Wire Filament Research Articles

Effects of the germanium addition to the matrix of bronze-processed Nb 3Sn wires

The simultaneous addition of 0.5 at%Ge to the matrix and 1 at%Ta to the coreenhances the Jc of Nb 3Sn at 12T by more than one order of magnitude. The increase in the Jc seems to be attributed to the grain refinement of Nb 3Sn by the Ge addition. The formation of thin layer richer in Ge is observed at the interface between the Nb 3Sn and matrix, which may be effective for reducing the proximity effect among Nb 3Sn filaments in the AC use. Ultrafine filamentary Nb 3Sn wires with Ge addition to the matrix have been successfully fabricated. The addition of 0.25 at%Ge to the matrix and 1 at%Ta to the core improves the Qh/Jc ratio at 0.5 T by a factor of nearly four.

Force on insulated wire at the interface of two dielectric media

The electric field is calculated and the forces are evaluated for the system consisting of an infinitely long charged filamentary conductor located parallel to the plane boundary surface between two dielectric media. The straight filamentary wire is surrounded by a cylindrical insulator. It is established that the direction of the force acting on the charged wire is determined only by a difference in value between the permittivities of the two media and does not depend on the permittivity of the insulation of the wire. The solution of the problem is derived in an analytical form that shows directly the influence of the dielectric materials on the distribution of the electric field and on the values of the forces in the examined system. >

Ultrafine multifilamentary Nb  Ti wires with Cu  Si alloy matrix

The Cu  Si alloy has been proposed as a new matrix material for filamentary Nb  Ti wires in a.c. use. The Cu  Si alloy shows appropriate mechanical and electrical properties, and is economically more favourable than the Cu  Ni alloy matrix used currently. Moreover, the addition of Si to Cu prevents the formation of intermetallic compounds around the filaments. After extensive investigations on CuSi alloy as a matrix material, an ultrafine multifilamentary Nb  Ti/Cu − 2.5 wt% Si composite wire has been successfully fabricated. The d.c. superconducting properties of the wire were adequate for use in electrical apparatus. A preliminary study has revealed that the a.c. loss of the new wire is equivalent to that of a typical ultrafine multifilamentary Nb  Ti/Cu  Ni composite wire.

Ｃｕ‐Ｓｉ合金マトリックスを用いた新しい交流用超電導線材

The Cu-Si alloy has been proposed as a new matrix material for filamentary Nb-Ti wires in AC use. The Cu-Si alloy shows appropriate mechanical and electrical properties. The addition of Si to the Cu matrix prevents the formation of intermetallic compounds around the Nb-Ti filaments, Ultrafine multifilamentary Nb-Ti/Cu-3.5wt%Si composite wires have been successfully fabricated. The wires show excellent performances with respect to AC loss and critical current density.

Temperature dependence of the critical current and pinning behaviour in superfine filamentary NbTi wires

Field dependence of critical current density Jc and its temperature dependence in superfine filamentary NbTi wires were measured to investigate the effect of filament diameter df on Jc. Samples which are in the df range of 0.061-1.53 mu m have CuNi matrix or Cu-CuNi mixed matrix. Field dependences of Jc at 4.2 K are very different among samples with different values of df. As df is decreased, Jc values at 2 T reach a maximum, 1*106 A/cm2, around df=0.072 mu m. In high fields, the Jc of these samples depends on df and lower Jc values are obtained in samples with finer filaments. As the sample temperature rises, the Jc is highly reduced, especially, for finer filamentary samples.

Development of superconducting linear induction motor for steel making processes

A superconducting linear induction motor (SLIM) is being developed for steel-making processes using ultrafine filamentary NbTi wires. A SLIM can produce a strong magnetic field and large thrust in a wide gap. Applying SLIMs to a steel making plant could result in important innovations. A model of the SLIM has been made and tested. The model SLIM worked in a frequency range of 20-30 Hz. The feasibility of a SLIM as hardware has been demonstrated.

Design and Synthesis of Metals (Tungsten) with Structural Hierarchy for Very High Temperatures

AbstractThe strength of metals is limited by the weakest link in their microstructures. At high temperature, the weakest link is usually a grain boundary. Mobile dislocations represent another type of weak link. The strength-limitation by this two-level hierarchy of crystal defects can be minimized through microstructure design. Although the strengthening mechanisms differ for grain boundaries and dislocations, it is possible to design microstructural architectures that strengthen both. The design must take the stress state into consideration that the component will encounter during its later use. Processing strategies can then be devised for the synthesis of such components. It is imperative to stabilize the designed microstructure at high temperature because this will determine how well and how long the material will be able to perform. Design, synthesis and stabilization are discussed in the present paper. The lamp filament wire technology is the basis for a new method that enables the synthesis and stabilization of artificial microstructures in high-temperature materials.

