Kernforschungszentrum Karlsruhe Gmbh

Rene Flukiger

Wilfried Goldacker

Stephen Gauss

Silver alloy sheathing material for ceramic superconducting wires

A process for the production of at least a one kilogram block of Chevrel-phase Pb.sub.x Mo.sub.y S.sub.z, wherein x=0.9 to 1.2, y=6.0 to 6.4, and z=7 to 8, includes mixing thoroughly stoichiometric quantities of starting materials in powdered form. The starting materials are selected from elemental Pb, Mo and S, sulfides of elemental Pb and Mo, and mixtures thereof. The starting mixture is introduced into a metallic container and evacuated to a pressure to 10.sup.4 Pa or less. The evacuated container is subjected to hot isostatic pressing at a constant pressure selected from a pressure ranging from 100 to 300 MPa, at a heating rate ranging from 10.degree. to 100.degree. C./hr., at a final pressing temperature ranging from 800.degree. to 1200.degree. C., and for a pressing period ranging from 10 to 100 hours, whereby the starting materials react to form the block of Chevrel-phase Pb.sub.x Mo.sub.y S.sub.z. The block is cooled at a cooling rate ranging from 50.degree. to 500.degree. C./hr. while maintaining the constant pressure. The process may include the further steps of filling the metallic container after evacuation with an inert gas; re-evacuating the metallic container to remove the inert gas; and heating the metallic container after re-evacuation at a temperature ranging up to but less than 300.degree., prior to subjecting the metallic container to hot isostatic pressing.

Process for the production of Pb.sub.x Mo.sub.y S.sub.z Chevrel-phase

A multifilamentary, copper or copper alloy clad superconductive wire, comprising a superconductive, intermetallic compound Nb.sub.3 Sn or V.sub.3 Ga, having an A-15 crystal structure, and at least one additive metal from the group consisting of rare earth elements of atomic number 57 to 71, Th, U, Ti, Zr, Hf, V, Nb, Ta, Mo, Fe, Co, Ni, Pd, Cu, Ag, Al, and Pt. The additive is present in the wire within the A-15 phase in the form of uniformly and finely distributed, at least partially undissolved axially parallel inclusions at grain boundaries of the crystals and/or at an interface between the A-15 phase and the copper or copper alloy, or at an interface between the A-15 phase and a separate phase.

Multifilamentary superconductive wires composed of filaments Nb.sub.3 Sn

The present invention relates to a method for producing multifilament superconductive wires of Nb.sub.3 Sn or V.sub.3 Ga filaments embedded in a Cu or Cu alloy matrix, with the wires containing metal additive elements from the group including Ti, Zr, Hf, V, Nb, Ta, Fe, Co, Ni in the filaments and/or in the matrix. The superconductive characteristics of the wires are predetermined for medium magnetic fields (below 12 T) as well as for high magnetic fields (12 T and above). The percentage of the additive (or additives) can be set to a predetermined value and thus the superconductive properties can be set as desired. This is accomplished by mixing metal additives in powder form with a powder of niobium or a niobium alloy, or of vanadium or a vanadium alloy, in a defined grain size and in a defined quantity. The resulting powder mixture is compacted in a container of copper or a copper alloy, the compacted container is shaped into a wire and, upon removal of the container layer, is processed further into wires. Depending on the desired superconductive properties, the final reaction heat treatment of the wires is performed at a selected temperature in a range from 500.degree. C. to 1000.degree. C. and at a selected heat treatment duration in a range from 48 to 300 hours.

Method for producing superconductive wires

A method for producing a superconductive wire of multifilaments having components comprising niobium and aluminum encased in copper or a copper alloy, wherein the multifilament configuration and the formation of a superconductive Al5 phase are positively developed from the components disposed in a copper or copper alloy tube having an interior metallic coating serving as a diffusion barrier, by cold forming and subsequent heat treatment.

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Karlsruhe, Germany

Rene Flukiger