Influence of milling time and glycerin treatment for boron powder on the superconducting properties of MgB2 bulk

摘要

A correlation between the ball milling time and glycerin treatment of boron powder on the superconducting properties of MgB2 was elucidated. The aim of the planetary ball milling was to enhance the high field critical Current density (J(c)) by controlling the particle size of the boron powder. The boron powder was ball-milled for 1, 2, 5 and 7 h at 200 rpm in toluene. Each of the different ball-milled boron powders were then treated with glycerin as a source for carbon doping. The results showed that by combining mechanical milling and glycerin treatment for the boron powder, the J(c) increased significantly over the entire range of magnetic fields as compared to the pure MgB2 sample. The optimum level of milling time + glycerin treatment was found to be 2 h, and further milling decreased the J(c) due to substantial decreased in T-c.