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28 results on '"Grimm, Nico"'

1. Temperature-dependent EXAFS measurements of the Pb L3-edge allow quantification of the anharmonicity of the lead-halide bond of chlorine-substituted methylammonium (MA) lead triiodide

Author

Schuck, Götz, Többens, Daniel M., Wallacher, Dirk, Grimm, Nico, Tien, Tong Sy, and Schorr, Susan

Subjects
Condensed Matter - Materials Science
Abstract

This article reports on studies of chlorine-substituted MAPbI3 using combined temperature-dependent XRD synchrotron and Pb-L3 edge EXAFS to analyze the anharmonicity of the lead halide bond. The EXAFS parameters were described in the orthorhombic phase by an Einstein or T2 type behavior, which was then compared with the experimental EXAFS parameters of the tetragonal/cubic phase. In the orthorhombic phase, it was observed that the asymmetry of the pair distribution function (cumulant C3) in MAPbCl3 is much lower than in MAPbI3. Compared with the behavior in the orthorhombic phase, the anharmonicity changed after the phase transition to the room temperature phase, with MAPbCl3 showing an increased anharmonicity and MAPbI3 a decrease. The differences between MAPbI3 and 2% chlorine substitution were small, both in the orthorhombic and tetragonal phases. By determining the structural parameters required to convert the effective force constants k0 and k3 resulting from the EXAFS analysis into the Morse potential parameters {\alpha} and D, we could establish that our results agree with other experimental findings. Moreover, by using XRD we found that the [PbX6] octahedra shrink slightly in the tetragonal phase of MAPbI3 and MAPbI2.94Cl0.06, towards increasing temperatures. This behavior in the tetragonal phase is related to the dominant negative tension effects observed by EXAFS.

Published
2021
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8. The Role of Temperature and Adsorbate on Negative Gas Adsorption in the Mesoporous Metal-Organic Framework DUT-49

Author

Senkovska, Irene, Krause, Simon, Evans, Jack, Bon, Volodymyr, Senkovska, Irena, Coudert, François-Xavier, Többens, Daniel, Wallacher, Dirk, Grimm, Nico, Kaskel, Stefan, Technische Universität Dresden = Dresden University of Technology (TU Dresden), Stratingh Institute for Chemistry, University of Groningen [Groningen], Institut de Recherche de Chimie Paris (IRCP), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Ministère de la Culture (MC), and Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)

Subjects
[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, [CHIM.MATE]Chemical Sciences/Material chemistry
Abstract

International audience; Unusual adsorption phenomena, such as breathing and negative gas adsorption (NGA), are rare and challenge our thermodynamic understanding of adsorption in deformable porous solids. In particular, NGA appears to break the rules of thermodynamics in these materials by exhibiting a spontaneous release of gas accompanying an increase in pressure. This anomaly relies on long-lived metastable states. A fundamental understanding of this process is desperately required for the discovery of new materials with this exotic property. Interestingly, NGA was initially observed upon adsorption of methane at relatively low temperature, close to the respective standard boiling point of the adsorptive, and no NGA was observed at elevated temperatures. In this contribution, we present an extensive investigation of adsorption of an array of gases at various temperatures on DUT-49, a material which features an NGA transition. Experiments, featuring a wide range of gases and vapors at temperatures ranging from 21–308 K, were used to identify for each guest a critical temperature range in which NGA can be detected. The experimental results were complemented by molecular simulations that help to rationalize the absence of NGA at elevated temperatures, and the non-monotonic behavior present upon temperature decrease. Furthermore, this in-depth analysis highlights the crucial thermodynamic and kinetic conditions for NGA, which are unique to each guest and potentially other solids with similar effects. We expect this exploration to provide detailed guidelines for experimentally discovering NGA and related “rule breaking” phenomena in novel and already known materials, and provide the conditions required for the application of this effect, for example as pressure amplifying materials.

