Carbon fiber reinforced silicon carbide ceramic composite material and direct writing forming method

Abstract

The application belongs to the technical field of ceramic materials, and discloses a carbon fiber reinforced silicon carbide ceramic composite material and a direct writing forming method.The direct writing forming method comprises the following steps: mixing carbon fibers and silicon carbide powder to obtain mixed powder, mixing a solvent and an additive to obtain a mixed solution, then mixing the mixed powder and the mixed solution, stirring and defoaming to obtain carbon fiber reinforced ceramic slurry; printing and forming the carbon fiber reinforced ceramic slurry by using a direct writing forming technology to obtain a green body; curing and drying the green body to remove free water of the green body; and performing debinding and sintering on the green body from which the free water is removed.The application can realize one-time forming of a product with a complex structure by using the direct writing forming method, and does not need to use a mold and perform complex densification treatment, so that the preparation cost is low; and the prepared product has no warping and cracking problems, and has good bending strength and fracture toughness.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, and specifically relates to a carbon fiber reinforced silicon carbide ceramic composite material and a direct writing molding method. Background Technology

[0002] Silicon carbide ceramics possess numerous advantages, including high temperature resistance, wear resistance, corrosion resistance, high hardness, and relatively low density, making them widely used in aerospace, semiconductor microelectronics, and machining. Pressureless sintering of silicon carbide ceramics typically involves liquid-phase sintering and solid-phase sintering. Solid-phase sintering, with sintering temperatures exceeding 2000℃, causes the silicon carbide grain size to gradually increase during sintering. This often results in transgranular fracture and poor toughness in solid-phase sintered silicon carbide ceramics, a major limitation restricting their application. Existing methods for enhancing ceramic toughness include fiber toughening, whisker toughening, particle toughening, and phase transformation toughening, with fiber doping being a commonly used method. Adding fibers as a second phase to the ceramic matrix increases the energy consumed by crack propagation during fracture through mechanisms such as crack deflection, fiber bridging, and fiber pull-out, thereby enhancing the fracture toughness. Fiber-toughened ceramic matrix composites exhibit significantly improved fracture toughness.

[0003] Currently, methods for preparing fiber-reinforced ceramic composites can be mainly divided into traditional manufacturing processes and 3D printing processes. Traditional manufacturing processes mainly include dry pressing, injection molding, and gel casting, where mixed powders are shaped into the desired form using a specific mold, and then sintered at high temperatures to achieve densification. These traditional molding methods are difficult to produce products with complex shapes and structures, and subsequent processing often requires grinding or cutting, which not only results in long preparation cycles and high costs, but may also cause defects such as internal cracks in the ceramic parts during processing. While 3D printing does not require pre-prepared molds and has no size or shape limitations, allowing for the fabrication of complex structures, the products are highly susceptible to warping and cracking during the manufacturing process, and require complex densification processes such as liquid phase silicate infiltration or hot isostatic pressing.

[0004] Therefore, it is essential to develop a relatively simple preparation method that can avoid warping and cracking problems for the preparation of carbon fiber reinforced silicon carbide ceramic composites. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention provides a carbon fiber reinforced silicon carbide ceramic composite material and a direct-write molding method. The direct-write molding method can realize the one-time molding of complex structural products without the need for molds and complex densification treatment, resulting in low manufacturing costs. The products obtained have no warping or cracking problems and have good flexural strength and fracture toughness.

[0006] The first aspect of this invention provides a direct-write molding method for carbon fiber reinforced silicon carbide ceramic composite materials, comprising the following steps:

[0007] Carbon fiber and silicon carbide powder are mixed to obtain a mixed powder, and solvent and additives are mixed to obtain a mixed solution. Then, the mixed powder and the mixed solution are mixed and stirred to remove bubbles, thereby obtaining a carbon fiber reinforced ceramic slurry.

[0008] The carbon fiber reinforced ceramic slurry was printed using direct writing technology to obtain a green body;

[0009] The green body is cured and dried to remove the free water from the green body;

[0010] The preform, from which free water has been removed, is degreased and sintered to obtain a carbon fiber reinforced silicon carbide ceramic composite material.

