EP2686460A1

EP2686460A1 - Coating, and method and device for coating

Info

Publication number: EP2686460A1
Application number: EP12714242.0A
Authority: EP
Inventors: Michael Bisges; Christian Wolfrum; Marco Greb; Markus Rupprecht
Original assignee: Eckart GmbH; Reinhausen Plasma GmbH
Current assignee: Eckart GmbH; Maschinenfabrik Reinhausen GmbH
Priority date: 2011-03-16
Filing date: 2012-03-15
Publication date: 2014-01-22
Also published as: KR20140052982A; US20140023856A1; JP2014511941A; WO2012123530A1; CN103415644A; JP5888342B2; CN103415644B

Abstract

The invention relates to a method and a device for applying a coating to a substrate (20), wherein a plasma jet (2) of a low-temperature plasma is produced by conducting a working gas (3) through an excitation zone. The plasma jet is directed at the substrate (20), and plate-shaped particles (10) having an average thickness (H) between 10 and 50,000 nanometers and a shape factor (F) in a value range from 10 to 2000 are fed into the plasma jet (2). The plate-shaped particles are fed into the plasma jet (2) by means of a carrier gas (14). The plasma jet (2) is produced by exciting the working gas (3) by means of an alternating voltage or a pulsed direct voltage.

Description

COATING AND METHOD AND DEVICE FOR

COATING

The present invention relates to a method and a device for applying a coating to a substrate, in which by passing a working gas through an excitation zone a plasma jet of a

Low-temperature plasma is generated.

In addition, the invention relates to a coating on a substrate of at least partially intergrown platelet-shaped particles and the use of platelet-shaped particles.

The generation of layers on substrates has long been known and of high economic interest. It is used a variety of different methods that require partially procedurally reduced pressure, very high gas velocities or high temperatures.

A known method is the plasma spraying, in which a by a

Arc of a plasma burner flowing gas or gas mixture is ionized. During ionization, a highly heated, electrically conductive gas with a temperature of up to 20,000 K is generated. In this plasma jet powder, usually injected in a particle size distribution between 5 to 120 μιη, which is melted by the high plasma temperature. The plasma jet entrains the powder particles and places them on the substrate to be coated. The plasma coating by way of plasma spraying can be under normal

Atmosphere done. The high gas temperatures of over Ι Ο.ΟΟΟΌ are required to melt the powder and thus be able to deposit as a layer. So that's it Plasma spraying energetically very expensive, creating a cost-effective

Coating of substrates is often not possible. In addition, expensive apparatus must be used to produce the high temperatures. Due to the high temperatures, temperature-sensitive and / or very thin substrates, such as polymer films and / or paper, can not be coated. Due to the high thermal energy, such substrates are involved

Damage. In some cases, elaborate pretreatment steps are necessary to ensure adequate adhesion of the deposited layers to the surface. A further disadvantage is that during plasma spraying, a high thermal load of the particles used occurs, as a result of which they can at least partially oxidize, in particular when metallic particles are used. This is particularly disadvantageous when metallic layers are to be deposited, for example, for printed conductors or as

Corrosion protection should be used. For these reasons, methods have been developed which use so-called atmospheric cold plasma, also referred to as low temperature plasma, to create layers on substrates. In the methods, a cold plasma jet is generated at atmospheric conditions by methods known in the art and introduced into the plasma jet, a powder, which is then deposited on the substrate.

From EP 1 230 414 B1 a generic method for applying a coating to a substrate is known, in which by passing the

Working gas through an excitation zone a plasma jet of a

Low-temperature plasma is generated under atmospheric conditions. In the plasma jet, a precursor material consisting of monomeric compounds is fed separately from the working gas. For sensitive precursor materials, the feed can be made into the relatively cool plasma jet downstream of the excitation zone. As a result, it is possible to coat the substrate with precursor materials which are stable only at temperatures of up to 200 degrees Celsius or less. A disadvantage of this method is that monomeric compounds as

Precursor material are fed into a plasma and reacted there, whereby only relatively low deposition rates of 300 - 400 nm / sec can be achieved. These are compared to the deposition rates, which are achieved in corresponding processes with powdery starting materials, even with the use of particles which are in the order of 100 μιη, by a factor of 10-1000 lower. Accordingly, is an economic

Coating on an industrial scale is not possible with this method.

From EP 1 675 971 B1 is another method for coating a substrate surface using a plasma jet of a

Low-temperature plasma known to which a fine-grained, coating-forming powder in a size of 0.001 - 100 μιη is supplied by means of a powder conveyor. In contrast to the thermal plasmas, the temperature of a low-temperature plasma in the core of the plasma jet at ambient pressure reaches less than 900 degrees Celsius. For thermal plasmas, however, EP 1 675 971 B1 specifies temperatures in the core of the occurring plasma jet of up to 20,000 degrees Celsius.

A disadvantage is that powders of materials with higher melting points, e.g. ceramic materials or refractory metals, can not be melted in the process. The speed of the plasma jet is so high that the residence time of the small particles of the powder in the hot zones of the plasma is insufficient to achieve a complete melting of the particles. Therefore, in materials having an elevated melting temperature (for example, Ag, Cu, Ni, Fe, Ti, W), at most, melting of the particle surface occurs, and a porous layer in which the particles are almost in their formation

Adhere to the initial dimension. The method is therefore primarily suitable for coating substrates with low-melting metals such as tin and zinc.

The object of the invention is to provide a generic method for applying a coating to a substrate, wherein the required Reaction energy, in particular for melting, breaking up of atomic or molecular assemblies, deagglomerating and atomizing

Coating materials is reduced, so that a perfect coating especially with coating materials with higher

Melting temperatures is possible. Furthermore, an advantageous device for carrying out the method and a producible by the method

Coating can be specified.

The object is achieved in a method of the type mentioned in that platelet-shaped particles having an average thickness H between 10 and 50,000 nanometers and a form factor F in the value range from 10 to 2000 are fed into the plasma jet directed onto the substrate.

