Drawing induced texture and the evolution of superconductive properties with heat treatment time in powder-in-tubein situprocessed MgB₂strands

Abstract

Monocore powder-in-tube MgB 2 precursor strands were cold-drawn and heat- This effect is attributed to the fibrous macrostructure and its accompanying anisotropic connectivity. Magnetic measurements with the field directed along the strand axis yielded a critical density, J cm ┴ (B), for current flowing transversely to the strand axis that was less than and dropped off more rapidly than J ct (B). In the conventional magnetic measurement, the loop currents that support the magnetization are restricted by the lower of J ct (B) and J cm  (B). In the present case the latter, leading to the premature dropoff of the measured J cm (B) compared to J ct (B) with increasing field. This result is supported byKramer plots of the J cm  (B) and J ct (B) data which lead to an irreversibility field for transverse current that is very much less than the usual transport-measured longitudinal one, B irr,t .

Evidence of Point Pinning Centers in Un-Doped Mgb2 Wires at 20 K after HIP Process

“…This suggests that the starting composition of the material may influence B c2 . The results in Figure 6a show that 1 GPa pressure can increase B irr from 10 K to 27 K, and slightly reduce B irr above 27 K. By contrast, an increase in annealing temperature (Figure 6b) reduces B irr in between 15 K to 25 K and does not change B irr from 10 K to 15 K and above 25 K. Maeda and Susner claim that the value of the B irr is dependent on dislocation [28,29]. Moreover, Serquis showed that the HIP process can increase the density of dislocations [13].…”

Microstructure of MgB 2 superconducting wire prepared by internal magnesium diffusion and in-situ powder-in-tube processes – Secondary phase intergrain nanolayers as an oxygen content indicator

“…This value could not be regarded as the exact atomic ratio in MgB 2 phase because the average volumes with dimensions larger than MgB 2 grain size observed by TEM (see Section 3.1.2) are measured. Casino software calculation [21] helped us to estimate that 5 keV electron beam with optimized beam current of 3.55 nA gave information signal from MgB 2 volume of about 400 Â 400 Â 400 nm 3 .…”

“…Powder-in-tube (PIT) process is frequently used for the manufacture of superconducting MgB 2 wires [1][2][3][4][5]. Apparent in-field increase of critical current densities has been reached by different types of doping [6][7][8][9].…”

Pressure-induced property improvement of magnesium diboride wire

“…The longitudinal cross section areas of W00 and W15 are shown in Figure 12 and Figure 13. Susner et al [10] described that continuous MgB2 stringers in PIT in-situ wire were aligned along drawing direction and elongated voids which were left…”