Wetting Phenomena Research Articles

Quantifying Wetting and Wicking Phenomena in Cotton Terry as Affected by Fabric Conditioner Treatment

To enable the simultaneous determination of both the speed and extent of liquid absorption in cotton fabrics, we have developed a radial, horizontal wicking experiment. The initial part of the absorbed mass versus time profile is linear, which allows us to determine the wicking rate. After a given time, a constant mass is reached, corresponding to the liquid absorption capacity of the fabric. Using the method proposed, we show that a fabric conditioner does not affect the physical characteristics. such as porosity and pore size, and hence the water absorption capacity of cotton terry. On the other hand, there is a pronounced effect on the wicking rate. Based on the experimentally determined values of the contact angle of water on the treated fabrics, the differences in wicking rates as a function of the kind of fabric conditioner can be ascribed to differences in wettability.

Interfacial reactions of zirconium and zirconium-alloy liquid metals with beryllia at elevated temperatures.

Argonne National Laboratory and Integrated Thermal Sciences, Inc. are developing crucible materials for melting reactive metals. A major part of this effort involves identifying reusable materials because they would have little or no interaction with the molten metals at elevated temperatures. Sessile drop-type experiments have been performed using pure zirconium and stainless steel-zirconium alloys (e.g., HT9-15Zr) on beryllia (BeO) substrates. The system was heated in high-purity argon to about 2000°C, held for 5 minutes, and cooled to room temperature. An external video camera monitored the interfacial interaction and wetting behavior. The zirconium melted and wetted the BeO at 1600°C, far below its melting point (1855°C). Post-test examinations show beryllium and oxygen dissolving in the zirconium metal. In addition, zirconium infiltrated the BeO substrate. No third phase reaction product was present at the zirconium-beryllia interface either at the top of the substrate or in the infiltrated region. HT9-15Zr also reacted with BeO; the alloy infiltrated partially into the BeO and formed a reaction-like layer attached to the ceramic substrate at the interface with the solidified metal. The rest of the liquid metal alloy did not wet the reaction product band. The results indicate that BeO is a poor crucible for the present application, but the observed wetting and infiltration phenomena are relevant to understanding the behavior of the liquid metal-ceramic interfaces.

Molecular dynamics study of Cu deposition on Mo and the effects of low-energy ion irradiation

Molecular dynamics simulations were performed to study the growth of Cu films on a Mo(1 1 0) substrate, both by thermal evaporation and by ion-beam assisted deposition (100 eV Ar assistance). The growth mode of the Cu films goes to a 2D–3D–2D transition; the evolving microstructures are also discussed. The influence of the energetic ion impacts is significant, notably affecting wetting phenomena, but also leading to a different film structure. The effects of 75 eV He ion irradiation of a few completed films are also investigated, to help assessing the information on the defect state of the deposited films that is provided by thermal helium desorption experiments.

Liquid Bridges in Chemically Structured Slit Pores

Wetting phenomena are theoretically studied for a slit pore or slab geometry between two structured surfaces which contain stripes of lyophilic surface domains. Two different approaches are used and compared: Monte Carlo simulations of lattice gas models and minimization methods applied to effective interface models. Both types of calculations show that the wetting liquid often attains anvil-like bridges which are not translationally invariant parallel to the surface stripes. As a control parameter such as the liquid volume or the surface separation is changed, these bridges undergo morphological wetting transitions to symmetric or asymmetric channel states.

A Numerical Simulation of Acid Deposition in East Asia

The goal of the present study is to do a long term simulation and to derive a source receptor-relation using a comprehensive Eulerian acid deposition model coupled with a dynamic meteorological model. The selected modeling period is from March 1 to April 30, 1996. A dynamic meteorological model named MM5 was first used to calculate meteorological fields and then STEM preprocessors were invoked to generate dry deposition velocities and eddy diffusivities. Finally, a multi-scale STEM was applied to simulate both wet and dry acid deposition phenomena. The source-receptor relations were also estimated for sulfate and nitrate species using a counter species method.

The Ising model as a playground for the study of wetting and interface behavior

Computer simulations have played an important role in the elucidation of wetting and interface unbinding phenomena. In particular, use of the Ising-lattice-gas model in a film geometry and subject to diverse surface and bulk magnetic fields has permitted extensive Monte Carlo simulations to reveal new features of the phase diagrams associated with these phenomena and to provoke new theoretical studies. The status of our knowledge about the nature of wetting and interface-delocalization transitions which has resulted from these Ising model simulations will be summarized.

