Method for treating porous graphite substrate, treated substrate, and use thereof

Abstract

To provide a method for treating a porous graphite substrate having improved corrosion resistance, and to provide a treated substrate.SOLUTION: A method for treating a porous graphite substrate includes: a) providing at least one film, the at least one film containing silicon particles and at least one binder; b) applying the at least one film to at least one surface of the porous graphite substrate; and c) subjecting at least one coating film to at least one heat treatment. During the heat treatment, the silicon particles are melted to form a melt, the melt partially penetrates into micropores of the porous graphite substrate, and silicon contained in the melt is converted, at least partially, into silicon carbide.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for treating a porous graphite substrate, the method comprising the steps of forming at least one film, the at least one film containing silicon particles and at least one binder, applying the at least one film to at least one surface of a porous graphite substrate, and subjecting the at least one coated film to at least one heat treatment. During the heat treatment, the silicon particles melt and the melt at least partially penetrates the porosity of the graphite substrate, whereby the silicon contained in the melt is at least partially converted to silicon carbide. The present invention also relates to the treated substrate (treated substrate) and its use. In the context of the present invention, "at least one film" can also be expressed as "at least one foil."

[0002] The manufacturing and processing of semiconductor materials (e.g., silicon, silicon carbide, nitrides) relies on the provision of high-density graphite components coated with a ceramic-based protective coating to keep production equipment running. This protective layer minimizes graphite corrosion (e.g., by oxidizing or reducing media) during semiconductor material processing, ensuring the longest possible component life or even usability. Silicon carbide (SiC) is the primary material used in such protective coating systems. Fabricating these components entirely from corrosion-resistant materials (usually ceramic) is technically impossible or economically impractical due to their size and structural complexity.

[0003] Commercially available SiC-coated graphite components are typically manufactured using chemical vapor deposition (CVD). However, applying the coating is challenging, especially on large, complex-shaped components, because uniform gas flow must be maintained across the entire surface. The difference in thermal expansion coefficients between the substrate and the coating can lead to cracking and delamination of the coating, especially under thermal stress caused by repeated thermal expansion and contraction, potentially resulting in accelerated corrosion of the component during use (see, for example, Park et al., "Improving the Oxidation Resistance of Graphite Using a Self-Healing SiC Coating at High Temperatures," Applied Surface Science, Vol. 378, 2016, pp. 341–349).

[0004] Other silicon carbide coating techniques such as powder sintering (see, for example, Paccaud et al., "Silicon carbide coatings by reactive powder sintering - Part II: Silicon monoxide / carbon reaction", Chem. Vap. Deposition 2000, 6, No. 1, pp. 41-50) and reactive silicon melt infiltration (see, for example, EP 3 330 240 B1) offer the advantage of improved layer adhesion even with large differences in thermal expansion coefficients, but are less successful in terms of layer quality, resource efficiency and suitability for large-scale production.

[0005] It should also be noted that coating graphite materials is fundamentally more challenging and a much more complex process than coating other materials, such as ceramic composites. Therefore, conventional coating methods used for other substrates are generally inappropriate for applying to graphite substrates or graphite components. Graphite substrates have a porosity of up to 25% by volume, but the pore distribution is not necessarily uniform. The low porosity of graphite compared to other materials, such as ceramic composites, combined with localized porosity and density differences, makes coating graphite components challenging. In particular, infiltration is significantly more difficult due to the low porosity of graphite compared to other materials, such as ceramic composites. As a result, coating methods applied to substrates made of other materials, such as ceramic composites, generally do not result in successful coatings when applied to graphite components.

[0006] Based on this, it was an object of the present invention to provide a method for treating a porous graphite substrate, by means of which it is possible to obtain a substrate with improved corrosion resistance.

[0007] The object of the invention is achieved by a method for treating a porous substrate according to claim 1 and a treated substrate according to claim 11. Possible uses of the treated substrate according to the invention are indicated in claim 15. The dependent claims indicate advantageous developments of the invention.

[0008] The present invention relates to a method for (surface) treatment of a porous graphite substrate, which method comprises the following steps: a) providing at least one film comprising silicon particles and at least one binder; b) coating said at least one film onto at least one surface of a porous graphite substrate; c) subjecting the at least one coating obtained to at least one heat treatment step, in which the silicon particles melt to form a melt that at least partially penetrates the pores of the porous graphite substrate, and in which the silicon contained in the melt is at least partially, preferably completely, converted to silicon carbide, more preferably polycrystalline silicon carbide.

[0009] In step a) of the method of the present invention, at least one film is used. This at least one film contains silicon particles and at least one binder. Preferably, the at least one film may further contain at least one plasticizer. Furthermore, the at least one film may optionally contain other components such as at least one antifoaming agent (e.g., fatty alcohol polyethylene glycol ether), at least one dopant, and / or at least one surfactant (or surface tension reducing agent). For example, the at least one film may be composed of silicon particles, at least one binder, optionally at least one plasticizer, optionally at least one antifoaming agent (e.g., fatty alcohol polyethylene glycol ether), optionally at least one dopant, and optionally at least one surfactant (or surface tension reducing agent). Preferably, the silicon particles contained in the at least one film are silicon granules or silicon powder, with silicon granules being particularly preferred.

[0010] In this context, a binder can generally be understood as a substance that creates or promotes chemical bonding at the interface of other substances, or that causes or enhances effects such as cohesion, adsorption, adhesion, or friction.

[0011] The at least one binder serves to firmly bind the silicon particles together, thereby ensuring the stability and adhesion of the at least one film. A plasticizer added to the film can increase the flexibility of the film. However, it is also possible (or, in addition) for the at least one binder to also act as a plasticizer, thereby imparting a certain flexibility to the film. It is also possible that the film does not contain any plasticizer, or that the at least one binder acts as a plasticizer.

[0012] Preferably, a suspension based on a solvent (e.g., water) can be used as the base material for producing at least one membrane. This suspension contains silicon particles (e.g., with an average particle size d50 of 1 to 2000 μm) and at least one binder (e.g., carboxymethyl cellulose (CMC) or polyvinyl alcohol (PVA)), and optionally at least one plasticizer (e.g., polyethylene glycol (PEG)). For example, the thin film of the present invention can be produced by forming the suspension into a thin film using a doctor blade method or a film casting method. The thickness of the thin film can be set to, for example, about 500 to 5000 μm, and after drying and solvent removal, a (flexible) thin film with dispersed Si particles is obtained. The density per unit area of ​​the membrane can be determined (or adjusted) by the membrane thickness and the proportion of silicon solids used.

[0013] In step b) of the method of the present invention, at least one membrane is applied to at least one surface of a porous graphite substrate. The membrane can be applied to the surface by, for example, wetting it with a solvent capable of dissolving at least one binder and, preferably, other organic components (such as plasticizers), then pasting it onto the substrate, pressing it, and drying it. The at least one binder is reactivated by drying, resulting in a strong bond to the substrate after drying. Preferably, the membrane is cut, perforated, or folded into any desired shape before, during, and / or after step b). For example, multiple membranes or membrane pieces can be used, and these membranes or membrane pieces can be stretched, widened, stacked, or laminated as needed by applying or spraying a solvent to the connecting ends or surfaces. Preferably, silicon solids (or silicon particles) can be recovered from the membrane residue by dissolving and washing with a solvent, and then processed for reuse. For example, water can be used as the solvent. In step b), the at least one film is applied to at least one surface of the porous graphite substrate and, after application, is positioned so as to contact at least one edge of the substrate. That is, the at least one film applied is in contact with at least one edge of the substrate. Preferably, in step b), the at least one film is applied to at least one surface of the porous graphite substrate so as to completely cover the at least one surface.

