EP2167445A1

EP2167445A1 - Diffusion-joined ceramic component and method for the production thereof

Info

Publication number: EP2167445A1
Application number: EP08785991A
Authority: EP
Inventors: Hans-Peter Martin; Hans-Jürgen Richter; Steffen Dahms
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2007-07-13
Filing date: 2008-07-08
Publication date: 2010-03-31
Also published as: WO2009010427A1; DE102008040260A8; DE102008040260A1

Abstract

The invention pertains to the field of ceramics and relates to a component such as can be used as a wear component. The aim of the present invention is to provide a component having joint zones comprising a chemical composition materially extensively approximated to that of the base component. The aim is achieved by a component having base components to be joined made of the same or different ceramic materials, the chemical composition of the joint zone differing by 1 to a maximum of 40 at.-% from the chemical composition of the base components, and thermal expansion coefficients differing by a maximum of 2.10-6 K-1. The invention further relates to a method in which at least two ceramic base components are coated with a film in the area of the joint zone, the film comprising materials having a maximum of 70% sinter additives that are not materials of the respective base components, and said compound body being exposed to an increase in temperature for a fluid phase reaction.

Description

Diffusion-bonded ceramic component and method for its production

The invention relates to the field of ceramics and relates to a diffusion-bonded ceramic component, as it can be used, for example, as a wear component, at very high temperatures (> 1200 ⁰ C) or under highly corrosive conditions, and method for its preparation.

Monolithic ceramic components are severely limited in their dimension, design and combination of different ceramics. The more complicated the shape and larger the size of a component, the more costly the production becomes. If different property spectra are to be realized that can not be combined in one material at the same time (eg electrical conductivity and electrical insulation), a combination of different materials is required. When joining ceramic materials in particular properties such as mechanical strength, temperature resistance, gas tightness or chemical resistance lost, because the joint area is usually a weak point of the component.

So far, various joining techniques such as active soldering, glass soldering, metallization

+ Soldering, Garnierverfahren or gluing applied for ceramic components.

These processes are characterized by a joining zone that differs materially from the base material.

In general, the material deposition of the base material is necessary to the

Joining process with the enumerated methods to be able to master technologically.

Alternatively, local heating methods, such as laser joining, are used in order to create a joining region by means of soldering materials, which has similar properties to the base component. For example, WO 03/106374 describes solders based on Y 2 O 3, Al 2 O 3, SiO 2 and Si, which are heated and melted by means of a laser beam. This method can be used for joining high temperature stable and gas-tight composites of ceramic materials.

However, also with this method, a joining zone, which deviates materially from the base components, is produced, so that e.g. thermal expansion differences must be compensated as far as possible.

Furthermore, diffusion bonding processes for bonding ceramic and ceramic or ceramic and metal are known. For this purpose, the basic components are connected directly to one another via diffusion at high temperatures or films are used.

A direct connection of basic components can be realized by means of diffusion joining only at almost the same thermal expansion coefficient, which severely restricts the applicability. In addition, the surfaces of the regions to be joined must have a very low roughness so that there are sufficient direct contact points for the diffusion processes. Otherwise, the joint does not have sufficient strength. The introduction of films to the joint is advantageous for the joining technology, but in turn limits the resilience of the composite thus produced, since other materials are introduced which adversely affect the properties of the bond in the area of the joining zone (US 3,946,932, US 4,000,026).

A compound of SiC parts is also known (Rabin, et al., Mat. Res.Soc. Symp. Proc. Vol. 314, 1993, 197-203, DE196 36 223 A1). In this case, SiC / C films are produced, which are placed between the parts to be joined. The film is infiltrated with silicon during the joining process, whereby it differs significantly with respect to the material structure of the base component. Identical strength values are achieved with respect to the base component, but a significant drop in strength is observed at temperatures above 1200 ^° C. because of the free silicon.

