Composite electrically conductive structures

An electrically conductive structure including a substrate material and graphene. A first cross-section taken along an axial direction of the electrically conductive structure includes a plurality of layers of the substrate material and at least one internal layer of the graphene alternatingly disposed between the plurality of layers of the substrate material. A method of tailoring an amount of graphene in an electrically conductive structure is also included.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to electrically conductive structures and, in particular, to composite electrically conductive structures including graphene and a substrate material.

Wires and other electrically conductive structures are utilized to enable the transmission of power and/or electrical signals. Different operating conditions lead to different types or sizes of wires being used.

SUMMARY

According to one embodiment, an electrically conductive structure is disclosed. The electrically conductive structure includes a substrate material and graphene. A first cross-section taken along an axial direction of the electrically conductive structure includes a plurality of layers of the substrate and at least one internal layer of the graphene alternatingly disposed between the plurality of layers of the substrate material.

According to another embodiment, a method of tailoring an amount of graphene in an electrically conductive structure is disclosed. The method includes disposing graphene with a substrate material and arranging the graphene and the substrate material to form the electrically conductive structure such that a cross-section of the electrically conductive structure taken in a longitudinal direction of the electrically conductive structure includes a plurality of layers of the substrate material and at least one internal layer of the graphene disposed alternatingly between the plurality of layers of the substrate.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates generally to wires and other electrically conductive structures. These electrically conductive structures are arranged to enable the transmission of power and/or electrical signals. The electrically conductive structures comprise a composite of graphene and an electrically conductive substrate, such as copper, aluminum, nickel, steel, or another metal. Non metallic, electrically conductive substrates such as ceramics, plastics and glasses are also contemplated.

As used herein, graphene may refer specifically to a single atom-thick layer of carbon atoms arranged in a hexagonal pattern, and more generally to any combination of such atom-thick hexagonally patterned carbon layers disposed together, or a nanostructure made from one or more such layers, e.g., multilayered sheets, platelets or graphene nanotubes. While graphene is often praised for its low density, corrosion resistance, and high thermal and electrical conductivity, it is currently unfeasible to produce entire electrically conductive structures suitable for use in power and/or signal transmission, e.g., wires, solely from graphene. According to one embodiment, a substrate material (e.g. a wire or other electrically conductive element) can be included to provide structural integrity to the electrically conductive graphene structure. Graphene can be applied to a conductive substrate material in any known, desired, or discovered manner, such as vapor deposition, mechanical work, sintering substrate particles with graphene particles, combining, embedding, or distributing graphene layer portions or “chunks” into a bulk of liquid or molten substrate, etc.

Aircraft include a myriad of components that must be connected by electrically conductive structures capable of reliable and high load data and power transmission, and a copper or other conductive metal substrate wire or cable imbued with graphene will enable higher power loads and more efficient power transmission, which can in turn lead to performance enhancements, e.g., increased fuel economy, for the aircraft. For example, in the embodiment ofFIG. 6, the electrically conductive structures, e.g., as discussed below, are utilized to transmit power, data, and/or electrical signals within components of an aircraft100. For example, the aircraft100includes several components which may be in data, power, and/or signal communication with each other or other components of the aircraft100and connected by the electrically conductive structures disclosed herein.

Other devices, machines, and mechanisms can similarly benefit from composite structures. To this end, embodiments discussed herein involve the maximization of the amount of graphene and/or tailoring of the ratio of graphene to substrate material that can be achieved in an electrically conductive structure, e.g., in order to enable a balancing between the properties of the two materials. In one embodiment, the graphene is in an amount of about 5% to 40% per unit volume (and/or unit area with respect to a cross-section of the electrically conductive structure taken perpendicular to its axial or longitudinal direction (e.g., as shown inFIG. 1). In a further embodiment, the graphene is in an amount of about 15% to 30% per unit volume (and/or unit area as noted above), which provides a good balance of decreased power dissipation and structural or mechanical integrity in comparison to a conductive structure made solely from the substrate material.

