Thermal Analysis of Solidification in a Czochralski-Type Rotating System

2000 ◽  
Author(s):  
J. Xu ◽  
M. Ferland ◽  
H. Zhang ◽  
V. Prasad
Keyword(s):  
Thermal Analysis ◽  
Rotating System ◽  
Convection Diffusion ◽  
Solidification Model ◽  
Rotation Rates ◽  
Diffusion Controlled ◽  
Visualization Experiments ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Good Agreement

Abstract A continuum solidification model is used to study transport phenomena in a simulated Czochralski system for various rotation rates of the crystal and crucible. Solidification occurs on a cylindrical seed from the top surrounded by water in the crucible. An enthalpy formulation is adopted for numerical solution of convection-diffusion controlled solidification problems. Predicted solid-liquid interface and temperature distribution are in good agreement with the liquid crystal visualization experiments.

Prediction of Solid-Liquid Interface Stability and Dendritic Growth in Multi-Component Alloys with Calphad Method

2005 ◽  
Vol 475-479 ◽  
pp. 2721-2724
Author(s):  
Rui Jie Zhang ◽  
Zhi He ◽  
Wan Qi Jie
Keyword(s):  
Experimental Data ◽  
Present Method ◽  
Dendritic Growth ◽  
Calphad Method ◽  
Liquid Interface ◽  
Interface Stability ◽  
Calculation Results ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Good Agreement

A method to predict the solid-liquid interface stability and the constrained dendrite growth of multi-component alloys was developed based on the Calphad method. The method was applied to several industrial Al-Si-Mg alloys, and the predicted results were compared with some former experimental data. The good agreement between the calculation results and the experimental data demonstrates the superiority of the present method to the classical one based on constant parameter assumptions.

scholarly journals Confined Pulsed Diffuse Layer Charging for Nanoscale Electrodeposition with an STM

2021 ◽  
Author(s):  
Mark Aarts ◽  
Alain Reiser ◽  
Ralph Spolenak ◽  
Esther Alarcon-Llado
Keyword(s):  
Electric Fields ◽  
Scanning Tunneling Microscope ◽  
Electrochemical Etching ◽  
Scanning Probe ◽  
Diffuse Layer ◽  
Scanning Tunneling ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
And Control ◽  
Good Agreement

Regulating the state of the solid-liquid interface by means of electric fields is a powerful tool to control electrochemistry. In scanning probe systems, this can be confined closely to a scanning (nano)electrode by means of fast potential pulses, providing a way to probe the interface and control electrochemical reactions locally, as has been demonstrated in nanoscale electrochemical etching. For this purpose, it is important to know the spatial extent of the interaction between pulses applied to the tip, and the substrate. In this paper we use a framework of diffuse layer charging to describe the localization of electrical double layer charging in response to a potential pulse at the probe. Our findings are in good agreement to literature values obtained in electrochemical etching. We show that the pulse can be much more localized by limiting the diffusivity of the ions present in solution, by confined electrodeposition of cobalt in a dimethyl sulfoxide solution, using an electrochemical scanning tunneling microscope. Finally, we demonstrate the deposition of cobalt nanostructures (<100 nm) using this method. The presented framework therefore provides a general route for predicting and controlling the time-dependent region of interaction between an electrochemical scanning probe and the surface.

scholarly journals Diffusion-Controlled Growth of Oxygen Bubble Evolved from Nanorod-Array TiO2Photoelectrode

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Xiaowei Hu ◽  
Yechun Wang ◽  
Liejin Guo ◽  
Zhenshan Cao
Keyword(s):  
Bubble Growth ◽  
Aqueous Electrolyte ◽  
Experimental Studies ◽  
Nanorod Array ◽  
Diffusion Controlled ◽  
Oxygen Bubble ◽  
Starting Point ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Interface Movement

Nanorod-array structure gains its popularity in photoelectrode design for water splitting. However, the structure’s effects on solid-liquid interface interaction and reaction product transportation still remain unsolved. Gas bubble generally evolved from photoelectrodes, which provides a starting point for the problem-solving. Based on this, investigations on the gas-evolving photoelectrode are carried out in this paper. By experimental studies of wettability on the photoelectrode nanorod-array surface and oxygen bubble growth from anode, we analyzed the interaction affecting the gas-solid-liquid contact behaviors and product transportation mechanism, which is controlled by diffusion due to the concentration gradient of dissolved gases in the aqueous electrolyte and the microconvection caused by the bubble interface movement. In the end, based on the bubble growth characteristics ofRB(t)~t0.5in the experiment, a model describing the product transport mechanism was presented.

Melt-Stirring Method: Influence on Ingot Purity During Ohno Continuous Casting

2019 ◽  
Author(s):  
Simbarashe Fashu ◽  
Lynette Mudzingwa ◽  
Aaron Mukuya ◽  
Macdonald Tozvireva ◽  
Rajwali Khan
Keyword(s):  
Flow Field ◽  
Continuous Casting ◽  
Melt Mixing ◽  
Mechanical Stirring ◽  
Solidification Model ◽  
Velocity Flow ◽  
High Purity Aluminum ◽  
Optimum Velocity ◽  
Solid Liquid Interface ◽  
Solid Liquid

This article outlines the findings in the comparison of the influence of mechanical and electromagnetic stirring (EMS) on ingot long-term purity and uniformity during Ohno continuous casting (OCC). The magnitude of the average optimum velocity flow field and stirring parameters required to effectively purify aluminum ingots using mechanical stirring of the melt was determined and analyzed. Basing on the determined optimum mechanical flow field, electromagnetic parameters producing almost the same flow field near the interface were obtained through careful adjustments of parameters. Optimum parameters of the mechanical and EMS were obtained by numerically solving the solidification model coupled with either the multi-reference frame model (for mechanical stirring) or the magnetohydrodynamic model (for EMS) in CFD Fluent 6.3.26 software. For mechanical stirring, an optimum stirring intensity of 2 mm/min was determined whilst for EMS, the optimum magnetic field with an amplitude of 20 mT and a frequency of 2.7 Hz was determined, and these produced same magnitude optimum flow fields resulting in high-purity aluminum ingots. Comparison of the two methods showed that EMS is good in covering all the regions near the solid–liquid interface and is more effective in bulk melt mixing; thus it produces more uniform and purer ingots for longer casting times.

