Beta-silicon carbide protective layer coated rb-sic composite material and preparation method

Abstract

The present application relates to the technical field of silicon carbide composite material preparation, and particularly relates to a beta-type silicon carbide protective layer coated RB-SiC composite material and a preparation method thereof. The method comprises the following steps: preparing a silicon carbide preform by using silicon carbide powder; after high-temperature degreasing and degassing treatment of the silicon carbide preform at 600-1000 DEG C, a porous silicon carbide preform is obtained; the porous silicon carbide preform is placed in a cracking furnace, and chemical vapor infiltration is carried out under a flowable mixed gas atmosphere to obtain a beta-type silicon carbide protective layer; a silicon infiltration channel with a depth of 50-200 microns is selectively processed on the non-service surface of the preform; the preform is subjected to reaction sintering densification treatment, the sintering temperature is 1420 DEG C-1700 DEG C, and the holding time is 3h-24h; and the preform is cooled to room temperature after sintering. The method has the advantages that silicon in the RB-SiC is prevented from being exposed to the service environment, and material failure is avoided; a high-performance protective layer is prepared, and the dimensional accuracy of the component structure is not reduced.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide composite material preparation technology, and in particular to a β-type silicon carbide protective layer coated RB-SiC composite material and its preparation method. Background Technology

[0002] Silicon carbide (SiC) possesses high strength, high specific stiffness, good corrosion resistance, and strong thermal dimensional stability, making it widely used in optical systems, semiconductor equipment, and photovoltaic fields. In particular, SiC's high specific stiffness allows for significant weight reduction while maintaining overall structural stiffness, showing broad application prospects in SiC microchannel reactors, SiC vacuum chucks, and heat exchangers. Silicon carbide ceramics prepared using reaction sintering technology, namely RB-SiC, not only possess the various excellent properties of SiC but also offer advantages such as short preparation cycle, low cost, and near-net-shape sintering. RB-SiC consists of SiC and a small amount of silicon. Compared to SiC, silicon has poor oxidation resistance, wear resistance, and corrosion resistance, limiting the application range of RB-SiC in high-temperature fields or extreme conditions.

[0003] Typically, under high-temperature environments and strong acid / alkali conditions, high-temperature oxidation, friction and wear, and chemical corrosion mainly occur on the material surface, deteriorating the overall performance of the material from the surface inwards and ultimately leading to component failure. Therefore, adopting appropriate surface treatment technologies is an effective way to improve the service life of RB-SiC or broaden its application range. In existing surface treatment technologies, the protective layer grows from the surface of the target component outwards, altering the dimensional accuracy of the component.

[0004] Patent application CN113307644A, published on August 27, 2021, entitled "A Method for Nitration-Modified Reactive Sintering of Silicon Carbide Ceramic Surfaces," discloses a method of placing RB-SiC in a high-temperature furnace with flowing high-purity nitrogen gas. The method utilizes the chemical reaction between nitrogen and silicon in RB-SiC under high-temperature conditions to form a silicon nitride protective layer in situ on the surface, resulting in a silicon nitride-coated RB-SiC composite material. However, the formation of silicon nitride in this method is accompanied by volume expansion. For example, after growing silicon nitride on the surface of a 2mm diameter hole, its size will be less than 2mm, leading to a decrease in the structural precision of the component. Therefore, employing a suitable surface treatment method while ensuring the structural precision of RB-SiC is crucial for the application of high-performance RB-SiC with complex structures. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a β-type silicon carbide protective layer-coated RB-SiC composite material and its preparation method.

[0006] The primary objective of this invention is to provide a method for preparing an RB-SiC composite material coated with a β-type silicon carbide protective layer, specifically comprising the following steps:

[0007] S1. Preparation of porous silicon carbide preform: Silicon carbide preform is prepared using silicon carbide powder; after high-temperature degreasing and debinding treatment at 600~1000℃, porous silicon carbide preform is obtained.

[0008] S2. Preparation of β-type silicon carbide protective layer: The porous silicon carbide preform is placed in a pyrolysis furnace and chemical vapor infiltration is carried out in a flowing mixed gas atmosphere to obtain a β-type silicon carbide protective layer.

[0009] S3. Silicon infiltration channel processing: Selectively process silicon infiltration channels with a depth of 50~200μm on the non-service surface of the preform;

[0010] S4. Preparation of composite material by sintering: The preform with silicon infiltration channels prepared in step S3 is subjected to reaction sintering densification treatment at a sintering temperature of 1420℃~1700℃ and a holding time of 3h~24h; after sintering, it is cooled to room temperature to obtain RB-SiC composite material with β-type silicon carbide protective layer.

