DE102013017109A1 - Method and device for producing particles in an atmospheric pressure plasma - Google Patents

Abstract

The invention relates to a method for the production of particles (30) using an atmospheric pressure plasma, in which the plasma 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 abraded material is particulate matter and / or the abraded material Particles are created. 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 region (17, 17 ', 17' ') of the sacrificial electrode is lower than within the discharge region of the sacrificial electrode. The invention further relates to 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 5, 32) disposed at least partially in the channel and a voltage source (22) arranged to apply a voltage between the at least two electrodes. The at least two electrodes are configured 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 '). '), is removed from the material through the discharge, wherein the removed material is particles and / or arise from the removed material particles. The apparatus further comprises cooling means (2) adapted to actively cool a portion of the sacrificial electrode such that the mean temperature of the sacrificial electrode in an area of the sacrificial electrode is outside the discharge region (17, 17 ', 17' ') of the sacrificial electrode is lower than within the discharge area of the sacrificial electrode.

Description

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 (eg, conductivity), thermal (eg, 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.

The DE-A-198 24 364 relates, for example, to a method of applying wear protection layers having optical properties to surfaces. The method comprises at least two different deposition steps. One step is a plasma enhanced CVD process to deposit a wear protection matrix and the other step is a 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.

The 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 a second material is applied to the substrate by means of a second deposition method. As a second deposition method, among others, PVD, such as sputtering, is called.

The 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 applied by a low-pressure DC magnetron sputtering process and the transport control layer in a second step by a plasma polymerization process.

All low-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 to coat locally. Further, due to the limited capacity of vacuum chambers, there are limits to the size of substrates that can be coated.

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

For example, in the DE-A-199 58 473 used a plasma jet source which is said to operate in a fine vacuum 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.

The 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 the WO 01/32949 For example, 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 with particles dispersed therein 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.

The DE-B-102 23 865 relates to a method for plasma coating of workpieces, in which by means of a plasma nozzle by electrical high-frequency discharge a beam of atmospheric Plasmas is generated, which is painted over the workpiece surface to be coated. 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.

Evidently the DE-B-102 23 865 the sputtered material is predominantly in the form of highly 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.

The US 5,808,270 relates to an apparatus and method for thermal plasma arc metal wire spraying, by which an extended arc and a supersonic plasma jet are generated. A metal wire serving as an anode is continuously introduced into the plasma jet where the expanded plasma arc jumps over 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.

The 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. Particulate production does not occur in the plasma torch.

The DE-A-10 2009 048 397 relates to a method for producing surface-modified particles in an atmospheric pressure plasma using a sputter 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 a discharge generating voltage generator or by rotating or oscillating the sputtering electrode becomes.

However, this limitation of the power input to the sputtering electrode leads to a reduction in the sputtering yield, ie the production rate of the particles, so that, for example, long coating times are necessary in order to deposit the particles on a surface of a substrate. Therefore, the achievable 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 independent claim 1 and the device according to independent claim 17. 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 target electrode, by the discharge Material is abraded or detached, (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 is in a range the sacrificial electrode is lower outside the discharge area of the sacrificial electrode than inside the 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 by agglomeration processes of the removed material, in particular in a relaxing region of the atmospheric pressure plasma, to be formed or formed. 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 residence time in the relaxing region of the atmospheric pressure plasma can be increased by increasing the path length in the relaxing region of the atmospheric pressure plasma.

The control of the residence time is advantageously made taking into account the finding that by increasing the residence time of the material in the relaxing region of the atmospheric pressure plasma, first the yield of nanoparticles can be further increased, with an upper limit of the residence time, from which it is increased larger particles, especially microparticles comes.

An "active" plasma region is generally understood to mean a plasma region that is within the volume bounded by the electrodes between which a voltage is applied, through 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 relaxing area of the plasma is sometimes referred to as the "after glow" area. 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 outlet 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 o. G. 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, for. B. each component of the apparatus used for the inventive method, in particular a plasma nozzle, understood that 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 method according to the invention material is removed or detached by the plasma-generating discharge material is referred to as "sacrificial electrode" or "target electrode". In the method according to the invention, a plurality of electrodes, in particular electrodes made of the same or different electrode materials, can be sacrificial electrodes. However, exactly one of the electrodes can 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 the atmospheric pressure. C. Tendern et al. in "Atmospheric pressure plasmas: A review", Spectrochimica Acta Part B: Atomic Spectroscopy, 2006, pp. 2-30 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 of time, namely the period in which the discharge occurs, and over a certain surface area of the sacrificial electrode, such as the discharge area of 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 is, 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 minutes, more preferably not more than 1 minute, and most preferably not more than 40 seconds, to a value of 1 / e × TE1, where e is Euler's 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 outside the discharge area of the sacrificial electrode is lower than within the discharge area of the sacrificial electrode. Consequently, a temperature difference or a temperature gradient between the discharge region and the region of the sacrificial electrode is outside the discharge region, so that heating of the discharge region can be compensated or compensated for by the discharge by heat transport from the discharge region to the region of the sacrificial electrode outside the discharge region.

