Silicon carbide ceramic part and preparation method thereof

Abstract

The invention relates to a silicon carbide ceramic part and a preparation method thereof, and belongs to the technical field of ceramic forming. The preparation method comprises the following steps that prepolymerized resin is dissolved in water to form a resin solution, silicon carbide powder is dispersed in the resin solution, mixed slurry is obtained, and the prepolymerized resin comprises at least one of resol, resorcinol formaldehyde resin prepolymer or prepolymerized furfural resin; adjusting the pH value of the mixed slurry, injecting the mixed slurry into a mold, carrying out heating curing molding, demolding, and drying to obtain a preformed blank; performing pyrolysis biscuit firing treatment on the preformed green body to obtain a formed green body containing pyrolytic carbon; and carrying out siliconizing treatment and reactive sintering on the formed green body to obtain the silicon carbide ceramic part. The prepolymerized resin is adopted as a carbon source, polymerization can be initiated by adjusting the pH value, the polymerization reaction is controllable, the uniformity of a green body can be improved, then the structural defects of ceramic parts are effectively reduced, and high-dimensional-precision forming of complex structures is achieved.

Description

Technical Field

[0001] This application relates to the field of ceramic forming technology, and in particular to a silicon carbide ceramic component and its preparation method. Background Technology

[0002] Gel casting is currently the mainstream method for fabricating complex ceramic components due to its low dimensional shrinkage and good structural integrity. For gel casting of silicon carbide ceramic components, the selection of the carbon source and the construction of the gel system are crucial. Existing technologies typically use carbon black as the carbon source, with acrylamide as the main component and azo initiators added for free radical polymerization to construct the gel system. However, the polymerization rate using current processes is relatively fast and difficult to control. Furthermore, the nitrogen gas released from the decomposition of the azo initiators often leads to porosity in the green body, resulting in structural defects in the prepared silicon carbide ceramic components that cannot effectively meet application requirements. Summary of the Invention This application is made in view of the above-mentioned problems, and its purpose is to provide a silicon carbide ceramic component and a method for preparing the same, so as to solve the problems that the silicon carbide ceramic components prepared by existing methods have low density and the mechanical properties need to be improved.

[0003] In a first aspect, this application provides a method for preparing a silicon carbide ceramic component, comprising the following steps: S1: Dissolve the prepolymerized resin in water to form a resin solution, disperse the silicon carbide powder in the resin solution, and obtain a mixed slurry; wherein, the prepolymerized resin includes at least one of methyl phenolic resin, resorcinol formaldehyde resin prepolymer or prepolymerized furfural resin; S2: After adjusting the pH of the mixed slurry, it is injected into a mold for heating and curing. After demolding and drying, a preform is obtained. S3: Pyrolytic sintering is performed on the preform to obtain a preform containing pyrolytic carbon; S4: The formed blank is subjected to silicon diffusion treatment and reaction sintering to obtain silicon carbide ceramic parts.

[0004] In the above technical solution, this application uses a prepolymerized resin with high pyrolysis carbon yield as the carbon source. Polymerization can be initiated by adjusting the pH without the need for an initiator, making the curing speed of the mixed slurry controllable and the molding uniformity good. Combining gel casting, pyrolysis sintering, and reaction sintering, it effectively reduces structural defects in silicon carbide ceramic parts, making it suitable for high-dimensional precision molding of complex structures. Furthermore, this preparation method is applicable to silicon carbide powders with different particle size distributions and volume solid content, and the process parameters can be flexibly adjusted. It is also suitable for high-dimensional precision molding of porous and dense complex silicon carbide ceramics.

[0005] In some embodiments, the weight-average molecular weight of the prepolymerized resin is 150 to 4000.

[0006] In some embodiments, the weight-average molecular weight of the methyl phenolic resin is 150-3000; the weight-average molecular weight of the resorcinol formaldehyde resin prepolymer is 600-1200; and the weight-average molecular weight of the prepolymerized furfuryl alcohol resin is 3000-4000.

