Prediction of surface and interfacial tension based on thermodynamic data and CALPHAD approach

In this article, following a brief introduction concerning experimental measurements of surface and interfacial tensions, methods for calculating surface tension and surface segregation for binary, ternary, and multicomponent high-temperature melts based on Bulter＇s original treatment [ 1] and on available physical properties and thermodynamic data, especially excess Gibbs free energies of bulk phase and surface phase versus temperature obtained from thermodynamic databases using the calculation of phase diagram （CALPHAD） approach, with special attention to the model parameter β, have been described. In addition, the geometric models can be extended to predict surface tensions of multicom- ponent systems from those of sub-binary systems. For illustration, some calculated examples, including Pb-free soldering systems and phase-diagram evaluation of binary alloys in nanoparticle systems are given. On the basis of surface tensions of high-temperature melts, interracial tensions between liquid alloy and molten slag as well as molten slag and molten matter can be calculated using the Girifalco-Good equation [2]. Modifications are suggested in the Nishizawa＇s model [3] for estimation of interracial tension in liquid metal （A）/ceramics （MX） systems so that the calculations can be carried out based on the sublattice model and thermodynamic data, without deliberately differentiating the phase of MX at high temperature. Finally, the derivation of an approximate expression for predicting interfacial tension between the high-temperature multicomponent melts, employing Becker＇s model [4] in conjunction with Bulter＇s equation and inteffacial tension data of the simple systems is described, and some examples concerning pyrometallurgical systems are given for better understanding.

Interactions of ferro-nanoparticles(hematite and magnetite) with reservoir sandstone: implications for surface adsorption and interfacial tension reduction

There are a few studies on the use of ferro-nanofluids for enhanced oil recovery,despite their magnetic properties;hence,it is needed to study the adsorption of iron oxide(Fe2 O3 and Fe3 O4) nanoparticles(NPs) on rock surfaces.This is important as the colloidal transport of NPs through the reservoir is subject to particle adsorption on the rock surface.Molecular dynamics simulation was used to determine the interfacial energy(strength) and adsorption of Fe2 O3 and Fe3 O4 nanofluids infused in reservoir sandstones.Fourier transform infrared spectroscopy and X-ray photon spectroscopy(XPS) were used to monitor interaction of silicate species with Fe2 O3 and Fe3 O4.The spectral changes show the variation of dominating silicate anions in the solution.Also,the XPS peaks for Si,C and Fe at 190,285 and 700 eV,respectively,are less distinct in the spectra of sandstone aged in the Fe3 O4 nanofluid,suggesting the intense adsorption of the Fe3 O4 with the crude oil.The measured IFT for brine/oil,Fe2 O3/oil and Fe3 O4/oil are 40,36.17 and 31 mN/m,respectively.Fe3 O4 infused with reservoir sandstone exhibits a higher silicate sorption capacity than Fe2 O3,due to their larger number of active surface sites and saturation magnetization,which accounts for the effectiveness of Fe3 O4 in reducing IFT.

SURFACE TENSION OF MOLTEN IF STEEL CONTAINING Ti AND ITS INTERFACIAL PROPERTIES WITH SOLID ALUMINA

Surface tension of molten IF steel containing Ti and contact angle between the liquid steel and solid alumina were measured with sessile droplet method under Ar gas atmosphere at 1500, 1575 and 1600°C. The results show that titanium decreases the surface tension of the molten IF steel and the contact angle. The interfacial tension between the molten IF steel containing Ti and solid alumina decreases with increase in titanium content. The work of adhesion between molten IF steel containing Ti and solid alumina decreases slightly at 1550°C, but increases at 1600°C with increasing titanium content. It can be deduced that fine bubbles and fine alumina inclusions are easily entrapped in solidifying interface for IF steel containing Ti.

Molecular design and applications of a nanostructure green Tripodal surface active ionic liquid in enhanced oil recovery: Interfacial tension reduction, wettability alteration, and emulsification

Surface active ionic liquids (SAILs) are considered as prominent materials in enhanced oil recovery thanks to their high interfacial activity. This study reports the preparation and applications of a nanostructure Tripodal imidazolium SAIL as an environmentally-friendly substitute to the conventional surfactants. The product has a star-like molecular structure centered by a triazine spacer, namely [(C_(4)im)_(3)TA][Cl_(3)], prepared by a one-step synthesis method and characterized with FT-IR, NMR, XRD, and SEM analysis methods. The interfacial tension of the system was decreased to about 78% at critical micelle concentration of less than 0.08 mol·dm^(−3). Increasing temperature, from 298.2 to 323.2 K, improved this capability. The solid surface wettability was changed from oil-wet to water-wet and 80% and 77% stable emulsions of crude oil–aqueous solutions were created after one day and one week, respectively. Compared to the Gemini kind homologous SAILs, the superior effects of the Tripodal SAIL were revealed and attributed to the strong hydrophobic branches in the molecule. The Frumkin adsorption isotherm precisely reproduced the generated IFT data, and accordingly, the adsorption and thermodynamic parameters were determined.

