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A new radio telescope in the Atacama desert, Chile, is currently under design and envisaged to be powered by an off-grid energy system of photovoltaic arrays during the day-time and a hybrid energy storage system for non-sunny hours. Similar isolated solar energy systems employ Lithium-ion or Lead-acid batteries as storage, which either increase the pressure on critical materials like lithium and cobalt or contain lead which mining brings a set of harmful environmental impacts. Hydrides based on intermetallic compounds are emerging as a viable solution for energy storage in stationary applications and are particularly appealing due to their abundance and non-toxicity. Here, by developing a multi-objective techno-environmental optimization, we size a power system that can fuel the telescope’s demand economically while also maintaining a low life cycle carbon footprint. The optimization includes life cycle inventory data of potential components next to costs, including monocrystalline photovoltaic arrays, lithium-ion batteries, hydrogen storage in metal hydrides and as compressed gas, alkaline electrolyzers, PEM fuel cells and diesel generators.Pure techno-economical optimization without life-cycle inventory optimizes towards power systems with up to 32% of curtailed photovoltaic power. Levelized costs of electricity resulted in $120/MWh with photovoltaics, hybrid storage systems and diesel generators as a backup, and $140/MWh for systems relying on solely batteries and photovoltaics. With our optimization, we propose a system resulting in a low life cycle carbon footprint and acceptable electricity prices, analyzing indirect carbon emissions of the stationary system as well as costs.The life-cycle carbon footprint optimization performed allows both the remote telescope in question and other off-grid energy systems to make informed decisions on sustainable solutions to fuel their power needs.

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM, Hydrides based on magnesium and intermetallic compounds provide a viable solution to the challenge of energy storage from renewable sources, thanks to their ability to absorb and desorb hydrogen in a reversible way with a proper tuning of pressure and temperature conditions. Therefore, they are expected to play an important role in the clean energy transition and in the deployment of hydrogen as an efficient energy vector. This review, by experts of Task 40 'Energy Storage and Conversion based on Hydrogen' of the Hydrogen Technology Collaboration Programme of the International Energy Agency, reports on the latest activities of the working group 'Magnesium- and Intermetallic alloys-based Hydrides for Energy Storage'. The following topics are covered by the review: multiscale modelling of hydrides and hydrogen sorption mechanisms; synthesis and processing techniques; catalysts for hydrogen sorption in Mg; Mg-based nanostructures and new compounds; hydrides based on intermetallic TiFe alloys, high entropy alloys, Laves phases, and Pd-containing alloys. Finally, an outlook is presented on current worldwide investments and future research directions for hydrogen-based energy storage

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM, Industrial and public interest in hydrogen technologies has risen strongly recently, as hydrogen is the ideal means for medium to long term energy storage, transport and usage in combination with renewable and green energy supply. In a future energy system, the production, storage and usage of green hydrogen is a key technology. Hydrogen is and will in future be even more used for industrial production processes as a reduction agent or for the production of synthetic hydrocarbons, especially in the chemical industry and in refineries. Under certain conditions material based systems for hydrogen storage and compression offer advantages over the classical systems based on gaseous or liquid hydrogen. This includes in particular lower maintenance costs, higher reliability and safety. Hydrogen storage is possible at pressures and temperatures much closer to ambient conditions. Hydrogen compression is possible without any moving parts and only by using waste heat. In this paper, we summarize the newest developments of hydrogen carriers for storage and compression and in addition, give an overview of the different research activities in this field

