Kuhs, Werner F.

[["dc.bibliographiccitation.firstpage","4295"],["dc.bibliographiccitation.issue","17"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry Letters"],["dc.bibliographiccitation.lastpage","4299"],["dc.bibliographiccitation.volume","8"],["dc.contributor.author","Amos, Daniel M."],["dc.contributor.author","Donnelly, Mary-Ellen"],["dc.contributor.author","Teeratchanan, Pattanasak"],["dc.contributor.author","Bull, Craig L."],["dc.contributor.author","Falenty, Andrzej"],["dc.contributor.author","Kuhs, Werner F."],["dc.contributor.author","Hermann, Andreas"],["dc.contributor.author","Loveday, John S."],["dc.date.accessioned","2020-12-10T15:22:46Z"],["dc.date.available","2020-12-10T15:22:46Z"],["dc.date.issued","2017"],["dc.identifier.doi","10.1021/acs.jpclett.7b01787"],["dc.identifier.issn","1948-7185"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/16715"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/73532"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.notes.intern","Merged from goescholar"],["dc.rights","Goescholar"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.title","A Chiral Gas–Hydrate Structure Common to the Carbon Dioxide–Water and Hydrogen–Water Systems"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1381"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Journal of the American Ceramic Society"],["dc.bibliographiccitation.lastpage","1392"],["dc.bibliographiccitation.volume","101"],["dc.contributor.author","Neher, Sigmund H."],["dc.contributor.author","Klein, Helmut"],["dc.contributor.author","Kuhs, Werner F."],["dc.date.accessioned","2020-12-10T18:28:54Z"],["dc.date.available","2020-12-10T18:28:54Z"],["dc.date.issued","2017"],["dc.identifier.doi","10.1111/jace.2018.101.issue-3"],["dc.identifier.issn","0002-7820"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/76448"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Determination of crystal size distributions in alumina ceramics by a novel X-ray diffraction procedure"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","6275"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","Energy & Fuels"],["dc.bibliographiccitation.lastpage","6283"],["dc.bibliographiccitation.volume","28"],["dc.contributor.author","Falenty, Andrzej"],["dc.contributor.author","Kuhs, Werner F."],["dc.contributor.author","Glockzin, Michael"],["dc.contributor.author","Rehder, Gregor"],["dc.date.accessioned","2018-11-07T09:34:23Z"],["dc.date.available","2018-11-07T09:34:23Z"],["dc.date.issued","2014"],["dc.description.abstract","Self-preservation is a kinetic anomaly that allows for storing a substantial amount of gas locked in gas hydrate far outside its thermodynamic stability field for a period of days, weeks, or even months under very mild pressuretemperature (pT) conditions, by merely maintaining temperatures below the melting point of ice. Utilizing this phenomenon for low-cost storage and transportation of natural gas is not yet sufficiently developed to be competitive with already existing, well-established methods (e.g., liquefied natural gas (LNG), gas to liquid (GTL), compressed natural gas (CNG), or pipeline (PL)). Aside from the refinement of numerous engineering and safety aspects, a deeper understanding of the self-preservation phenomenon is needed in order to promote these technologies. We address some of these outstanding issues in a series of isothermalisobaric pressurevolumetemperature (pVT) experiments exploring the kinetics of the dissociation of pure sI methane hydrate to ice and CH4 gas in a wide pT field applicable to gas-hydrate-based technologies. By means of ex situ cryo-SEM, we correlate the kinetic data with the morphology of initially formed ice coatings recovered at various stages of the transformation. The pT dependence of the self-preservation strength is seen as a complex interplay between (1) ice microstructures (shape, arrangement, and size of ice crystals) and (2) annealing rate of the ice coating that acts as a diffusion barrier for escaping gas. Moreover, we recognize a progressive sintering of ice coatings of individual particles when close to the melting point of ice. The optimal conditions for the transport and storage at ambient pressure, where this issue is minimized and the preservation strength is still very high, have been found at similar to 250 K. Further fine-tuning of the storage capacity may involve elevating the storage pressure and active temperature control."],["dc.description.sponsorship","German Federal Ministry of Economics and Technology (BMWi) [03SX250J]"],["dc.identifier.doi","10.1021/ef501409g"],["dc.identifier.isi","000343336000011"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/32160"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1520-5029"],["dc.relation.issn","0887-0624"],["dc.title","\"Self-Preservation\" of CH4 Hydrates for Gas Transport Technology: Pressure-Temperature Dependence and Ice Microstructures"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","27159"],["dc.bibliographiccitation.issue","48"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry C"],["dc.bibliographiccitation.lastpage","27172"],["dc.bibliographiccitation.volume","120"],["dc.contributor.author","Falenty, A."],["dc.contributor.author","Qin, Jian-Chun"],["dc.contributor.author","Salamatin, Andrey N."],["dc.contributor.author","Yang, L."],["dc.contributor.author","Kuhs, Werner F."],["dc.date.accessioned","2018-11-07T10:04:36Z"],["dc.date.available","2018-11-07T10:04:36Z"],["dc.date.issued","2016"],["dc.description.abstract","The exchange process between CO2 and methane hydrate has been observed in numerous laboratory experiments, computer simulations, and recently confirmed in a field test. Yet, to date there is no kinetic model capable of accurately predicting the swapping process at given fluid composition and p-T conditions. Major obstacles on the way to an adequate mathematical description are caused by the insufficient characterization of experimental environments and a nearly complete lack of information on the time-resolved composition of the two-phase fluid at the gas hydrate interface. Here we show that all necessary data can be provided by a combination of cryo-SEM, Raman, and neutron diffraction measurements that deliver accurate space-averaged, time-resolved in situ data on the CH4-CO2 exchange reactions at conditions relevant to sedimentary matrixes of continental margins. Results from diffraction are cross-correlated with ex situ Raman spectroscopy to provide reliable information on the preferential sites for CO2 and CH4 in the (partially) exchanged hydrate. We also show a novel approach based on scattering of neutrons to probe the fluid composition during the in situ replacement in a time-resolved, noninvasive manner. The replacement is seen as a two-step process including (1) a fast surface reaction parallel to a fast enrichment of the surrounding fluid phase with CH4 followed by (2) a much slower permeation-limited gas swapping between the gas hydrate and mixed ambient CH4-CO2 fluid. The main part of the replacement reaction takes place in the second stage. Based on our earlier experimental studies and existing literature we work toward a quantitative gas exchange model which elaborates the hole-in-cage-wall diffusion mechanism to describe the two-component gas replacement."],["dc.identifier.doi","10.1021/acs.jpcc.6b09460"],["dc.identifier.isi","000389624400009"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/38730"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1932-7447"],["dc.title","Fluid Composition and Kinetics of the in Situ Replacement in CH4-CO2 Hydrate System"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","75"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Zeitschrift für Kristallographie - Crystalline Materials"],["dc.bibliographiccitation.lastpage","86"],["dc.bibliographiccitation.volume","230"],["dc.contributor.author","Hansen, Thomas C."],["dc.contributor.author","Sippel, Christian"],["dc.contributor.author","Kuhs, Werner F."],["dc.date.accessioned","2018-11-07T10:04:06Z"],["dc.date.available","2018-11-07T10:04:06Z"],["dc.date.issued","2015"],["dc.description.abstract","Different descriptions of the stacking disorder of the so-called \"cubic\" phase \"ice I-c\" and stacking-faulted hexagonal ice I-h exist. We present an overview of the effect of different stacking disorder interaction ranges s from s = 2 to s = 4 after Jagodzinski on the (neutron) powder diffraction patterns of stacking-disordered ice I, which we propose to name ice I-ch. We fit in a systematic approach simulated diffraction data of ice I-ch for s up to 4 with a multi-peak approach. In this way we allow for estimating the relative proportion of cubic sequences in the stacking sequences by using readily accessible observables of a diffraction pattern."],["dc.description.sponsorship","ILL"],["dc.identifier.doi","10.1515/zkri-2014-1780"],["dc.identifier.isi","000346764800010"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/38623"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Walter De Gruyter Gmbh"],["dc.relation.issn","2196-7105"],["dc.relation.issn","2194-4946"],["dc.title","Approximations to the full description of stacking disorder in ice I for powder diffraction"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1228"],["dc.bibliographiccitation.issue","8-9"],["dc.bibliographiccitation.journal","American Mineralogist"],["dc.bibliographiccitation.lastpage","1239"],["dc.bibliographiccitation.volume","89"],["dc.contributor.author","Genov, G."],["dc.contributor.author","Kuhs, Werner F."],["dc.contributor.author","Staykova, D. K."],["dc.contributor.author","Goreshnik, E."],["dc.contributor.author","Salamatin, Andrey N."],["dc.date.accessioned","2018-11-07T10:46:30Z"],["dc.date.available","2018-11-07T10:46:30Z"],["dc.date.issued","2004"],["dc.description.abstract","Gas hydrates grown at gas-ice interfaces were examined by electron microscopy and found to have a sub-micrometer porous structure. In situ observations of the formation of porous CH4- and CO2-hydrates from deuterated ice Ih powders were made at different pressures and temperatures, using time-resolved neutron diffraction data from the high-flux D20 diffractometer (ILL, Grenoble) as well as in-house gas consumption measurements. The CO2 experiments conducted at low temperatures are particularly important for settling the open question of the existence Of CO2 hydrates on Mars. We found that at similar excess fugacities, the reaction of CO2 was distinctly faster than that of CH4. A phenomenological model for the kinetics of the gas hydrate formation from powders of spherical ice particles is developed with emphasis on ice-grain fracturing and sample-consolidation effects due to the outward growth of gas hydrate. It describes (1) the initial stage of fast crack-filling and hydrate film spreading over the ice surface and the two subsequent stages which are limited by (2) the clathration reaction at the ice-hydrate interface and/or by (3) the diffusive gas and water transport through the hydrate shells surrounding the shrinking ice cores. In the case Of CO2-hydrate, the activation energies of the ice-surface coating in stage I are estimated to be 5.5 kJ/mol at low temperatures and 31.5 kJ/mol above 220 K, indicating that water molecule mobility at the ice surface plays a considerable role in the clathration reaction. Comparable activation energies of 42.3 and 54.6 kJ/mol are observed in the high temperature range for the reaction- and diffusion-limited stages 2 and 3, respectively."],["dc.identifier.isi","000223448100011"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/47760"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Mineralogical Soc Amer"],["dc.relation.issn","0003-004X"],["dc.title","Experimental studies on the formation of porous gas hydrates"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","231"],["dc.bibliographiccitation.issue","7530"],["dc.bibliographiccitation.journal","Nature"],["dc.bibliographiccitation.lastpage","+"],["dc.bibliographiccitation.volume","516"],["dc.contributor.author","Falenty, Andrzej"],["dc.contributor.author","Hansen, Thomas C."],["dc.contributor.author","Kuhs, Werner F."],["dc.date.accessioned","2018-11-07T09:31:19Z"],["dc.date.available","2018-11-07T09:31:19Z"],["dc.date.issued","2014"],["dc.description.abstract","Gas hydrates are ice-like solids, in which guest molecules or atoms are trapped inside cages formed within a crystalline host framework (clathrate) of hydrogen-bonded water molecules(1). They are naturally present in large quantities on the deep ocean floor and as permafrost, can form in and block gas pipelines, and are thought to occur widely on Earth and beyond. A natural point of reference for this large and ubiquitous family of inclusion compounds is the empty hydrate lattice(1-6), which is usually regarded as experimentally inaccessible because the guest species stabilize the host framework. However, it has been suggested that sufficiently small guests may be removed to leave behind metastable empty clathrates(7,8), and guest-free Si-and Ge-clathrates have indeed been obtained(9,10). Here we show that this strategy can also be applied to water-based clathrates: five days of continuous vacuum pumping on small particles of neon hydrate (of structure sII) removes all guests, allowing us to determine the crystal structure, thermal expansivity and limit of metastability of the empty hydrate. It is the seventeenth experimentally established crystalline ice phase(11), ice XVI according to the current ice nomenclature, has a density of 0.81 grams per cubic centimetre (making it the least dense of all known crystalline water phases) and is expected(7,12) to be the stable low-temperature phase of water at negative pressures (that is, under tension). We find that the empty hydrate structure exhibits negative thermal expansion below about 55 kelvin, and that it is mechanically more stable and has at low temperatures larger lattice constants than the filled hydrate. These observations attest to the importance of kinetic effects and host-guest interactions in clathrate hydrates, with further characterization of the empty hydrate expected to improve our understanding of the structure, properties and behaviour of these unique materials."],["dc.description.sponsorship","Bundesministeriums fur Bildung und Forschung (BMBF)"],["dc.identifier.doi","10.1038/nature14014"],["dc.identifier.isi","000346383500041"],["dc.identifier.pmid","25503235"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/31515"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Nature Publishing Group"],["dc.relation.issn","1476-4687"],["dc.relation.issn","0028-0836"],["dc.title","Formation and properties of ice XVI obtained by emptying a type sII clathrate hydrate"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1"],["dc.bibliographiccitation.issue","1-4"],["dc.bibliographiccitation.journal","Marine