Patent Application
20230307154
The disclosed teachings relate to metal composites for busbar applications.
In electric power distribution, busbars are metallic strips or bars, typically housed inside switchgears, panel boards, and busway enclosures for local high current power distribution. They are also used to connect high voltage equipment at electrical switchyards, and low voltage equipment in battery banks. They are generally uninsulated and have sufficient stiffness to be supported in air by insulated pillars. These features allow sufficient cooling of busbar conductors, and the ability to tap into a conductor at various points without creating a new joint.
The material composition and cross-sectional size of a busbar determines a maximum amount of current that can be safely carried. Busbars can have a cross-sectional area of as small as 10 square millimeters (mm2), but electrical substations may use metal tubes about 50 mm in diameter (or about 2,000 mm2) or more as busbars.
Busbars are produced in a variety of shapes, such as flat strips, solid bars, or rods, and are typically composed of copper, brass, or aluminum (Al). Some of these shapes allow heat to dissipate more efficiently due to their high surface area to cross-sectional area ratio. The skin effect makes 50-60 Hz AC busbars inefficient when greater than about 8 mm thick; accordingly, hollow or flat shapes are prevalent in higher-current applications. A hollow section also has higher stiffness than a solid rod of equivalent current-carrying capacity, which allows for a greater span between busbar supports in outdoor electrical applications.
One or more embodiments of the present disclosure are illustrated by way of example and not limitation in the Figures of the accompanying drawings, in which like references indicate similar elements.
The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts that are not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying embodiments.
In electric power distribution, a busbar is a metal strip or bar for local high current power distribution.
Efficiently mounting and connecting electrical components in vehicles is of growing importance and, for this purpose, wires, cables, and busbars are commercially used to distribute power to the vehicles' various subsystems. In an HEV/EV battery module connection assembly, connectors preferably have high strength, conductivity (e.g., thermal, electrical) and thermal stability. Standard current carrying capacity for Al is around 0.7 A/mm2, which is sufficient for use in connecting the battery module in HEVs/EVs. The electrical power requirements of HEVs/EVs continue to increase each year, and therefore the need for efficient connections is also increasing. However, merely increasing the number or cross-sectional size of busbars to meet the rising demand goes against goals of reducing weight and costs.
Commercially available Al alloys are not ideal substitutes for Cu in busbar applications, as they do not possess the necessary combination of properties such as strength, electrical conductivity, creep resistance, thermal stability, etc. For example,
The disclosed embodiments include busbars and related products made of an Al-based metal matrix composite (MMC) comprising particles that are not soluble in the α Al phase, which offer a significant amount of strengthening and creep resistance. More particularly, the disclosed technology relates to aluminum carbon (Al-C) MMCs for electrical busbar applications. In one example, an MMC includes an Al matrix with carbon nanotubes (CNTs) distributed therein. A CNT is a molecular-scale structure consisting of carbon (C) atoms arranged in one or more cylindrical layers (e.g., single-walled, multi-walled), joined by covalent bonds in a hexagonal tiling or other geometric pattern within each layer, so as to form a hollow tube having a diameter of up to a few hundred nanometers. Carbon nanotubes are considered to be allotropes of carbon, intermediate between fullerene cages and flat graphene sheets (as in graphite).
An Al-C MMC has many advantages for electrical busbar applications. The disclosed MMCs demonstrate desirable strength, thermal stability, and creep resistance while maintaining electrical conductivities near that of pure aluminum. Use of MMCs in busbar applications could allow for improved ampacity for a given busbar cross sectional area, as the high thermal stability can allow for increased operational temperature. This could enable weight reduction through a decrease of busbar dimensions, or if the busbar size remains constant, it could allow for a higher peak current draw without causing structural or performance issues. In addition, the creep resistance of the MMC could help reduce complications associated with connections between busbars and other electrical components. While these busbars could be used in any industry, emphasis is placed in this disclosure on the potential benefits for the automotive industry.
The busbar can have an electrical conductivity greater than 50% International Annealed Copper Standard (IACS), an ultimate tensile strength (UTS) greater than 80 MPa, and an elongation greater than 10%. In one example, a busbar has a conductivity greater than 50%, or greater than 55%, or greater than 58% IACS, a UTS greater than 120 MPa, and an elongation greater than 30%. However, the busbar can have properties in other ranges. In another example, the busbar has a conductivity greater than 50%, or greater than 55%, or greater than 58% IACS, a UTS greater than 200 MPa, and an elongation greater than 1%. In another example, the busbar has a conductivity greater than 50%, or greater than 55%, or greater than 58% IACS, a UTS greater than 300 MPa, and an elongation greater than 3%.
