The influence of ordered mesoporous carbon (CMK-3) on the hydrogen storage properties of the 6Mg(NH2)2-9LiH-2LiBH4 reactive hydride composite (6 : 9 : 2-RHC) is systematically investigated. Incorporation of 10 wt% CMK-3 into the pristine composite (6 : 9 : 2-RHC + 0.1CMK3) leads to substantial improvements in hydrogen sorption kinetics. Under identical thermodynamic conditions, the CMK-3 incorporated composite exhibits significantly enhanced reaction kinetics, with the absorption time reduced from similar to 30 minutes to only 3 minutes (approximate to 90% improvement) and the full desorption completed within 25 minutes instead of 60 minutes (approximate to 58% improvement) compared to the pristine system. Moreover, the modified composite maintains excellent cycling stability, with 98% capacity retention over the first ten dehydrogenation/hydrogenation cycles compared to 90% for the pure composite. To elucidate the mechanism underlying this kinetic enhancement, we use a combination of advanced characterization techniques, including differential thermal analysis (DTA), synchrotron radiation X-ray powder diffraction (SR-XRPD), Fourier transform infrared (FT-IR) spectroscopy, small-angle and ultra-small-angle neutron scattering (SANS/USANS) and quasi-elastic neutron scattering (QENS). DTA analysis shows an 11 kJ mol-1 decrease in apparent activation energy barrier upon CMK-3 addition. SANS/USANS results reveal that CMK-3 effectively suppresses particle agglomeration during the dehydrogenation/hydrogenation cycle and maintains structural integrity, preserving the high accessible surface area for long-term cycling stability. QENS measurements confirm that the incorporation of mesoporous carbon lowers the reorientational energy barriers of [BH4]- anions, leading to faster local dynamics. This enhanced mobility facilitates the elementary reaction steps involved in hydrogen release and uptake, which contributes to the improved sorption kinetics of the CMK-3 modified composite.

Complex hydrides offer high H2 storage capacities but suffer from kinetic degradation and microstructural coarsening, requiring operations at elevated temperatures, typically above 180°C. Here, we demonstrate grain boundary complexion-mediated structural stabilization using ultra-low loading of Zr-based metal-organic frameworks (Zr-MOFs; 1 at.% Zr; UiO-66 vs. MIP-206) in the reactive hydride composite system 6Mg(NH2)2-9LiH-2LiBH4 (6.9.2-RHC). Incorporation of microporous Zr-UiO-66 significantly lowers the hydrogen absorption onset temperature from 162°C to 81°C, enables measurable hydrogen uptake at 35°C (1.07 wt.% under 80 bar H2). In addition, UiO-66 accelerates desorption by more than threefold at 140°C, increases reversible capacity from 3.2 to 4.1 wt.%, and maintains the capacity over 15 cycles compared with the pristine 6.9.2-RHC. In situ synchrotron radiation X-ray diffraction confirms that the intrinsic amide–imide reaction pathway remains unchanged, suggesting that structural stabilization plays a dominant role in the enhanced hydrogen storage performance. SAXS reveals stabilized nanoscale domains (≈2.4–3.3 nm), while SANS/USANS demonstrates suppression of hierarchical aggregation relative to pristine 6.9.2-RHC. Ball-milling of UiO-66 preserves short-range tetrahedral structural units (≈0.76 nm) that are proposed to stabilize grain-boundary complexions capable of accommodating the large (20–30 per cent) volume changes associated with hydrogen cycling. The performance hierarchy (UiO-66 > MIP-206 > pristine) demonstrates that MOF-derived short-range structural motifs suppress coarsening by promoting grain-boundary complexions, enabling practical low-temperature hydride operation through stabilized reactive interfaces.

