Properties of MgB₂wires made by internal magnesium diffusion into different boron powders

Abstract

Different boron powders were used for MgB 2 wires manufactured by internal magnesium diffusion. The structure of the MgB 2 core, critical temperature and critical currents of Cu/Ti sheathed wires differing only in boron powder were analyzed and compared. It was found that the particle size and purity of boron powders influence the creation of the MgB 2 phase and, consequently, also considerably influence its superconducting properties. The highest critical current density in the low external field was measured for wire with a boron purity of 98.5% produced by Pavezyum. It was used also for stabilized multi-core MgB 2 wire with high engineering current densities in low magnetic fields at 20 K, which may be attractive for some low field applications, e.g. high-power wind generators.

Lightweight MgB2 wires with a high temperature aluminum sheath made of variable purity Al powder and Al2O3 content

“…The critical currents of the groove rolled wires HT at 640 °C/ 60 min and the rotary swaged ones annealed at 635 °C/ 15 min were measured at 4.2 K. Figure 8(a) shows lower engineering current densities for the rolled wires with the typical value of 10 4 Acm −2 measured between 4.2 and 5.5 T. The engineering current densities of the swaged wires (see figure 8(b)) are higher and less different (10 4 Acm −2 between 5.45 and 5.9 T), which can be attributed to a more dense and uniform boron layer prior to the final heat treatment. Nearly the same engineering current densities were measured for similarly made single-core IMD wires using the same boron powder but different metallic components MgB 2 /V/Cu [29] and MgB 2 /Ti/Cu [30].…”

Effect of cold isostatic pressing on the transport current of filamentary MgB2wire made by the IMD process

“…An attempt has been already made by Li et al [8] to describe two steps of this process: Mg penetration and consecutive MgB 2 formation [8]. There are several critical factors that may control the formation rate of the MgB 2 layer: (i) the annealing parameters (temperature and time) [7], (ii) the morphology of the boron powder [9], (iii) the thickness of the boron layer [10], and (iv) the density of the boron layer before the MgB 2 phase formation. Up to now, the effect of the boron layer density in IMD wires has not been systematically studied.…”

Effect of Rapidly Annealing Process on MgB2 Superconducting Wires

“…In-situ MgB2 in the fabrication of superconductor wires has preferred due to the benefit as possible heat treatment at low temperature, comfortable doping, control of particle size, and high critical current density under applied external magnetic field [21]. Additionally, there are various parameters that may control and affect the formation rate of the MgB2 layer as annealing temperature and time [22], cooling and heating rate [23,24], morphology of the B powder [25] thickness of the B layer [26] and also density of the B layer [27]. The factors affecting Jc performance are weak inter-grain connectivity, porosity, and low MgB2 core density [28,29].…”