US20110100825A1

US20110100825A1 - Component with a Layer into which CNT (Carbon Nanotubes) are Incorporated and a Method for the Manufacture of Said Component

Info

Publication number: US20110100825A1
Application number: US13/000,684
Authority: US
Inventors: Frank Heinrichsdorff; Jens Dahl Jensen; Ursus Krüger; Manuela Schneider; Raymond Ullrich; Gabriele Winkler
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2008-06-27
Filing date: 2009-06-23
Publication date: 2011-05-05
Also published as: CN102077423A; DE102008030988A1; WO2009156386A1; DE102008030988B4; JP2011527487A; CA2729310A1; EP2294656A1

Abstract

A component with a layer with CNT incorporated into thereof is disclosed. Particles of a dry lubricant are also embedded into the layer. The layer is particularly suited for electrical contact surfaces due to the embedded CNT. Further provided is a method for electrochemically producing the layer in which preferably ionic fluids are used as an electrolyte.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2009/057788, filed Jun. 23, 2009 and claims the benefit thereof. The International Application claims the benefits of German application No. 10 2008 030 988.5 DE filed Jun. 27, 2008. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a component with a layer with CNT incorporated into the grains thereof.

BACKGROUND OF INVENTION

A layer with CNT, as mentioned above, can typically be produced on a contact element as described in WO 2007/118337 A1. This electrical contact element is used for closing and opening an electrical contact and is subject to great stress during this process. This stressing is attributable to the transmission of the electrical switching current, wherein, in accordance with WO 2007/118337 A1, an increase in the service life of the contact is to be achieved by the fact that carbon nanotubes (referred to below as CNT) are present in the contact layer. The increase in the service life is attributable to the fact that the CNT on the one hand improve the electrical conductivity of the layer and on the other hand also bring about improved heat dissipation during the switching process. The thermal stress during the switching process is reduced by this method and the contact layer is subject to less of a strain.

