Fabrication and characterization of MgB2 powders and Cu-Clad MgB2 wires

Abstract

In 2001, a new superconducting material, MgB2 (39K), which raised new hopes for electrical power applications due to its superior superconducting properties was discovered.In the first part of this study, elementary B is obtained by reacting B2O3, and Mg in Argon atmosphere at 800°C. EDX results revealed that the powder obtained was Boron in 93% purity with Mg as a major impurity. MgB2 is produced from acquired B and Mg in Ar atmosphere at 900°C by a conventional solid-state reaction. MgB2 powders were pressed to a pellet at 500°C at 1 GPa. Microstructural properties of MgB2 were determined by XRD, EDX, and SEM techniques. Electrical properties of fabricated MgB2 were analyzed by resistivity measurements with closed-cycle cryopump system between 20 and 300K. It is found that the Tc onset value of the pellet is around 32K. In the second part, different weight ratios of C is added to commercial MgB2 and pressed at 500°C at 1 GPa. R-T measurements revealed that transition temperature increases with an increase in the C addition concentration. In the third part, MgB2/Mg composite wires were prepared by packing blend of MgB2 and Mg powders inside Cu tubes using PIT method. The microstructure studies MgB2 and Mg powders inside Cu tubes using PIT method. The microstructure studies using XRD, EDX and SEM techniques showed that MgCu2 layer forms at the interface between Cu sheath and core because of Mg diffusion from superconducting core, and excess Mg prevents further reaction of Cu with MgB2. R-T measurements were performed to investigate the influence of excess Mg on Tc. The effect of annealing showed that excess Mg gives better results at annealing temperature of 400°C for 2 hours.