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Sean P. Rigby - One of the best experts on this subject based on the ideXlab platform.

  • Combining Mercury thermoporometry with integrated gas sorption and Mercury Porosimetry to improve accuracy of pore-size distributions for disordered solids
    Journal of colloid and interface science, 2014
    Co-Authors: Buhari Bafarawa, Jiawei Wang, Artjom Nepryahin, Elizabeth M. Holt, Sean P. Rigby
    Abstract:

    The typical approach to analysing raw data, from common pore characterization methods such as gas sorption and Mercury Porosimetry, to obtain pore size distributions for disordered porous solids generally makes several critical assumptions that impact the accuracy of the void space descriptors thereby obtained. These assumptions can lead to errors in pore size of as much as 500%. In this work, we eliminated these assumptions by employing novel experiments involving fully integrated gas sorption, Mercury Porosimetry and Mercury thermoporometry techniques. The entrapment of Mercury following Porosimetry allowed the isolation (for study) of a particular subset of pores within a much larger interconnected network. Hence, a degree of specificity of findings to particular pores, more commonly associated with use of templated, model porous solids, can also be achieved for disordered materials. Gas sorption experiments were conducted in series, both before and after Mercury Porosimetry, on the same sample, and the Mercury entrapped following Porosimetry was used as the probe fluid for theromporometry. Hence, even if one technique, on its own, is indirect, requiring unsubstantiated assumptions, the fully integrated combination of techniques described here permits the validation of assumptions used in one technique by another. Using controlled-pore glasses as model materials, Mercury Porosimetry scanning curves were used to establish the correct correspondence between the appropriate Gibbs–Thomson parameter, and the nature of the meniscus geometry in melting, for thermoporometry measurements on entrapped Mercury. Mercury thermoporometry has been used to validate the pore sizes, for a series of sol–gel silica materials, obtained from Mercury Porosimetry data using the independently-calibrated Kloubek correlations. The pore sizes obtained for sol–gel silicas from Porosimetry and thermoporometry have been shown to differ substantially from those obtained via gas sorption and NLDFT analysis. DRIFTS data for the samples studied has suggested that the cause of this discrepancy may arise from significant differences in the surface chemistries between the samples studied here and that used to calibrate the NLDFT potentials.

  • Improving the interpretation of Mercury Porosimetry data using computerised X-ray tomography and mean-field DFT
    Chemical Engineering Science, 2011
    Co-Authors: Sean P. Rigby, Peter I. Chigada, Jiawei Wang, Sam K. Wilkinson, Henry Bateman, Bushra Al-duri, Joseph Wood, Serafim Bakalis, Taghi Miri
    Abstract:

    Despite widespread use of the technique for a long time, the proper interpretation of Mercury Porosimetry data, particularly retraction curves, remains uncertain. In this work, the usefulness of two complementary techniques, mean-field density functional theory (MF-DFT) and micro-computerized X-ray tomography (micro-CXT), for aiding interpretation of ambiguous Mercury Porosimetry data has been explored. MF-DFT has been used to show that a specific, idiosyncratic form for the top of the Mercury intrusion and extrusion curves is probably associated with a particular network structure where the smallest pores only form through connections between larger pores. CXT has been used to study the pore potential theory of hysteresis and entrapment directly using a model porous material with spatially varying pore wetting properties. CXT has also been used to directly study the percolation properties, and entrapment of Mercury, within a macroporous pellet. Particular percolation pathways across the heart of the pellet have been directly mapped. The forms of entrapped Mercury ganglia have been directly observed and related to retraction mechanisms. A combination of CXT and Mercury Porosimetry can be used to map spatial variation in pore neck sizes below the spatial resolution of imaging.

  • MF-DFT and experimental investigations of the origins of hysteresis in Mercury Porosimetry of silica materials.
    Langmuir : the ACS journal of surfaces and colloids, 2010
    Co-Authors: Sean P. Rigby, Peter I. Chigada
    Abstract:

    In order to be able to make a proper interpretation of Mercury Porosimetry data, to obtain a structural characterization of a porous solid, a full understanding of the causes of hysteresis in Mercury Porosimetry is required. Several different theories have previously been proposed, but it is still difficult to make a priori predictions of the level of hysteresis anticipated. In this work, the effect of the degree of smaller scale surface roughness on the hysteresis width has been studied using mean-field density functional simulations and the results obtained confirmed by experiments on silica materials. It has been found that the hysteresis width decreases with increased degree of surface roughness, as characterized experimentally by the surface fractal dimension.