[0007] In some embodiments, the volume distribution particle size D of the silicon carbide powder 50 The range is 0.5μm to 30μm.

[0008] In some implementations, in step S1, D 50 Silicon carbide powder with a diameter of 0.5μm to 5μm and D 50 Silicon carbide powder with a diameter of 5μm to 10μm and / or D 50 The volume ratio of silicon carbide powder with a particle size of 10μm to 30μm is (1~5):(5~10). In some embodiments, the prepolymerized resin in the resin solution accounts for 5 wt% to 30 wt% by mass.

[0009] In some embodiments, the mass ratio of silicon carbide powder to prepolymerized resin is (6:4) to (10:1). In some embodiments, the dispersion method includes at least one of ball milling, sand milling, or ultrasonic homogenization. In some embodiments, the volume solids content V of the mixed slurry 固 It ranges from 20 vol% to 60 vol%. In some embodiments, in step S2, the temperature for heating and curing is 40°C to 180°C, and the time is 10 min to 6 h. In some embodiments, before injection into the mold, the mixture is further subjected to a degassing process. In some embodiments, the drying method includes at least one of hot air drying, microwave drying, or infrared drying. In some embodiments, adjusting the pH of the mixed slurry includes adjusting the pH of the mixed slurry to a viscosity of 2000cp to 15000cp. In some embodiments, when the volume solids content V of the mixed slurry 固 Satisfying 20vol%≤V 固 When the volume solids content of the mixed slurry is <40 vol%, adjust the pH value of the mixed slurry to 3~6; when the volume solids content of the mixed slurry is V 固 Satisfying 40vol%≤V 固 When the vol% is <60%, adjust the pH of the mixed slurry to 8~10. In some embodiments, the conditions for pyrolysis calcination in step S3 include: an inert atmosphere or vacuum environment, a temperature of 500℃~1000℃, a time of 0.5h~6h, and a heating rate of 2℃ / min~10℃ / min. In some embodiments, the reaction sintering conditions in step S4 include: an inert atmosphere or vacuum environment, a temperature of 1420°C to 1650°C, and a time of 1 hour to 8 hours. In some embodiments, the silicon diffusion process includes liquid-phase silicon diffusion and / or vapor-phase silicon diffusion. Secondly, embodiments of this application provide a silicon carbide ceramic component, which is prepared by the above-described preparation method.

[0010] In the above technical solutions, the silicon carbide ceramic components provided in this application can be dense silicon carbide ceramic components with high density and mechanical strength, or porous silicon carbide ceramic components with fewer structural defects, both of which can meet the high dimensional accuracy requirements of complex structures. Attached Figure Description To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 A process flow diagram of a method for preparing a silicon carbide ceramic component provided in this application embodiment. Detailed Implementation

[0012] The embodiments of the silicon carbide ceramic component and its preparation method of this application are disclosed in detail below with appropriate reference to the accompanying drawings, but unnecessary detailed descriptions may be omitted.

[0013] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is expected that the ranges 60~110 and 80~120 will also be understood.

[0014] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions. Unless otherwise specified, all steps of this application can be performed sequentially or randomly, preferably sequentially.

[0015] Gel casting is currently the mainstream method for fabricating complex ceramic components due to its low dimensional shrinkage and good structural integrity. For gel casting of silicon carbide ceramic components, the selection of the carbon source and the construction of the gel system are crucial. Existing technologies typically use nanoscale carbon black powder as the carbon source, and acrylamide as the monomer, with the addition of azo initiators for free radical polymerization to construct the gel system. This is then combined with reaction sintering to prepare the silicon carbide ceramic components.

