Plasma treatment with liquid cooling

Abstract

The invention relates to a method for the treatment, in particular for the cleaning, reduction treatment and / or coating of a workpiece (202, 302, 502, 602, 702), in which: an atmospheric plasma jet (26, 230, 230', 330, 530, 630, 730, 730') is generated; a workpiece (202, 302, 502, 602, 702) that is to be treated, in particular a workpiece that is to be cleaned, reduced and / or coated, is brought into contact with a liquid (210, 510, 610, 710); and the atmospheric plasma jet (26, 230, 230', 330, 530, 630, 730, 730') is applied to a surface (204, 304, 504, 604, 704) of the workpiece (202, 302, 502, 602, 704) that is to be treated, or to the liquid (210, 510, 610, 710). The invention furthermore relates to a device (601) for the treatment, in particular cleaning, reduction treatment and / or coating of a workpiece (602) in strip form, in particular a metal strip, in particular in order to carry out the above-stated method.

Description

[0001]September 25, 2023 Plasma treatment with liquid cooling The present invention relates to a method for treating a workpiece, in particular for cleaning, reducing, and / or coating a workpiece, as well as to a device for treating, in particular cleaning, reducing, and / or coating, a strip-shaped workpiece. Methods for reducing the workpieces are carried out, for example, to achieve better thermal and / or electrical contactability or better wettability of the workpiece surfaces, for example with solder. The reduction treatment of workpieces often aims to facilitate subsequent process steps on the workpieces, such as bonding or soldering to other workpieces, or to make them possible in the first place. Various methods for reducing the workpieces are known from the prior art.Some of these processes, for example, use chemical reducing agents such as fluxes. However, these are typically corrosive and harmful, or release harmful vapors. Reduction processes using low-pressure plasmas are also known, for example, from WO 00 / 29642 A1. However, due to the required inlet and outlet processes, such low-pressure processes have the disadvantage that they can only be integrated into continuous production operations with considerable technical effort. Furthermore, selective reduction treatments, in which only specific parts of a workpiece surface are to be reduced, are difficult to implement with such low-pressure processes. The use of atmospheric plasma processes for reduction treatment has also been considered.However, it has been found that these processes often result in rapid reoxidation of the reduced workpiece surface, so that the workpiece surfaces in question are ultimately not reliably freed of oxides. Furthermore, various methods for coating workpieces using an atmospheric plasma jet are known from the prior art, for example from EP 1230414 B1, and there is a need to further improve coating processes using an atmospheric plasma jet. Furthermore, various methods for cleaning workpieces, in particular for subsequent coating, are known from the prior art, and there is a need to carry out such a cleaning process efficiently.Against this background, the present invention is based on the object of providing an improved method and an improved device for the reliable treatment, in particular cleaning, reduction treatment and / or coating, of workpieces, which are particularly suitable for inline use and preferably enable selective treatment, in particular cleaning, reduction treatment and / or coating, on workpiece surfaces. This object is achieved according to the invention by a method for treating a workpiece, in which an atmospheric plasma jet is generated, in which a workpiece to be treated is brought into contact with a liquid, and in which a surface of the workpiece to be treated, in particular the workpiece to be cleaned, reduced and / or coated, and / or the liquid is exposed to the atmospheric plasma jet.The aforementioned object is achieved according to the invention in particular by a method for the reduction treatment of a workpiece, in which an atmospheric plasma jet is generated, in which a workpiece to be reduced is brought into contact with a SE / fu 220174WO September 25, 2023 liquid, and in which a surface of the workpiece to be reduced and / or the liquid is exposed to the atmospheric plasma jet. It has been found that a surface of a workpiece can be reliably reduced in this way. A reduction treatment of a surface of a workpiece is understood in particular to mean that oxides on the workpiece surface are chemically converted, so that after the reduction treatment, no or at least minor oxide components are present on the then reduced workpiece surface or the reduced workpiece surface section.The oxides on the workpiece surface can be reduced, in particular, by removing oxygen from the oxides and chemically binding them, for example, by other means, particularly by species contained in the plasma jet. For example, by a reduction treatment of a copper workpiece surface, copper oxides present on the surface can be converted into copper by removing the oxygen. Within the scope of the present invention, it was found that in previous attempts to reduce workpiece surfaces using an atmospheric plasma jet, it was primarily the heating of the workpiece by the plasma jet that led to increased reoxidation of the workpiece surface.By bringing the workpiece into contact with a liquid, the method described here can cool the workpiece in the area of ​​the surface to be reduced, so that this area is less prone to reoxidation after the reduction treatment. Furthermore, the workpiece surface can be at least partially covered by the liquid through contact with the liquid, thereby preventing or at least reducing direct contact of the workpiece surface with an oxygen-containing atmosphere in the environment, so that reoxidation is also prevented or reduced in this way. SE / fu 220174WO September 25, 2023 For the reduction treatment, an atmospheric plasma jet is generated, and a surface of the workpiece to be reduced and / or the liquid is exposed to the atmospheric plasma jet.The actual reduction of oxides on the workpiece surface can therefore be achieved in particular by exposing a surface of the workpiece, in particular a section of the workpiece surface to be reduced, to the atmospheric plasma jet. Additionally or alternatively, the reduction of oxides on the workpiece surface can also be carried out in such a way that, instead of directly exposing the workpiece to the atmospheric plasma jet, the liquid is exposed to the atmospheric plasma jet, thereby plasma-activating it. It has been found that a liquid plasma-activated in this way can also have a reducing effect on the surface of the workpiece. In this embodiment, the liquid also achieves particularly effective cooling and reduced contact with an oxygen-containing atmosphere.It was also recognized that exposing the liquid to the atmospheric plasma jet increases the effective range of the reduction treatment beyond the width of the plasma jet, since the liquid exposed to the plasma jet also effects a reduction treatment on the workpiece surface outside the immediate area of ​​influence of the plasma jet. Unlike dry reduction treatment using a plasma jet, in which a workpiece surface is only subjected to a reduction treatment in the area exposed to the plasma jet, the present method using a plasma jet allows a larger workpiece surface area to be subjected to a reduction treatment, so that, for example, a larger workpiece can be subjected to a plasma reduction treatment with a smaller number of plasma nozzles or with a smaller number of passes.The reducing effect of the atmospheric plasma jet can be achieved by generating the atmospheric plasma jet with a reducing gas or gas mixture, for example forming gas. Additionally or alternatively, it is possible for a reducing agent to be supplied to the atmospheric plasma jet or to be brought into contact with the surface of the workpiece to be reduced in some other way, for example with the liquid. In particular, the method serves for the reduction treatment of at least partially metallic workpiece surfaces of a workpiece which consists at least partially of metal, for example a metal alloy. The metal can be copper, for example. The workpiece can in particular be a strip-shaped workpiece, in particular a metal strip.The reduction treatment of strip-shaped workpieces can, for example, be carried out to prepare the workpiece surface for subsequent coating, in particular strip coating. The aforementioned object is further achieved according to the invention in particular by a method for coating a workpiece, in which an atmospheric plasma jet is generated, in which a workpiece to be coated is brought into contact with a liquid, and in which a surface of the workpiece to be coated and / or the liquid is exposed to the atmospheric plasma jet. It has been found that a surface of a workpiece can be coated reliably and evenly in this way. The workpiece can, in particular, be coated with a metal layer in the method. For the coating, in particular a precursor, preferably a salt, is added to the liquid, in particular a salt is dissolved in the liquid.It has been found that a workpiece surface can be effectively coated in this way, with the precursor or a reaction product of a reaction of the precursor forming the coating. The atmospheric plasma jet or reactive species generated in the liquid by the SE / fu 220174WO September 25, 2023 atmospheric plasma jet, such as OH-, can in particular cause a chemical redox reaction in which the precursor or a component thereof, in particular a dissociated component of a salt dissolved as a precursor in the liquid, is reduced by electron absorption and forms a coating on the surface of the workpiece. The dissociated component can in particular be an ionic residue of a salt, in particular a cationic residue, in particular a metal ionic residue of a salt.If, for example, a metal salt, such as a copper salt, is used as a precursor, the metal cation of the metal salt, such as Cu. 2+, by interaction with the atmospheric plasma jet or with the liquid acted upon by the atmospheric plasma jet, the elemental metal, such as Cu, is reduced, so that elemental metal, such as Cu, is deposited on the surface of the workpiece to be coated and a metal coating, such as a copper coating, is formed in this