Patent Application
20250140448
The present invention relates generally to superconductor technology. More particularly, this invention pertains to assemblies and associated fabrication methods for high temperature superconductors (HTS) employed in high-field magnetic applications.
Superconductor materials can carry high loss-less currents and generate high magnetic fields and, therefore, are often employed for building high-field magnets. Of the superconductors that are relevant for magnet applications, low temperature superconductors (LTS), such as niobium-titanium (NbTi) and niobium-tin (Nb3Sn), have been demonstrated in magnet designs to deliver a field range up to 16 Tesla (T) for accelerator magnets and 23 T for solenoid magnets and at acceptable costs. However, the need to achieve even higher field ranges requires use of high temperature superconductors (HTS). Common HTS materials such as bismuth strontium calcium copper oxide (BSCCO) and rare-earth barium copper oxide (ReBCO) have achieved significant improvement in critical current density (Jc) in recent years, but the feasibility to build high-field accelerator magnets is still to be demonstrated due to some technical issues. The costs of current BSCCO and ReBCO superconductors are also much higher than LTS.
The emerging Iron-based superconductors (IBS) may hold promise for high-field magnet applications requiring field ranges beyond what LTS may provide. This relatively new type of superconductor has relatively high critical temperature (Tc), high upper critical field (Bc2), and low anisotropy y. For example, the 122-type Ba(Sr)1-xKxFezAs2 superconductors, which currently hold the highest γ, among all IBS, have Tc of up to 38 K, Bc2 larger than 100 T, and γ<2. Furthermore, these superconductors can be fabricated into multifilamentary wires using the simple powder-in-tube (PIT) technology. Such multifilamentary wires, compared with ReBCO conductors that are mainly available in coated tapes, are a preferred form for building magnets (particularly accelerator magnets), and can have lower persistent-current magnetization (such magnetization leads to undesirable field errors and AC loss). Compared with BSCCO conductors in which a high fraction (typically >70 vol. %) is pure (or nearly pure) silver, such IBS conductors can use other matrix materials (e.g., Cu), which leads to much lower cost and higher mechanical strength.
A preferred method for fabricating IBS wires based on the PIT technology is the ex-situ method, which uses already-formed IBS powders. For certain types of IBS wires (e.g., 122-type), silver (Ag) is a preferred sheath material contacting the IBS powders because other metals can react with the IBS powders during the subsequent heat treatment. However, use of only Ag as the sheath material is undesirable because (1) Ag is expensive, leading to high conductor cost, and (2) Ag is soft, making the conductors mechanically weak. A solution is to use a matrix material (e.g., copper, iron, monel, or other high-strength alloys) outside the Ag sheath. Pure Cu is preferred for the matrix because Cu has high electrical and thermal conductivities, which is important for the electromagnetic stability of conductors. Referring to
However, a problem with known IBS designs using Ag+Cu as sheath materials such as those illustrated 100, 200 in
Accordingly, a need exists for a solution to at least one of the aforementioned challenges in design and implementation of iron-based superconductors (IBS) for high-field magnet applications.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.
With the above in mind, embodiments of the present invention are related to bi-layer barrier assemblies for iron-based superconductor (IBS) and associated fabrication methods that may employ insulating material to prevent a reaction or interdiffusion between silver (Ag) and matrix components during heat treatments.
In one embodiment of the present invention, a superconductor assembly may comprise at least one IBS material (e.g., IBS powder), an Ag barrier material layered upon a respective outer surface of each filament of IBS material present, an insulating barrier material layered upon an outer surface of the Ag barrier material opposite the IBS material; and a matrix material layered upon an outer surface of the insulating barrier material opposite the Ag barrier material. The matrix material may be Cu or Cu alloy or monel. The IBS material may be of a mono-filamentary type or a multi-filamentary type. The insulating barrier material may comprise one or more of niobium (Nb), tantalum (Ta), and a Nb—Ta alloy. Such a barrier material may be ductile enough so that the assembly can be drawn/extruded/swaged/rolled from a big billet to wires/tapes with much smaller cross sections. The IBS material, the Ag barrier material, the insulating barrier material, and the matrix material may be configured as a sheathed wire having a fixed and substantially uniform cross-sectional profile such that the insulating material may be configured to prevent a reaction or interdiffusion between the Ag sheath material and the matrix material during heat treatments.
In a method aspect of the present invention, fabrication of bi-layer barrier assemblies for iron-based superconductor (IBS) according to certain embodiments of the present invention may comprise the steps of 1) packing at least one IBS material into an Ag sheath material, to define a packed first assembly; 2) layering an insulating material comprising at least one of Nb, Ta, and Nb—Ta alloy upon the Ag sheath material opposite the at least one IBS material, to define an insulated second assembly; and 3) layering a matrix material upon the insulating material opposite the Ag sheath material, to define a matrixed third assembly. The IBS material may be one of a mono-filamentary type and a multi-filamentary type and characterized by a (mono- or multi-) core radius less than one (1) mm. Similarly, each of the Ag sheath material, the insulating material, and the matrix material may be characterized by a respective thickness less than one (1) mm. Certain method aspects of the present invention may further comprise a respective extrusion/drawing/swaging/rolling step for one or more of the packed first assembly, the insulated second assembly, and/or the matrixed third assembly.
These and other objects, features, and advantages of the present invention will become more readily apparent from the attached drawings and the detailed description of the preferred embodiments, which follow.
The preferred embodiments of the invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the invention, where like designations denote like elements, and in which:
Like reference numerals refer to like parts throughout the several views of the drawings.
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
Although the following detailed description contains many specifics for the purposes of illustration, anyone of ordinary skill in the art will appreciate that many variations and alterations to the following details are within the scope of the invention. Accordingly, the following embodiments of the invention are set forth without any loss of generality to, and without imposing limitations upon, the claimed invention.
As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art to make or use the embodiments of the disclosure and are not intended to limit the scope of the disclosure, which is defined by the claims.
Furthermore, in this detailed description, a person skilled in the art should note that quantitative qualifying terms such as “generally,” “substantially,” “mostly,” and other terms are used, in general, to mean that the referred to object, characteristic, or quality constitutes a majority of the subject of the reference. The meaning of any of these terms is dependent upon the context within which it is used, and the meaning may be expressly modified.
Referring initially to
Referring more specifically to
Referring now to
A person of skill in the art will immediately recognize that the various assembly and drawing/extrusion/swaging/rolling steps described hereinabove may be accomplished in alternative order (e.g., complete assembly steps such as those at Blocks 514 and 518, in turn, followed by a single drawing/extrusion/swaging/rolling step such as Block 520 to make the assembled materials 310, 320, 330, 340 into an IBS wire 300) without departing from the scope of the invention. Furthermore, additional fabrication steps to address specific handling requirements due to respective properties of Nb, Ta, and/or other metals or malleable alloys that react with neither Ag nor the matrix material may complement the method described hereinabove without departing from the scope of the invention.
Some of the illustrative aspects of the present invention may be advantageous in solving the problems herein described and other problems not discussed which are discoverable by a skilled artisan.
While the above description contains much specificity, these should not be construed as limitations on the scope of any embodiment, but as exemplifications of the presented embodiments thereof. Many other ramifications and variations are possible within the teachings of the various embodiments. While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best or only mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items.
Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, and not by the examples given.
The invention described in this patent application was made with Government support under the Fermi Research Alliance, LLC, Contract Number DE-AC02-07CH11359 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/014471 | 1/30/2022 | WO |