Irrespective of the material, the platelet-shaped particles preferably have an average thickness H of between 50 and 5,000 nm, more preferably between 100 and 2,000 nm. The exact mean thickness H of the 10 platelet-shaped particles is determined by the degree of water coverage (spread to DIN 55923) and / or by scanning electron microscopy (SEM).

Below a mean thickness H of the platelet-shaped particles of 10 nm, proper separation of particles by means of the plasma jet is no longer guaranteed. If opaque coatings are desired, the opacity of the coating decreases due to the increasing transparency of such thin platelet-shaped particles. The shape factor is defined as the ratio of the mean linear expansion D to the mean thickness H of the platelet-shaped particles. In the process according to the invention, platelet-shaped particles having an average thickness H of 10 nm and a

Form factor 10, the particles have a value for the middle

Length expansion D of 0.1 μιη on. If platelet-shaped particles with an average thickness H of 50,000 nm and a form factor 10 are used in the method according to the invention, the particles have a value for the middle one Length expansion D of 500 μιη on. The desired mean length expansion of the particles depends strongly on the respective

Coating purpose. By means of a high form factor and, at the same time, the lowest possible average thickness H, a better orientation of the platelet-shaped particles deposited on the substrate can be ensured. This is of particular interest in color coatings of surfaces.

The feeding of the platelet-shaped particles into the plasma jet, in particular via the feed opening of a jet generator arranged immediately adjacent to the outlet for the plasma jet, does not necessarily have to take place in the gaseous state, but can also be carried out in the liquid or solid state Feed of the platelet-shaped particles, however, by means of a carrier gas for the

platelet-shaped particles. To produce the mixture of the

platelet-shaped particles and the carrier gas, the feed opening of the jet generator is connected via a line with a vortex chamber. The vortex chamber is listed as a closed container and filled at most up to a maximum level with the platelet-shaped particles. The platelet-shaped particles are acted upon by at least one gas inlet with a pressurized carrier gas, in particular in a periodic sequence, whereby the fluidized platelet-shaped particles together with the carrier gas as a mixture via at least one above the maximum level of the vortex chamber arranged outlet from the container

Direction of the feed opening of the jet generator flow. The periodic loading of the platelet-shaped particles in the vortex chamber with the carrier gas takes place at a frequency in the range of 1 Hz to 100 Hz. In particular, the particles are subjected to the carrier gas in succession over several gas inlets. The gas inlet (s) can open directly into the usually existing supply of platelet-shaped particles. In addition to this preferred direct blowing of the carrier gas into the particles, however, it is also possible to arrange the gas inlet or passages above the maximum fill level of the particles in the vortex chamber, so that the carrier gas is applied to the gas Surface of the particle hits.

The plasma jet is generated under a pressure in a pressure range of 0.5-1.5 bar, but preferably under the conditions of ambient pressure. It is also called an atmospheric plasma. Quite surprisingly, it has been found that with the use of platelet-shaped particles, layers with outstanding properties can also be produced with metals of higher melting point and non-metals. The higher specific surface area of platelet-shaped particles compared to spherical particles is probably responsible for the very good properties.

With a specific surface is referred to the mass related to the outer surface, the surface per kilogram of

platelet-shaped particles and is defined as follows:

Surface m ²

M ^~

Mass kg For an ideal sphere with the particle diameter dp results

accordingly for the specific surface m ²

d _p xp kg

It is known in the literature that nanoparticles are characterized by a reduced melting point compared to the macromaterial. Such nanoparticles have a very large surface area in relation to their volume. This means that they have far more atoms on their surface than larger particles. Since atoms on the surface are less binding partners available, as atoms in the core of the particle, such atoms are very reactive. Because of this, they can be much more involved with particles in their immediate environment Interaction occur as is the case with macroparticles. The platelet-shaped particles used in the invention have a significantly increased surface area compared to mass-like spherical particles. The surface of a spherical particle with a radius of 1 μιη is opposite to a

mass same platelet-shaped particles with a thickness of 0.01 μιη by a factor of 30 larger. Since essentially the surface of the particles reacts with the plasma, it is currently assumed that this enlarged surface results in a significantly better melting behavior of the particles.

As a result, higher-melting metals and ceramic particles can also be melted with the method according to the invention in low-temperature atmospheric low-temperature plasmas and deposited on surfaces as a layer.

The increased surface area of the platelet-shaped particles enhances binding between the deposited particles with each other as well as between the particles and the substrate.

A further advantage of the platelet-shaped particles is that their specific larger surface compared with mass-like spherical particles covers the substrate to be coated more efficiently. In particular with opaque coatings, therefore, the coating process can be done with less

Apply coating material.

The use of platelet-shaped particles also increases the

Process reliability, in which the danger of explosion occurring with very fine spherical particles is reduced. In addition, the platelet shape of the particles results in a better ability to convey the particles in the plasma jet. Below a mean thickness H of the platelet-shaped particles of 10 nm, proper separation of particles by means of the plasma jet is no longer guaranteed. If opaque coatings are desired, diminishes due to the increasing transparency of such a thin platelet-shaped Particle the opacity of the coating.

