Applications Of Metal Hydrides Research Articles

Elaboration and outlook for metal hydride applications in future hydrogen-powered aviation

Elaboration and outlook for metal hydride applications in future hydrogen-powered aviation

From nickel–metal hydride batteries to advanced engines: A comprehensive review of hydrogen's role in the future energy landscape

Hydrogen has emerged as a disruptive force in the energy landscape, poised to revolutionise the automotive sector with its use in both fuel cell and internal combustion engines. This article covered two topics: application of metal hydrides for hydrogen storage and use of cutting-edge engine technology in hydrogen-powered vehicles. This article begins with discussing the different characteristics of materials that are used to store hydrogen. Metal hydrides, rare earth elements, and carbon-based compounds are among the materials that are carefully studied in this work. Understanding how effectively these materials can store hydrogen was another goal of this research. In order to fully utilize hydrogen's potential, it is imperative to compare them with conventional fossil fuels highlighting their significance. Additionally, this study explains how hydrogen can be used to power existing and newer automobile vehicles. Also discussed are the viability and potential mechanisms of operation for various hydrogen-using engine technologies, such as compression ignition and spark ignition engines. Cutting-edge on vehicles with fuel cell and engine technology powered by hydrogen along with their challenges are explained. They include discussions of several techniques such as homogenous charge compression ignition (HCCI), dual-fuel, and reactivity-controlled combustion ignition (RCCI). Additionally, the advantages and disadvantages of utilizing hydrogen in these state-of-the-art engine technologies are discussed. This research offers insights on the future of automobiles in addition to hydrogen storage. This study points the path towards a more creative and sustainable energy environment in which hydrogen plays a major role in the storage and utilization for automobile vehicles.

Pulsed laser activation method for hydrogen storage alloys

The activation procedures of metals and alloys, crucial for hydrogen absorption, pose a significant challenge in the large-scale application of metal hydrides. This study introduces, for the first time, the Pulsed Laser Activation (PLA) method for hydrogen storage alloys. We demonstrated that the hydrogen storage ability of an aged (exposed to air for 30 days) Ti11V30Nb28Cr31 body-centered cubic alloy can be restored by scanning the sample with a nanosecond pulsed laser for only 3 min. X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) analyses were conducted to investigate structural features that changed in the Ti11V30Nb28Cr31 samples after ageing and after the PLA treatment. Surface remelting, the formation of oxide layers, and crack formation appear to be factors influencing the hydrogen storage ability of the Ti11V30Nb28Cr31 alloy activated via PLA. While the mechanisms involved in the PLA are not clear yet, this procedure paves the way for the development of activation methods based on laser-metal interactions that can be easily applied to metals and alloys for hydrogen storage systems.

Gas-phase applications of metal hydrides

Applications of metal hydrides (MHs) utilise a reversible interaction of hydride-forming metals, alloys and intermetallic compounds with hydrogen. The reversible process of the formation-decomposition of the MH when interacting with hydrogen allows to utilise several unique features of the hydrogenation-dehydrogenation process. These features enable efficient storage of hydrogen gas resulting in a high volumetric efficiency of hydrogen storage while also storing thermal energy and converting it to the energy of compressed hydrogen gas or utilising the hydrides for the electrochemical energy conversion and storage. Thus, MH applications are very important as the components of the hydrogen energy systems integrating hydrogen supply from the metal hydride store and PEM fuel cells. Compact and safe hydrogen storage together with utilisation of the waste heat opens up for the commercial market of the hydrogen energy systems of green energy storage and supply.

Piezovoltaics from PdHx

Metal hydrides have wide applications in energy science. A large pressure gradient propels the hydrogen atoms out. A piezovoltaic device, a pressure gradient-driven battery, can therefore be realized when the migrations of protons and electrons are separated by different conductors. Here we investigate the piezovoltaic performance of PdHx with various proton conductors as electrolytes and experimentally detect an output current of ≲40 nA and a voltage of ∼0.8 V for a 3 μg sample. We also demonstrate the escape of hydrogen atoms from a palladium lattice under an increasing pressure gradient using X-ray diffraction. The relationship between piezovoltaics (chemical process) and piezoelectricity (physical process) is like that between a chemical battery and a capacitor. Our work demonstrates the piezovoltaic application of metal hydrides and provides a new way to convert mechanical energy into electrical energy.

