Showing papers on "Liquid metal published in 1998"

Oxide‐metal equilibria to 2500°C and 25 GPa: Implications for core formation and the light component in the Earth's core

Abstract: The solubility of O in Fe-rich liquid metal in equilibrium with magnesiowustite (Mg,Fe)O was investigated at pressures to 25 GPa and temperatures to 2500°C in a 6–8 type multianvil apparatus. The experiments were designed to produce near millimetre sized pools of quenched liquid metal free of other phases, so that the equilibrium composition of the liquid metal could be recovered, taking into account the effects of quench modification. The amounts of O found in the metal are relatively small ( 3-perovskite produce only small amounts of Si (∼1 wt %) dissolved in Fe-rich metal. These results, in conjunction with cosmochemical constraints on the bulk composition of the Earth (the depletion of the Earth in cosmochemically volatile elements), leave the identity of the putative “light component” in the Earth's core as an enigma. It is difficult to account for the light component if it constitutes more than just a few percent of the core. The experiments also measure the partitioning of Fe, Ni, Co, Cr, and Ti between the Fe-rich liquid metal and magnesiowustite phases. Ti is not significantly siderophile under the investigated conditions. When normalized to a constant metal/oxide partition coefficient for Fe, both Ni and Co become less siderophile with increasing pressure and Cr becomes more siderophile. The effect of temperature on Ni and Co partitioning is small at high temperatures, but important for Cr. The presently observed mantle abundances of Fe, Ni, Co, and Cr cannot be explained by equilibrium partitioning into the metal of the Earth's core under the pressure temperature conditions covered by the present experiments.

Process for the electrolytic production of metals

Abstract: Process for the electrolytic production of metals particularly titanium and alloys starting from the corresponding compounds, by means of an apparatus for the electrochemical extraction including: a cathode-crucible (1) containing a mass of solidified metal (3), a liquid electrolyte (22) with a density which is lower than that of the metal and a pool of liquid metal (25) produced; one or more non-consumable anodes (8) partially immersed in the electrolyte with means for regulating their distance from the cathodic surface; a feeding system (21) to the electrolyte of the compounds of the metals, of the electrolyte constituents and of alloying materials; a power supply which feeds direct current to the liquid metal, and through the electrolyte, to the anodes, and causes the cathodic reduction of the metal in liquid form and the evolution of anodic gas, with the heat generation which maintains the electrolyte in the molten state; an air-tight containment structure in which the anodic gases generated during the electrolysis are collected.

Synthesis and Processing

Abstract: Rapid Solidification (RS) involves propagation of a solidification front at high velocity. This is most readily achieved by suitable treatment of a volume of melt. Suitable treatments include: (i) dividing it up into a multitude of small droplets (atomisation, emulsification or spray-forming) so that most of them can under-cool deeply prior to solidification; (ii) stabilising a meltstream of small cross section in contact with an effective heat sink (melt-spinning or thin-section continuous casting); (iii) rapid melting of a thin layer of material in good contact with an extensive heat sink, which may be the same or related material (electron or laser beam surface pulse or traverse melting). In each case rapid solidification results from rapid extraction of the heat of transformation either directly by the external heat sink and/or internally by the undercooled melt (in which case the system rapidly reheats, i. e., recalesces during solidification). The large undercoolings developed amount to large departures from equilibrium leading to formation of extended solid solutions and new non-equilibrium phases (crystalline, quasicrystalline or glassy) while the short freezing times give rise to sizerefined and compositionally rather uniform microstructures as well as relatively high rates of throughput of material. The products of RS range from powder or flake particulate, through thin discontinuous or continuous ribbon or filament to thick spray deposits containing some trapped porosity. These products can sometimes be applied directly as in the cases of finely divided light metal particulate used as the basis for space shuttle and satellite launch rocket fuel and signalling flares, and planar-flow-cast strip used in certain magnetic applications or for braze assembly of engine components. For most applications, however, they must be suitably incorporated or consolidated into full size, fully dense sections or components. This may involve processes such as polymer bonding or liquid metal infiltration but most commonly involves powder metallurgy techniques such as die or isostatic pressing and/or hot working.