[0011] Preferably, the pyrolysis temperature in step S2 is 1000~1100℃, and the thickness of the prepared β-type silicon carbide protective layer is 10~200μm.

[0012] Preferably, the mixed gas includes methyltrichlorosilane, hydrogen, and argon.

[0013] Preferably, the gas flow rates of methyltrichlorosilane, hydrogen, and argon are 0.5~1L / min, 0.5~1L / min, and 1.5~2L / min, respectively.

[0014] Preferably, the method for preparing the silicon carbide preform in step S1 includes at least one of gel casting molding, isostatic pressing molding, slurry casting molding, and additive manufacturing molding; the silicon carbide powder is one or more of silicon carbide powders with a particle size of 100nm to 120μm.

[0015] Preferably, the gel casting molding preparation method specifically includes the following steps: fully mixing acrylamide, methylenebisacrylamide and tetramethylammonium hydroxide to form a premix, adding silicon carbide powder to prepare a silicon carbide slurry, injecting it into a mold and then curing it to form a silicon carbide preform.

[0016] Preferably, the isostatic pressing preparation method specifically includes the following steps: using silicon carbide powder as raw material, adding phenolic resin binder, and dry pressing under a pressure of 40~80MPa to obtain a silicon carbide preform.

[0017] Preferably, the additive manufacturing method specifically includes the following steps: mixing 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, polyvinylpyrrolidone and silicon carbide powder in a certain proportion to form a liquid photosensitive silicon carbide slurry, and irradiating the liquid photosensitive silicon carbide slurry with light of wavelength 380~450nm to transform it into a solid silicon carbide preform.

[0018] Preferably, the silicon diffusion channel is a silicon diffusion point or a silicon diffusion plane, with a depth of 50~200μm; the number of silicon diffusion points is not less than 2.

[0019] The second objective of this invention is to provide a β-type silicon carbide protective layer coated RB-SiC composite material, prepared by the above-mentioned method for preparing the β-type silicon carbide protective layer coated RB-SiC composite material.

[0020] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0021] (1) The present invention uses chemical vapor infiltration technology to prepare a uniform and dense β-type silicon carbide protective layer to prevent silicon in RB-SiC from being exposed to the service environment and avoid the problem of material failure caused by silicon performance deterioration;

[0022] (2) The present invention performs chemical vapor infiltration treatment on porous silicon carbide preforms. This method penetrates and deposits into the interior of the preforms, gradually densifying them from the surface to the inside, without causing excessive size changes.

[0023] (3) This invention does not introduce other phase substances besides RB-SiC material, which can improve the service performance or broaden the application range of RB-SiC components;

[0024] (4) During the reaction melting and infiltration sintering process, liquid silicon fills the pores and also plays the role of connecting the protective layer and RB-SiC. Therefore, the advantage of this invention compared with directly depositing the protective layer on the surface of RB-SiC is that it not only preserves the structural accuracy, but also ensures a high bonding strength between the protective layer and RB-SiC.

[0025] In summary, the target component used in this invention is a porous silicon carbide preform. Its main advantage lies in the fact that during the chemical vapor infiltration process, the β-type silicon carbide protective layer grows from the surface of the porous preform inwards, ultimately forming a dense protective layer on the preform surface. To avoid gas-supporting effects or skin-shell formation during reactive infiltration sintering, silicon infiltration channels are selected on the surface of the preform coated with the dense protective layer, based on Washburn theory. Finally, a dense RB-SiC component is prepared by reactive infiltration sintering. Therefore, the significant advantage of this invention is that it prepares a high-performance protective layer without reducing the dimensional accuracy of the component structure. Attached Figure Description

[0026] Figure 1 This is a scanning electron microscope image of a porous silicon carbide preform and a β-type silicon carbide protective layer prepared on its surface, provided according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of silicon diffusion channel processing according to an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the reaction melting and infiltration process provided in an embodiment of the present invention.

[0029] Figure 4 This is a schematic diagram of the RB-SiC composite material structure after reactive melting and sintering of a β-type silicon carbide protective layer according to an embodiment of the present invention.

[0030] Figure label:

[0031] 1. Porous silicon carbide preform;

[0032] 2. β-type silicon carbide protective layer;

[0033] 3. Silica infiltration channels. Detailed Implementation

[0034] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0036] This invention employs chemical vapor infiltration technology to deposit a β-type silicon carbide protective layer on the surface of a porous silicon carbide preform, and combines it with reaction sintering technology to prepare RB-SiC ceramics, providing a method for high-performance protective layer and high-precision structural preservation.

