Liquid Surface Energy Research Articles

Effect of chemical treatment on wettability of Zalacca fibres as composites reinforcements

The aim of this research is to study the influence of sodium hydroxide, sodium bicarbonate and calcium hydroxide treatment on the wettability characteristics of zalacca fibres. The wettability test was carried out by measuring the contact angle between the fluid and fibre surface. The distilled water and ethylene glycol represent the polar and dispersive fluid, respectively. By entering the contact angle and liquid surface energy of distilled water and ethylene glycol simultaneously into the substitution of Young-Dupres and Owen-Wendt equation, the surface energy of fibres was determined. The treatment caused the decrease in contact angle inducing the enhancement in surface energy. The increase of surface energy of the zalacca fibres by NaOH treatment was the highest, followed by Ca(OH)2 and NaHCO3 treatment. Based on the fibre content analysis and SEM examination, this is due to the basicity of the solution causing the cleaning effect, in which the sodium hydroxide is the strongest, followed by calcium hydroxide and sodium bicarbonate solution. The wettability of zalacca fibres as composite reinforcement is raised by NaOH, Ca(OH)2 and NaHCO3 treatment.

Freeze-on limits bed strength beneath sliding glaciers

Discharge from sliding outlet glaciers controls uncertainty in projections for future sea level. Remarkably, over 90% of glacial area is subject to gravitational driving stresses below 150 kPa (median ∼70 kPa). Longstanding explanations that appeal to the shear-thinning rheology of ice tend to overpredict driving stresses and are restricted to areas where ice sheets only deform (roughly 50%). Over the more dynamic portions that slide, driving stresses must be balanced by thermo-mechanical interactions that control basal strength. Here we show that median bed strength is comparable to a threshold effective stress set by ice–liquid surface energy and till pore size. Above this threshold, ice infiltrates sediment to produce basal layers of debris-rich ice, even where net melting takes place. We demonstrate that the narrow range of inferred bed strengths can be explained by the mechanical resistance to sliding where roughness is enhanced by heterogeneous freeze-on.

Transient Nucleation in Ge–Sb–S Thin Films

The crystal nucleation behavior and kinetics in Ge1.8Sb36.8S61.4 thin films were studied using optical microscopy coupled with a computer-controlled heating stage. The single-stage in situ heat treatment method was chosen for the study of nucleation. In-situ experiments were performed in the temperature range of 236–295 °C. The time evolution of the number of nuclei at various temperatures revealed transient behavior at low nucleation times. The transient nucleation data were described using the Shneidman equation to get values of steady-state nucleation rate, induction period, and time-lag of nucleation for the studied temperatures. On the basis of nucleation experiments, the temperature dependence of crystal–liquid surface energy and decoupling of nucleation rate and viscosity was assessed. The nucleation rate data obtained from microscopy measurements were discussed in terms of classical nucleation theory. It was found that the nucleation curve with the maximum at 288 °C and previously published growth...

Capillary pumping independent of the liquid surface energy and viscosity

Capillary pumping is an attractive means of liquid actuation because it is a passive mechanism, i.e., it does not rely on an external energy supply during operation. The capillary flow rate generally depends on the liquid sample viscosity and surface energy. This poses a problem for capillary-driven systems that rely on a predictable flow rate and for which the sample viscosity or surface energy are not precisely known. Here, we introduce the capillary pumping of sample liquids with a flow rate that is constant in time and independent of the sample viscosity and sample surface energy. These features are enabled by a design in which a well-characterized pump liquid is capillarily imbibed into the downstream section of the pump and thereby pulls the unknown sample liquid into the upstream pump section. The downstream pump geometry is designed to exert a Laplace pressure and fluidic resistance that are substantially larger than those exerted by the upstream pump geometry on the sample liquid. Hence, the influence of the unknown sample liquid on the flow rate is negligible. We experimentally tested pumps of the new design with a variety of sample liquids, including water, different samples of whole blood, different samples of urine, isopropanol, mineral oil, and glycerol. The capillary filling speeds of these liquids vary by more than a factor 1000 when imbibed to a standard constant cross-section glass capillary. In our new pump design, 20 filling tests involving these liquid samples with vastly different properties resulted in a constant volumetric flow rate in the range of 20.96–24.76 μL/min. We expect this novel capillary design to have immediate applications in lab-on-a-chip systems and diagnostic devices.

