WO2015055711A1

WO2015055711A1 - Method and device for producing particles in an atmospheric pressure plasma

Info

Publication number: WO2015055711A1
Application number: PCT/EP2014/072106
Authority: WO
Inventors: Jörg IHDE; Ralph Wilken; Jost Degenhardt; Sergey Stepanov
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2013-10-15
Filing date: 2014-10-15
Publication date: 2015-04-23
Also published as: DE102013017109A1

Abstract

The invention relates to a method for producing particles (30) using an atmospheric pressure plasma, in which the plasma is generated by a discharge (15, 15') between electrodes (16, 16', 16"; 5, 32) in a process gas (18), and at least one of the electrodes is a sacrificial electrode (16, 16', 16") from which material is removed by the discharge, wherein the removed material is particles and/or particles arise from the removed material. A portion of the sacrificial electrode is actively cooled so that the mean temperature of the sacrificial electrode, in a region of the sacrificial electrode outside of the discharge region (17, 17', 17") of the sacrificial electrode, is lower than within the discharge region of the sacrificial electrode. The invention also relates to a device for producing particles (30) using an atmospheric pressure plasma, which comprises: a housing (5) having a channel (7, 7', 7"), at least two electrodes (16, 16', 16"; 5, 32) which are arranged at least partially in the channel, and a voltage source (22) which is designed to apply a voltage between the at least two electrodes. The at least two electrodes are designed to generate the plasma by a discharge (15, 15') between the electrodes in a process gas (18) in the channel, and at least one of the electrodes is a sacrificial electrode (16, 16', 16") from which material is removed by the discharge, wherein the removed material is particles and/or particles arise from the removed material. The device further comprises a cooling device (2) which is designed to actively cool a portion of the sacrificial electrode so that the mean temperature of the sacrificial electrode, in a region of the sacrificial electrode outside of the discharge region (17, 17', 17") of the sacrificial electrode, is lower than within the discharge region of the sacrificial electrode.

Description

METHOD AND DEVICE FOR PRODUCING PARTICLES IN ONE

ATMOSPHERIC PRESSURE PLASMA

FIELD OF THE INVENTION

The present invention according to a first aspect relates to a method of producing particles using an atmospheric pressure plasma. The method can be used to efficiently form particles, in particular microparticles and nanoparticles. According to a further aspect, the invention relates to an apparatus for producing particles, in particular microparticles and nanoparticles, using an atmospheric pressure plasma.

STATE OF THE ART

Micro- and nanoparticles have been used for several years in various fields of technology to modify the properties of products. For example, incorporation of such particles can improve optical, electrical (e.g., conductivity), thermal (e.g., thermal conductivity), electro-magnetic, and mechanical properties (such as stability or abrasion resistance).

In order to meet the demand for such particles, numerous methods have been proposed.

First of all, the low-pressure procedures should be mentioned here.

For example, DE-A-198 24 364 relates to a method for applying wear protection layers having optical properties to surfaces. The method comprises at least two different ones

Abscheidesch ritte. One step is a plasma assisted CVD process for deposition of a wear protection matrix and the other step is material deposition by a PVD technique for incorporation of optically functional material into the matrix. The PVD technique used can be, for example, a sputtering method.

WO 2005/061754 relates to a method for producing a functional layer, wherein a deposition material is deposited on a substrate under the influence of a plasma and at the same time at least one second material is applied to the substrate by means of a second deposition method. As a second

Deposition experienced is called among other PVD, such as sputtering.

WO 2005/048708 deals with an antimicrobial and non-cytotoxic coating material comprising a biocide layer and a transport control layer covering this layer. In Embodiment 6 of this document, the biocide layer is formed by a low-pressure DC magnetron sputtering process and the

Transport control layer applied in a second step by a plasma polymerization process. Atmospheric pressure processes place high demands on the apparatus, since vacuum chambers are required, usually allow only low deposition rates (in the range of a few nm / s) and make masks necessary in order to coat locally. Furthermore, due to the limited capacity of

Vacuum chambers limits on the size of substrates or components that can be coated.

To avoid these disadvantages of the low pressure processes, atmospheric pressure plasma processes have been proposed.

For example, DE-A-199 58 473 uses a plasma-based high-temperature source which is said to operate in a fine vacuum up to the near-atmospheric pressure range. Specifically described is the simultaneous deposition of a matrix layer and particles embedded therein as a functional coating. For this purpose, a micro-scale or nanoscale metal powder, such as TiN powder, is introduced into the plasma together with a carrier gas via the gas supply.

DE-A-198 07 086 relates to a method for coating substrate surfaces in a plasma-activated process at atmospheric pressure. In this case, a gas phase, which may contain a pulverulent solid, introduced into the plasma jet.

Also in WO 01/32949 a precursor material is fed into the plasma jet so as to coat surfaces. The precursor material may contain solid, for example pulverulent constituents. This allows particles to be embedded in the deposited layers.

All the atmospheric pressure plasma processes described above for producing layers having dispersed therein particles have in common that the particles, for example in the form of powders, are fed from outside into the plasma jet. This approach poses considerable problems when microparticles are involved and even more so when nanoparticles are to be incorporated in layers. The reason is that microparticles, and especially nanoparticles, when present in the form of powders, are highly prone to agglomeration.

DE-B-102 23 865 relates to a process for the plasma coating of workpieces, in which with the aid of a plasma nozzle by electric high-frequency discharge, a beam of atmospheric plasma is generated, with which the workpiece surface to be coated is painted over. The method is characterized in that at least one component of the coating material is contained as a solid in an electrode of the plasma nozzle and is sputtered off the electrode by the high-frequency discharge, According to DE-B-102 23 865, the sputtered material is present predominantly in the form of very reactive ions or radicals. According to the teaching of this patent, these species form homogeneous coatings, for example of metals or metal compounds. The production of particles, let alone micro- or

Nanoparticles, is not disclosed in DE-B-102 23 865.

US 5,808,270 relates to an apparatus and method for thermal plasma arcfie metal wire spraying which produces an extended arc and a supersonic plasma jet. A metal wire serving as an anode is continuously introduced into the plasma jet where the extended plasma arc jumps onto the wire tip and melts the wire, and the supersonic plasma jet atomizes and discharges the molten metal particles to form a coating. Also US 5,808,270 teaches no generation of particles, let alone micro- or nanoparticles.

DE-B-10 2009 031 857 discloses a plasma torch for cutting a material by means of a high-energy plasma jet. Since the high energy density of the plasma jet leads to a thermal load on a nozzle of the plasma torch, it is cooled in order to extend its service life. A production of particles does not occur in the plasma torch.

DE-A-10 2009 048 397 relates to a process for the preparation of surface-modified particles in an atmospheric pressure plasma using a sputtering electrode from which particles are sputtered by a discharge. In order to prevent an excessive increase in the temperature at the sputtering electrode, DE-A-10 2009 048 397 teaches to limit a discharge induced power input to the sputtering electrode by pulsing or driving a discharge generating voltage generator

Sputter electrode is rotated or oscillated.

However, this limitation of Leistungsetntrags on the sputter electrode leads to a reduction in the sputter yield, ie the rate of manufacture of the particles, so that, for example, long coating times are necessary to deposit the particles on a surface of a substrate. Therefore, the realizable

Coating speeds are small or the number of cycles is large, so that a process-dependent heat flow can lead to substrate damage or the substrates to be treated are limited due to the permissible temperature limit. Moreover, the achievable concentration of separated particles on a surface to be coated is limited, since at high concentrations, in particular at higher temperatures, the particles can combine or agglomerate into larger clusters.

The invention has for its object to provide a method and apparatus for the production of particles using an atmospheric pressure plasma, which allow efficient production of particles, in particular of microparticles and nanoparticles, with high production rate and controlled particle size distribution. SUMMARY OF THE INVENTION

This object is achieved by the method according to the independent claim 1 and

Device according to independent claim 17 solved. Advantageous embodiments of the invention follow from the dependent claims.