Systematic studies on optimizing deposit performance in cold spraying mainly concern the variation in primary process parameters such as gas pressure and temperature. However, energy densities of the spray jet exposed to the deposit surface might have similar influence as substrate heating. To provide further insights, this study systematically investigates the influence of secondary parameters by robot kinematics on deposit performance. As model material, an Al6061 powder in sizes of 20-45 μm was sprayed on Al6061-T6 substrates. Fixed primary process parameter sets were adjusted for sufficiently high particle impact to critical velocity ratios. Secondary parameters were varied with respect to the stand-off distance, the traverse or spray velocity of the cold spray gun, and the line spacing. In addition, the effects of variations in powder feed rate and powder injection distance were investigated. Deposit analyses concerned deposition efficiency, microstructure, porosity, hardness, electrical conductivity and for selected conditions also deposit strengths. The results show that lower spray velocities and to some extent shorter stand-off distances lead to better deposit performance. Similarly, lower feed rates also have beneficial effects, possibly due to reaching higher particle impact energy. Apart from individual contributions, the combination of these parameters could enhance improved deposit performance, revealing potential synergistic effects among the secondary parameters. With that, this study demonstrates potentials to use careful tuning of secondary parameters as an additional way for adjusting the needed performance in cold spray to reach thresholds given in applications.

Cold spraying (CS), as a solid-state additive manufacturing technique, offers a unique metallurgical process in metal deposition. This work focuses on Al powder properties, particularly particle size and oxide film, which influence deposition efficiency (DE) and the final properties of the Al deposits produced by cold spray additive manufacturing (CSAM). Fine-sized powder exhibits the highest strength among the three powder sizes studied; however, pre-oxidation at 550 degrees C for 10 h increases its oxygen content from 0.09 wt.% to 0.31 wt.% and the oxide film thickness from 8 nm to 31 nm, leading to an approximately 25 MPa reduction in its strength. The softening effect induced by high-temperature pre-oxidation makes the DE of oxidised Al powders higher than that of as-atomised ones when the spray gas temperature during CSAM exceeds 300 degrees C, which is also reflected by the single-particle deposition efficiency increasing from 45% to 75%. However, high-temperature pre-oxidation decreases particle bonding quality and reduces the mechanical and electrical properties of the Al deposits. These effects become more pronounced under increased spray gas temperatures, emphasising the need for finding the right balance between powder pre-oxidation with spray parameters to optimise the deposit performance.

This paper systematically investigates the interplay between particle oxidation and its strength response of Ti powder and their subsequent influences on particle deposition in cold spraying. After oxidation in air at 500 degrees C for 4 h, fine-sized Ti powder exhibits the highest uptake of oxygen and hydrogen among the used three powders of different size ranges, accompanied by a decrease in average particle strength from 811 to 715 MPa. Oxidation results in the formation of nano-crystalline tetragonal TiO2 layers on particle surfaces, which act as barriers to metallic bonding during deposition. Consequently, the oxide films suppress particle deformation, as reflected by the reduced flattening ratio and bonding efficiency of oxidized particles. The results not only reveal the microstructure evolution of the bonding interface, as well as deepen the understanding of interactions between Ti powder and substrate under extreme strain-rate condition, but also highlight the necessity of controlling powder oxygen to achieve reliable microstructural integrity and performance in cold spray additive manufacturing of Ti workpieces.

Storing hydrogen in interstitial metal hydrides has several advantages. These include high volumetric capacity (50-100 kg/m(3)), fast kinetics, and safer conditions due to mild operating temperatures (<100 degrees C) and pressures (<50 bar). However, thermal management and stress development remain challenges to be overcome. There have already been promising methods to improve the performance of metal hydrides, but most are only proof of concept. They have only been investigated on a lab-scale with a few grams of sample. In this work, a commercially available AB(2)-metal alloy is coated with 10 wt% expanded natural graphite (ENG) and 10 wt% elastomeric binder. The focus is on methods that can easily be scaled up. Two methods (wash-coating and spray-coating) have been successfully applied to prepare hydride-forming materials on a kilogram scale. The performance of the coated material in terms of heat management, stress development, hydrogen capacity, and kinetics is evaluated to be over 50 cycles of hydrogen absorption/desorption. The results are confirmed by a larger-scale set of experiments with approximate to 0.5 kg of sample. The spray-coating method shows promising results, combining fast preparation, reasonable hydrogen capacity, and the potential to compensate for the bulk of the expansion stress.