Wettability of Si and Al–12Si alloy on Pd-implanted 6H–SiC**Project supported by the National Natural Science Foundation of China (Grant Nos. 51572112 and 51172177), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20151340), the Six Talent Peaks Project of Jiangsu Province, China (Grant Nos. 2014-XCL-002 and TD-XCL-004), the Innovation/Entrepreneurship Program of Jiangsu Province, China (Grant No. [2015]26), and the

SiC monocrystal substrates are implanted by Pd ions with different ion-beam energies and fluences, and the effects of Pd ion implantation on wettability of Si/SiC and Al–12Si/SiC systems are investigated by the sessile drop technique. The decreases of contact angles of the two systems are disclosed after the ion implantation, which can be attributed to the increase of surface energy (σSV) of SiC substrate derived from high concentration of defects induced by the ion-implantation and to the decrease of solid–liquid surface energy (σSL) resulting from the increasing interfacial interactions. This study can provide guidance in improving the wettability of metals on SiC and the electronic packaging process of SiC substrate.

Liquid sorption, swelling and surface energy properties of unmodified and thermally modified Scots pine heartwood after extraction

AbstractThe effect of extractives removal on liquid sorption, swelling and surface energy properties of unmodified wood (UW) and thermally modified Scots pine heartwood (hW) (TMW) was studied. The extraction was performed by a Soxtec procedure with a series of solvents and the results were observed by the multicycle Wilhelmy plate method, inverse gas chromatography (IGC) and Fourier transform infrared (FTIR) spectroscopy. A significantly lower rate of water uptake was found for the extracted UW, compared with the unextracted one. This is due to a contamination effect in the latter case from water-soluble extractives increasing the capillary flow into the wood voids, proven by the decreased water surface tension. The swelling in water increased after extraction 1.7 and 3 times in the cases of UW and TMW, respectively. The dispersive part of the surface energy was lower for the extracted TMW compared to the other sample groups, indicating an almost complete removal of the extractives. The FTIR spectra of the extracts showed the presence of phenolic compounds but also resin acids and aliphatic compounds.

5-5 液晶の表面配向と表面エネルギーの関係

5-5 液晶の表面配向と表面エネルギーの関係

The ejection of molten aluminum after the interaction with millisecond pulsed laser

The ejection process of molten aluminum after the interaction with millisecond pulsed laser is studied through building a flow model of molten liquid after the end of pulse. Through the analytical and numerical calculations, the pressure in molten liquid near the surface, the liquid ejection duration, and the average velocity of the liquid at end of pulse can be obtained. From these calculation results and the images of ejection process recorded by the high speed camera, it can be inferred that liquid ejection after the interaction with millisecond pulsed laser is due to the release of surface energy of molten liquid. The calculation result accords well with the experimental result reported in literature, and the flow model of molten liquid can be used to further explain the ejection types in the experiment. The dependences of the ejection duration on radius of molten pool and on laser pulse power density are discussed.

Liquid evaporation-driven folding of graphene sheets

We propose a theory of folding graphene sheets from rapid evaporation of its liquid suspension. Using an energy criterion that contains the competition among bending energy of graphene sheets, surface energy of graphene sheets and liquid and their interfacial energy, and binding energy of folded graphene sheets, we are able to quantitatively correlate folded three-dimensional (3D) graphene structures with both geometric size and surface wettability of original graphene sheets. Theoretical predictions of folded 3D graphene patterns and sizes agree well with the parallel molecular dynamics simulations. Our theory is of immediate interest to the study of crumpling/folding original two-dimensional structures to 3D shapes through evaporation of a liquid suspension.

Constrained and extended free energy minimisation for modelling of processes and materials

Computational methods in chemical equilibrium thermodynamics have found numerous application areas in diverse fields such as metallurgy, petrochemistry, the pulp and paper industry, the study of advanced inorganic materials, environmental science and biochemistry. As many of the cases of interest are not actually in equilibrium, there is a need for methods that extend the application area of multiphase equilibrium solvers to non-equilibrium systems. Likewise there is a need for efficient handling of thermochemical systems that are described by parameters other than those most commonly associated with Gibbs energy, namely temperature, pressure and fixed elemental (and charge) balances.In the work computational methods and related theory are presented that can be used with a standard Gibbs energy minimiser to solve advanced thermochemical problems. The actual calculations have been performed using the ChemSheet software, but the presentation has aimed to be generic and applicable to other thermochemical codes that allow the user to define thermodynamic data and the stoichiometries of the constituent species in the system.The examples discussed include electrochemical Donnan equilibrium (particularly applied to aqueous pulp suspensions), surface and interfacial energies of liquid mixtures, systems affected by external magnetic fields and systems with time-dependent reaction extents and diffusion-constrained paraequilibrium. A number of practical applications have been achieved with the models that combine reaction kinetics with partial thermodynamic equilibrium calculation and ion exchange models based on Donnan equilibrium, that have both been applied with success in real-life industrial design and development work with multicomponent, multiphase systems. The method has been successfully applied to liquid surface energies of systems with multiple components and complex non-equilibrium data.

