MgB2 wires and tapes for magnet applications

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

Campos do Jordaõ

Congreso; XII Encontro da SBPMat; 2013

SBPMat

The low cost, low weight and high superconducting critical temperature (Tc) make the MgB2 attractive for technological applications, in particular at the Magnetic Resonance Imaging (MRI) medical industry. When compared with permanent magnets, there are two potential advantages of  MgB2. The first one is the possibility of achieving the typical magnetic field strengths of considerably more than 0.4 Tesla (up to 1.5-2.0 Tesla) with a lower initial capital equipment cost and lower life-cycle cost. Second, higher field strengths and larger zones of homogeneous magnetic field can be achieved with MgB2 superconductor than with permanent magnets.  The powder in tube (PIT) method [1] has been preferred early on by several groups to prepare MgB2 wires or tapes [1]. Presently, one of the most important issues for MgB2 magnet applications is the enhancement of its critical current density (Jc). Thus, the pinning force may be improved by the incorporation of defects (nano particle doping, chemical substitutions, etc.) and by optimizing processing parameters [2-3]. For the present work we used three different types of powders and different sheath materials (Copper, Stainless Steel and Titanium) to fabricate wires with large amounts of nanodefects that may act as excellent pinning centers: attrition milled commercial MgB2 [4], commercial MgB2 with 5% wt SiC and a non-commercial MgB2 produced in our laboratories. The synthesis of the non-commercial powder was performed by reaction of an as-milled LiBH4-MgH2 mixture under controlled conditions of hydrogen pressure and temperature, simultaneously with LiH formation as co-product. Powder in tube (PIT) method was used to prepare stainless steel single and multifilamentary MgB2 wires. We investigated different thermal treatments and mechanical paths during the processing of the wires The superconducting properties were analyzed by magnetization measurements in a SQUID magnetometer. The correlation between the thermal treatments, structure, composition of the reaction layers and superconducting properties is discussed.