Preparation of SiC Doped In-Situ MgB_2 Mono- and 7-Filamentary Wires by Continuous Tube Forming and Filling Technique

摘要

Long lengths of in-situ SiC doped MgB_2/Fe mono- filamentary wires with high critical current densities and 7- filamentary MgB_2/Nb/Cu/Fe wires with better thermal stability have been fabricated by either continuous tube forming & filling (CTFF) technique or combining both powder in tube (PIT) and CTFF process, respectively. Particular efforts were made in view of the optimization of the manufacturing and annealing processes of the wires. The as obtained wires were sintered under a vacuum furnace at different sintering temperatures and the optimized sintering of the MgB_2 wires were investigated by the analysis of optical microscope, XRD, SEM, and the transport J_c measurements. The J_c value in a 8 at.% SiC doped MgB_2/Fe mono- filamentary wire is more than 10~4 A/cm~2 at 4.2 K and a field of 11 T. While in doped 7- filamentary wire, the similar J_c value (10~4 A/cm~2) is obtained at 4.2 K and a field of 7.5 T. Moreover, the n factors are determined to be 33 and 10 at 11 T in the mono- and 7- filamentary MgB_2 wires with SiC doping, respectively, indicating the possibility to use the as fabricated MgB_2 wires in the persistent mode for fields from 0.5 T to 10 T at 4.2 K.