Superconducting fibers

Typically, fibers having diameters up to 100 (jm are readily possible fibers with diameters above 2()0 pm are technically speaking no longer fibers but rods. This includes the niobate fibers [46] and the superconducting fibers [14] [50] [33] [63] discussed below. In principle, the float zone method is a containerless process. There is a nominal diameter reduction in the float zone from that of the preform rod to that of the final fiber. Zone (or overall process) stability for the growth of oxide and fluoride fibers is usually achieved with diameter reductions in the range of 1/2 to 1/3 [14]. 

Figure 11. Bushing tips for produdng hollow glass fibers. Left Redrawn from L. J. Huey, Method and apparatus for producing hollow glass filaments, U. S. Patent 4,846,864, July 11,1989. Right redrawn from J. Huang, Hollow high temperature ceramic superconducting fibers, International Patent Application WO 97/22128, June 19,1997.

J. Huang, Hollow high temperature ceramic superconducting fibers. International Patent Application WO 97/22128, June 19,1997. 

Tsuchida H. Science of High Polymers. Tokyo Baihukan, 1975, pp. 85-87 Umeda T., Kozuka H., Sakka S. Fabrication of YBa2Cu307 j superconducting fibers by the sol-gel method. Adv. Ceram. Mater. 1988 3 520-522... 

Yttrium—barium—copper oxide, YBa2Cu202 is a newly developed high T material which has been found to be fully superconductive at temperatures above 90 K, a temperature that can be maintained during practical operation. The foremost challenge is to be able to fabricate these materials into a flexible form to prepare wines, fibers, and bulk shapes. Ultrapure powders of yttrium—barium—copper oxide that are sinterable into single-phase superconducting... 

Pike, G., Pierson, H. O., Mullendore, A., and Schirber, J., Superconducting Thin Film Niobium Carbonitrides on Carbon Fibers, / / . Polymer Symp., No. 29, pp. 71-81, John Wiley Sons, New York (1976)... 

Brennfleck, K., Dietrich, M., Fitzer, E., andKehr, D., Chemical Vapor Deposition of Superconducting Niobium Carbonitride Films on Carbon Fibers, Eroc. 7th Int. Conf. on CVD, (T. Sedgwick andH. Lydtin, eds.), pp. 300-314, Electrochem Soc., Pennington, NJ 08534 (1979)... 

The importance of materials science to U.S. competitiveness can hardly be overstated. Key materials science areas underlie virtually every facet of modem life. Semiconductors underpin our electronics industry. Optical fibers are essential for communications. Superconducting materials will probably affect many areas ceramics, composites, and thin films are having a big impact now in transportation, construction, manufacturing, and even in sports—tennis rackets are an example. 

Another way to dissolve the ethoxides was described by Uchikawa et al. (21) and used a mixture of water, diethylenetriamine and acetic acid, in which cations are both hydrolyzed and complexed. Upon solvent evaporation, very viscous thermoplastic gels are obtained from which fibers may be prepared. The unfired fibers contain 45% by weight inorganic materials. They yield good superconducting transitions once heat-treated. 

Fullerene, black and shiny like graphite, is the subject of active current research because of its interesting electronic properties. When allowed to react with rubidium metal, a superconducting material called rubidium fulleride, Rb3C6o, is formed. (We ll discuss superconductors in more detail in Section 21.6.) Carbon nanotubes are being studied for use as fibers in the structural composites used to make golf clubs, bicycle frames, boats, and airplanes. On a mass basis, nanotubes are up to ten times as strong as steel. 

If the superconducting film developed at Cornell is ever put into a telecommunications system, those stats would pale in comparison. Fast as they are, fiber-optical pulses must work in three steps conversion of electricity to light and back to electricity, a process that is relatively slow. A superconductor transmitting electrical pulses alone could, theoretically, carry more than a trillion bits of information per second—enough to handle 15 million simultaneous phone conversations, or to transmit everything in print in the Library of Congress in a couple of minutes ... 

Several oxide fibers on the basis of Zr02, Pb(Zr,Ti)03 (PZT), Y3AI5O12 (YAG) and YBa2Cu30x, which exhibit e.g. catalytic, magnetic, dielectric or superconducting properties, are currently under development or in evaluation for special applications. 

Copper is so widely used, especially in its alloys such as bronze (Cu and Sn) and brass (Cu and Zn), that it is becoming very scarce. The U.S. Bureau of Mines estimates that the known worldwide reserves of copper ore will be exhausted during the first half of the twenty-first century (Figure 22-10). It is now profitable to mine ores containing as little as 0.25% copper. The increased use of fiber optics in place of copper in communications cables may help to lessen the demand for this metal. The use of superconducting materials in electricity transmission lines could eventually provide enormous savings. 

Various directions of future research needs and opportunities are discussed. These directions include the development of theoretical descriptions of the superconducting behavior and formation of high T materials, the synthesis and characterization of such materials, and the fabrication of corresponding wires, fibers, thin films and device structures, with applications such as in microcircuitry. New types of chemistry associated with superconducting solids and surfaces are also suggested. 

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