Hydride Alloys Research Articles

Comparative study of solid-solution treatment and hot-extrusion on hydrogen storage performance for Mg96Y2Zn2 alloy: The nonnegligible role of elements distribution

The utilization of Mg alloys for solid-state hydrogen storage has attracted considerable attention, and the Mg-based alloys with long period stacking ordered (LPSO) structure show optimized hydrogen storage properties. In this study, solid-solution treatment and hot-extrusion are utilized to modify the hydrogen storage properties of Mg96Y2Zn2 alloy. The results indicate 14H-type LPSO structure is precipitated after solid-solution treatment. Dynamic recrystallization occurs during deformation process with the refined grain size of 2 μm approximately and the dynamic precipitation of Mg3Y2Zn3 particles leads to the aggregation of Y and Zn atoms. Hot-extrusion can enhance the pulverization resistance of Mg96Y2Zn2 alloy by increasing the lattice parameter ratio of c to a. The reduced hydrogen capacity of hot-extruded Mg96Y2Zn2 alloy is attributed to the increased pulverization resistance and decreased lattice parameters. The apparent activation energies for hydrogenation and dehydrogenation of solid-solution treated alloy are 6.86 and 13.65 kJ·mol−1 less than those of hot-extruded alloy, respectively. The dehydrogenation temperature of solid-solution treated alloy hydride is 18 °C lower than that of hot-extruded alloy. More abundant and uniform distribution of Y atoms can generate accordingly more abundant and uniform YH2 nanoscale particles that embed in the α-Mg matrix, which contributes to faster de/hydrogenation kinetics.

Performance tests on embedded cooling tube type metal hydride reactor for heating and cooling applications

• Heating and cooling traits of two AB 5 -type metal hydride alloys were investigated. • Heating performances of the alloys were found to be superior compared to cooling. • Peak heating rate of 3.5 kW was accomplished, producing 514 kJ heat within 361 s. • A decentralized heating cum H 2 storage system was suggested based on test results. The present work reports the heating and cooling characteristics of two AB 5 type metal hydride (MH) alloys commercially labelled as A3® and LCC1®. A cylindrical MH reactor configuration comprising 48 Embedded Cooling Tubes (ECT) in a circular pattern and an outer jacket was considered to accomplish the set objectives. Two identical reactors were each filled with 3.4 kg of one of the alloys. The reactor configuration allows MH alloy to be filled in the shell space while the heat transfer fluid (HTF) could flow through the tubes and the outer jacket. A set of parametric investigations was conducted on the aforementioned alloys by varying the operational parameters. During the absorption set of the parametric study, hydrogen supply pressure was varied from 10 bar to 30 bar, and HTF temperature was varied from 15 °C to 35 °C, while during the desorption study, HTF temperature was varied from 5 °C to 25 °C. At the absorption condition of 30 bar and 25 °C, the alloys A3® and LCC1® attained absorption capacity of 1.24 wt.% and 1.38 wt.%, respectively. At this condition, LCC1® was able to generate 514.5 kJ cumulative heat output in 361 s, yielding a maximum heating rate of 3.57 kW. The parametric study revealed that the absorption behaviour of A3® was more sensitive towards changes in supply pressure as well as HTF temperature compared to LCC1®. Compared to heating performance, the cooling performance of both the alloys was lower. Based on the outcomes of the experimental study, it was suggested to utilize LCC1® for decentralized hydrogen storage cum heating applications in the temperature range of 15–35 °C.

A comprehensive review of the prospects for future hydrogen storage in materials‐application and outstanding issues

The ongoing population explosion has led to the rapid consumption of different energy sources. The continuous demand for energy and its associated services for socio-economic development is concerning due to the reduction of natural energy sources. Therefore, research to explore clean and sustainable energy sources to fulfill this energy demand has continuously been conducted over the past decades. Hydrogen is widely accepted as a possible energy carrier owing to its advantages, such as ease of availability, renewability, and environmentally friendly nature. Hydrogen storage in the liquid or gaseous form poses safety and transportation challenges. In this context, metal hydrides are a vital solution. This review article discusses unique collections of HEA-based metal hydrides for the first time in conjunction with conventional metal hydrides. This article can potentially guide the materials research community in understanding the current challenges associated with designing novel hydrogen storage alloys from a clean energy perspective and their applications. The review suggests improving the thermodynamics and hydrogen reaction kinetics to enhance hydrogen storage capacity. Finally, the global developing trends are reviewed and critical challenges and promising opportunities are identified. Highlights Essential aspects of various alloys and their hydrides are analyzed. This review supports the utilization of hydrogen as clean energy fuel and its possible storage measures. The review provides an imperative connection of the metal hydrides, including emerging high-entropy alloy hydrides, with renewable and sustainable energy. Metal hydrides are an economic option for hydrogen-based energy applications. This review focuses on present issues and the prospective application of hydrogen storage.