[0014] In step c) of the method of the present invention, at least one coating film is subjected to at least one heat treatment. During the at least one heat treatment, the silicon particles melt to form a melt, which partially infiltrates the pores of the porous graphite substrate. The silicon contained in the melt then reacts at least partially, preferably completely (with carbon from the porous graphite substrate) to produce silicon carbide, particularly polycrystalline silicon carbide. In this case, the melt does not completely infiltrate the pores of the porous graphite substrate, but only partially. That is, not all of the melt penetrates the pores of the porous graphite substrate. Instead, the part of the melt that does not penetrate the pores of the porous graphite substrate forms a silicon carbide layer on at least one surface (while the silicon carbide present in the pores is formed from the part of the melt that penetrates the pores of the porous graphite substrate). The substrate obtained in this way (the substrate produced by the method of the present invention) has a silicon carbide layer on the treated surface (or at least one surface) and an infiltrated layer below it. In this infiltration layer, the micropores of the graphite material are at least partially filled with (or contain) silicon carbide. The composite structure of the silicon carbide layer formed on the surface and the porous infiltration layer (at least partially) filled with (or containing) silicon carbide is sometimes called a protective layer.

[0015] The substrate produced by the method of the present invention has a very low gas permeability, preferably completely impermeable, due to the aforementioned protective layer (i.e., a composite structure of a silicon carbide layer (on the surface) and an infiltration layer (at least partially) filled with silicon carbide (or containing silicon carbide)). This suppresses the penetration of gases and liquids into the substrate material, and ultimately reaction with corrosive substances (e.g., oxygen), thereby preventing deterioration of the carbon material of the substrate. This is achieved by almost completely sealing the treated surface or almost completely closing the micropores near the surface. This contributes to improving the resistance of the substrate obtained by the method of the present invention. Furthermore, the silicon carbide layer in the infiltration region of the substrate and the silicon carbide particles present in the micropores improve the hardness and wear resistance of the produced substrate, which also contributes to improving resistance.

[0016] Furthermore, the method of the present invention is characterized by the use of at least one film, which allows for extremely precise application of silicon particles to the target area of ​​the substrate. Compared to other application methods, such as CVD coating or particle application using a suspension (e.g., spray coating), the present method allows for more precise and targeted coating, resulting in a more uniform protective layer (i.e., a more uniform silicon carbide layer and a more uniform infiltration layer). Other application methods, such as applying silicon particles to a substrate using an (aqueous) suspension (e.g., spray coating), have the problem of not forming a coating of sufficient thickness at the edges and corners of the substrate. This is because the coating thickness at these areas is thinner than at the interior. As a result, an uneven layer structure is formed, where the protective layer is thinner near the edges of the substrate than in other areas, resulting in lower resistance at the edges of the substrate. The method of the present invention avoids this problem because the use of at least one film allows for uniform application of silicon particles to the entire desired area of ​​the surface of the substrate to be treated, thereby forming a protective layer of sufficient thickness even at the edges and corners of the substrate. As a result, the method of the present invention makes it possible to form a uniform protective layer over the entire desired area, and achieve the desired corrosion resistance of the substrate over the entire substrate, especially in areas such as the edges and corners of the substrate. As a result, the corrosion resistance of the substrate produced by this technique is further improved. For example, the substrate produced using the method of the present invention exhibits excellent oxidation resistance for a very long period of time. Compared to substrates treated using a method in which silicon particles are applied to the substrate using an (aqueous) suspension (e.g., spray coating), this method maintains excellent oxidation resistance for a longer period of time.

[0017] In the context of the present invention, it has surprisingly been found that the method of the present invention and the resulting homogeneous protective layer allow for excellent coating formation on graphite substrates or graphite parts. Coating graphite substrates or parts is in fact very challenging and much more complicated than coating other materials, such as ceramic composites. This is because the porosity of graphite is low compared to other materials, such as ceramic composites, making penetration coatings particularly difficult. Another advantage of using at least one film is that the coating system can be precisely tailored to the properties of the graphite (e.g., silicon content, etc.).

[0018] It is also noteworthy that the melt penetrates into the micropores of the substrate, resulting in the pores being (at least partially) filled with (or containing) silicon carbide, resulting in very high adhesive strength. This significantly reduces or completely prevents problems such as cracking and delamination due to differences in thermal expansion coefficients. On the one hand, this method achieves high coating quality and an excellent surface finish. On the other hand, it also prevents defects such as cracking and delamination in the protective layer, thereby suppressing a decrease in resistance.

[0019] "Using at least one film to apply the silicon particles also simplifies and simplifies coating complex substrates and components, as the at least one film can be machined or cut to any desired shape, eliminating the risk of dripping or blurring during application, as occurs with applying a suspension. Surfaces can also be coated in a variety of ways, such as by stacking multiple layers with different silicon particle concentrations or by placing different concentrations of silicon particles in different areas of a single layer."

[0020] Furthermore, the method of the present invention can also be used to regenerate parts whose surface coating has deteriorated or been damaged after use by repeatedly coating them.

[0021] The use of at least one film simplifies the application of silicon particles, increasing substrate and component throughput and reducing the manufacturing cost per unit, resulting in a simpler, faster, and less expensive manufacturing process.

[0022] A preferred embodiment of the method according to the invention has the following features: The silicon particles have an average particle size (d50) in the range of 1 μm to 2000 μm, preferably 50 μm to 1500 μm, more preferably 100 μm to 1000 μm, even more preferably 510 μm to 950 μm (or more than 500 μm to 950 μm), and particularly preferably 600 μm to 900 μm. the thickness of at least one membrane is equal to or greater than 500 μm (or greater than 500 μm), preferably in the range of 500 μm to 5000 μm (or greater than 500 μm to 5000 μm), more preferably in the range of 600 μm to 4000 μm, even more preferably in the range of 700 μm to 3000 μm, in particular in the range of 800 μm to 2000 μm;

[0023] By forming at least one coating of this thickness, the resistivity of the treated substrate can be made very high, especially in the case of graphite substrates.

[0024] The average particle size (d50) of the silicon particles can be measured, for example, using a laser diffraction method (for example, measured in accordance with ISO 13320:2020-01).

[0025] A further preferred embodiment of the method according to the present invention is characterized in that the silicon particles have a unimodal particle size distribution (across at least one film or across multiple regions thereof) or a multimodal particle size distribution, particularly a bimodal particle size distribution (across at least one film or across multiple regions thereof). For example, the silicon particles may have a multimodal particle size distribution, preferably a bimodal particle size distribution, in which the first group of silicon particles has an average particle size (d50) in the range of 1 μm to 50 μm, more preferably 3 μm to 20 μm, and the second group of silicon particles has an average particle size (d50) in the range of 100 μm to 2000 μm, more preferably 510 μm to 950 μm, or is composed of these.

[0026] The particle size distribution and / or average particle size (d50) of the silicon particles can be measured, for example, using a laser diffraction method (such as ISO 13320:2020-01 standard).

[0027] The use of silicon particles with a multimodal or bimodal particle size distribution improves the adhesion and packing density of the silicon particles in at least one film, resulting in a higher silicon particle density and a more uniform film layer, which in turn leads to a more uniform and homogeneous surface coverage and ultimately to a more uniform protective layer (i.e., a more uniform silicon carbide layer and a more uniform infiltration layer).

[0028] According to a further preferred embodiment, the silicon particles (over at least one entire membrane or over multiple membrane regions) can have a unimodal particle size distribution. For example, the average particle size (d50) of the silicon particles (overall region or each region) constituting at least one membrane is in the range of 1 μm to 2000 μm, preferably 50 μm to 1500 μm, more preferably 100 μm to 1000 μm, even more preferably 510 μm to 950 μm (or more than 500 μm to 950 μm), and particularly preferably 600 μm to 900 μm.