The inherently low thermal conductivity of metal hydrides significantly hinders heat transfer and, consequently, the kinetics of hydrogen absorption and desorption processes. To address this limitation, strategies such as adding high-thermal-conductivity materials have been explored to enhance the effective thermal conductivity of hydride beds. In this work, we investigate the effects of expanded natural graphite (ENG) addition on the thermal and kinetic performance of composite metal hydride materials. The used alloy is a commercially available AB2 intermetallic compound, Hydralloy®C5. Materials composed of this AB2 alloy, ethylene-vinyl acetate copolymer (EVA) used as binder, and ENG are investigated here. Experimental tests are conducted in conjunction with multi-scale finite element method (FEM) simulations to evaluate the effects of EVA on the hydrogen storage performance, hydride bed temperature development, and the effective thermal conductivity. Among the tested compositions, the mixture C5 + 10 wt% ENG + 2.5 wt% EVA exhibited the best balance of thermal behavior and storage properties, achieving a capacity close to that of the pristine AB2 (about 1.7 wt%, calculated on the basis of the active material), showing an improvement of the kinetics around 35–40% and reducing the peak temperature upon hydrogenation in the milligram scale by approximately 8 °C. The proposed model introduces several novel elements, including a modified approach for the evaluation of the effective thermal conductivity and a mathematical model for the porosity of metal hydride composite beds. Validated FEM simulations at different scales (mg, g, and hundreds of grams), incorporating an effective thermal-conductivity model modified for composite materials, provide valuable input for the development and design of hydride-based vessels containing pure and composite hydride-forming materials.

Cold spray additive manufacturing (CSAM) offers a solid-state method for producing high-performance Ti components, yet the interplay among powder size, surface oxidation, and process parameters on deposits' microstructures and properties remains insufficiently understood. This work systematically investigates how the above factors influence powder deposition efficiency, microstructure, mechanical performance, and electrical conductivity of related Ti deposits. As a result, fine powder produces denser deposits with enhanced tensile strength, hardness, and conductivity, while coarse powder achieves higher deposition efficiency. The surface oxide films reduce inter-particle bonding, leading to more rebound particles, then increasing the hardness of Ti deposits. Increasing gas temperature increases particle kinetic energy, thus promoting oxide films fracture and mitigating the negative impact of oxidation. The study reveals the synergistic effects of powder characteristics and process conditions, providing mechanistic insights into microstructural evolution and property control. These findings offer practical suggestions for optimizing powder selection and processing strategies, enabling efficient utilization of partially oxidized powders and advancing the reliable production of high-performance titanium components via CSAM.

Clean hydrogen is vital for achieving net-zero emissions and reducing carbon output in society. Anion exchange membrane water electrolysis is gaining momentum in the growing electrolyzer market as a means of producing climate-neutral hydrogen when paired with renewable energy sources. Anion exchange membrane water electrolyzers do not rely on precious metals for electrocatalysts and do not require harsh caustic conditions, making them a safe, scalable, efficient, and potentially affordable method for splitting water. This investigation uses a zero-dimensional numerical model to assess the operation of a market-ready anion exchange membrane water electrolyzer and its capacity to generate clean hydrogen and recover waste heat. A commercial electrolyzer rack with four nominal 2.4 kWel electrolyzer modules is used to collect experimental data and examine multiple process parameters during dynamic operation from start to steady-state conditions. These include stack temperature, pressure, hydrogen production rate, cell voltage, and current density. The observed average electrolysis efficiencies at the stack and system levels, based on the lower heating value of hydrogen, reach 68.4% and 61.5%, respectively. The recoverability of the generated waste heat at the stack level is approximately 79.4% at 46 degrees C, providing approximately 340 Wth of heating power and about 111 Wth of exergy heating rate per module. The developed model accurately reproduces the dynamic behavior of electrolyzers, showing strong correlations with experimental data, achieving R2 values of 0.95 or higher across various time-dependent process parameters, and providing new insights into process simulation for system integration, design, and scaling.

