The effects of attrition and ball milling on the properties of magnesium diboride C E J Dancer 1, D Prabhakaran2, A Crossley,RITodd1 and C R M Grovenor1 1 Department of Materials, University of Oxford,Parks Road, Oxford OX1 3PH, UK 2 Department of Physics, University of Oxford,Clarendon Laboratory,Parks Road, Oxford OX1 3PU, UK Email: Received 21 .