The mono-filamentary and multi-filamentary MgB2 wires sheathed with Nb/Cu composite tube were fabricated by in-situ powder-in-tube (PIT) technique with the carbon and TiC doping. The results show that there is a diffusion layer at the interfacial region between the Nb sheath and MgB2, which is non-superconducting phase for the sample heat-treated at high temperature, and this diffusion layer obstructs the current transmission at high heat-treatment temperatures and the best heat-treatment temperature for the MgB2 wires with Nb as the barrier layer should be lower than 750°C. Effects of amorphous carbon and TiC doped MgB2 wires were investigated by XRD, SEM and magnetization. The results show that substitution of B for C enhances the flux pinning but depresses Tc slightly. By controlling the processing parameters, an optimized Jc(H) performance is achieved under a partial amorphous C substitution. The Cu-clad 6-, 12-, and 36-filamentary MgB2 wires with Nb buffer layer also have been fabricated by the in-situ PIT method. To improve the strength of wires, the Nb-core was used as the central filament. The results show that the in-situ PIT technique can be used to produce the certain long length MgB2/Nb/Cu wires. The superconducting filaments of MgB2/Nb/Cu composite tubes have well workability suitable for the MgB2 wires long length and multi-filament.
