The surface tensions of indium and cadmium

The surface tensions of 99.9999 pct In and Cd have been measured by the sessile drop method. The surface tension/temperature behavior of liquid indium is nonlinear and within a certainty of 99.5 pct, can be represented by the following quadratic equation:γ _In = 568.0 − 0.04t − 7.08 × 10⁻⁵ t ² ± 5 dyne per cm At its melting point, the surface tension of liquid indium is 560 ± 5 dyne per cm. The slope of the temperature coefficient of the surface tension of liquid cadmium is strongly positive at the melting point, becomes zero about 100°C above the melting temperature (at which point the surface tension is a maximum), and is negative at higher temperatures. At the melting point, the surface tension of cadmium is 590 ± 5 dyne per cm. The surface tension of cadmium is not as readily affected by nonequilibrium thermal conditions as is the surface tension of zinc. The form of the surface tension/temperature curve of indium and cadmium together with similar data for Zn, Cu, Pb, and Sn support a theoretical scheme which generalizes liquid metal surface tension behavior and which, on the basis of calculations, lists liquid metals according to their propensity for surface ordering.     

Comparison of Surface Tension Measured Values for Molten Tin at Different Oxygen Potentials

The surface tension of molten tin has been determined by a set of a self‐developed digital equipment with the sessile drop method at an oxygen partial pressure of 1.0×10^?6 MPa at different temperatures. The dependence of surface tension of molten tin on temperature was discussed as well. Based on the summarized relationships of the surface tension of molten tin to temperature and oxygen partial pressure reported in the literature, the reasons for the differences in those reported data were analysed. The emphasis was placed on the comparison of surface tension of the same molten tin sample measured by using different equipments according to the sessile drop method. Results of the comparison indicate that the measurement results obtained with the sessile drop method under similar experimental conditions are coincident, and the self‐developed digital equipment for surface tension measurement has a higher stability and accuracy. The relationships of surface tension of molten tin and its temperature coefficient with temperature and oxygen partial pressure were also elucidated from the thermodynamic analysis in this paper.     

Surface tension measurements on pure liquid iron and nickel by an oscillating drop technique

A novel experimental technique for the measurement of surface tension of molten metals has been developed. It is based on the Rayleigh equation which relates frequency and surface tension for an oscillating drop. A systematic study has shown this equation to be valid for a liquid metal droplet levitated electromagnetically in an inert flowing gas with no prior calibration required. It is, therefore, an absolute method. The frequencies of oscillation of droplets of pure iron and nickel in a 6 pct H₂-He gas mixture were measured by high speed cinematography. Surface tensions were obtained for temperatures of 1550° to 1780°C for iron and 1475° to 1650°C for nickel. M. E. FRAZER, Formerly Graduate Student, Department of Metallurgy and Materials Science, McMaster University, Hamilton, Ontario, Canada.     

Measurement of the density and surface tension of Ni-based superalloys in the liquid and mushy states

The densities of three Ni-based superalloys have been measured in both liquid and mushy states by both a modified sessile drop method (MSDM) and a modified pycnometric method (MPM) for alloys CMSX-4 and CM186LC, and for CMSX-10 alloy by MSDM only. The surface tensions of liquid CMSX-4, CM186LC, and CMSX-10 superalloys were measured using the sessile drop method. All measurements were carried out in a highly purified argon atmosphere with the oxygen partial pressure of less than 10⁻¹⁹ MPa in the gas outlet. The densities of all superalloys in both liquid and mushy states were found to decrease with increasing temperature. The volume thermal expansion of each superalloy in the mushy state was found to be higher than that in the liquid state. The densities determined by different methods have been critically assessed and recommended values in both liquid and mushy states are given as a linear function of temperature for the three Ni-based superalloys. The surface tension of liquid CMSX-4 superalloy was found to decrease with increasing temperature, while that of liquid CMSX-10 superalloy increases with increasing temperature. The wetting behavior of liquid CM186LC on the alumina substrate was found (1) to differ significantly from that of CMSX-4 and CMSX-10 and (2) to vary with time. A HfO₂-rich layer was found in the contact area of CM186LC with the alumina substrate, which could lead to some uncertainty in the value obtained for the surface tension determined for CM186LC.     

