Enhancement of Critical Currents wires of MgB2 using different sheath materials

C. SOBRERO; M.T. MALACHEVSKY; A. SOLDATI; A. SERQUIS

Anchorage

Conferencia; CEC/ICMC 2013; 2013

The highest superconducting critical temperature (Tc) reported for a binary compound makes MgB2 attractive for technological applications. Some of the advantages for the use of MgB2 are its low cost, low weight, and the absence of weak link grain boundaries. Since its discovery, a remarkable progress has been done in increasing the critical current densities (Jc) by optimizing processing parameters. The powder in tube (PIT) method has been preferred early on by several groups to prepare MgB2 wires or tapes but the influence of the possible reaction between the sheath material and MgB2 core had not been fully studied. We reduced commercial MgB2 powder by attrition milling in nitrogen atmosphere using tungsten balls. We obtained powders with grain sizes lower than 150 nm and different strains states through this process. Several Ti, Stainless steel and copper mono and multifilamentary wires were prepared using these powders by the PIT method. We investigated different thermal treatments and mechanical path during the processing of the wires for the enhancement of the critical currents. The superconducting properties were determined by magnetization measurements in a SQUID magnetometer. We also analyzed the evolution of the react layers between the MgB2 and the materials used as support for the wires by electron microscopy techniques. The correlation between the thermal treatments, structure, composition of the reaction layers and superconducting properties is discussed.