Solid Surface Tension Research Articles

プレコート鋼板の耐汚染性に与える固体表面張力の影響

Stain resistance is a key performance criterion of pre-painted steel sheet used outdoors. The addition of organosilicate to paint is known to prevent a paint film from staining by hydrophilicity. To clarify the mechanisms related to this technology, we investigated the stain-resistance effects of adding organosilicate to paint used for pre-painted steel sheets. We considered them from the point of solid surface tension, which was divided into three force elements: hydrogen bond force, dipole-dipole force, and dispersion force.

New insights into the study of the destabilization of oil-in-water emulsions with dextran sulfate provided by the use of light scattering methods

Emulsions are non-thermodynamically-stable systems. Being able to characterize their evolution upon time without disturbing them would be of great interest. Mechanisms of destabilization: depletion and bridging flocculation were reproduced by using dextran sulfate respectively with Tween 20 and whey-protein-stabilized oil-in-water emulsions. Two light scattering methods were combined: Multiple Light Scattering, MLS, specially adapted to characterize turbid systems (Turbiscan®) and Multi-Speckle Diffusing Wave Spectroscopy, MS-DWS (Rheolaser™). The Tween 20-stabilized emulsion showed a very stable-versus-time elasticity index (EI) measured by MS-DWS up to 24 h. On the contrary, the whey-protein-stabilized emulsions showed a large variation of EI that decreased continuously during 10 h and dropped to zero suddenly. On the basis of the physico–chemical interaction knowledge and the MLS profile evolution versus time, a variation of the destabilization kinetics depending on the droplet network stabilization but also on the interactions between droplets and the surface of the recipient was proposed. It was confirmed by the modification of the destabilization kinetics when changing the solid surface tension of the recipient.

Dry-Surface Simulation Method for the Determination of the Work of Adhesion of Solid-Liquid Interfaces.

We introduce a methodology, referred to as the dry-surface method, to calculate the work of adhesion of heterogeneous solid-liquid interfaces by molecular simulation. This method employs a straightforward thermodynamic integration approach to calculate the work of adhesion as the reversible work to turn off the attractive part of the actual solid-liquid interaction potential. It is formulated in such a way that it may be used either to evaluate the ability of force fields to reproduce reference values of the work of adhesion or to optimize force-field parameters with reference values of the work of adhesion as target quantities. The methodology is tested in the case of water on a generic model of nonpolar substrates with the structure of gold. It is validated through a quantitative comparison to phantom-wall calculations and against a previous characterization of the thermodynamics of the gold-water interface. It is found that the work of adhesion of water on nonpolar substrates is a nonlinear function of the microscopic solid-liquid interaction energy parameter. We also comment on the ability of mean-field approaches to predict the work of adhesion of water on nonpolar substrates. In addition, we discuss in detail the information on the solid-liquid interfacial thermodynamics delivered by the phantom-wall approach. We show that phantom-wall calculations yield the solid-liquid interfacial tension relative to the solid surface tension rather than the absolute solid-liquid interfacial tension as previously believed.

Comparison of Different Methods To Determine the Surface Wettability of Fine Solids Isolated from Alberta Oil Sands

The wettability of fine solids in Alberta oil sands is one of the most important factors affecting nonaqueous bitumen extraction and subsequent solvent recovery from the extraction gangue. However, there is some controversy as to which method is most suitable for wettability determination of fine solids isolated from the oil sands. In this paper, four different methods—i.e., particle partition, static sessile drop contact angle coupled with penetration time, Washburn capillary rise, and film flotation—were investigated and compared in order to determine suitable methods to examine the wettability of these fine solids. Two model samples, high-purity kaolinite (hydrophilic) and bitumen-treated kaolinite (hydrophobic), were used to investigate the suitability of the above four methods. These methods were then used to measure the surface wettability of fine solids isolated from the oil sands (marine clay) after toluene extraction, either untreated or heated at 400 °C for 2 h. The results showed that the Washburn capillary rise method was not applicable. In addition, the particle partition and static sessile drop contact angle coupled with penetration time methods had some deficiencies and were not very suitable to determine the wettability of fine solids isolated from the oil sands. The film flotation method was determined to be the most appropriate method, because (i) it was sufficiently sensitive to distinguish solid surface hydrophilicity and hydrophobicity; (ii) it could quantify the hydrophilicity and hydrophobicity, based on the measured “mean critical surface tension”; and (iii) it could be used to determine the surface heterogeneity of the solids, based on the standard deviation of the measurements. By using the film flotation method, the mean critical surface tensions of fine solids was >68.1 mN/m, while that of the heat-treated solids was >72.0 mN/m, and the standard deviation of the critical surface tensions of the floating particles (0–25.9 wt %) for fine solids was 40.5 mN/m, which indicated that heat treatment caused the fine solids to become more hydrophilic and the hydrophobicity of the fine solids was heterogeneous. In addition to direct application of the four standard methods, we have further developed the methods and gained some new insights into them.