Thermodynamic evaluation of surface tension of liquid metal‐oxygen systems

Thermodynamic equations have been derived to evaluate the surface tension of liquid metal‐oxygen systems. On the basis of these equations, the effect of the oxygen on the surface tension of liquid metals has been evaluated by using the fundamental information on the oxygen solubility in the metals, the surface tension and the molar volume of pure liquid metals and oxides. The calculated results from these equations agree with the literature values of the surface tension of liquid Fe‐O, Co‐O, Ni‐O, Cu‐O and Si‐O systems.     

The surface tension of molten aluminum and Al-Si-Mg alloy under vacuum and hydrogen atmospheres

The surface tensions of pure molten aluminum, A356 alloy (Al-7 pct Si-0.3 pct Mg), and strontium-modified A356 alloy have been measured under vacuum and hydrogen atmospheres using the sessile drop technique. The values obtained for pure aluminum at 680 °C and for A356 alloy and modified A356 alloy at 630 °C are 1.007, 0.889, and 0.844 N/m, respectively, when measured under vacuum. The addition of hydrogen gas to the atmosphere of the liquid droplet has no significant effect on the surface tension of the unmodified A356 alloy, while it lowers the surface tension of the modified alloy to 0.801 N/m. This effect is possibly due to the formation of SrH₂.     

Theoretical Calculations of the Surface Tension of Liquid Transition Metals

The surface tension of pure liquid mercury in the temperature range 273 K to 523 K (0 °C to 250 C°) was calculated using our previously reported equation. The results were compared with the experimental data and showed a good agreement. The surface tension of mercury decreases linearly with temperature, confirming a negative slope, and therefore shows the usual linear temperature dependence. The calculated surface excess entropy (0.21) is in excellent consistence with the experimental value (0.22). The surface tension also was calculated for many d-block metals (Ti, Zr, Fe, Co, Ni, Cu, Zn, Cd, Ag, Au, Pd, and Pt) at their melting points. The calculated values were compared with the existing experimental data.     

Interfacial Phenomena among Liquid Iron-Carbon Alloy, Liquid Slag, and Solid CaO

Interfacial phenomena between hot metal, liquid slag and solid CaO are important to the understanding of the desulfurization reaction in hot-metal treatment processes. In the current work, the surface tension of molten iron-carbon alloy and liquid slag as well as the interfacial tensions among molten iron-carbon alloy-solid CaO, liquid slag-solid CaO, as well as molten iron-carbon alloy-liquid slag were measured in the temperature range 1623?K to 1723?K (1350?°C to 1450?°C). The sessile drop method has been used for these measurements. To analyze the experimental results, two types of graphical analysis programs have been developed to determine the coordinates of the X-ray shadow or charge-coupled device (CCD) image of the droplet. Furthermore, a software package that uses the Gauss-Newton method to minimize an error function between the physically observed and a theoretical Laplacian curve has also been developed in this work.     

Density of Liquid Steel over Temperature Range of 1 803-1 873 K

The density of three kinds of liquid steel was measured by a modified sessile drop method over the temperature range of 1 803-1 873 K. It is found that the density of liquid steels decreases with increasing temperature and carbon content in steel. Both of the density and its absolute temperature coefficient of studied steels are smaller than the literature values of pure iron. The molar volume of the steels increases with increasing temperature.     

Surface Properties of Manganese – Tin Liquid Alloys

We used the sessile drop method to study the temperature and concentration dependences of the density and surface tension of melts in the manganese – tin system. The density polytherms are linear dependences which are consistent with those calculated by the additivity rule for the specific volumes of the pure components. The temperature dependences of the surface tension are also linear and their temperature coefficient changes from negative values for tin-rich melts to positive values for melts with high manganese content. The surface tension isotherm is satisfactorily described by the Popel-Pavlov equation. We calculated the composition of the surface layer of the studied melts as a function of the composition of the bulk phase. We have shown that the model for the surface layer of melts in the Mn – Sn system at 1300°C is close to monolayer.     

