Preparation method of fiber-reinforced porous SiC ceramic sandwich structure

Abstract

The invention relates to the technical field of 3D printing, and particularly discloses a preparation method of a fiber-reinforced porous SiC ceramic sandwich structure. The DIW technology is used for achieving one-time forming of the component with the complex three-dimensional structure, a mold does not need to be prepared in advance, the prepared ceramic component does not need to be subjected to follow-up machining, and the preparation cost is low. After the blank is printed, densification can be completed only through one-time sintering, and a complex post-treatment process is not needed. The shrinkage rate of the core material and the shrinkage rate of the panel material can be matched with each other by adjusting the proportion of the PMMA to the carbon fiber of the core slurry, so that the damage of the interface between the panel layer and the core layer caused by mismatching of the shrinkage rates in the sintering process is reduced, and the mechanical strength of the sandwich structure is improved. The thickness of the panel and the core of the sandwich structure can be flexibly and conveniently adjusted through the DIW technology, and therefore differential regulation and control over the functionality or the mechanical property of the sandwich structure are achieved.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology, specifically to a method for preparing a fiber-reinforced porous SiC ceramic sandwich structure. Background Technology

[0002] Porous ceramics are functional materials containing numerous micropores. They possess a large specific surface area, low density, excellent high-temperature resistance, and stable chemical properties, making them widely used in filtration and separation, catalyst supports, biomedicine, energy storage, and sound and heat insulation. However, the unique structure of porous ceramics also leads to defects in their mechanical properties. The presence of pores can induce stress concentration effects, significantly reducing the material's fracture toughness and flexural strength, thus severely limiting its engineering applications under high mechanical load environments.

[0003] To improve the mechanical properties of porous ceramics, researchers have proposed the concept and design methods of porous ceramic sandwich structures. These structures consist of two layers of dense ceramic panels and a porous ceramic core in the middle. The upper and lower panels are thin and possess strong mechanical properties, which significantly increases the moment of inertia of the porous ceramic, thereby enhancing its mechanical properties. Because the upper and lower panels are very thin, the porous ceramic sandwich structure retains the lightweight and multifunctional characteristics of porous ceramics. However, existing fabrication methods for porous ceramic sandwich structures face significant technical bottlenecks. Traditional processes (such as gel casting, tape casting, and chemical vapor infiltration) struggle to achieve synergistic optimization in terms of fabrication accuracy, process cycle, and cost-effectiveness. This limitation severely restricts the industrial application of porous ceramic sandwich structures in precision engineering.

[0004] Therefore, it is necessary to provide a method for preparing fiber-reinforced porous SiC ceramic sandwich structures to achieve one-time molding of complex three-dimensional structural components, improve the mechanical properties of the sandwich structure, and differentiate the functionality or mechanical properties of the sandwich structure. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a method for preparing fiber-reinforced porous SiC ceramic sandwich structures, which realizes one-time molding of complex three-dimensional structural components, improves the mechanical properties of the sandwich structure, and allows for differentiated control of the functionality or mechanical properties of the sandwich structure.

[0006] The first aspect of the present invention provides a method for preparing a fiber-reinforced porous SiC ceramic sandwich structure, characterized by comprising the following steps:

[0007] (1) Sift 20-25g of silicon carbide powder, dry it and place it in a mixing container, then add 1-1.5wt% sodium carboxymethyl cellulose, 2-3wt% boron carbide and 0.1-8vol% carbon fiber to obtain mixed powder A; stir 0.5-1wt% trisodium citrate and 5-10wt% sucrose in 15-20mL of water to prepare a mixed solution, then add the mixed solution to the mixed powder A to obtain a carbon fiber reinforced silicon carbide ceramic slurry with a solid content of 40-45vol%;

[0008] (2) Sift 20-25g of silicon carbide powder, dry it and place it in a mixing container, then add 1-1.5wt% sodium carboxymethyl cellulose, 2-3wt% boron carbide, 30-60vol% polymethyl methacrylate and 0.5-1.5vol% carbon fiber to obtain mixed powder B; stir 0.5-1wt% trisodium citrate and 5-10wt% sucrose in 20-25mL of water to prepare a mixed solution, then add the mixed solution to the mixed powder B to obtain a porous silicon carbide ceramic slurry with a solid content of 40-45vol%;

[0009] (3) The carbon fiber reinforced silicon carbide ceramic slurry and the porous silicon carbide ceramic slurry are homogenized and degassed respectively; then the carbon fiber reinforced silicon carbide ceramic slurry and the porous silicon carbide ceramic slurry are transferred into syringes and degassed respectively.

[0010] (4) Using 3D printing technology, firstly, a syringe filled with carbon fiber reinforced silicon carbide ceramic slurry is used to print the lower panel layer. After the panel is printed, the syringe is switched to use a syringe filled with porous silicon carbide ceramic slurry to print the core layer. After the core layer is printed, the syringe filled with carbon fiber reinforced silicon carbide ceramic slurry is switched back to print the upper panel layer. After printing, a blank is obtained.

[0011] (5) Curing, drying and sintering the green body to obtain a fiber-reinforced porous SiC ceramic sandwich structure.

