Effects of ball milling on the sintering process and superconducting properties of (MgB2)0.96Ni0.04 bulks
Samples of (MgB 2) 0.96Ni 0.04 prepared by mechanical alloying were sintered at 750 °C for 30 min. The reactive process and generating temperature of the second phase were investigated by employing differential thermal analysis, X-ray diffraction, and scanning electronic microscopy. Corresponding microstructures and superconducting properties have also been analyzed. It is found that two-step milling is effective in refining the structure and in eliminating flux jumps, although the corresponding J c is slightly lowered due to the existence of excessive MgO. This observation indicates that the bulk samples prepared by two-step milling possess stable properties of magnetism and heat compared with the sample prepared by manual milling. 2012 IEEE.