Webber, J.B.W. and Bland, P.A. and Strange, J.H. and Anderson, R.A. and Tohidi, B. (2009) Why you can't use water to make cryoporometric measurements of the pore size distributions in meteorites - or in high iron content clays, rocks or concrete. Diffusion Fundamentals, 10 (1). 3.1-3.3. ISSN 1862-4138. (Full text available)
PDF (Cryoporometric Measurements of the Pore Size Distributions in Meteorites)
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Many porous materials have high susceptibility magnetic gradients in the pores, due to the presence of iron or other magnetic materials. Thus if probe liquids are placed in the pores they exhibit fast decaying signals with a short T2*. Usually the actual T2 of the liquids is also reduced, due the presence of paramagnetic ions in the pore walls. The usual solution in NMR is to measure an echo (or echo train) at short times. However, recent work [J. Phys.: Condens. Matter 19, 415117, 2007.] has shown that water/ice systems near a pore wall form rotator phase plastic ice, with T2 relaxation times in the region of 100 to 200 ms. Thus if a NMR cryoporometric measurement is attempted with a measurement time significantly less than 1 or 2 milli-seconds, the result is to make a measurement based on the phase properties of the brittle to plastic ice phase transition, not that of the brittle ice to water phase transition. This gives rise to artefacts of small pore sizes that may not actually be present. This work successfully uses a-polar liquids instead.
|Uncontrolled keywords:||confined geometry, plastic ice, cryoporometry, meteorite, porosity.|
|Subjects:||Q Science > QC Physics > QC807 Geophysics (for Applied Geophysics see TN269)
Q Science > QB Astronomy
Q Science > QC Physics > QC176.8.N35 Nanoscience, nanotechnology
Q Science > QC Physics
|Divisions:||Faculties > Science Technology and Medical Studies > School of Physical Sciences > Functional Materials Group|
|Depositing User:||J.B.W. Webber|
|Date Deposited:||27 Oct 2009 15:42|
|Last Modified:||09 May 2012 09:04|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/23117 (The current URI for this page, for reference purposes)|