The use of a metallic molybdenum foil is described by Cockeram, J. Am. Ceram. Soc. 88 (2005), 1892-1899. Although strengths in the range of monolithic materials can be achieved by means of this joining method, thermal stability and oxidation stability at temperatures> 500 ° C. under air are not sufficient. Since molybdenum has significant disadvantages compared to the base component, these disadvantages are also present for the composite.

Also known is a ceramic film consisting of TiC and Si or other combinations of carbides and metals that can be used to reactively join SiC (US 6,277,493). Again, the composition of the joint zone differs from the base components and has disadvantages in terms of thermal and chemical resistance to the base component in the examples given.

Similar disadvantages result from the use of borides for the connection of carbide materials (DE 32 00 200 A1).

The object of the present invention is to specify a diffusion-bonded ceramic component whose joining zone has a materially largely approximated chemical composition to the chemical composition of the base components and in specifying a simple and economical method for its production. The object is achieved by the invention specified in the claims. Advantageous embodiments are the subject of the dependent claims. The diffusion-bonded ceramic component according to the invention contains ceramic materials which are carbides, nitrides, oxides, borides or silicides of the elements Si, Al, Zr and / or Ti, where a) the base components to be joined consist of identical ceramic materials and whose joining zone is a chemical composition which differs by 1 to at most 40 at.% of the chemical composition of the ceramic materials of the base components and the joining zone has dopants of sintering additives, has been formed by liquid phase sintering, has a graded chemical composition over the thickness of the joint zone as a result of diffusion, and the chemical composition of the joining zone in the direction of the base components more and more approximates the chemical composition of the base components, or b) the base components to be joined consist of different ceramic materials whose thermal expansion coefficients differ by a maximum of 2-10 ^"6 K ^{" 1} iden, and whose joining zone has a chemical composition which differs by 1 to at most 40 at.% from the chemical composition of the ceramic materials of the base components, has been produced by liquid phase sintering, due to diffusion has a graded chemical composition across the thickness of the joint zone, and the chemical composition of the joining zone from the inner region of the joining zone in the direction of the respective base component more and more approximates the chemical composition of the respective base component, or c) the base components to be joined consist of the same ceramic materials and the joining zone has a chemical composition which is 1 to a maximum of 40 at .-% different from the chemical composition of the ceramic materials of the base components and other ceramic materials than in the As a result of diffusion, basic components present, contained by liquid-phase sintering, have a graded chemical composition over the thickness of the joining zone, and the chemical composition of the joining zone approaches more and more of the chemical composition of the respective base component from the inner region of the joining zone in the direction of the respective base component , or d) its base components to be joined of different ceramic

Materials whose thermal expansion coefficients differ by a maximum of 2-10 ^"6 K ^{" 1} , and whose joining zone is a chemical

Has composition of 1 to a maximum of 40 at .-% of the chemical composition of the ceramic materials of the

Base components differs and other ceramic materials than in the

Base components are present, are contained, formed by liquid phase sintering, due to diffusion a graded chemical

Has composition over the thickness of the joint zone, and the chemical composition of the joint zone from the interior of the

Joining zone in the direction of the respective base component more and more approximates the chemical composition of the respective base component, wherein in all cases at least the joining zone no glass phase components of> 2

Vol .-%, the joining zone exclusively by diffusion of sintering additives as

Dopings has arisen during the joining process and no measures have been taken to reduce the surface roughness.

The joining zone is considered to be the region of the component composite which has been morphologically or chemically altered by the diffusion joining process with respect to the starting state. The core area of the joining zone is always the area of the originally used ceramic film. This core region can occupy an extent of about 20% of the volume of the film originally used as a result of shrinkage processes during diffusion joining up to 100% of the volume of the film originally used, if no shrinkage of the film occurs. In addition, the joining zone extends into the original base components, which are morphologically or chemically altered by diffusion either from the joining film or into the joining film. The extension of this secondary joining zone range may be up to 10 mm, depending on the intensity of the diffusion processes occurring, but is in most cases <100 μm.

Advantageously, the ceramic materials SiC, SisN ₄ , Al 2 O 3, ZrO 2, TiC, AIN, OO 2 or other carbides, nitrides, oxides, borides or silicides or mixtures or compounds thereof are present.

