Temperature Dependence Of Surface Tension Research Articles

Identification of surface active components in glass forming melts by thermodynamic model

Nine compositional series of 15(Na2O, K2O)•10(CaO, ZnO)•75(ZrO2, SiO2) glass-forming melts were studied, all with the ZrO2 content of 0, 1, 3, 5 and 7 mol.%. The investigated glass compositions were obtained by equimolar substitutions ZrO2 / SiO2, ZnO / CaO and K2O / Na2O. Surface tension of studied glassforming melts was determined by the sessile and pendant drop profile numerical analysis in the temperature range (1250 - 1500) °C. The experimental values of melt density were used. The linear temperature dependence of surface tension was observed for all samples with only small differences between values obtained from sessile and pendant drop profiles. The Shakhmatkin and Vedishcheva thermodynamic model (TDM) was evaluated for each glass melt at temperature of 1400 °C. The total number of 36 components was considered in TDM. Only 26 components were present with non-negligible equilibrium amount. The surface tension was described by the multilinear function of equilibrium amounts of statistically independent non-negligible components of the TDM. The surface active components were identified by negative values of their coefficients. Such way the N3S8 and C2ZrS4 were identified as “strongly” surface active and NCS5 and KS4 as probably surface active. Regarding the oxide compositional point of view, the surface tension was mostly influenced by ZnO (increase with the addition of the oxide) and by K2O (decrease with the addition of the oxide).

Density and Surface Tension of Fe-Cu Melts

Fe-Cu alloys are used as structural materials for manufacture of large machine parts subjected to shock loads. Fe-Cu alloys have a higher corrosion resistance in a humid atmosphere and in salt solutions than cast steel. Fe-Cu alloys have high enough damping characteristics. Upon cooling the Fe-Cu melts is stratified into two phases before crystallization which in field of gravity are separated by density. It is possible to suppress delamination and obtain a material with structure of a “frozen emulsion” by heating melt to the temperature T* determined for each composition by a specific way. In this paper, we studied surface tension of liquid alloys of Fe-1wt.% Cu, Fe-20wt.% Cu, and Fe-30wt.%Cu in order to determine the temperature T*. For the melt of Fe-20wt.% Cu value T*=1670°C is highest. It is confirmed by results of measuring temperature dependence of surface tension. Temperature dependence of the surface tension Fe-Cu melts is characterized by a positive value of the temperature coefficient of surface tension dσ/dT which is abnormal for metal melts. Experimental data on the density, the surface tension of Fe-Cu liquid alloys have of independent metrological importance for practical foundry.

Sensitivity analysis of Marangoni convection in TiO2–EG nanoliquid with nanoparticle aggregation and temperature-dependent surface tension

The sensitivity analysis of the magnetohydrodynamic thermal Marangoni convection of ethylene glycol (EG)-based titania (TiO2) nanoliquid is carried out by considering the effect of nanoparticle aggregation. The rate of heat transfer is explored by utilizing response surface methodology and estimating the sensitivity of the heat transfer rate toward the effective parameters: radiation parameter (1 ≤ R ≤ 3), magnetic parameter (1 ≤ M ≤ 3) and nanoparticle volume fraction $$(1\% \le \phi \le 5\%$$ ). The heat transfer phenomenon is scrutinized with thermal radiation and variable temperature at the surface. The effective thermal conductivity and viscosity with aggregation are modeled by using the Maxwell–Bruggeman and Krieger–Dougherty models. The governing equations are solved by using the apposite similarity transformations. It is found that when the effect of aggregation is considered, the velocity profile is lower. A positive sensitivity of the Nusselt number toward thermal radiation is observed. Further, a negative sensitivity of the heat transfer rate is observed toward the magnetic field and nanoparticle volume fraction.