[0029] A preferred embodiment of the method according to the invention is characterized in that at least one membrane comprises at least one first region and at least one second region, wherein the average particle size (d50) of the silicon particles in at least one second region is larger than the average particle size (d50) of the silicon particles in at least one first region. Preferably, the average particle size (d50) of the silicon particles in at least one first region is in the range of 1 μm to 50 μm, more preferably in the range of 3 μm to 20 μm, and / or the average particle size (d50) of the silicon particles in at least one second region is in the range of 100 μm to 2000 μm, more preferably in the range of 510 μm to 950 μm.

[0030] By using silicon particles with different average particle sizes in different regions of the film, more uniform and higher surface coverage can be achieved on parts with different thicknesses and / or complex shapes and / or significant local porosity differences, resulting in a more homogeneous protective layer (i.e., a more homogeneous silicon carbide layer and a more homogeneous infiltration layer).

[0031] According to a more preferred embodiment, the silicon particles have an average particle size (d50) in the range of 1 μm to 2000 μm, preferably 50 μm to 1500 μm, more preferably 100 μm to 1000 μm, most preferably 510 μm to 950 μm (or more than 500 μm to 950 μm), and particularly preferably 600 μm to 900 μm, throughout the entire region of at least one film. For example, the average particle size (d50) of the silicon particles may be substantially the same throughout the entire region of at least one film.

[0032] A further preferred embodiment of the method according to the invention is characterized in that the at least one film comprises at least one first region and at least one second region, wherein the silicon concentration per unit area (or amount of silicon per unit area) of the at least one second region is higher than that of the at least one first region. Furthermore, preferably, the at least one film comprises at least one third region having a silicon concentration per unit area (or amount of silicon per unit area) higher than that of the at least one second region.

[0033] The silicon concentration per unit area (or silicon amount per unit area) in each region can be appropriately adjusted by using a different silicon concentration or silicon amount for each region when manufacturing at least one membrane. The silicon concentration per unit area (or silicon amount per unit area) can be measured on an already manufactured membrane, for example, by cutting out a piece of membrane with a predetermined area and measuring its weight. The area of ​​the defined region is preferably 1 cm 2 More than 150cm, preferably 2 More than 250 cm 2 It's super.

[0034] According to a further preferred embodiment, at least one membrane may be configured so that the silicon concentration per unit area (or amount of silicon per unit area) is approximately constant over its entire area or in each of its areas.

[0035] A further preferred embodiment of the method according to the present invention is characterized in that in step a), at least one suspension is prepared, comprising silicon particles, at least one binder, and at least one solvent, preferably water, and optionally further adding at least one plasticizer, and then this suspension is processed to form at least one film, preferably by doctor blade or film casting.Furthermore, at least one of the suspensions may optionally contain other components, such as at least one antifoaming agent (e.g., fatty alcohol polyethylene glycol ether), at least one dopant, and / or at least one surfactant (or surface tension reducing agent).For example, at least one suspension contains silicon particles, at least one binder, at least one solvent (preferably water), optionally at least one plasticizer, optionally at least one antifoaming agent (e.g., fatty alcohol polyethylene glycol ether), optionally at least one dopant, and optionally at least one surfactant (or surface tension reducing agent). Preferably, the silicon particles contained in at least one suspension are silicon granules or silicon powder, with silicon granules being particularly preferred.

[0036] Further preferred embodiments of the method according to the invention have the following characteristics: the at least one binder is selected from the group consisting of polyvinyl alcohol, polyethylene glycol, polyvinyl butyral, polyacetic acid, polyurethane, polymethyl methacrylate, vinyl chloride rubber, phenolic resins, acrylic resins, cellulose, cellulose derivatives, preferably carboxymethyl cellulose, hydroxyethyl cellulose, alginic acid, dextrin, and mixtures thereof, whereby the at least one binder is preferably selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, and mixtures thereof; and / or the at least one membrane comprises at least one plasticizer different from the at least one binder, wherein the at least one plasticizer is preferably selected from benzyl butyl phthalate, dibutyl phthalate, dimethyl phthalate, dioctyl phthalate, glycerol, polyvinylpyrrolidone, polypropylene glycol, butyl octadecanoate, or mixtures thereof;

[0037] A further preferred embodiment of the method according to the invention is characterized in that at least one membrane has the following characteristics: - containing 40 to 99.9% by weight, preferably 55 to 95% by weight, more preferably 60 to 90% by weight of silicon particles relative to the total weight of the at least one membrane; and / or - at least one binder agent in an amount of 0.1 to 25% by weight, preferably 1 to 10% by weight, more preferably 3 to 5% by weight, relative to the total weight of the at least one membrane; and / or - 0 to 35% by weight, preferably 1 to 15% by weight, more preferably 5 to 10% by weight, of at least one plasticizer different from the at least one binder, relative to the total weight of the at least one membrane.

[0038] A further preferred embodiment of the method according to the invention is characterized in that at least one membrane is made of a composition comprising the following components: - silicon particles: 40 to 99.9% by weight, preferably 60 to 97.9% by weight, more preferably 75 to 91% by weight, - at least one binder: 0.1 to 25% by weight, preferably 1 to 10% by weight, more preferably 3 to 5% by weight, - at least one plasticizer different from the at least one binder: 0 to 35% by weight, preferably 1 to 15% by weight, particularly preferably 5 to 10% by weight, based on the total weight of the at least one membrane; - at least one additive selected from the group consisting of antifoaming agents (such as fatty alcohol-based polyethylene glycol ethers), dopants, surfactants (or surface tension reducing agents), and mixtures thereof: 0 to 35% by weight, preferably 0.1 to 15% by weight, more preferably 1 to 10% by weight, However, the total of all components is 100% by weight.

[0039] Further preferred embodiments of the method according to the invention have the following characteristics: - at least one membrane is cut, punched and / or folded before, during and / or after step b); and / or - at least one membrane is composed of at least two membranes combined together, which membranes are joined before, during and / or after step b).

[0040] A further preferred embodiment of the method according to the present invention is characterized in that, in step b) of depositing at least one film on at least one surface of the porous graphite substrate, at least one surface of the porous graphite substrate and / or at least one film are first wetted with a solvent, preferably water, in which at least one binder is at least partially soluble, then at least one film is brought into contact with at least one surface of the porous graphite substrate, and finally, at least one drying treatment is carried out while the film is in contact with the surface of the porous substrate. This drying treatment is preferably carried out at a temperature in the range of 10°C to 200°C, more preferably 80°C to 100°C, and / or for a period of 15 minutes to 48 hours, more preferably 1 hour to 12 hours.

[0041] A further preferred embodiment of the method according to the invention is characterized in that at least one heat treatment satisfies the following conditions: the temperature is in the range of 1400°C to 1800°C, preferably 1410°C to 1700°C, particularly preferably 1450°C to 1550°C; and / or the treatment time is between 1 hour and 10 hours, preferably between 4 hours and 6 hours; and / or - It is carried out in a vacuum or in an inert gas atmosphere, preferably an argon gas atmosphere, at a (process) pressure of 10 mbar to 2000 mbar, preferably 100 mbar to 1800 mbar, more preferably 500 mbar to 1500 mbar, and even more preferably 800 mbar to 1200 mbar.

[0042] By varying the gas atmosphere, temperature, treatment time, and / or treatment pressure, it is possible to control and adjust the thickness of the permeation layer, and thus properties such as airtightness and gas permeability.

[0043] Further preferred embodiments of the method according to the invention are characterized in that they have the following features: - the porous graphite substrate is a porous isotropic graphite substrate; and / or - The porous graphite substrate has a thermal expansion coefficient of at least 2.8 x 10 -6 K -1 , preferably at least 3.0 x 10 -6 K -1 , more preferably at least 3.2×10 -6 K -1 and / or the porous graphite substrate has an open porosity, as measured by mercury intrusion porosimetry, of at least 12%, preferably between 12% and 30%, more preferably between 14% and 25%, and even more preferably between 15% and 20%; and / or The pore size of the porous graphite substrate is in the range of 0.1 μm to 10 μm on average, preferably in the range of 1 μm to 5 μm, and more preferably in the range of 1.5 μm to 5 μm.

