EP2740943B1 - Vacuum pump - Google Patents

Description

The present invention relates to a vacuum pump, in particular a turbomolecular pump, and a method for producing a vacuum pump.

Vacuum pumps, in particular turbomolecular pumps, are suitable for producing a high-purity vacuum in a vacuum chamber and are used, for example, in coating and semiconductor technology in order to produce the vacuum necessary for the process steps to be carried out there. Typical semiconductor processes consist of a multiplicity of successive process steps in which different process gases are respectively introduced into the vacuum chamber, which subsequently have to be pumped off by the vacuum pump. In order to reduce as far as possible the cycle times that are decisive for the cost-effectiveness of these methods, there is an attempt to increase the delivery rate and delivery rate of the vacuum pumps and, for example, to operate them at increased rotational speeds.

The higher flow rates and rotational speeds lead in addition to an increased mechanical load to a considerable heating and thus thermal load on the pump components.

The prior art proposes various materials for the rotor disks of a turbomolecular pump which are intended to withstand increased thermal and mechanical stresses. For example describes US 6,095,754 A the use of a composite of a metal matrix and a reinforcing additive for the blades of the rotor disk of a turbomolecular pump. WO 2007/125104 A1 describes a rotor or stator of a turbomolecular pump with aluminum alloy blades comprising an Al-Cu-Mg-Mn wrought alloy intended to withstand elevated temperatures.

The suitability of the known vacuum pumps for operation with high gas loads and conveying speeds, for example in semiconductor technology, is also limited in the use of the materials mentioned. For example, the short-term amount of the gas to be delivered during the semiconductor production in special process steps leads to a short-term speed drop of the rotor, which results in a high material load and temperature increase of the rotating pump components, especially at high speeds. It thus occurs suddenly a high mechanical and thermal stress, which due to the limited thermal and mechanical load capacity of the pump components can lead to premature failure of the known vacuum pumps and reduces their life.

The WO 2007/022332 A2 describes a vacuum pump, to whose rotor a device with field emission tip is arranged, which contains nanoparticles.

In the DE 600 30 833 T2 For example, a vacuum pump with a magnetic shield having a nanocrystal alloy is described.

The DE 10 2010 021 240 A1 describes that elements of a vacuum pump have a surface coating containing nano-zinc oxide.

In the DE 100 53 663 A1 there is described a vacuum pump having a rotor made of powder metallurgically produced alloys.

The GB 2 490 127 A describes rotor blades for a turbine made of fiber reinforced material with nanoparticles.

Products reinforced with nanofibers are also available in the WO 2008/130739 A1 described.

Finally, that describes DE 10 2008 025 700 A1 a radial fan blade containing an admixture of carbon nanotubes.

The object of the invention is to provide a vacuum pump which can be reliably operated with a high gas load and conveying speed, which at the same time has a long service life and which is also inexpensive to produce. In particular, the vacuum pump should also withstand high mechanical and thermal stresses that occur simultaneously and in particular cyclically recurring, such as in semiconductor manufacturing, without the life of the vacuum pump is thereby reduced.

The object is achieved by a vacuum pump, in particular a turbomolecular pump, with the features of claim 1. According to the invention, at least one component of the vacuum pump comprises a material or consists of a material which contains a metal and nanoparticles, wherein the material contains between 0.5 to 10 wt .-% of nanoparticles. By adding the nanoparticles, an enhancement of the pump component is achieved, which increases the resistance of the component, for example the rotor disk of a turbomolecular pump, to the mechanical and thermal loads occurring during operation of the vacuum pump with high gas loads and conveying speeds. At the same time, the pump component retains its favorable metal or metal-like material properties for use in the vacuum pump.
In particular, as a result of the reinforcement of the metallic material by the nanoparticles, the pump component has increased strength, in particular particularly high heat resistance and fatigue strength. It is believed that the nanoparticles are obstacles to the movement of dislocations or lattice defects in the metal and thereby ensure a high dislocation density and a correspondingly high strength of the material. At the same time, the material has a low creep, even at high loads, whereby the risk of damage caused by a creep deformation of the rotor discs is avoided.
Thus, a vacuum pump is provided which can be operated with high gas loads and flow rates and yet has a long service life. As explained in detail below, can be make the vacuum pump with simple means and in a cost effective manner and is thus also available at low cost.

