On Hamaker constants: A comparison between Hamaker constants and Lifshitz-van der Waals constants

Visser, Jan

doi:10.1016/0001-8686(72)85001-2

Cited by 842 publications

(317 citation statements)

References 99 publications

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“…The results obtained are presented in Fig. 9 34]. It is seen that the theoretical curve can approximate the experimental data reasonably in the region below and around the c.m.c.…”

Section: Theoretical Considerations and Discussionmentioning

confidence: 66%

Effect of the surfactant concentration on the kinetic stability of thin foam and emulsion films

Velikov¹,

Velev²,

Marinova³

et al. 1997

Faraday Trans.

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The thinning and the lifetime of foam and emulsion Ðlms formed in a model experimental cell have been investigated. The foam Ðlms were stabilised by either sodium dodecyl sulfate or sodium dodecyl polyoxyethylene-2 sulfate. The emulsion Ðlms contained either Tween 20 or Span 20. The time of hydrodynamic drainage of the Ðlms increased linearly as the logarithm of the surfactant concentration. This linear dependence was valid whatever the type of Ðlm or surfactant and not only below the critical micelle concentration (c.m.c.) but also much above this concentration threshold. The experimental results are relevant to the hydrodynamic basis of foam and emulsion stabilisation. They are compared with the earlier hydrodynamic theories of Ðlm drainage. A reasonable, but not excellent, agreement between the experimental data and the theory could be achieved in the region below the c.m.c. of the surfactant. The data about the complex system above the c.m.c. still remain unexplained by an adequate theory. The investigation provides some guidelines for choosing the optimal type and concentration of surfactant in colloid systems of practical importance.The stability of foams and emulsions is of high importance for many practical systems in the food, paint, oil, pharmaceutical and other industries. The breakdown of these colloid systems occurs mainly because of the rupture of the thin liquid Ðlms which form between the bubbles or droplets when these are pressed against each other either in collisions or by buoyancy.1,2 Therefore, the behaviour and the stability of these thin liquid Ðlms is a problem of major experimental and theoretical importance.1,2 It has been established, in principle, that one can distinguish between two types of foam and emulsion Ðlm stability, thermodynamic and kinetic.1,3 The thermodynamic stability is associated with the repulsive intermolecular interactions that act between the Ðlm surfaces and oppose their approach.1 The kinetic stability arises from the hydrodynamic friction in the Ðlm, that delays its thinning. Although the kinetic stabilisation is transient, it has been recognised1 that, in many cases, the hydrodynamic forces alone, or through enhancing the thermodynamic factors are the key to the stability of the foam or emulsion systems.There are many theoretical and experimental investigations dedicated to the hydrodynamics of thinning of foam and emulsion Ðlms4h7 (for a detailed review of the recent advances in this Ðeld see also ref. 1). The majority of these studies, however, deal with the case of Ðxed surfactant concentration (and usually below the c.m.c.). Of major practical importance is investigation of the e †ect of the surfactant concentration on the stability of thin Ðlms, foams and emulsions. The quantity of surface-active agent, that is introduced in practical foams and emulsions, is usually quite large and orders of magnitude higher than the c.m.c. Finding ways of reducing this quantity could be advantageous from both Ðnancial and environmental view points.Our study is dedicated t...

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“…The results obtained are presented in Fig. 9 34]. It is seen that the theoretical curve can approximate the experimental data reasonably in the region below and around the c.m.c.…”

Section: Theoretical Considerations and Discussionmentioning

confidence: 66%

Effect of the surfactant concentration on the kinetic stability of thin foam and emulsion films

Velikov¹,

Velev²,

Marinova³

et al. 1997

Faraday Trans.

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“…A SF-H2O-UFP and A UFP-H2O-UFP were computed by equations (5) and (6), respectively, which were taken from Visser's work (22). When the energy barrier, VTmax, is larger than 25 kT it is widely accepted that coagulation or attraction is prevented (17).…”

Section: Discussionmentioning

confidence: 99%

Utilization of slag fibers as ecomaterial. II. Collection of Ultrafine Silica and Oil-Water Emulsion.

Ibáñez

Murakami

Sasaki

1997

Int. J. Soc. Mater. Eng. Resour

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The collection of ultrafine silica particles (23 nm in diameter) and oilwater emulsion (500 nm in diameter) from low concentrated suspensions were studied by using an ecomaterial (slag fibers)-collector bed system.The collec tion efficiency was highly dependent on the sol's pH and less on the specific surface area ratio between collector and ultrafine particles.The highest collec tion efficiency was attained at pH 4 for silica and at pH 3 for oil-water emulsion. The experimental results were partially interpreted by the total interac tion potential theory.In the case of the collection of ultrafine silica a second. mechanism regarding flocculation by the dissolved fraction of the SF comple mented the DLVO theory.In the case of the collection of oil-water emulsion effects regarding the deformable character of the oil drops as well as the hydrodynamic effects derived from the high molecular weight of the oil comple mented the DLVO theory.

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“…These Hamaker constants in vacuum were obtained from the results of the microscopic approximation for theoretical calculation of the Hamaker constants. 13) The obtained Hamaker constant for glass-water-polystyrene system was 5.8×10…”

Section: (1) the Effect Of Ionic Strengthmentioning

confidence: 98%

Effect of Flow Field on Colloid Deposition in Filtration Process of Polystyrene Latex Particles through Columns Packed with Glass Beads

Chinju

Nagasaki

Tanaka

et al. 2001

Journal of Nuclear Science and Technology

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The effect of flow field on the deposition rate of colloidal particles onto solid surface in a column packed with spherical collectors was investigated theoretically and experimentally. A new analysis for calculating the colloid deposition efficiency was developed. The analysis includes the effect of the flow field on the deposition of a colloidal particle through the interactive potential barrier between the particle and the solid surface. The deposition behavior of polystyrene latex particles (diameter: 102 nm) in transport process through columns (length: 100 mm) packed with glass beads (diameter: 0.35-0.40 mm) was observed. The colloid deposition efficiencies calculated by the new analysis were comparable with those obtained by the experiments. The result indicates that the effect of the flow field would cause the difference between the flow velocity dependence of the efficiency obtained by a classical analysis and that by the experimental results. The colloid deposition efficiencies were also obtained by estimating the deposited particles onto the glass beads surface suspended in the colloidal suspension from the SEM observation of the glass beads surface. The effect of the heterogeneity of the collector surface was discussed by calculating the colloid deposition efficiency using the evaluated interaction potential between the particle and the heterogeneous collector surface.

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On Hamaker constants: A comparison between Hamaker constants and Lifshitz-van der Waals constants

Cited by 842 publications

References 99 publications

Effect of the surfactant concentration on the kinetic stability of thin foam and emulsion films

Effect of the surfactant concentration on the kinetic stability of thin foam and emulsion films

Utilization of slag fibers as ecomaterial. II. Collection of Ultrafine Silica and Oil-Water Emulsion.

Effect of Flow Field on Colloid Deposition in Filtration Process of Polystyrene Latex Particles through Columns Packed with Glass Beads

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