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. In this way, an undesired large-scale melting of sacrificial electrode material and thus a transfer of spattered material to the substrate surface can be avoided.

Therefore, in particular by the thus possible high power input to the sacrificial electrode or sacrificial electrodes, a high production 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 sacrificial electrode outside the discharge region, can be actively cooled.

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, CO ₂ ice, etc. can be used. 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, the high temperature difference caused by the cooling between the region of the sacrificial electrode cooled by the cooling medium outside the discharge region and the discharge region ensures rapid heat removal from the discharge region.

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 difference between 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 in the range of T _S - 393 K to T _S - 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 T _S - 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 in contact with a solid, liquid or gaseous cooling medium in the cooling region, in particular in direct or direct or thermal 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 minute, and most preferably not more than 40 seconds, fall to a value of 1 / e × 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 thermally conductive 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 thermally 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 area 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 area opposite to the discharge area 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 these average temperatures of the sacrificial electrode at the point of entry, 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 at the entry point in the range of T _s - 393 K to T _s - 77 K may be preferred from T _S - 373 K to T _S - 77 K, more preferred from T _S - 323 K to T _S - 77 K, and most preferably from T _S - 293 K to T _S - 77 K.

In the method according to the invention, the average temperature of the sacrificial electrode within the discharge region of the sacrificial electrode can be selected such 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, a wire, a rod or a hollow profile, for. B. an elongated hollow profile, be.

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 may 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.

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.

The material of the sacrificial electrode or sacrificial electrodes are metals such as copper, aluminum, indium, zinc, titanium and magnesium, in particular noble metals such as gold, silver, platinum and palladium, but also metal alloys, metal oxides (eg BaO, zinc oxide, tin oxide). and carbon in question. 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 detection device, in particular an optical and / or electronic detection device, can 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 area 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. B. relative to the housing, during the process, ie during the implementation of the method, remains substantially unchanged or 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 too little sacrificial electrode material is present in the discharge channel, the formation of a sufficient temperature difference between the discharge region and the region of the sacrificial electrode outside the discharge region is made 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 can also adversely affect the particle generation efficiency.

For example, the sacrificial electrode may be a traceable sacrificial electrode, in particular a traceable wire sacrificial electrode. In the context of the present application, "trackable" in connection with an electrode means that the position of the discharge area of the sacrificial electrode can be controlled or adjusted by pushing or pulling back the sacrificial electrode.

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. The pulsed or pulsating discharge can in particular by a pulsed or pulsating operation of a voltage source, such. As a generator, which is adapted to a voltage (eg., DC voltage), in particular a high voltage to apply between the electrodes, and with the discharge, which is preferably an arc discharge, 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, z. As the generator, is not particularly limited and may be 5 to 70 kHz, with the range of 15 to 40 kHz is 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 (NH ₃ ), hydrogen sulfide (H ₂ S) 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 pressure plasma 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 particle yield, 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 micrometers or nanometers. The particles may have a particle size or diameter ranging 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 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 produced by the process according to the invention with a high production rate and controlled particle size distribution, as has already been explained 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 nano or micrometers, more preferably in the range of 2 nm to 20 microns, most preferably in the range of 2 to 100 nm.

The determination of the particle size of very small particles, such as nanoparticles, is possible for example with laser scattering or transmission electron microscopy (TEM). 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 Material is removed, (i) the abraded material is particles 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 region of the sacrificial electrode during the process, ie while performing the procedure, remains essentially 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 includes a housing having a channel, at least two electrodes at least partially disposed in the channel, and a voltage source configured 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 the abraded material is particles and / or particles are formed from the abraded material.

In addition, the device according to the invention comprises a cooling device which is adapted 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 the discharge region of the sacrificial electrode is lower than within the discharge region 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 plasma 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, during the application or deposition of the particles, for. 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 point being on a side of the cooling area opposite to the discharge area of the sacrificial electrode, and the cooling means is arranged 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 T _s - 393 K to T _s - 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 T _S - 77 K, where T is the Melting temperature of the material of the sacrificial electrode 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 thermal or indirect contact.

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 point being on a side of the cooling area opposite to the discharge area of the sacrificial electrode, and the cooling means is 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. In particular, for these average temperatures of the sacrificial electrode in the entrance region, the difference between the average 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 T _s - 393 K to T _s - 77 K may be preferred from T _S -373K to T _S -77K, more preferably from T _S -323K to T _S -77K, and most preferably from T _S -293K to T _S -77K.

