A new route to synthesize the Mg(NH2)2–2LiH composite is proposed starting from magnesium waste alloy and LiH, after a multi-step treatment. This is an effective way to convert magnesium waste into light weight hydrogen storage materials.

This work investigates the hydrothermal synthesis and characterization of zeolite-4A from kaolin found in Ajebo, Nigeria calcined at 700 and 900 degrees C respectively. The synthesized zeolite-4A was further characterised using X-ray Fluorescence (XRF), Fourier Transform Infrared spectrometer (FTIR), Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD), Brunauer-Emmet-Teller (BET) surface area analysis as well as Differential Thermal Analysis/Thermo-gravimetric (TG). Water adsorption capacity tests were also carried out on the synthesized zeolite-4A. The results from the XRF measurements indicated that the amount of Al2O3 and SiO2 in the studied kaolin was similar to the standard kaolin composition making it a perfect candidate for zeolite-4A synthesis. FTIR showed the characteristic zeolite peaks while XRD confirmed the crystalline nature of the synthesized zeolite-4A. TG studies showed that the zeolite-4A samples were stable up to temperatures of 700 degrees C. This stability as well as the surface area and pore size of 7 A makes it potentially suitable for use in water treatment applications. The SEM showed cubic crystals which were typical of the morphology of zeolite-4A with water adsorption capacity of approximately 29%. These results indicate that zeolite-4A can be synthesized from kaolin found in Ajebo as an inexpensive alternative to traditionally sourced materials and also is suitable for use as adsorption agent.

Kaolin samples from Ajebo and Darazo in Nigeria were characterized and used to produce zeolite - A crystals. The thermal analysis indicates that both samples under gode-hydroxylation from 450oC to about 700oC and are converted to metakaolin with a weight lo ss of about 11.39 and 10.43% for the Ajebo and Darazo samples respectively. Characteristic OH, Al-OH, Si-OH and Si-O-Albands were confirmed in both samples with Infra-red spectroscopy studies. The X - ray diffraction patterns clearly show the presence of the characteristic peaks (12.35 and 24.88o ) of kaolinite with little quartz impurities. X - ray diffraction measurements (2Ɵ peaks at 7 – 18o and 21 – 35o ) and scanning electron micro graphs clearly show that zeolite - A crystals are produced. The microstructures of kaolin, metakaolin and zeolite - A crystals reveal the presence of platy crystals, amorphous spherical aggregates and cubic - shaped crystals with some amorphous gel respectively . The results show that both Ajebo and Darazo kaolin are suitable for zeolite - A synthesis. Keywords: Kaolin, Metakaolin, Thermal analysis, X - ray Diffraction, Zeolite - A

Magnesium has been studied as a potential hydrogen storage material for several decades because of its relatively high hydrogen storage capacity, fast sorption kinetics (when doped with transition metal based additives), and abundance. This research aims to study the possibility to use waste magnesium alloys to produce good quality MgH2. The production costs of hydrogen storage materials is still one of the major barriers disabling scale up for mobile or stationary application. The recycling of magnesium-based waste to produce magnesium hydride will significantly contribute to the cost reduction of this material. This study focuses on the effect of different parameters such as the addition of graphite and/or Nb2O5 as well as the effect of milling time on the material hydrogenation/de-hydrogenation performances. In addition, morphology and microstructural features are also evaluated for all the investigated materials.

The formation of MgNi2.5B2 upon dehydrogenation allows a reversible transfer of the boron atoms between the starting reactants and products.

Porous Al scaffolds were synthesised and melt-infiltrated with various eutectic metal borohydride mixtures (0.725LiBH(4)-0.275KBH(4), 0.68NaBH(4)-0.32KBH(4), 0.4NaBH(4)-0.6 Mg(BH4)(2)) to simultaneously act as both a confining framework and a reactive destabilising agent for H-2 release. The scaffolds were synthesised by sintering a pellet of NaAlH4/2 mol%TiCl3 at 450 degrees C under dynamic vacuum. During the sintering process the sodium alanate (NaAlH4) decomposed to Al metal. The vacuum applied at elevated temperature promoted the Na metal to vaporise and be extruded from the pellet. The pores of the resulting Al scaffold were created during removal of the H-2 and the Na from the body of the NaAlH4/2 mol%TiCl3 pellet. According to the morphological observations carried out by a Scanning Electron Microscope (SEM), melt-infiltrated eutectic mixtures of metal borohydrides were highly dispersed into the porous scaffolds. Temperature Programmed Desorption (TPD) experiments, revealed that the melt-infiltrated samples exhibited faster H-2 desorption kinetics in comparison to bulk samples, with onset temperatures (T-des) lower than the bulk by 150-250 degrees C. The as-synthesised porous Al scaffolds acted as a reactive containment vessel for these eutectic mixtures that simultaneously nanoconfined and destabilised the mixtures. (C) 2018 Published by Elsevier B.V.

