Effect of Ball Milling and Fatty Acid Addition on the Properties of MgB2 Wires.

Improved inductive critical current density Jc, at medium and high magnetic fields B, has been obtained in MgB2 wires made from ball-milled and carbon-doped precursors. The analyzed Fe-sheathed monofilamentary wires have been manufactured by the powder-in-tube and in-situ methods. Carbon doping has been achieved by the addition of fatty acids, in particular oleic acid (C18H34O2). In order to enhance the Jc(B) performance and the homogeneity of the wires, we have analyzed the combined effects of ball milling and oleic acid addition. The changes in the microstructure, phase composition, and superconducting properties for different milling parameters and the fixed amount of acid addition have been analyzed.