Powder-in-Tube

The most widely used development in HTS wire production is tlie powder-in-tube procedure with BSCCO ceramic materials. In this procedure very fine HTS powder, placed inside of a hollow silver tube, is fused as the tube lengtn is mechanically increased to form a wire. Very high magnetic fields with this wire have been reported at 4 K however, the performance degrades substantially above 20 to 30 K. 

HTS materials, because of their ceramic nature, are quite brittle. This has introduced problems relative to the winding of superconducting magnets. One solution is to first wind the magnet with the powder-in-tube wire before the ceramic powder has been bonded and then heat treat the desired configuration to form the final product. Another solution is to form the superconductor into such fine fila-... 

Piston type aerosol system, 1 784 PIT (powder-in-tube) conductors, critical current density in, 23 833-834. See also PIT technique Pitch-based carbon fibers, 26 733-735 asbestos substitute, 3 314t compressive strength versus tensile modulus for, 26 742-743 Pitch-based fibers, 26 760 Pitch binders, 12 724-726 Pitchblende, 25 396-397 Pitch control, 10 304 Pitched blade turbine (PBT), 16 672 Pitches... 

Pi theorem (Buckingham), 3 582 11 744 Pitot tubes, 11 661-662 Pit sealants, 3 334-335 PIT technique, 23 845. See also PIT (powder-in- tube) conductors Pitting corrosion... 

An alternative manufacturing route exploits the powder-in-tube technology described below, except that a metal with poorer thermal conductivity replaces the silver matrix. 

Cables via the powder-in-tube (PIT) method The approach is especially suited to processing Bi-2223 into leads and cables for power applications. A silver or silver alloy tube, filled with the partially reacted precursor powders formulated to yield Bi-2223, is drawn down to a wire 1-2mm diameter. The wire is rolled into a tape if that is the required form, usually with a width-to-thickness ratio of approximately 10 1. The composite is then heated to 800-900 °C when the powder partially melts. The recrystallization process is controlled and the pure Bi-2223 phase develops with large grains oriented so that the Cu-O planes lie parallel to the silver surface to optimize Jc. 

FIGURE 23.12 Typical manufacturing procedure for the powder-in-tube method. 

FIGURE 23.13 A typical pattern of the final heat treatment step for Bi2Sr2CaCu20g powder-in-tube wire. 

Fig. (..2- (.9 Scheme of the powder-in-tube method, excluding the thermal and thermomechanical treatments... 

R. L. Sabatini, T. R. Thurston, M. Suenaga A ki- 2.119 netic mechanism for the formation of aligned (Bi,Pb)2Sr2Ca2Cu3 0io in a powder-in-tube processed tape, Appl. Phys. Lett. 69, 580 (1996) 2.120... 

Bronze process Internal Tin (IT) process Powder-in-tube process (PIT)... 

The strongly anisotropic shape of the crystallites favors the development of a texture parallel to the surface of the Ag tube in powder-in-tube (PIT) processing, and this is highly desirable for the superconducting properties. The Ag content also serves as a source of pinning centers that hinder the flux line motion. 

Fig. 16. Magnetic field dependence of the critical current density for a range of short sample YBCO conductors produced using either IBAD or RABiT substrates. These data are compared with typical values obtained for NbTi and Nb3Sn wires at 4.2 K and for BSCCO, oxide-powder-in-tube wires at 77 K. From Hawsqr and Peterson (1996).

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