The high load capacity of the vacuum pump also makes it possible to increase the outlet pressure of the vacuum pump, i. to increase the fore-vacuum pressure to which the vacuum pump compresses the pumped gas during its operation, compared to known vacuum pumps. For this reason, it is possible to work with less powerful fore-vacuum pumps connected to the outlet of the vacuum pump in order to compress the gas from the fore-vacuum pressure to atmospheric pressure. In principle, it is even possible to dispense entirely with the use of a backing pump, i. a vacuum pump, and in particular a turbomolecular pump, can be provided which can be reliably operated with such a high pumping capacity that the pump directly compresses the delivered gas to atmospheric pressure.

Advantageous embodiments of the invention are described in the subclaims, the description and the figures.

The nanoparticles may be carbon nanoparticles, in particular carbon nanotubes.

Preferably, the vacuum pump to a stator and at least one rotor member, wherein the rotor member is rotatably mounted relative to the stator. The vacuum pump can in principle be designed as a turbomolecular pump, as a Holweck pump, as a side channel pump, as a Roots pump or as a combination or composite vacuum pump of several of the abovementioned pump types.

A metal is understood here to mean both a pure metal, that is to say a one-component metal alloy, and an alloy in the conventional sense, that is to say a multicomponent metal alloy.

Preferably, the metal is a light metal such as aluminum, magnesium, titanium or a metal alloy having one or more of the above elements. Likewise, the metal may comprise copper or a copper alloy. Due to the low specific weight of aluminum and the concomitant low centrifugal force loading of a rotating component made of aluminum, aluminum or an aluminum alloy or aluminum wrought alloy is particularly suitable as metal. The mechanical and thermal properties are thereby improved by the addition of the nanoparticles compared to the pure metal such that the component produced from the resulting material has a significantly improved resistance to the high mechanical and thermal loads. A particularly high load capacity results when an aluminum alloy of the type 5XXX, in particular of the type 5083, is used. Even when using an aluminum alloy of the type 2XXX, in particular of the type 2618, a high mechanical and thermal resistance can be achieved. The aluminum alloy, in particular of one of the types 5XXX, eg 5083, or 2XXX, eg 2618, preferably corresponds to a corresponding definition in DIN EN 573-1,2,3, ie the aluminum alloy of type 5083 corresponds to the aluminum alloy EN AW defined there -5083 or the aluminum alloy of type 2618 corresponds to the aluminum alloy EN AW-2618A defined therein. To obtain a high strength, a mixed crystal-strengthened metal alloy can be used. The material of the pump component may generally have a Vickers hardness of greater than 160 HV.

A particularly high strength of the component is achieved if the material contains between 0.5 and 10% by weight, preferably between 1 and 9% by weight and furthermore preferably between 2 and 4% by weight of nanoparticles. The rest of the material may consist at least approximately completely of the metal or the metal alloy.

The metal and the nanoparticles together preferably form a solid structure, wherein the metal can form a matrix in which the nanoparticles are embedded. A particularly high strength is achieved if the nanoparticles are present at least partially isolated in the metal and at least partially isolated embedded in a matrix formed by the metal. The nanoparticles preferably have an at least approximately isotropic and in particular substantially homogeneous distribution in the material. As a result, the same advantageous mechanical and thermal properties can be ensured in all areas of the component and in all spatial directions.

According to an advantageous embodiment, the material comprises grains formed by the metal with an average particle size between 1 and 400 nm, preferably between 1 and 200 nm. The grains, which are also referred to as crystallites, are preferably at least partially separated from one another by the nanoparticles. This results in a particularly high strength of the material. It is believed that the nanoparticles, preferably along the grain boundaries, inhibit grain growth and the movement of dislocations in the metal, thereby ensuring a particularly high strength of the material. In addition to nanoparticles extending along the grain boundaries of the metal, nanoparticles may also be present which extend at least partially within a grain, thereby further increasing strength. It is believed that such nanoparticles the Cohesion of the grain with adjacent grains and thus increase the strength of the material in addition.

The solidification effected by the nanoparticles is particularly pronounced when the nanoparticles have an aspect ratio, ie a ratio of length to cross-sectional diameter, of at least 3, preferably at least 10 and particularly preferably at least 30, at least or on average.

A nanoparticle is understood in particular to mean a particle which has two or three outer dimensions in the nanoscale range, that is to say in the range from 1 to 1000 nm, preferably in the range from 1 to 100 nm, so that nanofibers are also included in the term. Advantageous results in terms of the strength of the material and its processability are achieved in particular with the use of inorganic nanoparticles, in particular nanoparticles of carbides, nitrides and silicides. Particularly high strengths are achieved with carbon nanoparticles and in particular carbon nanotubes ("CNTs"). Therefore, it is preferred if the nanoparticles are at least partially and in particular substantially completely formed by carbon nanotubes.