Also advantageously, several joining zones are present in the component.

Further advantageously, the joining zone has a thickness of 10 to 1000 microns.

And also advantageously corresponds to base components of the same chemical composition, the chemical composition of the entire joint zone to 80 - 99 at-% of the chemical composition of the base components.

It is also advantageous if, in the case of basic components of different chemical composition, the chemical composition of the joining zone from the inner region of the joining zone in the direction of the respective base component to 70 to 95% of the chemical composition of the respective base component, advantageously 80-95% of the chemical composition of the respective base component, equivalent.

It is furthermore advantageous if the joining zone, via the thickness, consists of a multi-layer structure with a gradual gradation of the composition in each case in the direction of the different base components.

It is also advantageous if residues and / or reaction products of sintering additives in the joining zone are contained as dopants, wherein the sintering additives have been the basic substances for the formation of the liquid phase in the joining process.

It is also advantageous if the joining zone has no glass phase components. In the method according to the invention for producing a diffusion-bonded ceramic component, at least two basic ceramic components containing ceramic materials of carbides, nitrides, oxides, borides or silicides of the elements Si, Al, Zr and / or Ti, and wherein the at least two ceramic base components the same materials or different ceramic materials, wherein in the case of different ceramic materials whose thermal expansion coefficients differ by a maximum of 2-10 ^"6 K ^{" 1} , coated in the joining zone with at least one film, the film with sintering additives a share of has a maximum of 70% of materials that are not materials of the respective base components, subsequently the base components are brought into contact with the film at least in the region of the joining zone and this composite body is subjected to a temperature increase, wherein the temperature and / or the trough it allows at least the liquid phase reaction of the film material at a temperature and then the component is cooled.

SiC, SisN ₄ , Al 2 O 3, ZrO 2, TiC, AlN, TiO 2 or other carbides, nitrides, oxides, borides or silicides or mixtures or compounds are advantageously used as crystalline base components as crystalline phases.

Further advantageously, a film with a chemical composition of 40-99 at-% of the chemical composition of the base components is used.

It is also advantageous if a film is used which contains, in addition to the constituents of the base components, additional crystalline ceramic substances which serve to form a liquid phase in the joining process, wherein sintering additives are used as additional crystalline ceramic substances, the binders and / or sintering aids being formed a liquid phase in the joining process.

It is also advantageous if the composite body temperatures of 800 - 2200 ⁰ C, advantageously from 1200 to 2200 ⁰ C, exposed, wherein the composite body temperatures of 800 to 2200 ⁰ C within a residence time of 15 to 500 min is exposed, and the Residence times become shorter at higher temperatures. It is also advantageous if a pressure of 1 to 100 MPa for pressing the joining region and / or hot isostatic pressure of 1 to 300 MPa is exerted on the composite body.

It is also advantageous if a ceramic multilayer film is used, which is composed of different individual ceramic foils for the realization of various functionalities, advantageously the ceramic individual foils of 10 .mu.m to 1000 .mu.m thickness are used.

The invention is initially based on the combination of LPS-SiC materials. However, it can be used in principle for all ceramic materials. In order to be able to carry out a diffusion joining process without high preparation costs, at least one ceramic film is produced which, owing to its composition, forms a liquid phase at high temperatures and has a relatively low softening range compared to the base component. At the same time, the composition of the film in ceramic base components of the same chemical composition to be joined corresponds to at least 40% of the chemical composition of the base components or, in the case of ceramic base components of different chemical composition, to at least 40% of the chemical composition of the base components. In the case of LPS SiC, for example, exactly the same components can be used for the film and the base component.

