Showing papers on "Wetting transition published in 1990"
TL;DR: In this article, the authors review some recent theoretical and computer simulation studies of simple atomic fluids adsorbed at structureless substrates and place emphasis on phase transitions, especially the various types of wetting transition, which is associated with capillary wave-like fluctuations in a continuously growing wetting film.
Abstract: Reviews some recent theoretical and computer simulation studies of simple atomic fluids adsorbed at structureless substrates. Emphasis is placed on phase transitions, especially the various types of wetting transition. Criticality is associated with capillary-wave-like fluctuations in a continuously growing wetting film. This is of a subtle nature, which is best understood in terms of the pairwise correlation function of the fluid. Other surface phase transitions, such as prewetting and layering, occur out of bulk coexistence. Theory suggests that for sufficiently attractive substrates a sequence of first-order transitions, corresponding to the growth of new adsorbed liquid layers, should occur as the pressure of the bulk gas increases towards saturation at temperatures not too far above the bulk triple point. The extent to which such behaviour is found in adsorption experiments is discussed. The authors also argue that a simple fluid confined between two parallel hard-walls can exhibit surprisingly rich equilibria.
285 citations
TL;DR: In this article, the apparent contact angles formed when a solid is immersed into a liquid were measured and the authors concluded that the values measured are unambiguously determined by the bulk viscosity and the difference between the cosine values of the static and dynamic apparent contact angle.
76 citations
TL;DR: In this article, the authors used total internal reflection fluorescence (TIRF) to study the adsorption of three fluorescein-labeled proteins: human serum albumin, IgG and fibrinogen.
66 citations
55 citations
43 citations
TL;DR: The Ising square lattice with nearest-neighbor exchangeJ>0 and a free surface at which a boundary magnetic fieldH1 acts has a second-order wetting transition.
Abstract: The Ising square lattice with nearest-neighbor exchangeJ>0 and a free surface at which a boundary magnetic fieldH1 acts has a second-order wetting transition. We study the surface excess magnetization and the susceptibility ofL×M lattices by Monte Carlo simulation and probe the critical behavior of this wetting transition, applying finite-size scaling methods. For the cases studied, the results are not consistent with the presumably exactly known values of the critical exponents, because the asymptotic critical region has not yet been reached. Implication of our results for critical wetting in three dimensions and for the application of the present model to adsorbed wetting layers at surface steps are briefly discussed.
42 citations
TL;DR: A hydrophobicity gradient was created by gradually exposing a polydimethylsiloxane film to a radio frequency glow discharge in an oxygen atmosphere and the adsorption decreased towards the hydrophilic end in correspondence with the change in contact angle.
39 citations
TL;DR: In this article, the dispersive and polar components of surface free energies of the fibers were determined from the advancing and receding contact angles, respectively, and the Hamaker constants were estimated from the dispersion components of their surface free energy.
Abstract: Wetting force at three-phase line was measured by the Wilhelmy technique using fibrous solids/liquid/liquid systems. Advancing and receding contact angles were calculated from the wetting forces during fiber immersion and emersion. The obtained results showed that contact angle hysteresis was due to the heterogeneity of the fiber surfaces. The dispersive and polar components of surface free energies of the fibers were determined from the advancing and receding contact angles, respectively. The Hamaker constants of the fibers were estimated from the dispersive components of their surface free energies.
37 citations
TL;DR: In this article, the authors studied continuous wetting on self-similar roughness (either fractal or self-affine) and showed that surface tension forces control the asymptotic divergence of film thickness for fractal substrates, and for sufficiently rough selfaffine substrates.
Abstract: Continuous wetting is studied on substrates with self-similar roughness (either fractal or self-affine). Surface tension forces control the asymptotic divergence of film thickness for fractal substrates, and for sufficiently rough self-affine substrates. Exponents are obtained by scaling arguments for complete wetting, and by replica methods for critical wetting. Recent experiments of nitrogen adsorbed on flash-deposited silver are reanalysed. They suggest that the substrate roughness is self-affine with a roughness exponent ζS 0.37.
35 citations
TL;DR: In this article, the growth of a nematic wetting layer at a surface in an isotropic fluid close to the nematic-isotropic transition is discussed, using general principles.
Abstract: We discuss, using general principles, the growth of a nematic wetting layer at a surface in an isotropic fluid close to the nematic-isotropic transition. The effect of competition between the nematic anchoring at a wall and at the incipient isotropic surface can lead to effects which are particular to systems with orientational order. Such effects also change the Kelvin equation which governs the shift in the nematic-isotropic phase transition in a finite geometry.
33 citations
TL;DR: In this article, the authors show that the tension of the line in which three phases meet vanishes at the wetting transition, and that the line tension vanishes proportionally to the contact angle that closes down to 0 at the transition.