According to the first aspect, the present invention provides a method of producing particles using an atmospheric pressure plasma, wherein the plasma is generated by a discharge between electrodes in a process gas, at least one of the electrodes is a sacrificial electrode or

A target electrode from which material is ablated or detached by the discharge, (i) the abraded material is particulate, and / or (ii) particles are formed from the abraded material, and a portion of the sacrificial electrode is actively cooled such that the average temperature of the sacrificial electrode in a region of the sacrificial electrode outside the discharge area of the sacrificial electrode is lower than inside the area of the sacrificial electrode

Discharge area of the sacrificial electrode.

The term "area of the sacrificial electrode outside the discharge area of the sacrificial electrode" means the entire area of the sacrificial electrode which is outside the discharge area of the sacrificial electrode.

According to the method of the invention, at least a portion of the sacrificial electrode is actively cooled.

The terms "sacrificial electrode" and "target electrode" are used interchangeably herein.

Particles can be formed or formed by agglomeration processes of the ablated material, in particular in a relaxing region of the atmospheric pressure plasma. In particular, in the period between the removal of the material from the sacrificial electrode and any deposition of the particles on the surface of a substrate, particles may form or form. As it turned out, the formation or formation of particles takes place above all in a relaxing region of the atmospheric pressure plasma. The inventors have found that in the context of the method according to the invention the yield of particles, in particular nanoparticles, can be further increased by controlling the residence time of the material in the relaxing region of the atmospheric pressure plasma. The length of stay in the relaxing area of the

Atmospheric pressure plasma can be achieved by increasing the path length in the relaxing region of the

Atmospheric pressure plasma can be increased.

The control of the residence time is advantageously carried out taking into account the finding that, by increasing the residence time of the material in the relaxing region of the atmospheric pressure plasma, first Yield of nanoparticles can be increased further, wherein there is an upper limit of the residence time, from which it comes to the increased formation of larger particles, in particular microparticles.

An "active" plasma region is generally understood to mean a plasma region which is within the volume delimited by the electrodes between which a voltage is applied, by which the plasma is generated.In the active plasma region, free electrons and ions are present separately ,

By contrast, the relaxing region of the plasma is outside the excitation zone, which is delimited by said electrodes. The relaxant region of the plasma is sometimes referred to as an "after-gtow." There are no more free electrons and ions in the relaxing region of the plasma, but rather excited atoms or molecules.

In the case of a plasma nozzle, the relaxing region of the atmospheric pressure plasma is the region on the downstream side of the excitation zone (that is, starting at the electrode closer to the outlet of the plasma nozzle), which is delimited by the end of the visible plasma flame. Typically, the plasma flame extends about 10 mm beyond the exit of the plasma nozzle.

In a standard atmospheric pressure plasma nozzle, the distance between the electrode closer to the outlet of the plasma nozzle and the outlet is typically in the range of 2-5 mm. As the inventors have found, the yield of nanoparticles was compared to the above mentioned. Standard atmospheric pressure plasma nozzle, significantly larger when an atmospheric pressure plasma nozzle with a distance between the electrode closer to the outlet of the plasma nozzle and the outlet of the nozzle of about 50 mm was used. In both cases, the length of the plasma flame, which extended beyond the outlet of the plasma nozzle, was comparably large (about 10 mm).

As an electrode in the sense of the invention, each element, e.g. each component of the apparatus used for the inventive method, in particular a plasma nozzle understood, which is at least temporarily starting or end point of the discharge filament.

For the purposes of the present application, the electrode, from which in the inventive method by the plasma-generating discharge material is removed or detached, as a "sacrificial electrode" or

In the method according to the invention, a plurality of electrodes, in particular electrodes made of the same or different electrode materials, may be sacrificial electrodes. However, exactly one of the electrodes may also be a sacrificial electrode.

By "atmospheric pressure plasma", also referred to as AD plasma or normal pressure plasma, is meant a plasma in which the pressure is approximately equal to atmospheric pressure C. Tendero et al "Atmospheric pressure plasmas: A review", Spectrochimica Acta Part B: Atomic Spectroscopy, 2006, pp. 2-30 for an overview of atmospheric pressure plasmas.

The term "particle" refers to particles of a particular material, in particular macroscopic particles, as distinct from individual atoms or molecules or clusters thereof.

The term "average temperature of the sacrificial electrode" refers to the temporal and local mean value of the temperature, ie the mean value of the temperature over a certain period, namely the period in which the discharge occurs, and over a certain Fiächenbereich the sacrificial electrode, such as the Entiadungsbereich the sacrificial electrode or the area of the sacrificial electrode outside the discharge area.

The discharge area of the sacrificial electrode is the area of the sacrificial electrode in which the discharge predominantly takes place. The term "predominantly" herein defines that the discharge area of the sacrificial electrode is the area of the sacrificial electrode in which the discharge occurs over a period of time that is 50% or more of the total

Discharge period, ie the entire period in which the discharge takes place at the sacrificial electrode.

By actively cooling the portion of the sacrificial electrode, the discharge TE1 of the mean temperature of the sacrificial electrode in the portion of the sacrificial electrode after the discharge is shut off falls within a period of not more than 4 minutes, more preferably not more than 3 minutes, more preferably not more as 2 min, more preferably not more than 1 min, and most preferably not more than 40 s, to a value of 1 / e ^χ TE1, where e is the Euler number. Active cooling takes place by means of a cooling device.

The sacrificial electrode is made of an electrically conductive and thermally conductive material, such as metal.

According to the method of the invention, the portion of the sacrificial electrode is actively cooled such that the average temperature of the sacrificial electrode in the region of the sacrificial electrode is outside the discharge area of the sacrificial electrode

Sacrificial electrode is lower than within the discharge area of the sacrificial electrode. Consequently, there is one

Temperature difference or a temperature gradient between the discharge area and the area of

Sacrificial electrode outside the discharge region, so that heating of the discharge region by the discharge by heat transfer from the discharge region to the region of the sacrificial electrode outside the discharge region can be compensated or compensated.

Thus, even with a high power input by the discharge based on the area of the sacrificial electrode or sacrificial electrodes excessive heating of the sacrificial electrode or sacrificial electrodes can be avoided, so that a so-called Abspatzen from the material is reliably prevented. This way you can

unwanted large-scale melting of Opferelektrodenmateriai and thus a transfer of spratzigem material can be avoided on the substrate surface. Therefore, in particular by the thus possible high power input to the sacrificial electrode or sacrificial electrodes, a high manufacturing or production rate of the particles can be achieved while the particle size is kept low and the size distribution of the particles can be precisely controlled or controlled. Consequently, efficient production of particles of defined size is made possible.

Furthermore, due to the higher production rate and thus also higher separation efficiency of the particles when depositing the particles on a surface of a substrate, temperature-sensitive substrate materials can also be coated since the process times and thus the heat input per time and area are considerably reduced.

The method according to the invention can also be combined with a chemical vapor deposition (CVD) process, in particular in one step, in particular to form a continuous layer with particles dispersed therein. In this case, the method according to the invention enables a balanced and uniform concentration of particles in the layer. Moreover, the concentration of particles in the layer can be significantly increased compared to methods without active cooling.

The portion of the sacrificial electrode may be actively cooled so that the average temperature of the sacrificial electrode in a region of the sacrificial electrode in which no material is removed is lower than in a region of the sacrificial electrode in which material is removed.

The portion of the sacrificial electrode may be actively cooled such that the average temperature of a portion of the sacrificial electrode that is in the region of the discharge is higher than the average temperature of a portion of the sacrificial electrode that is outside of the discharge.