Surface tension of binary mixtures composed of N, N-dimethylcyclohexylamine and alcohols at different temperatures

Surface tension (γ) for five binary mixtures containing N, N-dimethylcyclohexylamine (DMCA) and alcohol, ethanol, n-propanol, iso-propanol, n-butanol or iso-butanol were measured over the whole range of composition at 0.1 MPa and different temperatures ranging from (288.15 to 308.15) K. From the experimental data, the surface tension deviations (δγ) for the binary mixtures were calculated. The δγ values are positive for all the studied systems and increase with the decreasing of alky chain length of alcohol. For the mixture containing the branched alkyl alcohol, the increase is significant compared with the equivalent molecules with straight chains. According to temperature dependence of surface tension, the thermodynamic parameters, surface enthalpy (Hγ) and surface entropy (Sγ) were also estimated and further discussed.

Corresponding state principle based correlation for the surface tension of carboxylic acids

Motivated by the recent work by G. Di. Nicola et al. [Fluid Phase Equilibria 417 (2016) 229], based on the DIPPR data for carboxylic acids, we here report a corresponding state based correlation for the temperature dependent surface tension of carboxylic acids fluids. Underneath the two reduced quantities defined here, the DIPPR data show a unique trend. It is found that the proposed correlation can be used for different subfamilies of the carboxylic acids, and can describe the DIPPR data with high accuracy with the absolute average deviation (AAD) less than 1% for 14 carboxylic acids, AAD<2% for 20 carboxylic acids, and AAD<5% for all the 29 carboxylic acids.

Temperature dependences of surface tension, density and viscosity study of Sn-Ag-Cu with Bi additions using theoretical models

In this work, the kohler, Muggianu,Toop and Hillert geometric models were used to calculate the surface tension, molar volume and density of the liquid Sn-Ag-Cu-Bi quaternary alloys along three selected sections xSn:xAg:xCu = 1:1:1, 1:1:2 and 1:2:1 in the temperature range of 923 K–1423 K. The choice of this temperature range was made on the basis of the calculation results of the liquidus line of the alloys belonging to the three sections. The same properties have been estimated for five selected Sn2.7Ag0.86Cu3.86Bi, Sn3.13Ag0.48Cu4.02Bi, Sn2.95Ag0.53Cu6.81Bi, Sn2.68Ag1.01Cu6.62Bi and Sn3.24Ag0.75Cu1.76Bi quaternary alloys between 623 K and 1123 K for comparison with the available experimental data. Moreover, the surface tension and density of these five alloys have also been calculated on the basis of Guggenheim and theoretical equation, respectively. In addition, the Seetharaman-sichen and Kaptay equations were extended to estimate the viscosity of SAC + Bi alloys. We also discussed the influence of Bismuth addition in liquid Sn-Ag-Cu-Bi. Estimated values show that Bi increases molar volume and density but decreases the surface tension and viscosity. On the other hand, the surface tensions diminish with the temperature for the all studied models, with the exception of some concentration of Bismuth; an inverse tendency is observed (dσ/dT) > 0. While, the density diminishes with increasing temperature for all alloys (dσ/dT) < 0. These models have been shown to be a great alternative for calculating the thermo-physical properties of quaternary systems.

Rayleigh-Benard-Marangoni Ferro Convection with Concentration and Temperature Dependent Viscosity

The inception of Rayleigh-Benard-Marangoni (RBM) Ferro convection with concentration and temperature dependent viscosity is investigated theoretically and the resultant is further enhanced numerically using Galerkin method. We observed that the effect of Rayleigh number together with internal heating suppressed the onset of RBM Ferro convection. The nonlinear nature of magnetic fluid parameter has no impact on the onset of Ferro convection. The latent values found numerically by Galerkin weighted Residual technique and regular perturbation technique are found to be alike, indicating the fact that the obtained solutions are near exact in nature. The result of the BC’s for lower and upper free rigid boundary at temperature dependent surface tension forces are found to be immaculately insulate to temperature perturbation.