[0012] The mass fraction is calculated based on the mass of silicon carbide powder, and the volume fraction is calculated based on the total volume of the mixed powder.

[0013] Preferably, in step (1), the particle size of the silicon carbide powder is 0.5 to 0.7 μm.

[0014] More preferably, in step (1), the particle size of the silicon carbide powder is 0.6 to 0.7 μm.

[0015] More preferably, in step (1), the particle size of the silicon carbide powder is 0.7 μm.

[0016] Preferably, in step (1), the mesh size of the sieve is 180 to 200 mesh.

[0017] Preferably, in step (3), the homogenization mixing step includes: first mixing at a speed of 2000-2200 r / min for 25-30 s; then mixing at a high speed of 2500-3000 r / min for 25-30 s, and repeating 2-3 times.

[0018] More preferably, in step (3), the homogenization mixing step includes: first mixing at a speed of 2100-2200 r / min for 28-30 s; then mixing at a high speed of 2800-3000 r / min for 28-30 s, and repeating 2-3 times.

[0019] More preferably, in step (3), the homogenization mixing step includes: first mixing at a speed of 2200 r / min for 30 s; then mixing at a high speed of 2800 r / min for 30 s, and repeating 3 times.

[0020] Preferably, in step (3), the degassing step includes: degassing in a vacuum environment, mixing at a speed of 2500-3000 r / min for 50-60 s, and repeating 3-4 times.

[0021] More preferably, in step (3), the degassing step includes: degassing in a vacuum environment, mixing at a speed of 2500-2800 r / min for 55-60 s, and repeating 3-4 times.

[0022] More preferably, in step (3), the degassing step includes: degassing in a vacuum environment, mixing at a speed of 2500 r / min for 55 s, and repeating 3 to 4 times.

[0023] Preferably, the vacuum level of the vacuum environment is -95 to -100 kPa.

[0024] More preferably, the vacuum level of the vacuum environment is -96 to -98 kPa.

[0025] More preferably, the vacuum level of the vacuum environment is -96 kPa.

[0026] Preferably, in step (5), the maintenance steps include: temperature 24-26℃, humidity 95-100%, 1-2h; temperature 29-31℃, humidity 85-90%, 1-2h; temperature 33-35℃, humidity 75-80%, 1-2h; temperature 38-40℃, humidity 65-70%, 1-2h; temperature 33-35℃, humidity 55-60%, 1-2h; temperature 28-30℃, humidity 45-50%, 1-2h.

[0027] More preferably, in step (5), the maintenance steps include: temperature 25-26℃, humidity 99-100%, 1-2h; temperature 30-31℃, humidity 88-90%, 1-2h; temperature 34-35℃, humidity 78-80%, 1-2h; temperature 39-40℃, humidity 68-70%, 1-2h; temperature 34-35℃, humidity 58-60%, 1-2h; temperature 29-30℃, humidity 48-50%, 1-2h.

[0028] More preferably, in step (5), the maintenance steps include: temperature 25℃, humidity 100%, 2h; temperature 30℃, humidity 90%, 2h; temperature 35℃, humidity 80%, 2h; temperature 40℃, humidity 70%, 2h; temperature 35℃, humidity 60%, 2h; temperature 30℃, humidity 50%, 2h.

[0029] Preferably, in step (5), the drying step includes drying at 45-55°C for 2-6 hours.

[0030] More preferably, in step (5), the drying step includes drying at 50-55°C for 2-4 hours.

[0031] More preferably, in step (5), the drying step includes drying at 50°C for 3 to 4 hours.

[0032] Preferably, in step (5), the sintering step includes: placing the sintering apparatus under vacuum, raising the temperature from room temperature to 550-650°C at a rate of 4-5°C / min and holding it for 0.5-2 hours, then filling the sintering apparatus with an inert atmosphere, raising the temperature from 550-650°C to 1750-1850°C at a rate of 5-10°C / min, raising the temperature from 1750-1850°C to 2100-2200°C at a rate of 1-5°C / min and holding it for 1-3 hours, cooling the temperature to 1000-1200°C at a rate of 5-10°C / min after the holding period, and finally cooling the sintering apparatus to room temperature.

[0033] More preferably, in step (5), the sintering step includes: placing the sintering apparatus under vacuum, raising the temperature from room temperature to 600-650°C at a rate of 4.5-5°C / min and holding it for 1-2 hours, then filling the sintering apparatus with an inert atmosphere, raising the temperature from 600-650°C to 1800-1850°C at a rate of 6-8°C / min, raising the temperature from 1800-1850°C to 2150-2200°C at a rate of 3-5°C / min and holding it for 2-3 hours, cooling the temperature to 1100-1200°C at a rate of 8-10°C / min after the holding period, and finally cooling the sintering apparatus to room temperature.

[0034] More preferably, in step (5), the sintering step includes: putting the sintering apparatus under vacuum, raising the temperature from room temperature to 600°C at a rate of 4.5°C / min and holding it for 1 hour, then filling the sintering apparatus with an inert atmosphere, raising the temperature from 600°C to 1800°C at a rate of 6°C / min, raising the temperature from 1800°C to 2150°C at a rate of 3°C / min and holding it for 2 hours, lowering the temperature to 1100°C at a rate of 8°C / min after the holding is completed, and finally cooling the sintering apparatus to room temperature.

