Enhancement effect of bimetallic amide K2Mn(NH2)4 and in-situ formed KH and Mn4N on the dehydrogenation/hydrogenation properties of Li–Mg–N–H system

In this work, we investigated the influence of the K2Mn(NH2)4 additive on the hydrogen sorption properties of the Mg(NH2)2 + 2LiH (Li–Mg–N–H) system. The addition of 5 mol% of K2Mn(NH2)4 to the Li–Mg–N–H system leads to a decrease of the dehydrogenation peak temperature from 200 ◦C to 172 ◦C compared to the pristine sample. This sample exhibits a constant hydrogen storage capacity of 4.2 wt.% over 25 dehydrogenation/rehydrogenation cycles. Besides that, the in-situ synchrotron powder X-ray diffraction analysis performed on the as prepared Mg(NH2)2 + 2LiH containing K2Mn(NH2)4 indicates the presence of Mn4N. However, no crystalline K-containing phases were detected. Upon dehydrogenation, the formation of KH is observed. The presence of KH and Mn4N positively influences the hydrogen sorption properties of this system, especially at the later stage of rehydrogenation. Under the applied conditions, hydrogenation of the last 1 wt.% takes place in only 2 min. This feature is preserved in the following three cycles.Fil: Gizer, Gökhan. Helmholtz zentrum Geesthacht; AlemaniaFil: Cao, Hujun. Helmholtz zentrum Geesthacht; Alemania. Chinese Academy of Sciences; República de ChinaFil: Puszkiel, Julián Atilio. Helmholtz zentrum Geesthacht; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Pistidda, Claudio. Helmholtz zentrum Geesthacht; AlemaniaFil: Santoru, Antonio. Helmholtz zentrum Geesthacht; AlemaniaFil: Zhang, Weijin. Chinese Academy of Sciences; República de ChinaFil: He, Teng. Chinese Academy of Sciences; República de ChinaFil: Chen, Ping. Chinese Academy of Sciences; República de ChinaFil: Klassen, Thomas. Helmholtz zentrum Geesthacht; Alemania. Helmut Schmidt Universität; ArgentinaFil: Dornheim, Martin. Helmholtz zentrum Geesthacht; Alemani

Efficient synthesis of alkali borohydrides from mechanochemical reduction of borates using magnesium-aluminum-basedwaste

Lithium borohydride (LiBH4) and sodium borohydride (NaBH4) were synthesized via mechanical milling of LiBO2, and NaBO2 with Mg-Al-based waste under controlled gaseous atmosphere conditions. Following this approach, the results herein presented indicate that LiBH4 and NaBH4 can be formed with a high conversion yield starting from the anhydrous borates under 70 bar H2. Interestingly, NaBH4 can also be obtained with a high conversion yield by milling NaBO2·4H2O and Mg-Al-based waste under an argon atmosphere. Under optimized molar ratios of the starting materials and milling parameters, NaBH4 and LiBH4 were obtained with conversion ratios higher than 99.5%. Based on the collected experimental results, the influence of the milling energy and the correlation with the final yields were also discussed.Fil: Le, Thi Thu. Helmholtz Zentrum Geesthacht GmbH. Institute of Materials Research, Materials Technology; AlemaniaFil: Pistidda, Claudio. Helmholtz Zentrum Geesthacht GmbH. Institute of Materials Research, Materials Technology; AlemaniaFil: Puszkiel, Julián Atilio. Helmholtz Zentrum Geesthacht GmbH. Institute of Materials Research, Materials Technology; Alemania. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Milanese, Chiara. Universita Degli Studi Di Pavia; ItaliaFil: Garroni, Sebastiano. University of Sassari; ItaliaFil: Emmler, Thomas. Helmholtz Zentrum Geesthacht GmbH. Institute of Materials Research, Materials Technology; AlemaniaFil: Capurso, Giovanni. Helmholtz Zentrum Geesthacht GmbH. Institute of Materials Research, Materials Technology; AlemaniaFil: Gizer, Gökhan. Helmholtz Zentrum Geesthacht GmbH. Institute of Materials Research, Materials Technology; AlemaniaFil: Klassen, Thomas. Helmholtz Zentrum Geesthacht GmbH. Institute of Materials Research, Materials Technology; Alemania. Helmut Schmidt University; Alemania. University of the Federal Armed Forces Hamburg; AlemaniaFil: Dornheim, Martin. Helmholtz Zentrum Geesthacht GmbH. Institute of Materials Research, Materials Technology; Alemani