The Al-MMC material can be pure Al, or it can be an Al alloy containing metallic elements other than Al. Preferably, the Al matrix is pure Al or an Al alloy having an electrical conductivity of at least 50% IACS, for example, wrought alloys of the 1XXX series, having a minimum Al content of 99%. Al alloys in the other wrought alloy series from 2XXX-7XXX may be suitable, provided they have conductivity of 50% IACS or above. Al alloys of other non-commercial compositions may also be suitable. For example, an aluminum-scandium (Al—Sc—X) alloy having Sc and optionally other elements such as zirconium (Zr), erbium (Er), and/or ytterbium (Yb), having conductivity of greater than 50% IACS, is suitable. As used herein, the terms “Al-C,” “Al-CNT,” and “Al-CNT MMC” may refer to an MMC of pure Al or an Al alloy, with C or CNT particles distributed in the matrix.
In a soft condition, such as after extrusion at high temperatures, a 2×20 mm rectangular Al-0.5 wt % CNT MMC busbar can have a desirable combination of tensile and electrical properties, with UTS of about 120 MPa, elongation of about 30%, and electrical conductivity of greater than 50%, or greater than 55%, or greater than 58% IACS. These examples have improved creep behavior (e.g., minimal creep after 500 hours (hr) at 80% of yield strength and 150° C.). Moreover, cracking is not observed in 180 degree flatwise bend tests of Al-0.5 wt % CNT busbars that have CNT more evenly distributed throughout the matrix of the MMC.
In some embodiments, cold working the Al-0.5 wt % CNT MMC has minimal impact on electrical conductivity and the tensile strength can increase significantly while the elongation can decrease. A greater UTS of about 335 MPa can be observed, although there is no indication that this value is an upper limit to the strength that can be achieved with the disclosed method. The elongation remains at about 4% for all cold worked examples. The strength that is achieved through cold working can be thermally stable, as described for material type AT4 in International Standard IEC 62004 “Thermal-resistant aluminium alloy wire for overhead line conductor,” after an initial stress relaxation heat treatment. According to the standard, to qualify as type AT4, an Al alloy wire must retain 90% of its initial tensile strength after undergoing heat treatment at 310° C. for 400 hours, or at 400° C. for 1 hour.
For example, for an Al-0.5 wt % CNT MMC with an initial as-drawn tensile strength of 335 MPa, heat treatment at 325° C. for 1 hr will typically reduce the strength by about 30 MPa to a thermally stable condition, e.g., with a UTS of ˜305 MPa. Subsequently, heat treatment at either 310° C. for 400 hours or at 400° C. for 1 hour will result in a reduction in UTS of less than 10%. Therefore, heat treated material meets the requirements for type AT4 according to the IEC 62004 standard.
A significant factor in the effectiveness of Al-C MMC is the distribution of the nanoscale carbon particles within the MMC. For example, if CNTs are present in an Al matrix as aggregates greater than, for example, 10 microns wide, a large fraction of the CNTs in an Al-CNT MMC can be wasted in terms of not contributing to an increase in the strength of the matrix. The fabrication of Al-CNT MMCs with an even distribution of CNT, and in a manner conducive to large scale manufacturing, remains a major hurdle to the wide-scale application of these materials. With the solution disclosed herein, CNT distribution and therefore the properties of an Al-CNT MMC with an initially poor CNT distribution are improved by solid-state deformation in accordance with extrusion processing, ECAP, etc. Examples described herein have improved strength, thermal stability, creep resistance, and bending behavior.
In general, a small addition of well-distributed nanoscale carbon particles (e.g., CNTs) to Al provides for an increased tensile strength while maintaining a substantially similar electrical conductivity, modulus of elasticity, and coefficient of thermal expansion compared to substantially pure aluminum. Nanoscale particles can be broadly defined as particles that have at least one critical dimension less than 100 nanometers and possess unique optical, magnetic, or electrical properties. Nanoscale carbon particles are nanoscale particles composed primarily of carbon, such as CNT, graphene, fullerenes, nanodiamonds, and the like.