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 apparatus 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 region of the sacrificial electrode detected by the detection device, such that the position of the discharge region of the sacrificial electrode during operation of the device, especially during stationary operation of the device, despite the process-related material removal remains substantially the same.

The voltage source may be arranged such that the discharge is a pulsed discharge. The voltage source may be a DC voltage source or an AC voltage 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 may also be in a range of 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.

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

1 a schematic cross-sectional view of an apparatus according to a first embodiment of the present invention;

2 a schematic cross-sectional view of a portion of a device according to a second embodiment of the present invention;

3 a schematic cross-sectional view of a portion of a device according to a third embodiment of the present invention; and

4 (a) and (b) scanning electron micrographs of substrate surfaces, wherein 4 (a) shows a coated without cooling the sacrificial electrode with particles surface and 4 (b) shows a coated with the method according to the invention with particles surface.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

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.

In the 1 The device shown 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 controller 6 , The plasma nozzle 10 has an electrically conductive housing 5 , which is preferably elongated, in particular tubular, and an electrically conductive nozzle head 32 on. The housing 5 and the nozzle head 32 form one of a process gas 18 flowed through the nozzle channel 7 ,

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

The cooling device 2 may also be at another location on or in the plasma nozzle 10 be provided. In particular, the cooling device 2 closer to the discharge area 17 , for example, within the in 1 schematically shown, an upper part of the sacrificial electrode 16 surrounding cone-shaped housing, be arranged.

By means of the generator 22 , which is formed as a pulse generator, a voltage between the sacrificial electrode 16 and the housing 5 / Nozzle head 32 created. 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 can advantageously a rectifier (not shown) are switched. The housing 5 and the nozzle head 32 are in the in 1 grounded embodiment shown.

The process gas 18 is through the gas supply 20 in the nozzle channel 7 initiated in the in 1 shown embodiment so that it is swirl-shaped through the nozzle channel 7 flows through it. The swirl-shaped or vortex-shaped flow of the process gas 18 is in 1 through the spiral-like line 26 illustrated. Such a flow of the process gas 18 can by a twisting device 12 be achieved. It can be a plate with openings or holes.

By one of the generator 22 between the sacrificial electrode 16 and the housing 5 / Nozzle head 32 applied high voltage becomes a discharge, in particular an arc discharge, from the sacrificial electrode 16 not with the insulating pipe 14 covered part of the housing, here the nozzle head 32 ignited. The discharge area 17 the sacrificial electrode 16 , that is the area of the sacrificial electrode 16 in which the discharge is predominantly done, its tip is as in 1 is illustrated schematically.

The discharge is from the tip of the sacrificial electrode 16 , that is from the discharge area 17 , Material removed. Particles are formed from the removed material 30 , preferably micro- and nanoparticles, with the vortex-shaped gas flow 28 be transported further.

The detection device 4 is designed as an optical detection device, for example as an endoscopic camera, and on an inner side of the tube 14 intended. The detection device 4 is set up the position of the discharge area 17 the sacrificial electrode 16 visually detect.

The control device 6 For example, it includes 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 for the sacrificial electrode 16 along the longitudinal direction of the sacrificial electrode 16 move forwards or backwards.

The control device 6 is via a feedback loop 8th with the detection device 4 connected. A detection signal indicating the position of the discharge area 17 the sacrificial electrode 16 is displayed by the detector 4 over the feedback loop 8th the control circuit of the control device 6 fed. Based on this detection signal, the control circuit controls the stepping motor or the piezo element around the sacrificial electrode 16 so move that the position of the discharge area 17 relative to the housing 5 during operation of the device, in particular during steady-state operation of the device, remains essentially the same, ie does not deviate from a predetermined position.

A section of the sacrificial electrode 16 that's outside the case 5 is arranged, is in the cooling device 2 in direct contact with a cooling medium 11 , such as water or liquid nitrogen, brought and thus cooled. The cooling medium 11 is through lines 13 the cooling device 2 supplied and discharged from this. For example, the cooling device 2 over the wires 13 to be connected to a cooling water circuit (not shown).

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

By the active cooling of the outside of the case 5 arranged portion of the sacrificial electrode 16 in the cooling device 2 There is a high temperature difference between this section and the discharge area 17 , allowing efficient and rapid heat dissipation from the discharge area 17 he follows.

In particular, the cooling device 2 arranged so that when operating the device, the difference between the average temperature of the sacrificial electrode 16 within the discharge area 17 the sacrificial electrode 16 and the mean temperature of the sacrificial electrode 16 at an entry point 21 at the sacrificial electrode 16 in a cooling area, namely the cooling device 2 , occurs in the range of T _S - 373 K to T _S - 77 K, where T _{S 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 17 be achieved.

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

As follows from the above statements, the in 1 apparatus shown a plasma in the process gas 18 by a discharge between the sacrificial electrode 16 and the housing 5 / Nozzle head 32 generated. This discharge is from the sacrificial electrode 16 Material removed from the particles before deposition on the substrate surface 30 arise.

