A Simple Experimental Way of Measuring the Hamaker Constant A11 of Divided Solids by Immersion Calorimetry in Apolar Liquids

Médout-Marère, V.

doi:10.1006/jcis.2000.6984

Cited by 56 publications

(18 citation statements)

References 31 publications

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“…The Hamaker constant represents the strength of the Van der Waals interactions between the macroscopic bodies; therefore, for a soil in water it changes mostly depending on the type of minerals in the soil's composition. Medout-Marere (2000) found the value of the Hamaker constant for montmorillonite A = -7.8 Á 10 -20 J, while Mitchell and Soga (2005) suggested the value A = -2.2 Á 10 -20 J. In calculating the w À w m relationship for the tested Ca-montmorillonite (sample 1) the best fitting values compared to the measured were achieved using A = -7.8 Á 10 -20 J.…”

Section: Resultsmentioning

confidence: 96%

“…Because of the presence of Ca-montmorillonite in the sample, the calculated water content was increased for an appropriate portion of the interlayer water w ai & 11.9 %. The Hamaker constant for kaolinite in water quoted by Medout-Marere (2000) and Mitchell and Soga (2005) is A = -6.8 Á 10 -20 J or A = -3.1 Á 10 -20 J. Sample 3 (grey clay) contains mostly illite and quartz.…”

Section: Resultsmentioning

confidence: 99%

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Prediction of the soil-water characteristic curve based on the specific surface area of fine-grained soils

Dolinar

2014

Bull Eng Geol Environ

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This paper presents a new, mathematical expression for describing the soil-water characteristic curve (SWCC) over a range of water contents where finegrained soils exhibit plastic properties. The finding that the relationship between the soil suction and the water content can be expressed in terms of the specific surface area of soils was based on experimentally determined relationships between the water content and the soil's specific surface area, as well as between the thickness of the adsorbed water layer on the external surfaces of clay minerals and the quantity of free-pore water for the water content between the liquid and plastic limits. The double-porosity model for the pore-space geometry was considered, as well as that all the water in the clay-aggregates is adsorbed, and that the adsorption mechanism is dominated by the van der Waals forces. The validity and applicability of the proposed equation for the SWCC estimation was verified on three samples in which the SWCC was measured, as well as the specific surface area, the mineralogical and chemical compositions, the grain size distribution, and the Atterberg limits. Despite the fact that good correlations were found between the calculated parts of the SWCC and the measured, the practical applicability of the proposed equation remains problematic due to the values of Hamaker constant, which are not yet well defined for different minerals.

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Prediction of the soil-water characteristic curve based on the specific surface area of fine-grained soils

Dolinar

2014

Bull Eng Geol Environ

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“…Moreover, literature data for A 11 for water (3.7-5.8 × 10 −21 J), acetonitrile (2.4-4.0 × 10 −21 J) silica (5.6-8.4 × 10 −21 J), and polymers of different nature (4.4-9.0 × 10 −21 J) allow to calculate the interaction constants A 123 for the triads of solute-solvent-solid here studied using Eq. (T2-4), and the ranges of values obtained for each triad contains the A 0 value calculated by fitting f vs. data in each case (Fernandez-Varea and Garcia-Molina, 2000;Medout-Marere, 2000;Blomberg et al, 1998;Bergström, 1997). It can be seen that there is a considerable divergence in the measured value of A 11 , being this divergence considerably greater when solvents such as water are used.…”

Section: Resultsmentioning

confidence: 97%

Hindered diffusion of proteins and polymethacrylates in controlled-pore glass: An experimental approach

Ladero

Santos

Garcı́a-Ochoa

2007

Chemical Engineering Science

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“…It can be defined as the force required to pull two particles apart. The intermolecular interaction energy is considered as the sum of two contributions [46]: one is due to the electromagnetic effects of electron clouds and leads to van der Waals interactions, the other is due to the surface charge effects and leads to electrostatic interactions. These two contributions are additive.…”

Section: Estimation Of Energy and Forces Between The Platelets In A Cmentioning

confidence: 99%

“…Medout-Marere [46] measured values of the Hamaker constant for different materials by immersion calorimetry in apolar liquids. The Hamaker constant for Montmorillonite is given as 7.8 3 10 220 J.…”

Section: Estimation Of Energy and Forces Between The Platelets In A Cmentioning

confidence: 99%

Estimation of stresses required for exfoliation of clay particles in polymer nanocomposites

Borse¹,

Kamal²

2008

Polymer Engineering & Sci

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The dispersion of clay in a polymer matrix is influenced by two factors: the choice of organic treatment for the clay and the processing or mixing method. Maximum benefits are achieved when the platelets are well dispersed or exfoliated. Exfoliated nanocomposites are formed when the individual clay layers break off the agglomerated particles or tactoids and are either randomly dispersed in the polymer (a disordered nanocomposite) or left in an ordered array. It is suggested that size reduction of clay particles and platelet delamination occur by erosion or surface peeling. A model based on the classical theories of interparticle interactions was formulated for the exfoliation of the clay platelets in a polymer matrix. The model involves the estimation of the binding energy and the adhesive force between the platelets in a clay particle, which indicate the forces required for breaking apart or delamination of clay particles. Then, the shear force required for breakup or delamination of the tactoids is estimated and compared to the hydrodynamic shear forces available during processing. POLYM INTRODUCTIONPolymer/clay nanocomposites are materials composed of a polymer matrix and nanometer size clay particles. They exhibit significant improvements in tensile modulus and strength and reduced permeability to gases and liquids, in comparison with the pure polymer. These property improvements can be realized, while retaining clarity of the material with a little increase in density, since the typical clay loading is 2-5 wt%. It is well known that some polymers interact with montmorillonite and that the clay surface can act as an initiator for polymerization [1,2]. However, clay/polyamide-6 (PA-6) nanocomposites were commercialized mainly after practical methods were developed for appropriate dispersion of the clays at the nanometer scale [3].The first step in achieving nanoscale dispersion of clays in polymers is to expand the galleries and to match the polarity of the polymer or monomer, so that it will intercalate between the layers [4]. This is done by exchanging an inorganic cation, generally sodium cation present in the clay, with an organic cation of a quaternary ammonium compound. The larger organic cations swell the layers and increase the hydrophobic (or organophilic) properties of the clay [5], resulting in an organically modified clay. The organically modified clay can then be intercalated with polymer by several routes. Highly polar polymers, such as polyamides and polyimides, are more easily intercalated than nonpolar polymers, such as polypropylene and polyethylene [6,7]. Melt intercalation involves mixing the clay and polymer melt, with or without shear. Nanocomposites can have several structures. Intercalated nanocomposites usually appear as tactoids with expanded interlayer spacing, but the clay basal spacing remains in the few nanometer range. Exfoliated nanocomposites are formed when the individual clay layers break off the tactoid and are either randomly dispersed in the polymer (a disordered nanocom...

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A Simple Experimental Way of Measuring the Hamaker Constant A11 of Divided Solids by Immersion Calorimetry in Apolar Liquids

Cited by 56 publications

References 31 publications

Prediction of the soil-water characteristic curve based on the specific surface area of fine-grained soils

Prediction of the soil-water characteristic curve based on the specific surface area of fine-grained soils

Hindered diffusion of proteins and polymethacrylates in controlled-pore glass: An experimental approach

Estimation of stresses required for exfoliation of clay particles in polymer nanocomposites

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