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J Magn Reson. 2014 Aug;245:143-9. doi: 10.1016/j.jmr.2014.06.013. Epub 2014 Jun 28.

Visualizing skin effects in conductors with MRI: (7)Li MRI experiments and calculations.

Author information

1
Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003, USA.
2
National High Magnetic Field Laboratory and Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310, USA.
3
Department of Computer Science, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
4
Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, USA.
5
Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, USA; Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
6
Courant Institute of Mathematical Sciences, New York University, New York, NY 10012, USA.
7
Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003, USA. Electronic address: alexej.jerschow@nyu.edu.

Abstract

While experiments on metals have been performed since the early days of NMR (and DNP), the use of bulk metal is normally avoided. Instead, often powders have been used in combination with low fields, so that skin depth effects could be neglected. Another complicating factor of acquiring NMR spectra or MRI images of bulk metal is the strong signal dependence on the orientation between the sample and the radio frequency (rf) coil, leading to non-intuitive image distortions and inaccurate quantification. Such factors are particularly important for NMR and MRI of batteries and other electrochemical devices. Here, we show results from a systematic study combining rf field calculations with experimental MRI of (7)Li metal to visualize skin depth effects directly and to analyze the rf field orientation effect on MRI of bulk metal. It is shown that a certain degree of selectivity can be achieved for particular faces of the metal, simply based on the orientation of the sample. By combining rf field calculations with bulk magnetic susceptibility calculations accurate NMR spectra can be obtained from first principles. Such analyses will become valuable in many applications involving battery systems, but also metals, in general.

KEYWORDS:

Lithium batteries; Magnetic resonance imaging; Rf field calculations; Skin effect; Susceptibility effects

PMID:
25036296
DOI:
10.1016/j.jmr.2014.06.013

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