Laves type intermetallic compounds as hydrogen storage materials: A review

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Hydrogen storage behavior of magnesium catalyzed by nickel-graphene nanocomposites

In present study nanocomposites of Graphene Like Material (GLM) and nickel containing 5–60 wt % Ni were prepared by a co-reduction of graphite oxide and Ni2+ ions. These nanocomposites served as effective catalysts of hydrogenation-dehydrogenation of magnesium based materials and showed a high stability on cycling. Composites of magnesium hydride with Ni/GLM were prepared by high-energy ball milling in hydrogen. The microstructures and phase compositions of the studied materials were characterized by XRD, SEM and TEM showing that Ni nanoparticles have size of 2–5 nm and are uniformly distributed in the composites. The kinetic curves of hydrogen absorption and desorption by the composites were measured using a Sievert's type laboratory setup and were analyzed using the Avraami – Erofeev approach

Metal hydride hydrogen compressors: A review

AbstractMetal hydride (MH) thermal sorption compression is an efficient and reliable method allowing a conversion of energy from heat into a compressed hydrogen gas. The most important component of such a thermal engine – the metal hydride material itself – should possess several material features in order to achieve an efficient performance in the hydrogen compression. Apart from the hydrogen storage characteristics important for every solid H storage material (e.g. gravimetric and volumetric efficiency of H storage, hydrogen sorption kinetics and effective thermal conductivity), the thermodynamics of the metal–hydrogen systems is of primary importance resulting in a temperature dependence of the absorption/desorption pressures). Several specific features should be optimised to govern the performance of the MH-compressors including synchronisation of the pressure plateaus for multi-stage compressors, reduction of slope of the isotherms and hysteresis, increase of cycling stability and life time, together with challenges in system design associated with volume expansion of the metal matrix during the hydrogenation.The present review summarises numerous papers and patent literature dealing with MH hydrogen compression technology. The review considers (a) fundamental aspects of materials development with a focus on structure and phase equilibria in the metal–hydrogen systems suitable for the hydrogen compression; and (b) applied aspects, including their consideration from the applied thermodynamic viewpoint, system design features and performances of the metal hydride compressors and major applications

The use of economic-mathematical modelling in the management of the company's capital

Обґрунтоване визначення складу і розміру капіталу є вкрай необхідним для об’єктивного оцінювання рівня ефективності виробництва, а також виявлення реального співвідношення між власним та позичковим капіталом з тим, щоб не перейти межу, за якою подальше залучення кредитних ресурсів може нести в собі загрози нормальному функціонуванню підприємства. Крім того, аналіз структури капіталу дозволить встановити напрями оптимізації величини його складових елементів з метою більш раціонального їх використання.А reasonable determination of the composition and size of capital is vital for an objective assessment of the level of production efficiency, and identifying real balance between its own and loan capital, in order not to cross the line beyond which a further attraction of credit resources may carry threats to the normal functioning of the enterprise. In addition, the analysis of the capital structure will set the direction of optimization values of its components to more efficient use

Hydrogen absorption study of high-energy reactive ball milled Mg composites with palladium additives

Hydrogenation behaviour, structure, morphology and dehydrogenation/re-hydrogenation performances of Mg–Pd nanocomposites prepared by high-energy reactive ball milling in H2 (HRBM) of Mg in the presence of amorphous and crystalline Pd black (0.1–5 wt.%) were studied. Improvements of hydrogenation kinetics during HRBM were observed only for the materials prepared using crystalline Pd black. The obtained nanocomposites were characterised by modest improvements in their dehydrogenation and re-hydrogenation performances associated with the formation of Mg–Pd intermetallides.Web of Scienc

The use of metal hydrides in fuel cell applications

This paper reviews state-of-the-art developments in hydrogen energy systems which integrate fuel cells with metal hydride-based hydrogen storage. The 187 reference papers included in this review provide an overview of all major publications in the field, as well as recent work by several of the authors of the review. The review contains four parts. The first part gives an overview of the existing types of fuel cells and outlines the potential of using metal hydride stores as a source of hydrogen fuel. The second part of the review considers the suitability and optimisation of different metal hydrides based on their energy efficient thermal integration with fuel cells. The performances of metal hydrides are considered from the viewpoint of the reversible heat driven interaction of the metal hydrides with gaseous H2. Efficiencies of hydrogen and heat exchange in hydrogen stores to control H2 charge/discharge flow rates are the focus of the third section of the review and are considered together with metal hydride-fuel cell system integration issues and the corresponding engineering solutions. Finally, the last section of the review describes specific hydrogen-fuelled systems presented in the available reference data.IS