way. In the method described here for coating a workpiece, reduction is understood to mean in particular the inclusion of one or more electrodes. Oxygen can be involved in the chemical redox reaction, but this is not required. By bringing the workpiece into contact with a liquid, a uniform coating can be achieved in the method for coating a workpiece, in particular by the precursor or by a reaction product of a reaction of the precursor.Furthermore, the workpiece can be cooled in the area of ​​the surface to be coated and / or protected from direct contact with an oxygen-containing ambient atmosphere, thereby counteracting a reversal of a redox reaction caused by the plasma jet (SE / fu 220174WO September 25, 2023) or an oxidation of the reduced components or the workpiece surface. For the coating process, an atmospheric plasma jet is generated, and a surface of the workpiece to be coated and / or the liquid is exposed to the atmospheric plasma jet.The actual coating of the workpiece surface can thus be achieved in particular by exposing a surface of the workpiece, in particular a section of the workpiece surface to be coated, to the atmospheric plasma jet, whereby the coating material is provided from the liquid, in particular by the precursor or a reaction product of a reaction of the precursor. Additionally or alternatively, the coating of the workpiece surface can also be carried out in such a way that, instead of directly exposing the workpiece to the atmospheric plasma jet, the liquid is exposed to the atmospheric plasma jet, thereby plasma-activating it.It has been found that a liquid plasma-activated in this way can, through the reactive species it contains, such as OH-, cause a redox reaction on a precursor dissolved in the liquid or a component thereof, in particular on a dissociated component of a salt dissolved as a precursor in the liquid, resulting in a coating of the surface of the workpiece. In this design, the liquid also achieves particularly effective cooling and reduced contact with an oxygen-containing atmosphere. It has also been found that exposing the liquid to the atmospheric plasma jet increases the effective range of the coating beyond the width of the plasma jet, since the liquid exposed to the plasma jet also creates a coating on the workpiece surface outside the immediate sphere of influence of the plasma jet.In contrast to dry coating using a plasma jet, in which a workpiece surface is only coated in the area exposed to the plasma jet, the present method using a plasma jet can be used to coat a larger workpiece surface area, so that, for example, a larger workpiece can be coated with a smaller number of plasma nozzles or with a smaller number of passes. The atmospheric plasma jet can, for example, be generated using nitrogen (N2), argon, air, forming gas (nitrogen-hydrogen mixture) or an argon-hydrogen mixture. The plasma jet itself already has a certain reducing effect, even if it is generated with a fundamentally non-reducing gas such as nitrogen, so that the plasma jet can, for example, trigger a redox reaction on a salt or hydroxide dissolved in the liquid as a precursor.a dissociated component of the salt. In order to cause or intensify a redox reaction on a precursor in the liquid, in particular on a salt dissolved as a precursor in the liquid or a dissociated component of the salt, using the atmospheric plasma jet, the atmospheric plasma jet is preferably generated with a reducing gas or gas mixture, for example, forming gas or an argon-hydrogen mixture. Additionally or alternatively, it is possible to add a reducing agent to the atmospheric plasma jet or to bring it into contact with the surface of the workpiece and / or the liquid to be coated in another way.If, for example, the plasma jet is generated with air, nitrogen or argon, a hydrogen-containing agent can be added to the plasma jet or the liquid, for example, or a hydrogen-containing liquid can be used to provide hydrogen for the redox reaction. In this way, a stronger coating effect can be achieved. The workpiece to be coated can, for example, be made of polymer, glass, metal, wood, ceramic, leather or textile material, such as SE / fu 220174WO September 25, 2023 fabric. The workpiece to be coated can also consist of different materials, whereby the workpiece in the area of ​​the surface to be coated preferably consists of one or more of the following materials: polymer, glass, metal, wood, ceramic, leather or textile material.The workpiece to be coated can furthermore be, in particular, a strip-shaped workpiece, in particular a metal strip. The aforementioned object is furthermore achieved according to the invention, in particular, by a method for cleaning a workpiece, in which an atmospheric plasma jet is generated, in which a workpiece to be cleaned is brought into contact with a liquid, and in which a surface of the workpiece to be cleaned and / or the liquid is exposed to the atmospheric plasma jet. It has been found that a surface of a workpiece can be cleaned reliably and evenly in this way. The workpiece to be cleaned can furthermore be, in particular, a strip-shaped workpiece, in particular a metal strip.The above-mentioned object is further achieved according to the invention by a device for treating, in particular for cleaning, reducing and / or coating, a strip-shaped workpiece, in particular a metal strip, in particular for carrying out the above-described method for treating a workpiece, in particular the above-described method for reducing treatment or the above-described method for coating or the above-described method for cleaning or a respective embodiment thereof, with an immersion bath device which is designed to guide a strip-shaped workpiece through an immersion bath and with a plasma source for generating an atmospheric plasma jet, wherein the plasma source is arranged and designed to apply an atmospheric plasma jet to the immersion bath or to a strip-shaped workpiece guided through the immersion bath of the immersion bath device during operation.With such a device, strip-shaped workpieces, in particular metal strips, can be treated effectively and reliably, in particular subjected to a reduction treatment and / or coated and / or cleaned. Furthermore, such a device can be easily integrated inline into a continuous production operation. The plasma nozzle can in particular be arranged and configured to subject a strip-shaped workpiece guided through the immersion bath device to the atmospheric plasma jet during operation. In this way, the treatment, in particular cleaning and / or reduction treatment and / or coating, can be achieved by directly exposing the workpiece to the plasma jet. Furthermore, the plasma nozzle can also be arranged and configured to subject the immersion bath to the atmospheric plasma jet during operation.As previously described with regard to the method, it has been found that the treatment effect, in particular the cleaning effect and / or reducing effect and / or coating, can also be achieved by exposing the liquid brought into contact with the strip-shaped workpiece to the atmospheric plasma jet, so that direct exposure of the workpiece to the plasma jet is not necessarily required.Exposure to the liquid of the immersion bath with the plasma jet also has the advantage that the treatment effect, in particular reduction effect and / or coating and / or cleaning effect, is increased beyond the width of the plasma jet, so that wider surface strips on the workpiece surface can be subjected to treatment, in particular reduction treatment and / or coating and / or cleaning, with one plasma nozzle and, for example, the number of plasma nozzles required for the treatment, in particular reduction treatment and / or coating and / or cleaning, of a strip-shaped workpiece per given width can be reduced, in particular compared to a dry plasma treatment process, in particular a dry plasma reduction process or a dry SE / fu 220174WO September 25, 2023 plasma coating process or a dry plasma treatment process.The immersion bath device can, in particular, comprise a container for holding a volume of liquid that forms an immersion bath, and guide means that are arranged and configured to guide a strip-shaped workpiece through the immersion bath. Suitable guide means can, for example, be guide rollers, which can also be easily integrated into a continuous production operation. The device can comprise dispensing and receiving means that are configured to dispense the strip-shaped material before treatment, in particular reduction treatment and / or coating and / or cleaning, and to receive the strip-shaped material after treatment, in particular reduction treatment and / or coating and / or cleaning. The dispensing and / or receiving means can, for example, be designed as roll(s), so that the strip-shaped material can be unrolled from the dispensing means for dispensing or rolled up onto the receiving means for receiving.This configuration enables compact storage of the material and advantageously reduces contact between its surface and the oxygen-containing atmosphere, thereby reducing the oxidative effect of atmospheric air on the surface of the strip-shaped workpiece. Furthermore, the device may comprise transport means for transporting the strip-shaped workpiece through the immersion bath device. These transport means may be formed by the guide means, for example, rotating rollers, and / or by the discharge and pick-up means, for example, driven discharge and / or pick-up means. Alternatively or additionally, separate transport means may be provided. Furthermore, the device may comprise sensors for measuring the temperature of the liquid and / or the workpiece, thereby enabling monitoring and / or control of the operation.In particular, the temperature of the workpiece can be regulated in this way, for example upon exiting the immersion bath, so that heating of the strip-shaped workpiece above a predetermined temperature value is prevented in the immersion bath, for example by cooling it with preferably provided coolants, in order to prevent reoxidation processes or general oxidation processes after exiting the immersion bath. If the temperature of the workpiece and / or the immersion bath increases too much, for example, the cooling capacity of the provided coolants can be increased, the transport speed of the workpiece through the immersion bath and / or