EP3880867A1

EP3880867A1 - Method for producing three-dimensional silicon carbide-containing objects

Info

Publication number: EP3880867A1
Application number: EP19798297.8A
Authority: EP
Inventors: Siegmund Greulich-Weber
Original assignee: PSC Technologies GmbH
Current assignee: PSC Technologies GmbH
Priority date: 2018-11-13
Filing date: 2019-11-05
Publication date: 2021-09-22
Also published as: WO2020099188A1; US20220118551A1; DE102018128434A1; JP2022534144A

Abstract

The invention relates to a method for applying silicon carbide-containing materials to a substrate surface, and to an apparatus for carrying out the method.

Description

Process for the production of three-dimensional silicon carbide-containing

Objects

The present invention relates to the technical field of additive manufacturing processes, in particular additive manufacturing.

In particular, the present invention relates to a method for applying silicon carbide-containing materials to a substrate, in particular for location-selective application to a substrate.

Furthermore, the present invention relates to the silicon carbide-containing objects obtainable with the method according to the invention.

Finally, the present invention relates to an apparatus for performing the method.

Generative manufacturing processes, also known as additive manufacturing or additive manufacturing (AM), are processes for the rapid production of models, samples, tools and products from shapeless materials, such as liquids, gels, pastes or powders .

Originally, the term 3D printing or rapid prototyping was generally used for generative manufacturing processes, especially additive manufacturing. However, these terms are now only used for special configurations of additive manufacturing processes. Generative production processes are used both for the production of objects from inorganic materials, in particular metals and ceramics, and from organic materials. For the production of objects from inorganic materials, high-energy processes such as selective laser melting, electron beam melting or cladding are preferably used, since the educts or precursors used only react or melt when the energy input is high. In principle, additive manufacturing enables the fast manufacture of highly complex components, but the manufacture of components from inorganic materials in particular poses a number of challenges to both the educt and Also the product materials: For example, the educts may only react in a predetermined manner under the influence of energy. In particular, disruptive side effects must be excluded. In addition, no separation of the products or phase separation or even decomposition of the products may occur under the influence of energy.

Silicon carbide, also called carborundum, is an extremely interesting and versatile material for the production of high-performance ceramics and for semiconductor applications. Silicon carbide with the chemical formula SiC has an extremely high hardness and a high sublimation point and is often used as an abrasive or as an insulator in high-temperature reactors. Siliciumcar bid also deals with a variety of elements and alloys or alloy-like compounds, which often have advantageous material properties, such as high hardness, high resistance, low weight and low sensitivity to oxidation even at high temperatures. The properties of the porous silicon carbide material produced via conventional sintering processes do not correspond to those of the compact crystalline silicon carbide, so that the advantageous properties of the silicon carbide cannot be fully exhausted. In addition, silicon carbide does not melt at high temperatures - depending on the respective crystal type - in the range from 2,300 to 2,700 ° C, but subsumes, i.e. changes from the solid to the gaseous state. This makes silicon carbide particularly unsuitable for additive manufacturing processes, such as laser melting.

Because of the versatility of silicon carbide or materials containing silicon carbide and the large number of positive application properties, attempts have nevertheless been made to process silicon carbide by means of generative manufacturing processes.

For example, DE 10 2015 105 085.4 describes a process for the production of bodies from silicon carbide crystals, the silicon carbide in particular by laser irradiation from suitable carbon and silicon containing Precursor compounds are obtained in a powder bed process based on selective laser melting (SLM).

The method described in DE 10 2015 105 085.4 is perfectly suitable for obtaining objects made of silicon carbide crystals, but a relatively large amount of precursor material must always be kept available for the powder bed method, which is not used and is also contaminated by by-products in the course of the manufacturing process and consequently contaminated cannot be used in full in other manufacturing processes without refurbishment.

A suitable method for the production of coatings or three-dimensional objects is cladding. With build-up welding, a material is applied to a substrate or workpiece by melting the substrate or workpiece while applying a material at the same time. A special form of cladding is laser cladding, with which the thermal energy provided for the melting process is provided by a laser. Cladding or laser cladding can be used with full use of educt materials, i.e. H. With no unused residues, targeted creation of three-dimensional objects and coatings. In addition, it is also possible to join or repair parts, for example, by replacing material loss with cladding. Laser cladding is usually used to deposit metallic materials.

So far, it has not been possible to process ceramic materials, in particular those containing silicon carbide, by means of build-up welding, since silicon carbide does not melt at high temperatures - as mentioned before - but sublimates.

There is therefore still no method in the prior art for producing objects from silicon carbide and materials containing silicon carbide in a targeted manner while using raw materials as efficiently as possible.

It is therefore an object of the present invention to avoid, but at least to mitigate, the above-described disadvantages and problems associated with the prior art.

In particular, an object of the present invention is to be seen in providing a method which makes it possible to use silicon carbide-containing materials or Structures made of silicon carbide-containing materials to be deposited or produced locally on a substrate in a locally limited manner.

Another object of the present invention is to provide a method which makes it possible to manufacture or repair components or objects from silicon carbide-containing materials by targeted application of material.

The present invention according to a first aspect of the present invention is a method for applying silicon carbide-containing materials to a substrate according to claim 1; Another advantageous embodiment of this aspect of the invention are the subject of the relevant subclaims.

Another object of the present invention according to a second aspect of the present invention is a silicon-containing three-dimensional object according to claim 13.

Finally, a further aspect of the present invention according to a third aspect of the present invention is a device for the location-selective deposition of silicon carbide-containing materials according to claim 14; Another advantageous embodiment of this aspect of the invention are the subject of the relevant dependent claims.

It goes without saying that the special configurations mentioned below, in particular special embodiments or the like, which are only described in connection with one aspect of the invention, also apply correspondingly to the other aspects of the invention, without this needing to be expressly mentioned. Furthermore, with all the relative or percentage, in particular weight-related, amounts stated below, it should be noted that within the scope of the present invention these are to be selected by the person skilled in the art such that the sum of the ingredients, additives or auxiliaries or the like is always 100% or 100% by weight result. However, this goes without saying for the person skilled in the art.

In addition, it applies that all of the parameter information specified below or the like in principle with standardized or explicitly specified determination methods drive or the determination methods known per se to the person skilled in the art, or can be determined.

Having said this, the subject matter of the present invention is explained in more detail below.

The present invention - according to a first aspect of the present invention - is thus a method for applying silicon carbide-containing materials to a substrate surface, wherein a gaseous, liquid or powdered precursor material containing a silicon source and a carbon source gasified by the action of energy and / or is decomposed and at least some of the decomposition products are locally selectively deposited on the substrate surface as silicon carbide-containing material. The inventive method allows the generation of high-resolution and detailed three-dimensional structures, i. H. the course of contours, such as corners or edges, is highly precise and in particular free of burrs.

In the context of the present invention, it is also possible, in particular, to obtain objects in the form of compact solids which do not have a porous structure but instead consist of crystalline materials containing silicon carbide. The materials and three-dimensional objects made of silicon carbide-containing materials obtainable with the method according to the invention thus have almost the same properties as crystalline silicon carbide or silicon carbide alloys in their material properties.

In particular, the method according to the invention allows a very fast and little complex production of three-dimensional objects or coatings containing silicon carbide and in particular does not require the use of pressure in order to provide compact, non-porous materials.

With the method according to the invention, coatings made of silicon carbide-containing materials can be applied to a substrate surface as well as three-dimensional objects made of silicon carbide-containing materials can be built up on the substrate surface, which are subsequently removed if necessary. Similarly, it is also possible to add components by applying silicon carbide-containing materials or to add material defects in components. In the context of the present invention, a compound containing silicon carbide is to be understood as a binary, ternary or quaternary inorganic compound, the molecular formula of which contains silicon and carbon. In particular, a compound containing silicon carbide does not contain any molecularly bound carbon, such as carbon monoxide or carbon dioxide; the carbon is much more in a solid structure.

In the context of the present invention, a silicon source or a carbon source is to be understood as meaning compounds which, under process conditions, can release silicon or carbon in such a way that compounds containing silicon carbide are formed. In this context, silicon and carbon do not have to be released in elemental form, but it is sufficient if they react to silicon carbide-containing compounds under process conditions.

The silicon source, the carbon source or the precursors for any doping or alloying elements can either be specific chemical compounds or, for example, their reaction products, in particular hydrolysates, as will be explained below.

In the context of the present invention, a substrate is to be understood as the material to which the preferably gaseous decomposition products of the precursor material are applied. In particular, a substrate in the context of the present invention is a three-dimensional or an almost two-dimensional structure with a surface on which the decomposition products of the precursor material are deposited. The substrate surface can be flat or contoured, in particular structured in three dimensions. The substrate can have almost any three-dimensional shape. The substrate can thus be a carrier material on which material containing silicon carbide is deposited in layers. The term substrate also includes, in particular, carrier materials which are partially coated with one or more layers of materials containing silicon carbide. However, a substrate can also be a three-dimensional object which is joined to a second substrate, in particular a further three-dimensional object, by deposited silicon carbide-containing material. With regard to the substrate to which the precursor material or its decomposition products are applied, this can be selected from a large number of suitable materials. In the context of the present invention it is possible that the substrate is selected from crystalline and amorphous substrates. According to a preferred embodiment of the present invention, the substrate is an amorphous substrate. Particularly good results are obtained when the material is selected from carbon, in particular graphite, and ceramic materials, in particular silicon carbide, silicon dioxide, aluminum oxide and metals and mixtures thereof. If the method according to the invention is used to produce objects made of silicon carbide-containing materials, the substrate often has several materials, in particular a carrier material and the three-dimensional object made of silicon carbide-containing material, which is at least partially built thereon. In the context of the present invention, the precursor material is preferably selected from gaseous, liquid or powdered precursor materials, the use of solid, in particular powdered precursor materials being preferred. The liquid precursor material can be a homogeneous solution or a dispersion, in particular also a solid-in-liquid dispersion.

In the context of the present invention, a precursor material is understood to mean a chemical compound or a mixture of chemical compounds which react under process conditions to the desired product materials, in particular materials containing silicon carbide.

The reaction to the target compounds can take place in a wide variety of ways. However, it is advantageously provided that the precursor compounds are gasified and split or decomposed under the action of energy, in particular under the action of a laser beam, if appropriate in the case of liquid or gaseous precursor materials, and as reactive Pass particles into the gas phase. Since silicon and carbon as well as doping or alloying elements are directly adjacent in the gas phase due to the special composition of the precursor, the silicon carbide or the doped silicon carbide or silicon carbide alloy, which only sublimates from 2,300 ° C, is separated. In particular, crystalline silicon carbide absorbs laser energy much less well than the precursor granulate and conducts heat very well, so that the defined silicon carbide compounds are deposited in a strictly local manner. Not Desired constituents of the precursor compound, on the other hand, preferably form stable gases, such as C0 ₂ , HCl, H ₂ 0 etc. and can be removed via the gas phase. In the context of the present invention, it is provided in particular that the precursor material is a solid precursor material, in particular a precursor granule. Particularly good results are obtained if the precursor granulate is not a powder mixture, in particular not a mixture of different precursor powders and / or granules. In the context of the invention, homogeneous granules, in particular precursor granules, are preferably used as precursor material for the process according to the invention.

In this way, the precursor granules can pass into the gas phase or the precursor compounds react to the desired target compounds by means of short exposure times of energy, in particular laser radiation, it not being necessary to sublimate individual particles of different inorganic substances with particle sizes in the mΐti range, the Components must then diffuse to form the corresponding compounds and alloys. Due to the homogeneous precursor granulate preferably used in the context of the present invention, the individual building blocks, in particular elements, of the target compound containing silicon carbide are homogeneously distributed and arranged in close proximity to one another, ie. H. less energy is required to produce the silicon carbide-containing compounds. This has the advantage that a multilayer structure of silicon carbide-containing material can be built up without the uppermost layer of the silicon carbide-containing material forming the substrate surface being heated to temperatures at which silicon carbide sublimes.

According to a preferred embodiment of the present invention, the precursor granules can be obtained from a precursor solution or a precursor dispersion, in particular a precursor sol. In the context of the present invention, the precursor granules are thus preferably finely divided from a liquid, in particular from a solution or dispersion. In this way, a homogeneous distribution of the individual components, in particular precursor compounds, can be achieved in the granulate, the stoichiometry of the silicon carbide-containing material to be produced preferably being pre-formed. If the precursor granules are obtainable from a solution or dispersion, in particular a gel, the precursor granules are obtained by drying the precursor solutions or dispersions or the resulting gel. As far as the particle sizes of the precursor granules are concerned, this can vary widely depending on the respective chemical compositions, the laser energy used and the properties of the material or object to be manufactured. In general, however, the precursor granules have particle sizes in the range from 0.1 to 150 pm, in particular 0.5 to 100 pm, preferably 1 to 100 pm, preferably 7 to 70 pm, particularly preferably 20 to 40 pm.

Particularly good results are obtained in the context of the present invention if the particles of the precursor granules have a D60 value in the range from 1 to 100 pm, in particular 2 to 70 pm, preferably 10 to 50 pm, preferably 21 to

35 pm. The D60 value for the particle size represents the limit below which the particle size of 60% of the particles of the precursor granules is below. H. 60% of the particles of the precursor granulate have particle sizes which are smaller than the D60 value.

In this context, it can equally be provided that the precursor granules have a bimodal particle size distribution. In this way, particularly precursor granules with a high bulk density are accessible. As already explained above, the method according to the invention is suitable for producing coatings or three-dimensional objects from a large spectrum of compounds containing silicon carbide. In the context of the present invention, the silicon carbide-containing compound is usually selected from silicon carbide, doped silicon carbide, non-stoichiometric silicon carbides, doped non-stoichiometric silicon carbide and silicon carbide alloys.

The method according to the invention can thus be used universally and is suitable for producing or depositing a large number of different silicon carbide compounds, in particular in order to specifically adjust their mechanical properties.

In the context of the present invention, a non-stoichiometric silicon carbide is understood to mean a silicon carbide which contains carbon and silicon not in a molar ratio of 1: 1, but in different ratios. In the context of the present invention, a non-stoichiometric silicon carbide usually has a molar excess of silicon. In the context of the present invention, silicon carbide alloys are to be understood as meaning compounds of silicon carbide with metals, such as, for example, titanium or also on their compounds, such as zirconium carbide or boron nitride, which contain silicon carbide in different and widely fluctuating proportions. Silicon carbide alloys often form high-performance ceramics, which are characterized by particular hardness and temperature resistance.

If a non-stoichiometric silicon carbide is produced in the context of the present invention, the non-stoichiometric silicon carbide is usually a silicon carbide of the general formula (I)

SiCi- _x (I)

With

x = 0.05 to 0.8, in particular 0.07 to 0.5, preferably 0.09 to 0.4, preferred

0.1 to 0.3.

Such silicon-rich silicon carbides have a particularly high mechanical strength and are suitable for a large number of applications as ceramics.

If, in the context of the present invention, the silicon carbide-containing compound is a doped silicon carbide, the silicon carbide is usually doped with an element selected from the group consisting of nitrogen, phosphorus, arsenic, antimony, boron, aluminum, gallium, indium and mixtures thereof. The silicon carbide is preferably doped with elements of the 13th and 15th group of the periodic table of the elements, as a result of which in particular the electrical properties of the silicon carbide could be manipulated and adjusted in a targeted manner. Doped silicon carbides of this type are particularly suitable for applications in semiconductor technology. As already stated above, the doped silicon carbide can be a stoichiometric silicon carbide or a non-stoichiometric silicon carbide, the doping of stoichiometric silicon carbides being preferred since these are increasingly being used in semiconductor technology. If a doped silicon carbide is produced in the context of the present invention, it has proven useful if the doped silicon carbide contains the doping element in amounts of 0.000001 to 0.0005% by weight, in particular 0.000001 to 0.0001% by weight .-%, preferably 0.000005 to 0.0001 wt .-%, preferably 0.000005 to 0.00005 wt .-%, based on the doped silicon carbide, ent. For the targeted adjustment of the electrical properties of the silicon carbide, extremely small amounts of doping elements are therefore completely sufficient. The quantities of the doping elements mentioned above apply to both stoichiometric and non-stoichiometric silicon carbides.