Improved kinetic behaviour of Mg(NH2)2-2LiH doped with nanostructured K-modified-LixTiyOz for hydrogen storage

The system Mg(NH2)2 + 2LiH is considered as an interesting solid-state hydrogen storage material owing to its low thermodynamic stability of ca. 40 kJ/mol H2 and high gravimetric hydrogen capacity of 5.6 wt.%. However, high kinetic barriers lead to slow absorption/desorption rates even at relatively high temperatures (>180 °C). In this work, we investigate the effects of the addition of K-modified LixTiyOz on the absorption/desorption behaviour of the Mg(NH2)2 + 2LiH system. In comparison with the pristine Mg(NH2)2 + 2LiH, the system containing a tiny amount of nanostructured K-modified LixTiyOz shows enhanced absorption/desorption behaviour. The doped material presents a sensibly reduced (∼30 °C) desorption onset temperature, notably shorter hydrogen absorption/desorption times and reversible hydrogen capacity of about 3 wt.% H2 upon cycling. Studies on the absorption/desorption processes and micro/nanostructural characterizations of the Mg(NH2)2 + 2LiH + K-modified LixTiyOz system hint to the fact that the presence of in situ formed nanostructure K2TiO3 is the main responsible for the observed improved kinetic behaviour.Fil: Gizer, Gökhan. Max-planck Strasse. Helmholtz-Zentrum Geesthacht GmbH. Institute of Materials Research; AlemaniaFil: Puszkiel, Julián Atilio. Max-planck Strasse. Helmholtz-Zentrum Geesthacht GmbH. Institute of Materials Research; Alemania. Comisión Nacional de Energía Atómica. Centro Atómico Ezeiza; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Castro Riglos, Maria Victoria. Max-planck Strasse. Helmholtz-Zentrum Geesthacht GmbH. Institute of Materials Research; Alemania. Comisión Nacional de Energía Atómica. Centro Atómico Ezeiza; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pistidda, Claudio. Max-planck Strasse. Helmholtz-Zentrum Geesthacht GmbH. Institute of Materials Research; AlemaniaFil: Ramallo Lopez, Jose Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Mizrahi, Martin Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Max-planck Strasse. Helmholtz-Zentrum Geesthacht GmbH. Institute of Materials Research; AlemaniaFil: Santoru, Antonio. Max-planck Strasse. Helmholtz-Zentrum Geesthacht GmbH. Institute of Materials Research; AlemaniaFil: Gemming, Thomas. IFW Dresden; AlemaniaFil: Tseng, Jo Chi. German Electron Synchrotron; AlemaniaFil: Klassen, Thomas. Max-planck Strasse. Helmholtz-Zentrum Geesthacht GmbH. Institute of Materials Research; AlemaniaFil: Dornheim, Martin. Max-planck Strasse. Helmholtz-Zentrum Geesthacht GmbH. Institute of Materials Research; Alemani

A comprehensive study on lithium-based reactive hydride composite (Li-RHC) as a reversible solid-state hydrogen storage system toward potential mobile applications

Reversible solid-state hydrogen storage is one of the key technologies toward pollutant-free and sustainable energy conversion. The composite system LiBH4–MgH2 can reversibly store hydrogen with a gravimetric capacity of 13 wt%. However, its dehydrogenation/hydrogenation kinetics is extremely sluggish (∼40 h) which hinders its usage for commercial applications. In this work, the kinetics of this composite system is significantly enhanced (∼96%) by adding a small amount of NbF5. The catalytic effect of NbF5 on the dehydrogenation/hydrogenation process of LiBH4–MgH2 is systematically investigated using a broad range of experimental techniques such as in situ synchrotron radiation X-ray powder diffraction (in situ SR-XPD), X-ray absorption spectroscopy (XAS), anomalous small angle X-ray scattering (ASAXS), and ultra/small-angle neutron scattering (USANS/SANS). The obtained results are utilized to develop a model that explains the catalytic function of NbF5 in hydrogen release and uptake in the LiBH4–MgH2 composite system

A comprehensive study on lithium-based reactive hydride composite (Li-RHC) as a reversible solid-state hydrogen storage system toward potential mobile applications

