Room: 315B
Session Chairperson: J.K. Hirvonen, Metals Research Branch, U.S. Army Research Laboratory, AMSRL-WM-ME, APG, MD 21005-5069
THE DARPA PROGRAM IN ADVANCED THIN FILM COATING TECHNOLOGY: Lawrence H. Dubois, Thomas J. Moran, Defense Sciences Office, Defense Advanced Research Projects Agency, Arlington, VA
Corrosion and wear of mechanical and structural components and systems cost U.S. Industry and the military millions of dollars every year and leads to excess waste, decreased product reliability, and poor worker safety. Unfortunately, the surface preparation, application and use of most coatings to protect to protect these components leads to the generation of significant quantities of hazardous wastes which are subsequently released to the air, water and land. Through the development of new, more advanced corrosion and wear resistant coating systems and/or surface preparation techniques, the DoD and its suppliers can not only minimize the environmental impact of these materials, but improve performance and decrease costs. The DARPA program in advanced thin film coatings is developing innovative technologies to eliminate volatile organic compounds, heavy metals and other hazardous waste materials in the manufacture, application and maintenance of high performance wear, fatigue and corrosion resistant coatings of utility to the DoD.
9:10 am
ADVANCES IN SURFACE TECHNOLOGY IN RUSSIA: Anthony J. Perry, ISM Technologies, San Diego, CA; Jesse N. Matossian, Hughes Research Labs, Malibu, CA; Michael O. Thompson, Cornell University, Ithaca, NY
Since the removal of the Berlin Wall and the changes in the relationships between the former Soviet Union with the rest of the world, a great deal of information has become available on their technology. Developments in some areas appear to have outpaced those in the West, specifically in the application of ion beams to surface modification. The present authors have had the opportunity to attend workshops in Russia and to visit laboratories. In the present work, a report is given on some of the technologies reviewed there and which are now becoming available to the West. These include novel designs in the fields of cathodic arc sources and gas ion sources, and intense ion and electron beams. These technologies will be presented.
9:45 am
THE JET DEPOSITION PROCESS: NEW TECHNIQUES AND APPLICATIONS: Brett Halpern, Jet Process Corporation, 24 Science Park, New Haven, CT 06511
Development of the "sonic jet sources in low vacuum" theme enables the Jet Vapor DepositionTM process (JVDTM) to make a wide range of thin film materials. Thus, we have developed jet sources, driven in the 0.1-10 torr range by mechanical pumps, for deposition of metals, semiconductors, oxides, nitrides, alloys and guest-host materials in multicomponent and multilayer form. These sources combine high rate, high efficiency, and low temperature operation with excellent control of microstructure. For example, we recently described and patented an "electron-jet, or e-jetTM "source, which combines metal thermal vaporization with an intense thermionic plasma and allows high rate deposition of metals, oxides and nitrides coupled with simultaneous ion bombardment at high flux and low energy. JVD's versatility opens new approaches to problems in electronic, automotive, aerospace, corrosion resistance and optical applications. In this talk we review the principles of JVD, new jet source developments, JVD's advantages over conventional CVD and PVD and recent commercial applications.
10:20 am BREAK
10:30 am
DoD ACTIVITIES IN ION BEAM PROCESSING: James K. Hirvonen, Metals Research Branch, U.S. Army Research Laboratory, AMSRL-WM-ME, APG, MD 21005-5069
The use of energetic ion beams for beneficially modifying the surface sensitive properties of critical military material has been pursued within DoD now for almost two decades demonstrating improved material properties including increased wear-, fatigue-, corrosion-, and oxidation-resistance. High dose ion implantation has been demonstrated to be technically suitable for extending the lifetime of precision aerospace bearings (U.S. Navy) and specific cutting tools (U.S. Army). Ion beam assisted deposition (IBAD) processing has increased both the number and the variety of DoD applications, including robust optical coatings and coatings for wear, corrosion and fatigue improvements. A DoD program exploring these benign, dry, ion beam techniques for supplanting the wet Cr/Cd electroplating processing is currently underway at the National Defense Center for Environmental Excellence in Johnstown, PA. This program includes the scheduled installation, (Fall 96) of a large ion beam system for the processing of selected DoD components. The status of this program and other recent DoD ion beam efforts will be discussed.
11:05 am
SURFACE PROCESSING BY GAS CLUSTER ION BEAMS: Allen Kirkpatrick, Epion Corporation, Bedford, MA 01730
Clusters consisting of hundreds or thousands of weakly bound atoms can be formed from various gases by expanding the gas through a small nozzle into high vacuum. The clusters can be ionized and subjected to acceleration potentials so as to produce beams of cluster ions which possess high total energy, mass and momentum in combination with low energy per constituent atom. Cluster ion beams have been shown to be capable of producing processing effects which have not been available with monomer ions. A number of prospective applications for gas cluster ions have been identified and commercial gas cluster ion beam equipment is now being developed. This paper will review the current status of gas cluster ion technology and will include discussion of methods for generation of the gas cluster beams, kinetics of the interactions of cluster ions with solid materials, anticipated applications and available equipment.
11:40 am
COMPARISON OF DEPOSITION TECHNOLOGIES FOR ION ASSISTED COATINGS A.J. Armini, S.N. Bunker, L.A. Stelmack, Implant Sciences Corporation
The current ion assisted coating methods and the corresponding equipment are compared, for depositing a variety of wear and/or corrosion resistant coatings. Ion beam assisted deposition (IBAD), unbalanced magnetron sputtering, and cathodic arc processes were used to deposit coatings of amorphous diamond, chromium, and noble metals for various applications in the aerospace, biomedical, and industrial markets. The three techniques were compared with respect to coating uniformity, deposition rate, adhesion, and microstructure. Coatings were evaluated for hardness, adhesion, smoothness, sliding wear, and friction coefficient. Coating-substrate adhesion was measured using the diamond scratch test. Wear and friction were measured against several opposing materials, using a high speed, high temperature pin-on-disk instrument. Scale-up issues and the suitability of each technology for various production applications will be discussed.
Room: 340B
Session Chairperson: S. Jin, Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974
8:30 am INVITED
ELECTRODE MATERIALS FOR LITHIUM BATTERIES AND FUEL CELLS: A. Manthiram, Center for Materials Science and Engineering, ETC 9.104, The University of Texas at Austin, Austin, TX 78712
Electrically conducting metal oxides find potential applications in electrochemical systems such as batteries and fuel cells. For example, several lithium insertion compounds are used as cathodes in rechargeable lithium batteries. However, the battery performance and cyclability of the cathodes are controlled partly by the microstructure and morphology, which in turn are influenced by the methods of synthesis and processing used. A novel approach involving the reduction of aqueous metallate solutions with aqueous alkali metal borohydrides at ambient temperatures to obtain amorphous or nanocrystalline transition metal oxide electrodes will be presented. The electrode performance of, for example, amorphous or nanocrystalline VO2, CrO2, MoO2, and LiMn2O4 will be discussed. In addition, the design and synthesis of perovskite-based metal oxides that exhibit mixed electronic and ionic conductivity will be presented. These mixed conductors are attractive not only as electrode materials for solid oxide fuel cells but also for oxygen separation membranes and catalysts.
9:00 am INVITED
EPITAXIAL THIN FILMS AND HETEROSTRUCTURES OF METALLIC OXIDES FOR DEVICE APPLICATIONS: C.B. Eom, Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708
For many electronic device applications, it is necessary to have epitaxial growth of metallic oxide thin films in a single heterostructure. We have grown epitaxial thin films of Sr1-xCaxRuO3 and La6.4Sr1.6Cu8O20 in-situ by 90 degree off-axis sputtering. These metallic oxides are pseudo-cubic perovskites, which could be ideal electrodes for ferroelectric devices, and normal metal barriers for SNS junctions in integrated superconducting devices. However, the properties of epitaxial thin films of the metallic oxides may be quite different from the corresponding bulk materials because of the existence of strain and cation disorder in the films. We have observed a strain stabilized metal-insulator transition in epitaxial Sr1-xCaxRuO3 thin films deposited on (100) SrTiO3 substrates that differed in crystalline quality. The growth mechanisms of the films and their correlation with the crystalline quality of the substrates is discussed. We have also grown epitaxial planar SNS heterostructures YBCO/La6.4Sr1.6Cu8O20/YBCO. We will discuss the microstructures, junction properties and the origin of the interface resistance between YBCO and La6.4Sr1.6Cu8O20.
9:30 am INVITED
FUNDAMENTAL INVESTIGATIONS OF CADMIUM STANNATE THIN FILMS: T.J. Coutts, W.P. Mulligan, X. Wu, National Renewable Energy Laboratory, Golden, CO 80215
We are investigating a variety of novel transparent conductive oxides, including cadmium stannate (Cd2SnO4), cadmium indate (CdIn2O4), zinc stannate (Zn2SnO4 and ZnSnO3), and zinc indium oxide (Zn2In2O5). To date, the cadmium stannate films have shown the highest conductivity, with resistivities as low as 1.3X10-4 ohm-cm. Films have been fabricated with sheet resistances as low 2 ohm/sq., while maintaining approximately 80% transmittance across the visible and near infrared. The conductivity of the films is high because of both high electron concentration and relatively high electron mobility. One possible explanation for the high mobility is that the electron effective mass is unusually low. Direct measurement of the effective mass by cyclotron resonance is not feasible due to the extremely short electron scattering times characteristic of these highly defective materials. Instead, we have estimated effective mass by Drude modelling of optical reflectance and transmittance data, and by analysis of a combination of electron transport measurements, including resistivity, Hall effect, thermopower, and transverse Nernst-Ettingshausen effect. Cadmium stannate films with a range of carrier concentrations were fabricated, and their optical and transport properties were measured. We will present the results of our comparative analysis of carrier effective mass by these two independent methods. Possible conduction band curvature, and carrier scattering time and mechanisms will also be reported. The implications for design of novel transparent conductive oxides will be discussed.
10:00 am BREAK
10:20 am INVITED
ELECTRICALLY ACTIVE POLYMERS: M. E. Galvin, Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974
It has been known for two decades that polymers with extended conjugation could be rendered highly conductive by doping, that is, by oxidizing or reducing the polymer chain. The commercialization of these polymers has, however, been limited by their poor chemical stability in the doped form. More recently these polymers have shown promise when used in their undoped forms in LEDs, light emitting diodes, or in thin film transistors. This talk will cover the recent developments in these two areas and describe the scientific challenges which still remain.
10:50 am INVITED
NOVEL ANISOTROPIC CONDUCTORS THROUGH THE DESIGN OF COMPOSITE STRUCTURES: S. Jin, Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974
Anisotropic electrical conductivity with many orders of magnitude change along different directions can be obtained by the design of novel, composite structures. Materials with such characteristics are useful for a variety of electronic applications including ultra-high density circuit interconnections, 3-D packaging, and solder-free interconnection. Optically transparent but electrically conductive medium can also be made via composite route. Novel composite structures with vertically aligned metal elements in ceramic or polymer sheets will be described. Materials fabrication process, electrical properties and reliability issues will also be discussed.
11:20 am
OPTICAL STUDIES FOR THE CHARACTERIZATION OF CONDUCTING POLYMERS:L.M. Abrantes, CECUL, Dept. Qumica, FCUL, Bloco C1-5 piso, 1700 Lisboa, Portugal; J.P. Correia, INETI, Dept. de Energias Renovaveis, 1699 Lisboa Codex, Portugal
The properties of conducting polymers have stimulated much interest in many fields of research and considerable effort has been directed towards reliable characterization of the envisaged properties for commercial applications. Apart from polyacetylene (PA) the major existing conducting polymers can be electrochemically synthesized and this encouraged the use of conventional electrochemical methods coupled to other techniques to study the electropolymerization and insulator/conductor conversion of these new materials. The purpose of this paper is to give an overview of the ability of optical methods to provide useful information on the properties of electronically conducting polymers. Three techniques will be focused and their contribution illustrated considering different systems: 1. The principles of the Probe Beam Deflection (also known as Mirage Effect) and respective data for polyaniline (PANI) systems discussed. 2. Recent applications of Photocurrent Spectroscopy are reviewed and photoeffects displayed by poly-3-methylthiophene (P3MeTh) analysed. 3. The information on structural changes during electropolymerization and doping processes, which can be provided by ellipsometry evidenced by the study of PANI, P3MeTh and polypyrrole.
11:40 am
HYDROSTATICALLY EXTRUDED COPPER-NIOBIUM SPARK ERODED POWDER: M.A. Hill, J.F. Bingert, F.E. Spada, A.E. Berkowitz, S.A. Bingert, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, Center for Magnetic Recording Research, University of California at San Diego, La Jolla, CA 92093
High strength, high conductivity copper-niobium wire is a promising conductor wire for use in pulsed high field magnets. Due to the high melting point of niobium, it is difficult to produce an ingot with a fine, homogeneous structure. One possibility for reducing the scale of the cast structure, improving the homogeneity of the ingot, and enhancing the strength at a given level of deformation strain is to use rapid solidification techniques, such as powder processing, to fabricate the Cu-Nb ingot. Both melt spinning and gas atomization of Cu-Nb are difficult due to problems associated with thermal shock of components, such as crucibles and stopper rods. Spark erosion provides a method for powder production without the use of components which may crack under thermal stresses. Furthermore, in the spark erosion process quench rates exceeding 106 K/s from temperatures above 104 K promote formation of fine particles with homogeneous composition. Spark eroded Cu-10 vol % Nb powder has been consolidated by cold pressing and subsequently hydrostatically extruded to form 2.5 cm diameter rod with a yield strength of 500 MPa and a conductivity of 85% IACS at a reduction of 
=2.6.
