Carbon nanohorn doping in MgB2 wire prepared by suspension spinning

Carbon nanohorn (CNH) doping in MgB2 wire prepared by suspension spinning was studied to enhance flux pinning. The mixed powders of MgB2 and CNH with nominal composition of (MgB2)0.95C0.05 were suspended in a mixed poly(vinyl alcohol) solution. The as-drawn filaments were hot-pressed under 20 MPa at 200 °C for 8 h. The samples were enveloped by an iron sheet with a pellet of mixed powder of Mg and B and vacuum-sealed in a fused quartz tube, and then sintered at the temperature ranging from 885 °C to 900 °C for 2-3 h. The superconductivity of the samples was studied by electrical resistivity and SQUID method. Serious deterioration of Tc was not observed for the doped sample. The CNH doping resulted in enhancement of the transport Jc values at 4.2 K in high fields ranging from 6 T to 10 T by sintering at 885 °C for 2 h. The superconductivity at 4.2 K was maintained by applying the field of 14 T for the doped sample sintered at 900 °C for 3 h.