Reversible solid-state hydrogen storage is one of the key technologies toward pollutant-free and sustainable energy conversion. The composite system LiBH4–MgH2 can reversibly store hydrogen with a gravimetric capacity of 13 wt%. However, its dehydrogenation/hydrogenation kinetics is extremely sluggish (∼40 h) which hinders its usage for commercial applications. In this work, the kinetics of this composite system is significantly enhanced (∼96%) by adding a small amount of NbF5. The catalytic effect of NbF5 on the dehydrogenation/hydrogenation process of LiBH4–MgH2 is systematically investigated using a broad range of experimental techniques such as in situ synchrotron radiation X-ray powder diffraction (in situ SR-XPD), X-ray absorption spectroscopy (XAS), anomalous small angle X-ray scattering (ASAXS), and ultra/small-angle neutron scattering (USANS/SANS). The obtained results are utilized to develop a model that explains the catalytic function of NbF5 in hydrogen release and uptake in the LiBH4–MgH2 composite system

Characterization of LiBH4–MgH2 Reactive Hydride Composite System with Scattering and Imaging Methods Using Neutron and Synchrotron Radiation

Reversible solid-state hydrogen storage in metal hydrides is a key technology for pollution-free energy conversion systems. Herein, the LiBH2–MgH2 composite system with and without ScCl3 additive is investigated using synchrotron- and neutron-radiation-based probing methods that can be applied to characterize such lightweight metal–hydrogen systems from nanoscopic levels up to macroscopic scale. Combining the results of neutron- and photon-based methods allows a complementary insight into reaction paths and mechanisms, complex interactions between the hydride matrix and additive, hydrogen distribution, material transport, structural changes, and phase separation in the hydride matrix. The gained knowledge is of great importance for development and optimization of such novel metal-hydride-based hydrogen storage systems with respect to future applications

Medeuro : the longing for identity and community among Maltese migrant settlers in North Africa

Based largely on materials held in the Service des Periodiques at the Bibliotheque Nationale de Tunisie in Tunis, and especially on content anaylsis of a 1930s newspaper Melita published in Sousse. this study explores the yearning for and the anguish of a cultural survivance among Maltese migrant settlers in North Africa, above all the retention of Maltese as a language of expression, affinity and identification, at a time when Maltese itself was experiencing a literary rebirth. However, such a campaign is undertaken in a 'non-Maltese' context, where moreover, in addition to separation and distance, the influence of European empires-the French, the British and the Italian-is pronounced, if not dominant, thus interfering with any continued loyalty to one mother tongue or mother country. Masterminding the intellectual push for a collective self-identity anchored in language, literature, history and religion, is a leading francophone litterateur whose family had settled in Algeria from the island of Gozo. What is also offered here, in the annotations, is a fairly comprehensive bibliography of Maltese migrant settlement in northern Africa with special reference to lesser known articles and other publications not available in English.peer-reviewe

Hydrogen storage in complex hydrides: past activities and new trends

publishedVersio

Hydrogen storage in complex hydrides: Past activities and new trends

Intense literature and research efforts have focussed on the exploration of complex hydrides for energy storage applications over the past decades. A focus was dedicated to the determination of their thermodynamic and hydrogen storage properties, due to their high gravimetric and volumetric hydrogen storage capacities, but their application has been limited because of harsh working conditions for reversible hydrogen release and uptake. The present review aims at appraising the recent advances on different complex hydride systems, coming from the proficient collaborative activities in the past years from the research groups led by the experts of the Task 40 'Energy Storage and Conversion Based on Hydrogen' of the Hydrogen Technology Collaboration Programme of the International Energy Agency. An overview of materials design, synthesis, tailoring and modelling approaches, hydrogen release and uptake mechanisms and thermodynamic aspects are reviewed to define new trends and suggest new possible applications for these highly tuneable materials

Katalizör ve Eng Katkılı Mgh2 Peletlerin Yapısal Özelliklerinin ve Hidrojen Kinetiğinin Araştırılması