Published
2021

11. Cooperative Light-Induced Breathing of Soft Porous Crystals via Azobenzene Buckling

Author

Krause, Simon, primary, Evans, Jack D., primary, Bon, Volodymyr, primary, Crespi, Stefano, primary, Danowski, Wojciech, primary, Browne, Wesley R, primary, Ehrling, Sebastian, primary, Walenszus, Francesco, primary, Wallacher, Dirk, primary, Grimm, Nico, primary, Többens, Daniel D., primary, Weiss, Manfred S., primary, Kaskel, Stefan, primary, and Feringa, Ben L., primary

Published
2020
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15. BerILL: The ultimate humidity chamber for neutron scattering

Author

Gonthier, Julien, primary, Barrett, Matthew A., additional, Aguettaz, Olivier, additional, Baudoin, Simon, additional, Bourgeat-Lami, Eric, additional, Demé, Bruno, additional, Grimm, Nico, additional, Hauß, Thomas, additional, Kiefer, Klaus, additional, Lelièvre-Berna, Eddy, additional, Perkins, Adrian, additional, and Wallacher, Dirk, additional

Published
2019
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19. CO2 Sorption to Subsingle Hydration Layer Montmorillonite Clay Studied by Excess Sorption and Neutron Diffraction Measurements

Author

Rother, Gernot, primary, Ilton, Eugene S., additional, Wallacher, Dirk, additional, Hauβ, Thomas, additional, Schaef, Herbert T., additional, Qafoku, Odeta, additional, Rosso, Kevin M., additional, Felmy, Andrew R., additional, Krukowski, Elizabeth G., additional, Stack, Andrew G., additional, Grimm, Nico, additional, and Bodnar, Robert J., additional

Published
2012
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23. Sorption Phase of Supercritical CO2in Silica Aerogel: Experiments and Mesoscale Computer Simulations

Author

Rother, Gernot, Vlcek, Lukas, Gruszkiewicz, Miroslaw S., Chialvo, Ariel A., Anovitz, Lawrence M., Bañuelos, José L., Wallacher, Dirk, Grimm, Nico, and Cole, David R.

Abstract

Adsorption of supercritical CO2in nanoporous silica aerogel was investigated by a combination of experiments and molecular-level computer modeling. High-pressure gravimetric and vibrating tube densimetry techniques were used to measure the mean pore fluid density and excess sorption at 35 and 50 °C and pressures of 0–200 bar. Densification of the pore fluid was observed at bulk fluid densities below 0.7 g/cm3. Far above the bulk critical density, near-zero sorption or weak depletion effects were measured, while broad excess sorption maxima form in the vicinity of the bulk critical density. The CO2sorption properties are very similar for two aerogels with bulk densities of 0.1 and 0.2 g/cm3, respectively. The spatial distribution of the confined supercritical fluid was analyzed in terms of two nanodispersed phases with sorption- and bulk-phase densities and their volumes by means of the adsorbed phase model (APM), which used data from gravimetric sorption and small-angle neutron scattering experiments. To gain more detailed insight into supercritical fluid sorption, large-scale lattice gas GCMC simulations were utilized and tuned to resemble the experimental excess sorption data. The computed three-dimensional pore fluid density distributions show that the observed maximum of the excess sorption near the critical density originates from large density fluctuations pinned to the pore walls. At this maximum, the size of these fluctuations is comparable to the prevailing pore sizes.

Published
2014
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24. Pore Size Effects on the Sorption of Supercritical CO2in Mesoporous CPG-10 Silica

Author

Rother, Gernot, Krukowski, Elizabeth G., Wallacher, Dirk, Grimm, Nico, Bodnar, Robert J., and Cole, David R.

Abstract

Excess sorption isotherms of supercritical carbon dioxide in mesoporous CPG-10 silica glasses with nominal pore sizes of 7.5 and 35 nm were measured gravimetrically at 35 and 50 °C and pressures of 0–200 bar. Formation of broad maxima in the excess sorption was observed at fluid densities below the bulk critical density. Positive values of excess sorption were measured at bulk densities below 0.7 g/cm3, i.e., the interfacial fluid is denser than the bulk fluid at low pressures. Zero and negative values were obtained at higher densities, i.e., the adsorbed fluid becomes equal to and eventually less dense than the corresponding bulk fluid. Pronounced confinement effects on sorption behavior have been found and further analyzed by normalizing the excess sorption to the adsorbent surface area and pore volume, yielding new insight into supercritical fluid adsorption in this range of pore sizes and P,Tconditions. If normalized to the specific surface area, the excess sorption is higher for the 35 nm pore size material, but the pore volume normalized excess sorption is higher for the 7.5 nm pore size material. With increasing pore width, the excess sorption peak position shifts to higher pressure. Both CPG-10 materials exhibit regions of constant mean pore fluid density as a function of bulk CO2density at 35 °C but not at 50 °C. This region is located between the excess sorption peak maximum and the adsorption/depletion transition point. Applied to the situation of CO2sequestration in dry sandstone formations, the results of this study indicate that carbon storage capacity is enhanced by sorption effects, particularly at low temperature and in narrow pores with high surface to volume ratios.