The discharge area of the sacrificial electrode may be a geometrically excellent area of the sacrificial electrode. For the purposes of the present application, a geometrically excellent region is understood to mean a region in which the discharge concentrates due to the high field strength prevailing there. Typical examples of such geometrically marked regions in electrodes are points, corners and edges.

In the method according to the invention, the entire sacrificial electrode, that is to say the discharge region of the sacrificial electrode and the region of the outer electrode, can be actively cooled outside the discharge region.

The cooling of the section of the sacrificial electrode or sacrificial electrodes can be carried out via heat conduction. Since heat conduction enables rapid and effective heat removal from the sacrificial electrode, the sacrificial electrode can thus be cooled in a particularly efficient manner. The cooling of the portion of the sacrificial electrode or sacrificial electrodes can be carried out by a cooling medium or coolant. The cooling medium or coolant may be a solid, liquid or gaseous cooling medium or coolant. In particular, water, water-glycol, dry ice in ethanol, liquid nitrogen, CO2 ice, etc. can be used as the cooling medium. The cooling by a cooling medium allows a particularly simple and effective cooling of the sacrificial electrode. Particularly preferably, a liquid cooling medium or coolant is used.

According to an embodiment of the present invention, the cooling medium only comes into contact with the area of the sacrificial electrode outside the discharge area of the sacrificial electrode or only with part of the area of the sacrificial electrode outside the discharge area of the sacrificial electrode. In this way, the area of the sacrificial electrode outside the discharge area can be efficiently cooled, whereby deterioration of the discharge in the discharge area by the cooling process is particularly reliably avoided. Moreover, due to the high temperature difference caused by the cooling between the area of the sacrificial electrode which is cooled by the cooling medium outside the discharge area and the discharge area, a rapid temperature difference occurs

Ensures heat dissipation from the discharge area.

According to an embodiment of the present invention, the sacrificial electrode enters a cooling region at an entry point of the sacrificial electrode, in which the portion of the sacrificial electrode is actively cooled, the entry point being on a side of the cooling region opposite to the discharge region of the sacrificial electrode, and the difference between average temperature of the sacrificial electrode within the discharge area of the sacrificial electrode and the mean temperature of the sacrificial electrode at the point of entry in the range of Ts-393K to Ts-77K, preferably from T _s- 373K to Ts-77K, more preferably T _s 323K to Ts - 77K, and most preferably from T _s - 293K to T _s - 77K, where T _{s is} the melting temperature of the sacrificial electrode material in Kelvin (K).

The cooling region may be the cooling device or a part of the cooling device. The sacrificial electrode may come in contact with a solid, liquid or gaseous cooling medium in the cooling region, in particular in direct or direct or indirect or indirect contact.

In this way, a particularly efficient heat dissipation from the discharge region of the sacrificial electrode can be ensured and melting of the sacrificial electrode in the discharge region can be prevented particularly reliably, so that a spattering of material of the sacrificial electrode is avoided even with a high power input to the sacrificial electrode.

By actively cooling the portion of the sacrificial electrode, the discharge TE2 caused by the discharge can increase the average temperature of the sacrificial electrode at the entry point after the discharge is turned off within a period of not more than 4 minutes, preferably not more than 3 minutes, more preferably not more than 2 min, more preferably not more than 1 min, and most preferably not more than 40 s, fall to a value of 1 / e χ TE2. The sacrificial electrode may be at least partially disposed in a channel of a housing. The housing may be the housing of a plasma nozzle. The channel can be traversed by the process gas. A portion of the sacrificial electrode may be disposed in the housing outside the channel and / or outside the housing.

The cooling medium may in particular come into contact with a part or region of the sacrificial electrode, in particular in direct or direct, ie physical, or thermal or indirect contact, which is arranged in the housing outside the channel and / or outside the housing. In particular, the cooling medium can come into contact only with this area, in particular in direct or direct or thermal or indirect contact.

The thermal or indirect contact is made by a secondary medium, such as a wärmeieitfähige wall or wall, which is arranged between the cooling medium and the part or region of the sacrificial electrode. For example, the sacrificial electrode can be guided at least in regions through a heat-conductive tube or the like. An active cooling of a portion of the sacrificial electrode can be done by direct contact of this tube with the cooling medium.

According to an embodiment of the present invention, the sacrificial electrode enters a cooling region at an entrance point of the sacrificial electrode, in which the portion of the sacrificial electrode is actively cooled, the entry point being on a side of the cooling region opposite to the discharge region of the sacrificial electrode, and exceeds the mean temperature of Sacrificial electrode in the entrance region not 393 K, preferably not 373 K, more preferably not 323 K and most preferably not 293 K. In this way, a particularly efficient heat dissipation from the discharge region of the sacrificial electrode is ensured. For this middle

In particular, temperatures of the sacrificial electrode at the point of entry may be the difference between the mean temperature of the sacrificial electrode within the discharge area of the sacrificial electrode and the average temperature of the sacrificial electrode at the entry point in the range of Ts-393K to Ts-77K, preferably Ts-373K to Ts-77K, more preferably from Ts-323K to Ts-77K, and most preferably from Ts-293K to Ts-77K.

In the method according to the invention, the mean temperature of the sacrificial electrode within the

Discharge range of the sacrificial electrode are chosen so that it does not exceed the melting temperature of the material of the sacrificial electrode. Consequently, a melting of the discharge region of the sacrificial electrode and thus a sputtering of sacrificial electrode material is particularly reliably avoided.

The sacrificial electrode may have an elongated shape. For the purposes of the present application, the term "elongated shape" designates a shape whose dimension is larger in one dimension, in particular considerably larger, than in the two other dimensions. In particular, the sacrificial electrode may be a wire, a rod or a hollow profile, for example an elongate hollow profile.

The discharge region may be located at one end of the elongate sacrificial electrode, in particular a wire. The end of the elongated sacrificial electrode may be in the form of a tip, in particular a wire tip. According to one embodiment of the present invention, the elongated sacrificial electrode, in particular the wire, the rod or the elongated hollow profile, has an average diameter of 0.1 to 20 mm, preferably 0.1 to 10 mm, more preferably 0.1 to 5 mm and more preferably from 0.5 to 1.5 mm.

The sacrificial electrode may be introduced into the plasma nozzle in a direction parallel to a flow direction of the process gas in the plasma nozzle or in a direction perpendicular to the flow direction of the process gas in the plasma nozzle. In the case of an elongated sacrificial electrode, the longitudinal axis of the sacrificial electrode can be parallel to the flow direction of the process gas in the plasma nozzle or perpendicular to the flow direction of the

Process gas in the plasma nozzle are.

A concentration of the discharge on a limited area of the sacrificial electrode or sacrificial electrodes can be promoted by the gas flow of the process gas. Here, for example, proves a directed vortex-shaped flow of the process gas, which can be generated by a twisting device, as advantageous.

As Materia! the sacrificial or sacrificial electrodes are metals such as copper, aluminum, indium, zinc, titanium and magnesium, especially noble metals such as gold, silver, platinum and palladium, but also metal alloys, metal oxides (e.g., BaO, zinc oxide, tin oxide) and carbon. In addition, the sacrificial electrode may be made of aluminum bronze.

The removal of material from the sacrificial electrode may be favored by the choice of electrode material. Silver, for example, is a material from which material can be removed very easily. In particular, a favorable removal of material for conventional electrode geometries can be achieved for silver electrodes.

In the method according to the invention, the position of the discharge region of the sacrificial electrode, for example by a Detektorsei device, in particular an optical and / or electronic

Detecting device to be detected, in particular optically and / or electronically detected. For example, the optical detection of the position of the discharge region of the sacrificial electrode can be carried out by an endoscope.

The term "position of the discharge area of the sacrificial electrode" herein denotes the position of the

Discharge region of the sacrificial electrode relative to a housing of a device for producing particles, such as a plasma nozzle, on which the sacrificial electrode is provided. Thus, a change of this position or a deviation of this position from a predetermined position can be determined reliably and accurately.

