Improved high field performance of Nb-Al powder metallurgy processed superconducting wires

Abstract

Improved overall critical current densities Jc’s were achieved with powder metallurgy processed Nb-A1 which combined reduced powder sizes and increased nominal areal reductions R. Increased Jc values were obtained for a variety of different heat treatments. For a Nb-8 wt. % A1 wire with R=3.4×105 a very short treatment at 1100 °C followed by a 750 °C treatment gave (at 4.2 K)Jc>104 A/cm2 at 19 T; a 900 °C treatment followed by a 750 °C treatment gave Jc=104 A/cm2 at 18 T and, at 2 K, Jc was greater than 104 A/cm2 at 20 T; and a treatment of 800 °C for 8 h gave (at 4.2 K)Jc=104 A/cm2 at 17.5 T.

Niobium based intermetallics as a source of high-current/high magnetic field superconductors

“…A bundle of these wires will give an Al layer thickness of 100nm [6]. Despite differences in cross sectional area, J c versus magnetic field curves are very similar for all processes.…”

“…•Powder metallurgy,(PM)-A mixture of hydride-dehydride Nb powder and Al powder are put in a copper tube can so that they can be extruded and drawn into a monofilament wire. A bundle of these wires will give an Al layer thickness of 100nm [6]. Despite differences in cross sectional area, J c versus magnetic field curves are very similar for all processes.…”

Superconducting Property of<tex>$hboxNb_3(hboxAl,hboxGe)$</tex>Conductors Prepared by Diffusion Process

“…2 shows critical temperature, , as a function of designed Al-Ge filament thickness for different diffusion reaction time. It is generally believed that in order to improve the stoichiometry of the Nb Al-based A15 phase in the diffusion reaction, the diffusion spacing of the Nb/Al-alloy should be reduced down to submicron less, because the reduced diffusion spacing promotes decomposition of unwanted -phase formed during the reaction [12], [13]. However, against our expectation, high was obtained around the Al-Ge filament size of 4 and the has a tendency to enhance with the reaction time.…”

Nb3Al formation in sputter-deposited Nb/Al multilayer samples

“…Heat treatment temperature ranges between 900-1100°C are commonly used in order to compromise between these effects, [2]- [5] These heat treatments, however, do not change the average A15 grain size and shape substantially. As a result, our study has focused on the factors which determine the A 15 (Nb3Al) phase volume fraction.…”