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A path to higher Q0 with large grain niobium cavities

Description: The improvement of the quality factor Q{sub 0} of superconducting radio-frequency (SRF) cavities at medium accelerating gradients ({approx} 20 MV/m) is important in order to reduce the cryogenic losses in continuous wave accelerators for a variety of applications. In recent years, SRF cavities fabricated from ingot niobium have become a viable alternative to standard high-purity fine-grain Nb for the fabrication of high-performing SRF cavities with the possibility of significant cost reduction. Initial studies demonstrated the improvement of Q{sub 0} at medium field in cavities heat treated at 800-1000 C without subsequent chemical etching. To further explore this treatment procedure, a new induction furnace with an all-niobium hot-zone was commissioned. A single-cell 1.5 GHz cavity fabricated from ingot material from CBMM, Brazil, with RRR {approx} 200, was heat treated with the new furnace in the temperature range 600-1200 C for several hours. Residual resistance values 1-5 nano-ohm have been consistently achieved on this cavity as well as Q{sub 0} values above {approx} 2 x 10{sup 11} at 2 K and 100 mT peak surface magnetic field. Q{sub 0}-values of the order of 10{sup 11} have been measured at 1.5 K.
Date: July 1, 2012
Creator: Pashupati Dhakal, Gianluigi Ciovati, Ganapati Rao Myneni
Partner: UNT Libraries Government Documents Department

AISI/DOE Technology Roadmap Program: Removal of Residual Elements in The Steel Ladle by a Combination of Top Slag and Deep Injection Practice

Description: The objective of this work was to determine if tin could be removed from liquid steel by a combination of deep injection of calcium and a reducing top-slag practice. The work was carried out in three stages: injection of Ca wire into 35 Kg heats in an induction furnace under laboratory condition; a fundamental study of the solubility of Sn in the slag as a function of oxygen potential, temperature and slag composition; and, two full-scale plant trials. During the first stage, it was found that 7 to 50% of the Sn was removed from initial Sn contents of 0.1%, using 8 to 16 Kg of calcium per tonne of steel. The Sn solubility study suggested that low oxygen potential, high basicity of the slag and lower temperature would aid Sn removal by deep injection of Ca in the bath. However, two full-scale trials at the LMF station in Dofasco's plant showed virtually no Sn removal, mainly because of very low Ca consumption rates used (0.5 to 1.1 Kg/tonne vs. 8 to 16 Kg/tonne used during the induction furnace study in the laboratory). Based on the current price of Ca, addition of 8 to 16 Kg/tonne of steel to remove Sn is too cost prohibitive, and therefore, it is not worthwhile to pursue this process further, even though it may be technically feasible.
Date: August 31, 2001
Creator: Street, S.; Coley, K.S. & Iron, G.A.
Partner: UNT Libraries Government Documents Department

TORO II simulations of induction heating in ferromagnetic materials

Description: TORO II is a finite element computer program that is used in the simulation of electric and magnetic fields. This code, which was developed at Sandia National Laboratories, has been coupled with a finite element thermal code, COYOTE II, to predict temperature profiles in inductively heated parts. The development of an effective technique to account for the nonlinear behavior of the magnetic permeability in ferromagnetic parts is one of the more difficult aspects of solving induction heating problems. In the TORO II code, nonlinear, spatially varying magnetic permeability is approximated by an effective permeability on an element-by-element basis that effectively provides the same energy deposition that is produced when the true permeability is used. This approximation has been found to give an accurate estimate of the volumetric heating distribution in the part, and predicted temperature distributions have been experimentally verified using a medium carbon steel and a 10kW industrial induction heating unit. Work on the model was funded through a Cooperative Research and Development Agreement (CRADA) between the Department of Energy and General Motors` Delphi Saginaw Steering Systems.
Date: September 1, 1997
Creator: Adkins, D.R.; Gartling, D.K.; Kelley, J.B. & Kahle, P.M.
Partner: UNT Libraries Government Documents Department

Glovebox heat test.