[0011] The specific curing process involves placing the green body under the following conditions for curing in sequence:

[0012] Temperature 22-25℃, humidity 95-100%, 1-2 hours;

[0013] Temperature 26-30℃, humidity 85-90%, 1-2 hours;

[0014] Temperature 31-35℃, humidity 75-80%, 1-2 hours;

[0015] Temperature 36-40℃, humidity 65-70%, 1-2 hours;

[0016] Temperature 31-35℃, humidity 55-60%, 1-2 hours;

[0017] Temperature 26-30℃, humidity 45-50%, 1-2h.

[0018] According to some embodiments of the present invention, the solid content of the carbon fiber reinforced ceramic slurry is 40-45%. By adjusting the solid content of the slurry, the microstructure of the product can be controlled, the shrinkage of the product during sintering can be reduced, cracking or warping during sintering can be avoided, and the product is also relatively denser.

[0019] According to some embodiments of the present invention, the carbon fiber reinforced ceramic slurry has shear-thinning properties.

[0020] According to some embodiments of the present invention, the mass ratio of the carbon fiber to the silicon carbide powder is (10-20):1.

[0021] According to some embodiments of the present invention, the carbon fiber is a short carbon fiber with a length of 150-250 μm.

[0022] According to some embodiments of the present invention, the particle size of the silicon carbide powder is 0.5-0.7 μm.

[0023] According to some embodiments of the present invention, the solvent is water; the additives include sucrose, boron carbide, sodium carboxymethyl cellulose and sodium citrate trihydrate.

[0024] According to some embodiments of the present invention, the mass ratio of the solvent, sucrose, boron carbide, sodium carboxymethyl cellulose and sodium citrate trihydrate is 13:(2-2.4):(0.4-0.45):(0.3-0.35):(0.2-0.25).

[0025] According to some embodiments of the present invention, the silicon carbide powder is placed in an oven and dried at 50-60°C for 5-6 hours before mixing to remove moisture from the powder.

[0026] According to some embodiments of the present invention, the specific mixing process is as follows: the mixed powder and the mixed solution are added to a mixing tank, the mixing tank is placed in a vacuum homogenizer, and initially mixed at a speed of 1900-2000 r / min for 20-30 s, repeated 1-2 times; then further mixed at a high speed of 3200-3300 r / min for 20-30 s, repeated 1-2 times, with the mixing environment at normal atmospheric pressure. Through the above mixing steps, the powder is more easily and uniformly dispersed in the liquid medium during the mixing process, which can reduce the occurrence of powder agglomeration in the molded green body.

[0027] According to some embodiments of the present invention, the stirring and degassing is vacuum stirring and degassing. Specifically, the slurry in the mixing tank is degassed under vacuum at a speed of 2500-2600 r / min for 30-60 seconds, repeated 3-4 times, with a vacuum degree of 95 kPa. Further, the slurry in the mixing tank is transferred to a syringe, and degassing is performed again at a speed of 1800-1900 r / min for 30-60 seconds. The number of repetitions depends on the degassing situation, generally 3-5 times. Degassing under negative atmospheric pressure effectively removes residual air bubbles from the slurry, ensuring that the slurry is uniform and dense, making it more suitable for printing, preventing obvious defects, and further improving the overall strength of the product.

[0028] According to some embodiments of the present invention, the nozzle inner diameter used for printing is 400-410 μm; the extrusion pressure is 25-35 Psi; and the printing speed is 15-20 mm / s.

[0029] According to some embodiments of the present invention, the drying temperature is 50-60°C and the drying time is 3-4 hours.

[0030] According to some embodiments of the present invention, the degreasing conditions include: heating from room temperature to 550-600°C at a heating rate of 3-5°C / min, and holding at that temperature for 1-2 hours.

[0031] According to some embodiments of the present invention, the sintering conditions include: heating from 550-600℃ to 1700-1800℃ at a heating rate of 4-6℃ / min, then continuing to heat to 2000-2200℃ at a heating rate of 1-3℃ / min, holding at that temperature for 1-3 hours, and then cooling to 1000-1100℃ at a heating rate of 6-8℃ / min. By judging the stability of the green body at various temperatures within the furnace, a suitable heating rate is set to better avoid warping or cracking of the product during sintering, while also resulting in higher product strength.

[0032] A second aspect of the present invention provides a carbon fiber reinforced silicon carbide ceramic composite material, which is prepared by the direct writing molding method described in the present invention.

