Showing papers on "Liquid metal published in 1984"

Theoretical determination of current-voltage curves for liquid metal ion sources

Abstract: A theoretical model is developed for calculating the current-voltage curves of capillary-type liquid metal ion sources. The solution derived is analytic, given in terms of known parameters. The agreement with experiment is found to be encouraging.

A liquid caesium field ion source for space propulsion

Abstract: Liquid metal ion sources usually employ a single point geometry for the anode either in the form of a wetted needle or a capillary. The realisation of high ion currents whilst, at the same time, maintaining a low neutral mass emission rate has necessitated a different approach. Here the authors report a Cs field ion source which is novel in that emissions issue from a multitude regularly spaced liquid cusps. These sites are anchored at the mouth of a micrometre-sized slit which forms a channel of high flow impedance through which liquid caesium is constrained to flow. The properties of this emitter have been investigated by electrical and mass-loss measurements, the latter having been performed on a sensitive dual-axis vacuum microbalance permitting independent real time measurements of the total mass emission rate and of the thrust. Some properties of the emitter may be understood from a consideration of the hydrodynamic stability where the applied electric field acts on the liquid surface at the mouth of the emitter slit. Following this, a simple viscous flow model of the emitter is given which agrees well with experiments.

The dynamics of liquid metal ion sources

Abstract: The emission of ions and other charged particles from sharpened solid needles wetted with a film of liquid metal is initiated by an electrically driven redistribution of the film at the needle's apex to form a Taylor Cone. The authors examine the effect of viscous fluid flow on the properties of the emitter, in particular the transient properties during redistribution and at onset. A purely inertial treatment is found to be inadequate and viscous effects are shown to dominate. Electric stress and surface tension pressure are not equal during emission and the liquid cone is in a state of tension with steady-state conditions maintained by the process of ion emission.

The direct correlation function of inhomogeneous quantum liquids

Abstract: Within the framework of the Kohn-Sham-Mermin scheme (1965), the direct correlation function of inhomogeneous quantum liquids is defined from a thermodynamic argument In terms of this quantal direct correlation function (QDCF), the WLMB equation derived by Wertheim, Lovett, Mou and Buff (1976) is extended to be applicable to a non-uniform quantum liquid, and the equation of state for inhomogeneous quantum liquids is derived with the use of the QDCF Also, the definition of the QDCF is extended to the case of a non-uniform mixture, and applied to a liquid metal treated as an electron-ion mixture As a result, the electron distribution around each ion in a liquid metal is obtained exactly within the neutral pseudo-atom model Thus, the electrical resistivity and the effective ion-ion potential in the pseudopotential theory are much improved, since the QDCFs in their expressions take account of the non-linear effect properly

Impregnated‐electrode‐type liquid metal ion source

Abstract: An impregnated‐electrode‐type liquid metal ion source has been developed in which a sintered porous tungsten tip is used. The flow rate of the liquid metal can be controlled by selecting the diameters of the tungsten powders to be sintered (10 and 100 μm). Since the liquid metal can be stably supplied to the tip head, stable operation in a wide range from low (a few μA) to high ion current (a few hundred μA) is possible for various metals such as gallium and gold. Moreover, it is also a potential ion source with liquid metals such as silver with high vapor pressure at the melting point. A new method of holding and directly heating the main component of the ion source by means of knife‐edged electrodes with a spring is extremely effective for high temperature operation.

Thermoacoustic magnetohydrodynamic electrical generator

Abstract: A thermoacoustic magnetohydrodynamic electrical generator includes an intrinsically irreversible thermoacoustic heat engine coupled to a magnetohydrodynamic electrical generator. The heat engine includes an electrically conductive liquid metal as the working fluid and includes two heat exchange and thermoacoustic structure assemblies which drive the liquid in a push-pull arrangement to cause the liquid metal to oscillate at a resonant acoustic frequency on the order of 1,000 Hz. The engine is positioned in the field of a magnet and is oriented such that the liquid metal oscillates in a direction orthogonal to the field of the magnet, whereby an alternating electrical potential is generated in the liquid metal. Low-loss, low-inductance electrical conductors electrically connected to opposite sides of the liquid metal conduct an output signal to a transformer adapted to convert the low-voltage, high-current output signal to a more usable higher voltage, lower current signal.