Image analysis for grain shape characterization in lamp filaments

Algorithms have been developed for appraising the quality of tungsten lamp filament wire microstructure with respect to its resistance to sag. They allow a numerical determination of grain aspect ratio, grain boundary contour, angle of boundary with wire diameter, and degree of grain boundary surface convolution. These values are combined algebraically to give a grain shape parameter (GSP) which reliably predicts how resistant the filament is to grain boundary sliding. Measurements are made of thermally etched grain boundaries on scanning electron microscopy (SEM) images of the surfaces on coiled filaments. Data are recorded and parameters computed by means of an image analyzer. The technique has been tested on samples made from the same wire modified in process to have varying strain after the last anneal. It has also been tested on samples purchased from various vendors. These applications indicate that the computed GSP is a sensitive predictor of filament creep resistance and reliably reflects variation in wire drawing strain after the last anneal.

超電導体技術開発の動向

The application of superconductivity is a key to produce a number of breakthroughs in a vast area of science and technology covering new energy systems, computer electronics, medical diagnosis, high-speed transportations, high-energy particle accelerators, etc. The recent discovery of high Tc oxide superconductors may provide a more positive prospect for the future development of the superconductivity technology. In the area of metallic superconductors, the development of ultrafine filamentary wires for AC use, which may bring about a large impact in electrical engineering, is being carried out. The high-field performance of Nb3Sn wires has been significantly improved by the Ti-doping, and multifilamentary (Nb, Ti)3Sn wires capable of generating fields up to 17 T have become commercially available. The development of Nb3Al and other superconductors with high-field performance superior to that of (Nb, Ti)3Sn is also being proceeded using new fabrication technologies.The application of techniques elaborated the fabrication of metallic superconductors, e.g. powder process using metal sheath, solidification process, diffusion process and high-rate deposition process has been attempted for the processing of high-Tc oxide superconductors. Ag-sheathed BPSCCO tapes show a Jc (77K, OT) of 3×104/cm2, and keep nearly the same Jc at 25T and 4.2K. The solidification process has achieved an encouraging result for obtaining enough Jc in bulk high-Tc oxides. Superconducting tubes coated with a thick YBCO layer, promising for cavities and magnetic shieldings, have been fabricated by a plasma spraying process. Meanwhile, large Jc's at 77K and high magnetic fields have been obtained in thin oxide films prepared by different physical and chemical deposition processes. Various problems to be solved, e.g. homogenization, densification, crystal orientation and introduction of pinning centers, for improving Jc in bulk high-Tc oxides are also described in this article.

Early diamond making at General Electric

This is an account of how GE’s early interest in a new super-hard metal, cobalt cemented tungsten carbide, for drawing tungsten lamp filament wire, led to a broader interest in the realm of super pressure and to diamond synthesis. P. W. Bridgman at Harvard University had demonstrated the new metal’s (‘‘Carboloy’’) ability to generate pressures of 100 000 atm (100 kbars). Armed with this new capability, GE initiated a diamond project in 1951. In December 1954 two synthesized diamonds emerged in a marginal experiment that for a while could not be reproduced. Nevertheless, that experiment gave the critical clue to the process that now provides 90% of the world’s industrial diamond needs. The high-pressure high-temperature process (HPHT) together with the new carbon vapor deposition process (CVD) brings diamonds’ unique and valuable properties to applications requiring crystals tailored to fit specific needs.

Thermo-electromagnetic stability of ultrafine multifilamentary superconducting wires for 50-60 Hertz use

The authors present calculations of the theoretical thermoelectromagnetic stability of ultrafine multifilamentary superconducting wires. These calculations take into account the self-field effect of the transport current. The authors then compare theoretical and experimental results for conductors comprising typically several hundred thousand 0.17- mu m diameter filaments. These first measurements of the electromagnetic stability of multifilamentary wires under AC conditions have given encouraging results and have shown good agreement with theory. The results are pertinent to the development of Nb-Ti ultrafine filamentary wires for 50-60-Hz applications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

抄紙用ワイヤーを介した脱水と紙層形成

Behaviour of water removal through clothing of a paper machine is dependent on wetting, penetration and draining, which occur dynamically in a very short time.Dynamic wettability of paper-making wire can be observed from contact angles of a water drop in every 10 milli-seconds after reaching a fabric surface. Physical characteristics of wire filaments influence the dynamic wettability in dry states. The contact angles of a plastic multi-layer and bronze fabric decrease rapidly in a wet states.The fabric of the small number has a higher drainage volume. The magnitude of the drainage volume is in the order of triple layer, double layer and single layer. Bronze wire, which is more wettable, shows larger drainge volume compared with plastic one. Higher water retention of a fabric, larger pore sizes and higher wettability of fabrics induce tendencies of better water removals.The surface structure of paper making wire, dewatering time and water removal by couching through the network of paper making wires are effective to the wire mark, respectively. Uneveness of surface of a handsheet prepared by the above fabric can be observed by a stereo scanning electron microscope. It shows such uneveness is approximately of the same pitch as the knuckle and the void of the fabric. Also, uneveness of the wire side of the wet web in a case of a short dewatering time is greater than that of in a extended time. Water removal by couching enhances the degree of uneveness.