Effect of carbon and sulphur on the surface tension of molten iron

Surface tensions of Fe‐4%C‐S alloys were measured at 1623 and 1823 K using the sessile drop technique. Thermodynamic models based on Butler's equation for surface tension of liquid alloys have been compared with experimental results. Calculated values are found to be in good agreement with those of the experimental data of the system. At the same sulphur activity, the effect of carbon on the surface tension of Fe‐C‐S alloys was found to extrude only when the sulphur content was less than 0.005 %.     

Levitation of liquid sodium droplets

Droplets of liquid sodium ranging from 1.2 to 2.1 g, immersed in mineral oil, were levitated in an electromagnetic field. The experimental setup was designed and constructed to levitate small metal droplets at audio frequencies. The levitated droplet was found to be very stable inside the inductor, and the equilibrium shape attained by the droplet in the electromagnetic field was measured during the experiment. A surface coupled mathematical model was used to calculate the self-consistent equilibrium droplet shape of liquid sodium under the influence of an electromagnetic field. The predicted shapes of the metal droplet and the position of the droplet inside the inductor compare well with the experimental data. S.S. ROY, formerly Graduate Student, Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh B. LALLY, formerly Post Doctoral Fellow with the Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh     

Thermophysical Properties of a Fe‐Cr‐Mo Alloy in the Solid and Liquid Phase

Results of a thermophysical characterization of a Fe‐Cr‐Mo alloy in the solid and liquid phases are reported. Methods applied include calorimetry, dilatometry; the laser flash technique for thermal diffusivity measurement and ultrasound pulse echo for the measurement of the room temperature sound velocities and elastic constants. Density in the liquid phase and surface tension were measured by optical dilatometry and by the oscillating drop method on electromagnetic levitated specimen. In addition, surface tension and viscosity were measured by the oscillating drop method on board parabolic flights under reduced gravity conditions. The methods applied and results obtained are presented. This work represents a collaborative effort, including round robin measurements in different laboratories for a characterization of the basic thermophysical properties needed for process simulation.     

Measurements and Calculation of Interfacial Tension between Commercial Steels and Mould Flux Slags

Surface quality of continuously cast is strongly influenced by the interfacial tension between steel and mould flux slag. The meniscus shape and the inclusion entrapment are directly determined by interfacial tension. To achieve a better understanding of the continuous casting process, the interface between four commercial steels and the mould fluxes used at the continuous casting of each steel grade have been investigated. The situation at this interface is determined by the surface tension of steel and slag respectively and also by the mass transfer occurring across the interface. The surface tensions of the mould flux slags have been measured by sessile drop method. The results indicate that the surface tension of mould flux slags decreases with increasing temperature but does not vary so much within the present composition range. Interfacial tensions between steel samples and mould flux slags have been measured in the same way with the aid of X‐ray unit. Estimation of interfacial tension from the steel and slag composition was done by applying empirical models. The measured and the calculated values were in agreement. The interfacial tension was lower for higher alloyed steel grades according to both experiments and calculations though the influence of surface active elements is significant.     

Influence of phosphorus addition on the surface tension of liquid iron and segregation of phosphorus on the surface of Fe-P alloy

This article presents a study of the surface tension and phosphorus surface segregation in Fe-P alloys. The surface tension was measured by the sessile drop technique. The result of the dynamic surface tension for the low phosphorus content alloys shows that the alloy surface vaporization has a clear effect on the surface tension and causes a positive surface tension temperature coefficient. However, from this article, it is evident that phosphorus in liquid iron acts as a surface active element similar to arsenic. The surface segregation was determined using Auger electron spectroscopy. The result on the surface analysis of as-solidified sample indicates that the adsorption of impurity elements, such as oxygen, carbon, and nitrogen, can conceal phosphorus segregation on the free surface. Phosphorus segregation was also examined in the samples as-cleaned by Ar⁺ and then treated 30 minutes at 650°C. Phosphorus was found to segregate extensively on the surface of the alloys. On the basis of the analysis of the published data, the surface active intensity sequence of some nonmetallic elements was arrayed, and the surface active intensity of fluorine and boron in liquid iron was estimated.     