Description: An existing argon atmosphere glovebox enclosure was to be refurbished for contaminated operations with a large, high temperature induction furnace. Thermal modeling indicated that glovebox temperatures would be high but acceptable without active cooling, but there were significant concerns that the analysis was inadequate and active cooling would be required. In particular, radiant heating of the glovebox walls by the furnace and pressure control system performance were concerns the thermal model had not addressed. Consequently, a thermal load test with a simulated furnace was designed to answer these questions. The purpose of the test was to determine if active cooling would be required to maintain containment integrity and, if not required, would it still be desirable for improved operations?
Date: August 21, 2002
Creator: Bushnell, C. G.; Rigg, R. H. & Solbrig, C. W.
Partner: UNT Libraries Government Documents Department

Induction furnace testing of the durability of prototype crucibles in a molten metal environment

Description: Engineered ceramic crucibles are commonly used to contain molten metal. Besides high temperature stability, other desired crucible characteristics include thermal shock resistance, minimal reaction with the molten metal and resistance to attack from the base metal oxide formed during melting. When used in an induction furnace, they can be employed as a “semi-permanent” crucible incorporating a dry ram backup and a ceramic cap. This report covers several 250-lb single melt crucible tests in an air melt induction furnace. These tests consisted of melting a charge of 17-4PH stainless steel, holding the charge molten for two hours before pouring off the heat and then subsequently sectioning the crucible to review the extent of erosion, penetration and other physical characteristics. Selected temperature readings were made throughout each melt. Chemistry samples were also taken from each heat periodically throughout the hold. The manganese level was observed to affect the rate of chromium loss in a non-linear fashion.
Date: September 1, 2005
Creator: Jablonski, Paul D.
Partner: UNT Libraries Government Documents Department

Mobile Melt-Dilute Technology Development Project FY 2005 Test Report

Description: The adaptation of Melt-Dilute technology to a mobile and deployable platform progressed with the installation of the prototype air-cooled induction furnace and power generator in an ISO cargo container. Process equipment tests were conducted in FY’05 on two fronts: the melt container and its associated hardware and the mobile furnace and generator. Container design was validated through tests at elevated temperature and pressure, under vacuum, and subjected to impact. The Mobile Melt-Dilute (MMD) furnace and power source tests were completed per the plan. The tests provided information necessary to successfully melt and dilute HEU research reactor fuel assemblies.
Date: January 1, 2006
Creator: Sell, David A. & Fisher, Donald
Partner: UNT Libraries Government Documents Department

Anisotropic porous metals production by melt processing

Description: The collapse of the Soviet Union has left many of its scientific institutes and technical universities without their traditional backbone of financial support. In an effort to stem the export of science to nations advocating nuclear proliferation, and to acquire potentially useful technology, several US government-sponsored programs have arise to mine the best of former USSR scientific advances. In the field of metallurgy, the earliest institutes to be investigated by Sandia National Laboratories are located in Ukraine. In particular, scientists at the State Metallurgical Academy have developed unique porous metals, resembling what could be described as gas-solid ``eutectic``. While porous metals are available in the US and other western countries, none have the remarkable structure and properties of these materials. Sandia began a collaborative program with the Ukrainian scientists to bring this technology to the US, verify the claims regarding these materials, and begin production of the so-called Gasars. This paper will describe the casting process technology and metallurgy associated with the production of Gasars, and will review the progress of the collaborative project.
Date: February 1, 1997
Creator: Shapovalov, V.; Boiko, L.; Baldwin, M.D.; Maguire, M.C. & Zanner, F.J.
Partner: UNT Libraries Government Documents Department

Application of Phosphor Thermometry to a Galvanneal Temperature Measurement System