[0035] Preferably, the inert atmosphere includes argon.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) DIW technology can realize one-time molding of components with complex three-dimensional structures without the need to prepare molds in advance. The resulting ceramic components do not require subsequent processing, and the manufacturing cost is low.

[0038] (2) After the blank is printed, densification can be completed by sintering only once, without the need for complicated post-processing.

[0039] (3) By adjusting the ratio of PMMA to carbon fiber in the core slurry, the shrinkage rate of the core material can be matched with that of the panel material, thereby reducing the damage to the interface between the panel layer and the core layer due to the mismatch in shrinkage rate during the sintering process and improving the mechanical strength of the sandwich structure.

[0040] (4) The thickness of the panel and core of the sandwich structure can be adjusted flexibly and conveniently through DIW technology, thereby achieving differentiated control of the functionality or mechanical properties of the sandwich structure. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the carbon fiber reinforced porous SiC ceramic sandwich structure in Example 1;

[0042] Figure 2 This is a schematic diagram of the fabrication process of the carbon fiber reinforced porous SiC ceramic sandwich structure in Example 1;

[0043] Figure 3 This is a schematic diagram of a DIW printing device.

[0044] Figure 4 The shear-thinning properties of carbon fiber reinforced silicon carbide ceramic slurry;

[0045] Figure 5 The shear-thinning properties of porous silicon carbide ceramic slurry;

[0046] Figure 6The failure phenomena of carbon fiber reinforced porous SiC ceramic sandwich structure specimens are: (a) bending, (b) cracking, and (c) interlayer delamination.

[0047] Figure 7 Microscopic morphology of the core-panel boundary of a carbon fiber reinforced porous SiC ceramic sandwich structure;

[0048] Figure 8 This is a schematic diagram of a carbon fiber reinforced porous SiC ceramic sandwich structure. Detailed Implementation

[0049] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0050] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0051] Example 1

[0052] Preparation of carbon fiber reinforced silicon carbide ceramic slurry (panel) with shear-thinning properties:

[0053] Carbon fibers with a length of 200 μm and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 100:1.44. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 11.89:3:0.45:0.34:0.24. The mixture was homogenized at high speed and degassed under vacuum to prepare a carbon fiber reinforced silicon carbide ceramic slurry with shear-thinning properties and a total solid phase content of 45.2 vol%. The carbon fiber volume fraction of this slurry was 2.5 vol%.

[0054] Preparation of porous silicon carbide ceramic slurry (core) with shear-thinning properties:

[0055] Polymethyl methacrylate (PMMA) particles with a diameter of 15 μm, carbon fibers with a length of 200 μm, and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 3.6:0.133:14. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 6.59:0.84:0.21:0.196:0.112. The mixture was homogenized at high speed and degassed under vacuum to prepare a porous silicon carbide ceramic slurry with a total solid phase of 53.7 vol% and shear-thinning properties. The volume fraction of carbon fiber in this slurry was 1 vol%, and the volume fraction of PMMA was 40 vol%.

[0056] Printing and shaping:

[0057] Import the model file to be printed into the computer. The printing software will automatically slice the model and generate the corresponding printing program, eliminating the need for manual editing. Set various printing parameters, adjust the air pressure controller to ensure the slurry extrusion speed is appropriate, and then control the 3D printer according to the printing program via the computer. First, use a syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the lower panel layer. After the panel is printed, quickly switch the syringe to a syringe filled with porous silicon carbide ceramic slurry to print the core layer. After the core layer is printed, switch back to the syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the upper panel layer, obtaining the formed green body. The program is set to a total of 10 layers, with 1 upper panel layer, 8 core layers, and 1 lower panel layer printed.

[0058] Dry care:

[0059] The printed blanks are transferred to a constant temperature and humidity drying oven and cured according to the set program. The curing program is as follows: temperature 25℃, humidity 100%, 2h; temperature 30℃, humidity 90%, 2h; temperature 35℃, humidity 80%, 2h; temperature 40℃, humidity 70%, 2h; temperature 35℃, humidity 60%, 2h; temperature 30℃, humidity 50%, 2h. After curing, the blanks are placed in a drying oven at 50℃ for 3-4h to completely remove the free water in the blanks.

[0060] Sintering densification process:

[0061] The green body was placed in a high-temperature atmosphere sintering furnace for debinding and sintering. The sintering procedure was as follows: First, the air inside the sintering furnace was evacuated to create a vacuum. The temperature was then increased from room temperature to 600℃ at a rate of 4.5℃ / min and held for 1 hour to allow for the complete decomposition of organic matter within the green body. Subsequently, the sintering furnace was filled with argon gas, and the temperature was increased from 600℃ to 1800℃ at a rate of 6℃ / min, followed by a further increase from 1800℃ to 2150℃ at a rate of 3℃ / min and held for 2 hours. After holding at this temperature, the temperature was decreased to 1100℃ at a rate of 8℃ / min, and finally cooled to room temperature within the furnace to obtain a fiber-reinforced porous SiC ceramic sandwich structure.