On the first application of Legendre transforms to the surface tension of solids

This is a short consideration of the latest articles [{xc1}, {xc2}] criticizing works [{xc3}, {xc4}] proposed a new approach to the surface tension of condensed matter. We underline some of his obviously incorrect statements about the Gokhshtein equations and focus on misleading interpretation of Legendre transforms and especially of complete Legendre transforms. All these mistakes show that the criticism [{xc1}, {xc2}] as a whole is incorrect and unacceptable.

Deformation of a Solid Film with Surface Tension by a Liquid Drop

A drop placed under a solid thin film causes it to bulge due to the action of liquid surface tension, Laplace pressure, difference in surface tension on two sides of the film, and gravity. Deformation is resisted by solid surface tension, bending, and in-plane stretching. For sufficiently thin films and small drops, the film mainly carries tension and the deformed configuration can be obtained simply by force balance of tensions at the contact line. In this work, we examine more closely the conditions under which this simplified situation exists. We show that generally the effect of surface tension asymmetry on two sides of the film is negligible, as is the effect of gravity on the local deformed shape. Further, we show that for sufficiently thin films, bending affects the solution only in a boundary layer near the contact region and that tensions in the films can still be estimated from force balance.

Investigation of nanofluid bubble characteristics under non-equilibrium conditions

We report experimental and theoretical investigations of the bubble characteristics during the oscillatory growth period for several nanofluids. The nanoparticles were found to affect liquid–gas and solid surface tensions, which modulated the bubble contact angle, radius of triple line, bubble volume and the dynamics of bubble growth. To increase the accuracy of the Young–Laplace equation predictions during the bubble growth in the oscillatory period, a new method multi-section bubble (MSB) approach was developed. In this method, the bubble was divided into n sections (i.e., n=1:N) and the Young–Laplace equation was solved for each section individually. As N increases, within each section the effects of inertia force and viscosity become reduced comparing to that of the liquid-gas surface tension. Unlike the conventional Young–Laplace approach (i.e., N=1), the new approach is able to predict the bubble characteristics reliably in the following cases: (a) the oscillatory period when bubble is fluctuating; (b) the departure period when bubble is stretched upward, right before departure; and (c) the high shear stress condition when gas velocity is relatively high.

Effect of liquid surface tension data on the validity and accuracy of solid surface tension components and parameters in the application of the van Oss–Chaudhury–Good approach

This paper studies the effects on valid domain of contact angles and error limits of solid surface tension components and parameters (SSTCPs)/square roots of SSTCPs (SQSSTCPs) from the changes in liquid surface tension components and parameters (LSTCPs) when applying the van Oss–Chaudhury–Good (vOCG) approach. The results of maximum absolute errors and maximum relative errors (MREs) in SQSSTCPs/SSTCPs, induced by errors in LSTCPs or contact angles, show that most SQSSTCPs/SSTCPs can be evaluated at moderate accuracy from the lowest condition number liquid triplets, assuming that |Δθi| = 1° and = 0.1 mN/m (i = 1, 2, 3, k = LW, +, −). This confirms the validity of the vOCG approach. The accuracy of each SQSSTSCP/SSTCP declines with increasing θi or decreasing parameter when θi > 0 or a critical value, provided the other two contact angles are kept fixed. This explains the underlying reasons for negative SQSSTCPs. At the scale proposed by vOCG, dimethyl sulphoxide is not suggested for use. Comparing with the MREs obtained at vOCG scale, considering the acidity of diiodomethane improves the accuracy of ; using the scales proposed by Lee and Shen do not affect the accuracy of SSTCPs, but using the scale proposed by Della Volpe et al. improves the accuracy of SSTCPs at low θ2 and θ3 while declines that at high ones. For a low , low surface tension apolar liquid is preferred for high accuracy. The dependence of the accuracy of SQSSTCPs/SSTCPs on contact angles suggests the importance of considering contact angle in accuracy evaluation.

Elastocapillary deformations on partially-wetting substrates: rival contact-line models.

A partially-wetting liquid can deform the underlying elastic substrate upon which it rests. This situation requires the development of theoretical models to describe the wetting forces imparted by the drop onto the solid substrate, particularly those at the contact-line. We construct a general solution using a displacement potential function for the elastic deformations within a finite elastic substrate associated with these wetting forces, and compare the results for several different contact-line models. Our work incorporates internal contributions to the surface stress from both liquid/solid Σls and Σsg solid/gas solid surface tensions (surface stress), which results in a non-standard boundary-value problem that we solve using a dual integral equation. We compare our results to relevant experiments and conclude that the generalization of solid surface tension Σls ≠ Σsg is an essential feature in any model of partial-wetting. The comparisons also allow us to systematically eliminate some proposed contact-line models.

