ELECTRICAL CONDUCTOR MADE OF GRAPHENE AND/OR CARBON NANOTUBES HAVING COATED JOINTS

Abstract

The present invention relates to an electrical conductor (1) having an electrically conductive material (2) comprising graphene and/or carbon nanotubes and a joint (3, 4), wherein a metal coating (6) is provided on the electrically conductive material (2) of the electrical conductor (1) at the joint (3, 4) for integrally joining the electrical conductor (1) to a metal conductor element, the metal coating (6) being in direct contact with the electrically conductive material (2), characterized in that the metal coating (6) of the joint (3, 4) comprises a metal that forms carbides in a boundary layer of the coating (6) by reaction of the metal of the coating (6) with the carbon of the electrically conductive material (2).

Claims

1. An electrical conductor (1) comprising an electrically conductive material (2) comprising graphene and/or carbon nanotubes and a joint (3, 4), the electrically conductive material (2) of the electrical conductor (1) having thereon, at the joint (3, 4) a metallic coating (6) configured to cohesively connect the electrical conductor (1) to a metallic conductor element, the metallic coating (6) being in direct contact with the electrically conductive material (2), wherein the metallic coating (6) of the joint (3, 4) comprises a metal which forms carbides in a boundary layer of the coating (6) through reaction of the metal of the coating (6) with the carbon of the electrically conductive material (2).

2. The electrical conductor (1) as claimed in claim 1, wherein the metallic coating (6) comprises titanium and/or zirconium and/or iron and/or vanadium and/or niobium and/or molybdenum and/or hafnium and/or tantalum and/or tungsten.

3. The electrical conductor (1) as claimed in claim 1, wherein nitrides are formed in the boundary layer of the coating (6).

4. The electrical conductor (1) as claimed in claim 1, wherein the coating (6) is a plasma coating.

5. An electrical machine (10) comprising a coil winding (7) formed of an electrical conductor (1) as claimed in claim 1.

6. A method for producing an electrical conductor (1), comprising the steps of: providing an electrically conductive material (2) comprising graphene and/or carbon nanotubes, and forming a joint (3, 4) of the electrical conductor (1) by coating a predefined subregion (5) of the electrically conductive material (2) with a metallic coating (6), where the metallic coating comprises a metal which forms carbides in a boundary layer of the coating (6) through reaction of the metal with the carbon of the electrically conductive material (2).

7. The method as claimed in claim 6, wherein the coating takes place with titanium and/or zirconium and/or iron and/or vanadium and/or niobium and/or molybdenum and/or hafnium and/or tantalum and/or tungsten.

8. The method as claimed in claim 6, wherein the coating takes place by means of thermal spraying processes.

9. The method as claimed in claim 8, wherein nitrogen is added to an inert gas used for the plasma spraying, in order to enable formation of nitrides in the metallic coating (6).

10. The method as claimed in claim 9, wherein the nitrogen is added to the inert gas at the start of the plasma spraying and is no longer added to the inert gas after a predefined period has expired.

11. The method as claimed in claim 6, wherein the coating is done by plasma spraying.

12. The electrical conductor (1) as claimed in claim 2, wherein nitrides are formed in the boundary layer of the coating (6).

13. The electrical conductor (1) as claimed in claim 12, wherein the coating (6) is a plasma coating.

14. An electrical machine (10) comprising a coil winding (7) formed of an electrical conductor (1) as claimed in claim 1, where the coil winding (7) is a winding of a rotor (12) or stator (11) of the electrical machine (10).

15. The method as claimed in claim 7, wherein the coating is done by plasma spraying.

16. The method as claimed in claim 15, wherein nitrogen is added to an inert gas used for the plasma spraying, in order to enable formation of nitrides in the metallic coating (6).

17. The method as claimed in claim 16, wherein the nitrogen is added to the inert gas at the start of the plasma spraying and is no longer added to the inert gas after a predefined period has expired.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0019] Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawing. In the drawing:

[0020] FIG. 1 is a schematic diagram of an electrical conductor according to one exemplary embodiment of the invention, and

[0021] FIG. 2 is a schematic diagram of an electrical machine according to one exemplary embodiment of the invention.