Characterization on Surface and Interfacial Properties of Nitramine Crystal Fillers and Polymeric Bonding Agents

The surface and interfacial properties of polymeric bonding agents and nitramine crystal fillers were studied. The surface free energy and adhesion work of polymeric bonding agents and nitramine fillers were calculated by using Kaeble′s equations. It was observed that the hydroxyl values of neutral polymeric bonding agents (NPBA) correlate well with the polar components of surface free energies. On the basis of the measurements of swelling ratio and initial modulus, the interfacial bonding through highly crosslinked polymeric shell formation around the nitramine particles and generating interfacial reinforcement were rationalized. The application of Tapping Mode AFM (atomic force micro scope) to observing the surface morphology of NPBA reveals that methyl acrylate monomer appears to play a role for aiding the formation of network like structure when nanometer scale images of NPBA are created.

Impact of ethanol on the flotation efficiency of imidazolium ionic liquids as collectors:Insights from dynamic surface tension and solvation analysis

To conduct extensive research on the application of ionic liquids as collectors in mineral flotation,ethanol(EtOH)was used as a solvent to dissolve hydrophobic ionic liquids(ILs)to simplify the reagent regime.Interesting phenomena were observed in which EtOH exerted different effects on the flotation efficiency of two ILs with similar structures.When EtOH was used to dissolve 1-dodecyl-3-methylimidazolium chloride(C12[mim]Cl)and as a collector for pure quartz flotation tests at a concentration of 1×10^(−5)mol·L^(−1),quartz recovery increased from 23.77%to 77.91%compared with ILs dissolved in water.However,quartz recovery of 1-dodecyl-3-methylim-idazolium hexafluorophosphate(C12[mim]PF6)decreased from 60.45%to 24.52%under the same conditions.The conditional experi-ments under 1×10^(−5)mol·L^(−1)ILs for EtOH concentration and under 2vol%EtOH for ILs concentration confirmed this difference.After being affected by EtOH,the mixed ore flotation tests of quartz and hematite showed a decrease in the hematite concentrate grade and re-covery for the C12[mim]Cl collector,whereas the hematite concentrate grade and recovery for the C12[mim]PF6 collector increased.On the basis of these differences and observations of flotation foam,two-phase bubble observation tests were carried out.The EtOH promoted the foam height of two ILs during aeration.It accelerated static froth defoaming after aeration stopped,and the foam of C12[mim]PF6 de-foaming especially quickly.In the discussion of flotation tests and foam observation,an attempt was made to explain the reasons and mechanisms behind the diverse phenomena using the dynamic surface tension effect and solvation effect results from EtOH.The solva-tion effect was verified through Fourier transform infrared(FT-IR),X-ray photoelectron spectroscopy(XPS),and Zeta potential tests.Al-though EtOH affects the adsorption of ILs on the ore surface during flotation negatively,it holds an positive value of inhibiting foam mer-ging during flotation aeration and accelerating the defoaming of static foam.And induce more robust secondary enrichment in the mixed ore flotation of the C12[mim]PF6 collector,facilitating effective mixed ore separation even under inhibitor-free conditions.

Eudragit®-PEG Nanoparticles: Physicochemical Characterization and Interfacial Tension Measurements