Modelling of metal hydride hydrogen compressors from thermodynamics of hydrogen – Metal interactions viewpoint: Part I. Assessment of the performance of metal hydride materials

This work presents a model to determine productivity and heat consumption of hydrogen compression utilising metal hydrides (MH) by using Pressure – Composition – Temperature (PCT) diagrams of the MH materials at defined operating conditions – temperatures and hydrogen pressures. The present Part I is focused on the analysis of hydrogen compression performances of several AB5- and AB2-type intermetallic alloys which, when operating between temperatures of 20 and 150 °C, provide H2 compression up to 500 atm, with a cycle productivity about 100 NL H2/kg MH and compression ratio of up to 10, at H2 suction pressure below 10–15 atm, or up to 5 at higher suction pressures. We show that calculated cycle productivities of hydrogen compression are related to the operating conditions and significantly vary for the different MH materials, even though showing similar trends in their changes

Metal hydride beds-phase change materials: Dual mode thermal energy storage for medium-high temperature industrial waste heat recovery

Heat storage systems based on two-tank thermochemical heat storage are gaining momentum for their utilization in solar power plants or industrial waste heat recovery since they can e ciently store heat for future usage. However, their performance is generally limited by reactor configuration, design, and optimization on the one hand and most importantly on the selection of appropriate thermochemical materials. Metal hydrides, although at the early stage of research and development (in heat storage applications), can o er several advantages over other thermochemical materials (salt hydrates, metal hydroxides, oxide, and carbonates) such as high energy storage density and power density. This study presents a system that combines latent heat and thermochemical heat storage based on two-tank metal hydrides. The systems consist of two metal hydrides tanks coupled and equipped with a phase change material (PCM) jacket

Poisoning-tolerant metal hydride materials and their application for hydrogen separation from CO2/CO containing gas mixtures

Metal hydride materials offer attractive solutions in addressing problems associated with hydrogen separation and purification from waste flue gases. However, a challenging problem is the deterioration of hydrogen charging performances resulting from the surface chemical action of electrophilic gases. In this work, the feasibility study of poisoning tolerance of surface modified AB5-type hydride forming materials and their application for hydrogen separation from process gases containing carbon dioxide and monoxide was carried out. Target composition of La(Ni,Co,Mn,Al)5 substrate was chosen to provide maximum reversible hydrogen capacity at the process conditions. The selected substrate alloy has been shown to be effectively surface-modified by fluorination followed by electroless deposition of palladium. The surface-modified material exhibited good coating quality, high cycle stability and minimal deterioration of kinetics of selective hydrogen absorption at room temperature, from gas mixtures containing 10% CO2 and up to 100 ppm CO. The experimental prototype of a hydrogen separation unit, based on the surface-modified metal hydride material, was tested and exhibited stable hydrogen separation and purification performances when exposed to feedstocks containing concentrations of CO2Web of Scienc

Magnesium–carbon hydrogen storage hybrid materials produced by reactive ball milling in hydrogen

Time-resolved studies uncovered kinetics and mechanism of Mg–hydrogen interactions during High energy reactive ball milling in hydrogen (HRBM) in presence of various types of carbon, including graphite (G), activated carbon (AC), multi-wall carbon nanotubes (MWCNT), expandable (EG) and thermally-expanded (TEG) graphite. Introduction of carbon significantly changes the hydrogenation behaviour, which becomes strongly dependent on the nature and amount of carbon additive. For the materials containing 1 wt.% AC or TEG, and 5 wt.% MWCNT, the hydrogenation becomes superior to that for the individual magnesium and finishes within 1 h. Analysis of the data indicates that carbon acts as a carrier of the ‘‘activated’’ hydrogen by a mechanism of spill-over. For Mg–G the hydrogenation starts from an incubation period and proceeds slower. An increase in the content of EG and TEG above 1 wt.% results in the deterioration of the hydrogenation kinetics. The effect of carbon additives has roots in their destruction during the HRBM to form graphene layers encapsulating the MgH2 nanoparticles and preventing the grain growth. This results in an increase of absorption–desorption cycle stability and a decrease of the MgH2 crystallite size in the re-hydrogenated Mg–C hybrid materials (40–125 nm) as compared to Mg alone (180 nm).Web of Scienc