Carbon Coating Layers on Boron Generated High Critical Current Density in MgB 2 Superconductor.

Boron particles with homogeneous carbon coating layer were employed as the precursor to fabricate MgB superconductors to generate artificial two-dimensional (2D) flux pinning centers. Systematic microstructure investigation reveals that the carbon layers are well-distributed in the MgB matrix without agglomeration. The thickness of the carbon layers is less than the coherent length of MgB, which enable them to be transparent to supercurrent. The enhancement of the critical current density can be attributed to the strong flux pinning effects of the 2D carbon layers as flux pinning centers and the increased irreversibility field due to the carbon doping effects.