The shape factor is defined as the ratio of the mean linear expansion D to the mean thickness H of the platelet-shaped particles. If platelet-shaped particles having an average thickness H of 10 nm and a shape factor 10 are used in the method according to the invention, the particles have a value for the mean longitudinal extent D of 0.1 μm. Be in the inventive

When the method uses platelet-shaped particles having an average thickness H of 50,000 nm and a shape factor 10, the particles have a value for the mean longitudinal extent D of 500 μm. The desired mean longitudinal expansion of the particles depends strongly on the respective coating purpose. By way of a high form factor with the lowest possible average thickness H, a better orientation of the platelet-shaped particles deposited on the substrate can be ensured. This is of particular interest in color coatings of surfaces. The thickness distribution is an important parameter for the characterization of platelet-shaped particles according to the invention

Thickness distribution exist in the prior art no measuring devices that can easily determine this value. A determination is therefore made by default by determining the thickness of a statistically sufficient number

platelet-shaped particles with a SEM (scanning electron microscope);

Usually about 50 to 100 particles are measured. For this purpose, the particles are dispersed, for example in a paint and then applied to a film. The varnish containing the platelet-shaped particle

coated film is then cut with a suitable tool so that the cut runs through the paint. Subsequently, the prepared film is introduced into the SEM such that the observation direction is perpendicular to the cut surface. In this way, the majority of the particles are viewed from the side so that their thickness can be easily determined. »The determination is carried out by default by marking the corresponding boundaries using a suitable tool such as the SEM devices of Manufacturer supplied software packages. For example, the determination can be carried out by means of a REM device of the Leo series of the manufacturer Zeiss (Germany) and the software Axiovision 4.6 (Zeiss, Germany). The thickness distribution of the platelet-shaped particles is not homogeneous. The

Thickness distribution is expediently represented in the form of a cumulative passage curve. The mean value is the hso value of

Dickensummendurchgangskurve on. It states that 50% of all particles have a thickness equal to and / or below this value.

Alternatively, the thickness distribution can also be described with the Hi ₀ or H ₉₀ value.

The platelet-shaped particles are preferably by means of a

Carrier gas is fed into the plasma jet. The feed of the

However, platelet-shaped particles in the plasma jet need not necessarily be in the gaseous state, but can also be in the liquid or solid state. The volume flow of the carrier gas is preferably in a range of 1 l / min to 1 5 l / min and the pressure in a range between 0.5 bar to 2 bar.

Homogeneous feeding of the platelet-shaped particles into a core zone of the plasma jet with a gas temperature of less than 900 degrees Celsius preferably takes place transversely to the propagation direction of the plasma jet.

Such platelet-shaped particles can be prepared by various methods. Depending on whether they are metallic or non-metallic materials, such as, for example, ceramic or oxidic materials, different methods of production can be used. The production of metallic platelet-shaped particles preferably takes place by mechanical deformation of powders, in particular metal powders. The mechanical deformation usually takes place in mills, in particular in

Agitator ball mills, edge mills, drum ball mills,

Rotary tube ball mills, etc. The mechanical deformation is usually carried out by wet milling, ie by grinding the powder together with solvent, in particular organic solvent such as white spirit, and in the presence of lubricants or wetting and / or dispersing additives such as oleic acid, stearic acid etc .. The grinding takes place in Presence of grinding media, usually grinding balls, wherein the ball diameter is usually in a range of 0.1 to 10 mm, preferably from 0.2 to 4.0 mm. The grinding media are usually made of ceramic, glass or metal, such as steel. Preferably, steel balls are used as grinding bodies. Such a deformation is described for example in DE 10 2007 062 942 A1, the content of which is hereby incorporated by reference.

In order to obtain metallic platelet-shaped particles according to the invention, the powder used is preferably classified by size and this is then mechanically deformed to obtain platelet-shaped particles in a size distribution with a D50 value from 0.5 to 200 μm. The classification can be carried out, for example, with air classifiers, cyclones, sieves and / or other known devices.

In this method, the metal particles can be measured in the form of a dispersion of particles. The scattering of the irradiated laser light is in

recorded in different spatial directions and according to the Fraunhofer

Diffraction theory by means of in conjunction with the CILAS device according to

Evaluated manufacturer information. The particles are treated mathematically as spheres. Thus, the determined diameters always relate to the equivalent spherical diameter averaged over all spatial directions, irrespective of the actual shape of the metal particles. It determines the size distribution, which is calculated in the form of a volume average (based on the equivalent spherical diameter). This volume-averaged size distribution can i.a. when

Summed passage curve are shown. The sum curve in turn is usually characterized simplifying by certain characteristics, z. For example, the D50 or D90 value. By a D90 value is meant that 90% of all particles are below the specified value. In other words, 10% of all Particles above the specified value. At a D50 value, 50% of all particles are below and 50% of all particles are above the specified value.

According to a further embodiment of the invention, the powder may first be ground and then classified by size in order to obtain the platelet-shaped particles according to the invention having a size distribution with a D50 value from a range from 1 to 150 μm. According to a further preferred embodiment, the size distribution between 1, 5 μιη and 100 μιη. According to a very preferred embodiment, it is between 2 μιη and 50 μιη.

The degree of purity of the metals is preferably more than 70 wt .-%, more preferably more than 90 wt .-%, particularly preferably more than 95 wt .-%, each based on the total weight of the metal, the alloy or

Mixture. To produce the platelet-shaped particles, the metal, the metal mixture or metal alloy can be melted under heat, for example, and then converted into a powder by atomization or by application to rotating components. For example, metallic powders produced in this way have a particle size distribution with an average size (D 50 value) in the range from 1 to 100 μm, preferably from 2 to 80 μm.

If non-metallic layers are to be applied to substrates, preferably non-metallic platelet-shaped particles are used in the

Coating process used. In this case, completely oxidized or even partially oxidized, e.g. only surface-oxidized educts are used. Such can be generated by targeted oxidation of metallic platelet-shaped particles. This oxidation can be carried out by all methods known to the person skilled in the art. Further oxidation is possible in particular in oxygen-containing plasmas and, depending on the amount of energy input and the coating material, the rule. By adjusting the oxygen content in the working gas, oxidation can optionally be controlled.

The metallic particles may be by gas phase oxidation and / or by Liquid phase oxidation are oxidized. Preferably, the oxidation is carried out in a liquid or by combustion in a gas stream.

When the oxidation is carried out in a liquid phase or liquid, this is preferably done by first distributing the powder in the liquid phase or liquid. This can be done with or without addition of excipients and with or without the input of energy. Preferably, the dispersion takes place without the addition of auxiliaries and with stirring. The liquid can be an inert

Be liquid that does not oxidize, or be a reactive liquid that acts oxidizing and reacts with the metallic particles. After

Accordingly, the dispersion either begins immediately or is initiated by the addition of an oxidizing agent and / or oxidation catalyst and / or by increasing the temperature.

