Process for manufacturing a shaped si-sic article, shaped article, and use
Patent Information
- Application Number
- EP2022843182
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2022-12-20
- Publication Date
- 2025-10-29
AI Technical Summary
Existing methods for producing recrystallized silicon carbide are limited by the inability to create complex geometries using additive manufacturing and the presence of free metallic silicon, which restricts application temperatures to below 1400 °C.
A method involving the formation of a green body using additive manufacturing followed by high-temperature treatment to recrystallize silicon carbide, allowing for complex geometries and eliminating free metallic silicon through evaporation, thereby enabling use at temperatures above 1400 °C.
This method expands the application range of silicon carbide molded bodies to high-temperature environments by enabling complex geometries and eliminating metallic silicon, resulting in a recrystallized silicon carbide with enhanced temperature, creep, and chemical resistance.
Abstract
Description
[0001] METHOD FOR PRODUCING A SI-SIC MOULDED BODY, MOULDED BODY AND USE
[0002] The invention relates to a method for producing a shaped body and to a shaped body made of recrystallized silicon carbide. Furthermore, the invention relates to the use of reaction-bonded silicon-infiltrated silicon carbide for producing recrystallized silicon carbide.
[0003] A molded body made of silicon carbide (SiC) is well known in the art and is used particularly in high-temperature applications.
[0004] There are a number of silicon carbide material variants, including recrystallized silicon carbide (RSiC) and reaction-bonded silicon infiltrated silicon carbide (SiSiC).
[0005] Due to its comparatively very high temperature resistance, a molded body made of recrystallized silicon carbide is regularly used for high-temperature applications with an application temperature of > 1400 °C. Typically, to produce such a molded body, a green body is produced using a silicon carbide grain mixture comprising a coarse grain fraction and a fine grain fraction, for example in a slip casting process. This green body is then fired at comparatively very high temperatures of 2300 °C to 2500 °C. As a result of diffusion processes, comparatively smaller grains are dissolved and comparatively larger grains are formed or grow, resulting in a molded body made of a comparatively coarse-grained and porous ceramic that no longer exhibits any material changes even at high temperatures.A disadvantage, however, is that the shaping of such a molded body is limited to ceramic molding processes such as casting, pressing, and injection molding. In particular, such a molded body cannot currently be produced using an additive manufacturing process or a 3D printing process. This results in limited shaping options and geometries, thus restricting the range of applications for such a molded body.
[0006] A shaped body made from reaction-bonded silicon-infiltrated silicon carbide, which is also used in high-temperature applications, is obtained, for example, by first forming a base body from silicon carbide, which is subsequently impregnated with a soot suspension and then infiltrated with (metallic) silicon. It is possible to produce the base body using an additive manufacturing process, as described, for example, in DE 10 2013 017 193 A1. Advantageously, such a shaped body can in principle also be produced with a complex geometry. A disadvantage here, however, is that such a shaped body always contains a proportion of free (metallic) silicon. Due to the melting point of free (metallic) silicon, the application range of such a shaped body is therefore limited to an application temperature of < 1400 °C.The present invention is therefore based on the object of proposing a method for producing a shaped body, a shaped body and a use which increases the field of application of the shaped body.
[0007] This object is achieved by a method having the features of claim 1, a shaped body having the features of claim 19 and a use having the features of claim 23.
[0008] In the method according to the invention for producing a shaped body, a green body is formed from a ceramic material based on silicon carbide using an additive manufacturing process, wherein the green body is subsequently subjected to a high-temperature treatment, wherein the silicon carbide is recrystallized as a result of the high-temperature treatment.
[0009] According to the invention, a green body is formed from a suitable ceramic material based on silicon carbide or a silicon carbide material or from silicon carbide using an additive manufacturing process or 3D printing process, so that a green body formed from the ceramic material based on silicon carbide or from the silicon carbide material or from the silicon carbide is obtained. Several process steps can be provided for forming the green body, of which the use of the additive manufacturing process can also constitute only one process step. The use of the additive manufacturing process allows the green body or molded body to be formed with a high degree of design freedom and a variety of shapes, so that the molded body can fundamentally also have a complex geometry and can therefore be used more widely.
