Method for obtaining at least one ceramic part by joining at least two ceramic preforms and ceramic part obtained by said method

Abstract

The present invention relates to a method for obtaining at least one ceramic component by bonding at least two SiC preforms, comprising providing at least two porous SiC preforms, each having at least one bonding surface, and a bonding slurry, the bonding slurry comprising 40-80 wt. % of at least one binder, a particle size D 50 2 to 20% by weight of silicon carbide particles having a particle diameter D 50 The bonding slurry contains 8-25 wt% silicon carbide particles with a particle size of 1-10 μm and 10-30 wt% carbon black, with the total of all components always equaling 100 wt%. The bonding surfaces of at least two SiC preforms are pressed together. The at least two SiC preforms are dried. The at least two SiC preforms are heated, whereby the SiC preforms containing the dried bonding slurry are impregnated with Si, resulting in a physically bonded SiSiC ceramic part.

Description

[Technical Field]

[0001] The present invention relates to a method for obtaining at least one SiSiC ceramic part by joining at least two SiC preforms during impregnation with liquid silicon (Si). [Background technology]

[0002] Ceramic substrates or components are used in various technical fields, such as the electronics, automotive, and pharmaceutical industries. Due to the requirements for hardness, chemical resistance, and heat resistance, silicon carbide (SiC) is used for ceramic substrates. To manufacture such ceramic components, for example, a compact made from a carbon-containing starting material can be subjected to a siliconization process, whereby the carbon reacts with externally supplied silicon to form silicon carbide, and the appropriate pore network present or formed in the compact is filled with pure silicon. In the latter case, the pores of the compact are impregnated with silicon, resulting in a silicon-impregnated silicon carbide (SiSiC) compact characterized by the substantial absence of residual porosity.

[0003] Larger ceramic substrates or components can be obtained by joining two or more smaller compounds or preforms. This includes gluing with polymer adhesives such as epoxy adhesives, or soldering with metal or inorganic solders (such as glass). The drawback of the non-material joining methods mentioned above is the insufficient temperature, mechanical or chemical stability of the joining seam.

[0004] European Patent No. 3599229B1 (Patent Document 1) discloses a reaction-bonded ceramic component having a joint seam made of a material having essentially the same or very similar properties as the material of the ceramic components or prebody to be joined. The material of the joint seam is composed of 30% silicon carbide by volume and at least 8% silicon by volume. At least one of the ceramic components to be joined has at least one cavity at least partially filled with silicon and / or a silicon alloy. The cavity is adjacent to the material of the joint seam, or the silicon in the cavity is at least partially adjacent to the material of the joint seam. Thus, the pores provided in the ceramic components are filled with silicon and can be considered as a kind of storage space for the silicon that is then used to bond the ceramic components together at the joint seam.

[0005] German Patent No. 102011007815B4 (Patent Document 2) describes a process for obtaining a ceramic compound in which two pre-bodies are formed from a carbon composite having a matrix of amorphous carbon and porous carbon, and the two pre-bodies are bonded to each other by adhesive surfaces by applying and curing an adhesive paste containing silicon carbide and a polymer adhesive, and subsequently siliconizing the pre-bodies into a compound.

[0006] Ceramic compounds can also be obtained by 3D printing, as described, for example, in WO 2019 / 063833 A1 or WO 2018 / 206250 A1. However, a drawback of this printing method is that the printing volume of 3D printing is limited by the printer design. This means, for example, that particularly large parts cannot be realized using 3D printing. Furthermore, 3D-printed SiSiC has a coarse grain size and a high Si content. Both factors reduce mechanical properties and affect electrical properties. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent No. 3599229B1 [Patent Document 2] German Patent No. 102011007815B4 [Patent Document 3] International Publication No. 2019 / 063833A1 [Patent Document 4] International Publication No. 2018 / 206250A1 Summary of the Invention [Problem to be solved by the invention]

[0008] The objective of the present invention is to provide a joining method that allows for the assembly of unimpregnated SiC preforms to form bonded SiSiC parts after Si infiltration. More specifically, it provides a joining method that allows for the joining of porous, unimpregnated SiC parts, so-called SiC preforms, during Si infiltration to form larger SiSiC parts. SiC preforms can be produced as green bodies by several manufacturing methods, such as press molding, slip casting, tape casting, 3D printing, and / or extrusion, and can be further machined to achieve a desired shape. To provide better mechanical stability during the machining and / or infiltration process, the green parts may be heated to 800-1250°C to obtain coked parts. In this context, a joining slurry is required, but for parts with very coarse porosity, the joining slurry remains in the joining area and does not penetrate into the part.