the intensity of the plasma jet can be regulated. Furthermore, the device can have multiple plasma sources.For the treatment, in particular reduction treatment and / or coating and / or cleaning, of large surfaces, for example, wide strip-shaped workpieces or a plurality of strip-shaped workpieces arranged side by side, the plasma sources can be arranged, in particular, transversely to the transport direction of the strip-shaped workpiece. Additionally or alternatively, several plasma sources can also be provided along the transport direction of the strip-shaped workpiece to enable particularly rapid guidance of the strip-shaped workpiece with sufficient treatment effect, in particular sufficient reduction treatment effect and / or sufficient coating and / or sufficient cleaning.Various embodiments of the method and the device are described below, wherein the individual embodiments each apply independently of one another to the treatment method, in particular to the reduction treatment method, to the coating method and the cleaning method, and to the treatment device, in particular reduction treatment and / or coating and / or cleaning. Furthermore, the individual embodiments can be combined with one another as desired. SE / fu 220174WO September 25, 2023 In one embodiment of the treatment method, in particular reduction treatment and / or coating and / or cleaning, the workpiece is brought into contact with the liquid by arranging the workpiece in a liquid volume, in particular submerging it, before the surface or the liquid is exposed to the plasma jet.In this way, the contact between the liquid and the workpiece is increased, allowing for better cooling of the workpiece, particularly in the area of ​​the workpiece surface to be treated, in particular the surface to be reduced and / or coated and / or cleaned. Furthermore, this method can reduce the contact of the workpiece surface with a potentially oxygen-containing atmosphere. In this way, oxidation or reoxidation of the treated, in particular the reduced and / or coated and / or cleaned, workpiece surface can be prevented or at least reduced.Preferably, the workpiece is arranged in the liquid volume in such a way that the coverage height of the liquid volume above a surface of the workpiece directed towards the surface of the liquid volume, in particular the surface of the workpiece to be treated, in particular to be reduced and / or coated and / or cleaned, is at least 1 mm, preferably at least 3 mm, particularly preferably at least 5 mm. In a further embodiment of the method for treatment, in particular reduction treatment and / or coating and / or cleaning, the exposure to the atmospheric plasma jet is effected in such a way that a portion of the liquid volume located above the workpiece is locally displaced by the atmospheric plasma jet.In this way, effective exposure of the workpiece surface to be treated, in particular to be reduced and / or coated and / or cleaned, to the atmospheric plasma jet can be achieved even when the workpiece is arranged in the liquid, in particular submerged therein. By locally displacing the liquid with the plasma jet, a stronger reduction effect and / or more targeted coating and / or cleaning can be achieved. The atmospheric plasma jet can locally displace the liquid volume above the workpiece, in particular practically completely, so that at the location of the plasma application, no liquid or only a thin liquid film with a height above the workpiece surface of less than 1 mm, in particular less than 10 µm, for example in the size range of a few molecular layers, remains.In this way, a virtually direct application of the plasma jet to the workpiece can be achieved, resulting in particularly strong and targeted treatment, in particular a reduction effect and / or coating and / or cleaning. Since the displacement of the liquid occurs locally, the workpiece remains sufficiently covered with liquid outside the plasma jet and can thus be effectively cooled and / or shielded from an oxygen-containing atmosphere. Alternatively, the atmospheric plasma jet can also displace the liquid volume above the workpiece in such a way that a macroscopic liquid volume, for example with a height of at least 1 mm, preferably at least 2 mm, more preferably at least 3 mm, remains above the workpiece surface even at the point of plasma application.In this way, a good and targeted treatment effect, in particular a reduction effect and / or coating and / or cleaning, can also be achieved. At the same time, the liquid is continuously covered by the liquid during plasma application, so that more efficient cooling of the workpiece surface is achieved and direct contact with oxygen in the surrounding atmosphere is prevented. The displacement of the liquid volume, in particular the degree of displacement, can be adjusted, for example, via the distance between the plasma nozzle and the surface of the workpiece and / or via the working gas flow or working gas pressure of the plasma nozzle. Furthermore, the displacement of the liquid volume, in particular the degree of displacement, can be influenced by adjusting the height of the liquid above the workpiece.For example, with lower liquid heights for local liquid displacement, sufficient local water displacement can be achieved even with a greater distance between the plasma nozzle and the workpiece, or with a lower working gas flow or pressure. In another embodiment of the method, particularly for cleaning and / or reduction treatment, the workpiece is brought into contact with the liquid by applying, in particular spraying, the liquid to the workpiece during and / or after exposure to the plasma jet. The liquid can be applied over the entire surface of the workpiece or locally in the area where the plasma jet is applied.By applying the liquid to the workpiece surface while it is being subjected to the plasma jet, the workpiece can be cooled and / or contact with the oxygen-containing atmosphere can be reduced, for example as long as the workpiece has an elevated temperature due to the exposure to the plasma jet. Furthermore, the reducing effect of the atmospheric plasma jet can be enhanced or even generated by applying the liquid, for example by using a liquid with a reducing effect, possibly under the influence of the plasma jet. The application, in particular spraying, of the workpiece can be carried out in a targeted and metered manner. In particular, with this embodiment of the method, large-area, prolonged contact between the workpiece and the liquid can be avoided as required, which can be advantageous in certain applications or with certain workpiece materials.SE / fu 220174WO September 25, 2023 By applying the plasma jet during or after exposure to the plasma jet, a property of the liquid can also be specifically influenced, for example by controlling the liquid's temperature. Furthermore, local application results in the advantage of requiring less liquid to be provided. In a further embodiment of the method for treatment, in particular reduction treatment and / or coating and / or cleaning, the atmospheric plasma jet is generated using a reducing working gas, in particular a hydrogen-containing working gas. The working gas can contain, for example, hydrogen (H2) and one or more inert gases such as nitrogen (N2) or noble gases (e.g., Ar). One conceivable working gas is, for example, forming gas, which is a mixture of hydrogen and nitrogen.The forming gas can, for example, have a hydrogen content (H2) in the range of 1 to 15 vol.% and a nitrogen content (N2) in the range of 99 - 85 vol.%. When a hydrogen-containing working gas is used, the hydrogen it contains, together with the atmospheric plasma jet, causes a strong reducing effect on the workpiece or - if the liquid is exposed to the plasma jet - in the liquid. In particular, the plasma jet generated with a hydrogen-containing working gas has a reducing effect in itself, without this having to be caused by another means, such as the liquid. In this way, the liquid can, for example, be a hydrogen-free liquid or a liquid that contains hydrogen only in strongly bound form, e.g. an organic liquid.In the coating process, the reducing effect of the plasma jet can, in particular, result in a reduction of metal ions to elemental metal in order to coat the workpiece with metal. The reduction of the metal ion SE / fu 220174WO September 25, 2023 can, in particular, be achieved by reactive species, such as OH-, which are generated by exposing the liquid to the plasma jet. In a further embodiment of the treatment process, in particular reduction treatment and / or coating and / or cleaning, a hydrogen-containing liquid, preferably a water-containing liquid, in particular water, is used as the liquid. In this way, the liquid can provide hydrogen, which, in combination with the atmospheric plasma jet, brings about a strongly reducing effect.In this case, it is conceivable, for example, that a non-reducing, for example inert, working gas is used to generate the plasma jet, since the reducing effect is brought about by the hydrogen from the liquid. For example, air can be used to generate the atmospheric plasma jet, whereby the operating costs of the method and the device can be kept low. In particular, by exposing the liquid to the plasma jet, reactive species, such as OH-, with a reducing effect can be generated. In the coating process, for example, metal ions can be reduced to elemental metal by the reactive species. In one embodiment of the treatment process, in particular reduction treatment and / or coating and / or cleaning, an organic liquid is used as the liquid.This is particularly advantageous when treating workpieces made of water-sensitive materials, for example materials susceptible to corrosion, or when liquid water present on the workpiece is detrimental to subsequent process steps. In particular, the use of an organic liquid can achieve rapid or simple drying of the material surface, especially when using a highly volatile organic liquid. SE / fu 220174WO September 25, 2023 The organic liquid can, for example, be a bromine-containing solution, whereby a disinfecting effect on the surface of the workpiece can be achieved, in particular in addition to a reduction treatment and / or coating and / or cleaning. This embodiment is therefore particularly relevant, for example, for production processes for workpieces