Diffusion Fundamentals (E-Journal)
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Electrochemical Behavior of Nanostructured Copper Particles on Graphite for Application in Lithium Ion Batteries
Get PDFSynthesis of Coarse-grained Garnet-type Li-ion Conductor Li7-3x(Al/Ga)xLa3Zr2O12 and its Li-ion Dynamics
Get PDFChanges in specific surface as observed by NMR, caused by saturation of chalk with porewater bearing divalent ions
Get PDFNuclear Magnetic Resonance (NMR) spectrometry has proved to be a good technique for determining the petrophysical properties of reservoir rocks; such as porosity and pore size distribution. We investigated how pore water rich in divalent ions affect the NMR signal from chalk with two different depositional textures. We compared two cases. The first experiments on outcrop chalk with high salinity brines showed that saturation with divalent ions (Mg2+, Ca2+ and SO42-) cause major shifts in the T2 distribution curve, probably due to precipitation in the pore space. In a second set of experiments, fluid samples where precipitation takes place were found to show shifts in the T2 relaxation curve due to the creation of crystals. We were able to identify how differences in the rock texture and precipitants within the pore space may affect the transverse relaxation time by altering the surface-to-volume ratio of the pore space. The results of this work could benefit the ongoing study on the optimization of the water composition for Enhanced Oil Recovery (EOR) methods and shed light on how it can affect the mechanical and physical properties of the rock
Matrix factorisations for the estimation of NMR relaxation distributions
Get PDFThe two most successful methods of estimating the distribution of NMR relaxation times from two dimensional data are firstly a data compression stage followed by application of the Butler-Reeds-Dawson (BRD) algorithm, and secondly a primal dual interior point method using a preconditioned conjugate gradient (PCG). Both of these methods have been presented in the literature as requiring a truncated singular value decomposition of matrices representing the exponential kernels. Other matrix factorisations are applicable to each of these algorithms, and which demonstrate the different fundamental principles behind the operation of the algorithms. In the case of the data compression approach the most appropriate matrix decomposition specifically designed for this task is the rank-revealing QR (RRQR) factorisation. In the case of the interior point method, the most appropriate method is the LDL factorisation with diagonal pivoting, also known as the Bunch-Kaufman-Parlett factorisation. The details of these differences are discussed, and the performances of the algorithms are compared numerically
A review on bulk diffusion in metallic solids
Get PDFIn this paper bulk diffusion techniques in case of metals and alloys will be reviewedwith a special emphasis on resistometric technique. The experiment is restricted only to those metals, which can be made in the form of wire but has the advantage of applying to materials whose suitable radioactive isotopes are not available. A brief introduction along with different diffusion mechanisms with corresponding activation energies, diffusion coefficients, correlation factors, isotope effect, enhancement factor, etc. is also incorporated. Three models for bulk diffusion are also mentioned
Lithium Ion and Water Mobility in Hydrated Li-LSX Zeolite Studied by 1H, 6Li and 7Li NMR Spectroscopy and Diffusometry
Get PDFNuclear Magnetic Resonance and Impedance Spectroscopy Studies on Lithium Ion Diffusion in γ-LiAlO2
Get PDFNew instrumental platform for the exploitation of the field-dependence of T 1 in rock core analysis and petroleum fluids: application to T 1-T 2 correlation maps
Get PDFWe propose using the latest wide bore fast field cycling NMR relaxometers for measuring the nuclear magnetic relaxation dispersion (NMRD) profiles of the logarithmic average proton-water <1/T1> in carbonate rock cores samples of 1 inch diameter and in different crude oil/brine mixings. The observed bilogarithmic frequency behaviours of the NMRD have been interpreted with a proposed theoretical model yielding a measurement of the water local wettability at the pore surface. We have also proposed a NMR platform that uses a variable wide-bore cryogen-free superconducting magnet to acquire 2D T1-T2 correlation spectrum of a mixing of bulk water and crude oil pools. Such a T1-T2 plot allows quantitative separation of mixed bulk water and crude oil. The 2D plot does not reveal any exchange between the different and independent pools
Accessible catalyst pore volumes, for water and organic liquids, as probed by NMR cryoporometry
Get PDFChemical reaction speed is frequently enhanced at a surface, particularly when materials like platinum are present. It is well known that porous materials such as sol-gel silicas, controlled pore glasses, templated porous materials such as SBA-15, MCM-41, MCM-48, and zeolites, offer large surface areas. This in turn makes them ideal for catalysing chemical reactions. Thus an important use for porous materials is as a substrate and media to promote chemical reactions. However small pores are not always easily accessed by some of the organic liquids in which these catalytic reactions ideally take place. Cryoporometric techniques offer the possibility of directly probing the fraction of a pore that is actually accessible to a probe liquid. This fractional volume has significant impact on the catalytic efficacy of a particular solvent that is used to promote a reaction in the pores. Pore size, pore geometry, pore throat, pore surface material (hydrophilic/hydrophobic) and choice of probe liquid all influence the accessible fraction. By performing an NMR cryoporometric measurement using a particular liquid of interest, it is possible to directly access this information, which is of prime importance for catalysis, and financially very significant on an industrial scale. Results are reported here for a set of liquids, some simple alkanes (dodecane, tetradecane and hexadecane) plus water and cyclohexane, accessing pores in sol-gel silicas of nominal pore diameters 60Å, 100Å, 200Å, 500 Å. The key conclusions were that for the alkanes, the dimension of chain length was not relevantto the filling fraction, however for the cyclohexane a molecular diameter of 3.8 Å fitted the data well