Further, in general, an Al-CNT MMC product gains its tensile strength through work and dispersion hardening. For example, during cold working by rolling and/or drawing of extruded material to a final size, the grain structure is refined, and CNT disperses more evenly in the matrix. While the tensile strength of Al-CNT increases with CNT content, the electrical conductivity slightly decreases. From that perspective, a preferred concentration is between about 0.01 to 2 weight percent (wt %), such as between 0.1 to 1 wt %, or between 0.2 to 0.8 wt %, or between 0.25 to 0.75 wt %, or between 0.4 to 0.6 wt %, or about 0.5 wt % CNT, with which the MMC maintains an electrical conductivity of greater than 50%, or greater than 55%, or greater than 58% IACS, while substantial gains in UTS can be achieved.
In the case of an Al-CNT MMC rod or wire, the effect of cold work through drawing from an initial extruded diameter to a final diameter is illustrated by the following relationship:
where A and B are constants that depend on an amount of CNT. This equation can be used to calculate the initial extrusion diameter, Di of an Al-CNT rod that is needed in order to achieve a desired UTS and final diameter, Df of an extruded and drawn wire. For a matrix consisting of 1070 Aluminum (Al99.7) combined with a 0.5 wt % CNT, constants A and B were found to be about 145 and about 60, respectively.
In particular, the electrical conductivity of conductor grade Al such as AA 1350 is 61.2 to 61.8% IACS, and its strength is low as compared to Cu. As described above, the addition of alloying elements to Al increases the strength (e.g., 2xxx, 5xxx, 6xxx and 7xxx series alloys) but typically reduces the conductivity. The thermal stability of Al alloys is low, as the strengthening particles used in commercially available alloys have relatively high mobility in the Al matrix. Because of this, Al alloys are typically not used for applications that see temperatures greater than about 150° C. However, as indicated above, Al-CNT MMCs provide high mechanical strength and thermal stability for temperatures greater than about 150° C. without a significant loss of electrical conductivity.
The disclosed technology can thus provide advancements over pure Al and Al alloy busbars with improved electrical conductivity, strength, usage temperatures, and creep resistance, particularly in the automotive industry. Examples in the automotive industry that can benefit from the disclosed technology include busbars that connect individual cells in a battery pack, connect multiple battery packs, and connect battery packs to motor inverters and other electrical components. Some busbars are used in parts of the vehicle that see elevated temperatures. The busbars can be simple straight connections between two or more components, or they can have complex geometries to navigate through tightly packed areas of the vehicle. These busbars are typically tin-plated copper and are good examples of busbars that could be replaced with the Al-CNT MMCs discussed herein. Because of this, ideal Al MMCs for busbars are capable of both being formed into complex shapes without forming cracks and being strong enough to maintain those shapes throughout the life cycle of the busbar.
Al MMCs that are reinforced with CNTs provide high specific strength and have excellent thermal/electrical properties. The quantity of CNT used and its distribution in the Al matrix are key parameters to reach a maximum strength of the Al-CNT composite. For example, it has been observed that an MMC with a lower concentration of CNT (0.1 wt %) and uniform dispersion in the matrix, can have higher strength than similarly-prepared MMCs with relatively higher concentrations of CNT (0.25-1.0 wt %) but with poor dispersion and large aggregates in the matrix.
To produce an Al busbar with desirable strength, thermal stability, and creep resistance, without significantly reducing the electrical conductivity below that of pure Al, it is beneficial to create a fine dispersion of strengthening particles surrounded by an a Al matrix that is relatively devoid of solute atoms. To achieve this result, MMC additions that have no significant solubility in a-Al should be used. As carbon has no reported solid solubility in Al and can be produced in several nanoscale structures, it is an ideal candidate as an addition for Al-based MMC busbars for electrical power distribution applications. Examples of suitable nanoscale particles in addition to CNTs include graphene nanoplatelets (GNPs), fullerenes (e.g., form of carbon having a large spheroidal molecule consisting of a hollow cage of atoms), and nanodiamonds (e.g., a diamond particle with dimensions of only a few nanometers).
