Studies of freezing–melting hysteresis in cryoporometry scanning loop experiments using NMR diffusometry and relaxometry

Hitchcock, Iain; Holt, Elizabeth M.; Lowe, John P.; Rigby, Sean P.

doi:10.1016/j.ces.2010.10.027

Cited by 33 publications

(13 citation statements)

References 18 publications

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“…pores in the cylinder samples observed from the calculated differential PSD curves, it is possibly related to the so-called advanced melting phenomenon [42,63]. It is normally assumed that for cylindrical pores, the melting would take place in a radical direction [42], or melting from the side (the direction perpendicular to the diameter) [26].…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Impact of sample crushing on porosity characterization of hardened cement pastes by low temperature calorimetry: Comparison of powder and cylinder samples

Fridh

Johannesson

2018

Thermochimica Acta

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The impact of sample crushing on the detected porosity of hardened cement pastes by low temperature calorimetry (LTC) was studied using powder and cylinder samples. Two types of cements, CEM I and CEM III, were used to prepare the pastes. A model porous material, MCM-41, was also used in order to investigate some aspects of the measurement and the evaluation approach. The powder and cylinder samples of the cement pastes were compared in terms of the calculated ice content curves, total pore volumes and pore size distribution curves. For the two studied cement pastes, the calculated ice content curves of freezing of the powder sample differed from that of the cylinder samples, especially for the paste CEM III. The results indicate that sample crushing changed the pore connectivity as compared to non-crushed samples. One important difference between the powder sample and the cylinder samples of the paste CEM III was that the determined maximum ice content in the powder sample was much higher than that in the cylinder samples, the relatively difference being about 40-50%. However, this kind of marked difference was not found in the paste CEM I. The observed difference between the calculated pore volume of the powder and the cylinder samples of the paste CEM III is possibly due to some of the "isolated" pores which, presumably, cannot be fully filled with water in the preparation of the cylinder samples. However, sample crushing makes it possible to saturate the pores to a greater

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Section: Accepted Manuscriptmentioning

confidence: 99%

Impact of sample crushing on porosity characterization of hardened cement pastes by low temperature calorimetry: Comparison of powder and cylinder samples

Fridh

Johannesson

2018

Thermochimica Acta

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“…The batch average BET specific surface area is $200 m 2 g À1 , and the batch average specific pore volume estimated from the sample studied in this work is $0.80-0.92 cm 3 g À1 , but there are some differences between individual pellets due to intra-batch variability. This material has been extensively characterised in our earlier work, including pore size distributions obtained from gas sorption, mercury porosimetry and NMR cryoporometry [15,25]. We have also applied our novel integrated gas sorption and mercury porosimetry technique to this material [25].…”

Section: Methodsmentioning

confidence: 98%

“…In cylindrical pores, melting would occur at a lower temperature via a hemispherical meniscus (between solid and molten phases), than it would via a sleeveshaped meniscus. By using scanning curves and loops, Hitchcock et al [15] have recently shown that cryoporometry melting curves are prone to a pore-pore cooperative effect analogous to advanced condensation in gas adsorption. For a through cylindrical pore, melting is initiated, in a radial direction, from the thin cylindrical sleeve of permanently unfrozen liquid-like fluid that exists at the pore wall.…”

Section: Introductionmentioning

confidence: 98%

“…If the larger pore radius is smaller than the critical size for melting via a hemispherical meniscus at the current temperature, then the larger pore will also melt at the same temperature as the smaller pore. Hitchcock et al [15] have shown that such advanced melting effects can lead to a dramatic skew towards smaller pores in PSDs for mesoporous sol-gel silicas, determined from cryoporometry melting curves.…”

Section: Introductionmentioning

confidence: 99%

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Probing the impact of advanced melting and advanced adsorption phenomena on the accuracy of pore size distributions from cryoporometry and adsorption using NMR relaxometry and diffusometry

Shiko

Edler

Lowe

et al. 2012

Journal of Colloid and Interface Science

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The accuracy of pore size distributions (PSD) obtained from gas adsorption and cryoporometry is compromised by the presence of advanced adsorption and advanced melting effects, respectively. In order to improve PSD accuracy, it is necessary to know the extent of such effects. In this work cryoporometry and adsorption have been combined to study the onset of advanced melting effects in a sample partially-saturated with different volumes of condensate, in turn, by pre-equilibration with different vapour pressures of adsorbate. NMR relaxometry and diffusometry have been used to independently study the size and connectivity of adsorbed liquid ganglia at different molten fractions. It has been found that the onset of significant advanced melting coincided with abrupt changes in levels of individual pore-filling and ganglia inter-connections determined by NMR. These findings also highlighted where significant advanced adsorption processes were occurring, where larger pores were being filled with condensate before smaller pores. These studies have enabled the critical pores governing the advanced processes to be identified, and the likely errors in PSDs arising from advanced effects to be quantified.

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“…However, it should be mentioned that thermo-/cryo-porometry methods also suffer from a pore-pore co-operative effect known as advanced melting [32][33][34]. Advanced melting occurs when the melting of the probe fluid in a narrow neck, via a cylindrical-sleeve shaped meniscus facilitates the melting of the probe fluid in a neighbouring larger pore body via a hemispherical meniscus formed at the join between neck and body.…”

Section: Discussionmentioning

confidence: 99%

Detection of the delayed condensation effect and determination of its impact on the accuracy of gas adsorption pore size distributions

Rigby

Hasan

Hitchcock

et al. 2017

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription.For more information, please contact eprints@nottingham.ac.uk 1 normally requiring assumptions about the correct model for data analysis. In this work we present a novel method to both expand the range, and obtain greater accuracy, for the information obtained from the main boundary adsorption isotherms by using a combination of data obtained for two adsorptives, namely nitrogen and argon, both before and after mercury porosimetry. The method makes use of the fact that nitrogen and argon apparently 'see' a different pore geometry following mercury entrapment, with argon, relatively, 'ignoring' new metal surfaces produced by mercury porosimetry. The new method permits the study of network and pore-pore co-operative effects during adsorption that substantially affect the accuracy of the characteristic parameters, such as modal pore size, obtained for disordered materials. These effects have been explicitly quantified, for a typical sol-gel silica catalyst support material as a case study. The technique allowed the large discrepancies between modal pore sizes obtained from standard gas adsorption and mercury thermoporometry methods to be attributed to the network-based delayed condensation effect, rather than spinodal adsorption. Once the network-based delayed condensation effect had been accounted for, the simple cylindrical pore model and macroscopic thermodynamic Kelvin-Cohan equation were then found sufficient to accurately describe adsorption in the material studied, rather than needing a more complex microscopic theory. Hence, for disordered mesoporous solids, a proper account of inter-pore interactions is more important than that of intra-pore adsorbate density distribution, to obtain accurate pore size distributions. Detection of the Delayed Condensation Effect and Determination of its

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Studies of freezing–melting hysteresis in cryoporometry scanning loop experiments using NMR diffusometry and relaxometry

Cited by 33 publications

References 18 publications

Impact of sample crushing on porosity characterization of hardened cement pastes by low temperature calorimetry: Comparison of powder and cylinder samples

Impact of sample crushing on porosity characterization of hardened cement pastes by low temperature calorimetry: Comparison of powder and cylinder samples

Probing the impact of advanced melting and advanced adsorption phenomena on the accuracy of pore size distributions from cryoporometry and adsorption using NMR relaxometry and diffusometry

Detection of the delayed condensation effect and determination of its impact on the accuracy of gas adsorption pore size distributions

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