If the liquid is reactive and reacts with the metal, the oxidation may already begin during the dispersion. Whether the oxidation reaction starts immediately depends on the chosen combination of liquid / metallic powder and possibly catalyst presence. The oxidation is preferably started by adding an oxidizing agent and / or oxidation catalyst. Preferably, to accelerate the oxidation reaction, the reaction mixture is heated during the oxidation. Examples of oxidizing agents are sulfuric acid, potassium permanganate, hydrogen peroxide and other oxidizing agents known to those skilled in the art. Examples of oxidation catalysts are metals, metal salts, acids and bases. In particular, in the case of the addition of acids and bases, the addition is preferably carried out so that a pH value suitable for the oxidation reaction is set in the reaction mixture. After the reaction is started, it is preferably maintained until the metal is at least 90% by weight, more preferably at least 95% by weight, even more preferably at least 99% by weight, based on the total weight the metallic particle is present in a non-zero oxidation state. According to a preferred embodiment, particles are completely present as metal oxide after the oxidation treatment. The metal oxide content can be determined experimentally by methods known to the person skilled in the art. During the oxidation reaction, the temperature can be raised, lowered or kept constant. In addition, a further addition of one or more oxidizing agents and / or oxidation catalysts can take place, whereby the oxidation process can be controlled. During the oxidation, optionally with the addition of further reaction components, additional chemical reactions may be initiated and / or further

Components, for example metals or metal oxides, are incorporated into the resulting metal oxide particles, for example as doping. By choosing these reaction parameters, the chemical and physical properties of the metal oxide particles, their size and their morphology can be adjusted specifically. Preference is given to

Reaction parameters adjusted so that the oxidation product has properties that the subsequent coating of substrates by

Facilitate introduction of the particles into a plasma and / or are advantageous for a desired application.

Preferred chemical reactions which lead to the oxidation of the metallic powder are:

2Al + 4H ₂ O -> 2AIOOH + 3H _{2 2} Fe + 2H ₂ O -> ₂ Fe (OH) + H ₂

2Zn + H ₂ O -> ZnO + H ₂

2Cu + H ₂ O -> Cu ₂ O + H ₂

These oxidation reactions are given as examples for illustration. The exact chemical reaction mechanism is often difficult to determine. Further possible reaction mechanisms of the oxidation of metals are, for example, in the literature, as for example in Hollemann, Wiberg, Lehrbuch der Inorganischen Chemie, 101st edition, de Gruyter Verlag, 1995 described.

After oxidation, the metal oxide particles can be separated from the liquid in which the oxidation was carried out. The separation can be carried out by directly removing the liquid from the reaction mixture. This can be done by methods known in the art such as thermal drying, preferably in a reduced pressure atmosphere. Preferably, the separation of the liquid takes place after a first concentration of the solid has been carried out by a simple process, in particular by filtration.

Following the separation, the metal oxide particles may optionally be subjected to annealing, i. be supplied to an additional temperature treatment. By annealing or this temperature treatment, in particular the chemical composition and / or the crystal structure of the above

metal oxide particles are changed. The temperatures of such a temperature treatment are typically above 200 ° C but below the melting or decomposition temperature. The duration is typically a few minutes to a few hours. For example, by a thermal treatment, aluminum hydroxide prepared by reacting aluminum metal powder in water by heating

Temperatures of more than 400 ° C with elimination of water to

Alumina are converted. With further temperature treatment in the range between 800 ^< Ό and 1300 ^< Ό, the crystal structure of the

Alumina can be adjusted specifically. Thus, for example, converts v- Al ₂ O ₃ upon heating to temperatures greater than 800 ° C in oc-Al ₂ O ₃ in order.

In addition to the conversion of metallic particles into non-metallic particles, non-metallic platelet-shaped particles can also be produced directly.

For example, platelet particles can be made from crystalline, semi-crystalline or amorphous material. For example, glass flakes are produced in which a jet of molten glass is poured onto a rotating, cup or cup-shaped vessel. Due to the rotation of the vessel, the glass melt is squirted out of the vessel in the form of a thin lamella. During this process, the melt solidifies, forming platelet-shaped particles of glass.

Furthermore, non-metallic platelet-shaped particles may be obtained by mechanical delamination of layered materials, e.g. Phyllosilicates, are generated. The platelet-shaped particles may consist of different materials. In the case of metallic particles, these may consist, for example, of aluminum, zinc, tin, titanium, iron, copper, silver, gold, tungsten, nickel, lead, platinum, silicon, further alloys or mixtures thereof. According to a variant of the method according to the invention, aluminum, copper, zinc and tin or alloys or mixtures thereof are particularly preferred. In the case of non-metallic particles, these may consist, for example, of oxides or hydroxides of the metals already mentioned or of other metals. Furthermore, the particles may consist of glass, layer silicates such as mica or bentonites. In addition, the particles may consist of carbides, silicates and sulfates. The recovery and processing for the process of suitable particles may also be by other means (e.g., artificially by crystallization, drawing, etc.), breeding methods, or conventional scouring and flotation, etc.). The particles may also be organic and inorganic salts. Furthermore, the particles may consist of pure or mixed homo-, co-, block- or prepolymers or plastics or mixtures thereof, but also be organic pure or mixed crystals or amorphous phases.

The particles may also consist of mixtures of at least two materials. According to a further embodiment, the platelet-shaped particles have at least one, preferably enveloping coating. The at least simple coating can be, for example, a protective layer against corrosion, which is also referred to as a corrosion protection layer.

The platelet-shaped particles according to the invention can, for example, with be provided at least one metal oxide layer. The coating with

Metal oxides, metal hydroxides and / or metal oxide hydrates are preferably carried out by precipitation, by sol-gel methods or by wet-chemical oxidation of the particle surface. Oxides, hydroxides and / or hydrated oxides of silicon, aluminum, cerium, zirconium, yttrium, chromium and / or mixtures / admixtures thereof are preferably used for the metal oxide coating.

