Impact of Internal Magnetic Gradients on Nuclear Magnetic Resonance Measurements and NMR-Based Pore Network Characterization

2016 ◽  
Author(s):  
Saurabh Tandon ◽  
Zoya Heidari
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Pore Network ◽  
Network Characterization ◽  
Magnetic Gradients ◽  
Nuclear Magnetic

Interaction of Alkalis (CS+) With Calcium Silicates Hydrates

1997 ◽  
Vol 506 ◽  
Author(s):  
P. Faucon ◽  
T. Charpentier ◽  
P. Henocq ◽  
J.C. Petit ◽  
J. Virlet ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Interlayer Space ◽  
Cesium Chloride ◽  
Pore Network ◽  
Silanol Groups ◽  
Cesium Ions ◽  
Calcium Silicates ◽  
Nuclear Magnetic

ABSTRACTC-S-H of different Ca/Si ratios were synthesized in suspension. Cesium chloride (0.5 M) was put in contact with these C-S-H in reactors for 30 days at 25 °C with solution/solid ratios of 50. The quantities of cesium fixed by the C-S-H was determined by microanalyses and the mechanisms of retention in relation with the C-S-H structure was investigated by 133Cs Nuclear Magnetic Resonance (NMR). The influence of the humidity yield in which the C-S-H were stored was also studied.At 100% of humidity, some cesium ions are trapped in the pore network of the C-S-H. However, most cesium ions are incorporated in the hydrated interlayers of the C-S-H between the silica chains of the structure. They are mobile in this interlayer space. At high Ca/Si ratio, the charge of incorporated Cs+ ions in the structure should be compensated by the associated Cl- incorporation. At low Ca/Si, the presence of silanol groups in the C-S-H structure, which becomes closer to that of tobermorite (Ca/Si about 0.8), makes possible the exchange or substitution H'<->Cs'. The resulting retention of cesium in the C-S-H then becomes higher.

An emerging technology: Nuclear magnetic resonance microscopy

1988 ◽  
Vol 46 ◽  
pp. 1000-1001
Author(s):  
M.J. Hennessy ◽  
E. Kwok
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Basic Research ◽  
Local Environment ◽  
Magnetic Resonance Images ◽  
Nmr Microscopy ◽  
Mri Scans ◽  
Temperature Relaxation ◽  
Nuclear Magnetic

Much progress in nuclear magnetic resonance microscope has been made in the last few years as a result of improved instrumentation and techniques being made available through basic research in magnetic resonance imaging (MRI) technologies for medicine. Nuclear magnetic resonance (NMR) was first observed in the hydrogen nucleus in water by Bloch, Purcell and Pound over 40 years ago. Today, in medicine, virtually all commercial MRI scans are made of water bound in tissue. This is also true for NMR microscopy, which has focussed mainly on biological applications. The reason water is the favored molecule for NMR is because water is,the most abundant molecule in biology. It is also the most NMR sensitive having the largest nuclear magnetic moment and having reasonable room temperature relaxation times (from 10 ms to 3 sec). The contrast seen in magnetic resonance images is due mostly to distribution of water relaxation times in sample which are extremely sensitive to the local environment.

Nuclear magnetic resonance microscopy

1989 ◽  
Vol 47 ◽  
pp. 828-829
Author(s):  
Paul C. Lauterbur
Keyword(s):  
Magnetic Field ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Fields ◽  
Signal To Noise ◽  
Field Gradients ◽  
Useful Signal ◽  
Magnetic Field Gradients ◽  
Observation Times ◽  
Nuclear Magnetic

Nuclear magnetic resonance imaging can reach microscopic resolution, as was noted many years ago, but the first serious attempt to explore the limits of the possibilities was made by Hedges. Resolution is ultimately limited under most circumstances by the signal-to-noise ratio, which is greater for small radio receiver coils, high magnetic fields and long observation times. The strongest signals in biological applications are obtained from water protons; for the usual magnetic fields used in NMR experiments (2-14 tesla), receiver coils of one to several millimeters in diameter, and observation times of a number of minutes, the volume resolution will be limited to a few hundred or thousand cubic micrometers. The proportions of voxels may be freely chosen within wide limits by varying the details of the imaging procedure. For isotropic resolution, therefore, objects of the order of (10μm) may be distinguished.Because the spatial coordinates are encoded by magnetic field gradients, the NMR resonance frequency differences, which determine the potential spatial resolution, may be made very large. As noted above, however, the corresponding volumes may become too small to give useful signal-to-noise ratios. In the presence of magnetic field gradients there will also be a loss of signal strength and resolution because molecular diffusion causes the coherence of the NMR signal to decay more rapidly than it otherwise would. This phenomenon is especially important in microscopic imaging.

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