Large upper critical field and irreversibility field in MgB2 wires with SiC additions

Resistive transition measurements are reported for MgB2 strands with SiC dopants. The starting Mg powders were 325 mesh 99.9% pure, and the B powders were amorphous, 99.9% pure, and at a typical size of 1–2 µm. The SiC was added as 10 mol % of SiC to 90 mol % of binary MgB2 fsMgB2d0.9sSiCd0.1g. Three different SiC powders were used; the average particle sizes were 200 nm, 30 nm, and 15 nm. The strands were heat treated for times ranging from 5 to 30 min at temperatures from 675 °C to 900 °C. Strands with 200 nm size SiC additions had m0Hirr and Bc2 which maximized at 25.4 T and 29.7 T after heating at 800 °C for 30 min. The highest values were seen for a strand with 15 nm SiC heated at 725 °C for 30 min which had a m0Hirr of 29 T and a Bc2 higher than 33 T.