[0033] The third aspect of this invention provides the application of the above-mentioned carbon fiber reinforced silicon carbide ceramic composite material in the preparation of aerospace materials and semiconductor materials.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] This invention employs direct-write molding (DIW) technology to achieve one-time molding of carbon fiber reinforced silicon carbide ceramic composites with complex three-dimensional structures, eliminating the need for pre-prepared molds. The resulting carbon fiber reinforced silicon carbide ceramic composites require no subsequent processing (grinding or cutting), resulting in low manufacturing costs. Using the manufacturing method of this invention, densification can be achieved with only one sintering after the green body is printed, eliminating the need for complex post-processing (such as liquid phase silicon infiltration or hot isostatic pressing). At the same time, a specific curing method can gradually remove free water from the green body during the slow gradient change of temperature and humidity, maintaining relative stability and solving the problem of warping and cracking during the drying process, thus reducing the loss rate of the product from printing to sintering.

[0036] The carbon fiber reinforced silicon carbide ceramic composite material prepared by this invention has good mechanical properties, with a flexural strength of 391.5±19.8 MPa and a fracture toughness of 5.973±0.075 MPa·m. 1 / 2 . Attached Figure Description

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] Figure 1 This is a schematic flowchart of the direct writing molding method for the carbon fiber reinforced silicon carbide ceramic composite material of the present invention.

[0039] Figure 2 This is a rheological test diagram of the carbon fiber reinforced ceramic slurry prepared in Example 1;

[0040] Figure 3 This is a scanning electron microscope image of the carbon fiber reinforced silicon carbide ceramic composite material prepared in Example 1;

[0041] Figure 4 These are physical comparison images of the samples prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0042] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments can be obtained from conventional commercial sources or by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0043] In this invention, room temperature refers to 25±5℃.

[0044] Example 1

[0045] A direct-write molding method for carbon fiber reinforced silicon carbide ceramic composites, the process of which is as follows: Figure 1 As shown, the specific steps include:

[0046] (1) Preparation of carbon fiber reinforced ceramic slurry

[0047] Short carbon fibers of 200 μm and silicon carbide powder of 0.7 μm were mixed at a mass ratio of 20:1 to obtain a mixed powder.

[0048] Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were mixed in a mass ratio of 13:2:0.4:0.3:0.2 to obtain a mixed solution.

[0049] Add the mixed powder and mixed solution into a mixing tank, place the mixing tank in a vacuum homogenizer, first mix at a speed of 1900 r / min for 25 s, repeat twice, then mix further at a high speed of 3200 r / min for 25 s, repeat twice, the mixing environment is normal atmospheric pressure;

[0050] The slurry in the mixing tank was degassed under a vacuum of 95 kPa and stirred at 2500 r / min for 60 s. This process was repeated 3 times. Then, the slurry in the mixing tank was transferred to a syringe and degassed again at 1800 r / min for 60 s. This process was repeated 3 times to obtain a carbon fiber reinforced ceramic slurry with a solid content of 40%.

[0051] (2) Printing and shaping

[0052] Import the model file to be printed into the computer. The printing software will automatically slice the model to generate the corresponding printing program. Then, the computer controls the DIW3D printer to print according to the printing program to obtain the formed blank. The nozzle inner diameter used for printing is 410μm; the extrusion air pressure is 30Psi; and the printing speed is 18mm / s.

[0053] (3) Maintenance and drying

[0054] The green body was transferred to a constant temperature and humidity drying oven and cured according to the set program. The specific 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.

[0055] After the curing of the green body is completed, the green body is placed in a forced-air drying oven and dried at 50°C for 3 hours to remove the free water in the green body.

[0056] (4) Degreasing and sintering

[0057] The dried green body was placed in a high-temperature atmosphere sintering furnace for degreasing and sintering. The specific procedure was as follows: First, the air inside the sintering furnace was removed to create a vacuum. The temperature was increased from room temperature to 600°C at a rate of 5°C / min and held for 1 hour to allow the organic matter in the green body to fully decompose. Then, 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. Finally, the temperature was increased from 1800°C to 2150°C at a rate of 3°C / min and held for 2 hours.

[0058] After the heat preservation is completed, the temperature is increased by 8℃ / min and then decreased to 1100℃. Finally, the temperature is cooled to room temperature in the furnace to obtain carbon fiber reinforced silicon carbide ceramic composite material.