It is also within the scope of the invention that in the case of basic components made of identical or different materials, in each case a ceramic film is used which, in terms of its composition, does not correspond to either of the two base components to be joined. However, it should be noted that the film material has a coefficient of thermal expansion which differs by a maximum of 2-10 ^"6 K ^{" 1} from those of the base components. Such a solution may be important for introducing functions into the joining zone. For example, conductive or non-conductive regions can be produced within the diffusion-bonded ceramic component. For example, while the base components to be joined have a composition of SiC + 5 Ma. -% additives (Y2O3 and AI2O3), then according to the invention, the film of SiC and 10-50 Ma .-% (Y2O3 and AI ₂ O ₃ ) exist.

The film is placed between the base components and subjected to a temperature treatment with or without pressure. More advantageous is the use of low pressures. Depending on the composition in the present case, between 1500 and 1900 ^° C., a melt which softens the film is formed from the additives of the film. In the further course, due to the concentration difference, the additives diffuse into the base components, so that only an increasingly smaller gradual difference between the base component and the joining region is present in the joining region.

Thus, the previously existing problems of difficult and complicated to implement joining technology when dispensing with auxiliary films or low-quality joining zones in the use of joining films are overcome at the same time.

The film used according to the invention consists of the components of the basic components (eg SiC, SisN ₄ , AlN, Al ₂ O 3, ZrO ₂ ) and dopants in the form of a mixture of substances which promote the joining process. These are advantageously sintering additives, as used for example for sintering LPS-SiC. These sintering additives must form a melt phase. In the case of sintering additives for LPS-SiC, these form a melt phase at temperatures above 1500 ^° C. and usually include combinations of rare earth oxide, silicon oxide, aluminum oxide or aluminum nitride. According to the proportions of the individual components of the film, a certain softening range results, so that the film at the intended joining temperature, which may be in the range of 1200 - 2200 ° C, consists of a melt and a solid phase.

For the joining process foils are made, which consist of ceramic powders and organic binders. The organic binders are burned out before or during the joining process. The ceramic powders are exclusively crystalline phases of ceramic compounds such as oxides, carbides, nitrides, borides or silicides. They are essentially neither elementary Metal powder still contain glass powder in the film. As a result, avoided by the films used for the invention, chemical reactions that can affect the joining process unfavorable by leading to material inhomogeneities. By a maximum content of> 2 vol .-% glass phase in the joining zone, but advantageously no glass phase in the joining zone, high application temperatures are ensured in the joined components in contrast to the films described in DE 4425209 A1. Since complete crystallization of glasses, even via the targeted formation of nuclei, can not be achieved or at least lead to melting and reglazing at high temperature stress, the starting composition of the invention described ensures a virtually glass-free joining zone due to the almost complete absence of glass formers.

In the context of this description of the invention, the term doping of the ceramic is intended to describe all additives which are added to the main constituent of the film (eg SiC, Si ₃ N ₄ , O ₂ , etc.) in order to favor the production process. The term doping includes sintering additives, minor additives and impurities of the ceramic. Not included are organic binders which, although they can introduce impurities via impurities, which are then to be classified in the group of minor additives or impurities. Organic binders are either completely or partially burned or vaporized. Residues after partial evaporation or combustion are mainly carbon, which acts as a sintering additive or a minor additive during the sintering process. The above terms in detail in the context of this invention mean:

- Binders are organic additives that serve the processing of ceramic powders and in particular allow the shaping. Binders are mostly burned or pyrolyzed during the heat treatment during a debinding or pyrolysis process. After firing, the binders are removed from the ceramic residue-free. After pyrolysis, carbon residues of the binders are still present in a small amount in the ceramic, which are incorporated into the ceramic during sintering. Sintering additives are ceramic powders which are added to the main component in order to enable and / or to improve sintering according to the prior art. Either they accelerate the diffusion and thus the mass transfer during sintering, so that a compaction of the ceramic powder succeeds or they form a melting phase during sintering, which promotes the densification of the ceramic via solution and re-precipitation processes. This melt phase can also contribute to diffusion and individual constituents can diffuse into the other ceramic constituents. After the end of the sintering, the melt phase solidifies into mixed compounds or the original individual compounds of the sintering additives used.

