Silicon carbide ceramic-based composite material for in-situ construction of channel and preparation method of silicon carbide ceramic-based composite material

Abstract

The invention discloses a silicon carbide ceramic-based composite material for in-situ construction of a channel and a preparation method thereof, and belongs to the technical field of ceramic-based composite materials. The preparation method comprises the following steps: cross-linking and curing liquid-phase polycarbosilane, crushing and sieving to obtain precursor powder; mixing the mixed powder with silicon carbide whiskers to obtain mixed powder; preparing a sacrificial template subjected to pyrolysis removal by adopting a 3D printing technology; filling a mold with the template and the mixed powder, and carrying out hot press molding to obtain an original blank; finally, through programmed pyrolysis treatment, removal of the sacrificial template and conversion of the precursor to the ceramic are synchronously realized, so that a channel structure consistent with the template in morphology is formed in a ceramic matrix in situ. According to the method, the designability of the sacrificial template is utilized, flexible control over the section shape, the space trend and the complexity of the channel is achieved, and a key material basis is provided for advanced heat management systems such as high-performance heat dissipation and active cooling.

Description

Technical Field

[0001] This invention belongs to the field of silicon carbide ceramic material preparation technology, and specifically relates to a silicon carbide ceramic matrix composite material with in-situ channel construction and its preparation method. Background Technology

[0002] Silicon carbide ceramic matrix composites have become important candidate materials for hot-end components in aerospace, energy and power fields due to their excellent high strength, high hardness and high temperature resistance. With the continuous improvement of equipment performance, there is an urgent need for integrated structural and functional materials. Among them, constructing continuous and complete channel structures within the material has become a key technical approach to achieve functions such as efficient active cooling and medium transport.

[0003] Currently, introducing channel structures into silicon carbide ceramic matrix composites is an effective way to achieve functional integration. By rationally designing internal channels, the thermal management efficiency of the material can be significantly improved, providing reliable heat dissipation for components operating in high-temperature environments. However, existing technologies struggle to achieve precise molding of the channel structures while maintaining the properties of the material matrix. Therefore, there is an urgent need to develop a preparation method that can achieve precise in-situ construction of channel structures while ensuring the overall performance of the material. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of fabricating customized channels in ceramic matrices using existing technologies, and to provide a silicon carbide ceramic matrix composite material for in-situ channel construction and its preparation method. This invention uses a sacrificial template with a designable configuration as a preform for the channel. Through a hot-pressing process, the template is encapsulated with ceramic precursor powder. Then, through a programmed pyrolysis process, the decomposition and escape of the sacrificial template and the transformation of the precursor into ceramic are synchronized, resulting in the in-situ generation of a channel within the ceramic matrix that is highly consistent with the template morphology and integrally formed with the matrix.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a silicon carbide ceramic matrix composite material with in-situ channel construction, the method comprising the following steps:

[0007] Step 1: Crosslink and cure the liquid-phase polycarbonylsilane precursor to obtain a cured block;

[0008] Step 2: The solidified block is ball-milled and sieved to obtain precursor powder;

[0009] Step 3: Mix the precursor powder with silicon carbide whiskers. The purpose is to improve the mechanical properties of the ceramic matrix through whisker reinforcement, and obtain a mixed powder.

[0010] Step 4: Prepare a 3D-printed sacrificial template;

[0011] Step 5: The sacrificial template and mixed powder are filled into the mold, hot-pressed, and demolded to obtain the original blank;

[0012] Step 6: The original green body is subjected to pyrolysis treatment to remove the sacrificial template and transform the mixed powder into ceramic, thereby obtaining a silicon carbide ceramic matrix composite material with an internal channel structure.

[0013] Further, in step one, the molecular weight of the polycarbosilane is 1050~1600; the cross-linking curing is carried out in an inert gas atmosphere, with a heating rate of 2~3℃ / min (for example, 2℃ / min, 2.5℃ / min or 3℃ / min), and the temperature is uniformly raised to 300~350℃ (for example, 300℃, 310℃, 320℃, 330℃, 340℃ or 350℃) and then held for 2~4h (for example, 2h, 2.5h or 3h).

