Investigation into the synthesis and carbon doping of MgB₂for possible bulk superconducting fault current limiters application.

Abstract

Magnesium Diboride (MgB₂) bulk superconductor has been manufactured for use in superconducting fault current limiters (SFCLs) via in situ reaction. SFCLs have proven to be a viable means for limiting surge currents on power lines by dissipating fault energy as the superconductor quenches. As the current limiting behaviour is determined by the normal resistance (Rn), research has been conducted to evaluate an effective means to increase Rn for bulk superconducting MgB₂. Other researchers have previously looked into the improvement and optimisation of the critical current, Jc, by carbon doping and other flux pinning techniques. Carbon doping has been confirmed as a means to increase Rn, and was implemented by chemical vapour deposition (CVD) at 600 ºC in a tubular furnace apparatus. Intragranular doping was achieved by CVD on the boron precursor powder. In situ manufacturing of MgB₂ bulk was performed using the reactive liquid magnesium infiltration technique. Carbon doping provided an adequate increase in Rn, for a small decrease in the critical temperature, Tc.