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Production of High Purity Metals: A Review on Zone Refining Process  [PDF]
Xiaoxin Zhang, Semiramis Friedrich, Bernd Friedrich
Journal of Crystallization Process and Technology (JCPT) , 2018, DOI: 10.4236/jcpt.2018.81003
Abstract: Purification is a primary application of zone melting, in which the improvement of efficiency, production yield and minimum achievable impurity level are always the research focus due to the increasing demand for high purity metals. This paper has systematically outlined the whole development of related research on zone refining of metals including basic theories, variants of zone refining, parametric optimization, numerical models, and high purity analytical methods. The collection of this information could be of good value to improve the refining efficiency and the production of high purity metals by zone refining.
Possible scenario of the melting of metals  [PDF]
M. I. Katsnelson,A. V. Trefilov
Physics , 1999,
Abstract: A microscopic picture of the ``preparation'' of a crystal to the transition to liquid state at the approach to melting temperature is proposed. Basing on simple crystallogeometric considerations and the analysis of the computational results for corresponding anharmonic characteristics an evaluation is given for the magnitude of atomic displacements leading to the appearance of close packed Bernal pseudonuclei in the solid phase. A physical meaning of the classical Lindeman criterion and the mechanisms of the formation of free volume in the crystal phase are discussed.
Stripe melting and quantum criticality in correlated metals  [PDF]
David F. Mross,T. Senthil
Physics , 2012, DOI: 10.1103/PhysRevB.86.115138
Abstract: We study theoretically quantum melting transitions of stripe order in a metallic environment, and the associated reconstruction of the electronic Fermi surface. We show that such quantum phase transitions can be continuous in situations where the stripe melting occurs by proliferating pairs of dislocations in the stripe order parameter without proliferating single dislocations. We develop an intuitive picture of such phases as "Stripe Loop Metals" where the fluctuating stripes form closed loops of arbitrary size at long distances. We obtain a controlled critical theory of a few different continuous quantum melting transitions of stripes in metals . At such a (deconfined) critical point the fluctuations of the stripe order parameter are strongly coupled, yet tractable. They also decouple dynamically from the Fermi-surface. We calculate many universal properties of these quantum critical points. In particular we find that the full Fermi-surface and the associated Landau quasiparticles remain sharply defined at the critical point. We discuss the phenomenon of Fermi surface reconstruction across this transition and the effect of quantum critical stripe fluctuations on the superconducting instability. We study possible relevance of our results to several phenomena in the cuprates.
Validation Experiments for LBM Simulations of Electron Beam Melting  [PDF]
Regina Ammer,Matthias Markl,Vera Jüchter,Carolin K?rner,Ulrich Rüde
Computer Science , 2014,
Abstract: This paper validates 3D simulation results of electron beam melting (EBM) processes comparing experimental and numerical data. The physical setup is presented which is discretized by a three dimensional (3D) thermal lattice Boltzmann method (LBM). An experimental process window is used for the validation depending on the line energy injected into the metal powder bed and the scan velocity of the electron beam. In the process window the EBM products are classified into the categories, porous, good and swelling, depending on the quality of the surface. The same parameter sets are used to generate a numerical process window. A comparison of numerical and experimental process windows shows a good agreement. This validates the EBM model and justifies simulations for future improvements of EBM processes. In particular numerical simulations can be used to explain future process window scenarios and find the best parameter set for a good surface quality and dense products.
Melting Temperature of Metals Based on the Nearly Free Electron Model  [PDF]
Tamifusa Matsuura,Hidenori Suzuki,Ken'ichi Takano,Fumihiro Honda
Physics , 2009, DOI: 10.1143/JPSJ.79.053601
Abstract: We propose a general formula for the melting temperature of metals in terms of electronic mass, electronic number, and nearest-neighbor lattice distance. We derive it from the instability of the transverse phonon in the solid phase, using the nearly free electron model. Including higher order terms of vibrations enhanced near the melting temperature, the electronic restoring force is reduced and the ionic one is negligible. This fact greatly brings down the melting temperature, bringing it close to experimental data in the range of 10 % for Cs, Cu, Au, and Ba. Also, this theory confirms the Lindemann criterion.
Effects Of Microwave On Molten Metals With Low Melting Temperatures  [PDF]
Xiang Sun, Jiann-Yang Hwang, Xiaodi Huang, Bowen Li, Shangzhao Shi
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2005, DOI: 10.4236/jmmce.2005.42010
Abstract: Different metals were tested to determine if microwave irradiation can heat liquid metals. Temperature profiles of different molten metals under microwave radiation revealed that molten metals are primarily microwave reflectors. To explain this phenomenon, microwave heating mechanisms and skin depths of conductors have been introduced. The influences of resistivities on metal skin depths are also discussed.