[0009] Thus, there is provided a method for obtaining at least one SiSiC ceramic part by joining at least two SiC preforms, the method comprising the following steps: providing at least two porous SiC preforms, such as green or sintered bodies, having at least one joining surface; 40 to 80% by weight, preferably 50 to 70% by weight, of at least one binder, A particle size D of 10 to 20 μm, preferably 11 to 18 μm, more preferably 11 to 16 μm 50 2 to 20 wt. %, preferably 5 to 18 wt. %, more preferably 8 to 15 wt. % of silicon carbide particles having a viscosity of 1000 psig (DIN EN 725-5, ISO 13320), A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm 50 8 to 25 wt. %, preferably 9 to 20 wt. %, more preferably 10 to 15 wt. % of silicon carbide particles having a viscosity of 1000 psig (DIN EN 725-5, ISO 13320), 10 to 30% by weight, preferably 12 to 20% by weight, more preferably 13 to 18% by weight of carbon black; - providing a bonding slurry in which the sum of all components always equals 100% by weight; - pressing the joining surfaces of at least two SiC preforms together; drying at least two SiC preforms; and -heating at least two SiC preforms and impregnating Si into the SiC preforms with the dried joining slurry to obtain a materially bonded silicon-silicon carbide (SiSiC) ceramic part; A method comprising:

[0010] The method allows for the joining of at least two SiC preforms to provide a SiSiC ceramic part. A joining slurry or paste is applied to the parts to be joined. It is characterized by an appropriate working time and consistency. As explained in more detail below, the joining slurry is composed of the following components: SiC particles having a bimodal or trimodal particle distribution, carbon black, another carbon source as a binder, and a solvent to adjust the viscosity of the joining slurry, if necessary. To reduce the occurrence of porosity, a centrifugal mixer is used to mix the slurry ingredients. To reduce the formation of porosity, a centrifugal mixer is used to mix the slurry components. The joining slurry promotes bonding between the materials of the two ceramic preforms.

[0011] The joining slurry is placed on the joining surface of at least one of at least two SiC preforms that will be joined to a larger part. The part then needs to be dried. Drying is sufficient when the surface of the slurry no longer shows any tendency to stick. The compound is then impregnated with Si, forming a material bond.

[0012] The SiC preforms bonded by the methods of the present invention are porous bodies comprising silicon, carbon, and / or silicon carbide.

[0013] In one embodiment of the method of the present invention, at least one SiC preform is obtained by 3D printing, having at least one joining surface. Therefore, the method of the present invention can also be used to join a 3D-printed SiC preform with another 3D-printed SiC preform or a SiC preform obtained by a conventional non-printing method. In this case, a joining slurry or paste is applied to the parts to be joined. The joining slurry is applied, for example, to the contoured portion of the SiC preform using a spatula, and to the flat portion of the SiC preform, for example, by screen printing or other methods. Due to the complex structure of the 3D-printed composite, it can be embedded in a filler material before being pressed to avoid fracture when axial force is applied.

[0014] The method of the present invention has the following advantages: - possibility of creating parts from different SiC preforms and achieving desired local technological properties; reduction of cutting times and saving of material; - Complex (support) structures can be reproduced by 3D printing. If the technical properties require it, conventional SiC preforms can be used. This means, for example, that the entire functional surface and support structure no longer needs to be milled out of a large block; -It is possible to create SiC preforms that exceed the printing volume of the printer or that cannot be produced by 3D printing for structural reasons; -Higher utilization of print volume: Parts can be split into smaller pieces and assembled after printing, allowing for a denser placement of parts in the job box.

[0015] As mentioned above, SiSiC ceramic composites obtained using 3D printed preforms may have a coarser SiC grain size compared to SiC preforms obtained by conventional methods. Therefore, SiC ceramic preforms obtained by 3D printing have a density of 1.3 to 3.0 g / cm in the unimpregnated state. 3 , preferably 1.5 to 2.5 g / cm 3 , more preferably 1.7 to 2.2 g / cm 3 Density is measured by Archimedes and / or geometrically.

[0016] A 3D printing method for obtaining a SiC preform is described, for example, in WO 2018 / 206250 A1. The 3D printing method described herein is based on a compact made of a composite material (such as SiC) that is built up stepwise from multiple layers with layer thicknesses of 50 to 250 μm by powder bed printing or binder jetting.

[0017] For the production of SiC preforms by 3D printing, various starting compositions are possible, but preferably 80-98 wt.% SiC and 2-20 wt.% C. The primary SiC particles of the SiC preforms used have an average particle size of 25-60 μm, preferably 40-55 μm.