Room: 230A
Session Chairperson: Michel Reverdy, Aluminium Pechiney, Pechiney-Balzac, France
8:30 am
CELL HOODING EFFICIENCY MEASUREMENTS FOR HS SØDERBERG CELLS: Alton T. Tabereaux, Jim Brown, Ivan Eldridge, Reynolds Metals Company, Manufacturing Technology Laboratory, 3326 East 2nd Street, Muscle Shoals, AL 35661
A method has been developed for measuring the gas capture efficiency of volatile gas emissions for the cell hooding system of HS Søderberg cells. No prior method for measuring the gas capture efficiency for HS Søderberg cells has been reported to date. This paper presents the newly developed procedures, techniques and results measured during plant tests for the gas capture efficiency of 92 kA HS Søderberg cells equipped with an improved cell hooding system to reduce plant emissions. The dependency of the gas capture efficiency upon the duct exhaust velocity was determined for the HS Søderberg cells using this method.
8:55 am
COS, CS2 AND SO2 EMISSIONS FROM PRE-BAKED HALL HEROULT CELLS: Frank M. Kimmerle, Luc Noël, Alcan International Ltd., Arvida Research and Development Centre, P.O. Box 1250, Jonquiere, QC, G7S-4K8, Canada; John T. Pisano, Unisearch Ass. Inc., 222 Snidercroft Rd., Concord, ONT, L4K 1B5, Canada
Measurements of CO2, CO, COS and CS2 emissions in collected gas samples by GC-MS and of SO2 by ion chromatography of scrubber solutions allowed us to complete a carbon and sulphur mass balance for P155 pre-bake electrolysis cells. COS and CS2 emissions were confirmed by continuous analysis using tunable diode laser absorption spectrometry of the flue cases from 64 cells over a two day period. While the volume mixing ratios of COS and CS2 of the flue gases agree with those reported recently for a German prebake smelter, the specific emissions were found to be considerably lower.
9:20 am
PERFLUOROCARBON (PFC) GENERATION IN LABORATORY-SCALE ALUMINUM REDUCTION CELLS: Steen Nissen, Donald R. Sadoway, Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-4307
The generation of CF4 and C2F6 is being studied in a laboratory-scale aluminum reduction cell. During electrolysis in well behaved cells and in cells on anode effect, anode gases have been analyzed by gas chromatography (GC) on-line. Process parameters have been systematically varied to determine how PFC generation depends upon anode material (industrial pre-bake and Søderberg), bath ratio (1.45, 1.15 and 0.56), LiF concentration (0 and 2.7%), current density (0.7 A cm-2 and higher), and temperature (970 and 800°C). Measurements agree with those reported for industrial cells with respect to total PFC level as well as the ratio of CF4 to C2F6. The main factor determining PFC concentration appears to be the anodic overvoltage. The functional relationship between the rate of PFC generation and anodic overvoltage is derived from the current-overpotential equation. Research sponsor: U.S. Environmental Protection Agency, Atmospheric Pollution Prevention Division.
9:45 am
REDUCTION OF THE CF4 EMISSIONS FROM PRE-BAKED HALL HEROULT CELLS: Frank M. Kimmerle, Gilles Potvin, Alcan International Ltd., Arvida Research and Development Centre, P.O. Box 1250, Jonquiere, QC, G7S-4K8, Canada; John T. Pisano, Unisearch Ass. Inc., 222 Snidercroft Rd., Concord, ONT, L4K 1B5, Canada
It has been established that CF4 and C2F6 are given off from the Hall-Heroult electrolysis cells during so-called anode effects. The introduction of a novel alumina feeding and cell operation algorithm in the Grande Baie smelter operating with P155 pre-bake electrolysis cells, has dramatically reduced the anode effect duration and anode effect frequency. The implementation of the new cell control logic constituted a unique opportunity to compare data from some two hundred events before and after commissioning on identical cells. Using tunable diode laser absorption spectrometry we measured PFC emissions from individual anode effects with a temporal resolutions of as little as 8 seconds. This communication will describe the experimental set-up, present the decrease in PFC emissions attained, discuss the CF4/C2F6 ratios observed and compare the data observed with model predictions.
10:10 am BREAK
10:30 am
POTROOM COMPARISON TRIAL OF A LASER HF MEASURING INSTRUMENT AND AN INTENSIVE AIR SAMPLING ARRAY OVER A 400 M PATH: D.L. Death, J.E. Eberhardt, R.P. Read, C.A. Rogers, CSIRO Division of Minerals, Private Mail Bag #5, Menai, NSW, 2234 Australia; M. Atkinson, Comalco Research Center, P.O. Box 316, Thomastown, Vic. 3074, Australia; D. Collins, Alcoa of Australia Ltd., Point Henry Works, P.O. Box 460, Geelong, VIC. 3220, Australia; K. Whiteley, Tomago Aluminium Co. Ltd., P.O. Box 405, Raymond terrace NSW, 2324, Australia
The laser hydrogen fluoride measuring instrument described at TMS '95 was compared with an optimised eighty-fold array of air sampling cassettes over a 400m path in a potroom of the Tomago (NSW) aluminium smelter. Thirteen one-hour comparison trials were performed at average HF concentrations over the range 0.07-3.7 mg/Nm3. For the twelve concentrations up to 2.0 mg/Nm3 the cassette array average and the laser average correlated with a slope of 0.93 and a regression coefficient r2=0.98. For the nine points up to 1.5 mg/Nm3 the slope was 1.02 and the regression coefficient r2=0.99. As configured during the comparison trial the laser instrument did not correctly indicate the 3.7 mg/Nm3 HF concentration due to insufficient signal to noise ratio. The correlation between array and laser was considered very good. The technique is being commercialised. The contributions of Frank Fleer of AirWaterNoise Ltd to this work are gratefully acknowledged. This work was partly supported by the Australian Aluminium Council.
10:55 am
THE MEASUREMENT OF GASEOUS FLUORIDE IN THE ALUMINIUM INDUSTRY: John M. Jones, Anglesey Aluminium Metal Ltd., Penrhos Works, P.O. Box 4, Holyhead, Gwynedd, LL65-2UJ, United Kingdom
The introduction of integrated Pollution Control (IPC) by means of the Environmental Protection Act (EPA 90), has brought with it regulatory requirements for operators of industrial processes in the U.K. to undertake continuous monitoring of gaseous atmospheric releases. In response to these changes Anglesey Aluminium Metal Limited (AAM) has chosen to install Tunable Diode Laser Spectroscopy (TDLAS). This method, operating in the Middle Infra Red region (MIR), is gaining increased acceptance as the choice for trace gas measurement where sensitivity, specificity, and fast response are required. This paper focuses on this change to the gaseous fluoride monitoring activities at AAM with particular attention to stack monitoring.
11:20 am
IMPROVED EFFICIENCIES IN THE DRY SCRUBBING PROCESS: Geir Wedde, ABB Environmental, P.O. Box 6260 Etterstad, 0603 Oslo, Norway
An advanced process for removal and recovery of fluorides and particulates from the aluminium reduction pot gas has been developed and tested in pilot plant prior to full scale installation. The dry scrubbing process is arranged in two stages with a counter-current flow of the alumina allowing for the reactive fresh alumina at the tail end of the process. The benefits and features of this concept include high process flexibility with stable and improved performance on removal of fluorides, reduced pressure drop and low particulate emission by optimized filter design and operating performance, and improved compactness through design and equipment developments.
11:45 am
TGT RI - A NOVEL REACTOR / FILTER CONCEPT FOR DRY SCRUBBING: B. Cloutier, Procedair Industries Inc., 625 President Kennedy, Montreal, Quebec, Canada H3A 1K2; Ph. Dumortier, B. Caratge, Procedair SA, 25-27 Boulevard de la Paix, 78951 St. Germain en Laye Cedex, France
The fluorine emissions from modern PFPB pots have led to a requirement to further improve gas scrubbing efficiency. This improvement has been achieved without any detrimental effect on scaling or attrition of alumina. Economic factors create a further technical challenge of reducing capital cost and lowering energy consumption. A novel process called the TGT-RI which combines an innovative reactor concept integrated in a new generation of fabric filter fully responds to the new requirements of aluminium producers. Several years of exhaustive tests have been conducted on gases emitted by large pots to develop the TGT filter and then the TGT-RI concept of integrating the reactor within the filter unit. The paper will incorporate a comprehensive set of test results. A descriptive of the first industrial applications on pot gases and baking furnaces is presented.
Room: 232A
Session Chairs: R.G. Reddy, Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487; D.J. Fray, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ, United Kingdom
8:30 am
STABILITY ANALYSIS OF MICROSTRUCTURE EVOLUTION PROCESSES: W.M. Mullins, Wright Laboratory, WL/MLIM-TMCI, Bldg. 653, 2977 P St., WPAFB, OH 45433-7746; R.D. Irwin, E.A. Medina, Department of Electrical and Computer Engineering, Stocker Center, Ohio University, Athens, OH 45701
Various stability criteria are introduced and thermo-kinetic models for metallurgical processes are used as concrete examples for evaluation. Kinetic criteria for the process of dynamic recrystallization are proposed. These criteria are compared to the non-equilibrium thermodynamic approaches discussed in the literature. The application of macroscopic stability criteria to materials processing is then discussed.
8:55 am
STATISTICAL ANALYSIS OF INTERFACE DYNAMICS IN NON-SPHERICAL MORPHOLOGIES: S.P. Marsh, Code 6325, Naval Research Laboratory, Washington, D.C. 20375-5000; M.E. Glicksman, Rensselaer Polytechnic Institute, Troy, NY
Complex interfaces can be described as a distribution of interfacial patches, each having a differential area. The patches are fully characterized by a mean curvature, a dimensionless shape factor, and an extensive variable such as solid angle or area. Using this approach, a statistical theory of Ostwald ripening has been extended to describe the diffusion-limited coarsening of non-spherical convex interfaces. Coarsening rate constants are calculated as a function of both the precipitate volume fraction and the geometric shape factor. Application of these results to ripening of ellipsoidal precipitates and other morphologies will be discussed.
9:20 am
ULTRA FINE PRECIPITATES IN REACTOR PRESSURE VESSEL STEELS INVESTIGATED BY MONTE CARLO SIMULATIONS: STRUCTURE, COMPOSITION, AND MORPHOLOGY: C.L. Liu, G.R. Odette, B.D. Wirth, and G.E. Lucas, Dept. of Chemical Engineering, University of California Santa Barbara, Santa Barbara, CA 93106
Ultra fine scale precipitates are the leading cause to the irradiation embrittlement of reactor pressure vessel (RPV) steels and may limit the continued operation or extended life of a number of nuclear power plants around the world. Tremendous effort in studying these precipitates has been made using various experimental techniques such as small angle neutron scattering (SANS) and atom probe field ion microscope (APFIM). However, detailed identity and characteristic of the precipitates o atomic scale are not well known. We propose a self-consistent model, combining advanced thermodynamics, small angle neutron scattering measurements, and Lattice Monte Carlo simulations, to examine detailed identity and characteristic of the ultra fine precipitates on atomic scale in Fe-based multicomponent systems Fe-Cu-Ni-Mn and Fe-Cu-Ni-Mn-Si. A systematic parametric study using both the metallurgical and simulation variables is carried out. Interaction parameters in an extended regular solution treatment, composition, and temperature as the metallurgical variables, and starting configurations, sizes of simulation cells, and simulation duration as the simulation variables, are exercised. The results from the simulations are in good agreement with those from SANS and APFIM.
9:45 am
OBSERVATION AND CALCULATION OF MARANGONI CONVECTION INDUCED THERMALLY IN A MOLTEN SALT: T. Takasu, J.M. Toguri, Dept of Metallurgy and Materials Science, University of Toronto, 184 College Street, Toronto, Ontario, Canada, M5S 1A4; H. Itou, T. Nakamura, Dept of Materials Science & Engineering, Kyushu Institute of Technology, Secsui-cho 1-1, Tobata-ku, Kitakyushu, 804 Japan
Marangoni convection has a large effect on materials processing since it remarkably promotes heat and mass transport near the free interface. In order to clarify the behavior of marangoni convection in a molten salt, observation and calculation of the thermal convection in a column held between a pair of Pt disks (2mm in diameter) which were fixed to hot thermocouples, were carried out. Calculated flow patterns and absolute values of fluid velocity agreed well with the observed results. When the temperatures of both disks were set equal and the height of liquid bridge was 2.4mm, four vortexes were generated on the longitudinal plane and typical velocity was 15mm/s. From the calculated isothermal lines the behavior of promotion of heat transport is obvious; fluid heated at the disks was conveyed to the free surface and fluid cooled at the surface was conveyed to the inner region. Increase in the height of column and/or increase in the absolute value of applied temperature difference lead to increase in fluid velocity lineally in this calculation range.
