scholarly journals Three-dimensional pulsed field gradient NMR measurements of self-diffusion in anisotropic materials for energy storage applications

2019 ◽  
Vol 21 (8) ◽  
pp. 4538-4546 ◽  
Author(s):  
S. Engelke ◽  
L. E. Marbella ◽  
N. M. Trease ◽  
M. De Volder ◽  
C. P. Grey
Keyword(s):  
Energy Storage ◽  
Porous Silicon ◽  
Field Gradient ◽  
Three Dimensional ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Silicon Structures ◽  
Energy Storage Applications ◽  
Nmr Methods ◽  
Pfg Nmr

The ability to resolve solvent in- and outside of the pores of mesoscopic porous silicon structures allows the effect of confinement on transport to be explored by 1H and 7Li PFG NMR methods and pore diameters and lengths to be estimated.

The Measurement of Tortuosity of Porous Media Using Imaging, Electrical Measurements, and Pulsed Field Gradient NMR

2021 ◽  
Author(s):  
Mahmoud Elsayed ◽  
Hyung Kwak ◽  
Ammar El-Husseiny ◽  
Mohamed Mahmoud
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Porous Media ◽  
Diffusion Coefficient ◽  
Magnetic Resonance ◽  
Field Gradient ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Pfg Nmr ◽  
The Relationship ◽  
Self Diffusion Coefficient

Abstract Tortuosity, in general characterizes the geometric complexity of porous media. It is considered as one of the key factors in characterizing the heterogonous structure of porous media and has significant implications for macroscopic transport flow properties. There are four widely used definitions of tortuosity, that are relevant to different fields from hydrology to chemical and petroleum engineering, which are: geometric, hydraulic, electrical, and diffusional. Recent work showed that hydraulic, electrical and diffusional tortuosity values are roughly equal to each other in glass beads. Nevertheless, the relationship between the different definitions of Tortuosity in natural rocks is not well understood yet. Understanding the relationship between the different Tortuosity definitions in rocks can help to establish a workflow that allows us to estimate other types from the available technique. Therefore, the objective of this study is to investigate the relationship between the different tortuosity definitions in natural rocks. A major focus of this work is to utilize Nuclear Magnetic Resonance (NMR) technology to estimate Tortuosity. Such technique has been traditionally used to obtain diffusional tortuosity which can be defined as the ratio of the free fluid self-diffusion coefficient to the restricted fluid self-diffusion coefficient inside the porous media. In this study, the following techniques were used to quantify hydraulic, electrical, and diffusional tortuosity respectively on the same rock sample: (1) Microcomputed Tomography 3D imaging (2) Four-Electrodes resistivity measurements (3) Pulsed-Field Gradient Nuclear Magnetic Resonance (PFG NMR). PFG NMR is very powerful, non-invasive technique employed to measure the self-diffusion coefficient for free and confined fluids. The measurements were done based on two carbonate rock core plugs characterized by variable porosity, permeability and texture complexity. Results show that PFG NMR can be applied directionally to quantify the pore network anisotropy created by fractures. For both samples, hydraulic tortuosity was found to have the lowest magnitude compared to geometric, electrical and diffusional tortuosity. This could be explained by the more heterogeneous microstructure of carbonate rocks. NMR technique has however advantages over the other electrical and imaging techniques for tortuosity characterization: it is faster, non-destructive and can be applied in well bore environment (in situ). We therefore conclude that NMR can provide a tool for estimating not only diffusional tortuosity but also for indirectly obtaining hydraulic and electrical tortuosity.

Robustness of Methane Diffusion in Geometrically Restricted Molecular Sieve Pores

1994 ◽  
Vol 366 ◽  
Author(s):  
Sriram S. Nivarthi ◽  
H. Ted Davis ◽  
Alon V. McCormick
Keyword(s):  
Field Gradient ◽  
Molecular Sieve ◽  
Pore Space ◽  
Pulsed Field Gradient Nmr ◽  
Pulsed Field ◽  
Zeolite Nay ◽  
Self Diffusion ◽  
Methane Diffusion ◽  
Pfg Nmr ◽  
Sieve Pores

ABSTRACTNMR measurements of sorbate mobility in zeolites are especially attractive because of their capability of measuring multicomponent and anisotropic self-diffusion. We have recently reported the application of the pulsed field gradient NMR technique using very large zeolite crystals to study how easily methane can diffuse when we attempt to slow its migration by crowding the pore space. Here we analyze the implications of these PFG NMR experiments involving (i) ethylene blocking of methane in zeolite NaY; and (ii) methane molecules trying to pass one another in the molecular sieve A1PO4-5.

