2005 年 40 巻 11 号 p. 493-497
The authors prepared powder-in-tube PIT MgB2 tapes through an in-situ process using a steel sheath. Magnesium hydride MgH2 and amorphous boron powders were mixed to synthesize MgB2 superconductors. The mixed powder was encased in a steel tube and rolled into a monocore tape of about 5 mm in width and 0.5 mm in thickness. Carbide powders (i.e., SiC and TiC) were added to the core. The addition of SiC or TiC nano-sized powder has been found to enhance appreciably the Jc in MgB2 tapes. The Ic for the 5 wt% SiC- or 10 wt% TiC-added tapes reaches 100 A at 4.2 K and 7 T, which corresponds to a core Jc higher than 10 kA/cm2. The improvement in Jc in a higher magnetic field may be the result of the increase in upper critical field Hc2 due to the incorporation of nano-sized powders such as SiC and TiC. Furthermore, the core Jc for the hot-pressed MgB2 tapes with 5 wt% SiC added reached 40 kA/cm2 at 7 T, which is an enhancement by a factor of 4 compared to that of tapes without pressing during heat treatment. The higher Jc of hot pressed tapes results from improving the density of the MgB2 structures, which have less voids and good linkage between the MgB2 grains.