The power of multifunctional metal hydrides: A key enabler beyond hydrogen storage

The metal-hydrogen interaction and its equilibrium conditions allow for distinct properties in metal hydrides (MHs). Based on these properties, MHs have been found to enable a range of novel technologies from thermal compression to sensors, and catalysis. Ni-MH batteries are currently the main application of hydrides in the market. However, new battery concepts such as Li-MgH 2 , Mn-MH, and hydride-based solid electrolytes have emerged. Fuel cells based on hydrides have also been proposed to convert the chemical “hydride energy” into electrical energy. Based on their unique thermodynamic properties, MHs are also the basis of new concepts in hydrogen compression, heat pumps, cooling systems, and thermal energy storage. Other important applications, including catalysis and chemical speciation have also been considered owing the chemical properties of hydrides. Sensors and smart mirrors based on the dynamic optical, structural, and electrical properties of MHs have been developed. This review summarizes current state-of-the-art along the multiple applications of MHs and provides recommendations on the future progress required to enable a more widespread adoption of MHs beyond their use as hydrogen storage materials. • Hydrides have a broad range of applications. • Enabling alternative applications beyond hydrogen storage could help in finally enabling the commercialization of hydrides. • The continuous development of new hydrides materials remains a critical enabler.

Applications of metal hydride based thermal systems: A review

Conventionally, metal hydrides have been explored for their application in hydrogen storage systems. However, metal hydride based thermal systems have attracted huge attention for a wide variety of applications such as thermal storage, hydrogen compression, heating, cooling, etc due to the availability of hydride materials covering a wide range of operating temperatures and pressures. These can deliver high energy densities leading to compact systems for stationary as well as mobile applications. Moreover, the thermal properties of hydrides can be tailored by tuning the proportion of constituent metals to fit the required thermal application. As metal hydride based thermal systems are identified as potential candidates for global energy needs, it is essential to understand their modes of operations and the status of their development. This paper presents a comprehensive review of theoretical and experimental studies on thermal applications of metal hydrides which include refrigeration, heat transformers, heat pumps, and thermal energy storage. Also, hydride selection criteria for specific applications and heat transfer augmentation techniques adopted to improve the performance of hydride beds are discussed.

Hydrogenation Kinetics of Metal Hydride Catalytic Layers.

Catalyzing capping layers on metal hydrides are employed to enhance the hydrogenation kinetics of metal hydride-based systems such as hydrogen sensors. Here, we use a novel experimental method to study the hydrogenation kinetics of catalyzing capping layers composed of several alloys of Pd and Au as well as Pt, Ni, and Ru, all with and without an additional PTFE polymer protection layer and under the same set of experimental conditions. In particular, we employ a thin Ta film as an optical indicator to study the kinetics of the catalytic layers deposited on top of it and which allows one to determine the absolute hydrogenation rates. Our results demonstrate that doping Pd with Au results in significantly faster hydrogenation kinetics, with response times up to five times shorter than Pd through enhanced diffusion and a reduction in the activation energy. On the other hand, the kinetics of non-Pd-based materials turn out to be significantly slower and mainly limited by the diffusion through the capping layer itself. Surprisingly, the additional PTFE layer was only found to improve the kinetics of Pd-based capping materials and has no significant effect on the kinetics of Pt, Ni, and Ru. Taken together, the experimental results aid in rationally choosing a suitable capping material for the application of metal hydrides and other materials in a hydrogen economy. In addition, the used method can be applied to simultaneously study the hydrogenation kinetics in thin-film materials for a wide set of experimental conditions.

Synthesis of Ti Powder from the Reduction of TiCl4 with Metal Hydrides in the H2 Atmosphere: Thermodynamic and Techno-Economic Analyses

Titanium hydride (TiH2) is one of the basic materials for titanium (Ti) powder metallurgy. A novel method was proposed to produce TiH2 from the reduction of titanium tetrachloride (TiCl4) with magnesium hydride (MgH2) in the hydrogen (H2) atmosphere. The primary approach of this process is to produce TiH2 at a low-temperature range through an efficient and energy-saving process for further titanium powder production. In this study, the thermodynamic assessment and technoeconomic analysis of the process were investigated. The results show that the formation of TiH2 is feasible at low temperatures, and the molar ratio between TiCl4 and metal hydride as a reductant material has a critical role in its formation. Moreover, it was found that the yield of TiH2 is slightly higher when CaH2 is used as a reductant agent. The calculated equilibrium composition diagrams show that when the molar ratio between TiCl4 and metal hydrides is greater than the stoichiometric amount, the TiCl3 phase also forms. With a further increase in this ratio to greater than 4, no TiH2 was formed, and TiCl3 was the dominant product. Furthermore, the technoeconomic study revealed that the highest return on investment was achieved for the production scale of 5 t/batch of Ti powder production, with a payback time of 2.54 years. The analysis shows that the application of metal hydrides for TiH2 production from TiCl4 is technically feasible and economically viable.