[0062] Example 2

[0063] Preparation of carbon fiber reinforced silicon carbide ceramic slurry (panel) with shear-thinning properties:

[0064] Carbon fibers with a length of 200 μm and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 100:1.44. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 11.89:3:0.45:0.34:0.24. The mixture was homogenized at high speed and degassed under vacuum to prepare a carbon fiber reinforced silicon carbide ceramic slurry with shear-thinning properties and a total solid phase content of 45.2 vol%. The carbon fiber volume fraction of this slurry was 2.5 vol%.

[0065] Preparation of porous silicon carbide ceramic slurry (core) with shear-thinning properties:

[0066] PMMA particles with a diameter of 15 μm, carbon fibers with a length of 200 μm, and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 3.6:0.133:14. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 6.59:0.84:0.21:0.196:0.112. The mixture was homogenized at high speed and degassed under vacuum to prepare a porous silicon carbide ceramic slurry with a total solid phase of 53.7 vol% and shear-thinning properties. The volume fraction of carbon fiber in this slurry was 1 vol%, and the volume fraction of PMMA was 40 vol%.

[0067] Printing and shaping:

[0068] Import the model file to be printed into the computer. The printing software will automatically slice the model and generate the corresponding printing program, eliminating the need for manual editing. Set various printing parameters, adjust the air pressure controller to ensure the slurry extrusion speed is appropriate, and then control the 3D printer according to the printing program via the computer. First, use a syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the lower panel layer. After the panel is printed, quickly switch the syringe to one filled with porous silicon carbide ceramic slurry to print the core layer. After the core layer is printed, switch back to the syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the upper panel layer, obtaining the formed blank. The program is set to a total of 10 layers, with 2 upper panel layers, 6 core layers, and 2 lower panel layers printed.

[0069] Dry care:

[0070] The printed blanks are transferred to a constant temperature and humidity drying oven and cured according to the set program. The curing program is as follows: temperature 25℃, humidity 100%, 2h; temperature 30℃, humidity 90%, 2h; temperature 35℃, humidity 80%, 2h; temperature 40℃, humidity 70%, 2h; temperature 35℃, humidity 60%, 2h; temperature 30℃, humidity 50%, 2h. After curing, the blanks are placed in a drying oven at 50℃ for 3-4h to completely remove the free water in the blanks.

[0071] Sintering densification process:

[0072] The green body was placed in a high-temperature atmosphere sintering furnace for debinding and sintering. The sintering procedure was as follows: First, the air inside the sintering furnace was evacuated to create a vacuum. The temperature was then increased from room temperature to 600℃ at a rate of 4.5℃ / min and held for 1 hour to allow for the complete decomposition of organic matter within the green body. Subsequently, the sintering furnace was filled with argon gas, and the temperature was increased from 600℃ to 1800℃ at a rate of 6℃ / min, followed by a further increase from 1800℃ to 2150℃ at a rate of 3℃ / min and held for 2 hours. After holding at this temperature, the temperature was decreased to 1100℃ at a rate of 8℃ / min, and finally cooled to room temperature within the furnace to obtain a fiber-reinforced porous SiC ceramic sandwich structure.

[0073] Example 3

[0074] Preparation of carbon fiber reinforced silicon carbide ceramic slurry (panel) with shear-thinning properties:

[0075] Carbon fibers with a length of 200 μm and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 100:1.44. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 11.89:3:0.45:0.34:0.24. The mixture was homogenized at high speed and degassed under vacuum to prepare a carbon fiber reinforced silicon carbide ceramic slurry with shear-thinning properties and a total solid phase content of 45.2 vol%. The carbon fiber volume fraction of this slurry was 2.5 vol%.

[0076] Preparation of porous silicon carbide ceramic slurry (core) with shear-thinning properties:

[0077] PMMA particles with a diameter of 15 μm, carbon fibers with a length of 200 μm, and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 3.6:0.133:14. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 6.59:0.84:0.21:0.196:0.112. The mixture was homogenized at high speed and degassed under vacuum to prepare a porous silicon carbide ceramic slurry with a total solid phase of 53.7 vol% and shear-thinning properties. The volume fraction of carbon fiber in this slurry was 1 vol%, and the volume fraction of PMMA was 40 vol%.

[0078] Printing and shaping:

[0079] Import the model file to be printed into the computer. The printing software will automatically slice the model and generate the corresponding printing program, eliminating the need for manual editing. Set various printing parameters, adjust the air pressure controller to ensure the slurry extrusion speed is appropriate, and then control the 3D printer to print according to the program. First, use a syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the lower panel layer. After the panel is printed, quickly switch the syringe to a syringe filled with porous silicon carbide ceramic slurry to print the core layer. After the core layer is printed, switch back to the syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the upper panel layer, obtaining the formed blank. The program is set to a total of 10 layers, with 3 upper panel layers, 4 core layers, and 3 lower panel layers printed.

