The Lifshitz-Van der Waals constant

Krupp, H.; Schnabel, W.; Walter, G.

doi:10.1016/0021-9797(72)90039-2

Cited by 99 publications

(37 citation statements)

References 13 publications

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“…2 Calculated from At2t and A2: (water-water) = 4.4 • 10 20 J (Krupp et al, 1972), using geometric mixing rule. tained in this study is equal to AI21 calculated using the geometric mixing rule, and Al, = 1.3 x 10 -19 J determined by Tabor and Winterton (1969) for mica plates in a vacuum and A22--4.38 x 10 -20 J determined by Krupp et al (1972) for water. No data relative to the Hamaker constants for kaolinite, montmorillonite, or palygorskite have been reported in the literature.…”

Section: Effective Hamaker Constantmentioning

confidence: 99%

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Colloid Stability of Clays Using Photon Correlation Spectroscopy

Novich

Ring

1984

Clays and clay miner.

101

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Abstract--Photon correlation spectroscopy (PCS), a dynamic light-scattering technique for particle size measurement, was used to determine the coagulation rates of aqueous dispersions of relatively monodisperse South Carolina Peerless kaolinite, Silver Hill, Montana, illite, Wyoming montmorillonite, and Florida palygorskite. This technique allows quantitative measurement of the rate of coagulation for clay particles where the traditional turbidity method gives only a qualitative measure. The critical coagulation concentrations for KC1 at pH = 10.0 were: 0.199 M for kaolinite, 0.202 M for illite, 0.290 M for montmorillonite, and 0.034 M for palygorskite. The effective Hamaker constants, calculated using DerjaguinLandau-Verwey-Overbeek theory, were: 3.1 • 10 -20 J for kaolinite, 2.5 x 10 -2o J for illite, 2.2 x 10 -20 J for montmorillonite, and i.63 x 10 -19 J for palygorskite. Stern potentials at the critical coagulation concentration at pH 10.0 were: -42.7 mV for kaolinite, -40.7 mV for illite, -21.2 mV for montmorillonite, and -66.9 mV for palygorskite.

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Section: Effective Hamaker Constantmentioning

confidence: 99%

“…This parallel plate analysis for palygorskite may be slightly inaccurate, inasmuch as palygorskite is a fiber and not a flat plate. Values of All (clay-clay)given in Table 3 were calculated using the geometric mixing rule and a value of A22 for water of 4.38 x 10 -20 J (Krupp et aL, 1972).…”

Section: Effective Hamaker Constantmentioning

confidence: 99%

Colloid Stability of Clays Using Photon Correlation Spectroscopy

Novich

Ring

1984

Clays and clay miner.

101

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“…This is, however, not the case. Wide distributions of adhesion forces are typically observed and adhesion forces vary by typically a factor of two to ten even within relatively monodisperse powders [17,19,22,[27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

On the Adhesion between Fine Particles and Nanocontacts: An Atomic Force Microscope Study

et al. 2006

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To optimize the handling of fine powders in industrial applications, understanding the interaction forces between single powder particles is fundamental. The forces between colloidal particles dominate the behavior of a great variety of materials, including paints, paper, soil, and many industrial processes. With the invention of the atomic force microscope (AFM), the direct measurement of the interaction between single micron-sized particles became possible. The adhesional contact between a particle and a substrate is a parameter for analyzing pull-off force data generated by AFM. The aim of this study was to understand surface interactions between fine particles. I measured the adhesion forces between AFM tips or particles attached to AFM cantilevers and different solid samples. Smooth and homogeneous surfaces such as silicon wafer, mica, or highly oriented pyrolytic graphite (HOPG), and more rough and heterogeneous surfaces such as iron particles or patterns of TiO 2 nanoparticles on silicon wafer were used. First, I addressed to the wellknown issue that AFM adhesion experiment results show wide distributions of adhesion forces rather than a single value. My experimental results show that variations in adhesion forces comprise fast (i.e., from one force curves to the next) random fluctuations and slower fluctuations, which occur over tens or hundreds of consecutive measurements. Slow fluctuations are not likely to be the result of variations in external factors such as lateral position, temperature, humidity, and so forth because those were kept constant. Even if two solid bodies are brought into contact under precisely the same conditions (same place, load, direction, etc.) the result of such a measurement will often not be the same as for the previous contact. The measurement itself will induce structural changes in the contact region which can change the value for the next adhesion force measurement.In the second part I studied the influence of humidity on the adhesion of nanocontacts. Humidity was adjusted relatively fast to minimize tip wear during one experiment. For hydrophobic surfaces, no signification change of adhesion force with humidity was observed. Adhesion force-versus-humidity curves recorded with hydrophilic surfaces either showed a maximum or continuously increased. I demonstrate that the results can be interpreted with simple continuum theory of the meniscus force. The meniscus force is calculated based on a model that includes surface roughness and takes into account different AFM tip (or particle) shapes by a two-sphere-model.Experimental and theoretical results show that the precise contact geometry has a critical influence on the humidity dependence of the adhesion force.Changes of tip geometry on the sub-10-nm length scale can completely change adhesion force-versus-humidity curves. Our model can also explain the differences between earlier AFM studies, where different dependencies of the adhesion force on humidity were observed.Keywords: Atomic force microscopy (AFM), cantile...

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“…The Hamaker constant for alumina surfaces interacting in water was taken as A awa = 4.8 × 10 −20 J, an average of several values reported in Refs. [35][36][37][38].…”

Section: Calculation Of the Theoretical Curvesmentioning

confidence: 99%