and magnetic properties of hydrides are investigated. This study considers Na2PdH4 as solid storage of hydrogen material. Hydrogen is highly soluble in palladium and can be stored in large amounts at ambient conditions. The structural evolution, electronic and elastic properties of Na2PdH4 has been investigated by means of density functional theory. The SIESTA software package is used with the generalized gradient approximation for the exchange-correlation functional and norm-conserving Troullier–Martins pseudopotentials. High-pressure computations have been carried out to reveal phase transitions. Na2PdH4 is transformed from I4/mmm tetragonal structure to Immm orthorhombic structure at 100 GPa. The electronic band structures and density of states are obtained for both phases. Mechanical stability is analyzed using the elastic constants. Moreover, several parameters such as Young’s modulus, shear modulus, and their ratios are obtained and discussed.

Ways of Increasing Specific Energy Intensity of Tritium-based beta-Voltaic Nuclear Batteries

Creating a beta-voltaic semiconductor battery based on long-lived radionuclide is an urgent task. However, today the technology of creating such energy sources and their output characteristics are far from perfect. This article analyzes ways to maximize energy intensity on the surface of the semiconductor carrier. Various methods of creating the maximum possible volume concentration of radioactive beta-emitter atoms based on the use of tritium are considered. A variety of variants using "associated" tritium are considered for application on the surface of the semiconductor carrier: metal tritids, intermetalides. One option may be the use of tritium-labeled organic molecules and polymers, as well as tritium, which is part of carbon nanomaterials — fullerenes, nanotubes, nanodiamonds, graphene and graphene oxide. The properties of intermet-allides hydrides (LaNi5, LaNi5T6) are considered. The dependence of the unit energy intensity of the battery's working body on the thickness of the emitter's film has been analyzed. As a result of the studies, the analysis of ways to achieve maximum energy intensity on the surface of the semiconductor carrier was analyzed. Various methods of creating the maximum possible volume concentration of radioactive beta-emitter atoms based on the use of tritium are considered. The dependence of the unit energy intensity of the battery's working body on the thickness of the emitter's film has been analyzed.

Surface Properties of LaNi5 and TiFe—Future Opportunities of Theoretical Research in Hydrides

Hydrogen in the solid state compounds is still considered as a safe method of energy storage. The ultimate metal hydrides or other materials that can be used for this purpose remain unknown. Such metal hydrides shall have favorable thermodynamics and kinetics of hydrogen ad/desorption, and it shall be resistant to contamination of H2 and should not constitute any environmental hazards. Theoretical investigations, based on quantum mechanics approach, have a well-established position in modern materials research; however, their application for design of new alloys with tailored properties for reversible hydrogen storage is rarely present in the literature. The mainstream research deals with accurate prediction of thermodynamic and structural properties of hydrides as a function of composition or external parameters. On the other hand, the kinetic effects related to hydrogen transport or interaction between solid and pure or contaminated H2 are more demanding. They cannot be easily automated. We present calculations of the equilibrium crystal shapes for LaNi5 and TiFe—two important materials that show reversible hydrogen cycling near ambient conditions. Understanding of the surface properties is crucial for development of materials with better cyclability or resistance to hydrogen impurities. Indeed, the calculated adsorption energy of carbon oxides or water is stronger than hydrogen. These molecules block the active sites for H2 dissociation, leading to formation of surface oxides. Particularly strong adsorption of CO/CO2 on TiFe explains large degradation of hydrogen storage capacity of this compound by carbon oxides. Over-representation of La on exposed facets of LaNi5 is related to formation of La2O3 and La(OH)3. Such examples show that the present development of computational methods allows reliable studies of intermetallic properties related to their surface or novel catalytic applications.

Catalytic mechanism of TiO2 quantum dots on the de/re-hydrogenation characteristics of magnesium hydride

In the present study, the catalyst anatase titanium dioxide (TiO2) quantum dots (QDs) of size ∼ (2.50–4.00)nm was successfully synthesized by the hydrothermal method. The formation of TiO2: QDs has been established by UV–Vis spectroscopy and confirmed by transmission electron microscopy. Here, we report the catalytic action of TiO2:QDs on de/re-hydrogenation properties of magnesium hydride (MgH2/Mg). By catalyzing MgH2 through this catalyst, the onset desorption temperature of MgH2 gets reduced significantly from ∼360 °C (for ball-milled MgH2) to ∼260 °C. Moreover, the Mg-TiO2: QDs sample absorbed a significant amount of hydrogen up to ∼6.10 wt% in just 77sec at 280 °C. Improved rehydrogenation kinetics has been found even at lower temperatures by absorbing ∼5.30 wt% in 74 s at 225 °C and ∼5.0 wt% of hydrogen in 30 min at 100 °C. Based on structural,.microstructural, and XPS investigations, a feasible mechanism for improved hydrogen sorption and cyclic stability in MgH2 catalyzed with TiO2:QDs has been explained and discussed. To our knowledge, no studies have been carried out on the sorption of hydrogen in MgH2 catalyzed by TiO2:QDs.

The Improvement in Hydrogen Storage Performance of MgH2 Enabled by Multilayer Ti3C2.

MgH2 has become a hot spot in the research of hydrogen storage materials, due to its high theoretical hydrogen storage capacity. However, the poor kinetics and thermodynamic properties of hydrogen absorption and desorption seriously hinder the development of this material. Ti-based materials can lead to good effects in terms of reducing the temperature of MgH2 in hydrogen absorption and desorption. MXene is a novel two-dimensional transition metal carbide or carbonitride similar in structure to graphene. Ti3C2 is one of the earliest and most widely used MXenes. Single-layer Ti3C2 can only exist in solution; in comparison, multilayer Ti3C2 (ML-Ti3C2) also exists as a solid powder. Thus, ML-Ti3C2 can be easily composited with MgH2. The MgH2+ML-Ti3C2 composite hydrogen storage system was successfully synthesized by ball milling. The experimental results show that the initial desorption temperature of MgH2-6 wt.% ML-Ti3C2 is reduced to 142 °C with a capacity of 6.56 wt.%. The Ea of hydrogen desorption in the MgH2-6 wt.% ML-Ti3C2 hydrogen storage system is approximately 99 kJ/mol, which is 35.3% lower than that of pristine MgH2. The enhancement of kinetics in hydrogen absorption and desorption by ML-Ti3C2 can be attributed to two synergistic effects: one is that Ti facilitates the easier dissociation or recombination of hydrogen molecules, while the other is that electron transfer generated by multivalent Ti promotes the easier conversion of hydrogen. These findings help to guide the hydrogen storage properties of metal hydrides doped with MXene.

The Effect of High-Energy Ball Milling Conditions on Microstructure and Hydrogen Desorption Properties of Magnesium Hydride and Single-Walled Carbon Nanotubes

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).