The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
Chao Zhou - One of the best experts on this subject based on the ideXlab platform.
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pressure promoted low temperature melting of metal organic frameworks
Nature Materials, 2019Co-Authors: Remo N Widmer, Chao Zhou, Giulio I Lampronti, Simone Anzellini, Romain Gaillac, Stefan Farsang, Ana M Belenguer, Craig W Wilson, Hannah Palmer, Annette K KleppeAbstract: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.
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metal organic framework glasses with permanent Accessible Porosity
Nature Communications, 2018Co-Authors: Chao Zhou, Louis Longley, Andraž Krajnc, Glen J Smales, Ang Qiao, Ilknur Erucar, Cara M Doherty, Aaron W Thornton, Anita J HillAbstract:To date, only several microporous, and even fewer nanoporous, glasses have been produced, always via post synthesis acid treatment of phase separated dense materials, e.g. Vycor glass. In contrast, high internal surface areas are readily achieved in crystalline materials, such as metal-organic frameworks (MOFs). It has recently been discovered that a new family of melt quenched glasses can be produced from MOFs, though they have thus far lacked the Accessible and intrinsic Porosity of their crystalline precursors. Here, we report the first glasses that are permanently and reversibly porous toward incoming gases, without post-synthetic treatment. We characterize the structure of these glasses using a range of experimental techniques, and demonstrate pores in the range of 4 – 8 A. The discovery of MOF glasses with permanent Accessible Porosity reveals a new category of porous glass materials that are elevated beyond conventional inorganic and organic porous glasses by their diversity and tunability. Metal–organic framework glasses have emerged as a new family of melt-quenched glass, but have yet to display the Accessible Porosity of their crystalline counterparts. Here, Bennett and colleagues report that glasses derived from ZIF-76 parent materials possess 4 – 8 A pores and exhibit reversible gas adsorption.
Esam M A Hussein - One of the best experts on this subject based on the ideXlab platform.
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three dimensional imaging of Porosity and tracer concentration distributions in a dolostone sample during diffusion experiments using x ray micro ct
Journal of Contaminant Hydrology, 2013Co-Authors: H M D Agbogun, Esam M A HusseinAbstract:X-ray micro-computed tomography (micro-CT) techniques for measuring the three-dimensional (3-D) distributions of diffusion-Accessible Porosity (φ(d)) and temporal tracer-concentrations (C(t)) within a dolostone sample subjected to solute diffusion are developed and tested in this work. The φ(d) and C(t) measurements are based on spatially resolved changes in X-ray attenuation coefficients in sequentially acquired 3-D micro-CT datasets using two (calibration and relative) analytical approaches. The measured changes in X-ray attenuation coefficient values are a function of the mass of X-ray absorbing potassium-iodide tracer present in voxels. Mean φ(d) values of 3.8% and 6.5% were obtained with the calibration and the relative approaches, respectively. The detection limits for φ(d) measurements at individual voxel locations are 20% and 36% with the calibration and the relative methods, respectively. The detection limit for C(t) are 0.12 M and 0.22 M with the calibration and the relative approaches, respectively. Results from the calibration method are affected by a beam-hardening artifact and although results from the relative approach are not affected by the artifact, they are subject to high detection limits. This work presents a quantitative assessment of micro-CT data for studies of solute transport. Despite limitations in precision and accuracy, the method provides quantitative 3-D distributions of φ(d) and C(t) that reflect solute diffusion in heterogeneous porous geologic media.
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measurement of spatial distribution of total and Accessible Porosity in sedimentary rocks using isotopic radiation transmission device design and testing
Applied Radiation and Isotopes, 2010Co-Authors: Ranjit K Subudhi, Esam M A HusseinAbstract:Abstract An isotopic radiation transmission technique for quantifying the spatial distribution of Porosity in sedimentary rocks is presented. A device was designed and constructed to examine rock samples of volumes sufficiently large for studying solute migration in rocks, so that a one-millimeter spatial resolution is attained with measurement acquisition time of one point per second. The paper demonstrates how the device was optimized for these specifications, while abiding by the restrictions implicit in the utilization of the exponential law of radiation attenuation to quantify physical parameters. Total Porosity was obtained from measurements of radiation attenuation in dry samples, while solute-Accessible Porosity was determined from measurements with samples saturated with either KNO 3 or KI solutions. Results are presented for three different rock types to demonstrate the capabilities and limitations of the technique.
Reinhard Fink - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of the dependence of Accessible Porosity and methane sorption capacity of carbonaceous shales on particle size
Geofluids, 2020Co-Authors: Garri Gaus, A G Kalmykov, Bernhard M Krooss, Reinhard FinkAbstract:Crushing and grinding of carbonaceous shale samples is likely to enhance the accessibility of pores and embedded organic matter as compared to the intact rock. This may lead to an overestimation of the total (volume and sorptive) gas storage capacity. In order to investigate the importance of these effects we have measured unconfined apparent grain densities (helium pycnometry) and methane sorption capacities (high-pressure methane excess sorption) of four carbonaceous shales (Cambro-Ordovician Alum Shale, Jurassic Kimmeridge Clay, Jurassic/Cretaceous Bazhenov Shale, and Late Cretaceous Eagle Ford Shale) as a function of particle size. Measurements were first conducted on 38 mm diameter core plugs, which then were crushed and milled to successively smaller particle sizes ( for the Alum and should be used for Porosity and sorption measurements because they are more likely to retain the properties of the rock fabric in terms of Accessible pore volume and sorptive storage capacity.
