The library system of the DFVLR: Present status, planned reorganization, user possibilities

This paper gives an overview of the present status, planned alterations, and the scope of users of the DFVLR library, as well as a survey of library related activities outside of the library department. Attention is given to the tasks of the DFVLR which include research, assistance in planning and carrying out projects, and the construction and operation of large test installations, showing how they relate to demands on the library

In situ characterization of the decomposition behavior of Mg(BH4)(2) by X-ray Raman scattering spectroscopy

We present an in situ study of the thermal decomposition of Mg(BH4)(2) in a hydrogen atmosphere of up to 4 bar and up to 500 degrees C using X-ray Raman scattering spectroscopy at the boron K-edge and the magnesium L2,3-edges. The combination of the fingerprinting analysis of both edges yields detailed quantitative information on the reaction products during decomposition, an issue of crucial importance in determining whether Mg(BH4)(2) can be used as a next-generation hydrogen storage material. This work reveals the formation of reaction intermediate(s) at 300 degrees C, accompanied by a significant hydrogen release without the occurrence of stable boron compounds such as amorphous boron or MgB12H12. At temperatures between 300 degrees C and 400 degrees C, further hydrogen release proceeds via the formation of higher boranes and crystalline MgH2. Above 400 degrees C, decomposition into the constituting elements takes place. Therefore, at moderate temperatures, Mg(BH4)(2) is shown to be a promising high-density hydrogen storage material with great potential for reversible energy storage applications.Peer reviewe

Deconvolving Instrumental and Intrinsic Broadening in Excited State X-ray Spectroscopies

Intrinsic and experimental mechanisms frequently lead to broadening of spectral features in excited-state spectroscopies. For example, intrinsic broadening occurs in x-ray absorption spectroscopy (XAS) measurements of heavy elements where the core-hole lifetime is very short. On the other hand, nonresonant x-ray Raman scattering (XRS) and other energy loss measurements are more limited by instrumental resolution. Here, we demonstrate that the Richardson-Lucy (RL) iterative algorithm provides a robust method for deconvolving instrumental and intrinsic resolutions from typical XAS and XRS data. For the K-edge XAS of Ag, we find nearly complete removal of ~9.3 eV FWHM broadening from the combined effects of the short core-hole lifetime and instrumental resolution. We are also able to remove nearly all instrumental broadening in an XRS measurement of diamond, with the resulting improved spectrum comparing favorably with prior soft x-ray XAS measurements. We present a practical methodology for implementing the RL algorithm to these problems, emphasizing the importance of testing for stability of the deconvolution process against noise amplification, perturbations in the initial spectra, and uncertainties in the core-hole lifetime.Comment: 35 pages, 13 figure

Compton scattering beyond the impulse approximation

We treat the non-relativistic Compton scattering process in which an incoming photon scatters from an N-electron many-body state to yield an outgoing photon and a recoil electron, without invoking the commonly used frameworks of either the impulse approximation (IA) or the independent particle model (IPM). An expression for the associated triple differential scattering cross section is obtained in terms of Dyson orbitals, which give the overlap amplitudes between the N-electron initial state and the (N-1) electron singly ionized quantum states of the target. We show how in the high energy transfer regime, one can recover from our general formalism the standard IA based formula for the cross section which involves the ground state electron momentum density (EMD) of the initial state. Our formalism will permit the analysis and interpretation of electronic transitions in correlated electron systems via inelastic x-ray scattering (IXS) spectroscopy beyond the constraints of the IA and the IPM.Comment: 7 pages, 1 figur

Understanding the Surface Regeneration and Reactivity of Garnet Solid-State Electrolytes

Garnet solid electrolyte-based Li-ion batteries can be used in energy storage devices with high energy densities and thermal stability. However, the tendency of garnets to form lithium hydroxide and carbonate on the surface in an ambient atmosphere poses significant processing challenges. In this work, the decomposition of surface layers under various gas environments is studied by using the surface sensitive techniques, near ambient pressure x-ray photoelectron spectroscopy and grazing incidence diffraction. It is found that heating to 500 °C under oxygen atmosphere (of 1 mbar and above) leads to a clean garnet surface, whereas low oxygen partial pressures (i.e., in argon or vacuum) lead to additional graphitic carbon deposits. The clean surface of garnets reacts directly with moisture and carbon dioxide below 400 and 500 °C respectively. This suggests that additional CO2 concentration controls are needed for the handling of garnets. By heating under O2 along with avoiding H2O and CO2, symmetric cells with less than 10 Ωcm2 interface resistance are prepared without the use of any interlayers; plating currents of greater than 1 mAcm-2 without dendrite initiation are demonstrated.S.V. acknowledges funding from the Cambridge Commonwealth European and International Trust, Faraday Institution (SOLBAT, FIRG007) and Royal Society (RP/R1/180147). F.N.S also acknowledges funding from The Faraday Institution CATMAT project (FIRG016). S.N. thanks the Royal Society (United Kingdom) and Science and Engineering Research Board (Government of India) for the award of Newton-Bhabha International Fellowship (NIF/R1/180075). C.P.G thanks the EU via an Advanced EU ERC grant (EC H2020 835073). Professor Norman Fleck and Professor Vikram Deshpande are thanked for access to their laboratories for sample preparation and for helpful discussions. We thank Simon Marshall and Graham Smith for assistance in operating hot-press and Anthony Dennis and Harry Druiff for assistance in cutting hot-pressed samples. We thank Diamond Light Source, UK for access to beamline B07 (SI29728) for NAP-XPS measurements and DELTA, Germany for providing synchrotron radiation at beamline BL9 for grazing incidence X-ray diffraction measurements. We also acknowledge I11 beamline for synchrotron XRD at Diamond Light Source, UK under BAG proposal (CY28349)

Understanding the Surface Regeneration and Reactivity of Garnet Solid-State Electrolytes

Garnet solid-electrolyte-based Li-metal batteries can be used in energy storage devices with high energy densities and thermal stability. However, the tendency of garnets to form lithium hydroxide and carbonate on the surface in an ambient atmosphere poses significant processing challenges. In this work, the decomposition of surface layers under various gas environments is studied by using two surface-sensitive techniques, near-ambient-pressure X-ray photoelectron spectroscopy and grazing incidence X-ray diffraction. It is found that heating to 500 °C under an oxygen atmosphere (of 1 mbar and above) leads to a clean garnet surface, whereas low oxygen partial pressures (i.e., in argon or vacuum) lead to additional graphitic carbon deposits. The clean surface of garnets reacts directly with moisture and carbon dioxide below 400 and 500 °C, respectively. This suggests that additional CO2 concentration controls are needed for the handling of garnets. By heating under O2 along with avoiding H2O and CO2, symmetric cells with less than 10 Ωcm2 interface resistance are prepared without the use of any interlayers; plating currents of >1 mA cm–2 without dendrite initiation are demonstrated