10:10 am BREAK
10:20 am
MIXING PHENOMENA PERTINENT TO FERROALLOY REFINING USING WATER MODELS: G. Akdogan, R.H. Eric, School of Process and Materials Engineering, University of the Witwatersraind, Johannesburg, Private Bag 3, Wits 2050 South Africa
Mixing phenomena in a bottom blown air-stirred one-seventh water model of CLU (Creusot-Loire Uddeholm) reactor was studied using three different configurations of straight circular nozzles fitted axially at the bottom of the vessel. The mixing time has been experimentally determined utilizing acid injection and pH measurements at various gas flow rates, bath heights and nozzle orientations in the presence and in the absence of a second phase. High air flow rates were utilized usually above the range of ordinary flow meters. During experiments the air flow rates varied from 0.00599m3/sec to 0.01465m3/sec. An integral orifice plate assembly, which is coupled to two pressure transmitters, was constructed to calculate gas flow rates from pressure readings. Experimental results reveal that the mixing time decreases with increasing gas flow rate. A critical gas flow rate exists after which the mixing time tends to increase for all tuyere configurations studied. For a given gas flow rate the mixing time increases non-linearly with increasing bath height. Off-center configuration gives slightly lower mixing times as compared to center configuration. The presence of an upper oil layer increases the mixing time significantly for all configurations showing its resistance to the recirculatory velocity of fluid near the surface of the bath. Under the very high flow rates employed in this investigation, it is found that the contribution of buoyancy to the total stirring energy density is very small, but its contribution increases with increasing bath height.
10:45 am
DIMENSIONAL ANALYSIS FOR PREDICTING THE STRESSES IN FORGING: T. Robert N., Congreso 128-A204, Col. La Joya, Del. Tlalpan, Mexico, D.F., 14090; J. Navarrete M., J. Ramirez V., G. Salas B., M. Noguez A., Departamento de Ing. Metalurgica, Facultad de Quimica, Universidad Nal. Autonoma de Mexico, Cuidad Universitaria, 04510 Mexico, D.F.
The stresses required in an axial closed die forging are determined by the geometry of the blank and that of the die, the yield stress of the working material and the process variables like temperature, strain, strain rate, friction, etc. Five adimensional groups of the mentioned parameters are proposed. Like the Reynolds number, they permit the characterization and evaluation of almost any axial forging process. A wide data base is experimentally obtained, which validates the model. This dimensional analysis is an alternative to the traditional methods for calculating the stresses in metal forming.
11:10 am
MODELING OF LIQUIDUS TEMPERATURE AND ELECTRICAL CONDUCTIVITIES OF MANGANESE SMELTING SLAGS BY THE USE OF NEURAL NETS: M.A. Reuter, Faculty of Mining and Petroleum Engineering, Delft University of Technology, Delft, The Netherlands, R H. Eric, A.A. Hejja, School of Process and Materials Engineering, University of the Witwatersrand, Johannesburg, Private Bag 3, WITS 2050, South Africa
Liquidus temperature and electrical conductivity data measured on synthetic slags were modeled by the use of neural nets(NN). In this work the applied multilayer feedforward NNs were trained by a conjugate-gradient optimization for which a three layer formulation was used. Very good fits were obtained for both the liquidus temperature and the conductivity data. The synthetic slags were prepared from pure oxides to represent a wide range of compositions likely to be encountered in ferromanganese and silicomanganese smelting. The slag constituents were in the following range: MnO, 5-30%; CaO, 20-35%; MgO, 5-15%; SiO2, 27-58%; and Al2O3, 5%. Liquidus temperatures varied from 1300°C to 1380°C and increased with increasing basicity ratio. The electrical resistivity of slags decreased with the increase of basicity ratio from 0.55 to 1.1 but above 1.1 basicity ratio the resistivity tended to increase depending upon the MnO content.
Room: 231A
Session Chairperson: Mrs. S. Young, BHP Copper Inc., 2400 Oracle Road, Suite 200, Tucson, AZ 85704
8:30 am
EFFECTS OF FLUID VELOCITY OF ELECTROLYTE ON COPPER ELECTROREFINING: A. Tsubouchi, T. Nakamura, F. Noguchi, I. Iakasu, Kyushu Institute of Technology, Department of Materials Science and Engineering, Kitakyushu, Japan 804
A high current density operation is desired to improve the productivity in copper electrorefining. However, a lot of problems still remain such as passivation of anode, dendritic deposition of cathode and contamination of impurity elements during the high current density electrorefining of copper. To clear the problems mentioned above, effects of the fluid velocity of the electrolyte on the morphology of copper deposition on cathode and the passivation behaviour of anode have been investigated at various current densities in the present study. Although a granular appearance of the copper deposition was obtained with increasing the current density, it was depressed by an increase of the fluid velocity of the electrolyte. Then an uniform deposition on the cathode was also observed when the fluid velocity of it became higher. Further more, no passivation behaviour of anode could be found by high speed circulating the electrolyte even in the high current density operation.
8:55 am
ENERGY SAVING IN COPPER ELECTROWINNING: C. Lupi, D. Pilone, Dip. ICMMPM, Università di Roma "La Sapienza", V. Eudossiana, 18, 00184 Roma, Italy
The energy consumption, in the electrowinning step of copper production by hydrometallurgical traditional process, generally represents more than 1/4 of the total energy requirement. The considerable saving can be achieved just in this step that requires about 8 GJ/tonne of the produced copper. To save energy the cell voltage, or more appropriately its anodic component, can be reduced: that is because the anodic voltage represents the main component of cell voltage and so it is responsible for the actual energy consumption in the copper sulphate electrowinning. In this work some ways are studied to lower the anodic voltage. First the cobalt ions were added to the sulphate solution in order to study the catalytic effect on oxygen discharge. Then lead alloys anodes (Pb-Ag, Pb-Sb-Ag and Pb-Ca) were used to promote a better oxygen evolution as a result of a different anodic surface. Their behaviour was compared with the Pb-Sb traditional ones. Finally, as already pointed out by several authors for zinc electrowinning, ethylene glycol was employed as anodic depolarizer in order to verify its effectiveness in the case of copper electrowinning. Combining all the above-mentioned ways energy saving ranging from 20% to 27% is achieved. All the tests were carried out on a laboratory pilot-plant for long time to simulate the industrial conditions. The obtained copper deposits were observed by SEM to highlight their morphology and were also analyzed by spectrometer to verify their purity.
9:20 am
RECENT IMPROVEMENTS IN THE STRIPPER SECTION OF ONAHAMA TANKHOUSE: Kiyotaka Abe, Fumihiko Shimizu, Onahama Smelter and Refinery, Onahama Smelting & Refining Co., Ltd., 1-1, Nagisa, Onahama, Iwaki-City, Fukushima, 971, Japan
Auto-stripping machine was developed and installed in 1971. Major modifications were performed in 1981 such as relocating conveyor lines, changing the stripping devise and stacking unit of stripped sheets and others. In 1988 stainless steel blanks with Edge Wise Protector which is highly efficient edge masking plastics were introduced from Mitsubishi Materials Corporation. Then the blank polishing machine and durable plastics for EWP were developed to improve stripability. Not only tremendous cost savings of labors, maintenance, supplies and others but also good quality of the starting sheets were attained and the capacity of cathode production was increased. According to the recent results of operation, the speed and the sheet production rate of stripping machine are 5.5 seconds per blank and 7,000 sheets per day respectively. The operation of commercial tanks is also satisfactory, of which current efficiency is keeping 98-99% at the tankhouses #1 &2 and 95-97% at the tankhouse #3.
9:45 am
INFLUENCE OF THE ELECTROCRYSTALLIZATION INHIBITORS DURING COPPER ELECTROREFINING: A NEW EXPERIMENTAL APPROACH: J.-L. Delplancke, M. Degrez, C. Temmerman, R. Winand, Université Libre de Bruxelles, Metallurgy, CP165, 50 Av. F.D. Roosevelt, B1050 Brussels, Belgium
The influence of the copper electrocrystallization inhibitors (mainly thiourea, gelatin and chloride ions) is studied in a new fully automatic pilot plan. This paper describes the conception and the building of this plan. The plan is in hydrodynamic similitude with an industrial copper electrorefining plan. Three cells with forced electrolyte flow may be connected in parallel or in series on order to model the copper production cells. The electrolyte is characterized chemically and electrochemically before and after electrolysis. One day and one week long experiments are performed. The structure of the deposits is characterized by SEM, EDX and metallographic cross-sections. The new approach for the study of these inhibitors is firstly to reproduce the experimental conditions observed in the industry with the three additives present simultaneously in the electrolyte and secondly to study the influence of a slight modification of the concentration of one inhibitor, the others being present in the electrolyte with their industrial nominal concentrations.
10:10 am
THE CHARACTERIZATION OF PASSIVATING FILMS ON COMMERCIAL COPPER ANODES USING IMPEDANCE SPECTROSCOPY: M.S. Moats, J.B. Hiskey, S.C. Campin, University of Arizona, Copper Research Center, Material Science and Engineering Department, College of Engineering and Mines, Tucson, AZ
Electrochemical techniques are a valuable means of analyzing the passivation of commercial copper anodes. Electrochemical impedance spectroscopy (EIS) provides information concerning transport and reaction phenomena occurring at an electrode surface. Commercial copper anodes of varying compositions have been examined using EIS. Experiments were conducted in a flat cell with an electrolyte of 40 g/l Cu2+ and 160 g/l H2SP4 maintained at 65°C. Impedance spectra were obtained at the potentials characteristic of the open circuit voltage and the passive region for each anode. The spectra of the passivating films exhibited a flattened resistive/capacitive loop at middle to high frequencies and an inductive loop at low frequencies. An equivalent circuit utilizing an inductor-resistor series in parallel with the double layer capacitance and charge transfer resistance was adequate in modeling the impedance data. The influence of anodes impurities on the components of the equivalent circuit is discussed and correlated with a bilayer passivation model.
10:30 am
SURFACE ROUGHENING OF ELECTROWON COPPER IN THE PRESENCE OF CHLORIDE IONS: E. Ilgar, P. Yu, T.J. O'Keefe, University of Missouri-Rolla, Department of Metallurgical Engineering and Graduate Center for Materials Research, Rolla, MO 65409-1170
A statistically designed screening test was carried out in the absence and presence of 20 ppm Cl- ions using a three factor, two-level factorial design in an electrolyte containing 36 gl-1 Cu2+ and 150 gl-1 sulfuric acid. The independent variables evaluated were agitation, current density and temperature; their influence on surface roughness was determined. Using the data generated, a model expression was developed to allow estimation of surface roughness of the copper deposits. X-ray diffraction, scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and profilometer techniques were used in the evaluation. The copper deposited at current densities where activation was the primary control mechanism appeared similar in morphology whether stirring was used or not. The addition of 20 ppm Cl- ions to the electrolyte gave rougher deposits under the same conditions. In the mixed control regions, where mass transfer effects were initiated, considerably rougher and more dendritic deposits were obtained when Cl- ions were present. Agitation was effective in reducing the copper surface roughness both in the apparent activation and mixed control regions in the presence of Cl- ions. The results of this study showed that 20 ppm Cl- polarized the copper deposition at low overpotentials but caused depolarization at higher overpotentials, and promoted roughening even where Cu2+ mass transfer was not a factor.
10:55 am
THREE-DIMENSIONAL CALCULATION OF CURRENT DISTRIBUTION IN ELECTRODEPOSITION OF COPPER: Y.S. Choi, N.S. Kim, S.H. Jeon, T. Kang, Seoul National University, Department of Metallurgical Engineering, Seoul, Korea; H.J. Sohn, Seoul National University, Department of Mineral and Petroleum Engineering, Seoul, Korea
The thickness uniformity of electrodeposits depends largely on the current density distribution over the cathode. The current distribution is determined by the geometrical characteristics of the electrodes and the cell, the polarization at the electrode surface and the mass transfer in the electrolyte. The calculation of the current distribution is possible by various numerical techniques, among which the boundary element method (BEM) is considered to be most efficient. In this study the program for the calculation of 3-dimensional current distribution by use of the BEM with a linear element of trigonal type was developed and applied to the rectangular cathodes in copper electroplating. For simplicity the anode potential was assumed to be constant and the nonlinear polarization curves obtained from the potentiodynamic experiments were fitted to a linear equation over the range of current densities, 20~80mA/cm2. The effect of the cell dimension and the anode shape on current distribution was simulated. The calculated values agreed fairly well with the measured values and the thickness uniformity could be improved by the proper combination of the cell geometry and the anode shape.