[0080] Dry care:

[0081] The printed blanks are transferred to a constant temperature and humidity drying oven and cured according to the set program. The curing program is as follows: temperature 25℃, humidity 100%, 2h; temperature 30℃, humidity 90%, 2h; temperature 35℃, humidity 80%, 2h; temperature 40℃, humidity 70%, 2h; temperature 35℃, humidity 60%, 2h; temperature 30℃, humidity 50%, 2h. After curing, the blanks are placed in a drying oven at 50℃ for 3-4h to completely remove the free water in the blanks.

[0082] Sintering densification process:

[0083] The green body was placed in a high-temperature atmosphere sintering furnace for debinding and sintering. The sintering procedure was as follows: First, the air inside the sintering furnace was evacuated to create a vacuum. The temperature was then increased from room temperature to 600℃ at a rate of 4.5℃ / min and held for 1 hour to allow for the complete decomposition of organic matter within the green body. Subsequently, the sintering furnace was filled with argon gas, and the temperature was increased from 600℃ to 1800℃ at a rate of 6℃ / min, followed by a further increase from 1800℃ to 2150℃ at a rate of 3℃ / min and held for 2 hours. After holding at this temperature, the temperature was decreased to 1100℃ at a rate of 8℃ / min, and finally cooled to room temperature within the furnace to obtain a fiber-reinforced porous SiC ceramic sandwich structure.

[0084] Comparative Example 1

[0085] Preparation of carbon fiber reinforced silicon carbide ceramic slurry (panel) with shear-thinning properties:

[0086] Carbon fibers with a length of 200 μm and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 100:1.44. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 11.89:3:0.45:0.34:0.24. The mixture was homogenized at high speed and degassed under vacuum to prepare a carbon fiber reinforced silicon carbide ceramic slurry with shear-thinning properties and a total solid phase content of 45.2 vol%. The carbon fiber volume fraction of this slurry was 2.5 vol%.

[0087] Preparation of porous silicon carbide ceramic slurry (core) with shear-thinning properties:

[0088] PMMA particles with a diameter of 15 μm, carbon fibers with a length of 200 μm, and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 3.6:0.133:14. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 6.59:0.84:0.21:0.196:0.112. The mixture was homogenized at high speed and degassed under vacuum to prepare a porous silicon carbide ceramic slurry with a total solid phase of 53.7 vol% and shear-thinning properties. The volume fraction of carbon fiber in this slurry was 1 vol%, and the volume fraction of PMMA was 40 vol%.

[0089] Printing and shaping:

[0090] Import the model file to be printed into the computer. The printing software will automatically slice the model and generate the corresponding printing program, eliminating the need for manual editing. Set the various printing parameters, adjust the air pressure controller to ensure the slurry extrusion speed is appropriate, and then control the 3D printer according to the printing program via the computer. First, use a syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the lower panel layer. After the panel is printed, quickly switch the syringe to one filled with porous silicon carbide ceramic slurry to print the core layer. After the core layer is printed, switch back to the syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the upper panel layer, obtaining the formed blank. The program is set to a total of 10 layers, with 0 layers for the upper panel, 10 layers for the core layer, and 0 layers for the lower panel.

[0091] Dry care:

[0092] The printed blanks are transferred to a constant temperature and humidity drying oven and cured according to the set program. The curing program is as follows: temperature 25℃, humidity 100%, 2h; temperature 30℃, humidity 90%, 2h; temperature 35℃, humidity 80%, 2h; temperature 40℃, humidity 70%, 2h; temperature 35℃, humidity 60%, 2h; temperature 30℃, humidity 50%, 2h. After curing, the blanks are placed in a drying oven at 50℃ for 3-4h to completely remove the free water in the blanks.

[0093] Sintering densification process:

[0094] The green body was placed in a high-temperature atmosphere sintering furnace for debinding and sintering. The sintering procedure was as follows: First, the air inside the sintering furnace was evacuated to create a vacuum. The temperature was then increased from room temperature to 600℃ at a rate of 4.5℃ / min and held for 1 hour to allow for the complete decomposition of organic matter within the green body. Subsequently, the sintering furnace was filled with argon gas, and the temperature was increased from 600℃ to 1800℃ at a rate of 6℃ / min, followed by a further increase from 1800℃ to 2150℃ at a rate of 3℃ / min and held for 2 hours. After holding at this temperature, the temperature was decreased to 1100℃ at a rate of 8℃ / min, and finally cooled to room temperature within the furnace to obtain a fiber-reinforced porous SiC ceramic sandwich structure.

[0095] Comparative Example 2

[0096] Preparation of carbon fiber reinforced silicon carbide ceramic slurry (panel) with shear-thinning properties:

[0097] Carbon fibers with a length of 200 μm and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 100:1.44. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 11.89:3:0.45:0.34:0.24. The mixture was homogenized at high speed and degassed under vacuum to prepare a carbon fiber reinforced silicon carbide ceramic slurry with shear-thinning properties and a total solid phase content of 45.2 vol%. The carbon fiber volume fraction of this slurry was 2.5 vol%.