Hydrogen storage in metal hydrides holds great promise for advancing a low-carbon energy future. Yet, fine-tuning the thermodynamics of hydrogen absorption remains challenging with traditional microalloying approaches. Here, we report a strategy inspired by compositionally complex alloy design to introduce atomic disorder into the prototypical TiFe intermetallic system. By progressively substituting Fe with Co, Ni, Cu, and Mn in equal proportions, we synthesize a series of near-single-phase B2-structured compositionally complex intermetallics, that is, Ti-50(FeCo)(50), Ti-50(FeCoNi)(50), Ti-50(FeCoNiCu)(50), and Ti-50(FeCoNiCuMn)(50) (at.%). These materials exhibit hydrogen storage capacities (measured by pressure-composition isotherm, PCI) of 1.39, 1.42, 1.31, and 1.14 wt.% under 100 bar of H-2 at 50 degrees C, respectively. Notably, Ti-50(FeCo)(50) demonstrates rapid hydrogen uptake kinetics, achieving 90% of its full capacity within 77 s under 50 bar of hydrogen pressure at 50 degrees C. Hydrogen storage thermodynamic analyses reveal that increasing atomic disorder stabilizes the hydride phase, with thermodynamic stability following the order: Ti-50(FeCoNiCuMn)(50) > Ti-50(FeCoNi)(50) > Ti-50(FeCoNiCu)(50) > Ti-50(FeCo)(50). Our findings establish atomic disorder as a versatile thermodynamic tuning knob for intermetallic hydrides, offering a rational framework for the design of advanced hydrogen storage materials.

Pure iron powder combines excellent plastic deformability under a high-velocity impact with high magnetizability and permeability, making it an economical candidate for cold spray additive manufacturing (CSAM) and repairs in magnetic applications. This work explores the fracture mechanics and electromagnetic (EM) properties of CSAM pure iron deposited using cheaper nitrogen as the process gas at temperatures of 900 degrees C and 1000 degrees C, achieving relative densities of 97.3 % and 98.0 %, respectively. The deposits exhibited an ultimate tensile strength greater than 250 MPa and elongation to fracture of less than 0.3 %, a behavior consistent with the characteristic results of as-sprayed CSAM deposits. The fatigue crack growth rate analyses showed the propagation being faster than in wrought iron through different mechanisms: trans-particle crack propagation near the threshold stress intensity factor, and inter-particle decohesion at higher loads. The EM testing indicated that CSAM pure iron saturated at a lower induction and had lower permeability than wrought low-carbon steel, while its coercivity and hysteresis losses were higher, and electrical resistivity was similar. Despite the lower mechanical and magnetic performance, CSAM pure iron or similarly deformable ferritic alloys can meet the requirements for low-field, low-frequency, or direct-current applications, and provide a route for direct near-netshape additive manufacturing or in-situ repair of magnetic components without scraping existing parts.