ChemInform Abstract: Hidden Problems in Interfacial Electrochemistry

AbstractReview: 36 refs.

Solid surface tension components and their error limits induced by contact angle measurement in application of the van Oss–Chaudhury–Good approach

The square roots of solid surface tension components/solid surface tension components (SQSSTCs/SSTCs) and their error limits, that is, maximum absolute errors (MAEs) and maximum relative errors (MREs) obtained from the van Oss–Chaudhury–Good (vOCG) approach were evaluated for various liquid triplets. The parameters were considered as functions of contact angles and the errors thereof. The valid domain of contact angles was defined from the physical nature of the problem as a domain composed of contact angles leading to positive LW SQSSTC and non-negative AB SQSSTCs. A sufficient broad common range of SQSSTCs/SSTCs determinable by various liquid triplets assures the validity of the vOCG approach. On the valid domain, both MAEs and MREs depend on contact angles, so the vOCG approach estimates different SSTCs at different accuracy with a given triplet. Using the smallest condition number triplets, most SSTCs can be evaluated at reasonable accuracy under the assumption of Δθi = 1° (i = 1, 2, 3). The SQSSTCs/SSTCs are monotone functions of contact angles of each contact angle provided the other two are kept fixed and the MRE in each SQSSTC/SSTC increases monotonically with a decreasing parameter. The opposite monotonicity of SQSSTCs/SSTCs and their MREs reveals the underlying reasons for disputable problems in application of the vOCG approach, for example, negative SQSSTCs. A comparison between the ranges of SQSSTCs/SSTCs and the valid domains of contact angles of diverse liquid triplets explains the general cause of liquid selection criteria.

Surface tension and contact with soft elastic solids

The Johnson-Kendall-Roberts theory is the basis of modern contact mechanics. It describes how two deformable objects adhere together, driven by adhesion energy and opposed by elasticity. Here we characterize the indentation of glass particles into soft, silicone substrates using confocal microscopy. We show that, whereas the Johnson-Kendall-Roberts theory holds for particles larger than a critical, elastocapillary lengthscale, it fails for smaller particles. Instead, adhesion of small particles mimics the adsorption of particles at a fluid interface, with a size-independent contact angle between the undeformed surface and the particle given by a generalized version of the Young's law. A simple theory quantitatively captures this behaviour and explains how solid surface tension dominates elasticity for small-scale indentation of soft materials.

Hidden problems in interfacial electrochemistry

We reconsider some old topics in interfacial electrochemistry using non-traditional approaches leading to formulation of new problems and their possible decisions. These problems are: the experimental evaluation of partial charge transfer during anion adsorption on metals, the important role of dissociative adsorption of water in platinum electrochemistry, the surface tension of solids, the Shuttleworth equation and the role of the “reversible cleavage” notion in surface thermodynamics. Remarkably, none of these innovations have been criticized in literature for a very long time (about 10 years).

Drop-on-demand inkjet printing of alumina nanoparticles in rectangular microchannels

A procedure has been developed for applying a piezoelectric drop-on-demand inkjet printing technology to deposit metal oxide nanoparticles such as alumina in stainless steel microchannels. The printability of inks having different solid concentrations, co-solvents, hydro-soluble polymers, viscosities, and surface tensions was tested. The effect of piezoelectric activation parameters on properties of generated microdrops such as drop size and velocity was investigated. Depending upon the ink composition, three different types of coated film shapes were observed in rectangular microchannels. A uniform coating in rectangular microchannels was achieved by correctly tuning the directional stability of microdrop, ink composition, and microdrop properties. It is observed that drying effects such as coffee ring effect have a large impact on the final shape of the deposited alumina layers. The adhesion of printed alumina layers was tested after drying and calcination in harsh environments such as ultrasonic baths, and it was satisfactory.

Designing a Dynamic Dissolution Method: A Review of Instrumental Options and Corresponding Physiology of Stomach and Small Intestine

Development of new pharmaceutical compounds and dosage forms often requires in vitro dissolution testing with the closest similarity to the human gastrointestinal (GI) tract. To create such conditions, one needs a suitable dissolution apparatus and the appropriate data on the human GI physiology. This review discusses technological approaches applicable in biorelevant dissolutions as well as the physiology of stomach and small intestine in both fasted and fed state, that is, volumes of contents, transit times for water/food and various solid oral dosage forms, pH, osmolality, surface tension, buffer capacity, and concentrations of bile salts, phospholipids, enzymes, and Ca(2+) ions. The information is aimed to provide clear suggestions on how these conditions should be set in a dynamic biorelevant dissolution test.