intended for use in medicine or for contact with food.In one embodiment of the method for treatment, in particular reduction treatment and / or coating and / or cleaning, the atmospheric plasma jet is generated with a plasma nozzle, wherein the plasma nozzle has a nozzle opening from which the plasma jet emerges during operation. In this way, the plasma jet can be directed in a targeted manner, in particular onto the workpiece surface to be treated. In particular, the use of such a plasma nozzle allows for targeted treatment, in particular reduction treatment and / or coating and / or cleaning, of specific sections of a workpiece surface.Furthermore, it is possible in this way to adjust the distance between the nozzle opening of the plasma nozzle and the surface of the workpiece, whereby the treatment effect, in particular reduction effect, coating and / or cleaning, or the displacement of liquid between the surface of the workpiece and the atmospheric plasma jet can be adjusted. In one embodiment, the plasma nozzle and the workpiece are moved relative to one another during exposure to the plasma jet. In this way, larger surface areas of a workpiece can be treated, in particular reduction treatment and / or coating and / or cleaning. Furthermore, targeted treatments, in particular reduction treatments and / or coatings and / or cleaning, can be carried out in specific sections of a surface of the workpiece.In one embodiment, the atmospheric plasma jet is generated by means of electrical discharges in a working gas. A plasma jet generated in this way can be easily aligned and has proven to be very efficient in reducing oxides on workpiece surfaces, particularly on metal surfaces, and / or in generating reactive species with a reducing effect. Furthermore, it has been shown that good coating and / or cleaning results can be achieved with such a plasma jet in the described coating or cleaning process. Furthermore, a working gas supply with different gases is possible. Furthermore, the working gas flow can be adjusted to provide sufficient reducing gas for the reduction or redox reaction and / or to effect the desired liquid displacement between the surface of the workpiece and the atmospheric plasma jet.In one embodiment of the method for treatment, in particular reduction treatment and / or coating and / or cleaning, the atmospheric plasma jet is generated by means of an arc-like discharge in a working gas, wherein the arc-like discharge is generated by applying a high-frequency high voltage between electrodes. In this way, a reactive plasma jet with a comparatively low ion temperature is generated, whereby the heating of the workpiece or the liquid upon exposure to the plasma jet and the tendency of the workpiece surface to reoxidize or the tendency of metal ions reduced to elemental metal to oxidize can be reduced. To generate the arc-like electrical discharge, in particular at least two electrodes can be provided, as well as a voltage source for applying a high-frequency high voltage to the electrodes.The high-frequency high voltage for generating a high-frequency arc-like discharge has, in particular, a voltage in the range of 1-100 kV, preferably 1-50 kV, more preferably 10-50 kV, and a frequency of 1-300 kHz, in particular 1-100 kHz, preferably 10-100 kHz, more preferably 10-50 kHz. SE / fu 220174WO September 25, 2023 In one embodiment, a precursor, in particular a metal-containing precursor, is or is added to the liquid. The precursor is preferably a salt. The salt is or is preferably dissolved in the liquid. A mixture of different precursors, in particular different salts, can also be added to the liquid. The salt can, in particular, be a metal salt. In this way, the surface of the workpiece can be coated with a metal layer.The metal-containing salt can in particular comprise one or more of the following metals: Ag, Cu, Zn, Ni, Sn, Au. For example, an Ag-containing precursor can be added to the liquid or can contain an Ag-containing precursor, wherein the Ag-containing precursor is preferably selected from the following list: silver acetate (CH3CO2Ag), silver carbonate (Ag2CO3), silver chloride (AgCl), silver iodide (AgI), silver nitrate (AgNO3), silver perchlorate monohydrate (AgClO4.H2O), silver sulfate (Ag2SO4), silver bromide (AgBr), silver trifluoroacetate (CF3COOAg), silver chromate (Ag2CrO4), silver sulfide (Ag2S), silver citrate (C6H5Ag3O7), mixtures of two or more of the aforementioned compounds, mixtures containing at least one of the aforementioned compounds.For example, a Cu-containing precursor can be added to the liquid or can contain a Cu-containing precursor, wherein the Cu-containing precursor is preferably selected from the following list: bis(2,4-pentanedionato)copper(II) (C10H14CuO4), copper(II) 2-ethylhexanoate (C16H30CuO2), copper glycinate, tetraamine copper sulfate 1-hydrate, copper(II) acetate hydrate, copper(II) acetate anhydrate, copper(II) bromide, copper(II) carbonate, copper(II) chloride, copper(II) chloride dihydrate, copper(II) chloride anhydrate, copper(II) chloride solution, copper(II) citrate hemihydrate, copper(II) formate 4-hydrate, copper(II) gluconate, copper(II) nitrate 3-hydrate, copper(II) nitrate solution, Copper(II) oxalate 1 / 2 hydrate, copper(II) phosphate, copper(II) sulfate 1-hydrate, copper(II) sulfate 5-hydrate, copper(II) sulfate anhydrate, SE / fu 220174WO 25.September 2023 Copper(I) bromide, copper(I) chloride, copper(I) iodide, copper(I) oxide, mixtures of two or more of the aforementioned compounds, mixtures containing at least one of the aforementioned compounds. For example, a Zn-containing precursor can be added to the liquid or can contain a Zn-containing precursor, wherein the Zn-containing precursor is preferably selected from the following list: zinc acetate 2-hydrate, zinc acetate anhydrate, zinc ascorbate, zinc asparate, zinc bromide anhydrate, zinc bromide solution, zinc carbonate, zinc chloride anhydrate, zinc citrate 2-hydrate, zinc citrate 3-hydrate, zinc formate anhydrate, zinc gluconate, zinc glycinate, zinc lactate 2-hydrate, zinc nitrate 6-hydrate, zinc picolinate, zinc sulfate 1-hydrate, zinc sulfate 7-hydrate, mixtures of two or more of the aforementioned compounds, mixtures containing at least one of the aforementioned compounds.For example, a Ni-containing precursor can be added to the liquid or contain a Ni-containing precursor, wherein the Ni-containing precursor is preferably selected from the following list: ammonium nickel(II) sulphate 6-hydrate, nickel(II) acetate 4-hydrate, nickel(II) bromide anhydrate, nickel(II) bromide hydrate, nickel(II) bromide solution, nickel(II) carbonate, nickel(II) chloride 6-hydrate, nickel(II) chloride anhydrate, nickel(II) chloride solution, nickel(II) citrate hydrate, nickel(II) formate 2-hydrate, nickel(II) gluconate, nickel(II) glycinate, nickel(II) lactate 4-hydrate, nickel(II) nitrate 6-hydrate, nickel(II) nitrate solution, nickel sulphamate solution, nickel sulphate 6-hydrate, nickel sulphate solution, mixtures of two or more of the aforementioned compounds, mixtures containing at least one of the aforementioned compounds.For example, a Sn-containing precursor can be added to the liquid or can contain a Sn-containing precursor, wherein the Sn-containing precursor is preferably selected from the following list: tin(IV) chloride, tin(II) bromide, tin(II) chloride, tin(II) fluoride, tin(II) iodide, tin(II) oxalate, tin(II) pyrophosphate, tin(II) selenide, tin(II) sulfate, tin(II) sulfide, tin(II) telluride, tin(IV) bromide, SE / fu 220174WO September 25, 2023 tin(IV) fluoride, tin(IV) iodide, tin(IV) sulfate, tin(IV) sulfate dihydrate, tin(IV) sulfide, mixtures of two or more of the aforementioned compounds, mixtures containing at least one of the aforementioned compounds.For example, an Au-containing precursor can be added to the liquid or can contain an Au-containing precursor, wherein the Au-containing precursor is preferably selected from the following list: gold(III) chloride, gold(I) chloride, gold(III) chloride trihydrate, gold(V) fluoride, gold(I) acetylide, gold(I) azide, gold(I) bromide, gold(I) cyanide, gold(I) iodide, gold(I) oxide, gold(I) sulfide, gold(I) thiocyanate, gold(III) bromide, gold(III) chloride, gold(III) fluoride, gold(III) iodide, gold(III) selenate, gold(III) sulfide, mixtures of two or more of the aforementioned compounds, mixtures containing at least one of the aforementioned compounds. The liquid represents, in particular, a solvent for the salt.The liquid can be selected, in particular, from the following list of liquids: water, alcohols such as ethanol, methanol, or isopropanol, ketones such as acetone, acids such as organic acids or inorganic acids, dimethyl sulfoxide, amino-based solvents such as pyridine, propionate, or ammonia, mixtures of two or more of the aforementioned solvents, mixtures containing at least one of the aforementioned solvents. Preferably, a liquid in which the selected precursor has good solubility can be selected as the solvent. The liquid can be heated, for example, to a temperature above 30°C, preferably above 50°C, to increase the solubility of the previously described precursors in the liquid. Further additives can be added to the liquid, for example, to create a buffer solution to stabilize the pH.When using a salt as a precursor, for example, a weak acid corresponding to the salt can be added to the liquid to create a buffer solution, such as carbonic acid when using a metal carbonate such as tin carbonate as a precursor or citric acid when using a metal citrate such as copper(II) citrate as a precursor. Further features and advantages of the method and the device will become apparent from the following description of exemplary embodiments, with reference to the accompanying drawings. In the drawings, Fig. 1 shows a plasma nozzle for generating an atmospheric plasma jet, Fig. 2 shows a first exemplary embodiment of the method for the reduction treatment of a workpiece, Fig. 3 shows a second exemplary embodiment of the method for the reduction treatment of a workpiece, Fig. 4 shows a third exemplary embodiment of the method for the reduction treatment of a workpiece, Fig.5 shows a fourth exemplary embodiment of the method for the reduction treatment of a workpiece, Fig. 6 shows an exemplary embodiment of the device for the reduction treatment and / or coating and / or cleaning of a strip-shaped workpiece