Aluminium or copper-carbon nanotube composite material and method for preparing same

Abstract

The present invention relates to a composite material based on aluminium or copper and tin oxide-functionalized carbon nanotubes, to the method for producing same and to a cable comprising said composite material as the electrically conductive element.

Claims

1. A composite material comprising: a metal matrix of aluminium, copper, aluminium alloy or copper alloy, and tin oxide-functionalized carbon nanotubes dispersed in said metal matrix.

2. The composite material according to claim 1, wherein said composite material comprises from 0.1 to 10% by mass of tin oxide-functionalized carbon nanotubes, relative to the total mass of the composite material.

3. The composite material according to claim 1, wherein said composite material has an electrical conductivity of at least 50% IACS.

4. The composite material according to claim 1, wherein said composite material has a tensile strength of between 100 and 1000 MPa.

5. A method for preparing the composite material as claimed in claim 1, wherein said method comprises at least the following steps: i) bringing the tin oxide-functionalized carbon nanotubes into contact with a metal chosen from among aluminium, copper, an aluminium alloy and a copper alloy, ii) mixing the tin oxide-functionalized carbon nanotubes with the metal in order to disperse them homogeneously in the molten metal, and iii) forming a solid mass.

6. The method according to claim 5, wherein said metal is in the molten state.

7. The method according to claim 6, wherein step i) is carried out by bringing at least one metal container made of aluminium, copper, aluminium alloy or copper alloy comprising tin oxide-functionalized carbon nanotubes into contact with said molten metal, said metal container comprising at least one opening intended to receive the tin oxide-functionalized carbon nanotubes and said opening being closed by a closure element that is able to melt, dissolve or detach from the metal container when said metal container is brought into contact with the molten metal.

8. The method according to claim 7, wherein step i) is carried out by introducing or injecting at least one metal container as defined in claim 7 into a liquid metal bath, said bath being at a sufficiently high temperature to cause the closure element of said container to melt, dissolve or detach, and to melt said metal container.

9. The method according to claim 8, wherein the sufficiently high temperature of step i) is between 550 and 1200° C.

10. The method according to claim 7, wherein the closure element is one or more nanometric filters made of paper.

11. The method according to claim 6, wherein step iii) is carried out by casting the mixture of the preceding step ii) to form said composite material.

12. The method according to claim 5, wherein said method further comprises a step i.sub.0) of preparing the tin oxide-functionalized carbon nanotubes, comprising the following sub-steps: possibly a sub-step i.sub.01) of functionalizing carbon nanotubes with appropriate chemical groups which may represent sites of attachment between the carbon nanotubes and the tin oxide, a sub-step i.sub.02) of bringing the commercial functionalized carbon nanotubes, or the functionalized carbon nanotubes as prepared in the preceding sub-step if such a sub-step exists, into contact with a tin precursor, and a sub-step i.sub.03) of heating.

13. The method according to claim 12, wherein sub-step i.sub.01) is carried out by acid treatment of the carbon nanotubes with sulfuric acid.

14. The method according to claim 12, wherein the tin precursor is tin sulfate.

15. A composite material, wherein said composite material comprises a metal matrix of aluminium, copper, aluminium alloy or copper alloy, and tin oxide-functionalized carbon nanotubes dispersed in said metal matrix, and wherein said composite material is obtained according to the method as defined in claim 5.

16. An electrical cable, wherein said electrical cable comprises at least one composite material as defined in claim 1.

17. The cable according to claim 16, wherein said cable is an OHL cable comprising an elongate reinforcing element and an assembly of composite strands positioned around the elongate reinforcing element.

18. The cable according to claim 16, wherein said cable comprises at least one electrically insulating layer surrounding said composite material or the plurality of composite materials, said electrically insulating layer comprising at least one polymer material.

19. The cable according to claim 16, wherein each one of the composite strands is a composite material comprising a metal matrix of aluminium, copper, aluminium alloy or copper alloy, and tin oxide-functionalized carbon nanotubes dispersed in said metal matrix.

20. The composite material according to claim 1, wherein said composite material comprises from 0.25 to 5% by mass of tin oxide-functionalized carbon nanotubes, relative to the total mass of the composite material.

21. The composite material according to claim 1, wherein said composite material has a tensile strength of between 110 and 600 MPa.

22. The composite material according to claim 1, wherein the tin oxide-functionalized carbon nanotubes are uniformly dispersed within the metal matrix of aluminium, copper, aluminium alloy or copper alloy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the present invention will emerge in light of the following examples with reference to the annotated figures, said examples and figures being provided by way of entirely non-limiting illustration.

(2) FIG. 1 shows, schematically, a structure in cross section of a first variant of an electrical cable according to the invention.

(3) FIG. 2 shows, schematically, a structure in cross section of a second variant of an electrical cable according to the invention.