A section of the sacrificial electrode 16 is through the cooling device 2 actively cooled so that the average temperature of the sacrificial electrode 16 in an area of the sacrificial electrode 16 outside the discharge area 17 the sacrificial electrode 16 is lower than inside the discharge area 17 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 be from the vortex-shaped gas flow 28 transported on and pass through an outlet 36 of the nozzle head 32 from the plasma nozzle 10 out. Thus, the produced particles 30 over the outlet 36 targeted to the surface of a substrate 50 be applied as in 1 is shown schematically. As by the arrow 52 in 1 is indicated, in this case, the substrate 50 relative to the plasma nozzle 10 be moved, creating a controlled local application of the particles 30 on the surface of the substrate 50 is possible.

The substrate 50 can be made of plastic, such as. As a polymer, or from wood, glass or ceramic.

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 substantially in that the sacrificial electrode 16 ' through a side wall 9 a housing of a plasma nozzle in a nozzle channel formed in the housing 7 ' is introduced.

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, e.g. B. a conductive nozzle head (eg., As the nozzle head 32 in 1 ), in a process gas in the nozzle channel 7 ' becomes material (not shown) from the discharge area 17 ' , ie the tip of the sacrificial electrode formed as a wire electrode 16 ' , removed and through the process gas along the nozzle channel 7 ' transported. The material may be in particulate form or it may be formed during transport, ie before deposition on the substrate surface, particles 30 it.

As indicated by the arrow A in FIG 2 is implied, the sacrificial electrode 16 ' by a control device, such as the control device 6 the device according to the first embodiment, in the direction perpendicular to the wall 9 of the nozzle channel 7 ' be moved back and forth. Consequently, the sacrificial electrode 16 ' be guided so that the position of the discharge area 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 arranged so that when operating the device, the difference between the average temperature of the sacrificial electrode 16 ' within the discharge area 17` the sacrificial electrode 16 ' and the mean temperature of the sacrificial electrode 16 ' at an entry point 21 ' at the sacrificial electrode 16 ' in the 'cooling device 2 ' occurs, in the range of T _S - 373 K to T _S - 77 K, where T _{S 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 17 ' be achieved.

The cooling device 2 ' includes a housing 23 in whose interior a chamber 24 is formed, and two lines 13 ' that with the chamber 24 in fluid communication. The sacrificial electrode 16 ' is about two seals 19 through the chamber 24 led and is from the seals 19 so movable that they are in the direction perpendicular to the wall 9 of the canal 7 ' can be moved.

Over the lines 13 ' becomes a gaseous or liquid cooling medium 11 ' , such as As water or liquid nitrogen, the chamber 24 fed and out of the chamber 24 dissipated. For example, the lines 13 ' be connected to a cooling water circuit.

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

The section of the sacrificial electrode 16 ' can be inside the cooling device 2 ' be included in a tube or the like of a thermally conductive material. In this case, the cooling of the portion of the sacrificial electrode takes place 16 ' via a thermal contact of the section with the cooling medium 11 ' over the tube.

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 through a side wall 9 ' a housing of a plasma nozzle in a nozzle channel formed in the housing 7 '' introduced. By a discharge 15 ' between the sacrificial electrode 16 '' and the housing in a process gas in the nozzle channel 7 ' 'Material (not shown) from the discharge area 17 '' , ie the tip of the sacrificial electrode formed as a wire electrode 16 '' , removed and through the process gas along the nozzle channel 7 '' transported. The material may be in particulate form or it may be formed during transport, ie before deposition on the substrate surface, particles 30 it.

As indicated by the arrow A 'in 3 is implied, the sacrificial electrode 16 '' by a control device, such as the control device 6 the device according to the first embodiment, in the direction perpendicular to the wall 9 ' of the canal 7 '' be moved back and forth. Consequently, the sacrificial electrode 16 '' be guided so that the position of the discharge area 17 '' during operation of the device, despite the process-related material removal, 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 arranged so that when operating the device, the difference between the average temperature of the sacrificial electrode 16 '' within the discharge area 17 '' the sacrificial electrode 16 '' and the mean temperature of the sacrificial electrode 16 '' at an entry point 21 '' at the sacrificial electrode 16 '' in the cooling device 2 '' occurs, in the range of T _S - 373 K to T _S - 77 K, where T _{S 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 17 '' be achieved.

As in 3 is shown schematically, the wall 9 ' the housing of the device, which may for example have a cylindrical shape, a cavity or a chamber 25 which can run along a portion of the circumference of the housing or along the entire circumference of the housing. The cooling device 2 '' includes two wires 13 '' via which a gaseous or liquid cooling medium 11 '' , such as As water or liquid nitrogen, the chamber 25 fed and out of the chamber 25 can be dissipated. For example, the lines 13 '' be connected to a cooling water circuit.