[0014] The cross-linking curing method of this invention causes the active groups on the liquid-phase polycarbosilane molecular chains to undergo a chemical reaction under heating conditions, forming covalent bonds between molecules, thereby transforming a linear or branched low-molecular-weight liquid into an insoluble and infusible solid with a three-dimensional network structure. This transformation significantly increases the molecular weight of the material, resulting in a substantial increase in its glass transition temperature and thermal decomposition temperature. Thanks to the enhanced thermal stability, the precursor powder does not soften or melt during subsequent hot pressing, ensuring that the mixed powder can tightly coat the sacrificial template and effectively maintain its predetermined shape and spatial position, ultimately obtaining a structurally complete preform.

[0015] The heating rate, final temperature, and holding time of the crosslinking curing process in this invention can effectively restrict the escape of small molecule volatiles during subsequent pyrolysis, reducing mass loss and thus achieving a higher ceramic yield. This not only improves material utilization and reduces preparation costs, but also reduces volume shrinkage and porosity caused by the large-scale decomposition and volatilization of precursors, contributing to the formation of a more compact silicon carbide ceramic matrix with fewer defects.

[0016] Further, in step two, the ball milling time is 6-8 hours (e.g., 6, 7, or 8 hours), and the mass ratio of the solidified block to the milling balls is 1:10 to ensure the block is fully pulverized and to avoid the presence of un-pulverized hard lumps in the precursor powder due to insufficient time; the rotation speed is 300-350 rpm (e.g., 300, 310, 320, 330, 340, or 350 rpm). This rotation speed range ensures pulverization efficiency while preventing oxidation of the precursor powder due to high temperature caused by high rotation speed; the sieve mesh size used for sieving is 200-300 mesh (e.g., 200, 230, 250, 270, or 300 mesh) to control the particle size distribution of the precursor powder. Precursor powder within this particle size range has both good flowability and filling density, and is beneficial for achieving a denser green body during subsequent hot pressing.

[0017] Further, in step three, the diameter of the silicon carbide whiskers is 400-600 nm (e.g., 400 nm, 450 nm, 500 nm, 550 nm, and 600 nm), and the length is 10-15 μm (e.g., 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, and 15 μm). Whiskers within this size range have a high aspect ratio, effectively providing toughening in the ceramic matrix. The mass ratio of the precursor powder to the silicon carbide whiskers is 10:1-1.5 (e.g., 10:1, 10:1.1, 10:1.2, 10:1.3, 10:1.4, and 10:1.5). If the silicon carbide whisker content is too low, the toughening effect is limited; if the silicon carbide whisker content is too high, agglomeration easily occurs, leading to uneven dispersion.

[0018] Further, in step four, the sacrificial template is prepared using additive manufacturing technology, and its raw material is a thermoplastic polymer material that can be completely removed by pyrolysis without residue; for example, it can be polylactic acid, polypropylene carbonate, or polymethyl methacrylate, preferably polylactic acid. The raw material of the sacrificial template of the present invention must meet the following requirements: it has good thermoformability and is suitable for fused deposition modeling additive manufacturing processes; its thermal decomposition temperature range should match the pyrolysis process of the ceramic precursor to ensure that the template is completely pyrolyzed before the precursor is completely ceramized; the pyrolysis products are small gaseous molecules that can be completely discharged under the action of an inert gas flow, without leaving any residue in the ceramic matrix.

[0019] Furthermore, in step four, the shape of the sacrificial template is flexibly designed and customized according to the required channel structure. Preferably, the sacrificial template is a cylinder, cuboid, cone, prism, or a three-dimensional structure with a curved axis, more preferably a cylinder with a diameter of 3-8 mm (e.g., 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, or 8 mm) and a height of 30-35 mm. The cross-section of the sacrificial template can be circular, rectangular, triangular, or other polygonal, and its three-dimensional structure can be linear, curved, or grid-like. This design flexibility enables the present invention to prepare silicon carbide ceramic matrix composites with complex internal channel networks.