and a further exemplary embodiment of the method for the reduction treatment and / or coating and / or cleaning using this device, SE / fu 220174WO September 25, 2023 Fig. 7 shows an exemplary embodiment of the method for coating and, if appropriate, cleaning a workpiece, Fig. 8 shows a photograph of a workpiece coated by means of the method according to Fig. 7 and Fig. 9 shows a photograph of a further workpiece coated by means of the method according to Fig. 7. Before the exemplary embodiments of the methods and devices are discussed, the structure and functional principle of a suitable plasma source shown in Figure 1 will first be explained.Figure 1 shows a plasma source in the form of a plasma nozzle 2 for generating an atmospheric plasma jet 26. The plasma nozzle 2 has a metal nozzle tube 4 that tapers conically to a nozzle opening 6. At the end opposite the nozzle opening 6, the nozzle tube 4 has a swirl device 8 with an inlet 10 for a gas stream, in particular a working gas, for example nitrogen, air, or forming gas. An intermediate wall 12 of the swirl device 8 has a ring of bores 14 arranged obliquely in the circumferential direction, through which the gas stream is swirled. The downstream, conically tapered part of the nozzle tube is therefore flowed through by the gas stream in the form of a vortex 16, the core of which runs along the longitudinal axis of the nozzle tube. An electrode 18 is arranged centrally on the underside of the intermediate wall 12 and projects coaxially into the nozzle tube in the direction of the tapered section.The electrode 18 is electrically connected to the intermediate wall 12 and the remaining parts of the swirl device 8. The swirl device 8 is electrically insulated from the nozzle tube 4 by a ceramic tube 20. A high-frequency high voltage, generated by a transformer 22, is applied to the electrode 18 via the swirl device 8. The inlet 10 is supplied with a working gas stream 23 via a line (not shown). The nozzle tube 4 is grounded. The applied voltage generates a high-frequency discharge in the form of an arc 24 between the electrode 18 and the nozzle tube 4. The electrode 18 connected to the transformer and the grounded nozzle tube 4 thus represent discharge means 25 designed to generate a high-frequency, high-voltage discharge in the form of the arc 24, i.e., an arc-like discharge, in a gas stream 23. The terms "arc," "arc discharge," and "arc discharge" are used interchangeably."Arc-like discharge" is used here as a phenomenological description of the discharge, since the discharge occurs in the form of an electric arc. The term "arc" is also used elsewhere as a discharge form for DC discharges with essentially constant voltage values. In this case, however, it is a high-frequency discharge in the form of an arc, i.e., a high-frequency, arc-like discharge. Due to the swirling flow of the working gas, this arc is channeled in the vortex core on the axis of the nozzle tube 4, so that it only branches out to the wall of the nozzle tube 4 in the area of ​​the nozzle opening 6.The working gas, which rotates at a high flow velocity in the region of the vortex core and thus in the immediate vicinity of the arc 24, comes into intimate contact with the arc and is thereby partially converted into the plasma state, so that an atmospheric plasma jet 26 exits the plasma nozzle 2 through the nozzle opening 6. Figure 2 shows a first embodiment of the method for the reduction treatment of a workpiece 202 in a schematic representation. SE / fu 220174WO September 25, 2023 In the method 200, a liquid volume 212 of a liquid 210 is provided in a container 218 provided for this purpose and the workpiece 202 to be treated is arranged in the liquid 210 and in particular submerged, so that the surface 204 of the workpiece 202 to be reduced is exposed to the liquid 210, in particular is covered by the liquid 210, for example with a coverage height of 5 mm.Preferably, the surface 204 of the workpiece 202 to be treated is oriented toward the liquid surface 213 of the liquid volume 212. The liquid 210 can be, for example, a hydrogen-containing liquid, preferably a water-containing liquid, in particular water, or an organic liquid. By means of a provided plasma nozzle 228, which can be designed, for example, like the plasma nozzle 2 shown in Figure 1, an atmospheric plasma jet 230 is generated by a high-frequency, high-voltage discharge in a working gas, which exits from a nozzle opening 232 of the plasma nozzle 228. The working gas can be a reducing working gas, in particular forming gas, or a non-reducing working gas, for example air. The plasma jet 230 is directed onto the surface 204 of the workpiece 202 to be reduced, which in this exemplary embodiment is submerged.In this exemplary embodiment, the working gas flow of the plasma nozzle 228 is adjusted such that the atmospheric plasma jet 230 locally almost completely displaces the liquid 210 between the plasma nozzle 228 and the surface 204, so that in a treatment region 214 on the surface 204 of the workpiece 202, no liquid or only a thin liquid film remains, so that the surface 204 in the treatment region 214 is practically directly exposed to the plasma jet 230. By exposing the surface 204 of the workpiece 202 to the atmospheric plasma jet 230, the surface is subjected to a reduction treatment SE / fu 220174WO September 25, 2023, in which oxides present there, if any.even a continuous oxide layer (schematically represented in the figures by a thick black line on the workpiece surface) can be effectively reduced, so that the surface 204, after exposure to the atmospheric plasma jet 230, in the treatment region 214 has a reduced surface area with a significantly lower oxide content or completely without oxides (schematically represented in the figures by a hatched area on the workpiece surface). The plasma nozzle 228 and the workpiece 202 are moved relative to one another, so that the surface 204 of the workpiece can be reduced in predetermined sections or even completely, leaving a reduced workpiece surface. In Fig. 2, for example, the plasma nozzle 228 is moved relative to the workpiece 202 using a moving device 229.By applying the atmospheric plasma jet 230, heat energy is locally introduced into the workpiece 202, in particular at the surface 204 of the workpiece 202 in the treatment area 214. This heat can be effectively dissipated through contact with the liquid 210, particularly when the liquid 210 flowing back into the previously applied area when the plasma nozzle is switched off or moved covers the previous treatment area again. In this way, the treatment area 214 is exposed to the liquid 210 immediately after the reduction treatment and is thus efficiently cooled. Furthermore, the returning liquid reduces, in particular prevents, contact with a possibly oxygen-containing atmosphere, thereby directly inhibiting reoxidation, in particular until the workpiece has cooled sufficiently.In order to displace sufficient liquid 210 and to effect direct impingement of the workpiece surface 204 with the plasma jet 230, in particular the distance between the plasma nozzle 228 and the surface 204 of the workpiece 202 can be adjusted. Additionally or alternatively, the working gas flow or the pressure of the working gas introduced into the plasma nozzle 228 can be adjusted. Furthermore, the liquid volume 212 present between the surface 204 of the workpiece 202 and the plasma nozzle 228 can be adjusted via the fill quantity of the container 218 with the liquid 210 and / or via the arrangement of the workpiece 202. Figure 3 shows a schematic representation of another embodiment of the method for the reduction treatment of a workpiece 302. The method 300 shown in Fig. 3 is similar to the method 200 shown in Fig. 2.Corresponding components are provided with the same reference numerals, and reference is made to the explanations for Fig. 2 in this regard. The method 300 differs from the method 200 in that a plurality of plasma nozzles 328 are provided for generating a respective atmospheric plasma jet 330, so that a larger area of ​​the workpiece surface 304 of the workpiece 302 can be subjected to a reduction treatment simultaneously in respective treatment regions 314. The plasma nozzles 328 can each have a structure and function like the plasma nozzle 2 from Fig. 1. The plasma nozzles 328 and the workpiece 302 are moved relative to one another, so that the surface 304 of the workpiece 302 can be reduced in predetermined sections or completely, so that a reduced workpiece surface remains. In Fig. 3, for example, the container 318 with the workpiece is moved relative to the plasma nozzles 328 using a moving device 329.Figure 4 shows a schematic representation of another embodiment of the method for the reduction treatment of a workpiece 202. The method 400 shown in Fig. 4 is similar to the method 200 shown in Fig. 2. SE / fu 220174WO September 25, 2023 Corresponding components are provided with the same reference numerals, and reference is made to the explanations for Fig. 2 in this respect. The method 400 differs from the method 200 in that the distance of the plasma nozzle 228 from the workpiece 202 and / or the working gas flow or pressure for supplying the plasma nozzle 228 are adjusted such that the liquid 210 between the plasma nozzle 228 and the surface 204 of the workpiece 202 in the treatment region 214 is only displaced to such an extent that a macroscopic liquid film 416 still remains on the workpiece surface 204 in the treatment region 214.The plasma jet 230 therefore acts in particular on the liquid 210 of the liquid film 416. In this way, the liquid 210 of the liquid film 416 is excited or activated by the atmospheric plasma jet 230. A reducing effect of this activated liquid 210 has been observed, so that oxides on the surface 204 of the workpiece 202 in the treatment area 214 are effectively reduced. By such indirect exposure to the surface 204 of the workpiece 202 due to the liquid film 416 remaining between the surface 204 of the workpiece 202 and the atmospheric plasma jet 230, a reduction treatment of a workpiece can thus also be carried out.Because the surface 204 of the workpiece 202 is covered by the liquid film 416 during the reduction treatment, the thermal energy introduced by the plasma jet 230 can be absorbed and dissipated by the liquid 210, so that no significant heating of the workpiece 