Surface and spectroscopic properties of CdSe/ZnS/PVC nanocomposites

It is valuable to understand the way the wettability is affected by the solid and the liquid surface free energies. For this study, transparent films of CdSe/ZnS/PVC nanocomposites have been prepared and characterized by FTIR and contact angle measurements. Moreover, the presence of polar interactions at the liquid/polymer interfaces, which show a proportionality to the polar components of the liquid surface energy for pure polyvinyl chloride (PVC) and all CdSe/ZnS/PVC nanocomposites, is also studied. By using the surface polarizability hypothesis, there is possibility to obtain the dispersion component of surface‐free energies of pure PVC and also its nanocomposites from the contact angles measurement of only polar liquids. This approximately is coincident with that published data for pure PVC obtained from both polar and nonpolar liquids' contact angles. In addition to this, the absorption spectra and the photoluminescence illustrate clearly the effect of CdSe/ZnS quantum dots on their host matrix. The calculated values of the optical parameters, such as energy gap and Urbach energy, illustrate an inverse proportionality between them. POLYM. COMPOS., 38:749–758, 2017. © 2015 Society of Plastics Engineers

A phase-field study on the formation of the intermetallic Al2Au phase in the Al–Au system

The growth mechanism of the intermetallic Al2Au phase in the Al–Au system during the process of soldering is investigated by a multiphase phase-field model. With the aid of the assessed thermodynamic data (Li et al., 2004), the binary phase diagram of the Al–Au system is reconstructed by assuming a regular solution model for the intermetallic Al2Au phase. The simulation setup is composed by placing an Al-liquid droplet on top of an Au-solid substrate. To capture the phase boundary evolution of the droplet and substrate interface with respect to the surrounding vacuum phase, the binary phase diagram is extended to a ternary model system at one particular temperature between the melting points of Al and Au. Due to diffusion of Al and Au at the droplet/substrate interface, intermetallic phase is formed. In simulations, we investigate the lateral and vertical growth velocities of the intermetallic phase as a function of the surface energy of liquid–intermetallic. Further, the instability of the liquid(Al)–solid(Au) interface is analyzed by examining the shrinking speed of the liquid–solid interface affected by the diffusivity of Au.

507 Effects of liquid surface energy on wettability of droplets on inclined low-surface-energy solid

507 Effects of liquid surface energy on wettability of droplets on inclined low-surface-energy solid

Effect of Process Variables on the Grain Size and Crystallographic Texture of Hot-Dip Galvanized Coatings

A galvanizing simulator was used to determine the effect of galvanizing bath antimony (Sb) content, substrate surface roughness, and cooling rate on the microstructural development of metallic zinc coatings. Substrate surface roughness was varied through the use of relatively rough hot-rolled and relatively smooth bright-rolled steels, cooling rates were varied from 0.1 to 10 K/s, and bulk bath Sb levels were varied from 0 to 0.1 wt pct. In general, it was found that increasing bath Sb content resulted in coatings with a larger grain size and strongly promoted the development of coatings with the close-packed {0002} basal plane parallel to the substrate surface. Increasing substrate surface roughness tended to decrease the coating grain size and promoted a more random coating crystallographic texture, except in the case of the highest Sb content bath (0.1 wt pct Sb), where substrate roughness had no significant effect on grain size except at higher cooling rates (10 K/s). Increased cooling rates tended to decrease the coating grain size and promote the {0002} basal orientation. Calculations showed that increasing the bath Sb content from 0 to 0.1 wt pct Sb increased the dendrite tip growth velocity from 0.06 to 0.11 cm/s by decreasing the solid–liquid interface surface energy from 0.77 to 0.45 J/m2. Increased dendrite tip velocity only partially explains the formation of larger zinc grains at higher Sb levels. It was also found that the classic nucleation theory cannot completely explain the present experimental observations, particularly the effect of increasing the bath Sb, where the classical theory predicts increased nucleation and a finer grain size. In this case, the “poisoning” theory of nucleation sites by segregated Sb may provide a partial explanation. However, any analysis is greatly hampered by the lack of fundamental thermodynamic information such as partition coefficients and surface energies and by a lack of fundamental structural studies. Overall, it was concluded that the fundamental mechanisms behind the microstructural development of solidified metallic zinc coatings have yet to be completely elucidated and require further investigation.

