Magnesium metal
Mg vapor has been applied for preparation of MgB2 by CVD. Long-length boron fiber that contained both TiB and TiB2 (with titanium co-deposired with boron) was exposed to Mg vapor, which reacted with boron/ borides producing MgB2 layers, having a superconducting critical current density of about 5×106 A/cm2 at 5 K and self-field; and critical current density at 25 K and 1 T ca.10,000 A/cm2. These MgB2 layers showed a fine dispersion of Ti throughout the grains and no conspicuous precipitation of TiB2 on the MgB2 grain boundaries. Optical methods were used to define grain boundaries, EDX applied to determine Ti and Mg concentrations. In contrast, the samples prepared by solid state reaction of Ti, Mg, and B powders displayed the precipitation of TiB2 on MgB2 grain boundaries. Thus, introducing Ti impurities into the B during the CVD deposition of the B gave a distribution of TiB2 in the resulting MgB2 different from solid state reaction of powders[PS1] [[i]]..
[i]D. K. Finnemore W. E. Straszheim, S. L. Bud’ko, P. C. Canfield, N. E. Anderson, Jr. and R. J. Suplinskas, Physica C: Superconductivity, Volume 385, Issues 1-2, 1 March 2003, Pages 278-285, “CVD routes to MgB2 conductors”