  • Simulation of Mercury Porosimetry using MRI images of porous media
    Studies in Surface Science and Catalysis, 2007
    Co-Authors: Matthew J. Watt-smith, Sean P. Rigby, John A. Chudek, Robin S. Fletcher
    Abstract:

    Abstract Models of the pore structure of pellets taken from a batch of sol-gel silica spheres have been constructed from magnetic resonance images of the macroscopic (∼0.04-1 mm), spatial distribution of spin density and spin-spin relaxation time within the material. Simulations of Mercury Porosimetry on these models gave rise to good predictions for the point of deviation of the intrusion and retraction curves, and the level of Mercury entrapment, in agreement with those found by experiment. This finding suggested that Mercury intrusion and retraction within the pellets are determined by the macroscopic structure of the material, as detected using MRI.

  • Integrating Gas Sorption with Mercury Porosimetry
    Adsorption-journal of The International Adsorption Society, 2005
    Co-Authors: Sean P. Rigby, Matthew J. Watt-smith, Robin S. Fletcher
    Abstract:

    Previous work has shown that it is possible to use intergrated nitrogen sorption and Mercury Porosimetry experiments to determine the distribution of average pore length with pore diameter for mesoporous solids. In this work, the previous data analysis method has been generalised such that it is also suitable for application to samples with higher levels of Mercury entrapment than before. This generalisation of the theory has facilitated the ability to use a series of progressively larger Mercury scanning loops, in integrated gas sorption and Porosimetry experiments, to potentially determine the full pore length distribution for pores of a given diameter, and the distribution of pore co-ordination number. The new analysis has been applied to a silica catalyst support.

René Pirard - One of the best experts on this subject based on the ideXlab platform.

  • Non Intrusive Mercury Porosimetry: Pyrolysis of Resorcinol‐Formaldehyde Xerogels
    Particle & Particle Systems Characterization, 2006
    Co-Authors: Nathalie Job, René Pirard, Jean-paul Pirard, Christelle Alié
    Abstract:

    When submitted to Mercury Porosimetry, some materials are penetrated by Mercury whereas others, among the most porous, are densified by the isostatic pressure. Notably, this is the case for materials whose structure is made of particles aggregated into filament-like clusters that are interconnected in a 3-D array. Indeed, that kind of material undergoes a volume variation due to hierarchical pore collapse. In the case of intrusion, the Mercury Porosimetry data are classically analyzed by the Washburn equation. In the case of hierarchical pore collapse, data can be correctly analyzed by the collapse model equation. Using an equation that does not correspond to the mechanism leads to large errors in the pore size distribution. Thus, an accurate data analysis requires prior determination of the mechanism leading to the volume variation recorded as a function of the pressure. The present work particularly examines the complex and unusual behavior of partially pyrolyzed resorcinol-formaldehyde gels when submitted to Mercury Porosimetry. The unusual behavior encountered complicates the mechanism identification and, therefore, the equation selection. However, the major part of the volume distribution as a function of the pore size can be determined with a good accuracy.

  • non intrusive Mercury Porosimetry pyrolysis of resorcinol formaldehyde xerogels
    Particle & Particle Systems Characterization, 2006
    Co-Authors: Nathalie Job, René Pirard, Jean-paul Pirard, Christelle Alié
    Abstract:

    When submitted to Mercury Porosimetry, some materials are penetrated by Mercury whereas others, among the most porous, are densified by the isostatic pressure. Notably, this is the case for materials whose structure is made of particles aggregated into filament-like clusters that are interconnected in a 3-D array. Indeed, that kind of material undergoes a volume variation due to hierarchical pore collapse. In the case of intrusion, the Mercury Porosimetry data are classically analyzed by the Washburn equation. In the case of hierarchical pore collapse, data can be correctly analyzed by the collapse model equation. Using an equation that does not correspond to the mechanism leads to large errors in the pore size distribution. Thus, an accurate data analysis requires prior determination of the mechanism leading to the volume variation recorded as a function of the pressure. The present work particularly examines the complex and unusual behavior of partially pyrolyzed resorcinol-formaldehyde gels when submitted to Mercury Porosimetry. The unusual behavior encountered complicates the mechanism identification and, therefore, the equation selection. However, the major part of the volume distribution as a function of the pore size can be determined with a good accuracy.