Hydrogen diffusion in AB5 type metal hydride anodes by potentiostatic intermittent titration technique

Metal hydrides are widely used for hydrogen-related energy storage applications due to their high volumetric capacity, safety, and selectivity to absorb hydrogen. One of the main applications of metal hydrides is their use as electrode material in Ni-MH batteries. Metal hydride electrodes provide high energy density, high rate capability, tolerance to overcharge and over-discharge, and no electrolyte consumption during the charge/discharge cycle. One of the key factors of metal hydride electrode performance is a hydrogen diffusion from the electrolyte to the bulk of metal hydride material. In the present study, effective hydrogen diffusion coefficients in AB5 type metal hydride electrodes during the charging process are investigated employing potentiostatic intermitent titration technique.

Performance investigation of a multi-stage sorption hydrogen compressor

Among several thermodynamic applications of metal hydrides, sorption hydrogen compressor (SHC) is more attractive for real-time application due to ease of construction and operation. In the present study, a four-stage sorption hydrogen compressor is proposed with detailed working principle for the compression output of >500 bar pressure. By adopting the screening methodology, four metal hydrides, i.e. La0.9Ce0.1Ni5, Ti0.99Zr0.01V0.43Fe0.99Cr0.05Mn1.5, MmNi5 and TiCrMn are selected for stages – 1, 2, 3 and 4 respectively with the supply temperature of 298 K and discharge temperatures of 373 K. The performance of sorption hydrogen compressor is estimated through finite volume approach and thermodynamic simulation in terms of variations in metal hydride bed pressure, temperature, hydrogen transmission, compressor work and efficiency. The numerical model is validated with experimentally measured metal hydride bed temperature and hydrogen concentration for single-stage hydrogen compressor, which are observed to be in good agreement. The cycle time of multi-stage SHC is predicted to be ~100 min with the maximum compression ratio of 73 with an overall efficiency of 10.62% employing 0.5 kg of each alloy and supply pressure of 9.5 bar. It is also observed that the discharge temperature greatly influences system performance. The dynamic performance of the system is also estimated with the implementation of simulation generated property data and observed that the performance parameters increased with the progression of hydrogen transmission.

Novel reactor design for metal hydride cooling systems

In this paper a plate reactor for metal hydride applications is presented and experimentally characterized. Through an optimized heat transfer characteristic the concept is suitable for all metal hydride high performance systems, where short reaction times are required. The experimental characterization using metal hydride Hydralloy® C5 reveals that very short half-cycle times (t < 60 s) are feasible enabling small and compact systems. With regard to the application of an open metal hydride cooling system for fuel cell vehicles and a cooling temperature of 10 °C, single reactor experiments lead to a high specific cooling power of 1.31 kW kgMeH−1. In a continuous working system where thermal losses are considered, still 690 W kgMeH−1 can be reached.

Thermodynamic analysis of novel multi stage multi effect metal hydride based thermodynamic system for simultaneous cooling, heat pumping and heat transformation

Metal hydride based heat transformer, heat pumping and cooling systems are the most important thermodynamic applications of metal hydrides due to the ability to utilise waste heat as input. For attaining higher efficiency and extensive operating temperature range, novel four alloys multi stage multi effect thermodynamic system is proposed. This paper brings systematic study of four alloys based thermodynamic cycle for simultaneous cooling, heat pumping and heat transformation. The performance of this thermodynamic cycle was studied using different combination of AB5 – type (La and Mm based) metal hydrides. The effect of operating temperatures (such as hot, driving, intermediate and cold temperatures) and different metal hydride combinations on the thermodynamic cycle performance was studied. Additionally, the cycle performance i.e. coefficient of performance (COP), specific alloy output (S), cooling capacity (CC), etc. were compared with three alloys based simultaneous heating and cooling system. The study shows that the employment of four alloy system for the development of metal hydride based thermodynamic system improves cycle efficiency as well as specific alloy output and facilitates extensive operating temperature range.

Metal hydrides for energy applications - classification, PCI characterisation and simulation

This short review discusses the classification, pressure concentration isotherm (PCI) characterisation and applications of metal hydrides. Special attention is paid to describe the design criterion and fabrication of Sievert's apparatus and PCI characterisation methods of metal hydrides. Different classes of metal hydrides and their properties are broadly discussed. Also, some of the important applications of metal hydrides are presented. The absorption and desorption PCIs of four Lanthanum based alloys namely La0.9Ce0.1Ni5, La0.8Ce0.2Ni5, LaNi4.7Al0.3 and LaNi4.6Al0.4 are measured using volumetric method in the temperature range of 20 to 80 °C. Later, different PCI simulation models are compared, and Zhou's model is used to simulate the experimentally measured PCIs at different temperatures. It is found that the simulation results are in good agreement with the experimentally measured results. Copyright © 2016 John Wiley & Sons, Ltd.