- Slight additions of ceramics are admixtures <2% by volume. They should either promote the sintering process, modify material properties or act as dopants in the true sense by storing themselves as impurities in the crystal lattice of the main components of the ceramic and thus change their electronic properties. Such dopants can also result from the sintering additives. For example, in the production of LPS-SiC, diffusion of Al atoms from the Y-Al-O melt always occurs in the SiC lattice, so that the SiC grains are doped with aluminum atoms after sintering.

The ceramic film is placed between the ceramic segments, which are advantageously already sintered. The composite of the individual segments is heated to a temperature at which the joining film used becomes viscous due to the forming melt and fills the gap between the base components and wets the surfaces and / or connects by diffusion processes. Therefore, no measures are required to reduce the surface roughness of the base components.

The joining process can be accelerated and reinforced by pressure application, which improves the quality of the connection. After cooling the component, all base components are firmly connected. By using species-specific components for the joining film, a joining zone is created which, purely on the outside and in its essential properties, no longer differs from that of the basic components. This allows an application temperature for the produced diffusion-bonded ceramic component can be achieved, which corresponds to that of the base components used. In addition, the achieved strength and tightness of the connection is maintained up to the specific application temperature. Since the joining zone consists of chemically identical or almost identical components as the base component, there are no compatibility problems with regard to thermal expansion and chemical reactivity. This is particularly advantageous for thermal cycling. Rapid temperature changes on the diffusion-bonded ceramic component are no more critical than for a corresponding monolithic component.

By selecting the composition of the joining film, the joining temperature can be set in an optimum temperature range for the diffusion-bonded ceramic component and the application.

The composition of the joining film can be 20 - 95 Ma. -% SiC, Si ₃ N ₄ , AIN, Al ₂ O ₃ or ZrO ₂ or combinations thereof. The remaining fractions are formed by substances that favor the joining process, such as sintering additives, which serve to form a liquid phase during the joining process.

Particularly preferred in the joining of LPS-SiC is the composition according to the invention of the joining film with 70 mass% SiC, 10 mass% Y ₂ O ₃ and 20 mass% Al ₂ O ₃ for joining SiC materials. For other basic components, the composition of the foil must be changed.

The composition according to the invention always consists of a proportion of the main components of the base component (eg Si ₃ N ₄ , AlN, Al ₂ O ₃ , ZrO ₂ or other ceramics) and a proportion to form a compatible liquid phase.

For this purpose, for example, the material components can be mixed as a powder in an aqueous or organic suspension with organic binders and cast in accordance with the known methods for film casting. The film thickness is adjusted by means of a squeegee. After drying the film, it can be used for the joining process.

The films can be produced with a thickness of 10 .mu.m to 1000 .mu.m. The thickness to be adjusted depends on the properties of the material to be joined Basic components and the desired component properties selected. The shape of the film is cut arbitrarily according to the requirements of the component.

After cutting the film, it is placed at the intended locations on the component and assembled the individual base components. If a specific grading of the joining zone is to be set, it is also possible to use a plurality of films which are identical or different in terms of their composition and which enable the connection of different base components (for example Si ₃ N ₄ and AlN). The composite is heated to a temperature in the range between 800 ⁰ C and 2200 ⁰ C. In particular, a bonding temperature in the range of 1200- 2200 ° C for the production of diffusion-bonded ceramic components for high temperature applications is advantageous. To improve the strength of the diffusion-bonded ceramic component, it is advantageous to apply a low pressure to the joining zones, which can be realized via a load on the component or by the use of a hot press. During the joining process, the resulting liquid phase predominantly diffuses into the base component, so that a concentration equalization occurs. As a result, the joining zone solidifies and stabilizes, so that it becomes almost identical to the basic components in terms of material properties with appropriate process control.

Thus, according to the invention diffusion-bonded ceramic components reach a maximum strength of up to 100% of the strength of the base material. The thermal load capacity is at least 90% of the joining temperature, the tightness at a vacuum pressure of 10 ^{~ 6} Pa / s A rapid thermal change from 1200 ⁰ C to about 500 ° C can be overcome without any damage, if the base components with respect to the thermal Elongation are similar. The materials of the base components can be selected from the named range and the base components do not require further preparation of the surface before or after sintering.

