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

Stability and Failure Mechanisms of Al2O3|Al Bilayer Coatings Exposed to 300 Bar Hydrogen at 673 K

Hydrogen barrier coatings are important for future hydrogen economy to enable materials for applications in hydrogen tanks. In the present study, coatings consisting of amorphous Al2O3 (≈100 nm) synthesized by plasma ion-assisted deposition on top of crystalline metallic Al (≈100 nm) are exposed to 300 bar hydrogen pressure at 673 K for 6 days. This is done to mimic and accelerate conditions in hydrogen storage containers for metallic hydrides. They remain intact after such harsh conditions, although changes do occur. Blister-like features are observed consisting of a buckled oxide layer while the metallic Al layer underneath is retracted. As these features are also found for coatings annealed under 1 bar Ar atmosphere it is concluded that they are not related to the formation of gas bubbles but they form due to solid-state dewetting. This is different to literature observation where H2 bubbles are reported as a consequence of interface diffusion of H/H+ species present due to the initial precursor used for film deposition. The mechanical properties of the coatings, which are evaluated from nanoindentation load–displacement curves, change only moderately. Overall, the study shows that Al2O3|Al coatings are suitable candidates to prevent hydrogen ingress, but dewetting due to long-term exposure at elevated temperatures must be prevented

Genealogisches Bewusstsein als Legitimation. Inter-und intragenerationelle Auseinandersetzungen sowie die Bedeutung von Verwandtschaft bei Amtswechseln

Dieser Band ist eine Zusammenstellung von Beiträgen, die auf eine vom Bamberger DFG-Graduiertenkolleg ´Generationenbewusstsein und Generationenkonflikte´ in Antike und Mittelalter veranstaltete interdisziplinären Nachwuchstagung zurückgehen. Darin werden weltliche und geistliche Amts- und Herrschaftswechsel der Vormoderne mit Fragen nach genealogischem Bewusstsein, inter- und intragenerationellen Auseinandersetzungen und der Bedeutung von Verwandtschaften verknüpft und beleuchtet. Der Untersuchungsraum erstreckt sich hierbei von Frankreich nach Persien sowie von Deutschland nach Ägypten; zeitlich wird ein Bogen gespannt vom 5. vorchristlichen bis zum 18. nachchristlichen Jahrhundert

Reformation als Kommunikationsprozess

Beim Hussitismus bzw. Utraquismus in Böhmen und der reformatorische Bewegung ab 1517 in Sachsen handelt es sich um zwei unterschiedliche Reformationen, jedoch mit einer Fülle von sachlichen und personalen Verbindungslinien. Diese rücken im vorliegenden Band erstmalig in einen gemeinsamen Fokus.»Wir sind alle Hussiten«, bekannte Martin Luther 1520 nach der Lektüre von Schriften des tschechischen Reformators Jan Hus, der gut einhundert Jahre zuvor als Ketzer verbrannt worden war. Die beiden Reformatoren verbinden, ebenso wie die von ihnen ausgehenden Erweckungs- und Erneuerungsbewegungen, viele Ähnlichkeiten, Übereinstimmungen und parallele Entwicklungsverläufe. Dennoch werden sie meist getrennt betrachtet. Der Sammelband analysiert Aspekte der Reformation in Böhmen und Sachsen und rückt so die beiden religiösen Brennpunkte in einen gemeinsamen Fokus. Methodisch wählen die Beiträgerinnen und Beiträger dabei einen kommunikationsgeschichtlichen Zugang

How to reveal metastable skyrmionic spin structures by spin-polarized scanning tunneling microscopy

We predict the occurrence of metastable skyrmionic spin structures such as antiskyrmions and higher-order skyrmions in ultra-thin transition-metal films at surfaces using Monte Carlo simulations based on a spin Hamiltonian parametrized from density functional theory calculations. We show that such spin structures will appear with a similar contrast in spin-polarized scanning tunneling microscopy (SP-STM) images. Both skyrmions and antiskyrmions display a circular shape for out-of-plane magnetized tips and a two-lobe butterfly contrast for in-plane tips. An unambiguous distinction can be achieved by rotating the tip magnetization direction without requiring the information of all components of the magnetization

