Improved upper critical field in bulk-form magnesium diborideby mechanical alloying with carbon

High-energy milling of magnesium diboride ( Mg B 2 ) prereacted powder renders the material largely amorphous through extreme mechanical deformation and is suitable for mechanically alloying Mg B 2 with dopants including carbon. Bulk samples of milled carbon and Mg B 2 powders subjected to hot isostatic pressing and Mg vapor annealing have achieved upper critical fields in excess of 32 T and critical current density approaching 10 6 A ∕ cm 2 .