202 occurs. Furthermore, contact with the oxygen-containing atmosphere is prevented, and reoxidation is inhibited particularly effectively overall. Furthermore, tests have shown that the reducing effect upon exposure of the liquid 210 to the plasma jet 230 is not locally limited to an immediate SE / fu 220174WO September 25, 2023 treatment area 214 in which the plasma jet 230 acts on the liquid 210.Rather, a reducing effect of the liquid 210 impinged on by the plasma jet 230 was also observed at a distance from the plasma jet 230, presumably because reducing species generated in the liquid 210 by the plasma jet 230 are distributed in the liquid 210. Therefore, the liquid 210 can also be impinged on by the plasma jet 230 at a distance from the surface 204 of the workpiece 202 - as an alternative to being impinged directly in the area of ​​the surface 204 of the workpiece 202 - as shown schematically in Fig. 4 by the position of the plasma nozzle 228' shown in dashed lines. In this embodiment, the liquid 210 is impinged on by the plasma jet 230' emerging from the plasma nozzle 228' at a distance from the workpiece surface 204. Tests have shown that such impingement on the liquid 210 imparts a reducing effect to it, so that the workpiece surface 204 was reduced.With this configuration, it is also possible, for example, to simultaneously subject several workpieces 202 arranged in the liquid volume 212 to a reduction treatment in order to remove oxides from their respective workpiece surfaces 204. Figure 5 shows a schematic representation of another embodiment of the method for the reduction treatment of a workpiece 502. In the method 500, a workpiece 502 with a surface 504 to be reduced is arranged such that the surface 504 of the workpiece 502 is accessible. By means of a plasma nozzle 528, which can be configured, for example, like the plasma nozzle 2 shown in Fig. 1, an atmospheric plasma jet 530 is generated and directed onto the workpiece surface 504, so that it is exposed to the plasma jet 530 in a treatment region 514. For generation SE / fu 220174WO 25.September 2023 of the plasma jet 530, the plasma nozzle 528 is supplied with a hydrogen-containing working gas, for example, forming gas. The plasma jet 530 thus has a reducing effect, so that oxides present on the workpiece surface 504 are reduced. During and / or after exposure to the atmospheric plasma jet 530, the workpiece surface 504 is subjected to, in particular sprayed, a liquid 510 by means of a spray device 516. In this way, the thermal energy introduced by the atmospheric plasma jet 530 can be effectively dissipated from the workpiece surface 504, so that the workpiece surface 504 heats up less, thereby reducing its susceptibility to reoxidation. In addition, the reduced workpiece surface 504 is covered by the liquid 510, thereby reducing contact with the oxygen-containing atmosphere and thus further inhibiting reoxidation.The flow rate of the liquid 510 is preferably adjusted at the spray device 516 so that the treatment area 514 is completely exposed to the liquid 510, thus ensuring sufficient cooling of the workpiece 502 at the workpiece surface 504. The liquid 510 can be water, for example. It has been determined that with this embodiment, the use of a hydrogen-containing working gas for the plasma nozzle 528 can even be dispensed with and an inert gas or air can be used instead, since the hydrogen contained in the water, in combination with the plasma jet 530, already leads to a reducing effect. Alternatively, the liquid 510 can also be an organic liquid, for example, if the workpiece surface 504 is sensitive to water or needs to dry quickly after the reduction treatment. SE / fu 220174WO 25.September 2023 The plasma nozzle 528 and the workpiece 502 can be moved relative to one another in order to subject the workpiece surface 504 to a reduction treatment in predetermined sections or completely. If the plasma nozzle 528 is moved, the spray device 516 is preferably moved along with it and / or the orientation of the spray device 516 is adjusted such that the treatment area 514 continues to be exposed to the liquid 510. In a further embodiment not shown, the method 500, similar to the method 300 shown in Figure 3, can also be carried out using multiple plasma sources 528 and / or multiple spray devices 516. Figure 6 shows an embodiment of the device for the reduction treatment and / or coating and / or cleaning of a strip-shaped workpiece.The device 601 comprises an immersion bath device 617 with an immersion tank 618 for receiving a liquid volume 612 of a liquid 610, which thus forms an immersion bath 620. The immersion tank 618 is open at the top so that a strip-shaped workpiece 602 can be introduced into the immersion bath 620 and removed again, for example, enabling inline integration into a continuous production process. The immersion bath device 617 further comprises guide means 622 arranged and configured to guide a strip-shaped workpiece 602 through the immersion bath 620.Preferably, the guide means 622 are arranged and configured such that the strip-shaped workpiece 602 can be guided during operation, at least in sections, in particular at least in a treatment area 614, completely below the surface 613 of the liquid volume 612, so that a workpiece surface 604 of the strip-shaped workpiece 602 to be reduced and / or coated and / or cleaned is covered by the liquid 610 in the treatment area 614. In the present example, the guide means 622 are designed as guide rollers. Furthermore, the device 601 comprises a plasma source 628 in the form of a plasma nozzle for generating an atmospheric plasma jet 630, which can be designed, for example, like the plasma nozzle 2 from Figure 1.The plasma nozzle 628 is arranged and configured such that the atmospheric plasma jet emerging from the plasma nozzle 628 during operation is directed in the treatment area 614 onto the workpiece surface 604 of the strip-shaped workpiece 602, which is guided through the immersion bath 620 by the guide means 622. The distance between the plasma nozzle 628 and the workpiece surface 604 of the strip-shaped workpiece 602 (moving device 629) and / or the working gas flow or pressure of the plasma nozzle 628 can be adjusted such that the liquid 610 in the treatment area is displaced almost completely (as shown in Fig. 6) or partially (analogous to Fig. 4 or 7), so that the workpiece surface 604 can be subjected to a reduction treatment and / or coating and / or cleaning by direct exposure to the plasma jet 630 and / or by exposure to the liquid 610 in the area of ​​the workpiece surface 604.In an alternative embodiment, the plasma nozzle 628 can be arranged such that the plasma jet 630 is directed away from the strip-shaped workpiece 602 onto the liquid 610 (analogous to the plasma nozzle 228' shown in dashed lines in Fig. 4). Furthermore, the device 601 can have delivery means 624 for delivery of the strip-shaped workpiece 602 with the workpiece surface 604 to be reduced and / or coated and / or cleaned and / or received, and / or receiving means 626 for receiving the strip-shaped workpiece 602 after the reduction treatment. In the present example, the delivery and receiving means 624, 626 are designed as, preferably driven, rollers, so that the strip-shaped workpiece 602 is unrolled from the delivery means 624 for delivery and rolled up onto the receiving means 626 for reception.In the case of driven discharge and receiving means 624, 626, these simultaneously represent transport means for transporting the strip-shaped workpiece 602 through the immersion bath 620. The transport means can also be formed by the guide means 622 if these are driven. With the device 601, a method 600 for reducing the strip-shaped workpiece 602 can be carried out by guiding the workpiece 602 through the immersion bath 620 by means of the transport means and exposing the surface 604 to be reduced and / or the liquid 610 to the plasma jet 630. In this way, an oxide layer can be reduced from the surface of the strip-shaped workpiece 602. In Fig. 6, the workpiece with the oxide layer is schematically shown as a black band and the reduced workpiece as a hatched band.Additionally or alternatively, a method 600' for coating the strip-shaped workpiece 602 can be carried out with the device 601. The method involves guiding the workpiece 602 through the immersion bath 620 by means of the transport means and exposing the surface 604 to be coated and / or the liquid 610 to the plasma jet 630. A metal salt is dissolved in the liquid 610 for the coating. Due to the reactive species generated in the liquid 610 by the plasma jet 630, the metal ion of the metal salt dissociated in the liquid is reduced to elemental metal and deposited on the surface of the strip-shaped workpiece 602 as a metal layer. In this way, the surface of the strip-shaped workpiece 602 can be coated with a metal layer.With the device 601, a method 600'' for cleaning the strip-shaped workpiece 602 can be carried out additionally or alternatively by guiding the workpiece 602 through the immersion bath 620 by means of the transport means and exposing the surface 604 to be cleaned and / or the liquid 610 to the plasma jet 630. The reactive species generated by the plasma jet 630 in the liquid 610 can interact with contaminants on the surface of the strip-shaped workpiece 602 to be cleaned and chemically decompose them and / or detach them from the surface. In this way, the surface of the strip-shaped workpiece 602 can be cleaned. Figure 7 shows a first exemplary embodiment of the method for coating and, if appropriate, cleaning a workpiece 702 in a schematic representation.In the method 700, a liquid volume 712 of a liquid 710 is provided in a container 718 provided for this purpose, and the workpiece 702 to be treated is arranged in the liquid 710 and in particular submerged, such that the surface 704 of the workpiece 702 to be coated is exposed to the liquid 710, in particular is covered by the liquid 710, for example with a coverage height of 5 mm. Preferably, the surface 704 of the workpiece 702 to be coated is aligned towards the liquid surface 713 of the liquid volume 712. A metal salt is dissolved in the liquid 710 as a precursor, for example an Ag, Cu, Zn, Ni, Sn, or Au salt. The liquid is a solvent for the metal salt.Depending on the metal salt used, the liquid 710 can contain, for example, water, an alcohol