This paper is a critical review of selected real-world energy storage systems based on hydrogen, ranging from lab-scale systems to full-scale systems in continuous operation. 15 projects are presented with a critical overview of their concept and performance. A review of research related to power electronics, control systems and energy management strategies has been added to integrate the findings with outlooks usually described in separate literature. Results show that while hydrogen energy storage systems are technically feasible, they still require large cost reductions to become commercially attractive. A challenge that affects the cost per unit of energy is the low energy efficiency of some of the system components in real-world operating conditions. Due to losses in the conversion and storage processes, hydrogen energy storage systems lose anywhere between 60 and 85% of the incoming electricity with current technology. However, there are currently very few alternatives for long-term storage of electricity in power systems so the interest in hydrogen for this application remains high from both industry and academia. Additionally, it is expected that the share of intermittent renewable energy in power systems will increase in the coming decades. This could lead to technology development and cost reductions within hydrogen technology if this technology is needed to store excess renewable energy. Results from the reviewed projects indicate that the best solution from a technical viewpoint consists in hybrid systems where hydrogen is combined with short-term energy storage technologies like batteries and supercapacitors. In these hybrid systems the advantages with each storage technology can be fully exploited to maximize efficiency if the system is specifically tailored to the given situation. The disadvantage is that this will obviously increase the complexity and total cost of the energy system. Therefore, control systems and energy management strategies are important factors to achieve optimal results, both in terms of efficiency and cost. By considering the reviewed projects and evaluating operation modes and control systems, new hybrid energy systems could be tailored to fit each situation and to reduce energy losses.

Hydrogen, the simplest of all molecules, made of the simplest of all atoms, is a material that has successfully accomplished many historic missions: it has powered the engines of space rockets and has served in the ammonia-based fertilizer revolution, the iron and steel sector, and electronics manufacturing. But the task of putting hydrogen in the center of the global energy scene has proven tantalizing, perpetually coming closer to materialization, but repeatedly being pushed to the future. Is it possible that the time has arrived for hydrogen to finally come into its own?

In this paper, we propose a novel parameter initial value estimation method of Lithium-ion battery for state of charge (SOC) estimation by using Local Regression Modeling (LRM) and Vector Fitting (VF). To estimate SOC accurately using nonlinear Extended Kalman Filter(EKF), an adequate set of initial parameters of the battery model are required. Therefore, we apply LRM and VF method to derive the initial parameters and the battery model from a constructed database of frequency response data. In addition, we demonstrate the SOC estimation method using EKF by the determined initial value and model. Finally, the effectiveness of the proposed method is shown via several experimental results.

In this paper, we report the microstructure and first hydrogenation properties of TiFe cast with 4 wt.% of Zr. Measurements were made in as-cast state and after processing by ball milling and cryomilling. It was found that ball milling and cryomilling significantly reduced the particle/crystallite sizes with most of the reduction occurring during the first 15 min of milling. While the cryomilled sample did not absorb any hydrogen, ball milling improved the initial kinetics of processed powders compared with the as-cast sample. However it also reduced the hydrogen storage capacity. The observed increased kinetics was likely caused by the reduction of crystallite sizes with longer ball milling times. However, the longer ball milling times might also be the reason of the capacity loss due to formation of new grain boundaries. Faster kinetics was not due to a change in the rate-limiting step, as all kinetics curves were fitted with the 3D growth, diffusion controlled with decreasing interface velocity model. Keywords: TiFe alloy, First hydrogenation kinetics, Rate limiting step, Ball milling, Cryomilling

As cost reductions have made photovoltaics (PV) a favorable choice also in colder climates, the number of PV plants in regions with snowfalls is increasing rapidly. Snow coverage on the PV modules will lead to significant power losses, which must be estimated and accounted for in order to achieve accurate energy yield assessment and production forecasts. Additionally, detection and separation of snow loss from other system losses is necessary to establish robust operation and maintenance (O&M) routines and performance evaluations. Snow loss models have been suggested in the literature, but developing general models is challenging, and validation of the models are lacking. Characterization and detection of snow events in PV data has not been widely discussed. In this paper, we identify the signatures in PV data caused by different types of snow cover, evaluate and improve snow loss modeling, and develop snow detection. The analysis is based on five years of data from a commercial PV system in Norway. In an evaluation of four snow loss models, the Marion model yields the best results. We find that system design and snow depth influence the natural snow clearing, and by expanding the Marion model to take this into account, the error in the modeled absolute loss for the tested system is reduced from 23% to 3%. Based on the improved modeling and the identified data signatures we detect 97% of the snow losses in the dataset. Endogenous snow detection constitutes a cost-effective improvement to current monitoring systems.