Determination of soluble anions and cations from waters of pulp and paper mills with on-line coupled capillary electrophoresis

When the degree of closure of the paper machine wet end waters increases, wet end problems also become more difficult to control without specific and selective on-line measurements. The need to measure the concentrations of individual compounds in order to explain wet end phenomena is growing. This study was performed to set up a CE system to a paper machine and to determine soluble inorganic and organic ions in different locations of pulp and paper process waters with real time analyses by two on-line CE methods. A reconstructed commercial CE apparatus was connected to a papermaking machine via an apparatus, which was a combined sampling and sample pretreatment instrument, the role of which was to filter and dilute the samples before on-line determination by CE. The on-line procedures were optimized for simultaneous determination of anions as chloride, sulfate, oxalate, formate and acetate and for determination of cations as potassium, calcium, sodium, magnesium and traces of aluminium. The quantification was performed with external standard methods using the programs available in the commercial CE instrument. The concentrations of the ions were transferred by using a computerized transfer algorithm exporting the results from the analysis instrument to the process control unit. The developed on-line procedures were tested three times in paper and paperboard mills for 1 month at a time. Correlations were observed between the CE results and changes in the processes.

Mechanisms of initial melt/substrate heat transfer pertinent to strip casting

An experimental study of initial solidification of 304 stainless steel melts in direct contact with copper substrates under conditions approximating the meniscus region of a strip caster has highlighted the importance of interfacial heat transfer during the first 30 ms of contact. The mechanisms governing initial heat transfer are strongly influenced by dynamic wetting phenomena. This has been illustrated experimentally by the effects of the buildup and melting of oxide films such as manganese silicates at the interface during successive immersions, by the role of surface active agents such as tellurium in the melt, and by the use of specially designed substrate textures to control contact areas.

研究論文 １０８８．ＰＷＲ炉内構造バッフルフォーマボルト材の粒界割れ機構に対する考察

In this study, the cause of intergranular cracking in baffle former bolts (BFBs) was estimated from metallurgical and chemical viewpoints based upon the experimental data and information published by EdF. At first, five kinds of possibilities were estimated as the cause of intergranular cracking in BFBs. Five possibilities estimated were (1) mechanical cracking caused by high strain in irradiation hardened austenitic stainless steels, (2) O 2 SCC due to residual oxygen in the bolt stagnant region, (3) caustic SCC due to dry and wet phenomenon, (4) low pH SCC due to oxygen concentration cell, and (5) PWSCC due to radiation induced segregation. In this study each possibility was evaluated by the calculation and some out of pile tests. And also, the cause of the intergranular cracking in BFBs was estimated by the data of the post-irradiation examinations and basic out of pile tests for Type 316CW and Type 347 stainless steels in the authors' previous study. From these evaluation, the intergranular cracking in BFBs seems to be caused by the PWSCC, but not caused by mechanical cracking O 2 SCC, caustic SCC or low pH SCC.

Phase-inversion applications beyond membrane formation. I. Lithography films

Polymeric films cast from a polymer solution can develop a bulk porosity, if the conditions are favorable for phase inversion (PI), a physical chemical process based on fluid–fluid demixing of which there are two known major variants: wet and dry PI. As the formation of polymeric coatings often involves a polymeric solution or gel precursor, dry or wet PI phenomena may affect the structure formation of the final solvent-free coating. In this article we identify the situations under which lithographic films can develop a PI structure and focus on solid polymer layers undergoing postcasting wet processing. Examples are provided from the wet processing of a fractionated epoxy novolac resin currently used in lithographic patterning. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2145–2157, 2000

TRANSPORT PHENOMENA IN THE IMPACT OF A MOLTEN DROPLET ON A SURFACE: MACROSCOPIC PHENOMENOLOGY AND MICROSCOPIC CONSIDERATIONS PART I: FLUID DYNAMICS