Geology"],["dc.bibliographiccitation.lastpage","14"],["dc.bibliographiccitation.volume","244"],["dc.contributor.author","Bohrmann, Gerhard"],["dc.contributor.author","Kuhs, Werner F."],["dc.contributor.author","Klapp, Stephan A."],["dc.contributor.author","Techmer, Kirsten S."],["dc.contributor.author","Klein, Helmut"],["dc.contributor.author","Murshed, M. Mangir"],["dc.contributor.author","Abegg, Fritz"],["dc.date.accessioned","2018-11-07T10:57:49Z"],["dc.date.available","2018-11-07T10:57:49Z"],["dc.date.issued","2007"],["dc.description.abstract","The state of preservation of natural gas hydrate samples, recovered from 6 sites drilled during ODP Leg 204 at southern summit of Hydrate Ridge, Oregon Margin, has been investigated by X-ray diffraction (XRD) and cryo-scanning-electron-inicroscopy (cryo-SEM) techniques. A detailed characterization of the state of decomposition of gas hydrates is necessary since no pressurized autoclave tools were used for sampling and partial dissociation must have occurred during recovery prior to the quench and storage in liquid nitrogen. Samples from 16 distinct horizons have been investigated by synchrotron X-ray diffraction measurements at HASYLAB/ Hamburg. A full profile fitting analysis (\"Rietveld method\") of synchrotron XRD data provides quantitative phase determinations of the major sample constituents such as gas hydrate structure I (sI), hexagonal ice (Ih) and quartz. The ice content (Ih) in each sample is related to frozen water composed of both original existing pore water and the water from decomposed hydrates. Hydrate contents as measured by diffraction vary between 0 and 68 wt.% in the samples we measured. Samples with low hydrate content usually show micro-structural features in cryo-SEM ascribed to extensive decomposition. Comparing the appearance of hydrates at different scales, the grade of preservation seems to be primarily correlated with the contiguous volume of the original existing hydrate; the dissociation front appears to be indicated by micrometer-sized pores in a dense ice matrix. (c) 2007 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.margeo.2007.05.003"],["dc.identifier.isi","000250150800001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/50340"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","0025-3227"],["dc.title","Appearance and preservation of natural gas hydrate from Hydrate Ridge sampled during ODP Leg 204 drilling"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","S3009"],["dc.bibliographiccitation.issue","40"],["dc.bibliographiccitation.journal","Journal of Physics Condensed Matter"],["dc.bibliographiccitation.lastpage","S3015"],["dc.bibliographiccitation.volume","17"],["dc.contributor.author","Kuhs, Werner F."],["dc.contributor.author","Hensel, E."],["dc.contributor.author","Bartels, H."],["dc.date.accessioned","2018-11-07T10:55:00Z"],["dc.date.available","2018-11-07T10:55:00Z"],["dc.date.issued","2005"],["dc.description.abstract","Gas pressure cells techniques are well adapted to neutron scattering applications. They can routinely be used at least up to pressures of 0.5 GPa in a wide temperature range, they allow for an accurate pressure control and also provide the chemical activity for the study of materials where the gas is not only the pressure transmitting medium but also a chemical constituent of the system. We present some of the gas pressure cells which were developed by us for specific needs and discuss their design and performance."],["dc.identifier.doi","10.1088/0953-8984/17/40/003"],["dc.identifier.isi","000232997300004"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/49689"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Iop Publishing Ltd"],["dc.publisher.place","Bristol"],["dc.relation.conference","International Workshop on Medium Pressure Advances for Neutron Scattering"],["dc.relation.eventlocation","Inst Laue Langevine, Grenoble, FRANCE"],["dc.relation.issn","0953-8984"],["dc.title","Gas pressure cells for elastic and inelastic neutron scattering"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1437"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Journal of Applied Crystallography"],["dc.bibliographiccitation.lastpage","1439"],["dc.bibliographiccitation.volume","52"],["dc.contributor.author","Neher, Sigmund H."],["dc.contributor.author","Klein, Helmut"],["dc.contributor.author","Kuhs, Werner F."],["dc.date.accessioned","2020-12-10T18:25:57Z"],["dc.date.available","2020-12-10T18:25:57Z"],["dc.date.issued","2019"],["dc.identifier.doi","10.1107/S1600576719012159"],["dc.identifier.eissn","1600-5767"],["dc.identifier.pmid","31798363"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/17179"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/75893"],["dc.notes.intern","DOI Import GROB-354"],["dc.notes.intern","Merged from goescholar"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.title","FXD-CSD-GUI : a graphical user interface for the X-ray-diffraction-based determination of crystallite size distributions"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]