According to a preferred development, oxides, hydroxides and / or hydrated oxides of silicon and / or aluminum are used. Most preferred are oxides, hydroxides and / or hydrated oxides of silicon.

The layer thicknesses of the metal oxide layers, in particular of silicon oxide and / or aluminum oxide layers, are in the range from preferably 5 to 150 nm, preferably from 10 to 80 nm, more preferably from 1 5 to 50 nm.

As a protective layer against corrosion, a protective layer of organic polymers can also be applied. Polyacrylate and / or polymethacrylate coatings have proven to be very suitable.

Of course, synthetic resin coatings consisting of e.g. Epoxies, polyesters, polyurethanes, or polystyrenes, and mixtures thereof. Instead of or in addition to a coating of metal oxides and / or polymerized synthetic resins, so-called passivation layers can also be applied. The mechanism of action of the passivation layers is complex. For inhibitors, it is mostly based on steric effects.

The inhibitors are usually in low concentrations of the order of 1 wt .-% to 1 5 wt .-%, based on the

Weight of the metal particle used, added. For inhibition, the following coating substances are preferably used:

• Organically modified phosphonic acids or their esters of

general formula R-P (O) (OFM) (OR2), wherein: R = alkyl, aryl, alkylaryl, aryl-alkyl and alkyl ethers, in particular ethoxylated alkyl ethers and

R1, R2 = H, CnH2n + 1, with n = 1 to 12, preferably 1-6, wherein each alkyl may be branched or unbranched. R1 may be the same or different than R2.

• Organically modified phosphoric acids and esters of

general formula R-O-P (OR1) (OR2) where R = alkyl, aryl, alkylaryl, arylalkyl and also alkyl ethers, in particular ethoxylated alkyl ethers, and R1, R2 = H, CnH2n + 1, where n = 1 to 12,

preferably 1-6, wherein each alkyl is branched or

can be unbranched. R1 may be the same or different from R2.

It is also possible to use pure, inorganic phosphonic acids or esters or phosphoric acids or esters or any mixtures thereof.

Furthermore, the coating of organically functionalized silanes, aliphatic or cyclic amines, aliphatic or aromatic

Nitro compounds containing oxygen, sulfur and / or nitrogen

Heterocycles, such as thiourea derivatives, sulfur and / or nitrogen compounds of higher ketones, aldehydes and / or alcohols

(Fatty alcohols) and / or thiols, or mixtures thereof, or include these. The passivating inhibitor layer can also consist of the aforementioned substances. Preference is given to organic phosphonic acids and / or phosphoric esters or mixtures thereof. When using

Amine compounds have these preferably organic radicals having more than 6 carbon atoms. Preference is given to the abovementioned amines together with organic phosphonic acids and / or phosphoric esters or mixtures thereof used.

The passivation via corrosion protection barriers with chemical and physical protective effect is possible in many ways.

Passivating anticorrosion coatings, which ensure particularly good corrosion protection in the case of platelet-shaped metallic particles, comprise or consist of silicon oxide, preferably silicon dioxide,

Chromium alumina, preferably by chromating, chromium oxide, zirconium oxide, cerium oxide, alumina, polymerized plastic resin (s), phosphate, phosphite or borate compounds or mixtures thereof.

Preference is given to silicon dioxide layers and chromium aluminum oxide layers (chromating). Further preferred are cerium oxide, hydroxide or

oxide hydrate layers and aluminum oxide, hydroxide or oxide hydrate layers, as described for example in DE 195 20 312 A1. The SiCV layers are preferably by sol-gel method with

average layer thicknesses of 10-150 nm and preferably 15-40 nm in organic solvents.

Furthermore, the listed coatings can be combined, so that, for example, in a particular embodiment of the invention particles a coating of a Si0 ₂ layer with subsequently applied

Have layer of functionalized silanes.

The highest possible packing density of the deposited particles is equal to a layer that is as similar as possible to a closed, non-particulate layer, thus a layer that corresponds to the ideal base material. A high packing density is achieved if the particles retain their shape and structure as far as possible during the coating process and are still present as individual particles, in particular in the resulting layer. Such behavior is demonstrated by the particles as described, if they are made of higher-melting metals (melting point> 500 ° C) and non-metallic

Material exist. The energy of the plasma activates such particles only on their surface, whereby the shape of the particles as such in the on

Substrate arising layer remains.

The coatings which can be produced by the process according to the invention on the substrate of platelet-shaped particles which are at least partially intergrown with one another can be produced without a binder between the coating and the substrate. The prerequisite for the production of coatings without binder between layer and substrate is the use of

platelet-shaped particles of a material, which at least partially melt by the action of the cold plasma jet on the surface, so that the platelet-shaped particles in the coating partially grow together. An advantageous device for applying a coating

platelet-shaped particles is characterized in that the device comprises a jet generator with an inlet for the supply of a flowing working gas and an outlet for a guided from the working gas plasma jet, the beam generator two connectable to an AC or a pulsed DC voltage source electrodes to form a

Discharge path along which the working gas is guided, the

Beam generator opening in the region of the discharge gap

Having feed opening, via which the plasma jet platelet-shaped particles can be fed. As the working gas of the device are supplied via the inlet ionizable gases, in particular pressurized air, nitrogen, argon, carbon dioxide or hydrogen. The working gas is previously cleaned so that it is free of oil and lubricant. The gas stream in a conventional jet generator is between 1 0 to 70 l / min, in particular between 1 0 to 40 l / min, at a speed of the working gas between 1 0 to 1 00 m / s, in particular between 10 to 50 m / s.

