Niobium demand and superconductor applications: An overview

Abstract

Niobium applications in applied superconductivity are described under six major categories following an examination of supply and demand to the turn of the century. The demand is relatively small. Somewhere between 500 and 1000 tonnes of niobium are expected to be used in superconducting devices to be produced over the next ten years; the large range in demand being due to the uncertainty about whether or not the latest proposals to build new particle physics colliders will be approved. The impact of possible space programs has not been considered. The quantity of niobium contained in the primary ore needed for alloy and compound production will be about double this amount, to compensate for losses incurred during the various stages of production to final product. By comparison, world-wide steel industry demands for niobium are around 15 000 tonnes per year. Thus the world superconductor industry is very small. Fears that there may be a shortage of niobium for superconducting applications are unfounded. A major world supplier of ferro-niobium and niobium oxide is Companhia Brasileira de Metalurgia e Mineracao (CBMM) of Brazil and most of the raw material used in the practical superconducting alloys comes from this source. Reserves in the CBMM mine alone are adequate to supply projected world needs for all purposes for at least 500 years. Other world sources of niobium exist and some are being worked, but they contain lower concentrations of niobium in the ore than those in the CBMM mine and therefore they cost more to extract. In spite of the importance of niobium in technology it is not a strategic mineral because of its world-wide abundance and the availability of substitutes for its major applications. A new development in superconductivity has been the discovery of the ceramic oxide superconductors in the last two years with critical temperatures close to 100 K, offering the possibility of cheaper and simpler liquid nitrogen cooling, as opposed to liquid helium cooling, for some future superconducting applications. Near-term applications in simple electronic devices are expected but for present day and projected applications, niobium-based alloys and compounds are likely to be the workhorses of superconductivity for the remainder of this century. The major commercial superconductor application, to date, is that for whole-body magnetic imaging as a tool in medical diagnostics. These units began to reach the market-place in 1982 and over one thousand are now in use world-wide. A further recent development is the use of superconducting r.f. cavities using high purity niobium sheet. Machines using these devices will need over 30% of the total niobium demand for applied superconductivity over the next five or six years. A potential demand is that for new colliding beam accelerators proposed for particle physics and nuclear physics research. If they are built, about 600 tonnes of niobium will be needed for these machines. Requirements for energy industry technologies and transportation, so high about 15 years ago, are likely to be dismally low for the next 20 years or so. Other commercial uses for superconducting magnets at present are those for gyrotrons, magnetic separators and research and development activities. In addition to machines for physics research, smaller accelerators with superconducting magnets are under development for use in medical and industrial applications and for the production of high intensity X-ray light sources. The energy related applications are not yet commercial but the required superconducting magnet technology has been developed over the last 25 years. Applications include magnetic fusion, superconducting generators, magnetohydrodynamic power generation, superconducting power transmission and energy storage, current limiters and superconducting transformers. Successful high-speed land transportation systems based on superconducting magnet levitation have been demonstrated, as have superconducting ship drives. A wide range of superconducting instrumentation is in everyday use and the possibilities for superconducting computers continue to be studied. The status of these various technologies is discussed in the following paragraphs.