scholarly journals Molecular and Ionic Diffusion in Ion Exchange Membranes and Biological Systems (Cells and Proteins) Studied by NMR

Membranes ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 385
Author(s):  
Vitaliy I. Volkov ◽  
Alexander V. Chernyak ◽  
Irina A. Avilova ◽  
Nikita A. Slesarenko ◽  
Daria L. Melnikova ◽  
...  
Keyword(s):  
Field Gradient ◽  
Diffusion Processes ◽  
Spatial Scales ◽  
Water Soluble ◽  
Fullerene Derivative ◽  
Wide Field ◽  
Pulsed Field Gradient Nmr ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Pfg Nmr

The results of NMR, and especially pulsed field gradient NMR (PFG NMR) investigations, are summarized. Pulsed field gradient NMR technique makes it possible to investigate directly the partial self-diffusion processes in spatial scales from tenth micron to millimeters. Modern NMR spectrometer diffusive units enable to measure self-diffusion coefficients from 10−13 m2/sec to 10−8 m2/sec in different materials on 1 H, 2 H, 7 Li, 13 C, 19 F, 23 Na, 31 P, 133 Cs nuclei. PFG NMR became the method of choice for reveals of transport mechanism in polymeric electrolytes for lithium batteries and fuel cells. Second wide field of application this technique is the exchange processes and lateral diffusion in biological cells as well as molecular association of proteins. In this case a permeability, cell size, and associate lifetime could be estimated. The authors have presented the review of their research carried out in Karpov Institute of Physical Chemistry, Moscow, Russia; Institute of Problems of Chemical Physics RAS, Chernogolovka, Russia; Kazan Federal University, Kazan, Russia; Korea University, Seoul, South Korea; Yokohama National University, Yokohama, Japan. The results of water molecule and Li+, Na+, Cs+ cation self-diffusion in Nafion membranes and membranes based on sulfonated polystyrene, water (and water soluble) fullerene derivative permeability in RBC, casein molecule association have being discussed.

Pulsed Field Gradient NMR Investigation of Molecular Mobility of Trimethoxymethane in Nafion Membranes

1997 ◽  
Vol 496 ◽  
Author(s):  
Y. Wu ◽  
T. A. Za Wodzinski ◽  
M. C. Smart ◽  
S. G. Greenbaum ◽  
G.K.S. Prakash ◽  
...  
Keyword(s):  
Field Gradient ◽  
Molecular Mobility ◽  
Alternative Fuels ◽  
Direct Oxidation ◽  
Effective Distance ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Lower Extent ◽  
The Difference ◽  
Nmr Signals

ABSTRACTMolecular mobility of water and trimethoxymethane (TMM) in NAFION membranes of two different equivalent weights (EW), 1100 and 1500, were investigated. Self-diffusion coefficients were determined by the NMR pulsed field gradient method, using the water and methyl protons NMR signals, in saturated NAFION samples containing concentrations of TMM in water varying between 0.5 and 14 M, and at temperatures varying from 30°C to 80°C. Diffusion of molecular species containing methyl protons is more than a factor of two slower in the 1500 EW membrane than in the 1100 EW membrane at 30°C and 1 M concentration. The difference rises to about a factor of four at 80°C and 14 M concentration. These differences are attributed to the lower extent of plasticization of the higher EW material as well as the greater effective distance between acid functional groups. NAFION samples containing methanol/water mixtures were also investigated. Comparison with the methanol results and the permeation behavior, as characterized by gas Chromatographie methods, show that more than half of the TMM is hydrolyzed to methanol as it passes through the acidic membrane. The implications of these findings for alternative fuels in direct oxidation fuel cells are discussed.

c , T-Dependence of the Self Diffusion in Concentrated Aqueous Sucrose Solutions

1994 ◽  
Vol 49 (3-4) ◽  
pp. 258-264 ◽  
Author(s):  
D. Girlich ◽  
H.-D. Lüdemann ◽  
C. Buttersack ◽  
K. Buchholz
Keyword(s):  
Field Gradient ◽  
Concentration Dependence ◽  
Diffusion Coefficients ◽  
The Self ◽  
Water Molecules ◽  
Pulsed Field Gradient Nmr ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Sucrose Solutions ◽  
Wide Range

The self diffusion coefficients D of the water molecules and of sucrose have been determined by the pulsed field gradient NMR technique over a wide range of temperatures and concentrations (cmax: 70% w/w suc.). All temperature dependencies can be fitted to a Vogel- Tammann-Fulcher equation. The isothermic concentration dependence of D for the sucrose is given by a simple exponential concentration dependence

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