[0044] The thermal expansion coefficient can be measured, for example, in accordance with the DIN 51909:2009-05 standard.

[0045] The open porosity of the porous graphite substrate is measured by mercury intrusion porosimetry (eg according to the DIN 66133:1993-06 standard).

[0046] The average pore size of the micropores in the porous graphite substrate can be measured using a mercury intrusion pore size measurement method (for example, in accordance with the DIN 15901-1:2019-03 standard).

[0047] The present invention also relates to a substrate made of porous graphite material, provided on at least one surface thereof with a silicon carbide layer and provided below (i.e., below the silicon carbide layer) with a permeated layer in which the pores of the graphite material are at least partially filled with silicon carbide (or the pores of the graphite material (at least partially) contain silicon carbide), wherein in a region (preferably each region) adjacent at least one edge of the treated substrate, the thickness of the silicon carbide layer corresponds to at least 70% of the average thickness of the silicon carbide layer (as a whole). Preferably, at least one region (of the silicon carbide layer) adjacent at least one edge of the treated substrate extends from that edge to a distance of: 2 mm, preferably 4 mm, particularly preferably 10 mm, and / or a distance of 10%, preferably 20%, of the distance between at least one edge of the substrate and its opposite edge.

[0048] A composite of a silicon carbide layer and a porous layer (permeation layer) filled (at least partially) with silicon carbide (or a material containing silicon carbide) can be considered a protective layer. That is, at least one surface of a substrate is provided with a silicon carbide layer as a protective layer, and a permeation layer located below it (for example, below the silicon carbide layer). In this permeation layer, the micropores of the graphite material are at least partially filled with silicon carbide (or contain silicon carbide). The permeation layer is located deeper in the substrate than the silicon carbide layer. That is, the protective layer has a structure in which the silicon carbide layer located directly on the surface is the outer layer and the permeation layer is located inside it.

[0049] The infiltrated region refers to a region of the treated substrate where silicon carbide has infiltrated into the pores of the graphite material. Regions of the treated substrate outside the infiltrated region are free of silicon carbide within the pores of the graphite material. Thus, the infiltrated region extends from the silicon carbide layer (or the inner edge of the silicon carbide layer) to the furthest point from at least one surface of the treated substrate, including the region where silicon carbide has infiltrated into the pores of the substrate material (the region that is continuous with the silicon carbide layer).

[0050] The thickness (thickness at a specific point) and / or average thickness of the silicon carbide layer can be measured, for example, in accordance with the DIN EN ISO 1463:2021-08 standard, for example, by observing a cross section (perpendicular to the penetration direction) with an optical microscope.

[0051] The average thickness of the silicon carbide layer can be determined, for example, by observing a cross section of the silicon carbide layer using an optical microscope, measuring the thickness at various positions along the length and / or width of the layer individually, and calculating the average of these measurements.

[0052] The average thickness of the silicon carbide layer is preferably 10 μm or more, more preferably 10 μm to 10,000 μm, and particularly preferably 100 μm to 2,000 μm.

[0053] The treated substrate according to the present invention is preferably produced or producible by the method of the present invention.

[0054] In a preferred embodiment, - in each case, the radius of at least one edge is in the range R0 (or 0 mm) to R5 (or 5 mm), preferably R 0.5 (or 0.5 mm) to R4 (or 4 mm), particularly preferably in the range of R1 (or 1 mm) to R3 (or 3 mm); and / or The angle between the two faces forming at least one end is in the range of 10° to 170°, preferably in the range of 30° to 150°, and particularly preferably in the range of 45° to 135°.

[0055] The edge radius and / or angle between two faces forming at least one edge can be measured, for example, in accordance with DIN EN ISO 13715:2020-01.

[0056] A preferred embodiment of the processing substrate according to the present invention is characterized by the following features. That is, the processing substrate is - (Gas) permeability up to 1 x 10 -16 m 2 , preferably up to 1 x 10 -17 m 2 , more preferably up to 1 × 10 -18 m 2 , particularly preferably up to 1 × 10 -19 m 2 is and / or - the (gas) permeability after treatment is at least 10 times, preferably at least 100 times, lower than the (gas) permeability of the substrate before treatment; and / or - the porosity in the infiltrated area is at most 10%, preferably at most 8%, more preferably at most 5%, as measured by mercury intrusion; and / or - the open porosity in the infiltrated region, measured by mercury porosimetry, is at least 7%, preferably at least 10%, more preferably at least 12% lower, relative to the volume of the entire treated substrate, than the open porosity of the treated substrate outside the infiltrated region; and / or - a resistivity of at most 1500 mΩcm, preferably at most 10 mΩcm; and / or - the treated substrate has an oxidation resistance such that after exposure in synthetic air (200 ml / min, 1 bar) at 1100°C for more than 162 hours, preferably more than 170 hours, more preferably more than 180 hours, even more preferably more than 190 hours, its mass (based on the mass of the substrate before exposure to synthetic air at 1100°C) loses less than 0.72%, preferably less than 0.5%, more preferably less than 0.3%, even more preferably less than 0.2%; and / or - does not contain elemental silicon, and / or - produced or producible by the method of the invention.

[0057] The (gas) permeability of the treated substrate and / or the (gas) permeability of the substrate before treatment can be measured, for example, using differential pressure measurements (for example, according to the EN 993-4:1995 standard).

[0058] To determine whether the processed substrate has the characteristic of exhibiting a (gas) permeability that is at least 10 times, preferably at least 100 times lower than that of the substrate before processing, first, for example, using a differential pressure method (for example, in accordance with EN 993-4:1995) to measure the (gas) permeability of the processed substrate. Next, the silicon carbide layer and the permeation layer are removed from the processed substrate, for example, by polishing, and the (gas) permeability of the resulting substrate from which the silicon carbide layer and the permeation layer have been removed is measured, for example, using a differential pressure method (for example, in accordance with EN 993-4:1995). Finally, the two measured (gas) permeabilities are compared, and their ratio is calculated. The (gas) permeability of the substrate after removing the silicon carbide layer and the permeation layer corresponds to the gas permeability of the substrate before processing.

[0059] The open porosity of the treated substrate in the infiltrated region and the open porosity of the treated substrate outside the infiltrated region can be measured by mercury intrusion porosimetry (eg according to the DIN 66133:1993-06 standard).

[0060] The porosity of the treated substrate outside the infiltrated area is approximately the same as that of the untreated substrate (as is the case in what will become the infiltrated area).

[0061] The resistivity of the treated substrate can be measured, for example, in accordance with the DIN IEC 60413 / 402 standard.

[0062] Preferably, the volume ratio of single crystal silicon in the substrate after processing is less than 5%, more preferably less than 3%, and particularly preferably less than 1%. Even more preferably, the substrate after processing contains no single crystal silicon at all. This can be confirmed, for example, by X-ray diffraction (XRD) or energy dispersive X-ray spectroscopy (EDX).

[0063] A further preferred embodiment of the processing substrate according to the present invention is characterized by having the following features. - the graphite material is an isotropic graphite material; and / or the average thickness of the permeation layer is at least 100 μm, preferably between 100 μm and 1200 μm, particularly preferably between 200 μm and 800 μm, and / or the silicon carbide that at least partially fills the pores of the graphite material in the infiltrated zone is preferably composed of 3C-SiC, and preferably contains 3C-SiC as the main phase; and / or - the local concentration of silicon carbide in the infiltrated region decreases with increasing distance from at least one surface, and / or the infiltrated region comprises at least one first region and at least one second region, the at least one second region being located the same distance from the at least one surface as the at least one first region and having a higher silicon carbide concentration per unit volume (or amount of silicon carbide per unit volume) than the at least one first region, and preferably the at least one infiltrated region also comprising at least one third region that is equidistant from the at least one surface as the at least one second region (and at least one first region), and the third region having a higher silicon carbide concentration per unit volume (or amount of silicon carbide per unit volume) than the at least one second region.