11: 20 am
THE SOUTHERN PERU ILO REFINERY, DESIGN FEATURES, OPERATION AND IMPROVEMENT: F. Begazo, W.A. Enrico, Southern Peru Limited, 180 Maiden Lane, New York, NY 10038
Southern Peru Limited's Ilo Refinery, the largest in Peru, began operations in 1975 with a production capacity of 165,000 stpy. Southern Peru bought the Refinery from the state owned Minero Peru S.A. on June 1, 1994. The refinery processes blister from Southern Peru's Ilo smelter. Blister copper is processed in an anode plant equipped with two 365 st. tilting reverberatory furnaces, a 26 mold casting wheel and an anode press machine. Copper is electrorefined in a tank house equipped with 768 commercial cells, 44 stripper cells and 40 liberator cells, utilizing two electrolyte circuits and a 21,000 ampere rectifier. During 1989 through 1994, a program for improving productivity was carried out by increasing the number of cells and increasing current density to the total rectifier capacity. As a result, a capacity of 215,000 stpy of refined copper, 2 million troy ounces of silver and 6,000 troy ounces of gold per year was achieved. In 1994, Southern Peru announced plans to increase the capacity to 250,000 stpy of cathode with a US$ 18 million investment and a US$2 million investment in environmental improvement projects, as part of the purchase agreement with the Peruvian government. This paper outlines the scope of the Southern Peru Limited refinery modernization and environmental program. It describes the implementation of the electrolytic plant expansion based on installation of polymer concrete cells, a new rectifier, a new selenium roaster and a precious metal plant upgrades.
Room: 230B
Session Chairperson: Einar K. Jensen, Elkem a/s Research, N-4602 Kristiansand S., Norway
8:30 am
MATHEMATICAL MODELLING OF THE METAL FLOW IN SIDEWELL FURNACES: Y.S. Kocaefe, R.T. Bui, D. Kocaefe, Department of Applied Sciences, University of Quebec at Chicoutimi 555, Boul. de l´Université, Chicoutimi, Quebec, Canada G7H 2B1
Many different types of furnaces are used in aluminum industry for melting and treating the metal. Sidewell furnaces are commonly used for scrap melting. Metal flow in the furnace is provided by different types of equipment such as pumps and impellers, and plays an important role in furnace performance. A three-dimensional model has been developed to simulate the metal flow in such furnaces. In this paper, the model will be described, and the results will be presented showing how various operating and design parameters such as impeller position and rotational speed, sidewell geometry and arch design affect the metal flow.
8:50 am
Na AND Ca PICK-UP FROM HALL BATH IN INGOT FURNACES: David H.DeYoung, Aluminum Company of America, Molten Metal Processing Center, Alcoa Technical Center, Alcoa Center, PA 15069
A series of laboratory tests were conducted to explore the reaction of bath with Al-Mg alloys, as may occur when Hall bath enters ingot furnaces in a smelter-supplied ingot plant. Results showed that Mg clearly reacts with bath and adds Na and Ca to the metal by the reactions: 2(Na3AlF6) + 3 Mg 
6 Na + 2 AlF3 + 3 MgF2 (1) and CaF2 + Mg Ca + MgF2 (2) Temperature, Mg concentration in the alloy, the quantity of bath added to the metal, and the particle size of the bath added all influenced the reaction. At 700°C the Na and Ca pick-ups that occurred from these reactions were approximately 15 ppm while at 900°C the pick-ups were greater than 300 ppm. The pick-ups increased with increasing quantity of bath up to a limiting amount, beyond which no further pick-up occurred. The variation of the reaction with particle size indicated that the reaction is limited by the available bath-metal surface area.
9:10 am
EFFECTS OF SOLUTE INTERACTIONS ON GRAIN REFINEMENT OF COMMERCIAL ALUMINIUM ALLOYS: M.A. Kearns, P.S. Cooper, London & Scandinavian Metallurgical Co. Limited, Fullerton Road, Rotherham, South Yorkshire, S60 1DL, England
An analysis of the effects of alloy additions on the grain refinement in a series of model and commercial aluminium alloy compositions is reported. The data of Birch and Fisher published earlier describing grain refinement in 32 systems, including AA3004, AA5083, AA6063 and AA7050, are considered in terms of the supercooling effect of each alloy addition. A simple model describing grain size in terms of additive supercooling effects of individual alloy additions is proposed which fits the data reasonably well. Deviations from simple additive behaviour are evident in systems where strong intermetallic interactions occur. Interaction coefficients amongst solutes are invoked to explain these deviations. Individual alloying effects on grain refinement are treated in terms of constitutional supercooling parameters and behaviour is shown to be similar to that described in earlier studies. Zirconium is shown to have a general poisoning effect in a range of alloy compositions.
9:30 am
THE BUBBLE SIZE AND MASS TRANSFER MECHANISMS IN ROTOR STIRRED REACTORS: Stein Tore Johansen, Svend Grådahl, Per Ola Grøntvedt, Pål Tetlie, Rune Gammelsæter, SINTEF Materials Technology, N-7034 Trondheim, Norway; Karl Venås, Pal Skaret, Karl Venås a.s., Trondheim, Norway; Erling Myrbostad, Bjørn Rasch, Hydro Aluminium a.s R&D Centre, N-6600 Sunndalsøra, Norway
The performance characteristics of the HYCAST Rotor has been investigated in a water model. The removal rate of oxygen from water is measured for a large number of operational conditions. By combining different techniques the energy dissipation in the reactor, the mass transfer at the top surface and the bubble sizes may be determined experimentally. Investigations of the bubble dynamics by high speed video show that the bubbles in this type of reactors are very different from what is hitherto believed. Based on such a picture the paper demonstrates that the mass transfer and bubble sizes in the HYCAST Unit may be explained by a relatively simple theory which seems to explain all available experimental data. It is also demonstrated how we from this theory can scale from the oxygen removal in water model to hydrogen removal in liquid aluminum.
9:50 am
MODELLING OF SURFACE SEGREGATION DEVELOPMENT DURING D.C. CASTING OF ROLLING SLAB INGOTS: A. Mo, H.J. Thevik, SINTEF Materials Technology, Box 124 Blindern, N-0314 Oslo, Norway; B.R. Henriksen, E.K .Jensen, Elkem Research, Box 40, N-4602 Kristiansand, Norway
A two dimensional mathematical model for the development of macrosegregation at and close to the ingot surface during DC casting of rolling slabs is presented. The model accounts for macrosegregation caused by exudation of interdendritic melt and macrosegregation associated with solidification shrinkage. Equations for the conservation of energy, solute, momentum, and mass during the stationary phase of the process are solved numerically by a finite element method in a solution domain defined by a vertical cross section of the ingot. The main simplifications in the modelling concept are to assume the solidified part of the mushy zone to move with the casting speed, and to consider a binary alloy solidifying according to the lever rule. The thickness and solute concentration of the surface layer and the macrosegregation close to the surface are calculated, and modelling results are compared with measurements on real castings.
10:10 am BREAK
10:20 am
A MODEL TO PREDICT THE STEADY STATE PULL-IN DURING D.C.-CASTING OF ALUMINIUM SHEET INGOTS: Arild Håkonsen, Hydro Aluminium R&D Materials Technology, P.O.Box 219, N-6601 Sunndalsøra, Norway
By combining empirical results with a dimensional analysis, a model for the prediction of pull-in during DC-casting of aluminium sheet ingots is constructed. The model predicts the steady state pull-in along the rolling faces of an ingot. By using an alloy dependent constant, the nominal geometry and the casting speed, the model can easily calculate a near optimal mould shape. It is also possible to calculate the resulting shape of the rolling faces of an ingot for a given mould geometry, alloy constant and casting speed. The model requires only a spread sheet for these calculations. Comparisons with experiments show a very good agreement. The best fit values of the alloy constant for several commercial aluminium alloys are presented. The value of this constant varies within 12%.
10:40 am
THE MECHANISM OF PULL-IN DURING D.C.-CASTING OF ALUMINIUM SHEET INGOTS: Hallvard G.Fjær, Institute for Energy Technology, P.O. Box 40, N-2007 Kjeller, Norway; Arild Håkonsen, Hydro Aluminium R&D Materials Technology, P.O. Box 219, N-6601 Sunndalsøra, Norway
The pull-in phenomenon apparent in the DC-casting process of aluminium sheet ingots is investigated both analytically and by use of numerical models calculating temperatures, strains and stresses. The major part of the pull-in takes place above the bottom of the sump, but is mainly caused by thermal contractions and deformations in regions below. The strong and almost exactly linear dependency of the pull-in on the casting speed is explained. The effects on the pull-in of different cooling conditions and of various thermophysical and thermomechanical properties are investigated. 2D plain strain approximations have been successfully applied in calculating the pull-in for the centre part of the rolling face, but 3D effects are significant close to the narrow ingot surface. This is illustrated by comparison of results from 3D and 2D calculations. Modelling results are also compared with measurements of ingot thickness variations. A very good agreement is obtained.
11:00 am
WATER COOLING IN DIRECT CHILL CASTING: PART I: BOILING THEORY AND CONTROL: John Grandfield, Comalco Research Centre, P.O.Box 316, Thomastown, Victoria 3074, Australia
The intensity of the water cooling in direct chill casting affects the process heat flow and the performance of the casting process. The intensity depends on the boiling behaviour on the ingot surface. The basic mechanisms of boiling, the different boiling modes (nucleate, unstable film and stable film boiling), the effect of water composition, temperature, flow and velocity on boiling behaviour and heat transfer are reviewed. A H h h F;j/ F MPSR BBST ̝ ĝ L;e xxx yyy {{{ ||| {{{ xxx ttt qqq sss ooo lll nnn rrr ttt qqq mmm nnn nnn nnn nnn nC casting requires a good knowledge of the heat transfer between ingot and cooling water. This is especially true for the starting phase, where most defects are initiated. An experimental set-up has been developed to characterize this heat exchange close to process operating conditions. The method is based on the measurement of the cooling of a preheated instrumented aluminium block quenched by a water curtain. A 2D transient inverse model allows to determine the distribution of heat transfer coefficient and temperature on the whole surface of the block. In this way, heat flux can be assessed both at the water impingement point and below. The results obtained with the experimental apparatus are in good agreement with heat transfer rates calculated from in-situ temperature measurements using cast-in thermocouples. This device is thus an efficient and economical method to determine the influence of cooling water characteristics on the law describing heat transfer coefficient as a function of surface temperature. These laws have been measured and introduced in a numerical simulation of DC casting in order to study the effect of water cooling and casting parameters on the thermal evolution of the ingot during the different phases of casting.
11:40 am
FUNDAMENTALS OF UBC DECOATING/DELAQUERING FOR EFFICIENT MELTING: Wesley Stevens, Francois Tremblay, Arvida Research and Development Centre, Alcan International Limited, 1955 Mellon Blvd., Jonquière, Québec, Canada G7S 4K8
Aluminum used beverage cans (UBC) should be cleaned to completely remove all organic and residues to maximize metal recovery on remelting. This process must also minimize oxide formation. The aluminum industry uses three principal decoating technologies. The most used is the rotary kiln. The other processes are the belt decoater and the fluidized bed decoater. The presentation will cover the fundamental science for decoating shredded UBC to minimize metal loss on remelting. Laboratory work and plant trials have shown the requirements for complete decoating. These are: correct temperature range for the coatings to be pyrolized, good process gas to shred contact for all the scrap, sufficient oxygen being present to complete the oxidation of the carbon compounds present. The basic principles of the three decoating technologies used for the decoating of UBC will be discussed in relation to how they correspond to the fundamental process requirements.
Room: 330C
Session Chairperson: Brent Fultz, 138-78, California Institute of Technology, Pasadena, CA 91125
8:30 am INVITED
KINETICS OF ATOMIC TRANSPORT IN THE FORMATION OF NONEQUILIBRIUM MATERIALS: Michael J. Aziz, Division of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge MA 02138
Rapid solidification can result in the production of nonequilibrium materials either primarily due to nucleation or primarily due to growth. Rapid growth can trap in solute or point defect supersaturations or chemical disorder, or can cause the formation of nonequilibrium microstructures. Additionally, large driving forces can permit the nucleation and growth of other metastable phases. The phenomenology and mechanisms for these processes will be discussed. Models and experiments will be reviewed.
9:00 am INVITED
DEVIATIONS FROM LINEAR DIFFUSION DURING SOLID-STATE AMORPHIZATION IN Ni-Hf DIFFUSION COUPLES: M. Atzmon, W.S.L. Boyer, The University of Michigan, Department of Nuclear Engineering and Radiological Sciences, Materials Science and Engineering, Ann Arbor, MI 48109-2104
When analyzing diffusion measurements, the diffusion coefficient is often assumed to be independent of composition and time. In this paper, studies of possible deviations from this simple picture will be reported. During amorphous alloy growth in an elemental diffusion couple, the amorphous phase has a wide homogeneity range, and the interdiffusion coefficient is unlikely to be uniform. Experimental results in Ni-Hf thin-film couples will be described, which indicate that the interdiffusion coefficient varies significantly with composition. This variation leads to significant systematic errors in determining the interfacial compositions from measured composition profiles. A more reliable measurement method will be presented. A number of authors have suggested that evolution of macrostress during amorphization by interdiffusion affects the rate of the latter. Using a combination of substrate curvature and lattice parameter measurements, we have determined the evolution of stress during interdiffusion in Ni-Hf thin-film couples. The amorphous phase is observed to form under large tensile stress, which relaxes by creep during subsequent growth. Neither this stress, nor that induced by ion irradiation, affects the interdiffusion coefficient.