such as ethanol, methanol, or isopropanol, a ketone such as acetone, an acid such as organic acids or inorganic acids, dimethyl sulfoxide, an amino-based solvent such as pyridine, propionitrile, or ammonia, or a mixture of two or more of the aforementioned solvents. To increase the solubility of the metal salt in the liquid 710, the liquid 710 can also be heated, for example, to a temperature above 30°C, preferably above 50°C. Furthermore, other substances can be added to the liquid 710, for example, a weak acid corresponding to the metal salt, to create a buffer solution for stabilizing the pH value.By means of a provided plasma nozzle 728, which can be configured, for example, like the plasma nozzle 2 shown in Figure 1, an atmospheric plasma jet 730 is generated by a high-frequency, high-voltage discharge in a working gas, which exits from a nozzle opening 732 of the plasma nozzle 728. The working gas can be a reducing working gas, in particular forming gas, or a non-reducing working gas, for example, air. The plasma jet 730 is directed onto the surface 704 of the workpiece 702 to be coated, which in this embodiment is submerged.In this exemplary embodiment, the working gas flow or pressure for supplying the plasma nozzle 728 is set such that the liquid 710 between the plasma nozzle 728 and the surface 704 of the workpiece 702 in the treatment area 714 is only displaced to such an extent that a macroscopic liquid film 716 still remains on the workpiece surface 704 in the treatment area 714. The plasma jet 730 therefore acts in particular on the liquid 710 of the liquid film 716. Alternatively, the working gas flow or pressure for supplying the plasma nozzle 728 can also be set such that only a microscopic liquid film remains on the workpiece surface 704 in the treatment area 714. By exposing the liquid 710 or the liquid film 716 to the plasma jet, a redox reaction occurs at the metal cation of the salt dissociated in the liquid. The metal cation (e.g. Cu. 2+) is thus reduced to elemental metal (e.g. Cu) in the area of ​​the workpiece surface 704 and thus forms a metal layer 740 on the workpiece surface 704. For example, the redox reaction can proceed as follows: SE / fu 220174WO 25 September 2023 where Me x+ (aq) a metal ion dissolved in water, x-fold ionized, xe- x electrons and Me 0 (s) the reduced metal is referred to as a solid. The electrons can be provided in particular by OH-, which are generated by exposing the liquid 710 to the plasma jet 730, for example, according to the reaction equation O2 + 2 H2O + 4e-^4 OH-. Thus, the redox reaction can proceed, for example, as follows: The plasma nozzle 728 and the workpiece 702 are moved relative to one another so that the surface 704 of the workpiece can be coated in predetermined sections or completely, so that a reduced workpiece surface remains. In Fig. 7, for example, the plasma nozzle 728 is moved relative to the workpiece 702 using a moving device 729. Because the surface 704 of the workpiece 702 is covered by the liquid film 716 during coating, the heat energy introduced by the plasma jet 730 can be absorbed and dissipated by the liquid 710, so that no significant heating of the workpiece 702 occurs. In addition, the liquid film 716 prevents contact with the oxygen-containing atmosphere. In this way, oxidation of the elemental metal or oxide produced during the redox reaction can be prevented.the formation of oxides on the coated surface can be inhibited, in particular until the workpiece has cooled sufficiently. Furthermore, tests have shown that the coating is not locally limited to an immediate treatment area 714 in which the plasma jet 730 acts on the liquid 710 due to the redox reaction at the precursor SE / fu 220174WO September 25, 2023 caused by the liquid 710 being exposed to the plasma jet 730. Rather, a redox reaction at the precursor can also be achieved remotely from the plasma jet 730, and thus a coating of the workpiece surface 704 can be detected, presumably because reducing species generated in the liquid 710 by the plasma jet 730, such as OH-, are distributed in the liquid 710 and can thus reduce metal ions to elemental metal even remotely from the plasma jet 730.Therefore, the liquid 710 can also be subjected to the plasma jet 730 at a distance from the surface 704 of the workpiece 702 – as an alternative to being subjected to it directly in the area of ​​the surface 704 of the workpiece 702 – as shown schematically in Fig. 7 by the position of the plasma nozzle 728' shown in dashed lines. In this embodiment, the liquid 710 is subjected to the plasma jet 730' emerging from the plasma nozzle 728' at a distance from the workpiece surface 704. Tests have shown that such exposure of the liquid 710 imparts a reducing effect to it, so that in the area of ​​the workpiece surface 704, metal ions are reduced to elemental metal, which is then deposited on the workpiece surface 704. With this embodiment, it is also possible, for example, to simultaneously coat several workpieces 702 arranged in the liquid volume 712.The species generated by the plasma jet 730 in the liquid 710, such as OH-, can also interact with any contaminants, for example organic contaminants, on the workpiece surface 704, in particular chemically converting them and / or detaching them from the workpiece surface 704. In this way, cleaning of the workpiece surface 704, in particular prior to its coating, can also be achieved. Coating of a workpiece can in principle also be achieved using one of the exemplary embodiments of the method described with reference to Figs. 2-5, for example by adding a precursor, in particular a salt, for example a metal salt, SE / fu 220174WO September 25, 2023, in particular by introducing it into the liquid or dissolving it therein. Furthermore, cleaning of the workpiece surface of the workpiece can also be achieved using the exemplary embodiments of the method from Figs. 2-5.Experiments were conducted to test the coating process shown in Fig. 7. Experiment 1: A card made of the plastic acrylonitrile butadiene styrene (ABS) was coated with silver. For this purpose, the uncoated card was placed in the liquid volume 712 (see Fig. 7) so that the top side of the card to be coated was covered with a macroscopic liquid film several millimeters thick. In Experiment 1, the liquid 710 was water (H2O) in which the metal salt silver nitrate (AgNO3) was dissolved as a precursor at a concentration of 5 g AgNO3 per 100 mL H2O. The plasma nozzle 728 was operated with nitrogen (N2) as the working gas, and the plasma jet was directed onto the liquid film 716 above the surface of the card to be coated and moved at a relative speed of 0.5 m / min relative to the surface of the card.To achieve a greater layer thickness, the surface of the card was passed over three times with the plasma jet. After the process, the surface of the card had a silver-colored coating. This coating was examined by LIBS (Laser Induced Breakdown Spectroscopy) using a Microscope EA300 LIBS device, distributed by Keyence Deutschland GmbH. The LIBS device was used to examine the element-specific composition of the coating at several points (9 points in a 3x3 grid). It was determined that the coating was a layer of silver SE / fu 220174WO September 25, 2023. Furthermore, the ohmic resistance of the coating was measured using a multimeter, and it was determined that the coating was electrically conductive, i.e., it was an electrically conductive silver layer. A photograph of the silver-coated card is shown in Fig.8. The coating is visible in the form of lettering (arrow 802) and a surrounding frame (arrow 804). The uncoated area (arrow 806) between the lettering and the frame was created by a mask that was glued to the card before the coating process and removed again after the coating process. Experiment 2: Another card made of the plastic acrylonitrile butadiene styrene (ABS) was coated with copper. For this purpose, the uncoated card was placed in the liquid volume 712 (see Fig. 7) so that the top side of the card to be coated was covered with a macroscopic liquid film several millimeters thick. In Experiment 2, the liquid 710 was ethanol in which a silver salt was dissolved as a precursor at a concentration of 5 g AgNO3 per 100 mL of solution.The plasma nozzle 728 was operated with nitrogen (N2) as the working gas, and the plasma jet was directed onto the liquid film 716 above the card surface to be coated, traveling at a relative speed of 0.5 m / min relative to the card surface. After completion of the process, the card surface exhibited a thin yellowish-reddish coating. This coating was examined by LIBS (Laser Induced Breakdown Spectroscopy) using a Microscope EA300 LIBS device, distributed by Keyence SE / fu 220174WO September 25, 2023 Deutschland GmbH. The LIBS device was used to examine the elemental composition of the coating at several points (9 points in a 3x3 grid). It was determined that the coating was a layer of copper.Furthermore, the ohmic resistance of the coating was measured using a multimeter, and it was determined that the coating was electrically conductive, i.e., a thin, electrically conductive copper layer. A photograph of the copper-coated card is shown in Fig. 9. The coating (arrow 902) exhibits a slightly visible striped structure corresponding to the path of the plasma jet across the surface of the card. This structure disappears when the layer thickness is increased, for example, by repeatedly passing the plasma jet over the surface. List of reference symbols: 2, 228, 228', 328, 528, 628, 728, 728' Plasma nozzle 4 Nozzle tube 6, 232, 732 Nozzle opening 8 Swirl device 10 Inlet 12 Partition wall 14 Bores 16 Vortex 18 Electrode 20 Ceramic tube 22 Transformer 23 Gas flow 24 Arc 25 Discharge means 26, 230, 230', 330, 530, 630, 730, 730' Plasma jet SE / fu 220174WO 25.September 2023 , 300, 400, 500, 600, 600', 600'', 700 Process 202, 302, 502, 602, 702 Workpiece 204, 304, 504, 604, 704 Workpiece surface 210, 510, 610, 710 Liquid 212, 612, 712 Liquid volume 213, 613, 713 Liquid surface 214, 314, 514, 614, 714 Treatment area 218, 718 Container 229, 329, 629, 729 Moving device 416, 716 Liquid film 516 Spray device 601 Device 617 Immersion bath device 618 Immersion tank 620 Immersion bath 622 Guide means 624 Release means 626 Receptacle means 740 Metal layer 802, 804, 902 Coated area 806 Uncoated area SE / fu 220174WO 25 September 2023.

