Surface Tension Of Liquid Metals Research Articles

Liquid metal surface tension measurements: a kinetic-fluodynamic model of surface oxygen availability

A kinetic and fluodynamic description of processes that may take place near the surface of some liquid metals in the presence of a gas flow containing definite oxygen amounts is given, with a particular regard to the thermodynamic properties of the metal-oxygen system and to the geometry of the experimental set-up. Diagrams have been obtained from which the following items of information are simultaneously available: (1) the range of P 02 and T in which the reaction considered is thermodynamically possible; (2) the accessibility of oxygen to the liquid metal surface, and the thermodynamic-kinetic conditions for which this surface can be considered oxygen free. Therefore, the treatment presented here and applied to many cases of technological interest allows us to define (a) the physical and chemical equilibrium conditions of a liquid metal surface in the presence of oxygen diluted in an inert gas carrier, under total pressures ranging from about 10 −4 to 0.1 MPa (10 −3−1 m), and (b) the kinetic and fluodynamic characteristics of the process through which the quilibrium conditions are reached, the geometry of the experimental set-up having been given.

Software package for determination of surface tension of liquid metals

The problems of the development of algorithms to process experimental results obtained by the sessile drop method are discussed. Algotithms are based on the numerical solution of the Young-Laplace equation and the regularization method for Dorsey formula. A software package for IBM PC AT has been developed. The results of calculations for droplets formed in a cup (liquid Fe) and on a plate (slag CaOB 2O 3) are given.

Surface tension measurements on levitated liquid metal drops

An improved method to measure the surface tension of liquid metals is presented. It is shown that the application of digital image processing can increase the precision of measurements performed with the oscillating drop technique. In experiments on nickel, a good reproducibility of measured surface tension and agreement with literature data were found. Measurements on iron show evidence for an influence of the oscillation amplitudes on the measured values. Experimental results on Ni-10 at.% Ti seem to show an influence of oxygen as a surface active element on the surface tension of the pure alloy.

Surface tension measurements on levitated aspherical liquid nickel drops

An improved method for measuring the surface tension of liquid metals is presented. Surface oscillations of an electromagnetically levitated liquid nickel droplet are observed by a high speed video camera and digital image processing is used to evaluate the obtained spectra. Identification of the oscillation modes increases the precision of measurements significantly. In our experiments on Nickel we found a very good reproducibility and a decrease of surface tension with increasing temperature.

Calculated surface-energy anomaly in the 3d metals.

Local-spin-density theory and a Green's-function technique based on the linear muffin-tin orbitals method have been used to calculate the surface energy of the 3d metals. The theory explains the variation of the values derived from measurements of the surface tension of liquid metals including the pronounced anomaly occurring between vanadium and nickel in terms of a decrease in the d contribution caused by spin polarization.

Surface energy and work function of elemental metals.

We have performed an ab initio study of the surface energy and the work function for six close-packed surfaces of 40 elemental metals by means of a Green's-function technique, based on the linear-muffin-tin-orbitals method within the tight-binding and atomic-sphere approximations. The results are in excellent agreement with a recent full-potential, all-electron, slab-supercell calculation of surface energies and work functions for the 4d metals. The present calculations explain the trend exhibited by the surface energies of the alkali, alkaline earth, divalent rare-earth, 3d, 4d, and 5d transition and noble metals, as derived from the surface tension of liquid metals. In addition, they give work functions which agree with the limited experimental data obtained from single crystals to within 15%, and explain the smooth behavior of the experimental work functions of polycrystalline samples as a function of atomic number. It is argued that the surface energies and work functions calculated by present day ab initio methods are at least as accurate as the experimental values.

Surface tension measurements of liquid metals using levitation, microgravity, and image processing

An improved method for measuring the surface tension of liquid metals is proposed. It makes use of the electromagnetic levitation technique for levitating a liquid metal droplet and of digital image processing to evaluate the surface oscillations of the droplet. The oscillation frequencies determine the surface tension. This paper contains a discussion of the theoretical background and a description of the experimental setup. In addition, preliminary results on FeNi samples in 1g and microgravity are presented.