The composition of the joining film and the application of the diffusion bonding chip make it possible to generate a joining zone which is almost identical in terms of its chemical composition with the base components. Thus, it is possible to achieve almost identical properties of the diffusion-bonded ceramic component to reach those of the basic component (s). According to the prior art, resulting reductions in the quality and limitations of the components are largely eliminated in the inventive diffusion-joined ceramic component. At the same time the effort remains similar compared to previously used joining methods. In addition, there are opportunities for combining different materials, since the joining zone can also be used as a graded transition, which was previously not possible according to the prior art.

The formation of a liquid phase wetting the ceramics from the sintering additives of the joining foils used ensures a close material connection of the joining zone to the base ceramic bodies. The joining film is easily deformed by the melting fraction and developed by the wetting of the melt on the ceramic body inherent forces for connecting the joining zone, which arises from the joining film. By means of this constellation, a complex surface treatment for smoothing the joining surfaces can be completely dispensed with for the joining process according to the invention. Surface qualities, as achieved by sintered ceramic surfaces, are sufficient to achieve outstanding mechanical strength of the joined components.

The invention is suitable for the production of ceramic components. Particularly advantageous is the production of complicated shaped ceramic components that could otherwise be obtained only with great effort. Furthermore, there are particularly many advantages if products with differing property spectra are to be produced. These can be composed of different materials, which in turn require different production conditions and are therefore manufactured separately. The joining process succeeds e.g. the combination of electrically conductive and electrically insulating materials or of hard and soft materials. At the same time, the joining results in no restrictions with regard to the conditions of use by the joining zone, since this is almost identical to the basic components.

The invention will be explained in more detail below with reference to several exemplary embodiments. example 1

Five LPS Siliziumcarbidkörper with the dimensions 20 x 20 mm and a height of 10 mm are sintered correspondingly at temperatures of 1950 ⁰ C and a gas pressure of 0.2 MPa.

A ceramic film is made from a powder mixture of 80 Ma. % SiC (d ₅ o <1 μm), 15 Ma. -% AI ₂ O ₃ and 5 Ma. -% Y ₂ O ₃ prepared by the film casting process at room temperature. It is cast a ceramic film with a thickness of 100 microns. The film is dried at 6O ⁰ C and then cut into squares of 20 x 20 mm. A film square is placed on a 20 x 20 mm area of one of the sintered LPS-SiC bodies. Subsequently, the 4 LPS-SiC bodies are alternately stacked with the films on the surface 20 x 20 mm, so that a ceramic part with a height of 50 mm + 400 microns is formed.

The stack is placed in a hot press and pressurized under argon atmosphere with a pressure of 20 MPa, while the temperature is raised at a heating rate of 10 K / min to 1850 ⁰ C and held there for 1 h. After cooling, the joined ceramic stack is removed from the press.

To characterize the ceramic stack was cut into bending fracture bars, so that the joints could be examined.

The chemical composition of the entire joining zone did not differ at any point of the joining zone more than 3% from the chemical composition of the joined LPS Siliziumcarbidkörper.

The strength was measured at room temperature and at 1000 ^° C. under vacuum. The determined average values of 6 or 3 samples were at room temperature and at 1200 ° C at 350 and 320 MPa, which corresponds to 100% of comparable monolithic bending bars of LPS silicon carbide and shows no significant difference between room temperature and 1200 ° C. The residual strength after a thermal cycling between 1200 and 500 ⁰ C (10 cycles) was also examined. The remaining strength of the examined bending bars was at an average value of 280 MPa. Such a relatively small drop corresponds to that of monolithic bending bars of the same material. Example 2