Steady flow of liquid aluminum in a rectangular-vertical ingot mold, thermally or electromagnetically activated

Abstract: Hydrodynamic and thermal fields were studied in liquid aluminum circulating in a specially built parallelepipedic ingot mold. Fluid flow could be produced either by using an electromagnetic linear motor or by natural convection effects. Velocity measurements were performed using a magnetodynamic probe during steady state flow experiments. A theoretical model of heat transfer and fluid flow was developed and used to solve simultaneously Navier-Stokes and energy balance equations. The comparison of theoretical and experimental results is satisfactory regarding general distribution of velocity and temperature. It gives a better understanding of the effects of fluid flow in the melt produced either by external stirring or by natural convection.

Metal powders and processes for production from oxides

Abstract: Method of forming metal powders from the liquid metal reduction of metal oxides are described. The methods described include the steps of low temperature liquid metal reduction of the oxide, agitation of the reduction reaction mixture and/or distillation of excess reductant upon completion of the reduction step. These steps are designed to limit agglomeration and enhance the purity of the final powder produced. Metal powder produced in accordance with this invention has a basic particle size of 0.1 to 0.5 microns.

Two-region analysis of interface shape in continuous casting with superheated liquid

Abstract: A slab ingot is being formed as a continuous casting by withdrawal from a mold with parallel walls. The sides of the ingot below the mold are cooled to remove heat of fusion and energy transferred to the solidification interface by superheated liquid metal in the mold. A two-region analysis is made to determine the non-uniform heat conduction from the liquid metal to the interface, and then from the interface to the cooled ingot sides. The solidification interface shape is found that is compatible with the removal of fusion energy and nonuniform heating from the liquid. The solution is obtained by two applications of a Cauchy boundary value method.

Reactions of chlorine with liquid metals. 1. Indium

Abstract: The reactions of molecular chlorine with liquid and solid indium surfaces were studied by modulated molecular beam-mass-spectrometric methods in the temperature range 300-650 K and equivalent chlorine pressures of 4 x 10/sup -6/ to 4 x 10/sup -4/ torr. In a separate chamber, the surface was monitored by AES as a function of temperature at an effective pressure of chlorine of 5 x 10/sup -4/ torr. At high temperatures InCl was the only reaction product, while at low temperatures some InCl/sub 2/ was observed. Near the melting point the behavior of the scattered Cl/sub 2/ signal suggested a drastic change in sticking probability from that on a bare indium surface to one characterizing a chloride-covered surface. The reaction probability and phase lag of the InCl product also showed rapid variations in a temperature range approximately 30/sup 0/C on either side of the melting point of the metal. A reaction model based on dissociative adsorption of chlorine was developed from the molecular beam and AES data. The model applies to both solid and liquid indium substrates and, in accord with the data, contains no discontinuity at the melting point.

Plasma x-ray generator

Abstract: PURPOSE:To enable highly repeated usage by employing liquid metal as a target then irradiating a beam to produce plasma and feeding the liquid metal synchronously with the beam. CONSTITUTION:A tubing 2 is arranged above a vacuum container 1 then liquid metal such as mercury to be employed as a target is fed from a sump 3. While a Piezo element 10 is provided near the tip of the tubing 2 then it is vibrated to drop the mercury droplet 9 thus to constitute a plasma X-ray generator. Plasma producing beam or laser 8 is irradiated through a light collection lens 6 to the droplet 9 thus to produce X-ray. When selecting the inner diameter of tubing, head h1, vibration, etc. to synchronize production of the droplet and the laser pulse, a system to be used repeatedly where feeding of target material is facilitated can be realized.

Experimental investigation of the density profile in the liquid-vapor interface of mercury and gallium

Abstract: From measurement of the angular dependence of X-ray reflectivity on mercury and gallium it is concluded that the density variation in the liquid-vapor interface near the triple point cannot be represented by a step-like profile. Our results suggest non-monotonic profiles.