Description: The Galvanneal Temperature Measurement System (GTMS) was developed for the American Iron and Steel Institute by the Oak Ridge National Laboratory through a partnership with the National Steel Midwest Division in Portage, Indiana. The GTMS provides crucial on-line thermal process control information during the manufacturing of galvanneal steel. The system has been used with the induction furnaces to measure temperatures ranging from 840 to 1292 F with an accuracy of better than {+-}9 F. The GTMS provides accurate, reliable temperature information thus ensuring a high quality product, reducing waste, and saving energy. The production of uniform, high-quality galvanneal steel is only possible through strict temperature control.
Date: June 1, 1999
Creator: Beshears, D.L.; Allison, S.W.; Andrews, W.H.; Cates, M.R.; Grann, E.B.; Manges, W.W. et al.
Partner: UNT Libraries Government Documents Department

Liquid Metal Processing and Casting Experiences at the U.S. Department of Energy's Albany Research Center

Description: In this paper we will discuss some of the early pioneering work as well as some of our more recent research. The Albany Research Center (ARC) has been involved with the melting and processing of metals since it was established in 1942. In the early days, hardly anything was known about melting refractory or reactive metals and as such, virtually everything had to be developed in-house. Besides the more common induction heated air-melt furnaces, ARC has built and/or utilized a wide variety of furnaces including vacuum arc remelt ingot and casting furnaces, cold wall induction furnaces, electric arc furnaces, cupola furnaces and reverberatory furnaces. The melt size of these furnaces range from several grams to a ton or more. We have used these furnaces to formulate custom alloys for wrought applications as well as for such casting techniques as spin casting, investment casting and lost foam casting among many. Two early spin-off industrializations were Wah Chang (wrought zirconium alloys for military and commercial nuclear applications) and Oremet (both wrought and cast Ti). Both of these companies are now part of the ATI Allegheny Ludlum Corporation.
Date: September 1, 2005
Creator: Jablonski, Paul D. & Turner, Paul C.
Partner: UNT Libraries Government Documents Department

The Preparation of Uranium

Description: The method used for the preparation of uranium metal in a fused state was reduction of uranium chloride with calcium in a refractory-lined bomb. The reaction was started by externally heating the bomb with a gas flame. The metal was obtained in a solid chunk which was covered with a layer of fused calcium chloride. The metal obtained by this process had a density of 17.6 which on remelting in a vacuum induction furnace rose to 18.8. The melting temperature of the metal was estimated to be no greater than 1400 C. The metal was malleable, and had a silvery surface when freshly cut which rapidly tarnished, becoming black in the course of a few days.
Date: August 26, 1948
Creator: Rodden, Clement J.
Partner: UNT Libraries Government Documents Department

Radioactive scrap metal decontamination technology assessment report

Description: Within the DOE complex there exists a tremendous quantity of radioactive scrap metal. As an example, it is estimated that within the gaseous diffusion plants there exists in excess of 700,000 tons of contaminated stainless steel. At present, valuable material is being disposed of when it could be converted into a high quality product. Liquid metal processing represents a true recycling opportunity for this material. By applying the primary production processes towards the material`s decontamination and re-use, the value of the strategic resource is maintained while drastically reducing the volume of material in need of burial. Potential processes for the liquid metal decontamination of radioactively contaminated metal are discussed and contrasted. Opportunities and technology development issues are identified and discussed. The processes compared are: surface decontamination; size reduction, packaging and burial; melting technologies; electric arc melting; plasma arc centrifugal treatment; air induction melting; vacuum induction melting; and vacuum induction melting and electroslag remelting.
Date: April 1, 1996
Creator: Buckentin, J.M.; Damkroger, B.K. & Schlienger, M.E.
Partner: UNT Libraries Government Documents Department