FE2 methodology for discrete cohesive crack propagation in heterogenous materials

To study the discrete crack growth of heterogeneous materials, a dual-scale discrete fracture calculation method is proposed in this paper. An equivalent cohesive energy criterion is proposed for the FE2 model based on the characteristics of the fracture zone. The representative volume element (RVE) with a cohesive zone is embedded into the Gauss points of the macro-element to replace the full FE model of the discrete crack. Therefore, the dual-scale method of discrete fractures not only improves the dual-scale modeling of discrete cracks but also greatly reduces the computational cost. We further demonstrate that the built-in capabilities of commercial software are naturally compatible with this method. Finally, the fracture process of a two-phase heterogeneous material containing a zirconium alloy matrix and hydride was studied using the dual-scale method. The macro-fracture direction was related to the precipitation direction of the brittle hydrides. This conclusion is consistent with existing experimental observations.

Elaboration and electrochemical characterization of CeZr2Ni4.5Al0.2Mn0.3Cr4-based metal hydride alloys

Elaboration and electrochemical characterization of CeZr2Ni4.5Al0.2Mn0.3Cr4-based metal hydride alloys

Hydrogen-induced change of oxidation combustion characteristics of Al2Mg alloy

The effects of solid-state hydrogen introduction on the oxidation combustion property and mechanism of Al 2 Mg alloy were investigated by means of thermal analysis, X-ray diffraction, scanning electron microscopy and energy dispersive spectrum. It was found that the starting combustion temperature of hydrogenated Al 2 Mg alloy is lowered by about 150 °C as compared with pristine Al 2 Mg alloy, due to its distinct phase composition of MgH 2 + Al as well as loose, porous and refined particle characteristics. The first-stage oxidation for the Al 2 Mg alloy hydride can be ascribed to the dehydrogenation of MgH 2 to form Mg followed by the reaction of Mg with oxygen to form MgO, which is entirely different from the oxidation mechanism of Al 2 Mg alloy. During the second-stage oxidation, MgAl 2 O 4 , γ-Al 2 O 3 and α-Al 2 O 3 were formed for both Al 2 Mg alloy and its hydride. However, almost no AlN can be generated for the Al 2 Mg alloy hydride with respect to Al 2 Mg alloy. • Solid-state hydrogen is introduced into Al 2 Mg alloy combustion agent. • The starting combustion temperature is reduced by 150 °C. • MgH 2 dehydrogenates and then reacts with oxygen during the first-stage oxidation. • Almost no AlN forms during the second-stage oxidation.

Enhancing hydrogen storage performance via optimizing Y and Ni element in magnesium alloy

Magnesium-based hydrogen storage materials are considered as one of the most promising candidates for solid state hydrogen storage due to their advantages of high hydrogen capacity, excellent reversibility and low cost. In this paper, Mg91.4Ni7Y1.6 and Mg92.8Ni2.4Y4.8 alloys were prepared by melting and ball milling. Their microstructures and phases were characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope, and hydrogen absorbing and desorbing properties were tested by the high pressure gas adsorption apparatus and differential scanning calorimetry (DSC). In order to estimate the activation energy and growth mechanism of alloy hydride, the JMAK, Arrhenius and Kissinger methods were applied for calculation. The hydrogen absorption content of Mg92.8Ni2.4Y4.8 alloy reaches 3.84 wt.% within 5 min under 350 ℃, 3 MPa, and the maximum hydrogen capacity of the alloy is 4.89 wt.% in same condition. However, the hydrogen absorption of Mg91.4Ni7Y1.6 alloy reaches 5.78 wt.% within 5 min, and the maximum hydrogen absorption of the alloy is 6.44 wt.% at 350 ℃ and 3 MPa. The hydrogenation activation energy of Mg91.4Ni7Y1.6 alloy is 25.4 kJ/mol H2, and the enthalpy and entropy of hydrogen absorption are -60.6 kJ/mol H2 and 105.5 J/K/mol H2, separately. The alloy begins to dehydrogenate at 210 ℃, with the dehydrogenation activation energy of 87.7 kJ/mol H2. By altering the addition amount of Ni and Y elements, the 14H-LPSO phase with smaller size and ternary eutectic areas with high volume fraction are obtained, which provides more phase boundaries and catalysts with better dispersion, and there are a lot of fine particles in the alloy, these structures are beneficial to enhance the hydrogen storage performance of the alloys.

