Effects of both addition and chemical treatment of SiC nanoparticles on the grain coupling and critical current density in ex situ processed MgB2 tapes

We have studied the effects of both addition and chemical treatment of SiC nanoparticles on the grain coupling and critical current density (Jc) of ex situ processed Fe-sheathed MgB2 tapes fabricated by a powder-in-tube (PIT) technique. The addition of SiC without treatment improves the grain coupling of MgB2 and increases Jc values by a factor of 6 at 4.2 K in 10 T when using untreated MgB2 powder. Whereas the chemical treatment of MgB2 is effective in pulverization and improving the pinning property, treatment of SiC results in a decrease in reactivity, and hence no improvement in grain coupling by addition. The addition of untreated SiC to treated MgB2 increases the Jc values to as high as 5.4 kA cm-2 at 4.2 K in 10 T. This increase corresponds to a factor of 13, compared with the untreated MgB2 powder without SiC addition. The removal of remnant solvent adsorbed to the surface of MgB2 and SiC is very important for obtaining high Jc values in this process