Automation of a wire-filament atomiser helium microwave-induced plasma system

An autosampler has been constructed to introduce microlitre samples into a low-power, helium microwave-induced plasma/electrothermal atomisation atomic emission spectrometry system resulting in improvements to the analytical precision. Computer control of sample introduction, wire filament heating and data acquisition has greatly enhanced the use of the technique and enables further processing of acquired data.

Full-array test results of the Swiss LCT coil

The Swiss contribution to the international Large Coil Task (LCT) is a D-shaped 2.5*3.5 m/sup 2/ bore, superconducting toroidal-field coil of 8-T. The conductor is made from fully transposed, Cu-stabilized filamentary NbTi wire. The data taken during the full-array test of the Swiss coil are discussed. In these experiments the coil was energized together with the five background coils and successfully reached several times its rated current of 13 kA, thereby subjecting its conductor to the maximum field of 8.0 T. Additional tests were performed with stationary heat load without driving the coil normal. The full-array and single-coil test results are presented and compared with each other and with predictions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Latest news about superconducting AC machines

A brief overview is given of progress relating to Nb-Ti ultrafine filamentary wires with greatly reduced 50-60-Hz losses. The prospective industrial applications in large superconducting 50-60-Hz equipment and the characteristics of different wires used in 50-60-Hz applications are noted. The calculated superconducting losses for a new Nb-Ti composite (AC 87/3A) where the proximity effect is strongly reduced and where a decrease of losses due to reversible fluxoid motion appears are also reported. >

Edison’s Electric Light: Biography of an Invention by Robert Friedel, et al

TECHNOLOGY AND CULTURE Book Reviews 153 Edison’s Electric Light: Biography of an Invention. By Robert Friedel and Paul Israel with Bernard S. Finn. New Brunswick, N.J.: Rutgers University Press, 1986. Pp. xvi+263; illustrations, notes, bibliography, index. $35.00 (cloth); $16.95 (paper). In the space of four years, from October 1878 to September 1882, Thomas Edison, with the help of able associates and wellequipped laboratories, created the essential elements of modern elec­ tric lighting systems. High-resistance, incandescent lamps in parallel circuits, constant-voltage dynamos, and a feeder-and-main system of distribution—all were unthought of before Edison began his cam­ paign to produce an electric lighting system that would supersede gas lighting systems—are still components in the generation, distribu­ tion, and consumption of electric power. This book, the joint work of Robert Friedel and Paul Israel, with brief interchapter essays by Bernard Finn, provides, as the authors are at pains to tell us, a more thorough history of those four years than any yet published. It is based chiefly on systematic research in the Edison archives in West Orange, New Jersey—research guided by “true probing questions asked about the act of invention itself’ (p. xi) that have “rarely” been asked by previous scholars. Nearly a dozen inventors were working on incandescent lamps dur­ ing the 1870s. Edison entered the field with characteristic vigor in the fall of 1878. He first made a filament of fine platinum wire that would become incandescent in open air when attached to a battery. To avoid melting the platinum, Edison added a thermostatic switch to interrupt the current when the incandescent platinum reached a specified temperature. Within a week of his first experiments, Edison announced in typically bombastic fashion that he had solved the problem of electric light and that once patents were secured he would make his invention public, after which gas lighting would rap­ idly be discarded. He immediately formed a company to obtain Wall Street money for research and development. He soon found “bugs” (his word) in his lamps, and a year later he was slowly and laboriously removing those bugs. His first major change was to put the platinum filament in an evacuated glass bulb. Next, he realized that his lamps should have high electrical resist­ ance, a requirement evident only by hindsight. In the fall of 1879, he tried to make a filament of carbon, and by the end of December he had succeeded in illuminating his Menlo Park laboratory and grounds with more than fifty carbon-filament lamps. Special trains brought numerous visitors from New York to see the welladvertised spectacle. When the lamp worked satisfactorily, Edison developed, in the same uncertain way as his lamp, the other components he would need to light a section of lower Manhattan. The several related inven­ tions have been described by others but never with specific evi­ 154 Book Reviews TECHNOLOGY AND CULTURE dence to show that Edison’s contributions were revolutionary, not merely incremental, improvements. Even so, the reader must make a special effort to apprehend Edison’s originality, so familiar have his inventions become and so difficult is it to imagine alternatives. Even the screw-in socket for light bulbs was an Edison innovation. We have here as detailed an account of a series of “acts of inven­ tion” as I have seen anywhere. Furthermore, sufficiently varied evi­ dence enables the reader to make independentjudgments regarding the topics treated. The authors squeezed everything they could from the volumi­ nous laboratory notebooks. Seventy-four notebook pages are repro­ duced, along with fifty other illustrations. All are placed close to the text they support or illuminate, and captions are full and inform­ ative. Unfortunately, laboratory notebooks, and indeed all technical drawings, are ambiguous unless (a) the reader is familiar with that particular kind of apparatus and (b) a verbal explanation clarifies the questions that the drawing leaves ambiguous. Despite the wealth of primary sources, the authors can tell us lit­ tle about the crucial steps of an invention. Their knowledge is never quite sufficient to explain how and why Edison reached a par­ ticular conclusion. How did the importance of high resistance hap­ pen to...