According to an advantageous embodiment, carbon nanotubes are provided as nanoparticles, which have a rolled-up structure or a scroll structure. Instead of a seamless closed cylinder structure, the one or more graphene layers of such a nanotube have a helical cross section, that is to say the rolled graphene layers have two longitudinal sides which are separated from one another and rolled into one another. Carbon tubes with this structure and their preparation are, for example, in Iijima, Nature 354, 56 - 58, 1991 and Bacon, Journal of Applied Physics 34, 1960, 283-90 , described.

The carbon nanotubes may also have a scroll structure with a plurality of coiled graphite layers, each graphite layer comprising two or more graphene layers arranged on top of each other. The several graphene layers together form the above-described screw structure, wherein the longitudinal edges of all graphene layers are rolled into one another. Such carbon tubes, whose structure is also referred to as a multi-scroll structure, as well as their preparation are in DE 10 2007 044 031 A1 described. The disruption formed between the open longitudinal sides of the graphene sheets of these nanotubes allows a particularly intimate connection of the nanotube to the metal, thereby increasing the strength of the material. The carbon nanotubes are also typically not rectilinear due to their open cross-section, but open in the region of the longitudinal sides of the graphene layers, along a curved curved path with relatively short straight sections between two bends and thus preferably form tangles or bundles with several entangled ones carbon nanotubes. Such balls can be compared to isolated carbon nanotubes easier and handle with fewer safety precautions, whereby the manufacturing cost is reduced.

The outermost layers of the multi-scroll nanotubes may be at least partially broken by a functionalization, in particular by pressurization, thereby allowing an even more intimate connection with the metal.

The mean outer diameter of the carbon nanotubes may be between 5 and 25 nm, in particular about 13 nm. The average length of the nanotubes can be between 0.5 and 20 .mu.m, preferably between 1 and 10 .mu.m, resulting in a very high aspect ratio of the nanotubes. The inner diameter of the nanotubes may be between 2 and 15 nm, preferably between 3 and 8 nm. The nanotubes may have an ashing determined carbon content of greater than 95% and preferably greater than 99%. For example, can be used by the company Bayer Material Science AG, 51368 Leverkusen, sold under the name Baytubes® carbon nanotubes.

According to an advantageous embodiment, the material of the component is obtainable by a powder metallurgy process from a powdery composite containing a metal and nanoparticles. With such a method, a particularly firm structure of the metal and the nanoparticles, in particular with a uniform distribution of the nanoparticles in the metal, ensure. The powder metallurgical process, which preferably converts the powdery starting material to a solid, coherent and preferably at least approximately pore-free or slightly porous main body, may comprise a mechanical forming, in particular with simultaneous heat supply. By forming an example elongated body can be made with a substantially circular cross-section, for example, is substantially cylindrical or bolt-shaped and may have a diameter between 50 and 200 mm, preferably between 60 and 120 mm. The main body may also be formed plate-shaped or sheet-shaped. For example, the powder metallurgical process may be hot isostatic pressing (HIP) or extruding the powdered composite include. In principle, the forming may also include rolling. The nanoparticles hinder the movement of dislocations or lattice defects in the metal during the powder metallurgy process, so that the material has a high dislocation density even after the powder metallurgy process and a heat treatment that may be required, and consequently the material produced by powder metallurgy has a correspondingly high strength having.

A pump component having particularly favorable properties is achieved when the powdery starting material is obtainable by mechanical alloying of a metal powder with nanoparticles. Such alloying results in a powdery starting material with thorough penetration of the metal with the nanoparticles and a strong bond between the nanoparticles and the metal in the individual powder particles, so that the material produced therefrom by powder metallurgy likewise has a particularly high strength.

Specifically, the powdery raw material may be obtainable by a method which comprises processing a metal powder and nanoparticles by mechanical alloying such that the produced composite metal grains, also referred to as crystallites, having an average size in the range of 1 to 100 nm , preferably 10 to 100 nm or in the range of more than 100 nm to 200 nm, which are at least partially separated by the nanoparticles. A material with such a grain size leads to a particularly high strength of the resulting pump component. Furthermore, the starting material can be produced on an industrial scale and is therefore available at low cost.