According to an embodiment of the present invention, the sacrificial electrode is guided or moved so that the position of the discharge area of the sacrificial electrode, e.g. relative to the housing, during the process, that is, while performing the method, remains substantially unchanged.

In this way it can be ensured particularly reliably that both the production rate of the particles and the size distribution of the particles remain essentially unchanged.

Moreover, it can be ensured that there is neither too much nor too little sacrificial electrode material in the process gas, for example in the channel of the housing. If there is too little sacrificial electrode material in the

Discharge channel is present, the formation of a sufficient temperature difference between the discharge region and the area of the sacrificial electrode outside the discharge region is difficult, so that the efficiency of the cooling can be impaired. On the other hand, the presence of too much

Sacrificial electrode material in the discharge channel negatively affect the particle generation efficiency.

For example, the sacrificial electrode may be a traceable sacrificial electrode, in particular a traceable wire sacrificial electrode. For the purposes of the present application "traceable" in connection with an electrode means that the position of the discharge region of the sacrificial electrode by Nachschieben or

Retracting the sacrificial electrode can be controlled or adjusted.

The sacrificial electrode may be guided or moved based on the detected position of the discharge area of the sacrificial electrode such that the position of the discharge area of the sacrificial electrode remains substantially unchanged during the process despite the process-related removal of material.

This approach allows a particularly accurate and reliable adjustment of the position of the discharge area. In particular, the process of correspondingly guiding or moving the sacrificial electrode may be automated based on the sensed position, for example, by means of a feedback loop or a feedback loop.

The discharge may be a pulsed or pulsating discharge. In particular, the pulsed or pulsating discharge may be provided by pulsed or pulsed operation of a voltage source, such as a voltage source. a generator adapted to apply a voltage (e.g., DC voltage), in particular a high voltage, between the electrodes, and with which the discharge, which is preferably one

Arc discharge is, is effected. In this way, a pulsed or pulsating voltage can be generated. Preferably, an asymmetrical AC voltage is generated. The pulse frequency of the voltage source, eg, the generator, is not particularly limited and may be 5 to 70 kHz, with the range of 15 to 40 kHz being preferred. For carrying out the method according to the invention, pulse frequencies of 16 to 25, in particular 17 to 23 kHz, have proved to be particularly advantageous.

Applicable process gases which can be used, for example, in plasma nozzles are familiar to the person skilled in the art. For example, nitrogen, oxygen, hydrogen, noble gases (especially argon), ammonia (NH3), hydrogen sulfide (H2S) and mixtures thereof, in particular compressed air, nitrogen-hydrogen mixtures and inert gas-hydrogen mixtures can be used.

The flow rate of the process gas through the atmospheric jerk piasma is not particularly limited and may be, for example, in the range of 300 to 10,000 l / h. Since it has been shown that lower flow rates of the process gas tend to increase the Partikeiausbeute, the flow rate according to the invention is preferably in the range of 500 to 4000 l / h.

In the method according to the invention, the particles are preferably transported by the process gas, in particular transported away from the discharge region of the sacrificial electrode.

Preferably, the particles are micro- and / or nanoparticles. For the purposes of the present application, micro- and nanoparticles are understood as meaning particles whose diameter is in the range of microns or nanometers. The particles can have a particle size or a particle diameter in the range from 2 nm to 20 μm, preferably from 5 nm to 10 μm, more preferably from 10 nm to 5 μm, even more preferably from 10 nm to 1 μm and most preferably from 10 nm to 200 μm nm. The particle size or the particle diameter of the particles can also be in a range from 2 nm to 10 μm, 2 nm to 5 μm, 5 nm to 5 μm, 2 nm to 1 μm, 5 nm to 1 μm, 2 nm to 200 nm, 5 nm to 200 nm, 20 nm to 200 nm or 50 nm to 200 nm.

Such micro- and / or nanoparticles can be generated by the process according to the invention with a high production rate and controlled particle size control, as has already been described in detail above.

According to a particularly preferred embodiment of the present invention, the particles are nanoparticles, that is to say particles whose diameter is in the nanometer range, in particular in the range from 2 to 100 nm.

Furthermore, the average (volume-averaged) particle diameter of the particles is preferably in the range of nanometers or micrometers, more preferably in the range of 2 nm to 20 μm, very particularly preferably in the range of 2 to 100 nm. The determination of the particle size of very small particles, such as nanoparticles, is for example with

Laser scattering or transmission electron microscopy (TE) possible. For larger particles, the sieve analysis and centrifugation methods are also available.

According to a further aspect, the present invention relates to a method for producing particles using an atmospheric pressure plasma, in particular in an atmospheric pressure plasma, wherein the plasma is generated by a discharge between electrodes in a process gas, at least one of the electrodes is a sacrificial electrode, from which the discharge of material is ablated, (i) the abraded material is particulate, and / or (ii) particles are formed from the abraded material, and the sacrificial electrode is guided or moved such that the position of the discharge area of the sacrificial electrode during the process That is, during the implementation of the method, remains substantially the same.

The position of the discharge region of the sacrificial electrode can be detected, in particular optically and / or electronically, for example by an endoscope.

The sacrificial electrode may be guided or moved based on the detected position of the discharge area of the sacrificial electrode such that the position of the discharge area of the sacrificial electrode remains substantially the same during the process, despite the process-related removal of material.

According to a further aspect, the present invention relates to an apparatus for the production of particles using an atmospheric pressure plasma, in particular in an atmospheric pressure plasma. The device comprises a housing with a channel, at least two electrodes, which are arranged at least partially in the channel, and a voltage source, which is adapted to apply a voltage (eg DC voltage), in particular a high voltage, between the at least two electrodes the at least two electrodes are adapted to generate the plasma by a discharge between the electrodes in a process gas in the channel, and at least one of the electrodes is a sacrificial electrode from which material is removed by the discharge, and the abraded material is particles and / or arise from the removed material particles.

In addition, the device according to the invention comprises a cooling device which is designed to actively cool a section of the sacrificial electrode such that the mean temperature of the sacrificial electrode in a region of the sacrificial electrode outside the discharge region of the sacrificial electrode is lower than within

Discharge area of the sacrificial electrode. The device according to the invention provides the advantageous effects which have already been described in detail above for the method according to the invention. In particular, the device enables production of particles with a high production rate with a controlled size distribution of the particles and small particle sizes.

The cooling device may be configured to cool the portion of the sacrificial electrode so that the average temperature of the sacrificial electrode in a region of the sacrificial electrode in which no material is removed or detached is lower than in a region of the sacrificial electrode, in the material or abraded is replaced.

The cooling device may be configured to cool the portion of the sacrificial electrode such that the average temperature of a portion of the sacrificial electrode that is in the region of the discharge is higher than the average temperature of a portion of the sacrificial electrode that is outside of the discharge.

The device according to the invention may comprise a PSasma nozzle or be designed as a plasma nozzle.

Using the device according to the invention, in particular, if this is designed as a plasma nozzle, the particles produced can be targeted, for example, from an outlet of the channel or the housing, applied. Consequently, a local coating with the produced particles can be performed on the surface of a substrate.

For example, the device, in particular a plasma nozzle, may be suspended during the dispensing or deposition of the particles, e.g. through the outlet of the channel or housing, on the surface of the substrate relative to the substrate. In particular, the device may be moved relative to the substrate in one or more directions that are substantially parallel to the surface of the substrate. In this way, a precisely controlled local application of the produced particles to the surface of the substrate is made possible.

The relative speed between the device according to the invention, in particular the plasma nozzle, and the substrate to be coated can be in the range of mm / s to m / s and, for example, up to 200 m / min. Due to the mentioned relative speed, the Partikelabscheidemenge per area can be adjusted.

