The effects of the addition of SiC nanoparticles were compared, for MgB2 tapes prepared from 2 different starting powders, with respect to the improvement in the critical current, JC, at 4.2K and 10T. The starting powder was prepared by blending premixed MgH2 and B(MgH2+2B) and pre-mixed (MgH2+2B) and MgB2 (30% MgB2) in the ratio of 7:3. All of the tapes were fabricated by using the in situ powder-in-tube method. The use of 30% MgB2 as standard powder yielded higher JC values than MgH2+2B in the case of pure MgB2 tape. However, the highest JC (1.8 x 104A/cm2) was obtained for tape made from MgH2+2B with 10mol%SiC additive. The tape made from 30%MgB2 contained regions with Si-free MgB2 grains, while Si compounds were distributed homogeneously across the tape prepared from MgH2+2B. Furthermore, the use of 30%MgB2 instead of MgH2+2B was found to reduce the effect of C substitution of the SiC additive. The data indicated that the technique, which enhanced the JC–B characteristics of the pure MgB2 tape, did not promise further improvement via the addition of nanosized impurity particles. It was concluded that the fabrication of MgB2 tape should be improved by maintaining, or improving, the overall reactivity between the standard powder and nanosized impurity particles.

Effect of SiC Nanoparticle Addition on the Critical Current Density of MgB2 Tapes Fabricated from MgH2, B and MgB2 Powder Mixtures. T.Nakane, C.H.Jiang, T.Mochiku, H.Fujii, T.Kuroda, H.Kumakura: Superconductor Science and Technology, 2005, 18, 1337-41