Liquid metal

About: Liquid metal is a research topic. Over the lifetime, 6947 publications have been published within this topic receiving 77785 citations. The topic is also known as: liquid alloy & liquid metal alloy.

Theory of transport in liquid metals. I. Calculation of self‐diffusion coefficients

Abstract: An approach is presented for the theoretical calculation of self‐diffusion coefficients of liquid metals. The basic assumption is that the self‐diffusion coefficient of a liquid metal is equal to that of an appropriate hard sphere fluid. The hard sphere diameter is dependent upon temperature, and a method is developed for estimating this temperature dependence by exploring the relationship between the diameter and the interatomic potential energy function of the liquid metal. The theory gives accurate results for the magnitude and temperature dependence of the self‐diffusion coefficient for many liquid metals. In addition, the physical basis for the theory is consistent with what has been learned about the liquid state from molecular dynamics calculations.

Metal-Mold interfacial heat transfer

Abstract: During the solidification of metal castings, an interfacial heat transfer resistance exists at the boundary between the metal and the mold. This heat transfer resistance usually varies with time even if the cast metal remains in contact with the mold, due to the time dependence of plasticity of the freezing metal and oxide growth on the surface. The present work has studied interfacial heat transfer on two related types of castings. In the first type, a copper chill was placed on the top of a cylindrical, bottom gated casting. Using the techniques of transducer displacements and electrical continuity, a clearance gap was detected between the solidified metal and the chill. The second type of casting had a similar design except that the chill was placed at the bottom. Owing to the effect of gravity, solid to solid contact was maintained at the metal-chill interface, but the high degree of interface nonconformity resulted in a relatively low thermal conductance as indicated by solution of the inverse heat conduction problem. Finally, the influence of interfacial heat transfer on solidification time with three mold ma-terials is compared by a numerical example, and criteria for utilizing Chvorinov's rule are discussed.

Inherently aligned microfluidic electrodes composed of liquid metal

Abstract: This paper describes the fabrication and characterization of microelectrodes that are inherently aligned with microfluidic channels and in direct contact with the fluid in the channels. Injecting low melting point alloys, such as eutectic gallium indium (EGaIn), into microchannels at room temperature (or just above room temperature) offers a simple way to fabricate microelectrodes. The channels that define the shape and position of the microelectrodes are fabricated simultaneously with other microfluidic channels (i.e., those used to manipulate fluids) in a single step; consequently, all of the components are inherently aligned. In contrast, conventional techniques require multiple fabrication steps and registration (i.e., alignment of the electrodes with the microfluidic channels), which are technically challenging. The distinguishing characteristic of this work is that the electrodes are in direct contact with the fluid in the microfluidic channel, which is useful for a number of applications such as electrophoresis. Periodic posts between the microelectrodes and the microfluidic channel prevent the liquid metal from entering the microfluidic channel during injection. A thin oxide skin that forms rapidly and spontaneously on the surface of the metal stabilizes mechanically the otherwise low viscosity, high surface tension fluid within the channel. Moreover, the injected electrodes vertically span the sidewalls of the channel, which allows for the application of uniform electric field lines throughout the height of the channel and perpendicular to the direction of flow. The electrodes are mechanically stable over operating conditions commonly used in microfluidic applications; the mechanical stability depends on the magnitude of the applied bias, the nature of the bias (DC vs. AC), and the conductivity of the solutions in the microfluidic channel. Electrodes formed using alloys with melting points above room temperature ensure mechanical stability over all of the conditions explored. As a demonstration of their utility, the fluidic electrodes are used for electrohydrodynamic mixing, which requires extremely high electric fields (∼105 V m−1).

Layering of a liquid metal in contact with a hard wall

Abstract: When a liquid makes contact with a solid wall, theoretical studies1,2,3,4 indicate that the atoms or molecules will become layered adjacent to the wall, giving rise to an oscillatory density profile. This expectation has not, however, been directly verified, although an oscillatory force curve is seen for liquids compressed between solid surfaces5. Here we present the results of an X-ray scattering study of liquid gallium metal in contact with a (111) diamond surface. We see pronounced layering in the liquid density profile which decays exponentially with increasing distance from the wall. The layer spacing is about 3.8 a, which is equal to the repeat distance of (001) planes of upright gallium dimers in solid α-gallium. Thus it appears that the liquid near thewall assumes a solid-like structure similar to the α-phase, which is nucleated on freezing at lower temperatures. This kind of ordering should significantly influence flow, capillary osmosis, lubrication and wetting properties5,6, and is likely to trigger heterogeneous nucleation of the solid.