A method for producing a suitable powdery composite material and a composite material obtainable thereby are, for example, in WO 2010/091790 A1 described by Bayer International SA. The pulverulent composite material may be, in particular, one after the in WO 2010/091790 A1 act as composite material obtainable according to the invention. Likewise, the powdery starting material can be replaced by a in one of the patent family members of WO 2010/091790 A1 be available as a process according to the invention. In particular, describe WO 2010/091704 A1 . WO 2010/102655 A2 . WO 2010/091789 A1 . WO 2010/091791 A1 and WO 2011/032791 A1 the company Bayer International SA such procedures.

A material from which the component of the vacuum pump can be made at least partially is available from Bayer Material Science AG, 51368 Leverkusen under the trade name Bayal-C DP®.

The component of the vacuum pump comprising the material described is preferably a component which, during operation of the pump, comes into contact with the conveyed media and in particular has a pump-active structure. Such components are particularly heavily stressed by the mechanical and thermal stresses occurring at high pump powers, so that the formation of such a component with the described material has a particularly significant influence on the life of the vacuum pump.

According to an advantageous embodiment, the component is a rotor member of the vacuum pump, which is driven in rotation during the operation of the vacuum pump and preferably has a pump-active structure. For example, the component may comprise or consist of a rotor disk of a turbomolecular pumping stage of the vacuum pump. In this case, a particularly significant increase in the possible pump power and the life of the pump is achieved by the material described, since the rotor disks and in particular their blades during operation of the vacuum pump with high gas loads and conveying speeds are mechanically and thermally particularly heavily loaded. The rotor disk can represent an independent component of the vacuum pump or be part of a larger rotating component. The rotor disk may e.g. be integrally formed with a rotor shaft or comprise a support ring connected to the rotor shaft. The component of the vacuum pump can also be formed by a bell-shaped rotor element, for example by a bell-shaped rotor of a turbomolecular pumping stage, which can in particular comprise one or more rotor disks of the turbomolecular pumping stage.

The rotor disk preferably comprises as a pump-active structure a plurality of rotor blades, which in each case consist wholly or partly of the described material and e.g. are arranged in a ring around a support ring of the rotor disk or a rotor shaft around. The blades have e.g. a longitudinal extent oriented in the radial direction and surfaces set in relation to the direction of rotation in order to deliver a pulse directed in the conveying direction, that is in particular perpendicular to the plane of the pane, to the gas molecules.

Instead of a turbomolecular pumping stage, the rotor organ can also be part of a Holweck pumping stage, Siegbahnpumpstufe, Seitenkanalpumpstufe or Wälzkolbenpumpstufe and can represent, for example, a rotating Holweck cylinder. A Holweck cylinder preferably has a smooth cylindrical shell-shaped pump-active surface, which rotates with respect to a stator sleeve, which is provided with spiral-shaped thread grooves in which the pumping-driven gas is guided. It is also possible that, instead of the stator sleeve, the rotating Holweck sleeve has a thread with helical thread grooves and, for example, rotates with respect to a smooth surface of the stator sleeve. It is also an embodiment possible in which a rotor sleeve rotates relative to a stator, wherein the opposing, in particular cylinder jacket-shaped surfaces of both the rotor sleeve and the stator each having a thread with helical grooves in which the pump-effective driven gas flows, the direction of rotation the thread of a sleeve is opposite to the direction of rotation of the thread of the other sleeve.

Preferably, the pump component is obtainable by a method which comprises the mechanical processing of a base body formed at least partially from the described material, which can represent a semifinished product. For example, the processing may include a material-removing and in particular machining. Despite the high mechanical strength of the material, this makes it possible to produce a pump component with the desired geometry and optionally pump-active structure, without the need for plastic deformation of the material during production and a concomitant risk of adverse changes in the material. For example, the rotor blades of a rotor disk, including its surfaces pointing in the direction of rotation and positioned opposite the direction of rotation, can be machined from the basic body substantially completely by a material removing process become. On a plastic deformation of the body can therefore be completely dispensed with in the preparation of the pump component accordingly.

The invention also relates to a component for a vacuum pump, in particular a rotor disk for a turbomolecular pump, which comprises or consists of a material which contains a metal and nanoparticles, in particular carbon nanotubes. The advantageous embodiments and advantages described above in connection with the vacuum pump according to the invention with respect to the component of the vacuum pump, when used appropriately, represent advantageous embodiments and advantages of the component according to the invention.

Another object of the invention is a method for producing a vacuum pump, in particular a turbomolecular pump, or a component for such a vacuum pump. The method includes that a component of the vacuum pump or the component is at least partially made of a material containing a metal and nanoparticles.

