Sponsored by: SMD Refractory Metals and Materials Committee and Jt. MDMD/EPD Synthesis, Control and Analysis in Materials Processing
Program Organizers: Andrew Crowson, U.S. Army Research Office, Research Triangle Park, NC; Edward S. Chen, U.S. Army Research Office, Research Triangle Park, NC; Prabhat Kumar, Cabot Corp, Boyertown, PA; William Ebihara, Picatinny Arsenal, Picatinny, NJ; Enrique J. Lavernia, UC Irvine, Irvine, CA
Monday, AM Room: A4-5
February 5, 1996 Location: Anaheim Convention Center
Session Chairpersons: Prabhat Kumar, Cabot Corp, Boyertown, PA; Robert H. Tritran, NASA Lewis Research Center, Cleveland, OH
9:00 am Invited
TANTALUM- AN OVERVIEW: George J. Korinek, Tantalum-Niobium International Study Center, Rue Washington 40,1050 Brussels, Belgium
Tantalum in nature is closely related to niobium and tin. The raw material basis is provided by tantalite and tantalum containing tin slags. Structural changes in the tin industry affected very seriously the production of tin slags, so that tantalite became by far the most important resource. These developments will be discussed in detail. The tantalum industry is of relative modest size. The total world consumption in 1994 was 2.2 million lbs. Ta. Over 60% of Ta was used in electronics in the form of powder, wire and furnace hardware for the production of solid electrolyte capacitors. Cemented carbides, equipment for the chemical industry and other uses in mill product form and addition to super alloys are the other main applications. A detailed discussion of the development of the individual applications will be given.
BENEFICIATION OF TANTALUM ORE-HOW IS IT ACHIEVED AND COULD IT BE BETTER?: Richard Burt, General Manager, Tantalum Mining Corporation of Canada Limited
Typically a tantalum ore contains less than 1 kg of tantalum in every tone ore; beneficiation of the ore is therefore an essential step in the production of tantalum. This paper briefly reviews the various tantalum minerals, and studies the mining and beneficiation routes used to concentrate the ore, citing examples from mines and mills throughout the world. The paper also looks at some newer techniques that have been tried, attempting to extend the envelope of recovery, and thereby improve production. The failures are noted; the successes highlighted.
THE PRODUCTION OF TANTALUM BY THE SODIUM REDUCTION PROCESS: Dr. Terrance B. Tripp, H.C. Starck Inc., 45 Industrial Place, Newton, MA 02161-1951
Tantalum metal was first produced in Germany on a commercial scale in the early 1900's by the reduction of potassium heptafluorotantalate with sodium. Today, virtually all of the tantalum metal produced in the world is obtained by variations of a stirred reactor version of this process. The powder is isolated in the form of a powder usually with properties designed to meet the requirements of the solid tantalum capacitor industry or capacitor grade wire production. This paper will briefly trace the history of tantalum production and describe how potassium heptafluorotantalate is reduced to tantalum metal with sodium in a molten salt system using a stirred reactor. The procedures for converting the primary powder to a form suitable for use as a capacitor grade powder or wire and furnace parts feedstock will be described. Examples of the performance of typical tantalum powders available today will be presented.
10:10 am BREAK
10:30 am Invited
SPREADSHEET SIMULATION OF A TANTALUM/NIOBIUM SEPARATION CIRCUIT: Donald Voit, Process Consultant, 4444 Parkview Dr., Ogden UT 84403
A spreadsheet has been developed that simulates the behavior of a tantalum/niobium solvent extraction circuit. The circuit consists of a niobium extractor, a solvent wash section, a tantalum extractor, a niobium scrubber, and a tantalum stripper. The simulation requires selection of the number of stages in each section and specification of feed composition, flows, and distribution coefficients. The simulation calculates compositions at each node in the circuit, chemical consumptions, yields and product quality. Reasonable choices for input variables and their impact on the system are discussed. Literature distribution behavior for the 2-methyl-4-pentanone (mibk) -H2SO4-HF aqueous syslem are reviewed. Regularities in the data permit distribution coefficient behavior prediction over a wide range of chemical environments. The logarithm of the niobium distribution coefficient increases linearly with the acidity. The tantalum/niobium separation factors decreases with niobium distribution coefficient.