Influence of laser energy distribution on laser surface microstructure processing

Laser surface microstructure can improve the friction properties, biomedical properties and optical properties of materials. In this paper, a two-dimensional finite element model based on temperature-dependent surface tension is proposed to study the effects of different laser energy density distributions on surface morphology. The results show that: when the laser energy density is applied to the molten pool under the Gaussian distribution and uniform distribution, respectively, the peak temperature of the molten pool surface is varied, and the difference of temperature gradient leads to the changes of surface tension. As the surface topography is mainly affected by the surface tension, different laser energy densities will produce different surface topography, therefore, its analysis will help us understand the formation mechanism of laser surface microstructures.

Healing of thermocapillary film rupture by viscous heating

Thin liquid films sitting on a heated solid substrate and surrounded by a colder ambient gas phase are strongly affected by surface-shear stresses induced by surface tension and temperature gradients, as well as by viscous and capillary forces. The temperature dependence of surface tension may lead to thinning of liquid-film depressions promoting instability which takes place when a critical temperature difference $\unicode[STIX]{x0394}\unicode[STIX]{x1D717}_{cr}$ between the substrate and the ambient gas phase is exceeded. In this article we show theoretically that viscous heating, previously neglected in related literature, may delay or suppress the thermocapillary instability and leads to film healing. The viscous heating effect, by inhibiting heat transfer, prevents the system from reaching the critical value $\unicode[STIX]{x0394}\unicode[STIX]{x1D717}_{cr}$ required to bring about instability. As a consequence, the system remains within the stability region, suppressing film rupture. The presence of the viscous heating effect leads to a persistent circulating motion of two counter-rotating vortices lying diametrically opposite to a depression of the liquid–gas interface reducing the wavelength of disturbances to one half of its initial value. This effect has yet to be observed in experiment.

Surface tension in bulk and bounded liquids

The paper is aimed at theoretical studying the following problems and its relation to the available experimental data: 1) the coefficient of surface tension and capillary constant in bulk and spatially bounded liquids in a wide range of thermodynamic parameters (temperature, density, pressure, etc.), including the critical region; 2) influence of size effects on surface tension and capillary constant in liquids with a varying spatial dimensionality, namely from the “surface” 2D-state to the “bulk” 3D-state, and then to regular 4D-state where the fluctuation effects may be neglected in liquids like water with the Ginzburg number, Gi < 1; 3) comparison the obtained results and empirical approach to the water surface tension in a wide intervals of thermodynamic variables, including confined supercooled water; 4) medical application of results for surface tension, using similarity between processes of carcinogenesis and nucleation.The theoretical formulas are proposed for dependence of surface tension and capillary constant in bulk and confined liquids on temperature, density, pressure, and size variables in a wide vicinity of the critical region. The agreement of theoretical and experimental data for the temperature dependence of surface tension and capillary constant appears to be quite satisfactory. The 2D↔3D dimensional crossover for surface tension and capillary constant is analyzed. The surface tension of liquids with a relatively small Ginzburg number, including bulk water, is studied with taking into account the dimensionality crossover from 3D-systems to 4D-systems, where the Landau mean-field theory is valid. The empirical formula for surface tension of pure water is discussed together with the Tolman correction and the fluctuation theory of phase transitions. The consequences of the similarity hypothesis of nucleation and carcinogenesis are discussed.

Experimental verification of anomalous surface tension temperature dependence at the interface between coexisting liquid-gas phases in magnetic and Stockmayer fluids

Our early experimental investigation has demonstrated the anomalous surface tension temperature dependence σ(T) at the interface between coexisting liquid-gas phases in magnetic fluids that undergo field-induced first-order phase transition. The σ(T) dependence is anomalous because the drops of a liquid phase condensed under the action of the applied magnetic field H at high temperature T2 exhibit larger surface tension σ(T2) &amp;gt; σ(T1) than the drops condensed at low temperature T1 &amp;lt; T2. This study verifies and confirms the results of the previous experimental investigation of σ(T) in magnetic fluids by performing the experiment, which is based on the analysis of the Plateau-Rayleigh instability of a gas-liquid interface in a zero magnetic field. A novel explanation of this phenomenon is given in the framework of the Stockmayer model. The anomalous increase in σ(T) is explained by the increase in particle concentration difference in gas and liquid phases, which can be attributed to the high field intensity H needed to generate the phase transition at high temperature.