Among metal hydrides, MgH2 operates at high temperatures (300-450oC) and low H2 pressures (0-20 bar). It is an abundant and well-studied material. These properties show that MgH2 can be used as a thermal energy storage material for concentrating solar power plants. H2 absorption of magnesium is exothermic, 75kJ/molH2 heat energy is released. This released energy can be used to carry on power plant's operation. Suitable thermochemical energy storage material should have high thermal conductivity and fast hydrogen kinetics. However reaction kinetics of MgH2 is slow and it has low thermal conductivity. In this work, mechanical milling process and metal oxide catalysts are used to improve reaction kinetics. Expanded natural graphite (ENG) is added to increase thermal conductivity of samples. MgH2-catalyst-ENG mixture is compacted with uniaxial press to reduce oxidation rate and increase volumetric hydrogen capacity. Effect of mechanical milling, pellet pressure, ENG concentration, catalyst type and concentration on material is investigated. Hydrogen kinetics of prepared samples are measured with Seivert's volumetric method. SEM and TEM analysis are done for structural analysis. Thermal conductivity measurement system, designed by SNTG members is used to measure thermal conductivities of pellets. Pellet consist of %90 MgH2, %5 TiO2 and ENG can store 5,6 wt. % hydrogen at 350oC. With %5 TiO2 addition, reaction kinetics are two times faster respect to sample without catalyst. Pellet can fully desorb hydrogen in 15 minutes. With %5 ENG addition, radial thermal conductivity of pellet is reached to 4,6 W/mK. This result is 5 times higher than MgH2 itself. There is not any physical distortion on pellet surfaces up to 20 hydrogen absorption-desorption cycle. Increasing pellet pressure improves the physical properties and pellet pressed under 600 MPa can keep pellet form until 50 cycle. These results show that catalyst and ENG addition clearly improves properties of pure MgH2 pellet. Prepared pellet can operate at 300-450oC temperature range and 0-20 bar H2. It has the potential to be used as a high temperature thermal energy storage material.Metal hidrürler arasında MgH2'nin yüksek sıcaklıkta (300-450oC) ve düşük H2 basınçlarında (0-20 bar) çalışması, bol bulunur olması ve özelliklerinin iyi bilinmesi nedeniyle yoğunlaştırılmış güneş enerji santrallerinde ısı depolama malzemesi olarak uygulama potansiyeli oldukça yüksektir. Magnezyumun hidrojen soğurması egzotermik bir reaksiyondur, 75kJ/molH2 ısı açığa çıkar. Açığa çıkan ısı enerjisi kullanılarak santralin çalışması devam ettirebilir. İyi bir ısı depolama malzemesinin yüksek reaksiyon hızına ve ısıl iletkenliğe sahip olması gereklidir. Fakat MgH2'nin reaksiyon hızı yavaş ve ısıl iletkenliği düşüktür. Bu nedenlerle çalışma kapsamında, MgH2'nin reaksiyon hızını iyileştirmek için metal oksit katalizörler ile birlikte mekanik öğütme işlemi kullanılmıştır. Yüksek ısıl iletkenliğe ulaşmak için ise yapıya yüksek ısıl iletkenliğe sahip genişletilmiş grafit (ENG) katılmıştır. Hacimsel depolama kapasitesini artırmak ve oksijene karşı reaktifliği azaltmak için MgH2-katalizör-ENG karışımı hidrolik pres ile basınçlandırılmıştır. Mekanik öğütme işleminin, presleme basıncının, ENG miktarının, katalizör miktarının ve cinsinin malzemenin yapısal özellikleri ve hidrojen kinetiği üzerindeki etkisi de ayrıca incelenmiştir. Oluşturulan peletlerin hidrojen kinetiği Sievert hacimsel metot ile belirlenirken, yapısal karakterizasyonu taramalı elektron mikroskobu ile irdelenmiştir. Isıl iletkenlik ölçümleri ise çalışma kapsamında tasarlanmış olan ölçüm düzeneği ile yapılmıştır. %90 MgH2, %5 TiO2 ve %5 ENG'den oluşan peletin hidrojen depolama kapasitesi 350oC'ta ağırlıkça %5,6'dır. %5 TiO2 katkısıyla peletlerin hidrojen salınım özellikleri 2 kat geliştirilmiş ve 350oC'ta 15 dakikada tüm hidrojeni salabilmektedir. %5 ENG katılmasıyla ise peletin radyal ısıl iletkenliği 5 kat artarak 4,6 W/mK değerine ulaşmıştır. Pelet, fiziksel özelliklerinde bir değişim olmadan 20 döngü boyunca çalışabilmektedir. Presleme basıncı arttığında fiziksel özelliklerin iyileştiği ve 50 döngüye kadar pelet formunun korunduğu görülmüştür. Bu sonuçlar saf MgH2 peletin hidrojen depolama ve ısıl özelliklerinin, katalizör ve ENG kullanımıyla belirgin olarak iyileştirildiğini göstermektedir. Hazırlanan pelet, 300-450oC sıcaklık aralığında ve 0-20 bar H2 basıncında ısı depolama özelliğiyle yüksek sıcaklık ısı depolama malzemesi olarak kullanılma potansiyeline sahiptir