The London—van der Waals attraction between spherical particles
TL;DR: In this article, the London-v.d. interaction between two spherical particles is computed as a function of the diameters and the distance separating them, and a table is calculated which enables numerical application of the formulae derived.
About: This article is published in Physica D: Nonlinear Phenomena.The article was published on 1937-10-01. It has received 3484 citations till now. The article focuses on the topics: Van der Waals surface & van der Waals force.
Citations
More filters
TL;DR: In this article, the authors describe a simple, nondestructive procedure for measuring the force constant, resonant frequency, and quality factor of an AFM cantilever spring and the effective radius of curvature of an AU tip.
Abstract: Images and force measurements taken by an atomic‐force microscope (AFM) depend greatly on the properties of the spring and tip used to probe the sample’s surface. In this article, we describe a simple, nondestructive procedure for measuring the force constant, resonant frequency, and quality factor of an AFM cantilever spring and the effective radius of curvature of an AFM tip. Our procedure uses the AFM itself and does not require additional equipment.
3,975 citations
TL;DR: In this article, it was shown that despite the van der Waals' forces being capable of increasing the elastic contact area between the ball and the plane, the force that is required to overcome the molecular forces arising when the contact is broken does not increase thereby.
3,951 citations
TL;DR: The atomic force microscope (AFM) is not only used to image the topography of solid surfaces at high resolution but also to measure force-versus-distance curves as discussed by the authors, which provide valuable information on local material properties such as elasticity, hardness, Hamaker constant, adhesion and surface charge densities.
3,281 citations
TL;DR: In this article, the surface forces that lead to wetting are considered, and the equilibrium surface coverage of a substrate in contact with a drop of liquid is examined, while the hydrodynamics of both wetting and dewetting is influenced by the presence of the three-phase contact line separating "wet" regions from those that are either dry or covered by a microscopic film.
Abstract: Wetting phenomena are ubiquitous in nature and technology. A solid substrate exposed to the environment is almost invariably covered by a layer of fluid material. In this review, the surface forces that lead to wetting are considered, and the equilibrium surface coverage of a substrate in contact with a drop of liquid. Depending on the nature of the surface forces involved, different scenarios for wetting phase transitions are possible; recent progress allows us to relate the critical exponents directly to the nature of the surface forces which lead to the different wetting scenarios. Thermal fluctuation effects, which can be greatly enhanced for wetting of geometrically or chemically structured substrates, and are much stronger in colloidal suspensions, modify the adsorption singularities. Macroscopic descriptions and microscopic theories have been developed to understand and predict wetting behavior relevant to microfluidics and nanofluidics applications. Then the dynamics of wetting is examined. A drop, placed on a substrate which it wets, spreads out to form a film. Conversely, a nonwetted substrate previously covered by a film dewets upon an appropriate change of system parameters. The hydrodynamics of both wetting and dewetting is influenced by the presence of the three-phase contact line separating "wet" regions from those that are either dry or covered by a microscopic film only. Recent theoretical, experimental, and numerical progress in the description of moving contact line dynamics are reviewed, and its relation to the thermodynamics of wetting is explored. In addition, recent progress on rough surfaces is surveyed. The anchoring of contact lines and contact angle hysteresis are explored resulting from surface inhomogeneities. Further, new ways to mold wetting characteristics according to technological constraints are discussed, for example, the use of patterned surfaces, surfactants, or complex fluids.
2,501 citations
TL;DR: A method to disperse and exfoliate graphite to give graphene suspended in water-surfactant solutions and suggests the flakes to be largely free of defects and oxides, although X-ray photoelectron spectroscopy shows evidence of a small oxide population.
Abstract: We have demonstrated a method to disperse and exfoliate graphite to give graphene suspended in water−surfactant solutions. Optical characterization of these suspensions allowed the partial optimization of the dispersion process. Transmission electron microscopy showed the dispersed phase to consist of small graphitic flakes. More than 40% of these flakes had <5 layers with ∼3% of flakes consisting of monolayers. Atomic resolution transmission electron microscopy shows the monolayers to be generally free of defects. The dispersed graphitic flakes are stabilized against reaggregation by Coulomb repulsion due to the adsorbed surfactant. We use DLVO and Hamaker theory to describe this stabilization. However, the larger flakes tend to sediment out over ∼6 weeks, leaving only small flakes dispersed. It is possible to form thin films by vacuum filtration of these dispersions. Raman and IR spectroscopic analysis of these films suggests the flakes to be largely free of defects and oxides, although X-ray photoelect...
2,086 citations
References
More filters
1,198 citations
TL;DR: In this paper, an expression for the cohesive force between two unequal spheres in geometrical contact is derived and the surface energy of the solid may be computed from the constant in this expression.
Abstract: Summary An expression is obtained for the cohesive force between two unequal spheres in geometrical contact From the constant in this expression the surface energy of the solid may be computed Results are obtained in agreement with the theory The surface energies of freshly fused surfaces of quartz and sodium pyroborate are 33·8 and 69 ergs per sq cm In the case of borate spheres, however, the cohesion is probably due to a surface film of water
446 citations
31 citations