The beam generator further comprises two, in particular coaxially spaced apart electrodes, which are connected to an AC voltage, but in particular a pulsed DC voltage source. Between the electrodes, the discharge path is formed. The pulsed DC voltage of the DC voltage source is preferably between 500 V to 12 kV. The pulse frequency is between 10 to 100 kHz, but in particular between 10 to 50 kHz.

Due to the pulsed operation of the DC voltage source, it can be assumed that there is no thermal equilibrium between the light sources

Electrons and the heavy ions can form. This results in a low temperature load of the injected platelet-shaped particles. Of the

Coating process with the jet generator according to the invention is preferably controlled such that the plasma jet of

Low temperature plasma in the core zone has a gas temperature of less than

900 degrees Celsius, but in particular of less than 500 degrees Celsius

(Low temperature plasma).

By the feed opening in the region of the discharge gap between the electrodes of the jet generator, the platelet-shaped particles reach a region in which a direct plasma excitation takes place through the plasma jet. By this measure, the required reaction energy is kept as low as possible.

Preferably, the feed opening is located immediately adjacent to the outlet for the plasma jet in the region of the discharge path. However, if the feed is below the outlet of the device, which is basically possible, it is only an indirect

Plasma excitation by the gas-guided plasma jet, which is energetically unfavorable. The method of the invention can be used to coat a variety of substrates. Substrates may be, for example, metals, wood, plastics or paper. The substrates can be present in the form of geometrically complex shapes, such as components or finished goods but also as a film or sheet. The coatings which can be produced by the process according to the invention on the substrate of platelet-shaped particles which are at least partially intergrown with one another can be produced without a binder between the coating and the substrate. A prerequisite for the production of coatings without binder between layer and substrate is the use of platelet-shaped particles of a

Material which at least partially melt on the surface due to the action of the cold plasma jet, so that the platelet-shaped particles in the coating partially grow together with one another.

The applications for the process according to the invention are also very diverse. For example, optically and electromagnetically reflecting or absorbing, electrically conductive, semiconducting or insulating layers, diffusion barriers for gases and liquids,

Sliding layers, wear and corrosion protection layers and layers for influencing the surface tension and layers for adhesion promotion are produced.

Conductive layers produced by the process can

For example, used to produce Heizleiterbahnen. Furthermore, such conductive layers can also be used as shields, as electrical contacts, as sensor surfaces and as antennas, in particular RFID (radio

Frequency Identification) antennas, find use.

The coatings can be applied over a large area, so that they cover the substrate to a large extent (greater than 70% of the surface of the substrate). However, the layers can also be applied over a small area, in particular in the form of webs or as sub-areas, which cover less than 10% of the area of the substrate. Especially in the application of coatings on small partial areas of the substrate, for example during the deposition of contacts, a relative movement between the substrate and the beam generator during the coating is not required. The layers can also be applied in the form of patterns, which are preferably adapted to the desired functionality. The generation of geometric patterns can also be done, for example, by the use of masks.

An advantageous device for applying a coating

platelet-shaped particles is characterized in that the apparatus comprises a jet generator with an inlet for the supply of a flowing working gas and an outlet for a plasma jet guided by the working gas, the jet generator two with an AC or a pulsed

DC voltage source connectable electrodes to form a

Discharge path along which the working gas is guided, the

Beam generator opening in the region of the discharge gap

Having feed opening, via which the plasma jet platelet-shaped particles can be fed.

As the working gas of the device are supplied via the inlet ionizable gases, in particular pressurized air, nitrogen, argon, carbon dioxide or hydrogen. The working gas is previously cleaned so that it is free of oil and lubricant. The gas stream in a conventional jet generator is between 10 to 70 l / min, in particular between 10 to 40 l / min, at a

Speed of the working gas between 10 to 100 m / s, in particular between 10 to 50 m / s.

The jet generator further comprises two, in particular coaxially spaced electrodes arranged with an AC voltage,

but in particular be connected to a pulsed DC voltage source. Between the electrodes, the discharge path is formed. The pulsed DC voltage of the DC voltage source is preferably between 500 V to 12 kV. The pulse frequency is between 10 to 100 kHz, but in particular between 10 to 50 kHz. Due to the pulsed operation of the DC voltage source is thereof

assume that no thermal equilibrium between the light electrons and the heavy ions can form. This results in a low temperature load of the injected platelet-shaped particles. Of the

Coating process with the jet generator according to the invention is preferably controlled such that the plasma jet of the low-temperature plasma in the core zone has a gas temperature of less than 900 degrees Celsius,

but especially less than 500 degrees Celsius

(Low temperature plasma). By the feed opening in the region of the discharge gap between the electrodes of the jet generator, the platelet-shaped particles reach a region in which a direct plasma excitation takes place through the plasma jet. By this measure, the required reaction energy is kept as low as possible. Preferably, the feed opening is located immediately adjacent to the outlet for the plasma jet in the region of the discharge path. Is this done?

Injection, however, below the outlet of the device, which is basically possible, it comes only to an indirect plasma excitation by the gas plasma jet, which is energetically unfavorable. As already mentioned, the feeding of the platelet-shaped particles preferably takes place by means of a carrier gas for the platelet-shaped particles. To produce the mixture of the platelet-shaped particles and the carrier gas, the feed opening of the jet generator via a line with a

Connected swirl chamber. The vortex chamber is listed as a closed container and at most up to a maximum level with the

filled platelet-shaped particles. The platelet-shaped particles are acted upon by at least one gas inlet with a pressurized carrier gas, in particular in a periodic sequence, whereby the fluidized platelet-shaped particles together with the carrier gas as a mixture over at least one above the maximum level of the vortex chamber arranged outlet from the container in the direction of the feed opening of the jet generator flow.

The periodic loading of the platelet-shaped particles in the vortex chamber with the carrier gas takes place at a frequency in the range from 1 Hz to 100 Hz.

In particular, the particles become consecutive over several times

Gas inlets with the carrier gas applied. The gas inlet (s) can open directly into the usually existing supply of platelet-shaped particles. In addition to this preferred direct blowing of the carrier gas into the particles, however, it is also possible to arrange the gas inlet or inlets above the maximum fill level of the particles in the vortex chamber so that the carrier gas strikes the surface of the particles.