[0010] According to the invention, it is further provided that the green body is subsequently subjected to a high-temperature treatment or annealing treatment or high-temperature annealing such that the material or the silicon carbide material or the silicon carbide is recrystallized as a result of the high-temperature treatment. In other words, the silicon carbide is converted into recrystallized silicon carbide, resulting in a molded body made of recrystallized silicon carbide that can be used at application temperatures of > 1400 °C.
[0011] As a result, the process according to the invention enables the production of a shaped body with an expanded range of applications.
[0012] Advantageously, reaction-bonded silicon-infiltrated silicon carbide (SiSiC) can be used as the silicon carbide or material to form the green body, so that the green body can be formed from reaction-bonded silicon-infiltrated silicon carbide. This is generally suitable for processing within the framework of additive manufacturing. The green body can be manufactured according to the process described in DE 10 2013 017 193 A1.
[0013] Advantageously, during the formation of the green body, a base body made of a grain containing silicon carbide or primary silicon carbide can be formed using the additive manufacturing process. The base body can be built up monolithically in layers from a formless grain using a physical or chemical hardening or melting process. The grain can have a proportion of at least 95% silicon carbide or primary silicon carbide. An average grain size can be, for example, 70 μm to 200 μm. A binder, for example in the form of a resin, can be used for hardening.
[0014] In one embodiment of the method, the grain or the silicon carbide of the grain can have a coarse grain fraction and a fine grain fraction. Accordingly, it can be provided to use a grain with a bimodal grain size distribution in the additive manufacturing process. For example, the additive manufacturing can then be carried out using fused filament fabrication (FFF). As a result of the high-temperature treatment or diffusion processes, fine grains of the fine grain fraction can be dissolved, and coarse grains of the coarse grain fraction can grow or form. The binder can co-form the fine grain fraction, or a silicon carbide precursor can be processed as a binder, from which the fine grain fraction can result.
[0015] Advantageously, the base body can be impregnated with a carbon suspension, in particular a carbon black suspension or graphite suspension. The base body can then be soaked with the carbon suspension at least once.
[0016] Alternatively, carbon can be introduced into the base body by means of a vapor deposition process.
[0017] Alternatively, the base body can be impregnated with a resin, which can subsequently be converted into carbon. The conversion of the resin into carbon can be achieved by means of a thermal treatment, particularly a high-temperature treatment.
[0018] The base body can advantageously be infiltrated with (metallic) silicon. Through contact of the carbon with liquid or gaseous (metallic) silicon, secondary silicon carbide can then be formed during a subsequent reaction firing, which can solidify a resulting interpenetration bond. The green body can then be obtained in this way. The infiltration of the base body with the (metallic) silicon preferably takes place after the base body has been impregnated with the carbon suspension or with the resin or after the carbon has been introduced into the base body. Advantageously, the silicon carbide of the green body can then have a coarse grain fraction which at least co-forms or forms primary silicon carbide and a fine grain fraction which at least co-forms or forms secondary silicon carbide, wherein as a result of the high temperature treatment orDiffusion processes cause fine grains of the fine-grain fraction to be dissolved, and coarse grains of the coarse-grain fraction to grow or form. In other words, the secondary silicon carbide, which is fine-grained compared to the primary silicon carbide, can form a kind of "sacrificial phase" for the subsequent recrystallization process. If the primary silicon carbide of the grain already has a coarse-grain fraction and a fine-grain fraction, the fine-grain fraction of the primary silicon carbide of the grain can co-form the fine-grain fraction of the green body. The coarse-grain fraction of the green body can then be formed from the coarse-grain fraction of the primary silicon carbide of the grain.