  • Characterization of hyperporous polyurethane-based gels by non intrusive Mercury Porosimetry
    Polymer, 2003
    Co-Authors: René Pirard, Arnaud Rigacci, J.c. Maréchal, D. Quenard, B. Chevalier, Patrick Achard, J.p. Pirard
    Abstract:

    Evaporative drying of polyurethane-based gels produces xerogels. Supercritical drying after replacement of interstitial liquid by supercritical CO2 produces aerogels. SEM micrographs show that both materials are made up of small size particles gathered up in filament-shaped, strongly cross-linked aggregates. Density measurements show that they both have a large pore volume. When submitted to Mercury Porosimetry, the behavior of these materials is similar to that of inorganic aerogels, as previously observed. Mercury does not penetrate the pore network, but the whole material is densified. The usual Washburn equation cannot be used to analyze the Mercury Porosimetry. A well-suited equation based on a buckling model of filament-shaped aggregates has been developed in order to determine the pore volume distribution of mineral dried gels. This equation is also valid for analyzing the texture of organic hyperporous materials like polyurethane dried nanoporous gel. © 2003 Elsevier Science Ltd. All rights reserved.

  • Characterization of porous texture of hyperporous materials by Mercury Porosimetry using densification equation
    Powder Technology, 2002
    Co-Authors: René Pirard, Christelle Alié, Jean-paul Pirard
    Abstract:

    Abstract The purpose of this paper is to propose a method of analyzing the Mercury Porosimetry data in the case of materials called hyperporous. This class of material does not undergo intrusion by Mercury; instead, it shrinks under the Mercury isostatic pressure and its density increases. The phenomenon is partially or completely irreversible. The proposed method enables computing the pore volume distribution as a function of the pore size in the same way as Washburn's method does in the case of Mercury intrusion.

  • Mercury Porosimetry applicability of the buckling intrusion mechanism to low density xerogels
    Journal of Non-crystalline Solids, 2001
    Co-Authors: Christelle Alié, René Pirard, Jean-paul Pirard
    Abstract:

    Mineral materials can be either crushed or invaded by Mercury during Mercury Porosimetry experiments. It has been shown here that many low-density xerogels exhibit the two volume variation mechanisms successively, compaction followed by intrusion, when submitted to Mercury Porosimetry and that a unimodal pore size distribution can be obtained by applying Pirard's collapse model below the pressure of transition Pt and Washburn's intrusion theory above Pt. To confirm the validity of the use of the buckling law, one low-density xerogel was wrapped in a tight membrane (intrusion is prevented and the sample is crushed during the whole Porosimetry experiment). The analysis of the Mercury Porosimetry data of the wrapped sample by the buckling law leads to a continuous unimodal distribution similar to the distribution of the unwrapped sample obtained by applying the buckling law below Pt and the intrusion law above Pt. The position of Pt is characteristic of the tested material: when submitted to Mercury pressure, aerogels and low-density xerogels only collapse in case of very small aggregates whereas they are crushed and then intruded in case of larger silica aggregates. The fact that compacted slabs of monodisperse non-aggregated silica spheres (of the same size range as the xerogels and aerogels) show only intrusion during Mercury Porosimetry experiments implies that the particles need to be aggregated so that the compaction mechanism takes place. The position of the change of mechanism from crushing to intrusion is not directly related to the size of the elementary particles but is linked to the size of the aggregates of silica particles.

Jean-paul Pirard - One of the best experts on this subject based on the ideXlab platform.

  • Non Intrusive Mercury Porosimetry: Pyrolysis of Resorcinol‐Formaldehyde Xerogels
    Particle & Particle Systems Characterization, 2006
    Co-Authors: Nathalie Job, René Pirard, Jean-paul Pirard, Christelle Alié
    Abstract:

    When submitted to Mercury Porosimetry, some materials are penetrated by Mercury whereas others, among the most porous, are densified by the isostatic pressure. Notably, this is the case for materials whose structure is made of particles aggregated into filament-like clusters that are interconnected in a 3-D array. Indeed, that kind of material undergoes a volume variation due to hierarchical pore collapse. In the case of intrusion, the Mercury Porosimetry data are classically analyzed by the Washburn equation. In the case of hierarchical pore collapse, data can be correctly analyzed by the collapse model equation. Using an equation that does not correspond to the mechanism leads to large errors in the pore size distribution. Thus, an accurate data analysis requires prior determination of the mechanism leading to the volume variation recorded as a function of the pressure. The present work particularly examines the complex and unusual behavior of partially pyrolyzed resorcinol-formaldehyde gels when submitted to Mercury Porosimetry. The unusual behavior encountered complicates the mechanism identification and, therefore, the equation selection. However, the major part of the volume distribution as a function of the pore size can be determined with a good accuracy.

