Author_Institution :
Sch. of Eng. Sci., Univ. of Southampton, Southampton, UK
Abstract :
Promising initial results on bulk Mg(B1-xCx)2 prepared with carbon doped boron are presented. Carbon doping is achieved by reaction of ethylene gas on boron powder using a stainless steel tube furnace, a technique suitable for industrial scale processing. The nominal amount of doping was controlled by varying the reaction time with a fixed volume of ethylene gas, and the actual carbon uptake was determined by weight change after the reaction. The amount of carbon substitution x in the Mg(B1-xCx)2 was found using the angular shift in the (100) X-ray reflection. Carbon substitution by the full nominal content in the C doped precursor boron was obtained for doping up to 7.2 at%, as shown by a o-axis compression consistent with that of carbon doped single crystals. The critical current density of the 4 at% C doped sample for temperatures at 20-30 K and fields up to 4 T, relevant to high temperature applications, was significantly higher than those in the published literature. The JC of a 10 wt% nano-SiC doped sample, used as a comparative benchmark, was found to be lower than the C doped sample at field below 2 T, but to reduce slower at higher fields. Structure analysis of the SiC doped sample revealed a coexistence of two C substitution levels of 2.25% at and 5.25% at.
Keywords :
critical current density (superconductivity); doping; magnesium compounds; superconducting transition temperature; MgB2-MgC2 - System; carbon chemical vapor coated boron; carbon substitution; critical current density; doping; industrial scale processing; Boron; Crystals; Doping; Furnaces; Gas industry; Metals industry; Powders; Reflection; Steel; Temperature; ${hbox{MgB}}_{2}$ superconductor; Boron powder; carbon doping; critical current;