The sacrificial electrode 16 '' is about two seals 19 ' through the chamber 25 guided and is through the seals 19 ' held so that they move along the direction perpendicular to the wall 9 ' of the housing is movable. In the chamber 25 comes the section of the sacrificial electrode 16 '' , outside the canal 7 '' is arranged with the cooling medium 11 '' in direct contact and is thereby cooled. Due to the resulting high temperature difference between the portion of the sacrificial electrode 16 '' outside the canal 7 '' and the discharge area 17 '' is an efficient and fast heat removal from the discharge area 17 '' guaranteed.

The section of the sacrificial electrode 16 '' can be inside the cooling device 2 '' be included in a tube or the like of a thermally conductive material. In this case, the cooling of the portion of the sacrificial electrode takes place 16 '' via a thermal contact of the section with the cooling medium 11 '' over the tube.

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

In the 4 The scanning electron micrographs were each recorded at an electron high voltage (EHT) of 5.00 kV. The distance between substrate and scanning electron microscope was at the in 4 (a) shown measurement 2.6 mm and at the in 4 (b) shown measurement 4.0 mm.

Again 4 can be seen, allows the active cooling of the sacrificial electrode 16 ' the production of considerably smaller or finer particles. Moreover, the deposition rate, that is, the rate at which a given amount of material is deposited on a unit area, could be reduced at the 4 (b) shown substrate compared to in 4 (a) shown substrate increased by a factor of approximately 12. This significant increase in the deposition rate is achieved by cooling the sacrificial electrode 16 ' achieved increase in the production rate of the particles allows.

The achievable by the inventive method and the inventive device high particle production rates, small particle sizes and homogeneous particle size distributions allow the use of the particles produced in a variety of applications, such. In the medical sector, household appliances, sanitary articles and electronic elements, e.g. B. 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 particles produced 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 effective coating to be installed. 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, such as. As ZnO particles can be incorporated into plasma polymer layers as a UV-absorbing scratch protection.