[0037] This invention provides a β-type silicon carbide protective layer coated RB-SiC composite material, the preparation method of which specifically includes the following steps:

[0038] S1. Preparation of porous silicon carbide preform: Silicon carbide preform is prepared using silicon carbide powder; after high-temperature degreasing and debinding treatment at 600~1000℃, porous silicon carbide preform is obtained.

[0039] Specifically, the preparation method of silicon carbide preforms includes at least one of gel casting, isostatic pressing, slip casting, and additive manufacturing. The silicon carbide powder is one or more of silicon carbide powders with a particle size of 100 nm to 120 μm; the porosity of the porous silicon carbide preform is adjusted by mixing powders of different particle sizes and proportions.

[0040] Preferably, the gel casting molding preparation method specifically includes the following steps: a premixed liquid is formed by thoroughly mixing acrylamide, methylenebisacrylamide and tetramethylammonium hydroxide, silicon carbide powder is added to prepare silicon carbide slurry, and the slurry is injected into a mold and cured to form a silicon carbide preform; in a specific embodiment, the solid content (silicon carbide powder) of the silicon carbide slurry is 65%, and the silicon carbide powder is a mixed powder made by mixing two types of silicon carbide powder with particle sizes of 10μm and 50μm in a mass ratio of 3:7.

[0041] Preferably, the isostatic pressing preparation method specifically includes the following steps: using silicon carbide powder as raw material, adding phenolic resin binder, and dry pressing under a pressure of 40~80MPa to obtain a silicon carbide preform; in a specific embodiment, the particle size of silicon carbide powder is 1μm, and the mass of phenolic resin accounts for 9.5% of the mass of silicon carbide powder.

[0042] Preferably, the additive manufacturing method specifically includes the following steps: mixing 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, polyvinylpyrrolidone, and silicon carbide powder in a certain proportion to form a liquid photosensitive silicon carbide slurry; and transforming the liquid photosensitive silicon carbide slurry into a solid silicon carbide preform under light irradiation at a wavelength of 380-450 nm; wherein the weight ratio of silicon carbide powder to other components is 20-30:70-80; in a specific embodiment, the weight ratio of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, polyvinylpyrrolidone, and silicon carbide powder is 16.2:5.4:0.5:2.9:75; and the wavelength of light irradiation is 405 nm.

[0043] S2. Preparation of β-type silicon carbide protective layer: The porous silicon carbide preform is placed in a pyrolysis furnace and chemical vapor infiltration is performed in a flowing mixed gas atmosphere to obtain a β-type silicon carbide protective layer; specifically, the mixed gas includes methyltrichlorosilane (MTS), hydrogen, and argon, with gas flow rates of 0.5~1L / min, 0.5~1L / min, and 1.5~2L / min, respectively; the pyrolysis temperature is 1000~1100℃; the thickness of the β-type silicon carbide protective layer prepared in this step is 10~200μm.

[0044] S3. Silicon infiltration channel processing: Since the surface of the porous silicon carbide preform processed by the above process is completely covered by the protective layer, the liquid silicon cannot be infiltrated into the preform during the subsequent reaction melting and sintering process. Therefore, a machining method is used to selectively process silicon infiltration channels on the non-service surface of the preform.

[0045] The silicon diffusion channels are silicon diffusion points or silicon diffusion planes with a depth of 50~200μm;

[0046] Specifically, the processing methods are as follows: using a diamond grinding head to process four silicon infiltration channels with a diameter of 1~3mm and a depth of 100~120μm on the surface of the preform; or using a milling machine to process silicon infiltration channels with a depth of 55~65μm on the non-service surface of the preform, which ensures that the porous channels on the non-service surface of the preform are fully exposed for silicon infiltration treatment; or using a diamond grinding head to process two silicon infiltration channels with a length of 10mm, a width of 5mm and a depth of 160μm on the surface of the preform.

[0047] S4. Sintering preparation of composite material: The preform with silicon infiltration channels prepared in step S3 is subjected to reaction sintering densification treatment at a sintering temperature of 1420℃~1700℃ and a holding time of 3h~24h; after sintering, it is cooled to room temperature to obtain RB-SiC composite material with β-type silicon carbide protective layer.

[0048] Specifically, the reaction sintering densification process is as follows: the preform is embedded in silicon powder and densified in a high-temperature reaction sintering furnace at a temperature of 1420℃~1700℃ for 3h~24h. After cooling to room temperature, a β-type silicon carbide protective layer-coated RB-SiC composite material is obtained. The dense RB-SiC surface is completely covered by a high-precision β-type silicon carbide protective layer, and the dimensional accuracy of the structure remains unchanged or changes very little.