On the current emitted by Taylor cone-jets of electrolytes in vacuo: Implications for liquid metal ion sources

Abstract: Approximate scaling laws for the charge and size of the drops ejected from the apex of Taylor cones run in the cone-jet mode (electrospray) are now available for highly conducting electrolytes (10−4 S/m

Analysis of Actual Blast Furnace Operations and Evaluation of Static Liquid Holdup Effects by the Four Fluid Model

Abstract: The purpose of this paper is to extend and validate a previously presented model of the blast furnace shaft. This model uses conservative differential equations to analyse simultaneous four phase motion, heat transfer and chemistry. First, the paper describes some enhancements to the model. After this, the model is validated against several sets of operational and descending probe data from various blast furnaces. The calculated temperature fields show good agreement with two dimensional fields measured by descending probes at both medium and high rates of PC injection. Finally, the third section considers the effect of including static liquid holdup on the model predictions. Three correlations for static liquid holdup were examined. For all correlations, when static liquid holdup was included in the calculations the net liquid flux towards the raceway increased due to the transport of static liquid by the solid. Further, as static holdup reduces the volume available for gas flow, the gas velocity increases causing greater gas-solid heat transfer. This increases the rates of direct reduction and solution loss, resulting in increased predicted production rates and decreased hot metal and top gas temperatures. Finally, for correlations that predict large static holdup in the raceway region, silicon transfer to hot metal is increased due to increased liquid metal residence times.

Finite element modeling of distortion during liquid phase sintering

Abstract: Liquid phase sintering (LPS) is a common technique to consolidate materials that are difficult to process by fusion techniques, such as tungsten heavy alloys. One of the major processing difficulties associated with liquid phase sintered alloys is component distortion and loss of component shape. In LPS, this distortion is the result of viscous flow driven by curvature effects and gravity. A finite element model is developed for viscous flow of the semisolid sintering structure using Stokes equations. This model considers solid volume fraction and effective viscosity of the solid-liquid mixture. The simulation predictions are compared to distortion results for microgravity and ground-based sintering experiments, and they show good agreement. The model results indicate that the effective semisolid viscosity is significantly greater than the liquid metal viscosity. Hence, future work needs to quantitatively examine the factors controlling viscosity and the benefits from such high viscosities in liquid phase sintered systems.

Method and system to directly produce electrical power within the lithium blanket region of a magnetically confined, deuterium-tritium (DT) fueled, thermonuclear fusion reactor

Abstract: A method for integrating liquid metal magnetohydrodynamic power generation with fusion blanket technology to produce electrical power from a thermonuclear fusion reactor located within a confining magnetic field and within a toroidal structure. A hot liquid metal flows from a liquid metal blanket region into a pump duct of an electromagnetic pump which moves the liquid metal to a mixer where a gas of predetermined pressure is mixed with the pressurized liquid metal to form a Froth mixture. Electrical power is generated by flowing the Froth mixture between electrodes in a generator duct. When the Froth mixture exits the generator the gas is separated from the liquid metal and both are recycled.

Oxygen transport and dynamic surface tension of liquid metals

Abstract: Theoretical models have been developed to study the behaviour of liquid metal surfaces in the presence of gaseous surface active elements, relating the mass exchange between the liquid metal and th...

II. Surface and interfacial phenomena: Surface phases in binary liquid metal alloys: An X‐ray study

Abstract: Surface-sensitive x-ray scattering techniques with atomic scale resolution are employed to investigate the microscopic structure of the surface of three classes of liquid binary alloys: (i) Surface segregation in partly miscible binary alloys as predicted by the Gibbs adsorption rule is investigated for Ga-In. The first layer consists of a supercooled In monolayer and the bulk composition is reached after about two atomic diameters. (ii) The Ga-Bi system displays a wetting transition at a characteristic temperature Tw ≈ 220°C. The transition from a Bi monolayer on Ga below Tw to a thick Bi-rich wetting film above Tw is studied. (iii) The effect of attractive interactions between the two components of a binary alloy on the surface structure is investigated for two Hg-Au alloys.