If the silicon carbide-containing compound produced in the context of the present invention is a silicon carbide alloy, the silicon carbide alloy is usually selected from MAX phases, alloys of silicon carbide with elements, in particular metals, and alloys of silicon carbide with metal carbides and / or metal nitrides. Such silicon carbide alloys contain silicon carbide in varying and strongly fluctuating proportions. In particular, it can be provided that silicon carbide is the main constituent of the alloys. However, it is also possible for the silicon carbide alloy to contain silicon carbide only in small amounts.

The silicon carbide alloy usually has the silicon carbide in amounts of 10 to 95% by weight, in particular 15 to 90% by weight, preferably 20 to 80% by weight, based on the silicon carbide alloy. Within the scope of the present invention, a MAX phase is to be understood as meaning carbides and nitrides of the general formula M _{n + i} AX _n with n = 1 to 3, which crystallize in hexagonal layers. M stands for an early transition metal from the third to sixth group of the periodic table of the elements, while A stands for an element of the 13th to 16th group of the periodic table of the elements. X is either carbon or nitrogen. Within the scope of the present invention, however, only those MAX phases are of interest whose sum formula contains silicon carbide (SiC), ie silicon and carbon.

MAX phases have unusual combinations of chemical, physical, electrical and mechanical properties, as they show both metallic and ceramic behavior depending on the conditions. This includes, for example, high electrical and thermal conductivity, high load Ability to withstand thermal shock, very high hardness and low thermal expansion coefficient.

If the silicon carbide alloy is a MAX phase, it is preferred if the MAX phase is selected from Ti ₄ SiC ₃ and Ti ₃ SiC.

In addition to the properties already described, the aforementioned MAX phases in particular are highly resistant to chemicals such as oxidation at high temperatures.

If the silicon carbide-containing compound is an alloy of the silicon carbide, it has proven itself in the event that the alloy is an alloy of silicon carbide with metals, if the alloy is selected from alloys of silicon carbide with metals from the group of Al, Ti, V, Cr, Mn, Co, Ni, Zn, Zr and their mixtures.

If the alloy of silicon carbide is selected from alloys of silicon carbide with metal carbides and / or nitrides, it has proven useful if the alloys of silicon carbide with metal carbides and / or nitrides is selected from the group of boron carbides, in particular B ₄ C, Chromium carbides, in particular Cr ₂ C3, titanium carbides, in particular TiC, molybdenum carbides, in particular Mo ₂ C, niobium carbides, in particular NbC, tantalum carbides, in particular TaC, vanadium carbides, in particular VC, zirconium carbides, in particular ZrC, tungsten carbides, in particular WC, boron nitride , especially BN, and their mixtures.

As far as the temperatures are concerned, at which precursor material gasifies and / or decomposes, it has proven to be useful if the precursor material, in particular the precursor granulate, in particular at least in regions at temperatures in the range from 1,600 to 2,100 ° C, in particular 1. 700 to 2,000 ° C, preferably 1,700 to 1,900 ° C, is heated. At the aforementioned temperatures, all components of the precursor material go into the gas phase and the precursor materials are decomposed into the desired reactive species, which then react to the target compounds.

As stated above, the use of solid, in particular powdery precursor materials is preferred. However, the method according to the invention can also be carried out with liquid or gaseous precursor materials. If gaseous precursor materials are used in the context of the present invention, the precursor materials are decomposed by the action of energy and at least some of the decomposed precursor materials are deposited in a location-selective manner on the substrate surface as silicon carbide-containing material.

If liquid or solid, in particular powdery precursor materials are used in the context of the present invention, these are usually gasified and decomposed and then at least some of the decomposition products are deposited in a location-selective manner on the substrate surface as a material containing silicon carbide. In the context of the present invention, location-selective deposition is understood to mean that the material is deposited locally to a location which, however, can change in the course of the method. The decomposition products are usually deposited on an area of 0.1 to 2 mm ² , in particular 0.5 to 1.5 mm ² , preferably 0.8 to 1, 2 mm ² .

Within the scope of the present invention, a locally sharply delimited, locally selective application of a silicon carbide-containing material on a substrate surface is possible.

Because, as the applicant has surprisingly found, it is possible to use three-dimensional objects made of materials containing silicon carbide or coatings of materials containing silicon carbide three-dimensionally in one, preferably by using precursor materials which have both a carbon and a silicon source Deposition welding to be carried out on lean processes.

While the problem with the use of silicon carbide is that it can be sublimed and not melted under normal conditions, it has been shown that by using suitable precursor materials by decomposing the precursor materials from the gas phase, location-selective materials containing silicon carbide, in particular, from the gas phase in the form of layers, can be deposited on substrate surfaces. The layer of silicon carbide-containing material can completely or only partially cover the substrate surface. If layers of material containing silicon carbide are applied repeatedly, an already completed layer of material containing silicon carbide is added to the substrate in the context of the present invention, its surface being surface where it covers a carrier material. In the context of the present invention, the substrate can have almost any three-dimensional structure. Through repeated and location-selective application, both targeted coating of objects can be carried out and three-dimensional objects can be created from materials containing silicon carbide. In addition, it is also possible not only to coat objects or components, but also to use silicon carbide-containing materials or to repair damage in the form of material defects.

Particularly good results are obtained within the scope of the present invention when powdered precursor materials are used. In this way, on the one hand, a high material application can be achieved in a layer thickness, on the other hand, powdery starting materials can be moved onto the substrate surface, for example by means of a nozzle, and gasified and decomposed by, for example, a laser beam without the decomposition products being deflected too strongly in their direction so that a location-selective order is still possible.

Within the scope of the present invention, as previously stated, it is usually provided that the silicon carbide-containing material is selected from optionally doped silicon carbide, optionally doped non-stoichiometric silicon carbide, silicon carbide alloys and mixtures thereof. The production of silicon carbide, in particular doped stoichiometric silicon carbide from precursor compounds, in particular powdery precursor compounds, is known in principle and is practiced, for example, in the context of German patent application 10 2015 105 085.4. So far, however, it is not known that it is possible to locally deposit almost any silicon carbide-containing materials by decomposing suitable starting compounds on a substrate and thus to create objects containing silicon carbide or to coat objects with materials containing silicon carbide.

In the context of the present invention, it is usually provided that the silicon carbide-containing material is deposited as a layer on the substrate surface. The deposition of the silicon carbide-containing material in the form of a layer is achieved in particular in that the location-selective deposition is carried out continuously or discontinuously at all desired and to be coated locations on the substrate surface. A continuous deposition can be obtained, for example, by continuously carrying out the method, the location of the deposition continuously changing, for example by selectively and continuously directing and moving a particle beam onto the substrate surface. In contrast, discontinuous application takes place, for example, by interrupting the deposition of silicon carbide-containing material and restarting the deposition at another point on the substrate surface.

The silicon carbide-containing material is usually deposited on the substrate surface with a layer thickness in the range from 0.01 to 5 mm, in particular 0.05 to 2 mm, preferably 0.1 to 1 mm. By applying a material with the layer thicknesses mentioned, three-dimensional objects made of silicon carbide-containing materials can be obtained in a short time by means of additive manufacturing, on the other hand, thin, yet resistant coatings with silicon carbide-containing materials are also possible. At the same time, almost any object can be joined using materials containing silicon carbide.