DETAILED DESCRIPTION

[0022] FIG. 1 shows schematically an electrical conductor 1 according to one exemplary embodiment of the invention. The electrical conductor 1 comprises an electrically conductive material 2 which comprises graphene and/or carbon nanotubes. Formed on the electrical conductor 1 are joints 3, 4 at which the electrical conductor 1 can be connected cohesively to other metallic electrical conductor elements. More particularly the joints 3, 4 allow the electrical conductor 1 to be soldered. In the exemplary embodiment shown, the joints 3, 4 are a first end 3 and a second end 4, it being possible for joints 3, 4 also to be formed at any other point of the electrical conductor 1. The electrical conductor 1 is configured preferably as a coil winding 7 for a rotor 12 or stator 11 of an electrical machine 10 (cf. FIG. 2).

[0023] As a result of the electrical conductor 1 being produced from the materials stated above, the electrical conductor 1 is ideally suitable for use as a coil winding 7 for electrical machines 10. However, the electrically conductive material 2 comprising graphene and/or carbon nanotubes has poor capacity for electrical contacting, especially soldering. At the joints 3, 4, i.e., at the first end 3 and at the second end 4, therefore, a metallic coating 6 is provided. The metallic coating 6 is applied on the electrically conductive material 2 and is in direct contact with said material.

[0024] The metallic coating 6 is applied by means of thermal spraying and more particularly by means of plasma spraying. For this purpose a plasma emitter 8 is provided which directs a plasma jet 9 onto predefined subregions 5 of the electrically conductive material 2 in order to form the joints 3, 4. Metal powder is jetted into the plasma jet, and melts before it impinges on the surface of the predefined subregion 5. The formation of the joints 3, 5, i.e., the coating of the subregion 5 at the first end 3 and of the subregion 5 at the second end 4, may take place simultaneously or in succession.

[0025] The plasma spraying enables the application of titanium and/or zirconium and/or iron and/or vanadium and/or niobium and/or molybdenum and/or hafnium and/or tantalum and/or tungsten to the electrical conductor 2. These materials form carbides with the carbon of the electrically conductive material 2. These carbides in turn have a low electrical resistance. Accordingly a boundary layer of the coating 6 is formed at which the metal of the coating 6 reacts with the carbon of the electrically conductive material 2 and forms said carbides. By means of a metallic coating 6 of this kind, therefore, an optimal electrical contacting of the electrical conductor 1 can take place, and more particularly the electrical conductor 1 can be soldered to other components via the coatings 6. This may be done advantageously using customary, standard solder; there is in particular no need to use specially adapted solders.

[0026] At the start of the coating operation, preferably, an inert gas needed for the plasma coating is admixed with nitrogen. The metals used for the coating therefore form nitrides, which have a higher electrical conductivity than the corresponding carbides of the metals used. The effect of adding nitrogen only at the start of the coating operation is that nitrides are formed only where the coating 6 is in direct contact with the electrical conductor 2, i.e., at the boundary layer of the coating. The addition of nitrogen is advantageous for the coating with titanium and/or zirconium and/or hafnium.

[0027] As already described, the electrical conductor 1 is ideally suited for windings of electrical machines 10. An electrical machine 10 according to one exemplary embodiment of the invention is shown in FIG. 2. This electrical machine 10 has a stator 11 and a rotor 12, with the coil winding 7 of the electrical conductor 1 being more particularly a winding of the stator 11. By virtue of the textile qualities of the electrically conductive material 2, this winding can be produced simply and at low cost and complexity, and is also robust toward external influences. Moreover, because of the metallic coating 6, the electrical conductor 1 can be connected cohesively to other metallic electrically conductive components simply and with little cost and complexity, so simplifying the assembly of the electrical machine 10. The cohesive connection is more particularly a soldered connection and hence a low-resistance electrical contacting.