[0098] Preparation of porous silicon carbide ceramic slurry (core) with shear-thinning properties:

[0099] PMMA particles with a diameter of 15 μm, carbon fibers with a length of 200 μm, and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 3.6:0.133:14. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 6.59:0.84:0.21:0.196:0.112. The mixture was homogenized at high speed and degassed under vacuum to prepare a porous silicon carbide ceramic slurry with a total solid phase of 53.7 vol% and shear-thinning properties. The volume fraction of carbon fiber in this slurry was 1 vol%, and the volume fraction of PMMA was 40 vol%.

[0100] Printing and shaping:

[0101] Import the model file to be printed into the computer. The printing software will automatically slice the model and generate the corresponding printing program, eliminating the need for manual editing. Set various printing parameters, adjust the air pressure controller to ensure the slurry extrusion speed is appropriate, and then control the 3D printer according to the printing program via the computer. First, use a syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the lower panel layer. After the panel is printed, quickly switch the syringe to a syringe filled with porous silicon carbide ceramic slurry to print the core layer. After the core layer is printed, switch back to the syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the upper panel layer, obtaining the formed blank. The program is set to a total of 10 layers, with 4 upper panel layers, 2 core layers, and 4 lower panel layers printed.

[0102] Dry care:

[0103] The printed blanks are transferred to a constant temperature and humidity drying oven and cured according to the set program. The curing program is as follows: temperature 25℃, humidity 100%, 2h; temperature 30℃, humidity 90%, 2h; temperature 35℃, humidity 80%, 2h; temperature 40℃, humidity 70%, 2h; temperature 35℃, humidity 60%, 2h; temperature 30℃, humidity 50%, 2h. After curing, the blanks are placed in a drying oven at 50℃ for 3-4h to completely remove the free water in the blanks.

[0104] Sintering densification process:

[0105] The green body was placed in a high-temperature atmosphere sintering furnace for debinding and sintering. The sintering procedure was as follows: First, the air inside the sintering furnace was evacuated to create a vacuum. The temperature was then increased from room temperature to 600℃ at a rate of 4.5℃ / min and held for 1 hour to allow for the complete decomposition of organic matter within the green body. Subsequently, the sintering furnace was filled with argon gas, and the temperature was increased from 600℃ to 1800℃ at a rate of 6℃ / min, followed by a further increase from 1800℃ to 2150℃ at a rate of 3℃ / min and held for 2 hours. After holding at this temperature, the temperature was decreased to 1100℃ at a rate of 8℃ / min, and finally cooled to room temperature within the furnace to obtain a fiber-reinforced porous SiC ceramic sandwich structure.

[0106] Comparative Example 3

[0107] Preparation of carbon fiber reinforced silicon carbide ceramic slurry (panel) with shear-thinning properties:

[0108] Carbon fibers with a length of 200 μm and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 100:1.44. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 11.89:3:0.45:0.34:0.24. The mixture was homogenized at high speed and degassed under vacuum to prepare a carbon fiber reinforced silicon carbide ceramic slurry with shear-thinning properties and a total solid phase content of 45.2 vol%. The carbon fiber volume fraction of this slurry was 2.5 vol%.

[0109] Preparation of porous silicon carbide ceramic slurry (core) with shear-thinning properties:

[0110] PMMA particles with a diameter of 15 μm, carbon fibers with a length of 200 μm, and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 3.6:0.133:14. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 6.59:0.84:0.21:0.196:0.112. The mixture was homogenized at high speed and degassed under vacuum to prepare a porous silicon carbide ceramic slurry with a total solid phase of 53.7 vol% and shear-thinning properties. The volume fraction of carbon fiber in this slurry was 1 vol%, and the volume fraction of PMMA was 40 vol%.

[0111] Printing and shaping:

[0112] Import the model file to be printed into the computer. The printing software will automatically slice the model and generate the corresponding printing program, eliminating the need for manual editing. Set various printing parameters, adjust the air pressure controller to ensure the slurry extrusion speed is appropriate, and then control the 3D printer to print according to the program. First, use a syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the lower panel layer. After the panel is printed, quickly switch the syringe to a syringe filled with porous silicon carbide ceramic slurry to print the core layer. After the core layer is printed, switch back to the syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the upper panel layer, obtaining the formed blank. The program is set to a total of 10 layers, with 5 layers for the upper panel, 0 layers for the core layer, and 5 layers for the lower panel.

[0113] Dry care:

[0114] The printed blanks are transferred to a constant temperature and humidity drying oven and cured according to the set program. The curing program is as follows: temperature 25℃, humidity 100%, 2h; temperature 30℃, humidity 90%, 2h; temperature 35℃, humidity 80%, 2h; temperature 40℃, humidity 70%, 2h; temperature 35℃, humidity 60%, 2h; temperature 30℃, humidity 50%, 2h. After curing, the blanks are placed in a drying oven at 50℃ for 3-4h to completely remove the free water in the blanks.