[0064] If the pores of the graphite material in the infiltrated region are at least partially filled with silicon carbide, the silicon carbide can be confirmed to be 3C-SiC using, for example, X-ray diffraction (XRD).

[0065] When the pores of the graphite material in the infiltrated region are at least partially filled with silicon carbide, the silicon carbide being predominantly 3C-SiC means that the silicon carbide filling the pores of the graphite material in the infiltrated region is predominantly 3C-SiC phase and does not contain other silicon carbide phases that are present in greater weight proportions than the 3C-SiC phase.

[0066] When the micropores of the graphite material in the infiltrated region are at least partially filled with silicon carbide, it can be confirmed, for example, by X-ray diffraction (XRD), that the main phase of the silicon carbide is 3C-SiC, which is also called β-SiC.

[0067] Preferably, the content of silicon carbide at least partially filling the pores of the graphite material in the infiltrated region is at least 50% by weight, more preferably at least 70% by weight, even more preferably at least 90% by weight, most preferably at least 95% by weight, for example at least 99% by weight, and the silicon carbide is 3C-SiC (3C-type silicon carbide) or β-SiC (β-type silicon carbide).

[0068] Preferably, the silicon carbide with which the pores of the graphite material in the infiltrated region are at least partially filled has an α-SiC content of not more than 5 wt.%, more preferably not more than 1 wt.%, and particularly preferably not more than 0.1 wt.%. Even more preferably, the silicon carbide with which the pores of the graphite material in the infiltrated region are at least partially filled does not contain α-SiC.

[0069] When the micropores of the graphite material in the infiltration region are at least partially filled with 3C-SiC or β-SiC and / or α-SiC, the proportion of 3C-SiC or β-SiC and / or α-SiC in the silicon carbide can be measured, for example, using X-ray diffraction (XRD) methods.

[0070] The local concentration of silicon carbide in the infiltrated region and / or the concentration of silicon carbide per unit volume (or amount of silicon carbide per unit volume) in specific regions within the infiltrated region (e.g., at least one first region, at least one second region, and / or at least one third region, etc.) can be measured using energy dispersive X-ray spectroscopy (EDX).

[0071] Preferably, the silicon carbide layer has a thickness in each region (of the silicon carbide layer) adjacent at least one edge of the handle substrate that is at least 70% of the average thickness of the silicon carbide layer.

[0072] A further preferred embodiment of the processing substrate according to the present invention has the following features. In at least one (preferably each) region (of the silicon carbide layer) adjacent at least one edge of the handle substrate, the thickness of the silicon carbide layer is at least 75%, preferably at least 80%, more preferably at least 85%, particularly preferably at least 90% of the average thickness of the (total) silicon carbide layer, and / or at most 125%, preferably at most 120%, even more preferably at most 115%, particularly preferably at most 110%, and most preferably at most 105%. Preferably, at least one region (of the silicon carbide layer) adjacent at least one edge of the handle substrate extends from said at least one edge to a distance of: a distance of 2 mm, preferably 4 mm, more preferably 10 mm, and / or a distance of 10%, preferably 20%, of the distance between at least one edge of the substrate and an edge of the substrate opposite said at least one edge, and / or the thickness of the silicon carbide layer at any point within 2 mm, preferably within 4 mm, particularly preferably within 10 mm of at least one edge of the treated substrate is at least 70%, preferably at least 75%, particularly preferably at least 80%, even more preferably at least 85%, in particular at least 90% of the average thickness of the silicon carbide layer (as a whole), and / or is at most 125%, preferably at most 120%, particularly preferably at most 115%, even more preferably at most 110%, in particular at most 105%; and / or the thickness of the silicon carbide layer at any point is at most 10%, preferably at most 20%, of the distance between at least one edge of the substrate and the edge opposite said at least one edge, and is at least 70%, preferably at least 75%, more preferably at least 80%, even more preferably at least 85%, in particular at least 90%, and / or at most 125%, preferably at most 120%, more preferably at most 115%, even more preferably at most 110%, in particular at most 105% of the average thickness of the silicon carbide layer (as a whole).

[0073] Further preferred embodiments of the handle substrate according to the invention have the following characteristics. the silicon carbide layer has a thickness in at least one (preferably each) region adjacent at least one edge of the handle substrate that is at least 75%, preferably at least 80%, more preferably at least 85%, particularly preferably at least 90% and / or at most 125%, preferably at most 120%, more preferably at most 115%, particularly preferably at most 110%, and even more preferably at most 105% of the average thickness of the silicon carbide layer in at least one untreated region of the silicon carbide layer (i.e., at least one region of the silicon carbide layer that is not adjacent at least one edge of the handle substrate), wherein at least one region of the silicon carbide layer adjacent at least one edge of the handle substrate preferably extends a distance from said at least one edge that is: a distance of 2 mm, preferably 4 mm, more preferably 10 mm, and / or a distance of 10%, preferably 20%, of the distance between at least one edge and the edge of the substrate opposite said at least one edge; and / or the thickness of the silicon carbide layer at any point within 2 mm, preferably within 4 mm, particularly preferably within 10 mm of at least one edge of the treated substrate is at least 70%, preferably at least 75%, particularly preferably at least 80%, even more preferably at least 85%, particularly preferably at least 90% of the average thickness of the silicon carbide layer in all other parts (i.e. parts more than 2 mm, more than 4 mm or more than 10 mm away from at least one edge of the treated substrate), and / or is at most 125%, preferably at most 120%, particularly preferably at most 115%, even more preferably at most 110%, particularly preferably at most 105%; and / or The thickness of the silicon carbide layer at any point is 10% or less, preferably 20% or less, of the distance between at least one edge of the substrate and the edge opposite the at least one edge, and is 70% or more, preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, in particular 90% or more, and / or 125% or less, preferably 120% or less, more preferably 115% or less, even more preferably 110% or less, in particular 105% or less of the average thickness of the silicon carbide layer, provided that the average thickness of the silicon carbide layer is greater than 10% or 20% of the distance between at least one edge of the substrate and the edge opposite the at least one edge.

[0074] A further preferred embodiment of the processing substrate according to the present invention has the following features. the thickness of the silicon carbide layer in at least one (preferably each) region (of the silicon carbide layer) adjacent at least one edge of the handle substrate is at least 75%, preferably at least 80%, more preferably at least 85%, particularly preferably at least 90%, and / or at most 125%, preferably at most 120%, more preferably at most 115%, particularly preferably at most 110%, and particularly preferably at most 105% of the thickness of the silicon carbide layer in (or all) the remaining regions (of the silicon carbide layer) of the handle substrate (i.e., at least one region of the silicon carbide layer not adjacent at least one edge of the handle substrate), wherein at least one region (of the silicon carbide layer) adjacent at least one edge of the handle substrate preferably extends a distance from said at least one edge that is: a distance of 2 mm, preferably 4 mm, and more preferably 10 mm; and / or a distance of 10%, preferably 20%, of the distance between at least one edge of the substrate and the edge opposite said at least one edge; and / or the thickness of the silicon carbide layer at any point within 2 mm, preferably within 4 mm, particularly preferably within 10 mm of at least one edge of the treated substrate is at least 70%, preferably at least 75%, particularly preferably at least 80%, even more preferably at least 85%, in particular at least 90% of the thickness of the silicon carbide layer at other parts of the treated substrate (i.e. parts that are more than 2 mm, more than 4 mm, or more than 10 mm away from at least one edge of the treated substrate), and / or is at most 125%, preferably at most 120%, particularly preferably at most 115%, even more preferably at most 110%, in particular at most 105%; and / or the thickness of the silicon carbide layer, at all points (of the silicon carbide layer) that are at a distance of 10% or less, preferably 20% or less, of the distance between at least one edge of the substrate and the edge opposite that at least one edge, is at least 70%, preferably at least 75%, more preferably at least 80%, even more preferably at least 85%, in particular at least 90%, and / or at most 125%, preferably at most 120%, more preferably at most 115%, even more preferably at most 110%, in particular at most 105%, of the thickness of the silicon carbide layer in all other parts of the substrate (i.e. parts that are at a distance of more than 10% or more than 20% of the distance between at least one edge of the substrate and the edge opposite that at least one edge);

[0075] Further preferred embodiments of the handle substrate according to the present invention are characterized in that the thickness of the silicon carbide layer at any position (of the silicon carbide layer) at least 4 mm, preferably at least 2 mm, more preferably at least 1 mm, even more preferably at least 0.5 mm from at least one edge of the handle substrate is at least 70%, preferably at least 75%, more preferably at least 80%, even more preferably at least 85%, in particular at least 90% of the average thickness of the silicon carbide layer (as a whole), and / or is at most 130%, preferably at most 125%, more preferably at most 120%, even more preferably at most 115%, in particular at most 110%.