[0018] To fix the required lower layers of the green body, a liquid fixing component consisting of a binder or a mixture of binder and hardener is used. This application can be carried out, for example, by a print head. The fixing component preferably wets the powder sufficiently so that the organic material is evenly distributed. Solidification of the printed areas within the layer can be achieved by removing the volatile portion of the fixing component or by thermal and / or light-induced crosslinking (e.g., IR or UV lamps). After solidification, the next layer of ceramic powder is applied. The fixing component is applied according to the next layer required for the green body and solidified. This process is repeated until the green body is built according to the layer model. The resulting SiC preform is then impregnated with silicon (Si).

[0019] Binders used in 3D printing processes can be prepared by thermal and / or photo-induced crosslinking, for example, by irradiation of large areas or points using IR or UV lamps. UV-curable components can be radical-curing or cationic-curing UV systems, or mixtures of both, such as acrylates, epoxies, enol ethers, and vinyls. Thermosetting binders can be components that are dried by a heat source and / or reaction. Exemplary components include phenolic resins, furan resins, epoxy resins, graphite resins, starch, sugar, or cellulose solutions. Binders can also be inorganic, such as water glass. A preferred binder is phenolic resin.

[0020] The SiC preforms produced by 3D printing have a grain size of 25-60 μm, preferably 40-55 μm, and a four-point bending strength of up to 250 MPa. The 3D printed SiC preforms preferably have a structure in which the structure of the individual layers within the microstructure is no longer visually discernible at the vertical cut edge of the part, for example, by optical or scanning electron microscopy.

[0021] As noted, to avoid breakage and protect the 3D printed SiC preform when pressure is applied, it is advantageous to embed the 3D printed SiC preform in a filler material. Suitable fillers include polymer granules, sand, or SiO2 powder.

[0022] In a preferred embodiment, the joining slurry used in the present method comprises the following components: 50 to 70% by weight of a binder; A particle size D of 10 to 20 μm, preferably 11 to 18 μm, more preferably 11 to 16 μm 50 5 to 18 wt. % of silicon carbide particles having a viscosity of 1000 MPa (DIN EN 725-5, ISO 13320), A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm 50 9 to 20 wt. % of silicon carbide particles having a viscosity of 1000 MPa (DIN EN 725-5, ISO 13320), 12 to 20% by weight of carbon black, In a preferred embodiment, the sum of all components always equals 100% by weight.

[0023] In a more preferred embodiment, the bonding slurry used in the present method comprises the following components: 50 to 70% by weight of a binder; A particle size D of 10 to 20 μm, preferably 11 to 18 μm, more preferably 11 to 16 μm 50 8 to 15 wt. % of silicon carbide particles having a viscosity of 1000 MPa (DIN EN 725-5, ISO 13320), A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm50 13 to 18 wt. % of silicon carbide particles having a specific surface area (DIN EN 725-5, ISO 13320), In a preferred embodiment, the sum of all components always equals 100% by weight.

[0024] In another preferred embodiment, the joining slurry comprises the following components: 40 to 80% by weight, preferably 50 to 70% by weight, of a binder; A particle size D of 30 to 65 μm, preferably 35 to 60 μm, more preferably 40 to 55 μm 50 2 to 20 wt %, preferably 5 to 18 wt %, more preferably 8 to 15 wt % of silicon carbide particles having the formula: A particle size D of 10 to 20 μm, preferably 11 to 18 μm, more preferably 11 to 16 μm 50 2 to 20 wt. %, preferably 5 to 18 wt. %, more preferably 8 to 15 wt. % of silicon carbide particles having A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm 50 8 to 25 wt %, preferably 9 to 20 wt %, more preferably 10 to 15 wt % of silicon carbide particles having the formula: 10 to 30% by weight, preferably 12 to 20% by weight, more preferably 13 to 18% by weight of carbon black; In a preferred embodiment, the sum of all components always equals 100% by weight.

[0025] In another embodiment, the joining slurry comprises the following components: 40 to 80% by weight, preferably 50 to 70% by weight, of a binder; A particle size D of 30 to 65 μm, preferably 35 to 60 μm, more preferably 40 to 55 μm 50 1 to 20 wt %, preferably 4 to 15 wt %, more preferably 6 to 10 wt % of silicon carbide particles having the formula: A particle size D of 10 to 20 μm, preferably 11 to 18 μm, more preferably 11 to 16 μm 501 to 20 wt %, preferably 4 to 15 wt %, more preferably 6 to 10 wt % of silicon carbide particles having the formula: A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm 50 8 to 25 wt %, preferably 9 to 20 wt %, more preferably 10 to 15 wt % of silicon carbide particles having the formula: 10 to 30% by weight, preferably 12 to 20% by weight, more preferably 13 to 18% by weight of carbon black; In a preferred embodiment, the sum of all components always equals 100% by weight.

