${\rm MgB}_{2}$ Superconductors With Addition of Other Diborides and SiC

Abstract

The discovery of superconductivity at 39 K in MgB 2 has been catching the attention of scientists due to the possibility of applying the material in magnets and electronic devices operating with cryocoolers (temperatures around 20 K). In the present work, a methodology to optimize the critical current densities of this material is described. MgB 2 bulk samples were prepared and analyzed with the addition of other diborides with the same C32 hexagonal structure as MgB 2 (TaB 2 , ZrB 2 , VB 2 , and AlB 2 ) and with simultaneous addition of SiC. Microstructural characterization, performed using SEM+EDS and XRD, was extremely important to determine the distribution and compositional characterization of the superconducting phase. Magnetic superconducting characterization using SQUID was performed to determine the best material addition. As a result we could analyze the behavior of each addition on the current transport capacity, including an analysis of the magnetic flux pinning mechanisms.Index Terms-Addition of diborides and SiC, crystallography, MgB 2 superconductors, microstructure, superconducting properties.

Development and Characterization of Cu–Nb–MgB2 and CuNi–Nb–MgB2 Wires With VB2 and Carbon Nanotube Additions

“…Testing these hypotheses and behaviors will be performed in the future with complete characterization of all samples, including microstructural and superconducting characterization. The influence of doping will be evaluated, together with previous work [3], [4], [6]- [9]. New heat treatments will be performed with argon flow.…”

“…VB 2 powder was added to the MgB 2 powder to obtain 5 at.% V doping (for Mg) [3], [4], [6], [7], [9], [14]- [17], and then 3 wt.% of carbon nanotubes (CNT) was added. The mixture of the MgB 2 powders with VB 2 and carbon nanotube were milled together for 300 minutes in a SPEX8000D high energy mill using tungsten carbide milling jar and balls.…”

“…The mixture of the MgB 2 powders with VB 2 and carbon nanotube were milled together for 300 minutes in a SPEX8000D high energy mill using tungsten carbide milling jar and balls. The ratio of ball to powder mass, was 3 : 1 [3], [4], [6], [7], [9]. All operations to prepare and mill the powder were performed inside an Ar atmosphere glove-box, that actively removed O 2 and water to avoid the formation of impurities and contamination, such as MgO.…”

“…However, flux pinning is relatively weak in MgB 2 , decreasing the maximum critical current density obtained in MgB 2 superconducting wires, tape and bulks. Adding secondary phases in a controlled way is important to create new pinning centers to improve the critical current density [3], [4].…”

“…This paper presents preliminary results on the development of MgB 2 multifilamentary superconducting wires using the powder-in-tube (PIT) methodology and powders prepared with doping conditions developed in previous studies [3], [4], [6], [7], [9]. It describes a methodology to produce wires using MgB 2 powders containing additions of VB 2 and carbon nanotubes [6]- [12].…”