• (1) Verfahren zur Herstellung von Partikeln unter Verwendung eines Atmosphärendruckplasmas, insbesondere in einem Atmosphärendruckplasma, bei dem das Plasma durch eine Entladung zwischen Elektroden in einem Prozessgas erzeugt wird, mindestens eine der Elektroden eine Opferelektrode ist, von der durch die Entladung Material abgetragen wird, es sich bei dem abgetragenen Material um Partikel handelt und/oder aus dem abgetragenen Material Partikel entstehen, und ein Abschnitt der Opferelektrode aktiv so gekühlt wird, dass die mittlere Temperatur der Opferelektrode in einem Bereich der Opferelektrode außerhalb des Entladungsbereichs der Opferelektrode niedriger ist als innerhalb des Entladungsbereichs der Opferelektrode.
• (2) Verfahren nach Punkt (1), bei dem die Kühlung des Abschnitts der Opferelektrode über Wärmeleitung erfolgt.
• (3) Verfahren nach Punkt (1) oder (2), bei dem die Kühlung des Abschnitts der Opferelektrode durch ein Kühlmedium erfolgt.
• (4) Verfahren nach Punkt (3), bei dem das Kühlmedium nur mit dem Bereich der Opferelektrode außerhalb des Entladungsbereichs der Opferelektrode in Kontakt kommt.
• (5) Verfahren nach einem der vorhergehenden Punkte, bei dem die Opferelektrode an einer Eintrittsstelle der Opferelektrode in einen Kühlungsbereich eintritt, in dem der Abschnitt der Opferelektrode aktiv gekühlt wird, wobei die Eintrittsstelle an einer dem Entladungsbereich der Opferelektrode gegenüberliegenden Seite des Kühlungsbereichs liegt, und die Differenz zwischen der mittleren Temperatur der Opferelektrode innerhalb des Entladungsbereichs der Opferelektrode und der mittleren Temperatur der Opferelektrode an der Eintrittsstelle in dem Bereich von T_S – 393 K bis T_S – 77 K, bevorzugt von T_S – 373 K bis T_S – 77 K, bevorzugter von T_S – 323 K bis T_S – 77 K und am bevorzugtesten von T_S – 293 K bis T_S – 77 K, liegt, wobei T_S die Schmelztemperatur des Materials der Opferelektrodein K ist.
• (6) Verfahren nach einem der vorhergehenden Punkte, bei dem die Opferelektrode an einer Eintrittsstelle der Opferelektrode in einen Kühlungsbereich eintritt, in dem der Abschnitt der Opferelektrode aktiv gekühlt wird, wobei die Eintrittsstelle an einer dem Entladungsbereich der Opferelektrode gegenüberliegenden Seite des Kühlungsbereichs liegt, und die mittlere Temperatur der Opferelektrode an der Eintrittsstelle 393 K, bevorzugt 373 K, bevorzugter 323 K und am bevorzugtesten 293 K, nicht überschreitet.
• (7) Verfahren nach einem der vorhergehenden Punkte, bei dem die mittlere Temperatur der Opferelektrode innerhalb des Entladungsbereichs der Opferelektrode die Schmelztemperatur des Materials der Opferelektrode nicht überschreitet.
• (8) Verfahren nach einem der vorhergehenden Punkte, bei dem die Opferelektrode eine längliche Form aufweist.
• (9) Verfahren nach einem der vorhergehenden Punkte, bei dem die Position des Entladungsbereichs der Opferelektrode erfasst wird.
• (10) Verfahren nach Punkt (9), bei dem die Position des Entladungsbereichs der Opferelektrode optisch und/oder elektronisch erfasst wird.
• (11) Verfahren nach einem der vorhergehenden Punkte, bei dem die Opferelektrode so geführt wird, dass die Position des Entladungsbereichs der Opferelektrode während des Verfahrens im Wesentlichen gleich bleibt.
• (12) Verfahren nach Punkt (11) wie abhängig von Punkt (9) oder (10), bei dem die Opferelektrode auf Grundlage der erfassten Position des Entladungsbereichs der Opferelektrode so geführt wird, dass die Position des Entladungsbereichs der Opferelektrode während des Verfahrens im Wesentlichen gleich bleibt.
• (13) Verfahren nach einem der vorhergehenden Punkte, bei dem die Entladung eine gepulste Entladung ist.
• (14) Verfahren nach einem der vorhergehenden Punkte, bei dem die Partikel eine Partikelgröße im Bereich von 2 nm bis 20 μm aufweisen.
• (15) Verfahren nach einem der vorhergehenden Punkte, bei dem das Erzeugen des Atmosphärendruckplasmas, das Abtragen des Materials und das Entstehen der Partikel unter Verwendung einer Plasmadüse erfolgen.
• (16) Verfahren nach einem der vorhergehenden Punkte, insbesondere nach Punkt (15), bei dem Partikel in einem relaxierenden Bereich des Atmosphärendruckplasmas aus dem abgetragenen Material entstehen.
• (17) Verfahren nach einem der vorhergehenden Punkte, insbesondere nach Punkt (15) oder (16), bei dem die Verweildauer des Materials in einem relaxierenden Bereich des Atmosphärendruckplasmas kontrolliert wird.
• (18) Vorrichtung zur Herstellung von Partikeln unter Verwendung eines Atmosphärendruckplasmas, insbesondere in einem Atmosphärendruckplasma, die umfasst: ein Gehäuse mit einem Kanal, mindestens zwei Elektroden, die zumindest teilweise in dem Kanal angeordnet sind, eine Spannungsquelle, die dafür eingerichtet ist, eine Spannung zwischen den mindestens zwei Elektroden anzulegen, wobei die mindestens zwei Elektroden dafür eingerichtet sind, das Plasma durch eine Entladung zwischen den Elektroden in einem Prozessgas in dem Kanal zu erzeugen, mindestens eine der Elektroden eine Opferelektrode ist, von der durch die Entladung Material abgetragen wird, und es sich bei dem abgetragenen Material um Partikel handelt und/oder aus dem abgetragenen Material Partikel entstehen, und eine Kühleinrichtung, die dafür eingerichtet ist, einen Abschnitt der Opferelektrode aktiv so zu kühlen, dass die mittlere Temperatur der Opferelektrode in einem Bereich der Opferelektrode außerhalb des Entladungsbereichs der Opferelektrode niedriger ist als innerhalb des Entladungsbereichs der Opferelektrode.
• (19) Vorrichtung nach Punkt (18), bei der die Kühleinrichtung dafür eingerichtet ist, den Abschnitt der Opferelektrode über Wärmeleitung zu kühlen.
• (20) Vorrichtung nach Punkt (18) oder (19), bei der die Kühleinrichtung dafür eingerichtet ist, den Abschnitt der Opferelektrode durch ein Kühlmedium zu kühlen.
• (21) Vorrichtung nach Punkt (20), bei der die Kühleinrichtung so eingerichtet ist, dass das Kühlmedium nur mit dem Bereich der Opferelektrode außerhalb des Entladungsbereichs der Opferelektrode in Kontakt, insbesondere direkt oder über eine Wandung thermisch in Kontakt, kommt.
• (22) Vorrichtung nach einem der Punkte (18) bis (21), bei der die Opferelektrode an einer Eintrittsstelle der Opferelektrode in einen Kühlungsbereich eintritt, in dem der Abschnitt der Opferelektrode aktiv gekühlt wird, wobei die Eintrittsstelle an einer dem Entladungsbereich der Opferelektrode gegenüberliegenden Seite des Kühlungsbereichs liegt, und die Kühleinrichtung so eingerichtet ist, dass bei Betrieb der Vorrichtung die Differenz zwischen der mittleren Temperatur der Opferelektrode innerhalb des Entladungsbereichs der Opferelektrode und der mittleren Temperatur der Opferelektrode an der Eintrittsstelle in dem Bereich von T_S – 393 K bis T_S – 77 K, bevorzugt von T_S – 373 K bis T_S – 77 K, bevorzugter von T_S – 323 K bis T_S – 77 K und am bevorzugtesten von T_S – 293 K bis T_S – 77 K, liegt, wobei T_S die Schmelztemperatur des Materials der Opferelektrode in K ist.
• (23) Vorrichtung nach einem der Punkte (18) bis (22), bei der die Opferelektrode an einer Eintrittsstelle der Opferelektrode in einen Kühlungsbereich eintritt, in dem der Abschnitt der Opferelektrode aktiv gekühlt wird, wobei die Eintrittsstelle an einer dem Entladungsbereich der Opferelektrode gegenüberliegenden Seite des Kühlungsbereichs liegt, und die Kühleinrichtung so eingerichtet ist, dass bei Betrieb der Vorrichtung die mittlere Temperatur der Opferelektrode an der Eintrittsstelle 393 K, bevorzugt 373 K, bevorzugter 323 K und am bevorzugtesten 293 K, nicht überschreitet.
• (24) Vorrichtung nach einem der Punkte (18) bis (23), bei der die Kühleinrichtung so eingerichtet ist, dass bei Betrieb der Vorrichtung die mittlere Temperatur der Opferelektrode innerhalb des Entladungsbereichs der Opferelektrode die Schmelztemperatur des Materials der Opferelektrode nicht überschreitet.
• (25) Vorrichtung nach einem der Punkte (18) bis (24), bei der die Opferelektrode eine längliche Form aufweist.
• (26) Vorrichtung nach einem der Punkte (18) bis (25), die ferner eine Erfassungseinrichtung umfasst, die dafür eingerichtet ist, die Position des Entladungsbereichs der Opferelektrode zu erfassen.
• (27) Vorrichtung nach Punkt (26), bei der die Erfassungseinrichtung dafür eingerichtet ist, die Position des Entladungsbereichs der Opferelektrode optisch und/oder elektronisch zu erfassen.
• (28) Vorrichtung nach einem der Punkte (18) bis (27), die ferner eine Steuereinrichtung umfasst, die dafür eingerichtet ist, die Opferelektrode so zu führen, dass die Position des Entladungsbereichs der Opferelektrode während des Betriebs der Vorrichtung im Wesentlichen gleich bleibt.
• (29) Vorrichtung nach Punkt (28) wie abhängig von Punkt (26) oder (27), bei der die Steuereinrichtung dafür eingerichtet ist, die Opferelektrode auf Grundlage der durch die Erfassungseinrichtung erfassten Position des Entladungsbereichs der Opferelektrode so zu führen, dass die Position des Entladungsbereichs der Opferelektrode während des Betriebs der Vorrichtung im Wesentlichen gleich bleibt.
• (30) Vorrichtung nach einem der Punkte (18) bis (29), bei der die Spannungsquelle so eingerichtet ist, dass die Entladung eine gepulste Entladung ist.
• (31) Vorrichtung nach einem der Punkte (18) bis (30), bei der die Partikel eine Partikelgröße im Bereich von 2 nm bis 20 μm aufweisen.