In addition, the amount of deposition per area can be adjusted by repeating the deposition process, ie the number of cycles. Increasing the relative speed while increasing the number of cycles can be particularly advantageous in temperature-sensitive materials, such as polymers. The distance between the device, in particular the plasma nozzle, and the substrate, which likewise influences the particle deposition amount per area, can be 1 mm to several cm, for example a maximum of 10 cm.

The apparatus may further include a gas supply device configured to supply a process gas into the channel of the housing. The cooling device may be configured to cool the portion of the sacrificial electrode via heat conduction.

The cooling device may be configured to cool the portion of the sacrificial electrode by a cooling medium or coolant, for example a solid, liquid or gaseous cooling medium or coolant.

The cooling device can be set up such that the cooling medium or coolant comes into contact only with the region of the sacrificial electrode outside the discharge region of the sacrificial electrode.

The cooling device can be set up so that the sacrificial electrode does not come into direct contact with the cooling medium, but is cooled by thermal contact via a solid wall, preferably by heat conduction.

According to an embodiment of the present invention, the sacrificial electrode enters a cooling area at an entrance point of the sacrificial electrode in which the portion of the sacrificial electrode is actively cooled, the entrance portions being on a side of the cooling area opposite the discharge area of the sacrificial electrode, and the cooling means is so in that, during operation of the device, in particular during stationary operation of the device, the difference between the mean temperature of the sacrificial electrode within the discharge area of the sacrificial electrode and the mean temperature of the sacrificial electrode at the entry point in the range of Ts - 393 K to Ts - 77 K , preferably from T _s - 373 K to T _s - 77 K, more preferably from T _s - 323 K to T _s - 77 K, and most preferably from T _s - 293 K to Ts - 77 K, where T _{s is} the melting temperature of the sacrificial electrode material in Kelvin (K).

The cooling region may be the cooling device or a part of the cooling device. The sacrificial electrode may come into contact with a solid, liquid or gaseous cooling medium in the cooling region, in particular in direct or direct or indirect or indirect contact.

According to an embodiment of the present invention, the sacrificial electrode enters a cooling region at an entrance point of the sacrificial electrode, in which the portion of the sacrificial electrode is actively cooled, the entry point being on a side of the cooling region opposite to the discharge region of the sacrificial electrode, and the cooling device is thus arranged in that during operation of the device, in particular during stationary operation of the device, the average temperature of the sacrificial electrode at the point of entry does not exceed 393 K, preferably 373 K, more preferably 323 K and most preferably 293 K. For these average temperatures of the sacrificial electrode in the entrance region, in particular the difference between the mean temperature of the sacrificial electrode within the discharge area of the sacrificial electrode and the mean temperature of the sacrificial electrode

Sacrificial electrode at the point of entry in the range of T _s - 393 K to Ts - 77 K, preferably from T _s - 373 K to T _s - 77 K, more preferably from T _s - 323 K to T _s - 77 K and most preferably from Ts - 293 K to T _s - 77 K. The cooling device can be set up such that during operation of the device, in particular during stationary operation of the device, the average temperature of the sacrificial electrode within the discharge region of the

Sacrificial electrode does not exceed the melting temperature of the material of the sacrificial electrode.

The sacrificial electrode may have an elongated shape and be designed in particular as a wire, rod or hollow profile.

The device may further comprise a detection device, in particular an optical and / or electronic detection device, such as an endoscope, which is adapted to detect the position of the discharge region of the sacrificial electrode, in particular optically and / or electronically.

The device may further comprise a control device which is adapted to guide or move the sacrificial electrode, in particular on the basis of the position of the discharge area of the sacrificial electrode detected by the detection device, such that the position of the discharge area of the sacrificial electrode during operation of the device, especially during stationary operation of the device, despite the process-related material removal it remains substantially the same.

The voltage source may be arranged such that the discharge is a pulsed discharge. The

Spannungsquelie can be a DC voltage source or an AC source. The voltage source may be a high voltage source

The particles may have a particle size in the range from 2 nm to 20 μm, preferably from 5 nm to 10 μm, more preferably from 10 nm to 5 μm, even more preferably from 10 nm to 1 μm and most preferably from 10 nm to 200 nm. The particle size of the particles can also be in a range from 2 nm to 10 μm, 2 nm to 5 μm, 5 nm to 5 μm, 2 nm to 1 μm, 5 nm to 1 μm, 2 nm to 200 nm, 5 nm to 200 μm nm, 20 nm to 200 nm or 50 nm to 200 nm.

The device according to the invention is a device for carrying out the method according to the invention. Therefore, the other features set forth in connection with the above description of the method according to the invention can also be applied to the device according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described purely by way of example with reference to the accompanying drawings, wherein

Figure 1 is a schematic cross-sectional view of a device according to a first

Embodiment of the present invention is; Figure 2 is a schematic cross-sectional view of a portion of a device according to a

second Ausführungsbeispie! the present invention;

Figure 3 is a schematic cross-sectional view of a portion of a device according to a third

Embodiment of the present invention is; and

Figures 4 (a) and (b) are scanning electron micrographs of substrate surfaces, Figure 4 (a) showing a surface coated with particles without cooling the sacrificial electrode and Figure 4 (b) showing a particle coated surface by the method of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 shows a schematic cross-sectional view of an apparatus for producing particles in an atmospheric pressure plasma according to a first embodiment of the present invention.

The device shown in FIG. 1 comprises a plasma nozzle 10, a gas supply device 20, a generator 22 as a voltage source, a cooling device 2, a detection device 4 and a control device 6. The plasma nozzle 10 has an electrically conductive housing 5 which is preferably elongated, in particular tubular, is formed, and an electrically conductive nozzle head 32. The housing 5 and the nozzle head 32 form a nozzle channel 7 through which a process gas 18 flows.

A sacrificial electrode 16 is provided so that it is partially disposed in the nozzle channel 7, passes through a wall of the nozzle channel 7, that is, the housing 5, is passed through the cooling device 2 and is connected to the control device 6. In the embodiment shown in Figure 1, the sacrificial electrode 16 is formed as a wire electrode. In the nozzle channel 7, a tube 14 of an insulator material, such as a ceramic used.

The cooling device 2 can also be provided at another point on or in the plasma nozzle 10.

In particular, the cooling device 2 can be arranged closer to the discharge region 17, for example within the cone-shaped housing which is shown schematically in FIG. 1 and which surrounds an upper part of the sacrificial electrode 16.

By means of the generator 22, which is designed as a pulse generator, a voltage between the sacrificial electrode 16 and the housing 5 / nozzle head 32 is applied. The pulse frequencies of the generator 22 are not particularly limited, and are preferably in the areas mentioned in the general part of the description. Between the generator 22 and the sacrificial electrode 16 may advantageously be a rectifier (not shown) are switched. The housing 5 and the nozzle head 32 are in the Ausführungsbeispie shown in Figure 1! grounded.

The process gas 18 is through the Gaszufiihreinrichtung 20 in the Düsenkana! Introduced 7 in the embodiment shown in Figure 1 so that it flows in a spiral shape through the nozzle channel 7 therethrough. The drauförmige or vortex-shaped flow of the process gas 18 is illustrated in Figure 1 by the spiral-like line 26. Such a flow of the process gas 18 can be achieved by a Dralieinrichtung 12. This can be a plate with openings or holes.

By means of a high voltage applied by the generator 22 between the sacrificial electrode 16 and the housing 5 / nozzle head 32, a discharge, in particular an arc discharge, from the sacrificial electrode 16 to the part of the housing not covered by the insulating tube 14, in this case the nozzle head 32, is ignited , The discharge region 17 of the sacrificial electrode 16, that is to say the region of the sacrificial electrode 16 in which the discharge predominantly takes place, is the tip thereof, as is illustrated schematically in FIG. 1,

As a result of the discharge, material is removed from the tip of the sacrificial electrode 16, that is to say from the discharge region 17. Particles 30, preferably microparticles and nanoparticles, which are transported further with the vortex-like gas flow 28, arise from the abraded material.