In the context of the present invention, it has proven to be useful if the precursor material, in particular the powdered precursor material, is moved in a finely divided and directed form, in particular in the form of at least one particle beam, in the direction of the substrate and before or when it hits the substrate Exposure to energy, in particular laser radiation, is gasified and decomposed or that the gaseous decomposition products are moved in the direction of the substrate, in particular in the form of a particle beam. In the context of the present invention, a particle beam is to be understood as a directed stream of particles or particles with a cross section which preferably remains constant and which preferably moves linearly. In the context of the present invention, the precursor materials or the decomposition products can be moved in one or more particle beams in the direction of the substrate surface and can meet, for example, in a focal point, for example the light beam from a laser, or on the substrate surface. The particle beam or the particle beams is or are preferably directed to the substrate surface. In the context of the present invention, it is therefore possible for the starting compounds to be moved in a finely divided form, preferably in the form of a finely divided powder, in particular a powder jet, in the direction of the substrate surface and before, in particular immediately before, or upon impact the substrate surface is gasified and decomposed by the action of energy, in particular by the action of a laser beam. In this way, the decomposition products are produced in the immediate vicinity of the surface to which they are applied and can be deposited on the cooler substrate surface in a preferably single-crystalline form. Alternatively, it is also possible for the decomposition products to be moved, for example, through a nozzle in the direction of the substrate surface and to be applied thereto, the decomposition products being deposited at least in part on the substrate surface as the desired silicon carbide-containing material. However, there is always a risk that larger agglomerates will form in the gas phase and that a less dense and homogeneous surface will be obtained.

In the context of the present invention, it can be provided that the partial beam has a cross section in the range from 0.1 to 2 mm ² , in particular 0.2 to 1.5 mm ² , preferably 0.5 to 1, 2 mm ² . The particle beam preferably has a cross section of 1 mm ² .

In the context of the present invention, it is usually provided that the energy is brought about by thermal energy, in particular an increase in temperature, in particular by means of resistance heating, arcing or radiation energy, preferably arcing or radiation energy, preferably by means of laser radiation.

As far as the energy input is concerned, it has proven useful if the energy input takes place, in particular by means of laser radiation, with a resolution of 0.1 to 150 pm, in particular 1 to 100 pm, preferably 10 to 50 pm. In this way, a high energy input can be guaranteed in a narrowly limited space, so that the precursors are completely gasified or decomposed.

A special feature of the method according to the invention is to be seen in particular in that it does not require subsequent sintering steps, ie in the context of the present invention the precursors are selected and in particular matched to the method implementation in such a way that directly from the Gaseous phase a homogeneous, compact three-dimensional body is obtained, which does not have to be subjected to sintering.

In the context of the present invention, it is preferred if the precursor material, in particular the powdery precursor material, or the gaseous decomposition products is or are moved in the direction of the substrate by means of at least one nozzle. By using a nozzle, it is in particular possible to obtain a sharply defined particle beam, preferably from gaseous particles or from powder particles, which are applied to the substrate surface in a location-selective manner. The nozzle is particularly preferably a powder nozzle or a gas nozzle.

The nozzle can either be arranged coaxially, for example, a laser beam, or laterally. In the coaxial arrangement, the laser beam and nozzle are usually in a processing head or an assembly, the laser beam being directed almost perpendicularly to the substrate surface and the partial beam intersecting it or several particle beams cutting the axis of the laser beam at a focal point . In the lateral arrangement, the laser beam is usually also arranged and movable perpendicular to the substrate surface, a particle stream being injected laterally into the axis of the laser beam.

As stated above, the use of powdered precursor materials is preferred, although gaseous or liquid precursor materials can also be used.

In the context of the present invention, it is usually provided that the powdered precursor material is moved in the form of a powder jet in the direction of the substrate or that the liquid precursor material is moved in atomized form or as a liquid jet in the direction of the substrate, but preferably always in the form of a particle beam . Furthermore, it is possible that the gaseous precursor material is moved in the form of a gas stream in the direction of the substrate. Alternatively, it is also possible for the gaseous decomposition products to be moved in the direction of the substrate in the form of a gas jet.

The method according to the invention is suitable for producing a large number of three-dimensional objects or for coating objects with materials containing silicon carbide. In the context of the present invention, it is particularly particularly preferred if the method is used for layer-by-layer construction of a three-dimensional object containing silicon carbide and / or for joining at least two components. The method according to the invention can thus be a generative production method on the one hand, but can also be used on the other hand as a joining method for connecting objects or for repairing objects.

According to a particularly preferred embodiment of the present invention, the method is laser deposition melting or a method based on laser deposition melting, in which the precursor materials are gasified and / or decomposed before or until contact with the substrate surface.

In the context of the present invention, it is preferred if the precursor material, in particular the powdered precursor material, is gasified and decomposed in the vicinity of the substrate surface by means of laser radiation, in particular in the immediate vicinity of the substrate surface. In this way side reactions and undesired agglomerations in particular are prevented. In the context of the present invention, moreover, the substrate is heated only very slightly by the energy introduced, in particular by the laser beam, so that, on the one hand, the silicon carbide-containing material can be applied as stress-free as possible.

It is usually provided that the gasification and decomposition of the powdered starting material and the deposition of the silicon carbide-containing material, preferably the entire process, is carried out in a protective gas atmosphere. In this way, undesired oxidation by oxygen is prevented.

If the process according to the invention is carried out in a protective gas atmosphere, it has proven useful if the process is carried out in a nitrogen and / or argon atmosphere, preferably an argon atmosphere. The method according to the invention is generally carried out in a protective gas atmosphere so that, in particular, carbon-containing precursor compounds are not oxidized. If the process is carried out in an argon atmosphere, it is usually also an inert gas atmosphere, since argon does not react with the precursor compounds under the process conditions. If nitrogen is used as the protective gas, silicon nitrides in particular can also be used be formed. This may be desirable, for example, in the case of an additionally mixed doping of the silicon carbide with nitrogen.

If incorporation of nitrogen into the silicon carbide or into the compound containing silicon carbide is not desired, however, the process according to the invention is carried out in an argon atmosphere.

According to a preferred embodiment, it is provided that the particle beam and / or the particle steels are surrounded by a protective gas stream. The particle streams are thus encased by a protective gas stream, which prevents a reaction with the surrounding atmosphere. In this way it is also possible, for example, to coat larger objects by means of silicon carbide-containing material, which cannot easily be transferred into a chamber filled with protective gas.

The method according to the invention in particular allows the simple production of almost any silicon carbide-containing materials - in particular from non-stoichiometric silicon carbides to silicon carbide-containing alloys for high-performance ceramics - from a large number of precursor materials.

Suitable precursor materials are described in more detail below.

In the context of the present invention it can be provided, for example, that precursor materials are used which are either mixtures of liquid and / or gaseous carbon and silicon sources, ie compounds which release carbon or silicon or reactive intermediates under reaction conditions, or liquid solutions or dispersions containing the carbon and silicon sources. If liquid and / or gaseous carbon sources are used as precursor materials in the context of the present invention, it can be provided that the liquid and / or gaseous carbon source is selected from alkanes, amines, alkyl halides, aldehydes, ketones, carboxylic acids, amides, carboxylic acid esters and their mixtures, in particular C to C ₈ alkanes, primary and secondary C to C 4 alkylamines, C to C ₈ alkyl halides, Cr to Cs aldehydes, C to C ₈ ketones, Cr to C ₈ carboxylic acids, C to C ₈ amides, Cr to C ₈ carboxylic acid esters and mixtures thereof. Particularly good results are obtained in this connection if the gaseous and / or liquid carbon source is selected from C to Cs alkanes, in particular Cr to Cr alkanes, and mixtures thereof. In the context of the present invention, it is therefore preferred if the gaseous or liquid carbon source is a short-chain and thus readily volatile alkane. In particular when using oxygen-containing functional groups, care must be taken to ensure that the excess of carbon is so high that carbon is always oxidized to carbon monoxide or carbon dioxide and silicon is not oxidized to silicon dioxide or silicon dioxide is immediately reduced again by carbon. is adorned because silicon dioxide would significantly disrupt the structure and function of the silicon carbide-containing fibers or foams.

In the context of the present invention, it has also proven useful if the liquid and / or gaseous silicon source is selected from silanes, siloxanes and mixtures thereof, preferably silanes.