Galvanneal Thermometry with a Thermographic Phosphor System

Description: The accurate determination of temperature of galvanneal sheet emerging from a zinc bath is a challenging process measurement. The line moves at high speeds, up to 900 feet per minute, and the emissivity varies widely as it moves through the radio-frequency (RF) induction heating ovens and subsequently cools. This presents a great source of error if the pyrometric approach is used since the accuracy is sensitive to emissivity variation. This problem has been circumvented by an approach described here which uses a thermally sensitive phosphor technique for temperature measurement. For this, a small amount of a phosphor material is deposited on the liquid surface of the sheet. When the small layer of phosphor moves to the measurement station, it is illuminated by a short laser pulse which produces fluorescence from the material. The time dependence of the fluorescence indicates the temperature. Introduction of the microgram quantities of material has been shown to have no detrimental impact on product quality! This presentation describes a phosphor-based system for measuring temperature on a galvanneal manufacturing line. To date, measurements with an accuracy of +/- 5 deg F have been made at National Steel=s Midwest facility. This effort is a part of the Advanced Process Controls Program. The overall goal of the project is to provide accurate on-line temperature information that can be used to increase the yield and quality of the product, thereby reducing energy consumption and time.
Date: December 31, 1997
Creator: Manges, W.W., Allison, S.W.
Partner: UNT Libraries Government Documents Department

A simplified thermal analysis of an inductively heated casting furnace

Description: A simplified thermal analysis technique was developed to analyze an inductively heated casting furnace. Initial operation of the vacuum casting furnace indicated that the outer shell of the vessel was exceeding the temperature design limit. The casting furnace is very complex and not easily modeled in a short period of time through the use of general purpose heat transfer codes. The model took into consideration conduction, natural convection, phase change, radiation heat transfer, and induction heating. The furnace was constructed from ceramic materials, stainless steel, copper, graphite, and other materials. To develop a model based on first principles within a couple of weeks was not considered possible. The alternate approach was to develop a simplified numerical model that relied heavily on experimental data. The purpose of the model was to accurately predict the maximum vessel shell temperatures. A basic 5 node transient model was developed for the complete system. The resultant model predicted the transient heatup of the casting furnace and was able to predict the maximum shell temperature to within 5 C. The model was also capable of predicting the effect of different operations on the shell temperature. This type of modeling approach can be used to troubleshoot existing heat transfer equipment problems, study the effect of different operating sequences, and give insight into the redesign of similar equipment.
Date: December 31, 1995
Creator: Clarksean, R. & Solbrig, C.
Partner: UNT Libraries Government Documents Department

Prevention of Porosity Formation and Other Effects of Gaseous Elements in Iron Castings

Description: Iron foundries have observed porosity primarily as interdendritic porosity in large freezing range alloys such as Ni-Hard I and hypoeutectic high Cr alloys or pinholes and fissure defects in gray and ductile irons. For most iron foundries, porosity problems occur sporadically, but even occasional outbreaks can be costly since even a very small amount of porosity can significantly reduce the mechanical properties of the castings. As a result when porosity is detected, the castings are scrapped and remelted, or when the porosity is undetected, defective parts are shipped to the consumer. Neither case is desirable. This project was designed to examine various factors contributing to the porosity formation in iron castings. Factors such as solubility of gases in liquid and solid iron alloys, surface tension of liquid iron alloys, and permeability of dendritic structures were investigated in terms of their effect on the porosity formation. A method was developed to predict how much nitrogen the molten alloy picks up from air after a given amount of holding time for a given melting practice. It was shown that small batches of iron melts in an induction furnace can end up with very high concentration of nitrogen (near solubility limit). Surface tension of liquid iron alloys was measured as a function of temperature. Effect of minor additions of S, Ti, and Al on the surface tension of liquid iron alloys was investigated. Up to 18% change in surface tension was detected by minor element additions. This translates to the same amount of change in gas pressure required in a bubble of a given size to keep the bubble stable. A new method was developed to measure the permeability of dendritic structures in situ. The innovative aspect of these experiments, with respect to previous interdendritic permeability measurements, was the fact that the dendritic ...
Date: April 1, 2005
Creator: Center, Albany Research
Partner: UNT Libraries Government Documents Department