Please do not adjust margins a. Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht GmbH, Max-Planck-Straße 1, D-21502, Geesthacht, Germany b.Pavia Hydrogen Lab, CSGI and Università di Pavia, Dipartimento di Chimica, Sezione di Chimica Fisica, Viale Taramelli, 16, 27100, Pavia, Italy c.Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2 P.O. Box 64, Helsinki, Finland d.ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, United Kingdom e.Servei de Ressonància Magnètica Nuclear, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain f.Department of Chemistry and NIS Centre, University of Torino, Via P. Giuria 7, Torino, Italy g.Departament de Física, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Cerdanyola del Vallès, Barcelona, Spain h.Helmut Schmidt University, Institute of Materials Technology, Hamburg, Germany Received 00th January 20xx, Accepted 00th January 20xx

Light metal hydrides are prone to react with oxygen and/or water to produce oxides and/or hydroxides leading to reduction of hydrogen capacities, and deterioration of the hydrogen storage properties. It is therefore critical to address these issues when the materials are to be exposed to air or moisture. In this work, the combination of light metal hydrides, Mg(NH2)(2)-nLiH with polymethylpentene (TPX (TM)), an air/moisture protective barrier is presented. It was found that the fabricated composites exhibit significant improvement of the metal hydrides stability in air. No oxidation reactions in air can be proven even after air exposure for 90 min. Extending the air-exposure time to 12 h, the reversible hydrogen capacities of these composites are much higher and more stable than they are in the case of the pure metal hydrides. In comparison to the pure metal hydrides, the composites retain the same hydrogen loading capacities and kinetic properties, with respect to the metal hydrides contents. Further, in situ synchrotron radiation powder X-ray radiation diffraction (SR-PXRD) experiments reveal that the thermal decomposition reaction pathways of the 90 min air-exposed composites are the same under air or H-2 atmosphere. Moreover, morphology analysis confirms that the metal hydrides remain stable in the polymeric matrix and the three-dimensional integrity is retained, even after performing tens of de/re-hydrogenation cycles. The present study shows a promising way to fabricate air-stable metal hydride-polymer composite hydrogen storage materials that can be handled in ambient conditions. (C) 2018 Elsevier Ltd. All rights reserved.

In previous studies, complex hydrides LiBH4 and Mg2FeH6 have been reported to undergo simultaneous dehydrogenation when ball-milled as composite materials (1 − x)LiBH4 + xMg2FeH6. The simultaneous hydrogen release led to a decrease of the dehydrogenation temperature by as much as 150 K when compared to that of LiBH4. It also led to the modified dehydrogenation properties of Mg2FeH6. The simultaneous dehydrogenation behavior between stoichiometric ratios of LiBH4 and Mg2FeH6 is not yet understood. Therefore, in the present work, we used the molar ratio x = 0.25, 0.5, and 0.75, and studied the isothermal dehydrogenation processes via pressure–composition–isothermal (PCT) measurements. The results indicated that the same stoichiometric reaction occurred in all of these composite materials, and x = 0.5 was the molar ratio between LiBH4 and Mg2FeH6 in the reaction. Due to the optimal composition ratio, the composite material exhibited enhanced rehydrogenation and reversibility properties: the temperature and pressure of 673 K and 20 MPa of H2, respectively, for the full rehydrogenation of x = 0.5 composite, were much lower than those required for the partial rehydrogenation of LiBH4. Moreover, the x = 0.5 composite could be reversibly hydrogenated for more than four cycles without degradation of its H2 capacity.