[0016] However, the surface of nanoscale carbon black powder contains various functional groups (hydroxyl, carboxyl, carbonyl, phenolic hydroxyl, etc.), which interfere with free radical polymerization reactions, reducing polymerization efficiency. Furthermore, nanoscale carbon black powder is difficult to disperse uniformly in a slurry system, preventing subsequent reaction with silicon to form a uniformly distributed silicon carbide. Simultaneously, azo initiators easily generate gas during polymerization, leading to numerous unevenly distributed large pores within the material. When fabricating porous silicon carbide ceramic components, these structural defects disrupt the original pore distribution, reducing mechanical properties and core functions (such as fluid transport performance). When fabricating dense silicon carbide ceramic components, these structural defects result in reduced density, decreased mechanical strength, and reduced service life and safety.

[0017] Based on this, this application provides a method for preparing a silicon carbide ceramic component. Please refer to [link to relevant documentation]. Figure 1 The method for preparing silicon carbide ceramic components provided in this application includes the following steps: S1: Dissolve the prepolymerized resin in water to form a resin solution, disperse the silicon carbide powder in the resin solution, and obtain a mixed slurry; wherein, the prepolymerized resin includes at least one of methyl phenolic resin, resorcinol formaldehyde resin prepolymer or prepolymerized furfuryl alcohol resin.

[0018] In this application, "prepolymerized resin," or prepolymer, refers to an intermediate product formed in the early stages of a polymerization reaction, possessing a certain molecular weight but not fully cross-linked and cured. Its molecular structure retains active groups that can continue to react, allowing for further polymerization or cross-linking in subsequent processing to form the final cured product. This application defines prepolymerized resins as including methyl phenolic resins, resorcinol-formaldehyde resin prepolymers, or prepolymerized furfuryl alcohol resins. These prepolymerized resins exhibit high pyrolysis carbon yield and good water solubility, and polymerization can be initiated by adjusting pH and increasing temperature without the need for additional curing agents or initiators.

[0019] In this application, "pyrolysis carbon yield" is also called pyrolysis residual carbon rate or carbon yield, which refers to the efficiency of converting the organic components of prepolymerized resin into solid carbon (pyrolysis carbon) after high-temperature pyrolysis in an inert atmosphere (such as nitrogen or argon) or under oxygen-deficient conditions. Essentially, it is the percentage of the mass of solid carbon after pyrolysis to the initial mass of the raw material.

[0020] Understandably, the prepolymerized resins in this application are not limited to the above-mentioned methyl phenolic resins, resorcinol formaldehyde resin prepolymers, or prepolymerized furfuryl alcohol resins. Any water-soluble prepolymerized resin that has a high pyrolysis carbon yield (≥40%) and can be cured by heating or adjusting the pH value and heating without adding a curing agent can be used in this application.

[0021] Preferably, the prepolymerized resin includes amorphous phenolic resin. Amorphous phenolic resin is an initial product in the synthesis of phenolic resin: it is formed by the condensation polymerization of phenol and excess formaldehyde under alkaline conditions. Its molecular structure is mainly linear or low-branched, containing a large number of active hydroxymethyl groups (-CH2OH), with a low molecular weight (usually several hundred to several thousand). It has not yet formed a three-dimensional network cross-linked structure and is thermoplastic (it can soften and flow when heated). By adjusting the pH (without additional curing agent), a condensation reaction between hydroxymethyl groups can occur, gradually cross-linking to form ethoxylated phenolic resin with a higher molecular weight and more branches, and finally curing into an insoluble and infusible three-dimensional network structure (propionic resin). Furthermore, the pyrolysis carbon yield of amorphous phenolic resin is as high as 55%, and it has high solubility in water.

[0022] In some embodiments, the weight-average molecular weight of the prepolymerized resin is 150 to 4000. By controlling the weight-average molecular weight within a suitable range, it is beneficial to further increase the polymerization rate, improve the dispersion uniformity of pyrolytic carbon, and thus further improve the performance of silicon carbide ceramic components.

[0023] Furthermore, the weight-average molecular weight of methyl phenolic resins is 150–3000. Classified according to their solubility in water (i.e., water solubility), methyl phenolic resins can be strongly water-soluble methyl phenolic resins with a weight-average molecular weight of 150–1200; or they can be water-dispersible methyl phenolic resins with a weight-average molecular weight of 800–3000.