Feasibility analysis of recycling radioactive scrap steel

Description: The purpose of this study is to: (1) establish a conceptual design that integrates commercial steel mill technology with radioactive scrap metal (RSM) processing to produce carbon and stainless steel sheet and plate at a grade suitable for fabricating into radioactive waste containers; (2) determine the economic feasibility of building a micro-mill in the Western US to process 30,000 tons of RSM per year from both DOE and the nuclear utilities; and (3) provide recommendations for implementation. For purposes of defining the project, it is divided into phases: economic feasibility and conceptual design; preliminary design; detail design; construction; and operation. This study comprises the bulk of Phase 1. It is divided into four sections. Section 1 provides the reader with a complete overview extracting pertinent data, recommendations and conclusions from the remainder of the report. Section 2 defines the variables that impact the design requirements. These data form the baseline to create a preliminary conceptual design that is technically sound, economically viable, and capitalizes on economies of scale. Priorities governing the design activities are: (1) minimizing worker exposure to radionuclide hazards, (2) maximizing worker safety, (3) minimizing environmental contamination, (4) minimizing secondary wastes, and (5) establishing engineering controls to insure that the plant will be granted a license in the state selected for operation. Section 3 provides details of the preliminary conceptual design that was selected. The cost of project construction is estimated and the personnel needed to support the steel-making operation and radiological and environmental control are identified. Section 4 identifies the operational costs and supports the economic feasibility analysis. A detailed discussion of the resulting conclusions and recommendations is included in this section.
Date: September 1, 1995
Creator: Nichols, F.; Balhiser, B. & Cignetti, N.
Partner: UNT Libraries Government Documents Department

Consolidation of cladding hulls from the electrometallurgical treatment of spent fuel.

Description: To consolidate metallic waste that is residual from Argonne National Laboratory's electrometallurgical treatment of spent nuclear fuel, waste ingots are currently being cast using an induction furnace located in a hot cell. These ingots, which have been developed to serve as final waste forms destined for repository disposal, are stainless steel (SS)-Zr alloys (the Zr is very near 15 wt.%). The charge for the alloys consists of stainless steel cladding hulls, Zr from the fuel being treated, noble metal fission products, and minor amounts of actinides that are present with the cladding hulls. The actual in-dated cladding hulls have been characterized before they were melted into ingots, and the final as-cast ingots have been characterized to determine the degree of consolidation of the charge material. It has been found that ingots can be effectively cast from irradiated cladding hulls residual from the electrometallurgical treatment process by employing an induction furnace located in a hot cell.
Date: April 10, 1998
Creator: Keiser, D. D., Jr.
Partner: UNT Libraries Government Documents Department

Metal waste forms from treatment of EBR-II spent fuel.

Description: Demonstration of Argonne National Laboratory's electrometallurgical treatment of spent nuclear fuel is currently being conducted on irradiated, metallic driver fuel and blanket fuel elements from the Experimental Breeder Reactor-II (EBR-II) in Idaho. The residual metallic material from the electrometallurgical treatment process is consolidated into an ingot, the metal waste form (MWF), by employing an induction furnace in a hot cell. Scanning electron microscopy (SEM) and chemical analyses have been performed on irradiated cladding hulls from the driver fuel, and on samples from the alloy ingots. This paper presents the microstructures of the radioactive ingots and compares them with observations on simulated waste forms prepared using non-irradiated material. These simulated waste forms have the baseline composition of stainless steel - 15 wt % zirconium (SS-15Zr). Additions of noble metal elements, which serve as surrogates for fission products, and actinides are made to that baseline composition. The partitioning of noble metal and actinide elements into alloy phases and the role of zirconium for incorporating these elements is discussed in this paper.
Date: May 18, 1998
Creator: Abraham, D. P.
Partner: UNT Libraries Government Documents Department