Reversible hydrogen storage over hydrides of light elements (HLEs) under ambient condition has been pursued actively for nearly two decades. However, because of unfavorable thermodynamics and/or severe kinetic barrier of HLEs, limited progress has been made. Here, it is demonstrated that the interaction of LiBH4 with Mg(NH2)2 and LiH, three of the most investigated HLEs, can lead to a fully reversible dehydrogenation/rehydrogenation cycle at temperatures below 373 K. More importantly, with the desorption enthalpy of 24 kJ (mol H2)−1 the dehydrogenation process at 1.0 bar H2 is theoretically possible to be as low as 266 K. Characterization of this combination of HLEs shows that LiBH4 serves as a reagent complexing with intermediates and products of the dehydrogenation of Mg(NH2)2‐LiH, and significantly alters the overall thermodynamic and kinetic properties of the system.

The doping effect of Sr(OH)2 on the Mg(NH2)2-2LiH system is investigated considering different amounts of added Sr(OH)2 in the range of 0.05 to 0.2 mol. Experimental results show that both the thermodynamic and the kinetic properties of Mg(NH2)2-2LiH are influenced by the presence of Sr(OH)2. The addition of 0.1 mol Sr(OH)2 leads to a decrease in both the dehydrogenation onset and peak temperatures of ca. 70 and 13 °C, respectively, and an acceleration in the de/re-hydrogenation rates of one time at 150 °C compared to Mg(NH2)2-2LiH alone. Based on differential scanning calorimetry (DSC) analysis, the overall reaction enthalpy of the 0.1 Sr(OH)2-doped sample is calculated to be 44 kJ per mol-H2 and there are two absorption events occurring in the doped sample instead of one in the pristine sample. For the applied experimental conditions, according to the in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and Fourier Transform Infrared spectroscopy (FT-IR) analysis, the reaction mechanism has been finally defined: Sr(OH)2, Mg(NH2)2 and LiH react with each other to form SrO, MgO and LiNH2 during ball milling. After heating, SrO interacts with Mg(NH2)2 producing MgO and Sr(NH2)2. Then Mg(NH2)2, LiNH2 and Sr(NH2)2 react with LiH to produce Li2NH, SrNH, Li2Mg(NH)2 and Li2Mg2(NH)3 in traces. After re-hydrogenation, LiSrH3, LiH and LiNH2 are formed along with amorphous Mg(NH2)2. The reasons for the improved kinetics are: (a) during dehydrogenation, the in situ formation of SrNH appears to increase the interfacial contacts between Mg(NH2)2 and LiH and also weakens the N-H bond of Mg(NH2)2; (b) during absorption, the formation of LiSrH3 at around 150 °C could be the key factor for improving the hydrogenation properties.

Mg2FeD6 is successfully synthesised with various degrees of purity using reactive ball milling and annealing under low pressure deuterium conditions to a maximum of 10 bar. The deuteride of the low cost ternary metal hydride Mg2FeH6, is synthesised to enable further characterisation studies such as isotopic exchange behaviour. Both on laboratory and industrial scales, keeping the pressure low reduces the need for expensive compression systems and also minimises the quantity of gas necessary for use; therefore it is important to assess synthesis under these cost effective conditions. This is especially the case when using a specialised gas such as high purity deuterium. The maximum pressure chosen is 10 bar, to comply with the High Pressure Safety Act in Japan. This Safety Act limits the use of any gas including hydrogen and deuterium to 10 bar eliminating the use of traditional synthesis methods for Mg2FeH6 or Mg2FeD6 synthesis at high pressure (120 bar). Ball milling parameters such as milling times, ball to powder ratios as well as sintering times were altered to achieve improved Mg2FeD6 yields under these low pressure conditions. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Metal hydrides (MHs) are promising candidates as thermal energy storage (TES) materials for concentrated solar thermal applications. A key requirement for this technology is a high temperature heat transfer fluid (HTF) that can deliver heat to the MHs for storage during the day, and remove heat at night time to produce electricity. In this study, supercritical water was used as a HTF to heat a prototype thermochemical heat storage reactor filled with MgH2 powder during H2 sorption, rather than electrical heating of the MH reactor. This is beneficial as the HTF flows through a coil of tubing embedded within the MH bed and is hence in better contact with the MgH2 powder. This internal heating mode produces a more uniform temperature distribution within the reactor by increasing the heat exchange surface area and reducing the characteristic heat exchange distances. Moreover, supercritical water can be implemented as a heat carrier for the entire thermal energy system within a concentrating solar thermal plant, from the receiver, through the heat storage system, and also within a conventional turbine-driven electric power generation system. Thus, the total system energy efficiency can be improved by minimising HTF heat exchangers.