The detection device 4 is designed as an optical detection device, for example as an endoscopic camera, and provided on an inner side of the tube 14. The detection device 4 is configured to optically detect the position of the discharge region 17 of the sacrificial electrode 16.

The control device 6 comprises, for example, a stepping motor or a piezo element for guiding or moving the sacrificial electrode 16, as well as a control circuit, e.g. a processor, and is adapted to move the sacrificial electrode 16 along the longitudinal direction of the sacrificial electrode 16 back or forth.

The control device 6 is connected to the detection device 4 via a feedback loop 8. One

A detection signal indicative of the position of the discharge region 17 of the sacrificial electrode 16 is supplied from the detection device 4 to the control circuit 6 via the feedback circuit 8 of the control circuit. Based on this detection signal, the control circuit controls the stepper motor or piezoelectric element to move the sacrificial electrode 16 so that the position of the discharge region 17 relative to the housing 5 remains substantially constant during operation of the device, particularly during stationary operation of the device , ie does not deviate from a given position.

A portion of the sacrificial electrode 16, which is arranged outside of the housing 5, is placed in the cooling device 2 in direct contact with a cooling medium 11, such as water or liquid nitrogen, and thus cooled. The cooling medium 11 is supplied through lines 13 of the cooling device 2 and discharged therefrom. For example, the cooling device 2 can be connected via lines 13 to a cooling water circuit (not shown).

Various possible types of cooling of the sacrificial electrode by means of a cooling device will be explained in more detail below with reference to FIGS. 2 and 3.

The active cooling of the portion of the sacrificial electrode 16 arranged outside the housing 5 in the cooling device 2 results in a high temperature difference between this section and the discharge area 17, so that an efficient and rapid heat removal from the discharge area 17 takes place.

In particular, the cooling device 2 is set up such that, during operation of the device, the difference between the average temperature of the sacrificial electrode 16 within the discharge region 17 of the sacrificial electrode 16 and the mean temperature of the sacrificial electrode 16 at an entry point 21 at which the sacrificial electrode 16 into a cooling region, namely, the cooling device 2 enters, is in the range of Ts - 373 K to Ts - 77 K, where Ts is the melting temperature of the material of the sacrificial electrode 16 in K. In this way, a particularly fast and efficient heat removal from the discharge region 17 can be achieved.

Consequently, the device according to the first embodiment of the present invention can be operated with high power inputs to the sacrificial electrode 16 and thus a high production rate of the particles 30, wherein the particles 30 have a small Teilchengröfie and a controlled and defined particle size distribution.

As follows from the above, in operation of the apparatus shown in FIG. 1, a plasma is generated in the process gas 18 by a discharge between the sacrificial electrode 16 and the housing 5 / nozzle head 32. As a result of this discharge, material is removed from the sacrificial electrode 16, from which particles 30 are formed on the substrate surface prior to deposition.

A portion of the sacrificial electrode 16 is actively cooled by the cooling device 2 so that the average temperature of the sacrificial electrode 16 in a region of the sacrificial electrode 16 outside of the discharge region 17 of

Sacrificial electrode 16 is lower than within the discharge region 17 of the sacrificial electrode 16. Consequently, the inventive method can be performed with the apparatus according to the first embodiment in a particularly efficient and simple manner.

The particles 30 are transported further by the vortex-shaped gas flow 28 and pass out of the plasma nozzle 10 through an outlet 36 of the nozzle head 32. Thus, the precipitated particles 30 can be selectively applied to the surface of a substrate 50 via the outlet 36, as shown schematically in FIG. As indicated by the arrow 52 in FIG. 1, in this case the substrate 50 can be moved relative to the plasma nozzle 10, thereby enabling a controlled local application of the particles 30 on the surface of the substrate 50,

The substrate 50 may be made of plastic, e.g. a polymer, or even wood, glass or ceramic.

Figure 2 shows a schematic cross-sectional view of a portion of an apparatus for producing particles in an atmospheric pressure plasma according to a second embodiment of the present invention.

The structure of the device according to the second embodiment differs from that of the device according to the first embodiment essentially in that the sacrificial electrode 16 'is inserted through a side wall 9 of a housing of a plasma nozzle into a nozzle channel T formed in the housing.

By a discharge 15 between the sacrificial electrode 16 'and a counter electrode (not shown), such as a conductive part of a housing of the device, for. In a process gas in the nozzle channel 7 ', material (not shown) from the discharge region 17', ie the tip of the sacrificial electrode 16 'designed as a wire electrode, is injected into a process nozzle, for example a conductive nozzle head (eg as the nozzle head 32 in FIG. removed and transported by the process gas along the nozzle channel 7 '. The material may be in particulate form or may be formed during transport, ie, prior to deposition on the substrate surface, of particles 30 therefrom.

As indicated by the arrow A in Figure 2, the sacrificial electrode 16 'by a control device, such as the control device 6 of the device according to the first embodiment, in the direction perpendicular to the wall 9 of the nozzle channel 7 ¹ are moved back and forth. Consequently, the sacrificial electrode 16 'can be guided so that the position of the discharge region 17' during operation of the device, despite the process-related material removal, remains substantially the same.

The device according to the second embodiment of the present invention comprises a cooling device 2 '. The cooling device 2 'is set up such that, during operation of the device, the difference between the mean temperature of the sacrificial electrode 16' within the discharge region 17 'of the sacrificial electrode 16' and the mean temperature of the sacrificial electrode 16 'at an entry point 21', at which the sacrificial electrode 16 'enters the' cooler 2 ', ranging from T _s - 373K to Ts - 77 K, where T _{s is} the melting temperature of the material of the sacrificial electrode 16' in K. In this way, a particularly fast and efficient heat removal from the discharge region 17 'can be achieved. The cooling device 2 comprises a housing 23, in the interior of which a chamber 24 is formed, and two lines 13 'which are in fluid communication with the chamber 24. The sacrificial electrode 16 'is passed through the chamber 24 via two seals 19 and is held movable by the seals 19 so that it can be moved in the direction perpendicular to the wall 9 of the channel 7'.

Via conduits 13 ', a gaseous or liquid cooling medium 1V, e.g. Water or liquid nitrogen supplied to the chamber 24 and discharged from the chamber 24. For example, the lines 13 'can be connected to a cooling water circuit.

In the chamber 24, the cooling medium 11 'comes into direct contact with a portion of the sacrificial electrode 16', which is arranged outside the housing of the device, thereby cooling the sacrificial electrode 16 '. The resulting high temperature difference between the portion of the sacrificial electrode 16 'outside the housing and the discharge region 17' ensures a fast and efficient heat removal from the discharge region 17 '.

The portion of the sacrificial electrode 16 'may be received within the cooling device 2' in a tube or the like made of a thermally conductive material. In this case, the cooling of the portion of the sacrificial electrode 16 'takes place via thermal contact of the portion with the cooling medium 11' via the tube.

Figure 3 shows a schematic cross-sectional view of a portion of an apparatus for producing particles in an atmospheric pressure plasma according to a third embodiment of the present invention.

The structure of the device according to the third embodiment differs from that of the device according to the second embodiment substantially by the structure of the cooling device used, as will be explained in detail below.

The sacrificial electrode 16 "is inserted through a lateral wall 9 'of a housing of a plasma nozzle into a nozzle channel 7" formed in the housing. By means of a discharge 15 'between the sacrificial electrode 16 "and the housing in a process gas in the nozzle channel 7", material (not shown) is removed from the discharge region 17 ", ie the tip of the sacrificial electrode 16" designed as a wire electrode, and is passed along through the process gas The material may be present in particulate form or else formed during transport, ie before deposition on the substrate surface, of particles 30 therefrom.

