Electrical and mechanical properties of Bi-2223/Ag tapes made by TIRT technique

Multi-core Bi-2223/Ag tapes with various number of filaments (21–162), different filament architecture and their changing orientation to the tape plane have been made by the tape-in-rectangular tube (TIRT) process. The transport current properties of TIRT tape samples with “parallel” and “perpendicular” filaments have been measured. The transversal Ic distribution obtained by spatially resolved transport measurements (“magnetic knife”) measurement illustrates that filament quality of TIRT tapes is better at the tape edges as in its centre. The Ic degradation due to bending shows a different behaviour for parallel and perpendicular filaments which is attributed to the difference in filament density and crack propagation

Improvement of the current carrying capability of ex situ MgB2 wires by normal particle additions

A wide variety of powders, including Nb, Ti, Zr, Hf and W, metal oxides like Nb2O5, Ti2O5, V 2O5 and other compounds like SiC, SrCO3 and boron nitride, have all been used at the 10 wt% level as additions into commercial MgB2 powder for the fabrication of single-core, ex situ wires using groove and two-axial rolling deformation and final heat treatment at 950°C/0.5 h in Ar. Transport current measurements have shown that metal particle addition leads to an especially significant improvement in current carrying capacity. The presence of normal particles influences both the resistivity and also the thermal conductivity of the MgB2 core, and the improved internal stability may be responsible for the increased critical current values. This observation may be very important for future development of practical MgB2 composite superconducting wires

Transport currents in Bi-2223/Ag tapes made using the tape-in-rectangular tube process, current distribution and Ic stress degradation

Using the tape-in-rectangular tube (TIRT) process, we have made multi-core Bi-2223/Ag tapes with various numbers of filaments (10-162), and with different filament architectures and orientations. We have measured the angular dependence of the transport current of the tape samples with 'parallel' and 'perpendicular' filaments. The transversal Ic distribution obtained by spatially resolved transport measurements ('magnetic knife') illustrates that the filament quality of the TIRT tapes is better at the tape edges than in the centre. The tapes were stressed by two types of tensioning set-up (a short straight sample and a U-shaped spring) and by bending at 77 K. The Ic degradation shows different behaviour for parallel and perpendicular filaments, which is attributed to the difference in filament density and crack propagation

Tensile and Bending Strain Tolerance of Ex Situ MgB2/Ni/Cu Superconductor Tape

This paper describes the strain tolerance of MgB2/Ni/Cu tape produced by Columbus Superconductors subjected to tension and bending stress. A tension test instrument with freestanding sample was used for stress-strain, I-c-stress, and I-c-strain characteristics at liquid helium temperature. Bending of MgB2/Ni/Cu tape to variable diameters was done at room temperature and in two directions: 1) with a Cu strip on the outer surface (Cu out) of a bent sample; and 2) with a Cu strip on the inner side (Cu in). I-c-bending strain characteristics were measured at 4.2 K and external field B = 6 T oriented perpendicularly to the sample's width. Obtained results have shown the strain limits, which should not be exceeded during the winding process of superconductor containing brittle MgB2 filaments.European Union Contract Number 308793 and Slovak Research and Development Agency under program APVV-0495-1