In this work, the hydrogen absorption and desorption properties of the system K2[Zn(NH2)4]-8LiH are investigated in detail via in situ synchrotron radiation powder X-ray diffraction (SR-PXD), Fourier transform infrared spectroscopy (FT-IR), and volumetric methods. Upon milling, K2[Zn(NH2)4] and 8LiH react to form 4LiNH2-4LiH-K2ZnH4, and then 4LiNH2-4LiH-K2ZnH4 releases H2 in multiple steps. The final products of the desorption reaction are KH, LiZn13, and Li2NH. During rehydrogenation, KH reacts with LiZn13 under 50 bar of hydrogen producing K3ZnH5. This phase appears to enhance the hydrogenation process which after its formation at ca. 220 °C takes place in only 30 s. The system 4LiNH2-4LiH-K2ZnH4 is shown to be reversible under the applied conditions of vacuum at 400 °C for desorption and 50 bar of H2 at 300 °C for absorption.

In the framework of the European Cooperation in Science and Technology (COST) Action MP1103 Nanostructured Materials for Solid-State Hydrogen Storage were synthesized, characterized and modeled. This Action dealt with the state of the art of energy storage and set up a competitive and coordinated network capable to define new and unexplored ways for Solid State Hydrogen Storage by innovative and interdisciplinary research within the European Research Area. An important number of new compounds have been synthesized: metal hydrides, complex hydrides, metal halide ammines and amidoboranes. Tuning the structure from bulk to thin film, nanoparticles and nanoconfined composites improved the hydrogen sorption properties and opened the perspective to new technological applications. Direct imaging of the hydrogenation reactions and in situ measurements under operando conditions have been carried out in these studies. Computational screening methods allowed the prediction of suitable compounds for hydrogen storage and the modeling of the hydrogen sorption reactions on mono-, bi-, and three-dimensional systems. This manuscript presents a review of the main achievements of this Action.

K2[Mn(NH2)4] and K2[Zn(NH2)4] were successfully synthesized via a mechanochemical method. The mixture of K2[Mn(NH2)4] and LiH showed excellent rehydrogenation properties. In fact, after dehydrogenation K2[Mn(NH2)4]-8LiH fully rehydrogenates within 60 seconds at ca. 230 °C and 5 MPa of H2. This is one of the fastest rehydrogenation rates in amide-hydride systems known to date. This work also shows a strategy for the synthesis of transition metal nitrides by decomposition of the mixtures of M[M'(NH2)n] (where M is an alkali or alkaline earth metal and M' is a transition metal) and metal hydrides.

The Ca(BH4)2-Mg2NiH4 system presented here is, to the best of our knowledge, the first described Ca(BH4)2-based hydride composite that reversibly transfers boron from the Ca-based compound(s) to the reaction partner. The ternary boride MgNi2.5B2 is formed upon dehydrogenation and the formation of Ca(BH4)2 upon rehydrogenation is confirmed.

Hydrogen sorption properties of the LiH-MgB2 system doped with TiCl3 were investigated with respect to milling conditions (milling times, ball to powder (BTP) ratios, rotation velocities and degrees of filling) to form the reactive hydride composite (RHC) LiBH4-MgH2. A heuristic model was applied to approximate the energy transfer from the mill to the powders. These results were linked to experimentally obtained quantities such as crystallite size, specific surface area (SSA) and homogeneity of the samples, using X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET) method and scanning electron microscopy (SEM), respectively. The results show that at approximately 20 kJ g (1) there are no further benefits to the system with an increase in energy transfer. This optimum energy transfer value indicates that a plateau was reached for MgB2 crystallite size therefore the there was also no improvement of reaction kinetics due to no change in crystallite size. Therefore, this study shows that an optimum energy transfer value was reached for the LiH-MgB2 system doped with TiCl3. (C) 2014 Elsevier B.V. All rights reserved.

The alkali metal amidozincates Li4 [Zn(NH2)4](NH2)2 and K2[Zn(NH2)4] were, to the best of our knowledge, studied for the first time as hydrogen storage media. Compared with the LiNH2-2 LiH system, both Li4 [Zn(NH2)4](NH2)2-12 LiH and K2[Zn(NH2)4]-8 LiH systems showed improved rehydrogenation performance, especially K2[Zn(NH2)4]-8 LiH, which can be fully hydrogenated within 30 s at approximately 230 °C. The absorption properties are stable upon cycling. This work shows that ternary amides containing transition metals have great potential as hydrogen storage materials.