New Development of Permanent Magnets Through Grain Boundary Diffusion and Nanostructuring

High-performance permanent magnets (PMs) have gained high and growing interest due to their excessive demand in energy conversion systems and electric vehicles. PM-based electric machines exhibit great advantages over traditional motors due to their high efficiency of energy conversion. Nd–Fe–B magnet is the best available magnet in terms of energy-product at room temperature. Replacement of Nd by heavy rare earth (HRE) and of Fe by Co results in an enhanced anisotropy field and an improved thermal stability, but also increases the production costs. Developing a strong PM with minimum use of HRE elements is required due to their high cost, low availability and issues associated with international politics. Grain boundary diffusion (GBD) process allows the HRE to diffuse around the grain boundaries, unlike adding expensive HRE to the middle of a grain. Here, we review the recent progress in PMs, especially the novel development of grain boundary-diffused magnets and nanostructured magnets. GBD processes using RE, fluorides or hydrides of RE and eutectic alloys are discussed. Development of nanostructured PMs using physical and chemical methods such as melt spinning, high-energy ball milling, surfactant-assisted ball milling, mechanochemical method, etc. is elucidated. The current and future trends in the area of high performance permanent magnets are outlined.

Temperature-dependent axial mechanical properties of Zircaloy-4 with various hydrogen amounts and hydride orientations

The effects of hydride amount (20–850 wppm), orientation (circumferential and radial), and temperature (room temperature, 100 °C, 200 °C) on the axial mechanical properties of Zircaloy-4 cladding were comprehensively examined. The fraction of radial hydride fraction in the cladding was quantified using PROPHET, an in-house radial hydride fraction analysis code. Uniaxial tensile tests (UTTs) were conducted at various temperatures to obtain the axial mechanical properties. Hydride orientation has a limited effect on the axial mechanical behavior of hydrided Zircaloy-4 cladding. Ultimate tensile stress (UTS) and associated uniform elongation demonstrated limited sensitivity to hydride content under UTT. Statistical uncertainty of UTS was found small, supporting the deterministic approach for the load-failure analysis of hydrided Zircaloy-4 cladding. These properties notably decrease with increasing temperature in the tested range. The dependence of yield strength on hydrogen content differed from temperature to temperature. The ductility-related parameters, such as total elongation, strain energy density (SED), and offset strain decrease with increasing hydride contents. The abrupt loss of ductility in UTT was found at ∼700 wppm. Demonstrating a strong correlation between total elongation and offset strain, SED can be used as a comprehensive measure of ductility of hydrided zirconium alloy.

In situ synchrotron radiation X-ray diffraction measurements of Fe–Mo alloy hydrides formed under high pressure and high temperature

Conventional hydrides obtained thus far contain at least one type of metal with high hydrogen affinity, which can form metal hydrides near ambient pressure. In contrast, we synthesized metal hydrides comprising only metals with low hydrogenation affinity which are metals that do not form metal hydrides MHx (M stands for metal element, x > 0.5) below 1 GPa. This is because such hydrides are rare and would demonstrate novel properties and functionalities. To provide a guideline for synthesizing such hydrides, we clarified the hydrogenation reaction processes of FexMo1−x alloys at 6 GPa and 750 °C over a wide composition range of 0.41 ≤ x ≤ 0.88, where both Fe and Mo demonstrate low hydrogen affinities. Depending on the alloy composition, the hydrogenation reaction process can be classified into three types. Two kinds of novel hydrides were synthesized herein. First, FexMo1−xH (0.50 ≤ x ≤ 0.74) with metal elements at the vertices of hexagonal close-packed (hcp) lattices, and second, Fe0.88Mo0.12H with a complex crystal structure, which is likely to be a long-period close-packed structure.