The production of the component from a material containing a metal and nanoparticles leads to a vacuum pump which can be operated permanently and reliably with high pumping powers and high gas loads while having a long service life. The method can be carried out in particular for producing a vacuum pump according to the invention as described above. The advantageous embodiments and advantages described herein in relation to the vacuum pump according to the invention as well as their manufacture or manufacturability provide correspondingly Application advantageous embodiments and advantages of the method according to the invention. The method thus provides a vacuum pump with a component having advantageous mechanical and thermal properties, wherein the properties of the component of the vacuum pump and its material can also be adjusted easily and selectively by influencing the process parameters ,

The nanoparticles may be carbon nanoparticles, in particular carbon nanotubes.

According to an advantageous embodiment, the forming of the component comprises a mechanical processing of a body at least partially formed from the material for the component. The processing preferably comprises a material-removing and in particular machining, such as milling, turning, grinding, sawing, drilling or cutting. Thereby, a pump component can be produced with the desired shape, without plastic deformation of the material is required, so that the advantageous properties of the material are not impaired, but in principle is not excluded that such a plastic deformation takes place.

For example, at least one rotor disk for a turbomolecular pumping stage of the vacuum pump can be machined out of the main body by material-removing machining, wherein the surfaces of the blades of the rotor disk pointing in the direction of rotation and facing the direction of rotation are preferably machined essentially completely by material-removing machining. The main body may originally have, for example, an elongated and in particular substantially cylindrical shape, wherein For example, a disk-shaped portion of the cylindrical base body can be cut off, from which then the pump-active blade structure of the rotor disk is machined by a material-removing machining. The main body may also be formed plate-shaped or sheet-shaped.

A bell rotor, in particular for a turbomolecular pump stage, can also be produced from the base body, in particular by a material-removing machining, wherein the bell rotor can comprise one or more rotor disks of the turbomolecular pump stage.

According to one embodiment, a powdered composite material is provided which contains a metal and nanoparticles and which is processed by a powder metallurgy process to the component or to a base for the component.

The processing of the powdered composite material may include mechanical forming, wherein heat is preferably simultaneously supplied to the composite material. For example, the component or its basic body can be produced from the powdered composite material by extrusion or / and hot isostatic pressing. The nanoparticles contained in the powdered composite material hinder movement of the dislocations or lattice defects present in the metal, so that a high dislocation density and correspondingly high strength of the material produced from the powder is ensured even when performing the forming with heat addition.

Preferably, providing the powdered composite comprises mechanically alloying a metal powder with nanoparticles.

The powdered composite material used is preferably obtainable according to one of the processes described in the above-cited Bayer International SA publications as a process according to the invention or is prepared by a process described therein.

In particular, the mechanical alloying is performed such that in the powdery composite material, the metal has a mean grain size or crystallite size between 1 and 200 nm, wherein the grains of the metal are at least partially separated by the nanoparticles.

The mechanical alloying preferably comprises milling, in particular high-energy milling, which can be carried out, for example, using a ball mill with a grinding chamber and balls which are freely movable therein as grinding bodies. Mechanical alloying may involve repeated deforming, breaking and welding together of the powder particles involved in the alloy. The mill may be operated at a speed of between 350 and 1000 rpm, preferably between 500 and 800 rpm, and the grinding chamber may have a diameter of between 250 and 1000 mm, preferably approximately 500 mm, in the plane perpendicular to the axis of rotation. The balls may be accelerated to a speed of at least 5 m / s, preferably at least 8 m / s and more preferably at least 11 m / s. The grinding time can be between 45 and 240 minutes, preferably between 90 and 120 minutes. The grinding action can reduce the grain size of the metal and at the same time establish an intimate bond between the metal and the nanoparticles. In this case, the nanoparticles can be joined to the metal material in such a way that they at least partially separate grains of the metal from each other, or even partially introduce them into the grains of the metal.

The nanoparticles are preferably present in the form of a powder of agglomerates of nanoparticles prior to mechanical alloying, in particular of tufts or bumps of tangled or entangled carbon nanotubes. As a result, the manageability of the nanoparticles can be significantly increased and simplify the necessary safety precautions for handling. Preferably, at least 95% of the agglomerates have a size greater than 100 microns.