The Surface Tension of Pure Aluminum and Aluminum Alloys

The surface tension of high purity and commercial purity aluminum in vacuo was determined using the sessile drop method and the results were found to compare favorably with published data. The effects of holding atmosphere, substrate, and “surface fracture” of the sessile drop on the measured surface tension values were investigated together with the effects of different solute elements commonly present in commercial aluminum alloys. The results obtained suggest that the nature of the surface oxide film formed on the droplets (affected by alloy composition and atmosphere) and the rupture of this film are the dominant factors influencing the surface tension values obtained. Changes in surface tension values of up to 60 pct were observed. The possible effect of this variable surface tension on practical casting processes, such as direct chill casting, is suggested.     

Interfacial tension and flotation characteristics of liquid metal-sodium flux systems

Interfacial tensions between two liquid phases are discussed based on Dupre’s and Good’s equations. Thermodynamically, it is argued that the interfacial tension will always be less than the sum of the surface tensions of the two pure phases. The interfacial tensions between different metals and sodium fluxes were measured using the sessile drop technique combined with X-ray radiography. The metal-flux systems studied were Ag, Bi, Cu, Pb, and Sn with NaF, NaCl, Na₂CO₃, Na₃AlF₆, and Na₂OSiO₂. The interfacial tension decreased with temperature for all the systems studied. For a given flux, the highest value of the interfacial tension was obtained for the system with the largest value of the surface tension of the metal. The average value of Good’s interaction parameter was 0.31 for metals and sodium fluxes. The lowest value of the interaction parameter was obtained when using cryolite as flux.     

Prediction of the densities of liquid Ni-based superalloys

The molar volume of nickel and the partial molar volumes of Cr, Co, W, Ta, Al, Mo, and Re are computed from the densities of liquid nickel and liquid Ni-based binary alloys measured by the modified sessile drop method (MSDM) and the modified pycnometric method (MPM). The molar volumes of Hf, Nb, and Ti are calculated from the literature density values of these elements. A prediction model for the densities of liquid Ni-based alloys is developed based on the obtained molar/partial molar volumes of the elements in liquid Ni-based alloys. The validity of this model is verified by the density data of liquid Ni-based ternary (Ni-Co-Al), quaternary (Ni-Co-Al-Cr, Ni-Co-Al-Mo, and Ni-Cr-Al-Mo), and commercial alloys measured by both MSDM and MPM. It is also verified by the density values of liquid Ni-based commercial alloys in the literature. It has been shown that the present model can provide reasonable estimation for the density and its temperature dependency of liquid Ni-based alloys. The difference between the predicted value and the measured/cited value is within ±2.5 pct.     

赣州市土壤重金属形态分布特征及污染评价

以赣州市6大功能区土壤重金属为研究对象,采取表层0~20cm土壤共50个样品,测定土壤中重金属Pb、Zn、Cu、Cd和Cr含量并分析其来源,采用改进BCR连续提取法进行形态分析,结合次生相与原生相分布比值法、单因子指数法进行污染评价。结果表明研究区土壤中Pb和Cu元素变异系数较大,重金属Zn, Cu和Pb之间相关性显著。通过单因子指数法评价结果可以看出,赣州市6大功能区都受到重金属Cd的重度污染,居民区和工业区受到重金属Cr的轻度污染,交通区受到重金属Pb和Zn的轻度污染。研究区土壤重金属Cd、Cr、Cu、Pb、Zn形态都以残渣态为主,次生相与原生相比值都是小于1的属于无污染。      

Surface Tension of Liquid Alkali,Alkaline, and Main Group Metals: Theoretical Treatment and Relationship Investigations

An improved theoretical method for calculating the surface tension of liquid metals is proposed. A recently derived equation that allows an accurate estimate of surface tension to be made for the large number of elements, based on statistical thermodynamics, is used for a means of calculating reliable values for the surface tension of pure liquid alkali, alkaline earth, and main group metals at the melting point, In order to increase the validity of the model, the surface tension of liquid lithium was calculated in the temperature range 454 K to 1300 K (181 °C to 1027 °C), where the calculated surface tension values follow a straight line behavior given by γ = 441 – 0.15 (T-Tm) (mJ m⁻²). The calculated surface excess entropy of liquid Li (–dγ/dT) was found to be 0.15 mJ m⁻² K⁻¹, which agrees well with the reported experimental value (0.147 mJ/m² K). Moreover, the relations of the calculated surface tension of alkali metals to atomic radius, heat of fusion, and specific heat capacity are described. The results are in excellent agreement with the existing experimental data.