[0024] Furthermore, the resorcinol formaldehyde resin prepolymer can be a water-soluble resorcinol formaldehyde resin prepolymer with a weight-average molecular weight of 600~1200.

[0025] Furthermore, the weight-average molecular weight of the prepolymerized furfuryl alcohol resin is 3000~4000.

[0026] In some embodiments, the mass ratio of silicon carbide powder to prepolymerized resin is (6:4) to (10:1). As examples, the mass ratio of silicon carbide powder to prepolymerized resin is 6:4, 3:1, 5:1, 8:1, 10:1, etc.

[0027] In some embodiments, the volume distribution particle size D of silicon carbide powder 50 The particle size ranges from 0.5 μm to 30 μm. Controlling the particle size of silicon carbide powder within a suitable range is beneficial for uniform dispersion, increasing packing density, thereby reducing subsequent molding shrinkage and further reducing structural defects.

[0028] As an example, the volume distribution particle size D of silicon carbide powder 50 The range is between any two values ​​of 0.5μm, 1μm, 5μm, 10μm, 15μm, 20μm, 30μm or above.

[0029] Furthermore, in step S1, D 50 Silicon carbide powder with a diameter of 0.5μm to 5μm and D 50 Silicon carbide powder with a diameter of 5μm to 10μm and / or D 50 The mass ratio of silicon carbide powder with a particle size of 10μm to 30μm is (1~5):(5~10). Using silicon carbide powder with a particle size distribution is beneficial to further improve the packing density and enhance the compactness and mechanical strength of the ceramic structure.

[0030] Understandably, the volume distribution particle size D of the silicon carbide powder in this application... 50 It can include 0.5μm~5μm, 5μm~10μm and 10μm~30μm; it can also include only 0.5μm~5μm and 5μm~10μm; or it can include only 0.5μm~5μm and 10μm~30μm.

[0031] In some embodiments, the volume solids content V of the mixed slurry 固 The volume solids content (V) of the mixed slurry ranges from 20 vol% to 60 vol%. 固 It is applicable to the preparation of porous or dense silicon carbide ceramics over a wide range.

[0032] As an example, the volume solids content V of the mixed slurry 固 It is a range between any two values ​​of 20vol%, 30vol%, 40vol%, 50vol%, 60vol%, or higher.

[0033] In some embodiments, the mass percentage of prepolymerized resin in the resin solution is 5 wt% to 30 wt%. As an example, the mass percentage of prepolymerized resin in the resin solution is within any two of the following values: 5 wt%, 10 wt%, 5 wt%, 20 wt%, 25 wt%, 30 wt%, or more.

[0034] Furthermore, the dispersion method includes at least one of ball milling, sand milling, or ultrasonic homogenization. Specifically, silicon carbide powder can be slowly or gradually added to the resin solution, and the slurry can be fully dispersed and homogenized using equipment such as a ball mill, sand mill, or ultrasonic homogenizer, so that the silicon carbide powder is evenly distributed in the slurry.

[0035] S2: After adjusting the pH of the mixed slurry, it is injected into a mold for heating and curing. After demolding and drying, a preform is obtained.

[0036] In some embodiments, adjusting the pH of the mixed slurry includes adjusting the pH of the mixed slurry to a viscosity of 2000 cp to 15000 cp. Adjusting the pH of the mixed slurry promotes a suitable polymerization reaction of the prepolymerized resin, thereby controlling the slurry viscosity within a suitable range, which is beneficial for maintaining the stability of the slurry, thereby further improving the density and mechanical strength of the silicon carbide ceramic component.

[0037] As an example, the pH of the mixed slurry is adjusted to a viscosity between any two values ​​of 2000cp, 5000cp, 10000cp, 15000cp or above.

