MgB2 wires and tapes for magnet applications

SOBRERO C; M. MALACHEVSKY; E. OLIBER; A. SERQUIS; F. C. GENNARI

Campos do Jordão, Brasil

Encuentro; XII Encontro da SBPMat, Brazilian MRS Meeting; 2013

Brazilian MRS Meeting

The low cost, low weight and high superconducting critical temperature (Tc) make the MgB2attractive for technological applications, in particular at the Magnetic Resonance Imaging(MRI) medical industry. When compared with permanent magnets, there are two potentialadvantages of MgB2. The first one is the possibility of achieving the typical magnetic fieldstrengths of considerably more than 0.4 Tesla (up to 1.5-2.0 Tesla) with a lower initial capitalequipment cost and lower life-cycle cost. Second, higher field strengths and larger zones ofhomogeneous magnetic field can be achieved with MgB2 superconductor than with permanentmagnets. The powder in tube (PIT) method [1] has been preferred early on by several groupsto prepare MgB2 wires or tapes [1]. Presently, one of the most important issues for MgB2magnet applications is the enhancement of its critical current density (Jc). Thus, the pinningforce may be improved by the incorporation of defects (nano particle doping, chemicalsubstitutions, 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 nanodefectsthat may act as excellent pinning centers: attrition milled commercial MgB2 [4], commercialMgB2 with 5% wt SiC and a non-commercial MgB2 produced in our laboratories. Thesynthesis 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 toprepare stainless steel single and multifilamentary MgB2 wires. We investigated differentthermal treatments and mechanical paths during the processing of the wires Thesuperconducting properties were analyzed by magnetization measurements in a SQUIDmagnetometer. The correlation between the thermal treatments, structure, composition of thereaction layers and superconducting properties is discussed.