RU-2861601-C1 - METHOD FOR OBTAINING METAL-INSULATOR PHASE TRANSITION COATING FOR HIGH-TEMPERATURE SUPERCONDUCTOR TAPES

Abstract

FIELD: superconductors. SUBSTANCE: use: for creating multilayer tapes of high-temperature superconductors (HTS) containing various functional layers. The essence of the invention lies in the fact that a method for obtaining a metal-insulator phase transition coating for high-temperature superconductor tapes includes applying to HTS tapes a dispersion solution containing vanadium sesquioxide as a phase transition material and a binder material. The dispersion solution for coating application includes vanadium sesquioxide nanowires, wherein the vanadium sesquioxide nanowires are obtained by preparing a gel based on vanadium pentoxide V 2 O 5 - a precursor for obtaining nanowires, synthesising V 2 O 5 nanowires by electrospinning followed by two-stage annealing to the V 2 O 3 phase, and the dispersion solution is prepared on the basis of low-molecular-weight polyvinylpyrrolidone (PVP) and V 2 O 3 nanowires. EFFECT: possibility of increasing the conductivity efficiency of the coating without the use of additional heat treatment. 1 cl, 3 dwg

Inventors

• BEREZINA OLGA YAKOVLEVNA

Dates

Publication Date

20260506

Application Date

20250919

Claims (1)

1. A method for producing a coating with a metal-insulator phase transition for high-temperature superconductor tapes, comprising applying a dispersed solution to the HTSC tapes, containing vanadium sesquioxide as a phase transition material and a binder material, characterized in that the dispersed solution for applying the coating includes vanadium sesquioxide nanowires, wherein the vanadium sesquioxide nanowires are obtained by preparing a gel based on vanadium pentoxide V 2 O 5 - a precursor for obtaining nanowires, synthesizing V 2 O 5 nanowires by electrospinning followed by two-stage annealing to the V 2 O 3 phase, and the dispersed solution is prepared based on low-molecular polyvinylpyrrolidone (PVP) and V 2 O 3 nanowires.

Description

Scope of application The invention relates to the production of multilayer high-temperature superconductor (HTSC) tapes containing various functional layers. The claimed method enables the production of coatings based on vanadium sesquioxide nanowires with a metal-insulator phase transition for HTSC tapes. The resulting coatings exhibit insulating properties at HTSC operating temperatures and high conductivity at temperatures above the superconductor's transition to the normal state. State of the art Currently, high-temperature superconductors (HTSC) with a superconducting transition temperature of about 90 K are widely used to create various superconducting magnetic systems, such as magnetic resonance imaging scanners, nuclear magnetic resonance installations, tokamaks, etc. As a rule, superconducting magnetic systems based on HTSC use uninsulated superconducting windings, usually with a Cu coating [1]. This is due to the low velocity of propagation of the normal zone along the HTSC tape upon exiting the superconducting state [2], which can cause significant ohmic heating and destruction of the material. The propagation velocity of the normal phase of HTSC is significantly lower than that of low-temperature superconductors and does not exceed 10 cm/s at currents close to the critical value [3]. In the superconducting state, the current flows along the uninsulated winding due to the higher resistance of copper compared to HTSC. Upon local exit from the superconducting state, the zone of the normal (non-superconducting) state propagates not only along the superconductor, but also in the transverse (radial) direction, which protects the HTSC layer from destruction due to local heat generation. The current is shunted by the copper coating. A disadvantage of non-insulated windings is the time lag (τ) between the current entering the winding and the magnetic field, with the lag time being inversely proportional to the resistance between the turns. This phenomenon does not affect the operation of permanent HTS magnets, but it significantly complicates the operation of alternating HTS magnetic systems at frequencies above 1/τ. As a result, a pressing task is to create coatings with high resistance at the operating temperatures of modern HTSCs (90 K and below) and relatively low resistance at temperatures above the transition of the superconductor to the normal state. Some of the most promising materials for solving this problem are vanadium oxides, which exhibit a metal-insulator phase transition (MIPT). In particular, vanadium sesquioxide V2O3 changes its resistivity by more than seven orders of magnitude at a MIPT of 140K [4]. The highest quality V2O3 coatings can be obtained using reactive magnetron sputtering [6]. However , this method is expensive and poorly suited for application to long strips on an industrial scale. A method for producing a ceramic film for a superconducting coil is known, presented in a patent [Patent KR 102567623 B1 "Ceramic film having the function of temperature switch and superconducting coils using the same" 08/16/2023]. The ceramic film is placed between the turns of the HTS coil and consists of two layers: a metal layer made of a conductive metal, such as copper, nickel, or stainless steel, and a layer containing a metal-insulator junction (MIJ) material. Among the materials with PMI, the patent proposes vanadium oxides from the V n O 2n-1 group, where (n=2-9), as well as other phase transition oxides such as Fe 3 O 4 , RNiO 3 (where R=La, Sm, Nd or Pr), La 1-x Sr x NiO 4 (for x<1), NiS 1-x Se x (for x<1) and BaVS 3 . The advantage of this method is that the ceramic film is produced separately from the HTS tapes, which allows it to be manufactured using various methods, including using high temperatures that can damage the structure and superconducting properties of HTS. The disadvantage of this method is that it does not disclose the method for producing material with PMI on a metal layer. The closest analogue, accepted as a prototype, is a method for insulating a superconducting coil using a layer of material with a metal-insulator transition (MIT), located in such a way as to electrically isolate the space between adjacent superconducting tapes, presented in the patent [Patent US 10861626 B “High-temperature superconducting coil having smart insulation, high-temperature superconducting wire used therefor, and manufacturing method therefor”, 12/08/2020]. The patent describes materials for a metal-insulator transition layer based on vanadium oxides VO 2 and V n O 2n-1 , where (n = 2-6 or 8), as well as other phase-change oxides. A preferred embodiment of the invention is a vanadium oxide-based coating applied to the surface in the form of a gel consisting of V 2 O 3 powder mixed with polyvinylidene fluoride (PVDF) and N-methyl-2-pyrrolidone (NML) as a binder. The viscosity of the mixture was controlled by adjusting the binder content, for example, 97% V 2 O 3 and 3% PVDF + NML. Af