[0038] Furthermore, when the volume solids content V of the mixed slurry 固 Satisfying 20vol%≤V 固 When the volume solids content of the mixed slurry is <40 vol%, adjust the pH value of the mixed slurry to 3~6; when the volume solids content of the mixed slurry is V 固 Satisfying 40vol%≤V 固 When the vol% is <60%, adjust the pH of the mixed slurry to 8~10.

[0039] Furthermore, citric acid, acetic acid, hydrochloric acid, ammonium chloride, etc. can be used to adjust the pH. Tetramethylammonium hydroxide, ammonia, triethanolamine, hexamethylenetetramine, ethylenediamine, sodium hydroxide, potassium hydroxide, etc. can also be used.

[0040] In some embodiments, the process further includes degassing the mixed slurry before injection into the mold. For example, the mixed slurry with adjusted pH value is placed in an ultrasonic vibration device or mechanical vibration and vacuum degassing device are used to remove air bubbles from the slurry, preventing unwanted large pores from appearing inside after molding and further reducing structural defects in silicon carbide ceramics.

[0041] In some embodiments, the grouting step may include: injecting the degassed mixed grout into a complex structure mold made of materials such as metal, glass, plastic, rubber, nylon, or plexiglass, to ensure that the grout fully fills all parts of the mold and forms the designed shape.

[0042] In some embodiments, the heating and curing molding process can employ various methods such as hot air heating, infrared heating, and microwave heating to meet the requirements of different mold materials and shapes.

[0043] In some embodiments, in step S2, the temperature for heat curing is 40°C to 180°C, and the time is 10 min to 6 h. As an example, the temperature for heat curing is within the range of any two values ​​of 40°C, 60°C, 80°C, 100°C, 120°C, 150°C, 180°C, or higher; and the time is within the range of any two values ​​of 10 min, 30 min, 1 h, 2 h, 4 h, 6 h, or higher.

[0044] In some embodiments, the drying method includes at least one of hot air drying, microwave drying, or infrared drying. The drying process can effectively remove solvents and moisture from the preform, resulting in a structurally stable silicon carbide / resin composite preform.

[0045] S3: The preform is subjected to pyrolysis sintering to obtain a preform containing pyrolytic carbon.

[0046] In some embodiments, the conditions for pyrolysis calcination in step S3 include: an inert atmosphere or vacuum environment, a temperature of 500°C to 1000°C, a time of 0.5h to 6h, and a heating rate of 2°C / min to 10°C / min. By controlling the pyrolysis calcination conditions, it is beneficial to fully pyrolyze the prepolymerized resin to form pyrolytic carbon, while simultaneously enabling the green body to form a porous structure (facilitating subsequent silicon infiltration).

[0047] As an example, the temperature of the pyrolysis calcination treatment is within the range of any two values ​​of 500°C, 600°C, 800°C, 1000°C or above; the time is within the range of any two values ​​of 0.5h, 1h, 2h, 4h, 6h or above; and the heating rate is within the range of any two values ​​of 2°C / min, 3°C / min, 4°C / min, 5°C / min, 8°C / min, 10°C / min or above.

[0048] S4: The formed blank is subjected to silicon diffusion treatment and reaction sintering to obtain silicon carbide ceramic parts.

[0049] In some embodiments, the silicon infiltration process includes liquid-phase silicon infiltration and / or gas-phase silicon infiltration. In liquid-phase silicon infiltration, the silicon source is silicon powder. By placing the molded preform and silicon powder together in a high-temperature environment, the silicon powder melts to form liquid silicon, which infiltrates into the pores of the porous preform and reacts with pyrolytic carbon to generate silicon carbide. In gas-phase silicon infiltration, the silicon source is silicon powder or silicon ingot, which becomes gaseous silicon at high temperatures and diffuses into the pores of the porous preform through gas diffusion.

[0050] In some embodiments, the reaction sintering conditions include: a temperature of 1420°C to 1650°C and a time of 1 h to 8 h under an inert atmosphere or vacuum. As an example, the reaction sintering temperature is within the range of any two values ​​of 1420°C, 1500°C, 1600°C, 1650°C, or higher; and the time is within the range of any two values ​​of 1 h, 2 h, 4 h, 6 h, 8 h, or higher.