The nanoparticles intended for mechanical alloying are preferably produced by a catalytic chemical vapor deposition or CCVD. In particular, the particles can be produced by a fluidized bed process, for example carried out in a fluidized bed reactor. Exemplary methods for producing corresponding nanoparticles or tufts of nanoparticles are described in the abovementioned publications by Bayer Technologies SA and in US Pat DE 10 2007 044 031 A1 described. The methods described there lead to carbon nanotubes of multi-scroll type, which form due to their curved and curvilinear longitudinal shape in a particularly favorable manner, the contiguous tufts or balls described above. For example, Baytubes® can be used.

Prior to mechanical alloying, the carbon nanotubes may be functionalized, which may include pressurizing the carbon nanotubes such that at least the outermost graphene layer of at least a portion of the carbon tubes ruptures. The tufts can be subjected to a pressure of at least 5 MPa and preferably at least 7.5 MPa.

The metal powder used in the mechanical alloying can be produced by, for example, sputtering a molten metal. Before or after the production of the powder, solid solution hardening of the metal can take place.

Another object of the invention is a vacuum pump or a component of a vacuum pump, which is obtainable by the inventive method described herein. The advantageous embodiments and advantages described above in relation to the method, when used appropriately, represent advantageous embodiments and advantages of the vacuum pump or component obtainable by the method.

Fig. 1

eine Vakuumpumpe gemäß einer Ausführungsform der Erfindung im Längsschnitt,

Fig. 2

einen Teil der in Fig. 1 gezeigten Vakuumpumpe in einer teilweise geschnittenen perspektivischen Ansicht,

Fig. 3

einen Wirbelschichtreaktor zu Verwendung in einem Verfahren gemäß einer Ausführungsform der Erfindung,

Fig. 4

eine geschnittene, perspektivische Ansicht eines mit dem Reaktor von Fig. 3 hergestellten Kohlenstoffnanoröhrchens,

Fig. 5

eine Vorrichtung zur Herstellung eines Metallpulvers zur Verwendung in dem Verfahren,

Fig. 6

eine Kugelmühle zur Verwendung in dem Verfahren, und

Fig. 7

einen Grundkörper zur Herstellung einer Komponente einer Vakuumpumpe gemäß einer Ausführungsform der Erfindung.

Hereinafter, the present invention will be described by way of example with reference to an advantageous embodiment with reference to the accompanying drawings. Show it:

Fig. 1

a vacuum pump according to an embodiment of the invention in longitudinal section,

Fig. 2

a part of in Fig. 1 shown vacuum pump in a partially sectioned perspective view,

Fig. 3

a fluidized bed reactor for use in a method according to an embodiment of the invention,

Fig. 4

a cut, perspective view of one with the reactor of Fig. 3 manufactured carbon nanotube,

Fig. 5

an apparatus for producing a metal powder for use in the method,

Fig. 6

a ball mill for use in the method, and

Fig. 7

a main body for producing a component of a vacuum pump according to an embodiment of the invention.

Fig. 1 shows a formed as a turbomolecular pump vacuum pump according to an embodiment of the invention. The multi-part housing 10 of the vacuum pump comprises on its high-vacuum side a flange 12 with which the vacuum pump can be connected to a vacuum chamber to be evacuated. The flange 12 surrounds the suction opening 14, through which the vacuum pump sucks gas.

The vacuum pump comprises a rotor with a rotor shaft 18 which is rotatably mounted about a rotation axis 16 of the vacuum pump and which can be driven in rotation by an electric motor drive. The drive comprises a stator-side drive coil 20 and a rotor-side drive magnet 22. The rotor shaft 18 is rotatably supported by two spaced apart in the direction of the axis of rotation 16, designed as a rolling bearing pivot bearing 24, 26. Instead of or in addition to the closer to the suction port 14 located pivot bearing 26 could also be provided a permanent magnet bearing, which may be arranged in the region of the suction port 14 of the pump and may be formed lubricant-free, to avoid contamination of the vacuum chamber.

The rotor shaft 18 carries a plurality of radially oriented and provided with rotor blades 28 rotor disks 30 which are arranged between the fixed to the housing 10 and also provided with blades stator disks 32 and alternate with these in the axial direction. The rotor and stator disks 30, 32 form a turbomolecular pump mechanism whose pumping action delivers the gas drawn in through the intake port 14 to the pump outlet 34. In principle, further, in particular molecular pump stages, such as, for example, one or more Holweck pump stages, Siegbahn pump stages or side channel pump stages, may be provided in the flow direction between the turbomolecular pumping stage and the outlet 34 in order to ensure a desired performance of the pump.