  • non intrusive Mercury Porosimetry pyrolysis of resorcinol formaldehyde xerogels
    Particle & Particle Systems Characterization, 2006
    Co-Authors: Nathalie Job, René Pirard, Jean-paul Pirard, Christelle Alié
    Abstract:

    When submitted to Mercury Porosimetry, some materials are penetrated by Mercury whereas others, among the most porous, are densified by the isostatic pressure. Notably, this is the case for materials whose structure is made of particles aggregated into filament-like clusters that are interconnected in a 3-D array. Indeed, that kind of material undergoes a volume variation due to hierarchical pore collapse. In the case of intrusion, the Mercury Porosimetry data are classically analyzed by the Washburn equation. In the case of hierarchical pore collapse, data can be correctly analyzed by the collapse model equation. Using an equation that does not correspond to the mechanism leads to large errors in the pore size distribution. Thus, an accurate data analysis requires prior determination of the mechanism leading to the volume variation recorded as a function of the pressure. The present work particularly examines the complex and unusual behavior of partially pyrolyzed resorcinol-formaldehyde gels when submitted to Mercury Porosimetry. The unusual behavior encountered complicates the mechanism identification and, therefore, the equation selection. However, the major part of the volume distribution as a function of the pore size can be determined with a good accuracy.

  • Characterization of porous texture of hyperporous materials by Mercury Porosimetry using densification equation
    Powder Technology, 2002
    Co-Authors: René Pirard, Christelle Alié, Jean-paul Pirard
    Abstract:

    Abstract The purpose of this paper is to propose a method of analyzing the Mercury Porosimetry data in the case of materials called hyperporous. This class of material does not undergo intrusion by Mercury; instead, it shrinks under the Mercury isostatic pressure and its density increases. The phenomenon is partially or completely irreversible. The proposed method enables computing the pore volume distribution as a function of the pore size in the same way as Washburn's method does in the case of Mercury intrusion.

  • Mercury Porosimetry applicability of the buckling intrusion mechanism to low density xerogels
    Journal of Non-crystalline Solids, 2001
    Co-Authors: Christelle Alié, René Pirard, Jean-paul Pirard
    Abstract:

    Mineral materials can be either crushed or invaded by Mercury during Mercury Porosimetry experiments. It has been shown here that many low-density xerogels exhibit the two volume variation mechanisms successively, compaction followed by intrusion, when submitted to Mercury Porosimetry and that a unimodal pore size distribution can be obtained by applying Pirard's collapse model below the pressure of transition Pt and Washburn's intrusion theory above Pt. To confirm the validity of the use of the buckling law, one low-density xerogel was wrapped in a tight membrane (intrusion is prevented and the sample is crushed during the whole Porosimetry experiment). The analysis of the Mercury Porosimetry data of the wrapped sample by the buckling law leads to a continuous unimodal distribution similar to the distribution of the unwrapped sample obtained by applying the buckling law below Pt and the intrusion law above Pt. The position of Pt is characteristic of the tested material: when submitted to Mercury pressure, aerogels and low-density xerogels only collapse in case of very small aggregates whereas they are crushed and then intruded in case of larger silica aggregates. The fact that compacted slabs of monodisperse non-aggregated silica spheres (of the same size range as the xerogels and aerogels) show only intrusion during Mercury Porosimetry experiments implies that the particles need to be aggregated so that the compaction mechanism takes place. The position of the change of mechanism from crushing to intrusion is not directly related to the size of the elementary particles but is linked to the size of the aggregates of silica particles.