[0026] In a further preferred embodiment, the joining slurry comprises the following components: 40 to 80% by weight, preferably 50 to 70% by weight, of a binder; A particle size D of 30 to 65 μm, preferably 35 to 60 μm, more preferably 40 to 55 μm 50 2 to 20 wt %, preferably 5 to 18 wt %, more preferably 8 to 15 wt % of silicon carbide particles having the formula: A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm 50 8 to 25 wt %, preferably 9 to 20 wt %, more preferably 10 to 15 wt % of silicon carbide particles having the formula: 10 to 30% by weight, preferably 12 to 20% by weight, more preferably 13 to 18% by weight of carbon black; In a preferred embodiment, the sum of all components always equals 100% by weight.

[0027] In a more preferred embodiment, the joining slurry comprises the following components: 50 to 70% by weight of a binder; A particle size D of 30 to 65 μm, preferably 35 to 60 μm, more preferably 40 to 55 μm 50 5 to 18 wt. % silicon carbide particles having the formula: A particle size D of 10 to 20 μm, preferably 11 to 18 μm, more preferably 11 to 16 μm50 5 to 18 wt. % silicon carbide particles having A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm 50 9 to 20 wt. % of silicon carbide particles having the formula: 12 to 20% by weight of carbon black, In a preferred embodiment, the sum of all components always equals 100% by weight.

[0028] In another embodiment, the joining slurry comprises the following components: 50 to 70% by weight of a binder; A particle size D of 30 to 65 μm, preferably 35 to 60 μm, more preferably 40 to 55 μm 50 4 to 15 wt. % silicon carbide particles having A particle size D of 10 to 20 μm, preferably 11 to 18 μm, more preferably 11 to 16 μm 50 4 to 15 wt. % of silicon carbide particles having the formula: A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm 50 9 to 20 wt. % of silicon carbide particles having the formula: 12 to 20% by weight of carbon black, In a preferred embodiment, the sum of all components always equals 100% by weight.

[0029] In a further preferred embodiment, the joining slurry comprises the following components: 50 to 70% by weight of a binder; A particle size D of 30 to 65 μm, preferably 35 to 60 μm, more preferably 40 to 55 μm 50 5 to 18 wt. % silicon carbide particles having the formula: A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm 50 9 to 20 wt. % of silicon carbide particles having the formula: 12 to 20% by weight of carbon black, In a preferred embodiment, the sum of all components always equals 100% by weight.

[0030] In the most preferred embodiment, the joining slurry comprises the following components: 50 to 70% by weight of a binder; A particle size D of 30 to 65 μm, preferably 35 to 60 μm, more preferably 40 to 55 μm 50 8 to 15 wt. % of silicon carbide particles having the formula: A particle size D of 10 to 20 μm, preferably 11 to 18 μm, more preferably 11 to 16 μm 50 8 to 15 wt. % silicon carbide particles, and / or A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm 50 10 to 15 wt. % of silicon carbide particles having the formula: 13 to 18% by weight of carbon black, In a preferred embodiment, the sum of all components always equals 100% by weight.

[0031] In a preferred embodiment, the joining slurry comprises the following components: 50 to 70% by weight of a binder; A particle size D of 30 to 65 μm, preferably 35 to 60 μm, more preferably 40 to 55 μm 50 8 to 15 wt. % of silicon carbide particles having the formula: A particle size D of 10 to 20 μm, preferably 11 to 18 μm, more preferably 11 to 16 μm 50 8 to 15 wt. % of silicon carbide particles having the formula: A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm 50 10 to 15 wt. % of silicon carbide particles having the formula: 13 to 18% by weight of carbon black, In a preferred embodiment, the sum of all components always equals 100% by weight.

[0032] In a further preferred embodiment, the joining slurry comprises the following components: 50 to 70% by weight of a binder; A particle size D of 30 to 65 μm, preferably 35 to 60 μm, more preferably 40 to 55 μm 50 8 to 15 wt. % of silicon carbide particles having the formula: A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm 50 10 to 15 wt. % of silicon carbide particles having the formula: 13 to 18% by weight of carbon black, In a preferred embodiment, the sum of all components always equals 100% by weight.

[0033] It should be noted that the particle size of the silicon carbide particles is adapted to the ceramic material of the ceramic preforms to be joined, and the silicon carbide particles can be provided in a bimodal or trimodal distribution, but preferably in a bimodal particle distribution, which has the advantage that the joining slurry mimics the material of the SiC preforms to be joined, i.e., the material properties of the joining slurry are comparable to those of the surrounding SiC preforms.

