Current transport and microstructural development in BSCCO tapes and joints fabricated by groove rolling

Abstract

The powder-in-tube technique, which includes wire drawing and rolling, has been widely used to fabricate superconducting tapes for possible electric power applications. In the present study the starting billet was reduced in size by groove rolling instead of by wire drawing. To optimize the deformation and thermomechanical treatment processes, BSCCO wires of various dimensions were fabricated. The wires were flat rolled to a final thickness of 250 µm. Short-length tapes were subjected to a series of thermal and deformation steps. Phase development and microstructural development during the process were monitored by XRD, SEM and TEM. Current transport properties of the tapes were determined in the temperature range of 20-77 K in self-field. Thermomechanical treatment resulted in tapes with average critical current densities of 18 000 A cm −2 at 77 K. High-resolution electron microscopy revealed better texturing and grain structure at the superconductor-silver interface. Superconducting lap-and butt-joints have been formed by a chemical etching technique. Detailed microstructural and current transport properties of the joints have also been measured.

Development of superconducting joints between iron-based superconductor tapes

“…The formation of joints between BiSCCO is typically fabricated by repeating the heat treatment process used for the conductor itself. This involves cold pressing of the exposed filaments of particularly reactive tapes followed by the same extensive thermomechanical treatment used to form the BiSCCO phase in the conductor [24,25]. The critical current of the joints could be higher than in the tapes, as reported by Chen et al [16], and the joint resistance was estimated to be below 10 −12 Ω at 4.2 K and self-field.…”

“…The formation of joints between BiSCCO is typically fabricated by repeating the heat treatment process used for the conductor itself. And this involves cold pressing of the exposed filaments of particularly reacted tapes followed by the same extensive thermomechanical treatment used to form the BiSCCO phase in the conductor [24,25].…”

“…So far, techniques for joining superconductor wires/tapes such as NbTi, BiSCCO, and MgB 2 wires/tapes have been well developed [16][17][18][19][20][21][22][23][24][25]. For the low temperature superconductors, especially for NbTi, joining methods are very mature and convenient for the manufacture of persistent mode magnets.…”

Persistent current joints between technological superconductors

“…The standard method for fabricating joints in mono-filamentary Ag/Bi-2223 PIT tapes was first employed by Tkaczyk et al [93]. It involves exposing the filament surface in a partially processed tape by mechanically removing [93] or chemically etching [15,[94][95][96][97][98] the Ag sheath from one side of the tape. The exposed ceramic cores are placed in contact with one another (usually in lap joint geometry) and uniaxially pressed under high pressure to cold-weld the Ag sheath and seal the joint.…”

Effect of Magnetic Field and γ Irradiation on the Properties of Tl-2212 Superconducting Tape

“…The Powder In Tube (PIT) method does not require sophisticated devices and is widely applied especially for Bi-based compounds (LI et al; DOU, LIU; LARBALASTIER et al). Extensive research studies have been carried out to produce Bi-based tapes before they were commercialized (DOU, LIU 1993;LARBALASTIER et al;GRASSO et al;IYER et al). But relatively less work has been done to produce Tl-based tapes (FOX et al; GLADYSHEVSKII et al; REN et al; GLOWACKI, ASHWORTH).…”