Laser-induced forward transfer of aluminium

The laser-induced forward transfer (LIFT) of aluminium is experimentally investigated for aluminium target thickness up to some μm. The aluminium is transferred to glazed ceramics and to silicon substrates with and without oxidized surface, respectively. Two types of laser beam sources are used: a Nd:YAG laser with a Gaussian beam profile and a Nd:glass laser system providing a homogenized flat top profile. The resulting deposition is determined by the removal mode of the Al from the target and by the interaction of the molten Al with the substrate. In a first removal mode (low laser intensities and/or thin targets) where melting through of the target precedes the onset of vaporization at the target front side the material can easily be transferred to the substrate. In a second mode (high laser intensities and/or thick targets) the blow-off process is characterized by higher vapor pressures which leads to disturbed deposits. The interaction of impacting material with the substrate causes the formation of droplets on oxidized surfaces due to the high surface tension of liquid metals.

Surface Tension of Liquid Metals

Surface Tension of Liquid Metals

Surface tension measurements of liquid metals by the oscillating drop technique

An improved method for measuring the surface tension of liquid metals is proposed. Surface oscillations of an electromagnetically levitated liquid metal droplet are observed by a video camera and digital image processing is used to evaluate the spectrum of oscillations. A discussion of the theoretical background and a description of the experimental apparatus are presented. In addition, preliminary results on an FeNi sample, and an outlook for future experiments, including the measurement of viscosity, are given.

A dynamic technique for measuring surface tension at high temperatures in a microgravity environment

The feasibility of a dynamic technique for measuring surface tension of liquid metals at high temperatures in a microgravity environment is considered. The basic method involves heating a tubular specimen resistively from ambient temperature through its melting point in about l s by passing an electrical current pulse through it, while simultaneously recording the pertinent experimental quantities. Static equilibrium for the molten specimen may be achieved (at least for a short time) in a microgravity environment by splitting the current after it passes through the specimen tube and returning a fraction along the tube axis and the remaining fraction outside the specimen. Adjustments to the current split enable a balance between the magnetic and surface tension forces acting on the specimen. Values for surface tension are determined from measurements of the equilibrium dimensions of the molten specimen tube, and the magnitudes of the currents. Preliminary rapid melting experiments, performed during microgravity simulations with NASA's KC-135 aircraft, yield a value for the surface tension of copper at its melting point which is in reasonable agreement with literature data.

Some theoretical considerations of the surface tension of liquid metals for metal matrix composites

This paper presents a model for calculating the surface tension of pure metals and their alloys. It is based upon the theory of Eyringet al. which uses classical statistical physics to describe the thermodynamic properties of metals in the liquid state. Calculations show the surface tension of pure aluminium to be nearly 9% greater than that measured for pure aluminium having a monolayer of oxide (Al2O3), and within about 10% of measured values for Al-xMg and Al−xCu, wherex is the weight percent of the alloying element. In the present calculations 0 ≤x≤8 wt% for magnesium and 0≤x≤30 wt% for copper were used. The values calculated are also in good agreement with results from other models. The model was also used to calculate the temperature coefficient. For pure aluminium the calculated values fall within experimental measurements, and exhibit a slight temperature dependence.

An automatic technique for measuring the surface tension of liquid metals

A methodology for automatic measurement of surface tension of liquid metals is presented. The procedure involves the digitization of a television image of a drop of the liquid metal, image processi...