Fig. 2 shows a part of the vacuum pump of Fig. 1 in a partially sectioned perspective view. Shown is a rotor disk 30 with a on the rotor shaft 18 ( Fig. 1 ) to be attached to the support ring 36 and radially projecting from the support ring 36 blades 28 which against the tangent to the rotational axis 16 directed rotational direction employed surfaces 40 to transmit a directional in the conveying direction impulse to the pumped gas molecules.

The rotor disk 30 is milled out in one piece from a base body and consists of a material which comprises a carbon nanotube staggered aluminum alloy. This ensures a long operating life of the vacuum pump even with high gas loads and pumping power.

Hereinafter, a method of manufacturing a vacuum pump according to an embodiment of the invention will be described with reference to FIG Fig. 3 to 7 described.

Fig. 3 shows a fluidized bed reactor 42 for the production of carbon nanotubes by catalytic chemical vapor deposition, CCVD, as a starting material for the process. The reactor 42 is heated by a heater 44. The reactor 42 has at its lower end an inlet 46 for supplying inert gases and reactant gases, an upper outlet opening 48 for the escape of nitrogen, inert gas and by-products of the reactor 42, a catalyst inlet 50 for supplying a catalyst and a removal opening for removal of the produced carbon nanotubes on.

To produce the nanotubes, nitrogen is first fed as inert gas via the lower inlet 46 and the reactor 42 is heated by the heating device 44 to a temperature of about 650 ° C. Thereafter, the catalyst is fed in the form of particle agglomerates 54 having a particle size between 30 and 100 microns through the upper inlet 50, which is preferably a transition metal catalyst based on cobalt or manganese and the molar mass ratio of cobalt to manganese, e.g. between 2: 3 and 3: 2. Next, the gaseous reactant 56 is supplied via the lower inlet 46, which comprises a hydrocarbon gas as a carbon donor and an inert gas. The ratio of reactant gas to inert gas may be about 9: 1.

In the fluidized bed process, carbon is deposited on the catalyst particles in the form of carbon nanotubes having a multi-scroll structure with a curved longitudinal curvature, with a plurality of tubes forming contiguous tufts with an average diameter between 0.05 and 5 mm can be removed as powder via the removal opening 52.

Fig. 4 shows a section of a cross-cut carbon nanotube prepared in the manner described above. The carbon nanotube includes several in Fig. 4 only schematically illustrated graphene layers 58, which are rolled into each other to form the tubular cross section. Because of this cross-sectional shape, the tubes assume a curvilinear or curved course, which promotes the formation of balls, and enter into a particularly intimate connection with the metal material during later processing.

The removed balls are functionalized by pressurization at about 9.8 MPa. As a result of the application of pressure, at least the outermost layers 58 of the individual carbon nanotubes partially break open, as a result of which their surface is, as it were, roughened and an even more intimate bond with the metal is made possible.

Fig. 5 shows an apparatus for producing a metal powder. The apparatus comprises a melting chamber 60 containing a molten aluminum alloy. The metal is sprayed by the pressure of an argon drive gas 62 through a nozzle 64 into a chamber 66 and thereby atomized. In the chamber 66, the atomized metal is quenched by an argon gas which is sprayed into the chamber 66 through another nozzle 68, solidifying the atomized metal drops into particles which collect at the bottom of the chamber 66 as metal powder.

Fig. 6 shows a ball mill for mechanically alloying the powder of carbon nanotube prepared in the above-described manner with the metal powder. The mill comprises a chamber 70 in which a rotor can be driven in rotation in the direction of an arrow 76 about a rotation axis oriented perpendicular to the plane of the drawing. The rotor includes a plurality of pairs of arms 72 arranged one behind the other in the axial direction, wherein the outer ends of the arms 72 can reach a speed of at least 8 m / s or at least 11 m / s during operation, whereby the hard metal balls 74 provided in the chamber 70 are correspondingly accelerated ,

To prepare the mechanical alloy, the chamber 70 is filled with the powder of the balls of carbon nanotubes and the metal powder. During grinding, the bumps between the balls 74 cause the material present between the balls 74, i. the metal particles and the carbon nanotubes are repeatedly deformed, broken and welded together so that the carbon nanotubes are sealed in the metal particles to result in a powdered composite whose particles contain the metal and the carbon nanotubes. The metal and carbon nanotubes are welded together in the particles and form an alloy, resulting in a substantially homogeneous distribution of the carbon nanotubes in the metallic particles. The grain size of the metal is reduced by the milling and the carbon nanotubes are embedded in the metal so that they extend along the grain boundaries of the metal or embedded within metal grains.

