Electrical Transport in a Disordered Medium: NMR Measurement of Diffusivity and Electrical Mobility of Ionic Charge Carriers

Combination of Time‐Dependent Self‐Diffusion Measurements (Dynamic Imaging) with Magnetic Resonance Imaging

“…In addition, the local S/V p ratio in the sectors with Sephadex gel matches the values of S/V p = 330,550 m -1 measured in previous work [8,14,16].…”

Characterization of Structure and Transport in Porous Media by Pulsed Field Gradient (PFG) NMR Technique. Part I: Master Curve and Characteristic Inner Length

“…8. The water diffusion measurements in Sephadex LH-20 (Pharmacia Biotech, Uppsala, Sweden), a widely used gel in gel permeation chromatography and gel filtration, were performed by Heil [2,24]. Sephadex LH-20 is a dextran gel and, according to the supplier, the wet particle size range is 30 to 160 lm.…”

“…observation time dependent diffusion path length (in z-direction) n D characteristic inner length (for diffusion), also called correlation length n V characteristic inner length (for flow) f porosity r average particle radius S/V p ratio of surface area to pore volume T tortuosity T 1 longitudinal nuclear magnetic relaxation time T 2 transversal nuclear magnetic relaxation time t time, here mostly "observation time" h fitting parameter in Padé approximation correlated with pore size…”

“…These porous systems range from comparatively simple packings used, for example, in certain chemical engineering processes, to complicated fractured rocks important in the exploitation of hydrocarbon reservoirs and heat mining. Since many years, the authors have applied pulsed-field-gradient nuclear magnetic resonance (PFG NMR) as a noninvasive tool for investigating different transport processes and structural properties in porous systems [2][3][4][5]. In the studies conducted, observation time dependent measurements of transport quantities, mainly of the self-diffusion coefficient D, have been used since a number of papers reported that observing diffusing species in a liquidfilled pore space allows their use as probes for the confining geometry (see, for example, [5][6][7][8]).…”

Field-Assisted Diffusion Studied by Electrophoretic NMR

“…Thus, it is not surprising that this field of ENMR application developed comparatively fast in the last years. The first successful measurements of ionic mobilities in porous systems, namely in gels, have been performed in the author's laboratory [26,27]. It could be demonstrated that in the fluidfilled pore space both the observed ionic self-diffusion coefficient D ± and the ionic mobility u ± in an external electric field show a dependence on the observation time ∆ (see Fig.…”