Improved Superconducting Properties in Bulk MgB2 Prepared by High Energy   Milling of Mg and B Powder
  The MgB2 bulks were prepared by high energy milling of Mg and B powder. The correlations among milling times, microstructure and superconducting properties were investigated in MgB2 bulks. Samples were characterized by x-ray diffraction (XRD), energy dispersive spectrometry (EDX) and scanning electron microscope (SEM), and the magnetization properties were examined by a Superconducting quantum interfere device (SQUID) magnetometer. It showed that the high energy milling is an effective approach to get fine crystalline (40-100nm) bulk MgB2 with good grain connectivity and high Jc performance. The critical current density reaches to 2.0X10E6A/cm2 at 15K and 0.59T, 5.7X10E5A/cm2 at 2T and 3.0X10E4A/cm2 at 5T. 
Y. F. Wu, Y. F. Lu, G. Yan, J. S. Li, Y. Feng, H. P. Tang, S. K. Chen,   H. L. Xu, C. S. Li and P.X.Zhang