Wetting Phenomena Research Articles

A simple density functional theory for inhomogeneous liquids

A simple free energy functional, which incorporates both ‘local’ thermodynamics and short ranged correlations, is formulated and applied to the calculation of the density profile of fluids near hard walls. For hard sphere fluids the calculated profiles are in reasonable agreement with Monte Carlo results. For a Lennard-Jones liquid the profiles exhibit the phenomenon of wetting by gas; the oscillations in the density profiles become much less pronounced and a layer of gas develops near the wall as the bulk density approaches its value at coexistence. Such behaviour was found earlier in Monte Carlo simulations but is not accounted for by existing integral equation theories based on closures of the wall-particle Ornstein-Zernike equation.

Walks, walls, wetting, and melting

New results concerning the statistics of, in particular,p random walkers on a line whose paths do not cross are reported, extended, and interpreted. A general mechanism yielding phase transitions in one-dimensional or linear systems is recalled and applied to various wetting and melting phenomena in (d=2)-dimensional systems, including fluid films and p×1 commensurate adsorbed phases, in which interfaces and domain walls can be modelled by noncrossing walks. The heuristic concept of an effective force between a walk and a rigid wall, and hence between interfaces and walls and between interfaces, is expounded and applied to wetting in an external field, to the behavior of the two-point correlations of a two-dimensional Ising model belowTc and in a field, and to the character of commensurate-incommensurate transitions ford=2 (recapturing recent results by various workers). Applications of random walk ideas to three-dimensional problems are illustrated in connection with melting in a lipid membrane model.

非水系溶媒の紙層への浸透 水系との対比

Paper is a multilayer structure of fibers with numerous micro-scale pores. Almost all the pores in paper consist of tortuous capillarylike tubes that are continuously interconnected.Therefore, paper is permeable and can absorb liquids and gases. The most obvious utilization of the tortuous capillary structure of paper are filter paper, blotting paper, and so on. Furthermore, paper-converting operations involve penetration into the voids of paper by coating, adhesives, ink, and so on. In these processes, liquids such as wax, paraffins, silicones, and oilbased ink are applied to paper in non-aqeous form, whereas latex, silicon emulsions, and waterbased ink are basically aqueous liquids.The fundamental theory of the wetting and penetration phenomena of paper holds for both aqueous and nonaqueous liquids.However, in the aqueous case, fiber swelling and wetting cause deviations from the clasical theory of the penetration of porous media. This paper includes the two kind of penetration phenomena such as an oil-based ink for nonaqueous liquid and water based coating colour for aqueous liquid.

The role of surfaces in the reactivity of solids

Abstract

Interface delocalization transitions in semi-infinite systems

The relationship between surface wetting transitions and surface-induced disorder (SID) transitions is studied. The correspondence between the scaling variables at these two types of interface delocalization transitions is derived and the connection between the scaling laws is made explicit. This wetting-SID correspondence is then used to obtain a number of new results. SID transitions are shown to correspond to special points in more general interface delocalization phase diagrams and it is argued that the SID transition is always continuous in $d=2$. Exact results for the surface exponents are obtained in this case. New higher-order multicritical wetting phenomena are also predicted and the scaling behavior of local surface quantities at the wetting transition is discussed in detail.

Absence of Critical Wetting in Systems with Long-Range Forces

Study of a solid-on-solid model within the Migdal approximation leads the authors to conclude that the phenomenon of critical wetting cannot occur in the presence of long-range, van der Waals forces.Received 26 May 1983DOI:https://doi.org/10.1103/PhysRevLett.51.1275©1983 American Physical Society

The calculation of hamaker constants from liftshitz theory with applications to wetting phenomena

The physical signifance of the function ϵ (iξ) for a dielectric material is discussed together with the rationale for the construction of ϵ (iξ) from dielectric data. The utility of refractive index/wavelength data in the visible region in providing the crucial unltraviolet relaxation frequency and oscillator strength is demonstrated. A variety of real systems is analysed to obtain the data necessary for the construction of ϵ(iξ). Hamaker constants for these materials are computed. The use of these Hamaker constants in describing wetting phenomena is discussed with examples.

表面張力法によるはんだのぬれの研究 Ｉ 平衡ぬれ

Important factors in testing methods of quantitatively evaluating the wettability of a soldering system are discussed. It is shown that adhesion tension obtained directly by the surface tension method is a basic important factor governing wetting phenomena, and that the wetting behaviour may be interpreted from various points of view such as spreading or penetration characteristics of the soldering system. Experimental results obtained by surface tension methods on the equilibrium wetting of copper by tin-lead solders with rosin flux are described. These give an explanation of the discrepancies between the results of area-of-spread and capillary-penetration tests and give an insight into the slight difference between the results of area-of-spread tests and the practical assessments of soldering performance. It is found that adhesion tension exerts dominant influences on practical soldering, and the surface tension method can be expected to be useful for the quantitative evaluation of actual solderability.