Estimation of the critical temperatures of alkaline metals on the basis of specified data on surface tension polytherms

The critical temperatures of alkali metals are calculated on the basis of refined data on temperature dependences of surface tension of alkali metals approximated with linear equations. It is shown that the calculated values of the critical temperatures of alkali metals are in satisfactory agreement with the experimental results and theoretical calculations available in the literature.

Revealing internal flow behaviour in arc welding and additive manufacturing of metals

Internal flow behaviour during melt-pool-based metal manufacturing remains unclear and hinders progression to process optimisation. In this contribution, we present direct time-resolved imaging of melt pool flow dynamics from a high-energy synchrotron radiation experiment. We track internal flow streams during arc welding of steel and measure instantaneous flow velocities ranging from 0.1 m s−1 to 0.5 m s−1. When the temperature-dependent surface tension coefficient is negative, bulk turbulence is the main flow mechanism and the critical velocity for surface turbulence is below the limits identified in previous theoretical studies. When the alloy exhibits a positive temperature-dependent surface tension coefficient, surface turbulence occurs and derisory oxides can be entrapped within the subsequent solid as result of higher flow velocities. The widely used arc welding and the emerging arc additive manufacturing routes can be optimised by controlling internal melt flow through adjusting surface active elements.

Thermocapillary instability of self-rewetting films on vertical fibers

The self-rewetting fluid has a quadratic temperature dependence of surface tension with a well-defined minimum, which is distinct from that of normal fluids whose surface tension decreases linearly with temperature. The instability of a self-rewetting film on a vertical hot or cold fiber is investigated using the long-wave asymptotic model, which discovers that the role of the thermocapillarity varies in three different regimes. In the normal regime, the behavior of this fluid is similar to that of a normal fluid while in another anomalous regime, it shows a reverse feature of instability. It is this reverse behavior that guarantees the potentials of this fluid in heat transfer applications. Transient numerical simulations are also performed to be compared with the linear theory and to explore the saturate states as well as the breakup for this special fluid. Apart from supporting the conclusions obtained in the linear analysis, noticeably, the numerical results predict a flatter saturate shape and a weaker breakup in the anomalous regime.

A numerical study of buoyancy-Marangoni convection of volatile binary fluids in confined geometries

A horizontal temperature gradient can cause a flow in a layer of liquid with a free surface via several different mechanisms. The most universal one is due to thermocapillary stresses that arise due to the temperature dependence of surface tension. For binary liquids, the flow can also be driven by solutocapillary stresses that arise due to the dependence of surface tension on the composition of the liquid. For some binary liquids, such as water-alcohol mixtures, solutocapillary stresses are primarily due to phase change (e.g., differential evaporation or condensation of the two components), and these two mechanisms can counteract each other. A recent experimental study (Li and Yoda, 2016) has demonstrated that the flow direction can be reversed by changing the amount of air present inside the experimental apparatus. To understand how the presence of air affects the interfacial stresses, we have developed and implemented numerically a comprehensive two-sided transport model, which accounts for transport of heat, mass, and momentum in both phases and phase change across the interface and is able to reproduce the experimental results. The detailed analysis of these results shows that air tends to suppress phase change and hence solutocapillary stresses. Removing the air enhances phase change, instead suppressing the variation in the interfacial temperature and hence thermocapillary stresses.