[0051] This application uses a prepolymerized resin as a carbon source, which can be uniformly mixed and dispersed with silicon carbide powder to form a homogeneous slurry. The viscosity of the slurry can be controlled by pH-initiated polymerization, thereby controlling the injection molding performance. Furthermore, no initiator or curing agent is required, making the curing speed of the slurry controllable and ensuring good molding uniformity. Pyrolytic carbon is formed through pyrolytic sintering, resulting in a molded green body. Silicon is then infiltrated, and the pyrolytic carbon reacts with silicon to generate new silicon carbide, completing the initial particle bonding and forming a complex-structured silicon carbide ceramic component with a complete shape. The use of a prepolymerized resin with a high pyrolytic carbon yield as the carbon source, instead of traditional nano-sized carbon black powder, reduces the problems of hindered free radical polymerization and gas generation from azo initiators, improving the controllability and uniformity of the slurry's polymerization reaction. It also reduces gas generation during polymerization, lowering the porosity during sintering. Combined with gel casting molding and reaction sintering technology, low drying and sintering shrinkage are achieved, making it suitable for high-dimensional precision molding of complex-structured silicon carbide ceramic components.

[0052] This preparation method is simple to operate and applicable to silicon carbide powders with different particle size distributions and volume solid content. The process parameters can be flexibly adjusted, and it has good process adaptability and scalability. It can prepare dense silicon carbide ceramic parts with high density and mechanical strength, as well as porous silicon carbide ceramic parts with fewer structural defects and uniform pore distribution.

[0053] In addition, this application also provides a silicon carbide ceramic component prepared by the above-described preparation method.

[0054] The silicon carbide ceramic components prepared by the method of this application can be porous or dense structures. By reducing structural defects, unwanted large pores can be avoided in porous silicon carbide ceramic components, thereby improving mechanical properties and the core functions of the components (such as fluid transport performance). Furthermore, it can effectively improve the density and mechanical strength of dense silicon carbide ceramic components, extend service life, and enhance safety.

[0055] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0056] Example 1 This embodiment provides a dense silicon carbide ceramic component, the preparation method of which includes the following steps: (1) 15g of methyl phenolic resin (weight average molecular weight of 200~400, pyrolysis carbon yield of 50%) was stirred evenly in 85mL of deionized water to fully dissolve it and form a stable resin solution. 160g of silicon carbide powder (volume distribution particle size D) 50 The particles (0.5μm, 5μm, and 20μm in mass ratio of 2:3:5) were slowly added to the resin solution, mixed, and dispersed in a sand mill (zirconia balls) for 2 hours to obtain a mixed slurry with a volume solids content of 50 vol%. The pH of the mixed slurry was adjusted to 9.5 and the viscosity to 6000 cp using tetramethylammonium hydroxide. No significant sedimentation was observed after standing for 24 hours.

[0057] (2) Vacuum exhaust of the mixed slurry (vacuum degree 0.09MPa, time 10min), then inject the degassed mixed slurry into a complex impeller mold made of metal, cure it at 120℃ for 2h by oven heating, then demold it, and dry it with hot air at 60℃ for 5h to obtain a preform.

[0058] (3) The preformed blank is placed in a vacuum furnace for pyrolysis calcination. Under nitrogen protection, the temperature is raised to 800°C at a heating rate of 5°C / min and held for 2 hours to remove the highly water-soluble methyl phenolic resin and generate a preformed blank containing pyrolytic carbon.

[0059] (4) The molded blank is placed in a vacuum silicon infiltration furnace and heated to 1600℃ for reaction sintering for 3 hours to obtain a complex structure dense silicon carbide ceramic impeller component with a density of 95%.