  • Mercury Porosimetry: applicability of the buckling–intrusion mechanism to low-density xerogels
    Journal of Non-crystalline Solids, 2001
    Co-Authors: Christelle Alié, René Pirard, Jean-paul Pirard
    Abstract:

    Mineral materials can be either crushed or invaded by Mercury during Mercury Porosimetry experiments. It has been shown here that many low-density xerogels exhibit the two volume variation mechanisms successively, compaction followed by intrusion, when submitted to Mercury Porosimetry and that a unimodal pore size distribution can be obtained by applying Pirard's collapse model below the pressure of transition Pt and Washburn's intrusion theory above Pt. To confirm the validity of the use of the buckling law, one low-density xerogel was wrapped in a tight membrane (intrusion is prevented and the sample is crushed during the whole Porosimetry experiment). The analysis of the Mercury Porosimetry data of the wrapped sample by the buckling law leads to a continuous unimodal distribution similar to the distribution of the unwrapped sample obtained by applying the buckling law below Pt and the intrusion law above Pt. The position of Pt is characteristic of the tested material: when submitted to Mercury pressure, aerogels and low-density xerogels only collapse in case of very small aggregates whereas they are crushed and then intruded in case of larger silica aggregates. The fact that compacted slabs of monodisperse non-aggregated silica spheres (of the same size range as the xerogels and aerogels) show only intrusion during Mercury Porosimetry experiments implies that the particles need to be aggregated so that the compaction mechanism takes place. The position of the change of mechanism from crushing to intrusion is not directly related to the size of the elementary particles but is linked to the size of the aggregates of silica particles.

Christelle Alié - One of the best experts on this subject based on the ideXlab platform.

  • Non Intrusive Mercury Porosimetry: Pyrolysis of Resorcinol‐Formaldehyde Xerogels
    Particle & Particle Systems Characterization, 2006
    Co-Authors: Nathalie Job, René Pirard, Jean-paul Pirard, Christelle Alié
    Abstract:

    When submitted to Mercury Porosimetry, some materials are penetrated by Mercury whereas others, among the most porous, are densified by the isostatic pressure. Notably, this is the case for materials whose structure is made of particles aggregated into filament-like clusters that are interconnected in a 3-D array. Indeed, that kind of material undergoes a volume variation due to hierarchical pore collapse. In the case of intrusion, the Mercury Porosimetry data are classically analyzed by the Washburn equation. In the case of hierarchical pore collapse, data can be correctly analyzed by the collapse model equation. Using an equation that does not correspond to the mechanism leads to large errors in the pore size distribution. Thus, an accurate data analysis requires prior determination of the mechanism leading to the volume variation recorded as a function of the pressure. The present work particularly examines the complex and unusual behavior of partially pyrolyzed resorcinol-formaldehyde gels when submitted to Mercury Porosimetry. The unusual behavior encountered complicates the mechanism identification and, therefore, the equation selection. However, the major part of the volume distribution as a function of the pore size can be determined with a good accuracy.

  • non intrusive Mercury Porosimetry pyrolysis of resorcinol formaldehyde xerogels
    Particle & Particle Systems Characterization, 2006
    Co-Authors: Nathalie Job, René Pirard, Jean-paul Pirard, Christelle Alié
    Abstract:

    When submitted to Mercury Porosimetry, some materials are penetrated by Mercury whereas others, among the most porous, are densified by the isostatic pressure. Notably, this is the case for materials whose structure is made of particles aggregated into filament-like clusters that are interconnected in a 3-D array. Indeed, that kind of material undergoes a volume variation due to hierarchical pore collapse. In the case of intrusion, the Mercury Porosimetry data are classically analyzed by the Washburn equation. In the case of hierarchical pore collapse, data can be correctly analyzed by the collapse model equation. Using an equation that does not correspond to the mechanism leads to large errors in the pore size distribution. Thus, an accurate data analysis requires prior determination of the mechanism leading to the volume variation recorded as a function of the pressure. The present work particularly examines the complex and unusual behavior of partially pyrolyzed resorcinol-formaldehyde gels when submitted to Mercury Porosimetry. The unusual behavior encountered complicates the mechanism identification and, therefore, the equation selection. However, the major part of the volume distribution as a function of the pore size can be determined with a good accuracy.

  • Characterization of porous texture of hyperporous materials by Mercury Porosimetry using densification equation
    Powder Technology, 2002
    Co-Authors: René Pirard, Christelle Alié, Jean-paul Pirard
    Abstract:

    Abstract The purpose of this paper is to propose a method of analyzing the Mercury Porosimetry data in the case of materials called hyperporous. This class of material does not undergo intrusion by Mercury; instead, it shrinks under the Mercury isostatic pressure and its density increases. The phenomenon is partially or completely irreversible. The proposed method enables computing the pore volume distribution as a function of the pore size in the same way as Washburn's method does in the case of Mercury intrusion.