Evaluation of surface energy of W and AlNi by the results of their milling

A method is proposed which is an alternative to existing methods of determining of the surface tension of solids and is based on a generalization of the Rittinger law and the Gibbs thermodynamic equations, as well as on a diffraction analysis of the granulometric characteristics of finely dispersed powders of templates (Fe, Co) and originals (W, AlNi). The surface tension coefficients of tungsten and AlNi are evaluated. The confidence intervals of varying their values are found.

Solid surface tension measured by a liquid drop under a solid film.

We show that a drop of liquid a few hundred microns in diameter placed under a solid, elastic, thin film (∼10 μm thick) causes it to bulge by tens of microns. The deformed shape is governed by equilibrium of tensions exerted by the various interfaces and the solid film, a form of Neumann's triangle. Unlike Young's equation, which specifies the contact angles at the junction of two fluids and a (rigid) solid, and is fundamentally underdetermined, both tensions in the solid film can be determined here if the liquid-vapor surface tension is known independently. Tensions in the solid film have a contribution from elastic stretch and a constant residual component. The residual component, extracted by extrapolation to films of vanishing thickness and supported by analysis of the elastic deformation, is interpreted as the solid-fluid surface tension, demonstrating that compliant thin-film structures can be used to measure solid surface tensions.

Mechanisms and critical properties in drying shrinkage of soils: experimental and numerical parametric studies

Mechanisms of free-shrinkage strains of desiccating deformable initially saturated soils are studied. The role of the surface evaporation rate, surface tension and viscosity of pore fluid, and soil compressibility and permeability is investigated in experimental and numerical parametric studies. Two different geomaterials with three different pore fluids are tested and numerically simulated using a macroscale Biot theory model and a mesoscale vessel model. Evolution of shrinkage strain and fluid content is reported and evaluated. The total amount of shrinkage and shrinkage limit are found to correlate with both solid fraction compressibility and surface tension of the fluid fraction. Most of the strain occurs in the saturated stage of drying concomitant with a build-up of fluid suction. The macroscopic Biot model yields good results in the saturated stage of drying. However, the air-entry criteria are all formulated at meso- or microscale. Hence, a mesoscale deformable pore vessel model is adopted, with pore fluid suction limited by a fluid tensile stress threshold identified with fluid cavitation. Beyond cavitation, air entry occurs. Subsequently, partially fluid-filled pore vessels are considered with fluid evaporation across a migrating fluid–gas interface within the vessel. A mesoscale model parametric study confirms that the total drying shrinkage strain and the shrinkage limit depend on the solids' compressibility, as well as on the fluid surface tension.

The Influence of Surface Anisotropy Crystalline Structure on Wetting of Sapphire by Molten Aluminum

The wetting of sapphire by molten aluminum was investigated by the sessile drop technique from 1073 K to 1473 K (800 °C to 1200 °C) at PO2 <10−15 Pa under Ar atmosphere. This study focuses on sapphire crystalline structure and its principle to the interface. The planes “a” and “b” are oxygen terminated structures and wet more by Al, whereas the “c” plane is an aluminum terminated structure. A wetting transition at 1273 K (1000 °C) was obtained and a solid surface tension proves the capillarity trends of the couple.

Gibbs citations and interpretations in the theory of surface tension of solids: A conceptual approach

Josiah Willard Gibbs is definitely the most respectable and citable author in the surface tension of solids, however there are many incorrect citations of concepts and notions ascribed to Gibbs, but completely alien to his scientific heritage. Unfortunately, they became decidedly important for development of the contemporary theory of the surface tension of solids. For example, the erroneous notion of the “reversible cleavage”, as the conceptual background of this theory, appeared half a century after the most recent Gibbs’ works. Here we discuss not just formal linguistic, but conceptual matters using the advanced statistical method to identify wrong concepts ascribed to Gibbs. They existed in the theory of surface tension of solids for long decades and were accepted and used by most experts in this field. Today, we should formally recognize the high status of the current theory of surface tension of solids since it is supported by the scientific majority. It is based on the Shuttleworth equation, the vague concept of “reversible cleavage” and incorrect citations and interpretations of Gibbs thermodynamics. Up till now, neither this equation nor the theory as a whole had any experimental confirmations; moreover, they were shown to contradict all available experimental data. In connection with incorrect citations and interpretations of Gibbs works, we underline some pseudo-concepts and terms that Gibbs never used (like “reversible cleavage” or just “cleavage”), and contrarily, the important notions that Gibbs introduced for the first time, but almost nobody heard about them, for example -”actual and possible components” and the principal absence of “pure phases” in equilibrium of multiphase systems. We have also considered in detail the key difference between citation (as a possible free and often incorrect interpretation of the original text) and quotation (as an exact part of the original). Semantically citations and quotations are usually regarded as synonyms, but in practice it is not always correct and the sequences of their proposed equivalence might be critical for development of new concepts and theories.