[0076] In a further preferred embodiment of the treated substrate according to the present invention, the thickness of the silicon carbide layer in each portion thereof is at least 70%, preferably at least 75%, more preferably at least 80%, most preferably at least 85%, in particular at least 90% of the average thickness of the silicon carbide layer (as a whole), and / or is at most 130%, preferably at most 125%, more preferably at most 120%, most preferably at most 115%, in particular at most 110%.

[0077] A further preferred embodiment of the processing substrate according to the present invention has the following features. The standard deviation of the average thickness of the silicon carbide layer is less than or equal to 50%, preferably less than or equal to 20%, more preferably less than or equal to 10%.

[0078] The thickness of the infiltration zone is measured from the edge of the infiltration zone adjacent the silicon carbide layer to the edge of the infiltration zone opposite the silicon carbide layer.

[0079] The thickness (at a specific point) of the infiltrated region and / or the average thickness of the infiltrated region can be measured, for example, by observing a cross section (perpendicular to the infiltration direction) with an optical microscope, for example in accordance with the DIN EN ISO 1463:2021-08 standard.

[0080] The average thickness of the permeation region can be determined, for example, by observing a cross section of the permeation region (a cross section perpendicular to the permeation direction) with an optical microscope, measuring the thickness of the permeation region at multiple positions along the length and / or width of the permeation region, and calculating the average of these measurements. The thickness of the permeation region can be calculated as an average across the entire length and / or width of the permeation region.

[0081] Furthermore, the invention relates to the use of the treatment substrate as a component of a high temperature furnace, in particular as a heater, a thermal insulator, a support, or a crucible or crucible element.

[0082] The present invention is illustrated by the following figures and examples, but is not limited to the specific parameters shown.

[0083] Example 1 a) Preparation of the suspension A membrane suspension is prepared with the following composition: - Purified water: 57.9% by weight - Carboxymethyl cellulose (binder): 0.9% by weight - Polyethylene glycol 400 (plasticizer): 3.9% by weight - Fatty alcohol-based polyalkylene diol ether (defoaming agent): 0.3% by weight - Silica fine particles (average particle size d50 approx. 180 μm): 37.0 wt%

[0084] First, distilled water (H2O dist.) and binder are weighed and placed in a container. To uniformly disperse and dissolve the binder, the suspension is stirred by gently shaking the container by hand until no lumps remain at the bottom of the container. Next, the plasticizer is weighed and added. To homogenize, the suspension is stirred on a roller mill at 30 revolutions per minute (rpm) for 20 hours. Next, silica microparticles and antifoaming agent are weighed and added to the suspension. To homogenize the solid suspension, the suspension is stirred on a roller mixer at 30 rpm for 15 minutes. The suspension is then formed into a film 1500 μm thick using a doctor blade and dried at room temperature for 24 hours.

[0085] b) Coating process A porous graphite substrate with an average pore size of 1.8 μm is provided. The dimensions of the substrate are 5 × 5 × 1 cm. 3 is.

[0086] Si concentration is 0.055±0.005g / cm 2 This film is made by wetting the substrate surface with water, then attaching and pressing the film onto the substrate surface (5 × 5 cm 2 ) is applied.

[0087] c) Drying process The film-coated substrate is dried in an oven at 90°C for 20 hours.

[0088] d) Permeation Treatment Process The dried substrate is placed in a graphite sample chamber and placed in a furnace. The coated surface is prevented from coming into direct contact with the components inside the furnace. The furnace is then evacuated (10 -3 After the pressure is increased to 1000 mbar, the furnace is heated from room temperature to 1500°C at a rate of 250 K / h. After maintaining the temperature at 1500°C for 5 hours, the furnace is cooled from 1500°C to room temperature at a rate of 200 K / h (below 700°C, the cooling device does not work, so the cooling rate drops to about 50 K / min). After cooling, the furnace is filled with argon gas up to atmospheric pressure, and the substrate is removed.

[0089] Comparative Example 1 a) Preparation of the suspension A spray suspension is prepared having the following composition: - Purified water: 66.7% by weight - Peptapon 520 (binder): 0.3% by weight - Silica fine particles (average particle size d50 approx. 800 μm): 33% by weight

[0090] First, distilled water (H2O dist.) and binder are weighed and placed in a container. To uniformly disperse and dissolve the binder, the suspension is stirred for 20 hours using a roller mixer rotating at 30 rpm. Next, silica fine particles are weighed and added to the suspension. To homogenize the solid suspension, the container is stirred for 15 minutes using a roller mixer rotating at 30 rpm.

[0091] b) Coating process A porous graphite substrate with an average pore size of 1.8 μm is provided. The dimensions of the substrate are 5 × 5 × 1 cm. 3 is.

[0092] The substrates are coated by spray coating. The suspension is atomized using compressed air (4 bar). The suspension is delivered through a nozzle (2.5 mm diameter). The substrate is positioned so that the surface to be coated is perpendicular to the nozzle and the direction of the spray jet, and is rotated at 10 rpm. The distance from the nozzle to the substrate surface is 20 cm. 0.04±0.015 g Si / cm 2 After drying, rotate the sample so that the uncoated side is perpendicular to the spray nozzle, and coat it in the same way. This process is repeated until all sides are coated.

[0093] c) Drying process The spray-coated substrate is placed in an oven at 90°C for 20 hours to dry.

[0094] d) Permeation Treatment Process The permeation treatment is carried out in the same manner as in Example 1.

[0095] Comparison and analysis of the processed substrates obtained in Example 1 and Comparative Example 1 All processed substrates were confirmed to have very high surface quality with no single crystal silicon residue on the processed surface. [Brief explanation of the drawings]

[0096] Observation of the sample surfaces after coating treatment using a scanning electron microscope (SEM) revealed differences in the morphology of the coating and the degree of adhesion of the coating to the sample surface between the two methods, spray coating and film coating. Examples of these differences are shown in Figure 1.

[0097] It is clear that film coating has better coating performance at corners and edges than spray coating because the crystallized regions are evenly distributed across the entire sample surface (Figure 1, left). On the other hand, spray coating has poorer crystallization at corners and edges than at the center of the surface (Figure 1, right).

[0098] To quantitatively evaluate the differences in optical properties, cross sections perpendicular to the penetration direction were observed using an optical microscope, and the thickness of the silicon carbide (SiC) layer was measured. The measurements were averaged over the entire length of the sample (5 cm) (Fig. 2), as well as over a region 10 mm or more from the sample edge (Fig. 3), and then compared.

[0099] To quantitatively evaluate the thickness of the SiC layer, the thickness of the SiC layer at each location was calculated as a ratio to the average SiC layer thickness of the entire sample.

