Preparation and enhancement of critical current density in MgB₂wires and tapes

Abstract

We have successfully prepared monofilamentary MgB2 wires and tapes with different sheathed metals such as Cu, Ta/Cu and Fe by the powder-in-tube method. The phase composition, superconducting properties and microstructure features are investigated by x-ray diffractometer, the standard four-probe technique, SQUID magnetometer, SEM and TEM. The results indicate that Jc in MgB2/Ta/Cu wires is higher than 105 A cm−2 at 5 K in 0.1 T and 104 A cm−2 at 20 K in 1 T. By Ti-doping, Jc can be significantly improved. MgB2/Fe wires show very high transport critical current densities of 1.43 × 105 A cm−2 (4.2 K, 4 T), 3.72 × 104 A cm−2 (15 K, 4 T) and 2.34 × 104 A cm−2 (25 K, 3 T). Also the results indicated that small grain size should respond to the large Jc in Ti-doped MgB2 tape and MgB2/Fe wire.

Critical current of an MgB2coil with a ferromagnetic matrix

“…Like in the previous case, the magnetostatic problem is solved. After the problem had been solved with several B gen values, a mapping G 2 : B max → B gen (10) was formed. Finally, a curve that gives the critical current of the coil as a function of B max was computed as…”

“…Copper can be used successfully as the matrix and stabilizing metal for in situ MgB 2 conductors provided that the formation temperature will not be higher than 750 • C [6][7][8]. Otherwise, during the heat treatment, the strong reaction between magnesium and copper drastically degrades the I c characteristics [9][10][11]. Therefore, if copper is added to the conductor, some barrier has to be used in order to prevent the diffusion.…”

“…Therefore, if copper is added to the conductor, some barrier has to be used in order to prevent the diffusion. Several barrier materials have been tested, like tantalum and niobium [10,11]. Another option is to replace copper with another material, e.g.…”

The effect of Mo addition on the microstructure and Jc properties of MgB2 tapes fabricated by PIT method

“…Most MgB 2 tapes are fabricated by the powder-in-tube (PIT) method [6,9,[20][21][22][23]. There are two type preparation techniques in the PITmethod; first, pre-reacted MgB 2 powders are filled into Cu, Al, Ag and/or Fe sheated tubes and cold-worked into tapes, which is called as ex situ method.…”

Reactivity of sheath materials with Mg/B in MgB2conductor fabrication

“…Of these, it is well accepted that the PIT method achieves higher quality tapes and wires. There are two variants of the PIT method: ex situ [6][7][8][9][10][11][12][13] involving the sintering of externally synthesized MgB 2 and in situ [7,[14][15][16][17][18][19] involving the reaction of a stoichiometric mixture of Mg and B 1 Author to whom any correspondence should be addressed. inside suitable metal tubes after deformation into the desired shape.…”