[0060] The density of the silicon carbide ceramic impeller component in Example 1 is 3.05 g / cm³. 3The flexural strength is 320 MPa, and the fracture toughness is 4.2 MPa•m. 1 / 2 Its thermal conductivity is 160 (W / m·K), and its coefficient of thermal expansion (RT-100℃) is 4.5×10⁻⁶. -6 .

[0061] Example 2 This embodiment provides a porous silicon carbide ceramic component, the preparation method of which includes the following steps: (1) Dissolve 30g of methyl phenolic resin (weight average molecular weight of 1200~2000, pyrolysis carbon yield of 55%) in 70mL of deionized water and stir until fully dissolved to form a stable resin solution. 140g of silicon carbide powder (volume distribution particle size D) was added. 50 The particles (1μm and 10μm, in a mass ratio of 4:6) were slowly added to the resin solution and dispersed using a ball mill for 30 minutes to obtain a mixed slurry with a volume solids content of 20 vol%. The pH of the mixed slurry was adjusted to 3.5 and the viscosity to 2500 cp using 5 wt% hydrochloric acid. No significant sedimentation was observed after standing for 24 hours.

[0062] (2) The mixed slurry was ultrasonically degassed (power 300W, time 15min), then injected into a complex flow channel mold made of nylon material, heated to 60℃ in a hot air furnace, and left to stand for 4h to complete curing; then demolded and dried by microwave (power 800W, time 30min) to obtain a preformed blank.

[0063] (3) The preform is placed in a vacuum furnace for pyrolysis calcination. Under nitrogen protection, the temperature is raised to 600°C at a rate of 3°C / min and held for 3 hours to remove water-dispersible methyl phenolic resin and generate a preform containing pyrolytic carbon.

[0064] (4) The molded blank is placed in a vacuum silicon infiltration furnace and heated to 1450℃ for reaction sintering for 2 hours to obtain a complex porous silicon carbide ceramic complex flow channel component with a porosity of 45%.

[0065] In Example 2, the density of the porous silicon carbide ceramic complex flow channel component was 2.1 g / cm³. 3 Its flexural strength is 40 MPa.

[0066] Example 3 This embodiment provides a dense silicon carbide ceramic component, the preparation method of which includes the following steps: (1) Dissolve 20g of methyl phenolic resin (weight average molecular weight of 200~400, pyrolysis carbon yield of 50%) in 80mL of water until it is fully dissolved and a stable resin solution is formed. 100g of silicon carbide powder (volume distribution particle size D) 50 The particles (2μm, 8μm, and 15μm, with a mass ratio of 3:4:3) were slowly added to the resin solution and dispersed using a ball mill (agate balls, ball-to-material ratio 3:1) for 120 min to obtain a mixed slurry with a volume solids content of 40 vol%. The pH of the mixed slurry was adjusted to 8.0 and the viscosity to 8000 cp using a 10 wt% ammonia solution. No significant sedimentation was observed after standing for 24 hours.

[0067] (2) Vibrate the mixed slurry to degas (frequency 50Hz, time 20min), then inject it into a complex metal support mold and cure it at 160℃ for 4h using hot air heating; then demold and dry it with infrared (70℃, 4h) to obtain a preformed blank.

[0068] (3) The preform is placed in a vacuum furnace for pyrolysis calcination. Under nitrogen protection, the temperature is raised to 700°C at a heating rate of 4°C / min and held for 2.5 hours to remove the highly water-soluble methyl phenolic resin and generate a preform containing pyrolytic carbon.

[0069] (4) Place the molded blank into a vacuum silicon infiltration furnace, heat it to 1500℃ and sinter for 2.5h to obtain a complex structured dense silicon carbide ceramic support component.

[0070] The density of the silicon carbide ceramic support component in Example 3 is 2.98 g / cm³. 3 It has a flexural strength of 300 MPa, a thermal conductivity of 160 (W / m·K), and a coefficient of thermal expansion (RT-100℃) of 4.2 × 10⁻⁶. -6 .