If siloxanes are used as precursors in the context of the present invention, it is possible when selecting suitable siloxanes that the siloxane or the siloxanes represent or represent both the carbon source and the silicon source and no further precursors with the exception of possible doping - or alloy reagents must be used.

However, solid, in particular special powdery, precursor materials are preferably used in the context of the present invention. The solid precursor materials are usually in the form of a precursor granulate containing at least one silicon source,

at least one carbon source and

possibly precursors for doping and / or alloying elements.

In the case of precursor granules, the silicon source is usually selected from silane hydrolyzates and silicas and their mixtures. In the context of the present invention, the silicon source, ie the precursor of the silicon in the silicon carbide-containing compound, is obtained in particular by hydrolysis of tetraalkoxysilanes, as a result of which the silicon is preferably present in the precursor granules in the form of silicic acid or silane hydrolyzates. As far as the carbon source in the precursor granules is concerned, this is usually selected from the group of sugars, in particular sucrose, glucose, fructose, invert sugar, maltose; Strength; Starch derivatives and organic polymers, in particular phenol-formaldehyde resin, resorcinol-formaldehyde resin, and their mixtures and / or their reaction product, in particular sugars and / or their reaction products. The carbon source is particularly preferably selected from sugars and their reaction products, preference being given to using sucrose and / or invert sugar and / or their reaction products. In the case of the carbon source as well, not only the actual reagent but also its reaction or reaction product can be used.

If a (stoichiometric) silicon carbide is produced with the precursor granules, the composition usually contains

(A) the silicon source in amounts of 40 to 60% by weight, preferably 45 to 55% by weight, based on the composition,

(B) the carbon source in amounts of 40 to 60% by weight, preferably 45 to 55% by weight, based on the composition, and

(C) optional precursors of doping elements.

The precursors for the doping elements are usually contained only in very small amounts, in particular in the ppm range, in the precursor granules.

If the precursor granulate is used to produce a non-stoichiometric silicon carbide, the composition usually contains

(A) the silicon source in amounts of 60 to 90% by weight, in particular 65 to 85% by weight, preferably 70 to 80% by weight, based on the composition,

(B) the carbon source in amounts of 10 to 40 wt .-%, in particular 15 to

35 wt .-%, preferably 20 to 30 wt .-%, based on the composition, and

(C) optional precursors for doping elements. With precursor granules, which have the carbon source and the silicon source in the abovementioned quantity ranges, non-stoichiometric silicon carbides with an excess of silicon can be produced in an excellent manner.

If the precursor granulate is used to produce a silicon carbide alloy, the composition usually contains

(A) the silicon source in amounts of 5 to 40% by weight, in particular 5 to 30% by weight, preferably 10 to 20% by weight,

(B) the carbon source in amounts of 10 to 60% by weight, in particular 15 to 50% by weight, preferably 20 to 50% by weight, and

(C) one or more alloy element precursors in amounts of 5 to

70% by weight, in particular 5 to 65% by weight, preferably 10 to 60% by weight, in each case based on the composition. A preferably used precursor granulate can be obtained from a precursor solution or a precursor dispersion. In this context, it is particularly preferred if the precursor granules can be obtained by a sol-gel process or by drying a sol. Sol-gel processes usually produce solutions or finely divided solid-in-liquid dispersions, which are converted into a gel which contains larger solid particles by subsequent aging and the condensation processes that occur.

After drying the gel or the sol, a particularly homogeneous composition, in particular a suitable precursor granulate, can be obtained, with which the desired silicon carbide-containing compounds can be obtained under the influence of energy in additive manufacturing with the choice of suitable stoichiometry.

Furthermore, it can be provided that the precursor granules are converted into reduced precursor granules by thermal treatment under reductive conditions. The reductive thermal treatment usually takes place in an inert gas atmosphere, the carbon source in particular, preferably a sugar-based carbon source, reacting with oxides or other compounds of silicon and possibly other compounds of other elements, as a result of which the elements are reduced and volatile oxidized carbon and water Hydrogen compounds, especially water and CO2, are formed, which are removed via the gas phase.

Precursor granules can be produced in particular by a sol-gel process, wherein

(i) in a first process step containing a solution or dispersion, in particular a sol

(I) at least one silicon-containing compound,

(II) at least one carbon-containing compound,

(III) at least one solvent or dispersant and

(IV) optionally doping and / or alloying reagents,

will be produced,

(ii) in a second process step following the first process step (i), the solution or dispersion is reacted, in particular is aged to a gel, and

(iii) in a third process step following the second process step (ii), the reaction product from the second process step (ii), in particular the gel, is dried and optionally comminuted.

A method for producing a suitable precursor granulate for producing silicon carbide by means of a sol-gel method is mentioned, for example, in German patent application DE 10 2015 105 085.4.

In the context of the present invention, a solution is to be understood as a single-phase system in which at least one substance, in particular a compound or its components, such as ions, is present in a homogeneous distribution in another substance. In the context of the present invention, a dispersion is to be understood as an at least two-phase system, a first phase, namely the dispersed phase, being distributed in a second phase, the continuous phase. The continuous phase is also called dispersion medium or dispersant. The transition from a solution to a dispersion is often fluid, particularly in the case of brines or polymeric compounds, so that it is no longer possible to clearly differentiate between a solution and a dispersion. As far as the selection of the solvent or dispersing agent in process step (a) is concerned, this can be selected from all suitable solvents or dispersing agents. In process step (a), however, the solvent or dispersant is usually selected from water and organic solvents and also their mixtures, preferably their mixtures. In particular in the case of mixtures containing water, inorganic hydroxides, in particular metal hydroxides and silicas, are often formed by the hydrolysis reaction of the starting compounds, which subsequently condense, so that the process can be carried out either in the form of a sol-gel process or else on the Level of a sol is stopped.

In addition, it can be provided that the solvent is selected from alcohols, in particular methanol, ethanol, 2-propanol, acetone, ethyl acetate and mixtures thereof. In this context it is particularly preferred if the organic solvent is selected from methanol, ethanol, 2-propanol and mixtures thereof, ethanol being particularly preferred.

The aforementioned organic solvents are miscible with water in a wide range and are also particularly suitable for dispersing or dissolving polar inorganic substances.

Mixtures of water and at least one organic solvent, in particular mixtures of water and ethanol, preferably as solvents or dispersants, are preferably used to produce the sol or gel. In this context, it is preferred if the solvent or dispersion medium prefers a weight-based ratio of water to organic solvent of 1:10 to 20: 1, in particular 1: 5 to 15: 1, preferably 1: 2 to 10: 1 1: 1 to 5: 1, particularly preferably 1: 3. The ratio of water to organic solvent can be used on the one hand to adjust the rate of hydrolysis, in particular of the silicon-containing compound and of the alloying reagents, and on the other hand also to adjust the solubility and reaction speed of the carbon-containing compound, in particular the carbon-containing precursor compound, such as, for example, sugars.

It is also preferred if, in the process for producing the precursor granulate in process step (i), the silicon-containing compound is selected from silanes, silane hydrolyzates, orthosilicic acid and mixtures thereof, in particular special silanes. In the context of the present invention, orthosilicic acid and also its hydrolysis products can be obtained, for example, from alkali silicates whose alkali metal ions have been exchanged for protons by ion exchange. Alkali metal compounds are, however, not used in the context of the present invention, if possible, since these, particularly when using a sol-gel process or when the sol dries, the resulting precursor granules are incorporated and consequently can also be found in the compound containing silicon carbide. However, alkali metal doping is generally not desirable in the context of the present invention. However, if this should be desired, suitable alkali metal salts, for example the silicon-containing compound or also alkali metal phosphates, can be used.

Particularly good results are obtained in the context of the present invention when silanes, in particular tetraalkoxysilanes and / or trialkoxyalkylsilanes, preferably tetraethoxysilane, tetramethoxysilane or triethoxymethylsilane, are used as the silicon-containing compound in process step (i), since these compounds are hydrolysed in an aqueous medium Orthosilicic acids or their condensation products or highly cross-linked siloxanes and the corresponding alcohols react.