[0019] Advantageously, free (metallic) silicon can be removed as a result of a (chemical) etching treatment or removed, in particular evaporated, as a result of the high-temperature treatment, such that the shaped body can be substantially free of the free (metallic) silicon. If the free (metallic) silicon remaining in the green body as a result of the infiltration with the (metallic) silicon is removed from the green body or shaped body during the high-temperature treatment, the shaped body thus obtained can then be used at application temperatures of > 1400 °C. Preferably, the free (metallic) silicon can be removed by means of evaporation, preferably vacuum evaporation. By removing the free (metallic) silicon, the shaped body is substantially or largely free of the free (metallic) silicon. Enclosed silicon residues can remain in the shaped body.The mass fraction of free (metallic) silicon remaining in the molded body should be significantly less than 5%. Advantageously, the free (metallic) silicon can be removed first, followed by recrystallization of the silicon carbide. These can therefore be two separate process steps. However, both processes can also take place simultaneously in a single process step.
[0020] Advantageously, the removal of the free (metallic) silicon can be carried out using first process parameters, while the recrystallization can be carried out using second process parameters that are at least partially different from the first process parameters. The term "process parameter" is understood here to mean, in particular, a temperature and / or pressure.
[0021] Advantageously, the silicon carbide can be sintered as a result of the high-temperature treatment. Silicon carbide grains can thus be sintered together.
[0022] Advantageously, the high-temperature treatment can be carried out at a temperature of > 2000 °C, preferably 2100 °C to 2500 °C. The high-temperature treatment can be carried out in a furnace or a process chamber. The residence time in the furnace or process chamber can be several hours.
[0023] Advantageously, the high-temperature treatment can be carried out at a reduced atmospheric pressure, preferably under a vacuum. The high-temperature treatment can be carried out, for example, at a pressure of 1 mbar to 300 mbar.
[0024] Binder jetting, or fine-jet binder application, can advantageously be used as an additive manufacturing process. However, other additive manufacturing processes are also conceivable or appropriate.
[0025] Advantageously, the silicon carbide can be converted into recrystallized silicon carbide (RSiC) as a result of the high-temperature treatment. Thus, a molded article made of recrystallized silicon carbide can be produced, which exhibits high temperature resistance, creep resistance, and chemical resistance.
[0026] Advantageously, the molded body can be coated with silicon carbide (SiC) following the high-temperature treatment using chemical vapor deposition (CVD). The molded body can then also be used in the semiconductor sector, particularly due to its corresponding purity. Because the molded body is made of recrystallized silicon carbide, there is a comparatively greater degree of flexibility regarding the choice of the subsequent coating process.
[0027] In the molded body according to the invention, a green body is formed from a ceramic material based on silicon carbide using an additive manufacturing process, wherein the green body is subsequently subjected to a high-temperature treatment, wherein the silicon carbide is recrystallized as a result of the high-temperature treatment.
[0028] The shaped body according to the invention is therefore produced by the process according to the invention.
[0029] For the advantageous effects of the shaped body according to the invention, reference is made to the description of the advantages of the process according to the invention.
[0030] Advantageously, the shaped body can be formed substantially free of free (metallic) silicon.
[0031] Advantageously, the molded body can be used for high-temperature applications with an application temperature of > 1400 °C, preferably > 1500 °C. The molded body can be or be designed as a component, in particular a high-temperature component, such as a furnace component, or a component usable in the semiconductor industry.
[0032] Further advantageous embodiments of the shaped body emerge from the descriptions of the features of the subclaims referring back to process claim 1.
[0033] According to the invention, reaction-bonded silicon-infiltrated silicon carbide (Si SiC) is used to produce recrystallized silicon carbide (RSiC) for or during the formation of a shaped body, wherein the reaction-bonded silicon-infiltrated silicon carbide is subjected to a high-temperature treatment such that the reaction-bonded silicon-infiltrated silicon carbide is converted to the recrystallized silicon carbide.
[0034] According to the invention, the starting point for forming a shaped body is not recrystallized silicon carbide, but rather reaction-bonded silicon-infiltrated silicon carbide, which is then converted into recrystallized silicon carbide. This "detour" via the reaction-bonded silicon-infiltrated silicon carbide on the "path" to forming the shaped body formed from the recrystallized silicon carbide makes it possible to flexibly determine the shape of the shaped body using an additive manufacturing process, since the reaction-bonded silicon-infiltrated silicon carbide, in contrast to the recrystallized silicon carbide, can be flexibly processed using additive manufacturing. This processing can take place before its conversion.