  • Mercury Porosimetry applicability of the buckling intrusion mechanism to low density xerogels
    Journal of Non-crystalline Solids, 2001
    Co-Authors: Christelle Alié, René Pirard, Jean-paul Pirard
    Abstract:

    Mineral materials can be either crushed or invaded by Mercury during Mercury Porosimetry experiments. It has been shown here that many low-density xerogels exhibit the two volume variation mechanisms successively, compaction followed by intrusion, when submitted to Mercury Porosimetry and that a unimodal pore size distribution can be obtained by applying Pirard's collapse model below the pressure of transition Pt and Washburn's intrusion theory above Pt. To confirm the validity of the use of the buckling law, one low-density xerogel was wrapped in a tight membrane (intrusion is prevented and the sample is crushed during the whole Porosimetry experiment). The analysis of the Mercury Porosimetry data of the wrapped sample by the buckling law leads to a continuous unimodal distribution similar to the distribution of the unwrapped sample obtained by applying the buckling law below Pt and the intrusion law above Pt. The position of Pt is characteristic of the tested material: when submitted to Mercury pressure, aerogels and low-density xerogels only collapse in case of very small aggregates whereas they are crushed and then intruded in case of larger silica aggregates. The fact that compacted slabs of monodisperse non-aggregated silica spheres (of the same size range as the xerogels and aerogels) show only intrusion during Mercury Porosimetry experiments implies that the particles need to be aggregated so that the compaction mechanism takes place. The position of the change of mechanism from crushing to intrusion is not directly related to the size of the elementary particles but is linked to the size of the aggregates of silica particles.

  • Mercury Porosimetry: applicability of the buckling–intrusion mechanism to low-density xerogels
    Journal of Non-crystalline Solids, 2001
    Co-Authors: Christelle Alié, René Pirard, Jean-paul Pirard
    Abstract:

    Mineral materials can be either crushed or invaded by Mercury during Mercury Porosimetry experiments. It has been shown here that many low-density xerogels exhibit the two volume variation mechanisms successively, compaction followed by intrusion, when submitted to Mercury Porosimetry and that a unimodal pore size distribution can be obtained by applying Pirard's collapse model below the pressure of transition Pt and Washburn's intrusion theory above Pt. To confirm the validity of the use of the buckling law, one low-density xerogel was wrapped in a tight membrane (intrusion is prevented and the sample is crushed during the whole Porosimetry experiment). The analysis of the Mercury Porosimetry data of the wrapped sample by the buckling law leads to a continuous unimodal distribution similar to the distribution of the unwrapped sample obtained by applying the buckling law below Pt and the intrusion law above Pt. The position of Pt is characteristic of the tested material: when submitted to Mercury pressure, aerogels and low-density xerogels only collapse in case of very small aggregates whereas they are crushed and then intruded in case of larger silica aggregates. The fact that compacted slabs of monodisperse non-aggregated silica spheres (of the same size range as the xerogels and aerogels) show only intrusion during Mercury Porosimetry experiments implies that the particles need to be aggregated so that the compaction mechanism takes place. The position of the change of mechanism from crushing to intrusion is not directly related to the size of the elementary particles but is linked to the size of the aggregates of silica particles.

Robin S. Fletcher - One of the best experts on this subject based on the ideXlab platform.

  • Simulation of Mercury Porosimetry using MRI images of porous media
    Studies in Surface Science and Catalysis, 2007
    Co-Authors: Matthew J. Watt-smith, Sean P. Rigby, John A. Chudek, Robin S. Fletcher
    Abstract:

    Abstract Models of the pore structure of pellets taken from a batch of sol-gel silica spheres have been constructed from magnetic resonance images of the macroscopic (∼0.04-1 mm), spatial distribution of spin density and spin-spin relaxation time within the material. Simulations of Mercury Porosimetry on these models gave rise to good predictions for the point of deviation of the intrusion and retraction curves, and the level of Mercury entrapment, in agreement with those found by experiment. This finding suggested that Mercury intrusion and retraction within the pellets are determined by the macroscopic structure of the material, as detected using MRI.