The coldest and densest structures of gas and dust in the Universe have unique spectral signatures across the (sub-)millimetre bands (υ ≈30 - 950 GHz). The current generation of single dish facilities has given a glimpse of the potential for discovery, while sub-mm interferometers have presented a high resolution view into the finer details of known targets or in small-area deep fields. However, significant advances in our understanding of such cold and dense structures are now hampered by the limited sensitivity and angular resolution of our sub-mm view of the Universe at larger scales. In this context, we present the case for a new transformational astronomical facility in the 2030s, the Atacama Large Aperture Submillimetre Telescope (AtLAST). AtLAST is a concept for a 50-m-class single dish telescope, with a high throughput provided by a 2 deg - diameter Field of View, located on a high, dry site in the Atacama with good atmospheric transmission up to υ ~1 THz, and fully powered by renewable energy. We envision AtLAST as a facility operated by an international partnership with a suite of instruments to deliver the transformative science that cannot be achieved with current or in-construction observatories. As an 50m-diameter telescope with a full complement of advanced instrumentation, including highly multiplexed high-resolution spectrometers, continuum cameras and integral field units, AtLAST will have mapping speeds hundreds of times greater than current or planned large aperture (< 12m) facilities. By reaching confusion limits below L* in the distant Universe, resolving low-mass protostellar cores at the distance of the Galactic Centre, and directly mapping both the cold and the hot (the Sunyaev-Zeldovich effect) circumgalactic medium of galaxies, AtLAST will enable a fundamentally new understanding of the sub-mm Universe.

The following footnote should be included in this article [1]: This paper was commissioned for publication by Elizabeth Kocs, who served as Editor-in-Chief of this journal from 2015-2018.

We report preferential orientation control in photochromic gadolinium oxyhydride (GdHO) thin films deposited by a two-step process. Gadolinium hydride (GdH2-x) films were grown by reactive magnetron sputtering, followed by oxidation in air. The preferential orientation, grain size, anion concentrations, and photochromic response of the films are strongly dependent on the deposition pressure. GdHO films show preferential orientation along the [100] direction and exhibit photochromism when synthesized at deposition pressures up to 5.8 Pa and. The photochromic contrast is larger than 20 % when the films are deposited below 2.8 Pa with 0.22 H2/Ar flow ratio. We argue that the degree of preferential orientation defines the oxygen concentration which is known to be a key parameter for photochromism in rare-earth oxyhydride thin films. The experimental observations described above are explained by the oxidation-induced decrease of the grain size as a result of the increase of the deposition pressure of the sputtering gas.

Small-angle neutron scattering combined with powder neutron diffraction was employed to study the phase formation upon absorption/desorption of hydrogen gas in Li- and Na-intercalated fullerides. The comparative system analysis, addressing changes in the sample phase compositions and the morphology of powders, revealed a higher degree of complexity in the Na-based samples. Results also showed that the disappearance of crystalline lithium/sodium hydride during desorption was accompanied by an increased surface roughness in both systems, most likely because of the formation of a local surface strain. Furthermore, an increased specific internal surface of the studied materials upon subsequent deuterium absorption/desorption cycles was demonstrated. This could indicate moderate fracturing of crystallites.

Results for (La,Mg)Ni3.5 and (La,Mg)(Ni,Al)3.5 systems synthesized by metallurgical and mechanochemical techniques are reported. Powder X-ray and neutron diffraction combined with Rietveld refinements and profile analysis show that depending on the applied synthesis method various structurally related phases can be obtained for the same nominal composition. The hexagonal A2B7-type structure incorporating aluminum, with the refined composition La0.77Mg0.23Ni3.41Al0.09, has been identified. Al atoms occupy 12% of the 6h site within the LaNi5 slabs. This intermetallic phase absorbs hydrogen (deuterium) when exposed to 10 bar of H2 (D2) gas at room temperature. The H(D)-containing phase expands isotropically and retains the original symmetry of the parent compound. © 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

Ammonia can supplement hydrogen gas as a clean fuel to combat climate change. It overcomes hindrances that currently impede the realization of the full potential of hydrogen gas, including economical storage, political commitment, and safety concerns.

