Effective carbon incorporation in MgB2 by combining mechanical milling and the glycerin treatment of boron powder

A combined process of a mechanical ball milling and liquid glycerin (C(3)H(8)O(3)) treatment of boron (B) powder has been conducted to enhance the superconducting properties of MgB(2). The individual aims of the mechanical milling and the glycerin treatment were to reduce the grain size of the MgB(2) and to achieve homogeneous carbon (C) incorporation into the MgB(2), respectively. Four kinds of B powders of as-received, glycerin treated, 2 h milled and 2 h milled + glycerin treated were prepared. MgB(2) bulks were fabricated by an in situ process using the prepared B powders. According to our experimental results, the mechanical ball milling was effective for grain refinement, and a lattice disorder was easily achieved by glycerin addition. It was found that the critical current density (J(c)) values were enhanced in the samples with milled B or glycerin-treated B only. In the MgB(2) bulk prepared with both milled and glycerin-treated B, the J(c) was further increased to 1.27 x 10(4) A cm(-2) at 5 K and 8 T due to a higher grain boundary density and a greater C substitution. The upper critical field and irreversibility field were also further enhanced by a combined treatment process of the B powder.