[0059] The rheological properties of the carbon fiber reinforced ceramic slurry prepared in this embodiment were tested, and the test results are as follows: Figure 2 As shown; from Figure 2 It can be seen that the apparent viscosity of the slurry decreases with increasing shear rate, exhibiting obvious shear-thinning properties, making it suitable as a slurry for direct-write 3D printing.

[0060] The scanning electron microscope image of the carbon fiber reinforced silicon carbide ceramic composite material prepared in this embodiment is shown below. Figure 3 As shown. From Figure 3 It can be seen that the fibers are basically arranged at 0°. Due to the high aspect ratio of short carbon fibers, the binder is difficult to wrap around the fiber surface, resulting in weak bonding. This makes short carbon fibers more prone to irregular shear slip under high shear stress. During printing, under the action of air pressure, the slurry is subjected to shearing action from the nozzle wall as it passes through the nozzle. Under this shearing action, the fibers in the slurry will be arranged in an orderly manner along the printing direction, thus preparing a ceramic composite material with fiber orientation structure. Fibers oriented in the matrix exhibit a more efficient reinforcing effect than fibers randomly distributed in the matrix. The fiber orientation angle includes 0° or 45°.

[0061] Example 2

[0062] A direct-write molding method for carbon fiber reinforced silicon carbide ceramic composites specifically includes the following steps:

[0063] (1) Preparation of carbon fiber reinforced ceramic slurry

[0064] Short carbon fibers of 200 μm and silicon carbide powder of 0.7 μm were mixed at a mass ratio of 15:1 to obtain a mixed powder.

[0065] Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were mixed in a mass ratio of 13:2.2:0.4:0.32:0.22 to obtain a mixed solution.

[0066] Add the mixed powder and mixed solution into a mixing tank, place the mixing tank in a vacuum homogenizer, first mix at a speed of 1900 r / min for 25 s, repeat twice, then mix further at a high speed of 3200 r / min for 25 s, repeat twice, the mixing environment is normal atmospheric pressure;

[0067] The slurry in the mixing tank was degassed under a vacuum of 95 kPa and stirred at 2500 r / min for 60 s. This process was repeated 3 times. Then, the slurry in the mixing tank was transferred to a syringe and degassed again at 1800 r / min for 60 s. This process was repeated 3 times to obtain a carbon fiber reinforced ceramic slurry with a solid content of 42.5%.

[0068] (2) Printing and shaping

[0069] Import the model file to be printed into the computer. The printing software will automatically slice the model to generate the corresponding printing program. Then, the computer controls the DIW3D printer to print according to the printing program to obtain the formed blank. The nozzle inner diameter used for printing is 410μm; the extrusion air pressure is 30Psi; and the printing speed is 18mm / s.

[0070] (3) Maintenance and drying

[0071] The green body was transferred to a constant temperature and humidity drying oven and cured according to the set program. The specific 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.

[0072] After the curing of the green body is completed, the green body is placed in a forced-air drying oven and dried at 50°C for 3 hours to remove the free water in the green body.

[0073] (4) Degreasing and sintering

[0074] The dried green body was placed in a high-temperature atmosphere sintering furnace for degreasing and sintering. The specific procedure was as follows: First, the air inside the sintering furnace was removed to create a vacuum. The temperature was increased from room temperature to 600°C at a rate of 5°C / min and held for 1 hour to allow the organic matter in the green body to fully decompose. Then, 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. Finally, the temperature was increased from 1800°C to 2150°C at a rate of 3°C / min and held for 2 hours.

[0075] After the heat preservation is completed, the temperature is increased by 8℃ / min and then decreased to 1100℃. Finally, the temperature is cooled to room temperature in the furnace to obtain carbon fiber reinforced silicon carbide ceramic composite material.

[0076] Example 3

[0077] A direct-write molding method for carbon fiber reinforced silicon carbide ceramic composites specifically includes the following steps:

[0078] (1) Preparation of carbon fiber reinforced ceramic slurry

[0079] Short carbon fibers of 200 μm and silicon carbide powder of 0.7 μm were mixed at a mass ratio of 10:1 to obtain a mixed powder.

[0080] Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were mixed in a mass ratio of 13:2.4:0.45:0.35:0.25 to obtain a mixed solution.