[0100] Within 10 mm from the sample edge, the coating thickness ranges from 59.0% to 121.7% for spray coating and from 93.5% to 100.9% for film coating. On the other hand, at distances greater than 10 mm from the sample edge, the coating thickness ranges from 103.3% to 119.0% for spray coating and from 101.4% to 108.3% for film coating. [Table 1]

[0101] To further quantitatively evaluate the thickness of the SiC layer, the thickness of the SiC layer was calculated as a percentage of the average SiC layer thickness in the non-edge region.

[0102] Within 10 mm of the sample edge, the coating thickness ranges from 52.9% to approximately 92.5% for spray coating and from 89.5% to 96.6% for film coating. Beyond 10 mm from the sample edge, the coating thickness ranges from 92.5% to 106.6% for spray coating and from 97.0% to 103.6% for film coating. [Table 2]

[0103] The measured thickness distribution curves of the SiC layer are shown in Figures 2 and 3. It can be seen that the thickness of the SiC layer formed by the spray coating method is thinner than that formed by the film coating method, especially in the region within 10 mm from the edge. The significantly larger deviation in the spray-coated sample suggests that the coating film is less uniform near the edge of the sample compared to the film-coated case. These results are in good agreement with the observations from SEM images.

[0104] Example 2 a) Preparation of the suspension A membrane suspension is prepared with the following composition: - Purified water: 57.9% by weight - Carboxymethyl cellulose (binder): 0.9% by weight - Polyethylene glycol 400 (plasticizer): 3.9% by weight - Fatty alcohol-based polyalkylene diol ether (defoaming agent): 0.3% by weight - Silica fine particles (average particle size d50 approx. 180 μm): 37.0 wt%

[0105] First, distilled water and binder are weighed and placed in a container. To uniformly disperse and dissolve the binder, the suspension is gently shaken by hand until no lumps remain at the bottom of the container. Next, the plasticizer is weighed and added. To homogenize the suspension, it is placed on a roller mixer and stirred at 30 rpm for 20 hours. After that, silicon microparticles and antifoaming agent are weighed and added to the suspension. To homogenize the suspension containing the solids, it is stirred on a roller mixer at 30 rpm for 15 minutes. Finally, the suspension is formed into a film 1500 μm thick using a doctor blade and dried at room temperature for 24 hours.

[0106] b) Coating process A porous graphite substrate with an average pore size of 1.8 μm is provided. The dimensions of the substrate are 5 × 5 × 1 cm. 3 is.

[0107] The film was attached to the substrate surface (5 × 5 cm) by wetting the surface with water and then lightly pressing the film onto the surface. 2 ) is glued to the

[0108] c) Drying process The film-coated substrate is dried in an oven at 90°C for 20 hours.

[0109] d) Permeation Treatment Process The dried substrate is placed in a graphite sample chamber and placed in a furnace. The coated surface is prevented from coming into direct contact with the components inside the furnace. The furnace is then evacuated (10 -3 After the pressure is increased to 1000 mbar, the furnace is heated from room temperature to 1500°C at a rate of 250 K / h. The temperature of 1500°C is maintained for 5 hours. The furnace is then cooled from 1500°C to room temperature at a rate of 200 K / h (below 700°C, the cooling device does not operate, so the cooling rate drops to about 50 K / min). After cooling, the furnace is filled with argon gas to atmospheric pressure, and the substrate is removed.

[0110] Comparative Example 2 a) Preparation of the suspension A spray suspension is prepared having the following composition: - Purified water: 66.7% by weight - Peptapon 520 (binder): 0.3% by weight - Silica fine particles (average particle size d50 approx. 800 μm): 33% by weight

[0111] First, distilled water (H2O dist.) and binder are weighed and placed in a container. To uniformly disperse and dissolve the binder, the suspension is stirred for 20 hours using a roller mixer rotating at 30 rpm. Next, silica fine particles are weighed and added to the suspension. To homogenize the solid suspension, the container is stirred for 15 minutes using a roller mixer rotating at 30 rpm.

[0112] b) Coating process A porous graphite substrate with an average pore size of 1.8 μm is provided. The dimensions of the substrate are 5 × 5 × 1 cm. 3 is.

[0113] The substrate is sprayed, and the suspension is atomized using compressed air (4 bar). The suspension is supplied through a nozzle (2.5 mm diameter). The substrate has a surface (5 × 5 cm) to be coated. 2 The nozzle and the substrate were positioned perpendicular to the spray direction, and each substrate was rotated at 10 rpm during treatment. The distance from the nozzle to the substrate surface was 20 cm. All substrates were sprayed for 8 seconds to achieve a coating rate of 0.06±0.015 g suspension / cm 2 , or 0.02±0.005g Si / cm 2 Apply a certain amount.

[0114] c) Drying process The spray-coated substrate is placed in an oven at 90°C for 20 hours to dry.

[0115] d) Permeation Treatment Process The permeation treatment is carried out in the same manner as in Example 2.

[0116] Comparison and analysis of the processed substrates obtained in Example 2 and Comparative Example 2 All processed substrates were confirmed to have very high surface quality with no single crystal silicon residue on the processed surface.

[0117] To investigate the oxidation behavior, spray-coated and film-coated substrates were exposed to synthetic air (200 ml / min, 1 bar) at a temperature of 1100 °C for up to 198 h, with mass changes measured every 6 and 24 h.

[0118] The results of this investigation into oxidation behavior are shown in Figure 4, which shows the mass change (left vertical axis) and mass loss (right vertical axis) of spray-coated and film-coated samples versus holding time at 1100°C in synthetic air. The error bars represent the left vertical axis values ​​only.

[0119] Within the measurement accuracy (±0.001g), the mass of the spray-coated sample did not decrease for 162 hours, and the mass of the sample was measured within 1cm of the surface. 2 The mass change per unit is also 5 x 10 -3 g / cm 2 However, when the holding time exceeded 162 hours, the mass of the spray-coated sample decreased by 0.72%.

[0120] For the film-coated sample, no mass loss was detected within the measurement accuracy (±0.001 g) for up to 174 hours, and the mass loss per sample surface was 5 × 10 -3 g / cm 2 However, when the holding time exceeded 162 hours, the film-coated sample showed a maximum mass loss of 0.16% at 198 hours.

[0121] The findings demonstrate the very high impermeability of the SiC layer and the infiltrated region, and thus the treated substrate surface.

[0122] Compared to spray coating, film coating provides a more uniform coating, resulting in a SiC layer even in the edge regions of the specimen. This significantly improves the oxidation resistance of the coated parts. In particular, this is due to the reduced mass loss.

Claims

1. 1. A method for treating a porous graphite substrate, comprising: a) providing at least one film, said at least one film comprising silicon particles and at least one binder; b) the at least one film is applied to at least one surface of a porous graphite substrate; c) subjecting the at least one coating to at least one heat treatment, during which the silicon particles melt into a melt, the melt partially infiltrating the pores of the porous graphite substrate, and wherein the silicon contained in the melt is at least partially converted into silicon carbide; A method for treating a porous graphite substrate, comprising:

2. The silicon particles have an average particle size d50 in the range of 1 μm to 2000 μm, preferably 50 μm to 1500 μm, more preferably 100 μm to 1000 μm, particularly preferably 510 μm to 950 μm, and even more preferably 600 μm to 900 μm; and / or The thickness of the at least one membrane is 500 μm or more, preferably 500 μm to 5000 μm, more preferably 600 μm to 4000 μm, particularly preferably 700 μm to 3000 μm, and even more preferably 800 μm to 2000 μm; 2. The method of claim 1.

3. the at least one membrane having at least one first region and at least one second region; the at least one second region has a higher silicon concentration per unit area than the at least one first region; Preferably, the at least one film has at least one third region having a silicon concentration per unit area higher than that of the at least one second region.