The Study for Recycling NORM - Contaminated Steel Scraps from Steel Industry

Description: Since 1994, most of the major steel industries in Taiwan have installed portal monitor to detect the abnormal radiation in metal scrap feed. As a result, the discovery of NORM (Naturally Occurring Radioactive Material) has increased in recent years. In order to save the natural resources and promote radiation protection, an experimental melting process for the NORM contaminated steel scraps was carried out by the Institute of Nuclear Energy Research (INER) Taiwan, ROC. The experimental melting process has a pretreatment step that includes a series of cutting and removal of scales, sludge, as well as combustible and volatile materials on/in the steel scraps. After pretreatment the surface of the steel scraps are relatively clean. Then the scraps are melted by a pilot-type induction furnace. This experiment finally produced seven ingots with a total weight of 2,849 kg and 96.8% recovery. All of the surface dose rates are of the background values. The activity concentrations of these ingots are also below the regulatory criteria. Thus, these NORM-bearing steel scraps are ready for recycling. This study has been granted by the regulatory authority.
Date: February 24, 2003
Creator: Tsai, K. F.; Lee, Y. S. & Chao, H. E.
Partner: UNT Libraries Government Documents Department

Stainless steel-zirconium alloy waste forms

Description: An electrometallurgical treatment process has been developed by Argonne National Laboratory to convert various types of spent nuclear fuels into stable storage forms and waste forms for repository disposal. The first application of this process will be to treat spent fuel alloys from the Experimental Breeder Reactor-II. Three distinct product streams emanate from the electrorefining process: (1) refined uranium; (2) fission products and actinides extracted from the electrolyte salt that are processed into a mineral waste form; and (3) metallic wastes left behind at the completion of the electrorefining step. The third product stream (i.e., the metal waste stream) is the subject of this paper. The metal waste stream contains components of the chopped spent fuel that are unaffected by the electrorefining process because of their electrochemically ``noble`` nature; this includes the cladding hulls, noble metal fission products (NMFP), and, in specific cases, zirconium from metal fuel alloys. The selected method for the consolidation and stabilization of the metal waste stream is melting and casting into a uniform, corrosion-resistant alloy. The waste form casting process will be carried out in a controlled-atmosphere furnace at high temperatures with a molten salt flux. Spent fuels with both stainless steel and Zircaloy cladding are being evaluated for treatment; thus, stainless steel-rich and Zircaloy-rich waste forms are being developed. Although the primary disposition option for the actinides is the mineral waste form, the concept of incorporating the TRU-bearing product into the metal waste form has enough potential to warrant investigation.
Date: July 1996
Creator: McDeavitt, S. M.; Abraham, D. P.; Keiser, D. D., Jr. & Park, J. Y.
Partner: UNT Libraries Government Documents Department

Melt-Dilute Treatment of Spent Nuclear Fuel Assemblies from Research and Test Reactors

Description: The Savannah River Site is the US Department of Energy''s preferred site for return and treatment of all aluminum-base, spent, research and test reactor fuel assemblies. There are over 20,000 spent fuel assemblies now stored in different countries around the world, and by 2035 many will be returned to SRS for treatment and interim storage, in preparation for disposal in a geologic repository. The early fuel assemblies for research and test reactors were made using aluminum clad plates that were fabricated from highly enriched (93 percent) uranium-aluminum alloy. Later, powder metallurgical fabrication methods were developed to produce plate fuels with higher uranium contents using either uranium aluminide, uranium oxide or uranium silicide powders mixed with aluminum. Silicide fuel elements generally are fabricated with low enriched uranium containing less than 20 percent 235U. Following irradiation, the spent fuel assemblies are discharged from the reactor, and most assemblies have been stored in under-water pools, some since the early 1950''s. A number of disposition options including direct/co-disposal and melt-dilute treatment were evaluated recently. The melt-dilute technique was identified as the preferred method for treatment of aluminum-base spent fuel. The technique consists of melting the spent fuel assembly and adding depleted uranium to the melt for isotopic dilution to less than 20 percent 235U. Aluminum is added, if necessary, to produce a predetermined alloy composition. Additionally, neutron poisons may be added to the melt where they form solid solution phases or compounds with uranium and/or aluminum. Lowering the enrichment reduces both criticality and proliferation concerns for storage. Consolidation by melting also reduces the number of storage canisters. Laboratory and small-scale process demonstration using irradiated fuel is underway. Tests of the off gas absorption system have been initiated using both surrogate and irradiated RERTR mini fuel plates. An experimental L-Area facility (LEF) is planned to ...
Date: September 29, 1999
Creator: Peacock, H.B.
Partner: UNT Libraries Government Documents Department