Method for obtaining high purity ductile iron

Abstract: A method for making high quality liquid iron with substantially no residual chemical elements and a controlled content of carbon, manganese, phosphorous, sulfur and silicon in the final metal. Sponge iron, as raw material, is melted in a vessel or converter with a basic refractory lining. The energy required for melting the sponge iron is provided by the exothermic reaction of carbon from any coal or carbonaceous material and oxygen in solution within the metal bath and by the combustion of other hydro-carbon fluids, all injected to the bath through nozzles preferably located in the bottom of the converter. Further energy is obtained with the post-combustion of gases leaving the metal bath when ascending to the upper port of the converter. Alloy additions might be made by injection in order to obtain a liquid bath chemical composition which permits that the final liquid metal be used as starting material with excellent properties for the fabrication of high quality iron, particularly ductile iron, which has a very stringent condition for reaching desired properties. Specifically important is the chemical analysis of the metal bath before solidification of the final cast piece. Final liquid metal from the converter can be solidified in form of small ingots for easy further handling. These ingots are excellent as starting material for ductile iron fabrication.

Properties of hot expanded liquid aluminum

Abstract: Measurement of temperature, volume, enthalpy, and electrical resistivity have been made on aluminum expanded isobarically by 50% in volume to temperatures of about 4000 K. These measurements are compared with the predictions of liquid metal pseudopotential theory.

Enhanced wetting of liquid metal alloy ion sources

Abstract: A process for enhancing the wettability of evaporation elements, such as substrates and metal reservoirs used in liquid metal ion sources, and the elements so produced wherein a coating material is wettably coated onto the evaporation element at a coating temperature greater than the ion source operating temperature. The coated element is cooled to the operating temperature, and then contacted with the molten ion source alloy. The coating material is selected to wet the substrate or reservoir at the coating temperature, but to be itself wet by the ion source alloy at the ion source operating temperature. The preferred coating metal is gold, which is first applied by electrodeposition onto the evaporation element, and the evaporation element and coating are heated to a coating temperature of about 800° C. to complete the coating step. The coated evaporation element is cooled to the source operating temperature of 200° C.-300° C. and dipped into the ion source alloy, which may be an alloy such as lead-gold-arsenic or lead-gold-antimony.

Modeling of liquid-metal corrosion/deposition in a fusion reactor blanket

Abstract: A model has been developed for the investigation of the liquid-metal corrosion and the corrosion product transport in a liquid-metal-cooled fusion reactor blanket. The model describes the two-dimensional transport of wall material in the liquid-metal flow and is based on the following assumptions: (1) parallel flow in a straight circular tube; (2) transport of wall material perpendicular to the flow direction by diffusion and turbulent exchange; in flow direction by the flow motion only; (3) magnetic field causes uniform velocity profile with thin boundary layer and suppresses turbulent mass exchange; and (4) liquid metal at the interface is saturated with wall material. A computer code based on this model has been used to analyze the corrosion of ferritic steel by lithium lead and the deposition of wall material in the cooler part of a loop. Three cases have been investigated: (1) ANL forced convection corrosion experiment (without magnetic field); (2) corrosion in the MARS liquid-metal-cooled blanket (with magnetic field); and (3) deposition of wall material in the corrosion product cleanup system of the MARS blanket loop.

Electrical resistivity of liquid chromium

Abstract: We have measured the electrical resistivity, ϱ, of Cr from room temperature to above its melting point. The resistivity, ϱL, of liquid Cr is found to be 150 ± 5 μ Ω- cm and (ϱL - ϱS)/ ϱS = 0.27. We also report a melting temperature for Cr of 1812 ± 10°C. We compare ϱL with values calculated on various theoretical models, and examine the implications of ϱS and ϱL for the density of states for solid and liquid Cr.

Cold trap apparatus

Abstract: © Cold trap apparatus for the purification of liquid metal such as sodium comprises a cooled vessel (20) within which a number of concentric cylinders (23) are located such that the liquid metal flow takes place downwardly in the gap between the vessel (20) and the outermost cylinder (23) and upwardly along the gaps between the cylinders (23). The cylinders (23) present extended surfaces across which the liquid metal flows with deposition of solute (24) along such surfaces. The surfaces of the cylinders (23) may be of a roughened nature with respect to the liquid metal flow, e.g. they may be covered with a single laver mesh (21).