9:30 am INVITED
SINTERING OF SMALL ASSEMBLIES: R.S. Averback, Huilong Zhu, M. Yeadon, J.M. Gibson, Materials Science and Engineering, University of Illinois, 1304 W. Green St., Urbana, IL 61801
The sintering of small assemblies of nanoparticles has been investigated by a combination of molecular dynamics computer simulations and in situ observations in a UHV transmission electron microscope. Because the radius of curvature of nanoparticles is so small, enormously large interfacial stresses are developed when nanoparticles come in contact with other nanoparticles or substrates, and this leads to sintering by plastic deformation of the particles on the time scale of some picoseconds. Surprisingly, these particles rotate and form twins and other low energy configurations. Several examples of such sintering will be illustrated, including nanoparticle assemblies of Cu, amorphous alloys and intermetallic compounds. Interactions between nanoparticles and substrates will also be discussed.
10:00 am INVITED
EFFECT OF FREE SURFACES ON THE KINETICS AND MORPHOLOGY OF SPINODAL DECOMPOSITION: Long-Qing Chen, Materials Science and Engineering, Penn State University, University Park, PA 16802
The kinetics of spinodal decomposition and morphological evolution near a crystalline surface were investigated by microscopic master equations in the point and pair approximations and a second-neighbor interaction model. Both two-dimensional (2-D) and 3-D model systems were considered. It is shown that, in the presence of a surface, spinodal decomposition initially involves surface segregation, followed by anisotropic decomposition in the near-surface region, and then followed by isotropic decomposition in the bulk. It is demonstrated that, due to segregation, a surface spinodal decomposition may take place for alloys whose overall average compositions are outside the bulk spinodal. It is found that the presence of a surface results in a dominant concentration wave which produces interesting transient morphological patterns such as distorted hexagonal precipitate lattices for relatively low-volume fractions and straight stripes at high volume fractions in the near-surface region. The relevance of these results to the mechanisms of diffusional phase transformations, such as spinodal ordering and decomposition, in nanoscale crystalline materials will be discussed.
10:30 am BREAK
10:45 am INVITED
SELF-PROPAGATING REACTIONS IN NANOSCALE MULTILAYER MATERIALS: Tim Weihs, Materials Science & Engineering, The Johns Hopkins University, Baltimore, MD 21218
This presentation describes self-propagating, exothermic reactions in nanoscale, multilayer materials. The talk begins with a review of self-propagating reactions in powder-based materials and then focuses on similar exothermic reactions in multilayer foils. The multilayer foils consist of alternate layers of materials that have high heats of mixing, such as Al and Ni. The individual layers (of Al or Ni) are only nanometers thick, but hundreds of these layers are sputter deposited to form one foil with a total thickness between 10 and 100 microns. The layered foils arc easily removed from their substrates, and their exothermic mixing can be started at room temperature with a small spark. Te exothermic reactions propagate al speeds greater than 10m/s and they reach final temperatures as high us 1600°C The reactions can propagate in air, vacuum, or liquids. The velocities, the heats, and the temperatures of the reactions will be presented for at least two different multilayer systems, and the chemical and structural parameters that control these properties will be addressed using an analytical model. The final segment of the talk will describe how reactive multilayer foils can be used as local heat sources to joint structural components.
11:15 am INVITED
NANOSTRUCTURED PALLADIUM ALLOY MEMBRANE MATERIALS: Kenneth J. Bryden, Jackie Y. Ying, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-4307
Membranes are often fabricated from palladium since it has a very high hydrogen permselectivity. Diffusion through the metal is often the rate-limiting step in hydrogen transport through palladium-based membranes. The flux through these membranes can be increased by tailoring a microstructure that allows for higher hydrogen diffusivity. Nanostructured palladium has a much higher hydrogen diffusivity than conventional palladium due to its large volume fraction of grain boundaries. Thus, nanostructured metal membranes would provide higher hydrogen fluxes and better performance. By doping palladium with another element, enhanced stability against grain growth, stability against the alpha to beta phase transition which causes cracking, and enhanced poisoning resistance can be achieved. In this study nanostructured pure palladium and palladium alloy membranes were synthesized by pulsed electrodeposition. The hydrogen permselectivity through these materials was determined in a membrane reactor and the effect of common poisons (e.g. carbon monoxide and hydrogen sulfide) on hydrogen diffusivity was also measured to relate the hydrogen permeation properties of these materials to their microstructure and elemental composition.
Room: 332
Session Chairperson: Ephraim Suhir, Lucent Technologies, Bell Laboratories, Room 7G-326, 700 Mountain Avenue, NJ 07974; Theodore Ejim, Lucent Technologies, Bell Laboratories, Engineering Research Center, P.O. Box 900, Princeton, NJ 08542
8:30 am
OPENING STATEMENTS: Dr. Darrel R. Frear, EMPMD Chair and, Senior Member of Technical Staff, Department 1811, Mail Stop 1411, P.O. Box 5800, Sandia National Laboratories, Albuquerque, NM 87185
8:40 am KEYNOTE
MICROELECTRONIC PACKAGE TRENDS--THE ROLE OF RELIABILITY IN PARTICULARLY, RELATED TO SOLDER JOINT RELIABILITY: C.P. Wong* and Rao Tummala**, Georgia Institute of Technology, Packaging Research Center (PRC), School of Materials Science & Engineering, and School of Electrical & Computer Engineering, 778 Atlantic Drive, Atlanta, GA 30332;*Professor and Assistant Director, PRC; **Pettit Chair Professor, Georgia Eminent Scholar and Director, PRC
The trends of microelectronic devices have advanced to the state that they operate in excess of 200 MHz with submicron feature size. Furthermore, these high performance IC requires Inputs/Outputs (I/O) signals that are in excess of a few 1000's. Low-cost, high performance flip-chip, area array solder joint interconnects are key to the success of this technology. In order to enhance the thermal cycle fatigue-life of these solder joints, underfill encapsulants are needed. In this talk, we will review the microelectronic packaging technology trends, the role of reliability, in particularly, the use of underfill encapsulants to enhance the thermal cycle fatigue life of solder joints will be discussed.
9:15 am KEYNOTE
SOLDER JOINTS IN ELECTRONICS--DESIGN FOR RELIABILITY: Werner Engelmaier, President, Engelmaier Associates, Inc., 23 Gunther Street, Mendham, NJ 07945
The emerging new technologies provide ever more challenges to assure the reliability of electronic products. The ever increasing demands in electronic products for higher performance, lower cost, less space (weight) is leading to ever denser interconnection needs. Solder joint reliability is becoming an even more important issue with the advent of new surface mount packages and the use of surface mounted electronics in such hostile environments as the automobile and space. The new packages are characterized by larger sizes, finer pitches, and/or problematic materials which require an up-front 'Design for Reliability (DfR)' to meet reliability requirements. The hostile environments can include thermal excursions over temperature ranges in which multiple interactive damage mechanisms are operative. The reliability of electronic assemblies requires a definitive design effort that has to be carried out concurrently with the other design functions during the developmental phase of the product. There exists a misconception in the industry, that quality manufacturing is all that is required to assure the reliability of an electronic assembly. While of course, consistent high quality manufacturing - and all that this implies is a necessary prerequisite to assure the reliability of the product, only a DfR-procedure can assure that the design - manufactured to good quality - will be reliable in its intended application. Explicit DfR-procedures need to be employed to account and compensate, at least in part, for the prevalent damage mechanisms. This needs to be complemented with 'Design for Manufacturability (DfM)' which widens the process windows and takes into account the manufacturing capabilities. These demands put an increasing burden on the designers who will require a heightened technical understanding of the underlying issues and more sophisticated design tools. Thus, adherence to quality standards, such as IPC-A-620, Acceptability of Electronic Assemblies with Surface Mount Technologies, and ANSI/J-STD-001, Requirements for Soldered Electrical and Electronic Assemblies does not assure reliable solder connections, only quality solder connections. It is for this reason that IPC-D-279, Design Guidelines for Reliable Surface Mount Technology Printed Board Assemblies, is being developed. The 'Design for Reliability (DfR)' for solder attachments in electronic interconnections will be the emphasis of the paper.
9:50 am KEYNOTE
MEETING MARKET DEMANDS--NEW AND CRITICAL TECHNOLOGIES FOR ELECTRONIC PACKAGING AND ASSEMBLIES: Jennie S. Hwang, President, H-Technologies Group Inc., 5325 Naiman Parkway, Cleveland, OH 44139
Advanced technologies are transforming manufacturing, and the information highway is speedily progressing. In this exciting and changing time, the electronic industry has responded and will continue to respond to competitive products in the global market place. The speaker will provide a capsule view of key segments of electronics hierarchy in market needs and the demands in new technologies. The presentation will separately address the market and technology in chip level, package level, and board level, as well as, the critical supporting materials and technologies. Dr. Hwang will conclude her talk by highlighting the important aspects of the reliability of solder joints in relation to the new market trends.
10:25 am BREAK
10:35 am INVITED
SOLDER MATERIALS AND SOLDER JOINTS IN FIBER OPTICS ENGINEERING--RELIABILITY REQUIREMENTS AND PREDICTED STRESSES: Ephraim Suhir, Lucent Technologies, Bell Laboratories, Physical Sciences and Engineering Division, Room 7G-326, 700 Mountain Avenue, NJ 07974
Typical solder materials and solder joints, employed in fiber-optics engineering, are examined from the stand-point of the requirements for optical performance of the devices, as well as for the short- and long term mechanical reliability of the soldered optical fibers and the solder materials themselves. We address the geometry's of, and the loading condition in, fiber-optics solder joints, and suggest several analytical stress models that enable one to evaluate thermally and mechanically induced stresses in solder joint assemblies in fiber-optics structures. These models include: thermal stresses in metallized fibers soldered into ferrules or capillaries; stresses at the menisci areas in soldered joints; comparison of the thermal stresses due to the application of "hard" (high modulus) and "soft" (low modulus) solders; interaction of the "global" and "local" thermal stresses in optical fibers whose end portions are soldered into capillaries; evaluation and interaction of mechanical and thermal stresses in solder joints during proof-testing of optical fibers soldered into ferrules; and others. The merits and shortcomings of soldered assemblies in comparison with adhesively bonded structures are also briefly discussed.
11:00 am INVITED
MICROSTRUCTURAL ANALYSIS OF ELECTRONIC MATERIALS: Aleksander Zubelewicz, IBM Microelectronics, W-64, Bldg. 4-2, 1701 North Street, Endicott, NY 13760
The electronic industry is changing at a rapid pace. Faster and more powerful processors and ASICs continuously replace the slower devices, while price competitiveness and time-to-market becomes the true challenge for many manufacturers. The dynamic nature of the electronic industry drives for the need of using smaller packages with higher I/O count. Recently, fine pitch, a family of BGA components, and Chip Scale Packages represent the "hottest" technologies allowing for high I/O density. However, the future electronics applications will require processors operating with speed of several hundred MHz, then the present packaging technology may need further modifications. Consequently, the traditional PTH interconnection technology is being replaced by Surface Mount Technology and Ball Grid Arrays. Furthermore, new interconnection materials such as lead free solders and conductive adhesives are being seriously considered as a replacement of the commonly used lead based alloys. The objective of the paper is to discuss the behavior and failure mechanisms for the interconnection materials. Obviously, solders are at the top of the list, followed by encapsulations and conductive adhesives. During manufacturing operations, solders are used in the form of a paste, and when reflowed becomes ductile polycrystalline materials. These pastes must maintain appropriate rheological characteristics. It will be shown that a typical paste (solder or conductive adhesive) exhibits three stages of behavior: paste as a viscous solid, paste as a viscous fluid, and the transition stage between solid and fluid. Solder joints (after reflow) are thought to carry input/output electrical functions of the assembly as well as are designed to provide a mechanical support for the package or chip. Solders exhibit very complex microstructural behavior. There is a need for material model of solders, a model that can be used in the form of constitutive equations with built-in damage criteria, equipped with functions that represent microstructural evolution of solders, and allowing to predict the effect of strain/damage localization in solder joints. Moreover, this theory should lead to simple fatigue equations when needed. One such theory exists and will be discussed in the paper. In many cases, solder joints become the weakest link. Enhancement of the joint reliability can be accomplished by encapsulating them with polymer based materials. A microstructural numerical study for encapsulant will be briefly presented in the paper. It will be shown that fracture originates at the microscopic level of the materials, coalesce, and forms a localized fracture zone.