Study of the design model of a liquid metal induction pump

Abstract: The design of an electromagnetic pump for liquid metal is optimized. The model includes both electrodynamics and fluid-dynamics of the liquid metal. End effects are included in the model, in order to take into account the finite length of the pump and consequently the decrease of efficiency. For the Electrodynamic model, the permeability of the ferromagnetic core is assumed to be infinite. A finite slot configuration of the primary windings is assumed. In the design problem considered, the optimization regards the electrical supply system, the pump dimensions and the slot configuration.

The magnetic field and performance calculations for an electromagnetic pump of a liquid metal

Abstract: For an annular-type electromagnetic pump of a liquid metal, the magnetic field is found in closed form by means of the Fourier transform method for two-dimensional field analysis based on an equivalent current sheet model, so that the terms contributing to the normal thrust and the end effect are analytically identified. Analytical solutions for the magnetic vector potentials are compared with numerical ones obtained from the finite difference equation, and they turn out to be in good agreement regardless of the assumption of infinite permeability used in the analytical approach. As a result of closed-form solutions, the electromagnetic body force exerted on a liquid metal flow and the efficiency of the pump are calculated without going through tedious time-consuming numerical work usually accompanied by troublesome convergence problems. The calculated results for estimating the influence of end effects on the performance of the electromagnetic pump clearly show that the end effects give rise to the obstructive force to the liquid metal flow at inlet and outlet ends of the pump. In addition, the efficiency is found to be lowered due to end effects, especially when the speed of the flow is high.

Bubble Behavior and Heat Transfer in Preheated Gas Injection into Liquid Bath

Abstract: Heat transfer between gas bubble and liquid bath has been studied by using cold models. The rising bubble diameter, velocity and the heat efficiency were measured to explain the mechanism of the heat exchange for various gas–liquid systems. Preheated gas (N2, He, Ar–He mixture) was injected into the bath of volatile (water) or non-volatile (ethylene glycol, methyl carbitol and ethylene glycol–glycerin mixture) liquid. It is shown that liquid surface tension, gas density and gas temperature are of great importance in determining the bubble diameter. The heat efficiency increases as the bath depth increases and the gas flow rate decreases. The heat exchange is found to be controlled by the heat transfer within the gas bubble. A model describing time variations in the average temperature and the vapor content inside the bubble has been developed. The computed and measured results reveal that the heat transfer is enhanced with thermal conductivity of gas in the case of gas injection into non-volatile liquid. However, when gas is injected into volatile liquid, the heat efficiency must be considered with accounting for the heat transfer and the vaporization proceeding concurrently.

Characteristic times of oxygen mass transfer at the liquid metal–vapour interface

Abstract: The interactions of liquid metals and alloys with the environment mostly depends on the thermodynamic properties of the liquid surface. In fact, the surface tension is strongly influenced by the presence in the surrounding atmosphere of reactive gases through solution, adsorption mechanisms and/or surface reactions. In particular, oxygen, which shows a high surface activity towards a large number of metallic systems, is the most important contaminant of liquid metals and alloys. Theoretical approaches for estimating the oxygen mass transfer at the liquid–vapour interface under inert atmosphere and vacuum have been developed already in order to relate the observed physical properties to the real surface composition data. In the present work a model of the interfacial transport of a liquid metal–oxygen system under Knudsen conditions that foresees the temporal evolution of the interfacial composition is presented. The diffusion characteristic times for reaching steady-state conditions are evaluated in order to define two system “sizes” depending on the different oxygen transport mechanisms in the liquid phase. An experimental study of the interface evolution is at present under way and preliminary results show a satisfactory agreement with theoretical studies.

Carbon Solution in Liquid Iron and Iron Alloys

Abstract: The dissolution of carbon into liquid iron and iron alloys was investigated using four independent experimental approaches, i.e., immersion of a graphite cylinder in a melt bath using an electric resistance furnace, immersion of a coke particle in a melt bath using an induction furnace, a molten droplet on a graphite plate using an induction furnace and sliding a metal droplet down a graphite spiral in a resistance furnace. The dissolution rate was analysed by assuming that this reaction is governed by the diffusion of carbon from the carbon-metal interface to the bulk liquid metal through a boundary layer. The experimental results for each case were well interpreted by both concentration and activity driven models. The variation in the carbon dissolution rate with the experimental method was explained by the Olsson relation or the penetration theory. An increase in carbon dissolution rate with temperature was observed. The carbon dissolution rate into liquid Fe-C alloy was not changed by addition of 1.9 wt% silicon to the melt, while a decrease in the dissolution rate of carbon was observed by adding 1 wt% sulfur to the melt.