The aluminium-scandium-lithium-magnesium system as a potential source of superplastically formable alloys

Description: Alloys from the aluminum-lithium-scandium-magnesium system have been cast and rolled for study. The goal is to evaluate this system for the development of superplastically formable, high strength alloys. Aluminum-scandium-magnesium alloys have shown potential as superplastic alloys. These alloys rely on small Al{sub 3}Sc (ordered L1{sub 2}) precipitates for grain structure stabilization and strengthening. Additional precipitation strengthening is required to raise their strength to levels sufficient for aircraft applications. The addition of lithium provides this additional strengthening through the formation of Al{sub 3}Li({delta}{prime}). To produce the alloys studied in this research, a unique induction melting furnace was constructed that incorporates special features to produce aluminum-lithium alloys with low hydrogen content. The furnace also features a water cooled, copper casting mold to achieve a moderately rapid solidification rate. This is because the amount of scandium used (0.5 wt %) is in excess of the solubility limit and Al{sub 3}Sc cannot be re-solutionized to any extent. It is therefore desired to super-saturate the matrix with as much scandium as possible for later precipitation. Two high lithium alloys were produced, ALS2 (nominal composition Al-2.2Li-O.5 Sc) and AlS4 (nominal composition Al-2.0Li-2.2Mg-0.5Sc) that were strengthened with {delta}{prime} (Al{sub 3}Li). These alloys exhibited strength and ductility superior to those of aluminum-lithium-(magnesium)-zirconium alloys. This is because the scandium containing alloys have developed a finer grain structure and the Al{sub 3}Sc precipitates contribute to the alloys strength. 41 refs., 29 figs.
Date: July 1, 1990
Creator: Emigh, R.A.
Partner: UNT Libraries Government Documents Department

High-frequency furnace. Technical progress report. Eighth quarterly report for period ending September 30, 1983

Description: An important phase of silicon solar cell production via ingot technology is the conversion of polycrystalline silicon to the single-crystal, ingot form that is required for wafering. In the current art such ingots are produced either by pulling from the melt or by various crucible growth techniques. A characteristic of all of these methods, which use bulk melting, is that a refractory crucible is required to hold the molten charge. This imposes the disadvantages that the silicon is always contaminated to some degree by dissolution of the refractory into the melt, which can reduce solar cell efficiency, and the crucibles themselves represent a significant cost factor. Clearly, elimination of the need for a refractory crucible in the melt growth of single-crystal silicon would be an important process improvement. Work to be conducted is to investigate a radical, new heating technique which holds potential for achieving crucibleless melting. Ingots would be pulled from the melt as per conventional practice. Briefly, a high frequency current (10 KHz) is caused to flow on the surface of a mass of metal as a result of skin effect and proximity effect. By controlling the power input and heat losses from the billet it is anticipated that it will be possible to form and maintain in its top surface a molten pool which will be contained in a solid, outer layer or skull of metal. The basic objectives of the project are to prove the general feasibility of this melting technique. This is to be accomplished by building and operating a small, experimental furnace. To simplify the project as much as possible and to minimize research costs, cast iron will be used in place of silicon for melt experiments.
Date: January 1, 1983
Creator: Zumbrunnen, A D
Partner: UNT Libraries Government Documents Department