3. The method according to claim 1 or 2.

4. the at least one membrane is obtained in step a) by preparing at least one suspension comprising the silicon particles, the at least one binder and at least one solvent, preferably water, and optionally adding at least one plasticizer, and then processing the resulting at least one suspension to form at least one membrane, preferably by doctor blade or film casting. The method according to any one of claims 1 to 3, characterized in that

5. the at least one binder is selected from the group consisting of polyvinyl alcohol; polyethylene glycol; polyvinyl butyral; polyacetic acid; polyurethane; polymethyl methacrylate; vinyl chloride rubber; phenolic resin; acrylic resin; cellulose; cellulose derivatives, preferably carboxymethyl cellulose, hydroxyethyl cellulose; alginic acid; dextrin; and mixtures thereof; wherein the at least one binder is preferably selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, and mixtures thereof; and / or the at least one film comprises at least one plasticizer different from the at least one binder; The at least one plasticizer is preferably selected from the group consisting of benzyl butyl phthalate, dibutyl phthalate, dimethyl phthalate, dioctyl phthalate, glycerol, polyvinylpyrrolidone, polypropylene glycol, butyl octadecanoate, and mixtures thereof; The method according to any one of claims 1 to 4, characterized in that

6. The at least one membrane comprises: the content of the silicon particles relative to the total weight of the at least one film is 40 to 99.9 wt %, preferably 55 to 95 wt %, more preferably 60 to 90 wt %, and / or the content of the at least one binder relative to the total weight of the at least one membrane is 0.1 to 25 wt %, preferably 1 to 10 wt %, more preferably 3 to 5 wt %, and / or the content of the at least one plasticizer different from the at least one binder is 0 to 35 wt %, preferably 1 to 15 wt %, more preferably 5 to 10 wt %, relative to the total weight of the at least one film; 6. The method according to any one of claims 1 to 5.

7. the at least one membrane is cut, punched and / or folded before, during and / or after step b); and / or The at least one membrane may comprise at least two membranes joined together before, during, and / or after step b).

7. The method according to any one of claims 1 to 6.

8. Step b) of applying the at least one film to at least one surface of the porous graphite substrate comprises: first wetting at least one surface of the porous graphite substrate and / or the at least one membrane with at least one solvent, preferably water, in which the at least one binder is at least partially soluble; Next, the at least one film is brought into contact with at least one surface of the porous graphite substrate, and a drying treatment is performed at least once while the at least one film is in contact with at least one surface of the porous substrate; The drying treatment is preferably carried out at a temperature ranging from 10°C to 200°C, more preferably from 80°C to 100°C, and / or for a period of from 15 minutes to 48 hours, more preferably from 1 hour to 12 hours; 8. The method according to any one of claims 1 to 7.

9. The at least one heat treatment and / or is carried out at a temperature in the range of 1400°C to 1800°C, preferably 1410°C to 1700°C, more preferably 1450°C to 1550°C; and / or a treatment time of 1 hour to 10 hours, preferably 4 hours to 6 hours; and / or under vacuum or inert gas atmosphere, preferably argon gas atmosphere, at a (process) pressure of 10 mbar to 2000 mbar, preferably 100 mbar to 1800 mbar, more preferably 500 mbar to 1500 mbar, even more preferably 800 mbar to 1200 mbar; 9. The method according to any one of claims 1 to 8.

10. the porous graphite substrate is a porous isotropic graphite substrate; and / or The porous graphite substrate has a thermal expansion coefficient of at least 2.8×10 －６ K －１ , preferably at least 3.0×10 －６ K －１ , particularly preferably at least 3.2 × 10 －６ K －１ and / or the porous graphite substrate has an open porosity, as measured by mercury intrusion porosimetry, of at least 12%, preferably 12 to 30%, particularly preferably 14 to 25%, and even more preferably 15 to 20%; and / or The pore size of the porous graphite substrate is in the range of 0.1 μm to 10 μm, preferably in the range of 1 μm to 5 μm, and particularly preferably in the range of 1.5 μm to 5 μm, on average.

10. The method according to any one of claims 1 to 9.

11. 1. A handle substrate comprising a microporous graphite material, the substrate has a silicon carbide layer on at least one surface and an underlying infiltrated region in which pores of the graphite material are at least partially filled with silicon carbide; A handle substrate, wherein the silicon carbide layer has a thickness in at least one region adjacent at least one edge of the handle substrate that is at least 70% of the average thickness of the silicon carbide layer.

12. The processing substrate is Transmittance up to 1x10 －１６ m ２ , preferably up to 1 × 10 －１７ m ２ , more preferably up to 1 × 10 －１８ m ２ , more preferably up to 1 × 10 －１９ m ２ and / or a transmittance that is at least 10 times, preferably at least 100 times, lower than the transmittance of said substrate before treatment; and / or and / or the open porosity in the infiltrated area is at most 10%, preferably at most 8%, more preferably at most 5%, as measured by mercury porosimetry; and / or the open porosity in the infiltrated region, as a percentage of the total volume of the treated substrate, is at least 7%, preferably at least 10%, more preferably at least 12% less than the open porosity of the treated substrate outside the infiltrated region, as measured by mercury porosimetry; and / or and / or exhibiting oxidation resistance such that the treated substrate loses less than 0.72%, preferably less than 0.5%, more preferably less than 0.3%, and even more preferably less than 0.2% mass after exposure to synthetic air (200 ml / min, 1 bar) at 1100°C for more than 162 hours, preferably more than 170 hours, more preferably more than 180 hours, and even more preferably more than 190 hours. does not contain monocrystalline silicon, and / or Produced or producible by the method according to any one of claims 1 to 10. The treated substrate according to claim 11 .

13. the graphite material is an isotropic graphite material; and / or the average thickness of the permeated zone is at least 100 μm, preferably between 100 μm and 1200 μm, particularly preferably between 200 μm and 800 μm; and / or the silicon carbide that at least partially fills the pores of the graphite material in the infiltrated region comprises 3C-SiC, preferably having 3C-SiC as the predominant phase; and / or the local concentration of silicon carbide in the infiltrated region decreases with increasing distance from at least one surface; and / or the infiltrated region includes at least one first region and at least one second region, the at least one second region being the same distance from the at least one surface as the at least one first region and having a higher silicon carbide concentration per unit volume than the at least one first region; and preferably, the at least one infiltrated region includes at least one third region being the same distance from the at least one surface as the at least one second region and having a higher silicon carbide concentration per unit volume than the at least one second region.

13. The substrate to be treated according to claim 11 or 12.

14. the silicon carbide layer has a thickness in at least one region, preferably in each region, adjacent at least one edge of the handle substrate that is at least 75%, preferably at least 80%, more preferably at least 85%, particularly preferably at least 90%, and / or at most 125%, preferably at most 120%, more preferably at most 115%, particularly preferably at most 110%, even more preferably at most 105% of the average thickness of the silicon carbide layer; and / or the silicon carbide layer has a thickness at all points at a distance of at most 2 mm, preferably at most 4 mm, more preferably at most 10 mm from at least one edge of the handle substrate of at least 70%, preferably at least 75%, more preferably at least 80%, particularly preferably at least 85%, even more preferably at least 90%, and / or at most 125%, preferably at most 120%, more preferably at most 115%, particularly preferably at most 110%, even more preferably at most 105% of the average thickness of the silicon carbide layer; and / or the silicon carbide layer has a thickness of at least 70%, preferably at least 75%, more preferably at least 80%, particularly preferably at least 85%, even more preferably at least 90%, and / or at most 125%, preferably at most 120%, more preferably at most 115%, particularly preferably at most 110%, even more preferably at most 105% of the average thickness of the silicon carbide layer at all points from at least one edge of the handle substrate to a distance of at most 10%, preferably at most 20%, of the distance between the at least one edge and the opposite edge of the handle substrate; The substrate to be processed according to any one of claims 11 to 13.

15. Use of a treated substrate according to any one of claims 11 to 14 as a component of a high-temperature furnace, in particular as a heater, heat insulator, support member etc., or as a crucible or crucible element.

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