Cold spraying is a solid-state deposition technology with great potential and application value for repairing metallic components. As a key parameter, the process gas temperature governs gas and particle velocity as well as the heat input to both the powder particles and the component surface. However, to avoid nozzle clogging and maintain process stability, the process gas temperature is typically kept below the solidus temperature of the feedstock material. This constraint limits the usable parameter regime, particularly with respect to further heating and thus softening of powder particles as well as component surfaces, which both would promote better bonding. In this study, a novel powder pre-cooling approach is proposed to shift the thermal limits, enabling stable cold spray conditions at elevated process gas temperatures by using Nitrogen as process gas. As a case study, Al6061 powder was pre-cooled using a custom dry-ice cooling system prototype prior to spraying. The results show that stable deposition could be maintained even at a process gas temperature of 720 °C, thereby widening so far applicable ranges from conventional cold spraying of Al6061 by 220 °C. In addition, the increased process gas temperature increased the component surface temperature from 144 °C to 209 °C, enhancing the surface softening and thereby improving overall deposit performance.

To achieve affordable, clean energy, incorporating renewable energy into existing energy systems is the key. One challenge is the fluctuating nature of renewable resources, which can be asynchronous with energy demands. Hydrogen storage, particularly metal hydride storage, is a favorable solution for balancing supply and demand. In particular, metal hydride storage, compared with pressurized or liquefied hydrogen storage, is a favorable technology choice due to its storage energy density (50-100 kg H˙2/m3) and its low operating temperature and pressure. This paper presents a simulation-based framework to investigate the optimal design and operation of a coupled Electrolyzer-Fuel Cell-Metal Hydride system (SET-Unit) for minimizing operational and capital expenses in a residential application. The results show that integrating heat pumps with a metal-hydride storage system and photovoltaics can achieve 83% energy self-sufficiency and a 7.1-year payback period. Combining SET-Unit, gas boilers, and photovoltaics can result in 28% energy self-sufficiency, annual savings of over 2221 EUR, and a payback period of 7.4 years. The SET-Unit, combined with renewable energy sources such as photovoltaics, and the in-market available gas boilers or heat pumps, shows benefits in efficiency, annual energy cost reduction, and a relatively short payback period for the household. Using the low end of published values for capital expenses, economic feasibility can be achieved.

Metal hydride hydrogen compressors have been explored as an alternative to mechanical hydrogen compressors since the first patents were filed in the 1970s. As heat engines, their productivity notably depends on the achievable heat transfer rate, which is limited by the pressure-bearing walls separating the heat transfer fluid from the reactive metal hydride beds and their effective thermal conductivity. Here we present and analyze an alternative metal hydride compressor system that uses hydrogen as a heat transfer fluid in direct convective contact with the metal hydride material. Following this principle, we demonstrate how an integrated compressor can be designed and how it behaves at both system and metal hydride bed levels. Simulations of a system operating at 10 - 90 °C indicate that specific productivities of 300 Ln h⁻¹ kg⁻¹ can be achieved at low electrical energy demand, with isothermal efficiencies surpassing the ~75 % typically attained by mechanical piston compressors.

Metal hydride hydrogen compressors (MHHCs) compress hydrogen without moving parts, are very reliable, and can use waste heat. Among hydrides, AB(2)-type Laves phase compounds are attractive because they can store large amounts of energy, have a wide equilibrium pressure range, and are cost-efficient. However, the slope of the pressure-composition-temperature (PCT) plateaus, quantified by the sloping plateau factor S-f > 0, strongly affects the compressor performance. This study applies a 2-D numerical model to evaluate a two-stage MHHC using LaNi4.7Sn0.3 and Ti0.72Zr0.28(Mn, Cr, Fe, Ni)(2), which operate over 25-150 degrees C. The results show that increasing S-f from 0 to 2 can reduce the average compression ratio and thermal efficiency by up to 42% and 12.1%, respectively. Although higher S-f reduces total heat input by 17.6%, the useful compression work decreases by a greater amount, reducing the overall efficiency to 3.4%. Therefore, materials with low S-f are required to achieve optimal MHHC performance.