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

• (1) A method of producing particles using an atmospheric pressure plasma, particularly 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 material is removed by the discharge, where the abraded material is particulate matter 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 is lower in a region of the sacrificial electrode outside the discharge area of the sacrificial electrode than inside the sacrificial electrode 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 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 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 mean temperature of the sacrificial electrode at the entry point in the range of T _s - 393 K to T _s - 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 T _S - 77 K, where T _{S is} the melting temperature of the sacrificial electrode material 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 to the discharge region of the sacrificial electrode, and the average temperature of the sacrificial electrode at the point of entry does not exceed 393K, preferably 373K, more preferably 323K, and most preferably 293K.
• (7) The method of 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 sacrificial electrode material.
• (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 discharge area of the sacrificial electrode during the process substantially stays the same.
• (13) The method according to any preceding item, wherein the discharge is a pulsed discharge.
• (14) The method according to any one of the preceding points, wherein the particles have a particle size in the range of 2 nm to 20 microns.
• (15) The method according to any one of the preceding claims, wherein generating the atmospheric pressure plasma, ablating the material, and forming the particles using a plasma nozzle.
• (16) Method according to one of the preceding points, in particular according to item (15), in which particles in arise from the abraded material a relaxing region of the atmospheric pressure plasma.
• (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) An apparatus 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 the abraded material is particulate matter and / or particles are formed from the abraded material, and a cooling device configured to actively cool a portion of the sacrificial electrode such that the average temperature of the sacrificial electrode in a region 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 when operating 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 T _S - 393 K to T _S - 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 T _S - 77 K, where T _{S is} the melting temperature of the material of the sacrificial electrode in K.
• (23) The device according to any one of (18) to (22), 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 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 (18) to (23), wherein the cooling means is arranged such that, during operation of the device, the average temperature of the sacrificial electrode within the discharge area of the sacrificial electrode does not exceed the melting temperature of the sacrificial electrode material.
• (25) The device according to any one of (18) to (24), wherein the sacrificial electrode has an elongated shape.
• (26) The device according to any one of (18) to (25), further comprising detecting means arranged to detect the position of the discharge area of the sacrificial 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 according to 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 of 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 power source is arranged so 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 μm.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19824364 A [0005]
• WO 2005/061754 [0006]
• WO 2005/048708 [0007]
• DE 19958473 A [0010]
• DE 19807086A [0011]
• WO 01/32949 [0012]
• DE 10223865 B [0014, 0015]
• US 5808270 [0016]
• DE 102009031857 [0017]
• DE 102009048397 A [0018]