Application of metal hydrides as pore-forming agents for obtaining metal foams

One of the well-known ways of metal foam production consists of adding powder which releases gaseous decomposition product at high temperatures into a melted metal. When producing aluminum foams, titanium hydride powder is most frequently used, while its main disadvantage is its insufficient thermal stability. This results in a premature gas loss in the process of the powder introduction into a melted metal matrix. The paper discloses approaches to suppression of the undesirable premature titanium hydride decomposition by means of its preliminary thermal treatment, as well as the external pressure elevation over that of the system being processed during the foam formation. A method of using the thermally treated powder is proposed, in order to obtain aluminum foam samples having a required geometry and sufficiently uniform porous structure.

Niche applications of metal hydrides and related thermal management issues

This short review highlights and discusses the recent developments and thermal management issues related to metal hydride (MH) systems for hydrogen storage, hydrogen compression and heat management (refrigeration, pump and upgrade, etc.). Special attention is paid to aligning the system features with the requirements of the specific application. The considered system features include the MH material, the MH bed on the basis of its corresponding MH container, as well as the layout of the integrated system.

First-principles prediction of new complex transition metal hydrides for high temperature applications.

Metal hydrides with high thermodynamic stability are desirable for high-temperature applications, such as those that require high hydrogen release temperatures or low hydrogen overpressures. First-principles calculations have been used previously to identify complex transition metal hydrides (CTMHs) for high temperature use by screening materials with experimentally known structures. Here, we extend our previous screening of CTMHs with a library of 149 proposed materials based on known prototype structures and charge balancing rules. These proposed materials are typically related to known materials by cation substitution. Our semiautomated, high-throughput screening uses density functional theory (DFT) and grand canonical linear programming (GCLP) methods to compute thermodynamic properties and phase diagrams: 81 of the 149 materials are found to be thermodynamically stable. We identified seven proposed materials that release hydrogen at higher temperatures than the associated binary hydrides and at high temperature, T > 1000 K, for 1 bar H2 overpressure. Our results indicate that there are many novel CTMH compounds that are thermodynamically stable, and the computed thermodynamic data and phase diagrams should be useful for selecting materials and operating parameters for high temperature metal hydride applications.

Thermally Driven Metal Hydride Hydrogen Compressor for Medium-Scale Applications

A promising method of hydrogen compression driven by low-grade heat and not requiring the usage of moving parts, is the application of metal hydrides (MH). However, being upscaled to higher productivities necessary for industrial processes (≥1 m3 H2/h STP), the method will inevitably meet a number of problems related to complication of system layout, high costs and significant labour resources for the manufacturing, and low thermal efficiency.This work presents a development of a prototype MH compressor operating in a temperature range 20 to 150°C and providing compression of hydrogen from 10 to 200bar with average productivity up to 1 m3/h. The compressorrealises two stage layout where the first stage uses AB5-and the second AB2-type hydride-forming intermetallic alloys. A special engineering solution allows for the usage of quite big MH containers (up to 15kg of the MH material, or ∼2 m3 STP H2 capacity), so that the required productivity is provided by just four containers assembled in two compression elements each of which comprises one first- and one second-stage MH containers. The compressor's layout also provides heat regeneration thus reducing the consumption of hot and cold heat transfer fluids and increasing the overall efficiency.

Analysis of a novel metal hydride cycle for simultaneous heating and cooling

Out of the many promising applications of metal hydrides, refrigeration, heat pumping and heat transformation are important. In order to achieve improved performance, a novel three-alloy cycle is proposed in which, for heat input at an intermediate temperature, heat outputs at high temperature and also at warm temperature are obtained in addition to refrigeration. The performance of this cycle using the alloys LaNi 4.6Sn 0.4, LaNi 4.7Al 0.3 and MmNi 4.5Al 0.5 is studied based on thermodynamics and reaction kinetics. Coefficients of performance, half-cycle times and specific alloy outputs are evaluated.

The recent research, development and industrial applications of metal hydrides in the People's Republic of China

Chief accomplishments in the research and development of hydrogen storage alloys and hydride technology in recent years in the People's Republic of China are summarized and reported.