Changes ofT c,J c,B c2 and the lattice parameter of the Nb3Sn phase formed at the initial stage of growth in a multifilamentary superconductive wire

Investigations were made of the superconducting transition temperature,T c, the upper critical flux density,B c2, and the critical current density,J c, of Nb3Sn layers in filamentary wire in a bronze matrix. The lattice parameter,a 0, andT c of Nb3Sn layers in 259-filament wire were determined after removal of the bronze matrix. The microstructure and layer thickness were studied using scanning electron microscopy. The diffusion formation of Nb3Sn phase at 1023 K was studied until the complete reaction of the niobium filaments. It was found that the Nb3Sn layer begins to form in the manufacturing process during the intermediate annealing at 793 K, and that there is a considerable degradation of critical parameters due to the non-stoichiometry of the Nb3Sn phase in layers thinner than 1μm.

Calculation of AC losses in ultra fine filamentary NbTi wires

The advent of Low loss Filamentary NbTi wires with very Fine Filaments, First developed hy Alsthom and the Laboratoires de Marcoussis, has led to the possibility of using superconductors in many AC 50/60 Hz applications. A computer program, based on the Bean Model, for any spacetime variation of the magnetic induction predicts losses successfully for filaments of diameter greater than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim 1 \mu</tex> m. However, for filaments of diameter less than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim 1 \mu</tex> m the theoretical calculation underestimates the losses dramatically. This is because the filament dimensions become comparable to ξ, the coherence length, λ the magnetic penetration depth, a <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> the flux line spacing and λ, the pinning penetration depth leading to electromagnetic coupling effects between filaments. In this paper these effects on loss calculations are investigated with a view to obtaining an improved prediction of the loss behaviour in these materials. The results are consistent with a model of flux penetration, whereby, due to proximity effects, the matrix is essentially behaving as a type II superconductor. The main effect of this is to strongly couple flux lines in the first compaction bundles so that hysteretic losses in A.C. fields are greater than those predicted by the Bean Model.

Superconducting microparticle composite wire

A novel concept of a ductile composite wire which incorporates filaments made of brittle superconductor powders was proposed and experimentally demonstrated. Unsintered, submicron NbC powders were encapsulated in copper tubes. These were fabricated down to single filament wires without sintering or high temperature annealing. Multifilamentary composites with up to 3000 filaments were then formed by successive rebundling of tubes into sealed billets and their mechanical reduction. Due to the fluid-like behavior of the unsintered powder core, the composites were ductile and resistant to filament fracture. The wire critical temperature was 10 to 11 K, the upper critical field was 2 ± 0.2 tesla and the superconductor self-field critical current density attained 6 × 108amps/m2. The critical current showed a remarkable tolerance of uniaxial and bending strains. While the NbC superconductor is not of great technical interest, it permitted one to prove the new concept. The subsequent use of NbCN powders confirmed that the observed wire behavior is also obtained in high magnetic fields, up to 15 tesla.

A Predictive Theory of Power Balance in Incandescent Lamps

The design of filaments for incandescent lamps using traditional methods is often a lengthy process involving a series of lamp trials. This paper describes a theory of the operation of filament lamps which is capable of predicting the performance of a wide range of lamps to a high degree of accuracy but, because the theory presented in this paper disregards the existence of temperature gradients in the filament wire, it may not be applied to automobile and miniature lamp types. A more detailed theory applicable to miniature lamps is under development and it is hoped to publish the results in a future paper.