Physical Dependence on Morphine, Phenobarbital and Diazepam in Rats by Drug-Admixed Food Ingestion

To produce physical dependence on morphine, phenobarbital and diazepam in rats, these drugs were mixed with the powder form of rat food in concentrations of 0.5 mg/g, 1 mg/g and 2 mg/g of food. One group of rats (the lower dose group) was continuously exposed for 1 week to two morphine-admixed foods with morphine to food ratios of 0.5 mg/g and 1 mg/g in a cage. The other group (the higher dose group) could choose between two morphine-admixed foods with morphine to food ratios of 1 mg/g and 2 mg/g. After 1 week, morphine-admixed foods were replaced with morphine free food for 2 days. Both groups of rats showed greatly reduced body weight and food intake after the first 24–48 hr withdrawal. The body weight decrease was greater for rats in the higher dose group. Control groups of morphine dependent rats were kept on the morphine added food diets and showed the same body weight increase as well as normal control rats during the course of these experiments. Physical dependence on phenobarbital and diazepam was produced using the same dosage schedules as with morphine. Both the lower and higher dose groups showed significant decrease in body weight due to withdrawal after 1 week of drug-food exposure. Levallorphan (0.5, 1, 3 and 5 mg/kg, s.c.) administered to morphine dependent rats had dose-dependent effects on the intensity of abstinence symptoms (e.g., diarrhea, pilocrection and wet shakes phenomena), maximal decrease in body weight and duration of decreased body weight. Cross-physical dependence between phenobarbital and diazepam was demonstrated by this method.

Adhesion and wetting in urea fiberglass plastics

Results of a study of the adhesion of urea polymers to fiberglass and of the phenomenon of wetting of the glass surface by oligomers are presented; the introduction of linear high-molecular-weight compounds with active functional groups into the make-up of the binder aids in an improvement of adhesion and wetting. It has been shown that an interrelationship exists between adhesion, wetting, and the physicomechanical properties of fiberglass plastics.

Correlations of surface measurements with the chromatographic performance of chemically modified glass capillary columns

Wetting phenomena for different liquids were studied on various surfaces “tailored” by the permanent bonding of selective monolayers of silanes to the inner wall of glass capillaries. Surfaces were characterized by graphic the cosine of advancing contact angle on differently modified glass against liquid surface tension. The thinknesses of coated films of stationary phases, measured chromatographically, were found to be in good agreement with those calculated from the Fairbrother—Stubbsequation. However, the presence of the monolayers significantly alters the surface characteristics of the glass, and the chromatographic performance of capillary columns the reflects the film homogeneity, which was found to be a sensitive function of the chemical similarities between the surface structure and the phase. The mechanism of compatibility proposed earlier for the wettability of glass capillary walls is discussed in terms of both the surface phenomena described and a molecular model of the modified surface.

Application of wetting theory to the non-reactive liquid metal-graphite systems

An attempt has been made to correlate the published contact angle data for graphite-liquid metal systems with the theory of liquid-solid wetting phenomena. To establish the reasonableness of the approach, the potential expression for dispersion interaction was employed for mercury, and the magnitude of the contribution from dispersion forces to the liquid surface energy of mercury, γLd, was calculated to be 193 erg/cm2. This compares favourably with the published experimental value of 200 erg/cm2. Similarly the γLd values for liquid metals of known contact angle with graphite were calculated and subsequently substituted in a modified Young equation in order to calculate the respective values of Φ. The parameter, Φ, has been defined by Girifalco and Good as the ratio of adhesion and cohesion forces for any two phases in contact. The calculated values of Φ were observed to rise to a maximum for all metals in the same periodic group as carbon, which would be predicted for “chemically similar” phases.

Contact Angles as a Measure of Surface Wetting Properties in Filth Flotation Analysis

Abstract A study was made of the surface wetting properties exhibited by insect fragments, animal hairs, and food particles in contact with oil and aqueous solvent systems used in oil flotation analytical procedures. The differential wetting phenomena involved in flotation separation procedures of both untreated and preliminarily treated materials can be studied by contact angle measurements, which provide valuable information about the degree of wettability and flotability of both filth and plant particles. The solid specimen material is immersed in an inverted position in the aqueous plase, and the applied oil droplet competes with the aqueous phase for "wetting" the solid. The contact angle is measured at the point where the oil droplet, the aqueous phase, and the solid surface meet. The instrument used for measuring contact angles and the accessory apparatus devised for the addition of oil droplets to inverted specimen mounts while immersed in aqueous media are illustrated.

平フライス削りの機構と切削油剤の効果

Plain milling is a special type of machining characterized by that the cutting process is intermittent, the area of cut varies continuously between zero and a certain amount, and generally more than one cutting edge engage with the work material. Such the situation makes the cutting mechanism much complicated, and especially in wet machining many interesting phenomena in view of lubricating effect seem to be involved.This paper treats with the investigation of cutting mechanism and lubricating effect in plain milling and the evaluation of cutting fluids from the standpoint of surface quality and cutting force.