As indicated by the arrow A 'in Fig. 3, the sacrificial electrode 16 "can be moved back and forth in the direction perpendicular to the wall 9' of the channel 7" by a controller such as the controller 6 of the apparatus of the first embodiment become. Consequently, the sacrificial electrode 16 "can be so be guided, that the position of the discharge region 17 "during the operation of the device, despite the process-related Materiaiabtrages, remains substantially the same.

The device according to the third embodiment of the present invention comprises a cooling device 2 ". The cooling device 2" is set up so that, during operation of the device, the difference between the mean temperature of the sacrificial electrode 16 "within the discharge region 17" of the sacrificial electrode 16 "and the middle Temperature of the sacrificial electrode 16 "at an entry point 21" at which the sacrificial electrode 16 "enters the chiller 2" is in the range of Ts-373K to Ts-77K where Ts is the melting temperature of the material of the sacrificial electrode 16 "in K is. In this way, a particularly fast and efficient heat removal from the discharge area 1 "can be achieved.

As shown schematically in Figure 3, the wall 9 'of the housing of the device, which may for example have a cylindrical shape, has a cavity or chamber 25 extending along a portion of the circumference of the housing or along the entire circumference of the housing can. The cooling device 2 "comprises two lines 13" via which a gaseous or liquid cooling medium 11 ", such as, for example, water or liquid nitrogen, can be supplied to the chamber 25 and removed from the chamber 25. For example, the lines 13" can be connected to a cooling water circuit become.

The sacrificial electrode 16 "is guided through the chamber 25 via two seals 19 'and is movably supported by the seals 19' so as to be movable along the direction perpendicular to the wall 9 'of the housing Sacrificial electrode 16 ", which is located outside the channel 7", with the cooling medium 11 "in direct contact and is thereby cooled. By the resulting high

Temperature difference between the portion of the sacrificial electrode 16 "outside the channel 7" and the

Discharge area 17 ", an efficient and rapid heat removal from the discharge area 17"

guaranteed.

The portion of the sacrificial electrode 16 "can also be inside the cooling device 2" in a tube or the like of a thermally conductive Materia! be included. In this case! the cooling of the portion of the sacrificial electrode 16 "via a thermal contact of the portion with the cooling medium 11" via the tube.

FIG. 4 shows scanning electron micrographs of glass slides as substrate surfaces on which silver particles have been deposited. The deposition of the particles was carried out by means of a device as shown in Figure 2 with a sacrificial electrode 16 'made of silver, wherein the silver particles shown in Figure 4 (a) without cooling the sacrificial electrode 16 and the silver particles shown in Figure 4 (b) with active cooling Sacrificial electrode 16 'were deposited by the cooling device 2'. The scanning electron micrographs shown in Figure 4 were each at a

Electron High Tension (EHT) of 5.00 kV The distance between substrate and scanning electron microscope was 2.6 mm in the measurement shown in Fig. 4 (a) and 4 in the measurement shown in Fig. 4 (b) , 0 mm.

As can be seen from FIG. 4, the active cooling of the sacrificial electrode 16 'makes it possible to produce considerably smaller or finer particles. Moreover, in the substrate shown in Fig. 4 (b), the deposition rate, that is, the rate at which a given amount of material is deposited on a unit area increased by a factor of approximately 12 as compared to the substrate shown in Fig. 4 (a) become. This considerable increase in the deposition rate is made possible by the increase in the manufacturing rate of the particles achieved by means of cooling the sacrificial electrode 16 '.

The achievable by the inventive method and the inventive device high

Particle production rates, small particle sizes, and homogeneous particle size distributions enable the use of the manufactured particles in a variety of applications, e.g. in the medical sector, for household appliances, for sanitary articles and for electronic elements, e.g. in battery technology.

The method and device according to the invention can be used for depositing layers, in particular dense nanoparticulate layers, on substrate surfaces. In addition, particles can be incorporated into layers, such as plasma polymer layers. As a further possibility, the produced particles can also be collected, for example by a powder separator, and subsequently supplied to further uses,

For example, by means of the apparatus and method of the invention, silver nanoparticles can be incorporated into plasma polymer layers to produce a non-cytotoxic and antimicrobial coating. Similarly, zinc particles can be incorporated into plasma polymer layers to provide active corrosion protection for metals that are above the stress series, more noble than zinc. A similar use is possible with magnesium particles.

UV-absorbing particles, e.g. ZnO particles can be incorporated into plasma polymer layers as UV-absorbing scratch protection.

In the following, the essential aspects of the present invention are summarized again:

(1) Method of producing particles using an atmospheric pressure plasma, especially in an atmospheric pressure plasma, in which the plasma is generated by a discharge between electrodes in a process gas, at least one of the electrodes is a sacrificial electrode from which material is removed by the discharge, when the removed material is particles and / or particles are formed from the abraded material, and a portion of the sacrificial electrode is actively cooled so that the average temperature of the sacrificial electrode in a region of the sacrificial electrode outside the discharge area of the sacrificial electrode is lower than within the discharge area of the sacrificial electrode.

(2) The method according to item (1), wherein the cooling of the portion of the sacrificial electrode is via heat conduction.

(3) The method of item (1) or (2), wherein the cooling of the portion of the sacrificial electrode is performed by a cooling medium.

(4) The method according to item (3), wherein the cooling medium comes into contact only with the area of the sacrificial electrode outside the discharge area of the sacrificial electrode.

(5) The method of any one of the preceding claims, wherein the sacrificial electrode enters a cooling region at an entry point of the sacrificial electrode in which the portion of the sacrificial electrode is actively cooled, the entry point being on a side of the cooling region opposite the discharge region of the sacrificial electrode, and the difference between the average temperature of the sacrificial electrode within the discharge area of the sacrificial electrode and the average temperature of the sacrificial electrode at the entry point in the range of Ts -393K to Ts-77K, preferably Ts-373K to Ts-77K, more preferably Ts - 323K to Ts - 77K, and most preferably from Ts - 293K to Ts - 77K, where Ts is the melting temperature of the material of the

Sacrificial electrode K is.

(6) Method according to one of the preceding points, in which the sacrificial electrode enters a cooling region at an entrance portion of the sacrificial electrode, in which the portion of the sacrificial electrode is actively cooled, the entry point being at a side of the cooling region opposite the discharge area of the sacrificial electrode, and the median temperature of the sacrificial electrode at the entrance portion 393K 373K, more preferably 323K, and most preferably 293K.

(7) The method according to any preceding item, wherein the average temperature of the sacrificial electrode within the discharge area of the sacrificial electrode does not exceed the melting temperature of the material of the sacrificial electrode.

(8) The method according to any preceding item, wherein the sacrificial electrode has an elongated shape.

(9) The method according to any preceding item, wherein the position of the discharge area of the sacrificial electrode is detected.

(10) The method according to item (9), wherein the position of the discharge region of the sacrificial electrode is optically and / or electronically detected.

(11) The method according to any one of the preceding claims, wherein the sacrificial electrode is guided so that the position of the discharge area of the sacrificial electrode remains substantially the same during the process.

(12) The method according to item (11) as dependent on (9) or (10), wherein the sacrificial electrode is guided based on the detected position of the discharge area of the sacrificial electrode such that the position of the sacrificial electrode

Entiadungsbereichs the sacrificial electrode during the process remains substantially the same.

(13) The method according to any preceding item, wherein the discharge is a pulsed discharge.

(14) Method according to one of the preceding points, wherein the particles have a particle size in the range of 2 nm to 20 μΐη.

(5) The method according to any one of the preceding claims, wherein generating the atmospheric pressure plasma, ablating the material and causing the particles to occur using a plasma nozzle.

