Enhancement of in-field Jc in MgB2 /Fe wire using single- and multiwalled carbon nanotubes

The authors investigated the doping effects of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) on the Tc, lattice parameters, Jc(B), microstructure, and Hc2 of MgB2∕Fe wire. These effects systematically showed the following sequence for Tc and the a axis: the SWCNT doped wire the MWshortCNT doped wire>the MWlongCNT doped wire>undoped wire. A dominating mechanism behind all these findings is the level of C substitution for B in the lattice.