A short pre-annealing and intermediate rolling process was applied to in situ processed MgB2/Fe tapes prepared by using MgH2 and B powders. The JC properties of both non-doped and 10at% nano-SiC-doped MgB2/Fe tapes were greatly improved by this modified in situ process. The best JC results were obtained in samples pre-annealed (600C, 0.25h) and further heat-treated (600C, 1h) after intermediate rolling. An enhancement of about 80% in JC in 10T and at 4.2K was achieved for both SiC-doped and non-doped tapes by using this optimum condition. The decomposition of MgH2 at the early reaction stage would generate many cracks and pores, and leave a porous core in the tapes before the formation of MgB2. In this modified in situ process, the decomposition of MgH2 was completed within 0.25h pre-annealing at 600C; the MgH2-decomposition-generated pores and cracks were effectively eliminated by the subsequent rolling. The core densities of the final tapes were significantly enhanced by utilizing this pre-annealing and intermediate rolling process, which in turn improved JC in the MgB2 tapes.

Preparation of MgB2/Fe Tapes with Improved JC Property Using MgH2 Powder and a Short Pre-Annealing and Intermediate Rolling Process. C.H.Jiang, H.Hatakeyama, H.Kumakura: Superconductor Science and Technology, 2005, 18, L17-22