Abstract: We ask whether the tension of the line in which three phases meet vanishes at the wetting transition. We answer affirmatively for a simple phenomenological model in which we find that the line tension vanishes proportionally to the contact angle that closes down to 0 at the transition. We show the connection between such line tension and two-dimensional boundary tension at a pre-wetting transition. It is plausible that if the former vanishes at wetting, then so does the latter in the limit where pre-wetting becomes bulk wetting.
TL;DR: Neutron-diffraction experiments are reported on thin films of methane adsorbed on magnesium oxide for temperatures ranging from below to above the melting point: 50{le}{ital T}{le}95 K.
Abstract: Neutron-diffraction experiments are reported on thin films of methane (10 layers) adsorbed on magnesium oxide (100) for temperatures ranging from below to above the melting point: 50{le}{ital T}{le}95 K. A continuous wetting transition is observed simultaneously with an increase of the thickness of the disordered layer when the melting point is approached from below. The adsorbed film is stratified (disordered layer on top of ordered layer), and the crystallinity profile is measured at the ordered-disordered phase interface. Above the triple point a few layers remain ordered. The results are discussed and compared with the previous works on surface melting performed by quasielastic neutron scattering.
TL;DR: In this paper, a review of recent experimental studies of alkali metal-alkali halide solutions is presented with emphasis on the following features: character of electron localization in salt-rich solutions, change of electronic structure approaching the metal-nonmetal transition, influence of the electronic transition on the thermodynamic equation of state, and wetting transition at the fluid-solid interface.
Abstract: Recent experimental studies of alkali metal-alkali halide solutions are reviewed with emphasis on the following features: character of electron localization in salt-rich solutions, change of electronic structure approaching the metal-nonmetal transition, influence of the electronic transition on the thermodynamic equation of state, and wetting transition at the fluid-solid interface.
TL;DR: In this article, a numerical study has been conducted to examine the influence of free surface curvature, due to the presence of various contact angles, on thermocapillary convection within a cavity.
Abstract: A numerical study has been conducted to examine the influence of free surface curvature, due to the presence of various contact angles, on thermocapillary convection within a cavity. The results indicate that the system hydrodynamics are changed by a combination of surface temperature gradient modification due to the presence of the adiabatic meniscus and variation in the length of the free surface, as well as viscous force dependence on the wetting angle. Local and overall heat transfer rates are, in turn, altered. Wetting liquids exhibit decreased surface fluid velocities and convective heat transfer rates, while non-wetting liquids are characterized by more complicated behavior with local increases and decreases in surface fluid velocities and an increase in local heat transfer near the free surface.
TL;DR: In this paper, a temperature-induced wetting transition involving a three-component C6H13(OC2H4)2OH/n•C16H34/H2O system was investigated.
Abstract: Experimental results have been found for a wetting transition involving a three‐component (amphiphile/oil/water) microemulsion system that forms top, middle, and bottom liquid phases. For all temperatures between the wetting transition temperature (Tw) and the upper critical endpoint temperature (Tuc) the middle phase microemulsion of the C6H13(OC2H4)2OH/n‐C16H34/H2O system appeared to wet the interface between the top and bottom phases, whereas below Tw it did not. Compositions of the phases below and above Tw are reported, also. Within the experimental uncertainties, Tw equaled the optimal temperature (at which the top–bottom tension passes through a minimum), as determined from the compositions of the middle phase. The wetting transition temperature, Tw=45.14±0.02 °C, was more than 15 °C below the upper critical endpoint temperature, Tuc=60.94±0.03 °C. This appears to be the first example of a temperature‐induced wetting transition that involves a middle‐phase microemulsion system.
TL;DR: In this article, the impact of interfacial reactions and the difference of surface state on wetting properties of three types of MgO, two sintered and one single crystal (100), were examined by means of the improved sessile drop method.
Abstract: The wetting characteristics, by molten aluminum, of three types of MgO, two sintered and one single crystal (100), were examined by means of the improved sessile drop method to make clear the effects of interfacial reactions and the difference of surface state on wetting.The reaction zone products vary with the initial characteristics of the ceramics such as impurity content and grain boundaries. The contact angle in each system progresses through three phases (I, II, III). Similar contact angles were produced in phase II, regardless of the type of MgO, although the single crystal showed a slightly higher angle than the polycrystalline types. In phase III, however, contact angles become significantly different.The phase III contact angle of the single crystal decreases more slowly than that of the sintered types since interfacial reactions progress relatively slowly. Different reaction products were formed at the interface depending on the type of MgO. These observations suggest that the chemical reactions at the interface must be clarified to understand the phase III behavior of wetting systems.