[0034] The binder used in the bonding slurry is preferably an organic material that cokes or pyrolyzes at or below the impregnation temperature of the ceramic material. That is, the organic material is converted to carbon during the coking process. The binder is made from renewable organic resources, particularly starch and sugar, and is an environmentally friendly alternative to commonly used phenolic resins and polymers. The binder can be added as a solution or suspension, preferably an aqueous solution or suspension.

[0035] In one embodiment, the bonding slurry may contain a solvent, preferably water, or a mixture of at least two solvents to adjust the viscosity of the slurry. In most cases, water is preferably added to the slurry along with the binder as a solution or suspension. The amount of solvent, particularly water, in the bonding slurry may be up to 20% by weight, for example, 2-20% by weight.

[0036] The components of the bonding slurry are mixed using the following mixing parameters: 400 rpm for 80 seconds, 600 rpm for 100 seconds, and 800 rpm for 120 seconds. This program is repeated 6 to 8 times. The mixing process is carried out under atmospheric pressure or in a vacuum.

[0037] It should be appreciated that the bonding slurry can be heated to a temperature of preferably 40-100°C, more preferably 150°C, such as 50-90°C. Heating or conditioning the bonding slurry reduces the viscosity of the slurry, facilitating application of the slurry to the ceramic component surface. Drying is carried out for at least 6 hours, preferably 6 hours or more.

[0038] The bonding surface region of the at least two SiC preforms may include voids intended to remain as voids after impregnation bonding. Therefore, at least one of the at least two SiC preforms may have voids in the bonding surface region. These voids can be filled with a filler material before impregnation. This filler material prevents Si from penetrating into the voids during impregnation with the liquid Si-based metal and does not react with the liquid Si-based metal during impregnation of the at least two SiC preforms with the bonding slurry. This filler material can be, for example, a boron nitride-based paste and preferably can be removed from the voids without leaving any residue after the impregnation step. The use of a filler material is important for internal voids because, due to capillary forces and the cooling behavior of silicon, the voids may otherwise fill with silicon during impregnation.

[0039] The joining slurry is applied to one or both of the joining surfaces of the two ceramic preforms to be joined by a spatula, screen printing, spraying, or other suitable method. The joining slurry is applied only to the areas of the joining surfaces that will be joined after the Si impregnation. The joining slurry is not applied to the surfaces of the cavities, whether or not they contain filler material.

[0040] The bonding slurry is applied to the bonding surfaces so that the slurry layer has a thickness of up to 200 μm, for example, 10 to 200 μm, preferably 30 to 150 μm, and more preferably 50 to 100 μm.

[0041] After applying the bonding slurry to the joining surfaces, the at least two compounds are stacked together so that their joining surfaces are in contact with each other. The joining surfaces of the at least two SiC preforms can be pressed together for at least 3 hours, preferably 5 hours or more. In one embodiment, the joining surfaces of the at least two SiC preforms are compressed or pressed together at a pressure of at least 0.3 MPa (3 bar), preferably at least 0.5 MPa (5 bar), for at least 3 hours, preferably at least 5 hours.

[0042] In a subsequent step, the at least two ceramic SiC preforms and the bonding slurry are dried at a temperature of 20° C. (preferably room temperature) to 150° C., preferably 40 to 100° C., and more preferably 50 to 90° C. Drying is sufficient when the surfaces of the bonding slurry no longer show any tendency to adhere to each other.

[0043] The loss on drying of the bonding slurry (determined according to DIN 51078, DIN EN 51078) is 5-70 wt. %, preferably 6-60 wt. %, more preferably 8-50 wt. (Drying parameters: drying temperature 105°C, shutdown criterion: weight loss of less than 1 mg in 120 seconds). The loss on ignition measured at 1000°C in an oxygen atmosphere according to DIN 51081, ISO 806 is 40-80 wt. %, preferably 50-75 wt. %, more preferably 60-75 wt. %.

[0044] By using such a bonding slurry, SiSiC is formed at the bonding seam, rather than a pure Si layer. Therefore, the bonding seam joining at least two SiC preforms is preferably chemically nearly identical to the surrounding bulk material of the resulting SiSiC part, although the silicon content may differ.

[0045] The bond seam may contain up to 50% by volume, preferably up to 30% by volume, for example 8-30% by volume, of silicon, while the silicon content in the ceramic compound surrounding the bond seam is up to 25% by volume, preferably 10-20% by volume.

[0046] In one embodiment, the material of the bonded joint comprises at least 50% by volume of silicon carbide and at least 8% by volume of silicon, advantageously 50-92% by volume of silicon carbide and 8-50% by volume of silicon, and even more advantageously 70-92% by volume of silicon carbide and 8-30% by volume of silicon, the sum of all phases always being 100% by volume.