The present invention will be apparent from the following examples

illustrated but not limited thereto.

Measurement methods used: Size-to-thickness ratio:

The size-thickness ratio of a particle sample from the examples listed was determined from the evaluation of SEM images. In each case, the longitudinal diameter was determined by means of Cilas 1064 and the thickness of a statistical number (at least 100) of particles and calculated the average size-thickness ratio by quotient of longitudinal diameter to thickness.

Example 1: Production of aluminum powder

In an induction crucible furnace (Induga, Cologne, Germany), about 2.5 tons of aluminum ingots (metal) were continuously introduced and melted. In the so-called forehearth, the aluminum melt was liquid at a temperature of about 720 ° C. Several nozzles, which work according to an injector principle, dipped into the melt and atomize the aluminum melt vertically upwards. The atomizing gas was injected into compressors (Messrs. Kaeser, Coburg, Germany) to 20 bar compressed and heated in gas heaters up to about 700 ° C. The aluminum powder produced after spraying / atomization solidified and cooled down in the air. The induction furnace was integrated in a closed system. The atomization was carried out under inert gas (nitrogen). The

Separation of the aluminum powder was carried out first in a cyclone, wherein there deposited powdered Aluminiumgrieß a D50 14-17 μιη possessed. For further deposition, a multicyclone was used in succession, the pulverulent aluminum powder deposited in this having a D50 of 2.3 to 2.8 μm. The gas-solid separation was carried out in a filter (Fa. Alpine, Thailand) with metal elements (Pall). Here was the finest fraction

Aluminum powder with a d10 of 0.7 μιη, (outside the range!) Won a d50 10 of 1, 9 μιη and a d90 of 3.8 μιη.

Example 2 Production of Metallic Platelet-shaped Particles by Milling

In a pot mill (length: 32 cm, width: 19 cm) 4 kg glass beads (diameter: 2 mm), 75 g of the finest aluminum powder, 200 g of white spirit and 3.75 g of oleic acid were abandoned. It was then ground for 15 hours at 58 rpm. The product was made by rinsing with white spirit from the

Separated grinding balls and then sieved in a wet sieving on a 25 μηΊ sieve. The fine grain was largely freed of white spirit via a suction filter (about 80% solids).

Example 3: Production of non-metallic platelet-shaped

Particles (aluminum hydroxide) by oxidation of metallic

platelet-shaped particles (aluminum): In a 5 L glass reactor, 300 g of a shaped aluminum powder described in Example 2 were dispersed in 1000 ml of isopropanol (VWR, Germany) by stirring with a propeller stirrer. The suspension was heated to 78 ° C. Subsequently, 5 g of a 25 wt .-% ammonia solution (VWR, Germany) were added. After a short time, a strong gas evolution was possible to be watched. Three hours after the first addition of ammonia, another 5 g of 25% by weight ammonia solution was added. After a further three hours, 5 g of 25% by weight ammonia solution were again added. The suspension was further stirred overnight. The next morning, the solid was separated by means of a suction filter and dried in a vacuum oven for 48 h at 50 ° C. A white powder was obtained. This powder was subsequently characterized. First, particle size and zeta potential as a function of pH were studied. The pH was adjusted by means of 1, 0 M NaOH or 1, 0 M HCl. At low as well as at high pH, the zeta potential indicates a maximum and the particle diameter

Minimum. From an XRD analysis of the material, a composition of about 33% by weight of boehmite (AIOOH) and 67% by weight of gibbsite (Al (OH) 3) can be derived.

Example 4: Preparation of non-metallic platelet-shaped particles (aluminum oxide) by temperature treatment of non-metallic

platelet-shaped particles (aluminum hydroxide).

500 g of a material prepared according to Example 3 were heated for 10 minutes in a rotary kiln (Nabertherm, Germany) to 1 100 ° C. There were obtained 335 g of a white powder. This was examined as described. in the

Difference to the uncalcined. Material is the particle diameter slightly larger and the zeta potential in the entire pH range positive. The XRD analysis shows theta-AI203.

The method according to the invention and a device for carrying out the method will be explained in more detail below with reference to the figures. FIG. 1 shows a schematic representation of an embodiment of a

beam generator according to the invention and

Figure 2 is an enlarged view of the beam generator of Figure 1 in

Area of the outlet. The jet generator 1 according to the invention for generating a plasma jet 2 of a low-temperature plasma comprises two electrodes 4, 5 arranged in the flow of a working gas 3 and a voltage source 6 for generating a pulsed DC voltage between the electrodes 4, 5. The first electrode 4 is designed as a pin electrode, while the spaced second

Electrode 5 is formed as an annular electrode. The distance between the tip of the pin electrode 4 and the ring electrode 5 forms a discharge path 16.

A jacket 7 of electrically conductive material is arranged concentrically to the pin electrode 4 and insulated from the pin electrode 4. At the, the annular electrode 5, opposite end face of the jet generator 1, the working gas 3 is supplied via an inlet 21. The inlet 21 is located on a frontally placed on the hollow cylindrical jacket 7, the pin electrode 4-holding sleeve 22 of electrically insulating material. At the

opposite end of the jacket 7 tapers nozzle-shaped to an outlet 8 for the plasma jet. 2

Immediately adjacent to the extending in the axial direction of the jet generator 1 outlet 8 is transverse to the longitudinal extent of a feed opening 9, via which the plasma jet 2 platelet-shaped particles 10 are fed. The feed opening 9 of the jet generator 1 is connected for this purpose via a line 12 with a vortex chamber 1 1, are stored in the platelet-shaped particles 10. The vortex chamber 1 1 is filled at most up to a maximum level 13 with the platelet-shaped particles 10. Below the maximum level 13 opens in the vortex chamber 1 1, an inlet 23 for a carrier gas 14 under a

compared to the ambient pressure increased pressure is injected into the particle supply. As a result, the particles 10 are fluidized in the space above the maximum level 20 and reach via an outlet 15, the conduit 12 and the feed opening 9 in the discharge path 16 of the jet generator. 1 As can be seen in particular from the enlargement in Figure 2, get the platelet-shaped particles 1 0 transverse to the propagation direction of the plasma jet 2 in a core zone 17 of the plasma jet 2, in which a temperature of less than 500 degrees Celsius prevails (low-temperature plasma). The