11:25 am INVITED
INCONSISTENCIES IN THE UNDERSTANDING OF SOLDER JOINT RELIABILITY PHYSICS: Liang-chi Wen, G. Mon, R. Ross, Jr., Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109
An inherent reliability problem associated with surface mount applications is that solder joints, which serve both as an electrical and a mechanical connection between part and board, are subject to thermal fatigue failure. Solder joint failure involves a complex interplay of creep and fatigue processes. Over the years, many analytical and experimental research studies have aimed to improve state-of-the-art assessment of solder joint integrity from a physics of failure perspective. Although considerable progress has been made, there still exist many inconsistent and even contradictory correlations and conclusions. This paper reviews the unique properties of near-eutectic tin-lead solder, properties such as age-softening and 'superplastic' behavior under low strain rate loading. Fundamental mechanical and thermomechanical processes are modeled to demonstrate many inconsistencies observed in the literature. These inconsistencies are to be found in both analysis and testing issues. Analytical inconsistencies arise in correlations involving Coffin-Manson and strain energy density algorithms for cycle-life prediction, the effects of mean temperature and cycle frequency, and the determination of test acceleration factors. Testing inconsistencies are to be found in the areas of mechanical versus thermal cycling, failure definations, detection methodology and treatment of failure statistics. The objective of this paper is to identify important unsettled analysis and testing issues whose resolution by the solder joint research community will assure a greater degree of solder joint reliability.
11:50 am INVITED
AUTOMATED SOLDER LIFE ANALYSIS OF ELECTRONIC MODULES: Stephen A. McKeown, Lockheed Martin Control Systems, 600 Main Street, Johnson City, NY 13790
The solder life analysis methods developed by Engelmaier and Steinberg have been incorporated into an automated method which combines the results of finite-element models, a component location file obtained from a computer-aided design tool, component data, and environment data to calculate the expected solder joint life for each surface mount technology component on an electronic module. The method uses the finite-element method to calculate the coefficient of thermal expansion at different locations on the surface of the module which is used in determining the thermal cycling life of the solder joints. Finite-element analysis is also used to determine the surface strains due to vibration of the module which also influences solder joint life. The component location is taken from a Mentor® neutral file which also provides component description and orientation. Component data includes the dimensions of the part and information on the solder joint fillet geometry. Environment data includes temperature ranges, dwell times, vibration levels, and durations of thermal/vibration missions. This information is combined in a ANSI C-language program to determine the calculated failure rate of each component for the combined environments, and the overall computed reliability of all of the analyzed solder joints.
12:10 am
WHEN IS A MODIFIED COFFIN-MANSON APPROACH VALID FOR SOLDER JOINT RELIABILITY PREDICTION?: Robert Darveaux, Amkor Electronics, 1900 S. Price Road, Chandler, AZ 85248
The Coffin-Manson approach is based on relating fatigue life to plastic strain range. The basic equation has been modified by Norris-Landzberg, Engelmaier, and others to include temperature, frequency or dwell time effects. These modifications were determined empirically on specific types of soldered assemblies. Today, they are commonly applied to a wide range of assemblies and test conditions, as well as field use conditions. The main advantage of these empirical relations is that they are easy to use. They are basically back of the envelope calculations that require almost no expertise on the part of the engineer. This paper explores the validity of modified Coffin-Manson approaches as applied to solder joint reliability analysis. Several case studies are examined, and the limits of the approach are defined.
Monday - Thursday Room: 332
February 10-13, 1997
Session Chairperson: R.K. Mahidhara, Tessera Inc., 3099 Orchard Drive, San Jose, CA 95134
ALLOY DESIGN OF Sn-Ag-In-Bi-Sb SOLDER SYSTEM USING THERMODYNAMIC CALCULATIONS: Byeong-Joo Lee and Hyuck Mo Lee, Materials Evaluation Center, Korea Research Institute of Standards and Science, Yusong P.O. Box 102, Taejon 305-600, Korea; Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Kusong-Dong 373-1, Yusong-gu, Taejon 307-701, Korea
TiN-BASED, ACTIVE METAL CONTAINING SOLDERS FOR JOINING OF ALUMINA: Tim Schwilm, O.T. Inal and Frederick G. Yost, Materials and Metallurgical Engineering Department, New Mexico Tech, Soccoro, NM 87801; Sandia National Laboratories, Albuquerque, NM 87815
THERMAL AGING CHARACTERISTICS AND WETTING FORCE MEASUREMENTS OF EUTECTIC Ag-Sn SOLDER ALLOY: Guna Selvaduray, Hason Fong and Kristine Griley, Department of Materials Engineering, San Jose State University, San Jose, CA 95192
EVALUATION OF INTERMETALLIC PHASE FORMATION AND CONCURRENT DISSOLUTION OF INTERMETALLIC DURING REFLOW SOLDERING: M. Schaefer, W. Laub, R.A. Fournelle and J. Liang, Materials Science Program, Marquette University, 1515 W. Wisconsin Ave., Milwaukee, WI 53201-1881; Allen-Bradley Company, 1201 S. Second St., Milwaukee, WI, 53204
NANOSTRUCTURAL ANALYSIS OF PADS-TREATED SOLDER SURFACE: James L. Marshall and Brett Piekarski, Department of Chemistry, University of North Texas, Denton, TX 76203-5068; Army Research Laboratory, AMSRL-EP-RC, 2800 Powder Mill Road, Adelphi, MD 20783
INTERFACIAL REACTION BETWEEN PALLADIUM AND LEAD-TIN SOLDERS: G. Ghosh, Dept. of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108
Room: 340C
Session Chairs: D.J. Srolovitz, Dept. of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109-2136; D.P. Adams, Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185
8:30 am INVITED
CORRECTION FACTORS TO THE CLASSICAL NUCLEATION RATE: David T. Wu, Dept. of Mechanical Engineering, Yale University, New Haven, CT 06520
The rate of nucleation can have a strong influence on the microstructure of thin films. This talk discusses corrections to the classical expression for nucleation rate. For heterogeneous nucleation's spherical cap model a new contact-angle dependence for the prefactor is presented, while in homogeneous nucleation the self-consistency correction is reconsidered using the idea of "kinetic potential." Both corrections can increase the nucleation rate significantly.
9:10 am INVITED
EVOLUTION OF THIN FILM MICROSTRUCTURE AND MORPHOLOGY DURING CHEMICAL VAPOR DEPOSITION: D.P.Adams, T.M. Mayer, E. Chason, B.S. Swartzentruber, Sandia National Laboratories, P.O. Box 5800, Albuquerque, N.M. 87185
We present a study of thin film growth by thermal chemical vapor deposition (CVD). In this investigation of metal growth onto Si substrates, the effects of chemical kinetic processes on both film structure and morphology are determined. Scanning tunneling microscopy is used to identify the nucleation sites and to monitor island growth during the submonolayer regime. Analysis of measured island size distributions reveals the importance of site-specific chemical reactions and precursor molecule diffusion. Also, we monitor the development of surface roughness of thicker films by x-ray reflectivity. These experiments demonstrate the influence of nucleation rate on surface morphology. Finally, we show how CVD kinetics can be manipulated by use of adsorbates which passivate chemically - reactive substrate sites. Adsorbate layers have been used to modify the nucleation rate and fabricate nanometer - size structures via selective - area growth. This work was supported by the U.S. Department of Energy under contract DE-AC04-94AL85000.
9:50 am
TEM INVESTIGATION OF CVD ALUMINA MULTILAYER COATINGS: M. Halvarsson, Department of Physics, Chalmers University of Technology, S-412 96 Göteborg, Sweden; S. Vuorinen, Research and Development, Seco Tools AB, S-737 82 Fagersta, Sweden
10:10 am BREAK
10:30 am INVITED
MOLECULAR VIEW OF CVD DIAMOND FILM GROWTH: David J. Srolovitz, Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109-2136; Corbett Battaile*, James E. Butler, DDGas/Surface Dynamics Section, Code 6174, Naval Research Laboratory, Washington DC 20375-0001
Kinetic Monte Carlo computer simulations of the growth of diamond thin films are presented as a function of hot filament chemical vapor deposition reactor conditions. The model includes chemical reactions between surface atoms, gaseous hydrogen and hydrocarbons, and between species on adjacent surface sites. Gas phase hydrocarbon composition is varied over six orders of magnitude. The effects of surface atomic structure and morphology on growth behavior are included explicitly. The evolution of surface structure (including reconstruction) during growth and evidence for step-flow growth and surface roughening will be presented. Model predictions for the growth rates of high symmetry facets will be presented and the influence of these growth rates on surface roughness, microstructure, point defect incorporation and texture will be discussed.
10:50 am
MICROSTRUCTURAL INVESTIGATION OF THE GROWTH OF YBa2Cu3O7-x /Nd2CuO4/YbA2Cu3O7-x TRILAYERED FILMS ON LaSrGaO4 SUBSTRATES: Y.H.Li, A.E. Staton-Bevan, Department of Materials, Imperial College, London SW7 2BP, UK; Z. Trajanovic, I. Takeuchi, T. Venkatesan, Department of Physics, University of Maryland, MD 20742
A HRTEM study of an YBCO/Nd2CuO4/YBCO trilayered films on LaSrGaO4 substrate with PBCO as a template layer has shown that in-plane aligned a-axis oriented YBCO films may be grown on (100) LaSrGaO4 substrates by pulsed laser deposition, which contain some domains with the c-axis misaligned by 90° in plane of the films. A Nd2CuO4 insulating layer, with a thickness of approximately 10nm, may be grown epitaxially between a-axis oriented YBCO layers with its c-axis parallel to the c-axis of the YBCO layers. A 90°-misoriented a-axis YBCO grain in the lower YBCO layer can nucleate a 90°-misoriented Nd2CuO4 grain in the a-axis oriented Nd2CuO4 layer and this grain can further nucleate a 90°-misoriented YBCO grain in the top YBCO layer. Narrow vertical Nd2O3 plates were observed in 90°-misoriented Nd2CuO4 grains formed epitaxially with the Nd2CuO4 grains. The interface between the PBCO template layer and the LaSrGaO4 substrate is quite rough with some amorphous islands in the template layer.
11:10 am
ADVANCES IN THE PROCESSING AND APPLICATIONS OF HIGH TEMPERATURE SUPERCONDUCTING FILMS: M. Sisodia, R.K. Yadava, Dept. of Metallurgical Engineering, Malaviya Regional Engineering College, Jaipur 302 017, India
High critical temperature (high-Tc) superconductors have captured the interest of engineers and scientists world wide. For its commercial utilization in the field of microelectronics and electronic systems, they must be fabricated into desirable configurations, thin and thick films. During studies it has been observed that these superconducting thin films operating at liquid N2 temperature offer great possibilities for faster, more sensitive and precise electronics devices. Present paper reviews the fabrication techniques of high-Tc superconducting thin films which primarily includes Pulsed-Laser Deposition, Molecular ion beam epitaxy, Chemical Vapour Deposition (CVD) by using epitaxial growth on single crystal substrates (YSZ, MgO, Si, etc.) with excellent microstructural control and properties relationship. In addition to it, thick film fabrication is also discussed with major techniques like Screen Printing and Plasma Spraying along with associated processing parameters. Furthermore, advanced applications of each are enumerated at length.
Room: 330E
Session Chairpersons: Michael J. Kaufman, Dept. of Materials Science and Engineering, Univ. of Florida, 201 Rhines Hall, Gainesville, FL 32611; Bruce A. MacDonald, National Science Foundation, 4201 Wilson Blvd., Arlington, VA 22203-9966
8:25 am
OPENING REMARKS: Kwai S. Chan, Southwest Research Institute, PO Drawer 28510, San Antonio, TX 78228-0510
8:30 am INVITED
KINETIC AND MECHANISTIC ASPECTS OF THE 
m MASSIVE TRANSFORMATION IN TIAL ALLOYS: Ping Wang, D. Veeraraghavan, Vijay K. Vasudevan, Dept. of Materials Science and Engineering, University of Cincinnati, Cincinnati, OH 45221-0012
The kinetics and temperature dependence of the 
transformation in Ti-(46-48) at.% Al alloys was studied using a novel computer-controlled temperature and electric resistivity acquisition system. Samples of the alloys were heated by controlled direct resistance heating and cooled at various rates by a helium jet quench. In situ, real time, high speed, simultaneous measurements of electrical resistivity and temperature were made during both heating and cooling. Using the resistivity and thermal arrest data, the start and finish temperatures of the various transformation modes, viz., lamellar, Widmanstatten/feathery and massive were determined as a function of cooling rate. The data obtained was correlated with light and electron microscope observations to establish transformation diagrams, and to determine the growth rate of the massive phase as a function of undercooling. The experimental data was fitted into physical models and thermodynamic quantities such as the enthalpies/driving forces of formation of the massive were determined. The activation enthalpy for boundary diffusion estimated from this data indicates that the massive transformation is controlled by interfacial (rather than volume) diffusion. Defect structures in the massive phase and the massive -parent interface were characterized in detail by TEM. The implications of these studies on the mechanism of the massive transformation will be discussed. This research is supported by grants from the National Science Foundation (Dr. Bruce MacDonald, Program Monitor) and UES/Wright Laboratory (Dr. Madan Mendiratta, Program Monitor).