  • Integrating Gas Sorption with Mercury Porosimetry
    Adsorption-journal of The International Adsorption Society, 2005
    Co-Authors: Sean P. Rigby, Matthew J. Watt-smith, Robin S. Fletcher
    Abstract:

    Previous work has shown that it is possible to use intergrated nitrogen sorption and Mercury Porosimetry experiments to determine the distribution of average pore length with pore diameter for mesoporous solids. In this work, the previous data analysis method has been generalised such that it is also suitable for application to samples with higher levels of Mercury entrapment than before. This generalisation of the theory has facilitated the ability to use a series of progressively larger Mercury scanning loops, in integrated gas sorption and Porosimetry experiments, to potentially determine the full pore length distribution for pores of a given diameter, and the distribution of pore co-ordination number. The new analysis has been applied to a silica catalyst support.

  • Interfacing Mercury Porosimetry with Nitrogen Sorption
    Particle & Particle Systems Characterization, 2004
    Co-Authors: Sean P. Rigby, Robin S. Fletcher
    Abstract:

    Combinations of gas sorption and Mercury Porosimetry experiments have been run in series on the same sample. This has been achieved by freezing entrapped Mercury in place before a subsequent gas sorption experiment was carried out. Several different bidisperse materials with similarly shaped Mercury intrusion curves and similar levels of Mercury entrapment have been studied. The entrapment of Mercury within certain pores in the porous medium can often lead to marked changes in the shape of the gas sorption hysteresis loop between the data obtained prior and subsequent to Porosimetry. It was found that the degree of the change of shape of the sorption hysteresis loops differed markedly between different materials. The analysis of the gas sorption hysteresis loops using percolation theory has allowed information to be obtained on the pore length distribution, and/or the distribution of pore co-ordination number and the spatial arrangement of pores within the sample, in addition to the pore connectivity and lattice size usually obtained. The interfaced experiments have also allowed the internal consistency of analysis methods based on percolation theory to be tested, semi-empirical alternatives to the Washburn Equation for the analysis of raw Mercury Porosimetry data to be independently validated, and the mechanisms of Mercury entrapment in various samples to be determined.

  • Characterisation of porous solids using integrated nitrogen sorption and Mercury Porosimetry
    Chemical Engineering Science, 2003
    Co-Authors: Sean P. Rigby, Robin S. Fletcher, Sandra N. Riley
    Abstract:

    Abstract The two different techniques of nitrogen sorption and Mercury Porosimetry, which are generally utilised completely separately, have been integrated into the same experiment to improve upon the information obtained from both methods. Nitrogen sorption isotherms have been run both before and after a Mercury Porosimetry experiment on the same sample. This experiment has revealed that for a particular type of sol–gel silica catalyst support the entrapped Mercury is confined to only the very largest pores in the material. Light micrograph studies have shown that the spatial distribution of entrapped Mercury is highly heterogeneous. These results suggest that Mercury entrapment within the material is caused by a mechanism involving macroscopic ( >0.1 mm ) heterogeneities in the pore structure. These findings conflict with the usual assumptions generally made in simulations of Porosimetry based on random pore bond network models. The new work has shown that, in conjunction with computer simulations involving the correct Mercury retraction mechanism, Mercury Porosimetry and nitrogen sorption can be used to study the spatial distribution of all pore sizes within a mesoporous material. A percolation analysis of the nitrogen sorption data, obtained both before and after Mercury entrapment, allowed broad features of the spatial disposition of variously sized pores to be determined. The results reported here also support the use of new, semi-empirical alternatives to the Washburn Equation to analyse raw Mercury Porosimetry data, rather than the traditional approach.

  • Determination of the multiscale percolation properties of porous media using Mercury Porosimetry
    Industrial & Engineering Chemistry Research, 2002
    Co-Authors: Sean P. Rigby, Robin S. Fletcher, Sandra N. Riley
    Abstract:

    A new technique using Mercury Porosimetry to characterize the percolation properties of porous media over several different length scales has been presented. The methodology employed a new theoretical model of a porous medium. The model may be used to represent a highly heterogeneous, porous material, with a wide pore-size distribution, over a broad range of length scales from ∼4 nm to 0.01 m. The characteristic statistical parameters which defined the model were obtained from Mercury Porosimetry scanning loop and miniloop experiments. Mercury Porosimetry miniloops have been shown to give rise to so-called “miniloop spectra”. These spectra describe the variation of the value of a characteristic Mercury entrapment function with pore size. The shapes of these spectra have been found to be sensitive to both the form of the pore-size probability density function and the pattern of the spatial geometric arrangement of pore sizes in the void space. Additional, complementary information on the pore structure was...