Low-field nuclear magnetic resonance (NMR) has been widely applied in the oil industry as a noninvasive technique for rock analysis. There are many organic compounds, such as kerogen, in unconventional shale resources. However, it is difficult to evaluate solid organic matter in shales using common NMR techniques. Previous work has shown the use of a solid echo on shale samples provides more information than the standard T 1–T 2 method with spin echo. But for multiple homonuclear dipolar coupling present in shales, solid echo is less efficient. We propose a new multimagic-echo sequence for T 1 and T 1–T 2 measurements. The magic echo and standard T 1 and T 2 measurement technologies are combined to provide a more complete evaluation of hydrogen-containing shale sample components. Compared with other measurements, magic-echo measurements provide more signal of organic matters in shale samples. The additional signal is contributed by homonuclear dipolar coupling in organic matter. The partial least-squares regression (PLSR) method is used to analyze the relationships between organic geochemical properties and T 1–T 2 correlation data. The results presented here show that the T 1–T 2 peak distributions provided by magic-echo NMR agree well with the organic geochemical properties of shales. This method should make the NMR measurement of shales for the detection of organic matter a common technique.

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A new-type binder-free Sn/C composite membrane with densely stacked Sn-in-carbon nanosheets was prepared by vacuum-induced self-assembly of graphene-like Sn alkoxide and following in situ thermal conversion. The successful implementation of this rational strategy is based on the controllable synthesis of graphene-like Sn alkoxide by using Na−citrate with the critical inhibitory effect on polycondensation of Sn alkoxide along the a and b directions. Density functional theory calculations reveal that graphene-like Sn alkoxide can be formed under the joint action of oriented densification along the c axis and continuous growth along the a and b directions. The Sn/C composite membrane constructed by graphene-like Sn-in-carbon nanosheets can effectively buffer volume fluctuation of inlaid Sn during cycling and much enhance the kinetics of Li + diffusion and charge transfer with the developed ion/electron transmission paths. After temperature-controlled structure optimization, Sn/C composite membrane displays extraordinary Li storage behaviors, including reversible half-cell capacities up to 972.5 mAh g −1 at a density of 1 A g −1 for 200 cycles, 885.5/729.3 mAh g −1 over 1000 cycles at large current densities of 2/4 A g −1 , and terrific practicability with reliable fullcell capacities of 789.9/582.9 mAh g −1 up to 200 cycles under 1/4 A g −1 . It is worthy of noting that this strategy may open up new opportunities to fabricate advanced membrane materials and construct hyperstable self-supporting anodes in lithium ion batteries.

Nuclear magnetic resonance (NMR) techniques are widely used to identify pure substances and probe protein dynamics. Oil is a complex mixture composed of hydrocarbons, which have a wide range of molecular size distribution. Previous work show that empirical correlations of relaxation times and diffusion coefficients were found for simple alkane mixtures, and also the shape of the relaxation and diffusion distribution functions are related to the composition of the fluids. The 2D NMR is a promising qualitative evaluation method for oil composition. But uncertainty in the interpretation of crude oil indicated further study was required. In this research, the effect of each composition on relaxation distribution functions is analyzed in detail. We also suggest a new method for prediction of the rotational correlation time distribution of crude oil molecules using low field NMR (LF-NMR) relaxation time distributions. A set of down-hole NMR fluid analysis system is independently designed and developed for fluid measurement. We illustrate this with relaxation-relaxation correlation experiments and rotational correlation time distributions on a series of hydrocarbon mixtures that employ our laboratory-designed downhole NMR fluid analyzer. The LF-NMR is a useful tool for detecting oil composition and monitoring oil property changes. Copyright © 2016 John Wiley & Sons, Ltd.