Effects of the high-pressure treatment ofex situMgB₂superconductors

Abstract

Single-core MgB 2 /Cu and MgB 2 /Fe/Cu wires and tapes have been made by the powder-in-tube method with the use of commercial MgB 2 powder (Alfa Aesar) involving hydrostatic extrusion and two-axial rolling processes. High-pressure post-treatments such as cold isostatic pressing, double hydrostatic extrusion and uniaxial pressing were applied. The grain connectivity, I c (B) curves, pinning in MgB 2 grains, upper critical field, deformation homogeneity, compact density and preferable alignment crystallites for the [0 0 1] (c-axis) direction were all improved and enhanced by application of various high-pressure treatments for the MgB 2 compound and composites. Hydrostatically extruded MgB 2 wires have been shown to be better than rolled wires and are very promising for possible application in windings.

Vortex edge barriers and critical current density in granular superconductors

“…We can see that in the strong coupling limit (this corresponds approximately to the MgB 2 case), U p decreases more rapidly with increasing field than in the weak coupling limit (HTS materials). Similarly, a rapid decrease of the vortex pinning potential was reported in inductive measurements of the flux creep rate [10], in ac susceptibility measurements [11] and in standard four-probe experiments [12]. The inset of Fig.…”

As-deformed filament's density and transport currents of MgB2/Ti/Glidcop wire

“…No literature data presenting the application of hydrostatic extrusion for long-length production of MgB 2 wires have been published yet. Several experiments with extruded single-core [7][8][9] and also 7-filament wires using ex situ and/or in situ process have been done [10,11]. These hydrostatically extruded wires with Fe and Nb/Cu sheaths had not yet sufficient filament uniformity after drawing and/or rolling [11].…”

Combined X-ray and electron microscopy study of MgB2powders, wires and tapes

“…We refer to specific publications for descriptions of the preparation processes. The samples included multi-filament tapes [1], single-filament tapes [2], wires with SiC additions [3] and bulk pellets sintered by hot isostatic pressing [4].…”