Carbon nanotube doping of material with a nominal stoichiometry of MgB1.9C0.1 synthesized under ambient pressure and high pressure led to an improvement of the critical current density and the upper critical field, HC2(T), with a slight depression in the superconducting transition temperature. The anomalous temperature dependence of HC2(T) with a positive curvature implied the existence of 2 gaps in both samples. In elevated fields, the fact that the current density decayed as JC(H)  H−β in high pressure samples suggested a possible route to prevent JC(H) decreasing rapidly with increasing field.

Comparison of Physical Properties for Carbon Nanotube Doped MgB2 Superconductors Synthesized with Different Process. G.Yuan, X.Xu, Z.Wang, D.Lu, X.Jin: Physica C, 2005, 432[3-4], 257-62