[0081] Add the mixed powder and mixed solution into a mixing tank, place the mixing tank in a vacuum homogenizer, first mix at a speed of 1900 r / min for 25 s, repeat twice, then mix further at a high speed of 3200 r / min for 25 s, repeat twice, the mixing environment is normal atmospheric pressure;

[0082] The slurry in the mixing tank was degassed under a vacuum of 95 kPa and stirred at 2500 r / min for 60 s. This process was repeated 3 times. Then, the slurry in the mixing tank was transferred to a syringe and degassed again at 1800 r / min for 60 s. This process was repeated 3 times to obtain a carbon fiber reinforced ceramic slurry with a solid content of 45%.

[0083] (2) Printing and shaping

[0084] Import the model file to be printed into the computer. The printing software will automatically slice the model to generate the corresponding printing program. Then, the computer controls the DIW3D printer to print according to the printing program to obtain the formed blank. The nozzle inner diameter used for printing is 410μm; the extrusion air pressure is 30Psi; and the printing speed is 18mm / s.

[0085] (3) Maintenance and drying

[0086] The green body was transferred to a constant temperature and humidity drying oven and cured according to the set program. The specific 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.

[0087] After the curing of the green body is completed, the green body is placed in a forced-air drying oven and dried at 50°C for 3 hours to remove the free water in the green body.

[0088] (4) Degreasing and sintering

[0089] The dried green body was placed in a high-temperature atmosphere sintering furnace for degreasing and sintering. The specific procedure was as follows: First, the air inside the sintering furnace was removed to create a vacuum. The temperature was increased from room temperature to 600°C at a rate of 5°C / min and held for 1 hour to allow the organic matter in the green body to fully decompose. Then, 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. Finally, the temperature was increased from 1800°C to 2150°C at a rate of 3°C / min and held for 2 hours.

[0090] After the heat preservation is completed, the temperature is increased by 8℃ / min and then decreased to 1100℃. Finally, the temperature is cooled to room temperature in the furnace to obtain carbon fiber reinforced silicon carbide ceramic composite material.

[0091] Example 4

[0092] A direct-write molding method for carbon fiber reinforced silicon carbide ceramic composites specifically includes the following steps:

[0093] (1) Preparation of carbon fiber reinforced ceramic slurry

[0094] Short carbon fibers of 200 μm and silicon carbide powder of 0.7 μm were mixed at a mass ratio of 20:1 to obtain a mixed powder.

[0095] Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were mixed in a mass ratio of 13:1.86:0.35:0.26:0.18 to obtain a mixed solution.

[0096] Add the mixed powder and mixed solution into a mixing tank, place the mixing tank in a vacuum homogenizer, first mix at a speed of 1900 r / min for 25 s, repeat twice, then mix further at a high speed of 3200 r / min for 25 s, repeat twice, the mixing environment is normal atmospheric pressure;

[0097] The slurry in the mixing tank was degassed under a vacuum of 95 kPa and stirred at 2500 r / min for 60 s. This process was repeated 3 times. Then, the slurry in the mixing tank was transferred to a syringe and degassed again at 1800 r / min for 60 s. This process was repeated 3 times to obtain a carbon fiber reinforced ceramic slurry with a solid content of 37.5%.

[0098] (2) Printing and shaping

[0099] Import the model file to be printed into the computer. The printing software will automatically slice the model to generate the corresponding printing program. Then, the computer controls the DIW3D printer to print according to the printing program to obtain the formed blank. The nozzle inner diameter used for printing is 410μm; the extrusion air pressure is 30Psi; and the printing speed is 18mm / s.

[0100] (3) Maintenance and drying

[0101] The green body was transferred to a constant temperature and humidity drying oven and cured according to the set program. The specific 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.

[0102] After the curing of the green body is completed, the green body is placed in a forced-air drying oven and dried at 50°C for 3 hours to remove the free water in the green body.

[0103] (4) Degreasing and sintering

[0104] The dried green body was placed in a high-temperature atmosphere sintering furnace for degreasing and sintering. The specific procedure was as follows: First, the air inside the sintering furnace was removed to create a vacuum. The temperature was increased from room temperature to 600°C at a rate of 5°C / min and held for 1 hour to allow the organic matter in the green body to fully decompose. Then, 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. Finally, the temperature was increased from 1800°C to 2150°C at a rate of 3°C / min and held for 2 hours.

[0105] After the heat preservation is completed, the temperature is increased by 8℃ / min and then decreased to 1100℃. Finally, the temperature is cooled to room temperature in the furnace to obtain carbon fiber reinforced silicon carbide ceramic composite material.