[0035] Free (metallic) silicon can be removed or evaporated during the high-temperature treatment. For further information on the advantageous effects of the inventive use, please refer to the description of the advantages of the inventive method.
[0036] Further advantageous embodiments of the use emerge from the descriptions of the features of the subclaims referring back to method claim 1.
Claims
Patent claims 1. A method for producing a shaped body, wherein a green body is formed from a ceramic material based on silicon carbide using an additive manufacturing process, wherein the green body is subsequently subjected to a high-temperature treatment, wherein the silicon carbide is recrystallized as a result of the high-temperature treatment.
2. Process according to claim 1, characterized in that reaction-bonded silicon-infiltrated silicon carbide (SiSiC) is used as silicon carbide.
3. Method according to claim 1 or 2, characterized in that during the formation of the green body, a base body is formed from a grain comprising silicon carbide using the additive manufacturing process.
4. A method according to claim 3, characterized in that the silicon carbide of the grain has a coarse grain fraction and a fine grain fraction.
5. Method according to claim 3 or 4, characterized in that the base body is impregnated with a carbon suspension, in particular soot suspension or graphite suspension.
6. Method according to claim 3 or 4, characterized in that carbon is introduced into the base body by means of a gas phase deposition.
7. A method according to claim 3 or 4, characterized in that the base body is impregnated with a resin which is subsequently converted into carbon.
8. Method according to one of claims 5 to 7, characterized in that the base body is infiltrated with silicon.
9. A method according to claim 8, characterized in that the silicon carbide of the green body has a coarse grain fraction at least co-forming primary silicon carbide and a fine grain fraction at least co-forming secondary silicon carbide, wherein as a result of the high temperature treatment fine grains of the Fine grain fraction is dissolved and coarse grains of the coarse grain fraction grow.
10. The method according to claim 8 or 9, characterized in that free silicon is removed as a result of an etching treatment or is removed, in particular evaporated, as a result of the high-temperature treatment, such that the shaped body is substantially free of the free silicon.
11. A method according to claim 10, characterized in that first the free silicon is removed, followed by recrystallization of the silicon carbide.
12. The method according to claim 11, characterized in that the removal of the free silicon is carried out under first process parameters, wherein the recrystallization is carried out under second process parameters which are at least partially different from the first process parameters.
13. A method according to any one of the preceding claims, characterized in that the silicon carbide is sintered as a result of the high-temperature treatment.
14. Method according to one of the preceding claims, characterized in that the high-temperature treatment is carried out at a temperature of > 2000 °C, preferably 2100 °C to 2500 °C.
15. A method according to any one of the preceding claims, characterized in that the high-temperature treatment is carried out at a reduced atmospheric pressure, preferably under a vacuum.
16. Method according to one of the preceding claims, characterized in that binder jetting is used as the additive manufacturing method.
17. A process according to any one of the preceding claims, characterized in that the silicon carbide is converted into recrystallized silicon carbide (RSiC) as a result of the high-temperature treatment.
18. Method according to one of the preceding claims, characterized in that the shaped body is coated with silicon carbide (SiC) by means of chemical vapor deposition (CVD) following the high-temperature treatment.
19. Shaped body, wherein a green body is formed from a ceramic material based on silicon carbide using an additive manufacturing process, wherein the green body is subsequently subjected to a high-temperature treatment, wherein the silicon carbide is recrystallized as a result of the high-temperature treatment.
20. Shaped body according to claim 19, characterized in that that the shaped body is essentially free of free silicon.
21. Shaped body according to claim 19 or 20, characterized in that the shaped body can be used for high-temperature applications with an application temperature of > 1400 °C, preferably > 1500 °C.
22. Shaped body according to one of claims 19 to 21, characterized in that the shaped body is a component, in particular a high-temperature component or a component usable in the semiconductor industry.
23. Use of reaction-bonded silicon-infiltrated silicon carbide (SiSiC) for producing recrystallized silicon carbide (RSiC) for forming a shaped body, wherein the reaction-bonded silicon-infiltrated silicon carbide is subjected to a high-temperature treatment such that the reaction-bonded silicon-infiltrated silicon carbide is converted to the recrystallized silicon carbide.