[0049] In a specific embodiment, the sintering temperature is 1600℃ or 1650℃, and the holding time is 6 hours.

[0050] Example 1

[0051] like Figures 1-4 As shown in the figure, this embodiment provides a method for preparing a β-type silicon carbide protective layer coated RB-SiC composite material, which specifically includes the following steps:

[0052] S1. Preparation of porous silicon carbide preform: Silicon carbide preform is prepared by gel casting molding technology. Acrylamide, methylenebisacrylamide and tetramethylammonium hydroxide are thoroughly mixed to form a premix, and silicon carbide powder with particle sizes of 10μm and 50μm is added. The silicon carbide slurry with a solid content of 65% is prepared according to a mass ratio of 3:7. After being injected into a mold, a silicon carbide preform is formed. The preform is degreased at 900℃ to obtain a porous silicon carbide preform.

[0053] S2. Preparation of a high-precision β-type silicon carbide protective layer: The protective layer was prepared using chemical vapor infiltration (CVI) technology. A fluid mixed atmosphere, including methyltrichlorosilane (MTS), hydrogen, and argon, was introduced into the pyrolysis furnace at flow rates of 0.8 L / min, 0.8 L / min, and 1.6 L / min, respectively. The pyrolysis temperature was 1050 °C, and a protective layer with a thickness of 70-110 μm was prepared. Figure 1 As shown.

[0054] S3. Silicon Infiltration Channel Processing: Using a diamond grinding head, four silicon infiltration channels (silicon infiltration points) with a diameter of 2 mm and a depth of 110 μm are processed on the surface of the preform. Figure 2 As shown.

[0055] S4. Reactive infiltration sintering: Place silicon powder on the surface of the preform, with the mass of the silicon powder being 10%~210% of the preform's mass. Perform reactive sintering densification treatment at a sintering temperature of 1650℃ for 4 hours. During this process, the silicon powder melts and fills the porous silicon carbide preform along the silicon infiltration points, such as... Figure 3 As shown. Its cross-sectional view after cooling to room temperature is shown below. Figure 4 As shown, an RB-SiC composite material with a dense β-type silicon carbide high-precision protective layer was obtained.

[0056] Example 2

[0057] A method for preparing a β-type silicon carbide protective layer coated RB-SiC composite material specifically includes the following steps:

[0058] S1. Preparation of porous silicon carbide preform: Silicon carbide preform is prepared by dry pressing technology. 1μm silicon carbide powder is used as raw material, and phenolic resin with a mass fraction of 9.5% of the raw material powder is added as a binder. The preform is dry pressed at a pressure of 55MPa. After hot degreasing at 900℃, the porous silicon carbide preform is obtained.

[0059] S2. Preparation of high-precision β-type silicon carbide protective layer: The protective layer is prepared by chemical vapor infiltration technology. A fluid mixed atmosphere, including methyltrichlorosilane (MTS), hydrogen and argon, is introduced into the pyrolysis furnace at flow rates of 0.6 L / min, 0.8 L / min and 1.6 L / min, respectively. The pyrolysis temperature is 1050℃, and the thickness of the protective layer is 30-60 μm.

[0060] S3. Silicon infiltration channel processing: A silicon infiltration plane with a depth of 60 μm is machined on the non-service surface of the preform using a milling machine. This depth ensures that the porous channels on the non-service surface of the preform are fully exposed for silicon infiltration processing.

[0061] Step S4 is the same as in Example 1.

[0062] Example 3

[0063] A method for preparing a β-type silicon carbide protective layer coated RB-SiC composite material specifically includes the following steps:

[0064] S1. Preparation of porous silicon carbide preforms. Silicon carbide preforms were prepared using photopolymerization additive manufacturing technology. A photosensitive silicon carbide slurry was formed by thoroughly mixing 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, polyvinylpyrrolidone, and silicon carbide powder in a mass ratio of 16.2: 5.4: 0.5: 2.9: 75. Under irradiation with 405 nm light, the liquid slurry transformed into a solid preform. This preform was then degreased at 640 °C to obtain the porous silicon carbide preform.

[0065] S1. Preparation of high-precision β-type silicon carbide protective layer: The protective layer is prepared by chemical vapor infiltration technology. A fluid mixed atmosphere, including methyltrichlorosilane (MTS), hydrogen and argon, is introduced into the pyrolysis furnace at flow rates of 0.8 L / min, 0.8 L / min and 1.6 L / min, respectively. The pyrolysis temperature is 1050℃, and a protective layer with a thickness of 100-160 μm is prepared.