01 Jan 1990
TL;DR: In this article, Monte Carlo simulation of lattice gas models for the wetting transitions in systems with short range forces is described, using a simple cubic lattice with nonconserved Glauber dynamics.
Abstract: Monte Carlo simulation of lattice gas models for the wetting transitions in systems with short range forces are described. A nearest-neighbor simple cubic lattice with nonconserved “Glauber dynamics” is used, applying a slab geometry (LxL cross section). It is shown that the growth proceeds in two stages: for short times t, the thickness of the wetting layer at an initially nonwet wall increases proportional to the logarithm of the time; for t » L2(lnL)2 the thickness increases proportional to t1/2/L. Generalizations to other systems are briefly discussed. Also two-dimensional growth of a wetting film at surface steps is considered, considering “terraces” of an LxM geometry with M»L as substrate for adsorption. The steps may act like a “boundary field” at the adsorbed layer. If this field couples quadratically to the order parameter only, rather than wetting one observes the film to spontaneously break up in a one-dimensional sequence of ordered domains.
TL;DR: An analysis of the Ising lattice-gas model with nearest-neighbor interactions and mean-field theory for defect-plane wetting in the continuum limit that is valid at temperatures close to the bulk critical temperature.
Abstract: We present a study of defect-plane wetting using an Ising lattice-gas model with nearest-neighbor interactions and mean-field theory. In addition to solving the mean-field equations for the lattice model, we present an analysis of the model in the continuum limit that is valid at temperatures close to the bulk critical temperature. The continuum limit of the model is equivalent to the Landau theory for wetting of a defect plane studied by Sevrin and Indekeu, except that we include a ``surface field'' that acts only on the layers adjacent to the defect plane and that represents a potential produced by the defect. This field, which is likely to be present in a real system, significantly alters the wetting phenomena relative to the case of no surface field, giving rise to critical wetting transitions and multicritical points. The phase diagrams resemble in some respects those found in analyses of wetting on an inert substrate and also contain new phenomena as a consequence of the possibility of forming wetting phases on both sides of the defect plane.
TL;DR: In this article, the first systematic study of the wetting behavior in fluid alkali metal-alkali halide systems on the metal-rich side of the phase diagram is presented.
Abstract: The authors report the first systematic study of the wetting behaviour in fluid alkali metal-alkali halide systems on the metal-rich side of the phase diagram. To this end the interface of fluid sample-inert substrate (sapphire) has been probed by ellipsometry. Of particular interest is the influence of differences of the bulk phase diagram on the wetting characteristics. If the bulk fluid phase exhibits homogeneous miscibility like Cs-CsCl the optical reflectivity changes continuously with composition consistent with metallic Drude type behaviour. However, in systems with a critical and a triple point like K-KCl and Na-NaCl a wetting transition is observed. This occurs in metal-rich solutions approaching the triple point along the phase boundary. In K-KCl a salt-rich wetting film of approximately=100 nm thickness and composition corresponding to K0.1KCl0.9 has been determined. This is the film thickness in thermal equilibrium as has been found by vigorous ultrasonic stirring.
TL;DR: In this article, an interpretation of critical wetting and flocculation phenomena is given, referring mainly to silica dispersed in lutidine-water mixtures, and the implications for related phenomena, and for applications such as the partitioning of particles between two-phase liquids are discussed.
Abstract: An interpretation of critical wetting and flocculation phenomena is given, referring mainly to silica dispersed in lutidine–water mixtures. The critical wetting behaviour of other systems, e.g. perfluoromethylcylohexane on alcohols, and the wetting of immersed solids, is made easier to understand. The silica flocculation is preceded by the formation of a thick adsorption layer on the silica, which then coalesces to the floc state. The wetting behaviour probably depends on the solid, giving a family of curves. Flocculation at the critical point is delayed until the coexistence curve is reached, because at the critical point the contact angle made by the interface formed between the conjugate phases and the solid would be 90°. The implications for related phenomena, and for applications such as the partitioning of particles between two-phase liquids are discussed.
TL;DR: In this article, the authors calculate a Landau mean-field phase diagram for the wetting transition on a cylindrical substrate as a function of the distance from coexistence and show that both the bulk field and the curvature of the substrate affect the phase diagram in different ways.
Abstract: The authors calculate a Landau mean-field phase diagram for the wetting transition on a cylindrical substrate as a function of the distance from coexistence. Although both the bulk field and the curvature cause the wetting layer to remain finite, they affect the wetting phase diagram in different ways.
TL;DR: In this paper, an asssumption was made for the Young's equation in order to consider the macroscopic wetting behavior of axisymmetric liquid meniscus formed under the solid surface.