Reliable monitoring of PV systems is essential to establish efficient maintenance routines that minimize the levelized cost of electricity. The existing solutions for affordable monitoring of commercial PV systems are however inadequate for climates where snow and highly varying weather result in unstable performance metrics. The aim of this work is to decrease this instability to enable more reliable monitoring solutions for PV systems installed in these climates. Different performance metrics have been tested on Norwegian installations with a total installed capacity of 3.3 MW: (i) comparison of specific yield, (ii) temperature corrected performance ratio, and (iii) power performance index based on both physical modelling and machine learning. The most influential effects leading to instability are identified as snow, low light, curtailment, and systematic irradiance differences over the system. The standard deviation of all the performance metrics is reduced when filters targeting these four effects are applied. Compared to general low irradiance or clear sky filtering, a greater reduction in the variation of the metrics is achieved, and more data remains in the useful dataset. The most suitable performance metrics are comparison of specific yield and performance index based on machine learning modelling. The analysis highlights two paths to accomplish increased reliability of PV monitoring systems without increased hardware costs. First, better reliability can be achieved by selecting a suitable performance metric. Second, the variability of the performance metric can be reduced by utilizing filters that specifically target the origin of the variability instead of using standard literature thresholds.

Norway is self-sufficient with ample renewables while exporting large amounts of fossils fuels: It is in a unique position to fully decarbonize itself and significantly contribute to deep decarbonization globally, but the small population and economy limit the effort and impact. We discuss the efforts in Norway to reach the country’s and the Paris/Katowice meetings’ ambitious goals of a carbon-neutral society. Energy sustainability and the abatement of CO2 emissions have a central place in the Norwegian debate. In this perspective, we take a look at policies, strategies, and actions in Norway to realize its ambitious goals from a technological and materials development standpoint, as we are facing the change of pace after the Paris agreement in 2015 and the Katowice 2018 global climate panel meeting. Among the largest exporters of fossil fuels, Norway compensates by intensive investments in the development of carbon capture and sequestration. Following a growing debate involving the entire society, the Norwegian government has taken on aggressive strategies toward the decarbonization of energy production. We herein discuss the activities going on and the peculiar situation in Norway, which lives the rich life provided by fossil fuels while tasting the dream of being the climate knight of the world.

KBaPO4 – recently reported to hydrate in steam at 80°C into a novel low-temperature protonic conductor – was synthesized by a solid state reaction and its electrical properties characterized by impedance spectroscopy. At high temperatures the conductivity of KBaPO4 was low (order of 10−6 S/cm at 600°C) and not significantly different in dry and wet atmospheres, suggesting that KBaPO4 does not take up and conduct protons to any significant extent under these conditions. It was also independent of oxygen partial pressure and increased by acceptor doping (K excess), suggesting that the transport is ionic and by an effectively positive charge carrying defect. Impedance spectroscopy displayed significant grain boundary series resistance, and the bulk and grain boundaries displayed activation energies of approximately 110 and 120 kJ/mol, respectively. At lower temperatures, the conductivity increased, typical of transport in adsorbed water in a porous sample. Exposure of KBaPO4 to steam at 80°C resulted in decomposition into Ba3(PO4)2 and a liquid phase, presumably a molten hydrate of K3PO4. We thus suggest that what literature proposes as protonic conduction in steamed KBaPO4 in fact represents transport of K+, OH− and HPO42− ions in the molten hydrate of the decomposition product K3PO4 held inside porous Ba3(PO4)2.

International audience; This paper is a collection of selected contributions of the 1st International Workshop on Mechanochemistry of Metal Hydrides that was held in Oslo in May 2018. In this paper, the recent developments in the use of mechanochemistry to synthesize and modify metal hydrides are reviewed. A special emphasis is made on new techniques beside the traditional way of ball milling. High energy milling, ball milling under hydrogen reactive gas, cryomilling and severe plastic deformation techniques such as High-Pressure Torsion (HPT), Surface Mechanical Attrition Treatment (SMAT) and cold rolling are discussed. The new characterization method of in-situ X-ray diffraction during milling is described.

