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12 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I20-EDE-Energy Dispersive EXAFS (EDE)	Effect of salinity, pressure and temperature on the solubility of smithsonite (ZnCO3) and Zn complexation in crustal and upper mantle hydrothermal fluids Stefan Farsang , Marion Louvel , Angelika D. Rosa , Monica Amboage , Simone Anzellini , Remo N. Widmer , Simon A. T. Redfern Chemical Geology 52 DOI: 10.1016/j.chemgeo.2021.120320 Diamond Proposal Number(s): [21869] Show Abstract ▼ Abstract: Modelling the reservoirs and fluxes of Zn in Earth's crust and mantle requires data on the solubility of its mineral hosts and ores in coexisting fluids, as well as on the complexation of Zn in these fluids as a function of fluid composition, pressure, and temperature. However, due to experimental challenges, the availability of such data is limited to pressures below 1 GPa, which are only representative of upper crust conditions. Here, we report the effects of salinity (0–4.5 m total Cl), pressure (0.5–6 GPa) and temperature (25–400 °C) on the solubility of smithsonite (ZnCO3) and speciation of Zn in aqueous fluids. Solubilities at mineral-fluid equilibria and Zn speciation in the coexisting aqueous fluids were determined in situ at high pressure-temperature conditions by synchrotron X-ray fluorescence (XRF) and X-ray absorption spectroscopy (XAS) using resistively heated diamond anvil cells (RH-DAC). The solubility of smithsonite increases with salinity, pressure, and temperature. In agreement with previous studies, conducted at lower pressures (below 1 GPa), we observed a gradual transition from octahedral hydrated [Zn(H2O)6]2+ to tetrahedral hydrated and chlorinated [Zn(H2O)4-nCln]2-n (n = 1–4) complexes with increasing salinity and temperature. Our results suggest that these tetrahedral complexes remain stable under the conditions relevant to cold slab dehydration. This change of coordination further enhances the solubility of smithsonite in Cl-rich fluids and provides a likely mechanism for the efficient uptake of Zn by slab-derived fluids.	May 2021
I15-Extreme Conditions	Rich polymorphism of a metal-organic framework in pressure-temperature space Remo N. Widmer , Giulio I. Lampronti , Siwar Chibani , Craig Wilson , Simone Anzellini , Stefan Farsang , Annette K. Kleppe , Nicola P. M. Casati , Simon Macleod , Simon A. T. Redfern , François-Xavier Coudert , Thomas D. Bennett Journal Of The American Chemical Society DOI: 10.1021/jacs.9b03234 Diamond Proposal Number(s): [19046] Open Access Show Abstract ▼ Abstract: We present an in-situ powder X-ray diffraction study on the phase stability and polymorphism of the metal-organic framework ZIF-4, Zn(Imidazolate)2, at simultaneous high-pressure and high-temperature, up to 8 GPa and 600 °C. The resulting pressure-temperature phase diagram reveals four, previously unknown, high-pressure-temperature ZIF phases. The crystal structures of two new phases – ZIF-4-cp-II and ZIF-hPT-II – were solved by powder diffraction methods. The total energy of ZIF-4-cp-II was evaluated using density functional theory calculations and was found to lie in between that of ZIF-4 and the most thermodynamically stable polymorph, ZIF-zni. ZIF-hPT-II was found to possess a doubly-interpenetrated diamondoid-topology and is isostructural with previously reported Cd(Imidazolate)2 and Hg(Imidazolate)2 phases. This phase exhibited extreme resistance to both temperature and pressure. The other two new phases could be assigned with a unit cell and space group, though their structures remain unknown. The pressure-temperature phase diagram of ZIF-4 is strikingly complicated when compared with that of the previously investigated, closely related ZIF-62, and demonstrates the ability to traverse complex energy landscapes of metal-organic systems using the combined application of pressure and temperature.	May 2019
I15-Extreme Conditions	Pressure promoted low-temperature melting of metal–organic frameworks Remo N. Widmer , Giulio I. Lampronti , Simone Anzellini , Romain Gaillac , Stefan Farsang , Chao Zhou , Ana M. Belenguer , Craig Wilson , Hannah Palmer , Annette K. Kleppe , Michael T. Wharmby , Xiao Yu , Seth M. Cohen , Shane G. Telfer , Simon A. T. Redfern , François-Xavier Coudert , Simon Macleod , Thomas Bennett Nature Materials 18, 370 - 376 DOI: 10.1038/s41563-019-0317-4 Diamond Proposal Number(s): [16133, 19046] Show Abstract ▼ Abstract: Metal–organic frameworks (MOFs) are microporous materials with huge potential for chemical processes. Structural collapse at high pressure, and transitions to liquid states at high temperature, have recently been observed in the zeolitic imidazolate framework (ZIF) family of MOFs. Here, we show that simultaneous high-pressure and high-temperature conditions result in complex behaviour in ZIF-62 and ZIF-4, with distinct high- and low-density amorphous phases occurring over different regions of the pressure–temperature phase diagram. In situ powder X-ray diffraction, Raman spectroscopy and optical microscopy reveal that the stability of the liquid MOF state expands substantially towards lower temperatures at intermediate, industrially achievable pressures and first-principles molecular dynamics show that softening of the framework coordination with pressure makes melting thermodynamically easier. Furthermore, the MOF glass formed by melt quenching the high-temperature liquid possesses permanent, accessible porosity. Our results thus imply a route to the synthesis of functional MOF glasses at low temperatures, avoiding decomposition on heating at ambient pressure.	Mar 2019
