Molecular diffusion and nuclear-magnetic-resonance relaxation of water in unsaturated porous silica glass

D’Orazio, F.; Bhattacharja, Sankar; Halperin, W. P.; Eguchi, Kiyohisa; Mizusaki, T.

doi:10.1103/physrevb.42.9810

Cited by 159 publications

(104 citation statements)

References 18 publications

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“…The relaxation times reported above may be interpreted in terms of pore sizes according to the fast diffusion model of relaxation 20,21,23,29 . Since the relaxation times rapidly approach constant values, it is concluded that the pores rapidly approach constant size.…”

Section: Analysis and Discussionmentioning

confidence: 99%

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Densification of C–S–H Measured by ¹H NMR Relaxometry

et al. 2012

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ABSTRACT:The nano-scale morphology of, and pore water interactions in, calcium-silicate-hydrate (C-S-H), the active component of cement, remain uncertain. 1 H nuclear magnetic resonance (NMR) can fully characterise the nano-porosity of C-S-H in as-prepared material without the need for damaging sample drying. We use NMR to follow the density of C-S-H in sealed cured pastes as a function of degree of hydration (α) and water to cement ratio. We show clear evidence for C-S-H densification. The C-S-H "solid" density, exclusive of gel pore water, slightly decreases from ! ! = 2.73 g/cm 3 at α ≈ 0.4 to 2.65 g/cm 3 at α ≈ 0.9 due to an increase in the number of layers in the nanocrystalline aggregates. In the same range, the C-S-H "bulk" density, including gel water, increases from around 1.8 to 2.1 g/cm 3 . The increase corresponds to a transition from growth of low density product containing gel pores to higher density product devoid of gel pores.We update Powers' classical model from 1947. In contrast to the single "hydrate" of Powers', NMR differentiates between C-S-H and calcium hydroxide and separates out the inter-layer water within the C-S-H. It shows a clear non-linearity in the growth of the different fractions with α.

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Section: Analysis and Discussionmentioning

confidence: 99%

“…According to this model 20 , first applied to cement by Halperin et al 21 , the surface to volume ratio of a filled pore is given by…”

Section: C-s-h Density and Compositionmentioning

confidence: 99%

Densification of C–S–H Measured by ¹H NMR Relaxometry

et al. 2012

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“…It has been reported that surface diffusion of most organic fluids in typical porous materials is reduced by roughly an order of magnitude from that of the pure liquid. 19,20 Since the diffusion of pure methanol 21 is 1.6 × 10 −9 m 2 /s, this is expected to be on the order of 10 −10 m 2 /s . This reduction can be largely attributed to the geometrical form factor often represented by the phenomenological relation known as Archie's Law.…”

Section: Theorymentioning

confidence: 99%

Enhanced self-diffusion of adsorbed methanol in silica aerogel

Lee

Mounce

et al. 2014

Phys. Rev. B

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Molecular transport of a two-component system of liquid and vapor in a porous medium can be anomalously increased owing to fast exchange between the two phases. 1 We have investigated this phenomenon measuring the self-diffusion coefficient of methanol adsorbed in a 98% porosity aerogel using nuclear magnetic resonance (NMR) field gradient techniques. We found enhancement of several orders of magnitude from which we determined the ballistic mean-free-path in the vapor phase. We have grown globally uniform anisotropic aerogels and applied the diffusion measurements to characterize the anisotropy. Our results are important for understanding the novel properties of superfluid 3 He confined within an aerogel framework and for application to other physical systems.

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“…Pore sizes may be measured by NMR using either the fast exchange model of relaxation [19] or the change in signal amplitudes with drying [20]. We have used both methods.…”

Section: Assuming Camentioning

confidence: 99%