The fundamental problem of a liquid droplet impacting on a surface appears in a wide range of phenomena from nature to technology. It offers many scientific challenges that cover the entire area of transport phenomena. In fluid dynamics, even in the limit of Newtonian liquids, the problem involves a severely deforming free liquid surface that interacts with a gaseous environment, on the one hand, and with a solid surface, on the other hand. Complex wetting, breakup, and re-coalescence phenomena may take place. The associated thermodynamic/heal transfer complexities can be exemplified if one considers the case where the impacting droplet is molten and solidifies upon impact. In addition to the interplay of the three heat transfer modes and thermocapillarity, the solidification may occur under nonequilibrium conditions. Mass transfer phenomena can also be present in the molten droplet impact problem. Adsorption and surfactant presence, for example, can give rise to a dynamic behavior of the surface tension coefficient during the droplet deformation. In the case of a molten metal in an oxidizing environment, the formation of oxides and their impact on the surface tension can affect the process profoundly. The opposite thermodynamic limit of a droplet evaporating upon impact on a surface can also serve to underline the relevant heat and mass transfer challenges, but it is outside the scope of this review article. The purpose of this pair of articles is to review the state of the art of research on the droplet/surface impact problem as it pertains to the deposition of molten droplets, and to identify trends of future research driven by emerging technologies. Part 1 of the review is focused on the fluid dynamics aspects of the problem, in the absence of temperature gradients. Axisymmetric as well as three-dimensional phenomena are discussed assuming incompressible flow, followed by compressibility phenomena, for flat as well as nonflat substrates. Wetting and capillary phenomena arc an important part of the review. The review of the fluid dynamics phenomena in the present paper is not limited to molten droplets, since the majority of these phenomena is common to all fluid droplets impacting on a surface. Part II of the review (Chapter 3) focuses on work relevant to the case where a temperature gradient is present, with as well as without solidification of the droplet material.

Wetting Phenomena on Structured Surfaces

Wetting phenomena on structured surfaces are reviewed. The interplay between the two-dimensional pattern of surface domains and the three-dimensional morphology of the wetting fluid is theoretically discussed. The results presented illustrate the novel morphological aspects in the wetting behavior. It is shown that these systems have potential both as models for fundamental research and as a templates for technologically relevant microscale structures with unique geometric and topological properties.

Wetting Phenomena on Structured Surfaces

Wetting phenomena on structured surfaces are reviewed. The interplay between the two-dimensional pattern of surface domains and the three-dimensional morphology of the wetting fluid is theoretically discussed. The results presented illustrate the novel morphological aspects in the wetting behavior. It is shown that these systems have potential both as models for fundamental research and as a templates for technologically relevant microscale structures with unique geometric and topological properties.

The “friction” of vacuum, and other fluctuation-induced forces

The static Casimir effect describes an attractive force between two conducting plates, due to quantum fluctuations of the electromagnetic (EM) field in the intervening space. Thermal fluctuations of correlated fluids (such as critical mixtures, super-fluids, liquid crystals, or electrolytes) are also modified by the boundaries, resulting in finite-size corrections at criticality, and additional forces that affect wetting and layering phenomena. Modified fluctuations of the EM field can also account for the ``van der Waals'' interaction between conducting spheres, and have analogs in the fluctuation-induced interactions between inclusions on a membrane. We employ a path integral formalism to study these phenomena for boundaries of arbitrary shape. This allows us to examine the many unexpected phenomena of the dynamic Casimir effect due to moving boundaries. With the inclusion of quantum fluctuations, the EM vacuum behaves essentially as a complex fluid, and modifies the motion of objects through it. In particular, from the mechanical response function of the EM vacuum, we extract a plethora of interesting results, the most notable being: (i) The effective mass of a plate depends on its shape, and becomes anisotropic. (ii) There is dissipation and damping of the motion, again dependent upon shape and direction of motion, due to emission of photons. (iii) There is a continuous spectrum of resonant cavity modes that can be excited by the motion of the (neutral) boundaries.