[0047] The silicon content of the bonded seam is determined by image analysis. Accordingly, the area of ​​the bonded seam to be analyzed is marked in a first step. The silicon is then marked with a range of gray values. Software (Stream from Olympus) calculates the proportion or percentage of pixels within the marked area that correspond to the silicon content in the analyzed area.

[0048] The thickness of the bonding seam is similar to the thickness of the bonding slurry layer, and is up to 200 μm, preferably up to 100 μm, for example, 10 to 200 μm, preferably 30 to 150 μm, more preferably 50 to 100 μm.

[0049] This bonding and drying process results in a porous SiC part that can be impregnated with liquid Si to fill the pores of the ceramic material and form a SiSiC part (see Figure 1).

[0050] The method thus makes it possible to provide a SiSiC ceramic part. - at least two SiC preforms are joined together by material bonding, At least two SiC preforms are impregnated with a Si containing dried bonding slurry.

[0051] In a preferred embodiment, the method makes it possible to provide a SiSiC ceramic part. - at least two SiC preforms are joined together by material bonding, - at least one SiC preform is a porous SiC ceramic preform obtained by 3D printing, The porous SiC preform is impregnated with a Si containing bonding slurry to bond at least two SiC preforms.

[0052] Using the joining slurry of the present invention, SiSiC forms at the joining seam rather than in the Si layer, forming a material-to-material bond. For SiSiC materials, the SiC particles present before Si impregnation are referred to as primary SiC, while the SiC particles formed during impregnation by the reaction of carbon in the preform or joining slurry with the impregnating liquid Si are referred to as secondary SiC. The joining seam of the joined SiSiC parts is composed of primary SiC from the joining slurry. Furthermore, the secondary SiC is formed from the carbon source of the joining slurry and the liquid Si from the impregnation step, resulting in a joining seam with the same phase as the surrounding SiSiC. The joined material exhibits the advantage of having material properties comparable to those of the bulk material.

[0053] The ceramic components obtained by the above-described method exhibit a bending strength of at least 65%, preferably at least 75%, more preferably at least 80%, and most preferably at least 85% of the mechanical strength of a single ceramic bulk material, i.e., a ceramic material without joints. The bending strength was measured by the four-point bending method using a bending bar made of two bars joined vertically in the middle in accordance with DIN 843-1, 843-5, ISO 14704, and ASTM C1161-13.

[0054] In contrast, a bonded part containing Si only at the bonded joint can achieve less than 50% of the mechanical strength. When an adhesive is used for bonding, carbon from the adhesive can react with secondary SiC at the interface between the SiC preform and the bonded joint. The bonded joint is primarily composed of Si, and the secondary SiC formed by carbon from the adhesive decreases from the interface with the SiC preform toward the center of the bonded joint. Therefore, bonding at least two SiC preforms using an adhesive can achieve less than 60% of the mechanical strength of the bulk material.

[0055] The ceramic parts obtained by the method of the present invention can be used, for example, in wafer processing systems (ie, wafer tables), sensors, cooling systems, heat exchangers, collectors, sensor frames, and the like. [Brief explanation of the drawings]

[0056] The invention will now be explained in more detail with reference to examples and drawings. [Figure 1] 1 is a diagram showing the final ceramic part obtained according to the first embodiment of the present invention. [Figure 2] Ceramic part obtained by joining two ceramic SiC preforms without using a joining slurry. [Figure 3] 1 is a photomicrograph of the bonded seam of the final SiSiC ceramic part according to the present invention. [Figure 4A]10 shows a joining seam in a component according to a second embodiment of the invention. [Figure 4B] A close-up of the bonded seam in Figure 4A. [Figure 5] Bonded SiSiC ceramic part obtained by joining a 3D printed SiC ceramic compound and a (standard) SiC preform without Si infiltration. DETAILED DESCRIPTION OF THE INVENTION

[0057] ( Example 1 ) To bond two SiC preforms, a bonding slurry containing SiC particles, carbon black, and other carbon sources such as polymers is used. An example bonding slurry composition is as follows: 55 wt% starch solution, 14 wt% SiC powder with FEPA particle size F500, 10 wt% SiC powder with FEPA particle size F1200, and 14 wt% carbon black / graphite. The bonding slurry is applied by screen printing or other suitable process.

[0058] ( Example 2 ) Another example of a joining slurry composition is: 62 wt% starch solution, 10 wt% SiC powder with FEPA particle size F500, 10 wt% SiC powder with FEPA particle size F1200, 10 wt% carbon black / graphite, 8 wt% water. The joining slurry is applied to the joining surface area of ​​at least one SiC preform by screen printing or other suitable process.