How to reveal metastable skyrmionic spin structures by spin-polarized scanning tunneling microscopy

<p>We predict the occurrence of metastable skyrmionic spin structures such as antiskyrmions and<br> higher-order skyrmions in ultra-thin transition-metal films at surfaces using Monte Carlo simulations<br> based on a spin Hamiltonian parametrized from density functional theory calculations.Weshow that<br> such spin structures will appear with a similar contrast in spin-polarized scanning tunneling<br> microscopy images. Both skyrmions and antiskyrmions display a circular shape for out-of-plane<br> magnetized tips and a two-lobe butterfly contrast for in-plane tips. An unambiguous distinction can<br> be achieved by rotating the tip magnetization direction without requiring the information of all<br> components of the magnetization.</p

Synchrotron Techniques for the Mg2FeH6−Mg(BH4)2\mathrm{Mg_{2}FeH_{6}-Mg(BH_{4})_{2}} Hydrogen Storage System

Complex hydrides are very promising hydrogen-storage materials, due to their high gravimetric and volumetric capacities. Presented here is a reactive hydride composite of Mg2FeH6 combined with the light metal borohydride Mg(BH4)2 characterised by different synchrotron techniques. Several photon sources were used to investigate this system in detail, including in situ powder X-Ray diffraction (PXRD) (SNBL, ESRF, France), X-ray Absorption Near Edge Structure (XANES), Extended X-Ray Absorption Fine Structure (EXAFS) (Diamond Light Source, UK) and X-ray micro-tomography (DESY, Petra III, Germany). Due to the sensitive nature of hydrogen storage materials to both oxygen and moisture, each of these techniques had limitations and required specific adaptations to accurately measure physical and chemical properties of the Mg2FeH6 / Mg(BH4)2 composite system. An overview of each technique with relation to the measurement of hydrogen storage materials as well as the analysis for the specific example of Mg2FeH6 / Mg(BH4)2 is given

SNG based energy storage systems with subsurface CO2 storage

Large-scale energy storage plants based on power-to-gas-to-power (PtG–GtP) technologies incorporating high temperature electrolysis, catalytic methanation for the provision of synthetic natural gas (SNG) and novel, highly efficient SNG-fired Allam reconversion cycles allow for a confined and circular use of CO2/CH4 and thus an emission-free storage of intermittent renewable energy. This study features a thorough technology assessment for large-scale PtG–GtP storage plants based on highly efficient sCO2 power cycles combined with subsurface CO2 storage. The Allam cycle employs supercritical CO2 as working fluid as well as an oxy-combustion process to reach high efficiencies of up to 66%. The entire PtG–GtP process chain assessed in this study is expected to reach maximum roundtrip efficiencies of 54.2% (with dedicated and sufficient O2 storage) or 49.0% (with a dedicated air separation unit). The implementation of said energy storage systems into existing national energy grids will pose a major challenge, since they will require far-reaching infrastructural changes to the respective systems, such as extensive installations of renewable generation and electrolysis capacities as well as sufficient subsurface storage capacities for both CO2 and CH4. Therefore, this study incorporates an assessment of the present subsurface storage potential for CO2 and CH4 in Germany. Furthermore, a basic forecast study for the German energy system with an assumed mass deployment of the proposed SNG-based PtG–GtP energy storage system for the year 2050 is conducted. In case of a fully circular use of CO2/CH4, when electricity is solely generated by renewable energy sources, 736 GW of renewables, 234 GW of electrolysis and 62 GW of gas-to-power capacities are required in the best case scenario in 2050. The total storage volume on the national scale of Germany for both CO2 and CH4 was determined to be 7.8 billion N m3, respectively, leading to a CH4 storage capacity of 54.5 TW h. The presented investigations illustrate the feasibility of large-scale energy storage systems for renewable electricity based on high temperature electrolysis, catalytic methanation and Allam power cycles paired with large subsurface storages for CO2 and CH4.Petroleum Engineerin