Experimental investigation on variations in geometric variables of a droplet on a low-surface-energy solid

The changes in droplet geometry associated with volume change are experimentally investigated focusing on low surface energy solids. In particular, two experiments are performed to confirm the detailed droplet behavior such as the changes in height, radius, and contact angle, on a solid surface for a range of liquid surface energies. The first experiment involves the natural evaporation of droplets; droplet sizes from micrometer to millimeter are investigated. The second involves simply depositing droplets on a solid surface, then withdrawing liquid using a microsyringe. In this experiment, volume change is quantitatively evaluated. Our experimental results reveal details of the variations in droplet geometry among droplet radius, height, contact angle, and surface energy of the liquid.

Theoretical Model of Droplet Wettability on a Low-Surface-Energy Solid under the Influence of Gravity

The wettability of droplets on a low surface energy solid is evaluated experimentally and theoretically. Water-ethanol binary mixture drops of several volumes are used. In the experiment, the droplet radius, height, and contact angle are measured. Analytical equations are derived that incorporate the effect of gravity for the relationships between the droplet radius and height, radius and contact angle, and radius and liquid surface energy. All the analytical equations display good agreement with the experimental data. It is found that the fundamental wetting behavior of the droplet on the low surface energy solid can be predicted by our model which gives geometrical information of the droplet such as the contact angle, droplet radius, and height from physical values of liquid and solid.

SPH BASED OPTIMIZATION OF ELECTROWETTING-DRIVEN DIGITAL MICROFLUIDICS WITH ADVANCED ACTUATION PATTERNS

Fast and thorough mixing is a crucial operation of digital microfluidic devices, where discrete and small fluid portions are moved and processed. In this paper, we want to analyze and to optimize the mixing process by substituting conventional motion and superposing oscillatory and translational modes. An accurate multiphase smoothed particle hydrodynamics (SPH) discretization for incompressible flow is instantiated. Different harmonic excitation patterns for the solid–liquid surface energy are applied and their influence on droplet mode shapes, formation of eddies and the Shannon entropy of droplet fluid components are measured. We tailor enhanced actuation patterns which improve mixing grade and reduce mixing time.

Slip flow of diverse liquids on robust superomniphobic surfaces

Water slips exist over superhydrophobic solid surfaces, but the slip flow of diverse liquids on a single surface has not been deliberately studied to date. Here, we report the slip flow behavior of a variety of liquids with different surface tensions and viscosities on a robust omniphobic surface. This surface displayed a dramatic slippage effect and thus a high drag reduction efficiency of approximately 10–20% for all liquids, depending on both liquid viscosity and surface energy. The observed liquid slip was attributed to the surface dual micro/nanostructure and the low-surface-energy coating.

Nanowire liquid pumps

The ability to form tiny droplets of liquids and control their movements is important in printing or patterning, chemical reactions and biological assays. So far, such nanofluidic capabilities have principally used components such as channels, nozzles or tubes, where a solid encloses the transported liquid. Here, we show that liquids can flow along the outer surface of solid nanowires at a scale of attolitres per second and the process can be directly imaged with in situ transmission electron microscopy. Microscopy videos show that an ionic liquid can be pumped along tin dioxide, silicon or zinc oxide nanowires as a thin precursor film or as beads riding on the precursor film. Theoretical analysis suggests there is a critical film thickness of ∼10 nm below which the liquid flows as a flat film and above which it flows as discrete beads. This critical thickness is the result of intermolecular forces between solid and liquid, which compete with liquid surface energy and Rayleigh-Plateau instability.

On the nucleation rate for the solidification of metals

The classical homogeneous nucleation rate theory for the solidification of metals has been in use for over 50 years, but it is almost universally used incorrectly. Because of this, solid–liquid surface energies calculated from nucleation rate theory are also incorrect. Herein, the correct usage of the homogeneous nucleation rate equation for the solidification of metals is presented. It is shown that because of the assumption of thermodynamic equilibrium, the homogeneous nucleation rate cannot be accurately calculated but is likely in the range 1012–1014s−1. Also, it is shown that the homogeneous nucleation temperature for a pure metal is essentially a material property. Calculations for the solidification of pure Ni are included.