Patent GB-1381722-A (GB)
Title: Composite materials
IPC: H01L39/14
Filed: 1972-02-17
Abstract: 1381722 Super-conductors IMPERIAL METAL INDUSTRIES (KYNOCH) Ltd 4 April 1972 [15 April 1971 17 Feb 1972] 9496/71 and 7427/72 Headings H1A A5 and A4D A super-conductor composite embedded in a matrix comprising portions of high conductivity metal surrounded by lower conductivity material is arranged so that where two or more superconductor elements are surrounded by a single annulus of high conductivity metal the annulus is electrically interrupted by a radially extending wall of the lower conductivity material. This arrangement is applied to individual filaments forming a bundle and also to a plurality of bundles making up a conductor. The structure suppresses eddy currents induced in the matrix. In a first embodiment, Fig. 3, a thick walled Cu can (1) has radial slots (2) milled in its outer face into which are inserted Cu-Ni strips (5). A Cu- Ni outer can (6) is provided, nose and tail plugs are attached by electron beam welding in vacuo and the resulting billet warm extruded and cold drawn. The internal Cu layer is machined off and a member 10 comprising a plurality of hexagonal Nb 44 wt. per cent Ti rods 13 embedded in a Cu-Ni matrix (14) is inserted into the resulting "shell-andrib" can. The assembly is extruded, drawn down, and cut into lengths which are inserted into a second "shell-and-rib" can 7, 8, 9, together with packing pieces 15 of Cu wires 16 coated with Cu- Ni layers 17. The resulting composite is extruded and drawn down to form the final wire. In a second arrangement, Fig. 5 (not shown). hexagonal super-conductor rods (18) are surrounded with layers of Cu (19) and Cu-Ni (20) and are placed in a "shell-and-rib" can (7, 8, 9) together with packing pieces of Cu rods (21) encased in Cu-Ni (22). The can is then extruded and drawn down. Al or Ag may be used in place of Cu, and the super-conductor may be Nb3Sn produced by mechanically processing the components which are reacted after the final drawing step or after final assembly into the finished unit. Another composite may be produced by placing a Cu rod in a tube of Cu 30 wt. per cent Ni, extruding, drawing down and cutting into lengths which are packed round Nb-Ti rods in a Cu-Ni can which is itself extruded and drawn preferably twisting it about its longitudinal axis to produce the final composite. An annular assembly of Cu- Ni clad Ca wires may be extruded and tube drawn to form a can to receive an assembly of Cu-Ni clad Cu rods and super-conductor rods or a single superconductor rod which may comprise a plurality of sub-filaments in a normally conductive matrix. In another embodiment, Fig. 6 (not shown), a billet of Cu is placed in a Cu-Ni can and extruded to form a hexagonal rod which is cut up and packed into a Cu-Ni can together with a centre core of Cu. The assembly is extruded and the centre core bored out and the resulting tube lined with a Cu-Ni tube to form a "honeycomb-wall" can. Alternatively the lengths of coated rod may be stacked between two concentric Cu-Ni tubes or between the walls of a special can produced by machining a groove in a block of Cu-Ni to form two concentric tubes joined by an end-plate The "honeycomb-wall" can is filled with a Nb-Ti core (100), extruded, drawn to a hexagonal crosssection, and cut into lengths which are stacked in a further can of the same structure this process being again repeated to produce the final composite. In another embodiment, Figs. 7 and 8 (not shown), super-conductor filaments (120) are surrounded by hexagonal Cu filaments (121) coated with Cu-Ni (122). The assembly is surrounded by Cu rods (123) in a matrix (124) of Cu-Ni and the whole arrangement is enclosed in a Cu-Ni layer (125). In a further embodiment, Fig. 9 (not shown), super-conductor sub filaments (130) each surrounded by a Cu annulus (131) and a hexagonal Cu-Ni layer (132) are assembled in a "honeycomb-wall" can (133-136), a plurality of such assemblies both enclosed in an outer can (107- 110). The high resistivity material may be Cu 30 wt. per cent Ni alloy or another Cu-Ni alloy, or Cu- Sn-P, Cu-Mn-Si or Cu-Zn-Sn-Fe alloys or even an insulating material.