Design and performance analysis of an annular metal hydride reactor for large-scale hydrogen storage applications

The present study is focused on developing a modular design of a metal hydride reactor for large-scale hydrogen storage applications. In this perspective, an annular metal hydride reactor that is cooled/heated on both inner and outer surfaces is designed and analyzed. A numerical model is developed to study the absorption and desorption characteristics of the designed annular metal hydride reactor. Three configurations of the annular metal hydride reactor that could offer a weight ratio (i.e., mass of metal hydride alloy to mass of the reactor) of 2 are investigated. The first two configurations are of annular metal hydride reactor with only change in the heat transfer fluid's flow direction. The third configuration is the same as the second one, with extra radial fins inside the metal hydride bed. The main objective of studying the three configurations is to visualize the enhancement achieved in the reaction rate and outlet temperature. The results showed that the peak outlet temperature is enhanced by 3.6 °C with the second configuration. At the same time, the third configuration improved the absorption and desorption rates by a factor of 2.07 and 1.92, respectively, while the radial fins occupying only 4.6% of reactor volume. Further, a sensitivity analysis is conducted on the third configuration to analyze the influence of operating parameters on absorption and desorption times. Furthermore, the performance of the third configuration is compared with several designs present in the literature.

New arrangement of the metal hydride linear drive

A new arrangement of a metal hydride linear drive is presented, in which a thermoelectric sorber—hydrogen desorber using the Peltier effect is located inside the working chambers. Variants of different versions of a linear drive with a new arrangement and their advantages in comparison with known metal hydride linear drives are shown. Recommendations for their practical application are given. Keywords: metal hydride alloys and their application, metal hydride linear drive, thermoelectric sorber—hydrogen desorber. S.Sayapin@rambler.ru

Au16Ag43H12(SPhCl2)34]5-: An Au-Ag Alloy Nanocluster with 12 Hydrides and Its Enlightenment on Nanocluster Structural Evolution.

The structural determination of alloy hydride nanoclusters with high nuclearity remains challenging. We herein report the synthetic procedure and the structural elucidation of an Au-Ag alloy nanocluster with 12 hydride ligands-[Au16Ag43H12(SPhCl2)34]5-. The structure of [Au16Ag43H12(SPhCl2)34]5- comprises an Au16Ag3 kernel that is stabilized by 12 hydride ligands, 8 thiol bridges, and 6 Agm(SR)n motif units. The 12 hydride ligands in Au16Ag43 have been confirmed by both 2H NMR and ESI-MS measurements, and their positions have been theoretically evaluated, located at the interlayer between the Au16Ag3 kernel and the Ag-SR shell. The metastable [Au16Ag43H12(SPhCl2)34]5- can convert to [Au12Ag32(SPhCl2)30]4- spontaneously. Structurally, the Au16Ag3 kernel of [Au16Ag43H12(SPhCl2)34]5- could be regarded as the overlapping of two hollow Au8Ag3 cages via sharing an Ag3 line, which is in contrast to the solely icosahedral Au12 kernel of [Au12Ag32(SPhCl2)30]4-. Besides, the overall construction of Au16Ag43 or Au12Ag32 follows a complementing or overlapping assembly mode, respectively. Overall, the structural anatomy of Au16Ag43H12(SPhCl2)34 sheds some new insight into the structural evolution of metal nanoclusters.