Claims

September 25, 2023 Patent Claims 1. Method (200, 300, 400, 500, 600, 600', 600'', 700) for treating, in particular for cleaning, reducing treatment and / or coating, a workpiece (202, 302, 502, 602, 702), - in which an atmospheric plasma jet (26, 230, 230', 330, 530, 630, 730, 730') is generated, - in which a workpiece (202, 302, 502, 602, 702) to be treated, in particular a workpiece to be cleaned, reduced and / or coated, is brought into contact with a liquid (210, 510, 610, 710) and - in which a surface (204, 304, 504, 604, 704) of the workpiece (202, 302, 502, 602, 702) to be treated, in particular the workpiece to be cleaned, reduced, and / or coated, and / or the liquid (210, 510, 610, 710) is exposed to the atmospheric plasma jet (26, 230, 230', 330, 530, 630, 730, 730').Method according to claim 1, characterized in that the workpiece (202, 302, 502, 602, 702) is brought into contact with the liquid (210, 510, 610, 710) by arranging the workpiece (202, 302, 502, 602, 702), in particular submerging it, in a liquid volume (212, 612, 712) before the surface (204, 304, 504, 604, 704) or the liquid (210, 510, 610, 710) is exposed to the plasma jet (26, 230, 230', 330, 530, 630, 730, 730').

3. Method according to claim 2, characterized in that. - 2 - that the application of the atmospheric plasma jet (26, 230, 230', 330, 530, 630, 730, 730') is effected in such a way that a portion of the liquid volume (212, 612, 712) located above the workpiece (202, 302, 502, 602, 702) is locally displaced by the atmospheric plasma jet (26, 230, 230', 330, 530, 630, 730, 730').

4. Method according to claim 1, characterized in that the workpiece (202, 302, 502, 602, 702) is brought into contact with the liquid (210, 510, 610, 710) by applying, in particular spraying, the liquid (210, 510, 610, 710) to the workpiece (202, 302, 502, 602, 702) during and / or after the application of the plasma jet (26, 230, 230', 330, 530, 630, 730, 730').

5. Method according to one of claims 1 to 4, characterized in that the atmospheric plasma jet (26, 230, 230', 330, 530, 630, 730, 730') is generated using a reducing working gas, in particular a forming gas.Method according to one of claims 1 to 5, characterized in that a hydrogen-containing liquid, preferably a water-containing liquid, is used as the liquid (210, 510, 610, 710).

7. Method according to one of claims 1 to 5, characterized in that an organic liquid is used as the liquid (210, 510, 610, 710).

8. Method according to one of claims 1 to 7, characterized in that the atmospheric plasma jet (26, 230, 230', 330, 530, 630, 730, 730') is provided with a plasma nozzle (2, 228, 228', 328, 528, 628, 728, SE / fu 220174WO September 25, 2023). - 3 - 728'), wherein the plasma nozzle (2, 228, 228', 328, 528, 628, 728, 728') has a nozzle opening (6, 232, 732) from which the plasma jet (26, 230, 230', 330, 530, 630, 730, 730') emerges during operation.

9. The method according to claim 8, characterized in that the plasma nozzle (2, 228, 228', 328, 528, 628, 728, 728') and the workpiece (202, 302, 502, 602, 702) are moved relative to one another during the application of the plasma jet (26, 230, 230', 330, 530, 630, 730, 730').

10. The method according to one of claims 1 to 9, characterized in that the atmospheric plasma jet (26, 230, 230', 330, 530, 630, 730, 730') is generated by means of electrical discharges in a working gas. 11.Method according to one of claims 1 to 10, characterized in that the atmospheric plasma jet (26, 230, 230', 330, 530, 630, 730, 730') is generated by means of an arc-like discharge in a working gas, wherein the arc-like discharge is generated by applying a high-frequency high voltage between electrodes.

12. Method according to one of claims 1 to 11, characterized in that a precursor, in particular a metal-containing precursor, is or is added to the liquid (210, 510, 610, 710), wherein the precursor is preferably a salt.

13. Method according to one of claims 1 to 12, characterized in that the workpiece is a strip-shaped workpiece (602), in particular a metal strip. SE / fu 220174WO September 25, 2023. - 4 - 14. Device (601) for treating, in particular for cleaning, reducing and / or coating, a strip-shaped workpiece (602), in particular a metal strip, in particular for carrying out a method (600, 600', 600'') according to claim 13, - with an immersion bath device (617) which is designed to guide a strip-shaped workpiece through an immersion bath (620) and - with a plasma source (2, 628) for generating an atmospheric plasma jet (26, 630), - wherein the plasma source (2, 628) is arranged and designed to apply an atmospheric plasma jet (26, 630) to the immersion bath (620) or to a strip-shaped workpiece (602) guided through the immersion bath (620) of the immersion bath device (617) during operation. SE / fu 220174WO September 25, 2023

Images