SUMMARY OF INVENTION

The object of the invention is thus to bring about a further improvement in the wear behavior of coated components, especially electrical contact elements.
This object is inventively achieved with the component mentioned at the start by a dry lubricant being incorporated into the grains in addition to the CNT particles. The background of the inventive measure is that the incorporation of CNT, contrary to the widely-held belief among those skilled in the art, only inadequately improves the wear behavior of a coating. CNT does actually improve the hardness of the coating, but the tribological behavior of surfaces is not solely influenced by their hardness. Instead the lubricating properties of the coating during frictional stress are also of primary importance. This is the starting point of the invention, in that the particles of a dry lubricant are also incorporated in addition to the CNT. Dry lubricants belong to a material group characterized by its ability to improve the lubricating properties of the surfaces involved. This advantageously reduces wear, which enables the component into the grains of which CNT and particles of a dry lubricant are incorporated to achieve a better service life. In this case the grains of the layer form a matrix in which the particles of the dry lubricant and the CNT, which can also be regarded as particles, are distributed dispersed. Because of their dimensions, the CNT represent nanoparticles. The particles of the dry lubricant can be embodied as nanoparticles but can also have dimensions in the micrometer range.
In accordance with an advantageous embodiment of the invention there is provision for at least one of the dry lubricants used, molybdenum sulfide, tungsten sulfide, tantalum sulfide, graphite, hexagonal boron nitride, graphite fluoride and silver niobium selenide, to be contained in the particles. The particles of the dry lubricant can thus consist of one or more of the dry lubricants listed and also be mixed with other dry lubricants which are not specified here. It is also possible to use particles of differing compositions, i.e. to mix particles of a dry lubricant with particles of another dry lubricant, with both types of dry lubricant being incorporated into the grains of the layer. Through a suitable mixture and choice of dry lubricants the layer can advantageously be optimized to a specific application in respect of its wear behavior. In such cases the circumstances of the application are to be taken into account, whereby it should be noted that the tribological behavior of two components generally can only be predicted to a restricted extent so that trials are necessary for an optimization, i.e. a selection of suitable dry lubricants. The dry lubricants specified generally exhibit good lubrication properties however, which is why they are the preferred choices in order to arrive at satisfactory results.
A further embodiment of the invention is obtained if the layer has metallic grains, especially made of a nickel-cobalt alloy. The metallic grains of the layer make it possible to conduct the electrical current with advantageously low electrical resistance. Nickel-cobalt alloys in particular are suitable for electrical switching elements since they combine comparatively good electrical and thermal conductivity with a satisfactory wear behavior. Thus the optimization potential through the incorporation of CNT and dry lubricant particles can advantageously be used especially well.
In accordance with another embodiment of the invention there is provision for the layer to have a ceramic grain or at least ceramic grain proportions, especially made of oxidic or nitridic ceramics such as titanium nitride. This advantageously enables very hard layers, for coating a tool for example, to be produced, with their tribological behavior able to be optimized by embedding of the dry lubricant particles. This enables the service life to be advantageously improved. At the same time the thermal conductivity of the CNT can be used in order for example to effectively dissipate the heat from cutting tools. The reduction in thermal stress advantageously simultaneously leads, at high cutting speeds of the tool, to an improved service life, or makes it possible to cut at higher speeds with the same service life.
It is also conceivable for only specific grain proportions to be ceramic while other grain proportions are metallic. An electrical conductivity of the layer is thus retained, with the ceramic grain proportions predominantly being employed to optimize the service life. Finally, electrically-conductive ceramics can also be used with which, even with purely ceramic layers, it is possible to establish electrical contact layers. This is especially the case with titanium nitride.
The invention further relates to a method for electrochemical coating of a component in which the component is placed in an electrolyte, where a layer of elements of the electrolyte is deposited, with CNT being dispersed in the electrolyte which are incorporated into the layer.
A method of the stated type is known for example in accordance with US 2007/0036978 A1, with CNT being dispersed in the electrolyte for the purposes of incorporation into an electrochemical layer to be produced. During the fabrication of the electrochemical layer these CNT will thus also be incorporated into the layer.
The object of the invention is to specify a method for electrochemical coating while incorporating CNT with which layers can be created with an enhanced functional scope.
This object is achieved inventively with the said method in that particles of a dry lubricant which will also be incorporated into the layer are also dispersed in the electrolyte in addition to the CNT. This enables layers to be created which advantageously meet requirement profiles, as have already been illustrated above in connection with the inventive layers.
Advantageously an aqueous electrolyte can be used for coating, with the CNT and the particles of a dry lubricant being dispersed using a wetting agent in the electrolyte. In such cases it is advantageously possible to draw on a plurality of available electrolytes, with use also able to be made of the wetting agents specified in US 2007/0036978 A1.
Another especially advantageous form of embodiment of the inventive method is obtained if an ionic fluid is used as an electrolyte for the coating. Fluid salts in which the salt is not dissolved in a solvent (preferably water) are referred to as ionic liquids. This involves organic liquids which are composed of cations and anions. In the present case alkalized imidazolium, pyridinium, ammonium or phosphonium ions are used as cations. Simple halogenides, tetrafluorborate, hexafluorphosphate, Bi(trifluoromethylsulfonyl)imide or Tri(pentafluoroethyl)trifluorphosphate can typically be used as anions. The effect of choosing these cations and anions is that the ionic fluids are available in the fluid state at temperatures of below 100° C., preferably even at room temperature. Because of their chemical structure, ionic fluids possess surfactant-type properties, which is why these fluids are excellently well suited to the production of dispersions. The ionic fluid acts in such cases as a means of dispersion, with the dispersants to be dispersed able to be microparticles or nanoparticles and being formed in the invention by the CNT and the particles of the dry lubricant. Advantageously this enables wetting agents for dispersal to be dispensed with, which avoids the properties of the particles incorporated into the electrochemically-fabricated layer being adversely affected by built-in wetting agents. In addition comparatively high concentrations of dispersed particles can be achieved in ionic fluids, whereby higher incorporation rates into the layer to be created are also advantageously achieved.
In addition the metals can also be deposited from the ionic fluid as nano crystalline metal layers. In this regard the parameters in accordance with WO 2006/061081 A2 or information provided by F. Endres, “Ionische Flüssigkeiten zur Metallabscheidung (Ionic fluids for metal deposition)”, Nachrichten aus der Chemie, 55, May 2007, Pages 507 to 511, should be taken into account. The structure of nano crystalline metal layers is advantageously especially well suited to the incorporation of CNT as well as the particles of the dry lubricant, so that advantageously especially high incorporation rates can be achieved.
The deposition from aqueous electrolytes and also deposition from ionic liquids can be undertaken both in direct current mode and also in pulsed mode. This advantageously makes it possible to vary the deposited proportions of CNT and particles of the dry lubricant. Copper and gold can also typically be used, in addition to those metals already mentioned, as possible metals for depositing the metallic layer. The CNT used can likewise have different characteristics. In particular the use of single wall CNT, multi-wall CNT or double-wall CNT is possible. Furthermore the CNT can feature functional groups which influence their characteristic profile.
An exemplary embodiment of the inventive method will be described below. In this exemplary embodiment the following steps are performed:
1. In an ionic fluid, such as 1-Butyl-3-methylimidazoliumtetrafluorborate, the appropriate salts for the ionic salts, such as nickel tetrafluoroborate and cobalt sulfamate, are dissolved as ion carriers.
2. Subsequently molybdenum or tungsten sulfide are dispersed in these electrolytes as nano particles or micro particles.
3. Once the said dispersants are distributed homogenously in the electrolyte, an anode consisting of nickel and cobalt is introduced into the bath. Such electrodes are soluble electrodes in order to achieve a constant Ni and Co concentration.
4. The tool which is to be coated and which is electrically-conductive is then immersed the electrolyte and connected to a power source as the cathode.
5. With a current of 0.5 to 20 A/dm², Ni/Co is deposited with the said sulfides and the CNT.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention are described below with reference to the drawing. Elements of the drawing which are the same or which correspond to one another are provided in the individual figures with the same reference signs in each case and are only explained more than once where there are differences between the individual figures. The figures show:

FIG. 1 an exemplary embodiment of the inventive component as an electrical contact element,

FIG. 2 the detail identified in FIGS. 1 and

FIG. 3 an exemplary embodiment of the inventive method in a schematic diagram.

DETAILED DESCRIPTION OF INVENTION

A component 11 in accordance with FIG. 1 is embodied as an electrical switching element. In its contact area this has a layer 12 into which, as can be seen from FIG. 2, on the one hand CNT 13 and on the other hand particles 14 of a dry lubricant are embedded. This advantageously gives a contact surface 15 formed by the layer 12 an increased resistance to wear, an increased ability to carry the switching current and thereby an enhanced service life.
In the method in accordance with FIG. 3 a container 17 is filled with an electrolyte 16 embodied as an ionic fluid. Dispersed in the electrolyte 16 are CNT and particles 14 of a dry lubricant. The component 11 to be coated as the working electrode and an opposing electrode 18 are in contact with a power source 19, enabling a layer to the produced on the component 11 by embedding the CNT 13 and the particles 14 of the dry lubricant.

Claims

1.-10. (canceled)

11. A component, comprising

carbon nanotubes;

particles of a dry lubricant; and

a layer on the component with the carbon nanotubes and the particles of the dry lubricant incorporated into the layer.

12. The component as claimed in claim 11,

wherein the particles of dry lubricant include at least one of the dry lubricants selected from the group of molybdenum sulfide, tungsten sulfide, tantalum sulfide, graphite, hexagonal boron nitride, graphite fluoride and silver niobium selenide.

13. The component as claimed in claim 11,

wherein the layer includes a metallic grain.

14. The component as claimed in claim 13,

wherein the metal grain consisting of nickel, cobalt, silver or of alloys of these metals.

15. The component as claimed in claim 11,

wherein the layer includes a ceramic grain or at least ceramic grain proportions.

16. The component as claimed in claim 15,

wherein in the ceramic grain is made of oxidic or nitridic ceramics.

17. The component as claimed in claim 17,

wherein in the ceramic grain is made of titanium nitride.

18. The component as claimed in claim 11,

wherein the surface of the layer is embodied as an electrical contact surface.

19. A method for electrochemical coating of a component, comprising:

providing an electrolyte, where carbon nanotubes and a dry lubricant are dispersed in the electrolyte;

introducing the component into an electrolyte, where a layer is deposited from elements of the electrolyte, the carbon nanotubes dispersed in the electrolyte are also incorporated into the layer,

the dry lubricant also dispersed in the electrolyte are likewise also incorporated into the layer.

20. The method as claimed in claim 19,

wherein an aqueous electrolyte is used for the electrochemical coating, and

wherein the carbon nanotubes and the particles of the dry lubricant are dispersed in the electrolyte using a wetting agent.

21. The method as claimed in claim 19,

wherein an ionic fluid is used as the electrolyte.

22. The method as claimed in claim 21,

wherein the ionic fluid is used without the addition of wetting agents.

23. The method as claimed in claim 21,

wherein the layer is deposited as a nanocrystalline metal layer.

24. A method for electrochemical coating of a component, comprising:

providing an electrolyte, where carbon nanotubes and a dry lubricant are dispersed in the electrolyte

the dry lubricant also dispersed in the electrolyte are likewise also incorporated into the layer,

wherein an ionic fluid is used as the electrolyte.

25. The method as claimed in claim 24,

wherein the ionic fluid is used without the addition of wetting agents.

26. The method as claimed in claim 24,

wherein the layer is deposited as a nanocrystalline metal layer.