Voltage source 6 increases, during each pulse, the voltage applied between the electrodes 4, 5, to between the electrodes 4, 5, the ignition voltage for the formation of an arc between the electrodes 4, 5 is applied. Due to the conductive shell 7, it also leads to discharges in the direction of the inner

Lateral surface, as indicated in Figure 1 by the dotted lines. Upon reaching the ignition voltage, the discharge path 16 between the

Electrodes 4, 5 conductive. The voltage source 6 is preferably designed such that it generates a voltage pulse with an ignition voltage for the arc discharge and a pulse frequency which causes the arc to extinguish between two consecutive voltage pulses. As a result, there is a pulsed gas discharge in the plasma jet 2. The pulse frequency is preferably in a range between 10 kHz to 100 kHz, in the illustrated embodiment at 50 kHz. The voltage of the voltage source 6 is a maximum of 12 kV. As working gas 3 compressed air is used, with 40 l / min are supplied in the normal operating condition.

Unless with the aid of the beam generator 1 deviating from the illustrated

Embodiment not only a punctiform coating on the substrate 20 is to be generated, it is in an embodiment of the invention the possibility that the plasma jet 2 and the substrate 20, during the application of the

Be moved coating at least temporarily relative to each other. The

Relative movement can be effected by moving the substrate 20, for example on a movable table in the horizontal plane. Alternatively, the beam generator 1 is arranged on an XY moving unit that is movable at least in a plane parallel to the substrate 20, so that the generator can be moved relative to the substrate at a defined speed. By the

Relative movement can be webs or even full-surface coatings of the substrate 20 produce.

Claims

claims:

Method for applying a coating to a substrate (20), in which a plasma jet (2) of a low-temperature plasma is generated by passing a working gas (3) through an excitation zone, characterized in that in the plasma jet (2) directed onto the substrate (20) ) platelet-shaped particles (10) having an average thickness (H) of between 10 and 50,000 nanometers and a shape factor (F) in the value range of 10 to 2,000.

The method of claim 1, wherein the platelet-shaped particles (10) are fed by means of a carrier gas (14) in the plasma jet (2).

The method of claim 2, wherein the volume flow of the carrier gas (14) in a range of 1 l / min to 15 l / min and the pressure in a range between 0.5 bar to 2 bar.

Method according to one of claims 1 to 3, wherein the plasma jet (2) and the substrate (20) during the application of the coating (19) are at least temporarily moved relative to each other.

Method according to one of claims 1 to 4, wherein the platelet-shaped particles (10) transversely to the propagation direction of the plasma jet (2) are fed into the plasma jet (2).

Method according to one of claims 1 to 5, wherein the plasma jet (2) with a gas temperature in a core zone (17) of the plasma jet (2) of less than 900 degrees Celsius is generated.

Method according to one of claims 1 to 6, wherein the plasma jet (2) under an ambient pressure in a pressure range of 0.5 - 1, 5 bar is generated. Method according to one of claims 1 to 7, wherein the plasma jet (2) by excitation of the working gas (3) by means of an AC voltage or a pulsed DC voltage is generated.

The method of claim 8, wherein the AC voltage or the pulsed

DC voltage is between 500 V and 15 kV and the frequency of

AC or the pulsed DC voltage between 10 kHz to 100 kHz. 10. The method according to any one of claims 1 to 9, wherein platelet-shaped particles (10) of metal in the plasma jet (2) are fed.

11. The method of claim 10, wherein the metal of the group consisting of aluminum, zinc, tin, titanium, iron, copper, silver, gold, tungsten, silicon or alloys or

Mixtures thereof, is taken.

12. The method of claim 10 or 11, wherein the metal is selected from the group consisting of oxides, carbides, hydroxides, carbonates, chlorides, fluorides, or mixtures thereof.

13. The method according to any one of claims 1 to 12, wherein the platelet-shaped particles

(10) are additionally at least partially coated with at least one further layer.

The method of claim 13, wherein the further layer is formed by a polymer.

15. The method according to any one of claims 1 to 14, wherein the substrate of the group

consisting of metals, wood, plastics, glass, ceramics, biomaterials or

Paper, is taken.

16. A device for applying a coating to a substrate by

characterized in that The device comprises a jet generator (1) with an inlet (21) for the supply of a flowing working gas (3) and an outlet (8) for a plasma jet (3) guided by the working gas (3),

• The beam generator (1) two with an AC voltage or a pulsed DC voltage source connectable electrodes (4,5) for forming a

Discharge path (16) along which the working gas (3) is fühbar; and

• The jet generator (1) has at least one in the region of the discharge path (16) emanating feed opening (9) through which the plasma jet (2) platelet-shaped particles (10) can be fed.

17. The apparatus of claim 16, wherein each feed opening (9) immediately adjacent to the outlet (8) for the plasma jet (2) is arranged.

18. Device according to claim 16 or 17, wherein each feed opening (9) of the

Beam generator (1) with a vortex chamber (11) for generating a mixture of the platelet-shaped particles (10) and a carrier gas (14) is connected.

19. coating (19) on a substrate (20) of at least partially with each other

grown platelet-shaped particles (10), produced by a method according to one or more of claims 1 to 15.

20. Use of platelet-shaped particles (10) having an average thickness H between 10 and 50,000 nanometers and a shape factor F in the range from 10 to 2000 for applying a coating (19) to a substrate (20) using a gas-guided plasma jet (2 ) of a low temperature plasma.