Black TiO2 has emerged as one of the most promising photocatalysts recently discovered. The reason behind its catalytic activity is considered to be due to the presence of defects and Ti3+ species at the surface of black TiO2 nanostructures, which are crucial for its diverse applications. Moreover, disordered/crystalline surface layers and bulk regions have been identified and appear to influence the intrinsic properties of the material. Here, we present the latest studies on the use of black TiO2 for metal free hydrogen production, as well as for CO2 photoreduction and N2 photofixation. After highlighting the structure/property relations, we conclude with some critical questions and suggest further topics of research in order to better understand the underlying mechanisms of light absorption in black TiO2 , especially towards solar fuels production.

Energy density and safety are the main factors that govern the development of the rechargeable battery technology. Currently, batteries beyond typical Li-ion batteries such as those based on solid-state electrolytes (SSEs) or other active elements (e.g., Na or Mg) are being examined as alternatives. For example, SSEs that would enable stable and reliable operation of all-solid-state Li-, Na-, and Mg-based batteries, with preferably improved capacity, are considered to be one of the most desired inventions. Lightweight complex metal hydrides are a family of solid compounds that were recently discovered to have extraordinary ionic conductivities and, in some cases, electrochemical properties that enabled battery reversibility. Consequently, they have become one of the promising electrolyte materials for future development of electrochemical storage devices. In this work, we present an overview of a wide range of lightweight hydride-based materials that could be used as electrolytes and/or anodes for mono-/divalent batteries and have a pivotal role in the implementation of new technological solutions in the field of electrochemistry.

Metal hydrides are known as a potential efficient, low-risk option for high-density hydrogen storage since the late 1970s. In this paper, the present status and the future perspectives of the use of metal hydrides for hydrogen storage are discussed. Since the early 1990s, interstitial metal hydrides are known as base materials for Ni – metal hydride rechargeable batteries. For hydrogen storage, metal hydride systems have been developed in the 2010s [1] for use in emergency or backup power units, i. e. for stationary applications. With the development and completion of the first submarines of the U212 A series by HDW (now Thyssen Krupp Marine Systems) in 2003 and its export class U214 in 2004, the use of metal hydrides for hydrogen storage in mobile applications has been established, with new application fields coming into focus. In the last decades, a huge number of new intermetallic and partially covalent hydrogen absorbing compounds has been identified and partly more, partly less extensively characterized. In addition, based on the thermodynamic properties of metal hydrides, this class of materials gives the opportunity to develop a new hydrogen compression technology. They allow the direct conversion from thermal energy into the compression of hydrogen gas without the need of any moving parts. Such compressors have been developed and are nowadays commercially available for pressures up to 200 bar. Metal hydride based compressors for higher pressures are under development. Moreover, storage systems consisting of the combination of metal hydrides and high-pressure vessels have been proposed as a realistic solution for on-board hydrogen storage on fuel cell vehicles. In the frame of the “Hydrogen Storage Systems for Mobile and Stationary Applications” Group in the International Energy Agency (IEA) Hydrogen Task 32 “Hydrogen-based energy storage” different compounds have been and will be scaled-up in the near future and tested in the range of 500 g to several hundred kg for use in hydrogen storage applications, The research for the lab-scale compressor is part of the activities of SCCER HaE, which is financially supported by Innosuisse - Swiss Innovation Agency . The authors thank the Alexander von Humboldt Foundation in the frame of the post-doctoral fellowship of Dr. J. Puszkiel (No. 1187279 STP ) as well as the European Union for their funding of projects STORHY (contract Nr. SES6-CT-2004-502667 , FP6-2002-Energy-1, 6.1.3.2.2), NESSHY (contract Nr. 518271 , FP6-2004-Energy-3, 6.1.3.2.2) and the EU Horizon 2020 /RISE project HYDRIDE4MOBILITY. Financial support from the S02 and KP8 S05), the European Union's Seventh Framework Programme ( FP7/2007e2013 ) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement no. 256653 (SSH2S), from the European Fuel Cells and Hydrogen Joint Undertaking in the framework of BOR4STORE (Grant agreement no. 303428 ), from the Australian Research Council for grants LP120101848 , LP150100730 , and LE0989180 , The Innovation Fund Denmark (project HyFill-Fast), DST within Hydrogen South Africa/HySA programme (projects KP3 National Research Foundation/NRF of South Africa , incentive funding grant number 109092 and the Research Council of Norway (project 285147 ) is thankfully acknowledged

Black TiO

Earth’s cryosphere is shrinking. The cryosphere is the frozen part of our planet that is covered by solid water and where ground temperature remains below 0°C for at least some part of the year. From the North to the South Pole, as well as on the highest altitudes, scientists have recently observed the seasonal snow cover decreasing, the permafrost thawing, and the ice retreating.

