Papers by Author: Sang Cheol Kim

Abstract: Bi-2223/Ag tapes are usually used for superconducting power cables and magnets. Bi- 2223 ceramic superconducting core can be damaged under complicated stress and strain conditions such as winding tension, bending and twisting. In this study, we have presented the effect of axial stress and bending strain on the superconducting properties of Bi-2223/Ag tapes. In order to establish the value for 95% retained Ic of the Bi-2223/Ag tapes under various stress-strain conditions, the tension apparatus with bending former was used to apply the tension and bending stress-strain. Tension and bending stress-strain simultaneously applied to the tapes could reduce the critical current even though each applied stress and strain values were not higher than that of 95% retained Ic of the tapes. Complex stress-strain conditions including the thermal stress-strain have accelerated the degradation of the Bi-223/Ag tapes. The deformation temperature was important to maintain the 95% retained Ic of the Bi-2223/Ag tapes after bending or tension deformation because mechanical strength of the tapes can be changed drastically between room temperature and 77 K.

Abstract: Five kinds of double stacked 385 (55ⅹ7) filamentary Bi2212/Ag round wires and 55 filamentary tapes with different Ag ratios (silver area/superconductor area) have been fabricated via PIT method, and the effects of Ag ratio and processing factors on critical current density were studied. The effects of the maximum temperature and average filament diameter on critical current density were also studied. The wire of 0.74 mm diameter having Ag ratio 3.7 showed critical current density of 2,218 A/mm2 at 4.2 K, 0 T.