Three LPS silicon carbide bodies and 2 aluminum nitride bodies of dimensions 20 x 20 mm and a height of 10 mm are sintered according to their material specificity. The LPS-SiC bodies are sintered as described in Example 1. The AI N bodies are sintered at 1800 ⁰ C under nitrogen without pressure. A ceramic film (S) is prepared as described in Example 1. Another ceramic film (A) is made of a powder mixture of 70 Ma. -% AIN (d ₅ o <2 μm), 15 Ma. -% AI ₂ O ₃ and 15 Ma. -% Y ₂ O ₃ prepared by the film casting process at room temperature. Another ceramic film (AS) is made of a powder mixture of 40 wt .-% AIN (d ₅ o <2 microns), 40 wt .-% SiC, 15 wt .- Al ₂ O ₃ and 5 wt .-% Y ₂ O _{3 produced} by the Foliengießverfahren at room temperature. The above-described ceramic films having a thickness of 100 μm are cast. The films are dried at 6O ⁰ C and then cut into squares of 20 x 20 mm. A film square (S) is placed on a 20 x 20 mm area of one of the sintered LPS-SiC bodies. Then a film square (AS) and another film square (A) are placed on the previously launched film square. Then a sintered AIN ceramic body with the area 20x20 mm is placed on the foil square (A). In turn, a film square (A) is placed on this ceramic body at the top, then a film square (AS) and subsequently a film square (S) onto which an LPS-SiC ceramic body is then placed. The stack is completed in this episode, so that there is always a ceramic foil (S) on the LPS-SiC and always a ceramic foil (A) on the AIN bodies and a foil square (AS) between the other foil squares.

The stack is placed in a hot press and pressurized under argon atmosphere with a pressure of 20 MPa, while the temperature is raised at a heating rate of 10 K / min to 1750 ⁰ C and held there for 1 h. After cooling, the joined ceramic stack is removed from the press.

Example 3

Five LPS Siliziumcarbidkörper with the dimensions 20 x 20 mm and a height of 10 mm are sintered as described in Example 1. A ceramic film (A) is prepared as described in Example 2. The ceramic foil is cast with a thickness of 100 μm. The film is dried at 60 ^° C. and then cut into squares of 20 × 20 mm.

A film square (A) is placed on a 20 x 20 mm area of one of the sintered LPS

SiC body laid. Then an LPS-SiC ceramic body is placed. The stack is completed in this episode so that there is always a ceramic foil (A) between the LPS

SiC bodies lies.

The stack is placed in a hot press and under argon atmosphere with a

Pressure of 20 MPa applied while the temperature with a

Heating rate of 10 K / min increased to 1750 ⁰ C and held there for 1 h.

After cooling, the joined ceramic stack is removed from the press.

Cut out bars are electrically insulating in the direction perpendicular to the joining foil surfaces, electrically conducting parallel to the foil surfaces. The thermal conductivity of the rods thus produced is not dependent on the direction of the film layers.

Claims

claims

A diffusion-bonded ceramic component produced by a method according to any one of claims 10 to 24, containing ceramic materials which are carbides, nitrides, oxides, borides or silicides of the elements Si, Al, Zr and / or Ti, a) of which mating base components consist of the same ceramic materials and whose joining zone has a chemical composition which differs by 1 to a maximum of 40 at .-% of the chemical composition of the ceramic materials of the base components and the joining zone has dopants of sintering additives, caused by liquid phase sintering, as a result Diffusion has a graded chemical composition across the thickness of the joining zone, and the chemical composition of the joining zone in the direction of the base components more and more approximates the chemical composition of the base components, or b) whose base components to be joined consist of different ceramic materials, the thermal Aus expansion coefficient differ by a maximum of 2-10 ^"6 K ^{" 1} , and its joining zone has a chemical composition which differs by 1 to a maximum of 40 at .-% of the chemical composition of the ceramic materials of the base components, caused by liquid phase sintering, as a result Diffusion has a graded chemical composition over the thickness of the joining zone, and the chemical composition of the joining zone from the inner region of the joining zone in the direction of the respective base component more and more approximates the chemical composition of the respective base component, or c) its base components to be joined of the same ceramic materials and whose joining zone has a chemical composition that differs from 1 to at most 40 at .-% of the chemical composition of the ceramic materials of the base components and other ceramic materials than in the As a result of diffusion, basic components present, contained by liquid-phase sintering, have a graded chemical composition over the thickness of the joining zone, and the chemical composition of the joining zone approaches more and more of the chemical composition of the respective base component from the inner region of the joining zone in the direction of the respective base component , or d) its base components to be joined of different ceramic