[0115] Sintering densification process:

[0116] The green body was placed in a high-temperature atmosphere sintering furnace for debinding and sintering. The sintering procedure was as follows: First, the air inside the sintering furnace was evacuated to create a vacuum. The temperature was then increased from room temperature to 600℃ at a rate of 4.5℃ / min and held for 1 hour to allow for the complete decomposition of organic matter within the green body. Subsequently, the sintering furnace was filled with argon gas, and the temperature was increased from 600℃ to 1800℃ at a rate of 6℃ / min, followed by a further increase from 1800℃ to 2150℃ at a rate of 3℃ / min and held for 2 hours. After holding at this temperature, the temperature was decreased to 1100℃ at a rate of 8℃ / min, and finally cooled to room temperature within the furnace to obtain a fiber-reinforced porous SiC ceramic sandwich structure.

[0117] Comparative Example 4

[0118] Preparation of carbon fiber reinforced silicon carbide ceramic slurry (panel) with shear-thinning properties:

[0119] Carbon fibers with a length of 200 μm and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 100:1.44. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 11.89:3:0.45:0.34:0.24. The mixture was homogenized at high speed and degassed under vacuum to prepare a carbon fiber reinforced silicon carbide ceramic slurry with shear-thinning properties and a total solid phase content of 45.2 vol%. The carbon fiber volume fraction of this slurry was 2.5 vol%.

[0120] Preparation of porous silicon carbide ceramic slurry (core) with shear-thinning properties:

[0121] PMMA particles with a diameter of 15 μm and silicon carbide powder with a diameter of 0.7 μm were uniformly mixed at a mass ratio of 3.6:14. Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were added to the powder at a mass ratio of 6.59:0.84:0.21:0.196:0.112. The mixture was homogenized at high speed and degassed under vacuum to prepare a porous silicon carbide ceramic slurry with shear-thinning characteristics and a total solid phase of 53.7 vol%. The slurry contained 0 vol% carbon fiber and 40 vol% PMMA.

[0122] Printing and shaping:

[0123] Import the model file to be printed into the computer. The printing software will automatically slice the model and generate the corresponding printing program, eliminating the need for manual editing. Set various printing parameters, adjust the air pressure controller to ensure the slurry extrusion speed is appropriate, and then control the 3D printer according to the printing program via the computer. First, use a syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the lower panel layer. After the panel is printed, quickly switch the syringe to one filled with porous silicon carbide ceramic slurry to print the core layer. After the core layer is printed, switch back to the syringe filled with carbon fiber reinforced silicon carbide ceramic slurry to print the upper panel layer, obtaining the formed blank. The program is set to a total of 10 layers, with 2 upper panel layers, 6 core layers, and 2 lower panel layers printed.

[0124] Dry care:

[0125] The printed blanks are transferred to a constant temperature and humidity drying oven and cured according to the set program. The curing program is as follows: temperature 25℃, humidity 100%, 2h; temperature 30℃, humidity 90%, 2h; temperature 35℃, humidity 80%, 2h; temperature 40℃, humidity 70%, 2h; temperature 35℃, humidity 60%, 2h; temperature 30℃, humidity 50%, 2h. After curing, the blanks are placed in a drying oven at 50℃ for 3-4h to completely remove the free water in the blanks.

[0126] Sintering densification process:

[0127] The green body was placed in a high-temperature atmosphere sintering furnace for debinding and sintering. The sintering procedure was as follows: First, the air inside the sintering furnace was evacuated to create a vacuum. The temperature was then increased from room temperature to 600°C at a rate of 4.5°C / min and held for 1 hour to allow for the complete decomposition of organic matter within the green body. Subsequently, the sintering furnace was filled with argon gas, and the temperature was increased from 600°C to 1800°C at a rate of 6°C / min, then increased to 2150°C at a rate of 3°C / min and held for 2 hours. After holding, the temperature was decreased to 1100°C at a rate of 8°C / min, and finally cooled to room temperature inside the furnace to obtain a fiber-reinforced porous SiC ceramic sandwich structure. In Comparative Example 2, most of the structural components exhibited interlaminar delamination or damage.

[0128] Performance testing:

[0129] During the fabrication of sandwich structures, specimens without added carbon fiber in the core material exhibited damage such as bending, cracking, and interlayer delamination after high-temperature sintering. (See...) Figure 6By introducing an appropriate amount of carbon fiber into the core material, the shrinkage rate of the panel layer and the core layer can be precisely matched by utilizing the regulating effect of carbon fiber on sintering shrinkage behavior. Taking a sandwich structure prepared with a panel material of carbon fiber reinforced silicon carbide ceramic with a carbon fiber volume fraction of 2.5 vol% and a core material of porous silicon carbide ceramic with 40 vol% PMMA and 1 vol% carbon fiber as an example, the structure is further developed by... Figure 7 It can be seen that after shrinkage rate optimization and matching, the porous core layer and the panel layer have good interfacial bonding, and no interfacial failure characteristics such as cracks or defects were observed. This proves that adding carbon fibers to the core material can precisely control the interlayer shrinkage rate and effectively solve the problem of core and panel delamination.