[0106] Example 5

[0107] A direct-write molding method for carbon fiber reinforced silicon carbide ceramic composites specifically includes the following steps:

[0108] (1) Preparation of carbon fiber reinforced ceramic slurry

[0109] Short carbon fibers of 200 μm and silicon carbide powder of 0.7 μm were mixed at a mass ratio of 10:1 to obtain a mixed powder.

[0110] Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were mixed in a mass ratio of 13:2.8:0.52:0.4:0.28 to obtain a mixed solution.

[0111] Add the mixed powder and mixed solution into a mixing tank, place the mixing tank in a vacuum homogenizer, first mix at a speed of 1900 r / min for 25 s, repeat twice, then mix further at a high speed of 3200 r / min for 25 s, repeat twice, the mixing environment is normal atmospheric pressure;

[0112] The slurry in the mixing tank was degassed under a vacuum of 95 kPa and stirred at 2500 r / min for 60 s. This process was repeated 3 times. Then, the slurry in the mixing tank was transferred to a syringe and degassed again at 1800 r / min for 60 s. This process was repeated 3 times to obtain a carbon fiber reinforced ceramic slurry with a solid content of 47.5%.

[0113] (2) Printing and shaping

[0114] Import the model file to be printed into the computer. The printing software will automatically slice the model to generate the corresponding printing program. Then, the computer controls the DIW3D printer to print according to the printing program to obtain the formed blank. The nozzle inner diameter used for printing is 410μm; the extrusion air pressure is 30Psi; and the printing speed is 18mm / s.

[0115] (3) Maintenance and drying

[0116] The green body was transferred to a constant temperature and humidity drying oven and cured according to the set program. The specific 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.

[0117] After the curing of the green body is completed, the green body is placed in a forced-air drying oven and dried at 50°C for 3 hours to remove the free water in the green body.

[0118] (4) Degreasing and sintering

[0119] The dried green body was placed in a high-temperature atmosphere sintering furnace for degreasing and sintering. The specific procedure was as follows: First, the air inside the sintering furnace was removed to create a vacuum. The temperature was increased from room temperature to 600°C at a rate of 5°C / min and held for 1 hour to allow the organic matter in the green body to fully decompose. Then, 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. Finally, the temperature was increased from 1800°C to 2150°C at a rate of 3°C / min and held for 2 hours.

[0120] After the heat preservation is completed, the temperature is increased by 8℃ / min and then decreased to 1100℃. Finally, the temperature is cooled to room temperature in the furnace to obtain carbon fiber reinforced silicon carbide ceramic composite material.

[0121] Comparative Example 1

[0122] A direct-write molding method for carbon fiber reinforced silicon carbide ceramic composites specifically includes the following steps:

[0123] (1) Preparation of carbon fiber (Cf) reinforced ceramic slurry

[0124] Short carbon fibers of 200 μm and silicon carbide powder of 0.7 μm were mixed at a mass ratio of 20:1 to obtain a mixed powder.

[0125] Deionized water, sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate were mixed in a mass ratio of 13:2:0.4:0.3:0.2 to obtain a mixed solution.

[0126] Add the mixed powder and mixed solution into a mixing tank, place the mixing tank in a vacuum homogenizer, first mix at a speed of 1900 r / min for 25 s, repeat twice, then mix further at a high speed of 3200 r / min for 25 s, repeat twice, the mixing environment is normal atmospheric pressure;

[0127] The slurry in the mixing tank was degassed under a vacuum of 95 kPa and stirred at 2500 r / min for 60 s. This process was repeated 3 times. Then, the slurry in the mixing tank was transferred to a syringe and degassed again at 1800 r / min for 60 s. This process was repeated 3 times to obtain a carbon fiber reinforced ceramic slurry with a solid content of 40%.

[0128] (2) Printing and shaping

[0129] Import the model file to be printed into the computer. The printing software will automatically slice the model to generate the corresponding printing program. Then, the computer controls the DIW3D printer to print according to the printing program to obtain the formed blank. The nozzle inner diameter used for printing is 410μm; the extrusion air pressure is 30Psi; and the printing speed is 18mm / s.