Published
2012
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26. Deuterium absorption in Mg70Al30 thin films with bilayer catalysts: A comparative neutron reflectometry study

Author

Poirier, Eric, Harrower, Chris T., Kalisvaart, Peter, Bird, Adam, Teichert, Anke, Wallacher, Dirk, Grimm, Nico, Steitz, Roland, Mitlin, David, and Fritzsche, Helmut

Subjects
*DEUTERIUM, *ABSORPTION, *THIN films, *ALUMINUM-magnesium alloys, *TEMPERATURE effect, *CATALYSTS, *HYDRIDES
Abstract

Abstract: We present a neutron reflectometry study of deuterium absorption in thin films of Al-containing Mg alloys capped with a Ta/Pd, Ni/Pd and Ti/Pd-catalyst bilayer. The measurements were performed at room temperature over the 0–1bar pressure range under quasi-equilibrium conditions. The modeling of the measurements provided a nanoscale representation of the deuterium profile in the layers at different stages of the absorption process. The absorption mechanism observed was found to involve spillover of atomic deuterium from the catalyst layer to the Mg alloy phase, followed by the deuteration of the Mg alloy. Complete deuteration of the Mg alloy occurs in a pressure range between 100 and 500mbar, dependent on the type of bilayer catalyst. The use of a Ti/Pd bilayer catalyst yielded the best results in terms of both storage density and kinetic properties. [Copyright &y& Elsevier]

Published
2011
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27. Massive Pressure Amplification by Stimulated Contraction of Mesoporous Frameworks*.

Author

Bon V, Krause S, Senkovska I, Grimm N, Wallacher D, Többens DM, and Kaskel S

Abstract

Herein we demonstrate mesoporous frameworks interacting with carbon dioxide leading to stimulated structural contractions and massive out-of-equilibrium pressure amplification well beyond ambient pressure. Carbon dioxide, a non-toxic and non-flammable working medium, is promising for the development of pressure-amplifying frameworks for pneumatic technologies and safety systems. The strong interaction of the fluid with the framework even contracts DUT-46, a framework hitherto considered as non-flexible. Synchrotron-based in situ PXRD/adsorption experiments reveal the characteristic contraction pressure for DUT-49 pressure amplification in the range of 350-680 kPa. The stimulated framework contraction expels 1.1 to 2.4 mmol g -1 CO 2 leading to autonomous pressure amplification in a pneumatic demonstrator system up to 428 kPa. According to system level estimations even higher theoretical pressure amplification may be achieved between 535 and 1011 kPa., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Published
2021
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28. CO2 sorption to subsingle hydration layer montmorillonite clay studied by excess sorption and neutron diffraction measurements.

Author

Rother G, Ilton ES, Wallacher D, Hauβ T, Schaef HT, Qafoku O, Rosso KM, Felmy AR, Krukowski EG, Stack AG, Grimm N, and Bodnar RJ

Subjects
Adsorption, Carbon Sequestration, Neutron Diffraction, Bentonite chemistry, Carbon Dioxide chemistry
Abstract

Geologic storage of CO(2) requires that the caprock sealing the storage rock is highly impermeable to CO(2). Swelling clays, which are important components of caprocks, may interact with CO(2) leading to volume change and potentially impacting the seal quality. The interactions of supercritical (sc) CO(2) with Na saturated montmorillonite clay containing a subsingle layer of water in the interlayer region have been studied by sorption and neutron diffraction techniques. The excess sorption isotherms show maxima at bulk CO(2) densities of ≈ 0.15 g/cm(3), followed by an approximately linear decrease of excess sorption to zero and negative values with increasing CO(2) bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO(2) are sorbed into the interlayer region, leading to depression of the interlayer peak intensity and an increase of the d(001) spacing by ca. 0.5 Å. The density of CO(2) in the clay pores is relatively stable over a wide range of CO(2) pressures at a given temperature, indicating the formation of a clay-CO(2) phase. At the excess sorption maximum, increasing CO(2) sorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak temperature dependence.

Published
2013
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