Expansion deformation behavior of zirconium alloy claddings with different hydrogen concentrations

In this paper, the expansion deformation behavior of zirconium alloy claddings with different hydrogen concentrations was evaluated by the advanced expansion due to compression (A-EDC) test and ring tensile test. The results showed that in the A-EDC test, both the fracture load and the maximum hoop strain of the zirconium alloy claddings decreased with the increase of hydrogen concentration, especially when the hydrogen concentration at 300 wppm, these decreases became stronger. The fracture surface analysis showed that the specimens gradually changed from ductile fracture to brittle fracture with the increase of hydrogen concentration, and a significant 45-degree shear fracture characteristics for all the specimens. In the ring tensile tests, either the tensile strength or the maximum hoop strain of the zirconium alloy claddings seemed to be independent of the hydrogen concentration, except the reduction of area that decreased with the increase of hydrogen concentration. The fracture surface analysis showed that the specimens also gradually changed from ductile fracture to brittle fracture with the increase of hydrogen concentration, and a transformation from cup-and-cone fracture to flat fracture. The results also showed that during the A-EDC tests and ring tensile tests, a large number of cracks appeared on the outside surfaces of the hydrided specimens along the axial direction, especially at a higher hydrogen concentration. The in-situ observations of ring tensile showed that compared with the circumferential hydrides, the radial hydrides preferred to crack. Combined with the results of in-situ observation and fracture surfaces analysis, a fracture model based on the expansion deformation of hydrided zirconium alloy cladding was proposed.

Data-Driven Discovery and Synthesis of High Entropy Alloy Hydrides with Targeted Thermodynamic Stability

Solid-state hydrogen storage materials that are optimized for specific use cases could be a crucial facilitator of the hydrogen economy transition. Yet, the discovery of novel hydriding materials has historically been a manual process driven by chemical intuition or experimental trial and error. Data-driven materials’ discovery paradigms provide an alternative to traditional approaches, whereby machine/statistical learning (ML) models are used to efficiently screen materials for desired properties and significantly narrow the scope of expensive/time-consuming first-principles modeling and experimental validation. Here, we specifically focus on a relatively new class of hydrogen storage materials, high entropy alloy (HEA) hydrides, whose vast combinatorial composition space and local structural disorder necessitate a data-driven approach that does not rely on exact crystal structures to make property predictions. Our ML model quickly screens hydride stability within a large HEA space and permits down selection for laboratory validation based on not only targeted thermodynamic properties but also secondary criteria such as alloy phase stability and density. To experimentally verify our predictions, we performed targeted synthesis and characterization of several novel hydrides that demonstrate significant destabilization (70× increase in equilibrium pressure, 20 kJ/molH2 decrease in desorption enthalpy) relative to the benchmark HEA hydride, TiVZrNbHfHx. Ultimately, by providing a large composition space in which hydride thermodynamics can be continuously tuned over a wide range, this work will enable efficient material selection for various applications, especially in areas such as metal hydride-based hydrogen compressors, actuators, and heat pumps.

Isotherm measurements of high-pressure metal hydrides for hydrogen compressors

Hydrogen absorption and desorption isotherms have been measured for several metal hydride alloys identified as possible candidates in the high-pressure (i.e. >80 MPa) stage of a two-stage hydrogen compressor. The isotherms were obtained using two independent Sieverts volumetric test systems built specifically for measuring hydrogen absorption and desorption parameters from 0.10 to 100 MPa. The results obtained enabled us to identify the alloy Ti0.8Zr0.2Fe1.6V0.4 as the most viable of the candidates investigated for use in the high-pressure stage of a prototype two-stage 80+ MPa compressor, as it produced the highest desorption pressures at moderate temperatures. Issues and challenges in determining reliable isotherms at pressures >50 MPa are also described.

Hydrogen storage behavior of Mg-based alloy catalyzed by carbon-cobalt composites

The composites comprised of Co nanoparticle and C nanosheet were prepared though a high-temperature carbonization reaction. The catalysis of [email protected] composites on the hydrogen storage behavior of Mg90Ce5Y5 alloy was investigated in detail by XRD, SEM, TEM, PCI, and DSC method. Because of the synergistic catalytic function of C and Co in [email protected] nanocomposites, the Mg90Ce5Y5 alloy with 10 wt.% [email protected] shows the excellent hydrogen absorption and desorption performances. Time for releasing hydrogen reduces from 150 min to 11 min with the addition of the [email protected] composites at the temperature of 300 °C. Meanwhile, the dehydrogenation activation energy also declines from 130.3 to 81.9 kJ mol−1 H2 after the addition of the [email protected] composites. This positive effect attributes to the C layer with the high defect density and the Co nanoparticles, which reduces the energy barriers for the nucleation of Mg/MgH2 phase and the recombination of hydrogen molecule. Besides, the [email protected] composites also improve the activation property of the Mg90Ce5Y5 alloy which was fully activated in the first cycle. Moreover, the temperature for initial dehydrogenation and the endothermic peak of the alloy hydride were also decreased. Although the addition of the [email protected] composites increases the plateau pressures and decreases the value of the decomposition enthalpy, these differences are so small that the improvement on thermodynamics can hardly be seen.