The objectives of this study are to understand the mechanisms involved in the stabilization of water/oil interfaces by polymeric nanoparticles (NPs) (Eudragit®). Eudragit L100 NPs of various sizes and Zeta potentials were studied and compared at a water/cyclohexane model interface using a droplet tensiometer (Tracker Teclis, Longessaigne, France). The progressive interfacial adsorption of the NPs in the aqueous phase was monitored by tensiometry. The model interface was maintained and observed in a drop tensiometer, analyzed via axisymmetric drop shape analysis (ADSA), to determine the interfacial properties. Given the direct relationship between the stability of Pickering emulsions (emulsions stabilized by solid nanoparticles) and the interfacial properties of these layers, different nanoparticle systems were compared. Specifically, Eudragit NPs of different sizes were examined. Moreover, the reduction of the Zeta potential with PEG-6000 induces partial aggregation of the NPs (referred to as NP flocs), significantly impacting the stability of the interfacial layer. Dynamic surface tension measurements indicate a significant decrease in interfacial tension with Eudragit® nanoparticles (NPs). This reduction correlates with the size of the NPs, highlighting that this parameter does not operate in isolation. Other factors, such as the contact angle and wettability of the nanoparticles, also play a critical role. Notably, larger NPs further diminished the interfacial tension. This study enhances our understanding of the stability of Pickering emulsions stabilized by Eudragit® L100 polymeric nanoparticles.

Effect of active species in crude oil on the interfacial tension behavior of alkali/synthetic surfactants/crude oil systems

The effect of active species present in crude oil on the interfacial tension （IFT） behavior of alkali/synthetic surfactants/crude oil systems was studied. The system consisted of heavy alkyl benzene sulfonate, sodium chloride, sodium hydrate and Daqing crude oil. Experimental results indicated that active species would diffuse from oil/aqueous interface to aqueous phase and finally an equilibrium could be reached in the system with increasing contact time. Moreover, the minimum IFT and equilibrium IFT values increased with increasing contact time and a linear relationship existed between dynamic IFT and f^-1/2 when IFT value approaching the minimum and after the minimum IFT was reached. This indicated that the dynamic IFT-time behavior was diffusion controlled. The oil and aqueous phases were analyzed by infrared （IR） spectroscopy. IR spectra of oil and aqueous phases illustrated that the content of active species in the oil phase decreased, but the content of active species in the aqueous phase increased after alkali reacted with crude oil. This indicated that the active species present in oil played an important role in reducing IFT.

Interfacial phenomena of water striders on water surfaces: a review from biology to biomechanics

Water striders have intrigued researchers for centuries from the viewpoints of biology to biomechanics. In this review, we introduce the basic theories and techniques of physics and force measurement for biomechanical research into water striders. Morphological and behavioral traits of water striders are summarized and discussed from biomechanical perspectives, along with comparative study. This integrated review also highlights potential directions for studies on water-walking arthropods,which might inspire future biological and biomechanical research.

Hydration film measurement on mica and coal surfaces using atomic force microscopy and interfacial interactions

The hydration film on particle surface plays an important role in bubble-particle adhesion in mineral flotation process. The thicknesses of the hydration films on natural hydrophobic coal and hydrophilic mica surfaces were measured directly by atomic force microscopy （AFM） based on the bending mode of the nominal constant compliance regime in AFM force curve in the present study. Surface and solid-liquid interfacial energies were calculated to explain the forming mechanism of the hydration film and atomic force microscopy data. The results show that there are significant differences in the structure and thickness of hydration films on coal and mica surfaces. Hydration film formed on mica surface with the thickness of 22.5 nm. In contrast, the bend was not detected in the nominal constant compliance regime. The van der Waals and polar interactions between both mica and coal and water molecules are characterized by an attractive effect, while the polar attractive free energy between water and mica （-87.36 mN/m） is significantly larger than that between water and coal （-32.89 mN/m）, which leads to a thicker and firmer hydration layer on the mica surface. The interfacial interaction free energy of the coal/water/bubble is greater than that of mica. The polar attractive force is large enough to overcome the repulsive van der Waals force and the low energy barrier of film rupture, achieving coal particle bubble adhesion with a total interfacial free energy of-56.30 mN/m.

Atomistic calculations of surface and interfacial energies of Mg_(17)Al_(12)-Mg system

It is well known that precipitation hardening in magnesium(Mg)alloys is far less effective than in aluminum alloys.Thus,it is important to understand the surface and interfacial structure and energetics between precipitates and matrix.In upscale modeling of magnesium alloys,these energy data are of great significance.In this work,we calculated the surface and interfacial energies of Mg_(17)Al_(12)-Mg system by carefully selecting the surface or interface termination,using atomistic simulations.The results show that,the higher fraction of Mg atoms on the surface,the lower the surface energy of Mg_(17)Al_(12).The interfacial energy of Mg/Mg_(17)Al_(12)was calculated in which the Burgers orientation relationship(OR)was satisfied.It was found that the(011)P|(0002)Mg interface has the lowest interfacial energy(248 mJ/m 2).Because the Burgers OR breaks when{10¯12}twin occurs,which reorients the matrix,the interfacial energy for Mg_(17)Al_(12)and a{10¯12}twin was also calculated.The results show that after twinning,the lowest interfacial energy increases by 244 mJ/m^(2),and the interface becomes highly incoherent due to the change in orientation relationship between Mg_(17)Al_(12)and the matrix.