[0130] Table 1 Results of bending strength, specific strength, and thermal conductivity of the sandwich structure

[0131]

[0132]

[0133] As shown in Table 1, Example 3 exhibits the highest specific strength at 125.39 kN / (m·kg), representing an 85.65% increase compared to Comparative Example 1. Its thermal conductivity is 88.67 W / (m·K), only an 18.02% increase compared to Comparative Example 1. This indicates that designing a carbon fiber reinforced porous SiC ceramic sandwich structure can effectively improve its mechanical properties while having minimal impact on the functionality of the porous SiC ceramic material. This is thanks to the DIW (Digital-Installed Welding) integrated molding technology, which allows for flexible and convenient adjustment of the panel and core thicknesses during the fabrication process, thereby achieving differentiated control over the structural functionality or mechanical properties. Compared to Example 1, Comparative Example 1 shows a 33.61% decrease in flexural strength and a only 3.65% decrease in thermal conductivity. Compared to Example 3, Comparative Example 2 shows a 1.76% increase in flexural strength but a 10.39% increase in thermal conductivity. Compared to Example 3, Comparative Example 3 shows a 3.17% increase in flexural strength but a 20.49% increase in thermal conductivity.

[0134] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, any technical solutions obtained by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concept of the present invention and on the existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a fiber-reinforced porous SiC ceramic sandwich structure, characterized in that, Includes the following steps: (1) Sift 20-25g of silicon carbide powder, dry it and place it in a mixing container, then add 1-1.5wt% sodium carboxymethyl cellulose, 2-3wt% boron carbide and 0.1-8vol% carbon fiber to obtain mixed powder A; stir 0.5-1wt% trisodium citrate and 5-10wt% sucrose in 15-20mL of water to prepare a mixed solution, then add the mixed solution to the mixed powder A to obtain a carbon fiber reinforced silicon carbide ceramic slurry with a solid content of 40-45vol%; (2) Sift 20-25g of silicon carbide powder, dry it and place it in a mixing container, then add 1-1.5wt% sodium carboxymethyl cellulose, 2-3wt% boron carbide, 30-60vol% polymethyl methacrylate and 0.5-1.5vol% carbon fiber to obtain mixed powder B; stir 0.5-1wt% trisodium citrate and 5-10wt% sucrose in 20-25mL of water to prepare a mixed solution, then add the mixed solution to the mixed powder B to obtain a porous silicon carbide ceramic slurry with a solid content of 40-45vol%; (3) The carbon fiber reinforced silicon carbide ceramic slurry and the porous silicon carbide ceramic slurry are homogenized and degassed respectively; then the carbon fiber reinforced silicon carbide ceramic slurry and the porous silicon carbide ceramic slurry are transferred into syringes and degassed respectively. (4) Using 3D printing technology, firstly, a syringe filled with carbon fiber reinforced silicon carbide ceramic slurry is used to print the lower panel layer. After the panel is printed, the syringe is switched to use a syringe filled with porous silicon carbide ceramic slurry to print the core layer. After the core layer is printed, the syringe filled with carbon fiber reinforced silicon carbide ceramic slurry is switched back to print the upper panel layer. After printing, a blank is obtained. (5) Curing, drying and sintering the green body to obtain a fiber-reinforced porous SiC ceramic sandwich structure.

2. The preparation method according to claim 1, characterized in that, In step (1), the particle size of the silicon carbide powder is 0.5 to 0.7 μm.

3. The preparation method according to claim 1, characterized in that, In step (1), the mesh size of the sieve is 180 to 200 mesh.

4. The preparation method according to claim 1, characterized in that, In step (3), the homogenization mixing step includes: first, mixing at a speed of 2000-2200 r / min for 25-30 s; then mixing at a high speed of 2500-3000 r / min for 25-30 s, and repeating 2-3 times.

5. The preparation method according to claim 1, characterized in that, In step (3), the degassing step includes: degassing in a vacuum environment, mixing at a speed of 2500-3000 r / min for 50-60 s, and repeating 3-4 times.

6. The preparation method according to claim 5, characterized in that, The vacuum level of the vacuum environment is -95 to -100 kPa.

7. The preparation method according to claim 1, characterized in that, In step (5), the maintenance steps include: temperature 24-26℃, humidity 95-100%, 1-2h; temperature 29-31℃, humidity 85-90%, 1-2h; temperature 33-35℃, humidity 75-80%, 1-2h; temperature 38-40℃, humidity 65-70%, 1-2h; temperature 33-35℃, humidity 55-60%, 1-2h; temperature 28-30℃, humidity 45-50%, 1-2h.

8. The preparation method according to claim 1, characterized in that, In step (5), the drying step includes drying at 45-55°C for 2-6 hours.

9. The preparation method according to claim 1, characterized in that, In step (5), the sintering step includes: placing the sintering apparatus under vacuum, raising the temperature from room temperature to 550-650°C at a rate of 4-5°C / min and holding it for 0.5-2 hours, then filling the sintering apparatus with an inert atmosphere, raising the temperature from 550-650°C to 1750-1850°C at a rate of 5-10°C / min, raising the temperature from 1750-1850°C to 2100-2200°C at a rate of 1-5°C / min and holding it for 1-3 hours, cooling the temperature to 1000-1200°C at a rate of 5-10°C / min after the holding period, and finally cooling the sintering apparatus to room temperature.

10. The preparation method according to claim 9, characterized in that, The inert atmosphere includes argon.

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