From the resulting powdery composite material is removed by a powder metallurgy process such as e.g. produced by extrusion a solid body, which serves as a base body for the rotor disks of the vacuum pump.

Fig. 7 shows a manufactured in this way, substantially cylindrical body 78. For producing a rotor disk, a the disk-shaped basic shape of the rotor disk corresponding disc are cut off from the base body 78, which can then be processed by milling a support ring and the radially adjoining blades to a rotor disk. Instead of a single rotor disk, for example, a bell rotor could be produced.

LIST OF REFERENCE NUMBERS

10

casing

12

flange

14

suction

16

axis of rotation

18

rotor shaft

20

drive coil

22

Impeller

24, 26

pivot bearing

28

rotor blade

30

rotor disc

32

stator

34

pump outlet

36

support ring

40

hired surface

42

Fluidized bed reactor

44

heater

46

inlet

48

outlet

50

catalyst inlet

52

removal opening

54

Catalyst Partikelagglomerat

56

reactant

58

graphene layer

60

melting chamber

62

drive gas

64

jet

66

chamber

68

jet

70

chamber

72

poor

74

Bullet

76

arrow

78

body

Claims (15)

1. A vacuum pump,
   wherein at least one component (30) of the vacuum pump comprises or consists of a material which includes a metal and nanoparticles,
   characterized in that
   the material includes between 0.5 to 10% by weight of nanoparticles.
2. A vacuum pump in accordance with claim 1,
   characterized in that
   a stator and at least one rotor member (30) are provided, with the rotor member (30) being rotatably supported with respect to the stator.
3. A vacuum pump in accordance with claim 1 or claim 2,
   characterized in that
   the metal comprises a light metal such as aluminum and in particular an aluminum alloy of the type 5083 or 2618.
4. A vacuum pump in accordance with any one of the preceding claims,
   characterized in that
   the material includes between 1 and 9% by weight, and preferably between 2 and 4% by weight, of nanoparticles.
5. A vacuum pump in accordance with any one of the preceding claims,
   characterized in that
   the metal forms grains having a mean grain size between 1 and 400 nm, in particular between 1 and 200 nm, with the grains preferably being at least partly separated from one another by the nanoparticles.
6. A vacuum pump in accordance with any one of the preceding claims,
   characterized in that
   the nanoparticles have an aspect ratio of at least 3, preferably of at least 10, and particular preferably of at least 30.
7. A vacuum pump in accordance with any one of the preceding claims,
   characterized in that
   carbon nanotubes are provided as nanoparticles and have a scroll structure comprising a plurality of rolled-up graphite layers, with each graphite layer comprising two or more graphene layers (58) arranged above one another.
8. A vacuum pump in accordance with any one of the preceding claims,
   characterized in that
   the material can be obtained from a powdery composite material including a metal and nanoparticles by a powder-metallurgical process, with the powdery composite material preferably being able to be obtained by a mechanical alloying of a metal powder with nanoparticles.
9. A vacuum pump in accordance with any one of the preceding claims,
   characterized in that
   the component is a rotor member of the vacuum pump and in particular comprises or consists of a rotor disk (30) of a turbomolecular pump stage of the vacuum pump.
10. A vacuum pump in accordance with claim 9,
    characterized in that
    the rotor disk (30) comprises a plurality of rotor vanes (28) which each completely or partly comprise the material.
11. A method of manufacturing a vacuum pump, in particular in accordance with any one of the preceding claims, which comprises at least one component (30) of the vacuum pump at least partly being manufactured from a material which includes a metal and nanoparticles, characterized in that
    the material includes between 0.5 to 10% by weight of nanoparticles.
12. A method in accordance with claim 11,
    characterized in that
    the formation of the component (30) comprises a mechanical machining of a base body (78), at least partly formed from the material, for the component, with the machining in particular comprising a material-removing machining.
13. A method in accordance with claim 11 or claim 12,
    characterized in that
    a powdery composite material is provided which includes a metal and nanoparticles; and
    in that the powdery composite material is processed into the component or into a base body for the component (30) by a powder-metallurgical process.
14. A method in accordance with claim 13,
    characterized in that
    the provision of the powdery composite material comprises a mechanical alloying of a metal powder with nanoparticles, with the alloying in particular being carried out such that the metal has a mean grain size between 1 and 200 nm in the powdery composite material, with the grains of the metal being at least partly separated from one another by the nanoparticles.
15. A vacuum pump which is obtained or can be obtained in accordance with a method in accordance with any one of the claims 11 to 14.

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