We present a comparative, combined ab initio and experimental study of sodium and lithium storage in amorphous (glassy) carbon (a-C) versus graphite. Amorphous structures are obtained by fitting stochastically generated structures to a reference radial distribution function. Li insertion is thermodynamically favored in both graphite and a-C. While sodium insertion is thermodynamically unfavored in graphite, a-C possesses multiple insertion sites with binding energies stronger than Na cohesive energy, making it usable as anode material for Na-ion batteries. Binding energy of Na is predicted to be stronger than the Na cohesive energy for Na concentrations corresponding to a capacity of about 200 mAh/g. These results are confirmed by experimental measurements using highly amorphous carbon, in which a specific capacity of 173 mAh/g for Na is obtained after 100 cycles.

International audience; A Round Robin Test exercise on magnesium hydride (MgH2) was performed by 14 laboratories with the aim to compare experimental isothermal data such PCI curves, kinetics curves and formation enthalpies together with a basic statistical evaluation of the results. The full hydrogen capacity was found to vary in the range 5.1-6.4 wt.% at 280 °C (553 K) and in the range 5.3-6.6 wt.% at 320 °C (593 K) (value for 1 MPa hydrogen pressure). The relative standard deviations of 6.9% and 7.2%, respectively, were measured for absorption. The absorption plateau pressure of magnesium hydride varies between 0.08 and 0.14 MPa with an average of 0.10 MPa and a relative standard deviation of 17.3% at 280 °C (553 K). At 320 °C (593 K) the absorption plateau pressure results fall in the range 0.26-0.45 MPa, with a relative standard deviation of 17.6%. Kinetics curves were affected by much higher data dispersion than the PCI data. The enthalpy of absorption was −75.7 KJ/moleH2, with a relative standard deviation of 4.4%. The results highlight the importance of well defined measuring and reporting protocols as a base for future standard procedures.

The effect of additives and mechanochemical processing at low temperature on β-AlD 3 has been studied. β-AlD 3 synthesized by wet chemistry was mixed with selected fluorides and cryomilled. Investigations of the fractions of α-, α′- and β-AlD 3 in the samples show that the additive and cryomilling affect the ratio of the polymorphs. Addition of AlF 3 leads to the highest ratio of α-AlD 3 , while addition of TiF 3 leads to full decomposition to Al. Formation of α′-AlD 3 during milling with NaF or MgF 2 is observed. The presence of fluorides in the synthesis of alane by cryomilling showed no notable impact on the ratios of the alane polymorphs compared to cryomilling without additives.

Understanding the thermodynamics of metal hydrides is crucial in order to employ them for reversible hydrogen storage. The use of a supporting nanoporous matrix for embedding the hydride can improve the kinetics of metal hydride reactions and even change the overall reaction path. In this study, density functional theory calculations were performed to understand the size effect of MgH2 particles and changes in the physical and chemical properties of these nano-objects embedded in an amorphous carbon matrix. A stable amorphous carbon structure was successfully generated with two different approaches and further used as a template to construct the scaffold for nanophases of MgH2. Using five different structure models, we have studied the physical and chemical changes of the nano-MgH2 in this carbon scaffold. In addition, from small-angle neutron scattering studies, we could demonstrate experimentally that it is possible to incorporate such ultrasmall objects into the carbon scaffolds.