Application of Electron Beam Melting to the Removal of Phosphorus from Silicon: Toward Production of Solar-Grade Silicon by Metallurgical Processes  [PDF]
Hideaki Sasaki,Yoshifumi Kobashi,Takashi Nagai,Masafumi Maeda
Advances in Materials Science and Engineering , 2013, DOI: 10.1155/2013/857196
Abstract: Removal methods of impurity from metallurgical-grade silicon (Si) are intensively studied to produce solar-grade silicon (SoG-Si) with a smaller economical load and lower cost. Removal of phosphorus (P) has been an important issue because of difficulties in application of conventional metallurgical methods such as solidification refining. Because P evaporates preferentially from molten Si due to its high vapor pressure, electron beam (EB) melting has been applied to the purification of Si. The evaporation of impurity P from Si is considered based on previous thermodynamic investigations here, and several research reports on EB melting of Si are reviewed. 1. Application of EB Melting to Removal of P from Si Photovoltaic power generation is drawing attention, and the most prevalent material for solar cells is silicon (Si). Monocrystalline, polycrystalline, and amorphous Si accounted for 90% of total solar cell production in 2011 [1]. Conversion efficiency of solar cells depends on the purity of Si [2], and it is generally believed that a purity of 99.9999% is required for solar grade silicon (SoG-Si). The Siemens process, which is used to produce semiconductor grade silicon (99.999999999%), has been applied to SoG-Si; however, the process consumes a large amount of energy because it includes chlorination, distillation, and reduction of Si. Therefore, a less expensive purification method of Si is required for widespread use of solar cells. To decrease the energy consumed in the production of SoG-Si, methods of removing impurities from metallurgical grade Si (MG-Si, ~99%) have been developed. These methods include, for example, directional solidifications making use of different solubility of impurity elements into solid and liquid Si. These methods are referred to as “metallurgical processes” to distinguish them from “chemical processes” such as the Siemens process. Table 1 shows examples of acceptable concentrations of impurities in SoG-Si. In one case, the values were defined as the impurity concentration which degrades the conversion efficiency of a solar cell by 10% [3]. Acceptable concentrations were defined more strictly elsewhere [4]. Table 1 also shows the segregation coefficient, which is the ratio of solubility of the element in solid Si and liquid Si at the melting point [5]. Elements with small segregation coefficients, such as Fe and Ti, can be removed from Si by directional solidification. Phosphorus (P) and boron (B), however, are difficult to remove by this means because of their large segregation coefficient. Therefore, new processes have
Possible ways of refining precious group metals (PGM) obtained from recycling of the used auto catalytic converters  [PDF]
M. Saternus,A. Fornalczyk
Metalurgija , 2013,
Abstract: Used auto catalytic converters contain PGM metals. There are many methods of recovering these metals from used auto catalytic converters, e.g. Rose method, cyanide extraction, chlorination, segregation, melting methods, blowing with metal vapours and metal collector method. They are based on pyro- and hydrometallurgical processes. As a result of such treatment the solution or metal collector with PGM metals is obtained. Then the important task is to separate the particular precious metals. In the paper review of such methods and short characteristics are presented. To those methods belong: classical precipitation method, solvent extraction method, solid–phase extraction method, chromatographic separation.
The property estimation of copper alloys refining slag with the stimulators addition use the database  [PDF]
S. Biernat,A. W. Byda?ek,P. Schlafka
Archives of Foundry Engineering , 2011,
Abstract: The paper presents the analysis and investigation of the state of art in the field of metallurgy copper alloy in the reduction conduction.This article contains information concerning the analysis of the possibility of defining refinery qualities of slag based of the thermophysical and thermodynamical data. The isues presented deals not only with refining copper and melting stages, but also the idea of building an optimization program. In its assumption the program is supposed to check and search specific data very quickly on the particular types of slag. In the presented work it has been decided to show the results of the industrial investigations obtained with reference to copper alloys in the reduced melting conduction.
The estimation of quality refining covers  [PDF]
S. Biernat,A. W. Byda?ek
Archives of Foundry Engineering , 2010,
Abstract: This article contains information concerning of the analysis the possibility of defining refinery qualities of the slag based thermophysical and thermodynamical data. The paper presents a model of slag refining processes and a method of determining the reduction capability of slag solutions. Slag was analysed with the use of the DTA methods. The study of computer programme including the satisfactory number of data, both thermodynamical how and experimental - gathered with literature and own investiganion, the simpler qualification of optimum proprieties of slags would make possible. Settled by programme of areas the verification it is possible to the end to conduct in the support about proposed by A. W. Byda ek method of the modelling processes of refinement from it utilization the derivatograph or directly in conditions industrial. The isues presented deals not only with refining copper and melting stages, but also of the idea building an optimization program. In its assumption the program is supposed to check and search specific data very quickly on the particular types of slag..User starting programme should have the possibility of choice kind of the information.
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