I11-High Resolution Powder Diffraction	Structural dynamics of a metal–organic framework induced by CO2 migration in its non-uniform porous structure Pu Zhao , Hong Fang , Sanghamitra Mukhopadhyay , Aurelia Li , Svemir Rudic , Ian J. Mcpherson , Chiu C. Tang , David Fairen-Jimenez , Edman Tsang , Simon A. T. Redfern Nature Communications 10 DOI: 10.1038/s41467-019-08939-y Open Access Show Abstract ▼ Abstract: Stimuli-responsive behaviors of flexible metal–organic frameworks (MOFs) make these materials promising in a wide variety of applications such as gas separation, drug delivery, and molecular sensing. Considerable efforts have been made over the last decade to understand the structural changes of flexible MOFs in response to external stimuli. Uniform pore deformation has been used as the general description. However, recent advances in synthesizing MOFs with non-uniform porous structures, i.e. with multiple types of pores which vary in size, shape, and environment, challenge the adequacy of this description. Here, we demonstrate that the CO2-adsorption-stimulated structural change of a flexible MOF, ZIF-7, is induced by CO2 migration in its non-uniform porous structure rather than by the proactive opening of one type of its guest-hosting pores. Structural dynamics induced by guest migration in non-uniform porous structures is rare among the enormous number of MOFs discovered and detailed characterization is very limited in the literature. The concept presented in this work provides new insights into MOF flexibility.	Mar 2019
B18-Core EXAFS	Melt-quenched glasses of metal–organic frameworks Thomas Bennett , Yuanzheng Yue , Peng Li , Ang Qiao , Haizheng Tao , Neville Greaves , Tom Richards , Giulio Lampronti , Simon Redfern , Frédéric Blanc , Omar K. Farha , Joseph T. Hupp , Anthony K. Cheetham , David Keen Journal Of The American Chemical Society DOI: 10.1021/jacs.5b13220 Diamond Proposal Number(s): [14249] Open Access Show Abstract ▼ Abstract: Crystalline solids dominate the field of metal-organic frameworks (MOFs), with access to the liquid and glass states of matter usually prohibited by relatively low temperatures of thermal decomposition. In this work, we give due consideration to framework chemistry and topology to expand the phenomenon of the melting of three-dimensional MOFs, linking crystal chemistry to framework melting temperature and kinetic fragility of the glass-forming liquids. Here we show that melting temperatures can be lowered by altering the chemistry of the crystalline MOF state, which provides a route to facilitate the melting of other MOFs. The glasses formed upon vitrification are chemically and structurally distinct from the three other existing categories of melt-quenched glasses (inorganic non-metallic, organic and metallic), and retain the basic metal-ligand connectivity of crystalline MOFs, which connects their mechanical properties to starting chemical composition. The transfer of functionality from crystal to glass points towards new routes to tunable, functional hybrid glasses.	Feb 2016
I13-2-Diamond Manchester Imaging	Revisiting diagenesis on the Ontong-Java plateau: Evidence for authigenic crust precipitation in Globorotalia tumida Oscar Branson , Elizabeth Read , Simon Redfern , Christoph Rau , Henry Elderfield Paleoceanography DOI: 10.1002/2014PA002759 Diamond Proposal Number(s): [8532, 5846] Show Abstract ▼ Abstract: The calcite tests of foraminifera lie in marine sediments for thousands to millions of years, before being analysed to generate trace element and isotope palaeoproxy records. These sediments constitute a distinct physio-chemical environment from the conditions in which the tests formed. Storage in sediments can modify the trace element and isotopic content of foraminiferal calcite through diagenetic alteration, which has the potential to confound their palaeoceanographic interpretation. A previous study of G. tumida from the Ontong Java Plateau, western equatorial Pacific, found that preferential dissolution of higher-Mg chamber calcite, and the preservation of a low-Mg crust on the tests significantly reduced whole-test Mg/Ca and Sr/Ca [Brown and Elderfield, 1996]. Here, we revisit these specimens with a combination of synchrotron X-ray computed tomography (sXCT) and electron probe micro-analyses (EPMA) to re-evaluate the nature of their diagenetic alteration. The dissolution of higher-Mg calcite with depth was directly observed in the sXCT data, confirming the inference of the previous study. The sXCT data further reveal a thickening of the chemically and structurally distinct calcite crust with depth. We propose that these crusts have a diagenetic origin, driven by the simultaneous dissolution of high-Mg chamber calcite and precipitation of low-Mg crust from the resulting modified pore-water solution. While the breadth of the study is limited by the nature of the techniques, the observation of both dissolution and re-precipitation of foraminiferal calcite serves to demonstrate the action of two simultaneous diagenetic alteration processes, with significant impacts on the resulting palaeoproxy signals.	Oct 2015
