Carbon doping of precursor boron powder for control of normal resistance of MgB₂bulks for specific use in fault current limiter applications

Abstract

View the article online for updates and enhancements. Abstract. Magnesium Diboride (MgB 2 ) bulk superconductor has been manufactured in order to study the enhancement of the normal resistivity for application to superconducting fault current limiters (SFCLs). SFCLs have proven to be a viable means for limiting surge currents by dissipating fault energy as the superconductor quenches. As the current limiting behaviour is determined by the normal resistivity (ρ n ), research has been conducted to evaluate an effective means to increase ρ n for bulk superconducting MgB 2 , which is intrinsically much lower than for high temperature superconductors. Intragranular carbon doping has been confirmed as a means to increase ρ n , and was implemented by chemical vapour deposition (CVD) on the boron precursor powder by ethylene gas at 600 ºC for durations up to 6 hours in a tubular furnace apparatus. In situ manufacturing of MgB 2 bulk was performed using the reactive liquid magnesium infiltration technique. Overall, carbon doping provided a factor of 11.00 increase in the residual resistivity, ρ 0 , which provides the initial limiting action to fault currents, for an accompanying decrease in the critical temperature, T c , of 2 K.