The features of transient plasma formation by the surface of metal hydride under the influence of intense electron flux

In this work, we study the features of a transient plasma formation close to a Zr50V50 metal hydride. The surface is immersed in a direct current primary plasma, which serves as the initial source of electrons. When the surface consists a hydride alloy, it releases the hydrogen stored therein followed by ionization with the electron flux. Due to the potential redistribution in a metal hydride layer and in a layer close to the wall of a vacuum chamber the current to the metal hydride element can be several times higher than the initial current of the primary plasma source. The transient plasma is created on released hydrogen and protects the sample from melting due to energy spending on the ionization and excitation of neutral hydrogen and decomposition of the hydride phases of the material. If there is no stored hydrogen, the plasma forms on the vapor of the sample material causing damage.

Analysis of the Heat Balance of a Metal Hydride Separator Used for the Separation of Hydrogen from Syngas

The present article discusses the potential for hydrogen separation using a metal hydride separator, which facilitates the generation of hydrogen contained in syngas following the thermal recovery of wastes. The article provides a detailed description of the separator heat balance using analytical calculations and optimised calculations, and by applying numerical methods. The proposed concept of a separator intended for hydrogen separation from syngas offers a solution to a problem associated with the use of metal hydride alloy powders; in particular, their low thermal conductivity. In order to eliminate big temperature differences in the alloy, a heat transfer intensifier was implemented in the metal hydride alloy volume; the intensifier was made of metal and exhibited high thermal conductivity. For the purpose of comparing the thermal fields, the first stage comprised the creation of a numerical simulation of hydrogen absorption without the use of an intensifier. Subsequently, three different geometries were created for an intensifier intended to remove heat from the metal hydride alloy powder towards the separator cover, and the effects of these three geometries were analysed. The implementation of heat transfer intensifiers into the metal hydride alloy powder improved the heat removal by as much as 43.9% and increased the thermal field homogeneity by 77%. A result of the heat removal optimisation was an increase in the hydrogen absorption kinetics and the efficiency of the separator operation.

High-pressure synthesis and thermodynamic stability of PdH1±ε up to 8 GPa

Palladium hydride alloys are superconductors and hydrogen storage materials. One synthesis route is compression of Pd to high pressure in a hydrogen-rich environment. Here we report the evolution of the unit cell volume of ${\mathrm{PdH}}_{x}$ synthesized by compressing Pd in a pure ${\mathrm{H}}_{2}$ medium to pressures from 0.2 to 8 GPa in a diamond anvil cell at room temperature. The volume of the face-centered cubic unit cell changes nonmonotonically with pressure, increasing upon compression from 0.2 to 1 GPa and decreasing upon compression from 1 to 8 GPa. Volume is reversible upon decompression and is independent of whether the sample was heated to 600 K at low pressure ($P<2$ GPa). The x-ray diffraction data show no evidence for a phase transition between 0.2 and 8 GPa. The volume maximum at 1 GPa must be caused by progressive hydrogenation from 0 to 1 GPa. Assuming a pressure-volume-composition equation of state derived from previously published data, the [H]:[Pd] ratio in this study increases to a maximum value of $x=1\ifmmode\pm\else\textpm\fi{}0.02$ at $2\ifmmode\pm\else\textpm\fi{}0.5$ GPa and remains stable upon further compression to and from 8 GPa. These results add to a mounting body of evidence that ${\mathrm{PdH}}_{1\ifmmode\pm\else\textpm\fi{}\ensuremath{\epsilon}}$ is in thermodynamic equilibrium with pure ${\mathrm{H}}_{2}$ at room temperature from 2 GPa to at least 8 GPa. The simplest interpretation is that H atoms occupy all octahedral sites and no tetrahedral sites in face-centered cubic ${\mathrm{PdH}}_{1.0}$.