Cl− to BH 4 − ion substitution was induced in NaBH4 through mechano-chemical reactions with all the first period transition metal chlorides and CdCl2. The products were identified by Rietveld refinement of powder X-ray and neutron diffraction data to be mainly Na(BH4)1−xClx. These possess cubic NaCl-type structures, with unit cell parameters between 5.7801(3) and 5.6576(2) A, and compositions ranging from x = 0.69 (with Cu) to 0.92 (with Zn). Infrared spectroscopy of selected samples confirms the substitution through a shift of the vibrational modes of the BH 4 − group towards higher wavenumbers. An observed shape change of the vibrational features from Lorentzian to Gaussian is related to the presence of the transition metal. There is no correlation between x and the thermal behavior of the samples. The lowest decomposition temperature is found for the Zn containing sample (103 °C), while Cd leads to the highest value (521 °C). Their behavior is related to the presence of NaZn(BH4)3 and metallic Cd in the samples, respectively.

Transition metals added to sodium aluminum hydride by high-energy ball milling have been shown to significantly enhance its absorption and desorption properties. In the present study, we have used small-angle X-ray scattering to elucidate how TiCl3 affects the nanostructure of NaAlH4 particles. Scattering data from as-purchased and ball milled NaAlH4 for 6 and 15 min are compared with NaAlH4 ball milled for the same time with 4 mol % TiCl3. Drastic differences were noticed in the two systems which cast a new light on the decomposition of NaAlH4, in particular on the effect of ball milling and of TiCl3 on the morphology, grain size, and distribution of the phases. The particle morphology of pure NaAlH4 showed significant evolution/changes during heating from room temperature to 290 °C, as evidenced by the variations in the power-low scattering parameter, α. Drastic changes were noticed in the particle surface structure during the phase transformation from NaAlH4 to Na3AlH6 + Al, when the system becomes les...

Nanoscale hydride systems have recently gained increased attention for their possible energy storage applications. In the present work, nanoscale particles of Mg(11BD4)2 infiltrated into an activated carbon scaffold were studied by small-angle scattering techniques, and their behavior was compared with that of the bulk powders. Upon heating to 400 °C, under dynamic vacuum, the nanoconfined particles maintain their size distribution, and the decomposition affects only the morphology of the particle surface. On the contrary, the bulk powders showed a significant modification of both particle size and surface morphology under the same conditions. The carbon scaffold therefore serves to ensure both the desired nanoscale organization of the magnesium borohydride and stabilization in size of the incorporated material.

Y(BH 4 ) 3 was synthesized by cryo-milling mixtures of LiBH 4 and YCl 3 and characterized by powder X-ray and neutron diffraction (PXD, PND), differential scanning calorimetry (DSC), and temperature programmed desorption (TPD). The crystal structure was refined in the space group Pa −3 (no. 205) with lattice constant a = 10.8522(7) A from 11 B and D ( 2 H) substituted samples using PND. It was found to contain Y 3+ cations in a highly distorted octahedral environment formed by six [BD 4 ] − complex anions. Heat treatment under 10 MPa of deuterium at 475 K led to a phase transformation from the primitive cubic room-temperature phase to a face-centered cubic high-temperature phase with space group Fm −3 c (no. 226) and lattice constant a = 11.0086(1) A. This high-temperature phase shows an ideal and undistorted octahedral coordination around the central Y 3+ cation. In situ synchrotron radiation powder X-ray diffraction experiments (SR-PXD) show the presence of an intermediate phase during the thermal decomposition of Y(BH 4 ) 3 with presumably orthorhombic symmetry, and lattice constants a = 12.170(14) A, b = 7.670(5) A, and c = 7.478 (6) A, in a narrow temperature region between 473 K and 520 K.

Alane can be synthesized by cryomilling alanate and aluminium halides. The yield of alane has been found to be increased using 3NaAlH4 + AlCl3 and 3LiAlD4 + AlBr3 compared to 3LiAlD4 + AlCl3. Furthermore the relative amount of α′- over α-alane has increased from 0.63–0.67 to 1.05 by adding small amounts of FeF3 to 3LiAlD4 + AlCl3. When synthesized from 3NaAlH4 + AlCl3 the ratio α′/α was also increased to 1.04. α′-AlH3 was confirmed to be less thermally stable than α-AlH3. The maximum amount of synthesized alane was obtained by using NaAlH4 as a starting material instead of Li-alanate. However, the synthesis route from NaAlH4 provided alane with less thermal stability than the synthesis from LiAlD4. The use of Na3AlH6, LiH or TiCl3 resulted in no alane formation.