To achieve the greatest benefit from nanoscale carbon particle additions, an even distribution of the particles throughout the MMC is preferred. Depending on the desired scale of production and the form of carbon used, an even distribution can be accomplished in several ways. For example, adding carbon particles to an Al melt and casting the MMC is one approach, although care must be taken to avoid segregation or burning of the carbon addition. A second method is to use powder metallurgy techniques to evenly mix and sinter Al and nanoscale carbon powders together into a solid billet. A third method involves mechanical stirring of nanoscale carbon particles into an Al matrix through solid state processing techniques such as friction stir processing, ECAP, extrusion, etc.
The resulting busbar has a carbon particle (e.g., CNT) concentration that is evenly distributed over the entire volume of the busbar. That is, there are no significant irregular voids or irregular empty spaces between carbon particles, the carbon particles are not aggregated (or any aggregations are negligible), and there are no areas of higher or lower concentrations of carbon particles throughout the entire busbar. The amount of carbon particles in a matrix is essentially the same in all portions of the matrix volume, i.e., there are no portions within the Al-MMC composite that have a distinct difference, i.e., more than 20%, 10%, or preferably 5% difference, in carbon particle concentration from any other portion.
In one example, the resulting busbar has a uniform density that is non-porous. For example, the density may deviate by 2% at most from a theoretical composite density, which can be calculated based on the volume of the material, the relative amounts of Al and carbon particles, and their respective densities. The even carbon particle concentration of a sample Al-C MMC provides consistent and uniform characteristics such as uniform conductance throughout the entire volume of the busbar. The uniform distribution of carbon particles in a sample Al-C MMC busbar can be verified by high resolution microscopy.
Whichever technique is used to produce the Al-C MMCs, the final amount of residual stress from processing will have an impact on the resulting strength and elongation of the MMC. For busbar applications that require significant elongation, such as those requiring bending of the busbar to achieve a specific geometry for installation, care should be taken to achieve a final condition that is relatively free of residual stresses. One method to achieve a final condition suitable for this application is through annealing of a busbar at high temperatures to relieve residual stresses after any necessary cold working procedures are performed. Another method is to initially produce the busbar with the desired final dimensions and geometry using a process that runs at elevated temperatures (e.g., casting, extrusion) to limit an occurrence of residual stresses. If a higher strength is desired and the elongation is of less importance, residual stresses through the application of cold work or the like are a viable way to increase the strength.
The disclosed embodiments include a method to produce Al MMC busbars containing small amounts e.g., (0.01-2 wt %) of nanostructure additions such as CNTs, GNPs, fullerenes, and/or nanodiamonds. Production of these busbars can be accomplished with several processing techniques, including some or all of the following processes.
Initial preparation of the Al-C MMC busbar could be made by a casting process. However, there could be challenges associated with this method. For example, a primary concern is that the carbon may separate from the molten Al and float to the surface of the melt. Furthermore, the nanoscale carbon particle additions will burn at liquid Al temperatures if oxygen is available. One offsetting factor to the latter point is that liquid Al aggressively forms Al2O3 in the presence of O2, so the danger of burning the carbon additions is reduced.
However, aluminum carbide may be formed instead, which can significantly degrade the mechanical and electrical properties of the Al-C MMC.
Powder metallurgy techniques are currently a common way to produce Al-C MMC material. This approach typically involves some combination of mixing Al and nanoscale carbon powders together, ball milling the powders, compacting the powder mixture, and/or sintering the material into a high-density product. Powders can be mixed in a dry condition or as part of a slurry, in which case the solvent of the slurry should be evaporated before compaction/sintering. Care should be taken when handling fine powders as they may be combustible, depending on the chemical composition. For example, according to The Aluminum Association and National Fire Protection Agency (NFPA) standard #484 “Standard for Combustible Metals, Metal Powders, and Metal Dusts,” aluminum powders with a particle size of 40 mesh (420 micrometers) or smaller can present a fire or explosion hazard.
Extrusion can be used to accomplish several objectives in the production of Al-C MMC busbars. The most basic of these objectives is to produce specific shapes and dimensions of an extruded product. These dimensions may coincide with the target final dimensions for the busbar in the case that more value is placed on elongation rather than strength of the busbar, or the dimensions may be oversized in the case that cold working (rolling, etc.) is employed to increase the strength while decreasing the cross-sectional area down to the target busbar dimensions.