Third-Order Stokes Wave Solutions of the Free Surface Capillary- Gravity Wave and the Interfacial Internal Wave

Based on the Stokes wave theory, the capillary-gravity wave and the interfacial internal wave in two-layer constant depth＇s fluid system are investigated. The fluids are assumed to be incompressible, inviscid and irrotational. The third-order Stokes wave solutions are given by using a perturbation method. The results indicate that the third-order solutions depend on the surface tension, the density and the depth of each layer. As expected, the first-order solutions are the linear theoretical results （the small amplitude wave theoretical results）. The second-order and the third-order solutions describe the nonlinear modification and the nonlinear interactions. The nonlinear impact appears not only in the n （n〉~2） times＇ high frequency components, but also in the low frequency components. It is also noted that the wave velocity depends on the wave number, depth, wave amplitude and surface tension.

Spatial interfacial heat transfer and surface characteristics during gravity casting of A356 alloy

As one of the key boundary conditions during casting solidification process, the interfacial heat transfer coefficient (IHTC) affects the temperature variation and distribution. Based on the improved nonlinear estimation method (NEM), thermal measurements near both bottom and lateral metal-mold interfaces throughout A356 gravity casting process were carried out and applied to solving the inverse heat conduction problem (IHCP). Finite element method (FEM) is employed for modeling transient thermal fields implementing a developed NEM interface program to quantify transient IHTCs. It is found that IHTCs at the lateral interface become stable after the volumetric shrinkage of casting while those of the bottom interface reach the steady period once a surface layer has solidified. The stable value of bottom IHTCs is 750 W/(m^2·℃), which is approximately 3 times that at the lateral interface. Further analysis of the interplay between spatial IHTCs and observed surface morphology reveals that spatial heat transfer across casting-mold interfaces is the direct result of different interface evolution during solidification process.

Synthesis of Petroleum Sulfonate Surfactant with Ultra-Low Interfacial Tension in Rotating Packed Bed Reactor

Petroleum sulfonate is one of the most important surfactants used in surfactant flooding for enhanced oil recovery, which is mainly obtained by treating high-boiling petroleum fractions in a stirred tank reactor(STR) or in a fallingfilm reactor(FFR). The synthesis of petroleum sulfonate with ultra-low interfacial tension from viscous petroleum fractions was carried out in a rotating packed bed(RPB) reactor using dilute liquid sulfur trioxide as the sulfonating agent in this study. The effects of various experimental conditions on components content and oil-water interfacial tension(IFT) were investigated. Under the optimum conditions, the active matter content could reach up to 50.3% and the IFT could be equal to 4.7×10-3 m N/m. Compared with the traditional reactor, the active matter content is by 14.12% higher in the RPB as compared to that obtained in the STR. The uneven change of the test oil droplets during the IFT measurement was also discussed. The increase of heavy components content not only can eliminate the contraction phenomenon, but also can reduce the IFT to a minimum. This can be conducive to explaining the reason for producing IFT and the preparation of proper formulations for practical application.

Surface assembly of cobalt species for simultaneous acceleration of interfacial charge separation and catalytic reactions on Cd_(0.9)Zn_(0.1)S photocatalyst

Although photocatalytic water splitting has excellent potential for converting solar energy into chemical energy,the challenging charge separation process and sluggish surface catalytic reactions significantly limit progress in solar energy conversion using semiconductor photocatalysts.Herein,we demonstrate a feasible strategy involving the surface assembly of cobalt oxide species(CoO_(x))on a visible-light-responsive Cd_(0.9)Zn_(0.1)S(CZS)photocatalyst to fabricate a hierarchical CZS@CoO_(x) heterostructure.The unique hierarchical structure effectively accelerates the directional transfer of photogenerated charges,reducing charge recombination through the smooth interfacial heterojunction between CZS and CoO_(x),as evidenced by photoluminescence(PL)spectroscopy and various electrochemical characterizations.The surface cobalt species on the CZS material also act as efficient cocatalysts for photocatalytic hydrogen production,with activity even higher than that of noble metals.The well-defined CZS@CoO_(x) heterostructure not only enhances the interfacial separation of photoinduced charges,but also improves surface catalytic reactions.This leads to superior photocatalytic performances,with an apparent quantum efficiency of 20%at 420 nm for visible-light-driven hydrogen generation,which is one of the highest quantum efficiencies measured among noble-metal-free photocatalysts.Our work presents a potential pathway for controlling complex charge separation and catalytic reaction processes in photocatalysis,guiding the practical development of artificial photocatalysts for successful transformation of solar to chemical energy.