Melting Rate of a Solid With Periodic Melt Removal

1999 ◽  
Author(s):  
Valerian Nemchinsky
Keyword(s):  
Heat Source ◽  
Liquid Layer ◽  
Practical Interest ◽  
Approximate Solutions ◽  
Melting Rate ◽  
Wide Range ◽  
Heat Processes ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Good Agreement

Abstract The melting rate of a solid, subjected to a heat flux at its surface, changes with time. When a fresh unmelted surface is first exposed to a heat source, the melting isotherm moves quickly inside the solid. Then its motion slows down: this decrease in melting rate is obviously because of increasing thermal resistance of the growing liquid layer that separates solid-liquid interface from the heat source. If the liquid layer is not removed, the melting rate approaches zero. The resultant melting rate depends on the manner in which the melt is removed. In a number of cases of practical interest, the melt is removed not continuously but periodically, in the form of drops. For example, during arc welding with a consumable electrode, these drops are accumulated at the tip of the electrode. When the drop becomes big enough, it is detached from the electrode under action of gravity or electromagnetic force the melt is removed not continuously but periodically, in the form of drops. A simple approximate method is suggested to calculate the melting rate of a solid in the case when melt is removed periodically in form of drops. The method allows one to consider separately the heat transfer in the solid and in the liquid and, thus, to include different heat processes in both phases. Good agreement was demonstrated for exact and approximate solutions for a wide range of parameters.

Study of Metal Solidification Model Based on Dissipative Structure

2013 ◽  
Vol 467 ◽  
pp. 112-115
Author(s):  
Fu Shuang Yang
Keyword(s):  
Temperature Fluctuation ◽  
Dissipative Structure ◽  
Liquid Interface ◽  
Structure Theory ◽  
Metal Solidification ◽  
Constitutional Undercooling ◽  
Solidification Model ◽  
Model Based ◽  
Solid Liquid Interface ◽  
Solid Liquid

The model of metal solidification based on dissipative structure theory is established, which is reduced to threshold depending on the constitutional undercooling criterion, and trigger depending on volume fluctuation and temperature fluctuation. In accordance with the relation of volume fluctuation and temperature fluctuation, the transformation of solid-liquid interface is discussed in three cases.

Comparison of Sharp Interface Dendritic Growth Simulation With Microscopic Solvability Theory

2001 ◽  
Author(s):  
H. S. Udaykumar ◽  
R. Mittal ◽  
L. Mao
Keyword(s):  
Dendritic Growth ◽  
Numerical Technique ◽  
Solidification Process ◽  
Sharp Interface ◽  
Property Variation ◽  
Lagrangian Framework ◽  
Solid Liquid Interface ◽  
Solvability Theory ◽  
Solid Liquid ◽  
Good Agreement

Abstract We present and validate a numerical technique for computing dendritic growth of crystals from pure melts. The solidification process is computed in the diffusion-driven limit. The mixed Eulerian-Lagrangian framework treats the immersed phase boundary as a sharp solid-fluid interface and a conservative finite volume formulation allows boundary conditions at the moving surface to be exactly applied. The case of discontinuous material properties is also computed. The results from our calculations are compared with two-dimensional microscopic solvability theory. It is shown that the method predicts dendrite tip details in good agreement with solvability theory. The ability of the method to treat the front as a sharp entity and therefore to respect discontinuous material property variation at the solid-liquid interface is also shown to produce results in agreement with solvability and with other sharp interface simulations.

Atom-probe analysis of the solid-liquid interface

1995 ◽  
Vol 53 ◽  
pp. 676-677
Author(s):  
J.A. Panitz
Keyword(s):  
Molecular Level ◽  
Selective Adsorption ◽  
Electronic Devices ◽  
Atom Probe ◽  
Chemical Agent ◽  
Hostile Environment ◽  
Solid Interface ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Chemically Selective

The first few atomic layers of a solid can form a barrier between its interior and an often hostile environment. Although adsorption at the vacuum-solid interface has been studied in great detail, little is known about adsorption at the liquid-solid interface. Adsorption at a liquid-solid interface is of intrinsic interest, and is of technological importance because it provides a way to coat a surface with monolayer or multilayer structures. A pinhole free monolayer (with a reasonable dielectric constant) could lead to the development of nanoscale capacitors with unique characteristics and lithographic resists that surpass the resolution of their conventional counterparts. Chemically selective adsorption is of particular interest because it can be used to passivate a surface from external modification or change the wear and the lubrication properties of a surface to reflect new and useful properties. Immunochemical adsorption could be used to fabricate novel molecular electronic devices or to construct small, “smart”, unobtrusive sensors with the potential to detect a wide variety of preselected species at the molecular level. These might include a particular carcinogen in the environment, a specific type of explosive, a chemical agent, a virus, or even a tumor in the human body.

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