[0059] ( Example 3 ) Another example of a joining slurry composition is: 50 wt% starch solution, 12 wt% SiC powder with FEPAF500 particle size, 16 wt% SiC powder with FEPA F1200 particle size, 17 wt% carbon black / graphite, 5 wt% water. The joining slurry is applied to the joining surface area of ​​at least one SiC preform by screen printing or other suitable process.

[0060] The two SiC preforms are then pressed together at a pressure exceeding 5 bar for at least 5 hours, and then dried at 50-90°C for at least 6 hours. This bonding and drying process results in a porous SiC part that can be impregnated with liquid Si to fill the pores of the ceramic material and form a SiSiC part.

[0061] By using a bonding slurry, a SiSiC layer is formed at the bonding seam during the impregnation process, instead of a pure Si layer, to establish a material bond.

[0062] In contrast, joining two ceramic SiC preforms without the use of a joining slurry results in the joining seam being completely filled with Si, resulting in no physically bonded connection, as best seen in Figure 2.

[0063] The photomicrograph in Figure 3 shows a bond seam after Si-impregnation bonding of two SiC preforms using the method of the present invention. The bright areas reflect the presence of silicon (Si) within the bond seam. Clearly, the silicon-rich regions are aligned roughly along the bond seam and are partially interrupted by darker areas containing little silicon. In the sample shown in Figure 3, the bond seam is composed of 8-30% silicon by volume, while the silicon content within the ceramic compound surrounding the bond seam is only 2-20% by volume.

[0064] ( Example 4 ) A bonding slurry containing SiC particles, carbon black, and other carbon sources such as polymers is used to bond the two SiC preforms.

[0065] The following is an example of a bonding slurry composition: 55 wt% starch solution, 14 wt% SiC powder with FEPA particle size F240 and / or F500, 10 wt% SiC powder with FEPA particle size F1200, 14 wt% carbon black / graphite, 7 wt% water.

[0066] The bonding slurry is applied to the bonding surface area of ​​at least one SiC preform by screen printing or other suitable process.

[0067] ( Example 5 ) Another example of a joining slurry composition is: 62 wt% starch solution, 10 wt% SiC powder with FEPA particle size F240 and / or F500, 10 wt% SiC powder with FEPA particle size F1200, 10 wt% carbon black / graphite, 8 wt% water. The joining slurry is applied to the joining surface of at least one SiC preform by screen printing or other suitable process.

[0068] ( Example 6 ) Another example of a joining slurry composition is: 50 wt% starch solution, 12 wt% SiC powder with FEPA particle size F240 and / or F500, 16 wt% SiC powder with FEPA particle size F1200, 17 wt% carbon black / graphite, 5 wt% water. The joining slurry is applied to the joining surface of at least one SiC preform by screen printing or other suitable process.

[0069] The two SiC preforms are then pressed together at a pressure exceeding 5 bar for at least 5 hours, and then dried at 50-90°C for at least 6 hours. This bonding and drying process results in a porous SiC part that can be impregnated with liquid Si to fill the pores of the ceramic material and form a SiSiC part.

[0070] 4A and 4B show the joining seam of a part made of a 3D porous SiC preform (top region of the image) and a conventionally manufactured porous SiC preform (bottom region of the image) using the joining slurry of any of Examples 4-6.

[0071] Figure 5 shows a SiSiC ceramic part obtained by joining a 3D printed SiC ceramic compound (1) with a (standard) SiC preform (2).

[0072] This combination of 3D printed SiC ceramic compounds and standard SiC preforms is used when parts are highly complex and difficult to produce economically using other manufacturing processes, and / or when only a small number of parts are required, such as for prototyping. In these cases, 3D printing is cheaper than creating a new mold.

[0073] On the other hand, the advantages of the conventional manufacturing method are excellent material properties and low manufacturing costs in mass production.

[0074] Therefore, when a high degree of complexity is required, the properties of the 3D printed compound are insufficient, or the overall size of the part exceeds the buildable volume of the 3D printer, a combination of 3D printed SiC ceramic compounds and standard SiC preforms is used.

