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Abstract: Magnetic resonance imaging has been introduced to study flow in microchannels using pure phase spatial encoding with a microfabricated parallel-plate nuclear magnetic resonance (NMR) probe. The NMR probe and pure phase spatial encoding enhance the sensitivity and resolution of the measurement. In this paper, 1H NMR spectra and images were acquired at 100 MHz. The B 1 magnetic field is homogeneous and the signal-to-noise ratio of 30 μl doped water for a single scan is 8×104. The high sensitivity of the probe enables velocity mapping of the fluids in the micro-channel with a spatial resolution of 13×13 μm. The parallel-plate probe with pure phase encoding permits the acquisition of NMR spectra; therefore, chemical shift resolved velocity mapping was also undertaken. Results are presented which show separate velocity maps for water and methanol flowing through a straight circular micro-channel. Finally, future performance of these techniques for the study of microfluidics is extrapolated and discussed. [Copyright &y& Elsevier]

An image processing workflow is presented for the characterization of pore and grain size distributions in porous geological samples from X-ray microcomputed tomography (μCT) and scanning electron microscopy (SEM) images. The pore and grain size distributions of five sandstone samples including Berea, Buff Berea, Nugget, Castlegate, and Bentheimer, and one carbonate sample, Indiana limestone, are extracted using the proposed workflow. Two-dimensional size distributions acquired from SEM images were found to be biased toward smaller sizes misrepresenting the actual 3D distributions. Stereological techniques unfolded the measured 2D size distributions from SEM images to 3D distributions comparable with μCT results. While larger pores and grains can easily be detected from μCT and SEM images, the quantification of small-scale heterogeneities is severely influenced by their limits of resolution. We show that microstructural details resolved by SEM can significantly impact the pore and grain size distributions in sandstone and carbonate rock samples. For example, SEM-resolved microporosities in Indiana limestone result in bimodal distributions of pore and grain sizes, whereas μCT observations exhibit unimodal distributions. The acquired images and processed results are openly available and may be used by researchers investigating image processing, magnetic resonance relaxation or fluid flow simulations in natural rocks. The proposed methodology can be implemented to process μCT and SEM images of natural rocks as well as other types of porous materials. • Image processing workflow computes pore/grain size distributions from images. • Stereological unfolding of pore/grain size from SEM agrees with that of μCT images. • SEM resolves microstructural details that affect pore and grain size distributions. • The agreement between μCT and SEM results was consistent in six sedimentary rocks. • A dataset of μCT and SEM images of six sedimentary rock samples made public. [ABSTRACT FROM AUTHOR]

Abstract: The cure of an epoxy resin/polyamidoamine hardener system was followed in real-time by magnetic resonance (MR) with a purpose-built portable probe that was designed with a magnet array and a radio-frequency coil geometry that maximize its sensitivity. The MR results demonstrated that the effects of cross-linking during the cure are manifest in changes in the experimental signal amplitude and decay time constant. The results also showed that, with a proper MR spin echo technique, it is possible to acquire knowledge about the evolution of the epoxy cross-linking process in a single scan measurement which takes less than one second. [Copyright &y& Elsevier]

Abstract: The single-point ramped imaging with T 1 enhancement (SPRITE) imaging technique has proven to be a very robust and flexible method for the study of a wide range of systems with short signal lifetimes. As a pure phase encoding technique, SPRITE is largely immune to image distortions generated by susceptibility variations, chemical shift and paramagnetic impurities. In addition, it avoids the line width restrictions on resolution common to time-based sampling, frequency encoding methods. The standard SPRITE technique is however a longitudinal steady-state imaging method; the image intensity is related to the longitudinal steady state, which not only decreases the signal-to-noise ratio, but also introduces many parameters into the image signal equation. A centric scan strategy for SPRITE removes the longitudinal steady state from the image intensity equation and increases the inherent image intensity. Two centric scan SPRITE methods, that is, Spiral-SPRITE and Conical-SPRITE, with fast acquisition and greatly reduced gradient duty cycle, are outlined. Multiple free induction decay (FID) points may be acquired during SPRITE sampling for signal averaging to increase signal-to-noise ratio or for T 2* and spin density mapping without an increase in acquisition time. Experimental results show that most porous sedimentary rock and concrete samples have a single exponential T 2* decay due to susceptibility difference-induced field distortion. Inhomogeneous broadening thus dominates, which suggests that spin density imaging can be easily obtained by SPRITE. [Copyright &y& Elsevier]