I13-2-Diamond Manchester Imaging	Determination of foraminifera species and the impacts for climate change Elizabeth Read , Andrew Bodey , Christoph Rau , Simon Redfern Bruker microCT User Meeting 2015 Diamond Proposal Number(s): [12240] Open Access	May 2015
I13-2-Diamond Manchester Imaging	X-ray imaging and 3D reconstruction of chemical alteration in plankton shells - a key indicator of past climate Simon Redfern , Elizabeth Read , Oscar Branson , Harry Elderfield , Tolek Tyliszczak , Christoph Rau , Andrew Bodey Bruker microCT User Meeting 2015 Diamond Proposal Number(s): [8532, 12240] Open Access Show Abstract ▼ Abstract: The trace element content of calcified shells of plankton (foraminifera) are commonly used as tracers of paleoceanographic conditions and provide a window in past global climate variations dating back tens of millions of years. Uncertainties surrounding these palaeoproxy records: arise from our poor understanding of the processes controlling biogenic calcite deposition and trace element incorporation as well as post-mortem chemical alteration that has the potential to alter or overwrite the original chemical composition of the shell. Here we have explored the role of chemical alteration on modification of the morphology of foraminifera shells by studying the structures of shells obtained from deep sea sediments on the Ontong-Java Plateau using phase contrast synchrotron tomography..	May 2015
I13-2-Diamond Manchester Imaging	Revisiting diagenesis on the Ontong-Java Plateau: evidence for authigenic crust precipitation in Globorotalia tumida Elizabeth Read , Oscar Branson , Simon Redfern , Christoph Rau , Henry Elderfield EGU General Assembly 2015 Diamond Proposal Number(s): [8532] Show Abstract ▼ Abstract: Foraminifera hold the key to the past climate of the Earth. They can be retrieved from core tops of sea floor sediments, allowing the record to extend back many thousands to millions of years. The time lag between the foraminifera formation, deposition, and the routine analysis can therefore be very long. The sites from which foraminifera are collected and cored experience different physicochemical conditions to those which they were formed and deposited in. The samples used in this study are from the Ontong-Java Plateau, west equatorial Pacific, and were studied in Brown and Elderfield, 1996. Synchrotron X-ray computed tomography (sXCT) and electron micro-probe analyses were carried out on samples collected from different core top depths, chosen to span the lysocline in the area, in order to re-asses the character and extent of diagenetic alteration.	Apr 2015
	Nanopaleomagnetism of meteoritic Fe-Ni studied using X-ray photoemission electron microscopy James Bryson , Julia Herrero-Albillos , Florian Kronast , Massimo Ghidini , Simon A. T. Redfern , Gerrit Van Der Laan , Richard J. Harrison Earth And Planetary Science Letters 396, 125 - 133 DOI: 10.1016/j.epsl.2014.04.016 Open Access Show Abstract ▼ Abstract: X-ray photoemission electron microscopy (XPEEM) enables natural remanent magnetisation to be imaged with resolution across a field of view of 5–20 μm. The method is applied to structural features typical of the Widmanstätten microstructure (kamacite – tetrataenite rim – cloudy zone – plessite) in the Tazewell IIICD iron meteorite. Kamacite lamellae and the tetrataenite rim are multidomain, whereas plessite consists of laths of different phases displaying a range of stable magnetisation directions. The cloudy zone (CZ) displays a complex interlocking domain pattern resulting from nanoscale islands of tetrataenite with easy axes distributed along three possible crystallographic directions. Quantitative analysis of the coarse and intermediate CZ was achieved using a combination of image simulations and histogram profile matching. Remanence information was extracted from individual regions of interest wide, demonstrating for the first time the capability of XPEEM to perform quantitative paleomagnetic analysis at sub-micron length scales. The three tetrataenite easy axis orientations occur with equal probability in the coarse and intermediate CZ, suggesting that spinodal decomposition in these regions was not strongly influenced by internal interaction fields, and that they are suitable candidates for future paleomagnetic studies. The fine CZ shows a strong dominance of one easy axis. This effect is attributed to island–island exchange interactions that render the fine CZ unsuitable for paleomagnetic study. Variations in the relative strength (proportion of dominant easy axis) and direction (direction of dominant easy axis) of a paleomagnetic field can be resolved from different regions of the CZ using XPEEM, raising the prospect of obtaining a time-resolved measurement of the active dynamo period in meteorites originating from the upper unmelted regions of differentiated asteroids (e.g. chondrites, pallasites, mesosiderites).	Jun 2014

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