Method and apparatus to produce and maintain a thick, flowing, liquid lithium first wall for toroidal magnetic confinement DT fusion reactors

Abstract: A system for forming a thick flowing liquid metal, in this case lithium, layer on the inside wall of a toroid containing the plasma of a deuterium-tritium fusion reactor The presence of the liquid metal layer or first wall serves to prevent neutron damage to the walls of the toroid A poloidal current in the liquid metal layer is oriented so that it flows in the same direction as the current in a series of external magnets used to confine the plasma This current alignment results in the liquid metal being forced against the wall of the toroid After the liquid metal exits the toroid it is pumped to a heat extraction and power conversion device prior to being reentering the toroid

Self-sustaining oxidation of liquid aluminium and its alloys containing magnesium and silicon

Abstract: An experimental investigation has been conducted into factors affecting the self-sustaining air oxidation of liquid aluminium and its alloys containing magnesium and silicon. Thermogravimetry and optical microscopy, scanning electron microscopy, and X-ray diffraction analysis have been performed to characterize the progress of oxidation and the nature of the products produced. On the basis of the results obtained, a comprehensive model is proposed capable of explaining the observed capability of producing an alumina composite material by a self-sustaining oxidation mechanism. It is proposed that aluminium/alumina transport occurs by means of the formation of gas-phase aluminium-bearing species which are then encapsulated by a liquid MgO–SiO2–Al2O3 slag phase. Subsequent precipitation of alumina from the slag phase provides the means by which alumina is continuously distributed throughout a growing alumina composite material. © 1998 Chapman & Hall

Investigation of the Heating Dynamics and Properties of Liquid Tungsten

Abstract: The dynamics of electrical explosion of tungsten wires under water in microsecond times was studied. A new optical method for temperature measurement has been developed. For tungsten, uniform heating took place at 1011

Method of manufacturing three dimensional parts using an inert gas

Abstract: A method for manufacturing metal structures in which minute drops of a liquid metal are emitted from an acoustic device through an inert gas. The presence of the inert gas at the surface of the liquid metal prevent the formation of an oxide skin which would absorb acoustic energy and hinder droplet formation and emission. The droplets are then emitted towards a substrate, which may form as a carrier, where they may be used to form solder bumps, circuit traces, or accepted to form a three dimensional device.

Advanced cooling technology for leading-edge computer products

Abstract: Cooling technology has been a vital prerequisite for the rapid and continued advancement of computer products, ranging from lap-tops to supercomputers. This paper provides a review of the recent development of cooling technology for computers. Both air cooling and liquid cooling are included. Air cooling is discussed in terms of the advantages of impinging flow. An example of module internal conduction enhancement is given. Liquid cooling is discussed in terms of indirect liquid cooling with water coupled with enhanced conduction, and direct immersion cooling with dielectric coolants. Special cooling technology is included in terms of the application of heat pipes and the possibility of using liquid metal flow to cool electronic packages.

The free-surface shape and temperature distribution produced in liquid metal droplets by heating coil pulses in the TEMPUS electromagnetic levitation facility

Abstract: We present the results of analytical and numerical calculations of the free-surface shape and temperature distribution produced in liquid metal droplets processed in the TEMPUS electromagnetic levitation facility. The mathematical models were developed to predict the behavior of liquid metal droplets in containerless experiments used to measure thermophysical properties aboard the Space Shuttle Columbia during the IML-2 mission in July 1994. A normal stress balance model was used to numerically calculate the equilibrium free-surface shapes for various samples produced by a number of induction coil voltages. Analytical and numerical calculations were performed to model the heat transfer in the liquid metal droplets during and following the heating coil pulses. The work illustrates the use of mathematical modeling in the design of microgravity experiments and is applicable to industrial processes such as casting and skull melting.