(16) Method according to one of the preceding points, in particular according to item (15), in which particles are formed in a relaxing region of the atmospheric pressure plasma from the abraded material. (17) Method according to one of the preceding points, in particular according to item (15) or (16), in which the residence time of the material in a relaxing region of the atmospheric pressure plasma is controlled.

(18) A device for producing particles using an atmospheric pressure plasma, in particular in an atmospheric pressure plasma, comprising: a housing having a channel, at least two electrodes at least partially disposed in the channel, a voltage source adapted to provide a voltage between the at least two electrodes, wherein the at least two electrodes are adapted to generate the plasma by a discharge between the electrodes in a process gas in the channel, at least one of the electrodes is a sacrificial electrode from which material is removed by the discharge, and wherein the abraded material is particulate matter and / or particles are formed from the abraded material, and cooling means configured to actively cool a portion of the sacrificial electrode such that the average temperature of the sacrificial electrode in an area of the sacrificial electrode is outside of the discharge range of the sacrificial electrode is lower than within the discharge area of the sacrificial electrode.

(19) The device of item (18), wherein the cooling means is adapted to cool the portion of the sacrificial electrode via heat conduction.

(20) The device of item (18) or (19), wherein the cooling means is arranged to cool the portion of the sacrificial electrode by a cooling medium.

(21) Device according to item (20), in which the cooling device is arranged such that the cooling medium only comes into contact with the region of the sacrificial electrode outside the discharge region of the sacrificial electrode, in particular directly or via a wall in thermal contact. (22) The device according to any one of (18) to (21), wherein the sacrificial electrode enters a cooling region at an entry point of the sacrificial electrode, in which the portion of the sacrificial electrode is actively cooled, the entry point being opposite to the discharge region of the sacrificial electrode Side of the cooling area, and the cooling device is arranged so that, during operation of the device, the difference between the average temperature of the sacrificial electrode within the discharge area of the sacrificial electrode and the average temperature of the sacrificial electrode at the entry point in the range of Ts - 393 K to Ts - 77 K, preferably from Ts-373K to Ts-77K, more preferably from Ts-323K to Ts-77K, and most preferably from Ts-293K to Ts-77K, where Ts is the melting temperature of the material of the sacrificial electrode in K is.

(23) The device according to any one of (18) to (22), wherein the sacrificial electrode enters a cooling region at an entrance point of the sacrificial electrode, in which the portion of the sacrificial electrode is actively cooled, the entry point being opposite to the discharge region of the sacrificial electrode Side of the cooling region, and the cooling device is arranged so that when operating the device, the average temperature of the sacrificial electrode at the point of entry 393 K, preferably 373 K, more preferably 323 K and most preferably 293 K, does not exceed.

(24) The device according to any one of items (18) to (23), wherein the cooling means is arranged so that, during operation of the device, the average temperature of the sacrificial electrode within the discharge region of the

(25) The device according to any one of (8) to (24), wherein the sacrificial electrode has an elongated shape.

(26) The device according to any one of (18) to (25), further comprising detection means arranged to detect the position of the discharge area of the electrode electrode.

(27) The device according to item (26), wherein the detection means is adapted to optically and / or electronically detect the position of the discharge area of the sacrificial electrode.

(28) The device of any one of (18) to (27), further comprising a controller configured to guide the sacrificial electrode so that the position of the discharge area of the sacrificial electrode remains substantially the same during operation of the device , (29) The device of item (28) as dependent on item (26) or (27), wherein the controller is configured to guide the sacrificial electrode based on the position of the discharge area of the sacrificial electrode detected by the detecting means so that the position the discharge area of the sacrificial electrode remains substantially the same during operation of the device.

(30) The device according to any one of (18) to (29), wherein the voltage source is arranged such that the discharge is a pulsed discharge.

(31) The device according to any one of (18) to (30), wherein the particles have a particle size in the range of 2 nm to 20 μηι.

Claims

A method of producing particles (30) using an atmospheric pressure plasma, wherein the plasma is generated by a discharge (15, 15 ') between electrodes (16, 16', 16 ", 5, 32) in a process gas (18) is at least one of the electrodes is a sacrificial electrode (16, 16 ', 16 "), is removed from the material through the discharge, it is the abraded Materia! are particles and / or particles are formed from the abraded material, and a portion of the sacrificial electrode is actively cooled such that the average temperature of the sacrificial electrode is lower in a region of the sacrificial electrode outside the sacrificial electrode discharge arc (17, 17 ', 17 ") as within the discharge area of the sacrificial electrode.

2. The method of claim 1, wherein the cooling of the portion of the sacrificial electrode via heat conduction takes place.

3. The method of claim 1 or 2, wherein the cooling of the portion of the sacrificial electrode by a cooling medium (11, 11 ', 11 ") takes place.

4. The method of claim 3, wherein the cooling medium comes into contact only with the region of the sacrificial electrode outside the discharge region of the sacrificial electrode.

5. The method according to any one of the preceding claims, wherein

the sacrificial electrode enters a cooling region at an entry point (21, 2Γ, 21 ") of the sacrificial electrode in which the portion of the sacrificial electrode is actively cooled, the entry point being on a side of the cooling region opposite the discharge region of the sacrificial electrode, and the difference between the the average temperature of the sacrificial electrode within the discharge area of the sacrificial electrode and the average temperature of the sacrificial electrode at the point of entry is in the range of Ts-393K to Ts-77K, where Ts is the melting temperature of the material of the sacrificial electrode in K.

6. The method according to any one of the preceding claims, wherein the sacrificial electrode enters a cooling region at an entry point of the sacrificial electrode in which the portion of the sacrificial electrode is actively cooled, the entry point being on a side of the cooling region opposite the discharge region of the sacrificial electrode, and the average temperature of the sacrificial electrode at the entry point does not exceed 393K ,

A method according to any one of the preceding claims, wherein the average temperature of the sacrificial electrode within the discharge area of the sacrificial electrode does not exceed the melting temperature of the material of the sacrificial electrode.

8. The method according to any one of the preceding claims, wherein the sacrificial electrode has an elongated shape.

9. The method according to any one of the preceding claims, wherein the position of the discharge region of the sacrificial electrode is detected.

10. The method of claim 9, wherein the position of the discharge region of the sacrificial electrode is detected optically and / or electronically.

A method according to any one of the preceding claims, wherein the sacrificial electrode is guided so that the position of the discharge area of the sacrificial electrode remains substantially the same during the process.

12. The method of claim 11 as dependent on claim 9 or 10, wherein the sacrificial electrode is guided based on the detected position of the discharge area of the sacrificial electrode such that the position of the discharge area of the sacrificial electrode remains substantially the same during the process.

13. The method according to any one of the preceding claims, wherein the discharge is a pulsed discharge.

14. The method according to any one of the preceding claims, wherein the particles have a particle size in the range of 2 nm to 20 μητι.

15. The method according to any one of the preceding claims, wherein the particles arise in a relaxing region of the atmospheric pressure plasma from the removed material.

16. The method according to any one of the preceding claims, wherein the residence time of the material is controlled in a relaxing region of the atmospheric pressure plasma.

17. An apparatus for producing particles (30) using an atmospheric pressure plasma, comprising: a housing (5) having a channel (7, 7 ', 7' '), at least two electrodes (16, 16', 16 '; 32) disposed at least partially in the channel, a voltage source (22) adapted to apply a voltage between the at least two electrodes, the at least two electrodes being adapted to remove the plasma by a discharge (15, 15 ') between the electrodes in a process gas (18) in the channel, at least one of the electrodes is a sacrificial electrode (16, 16', 16 ") from which material is removed by the discharge, and the abraded material particles and / or particles are formed from the abraded material, and a cooling device (2) adapted to actively cool a portion of the sacrificial electrode such that the average temperature of the sacrificial electrode in a region of the oppose outside of the

Discharge region (17, 17 ', 17 ") of the sacrificial electrode is lower than within the discharge region of the sacrificial electrode.