In addition to geometric objectives such as size and shape, extrusion with the proper tooling and parameters can be used to increase homogeneity of carbon additions in poorly homogenized Al-C feedstock that was produced by other means. Using this technique to increase the homogeneity of Al-C MMCs can result in a significant improvement of performance in terms of strength, thermal stability, etc. Depending on the extrusion process used, feedstock material can be in the form of Al-C rods, bars, granules, compacted powder billets, etc., and multiple passes through the extrusion process can be employed to further improve homogeneity if needed.
Rolling and related processes can be performed on Al-C MMCs to achieve the target size and dimensions for a busbar specification. This process can be performed at room temperature but it can also be performed at elevated temperatures (e.g., hot rolling) to relieve internal stresses if high elongation in the final busbar is desired, as the residual stresses from cold working the busbar will generally reduce elongation and increase strength. Alternatively to hot rolling, a heat treatment can be applied after cold rolling as a method to relieve residual stresses after production.
Bending and forming can be performed on a busbar to achieve useful shapes for use within an automobile. Bending can include flatwise bending, edgewise bending, twisting, etc. The ease of bending and forming processes will be dependent on the structure and amount of carbon included in the MMC, as well as the grain size and amount of residual stress present in the busbar at the time of bending. For optimal bending capability of any specific Al-C MMC, care should be taken to minimize residual stresses at the time of bending, by either avoiding cold working by fabricating the MMC as a near net shape object, or by annealing at a high enough temperature to relieve stresses accumulated during cold working procedures. However, if strengthening provided by the residual stresses is necessary for the properties of a final busbar application, minor bending can still be performed with little or no annealing. When setting up a new busbar bending application with Al-C MMC materials, it can be important to investigate the resulting bends for cracks and, if found, adjust the amount of annealing to relieve additional stresses and increase the elongation of the material, so that such cracking is avoided.
In one example, conductivity of as-extruded Al-0.5 wt % CNT MMC, measured on round wire samples produced in several different production runs, has been measured to be consistently greater than 58% IACS.
Al-0.5 wt % CNT busbars of the disclosure can show total displacement of less than about 5%, or less than 4%, or less than 3%, or less than 2%, or less than 1%, when creep tested for 100 hours at 150° C. with a sample load equivalent to 80% of their room-temperature yield strength. In some embodiments, the MMC busbars can show total displacement of less than about 5%, or less than 4%, or less than 3%, or less than 2%, or less than 1%, when creep tested for 500 hours under the same conditions.
Based on these data, strengths as high as about 335 MPa were observed in the Al-0.5 wt % CNT MMC with a sufficient cold working area reduction. In contrast, pure Al wire initially increased in strength with cold work but at a somewhat reduced rate compared with the MMC. Moreover, the UTS of the pure Al wire reached a plateau at about 140 MPa. The elongation of the MMC stays consistent at 3-5% at all levels of cold working. This behavior does not change significantly when using this material for busbar applications rather than wire. As an alternative to area reduction, processes that apply internal stresses without changing the cross-sectional area (ECAP, etc.) could be used to increase strength in busbars that were initially produced at or near final target dimensions.
In the example, electrical conductivity of drawn Al-CNT wires is observed to be in a similar range as wires before cold working is applied, at greater than 58% IACS.
To assess the thermal stability of Al-C MMC products, heat treatments for AT4 classification (the highest classification of thermal stability described in specification IEC 62004, “Thermal-resistant aluminum alloy wire for overhead line conductor”) are applied to drawn Al-0.5 wt % CNT wires with two different levels of applied cold work (85% and 98% reduction in cross sectional area). To qualify for AT4 thermal stability, the wires must maintain over 90% of their UTS after being held at either 310° C. for 400 hours, or at 400° C. for 1 hour.
As shown, there is improvement in CNT distribution after applying a compounding extrusion process to the material. These cross-sectional micrographs show an Al-0.5 wt % CNT MMC busbar with high levels of undesirable CNT agglomeration before (CNT MMC 800) and low levels of undesirable CNT agglomeration after (CNT MMC 802) an added extrusion process to achieve an even distribution of CNT. The visible black spots are CNT aggregates, and the notable decrease in the size and number density of these spots after the compounding extrusion process indicates that the process broke up the aggregates and evenly distributed the CNT. Carbon concentration measurements verified that the carbon content of these MMCs remained unchanged by this processing and, as such, the same quantity of CNT is expected to be present in both.