As far as the carbon-containing compound is concerned, it has proven useful if in process step (i) the carbon-containing compound is selected from the group of sugars, in particular sucrose, glucose, fructose, invert sugar, maltose; Strength; Starch derivatives and organic polymers, especially phenol-formaldehyde resin, resorcinol-formaldehyde resin, and mixtures thereof. Particularly good results are obtained within the scope of the present invention if the carbon-containing compound is used in an aqueous solution or dispersion in process step (i). If the carbon-containing compound is used in particular in an aqueous solution or dispersion, the carbon-containing compound is usually introduced in a small amount of the solvent or dispersion medium, in particular water, provided for the preparation of the precursor granules in process step (i). In this connection, particularly good results are obtained if the carbon-containing compound is used in a solution which contains the carbon-containing compound in amounts of 10 to 90% by weight, in particular 30 to 85% by weight, preferably 50 to 80% by weight. %, especially 60 to 70% by weight, based on the solution or dispersion of the carbon-containing compound, contains.

In particular, it is also possible, for example, to add catalysts, in particular acids or bases, to the solution or dispersion of the carbon-containing compound, for example in order to accelerate the inversion of sucrose and to achieve better reaction results.

With regard to the temperatures at which process step (i) is carried out, it has proven useful if process step (i) at temperatures in the range from 15 to 40 ° C., in particular 20 to 30 ° C., preferably 20 to 25 ° C.

Furthermore, it is possible that in process step (ii) the temperatures are slightly increased compared to process step (i) in order to reduce the reaction of the individual constituents of the solution or dispersion, in particular the condensation reaction when the sol ages to form a gel. to accelerate.

Particularly good results are obtained in this connection if process step (ii) is carried out at temperatures in the range from 20 to 80 ° C., in particular 30 to 70 ° C., preferably 40 to 60 ° C. In this context, it has proven particularly useful if process step (ii) is carried out at 50 ° C. With regard to the time span for which process step (ii) is carried out, this can vary depending on the respective temperatures, the solvents used and the precursor compounds used. However, process step (ii) is usually carried out for a period of 15 minutes to 20 hours, in particular 30 minutes to 15 hours, preferably 1 to 10 hours, preferably 2 to 8 hours, particularly preferably 2 to 5 hours. If the process is carried out as a sol-gel process, a complete reaction of the sol to a gel is usually observed within the aforementioned periods. As far as the quantities of the individual components in process step (ii) are concerned, this can vary widely depending on the intended use. For example, the precursor compositions for stoichiometric silicon carbide or non- stoichiometric silicon carbides have completely different compositions and proportions of the individual components than compositions which are intended for the production of silicon carbide alloys. When selecting the individual compounds, in particular the doping reagents or alloy reagents, care must also be taken that they can be processed into homogeneous granules with a carbon source and a silicon source, which can react in additive manufacturing processes to form compounds containing silicon carbide.

In particular, care should preferably be taken to ensure that the doping and / or alloying reagents decompose or split under the action of energy in such a way that the desired elements desublimate as reactive particles to form the desired alloy, while the other constituents of the compound form stable gaseous substances, if possible, such as water, CO, CO2, HCl etc., which can be easily removed via the gas phase. In addition, the compounds used should have sufficiently high solubilities in the solvents used, in particular in ethanol and / or water, in order to be able to form finely divided dispersions or solutions, in particular brine, and must not be used with other components of the solution during the production process the dispersion, especially the sol, react to form insoluble compounds. In addition, the reaction rates of the individual reactions taking place must be coordinated with one another, since the hydrolysis, condensation and, in particular, the gelation which may have been carried out must take place undisturbed before the formation of the granules. The reaction products formed must furthermore not be sensitive to oxidation and, moreover, should not be volatile.

Furthermore, it can be provided that the solution or dispersion contains at least one doping and / or alloying reagent. If the solution contains a doping and / or alloying reagent, it has proven useful if the solution or dispersion contains the doping or alloying reagent in amounts of 0.000001 to 60% by weight, in particular 0.000001 to 45% by weight %, preferably 0.000005 to 45% by weight, preferably 0.00001 to 40% by weight, based on the solution or dispersion.

If the solution or dispersion has a doping reagent, the solution or dispersion usually has the doping reagent in amounts of 0.000001 to 0.5% by weight, preferably 0.000005 to 0.1% by weight, preferably 0.00001 to 0.01% by weight, based on the solution or dispersion.

If the solution or dispersion contains an alloy reagent, it is usually provided that the solution or dispersion contains the alloy reagent in amounts of 5 to 60% by weight, in particular 10 to 45% by weight, preferably 15 to 45% by weight. -%, preferably 20 to 40 wt .-%, based on the solution or dispersion, contains. As far as the chemical nature of the doping reagent is concerned, it can be selected from suitable doping elements. The doping reagent or the doping element is preferably selected from elements of the third and fifth main groups of the periodic table. The doping reagent is preferably selected from compounds of an element of the third or fifth main group of the Periodic Table of the Elements, which is soluble in the solvent or dispersant. The doping reagent is usually selected from nitric acid, ammonium chloride, melamine, phosphoric acid, phosphonic acids, boric acid, borates, boron chloride, indium chloride and mixtures thereof. If doping with nitrogen is provided, the solution may contain nitric acid, ammonium chloride or melanin. If doping with phosphorus is provided, phosphoric acid or phosphates or phosphonic acids can be used, for example. If doping with boron is provided, boric acids, borates or boron salts such as boron trichloride, for example, are used.

If indium is doped, water-soluble indium salts, such as indium chloride, are usually used as the doping reagent.

If the solution or dispersion contains an alloy reagent, the alloy reagent is usually selected from compounds of Al, Ti, V, Cr, Mn, Co, Ni, Zn, Zr and mixtures thereof which are soluble in the solvent or dispersion medium. According to a preferred embodiment of the present invention, the alloy reagent is selected from chlorides, nitrates, acetates, acetylacetonates and formates of Al, Ti, V, Cr, Mn, Co, Ni, Zn, Zr and mixtures thereof. If a stoichiometric silicon carbide SiC, which is optionally doped, is to be obtained, particularly good results are obtained if the solution or dispersion in the first process step contains the silicon-containing compound in amounts of 10 to 40% by weight, in particular 12 to 30% by weight. -%, preferably 15 to 25 wt .-%, preferably 17 to 20 wt .-%, based on the solution or dispersion.

Equally, it can be provided according to this embodiment that the solution or dispersion contains the carbon-containing compounds in amounts of 6 to 40% by weight, preferably 8 to 30% by weight, preferably 10 to 25% by weight, particularly preferably 12 up to 20 wt .-%, based on the solution or dispersion.

In addition, it can be provided according to this embodiment that the solution or dispersion be the solvent or dispersant in amounts of 20 to 80% by weight, in particular 30 to 70% by weight, preferably 40 to 60% by weight preferably 45 to 55 wt .-%, based on the solution or dispersion.

If the silicon carbide is to be doped, the solution or dispersion usually contains the doping reagent in amounts of 0.000001 to 0.5% by weight, preferably 0.000005 to 0.1% by weight, preferably 0.00001 to 0 , 01 wt .-%, based on the solution or dispersion.

If a non-stoichiometric silicon carbide, in particular with a molar excess of silicon, is to be obtained, it has proven useful if the solution or dispersion in the first process step (a) contains the silicon-containing compound in amounts of 12 to 40% by weight. , in particular 15 to 40% by weight, preferably 18 to 35% by weight, preferably 20 to 30% by weight, based on the solution or dispersion.

According to this embodiment, it may further be provided that the solution or dispersion contains the carbon-containing compound in amounts of 6 to 40% by weight, preferably 8 to 30% by weight, preferably 10 to 25% by weight, particularly preferably 12 to 20 wt .-%, based on the solution or dispersion.