Anion exchange membrane water electrolysis is considered one of the most promising technological solutions for producing clean hydrogen. This technology has been demonstrated to be efficient, scalable, and cost-effective, with the benefit of not requiring platinum-group metals. However, there is a research gap in developing a robust electrochemical model of a market-ready anion exchange membrane electrolyzer for use in process and system simulations. Therefore, this study presents a zero-dimensional electrochemical anion exchange membrane-electrolyzer stack model. A commercial 2.3 kWel stack is used to acquire experimental data. This data is then utilized to validate the model, particularly through comparisons of the experimental polarization curve from 1.53 V at 0.08 A/cm2 to 1.87 V at 0.84 A/cm2 and evaluations of the resultant cell efficiencies. The model accurately reproduces the experimental voltage-current relationship (R2 >= 0.97). A subsequent parameter analysis, accounting for the given boundary conditions, shows that the charge transfer coefficient and electrolyte concentration significantly affect electrolysis performance, especially at the maximum current density investigated. The development of an electrochemical model for a market-ready anion exchange membrane electrolyzer, along with the analysis of performance affecting process parameters, contributes to future investigations into process simulation, system design, and scaling towards smart energy conversion.

In aerosol deposition, fine ceramic powders in sizes of less than typically 5 μm are deposited as a coating at room temperature. Aerosol deposition must be performed under a vacuum to apply such fine powders and avoid bow shock effects. According to experimental results, coating formation by aerosol deposition only occurs if particle velocities exceed a material-specific threshold velocity. Thus, knowledge of attained particle velocities over acceleration in the nozzle and under the expansion into a vacuum is essential for deriving conditions for successful deposition. In the present study, 3D CFD simulations were used to investigate the key geometric variables in particle acceleration. Three different nozzle geometries were investigated: a converging nozzle, a converging–diverging nozzle, and a converging nozzle followed by a constant cross section toward the exit. In addition, these three nozzle geometries were optimized to maximize the particle impact velocity. The results show that the converging–diverging nozzle supplies the highest particle velocities within this comparison. By the design of optimization, the particle velocities can be improved for all the geometry types. The most promising geometry from the CFD optimization was manufactured and compared to the original one, providing a gain in experimentally measured particle velocity of 24

In cold spray applications, optimum process conditions to accelerate particles may vary with different densities of the feedstock. These conditions could depend on the geometry of the spray nozzle, suggesting possible benefits of material-specific nozzle designs. The present study developed a nozzle geometry optimization concept based on three-dimensional computational fluid dynamics (3D-CFD) simulations to provide a specific nozzle design. Applying a design of experiments (DoE) approach, the proposed model seeks an optimal nozzle geometry, using aluminum Al6061 and pure copper with mean particle diameters of 40 µm as examples. Different geometry parameters were varied to reach the highest particle velocities before impact on the substrate, such as the nozzle’s divergent section length, throat cross section, and expansion ratio. The process gas was nitrogen with set stagnation pressure and temperature of 5 MPa and 500 °C, respectively. For high particle impact velocities, the simulation identified the divergent section length as the most influential parameter, followed by the throat cross section. In addition, the results show that the expansion ratio must be carefully tuned to avoid over-expansion of the gas already inside the nozzle, which is detrimental to the particle acceleration.

Modeling the impact of alloying on the hydrogenation properties of intermetallic compounds is a vital yet challenging task for hydrogen storage materials design: not only do these processes occur under thermodynamic para-equilibrium conditions, but for bcc-derived compounds, the task is further complicated through varying composition-dependent ordering transitions. Here, we tackle these challenges by providing a multicomponent thermodynamic modeling framework for FeTi, a representative bcc-derived material class, which is one of the most relevant room-temperature interstitial metal hydrides. We aim specifically to describe para-equilibrium FeTi-based multicomponent hydrides while ensuring compatibility with previously evaluated metallic systems. DFT point-defect calculations provide a physics-informed foundation to identify substitutional site preferences. Not only does our approach give detailed guidance for the selection of model parameters to evaluate phase equilibria for a broad range of FeTi-based multicomponent systems with high fidelity, but it also can be easily adopted to other interstitial hydrogen storage compounds.