FIG. 1illustrates one embodiment for an electrically conductive structure, which takes the specific form of a wire bundle10. The bundle10is shown in cross-section inFIG. 1, and it is to be appreciated that the wire bundle10can extend any desired longitudinal or axial length, e.g., in order to couple between two electric components for enabling power and/or data transmission therebetween. The wire bundle10is formed from a plurality of strands, wires, bars, rods, or fibers12(generally, the strands12) disposed with a coating, film, layer, or lamination14(generally, the coating14) at least partially thereon. The strands12are at least partially made of an electrically conductive substrate material, e.g., copper, aluminum, nickel, steel, etc., while the coating14is made of graphene or a graphene precursor that can be processed into graphene, e.g., graphene oxide. As used herein, “graphene” may generally refer to graphene in the forms discussed above as well as relatives and/or precursors to graphene, e.g., graphene oxide, which exhibit properties of graphene and/or can be processed into graphene.

In one embodiment each of the strands12, or selected ones of the strands12, are individually coated with the graphene coating14before arranging the strands12together to form the bundle10, while in another embodiment the strands12are first bundled together and then the graphene coating14is applied to the bundle. The strands12can take any desired dimension, e.g., milli-scale, micro-scale, nano-scale, etc. The strands12can be arranged longitudinally parallel to each other, intertwined, helixed or spiraled about each other or an axis, etc. In one embodiment, the strands12are made essentially entirely from an electrically conductive substrate material. In one embodiment, the bundle10is nano-scale with some of the strands12being individual nano-sized copper or other metal strands and others of the strands12being individual graphene nano-tubes or other graphene nano-structures. In one embodiment, the wire bundle10is additionally coated or disposed within a protective, non-conductive sheath or conduit. In one embodiment, the electrically conductive structure is formed as a ribbon of the strands12, e.g., by arranging the strands12adjacent to each other along an essentially straight line (instead of concentrically about an axis). Similarly, to the above, the individual ones of the strands12can be coated with the graphene coating14, or the ribbon can be so coated after arranging the strands12together.

FIGS. 2 and 3illustrate electrically conductive structures according to two additional embodiments. Specifically,FIG. 2illustrates a tube16formed from a sheet, foil, or plate18(generally, the sheet18) having a graphene coating, layer, film, or lamination20(generally, the coating20) disposed at least partially thereon, whileFIG. 3illustrates a wire, strand, or fiber22(generally, the wire22) similarly formed from the sheet18and the coating20. The coating20of graphene can be provided at least partially on one or both of the major surfaces of the sheet18. The sheet18is rolled, wrapped, or spiraled about a cavity24to form the tube16or tightly rolled or spiraled to form the wire20. It is to be appreciated that the sheet18, similar to the strands12, at least partially comprises a substrate material and can be any desired thickness, etc., milli-scale, micro-scale, nano-scale, etc. In one embodiment, a plurality of the sheets18and the coatings20are alternatingly stacked atop each other and then rolled to form a wire, tube, strand, fiber, etc. In one embodiment, one or more of the sheets18are arranged without rolling or wrapping, i.e., to form the electrically conductive structure as a ribbon.

A cross-section of a representative composite electrically conductive structure26is provided inFIG. 4to better describe various embodiments described herein. The cross-section is taken parallel to, or along, the longitudinal direction of the structure26(e.g., along the length of a wire, cable, etc. formed by the structure26). In cross-section the structure26includes alternating layers, laminas, or regimes (generally layers) of graphene represented with the base numeral28, and of substrate material represented with the base numeral30. Alphabetic identifiers ‘a’ and ‘b’ are used with the base numerals28to identify different types of the graphene layers28. Namely, the graphene layers28include two exterior layers28a, and two internal layers28b. By internal layer, it is meant that the layers28bare sandwiched, flanked by, or disposed between two of the layers30.