In addition, according to this embodiment, it can equally be provided that the solution or dispersion contains the solvent or dispersion medium in amounts of 20 to 80% by weight, in particular 30 to 70% by weight, preferably 40 to 60 wt .-%, preferably 45 to 55 wt .-%, based on the solution or dispersion, contains.

If the non-stoichiometric silicon carbide is to be doped, it has proven useful if the solution or dispersion contains the doping reagent in amounts of 0.000001 to 0.5% by weight, preferably 0.000005 to 0.1% by weight. -%, preferably 0.00001 to 0.01 wt .-%, based on the solution or dispersion.

If a silicon carbide alloy is to be produced, it has proven useful if the solution or dispersion in the first process step (a) contains the silicon-containing compound in amounts of 5 to 30% by weight, in particular 6 to 25% by weight, preferably 8 to 20 wt .-%, preferably 10 to 20 wt .-%, based on the solution or dispersion. Likewise, it is preferred according to this embodiment if the solution or dispersion contains the carbon-containing compound in amounts of 5 to 40% by weight, preferably 6 to 30% by weight, preferably 7 to 25% by weight, particularly preferably 10 to 20% by weight, based on the solution or dispersion. Furthermore, it is preferred according to this embodiment if the solution or dispersion contains the solvent or dispersion medium in amounts of 20 to 70% by weight, in particular 25 to 65% by weight, preferably 30 to 60% by weight, preferably 35 up to 50 wt .-%, based on the solution or dispersion. It is advantageously provided that the solution or dispersion contains the alloy reagent in amounts of 5 to 60% by weight, in particular 10 to 45% by weight, preferably 15 to 45% by weight, preferably 20 to 40% by weight , based on the solution or dispersion. It is particularly preferred if the alloy reagent is selected from the corresponding chlorides, nitrates, acetates, acetylacetonates and formates of the corresponding alloy elements.

As far as the implementation of process step (iii) is concerned, it has proven itself if, in process step (iii), the reaction product from process step (ii) at temperatures in the range from 50 to 400 ° C., in particular 100 to 300 ° C. preferably 120 to 250 ° C, preferably 150 to 200 ° C, is dried. In this context, it has proven useful if the reaction product in process step (iii) is dried for a period of 1 to 10 hours, in particular 2 to 5 hours, preferably 2 to 3 hours. In addition, it is possible for the reaction product to be comminuted in process step (iii), in particular after the drying process. In this context, it is particularly preferred if the reaction product is mechanically comminuted in process step (iii), in particular by grinding. Grinding processes can be used to specifically set the particle sizes required or advantageous for carrying out additive manufacturing processes. However, it is often also sufficient to mechanically stress the reaction product from process step (ii) during the drying process, for example by stirring, in order to set the desired particle sizes. Preferably, a fourth process step (iv) following process step (iii) is subjected to a reductive thermal treatment in the composition obtained in process step (iii), so that a reduced composition is obtained. The use of a reduced composition which has been subjected to a reductive treatment has the advantage that a large number of possible and disruptive by-products have already been removed. The resulting reduced precursor granulate is again significantly more compact and contains higher proportions of the elements that form the silicon carbide-containing compound.

If, following process step (iii), a reductive thermal treatment of the composition obtained in process step (iii) is carried out, it has proven useful if in process step (iv) the composition obtained in process step (iii) is heated to temperatures in the range from 700 to 1 .300 ° C, in particular 800 to 1,200 ° C, preferably 900 to 1,100 ° C, is heated. In this context, particularly good results are obtained if the composition obtained in process step (iv) is heated for a period of 1 to 10 hours, in particular 2 to 8 hours, preferably 2 to 5 hours. In the temperature ranges mentioned and the reaction times mentioned, carbonization of the carbon-containing precursor material can take place, which can significantly facilitate the subsequent reduction, in particular of metal compounds. Process step (iv) is generally carried out in a protective gas atmosphere, in particular in an argon and / or nitrogen atmosphere. In this way it is prevented that in particular the carbon-containing compound is oxidized.

If the above-described reducing thermal treatment of the precursor granules is provided in order to obtain a reduced precursor granulate, the precursor compounds must not evaporate at the temperatures used of up to 1,300, preferably up to 1,100 ° C, but must be below that reductive thermal conditions specifically break down into compounds which can be specifically converted into the desired silicon carbide-containing compounds during production.

Alternatively, the method for producing a precursor granulate can also be carried out in such a way that

(I) in a first process step, a solution or dispersion, in particular a sol, containing the components

(A) at least one silicon-containing compound,

(B) at least one carbon-containing compound,

(C) at least one solvent or dispersant and

(D) optionally doping and / or alloying reagents,

is manufactured, and

(II) in a second process step following the first process step (i), the solvent or dispersant is removed.

Because, as was surprisingly found, it is often possible to do without a solo gel process. In particular, comparable precursor granules can often be obtained if the solvent or dispersion medium is removed after the formation of the sol, for example in vacuo.

The precursor granules obtained in this way can be converted into reduced precursor granules by temperature treatment in the range from 400 to 800 ° C. The percentage distribution of the precursor granules obtained after the sol formation by removing the solvent or dispersion medium corresponds to that contained Elements of the precursor granules obtained by a sol-gel process and can be processed like these.

The figure descriptions according to

1 shows a device according to the invention for carrying out the method according to the invention with a pulse arranged laterally to the laser beam,

Fig. 2 shows a section of a device 1 according to the invention with coaxial powder feeds and

3 shows an example of the result of the method according to the invention in the form of a three-dimensional object and according to (b) an example of the result of carrying out the method according to the invention as a joining method.

Another object of the present invention - according to a second aspect of the present invention - is a silicon carbide-containing object which can be obtained by the process described above.

With the method according to the invention, objects containing silicon carbide can be produced by means of additive manufacturing. Equally, however, it is also possible for objects to be coated with a material containing silicon carbide or for parts to be joined using the method according to the invention.

For further details on the object containing silicon carbide according to the invention, reference can be made to the above statements regarding the method according to the invention, which apply accordingly with respect to the object containing silicon carbide.

Finally, another object of the present invention - according to a third aspect of the present invention - is a device for the location-selective deposition of silicon carbide-containing materials on a substrate surface, the device

(a) at least one device for the decomposition of gaseous starting compounds or for the gasification and decomposition of liquid or powder raw materials, the raw materials containing at least one carbon source and at least one silicon source, and

(b) has at least one device for generating at least one particle beam and / or for aligning a particle beam onto the substrate surface.

It is crucial in the context of the present invention that the gaseous decomposition products of at least one silicon source and at least one carbon source-containing precursor materials are directed in a location-selective and localized manner onto a substrate surface, so that materials containing silicon carbide are deposited on the substrate surface. As already stated above, the method according to the invention is preferably carried out as laser cladding or as a method based on laser cladding. To carry out the method, preference is given to using devices which largely correspond to those for powder laser cladding. In the context of the present invention, best results are obtained in particular if the particle beam is a powder. In this way it is ensured that, on the one hand, a relatively large amount of material arrives on the substrate surface and, on the other hand, the energy of the laser beam is also absorbed far better by the solid precursor material than, for example, by a gaseous starting material. As a result, heating of the substrate surface is largely avoided and good deposition of silicon carbide-containing material on the substrate surface is achieved.

In the context of the present invention, as already stated above, it is preferably provided that the starting materials are only decomposed in the vicinity of the substrate surface, which is easiest to achieve by using powdered starting materials.

In the context of the present invention, it is advantageously provided that the device for generating a particle beam and / or for aligning a particle beam onto a substrate surface is a nozzle, in particular a solid nozzle, preferably a powder nozzle. As already explained above, the best results are obtained in the context of the present invention if the starting materials or the precursor materials are in the form of a powder. In the context of the present invention, it is also advantageously provided that the device for the decomposition of gaseous starting compounds or for the gasification and decomposition of liquid or powdery starting materials has means for generating high temperatures, in particular means for generating laser radiation or means for generating of an arc.

By using an arc or laser radiation, preferably laser radiation, the starting materials can be easily decomposed in the vicinity of the substrate surface.

