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; Willam Ebihara, Picatinny Arsenal, Picatinny, NJ; Enrique J. Lavernia, UC Irvine, Irvine, CA
Wednesday, AM Room: A4-5
February 7, 1996 Location: Anaheim Convention Center
Session Chairpersons: Robert Balliet, H.C. Stark Inc., Newton, MA; George J. Korinek, Tantalum-Niobium International Study Center, Brussels, Belgium
8:30 am Invited
EVOLUTION OF APPLICATIONS OF TANTALUM: Prabhat Kumar, Cabot Performance Materials, County Line Road, Boyertown, PA 19512
This presentation will review the evolution of several applications of tantalum, such as in capacitors and in electronic industry, corrosion-resistant components for chemical processing industries, additives in superalloys, ballistics and carbides. Emphasis will be on critical requirements for these applications. Unique combination of properties of tantalum, such as high melting point, thermodynamic stability of its oxides and carbides, low temperature of coefficient of capacitance, high density and inertness of its oxide film, which make it suitable for these diversified applications will be reviewed.
9:00 am
TANTALUM INDUSTRY IN CHINA: MA Fukang, Chu Youyi, The Nonferrous Metals Society of China, 12B Fuxing Road, Beijing 100814, China; Zeng Fangping, Ningxian Nonferrous Metals Smeltery, Shizuishan, Ningxia 753000, China
The explored Ta reserves in 14 main mines in China are estimated to be of about 40,000 tons containing Ta2O5. Various Ta compounds and metal products are produced form 5 major plants, such as tantalum pentoxides, potassium tantalum fluoride, tantalum carbides, tantalum powder, electron beam melted tantalum ingot, tantalum wires, plates, strips and tubes, etc. Recently, the application of Ta in capacitors provided in the form of powder and wires is dominant in China, which accounts for more than half of total domestic consumption of Ta content. The application of Tantalum carbides in cemented carbide industry occupies about one fourth of the Ta consumption. The rest is mainly supplied as semis, sintered bars and tantalum oxides for electronics, chemical and metallurgical industries. In order to meet the increasing requirements for capacitors, importation of Ta powder and wires has been made since 1991. China has seen a prospective future for the development of tantalum industry.
9:20 am
NEW DEVELOPMENTS IN TANTALUM CAPACITOR MATERIAL TECHNOLOGY: Hongiu Chang, Cabot Performance Materials, Boyertown, PA 19512
Tantalum is an excellent capacitor material. Conventional powders are produced form sodium reduction of potassium tantalum fluoride, and ball milling of EB melted ingots. This paper will examine new technologies which hold promises for the future. These include fiberous materials, extruded anodes, and fine particle engineering.
9:40 am
MICROWAVE SINTERING OF TANTALUM FOR CAPACITOR APPLICATIONS: April D. McMillan, R.E. Clausing, R.J. Lockheed Martin Energy Systems, P.O. Box 2008, Oak Ridge, TN 37831- 6087; W.F. Vierow, AVX Tantalum Corporation, 69 Landry St., Biddeford, ME 04005
Tantalum capacitor anodes can be sintered using microwave heating provided the casket contains lossy materials to initiate heating from ambient temperatures. The use of Ta powder in the casket, along with the green capacitor bodies, improves the heating and eliminates contamination from the vacuum environment. Microwave sintered anodes often show unusual surface ripples on the individual Ta particles; their exact origin is presently unknown. This work is supported by the U.S. Department of Energy, Office of Energy Research, Laboratory Technology Applications Program, and conducted under Cooperative Research and Development Agreement No. ORNL 91-0056 between Lockheed Martin Energy Systems, Inc., and AVX Tantalum Corporation.
10:00 am BREAK
10:15am Invited
THE PRODUCTION OF CAPACITOR GRADE TANTALUM WIRE: Robert W. Balliett, H.C. Starck Inc., 45 Industrial Place, Newton, MA 02161-1951
Capacitor grade tantalum wire is a critical component in the manufacture of capacitors for the electronics industry. Todays capacitor grade wire is produced from tantalum powder using various powder metallurgical processes. Sodium reduced powders are microalloyed with elements that form a fine dispersion of a thermally stable second phase. This dispersion inhibits the motion of grain boundaries during elevated temperature sintering, thus reducing the wire's tendency to become embrittled. This paper briefly discusses the history of wire manufacturing and the major alloying techniques used to produce grain growth resistant wire. Current generation capacitor grade wire is also characterized in terms of chemical, physical and mechanical properties as well as surface chemistry and structure. The structure of the dielectric film formed on the tantalum wire during the anodization process is examined.
10:45 am
EFFECT OF PHOSPHORUS DOPANTS ON THE SINTERING OF TANTALUM POWDERS: Sophie G. Dubois, Andrew A. Marszalek, Randall M. German, P/M Lab, The Pennsylvania State University, 118 Research Building West, University Park, PA 16802-6809
The performance of tantalum capacitors is directly proportional to the sintered powder surface area; therefore, dopants such as phosphorus compounds are commonly added to the tantalum powder as a mean to preserve surface area during sintering. The fundamental explanation of the effects of these dopants is still lacking. In this study, the effect of phosphorus on tantalum sintering has been investigated. The effect of the amount of dopants and the sintering temperature have been studied and the mechanism responsible for the preservation of the surface area is being researched.
11:05 am
AN OVERVIEW OF THE APPLICATION OF TANTALUM AND ITS ALLOYS AS WARHEAD LINER MATERIALS: James F. Muller, Engineering Manager-Armament Systems, GenCorp-Aerojet, P.O. Box 13222, Sacramento, CA 95813- 6000
Modern anti-armor warheads require the use of high density metals as explosive cavity liners to achieve required performance levels against state-of-the-art reactive and composite armors. Those high density materials which possess dynamic ductility at high strain rates (103/sec) are appropriate candidates for these warhead liners. Tantalum and its alloys is one of the few classes of materials that have the requisite properties, and are not either economically or environmentally untenable. This paper will discuss the use of tantalum materials for various warhead liner applications. Results of laboratory materials properties testing and of actual warhead test firings from several development efforts will be presented. Data and information associated with the use of pure tantalum as the liner material for the TOW 2B warhead production program will also be discussed.
11:25 am
TANTALUM FOR HIGH TEMPERATURE APPLICATIONS: Tomoo Izumi, Showa Cabot Supermetals, Higashinagahra Factory, Kawahigashi-Machi, Kawanuma-gun, Fukushinma-Ken Japan
It is desirable to have tantalum of ultra-high purity for capacitors. Two
potential sources of impurities in the manufacturing of capacitors, heating
elements in the sintering furnace and the lead wire, are also expected to
maintain ductility and the fine grain-size after being exposed to high
temperature. These two somewhat contradictory requirements are satisfied by
micro-alloying tantalum with highly stable oxides, such as Y2O3. Effect of Y2O3
on mechanical and metallurgical properties are discussed.
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