Colloidal Protein Solutions as a New Standard Sensor for Adhesive Wettability Measurements

Wetting experiments are carried out for the investigation of the interfacial interactions that take place when various solid materials are in contact with protein colloidal solutions. These materials are chosen because they are widely used in the field of orthopedic surgery. Contact angles (sessile drop) and surface tension (du Nouy's ring method) are measured in standardized conditions which take into account the various parameters disturbing wetting phenomena. An original cumulative deposits method (CDM) described here permits observation of the evolution of the wettability and allows estimation of the protein adhesion rate. Two families of materials emerge according to their behavior when they are in contact with the protein solution. One set (a chromium cobalt alloy and two polyethylenes) presents no detectable adhesion. The other set (stainless steel, zirconia, alumina, virgin and nitrogen implanted titanium alloy) shows a cumulative adhesion of proteins. We propose to adopt a BSA buffered solution as a referential sensor to characterize solid surfaces. From the CDM, the practical parameterP*, called the adhesive wettability power, can be used in order to analyze and classify biomaterials.

Recent Highlights of X-Ray Magnetic Scattering Studies from Surfaces

In this work, recent studies of surface magnetism, as observed by x-ray scattering techniques, are described. The experiments were concerned with uranium dioxide crystals for which x-ray resonance effects enhance the small magnetic signal from the surface. The main result is that, in contrast to the bulk which exhibits a discontinuous magnetic ordering transition, both the (001) and (111) surface layers order continuously. This is reminiscent of the general phenomenon of surface wetting, but had not been previously observed for magnetic materials. Magnetic reflectivity studies show further that the near-surface magnetic layers are more disordered than layers deep in the bulk, even at low temperatures.

Correlation between surface tension and physical paint properties

Surface tension is a parameter of decisive importance for characterizing painted and unpainted surfaces related to wetting and adhesion phenomena. Measurements of the surface tension of solids by means of an automatic contact angle measurement device are presented. The theoretical evaluations provide for a separation of the surface tension into polar and disperse components. In addition, this paper briefly touches on other more far-reaching approaches (acid/base) and discusses a method for the determination of the dynamic surface tension of liquids.

Critical behavior of interacting surfaces with tension

Wetting phenomena, molecular protrusions of lipid bilayers and membrane stacks under lateral tension provide physical examples for interacting surfaces with tension. Such surfaces are studied theoretically using functional renormalization and Monte Carlo simulations. The critical behavior arising from thermally-excited shape fluctuations is determined both for global quantities such as the mean separation of these surfaces and for local quantities such as the probabilities for local contacts.

Three-Dimensional Molecular Dynamics Analysis of Atomic-Scale Indentation

The complete atomic-scale indentation cycle is analyzed using molecular dynamics simulations. A hysteresis is observed in the instantaneous normal force versus surface separation distance curve obtained with an atom or a rigid tip indenting and, subsequently, retracting from a dynamic face-centered-cubic substrate consisting of argon or copper. The generation of irreversible deformation in a Lennard-Jones solid is revealed in light of simulation results for indentation by a single atom. The direction of irreversible deformation is shown to coincide with that of macroscopic plastic flow. The compressive yield strength decreases with increasing substrate temperature and decreasing indentation speed. The phenomena of tip wetting by substrate atoms and connective neck formation, elongation, and rupture at the tip/substrate interface are elucidated by simulation results for the unloading process. It is shown that energy dissipation decreases as the substrate temperature increases and the energy consumed by irreversible deformation is always greater than that due to heating.

SOLVENT EXTRACTION ENHANCED MICROFILTRATION OF STRONTIUM AND TECHNETIUM WITH DI-2-ETHYLHEXYLPHOSPHORIC ACID AND QUATERNARY AMMONIUM SALTS

ABSTRACT Application of extractants in form of microphase (micelles or microdrops) separated from aqueous matrix by microfiltration, “solvent extraction enhanced microfiltration (SEEMF)” is closely related to micellar enhanced ultrafiltration (MEUF) technique. Uptake of strontium from aqueous solutions with microphase di-2-ethylhexylphosphoric acid (DEHPA) and pertechnetate with quaternary ammoniumsalts (QAS): trioctylmethylammonium chloride, benzyldodecyl-dimethylammonium bromide, and n-(α-carbethoxypenthadecyl)trimetyl-ammonium chloride was investigated as a function of microphase concentration and composition, pH and salinity of aqueous phase. Recovery of microfiltration on cellulose acetate 200 nm filters reached 95% for strontium with 4×10−3 M DEHPA and 99% for technetium with 10−4 M trioctyl-methylammonium chloride. A substantial part of 88-99% retention of technetium with investigated quaternary ammonium salts on microfilter may be caused by the filter wetting or sorption phenomena.