(4) FIG. 3 shows tin oxide-functionalized carbon nanotubes.

DETAILED DESCRIPTION

(5) For reasons of clarity, only the elements essential to the understanding of the invention have been presented diagrammatically, without regard to scale.

(6) FIG. 1 shows a first variant of an electrical cable 1 according to the invention, seen in cross section, comprising a composite material 3 according to the first subject matter of the invention or obtained in accordance with the method according to the second subject matter of the invention and an electrically insulating layer 2 surrounding said composite material 3.

(7) FIG. 2 shows a second variant of an electrical cable 4 for high-voltage electrical transmission of the OHL type according to the invention, seen in cross section, comprising three layers of an assembly 5 of composite strands 6, each composite strand consisting of a composite material according to the invention. These three layers 5 surround an elongate central reinforcing element 7. The composite strands 6 forming said layers 5 have a Z-shaped (or S-shaped, depending on the orientation of the Z) cross section. The elongate central reinforcing element 7 shown in FIG. 2 may for example be steel strands 8 or composite strands of aluminium in an organic matrix.

(8) In the embodiment shown in FIG. 2, it is possible to modify the number of composite strands 6 of each layer 5, their shape, the number of layers 5 or else the number of steel strands or composite strands 8.

(9) FIG. 3 shows tin oxide-functionalized carbon nanotubes obtained in accordance with the method according to the invention.

(10) Preparation of Composite Materials According to the Invention and Obtained in Accordance with the Method According to the Invention

(11) 1.1 Preparation of Tin Oxide-Functionalized Carbon Nanotubes

(12) A liquid medium comprising water and citric acid. Non-functionalized (i.e. naked) carbon nanotubes marketed under the identifier Nanocyl NC 7000 were then introduced into the liquid medium, then dispersed using ultrasound. The resulting dispersion was transferred to a round-bottomed flask containing sulfuric acid, then the resulting dispersion was brought to reflux for at least 1 h with agitation, then cooled. The functionalized carbon nanotubes were then filtered then washed in water until a neutral pH was reached.

(13) The carbon nanotubes functionalized with acid groups were introduced into a beaker of distilled water with magnetic agitation, then a dispersant of the cetyltrimethylammonium bromide (CTAB) or sodium dodecyl sulfate (SDS) type was added, still with intense magnetic agitation, then with the aid of ultrasound. Then, tin sulfate was added with magnetic agitation, then with the aid of sequenced ultrasound. The resulting mixture was dried between 80 and 150° C. until evaporation of the solvents and formation of a relatively compact paste. Then the paste was heat-treated in an oven at 150° C. for at least 2 h, then at 280° C. for at least 3 h (step i.sub.0).

(14) 1.2 Preparation of the Composite Material of the Invention

(15) Step i) was carried out using 6 metal containers as defined in the invention. The metal containers were in the form of tubes made of aluminium alloy (Al 1350®), 9.5 mm in diameter and between 5 and 10 cm in length. Each of the tubes was filled with 2 g of tin oxide-functionalized carbon nanotubes as prepared in example 1.1. The closure element consisted of two nanometric filters made of paper. The closure element closes the opening of said tube by means of a metal wire made of aluminium (Al 1350®).

(16) The metal contents comprising the tin oxide-functionalized carbon nanotubes were injected into 1.2 kg of a bath of an aluminium alloy (Al 1350®) by means of an injector under a nitrogen atmosphere.

(17) The contents were mixed with the bath of liquid aluminium alloy using a rotating paddle mixer (mechanical and electromagnetic agitation) (step ii)).

(18) Then, the resulting mixture was cast into a preformed metal mould so as to form a composite material according to the invention in the form of a solid mass (step iii)).

(19) The obtained composite material was rolled to pass from a diameter of approximately 30 mm to a diameter of approximately 10 mm, then drawn to the final desired diameter.

(20) Table 1 below shows the results in terms of electrical conductivity (in % IACS) and tensile strength (in MPa) of the composite materials M.sub.1 and M.sub.2 of the invention respectively having final diameters of 9.55 mm and 3.3 mm, and by way of comparison of aluminium alloys M.sub.1′ and M′.sub.2 comprising no tin oxide-functionalized carbon nanotubes (i.e. not in accordance with the invention), respectively having diameters of 9.55 mm and 3.3 mm.

(21) TABLE-US-00001 TABLE 1 Conductivity Tensile strength % IACS (MPa) M.sub.1 53.1 137.2 M′.sub.1 62.5 116.4 M.sub.2 53.5 193.1 M′.sub.2 62.5 162.6

(22) The presence of the tin oxide-functionalized carbon nanotubes serves to improve the mechanical strength of the composite material while ensuring acceptable electrical conductivity.

(23) M.sub.1 and M.sub.2 comprised approximately 1% by mass of tin oxide-functionalized carbon nanotubes.