Pore Structure Evolution of Cemented Paste Backfill Observed with Two-Dimensional NMR Relaxation Correlation Measurements

Robinson, Neil; Nasharuddin, Razyq; Luo, Ganhua; Fourie, Andy; Fridjonsson, Einar O.; Johns, Michael L.

doi:10.1021/acs.iecr.1c01819

Cited by 10 publications

(3 citation statements)

References 73 publications

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“…PFG NMR diffusion measurements are employed to investigate the mass transport of fluids in porous media [25][26][27], and to quantify the tortuosity of the attendant pore networks [28][29][30][31][32]. NMR relaxation measurements quantify the longitudinal (T1) and transverse (T2) relaxation time constants associated with confined fluids; these time constants are directly related to molecular dynamics and can provide valuable information on pore structure characteristics [33][34][35][36] and solid-liquid interactions [37][38][39][40], especially when screening adsorption processes in sorbents and in catalytically active systems [41][42][43]. Two-dimensional (2D) 𝑇1 − 𝑇2 relaxation time correlation measurements are now employed widely to provide comprehensive information on nuclear spin relaxation processes in porous materials [44][45][46][47][48][49][50][51].…”

Section: Introductionmentioning

confidence: 99%

Towards Quantifying the Chemical Sensitivity of Nuclear Spin Surface Relaxivity in Mesoporous Media

Dong,

Liu,

Ling

et al. 2024

Preprint

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Low-field nuclear magnetic resonance (NMR) relaxation is a promising non-invasive technique for characterizing solid-liquid interactions within functional porous materials. However, the ability of the solid-liquid interface to enhance adsorbate relaxation rates, known as the surface relaxivity, in the case of different solvents and reagents involved in various chemical processes has yet to be evaluated in a quantitative manner. In this study, we systematically explore the surface relaxation characteristics of ten liquid adsorbates (cyclohexane, acetone, water, and seven alcohols, including ethylene glycol) confined within mesoporous silicas with pore sizes between 6 nm and 50 nm using low-field (12.7 MHz) two-dimensional 1H T1 – T2 relaxation measurements. Functional group specific relaxation phenomena associated with the alkyl and hydroxyl groups of the confined alcohols are clearly distinguished; we report the dependence of both longitudinal (T1) and transverse (T2) relaxation rates of these 1H-bearing moieties on pore surface-to-volume ratio, facilitating the quantification and assignment of surface relaxivity values to specific functional groups within the same adsorbate molecule for the first time. We further demonstrate that alkyl group transverse surface relaxivities correlate strongly with the alkyl/hydroxyl ratio of the adsorbates assessed, providing evidence for a simple, quantitative relationship between surface relaxivity and interfacial chemistry. Overall, our observations highlight potential pitfalls in the application of NMR relaxation for the evaluation of pore size distributions using hydroxylated probe molecules, and provide motivation for the exploration of nuclear spin relaxation measurements as a route to adsorbate identity within functional porous materials.

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Section: Introductionmentioning

confidence: 99%

Towards Quantifying the Chemical Sensitivity of Nuclear Spin Surface Relaxivity in Mesoporous Media

Dong,

Liu,

Ling

et al. 2024

Preprint

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show abstract

“…Nuclear magnetic resonance (NMR) is a non-invasive and chemically selective technique for characterizing porous materials. − Traditional NMR spectroscopy approaches provide structural information via chemical shift analysis, and are regularly applied to inform the solid state structures of porous materials, including oxides, , zeolites, , and porous coordination frameworks and polymers (such as metal–organic and covalent–organic frameworks). − However, for liquids confined within the pore structures of such materials, chemical shift resolution is usually significantly limited by line-broadening effects (especially for standard 1 H NMR spectra, which typically exhibit narrow chemical shift ranges), which occur due to local magnetic field distortions caused by magnetic susceptibility differences at the solid–liquid interface. , Dynamic NMR measurements are comparatively unaffected by this problem, and instead provide information on the molecular translational and rotational motion of confined species by assessing the decay of NMR signals over time, with typical means including pulsed field gradient (PFG) NMR diffusion and NMR relaxation time measurements . PFG NMR diffusion measurements are employed to investigate the mass transport of fluids in porous media, − and to quantify the tortuosity of the attendant pore networks. − NMR relaxation measurements quantify the longitudinal ( T 1 ) and transverse ( T 2 ) relaxation time constants associated with confined fluids; these time constants are directly related to molecular dynamics and can provide valuable information on pore structure characteristics − and solid–fluid interactions, − especially when screening adsorption processes in sorbents and in catalytically active systems. − …”