Screening experiments were performed in order to investigate the formation of Al-based quaternary hydrides on the basis of multi-component mixtures treated by reactive ball milling under hydrogen pressure. The data indicated that the milling parameters and in particular the milling speed and milling time are of great importance to the formation of any new phase obtained by reactive ball milling. Indeed, a higher milling speed was shown to favour the formation of the new phases. In the case of (MgH 2 + Al + LiH) and (MgH 2 + LiAlH 4 ) mixtures, the formation of a new phase was observed, which exhibits relatively fast decomposition kinetics.

In this work Mg- and K-containing alanates have been investigated as possible hydrogen storage materials. Ball milling was carried out under argon or at moderate/high hydrogen pressure in order to obtain an improved driving force for the formation of potential new alanate phases. Powder X-ray diffraction and volumetric measurements were used in order to identify reaction mechanisms and phases forming in these systems. New unidentified peaks were detected for the mixtures 2MgH 2 + 3Al + KH and 2CaH 2 + Al + 2KH. However, they do not seem to belong to reversible hydride phases.

Energy is a key issue for future generation. Researches are conducted worldwide to develop new efficient means for energy conversion and storage. Electrochemical storage is foreseen as an efficient way to handle intermittent renewable energy production. The most advanced batteries are nowadays based on lithium-ion technology though their specific capacities should be significantly increased to bring solution to mass storage. Conversion reactions are one way to step forward larger capacities at the anode. We here review the possibility to use metallic or complex hydrides as negative electrode using conversion reaction of hydride with lithium. Moreover, promising alloying of lithium with the metallic species might provide additional reversible capacities. Both binary and ternary systems are reviewed and results are compared in the frame of the electrochemical application.

Recent progress on materials for hydrogen storage have pointed out that kinetics and thermodynamics can be modified by nano-confinement of hydrides in porous scaffolds. The investigation of the structural features of these particular systems is challenging with conventional methods, for instance due to the lack of peaks in the diffraction pattern. Small angle neutron scattering is suitable for studying porous systems containing hydrogen and it has been invaluable for the characterisation of the new hydride systems. This chapter presents the basic principles of the technique and gives examples of its application to the field of nano-confined materials for hydrogen storage.

Magnesium-rich Mg–Ni–Fe intermetallic compounds have been prepared by two different routes: (a) short time ball milling of ribbons obtained by melt spinning; (b) long time ball milling of a mixture of MgH 2 , Ni and Fe powders. The first type of samples displays an hydrogen desorption kinetics better than the second one. Pressure composition isotherm measurements exhibit for both type of samples two plateaux, the lower and wider corresponding to the MgH 2 phase and the upper and shorter corresponding to the Mg 2 NiH 4 phase. The presence of the two types of hydrides is confirmed by X-ray diffraction analysis. Mossbauer spectroscopy shows that in melt spun and subsequently milled samples iron is mainly in a disordered structure and segregates after hydrogenation, while in directly milled powders remains mainly unalloyed. After multiple hydrogen absorption/desorption cycles the main part of iron is in metallic state in samples of both types, those of first type preserving better hydrogen desorption kinetics.

Al–Cu–Fe samples were prepared by ball milling powders of elemental Al, Cu, Fe (first route) and of elemental Al mixed with previously mechanically alloyed Cu–Fe solid solution (second route). Phase and structure transformations by annealing the as-milled powders were investigated by differential scanning calorimetry, X-ray diffraction and Mossbauer spectroscopy. The influence of the thermodynamic driving forces, namely the heat of mixing, positive for the Cu–Fe system and negative for the Al–Fe and Al–Cu systems, was discussed and correlated to the sequence of phase transformations during heating.

Na2O·x Al2O3 (x= 9, 11)films have been obtained by sol–gel method. Crystallization processes during heat treatments have been investigated by X–ray diffraction analysis. A metastable phase with the mullite structure, λ–Na2O·xAl2O3, has been observed starting from 800°C. Films remained stable after a heat treatment at 1000°C for 250 h. Impedance spectroscopy measurements showed that the films of λ-Na2O·x Al2O3 possess a large three–dimensional ionic conductivity at 400°C.