Patent Publication Number: US-9903017-B2

Title: Composite electrically conductive structures

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. Ser. No. 13/915,038, filed Jun. 11, 2013, the contents of which are incorporated by reference herein in their entirety. 
    
    
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a cross-sectional view of an electrically conductive structure in the form of a wire bundle taken generally perpendicular to a longitudinal or axial direction of the electrically conductive structure; 
         FIG. 2  is a perspective view of an electrically conductive structure in the form of a tube; 
         FIG. 3  is a perspective view of an electrically conductive structure in the form of a wire; 
         FIG. 4  is a cross-sectional view of a representative electrically conductive structure taken generally in a longitudinal direction of the electrically conductive structure, and generally represents each of the electrically conductive structures of  FIGS. 1-3  taken along the lines  4 - 4  in those Figures; 
         FIG. 5  schematically illustrates a process of changing at least one dimension of the electrically conductive structure of  FIG. 1 ; and 
         FIG. 6  schematically illustrates an aircraft employing electrically conductive structures according to embodiments disclosed herein. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     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 of  FIG. 6 , the electrically conductive structures, e.g., as discussed below, are utilized to transmit power, data, and/or electrical signals within components of an aircraft  100 . For example, the aircraft  100  includes several components which may be in data, power, and/or signal communication with each other or other components of the aircraft  100  and 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 in  FIG. 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. 1  illustrates one embodiment for an electrically conductive structure, which takes the specific form of a wire bundle  10 . The bundle  10  is shown in cross-section in  FIG. 1 , and it is to be appreciated that the wire bundle  10  can 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 bundle  10  is formed from a plurality of strands, wires, bars, rods, or fibers  12  (generally, the strands  12 ) disposed with a coating, film, layer, or lamination  14  (generally, the coating  14 ) at least partially thereon. The strands  12  are at least partially made of an electrically conductive substrate material, e.g., copper, aluminum, nickel, steel, etc., while the coating  14  is 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 strands  12 , or selected ones of the strands  12 , are individually coated with the graphene coating  14  before arranging the strands  12  together to form the bundle  10 , while in another embodiment the strands  12  are first bundled together and then the graphene coating  14  is applied to the bundle. The strands  12  can take any desired dimension, e.g., milli-scale, micro-scale, nano-scale, etc. The strands  12  can be arranged longitudinally parallel to each other, intertwined, helixed or spiraled about each other or an axis, etc. In one embodiment, the strands  12  are made essentially entirely from an electrically conductive substrate material. In one embodiment, the bundle  10  is nano-scale with some of the strands  12  being individual nano-sized copper or other metal strands and others of the strands  12  being individual graphene nano-tubes or other graphene nano-structures. In one embodiment, the wire bundle  10  is 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 strands  12 , e.g., by arranging the strands  12  adjacent to each other along an essentially straight line (instead of concentrically about an axis). Similarly, to the above, the individual ones of the strands  12  can be coated with the graphene coating  14 , or the ribbon can be so coated after arranging the strands  12  together. 
       FIGS. 2 and 3  illustrate electrically conductive structures according to two additional embodiments. Specifically,  FIG. 2  illustrates a tube  16  formed from a sheet, foil, or plate  18  (generally, the sheet  18 ) having a graphene coating, layer, film, or lamination  20  (generally, the coating  20 ) disposed at least partially thereon, while  FIG. 3  illustrates a wire, strand, or fiber  22  (generally, the wire  22 ) similarly formed from the sheet  18  and the coating  20 . The coating  20  of graphene can be provided at least partially on one or both of the major surfaces of the sheet  18 . The sheet  18  is rolled, wrapped, or spiraled about a cavity  24  to form the tube  16  or tightly rolled or spiraled to form the wire  20 . It is to be appreciated that the sheet  18 , similar to the strands  12 , 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 sheets  18  and the coatings  20  are alternatingly stacked atop each other and then rolled to form a wire, tube, strand, fiber, etc. In one embodiment, one or more of the sheets  18  are 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 structure  26  is provided in  FIG. 4  to better describe various embodiments described herein. The cross-section is taken parallel to, or along, the longitudinal direction of the structure  26  (e.g., along the length of a wire, cable, etc. formed by the structure  26 ). In cross-section the structure  26  includes alternating layers, laminas, or regimes (generally layers) of graphene represented with the base numeral  28 , and of substrate material represented with the base numeral  30 . Alphabetic identifiers ‘a’ and ‘b’ are used with the base numerals  28  to identify different types of the graphene layers  28 . Namely, the graphene layers  28  include two exterior layers  28   a , and two internal layers  28   b . By internal layer, it is meant that the layers  28   b  are sandwiched, flanked by, or disposed between two of the layers  30 . 