According to a preferred embodiment of the present invention, it is provided that the device for the decomposition of gaseous precursor materials or for the gasification and decomposition of liquid or powdery precursor materials has means for generating laser radiation. The device for decomposing gaseous starting compounds or for gasifying and decomposing liquid or powdered starting materials is preferably a laser.

Furthermore, it is usually provided that the device has means for generating a protective gas atmosphere. In order to prevent undesired oxidation of the gaseous decomposition products by atmospheric oxygen, the process according to the invention is usually carried out in a protective gas atmosphere. It can either be provided that part of the device, in particular the part that contains the substrate, has a protective gas atmosphere. Alternatively and preferably, however, it is provided that the particle beam, for example the powder jet, is encased by a protective gas and thus a protective gas atmosphere is generated locally, in particular in the area of gasification and decomposition of the starting materials.

For further details, reference can be made to the above explanations regarding the further aspects of the invention, which apply accordingly in relation to the device according to the invention.

The subject matter of the present invention is illustrated below by way of example and in a non-limiting manner by the description of the figures. 1 shows a device according to the invention with a device for gasifying and / or decomposing precursor materials, in particular a device 2 for generating laser beams 3. Furthermore, the device has at least one device 4 for generating a particle beam from gaseous, liquid or solid precursor materials 5. The particle stream is preferably formed by powdered precursor materials. All precursor materials, however, have in common that they always have at least one silicon source and one carbon source as well as possibly alloy elements or doping elements or their compounds.

The laser beams 3 and the particle stream of the precursor material 5 are directed onto the surface 7 of a substrate 8 in such a way that the laser beams 3 hit the partial stream in the immediate vicinity of the substrate surface 7. This causes the precursor materials 5 contained in the particle stream to be decomposed or gasified and decomposed, whereby reactive fragments are obtained which separate as a desired silicon carbide material in the form of a layer of a silicon carbide-containing material 6 on the substrate surface 7.

The thickness of the layer of silicon carbide-containing material 6 can be between 0.01 to 5 mm, in particular 0.5 to 2 mm, preferably 0.1 to 1 mm.

The method according to the invention with the aid of device 1 thus allows a layer 6 of a material containing silicon carbide to be applied in a location-selective and locally sharply delimited manner. By movement, in particular method, of the substrate 8, or the devices 2 and 4, either a three-dimensional object with a multilayer structure can be obtained or the substrate surface 7 can be coated with a layer of the silicon carbide-containing material 6 in the desired manner. FIG. 2 shows an alternative embodiment of the device 1 according to the invention. In particular, FIG. 2 shows a section of a device 1. The device 1 has a device 2 for gasifying and / or decomposing gaseous, liquid or powdered precursor materials 5, the device 2 for gasifying and / or decomposing the starting materials preferably being in the form of a device for generating laser beams 2.

The device 1 also has devices 4 for generating a particle beam, in particular from gaseous, liquid or powdery starting materials. materials, in particular powdered starting materials. With the embodiments shown in FIG. 2, the devices 2 and 4 are integrated together in a preferably movable, in particular movable, nozzle head.

The particle beam from the precursor material 5, in particular the particle beam len 5, surround the laser beam 3 and cross it shortly before striking the surface 7 of a substrate 8, as a result of which the precursor materials decompose and a layer of a silicon carbide-containing material 6 is deposited on the substrate surface 7.

The device 1 also has means 9, in particular nozzles, for generating a protective gas atmosphere, in particular a protective gas stream 10. The protective gas stream 10 surrounds or surrounds the particle beam or the particle beams of the precursor material 5 and thus enables the starting materials to be decomposed in a protective gas atmosphere, in particular an argon atmosphere.

FIG. 3 finally shows various possible uses of the device 1 according to the invention and of the method according to the invention. In particular, three-dimensional objects can be obtained by repeated application of layers of silicon carbide-containing material 6, as shown in alternative A. Equally, it is also possible, by applying the silicon carbide-containing material 6, to connect components, in particular substrates 8a and 8b, via their surfaces, in particular their surfaces 7a and 7b.

List of reference numerals: device 5 precursor material

Device for producing 10 6 silicon carbide-containing material laser beams 7 substrate surface

Laser beams 8 substrate

Device for generating a

Particle beam

Claims

Claims:

1 . Process for applying silicon carbide-containing materials to a substrate surface,

characterized,

that a gaseous, liquid or powdery precursor material containing a silicon source and a carbon source is gasified and / or decomposed by the action of energy and at least some of the decomposition products are locally selectively deposited on the substrate surface as silicon carbide-containing material.

2. The method according to claim 1, characterized in that the silicon carbide-containing material is selected from optionally doped silicon carbide, optionally doped non-stoichiometric silicon carbide, silicon carbide alloys and mixtures thereof.

3. The method according to claim 1 or 2, characterized in that the silicon carbide-containing material is deposited as a layer on the substrate surface.

4. The method according to any one of the preceding claims, characterized in that the silicon carbide-containing material with a layer thickness in the range of 0.01 to 5 mm, in particular 0.05 to 2 mm, preferably 0.1 to 1 mm, deposited on the substrate becomes.

5. The method according to any one of the preceding claims, characterized in that the precursor material, in particular the powdered precursor material, in finely divided form, in particular in the form of at least one partial beam, is moved in the direction of the substrate, in particular the substrate surface, and before or gasified and decomposed when it hits the substrate by the action of energy, in particular laser radiation, or that the gaseous decomposition products are moved in the direction of the substrate, in particular in the form of at least one particle beam.

6. The method according to claim 5, characterized in that the precursor material, in particular the powdered precursor material, or the gas shaped decomposition products is moved in the direction of the substrate by means of at least one nozzle.

7. The method according to claim 5 or 6, characterized in that the powdered precursor material in the form of a powder jet in the direction of

Substrate is moved or that the liquid precursor material in atomized form or as a liquid jet is moved in the direction of the substrate or that the gaseous precursor material or the gaseous decomposition products in the form of a gas jet are moved in the direction of the substrate.

8. The method according to any one of the preceding claims, characterized in that the method is used for layer-by-layer construction of a three-dimensional object containing silicon carbide and / or for joining at least two components.

9. The method according to any one of the preceding claims, characterized in that the method is laser deposition welding.

10. The method according to claim 9, characterized in that the powdered ge precursor material in the vicinity of the substrate surface is gasified and decomposed by means of laser radiation, in particular in the immediate vicinity of the substrate surface.

1 1. The method according to any one of the preceding claims, characterized in that the gasification and decomposition of the precursor material and the separation of the silicon carbide-containing material, preferably the entire process, is carried out in a protective gas atmosphere.

12. The method according to any one of claims 5 to 1 1, characterized in that the particle beam or the particle beams is or are surrounded by a protective gas stream.

13. Silicon carbide-containing object, obtainable by a process according to one of claims 1 to 12.

14. Device (1) for the location-selective deposition of materials containing silicon carbide on a substrate surface (2), characterized,

that the device

(a) at least one device (2) for the decomposition of gaseous precursor materials or for the gasification and decomposition of liquid or powdery precursor materials, the precursor materials containing at least one carbon source and at least one silicon source, and

(b) at least one device (3) for generating at least one particle beam and / or for aligning a particle beam onto the substrate surface,

having.

15. The device (1) according to claim 14, characterized in that the device (3) for generating a particle beam and / or for aligning a particle beam onto a substrate surface, a nozzle, in particular a

Solid nozzle, preferably a powder nozzle.

16. The apparatus (1) according to claim 14 or 15, characterized in that the device (2) for the decomposition of gaseous precursor materials or for the gasification and decomposition of liquid or powdery precursor materials means for generating high temperatures, in particular means for generating laser radiation or Means for generating an arc, has.

17. The apparatus (1) according to claim 16, characterized in that the device (2) for the decomposition of gaseous precursor materials or for the gasification and decomposition of liquid or powdery precursor materials has means for generating laser radiation, in particular a laser.

18. The device (1) according to any one of claims 14 to 17, characterized in that the device has means (4) for generating a protective gas atmosphere.