Abstract: In order to consider the macroscopic wetting behavior, an asssumption was made for the well-known Young's equation in this study. For the axisymmetric liquid meniscus formed under the solid surface, the unstable wetting phenomenon mentioned above is investigated theoretically by considering the macroscopic energy change of the system. Based on the theoretical results for the condition that the liquid meniscus detaches and falls spontaneously, a novel method for measuring the contact angle is proposed
TL;DR: In this article, the authors follow the spreading of a magnetic liquid, a non wetting ferrofluid, along a wire and observe a rapid jump of this length corresponding to a sheath-like coverage of the wire.
Abstract: We follow the spreading of a magnetic liquid, a non wetting ferrofluid, along a wire. The external control parameter of the spreading length of the fluid is the magnetic field generated by a current travelling through the conducting wire. The spreading length results from a balance between capillary and magnetic forces. For a current threshold, we observe a rapid jump of this length corresponding to a sheath-like coverage of the wire. This magnetic wetting transition is analogous to the wetting transition on a fiber, predicted for a totally wetting fluid in the presence of van der Waals forces. The longer range of magnetic forces leads to a transition at a macroscopic scale. The crossover between micro and macro scales is studied. 1 associated with the Centre National de la Recherche Scientifique
TL;DR: In this article, the shape of a meniscus of one phase between two others is studied in two dimensions using random walk models, and the Herring relations between contact angles are established.
Abstract: The shape of a meniscus of one phase between two others is studied in two dimensions using random walk models. An interface with a meniscus is approximated by two random walks forming microscopic droplets of the intruding phase before and after a macroscopic lens. Within this class of models, we establish a Wulff construction and prove the Herring relations between contact angles. We give explicit formulas for the contact angles as functions of temperature, both at low temperatures and near the wetting transition.
TL;DR: In this article, the adsorption isotherms for C 2 H 4 on exfoliated graphite (Grafoil MAT) were measured near saturaton and around the triple point by using a double cell.
Abstract: The adsorption isotherms for C 2 H 4 on exfoliated graphite (Grafoil MAT) were measured near saturaton and around the triple point by using a double cell: one cell with the bulk phase of C 2 H 4 and the other with the adsorbed C 2 H 4 on graphite. Thus, the equilibrium vapor pressure, p, of the adsorbed C 2 H 4 and that of the bulk phase, p o , were concurrently determined
TL;DR: In this article, the authors derived a finite-size scaling representation for the partition function for an Onsager-Temperley string model with a wetting transition, and analyzed the zeros of this partition function in the complex scaled coupling parameter of relevance.
Abstract: We derive a finite-size scaling representation for the partition function for an Onsager-Temperley string model with a wetting transition, and analyze the zeros of this partition function in the complex scaled coupling parameter of relevance. The system models the one-dimensional interface between two phases in a rectangular two-dimensional region (x, y) ∈ℝ2,−L ≤y⩽L,o≤x≤N. The two phases are at coexistence. The string or interface has a surface tension 2KkT per unit length and an extra Boltzmann weighta per unit length if it touches the surfaces aty=±L. There is a critical valueac=1/2K and fora>ac the string is confined to one of the surfaces, while fora ťac the string moves roughly in the rectangular region. The finite-size scaling parameters are α=ac2N/L2 and ζ=L(a−ac)/ac2. We find that for |ζ| large, the zeros of the scaled partition function lie close to the lines arg(ζ)=±π/4 with re(ζ)>0. We discuss the motion of all the zeros as α changes by both analytic and numerical arguments.
TL;DR: Vapor pressure measurements of p-HZ adsorbed on uncompressed exfoliated graphite foam were made, as a function of coverage, for the temperature range of 8.0 to 20.0 K.
Abstract: Vapor pressure measurements of p-HZ adsorbed on uncompressed exfoliated graphite foam were made, as a function of coverage, for the temperature range of 8.0 to 20.0 K. The isotherms for the temperatures of 13.64, 14.14, 14.53 and 15.11 K were measured up to about 20 layers and the others up to about 6 layers. These preliminary results seems to indicate a wetting transition below the bulk triple point.
TL;DR: In this article, the authors present experimental results on microemulsions made with water-alkane nonionic surfactant systems that confirm the close relationship between the maximum characteristic size in the microemulsion and the persistence length of the surfactants layer.
Abstract: The authors present experimental results on microemulsions made with water-alkane nonionic surfactant systems that confirm the close relationship between the maximum characteristic size in the microemulsion and the persistence length of the surfactant layer. The microemulsion structures are found with surfactants that form films of small bending elasticity. When the bending elasticity is too large, ordered lamellar phases are obtained. When it is too small, the surfactant film cannot form, and the medium is a structureless molecular mixture. This evolution is associated with a wetting transition.