Adjusting the interfacial adhesion via surface modification to prepare high-performance fibers

Ultra-high molecular weight polyethylene(UHMWPE)fiber is a new kind of high-performance fiber.Due to its excellent physical and chemical characteristics,it is widely used in various fields.However,the surface UHMWPE fiber is smooth and demonstrates no-polar groups.The weak interfacial adhesion between fiber and resin seri-ously restricts the applications of UHMWPE fiber.Therefore,the surface modification treatments of UHMWPE fiber are used to improve the interfacial adhesion strength.The modified method by adding nanomaterials elu-cidates the easy fabrication,advanced equipment and proper technology.Thus,the progress of UHMWPE nanocomposite fibers prepared via adding various nanofillers are reviewed.Meanwhile,the effects of other various methods on surface modification are also reviewed.This work advances the various design strategies about nano technologies on improving interfacial adhesion performance via treatment methodologies.

Interfacial behaviors of epoxy asphalt surfacing on steel decks

A model for predicting the interface behavior of epoxy asphalt and steel composite beam under negative bending is developed incorporating partial interaction theory. Interfacial slips between the steel deck and the epoxy asphalt surfacing are included in the model with a new parameter of membrane stiffness. A series of analytical equations based on this model are derived to calculate slip and strain at the interface. Also, a numerical procedure for calculating the load responses of simply supported composite beams with concentrated force at the mid-span is established and verified with two samples. Characters of slip and strain at the interface, sensitivities of tensile stress and interface shear stress with material parameters are studied. It can be concluded that interfacial effects decrease the bending stiffness of the composite; hard and stiff bonding material is better for asphalt surfacing layer working at normal to low temperatures, and the damage of the asphalt surfacing layer will be accelerated with the damage accumulation of the bonding coat.

Calculating models on surface tension of RE_2O_3-Mg O-SiO_2(RE=La, Nd, Sm, Gd and Y) melts

A thermodynamic model was developed for determining the surface tension of RE2O3-MgO-SiO2(RE=La, Nd, Sm, Gd and Y) melts considering the ionic radii of the components and Butler's equation. The temperature and composition dependence of the surface tensions in molten RE2O3-MgO-SiO2 slag systems was reproduced by the present model using surface tensions and molar volumes of pure oxides, as well as the anionic and cationic radii of the melt components. The iso-surface tension lines of La2O3-MgO-SiO2 slag melt at 1873 K were calculated and the effects of slag composition on the surface tension were also investigated. The surface tensions of La2O3, Gd2O3, Nd2O3 and Y2O3 at 1873 K were evaluated as 686, 677, 664 and 541 m N/m, respectively. The surface tension of pure rare earth oxide melts linearly decreases with increasing cationic field strength, except for Y2O3 oxide, while Y2O3 has a much weaker surface tension. The evaluated results of the surface tension show good agreements with literature data, and the mean deviation of the present model is found to be 1.05% at 1873 K.

Calculation Model for Surface Tension of Slag Melt

Based on the coexistence theory of slag melt structure and Butler’s equation,a new calculation model has been proposed for the calculation of surface tension of slag melt.This model establishes a specific correlation between surface tension and mass action concentrations(activities) in the melt and on its surface on the basis of inner and surficial structures of slag melt.Calculated surface tensions of CaO-SiOand MnO-SiOslag melts are consistent with those measured.Furthermore,iso-surface tension lines of CaO-MnO-SiOslag melt have also been calculated.

Modeling bubble column reactor with the volume of fluid approach:Comparison of surface tension models

This work aims at comparing surface tension models in VOF(Volume of Fluid) modeling and investigating the effects of gas distributor and gas velocity. Hydrodynamics of a continuous chain of bubbles inside a bubble column reactor was simulated. The grid independence study was first conducted and a grid size of 1.0 mm was adopted in order to minimize the computing time without compromising the accuracy of the results. The predictions were validated by comparing the experimental studies reported in the literature. It was found that all surface tension models can describe the bubble rise and bubble plume in a column with slight deviations.