Claims

1. 1. A method for obtaining at least one SiSiC ceramic part by joining at least two SiC preforms, comprising: - providing at least two porous SiC preforms, such as green or sintered bodies, having at least one joining surface; - 40 to 80% by weight, preferably 50 to 70% by weight, of at least one binder; A particle size D of 10 to 20 μm, preferably 11 to 18 μm, more preferably 11 to 16 μm ５０ 2 to 20 wt. %, preferably 5 to 18 wt. %, more preferably 8 to 15 wt. % of silicon carbide particles having a viscosity of 1000 psig (DIN EN 725-5, ISO 13320); A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm ５０ 8 to 25 wt. %, preferably 9 to 20 wt. %, more preferably 10 to 15 wt. % of silicon carbide particles having a viscosity of 1000 psig (DIN EN 725-5, ISO 13320); - 10 to 30 wt. %, preferably 12 to 20 wt. %, more preferably 13 to 18 wt. % of carbon black; - to provide a bonding slurry in which the sum of all components always equals 100% by weight: - pressing the joining surfaces of at least two of said SiC preforms together; drying at least two of said SiC preforms; and - heating at least two of said SiC preforms and impregnating Si into said SiC preforms containing the dried joining slurry to obtain a materially bonded silicon-silicon carbide (SiSiC) ceramic part; A method comprising:

2. 10. The method of claim 1, wherein at least one of the SiC preforms is obtained by 3D printing, and each of the SiC preforms has at least one joining surface.

3. 3. The method of claim 2, wherein the at least one SiC preform obtained by 3D printing has a SiC density of 1.3 to 3.0 g / cm before impregnation with Si. ３ , preferably 1.5 to 2.5 g / cm ３ , more preferably 1.7 to 2.2 g / cm ３ A method having a density of .

4. 4. The method of claim 2 or 3, wherein the 3D printed SiC preform is embedded in a filler material.

5. The method according to any one of claims 1 to 3, wherein the joining slurry is - 50 to 70% by weight of said at least one binder; A particle size D of 10 to 20 μm, preferably 11 to 18 μm, more preferably 11 to 16 μm ５０ (DIN EN 725-5, ISO 13320) - a particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm ５０ 9 to 20 wt. % of silicon carbide particles having a viscosity of 1000 psig (DIN EN 725-5, ISO 13320); - 12 to 20 wt. % of carbon black, In a preferred embodiment, the total of all components always equals 100% by weight.

6. The method according to any one of claims 1 to 6, wherein the joining slurry is - 50 to 70% by weight of said at least one binder; A particle size D of 10 to 20 μm, preferably 11 to 18 μm, more preferably 11 to 16 μm ５０ (DIN EN 725-5, ISO 13320) - a particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm ５０ 10 to 15 wt. % of silicon carbide particles having a viscosity of 1000 psig (DIN EN 725-5, ISO 13320); - 13 to 18 wt. % of carbon black, In a preferred embodiment, the total of all components always equals 100% by weight.

7. The method according to any one of claims 1 to 6, wherein the joining slurry is - 40 to 80% by weight, preferably 50 to 70% by weight, of said at least one binder; A particle size D of 30 to 65 μm, preferably 35 to 60 μm, more preferably 40 to 55 μm ５０ 2 to 20 wt. %, preferably 5 to 18 wt. %, more preferably 8 to 15 wt. % of silicon carbide particles having a viscosity of 1000 psig (DIN EN 725-5, ISO 13320), and / or A particle size D of 1 to 10 μm, preferably 2 to 8 μm, more preferably 2 to 5 μm ５０ 8 to 25 wt. %, preferably 9 to 20 wt. %, more preferably 10 to 15 wt. % of silicon carbide particles having a viscosity of 1000 psig (DIN EN 725-5, ISO 13320); - 10 to 30 wt. %, preferably 12 to 20 wt. %, more preferably 13 to 18 wt. % of carbon black; - A method in which the total of all components always equals 100% by weight.

8. The method according to any one of the preceding claims, wherein the at least one binder of the joining slurry is an organic material, in particular from renewable organic sources.

9. 10. The method of claim 9, wherein the at least one binder of the bonding slurry comprises a starch or a sugar.

10. The method according to any one of the preceding claims, wherein the joining slurry comprises at least one solvent, preferably water, or a mixture of at least two solvents to adjust the viscosity of the slurry.

11. 12. The method according to claim 11, wherein the amount of solvent, preferably water, in the joining slurry is up to 20% by weight, in particular 2-20% by weight.

12. 12. The method according to any one of the preceding claims, wherein the slurry layer has a thickness of at most 200 μm, preferably at most 100 μm, for example 10 to 200 μm, preferably 30 to 150 μm, more preferably 50 to 100 μm.

13. 13. The method according to any one of claims 1 to 12, wherein the joining surfaces of the at least two SiC preforms using the joining slurry are pressed together for at least 5 hours, preferably 5 hours or more.

14. The method according to any one of claims 1 to 13, wherein drying of the SiC preforms pressed together is carried out at a temperature of from 20°C to 150°C, preferably from 40°C to 100°C, more preferably from 50°C to 90°C.

Images