9:00 am
CALCULATION OF THE TI-AL PHASE DIAGRAM: F. Zhang, S.L. Chen, Y.A. Chang, Department of Materials Science and Engineering, University of Wisconsin, Madison, WI 53706; U.R. Kattner, National Institute of Standards and Technology, Gaithersburg, MD 20899
A thermodynamic description of the Ti Al system is developed in this study. Nine phases were considered in this system. They are disordered solution phases: liquid, (Ti, Al), 
(Ti, Al), (Al); ordered intermetallic phases: 2Ti3Al, TiAl, TiAl3 and stoichiometric compounds: TiAl2, Ti2Al5. The Redlich Kister equation was used to describe the excess Gibbs energy for the disordered solution phases; the generalized quasi-chemical model recently developed in our research group was used to describe the ordered intermetallic phases. The parameters describing these models were obtained by optimization using the experimental phase equilibrium and thermodynamic data available in the literature. The quasi-chemical model is an extension of the Bragg Williams model similar to the extension of the regular solution model for disordered solution phases. Thermodynamic values obtained from the model parameters as well as the calculated phase diagram are in good agreement with the experimental data. The intrinsic defect concentrations calculated from the model parameters for TiAl are compared with the predictions of the first principle calculation, the semi empirical relationship and the available experimental data, reasonable agreement is obtained. The model parameters for the ordered intermetallic phases can be converted to the format of sublattice model and Wagner Schottky model.
9:20 am
PHASE DIAGRAM MODELLING OF TiAl ALLOYS: Nigel Saunders, Thermotech Ltd, The Surrey Research Park, Guildford GU2 5YG, UK; IRC in Materials for High Performance Applications, University of Birmingham, Birmingham B15 2TT, UK
The phase relations in Ti-Al based systems are by no means well established except for the case of a few specific ternary systems. This lack of information is now being exacerbated as new generation alloys are commonly multi-component in nature. Thermodynamic phase diagram modeling for Ti-Al-X systems has been presented previously which can now form the basis for the extension of the modeling technique to multi-component alloys. Examples of calculations for a variety of multi-component alloys will be shown and the effect of light elements such as O will also be modeled. An important factor in the success of the calculation method is that the ordering of the phase to 2 can now be incorporated. 1. N. Saunders, to be published in "Titanium '95: Science and Technology," eds. P. Bleckinsop et al (London: Inst. Materials, 1996).
9:40 am
EFFECTS OF SUBLATTICE ORDERING AND COMPOSITIONAL UNCERTAINITIES ON THE DETERMINATION OF ACCURATE AND PRECISE DEBYE-WALLER AND STRUCTURE FACTORS IN TIAL: S. Jayanthi, S. Swaminathan, H.L. Fraser, Department of Materials Science and Engineering, Ohio State University, Columbus, OH 43210; I.P. Jones, School of Metallurgy and Materials, University of Birmingham, Edgbaston B15 2TT, UK; D.M. Maher, Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC
There has been significant interest aimed at determining the anisotropy of charge densities in the intermetallic compound TiAl. Such determinations require the accurate measurement of low order structure factors, which in turn requires an accurate knowledge of the Debye-Waller factors of the given alloy/compound. Hence, the quest for assessments of charge densities in TiAl has involved determinations of the Debye-Waller factors and structure factors. The first of these are conveniently extracted from single crystal x-ray diffraction experiments, and it has been found that in samples whose compositions are Al rich sub-lattice ordering occurs, such that there are unequal values of the Debye-Waller factors for the two Ti sites. The effect of this sub-lattice ordering on the determination of the Debye-Waller factors has been assessed and will be discussed. Furthermore, the effect of compositional uncertainties on the determination of both Debye-Waller factors and structure factors has been investigated. It has been shown that sample compositions must be known to within ±0.15at.% for accurate determination of charge densities. These limitations will be discussed, and an experimental approach to overcome these will be detailed. This work has been supported by the National Science Foundation, Dr. Bruce MacDonald as Program Manager.
10:00 am BREAK
10:20 am
PHASE RELATIONS AND ALPHA DECOMPOSITION IN Ti-(25-50) Al ALLOYS: Y-W. Kim, UES, Inc., Dayton, OH 45432
The phase relations in Ti-(25-55) at.%Al involved in the decomposition and transformations of the high temperature alpha phase were investigated by conducting annealing/cooling experiments in a cooling/heating rate range of 0.2-100°C/min. X-ray and differential thermal analyses were conducted to determine phase relations, transformation temperatures and enthalpies involving various alpha-decompositions. Three types of decomposition reactions were found to exist, depending on composition and cooling rate, that is; I: 2; II: L(2 + ); and III: L(' + )L('2 + ). In Types II and III, the undercooling and the lamellar spacing (
L) for the lamellar structure (L) were related to cooling rate and Al content. The ordering reaction in Type III, 2 took place at increasingly higher temperatures (with Al content) than the Type I extrapolation due to the compositional changes. Both Type I and II reactions are favored in low Al-content alloys; however, they (Type II in particular) could take place even in Ti-48Al. This and the other reactions will be analyzed in detail.
10:40 am
GRAIN REFINEMENT AND LAMELLAR FORMATION IN HOT-WORKED Ti-(42-47)Al-(0-0.5)B ALLOYS: Y-W. Kim, UES, Inc., 4401 Dayton-Xenia Rd., Dayton, OH 45432
Small amounts of boron additions are known to effectively refine the alpha grains in hot worked TiAl alloys when heat treated in the alpha field, resulting in the formation of fine lamellar colony microstructures. The boron additions raise significantly the critical cooling rate above which the formation of fully lamellar structures begins to be suppressed. Since this cooling rate allows the lamellar spacing to be controllable to a greater range, it is critical to understand the formation mechanism and kinetics of gamma laths in the presence of boron (in the form of borides). For this, annealing and cooling experiments and microstructural observations have been conducted on forged alloys of Ti-(42-47)Al-(0-0.5)B. DTA measurements are underway to detect the undercoolings before gamma precipitation in the alpha matrix as a function of cooling rate. The results will be presented and analyzed to explain the role of borides on the grain refinement, the formulation of gamma precipitates, and the retardation of nonlamellar microstructure formation.
11:00 am
THE 2 SHEAR TRANSFORMATION: P.M. Hazzledine, UES, Inc., 4401 Dayton-Xenia Rd. Dayton, OH 45432; B.K. Kad, Dept. of Applied Mechanics & Engineering Science, University of California-San Diego, La Jolla, CA 92093; V.K. Vasudevan, Dept. of Materials Science and Engineering, Univ. of Cincinnati, Cincinnati, OH 45221
When a hexagonal close packed crystal, with ideal c/ ratio, is sheared by Shockley dislocations on alternate basal planes the resulting crystal is face centered cubic. The six Shockley vectors generate cubic structures in two orientations which are twins of each other. When the DO19 structure is sheared by the same six Shockley vectors the result is three different 12H structures and their three twins. These 12H structures are composed of tetragonal unit cell building blocks, having axial ratios 1:1:/2. In this description, all of the {100} planes have alternate compositions Ti, TiAl and the unique c axes are in six different directions, one resulting from each of the six Shockley shears. The 'tetragonal' description of the structures is the same as the tetragonal structure L10 except that in L10 the {100} planes have alternate compositions Ti, Al. Thus, shearing the DO19 structure in one of the Shockley directions by 1/2:/2 creates a crystal structure which is as close to L10 as the composition allows. The six variants of gamma may therefore be formed from a single crystal of 2 by the operation of dislocations with the six available Shockley Burgers vectors so long as the composition may be corrected by diffusion.
11:20 am
A SYSTEMATIC STUDY OF THE ELECTRONIC STRUCTURE OF STABLE AND METASTABLE FORMS OF -TIAL: J.M.K. Wiezorek, X.D. Zhang, R. Banerjee, H.L. Fraser, Department of Materials Science and Engineering, Ohio State University, Columbus, OH 43210
Numerous theoretical, first principle calculations studies have shown that the interatomic bonding in TiAl is a mixture of covalent and metallic. There is a need to complement these studies with experimental observations. Electron energy loss spectroscopy (EELS) is capable of providing electronic structure information through the near edge fine structure in core loss peaks, since these reflect the combined effects of bonding parameters such as charge transfer, hybridization, and variation of the crystal and ligand field. In this paper, EELS has been used to study the electronic structure of stable and metastable forms of -TiAl. The near-edge EELS signatures of the equilibrium phases at Ti-25at.%Al, Ti-75at.%Al and Ti-52at.%Al have been used to assess the suitability of this experimental method for the study of the electronic structure in -TiAl compounds. Metastable phases of -Ti-50at.%Al and 2-Ti-48at.%Al have been generated by very rapid quenching from the -phase field, and thin amorphous films of -Ti-48at.%Al have been deposited by magnetron sputtering. The near edge structure of these phases have been studied using a field emission TEM equipped with an imaging parallel EELS. Furthermore, results for 2-Ti-36at.%Al and -Ti-52at.%Al in binary lamellar TiAl are presented. The results of this study are discussed with a view to the mechanical behavior and the phase stability of -TiAl based compounds. This work has been supported by a grant from the National Science Foundation with Dr. Bruce MacDonald as program manager.
Room: 230C
Session Chairpersons: James C. Daley, Daley & Associates, 1020 W. Cactus Wren Drive, Phoenix, AZ 85021; John M. Rapkoch, Davy International, 2440 Camino Ramon, San Ramon, CA 94583
8:30 am
USE OF PVC AS A CHLORINATING AGENT IN THE RECYCLING OF METALS: F. Tailoka, D.J. Fray, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ, United Kingdom
The standard free energy of formation of the oxides of the ferrous metals is generally more negative than that for the chlorides whilst the reverse is true for the equivalent compounds of the non-ferrous metals. As a source of chlorinating agent PVC has been used. PVC has the nominal formula C2H2HCI. On combustion in air, considerable heat is generated and hydrogen chloride, water vapor and carbon dioxide are evolved. It can be regarded as a free source of heat and a chlorinating agent if scrap PVC is used. In this work, this gas has successfully been used to separate zinc, lead and copper from residues such as Jarosite, EAF dust and waste materials containing copper. Dioxins were not detected either in the residues or the condensed chlorides.
8:55 am
RECOVERING MAGNESIUM FROM SOAPSTONE AND ASBESTOS TAILINGS: V.A. Leão, C.A. Silva, M.G. Menenzes, J.C. Pires, L.G. Macedo, School of Mines, Federal University of Ouro Preto, Praca Tiradentes, 20; Ouro Preto, MG, 35400-000, Brazil
Asbestos industry produces large amounts of serpentine (magnesium silicate) tailings. The effect of this on human health is well-known. Besides this, the processing of a Brazilian rock known as "Pedra sabão" (soap stone) generates powders that are discharged in the environment. This material is also a potential resource of magnesium. Magnesium oxide is used in many industries like refractory, waste water treatment, among others. The applicability of hydrochloric leaching for the recuperation of magnesium oxide from those materials has been investigated. The effect of time, temperature, particle size and solid/liquid ratio, on the leaching of magnesium and impurities, is discussed.
9:20 am
THE RECOVERY OF TELLURIUM FROM COPPER ANODE SLIME BY HYDRO-METALLURGICAL PROCESSES: K.-I. Rhee, C.-K. Lee, Korea Institute of Geology, Mining and Minerals, P.O. Box 14, Taejon, Korea 305-350; H.S. Kim, T.H. Kim, C.S. Yoo, H.J. Sohn, Y.-J. Kim, Dept of Mining & Petroleum Engrg., Seoul National University, 151-742 Seoul, Korea
The recovery of tellurium from pretreated copper anode slime was carried out by a series of hydrometallurgical processes. These include leaching of cemented Te at high temperature with oxygen purging in NaOH solution, precipitation of TeO2 from leach liquor, leaching of TeO2 in alkaline solution, precipitation of impurities by Na2S, and electrowinning of tellurium. The optimum conditions of each process were determined and discussed in terms of various parameters associated with each step to maximize the recovery and purity of tellurium.
9:45 am BREAK
10:00 am
PRODUCTION OF NON-FERROUS METALLIC CONCENTRATES FROM ELECTRONIC SCRAP: Jorge Alberto Soares Tenorio, Ricardo Perez Menett, Arthur Pinto Chaves, Department of Metallurgical and Materials Engineering, University of Sao Paulo, 05508-900, Sao Paulo, Brazil
Electronic components have metals with important valor like Au, Ag and Cu. These metals have a high performance in electric conductance. The recycling of scrap, however is too difficult because we have the presence of other metals like Fe, Al, Zn, Sn, more ceramics and plastics, all together in electronic components. This work had for subject define one way for physical separation. We have researched methods that obtained metallic concentrates non-ferrous. By the way we have used three types of scrap. We have used equipment of mineral processing. The metallic concentration make more easy the recuperation of metals because short the volume of material used. We have obtained, since of types studied an middle compassion of plastic, ceramic and metals.