Some aspects of the surface tension temperature dependence of drop-like aggregates in magnetic fluids

Some aspects of the surface tension temperature dependence of drop-like aggregates in magnetic fluids

Effects of phosphorus and carbon content on the surface tension of FeSiBPC glass-forming alloy melts

Phosphorus and carbon content and temperature dependence of surface tension for FeSiBPC alloy melts were investigated by sessile drop method. The surface tension of investigated alloy melts decreased firstly approaching the minimum near 1325 °C, and subsequently increased with raising temperature. The contact angle monotonously decreased with increasing temperature. The surface tension was weakened by the addition of phosphorus and carbon elements in FeSiB-based alloy. The wettability of the melt on the ceramic substrate was improved by the increase of carbon amount. These phenomena above were further analysed and discussed in relation to the cluster interaction, and chemical interaction between the melt and the ceramic substrate. It provides theoretical reference for the metallurgical preparation of Fe-based amorphous alloys.

A novel method for the surface tension estimation of ionic liquids based on COSMO-RS theory

In the presented study, COSMO-RS sigma moments were utilized in a nonlinear multivariate QSPR model for the estimation of the temperature dependent surface tension of various ionic liquids in wide surface tension (15.5–65.1 mN m−1) and temperature (268–533 K) range. The developed model is supposed to be a generally applicable, robust and accurate method for the prediction of ionic liquid's surface tension. 880 data points ensure its reliability, which values were used to establish, validate and test the method. An artificial neural network was developed, optimized and used as regression model. The prediction power of the proposed model was validated with an external data set, with a squared correlation coefficient R2 = 0.97 and a mean absolute error MAE = 1 mN m−1. The estimation ability of the model was compared against widely known methods. Furthermore, the factor sensitivity analyses of the utilized molecular descriptors allowed shedding light on the intermolecular basis of ionic liquid's surface tension. Results showed that the kind of skewness of the sigma profile, the electrostatic interaction energy and the hydrogen bonding acceptor function play the most important roles in the formation of ionic liquid's surface tension.

The Temperature and Structure Dependence of Surface Tension of CaO-SiO2-Na2O-CaF2 Mold Fluxes

The surface tension of mold flux is one of the most important properties and varies with the temperature from the top to the bottom of the mold, which influences the adhesion and lubrication between the liquid mold flux and the solidified shell, further influencing the quality of the continuous billet. In the present paper, the effect of temperature on the surface tension of CaO-SiO2-Na2O-CaF2 mold-flux melts with different CaO/SiO2 mass ratios was investigated using the maximum-pull method. Furthermore, the microstructure of mold fluxes was analyzed using FT-IR and Raman spectra to discuss the change mechanism of surface tension. The results indicated that the temperature dependence of surface tension was different with different CaO/SiO2 mass ratios, and agreed with the modification of melt structure. When the CaO/SiO2 mass ratio was 0.67 and 0.85, the change of surface tension with temperature was relatively stable, and the influence of temperature on the structure was small. When the CaO/SiO2 mass ratio was 1.03 and 1.16, with an increase of temperature, the surface tension decreased linearly and the changing amplitude was large; the degree of polymerization of melts and average radii of silicon-oxygen anions also decreased, which intensified the molecular thermal motion and weakened the intermolecular interaction, resulting in a decrease of surface tension of melts.

Nonisothermal Spreading Dynamics of Self-Rewetting Droplets.

We experimentally studied the spreading dynamics of binary alcohol mixtures (and pure liquids for reference) deposited on a heated substrate in a partially wetting situation under nonisothermal conditions. We show that the spreading mechanism of an evaporating droplet exhibits a power-law growth with early-stage exponents that depend strongly and nonmonotonically on the substrate temperature. Moreover, we investigated the temporal and spatial thermal dynamics in the droplet using infrared thermography, revealing the existence of unique thermal patterns due to thermal and/or solutal instabilities, which lead to surface tension gradients, namely the Marangoni effect. Our key findings are that the temperature of the substrate drastically affects the early-stage inertial-capillary spreading regime owing to the nonmonotonic surface tension-temperature dependence of the self-rewetting liquids. At later stages of wetting, the spreading dynamics enters the viscous-capillary dominated regime, with the characteristic low kinetics mirroring the behavior of pure liquids.