Cited non-patent literature

• C. Tendern et al. in "Atmospheric pressure plasmas: A review", Spectrochimica Acta Part B: Atomic Spectroscopy, 2006, pp. 2-30 [0034]

Claims (17)

Process for the production of particles ( 30 ) using an atmospheric pressure plasma, in which the plasma by a discharge ( 15 . 15 ' ) between electrodes ( 16 . 16 ' . 16 ''; 5 . 32 ) in a process gas ( 18 ) is generated, at least one of the electrodes a sacrificial electrode ( 16 . 16 ' . 16 '' ) from which material is removed by the discharge, 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 is in a range the sacrificial electrode outside the discharge area ( 17 . 17 ' . 17 '' ) of the sacrificial electrode is lower than within the discharge area of the sacrificial electrode. The method of claim 1, wherein the cooling of the portion of the sacrificial electrode via heat conduction takes place. The method of claim 1 or 2, wherein the cooling of the portion of the sacrificial electrode by a cooling medium ( 11 . 11 ' . 11 '' ) he follows. 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. Method according to one of the preceding claims, wherein the sacrificial electrode at an entry point ( 21 . 21 ' . 21 '' ) of the sacrificial electrode enters a cooling region 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 mean temperature of the sacrificial electrode within the discharge region of the sacrificial electrode and the middle one Temperature of the sacrificial electrode at the point of entry in the range of T _S - 393 K to T _S - 77 K, where T _{S is} the melting temperature of the material of the sacrificial electrode in K. Method according to one of the preceding claims, in which 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 lying 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 point of entry does not exceed 393 K. Method according to 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. A method according to any one of the preceding claims, wherein the sacrificial electrode has an elongate shape. Method according to one of the preceding claims, wherein the position of the discharge region of the sacrificial electrode is detected. The method of claim 9, wherein the position of the discharge region of the sacrificial electrode is optically and / or electronically detected. Method according to one of the preceding claims, wherein the sacrificial electrode is guided so that the position of the discharge region of the sacrificial electrode remains substantially the same during the process. 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 so that the position of the discharge area of the sacrificial electrode remains substantially the same during the process. Method according to one of the preceding claims, wherein the discharge is a pulsed discharge. Method according to one of the preceding claims, wherein the particles have a particle size in the range of 2 nm to 20 microns. Method according to one of the preceding claims, in which particles are formed in a relaxing region of the atmospheric pressure plasma from the removed material. Method according to one of the preceding claims, wherein the residence time of the material is controlled in a relaxing region of the atmospheric pressure plasma. Device for producing particles ( 30 ) using an atmospheric pressure plasma, comprising: a housing ( 5 ) with a channel ( 7 . 7 ' . 7 '' ), at least two electrodes ( 16 . 16 ' . 16 ''; 5 . 32 ), which are at least partially disposed in the channel, a voltage source ( 22 ), which is adapted to apply a voltage between the at least two electrodes, wherein the at least two electrodes are adapted to discharge the plasma ( 15 . 15 ' ) between the electrodes in a process gas ( 18 ) in the channel, at least one of the electrodes has a sacrificial electrode ( 16 . 16 ' . 16 '' ), from which material is removed by the discharge, and the removed material is particles and / or particles are formed from the removed material, and a cooling device ( 2 ) configured to actively cool a portion of the sacrificial electrode so that the average temperature of the sacrificial electrode in an area of the sacrificial electrode outside the discharge area (FIG. 17 . 17 ' . 17 '' ) of the sacrificial electrode is lower than within the discharge area of the sacrificial electrode.

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