10:25 am
DESIGN AND CONSTRUCTION OF A SMALL-SCALE USED BEVERAGE CAN RECYCLING UNIT: Jim S-J. Chen, Frederick Higgins, Joseph Vinch, James Kelly, Steven Smigiel, Center for Environmental Studies, College of Engineering, Temple University, Philadelphia, PA 19122
A small-scale recycling unit for used beverage cans is designed, constructed and tested. The unit consists of a rotary kiln for delacquering, a gas-fired furnace crucible for melting, a baghouse for pollution control and an air recirculating system for heat recovery and oxygen control. The delacquering kiln utilizes a counter flow thermal decoating process and the optimized operating condition was found to be at 1000°F, 6-7% O2 and a residence time of 15 minutes. In melting, a special salt mixture is made by combining cryolite and sodium chloride. The salt mixture has a low melting temperature (<1250°F) and is effective for demagging and degassing. The yield of the small-scale unit is about 90% and the energy efficiency matches those reported for large-scale facilities.
10:50 am
OPTIMIZATION OF SALT COMPOSITION IN THE RECYCLING OF ALUMINUM CANS: Jorge Alberto Soares Tenorio, Fabio Delgado, Department of Metallurgical and Materials Engineering, University of Sao Paulo, 05508-900, Sao Paulo, Brazil
During the melting processing of aluminum can scrap there is a considerable loss of metal due of metal trapping in the dross. Among all techniques available to recover this kind of scrap, the one using saline fluxes, based on NaCl / KCl equimolar composition and fluorides addition is outstanding. The investigation into the melting of AA3004 and AA5182 alloys (materials which the body and the lid of beverage cans are made of), the effect of delacquering, and the influence of different fluxes and the temperatures on the process yield are the main objectives of this work. Melting tests were carried out in order to access the effect of fluorides and the melting temperature on the recycling process yield. The fluoride efficiency for the temperature of 750°C was: CaF2 < NaF < Na3AlF6 < KF.
Room: 231C
Session Chairpersons: Donald M. Hausen, Consultant, Salt Lake City, UT; Leonard Harris, Consultant and Former General Manager, Minera Yanacocha, Peru
8:30 am
OPENING REMARKS: Donald M. Hausen, Program Organizer and 1997 Chairman of the TMS Process Mineralogy Committee
8:40 am
MINE GEOLOGY AND PROCESS ORE CONTROL AT NEWMONT MINES, CARLIN, NV: Joseph C. Rota, Newmont Exploration Ltd., 1700 Lincoln Street, Denver, CO 80203
The Carlin Trend, located in NE Nevada, has produced over 17 million ounces of gold from Newmont's open pit and underground operations since 1965. Oxidized portions of sediment-hosted disseminated submicron-sized native gold is mostly amenable to dump or heap leaching, yielding 50 to 70% recovery of contained gold. Metallurgical control and grade of heap leach ores are maintained by geological techniques and standard assays. Mine geologists provide field observation and mineralogic data by daily visual blasthole logging. Refractory components are separated from oxide to ensure high recovery. Geologic and assay data are combined to create mine polygons in an engineering computer database. Mining selectivity is thus enhanced by ore control geologists who make production decisions based on direct mineralogic observations at active mine faces.
9:05 am
BASIC CONCEPTS OF OXIDE GOLD DEPOSITS AND EXPLORATION STRATEGY: E. Daniel Baker, Senior Mineralogist, Newmont Metallurgical Services, 417 Wakara Way, Salt Lake City, UT 841O8
The term oxide gold deposits, refers to gold-bearing veins, faults, and shear zones that typically contain appreciable amounts of oxidized ore or gossanous material, resulting from oxidation of sulfides. The concept of oxide gold deposits underwent a dramatic change after the discovery of the Carlin gold mine in north central Nevada in early 196O's, and now implies large tonnage, low-grade bulk minable deposits that are processed by milling and/or heap leach methods. Oxide gold deposits may be classified into two types: (1) primary oxide ores derived directly from the effects of hydrothermal alteration on oxidized host rocks, and (2) secondary oxide ores derived from the epigenetic effects of circulating post mineral fluids oxidizing gold-bearing sulfides. Each type of oxide gold deposit has unique diagnostic mineralogic and metallurgical characteristics, that must be addressed in order to achieve a successful exploration strategy.
9:30 am
BLUE STAR SUBDISTRICT ZONED ALTERATION AND GOLD MINERALIZATION AND ITS INFLUENCE ON MINE OPERATIONS, CARLIN TREND, EUREKA COUNTY, NV: Cindy L. Williams, Newmont Exploration Ltd., Carlin NV 89822
Blue Star subdistrict open-pit gold deposits include multiple mines with 1.194 million ounces reserve and past production totalling 3.144 million ounces. The deposits are characterized by zoned alteration, including: 1) silicified core with erratic gold grade; 2) adjacent mill-grade (>0.04 oz/st) intense quartz-sericite-pyrite alteration; 3) enveloping heap-leach grades (0.006-0.04 oz/st) weaker sericite-kaolinite-quartz-pyrite alteration; 4) surrounding decarbonatized and intensely argillized waste and leach grade ore; 5) pervasively decarbonated waste; and 6) peripheral waste with local propylitic and weaker decarbonated alteration. Each alteration assemblage is characterized by distinct rock strength parameters that influences geotechnical pit slope design, as well as metallurgy and optimizing of drill/blast cycles. Alteration of barren assemblages extend hundreds of feet beyond orebodies.
9:55 am BREAK
10:05 am
GEOLOGY AND MINERALOGY RELATED TO HEAP LEACHING AT THE RAIN MINE, ELKO COUNTY, NV: Dean G. Heite, Newmont Exploration Ltd., Carlin NV 89822
Gold Mineralization at Rain is largely hosted by Mississippian Webb Formation consisting of interbedded siltstones and mudstones. The NW-striking SE-dipping Rain fault is a main feeder structure for the deposit. Five ore types based on XRD and visual rock chip logging were identified: argillaceous (>30% clays); siliceous (<20% barite; siliceous-baritic (20-40% barite); baritic (>40% barite); and calcareous (major carbonate minerals). The Rain heap-leach pad was commissioned in 1988, and to date 10.3 million tons of ore averaging 0.023 oz/st have been treated. Recovery to date through December 95 is approximately 56% for a total 132,453 ounces of gold produced. Two major factors have contributed to low leach recoveries at Rain: 1) excess argillaceous ore than expected on the pad, mostly late in the mine life, and 2) about half of the heaps were run-of-mine ore with no agglomeration. Testwork on leach grade composites indicated recoveries near 69% for material crushed to minus 1 1/5".
10:30 am
GEOLOGY OF THE TUSC GOLD DEPOSIT, EUREKA COUNTY, NV: Paul O. Malan and Leroy Schutz, Newmont Exploration Ltd., Carlin NV 89822
The Tusc gold deposit, located 8 miles NW of Carlin, Nevada, along the Carlin trend, is one of several structurally controlled gold deposits associated with the Good Hope fault within the Maggie Creek Subdistrict. Mining commenced in 1994 with an oxide reserve of 780,000 ounces of gold averaging 0.039 opt Au. The Good Hope Fault forms the SW edge of the Schroeder Mountain uplift (Carlin Window) and juxtaposes carbonate rocks of the Roberts Mountains Formation against siliceous mudstone, chert and siltstone of the Rodeo Creek Unit. Submicroscopic gold is disseminated in the shear zones of the Good Hope fault system and in crosscutting northeast-striking, high-angle faults in the lower plate carbonates in the immediate hanging wall. Wallrock alteration includes argillization, decalcification, silicification, and alunite veining, supergene leaching and oxidation. Arsenic forms a strong halo around the ore and an antimony anomaly occurs in the upper part of the deposit.
10:55 am
MULTI-METAL RECOVERABLE RESERVE ESTIMATES AND WHITTLE PIT OPTIMIZATION OF MILL AND HEAP LEACHABLE GRADE ORES AT THE MCCOY BLACK COVE MINE, NV: Songlin Zhang, Mining Engineer, Echo Bay Minerals Company, McCoy/Cove Mine, #1 McCoy Mine Rd., Battle Mountain, NV 89820
The McCoy/Cove mine, located in Eureka-Battle Mountain trend of Nevada, is a gold and silver deposit. Case studies of recoverable reserve estimation for gold and silver were made using multiple indicator kriging and volume variance correction. The grade tonnage distributions of recoverable reserves were constructed and compared with the distributions defined by blast hole assays. Optimal pits were generated by Whittle 4D pit optimization package to analyze the impact of different processing recoveries at different economic cutoffs. The results were compared with ordinary kriging. The study indicates that the proposed method for multi-mineral recoverable reserve estimation is more accurate than kriging in terms of grade and tonnage. The method of using recoverable reserves for pit optimization will maximize global reserve recovery and revenue, and is more efficient than condition simulation regarding computing power.
Room: 315A
Session Chairpersons: Gye-Won Hong, Superconductivity Research Laboratory, KAERI, Taejeon, Korea; P. Haldar, Intermagnetics General Corp., Latham, NY
8:30 am INVITED
POWER APPLICATIONS OF HIGH TEMPERATURE SUPERCONDUCTORS: P. Haldar, M.S. Walker, D.W. Hazelton, J.G. Hoehn, Jr., Intermagnetics General Corporation, Latham, NY 12208
Intermagnetics has concentrated on manufacturing long lengths of silver sheathed Bi-2223 and surface coated Bi-2212 HTS conductor. Development work has led to the successful manufacture of Bi-2223 multifilament conductor in lengths exceeding 1 km, with properties useful for most electric power applications. Surface coated, low cost, Bi-2212 conductor in lengths over 400 meters are now also being produced. Several lengths of high performance tapes have already been delivered to GE to wind the first HTS generator coil. The coils were successfully tested in a steady state, conduction cooled environment generating 40,000 amp-turns at 23.5 K. Novel and unique hybrid magnet designs are being designed and built with the availability of both Bi-2212 and Bi-2223 HTS conductors. The demonstration and test of a pre-prototype 1 MVA transformer utilizing HTS windings is planned in collaboration with ORNL, Waukesha Electric, and RG&E. The development of the largest HTS coils is continuing, for the construction of a 15 KV fault current limiter as part of the DOE-SPI program with Lockheed Martin, Southern California Edison, and LANL. Several high amp-turn coils have also been fabricated and delivered to the U.S. Navy to demonstrate a high horse power HTS homopolar motor. These demonstrations indicate the rapid progress being made to develop commercial applications of high-temperature superconductors.
8:50 am INVITED
CONTROLLED PRECIPITATION OF SECOND PHASES IN (Bi,Pb)2223 CERAMICS AND ITS INFLUENCE ON THE PINNING: P. Majewski, S. Kaesche, A. Sotelo, F. Aldlinger, Max-Planck-Institut für Metallforschung, Pulvermetallurgisches Laboratorium, Heisenbergstr. 5, D-70569 Stuttgart
Taking the temperature dependent Pb solubility of (Bi,Pb)2+xSr2Ca2Cu2O10+d [(Bi,Pb)2223] into account, it is possible to precipitate various second phases in single phase (Bi,Pb)2223 ceramics at temperatures below 840°C, i.e., Pb4Sr5CuO10, Ca2CuO3, CuO and Bi2Sr2CaCu2O8 (Bi2212). At 800°C, the kinetic of the formation is fast resulting in mm-sized second phase precipitates after about 6 h. The Jc of the samples increases with precipitation, indicating increased pinning properties of the ceramics. After a maximum increase of Jc at about 3 h, Jc decreases again.
9:10 am INVITED
EFFECT OF LEAD CONTENT ON PHASE EVOLUTION AND MICROSTRUCTURAL DEVELOPMENT IN Ag-CLAD Bi-2223 COMPOSITE CONDUCTORS: N.N. Merchant, V.A. Maroni, A.K. Fischer, S.E. Dorris, W. Zhong, N. Ashcom, Argonne National Laboratory, Argonne, IL 60439
Silver-sheathed monofilamentary Bi1.8PbxSr1.98Ca1.97Cu3.08Oy (Bi-2223) tapes prepared by a two powder process that used powder containing varying lead contents, x, from 0.2 to 0.5 were subjected to thermomechanical processing and then characterized by XRD, SEM and EDX. Texture was studied using image analysis software on scanned SEM images. It was found that tapes with low lead content (0.20 and 0.25) showed incomplete conversion to Bi-2223, had small grain size, and poor c-axis texture. Tapes having higher lead content (0.4 and 0.5) also showed incomplete conversion and the presence of lead-rich secondary phases. Tapes with lead contents of 0.30 and 0.35 showed complete conversion to Bi-2223, had the least amount of secondary phases, showed best c-axis texture, and had the highest Jc. The carbon content of the precursor powder also had a strong influence on secondary phase chemistry. Work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, as part of a DOE program to develop electric power technology, under Contract W-31-109-Eng-38.
9:30 am INVITED
EFFECT OF PARTICLE SIZE REDUCTION ON THE MICROSTRUCTURE EVOLUTION AN