[0130] (3) Drying

[0131] The green body is placed in a forced-air drying oven and dried at 50°C for 12 hours to remove free water from the green body;

[0132] (4) Degreasing and sintering

[0133] The dried green body was placed in a high-temperature atmosphere sintering furnace for degreasing and sintering. The specific procedure was as follows: First, the air inside the sintering furnace was removed to create a vacuum. The temperature was increased from room temperature to 600°C at a rate of 5°C / min and held for 1 hour to allow the organic matter in the green body to fully decompose. Then, 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. Finally, the temperature was increased from 1800°C to 2150°C at a rate of 3°C / min and held for 2 hours.

[0134] After the heat preservation is completed, the temperature is increased by 8℃ / min and then decreased to 1100℃. Finally, the temperature is cooled to room temperature in the furnace to obtain carbon fiber reinforced silicon carbide ceramic composite material.

[0135] The mechanical properties of the 3mm×4mm×36mm specimens obtained in Examples 1-5 above are shown in Table 1.

[0136] Table 1

[0137] Group Bending strength (MPa) <![CDATA[Fracture toughness (MPa·m 1 / 2 )]]> Example 1 391.5±19.8 5.973±0.075 Example 2 318.7±27.0 5.499±0.373 Example 3 283.8±25.2 4.713±0.196 Example 4 261.1±12.6 4.143±0.135 Example 5 230.9±10.6 3.456±0.097

[0138] Figure 4 The images show physical photos of the samples prepared in Example 1 and Comparative Example 1, where (a) is a side view of the sample prepared in Example 1, (b) is a side view of the sample prepared in Comparative Example 1, and (c) is a bottom view of the sample prepared in Comparative Example 1. Figure 4 As shown, the sample prepared in Comparative Example 1 exhibited obvious warping, and even showed obvious cracks at the bottom, rendering it unusable.

[0139] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A direct-write molding method for carbon fiber reinforced silicon carbide ceramic composite materials, characterized in that, Includes the following steps: Carbon fiber and silicon carbide powder are mixed to obtain a mixed powder, and solvent and additives are mixed to obtain a mixed solution. Then, the mixed powder and the mixed solution are mixed and stirred to remove bubbles, thereby obtaining a carbon fiber reinforced ceramic slurry. The carbon fiber reinforced ceramic slurry was printed using direct writing technology to obtain a green body; The green body is cured and dried to remove the free water from the green body; The preform, from which free water has been removed, is degreased and sintered to obtain a carbon fiber reinforced silicon carbide ceramic composite material. The specific curing process involves placing the green body under the following conditions for curing in sequence: Temperature 22-25℃, humidity 95-100%, 1-2 hours; Temperature 26-30℃, humidity 85-90%, 1-2 hours; Temperature 31-35℃, humidity 75-80%, 1-2 hours; Temperature 36-40℃, humidity 65-70%, 1-2 hours; Temperature 31-35℃, humidity 55-60%, 1-2 hours; Temperature 26-30℃, humidity 45-50%, 1-2 hours; The solid content of the carbon fiber reinforced ceramic slurry is 40-45%; The degreasing conditions include: heating from room temperature to 550-600℃ at a heating rate of 3-5℃ / min and holding at that temperature for 1-2 hours; The sintering conditions include: heating from 550-600℃ to 1700-1800℃ at a heating rate of 4-6℃ / min, then continuing to heat to 2000-2200℃ at a heating rate of 1-3℃ / min, holding at that temperature for 1-3 hours, and then cooling to 1000-1100℃ at a heating rate of 6-8℃ / min. The mass ratio of the carbon fiber to the silicon carbide powder is (10-20):1; The additives include sucrose, boron carbide, sodium carboxymethyl cellulose, and sodium citrate trihydrate.

2. The direct-write forming method according to claim 1, characterized in that, The mass ratio of the solvent, sucrose, boron carbide, sodium carboxymethyl cellulose and sodium citrate trihydrate is 13:(2-2.4):(0.4-0.45):(0.3-0.35):(0.2-0.25).

3. The direct-write forming method according to claim 1, characterized in that, The drying temperature is 50-60℃, and the drying time is 3-4 hours.

4. A carbon fiber reinforced silicon carbide ceramic composite material, characterized in that, It is prepared by the direct writing molding method according to any one of claims 1 to 3.

5. The application of the carbon fiber reinforced silicon carbide ceramic composite material according to claim 4 in the preparation of aerospace materials and semiconductor materials.

Images