     The structure  26  as illustrated in  FIG. 4  can generally represent any of the wire bundle  10 , tube  16 , wire  22 , or structures according to other embodiments, e.g., as taken along the lines  4 - 4  in  FIGS. 1-3 , respectively. For example, in one embodiment the structure  26  represents the wire bundle  10 , with the graphene layers  28  representing the coating  14  and the substrate layers representing the strands  12 . In one embodiment, the structure  26  represents the tube  16  and/or the wire  22 , with the graphene layers  28  representing the coating  20  and the substrate layers  30  representing the overlapping turns of the sheet  18  to form the tube  16  and/or the wire  22 . It is noted that each of these embodiment includes a plurality of the graphene layers  28  alternatively arranged with and/or between a plurality of the substrate layers  30 . This alternating arrangement results in one or more of the internal graphene layers  28   b . Advantageously, providing at least one of the internal graphene layers  28   b  enables the electrically conductive structure  26  to exhibit a higher ratio of graphene to substrate material than if only the exterior layers  28   a , 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 strands  12  is individually coated by the graphene coating  14  while forming the bundle  10  than if only a few selected ones of the strands  12  are so coated. Similarly, the diameter, cross-sectional width, thickness, or other dimensions of the strands  12  and/or the sheet(s)  20  can be altered to change the number of the layers  28  and  30  and/or their relative amounts. Additionally, properties of the bundle  10 , the tube  16 , and/or the wire  22  can be altered to enable tailoring of the graphene to substrate ratio, such as the number of turns used to make the tube  16  and/or the wire  22 , the number of strands  12  in the bundle  10 , the composition of the strands  12  and/or the sheets  18 , (e.g., as discussed herein, the strands  12  and the sheets  18  can be formed by structures including both graphene and the substrate material). 
     In order to set the dimensions of the wire bundle  10 , the strands  12 , the tube  16 , the sheet(s)  20 , the wire  22 , etc. (collectively, the structure  26 ) e.g., to create a suitably dimensioned cable or wire for power and/or data transmission, the structure  26  can be first assembled as noted above, and then drawn, pressed, urged, or forced through a die. For example, as illustrated in  FIG. 5 , the bundle  10  has a first dimension D1 that is reduced to a second dimension D2 by compressing the strands  12  together as the bundle  10  passes through a die  32 . It is to be appreciated that the die  32  can include or be replaced by other rams, dies, presses, rollers, etc. for changing the dimensions, including the shape, of the bundle  10 . The other structures  26  (e.g., the strands  12 , the tube  16 , the sheet(s)  20 , the wire  22 , etc.) can be similarly processed with the die  32  in order to change the dimensions of the structures  26 . 
     In addition to setting the desired dimensions of the bundle  10  for use in a power or signal transmission cable or the like, compression of the layers  28  and/or  30  (e.g., the strands  12  and/or the coating  14 , turns of the sheet(s)  20  and/or the coating  22 , etc.) together may also improve the mechanical properties of the structure  26  (e.g., of the wire bundle  10 , the tube  28 , the wire  22 , etc.) and/or the bond between the graphene and the substrate material. Additionally, drawing the structure  26  can be used to assist in tailoring or setting the ratio of graphene to the substrate material. That is, the graphene coating  14  may 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 D1 to the dimension D2 can be borne by substrate material. Additionally, as particularly useful for various embodiments below, the dimensions of the structures  26  can be reduced, which structures can then be utilized to create further electrically conductive structures. 
     In one embodiment the wires  22  are arranged in a bundle, effectively replacing the strands  12  in the bundle  10 . The wires  22  in 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 strands  12 , or a bundle of the wires  22  can be so coated in graphene. In one embodiment, one of the bundles  10 , wires  22 , strands  12 , etc. are arranged as a core filling the cavity  24  of the tube  16 . In one embodiment, multiple ones of the bundles  10  are formed and bundled together to form a yet larger bundle, e.g., essentially replacing the strands  12  in the arrangement of  FIG. 1  to 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. 
     While the invention has been described with reference to an exemplary embodiment or 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 mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the 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 item.