The development of optimal fast charging protocols requires detailed information regarding lithium inventory in a battery. We built a parallel-plate resonator RF probe and a cartridge-type single layer cell of improved designs. The probe has excellent sensitivity and homogeneity of electromagnetic field, while the cartridge allows easy cell assembly, straight-forward multiplexing, and excellent cell-to-cell data reproducibility. Herein we present our findings from operando 7Li NMR measurements on a graphite//NMC622 cell. The usual/expected sequencing of Li x C 6 phases from dilute to concentrated observed during charging at low (

Magnetic resonance imaging was an effective means for visualizing moisture profiles during drying of starch molded confectionery, and clearly demonstrated the importance of moisture transfer between the confectionery gel and the molding starch. Rapid formation of a very dry “skin” was observed that resulted in case-hardening. Drying was effectively diffusion controlled after the first 30 min. Moisture profiles within the porous bed of molding starch, where total proton density is low and T2* is short, were visualized using single point ramped imaging with T1 enhancement (SPRITE). Similar images were not possible using more traditional spin-echo techniques. The long component of a bi-exponential T1 was linearly related to the solids content, and T1–null images were constructed to visualize iso-solids contour lines. [Copyright &y& Elsevier]

Emulsion stability is important in many environmental and industrial applications. Unstable emulsions tend to have a layered structure which will evolve in space and time. Magnetic Resonance (MR) is a nondestructive method that can be used to study emulsion instability based on relaxation times (T 1 , T 2), and/or diffusion (D). The bulk transverse relaxation lifetime (T 2) is the most useful parameter for analysis. Since breaking of emulsions creates different layers and phases, spatially resolved T 2 data is more valuable than bulk whole sample data. Previous literature studies were principally based on bulk T 1 , T 2 or self-diffusion measurements without spatial resolution. In this study, for the first time, spatially resolved T 2 distributions were used to examine oil and water behavior during emulsion breaking. Diluted bitumen was used as the oil phase in a synthetic emulsion. Measurements undertaken included spatially resolved T 2 distribution measurements and T 1 -T 2 relaxation correlation measurements. The results reveal changes in the relaxation times of oil and water caused by changes in the dynamics of the water and oil during emulsion breaking. In each layer of the sample, comparing peak T 2 values with bulk T 2 values of different components gives an insight into phase environments. Water and oil content in each layer was resolved by using peak areas of the T 2 distribution. The results of T 2 distribution imaging were consistent with optical microscopy images, which showed W/O emulsions in the oil dominant region and complex W/O/W emulsions in the water dominant region of the sample. With the above information one can obtain full spatial and temporal information on evolving phases as well as kinetics of phase dynamics in emulsion breaking. [Display omitted] • MR T 2 mapping helps identify different layers of an emulsion sample and observe their evolution. • Optical microscopy images confirmed MR T 2 mapping results. • The oil- and water-dominant regions were characterized by W/O and W/O/W emulsions respectively. • Spatial and temporal information on dispersed and free phases in the emulsion breaking is obtained. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magnetic resonance methods were performed to characterize kerogen in shales. • Relaxation correlation method quantifies water, oil, and kerogen hydrogen content. • T 1 -T 2 * method coupled with pyrolysis showed kerogen dominates short T 2 * signal. • Free induction decay is adequate to resolve and quantify kerogen signal. • An elemental balance estimated the kerogen pyrolysis path on Van Krevelen diagram. Kerogen assessment is essential to evaluation of shale reservoir quality. Routine analysis techniques are sample destructive and time-consuming. 1H magnetic resonance (MR) methods offer a fast, robust, and non-destructive alternative. However, kerogen MR signal detection and quantification is challenging due to its short signal lifetime and requires new MR methods. In this work, the T 1 -T 2 * relaxation correlation method was investigated for assessment of kerogen in shales. Step pyrolysis experiments were conducted coupled with MR T 1 -T 2 * relaxation correlation measurements and thermogravimetric analysis (TGA). The results show that the short relaxation lifetime signal observed in the shale samples was dominated by the kerogen species. The shale signal was resolved in the T 1 -T 2 * relaxation correlation measurement that was calibrated to report kerogen, oil, and water 1H content of the shale samples. Kerogen 1H content was then used to evaluate the hydrocarbon generation potential of kerogen. An elemental balance analysis was conducted to estimate the kerogen chemical evolution in the Van Krevelen diagram. The results proved that a simple FID measurement was adequate to resolve and quantify the kerogen signal component in shales. [ABSTRACT FROM AUTHOR]