STUDIES ON TANTALUM EXTRACTION: A.K. Suri, T.K. Mukherjee, C.K. Gupta; Materials Group, Bhabha Atomic Research Centre; Trombay, Bombay 400 085, India
This paper provides a brief account of research and development program on tantalum extraction at Bhabha Atomic Research Centre. In India, sources of tantalum are rather limited. It is known to occur as columbite-tantalite in association with mica pegmatites, with deposits of tin as columbite-tantalite and also in thc crystal lattice of cassiterits. Besides these, some quantity of niobium and tantalum is generated as sludge during the processing of cemented carbide tools. Processes have been developed to treat all these sources to prepare pure K2TaF7, and Ta2Os. Extensive studies have been carried out and number of processes have been developed to prepare pure tantalum using each of these compounds. While fused salt electrorowinning and sodium reduction techniques have been developed for the reduction of K2TaF7, reduction of oxide has been accomplished with calcium, aluminum, carbon and carbon-nitrogen. Final purification of metal, if necessary, was carried out generally by electron beam melt refining. An alternate purification route based on fused salt electrorefining has also been developed.
Nb-Ta ALLOYS BY THE ALUMINOTHERMIC REDUCTION OF (Nb2O5/Ta2O5) MIXTURES AND ELECTRON BEAM MELTING: Carlos A. Nunes, University of Wisconsin-Madison/ 1500 Eng. Drive, 53706 Madison Wl, on leave from FAENQUIL-DEMAR/ Polo Urbo-lnd. s/n-12600-000, Lorena, SP, Brazil; Daltro G. Pinatti, Alain L.M. Robin, FAENQUIL-DEMARI Polo Urbo-lndustrial s/n-12600-000, Lorena, SP, Brazil
The aluminothermic reduction (ATR) of Nb2O5 followed by the electron beam melting (EBM) of the ATR-electrodes has been successfully applied to the commercial production of pure niobium. In this work we will discuss the technical viability for obtention of Nb-Ta alloys by the same route. We will also present results on the application of metal-gas equilibrium (N)/steady-state (O) equations to estimate the limits ror refining Nb, Ta and Nb-Ta alloys in terms of oxygen and nitrogen, during EBM under practical vacuum conditions. Finally, it will be shown results of chemical/microstructural analysis and metallic yield on the obtainment of an ingot (~ 20 kg) of the Nb-20 wt% Ta alloy by the previously mentioned route.
THE INDUSTRIAL APPLICATION OF PYROMETALLURGY, CHLORINATION AND HYDROMETALLURGY FOR PRODUCING TANTALUM COMPOUNDS: Dr. Joachim Eckert, H.C. Starck GmbH & Co. KG, Im Schleeke 78-91, D-38642 Goslar, Germany
The modern industrial production of tantalum compounds, like potassium heptafluorotantalate (K2TaF7), is not restricted to the wet chemical processing of tantalum bearing ores, but includes the pyrometallurgical upgrading of tantalum containing slags and residues as well as the chlorination of ferroalloys and ores. Considerable progress in producing tantalum compounds by hydrometallurgy was made in the early seventies. Since then, this technique has been continuously modified and improved. Today, tantalum compounds of high purity are manufactured in large quantities for use as starting materials for the production of tantalum metal. Recent process improvements now make it possible to utilize raw materials with extremely unfavorable Ta/Nb ratios, thus assuring a stable supply of tantalum for the foreseeable future. Using actual flow charts, the state-of-the-art of the different techniques for producing tantalum compounds are described and discussed in detail.