[0071] As can be seen from Examples 1 to 3 above, the preparation method in this application can prepare dense silicon carbide ceramic parts with high density and mechanical strength by using prepolymerized resin as carbon source, initiating polymerization by adjusting pH, and then combining gel casting and reaction sintering; and by controlling the amount of silicon carbide powder, porous silicon carbide ceramic parts can also be formed.

[0072] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for preparing a silicon carbide ceramic component, characterized in that, Includes the following steps: S1: Dissolve the prepolymerized resin in water to form a resin solution, disperse the silicon carbide powder in the resin solution, and obtain a mixed slurry; wherein, the prepolymerized resin includes at least one of methyl phenolic resin, resorcinol formaldehyde resin prepolymer or prepolymerized furfuryl alcohol resin; S2: After adjusting the pH of the mixed slurry, it is injected into a mold for heating and curing. After demolding and drying, a preform is obtained. S3: The preformed blank is subjected to pyrolysis sintering treatment to obtain a shaped blank containing pyrolytic carbon; S4: The molded blank is subjected to silicon diffusion treatment and reaction sintering to obtain silicon carbide ceramic parts.

2. The preparation method according to claim 1, characterized in that, The weight-average molecular weight of the prepolymerized resin is 150-4000; Optionally, the weight-average molecular weight of the methyl phenolic resin is 150 to 3000. Optionally, the weight-average molecular weight of the resorcinol formaldehyde resin prepolymer is 600-1200; Optionally, the weight-average molecular weight of the prepolymerized furfuryl alcohol resin is 3000-4000.

3. The preparation method according to claim 1, characterized in that, The volume distribution particle size D of the silicon carbide powder 50 The range is 0.5μm to 30μm; Optionally, in step S1, D 50 Silicon carbide powder with a diameter of 0.5μm to 5μm and D 50 Silicon carbide powder with a diameter of 5μm to 10μm and / or D 50 The mass ratio of silicon carbide powder with a particle size of 10μm to 30μm is (1~5):(5~10).

4. The preparation method according to claim 1, characterized in that, The prepolymerized resin in the resin solution accounts for 5wt% to 30wt% by mass. Optionally, the dispersion method includes at least one of ball milling, sand milling, or ultrasonic homogenization.

5. The preparation method according to claim 1 or 4, characterized in that, The volume solids content V of the mixed slurry 固 20 vol%~60 vol% And / or, the mass ratio of the silicon carbide powder to the prepolymerized resin is (6:4) to (10:1).

6. The preparation method according to claim 1, characterized in that, In step S2, adjusting the pH of the mixed slurry includes: adjusting the pH of the mixed slurry to a viscosity of 2000cp~15000cp; Optionally, when the volume solids content V of the mixed slurry 固 Satisfying 20vol%≤V 固 When the volume solids content of the mixed slurry is <40 vol%, adjust the pH value to 3-6; when the volume solids content of the mixed slurry is V 固 Satisfying 40vol%≤V 固 When the content is <60 vol%, adjust the pH of the mixed slurry to 8~10.

7. The preparation method according to claim 1, characterized in that, In step S2, the temperature for heating and curing is 40℃~180℃, and the time is 10min~6h; Optionally, before injection into the mold, the mixture is further subjected to a degassing treatment. Optionally, the drying method includes at least one of hot air drying, microwave drying, or infrared drying.

8. The preparation method according to claim 1, characterized in that, In step S3, the conditions for the pyrolysis calcination treatment include: an inert atmosphere or vacuum environment, a temperature of 500℃~1000℃, a time of 0.5h~6h, and a heating rate of 2℃ / min~10℃ / min.

9. The preparation method according to claim 1, characterized in that, In step S4, the conditions for reaction sintering include: an inert atmosphere or vacuum environment, a temperature of 1420℃~1650℃, and a time of 1h~8h. Optionally, the silicon diffusion process includes liquid-phase silicon diffusion and / or gas-phase silicon diffusion.

10. A silicon carbide ceramic component, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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