Abstract: The development of predictive mathematical models for water management in polymer electrolyte membrane fuel cells requires detailed understanding of water distribution and water transport across the Nafion layer. The anisotropic microstructure of Nafion suggests the measurement of water content and mass transport should be along the fuel cell functional direction, i.e. across the membrane. Non-invasive, high resolution, microscopy measurements of this type are very challenging. We report here the calibration of a minimal mathematical model for diffusive water transport in Nafion against data from high-resolution water content maps determined with a new magnetic resonance imaging methodology developed for this purpose. A mock fuel cell was designed to permit well-controlled wetting and drying boundary conditions. With no chemical potential driving force involved, we assume the water transport behavior will be dominated by diffusion. Moreover we show that, in this context, our model is mathematically equivalent to the traditional permeation models based upon saturation dependent pressure gradients via a capillary pressure ansatz. The non-linear equilibrium water distribution across the Nafion membrane measured in this work suggests a bi-modal diffusivity. The model constructed associates distinct transport behaviors to water contents above and below a critical threshold, consistent with a rearrangement of a micro-structural pore network. The experimental observation and the model prediction agree with the primary features of Weber''s model of Nafion, which predicts distinct modes of transport for hydration fronts traversing the through-plane direction of the membrane. [Copyright &y& Elsevier]

Abstract: The results of a series of experiments to determine the sensitivity of magnetic resonance to water inside an aerospace–grade composite sandwich panel are presented. The measurements were performed with a purpose-built unilateral probe designed to overcome problems associated with attenuation of the radio frequency (RF) magnetic field used in magnetic resonance by the presence of conductive materials in the panel. The detection limit of the probe is 2–3 honeycomb core cells filled with water in 64 scans (measurement of approximately 1min). Profiles of a water containing region of cells were generated by displacing the probe laterally across the panel''s surface. By varying the amount of water in the cells, it was determined that the magnetic resonance signal is obtained from throughout the height of the cells, not just the region nearest the probe''s coil. [Copyright &y& Elsevier]

Abstract: Unilateral (one-sided) NMR, with easy sample access and rapid “through-package” measurement, is a promising new technology in food science. Here we investigated the applicability of two methods for fat and moisture content determination by unilateral NMR. One is a post-measurement decomposition of a Carr–Purcell–Meiboom–Gill (CPMG) signal using a classical least-squares (CLS) multivariate analysis. The other is based on a diffusion-weighted CPMG experiment, where the components are discriminated at the time of measurement through the diffusivity difference between fat and moisture. The experiments were carried out on model samples of cod liver oil emulsion in water and on commercial ground beef. The CLS analysis exhibits a good predictive performance provided the fat and moisture components conserve their characteristic relaxation times in different samples. The diffusion-weighted CPMG, although more complex experimentally, is free of this restriction. The methods will be of interest for online analysis of food materials and supplement laborious standard extraction methods. [Copyright &y& Elsevier]

Abstract: Oil migration is responsible for the poor keeping qualities of composite confectionery products. Quality defects arising from oil migration include softening of the coating, hardening of the filling, deterioration in sensory quality and a greater tendency toward fat bloom formation. For this reason, oil migration has been extensively studied, and yet a clear understanding of the oil migration mechanisms still remains a challenge. Traditional MRI techniques are unable to acquire images from the solid lipid in chocolate. In this paper we employ a newly developed one-dimensional, centric-scan MRI technique to acquire images from the short lived signal components from the solid lipid, as well as the longer timescale components of the liquid lipid in a chocolate sample. We present one-dimensional images of a dynamic hazelnut oil absorption experiment, and one-dimensional solid and liquid distribution maps in a 5mm thick chocolate sample in which oil migration occurs. [Copyright &y& Elsevier]

Abstract: Water ingress inside honeycomb sandwich panels during service has been linked to in-flight failure in some aircraft. There is an ongoing effort to develop nondestructive testing methods to detect the presence of water within the panels. Magnetic resonance (MR) represents an attractive approach in that it is sensitive to moisture. Using a unilateral MR sensor, testing can be applied directly to the surface of the panel. The viability of MR is demonstrated through laboratory imaging of both water within sandwich panels, as well as the adhesive itself. The detection of water using a one-sided handheld MR sensor is presented. It is shown that simple detection, as well as spatial localization of water within sandwich panels is possible. [Copyright &y& Elsevier]