Delphine Durce - One of the best experts on this subject based on the ideXlab platform.
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why tracer migration experiments with a pressure gradient do not always allow a correct estimation of the Accessible Porosity in clays
Applied Geochemistry, 2020Co-Authors: Marc Aertsens, Norbert Maes, Joan Govaerts, Delphine DurceAbstract:Abstract For assessing the radionuclide transport parameters, the apparent diffusion coefficient and the rock capacity factor ηR (being the product of the Accessible Porosity η and the retardation factor R) in host rocks used for nuclear waste disposal, mainly two classes of experiments are used: pure diffusive experiments e.g. through-diffusion, and experiments where next to a concentration gradient also a pressure gradient is applied e.g. pulse injection experiments. In Boom Clay, through-diffusion and pulse injection experiments lead to similar values for the Accessible Porosity of tritiated water (HTO), while for another unretarded tracer, iodide, significantly higher values are obtained by pulse injection. Similarly, in recompacted Na-illite, for chloride (another unretarded anion), lower Accessible Porosity values are observed by through-diffusion than by pulse injection. The difference increases while lowering the ionic strength. The reason for the discrepancy lies in the models used for analysing the migration experiments with a pressure gradient. Experiments with a pressure gradient allow fitting the apparent velocity Vapp of a tracer. The rock capacity factor is estimated as the ratio VDarcy/Vapp of the Darcy velocity VDarcy and Vapp. This is correct for HTO, but not for anions because the water flow through anion inAccessible Porosity is neglected. Making a correct water flow mass balance by taking the water flow through inAccessible Porosity into account, demonstrates that the rock capacity factor is given by the product FV VDarcy/Vapp with FV the fraction (0 ≤ FV ≤ 1) of the Darcy velocity flowing through tracer Accessible Porosity. Previously determined ηR values are in reality the ratio ηR/FV and overestimate ηR. In agreement with the experimental results, a lower ionic strength leads for (unretarded) anions to a lower Accessible Porosity η and consequently a lower FV and more overestimation of η. Besides charge related inAccessible Porosity, Porosity can also be inAccessible because of the size of the transported species: the Accessible Porosity becomes zero in case the particle size approaches the pore throat. Because the intention of experiments with a pressure gradient is to know ηR, we propose two models, which are basically two tracer distributions over a pore, for estimating FV. Considering Poiseuille flow, we calculate a typical pore radius, the hydraulic conductivity and for both distributions the Accessible Porosity, the fraction FV and the fitted ratio ηR/FV. Application to experimental data shows anisotropy in the pore radius, corresponding to the observed anisotropy in hydraulic conductivity. For anion exclusion, the model describes qualitatively the experimentally observed evolution as a function of double layer width. Because also for cations there is presently no valid relation between Vapp and ηR, migration experiments with a pressure gradient only provide a reasonable estimate for the rock capacity factor ηR in case of small (with respect to the average pore size) neutral particles like HTO.
T P Lach - One of the best experts on this subject based on the ideXlab platform.
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pore structure characterization of north american shale gas reservoirs using usans sans gas adsorption and mercury intrusion
Fuel, 2013Co-Authors: Christophe R Clarkso, N Solano, Robert Marc Usti, Amanda M M Usti, Gareth R L Chalmers, Yuri Melnichenko, Andrzej Pawel Radlinski, T P LachAbstract:Abstract Small-angle and ultra-small-angle neutron scattering (SANS and USANS), low-pressure adsorption (N2 and CO2), and high-pressure mercury intrusion measurements were performed on a suite of North American shale reservoir samples providing the first ever comparison of all these techniques for characterizing the complex pore structure of shales. The techniques were used to gain insight into the nature of the pore structure including pore geometry, pore size distribution and Accessible versus inAccessible Porosity. Reservoir samples for analysis were taken from currently-active shale gas plays including the Barnett, Marcellus, Haynesville, Eagle Ford, Woodford, Muskwa, and Duvernay shales. Low-pressure adsorption revealed strong differences in BET surface area and pore volumes for the sample suite, consistent with variability in composition of the samples. The combination of CO2 and N2 adsorption data allowed pore size distributions to be created for micro–meso–macroPorosity up to a limit of ∼1000 A. Pore size distributions are either uni- or multi-modal. The adsorption-derived pore size distributions for some samples are inconsistent with mercury intrusion data, likely owing to a combination of grain compression during high-pressure intrusion, and the fact that mercury intrusion yields information about pore throat rather than pore body distributions. SANS/USANS scattering data indicate a fractal geometry (power-law scattering) for a wide range of pore sizes and provide evidence that nanometer-scale spatial ordering occurs in lower mesopore–micropore range for some samples, which may be associated with inter-layer spacing in clay minerals. SANS/USANS pore radius distributions were converted to pore volume distributions for direct comparison with adsorption data. For the overlap region between the two methods, the agreement is quite good. Accessible Porosity in the pore size (radius) range 5 nm–10 μm was determined for a Barnett shale sample using the contrast matching method with pressurized deuterated methane fluid. The results demonstrate that Accessible Porosity is pore-size dependent.