Ion beam fabrication using piezo-actuator and liquid metal source

Liquid metal ion sources of AuSi and Ga are put on a piezo-actuator in order to precisely control a distance between an apex of the source and a cathode surface with an order of 1 μm. The ion extraction voltage decreases proportionally to the 0.2 power of the distance, which can be predicted from a balance between surface tension of liquid metal and electrostatic force at the emitter apex. The sputteretched hole diameter is always comparable to the distance for both ion sources, and the current density reaches up to about 20 A/cm 2. The minimum distance seems to be around 5 times the apex radius, within which a micro-discharge takes place and leads to destruction of the emitter apex. A sputtering yield in the AuSi source/Si substrate system is ranging between 1.5 and 6 atoms/ion. These higher values may be due to existence of Au-Si mixed layer on the ion bombarded Si surface.

Calculation of the surface tension of liquid metals using a one-component-plasma reference system

The authors use the one-component-plasma (OCP) model as a reference system instead of the traditional hard-sphere fluid to calculate the liquid-vapour interfacial surface tension of liquid metals within the density functional formalism. The calculated surface tensions of the alkali metals are in excellent agreement with experiment. For the polyvalent metal Al, the result the authors obtain is larger than experimental measurements. They conclude that the OCP system is not suitable to describe the liquid-vapour phase transition in simple metals which have a nominal plasma parameter Gamma -Z2e2/akBT larger than the usual freezing value of approximately 178. The calculated interfacial widths in all cases are narrower than the expected experimental values.

Nonlocal pseudopotential calculation of the surface tension of simple liquid metals

A full nonlocal pseudopotential calculation of the surface tension of simple liquid metals is presented. The basis of the theory is the direct perturbation expansion to second order in a weak electron–ion pseudopotential. By invoking the Born–Oppenheimer adiabatic approximation, an effective Hamiltonian is obtained. This effective Hamiltonian is then used, in conjunction with Gibbs–Bogoliubov inequality, to derive tractable expressions for the calculation of surface tension of simple liquid metals. It is found that, within the same approximation, our nonlocal pseudopotential calculations yield surface tensions of liquid metals much smaller than similar calculations obtained by Hasegawa and Watabe [J. Phys. C 15, 353 (1982)]. However, a review of the theory and a close examination of the various contributions to the surface tension show that the results of calculations by Hasegawa and Watabe are to some extent fortuitous. Various possible improvements and sources of discrepancies on the computation of surface tension will be checked and discussed in the text.

Density Functional Approach to the Surface Tension of Liquid Metals

AbstractThe local density functional formalism of Evans and Hasegawa, previously developed for the study of surface properties, is re‐examined by including nonlocality of pseudopotential in the theory. It is found that (i) when the pseudopotential is nonlocal, the fourth order density gradient correction of Ma and Sahni must be included in order that the density profiles obtained are physically meaningful and (ii) the first order perturbation is inadequate for understanding the surface tension of simple liquid metalsin accordance with conclusions made by other investigators.

The surface tension of liquid metals and its temperature dependence

The planar surface of liquid metal is studied in the framework of the density functional theory. The liquid metal is considered as a two-component electron-ion system. The expression for the Helmholz free energy in the consistent gradient expansion is used. The surface tension of alkali metals is calculated from the first principles in a broad temperature range. The calculated values are in a good agreement with experimental data.

Calculation of surface tension temperature coefficients

In three previous communications the relationship between bulk properties and the surface tension of liquid metals and alloys was demonstrated. The surface tension of liquid metals was correlated with plasma frequency. It was then shown that the surface tension of liquid metals as well as alloys could be obtained from the bulk modulus and most recently a method was given for predicting the surface tension from the plasma frequency of the constituents of a binary alloy. The purpose of the present communication is to show that the temperature coefficient of surface tension of liquid metals may be calculated from another bulk property - the bulk coefficient of thermal expansion.

A theory for liquid metal surface tension

A theory for the surface tension of liquid metals is presented and applied to the alkalis and the polyvalent metals, Mg, Zn and Al. The numerical results are in excellent agreement with experimental data. The theory also predicts realistic surface density profiles for the ions and the electrons.