[0066] S1. Silicon infiltration channel processing: Two silicon infiltration channels (silicon infiltration points) with a length of 10 mm, a width of 5 mm, and a depth of 160 μm are processed on the surface of the above preform using a diamond grinding head.

[0067] S1. Reactive melting and sintering: The above preform is subjected to reactive sintering densification treatment at a sintering temperature of 1600℃ for 6 hours. After cooling to room temperature, a dense β-type silicon carbide high-precision protective layer-coated RB-SiC composite material is obtained.

[0068] Brief Description of the Principle: Chemical vapor infiltration (CVI) is a type of chemical vapor deposition (CVD) technology that utilizes the principle of methyltrichlorosilane decomposing into solid-phase β-type silicon carbide at high temperatures to gradually densify the surface and interior of the target component. An inert gas is used as a dilution gas to regulate the growth of β-type silicon carbide, and hydrogen is used as a carrier gas to deliver the reactive gas to the target component. The main characteristic of this technology is that the densification process proceeds from the surface inwards; typically, even after the surface of the component is densified, a large number of pores still exist inside. To achieve material densification, reactive melt infiltration sintering technology is used to fill the pores with liquid silicon, preparing a dense RB-SiC composite material coated with a uniform, dense β-type silicon carbide high-precision protective layer.

[0069] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0070] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing an RB-SiC composite material coated with a β-type silicon carbide protective layer, characterized in that, Specifically, the steps include the following: S1. Preparation of porous silicon carbide preform: Silicon carbide preform is prepared using silicon carbide powder; after high-temperature degreasing and debinding treatment at 600~1000℃, porous silicon carbide preform is obtained; the silicon carbide powder is prepared by mixing two types of silicon carbide powder with particle sizes of 10μm and 50μm. S2. Preparation of β-type silicon carbide protective layer: A porous silicon carbide preform is placed in a pyrolysis furnace and subjected to chemical vapor infiltration in a flowing mixed gas atmosphere at a pyrolysis temperature of 1050℃ to obtain a β-type silicon carbide protective layer with a thickness of 10~200μm; the mixed gas includes methyltrichlorosilane, hydrogen, and argon, with gas flow rates of 0.5~1L / min, 0.5~1L / min, and 1.5~2L / min, respectively; S3. Silicon infiltration channel processing: Selectively process silicon infiltration channels with a depth of 50~200μm on the non-service surface of the preform; the silicon infiltration channels are silicon infiltration points with a depth of 50~200μm; the number of silicon infiltration points is not less than 2; S4. Preparation of composite material by sintering: The preform with silicon infiltration channels prepared in step S3 is subjected to reaction sintering densification treatment at a sintering temperature of 1420℃~1700℃ and a holding time of 3h~24h; after sintering, it is cooled to room temperature to obtain RB-SiC composite material with β-type silicon carbide protective layer.

2. The method for preparing a β-type silicon carbide protective layer coated RB-SiC composite material according to claim 1, characterized in that: The method for preparing the silicon carbide preform in step S1 includes at least one of gel casting molding, isostatic pressing molding, slurry casting molding, and additive manufacturing molding.

3. The method for preparing a β-type silicon carbide protective layer coated RB-SiC composite material according to claim 2, characterized in that: The gel casting molding preparation method specifically includes the following steps: a premixed liquid is formed by thoroughly mixing acrylamide, methylenebisacrylamide and tetramethylammonium hydroxide, silicon carbide powder is added to prepare silicon carbide slurry, and the slurry is injected into a mold and then cured to form a silicon carbide preform.

4. The method for preparing a β-type silicon carbide protective layer coated RB-SiC composite material according to claim 2, characterized in that: The isostatic pressing preparation method specifically includes the following steps: using silicon carbide powder as raw material, adding phenolic resin binder, and dry pressing under a pressure of 40~80MPa to obtain a silicon carbide preform.

5. The method for preparing a β-type silicon carbide protective layer coated RB-SiC composite material according to claim 2, characterized in that: The additive manufacturing method specifically includes the following steps: mixing 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, polyvinylpyrrolidone and silicon carbide powder in a certain proportion to form a liquid photosensitive silicon carbide slurry; and transforming the liquid photosensitive silicon carbide slurry into a solid silicon carbide preform under light irradiation at a wavelength of 380~450nm.

6. A β-type silicon carbide protective layer coated RB-SiC composite material, characterized in that: Prepared by the method for preparing a β-type silicon carbide protective layer coated RB-SiC composite material according to any one of claims 1-5.

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