Section: Introductionmentioning

confidence: 99%

Toward Quantifying the Chemical Sensitivity of Nuclear Spin Surface Relaxivity in Mesoporous Media

Dong,

Liu,

Ling

et al. 2024

Langmuir

Self Cite

View full text Add to dashboard Cite

Low-field nuclear magnetic resonance (NMR) relaxation is a promising non-invasive technique for characterizing solid−liquid interactions within functional porous materials. However, the ability of the solid−liquid interface to enhance adsorbate relaxation rates, known as the surface relaxivity, in the case of different solvents and reagents involved in various chemical processes has yet to be evaluated in a quantitative manner. In this study, we systematically explore the surface relaxation characteristics of 10 liquid adsorbates (cyclohexane, acetone, water, and 7 alcohols, including ethylene glycol) confined within mesoporous silicas with pore sizes between 6 and 50 nm using low-field (12.7 MHz) two-dimensional 1 H T 1 −T 2 relaxation measurements. Functional-group-specific relaxation phenomena associated with the alkyl and hydroxyl groups of the confined alcohols are clearly distinguished; we report the dependence of both longitudinal (T 1 ) and transverse (T 2 ) relaxation rates of these 1 H-bearing moieties on pore surface-to-volume ratio, facilitating the quantification and assignment of surface relaxivity values to specific functional groups within the same adsorbate molecule for the first time. We further demonstrate that alkyl group transverse surface relaxivities correlate strongly with the alkyl/hydroxyl ratio of the adsorbates assessed, providing evidence for a simple, quantitative relationship between surface relaxivity and interfacial chemistry. Overall, our observations highlight potential pitfalls in the application of NMR relaxation for the evaluation of pore size distributions using hydroxylated probe molecules, and provide motivation for the exploration of nuclear spin relaxation measurements as a route to adsorbate identity within functional porous materials.

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“…The underground environment of most coal mines, except open-pit ones, is complex and diverse due to the coupling of multiple thermos-mechanical fields and factors (Neil et al, 2021;Wang et al, 2011Wang et al, , 2021bWang et al, , 2022Zhang and Li, 2022). However, with gradual exhaustion of easily mined coal resources, coal mining under complex conditions became more and more topical.…”

Section: Introductionmentioning

confidence: 99%

Water-bearing effect on mechanical properties and interface failure mode of coal–rock combination samples

Zhang

Chi

Yang³

et al. 2023

Energy Exploration & Exploitation

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The coal and rock mass in water-rich mines with underground waterproof coal-and-rock pillars will be inevitably eroded by groundwater. The mechanical properties and interface failure mode of coal–rock mass under high-moisture conditions directly affect the mine stability and operation safety. This study performed uniaxial compression tests of samples from coal, rock, and their combination with different water contents, the evolution law of mechanical properties and acoustic emission (AE) damage characteristics of coal–rock combinations (C-RC) with different water contents were studied. The C-RC interface failure modes at different water contents were clarified. The results showed that the deterioration of average peak strength of coal, rock, and C-RC was obvious with increased water content. The deterioration degree in the descending order was as follows: C-RC > coal mass > rock mass. The maximum AE ringing number first increased rapidly and then sharply dropped, while the AE cumulative ringing number dropped slowly and then rapidly, reflecting the internal crack propagation patterns in C-RC. The failure mechanism of water-bearing C-RC was related to coal–rock strength ratio and the water-bearing effect of coal–rock interface. When the water-bearing state of C-RC changed from dry to saturated, the macro-failure mode showed the law of only coal fracture (0%)—minor fracture at the coal–rock interface (4%)—both coal and rock fracture (8%)—only coal fracture (12%). With increased water content, the water-bearing effect of C-RC interface gradually prevailed in the C-RC failure pattern.

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Pore Structure Evolution of Cemented Paste Backfill Observed with Two-Dimensional NMR Relaxation Correlation Measurements

Cited by 10 publications

References 73 publications

Towards Quantifying the Chemical Sensitivity of Nuclear Spin Surface Relaxivity in Mesoporous Media

Towards Quantifying the Chemical Sensitivity of Nuclear Spin Surface Relaxivity in Mesoporous Media

Toward Quantifying the Chemical Sensitivity of Nuclear Spin Surface Relaxivity in Mesoporous Media

Water-bearing effect on mechanical properties and interface failure mode of coal–rock combination samples

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