Progress on the Fabrication of Superconducting Wires and Tapes via Hot Isostatic Pressing

Abstract

Fabrication of high-performance superconducting wires and tapes is essential for large-scale applications of superconducting materials. The powder-in-tube (PIT) method involves a series of cold processes and heat treatments and has been widely used for fabricating BSCCO, MgB₂, and iron-based superconducting wires. The densification of the superconducting core is limited by traditional heat treatment under atmospheric pressure. The low density of the superconducting core and a large number of pores and cracks are the main factors limiting the current-carrying performance of PIT wires. Therefore, to improve the transport critical current density of the wires, it is essential to densify the superconducting core and eliminate pores and cracks to enhance grain connectivity. Hot isostatic pressing (HIP) sintering was employed to improve the mass density of superconducting wires and tapes. In this paper, we review the development and application of the HIP process in the manufacturing of BSCCO, MgB₂, and iron-based superconducting wires and tapes. The development of HIP parameters and the performance of different wires and tapes are reviewed. Finally, we discuss the advantages and prospects of the HIP process for the fabrication of superconducting wires and tapes.

Keywords: BSCCO; MgB2; hot isostatic pressing; iron-based superconducting wires; overpressure.

Figure 1

Schematic diagram showing the main structure of an HIP system.

Figure 2

Schematic diagram showing the main structure of a flow overpressure system.

Figure 3

Heat treatment schedule for Bi-2223 wires. The Bi-2223 wires are rolled after the first heat treatment and then treated using the overpressure method.

Figure 4

Comparison of SEM secondary electron micrographs of (a) Bi-2223 normal-pressure filament and (b) overpressure filament. AEC is alkaline earth cuprate, such as (Ca,Sr)-Cu-O [19]. Adapted with permission from Ref. [19]. 2005, Elsevier.

Figure 5

Heat treatment schedule for Bi-2212 wires. T_max is the maximum temperature and T_melt is the melting point of the Bi-2212 filaments. The time it takes for Bi-2212 filaments to melt is called t_melt.

Figure 6

Comparison of SEM micrographs of (a) a normal-pressure filament and (b) an HIP filament [40]. Adapted with permission from Ref. [40]. 2014, IOP Publishing.

Figure 7

Transport J_c of the (a) undoped MgB₂ samples at a pressure of 1 GPa and 0.1 MPa and (b) SiC-doped MgB₂ samples at a pressure of 1 GPa and 0.1 MPa. Some data are based on [40].

Figure 8

Transport J_c of the MgB₂ samples at a pressure of 1.1 GPa and 0.1 MPa. Some data are based on [41].

Figure 9

Transport J_c of the MgB₂ samples heat-treated by HIP (1.4 GPa) + CHPD (1.8 GPa), CHPD (1.8 GPa), and HIP (1.4 GPa), as well as samples fabricated under 0.1 MPa. Some data are based on [42].

Figure 10

The cross sections of (Ba,K)Fe₂As₂ (a) round wire, (b) round seven-filament wire, (c) square wire, (d) tape, and (e) seven-filament tape.

Figure 11

Magnetic J_c of the (Ba,K)Fe₂As₂ bulk samples heat-treated at 193 MPa and 0.1 MPa. Some data are based on [51].

Figure 12

SEM and microscope images of (a–c) HIP-processed samples and (d–f) ambient pressure-sintered sample at different magnifications [56]. Adapted with permission from Ref. [56]. 2021, Shifa Liu.

Figure 13

XRD patterns of precursor powder and the superconducting core of (Ba,K)Fe₂As₂ superconducting tapes with different sintering time [55]. Adapted with permission from Ref. [55]. 2019, IOP Publishing.

Figure 14

The introduction of groove rolling in (Ba,K)Fe₂As₂ wires. (a) Drawing is applied before and after a Ag wire is put into the Cu tube; (b) drawing and groove rolling are applied before and after a Ag wire is put into the Cu tube; (c) groove rolling is applied before and after a Ag wire is put into the Cu tube.

Figure 15

Comparison of the transport J_c performance of HIP (Ba,K)Fe₂As₂ superconducting wires from different groups [50,54,58,59].

Figure 16

HIP-processed seven-filament (Ba,K)Fe₂As₂ superconducting wires and tapes. (a) SEM image of a cross section of the wire; (b) SEM image of a cross section of the tape; (c) XRD pattern of the wire; (d) XRD pattern of the tape [61]. Adapted with permission from Ref. [61]. 2014, Elsevier.

Figure 17

Transport J_c of the CaKFe₄As₄ samples heat-treated at 175 MPa, 9 MPa, and 0.1 MPa. Some data are based on [62].

Figure 18

Transport J_c of overpressured Bi-2212 [29] and Bi-2223 [65] wires and HIP-processed MgB₂ [42], (Ba,K)Fe₂As₂ [58,59], and CaKFe₄As₄ [62] wires and tapes.