Electronic structure and properties of liquid and amorphous alloys

Abstract: We described the methods available for calculating the density of states of pure and alloys of liquid and amorphous transition metals with particular emphasis on the tight-binding description of the d band. We show, using various structural models, that the electronic properties are more sensitive to local compacity than to local geometry. For alloys chemical short range order is shown to be the most important parameter for the electronic structure and macroscopic properties in agreement with recent spectroscopical experiments. We applied these calculations to the thermodynamicals properties of liquid alloys between transition metal and p-metals (Si, Ge, Al). We calculate the mixing entropy and enthalpy whose strong negative behaviours are shown to be due to the electronic contribution. There is a charge rearrangement of the valence electrons of the p metal with the d band of the transition metal which explains the position of the minimum in these quantities.

The radial distribution function and structure factor of liquid and amorphous gallium as described by the quasi-crystalline model

Abstract: The far RDF oscillations and the main peak of the structure factor for liquid and amorphous gallium are described in terms of the quasi-crystalline model representing spatial correlations in liquids on the basis of a smeared crystal lattice. The initial lattice is a modified BCC lattice for liquid gallium and β-Ga structure for the amorphous state. The liquid gallium structure is inferred to be closely packed atoms complicated by their covalent coupling. Amorphous gallium has a microcrystalline structure with islets formed in a similar way as for β-Ga crystals.

Apparatus for sampling liquid metal

Abstract: PURPOSE:To prevent leakage of oxygen and to improve reliability of an apparatus by providing an apparatus for heating a sampling pot and a cooler at the other end of a vessel and distilling a liquid metal in an inert gas. CONSTITUTION:The liquid metal is charged into the sampling pot 4 from a charging nozzle 30, and the liquid metal in the pot 4 is evaporated by operating a heater 29. A distilled liquid metal is brought into contact with an inner wall 39 whose temp. is lowered by a cooling fin 31 at the other end of a cylindrical vessel 24 and condensed, and a metallic oxide remains at the bottom of the pot 4 after the evaporation of the liquid metal has finished. Next an upper surface franges 34 is detached and atomic absorption spectrometry of the metallic oxide in the pot is performed to measure the quantity of oxygen. Since the distillation is performed after the inner part of the vessel 24 is flashed with the inert gas from a nozzle 37, oxygen is not leaked, evacuating system for the vacuum distillation is unnecessary and the reliability of the apparatus can be improved.

Radiant heating tests of several liquid-metal heat-pipe sandwich panels

Abstract: Integral heat pipe sandwich panels, which synergistically combine the thermal efficiency of heat pipes and the structural efficiency of honeycomb sandwich construction, were conceived as a means of alleviating thermal stress problems in the Langley Scramjet Engine. Test panels which utilized two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and a liquid metal working fluid (either sodium or potassium) were tested by radiant heating at various heat load levels. The heat pipe panels reduced maximum temperature differences by 31 percent with sodium working fluid and 45 percent with potassium working fluid. Results indicate that a heat pipe sandwich panel is a potential, simple solution to the engine thermal stress problem. Other interesting applications of the concept include: cold plates for electronic component and circuit card cooling, radiators for large space platforms, low distortion large area structures (e.g., space antennas) and laser mirrors.

Fracture in liquid metal environments

Abstract: Many ductile metals fracture in a brittle manner when tested in the presence of a thin surface coating of certain liquid metals. The severity of embrittlement depends upon the metallurgical, mechanical, and physical factors and also on the chemical nature of the liquid and that of the solute dissolved in the liquid metals. Liquid metal embrittlement is considered a special case of brittle fracture and it is generally accepted that embrittlement is caused by the liquid metal “Adsorption Induced Reductions in the Cohesion” of atomic bonds at the crack tip. This paper describes the phenomena of fracture in liquid metal environments and discusses the effects of variables related to the solid, to the liquid and liquid metal solutions, and to the test conditions on the severity of embrittlement. It also discusses various mechanisms of embrittlement. Also, a summary is presented with suggestions for future work.

Theory of Equilibrium and Kinetic Properties of Liquid Metals

Abstract: If dense plasmas in the region of about 1021 particles per cm3 are cooled below the critical temperature T c ≈ 104 К the uniform state becomes unstable and the system divides into two phases, a liquid and a gaseous one. In metallic systems the liquid phase is highly conducting and shows many similarities with the plasma state. Because the theoretical description of dense gaseous plasmas should be consistent with the theory of liquid metals, in this chapter some aspects of the liquid metal theory are presented.