Base components differs and other ceramic materials than in the

Vol .-%, the joining zone exclusively by diffusion of sintering additives as

2. Component according to claim 1, wherein the ceramic materials SiC, SisN ₄ , Al ₂ O ₃ , ZrO 2, TiC, AlN, OO 2 or other carbides, nitrides, oxides, borides or silicides or mixtures or compounds thereof are present.

3. Component according to claim 1, in which a plurality of joining zones are present in the component.

4. Component according to claim 1, wherein the joining zone has a thickness of 10 to 1000 microns.

5. Component according to claim 1, wherein in the case of basic components of the same chemical composition, the chemical composition of the entire joining zone corresponds to 80-99 at-% of the chemical composition of the base components

6. Component according to claim 1, wherein in base components of different chemical composition, the chemical composition of the joining zone from the interior of the joining zone in the direction of the respective base component to 70 to 95% of the chemical composition of the respective base component, advantageously 80 - 95% of the chemical composition of the respective Base component corresponds.

7. Component according to claim 1, wherein the joining zone over the thickness consists of a multi-layer structure with a gradual gradation of the composition respectively in the direction of the different base components.

8. Component according to claim 1, in which residues and / or reaction products of sintering additives are contained in the joining zone as dopants, wherein the sintering additives have been the base materials for the formation of the liquid phase in the joining process.

9. Component according to claim 1, wherein the joining zone has no glass phase components.

10. A method for producing a diffusion-bonded ceramic component according to any one of claims 1 to 9, wherein at least two ceramic base components containing ceramic materials of carbides, nitrides, oxides, borides or silicides of the elements Si, Al, Zr and / or Ti, and wherein the at least two ceramic base components consist of the same materials or of different ceramic materials, wherein in the case of different ceramic materials their thermal expansion coefficients differ by a maximum of 2-10 ^"6 K ^{" 1} , be coated in the region of the joining zone with at least one film , wherein the film with sintering additives has a maximum proportion of 70% of materials that are not materials of the respective base components, hereinafter the base components at least in the Bonding zone are brought into contact with the film and this composite body is exposed to a temperature increase, wherein the temperature and / or the residence time at a temperature at least the liquid phase reaction of the film material allows and subsequently the component is cooled.

11. The method of claim 10, wherein as the ceramic base components SiC, Si ₃ N ₄ , Al ₂ O ₃ , ZrO ₂ , TiC, AlN, TiO ₂ or other carbides, nitrides, oxides, borides or silicides or mixtures or compounds as crystalline phases are used.

12. The method of claim 10, wherein a film having a chemical composition of 40-99 at-% of the chemical composition of the base components is used.

13. The method of claim 10, wherein a film is used, which contains in addition to the components of the base components additional crystalline ceramic materials, which serve to form a liquid phase in the joining process, being used as additional crystalline ceramics sintering additives, the binder and / or Sintering aids for the formation of a liquid phase in the joining process are.

14. The method of claim 10, wherein the composite body temperatures of 800 - 2200 ⁰ C, advantageously from 1200 to 2200 ⁰ C, is exposed, wherein the composite body temperatures of 800 to 2200 ⁰ C within a residence time of 15 to 500 min is exposed , and the residence times become shorter at higher temperatures.

15. The method of claim 10, wherein a pressure of 1 - 100 MPa for pressing the joining region and / or hot isostatically a pressure of 1 - 300 MPa is applied to the composite body.

16. The method of claim 10, wherein a ceramic multilayer film is used, which is composed of different individual ceramic foils for the realization of various functionalities, wherein advantageously the ceramic individual sheets of 10 .mu.m to 1000 .mu.m thickness are used.