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Model for the interpretation of nuclear magnetic resonance relaxometry of hydrated porous silicate materials.

Faux, DA, Cachia, SH, McDonald, PJ, Bhatt, JS, Howlett, NC and Churakov, SV (2015) Model for the interpretation of nuclear magnetic resonance relaxometry of hydrated porous silicate materials. Phys Rev E Stat Nonlin Soft Matter Phys, 91 (3).

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Abstract

Nuclear magnetic resonance (NMR) relaxation experimentation is an effective technique for probing the dynamics of proton spins in porous media, but interpretation requires the application of appropriate spin-diffusion models. Molecular dynamics (MD) simulations of porous silicate-based systems containing a quasi-two-dimensional water-filled pore are presented. The MD simulations suggest that the residency time of the water on the pore surface is in the range 0.03-12 ns, typically 2-5 orders of magnitude less than values determined from fits to experimental NMR measurements using the established surface-layer (SL) diffusion models of Korb and co-workers [Phys. Rev. E 56, 1934 (1997)]. Instead, MD identifies four distinct water layers in a tobermorite-based pore containing surface Ca2+ ions. Three highly structured water layers exist within 1 nm of the surface and the central region of the pore contains a homogeneous region of bulklike water. These regions are referred to as layer 1 and 2 (L1, L2), transition layer (TL), and bulk (B), respectively. Guided by the MD simulations, a two-layer (2L) spin-diffusion NMR relaxation model is proposed comprising two two-dimensional layers of slow- and fast-moving water associated with L2 and layers TL+B, respectively. The 2L model provides an improved fit to NMR relaxation times obtained from cementitious material compared to the SL model, yields diffusion correlation times in the range 18-75 ns and 28-40 ps in good agreement with MD, and resolves the surface residency time discrepancy. The 2L model, coupled with NMR relaxation experimentation, provides a simple yet powerful method of characterizing the dynamical properties of proton-bearing porous silicate-based systems such as porous glasses, cementitious materials, and oil-bearing rocks.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
AuthorsEmailORCID
Faux, DAUNSPECIFIEDUNSPECIFIED
Cachia, SHUNSPECIFIEDUNSPECIFIED
McDonald, PJUNSPECIFIEDUNSPECIFIED
Bhatt, JSUNSPECIFIEDUNSPECIFIED
Howlett, NCUNSPECIFIEDUNSPECIFIED
Churakov, SVUNSPECIFIEDUNSPECIFIED
Date : March 2015
Related URLs :
Additional Information : Copyright 2015 The American Physical Society.
Depositing User : Symplectic Elements
Date Deposited : 02 Jun 2015 12:52
Last Modified : 20 Jun 2015 13:36
URI: http://epubs.surrey.ac.uk/id/eprint/807580

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