• T 1 - T 2 * and T 1ρ - T 2 * relaxometry are used for 1H identification of coal rank. • High rank coals contain an abundance of crystallite structure based on Sinc Gaussian 1H FID. • Insight into the change of coal during low temperature oxidation using 2D 1H MR relaxometry. • T 1 - T 2 * technique provides 1H content evaluation of coal. 1H magnetic resonance (MR) is a useful technique for determining molecular structure of coals. Most previous MR studies were based on one-dimensional 1H magnetic resonance relaxometry. Two-dimensional (2D) 1H magnetic resonance relaxation correlation methods, T 1 – T 2 * and T 1ρ – T 2 *, were used to evaluate Argonne premium coals, including Beulah-Zap (BZ), Wyodak-Anderson (WA), Pittsburgh #8 (PIT), Upper Freeport (UF), and Pochontas #3 (POC) coals as received. Samples were also measured after oxidization at low temperature (110 and 210 °C). From the 2D relaxation correlations, various hydrogen-containing components were distinguished and characterized. The change of hydrogen during low temperature oxidation was analyzed, and the hydrogen content estimated. The technique captured significant differences between low rank coals (BZ and WA) and high rank coals (PIT, UF, and POC). The order of T 1 / T 2 * ratios is aliphatic hydrogen > aromatic hydrogen > hydrogen- and oxygen-containing functional groups > moisture in BZ and WA coals. The PIT, UF, and POC coals mainly contain aromatic hydrogens. The T 1 – T 2 * and T 1ρ – T 2 * spectra of BZ and WA coals change significantly during low temperature oxidation. Our new MR method provides new insight into coal behaviour. [ABSTRACT FROM AUTHOR]

• New insight in magnetic resonance relaxation mechanisms of 1 H -bearing compounds in shales. • A novel 2D magnetic resonance T 1 - T 2 ∗ technique is introduced for shale fluid typing. • T 1 - T 2 ∗ capability in quantifying water in adsorption/desorption process is studied. • A procedure is provided to quantify shale fluid content based on the T 1 - T 2 ∗ technique. • T 1 - T 2 ∗ technique provides quantitative 1 H content of kerogen allowing geochemical studies. Quantification of fluid and organic matter content of shale samples are principal goals of petrophysical and geochemical evaluation of shales that are essential to determine reservoir quality. While volumetric methods to characterize shales are cumbersome and destructive, 1 H magnetic resonance (MR) methods are robust, fast, and non-destructive. However, short-lived MR signal lifetimes of shale samples challenge existing MR methods and motivate the development of new MR methods. Two-dimensional (2D) MR T 1 - T 2 relaxation correlation is a powerful method to differentiate hydrogen-bearing species in porous materials. However, the experimental echo time limitation of the T 1 - T 2 method precludes acquisition of important short lifetime signal components. In addition, due to overlap of signal components in T 1 - T 2 correlations, quantification accuracy is impaired in shales. Here, we introduce the 2D MR T 1 - T 2 ∗ relaxation correlation measurement for quantitative determination of shale 1 H components. Liquid-rich shale samples from the Eagle Ford Formation were used in adsorption/desorption and evaporation experiments. 2D MR T 1 - T 2 and T 1 - T 2 ∗ correlations coupled with gravimetric measurements were performed to identify water, oil/bitumen, and kerogen peaks in the relaxation correlation maps. Peaks associated with shale components showed significant contrast in T 1 - T 2 ∗ correlations. This allowed quantitative measurement of water and oil content using the signal intensity of each peak. [ABSTRACT FROM AUTHOR]

Methane hydrate deposits worldwide are vast potential sources of natural gas. Although field tests, and many laboratory studies, of hydrate dissociation have been performed, long term gas recovery from hydrate deposits still requires a comprehensive knowledge of the pore gas pressure and related phenomena. Pore gas pressure can significantly affect the safety and efficiency of gas production from hydrate deposits. Capillary-trapped residual gas saturation, known to cause elevated pore gas pressure during methane hydrate dissociation, was measured by magnetic resonance. Elevated pore gas pressure was estimated to be 8500 psi. Different molecular species and fluid environments produced during the methane hydrate dissociation process were discriminated. The results show that the majority of gas is initially confined as capillary-trapped gas upon dissociation. The evolution of water and gas saturations was measured as a function of time. Water migration, bed failure, and crack growth, related to elevated pore gas pressure, were observed both spatially and temporally resolved. Hydrate dissociation proceeded from the sand pack exterior to the interior, in a shrinking core manner, due to heat transfer effects. It was observed that hydrate dissociation resulted in pronounced water migration toward the low-pressure surface. This study was undertaken with advanced magnetic resonance imaging (MRI) and magnetic resonance (MR) methods employing a MR/MRI-compatible metallic core holder. A hydrate-bearing sand pack, with 96% initial hydrate saturation, underwent dissociation by depressurization at 290 psi and 4 °C. • Elevated pore gas pressure was directly measured with MR measurements. • Capillary-trapped residual gas saturation was identified and monitored. • Elevated pore gas pressure was estimated to be 8500 psi. • Water migration/sand pack failure were observed spatially and temporally resolved. • Different molecular species and fluid environments were discriminated. [ABSTRACT FROM AUTHOR]