Transport current improvements of in situMgB2 tapes by the addition of carbon nanotubes, silicon carbide or graphite

Abstract

Various types of carbon nanotube (CNT), as well as SiC and graphitepowders, were used at the 5 wt% level as additions to a mixture of commercialMg and B powder for the fabrication of single-core, in situ tapes usingtwo-axial rolling deformation in an Nb/Fe sheath and final heat treatment at650 °C/0.5 h in Ar. Transport current measurements showed that well distributedCNT, SiC and graphite additions lead to an improvement ofJc(μ0H) characteristics. The presence of carbon-containing particles causes substitution of boron bycarbon, which decreases the critical temperature and increases the upper critical field aswell as the current density in high magnetic fields. The uniform distribution of CNTsor other carbon-containing particles is an important factor for effective carbonsubstitution. This observation may be important for the development of practicalMgB2 composite superconducting wires intended for magnets.