The structure26as illustrated inFIG. 4can generally represent any of the wire bundle10, tube16, wire22, or structures according to other embodiments, e.g., as taken along the lines4-4inFIGS. 1-3, respectively. For example, in one embodiment the structure26represents the wire bundle10, with the graphene layers28representing the coating14and the substrate layers representing the strands12. In one embodiment, the structure26represents the tube16and/or the wire22, with the graphene layers28representing the coating20and the substrate layers30representing the overlapping turns of the sheet18to form the tube16and/or the wire22. It is noted that each of these embodiment includes a plurality of the graphene layers28alternatively arranged with and/or between a plurality of the substrate layers30. This alternating arrangement results in one or more of the internal graphene layers28b. Advantageously, providing at least one of the internal graphene layers28benables the electrically conductive structure26to exhibit a higher ratio of graphene to substrate material than if only the exterior layers28a, e.g., just an exterior coating, was included.

It is also to be appreciated that the ratio of graphene to the substrate material can be further tailored as desired. For example, there will be greater ratio of graphene to the substrate material if each of the strands12is individually coated by the graphene coating14while forming the bundle10than if only a few selected ones of the strands12are so coated. Similarly, the diameter, cross-sectional width, thickness, or other dimensions of the strands12and/or the sheet(s)20can be altered to change the number of the layers28and30and/or their relative amounts. Additionally, properties of the bundle10, the tube16, and/or the wire22can be altered to enable tailoring of the graphene to substrate ratio, such as the number of turns used to make the tube16and/or the wire22, the number of strands12in the bundle10, the composition of the strands12and/or the sheets18, (e.g., as discussed herein, the strands12and the sheets18can be formed by structures including both graphene and the substrate material).

In order to set the dimensions of the wire bundle10, the strands12, the tube16, the sheet(s)20, the wire22, etc. (collectively, the structure26) e.g., to create a suitably dimensioned cable or wire for power and/or data transmission, the structure26can be first assembled as noted above, and then drawn, pressed, urged, or forced through a die. For example, as illustrated inFIG. 5, the bundle10has a first dimension D1that is reduced to a second dimension D2by compressing the strands12together as the bundle10passes through a die32. It is to be appreciated that the die32can include or be replaced by other rams, dies, presses, rollers, etc. for changing the dimensions, including the shape, of the bundle10. The other structures26(e.g., the strands12, the tube16, the sheet(s)20, the wire22, etc.) can be similarly processed with the die32in order to change the dimensions of the structures26.

In addition to setting the desired dimensions of the bundle10for use in a power or signal transmission cable or the like, compression of the layers28and/or30(e.g., the strands12and/or the coating14, turns of the sheet(s)20and/or the coating22, etc.) together may also improve the mechanical properties of the structure26(e.g., of the wire bundle10, the tube28, the wire22, etc.) and/or the bond between the graphene and the substrate material. Additionally, drawing the structure26can be used to assist in tailoring or setting the ratio of graphene to the substrate material. That is, the graphene coating14may not compress as readily as the substrate material, e.g., particularly if the graphene is disposed as a single atom-thick layer. In this way, the bulk of the change from the dimension D1to the dimension D2can be borne by substrate material. Additionally, as particularly useful for various embodiments below, the dimensions of the structures26can be reduced, which structures can then be utilized to create further electrically conductive structures.

In one embodiment the wires22are arranged in a bundle, effectively replacing the strands12in the bundle10. The wires22in this modified bundle, in addition to have the internal alternating spiraled pattern of graphene and substrate, can be further coated with graphene, as noted above with respect to the strands12, or a bundle of the wires22can be so coated in graphene. In one embodiment, one of the bundles10, wires22, strands12, etc. are arranged as a core filling the cavity24of the tube16. In one embodiment, multiple ones of the bundles10are formed and bundled together to form a yet larger bundle, e.g., essentially replacing the strands12in the arrangement ofFIG. 1to form a new, larger bundle, from a plurality of smaller bundles. For example, a plurality of individual nano-strands of substrate and graphene can be arranged in plurality of bundles, which are then bundled together to form a micro-scale bundle, and so on.