In some embodiments, it is desirable in Al-CNT MMCs for the number of aggregates or particles to be minimized, and for existing aggregates to be as small as possible. The presence of fewer and smaller aggregates indicates that CNT are better distributed within the Al matrix, and can provide more benefit in terms of mechanical properties and thermal stability. It is possible to roughly correlate the statistical distribution of CNT aggregates in an Al-CNT MMC with the extent of improvement in these properties.
In particular, plot 900 of
The reduction in size and density of large CNT aggregates results in a more even distribution of the CNT within the Al matrix, providing substantial benefits to the mechanical properties and thermal stability of the composite. An even distribution can be defined by the overall area fraction or percent of CNT aggregates but also depends on the total CNT content in the MMC.
Thus, in one example, an Al-CNT MMC having an even distribution of CNT contains ˜0.5 wt % CNT and exhibits a CNT aggregate area percent of <0.38% for aggregates of average diameters ˜1 μm or greater. The aggregate area percent of said Al-CNT MMC is preferably <0.20%, and more preferably <0.10%, for aggregates of average diameter ˜1 μm or greater.
In addition to the aforementioned benefits, achieving even distribution of CNT within Al-CNT MMCs can increase thermal stability. For example,
As a consequence of having internal regions where grains are free to grow without obstruction, the thermo-mechanical properties of an Al-0.5 wt % CNT sample 1100 with poorly dispersed CNT are significantly less thermally stable than the thermo-mechanical properties of an Al-0.5 wt % CNT sample 1102 with evenly distributed CNT. For example,
More specifically, the plots in
The disclosed embodiments include a busbar configured for electrical power distribution applications (e.g., an automotive application). The busbar can include an Al-MMC that has a concentration (e.g., amount) of nanoscale carbon particles. The concentration of the nanoscale carbon particles can be in a range of 0.01 to 2 weight percent (wt %), such as of 0.1 to 1 wt %, or such as of 0.2 to 0.8 wt %, or such as of 0.25 to 0.75 wt %, or such as of 0.4 to 0.6 wt %. The nanoscale carbon particles are evenly dispersed throughout an entirety of the Al-MMC.
The nanoscale carbon particles can include single-walled carbon nanotubes (CNTs), multi-walled CNTs, graphene nanoplatelets (GNPs), fullerenes, nanodiamonds, and/or nanoparticles with predominantly sp2 or sp3 carbon. In one example, the nanoscale carbon particles include a mixture of particles selected from the group consisting of CNTs, GNPs, fullerenes, nanodiamonds, and nanoparticles with predominantly sp2 or sp3 carbon.
In one example, the busbar can have a conductivity greater than 50% International Annealed Copper Standard (IACS), an ultimate tensile strength (UTS) greater than 80 MPa, and an elongation greater than 10%. For example, the busbar can have a conductivity greater than 50%, or greater than 55%, or greater than 58% IACS, a UTS greater than 120 MPa, and an elongation greater than 30%. Other ranges include a conductivity greater than 50%, or greater than 55%, or greater than 58% IACS, a UTS greater than 200 MPa, and an elongation greater than 1%. In yet another example, the busbar has a conductivity greater than 50%, or greater than 55%, or greater than 58% IACS, a UTS greater than 300 MPa, and an elongation greater than 3%.
The disclosed embodiments also include a process for achieving an even distribution of nanoscale carbon particles in an MMC component (e.g., an Al-C MMC busbar). The process can include obtaining an MMC feedstock material comprising a metal matrix and nanoscale carbon particles and processing the MMC feedstock material through a solid-state deformation process. As such, the MMC component can have an even distribution of the nanoscale carbon particles at a concentration range of 0.01 to 2 wt %, for example. Examples of the solid-state deformation process include an extrusion process and/or an ECAP process.
From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the scope of the invention.
This application claims priority to and is a 35 U.S.C. § 111(a) continuation of PCT International Application No. PCT/US2021/072493 filed on Nov. 18, 2021, incorporated herein by reference in its entirety, which claims priority to, and the benefit of, U.S. Provisional Application No. 63/115,861 filed on Nov. 19, 2020, incorporated herein by reference in its entirety. Priority is claimed to each of the foregoing applications.
| Number | Date | Country | |
|---|---|---|---|
| 63115861 | Nov 2020 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2021/072493 | Nov 2021 | US |
| Child | 18319412 | US |