[0020] Further, in step five, the hot pressing temperature is 80~90℃ (e.g., 80℃, 85℃, or 90℃), the pressure is 90~100 MPa (e.g., 90MPa, 95MPa, or 100MPa), and the holding time is 60~90 min (e.g., 60 min, 70 min, 80 min, or 90 min). The hot pressing temperature, pressure, and holding time range of this invention allow the mixed powder to flow fully and achieve densification, thereby obtaining a high-density preform while perfectly maintaining the initial geometry and spatial position of the sacrificial template. If the hot pressing temperature and pressure are too high, the sacrificial template will soften and deform, and after pyrolysis, the desired channels cannot be obtained; if the hot pressing temperature and pressure are too low, a dense preform cannot be formed. It should be noted that during the hot pressing process, the powder particles rearrange and densify under pressure, accompanied by a certain degree of volume shrinkage. Therefore, the size of the preform obtained after demolding will be correspondingly smaller than the size of the mold cavity. This shrinkage is an inherent phenomenon in the process of forming a high-density preform.

[0021] Furthermore, in step five, the filling sequence is as follows: fill a portion of the mixed powder, place the sacrificial template in a preset position (which is the location of the final channel), compact and fix it with the mixed powder, and then fill with the remaining mixed powder. The filling sequence and fixing method described in this invention ensures that the sacrificial template does not shift during subsequent processes, which is crucial for achieving precise replication of the channel structure. The mold can be flexibly designed and customized according to the required shape of the silicon carbide ceramic-based material. Preferably, the mold is a cuboid mold with an inner cavity length of 30mm, a width of 14mm, and a height of 20mm.

[0022] Furthermore, in step six, the pyrolysis treatment is carried out under an inert gas atmosphere, with argon gas continuously introduced throughout the pyrolysis process to ensure safety and maintain a stable protective atmosphere, and to achieve simultaneous decomposition and escape of the sacrificial template and conversion of the precursor into ceramic. Specifically, this includes:

[0023] (1) The temperature is raised to 300-400℃ (for example, 300℃, 350℃ or 400℃) at a constant heating rate of 1-2℃ / min (for example, 1℃ / min, 1.5℃ / min or 2℃ / min), and held for 1-2h (for example, 1h, 1.5h or 2h). During this stage, the slow heating rate and the holding treatment enable the polylactic acid sacrificial template to slowly and completely decompose into gaseous small molecules in the temperature range, and be effectively carried out of the original green body by the inert gas flow, thereby forming a complete channel cavity in the ceramic matrix.

[0024] (2) Heat the temperature at a constant rate of 1~2℃ / min (e.g., 1℃ / min, 1.5℃ / min or 2℃ / min) to 1000~1200℃ (e.g., 1000℃, 1100℃ or 1200℃), and hold for 3~4h (e.g., 3h, 3.5h or 4h). This stage is crucial for the inorganic ceramicization of the precursor. The slow heating rate and the final holding treatment minimize the internal stress and cracks caused by pyrolysis, thereby transforming it into a dense silicon carbide ceramic matrix with few defects.

[0025] A silicon carbide ceramic matrix composite material for in-situ channel construction, the composite material being prepared by the method described above.

[0026] The advantages of this invention compared to existing technologies are as follows: By combining a designable sacrificial template with a ceramic preparation process, this invention simultaneously completes the template removal and precursor-to-ceramic conversion, achieving in-situ generation of three-dimensional channels within a ceramic matrix. The preparation method provided by this invention is simple and low-cost. Utilizing the designability of the sacrificial template, it enables flexible control over the channel's cross-sectional shape, spatial orientation, and complexity, providing a key material foundation for advanced thermal management systems such as high-performance heat dissipation and active cooling. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of the operation steps of the present invention.

[0029] Figure 2 This is a photograph of a silicon carbide ceramic matrix composite material.

[0030] Figure 3 The XRD diffraction pattern of the silicon carbide ceramic matrix composite material.

[0031] Figure 4 This is a photograph of a silicon carbide ceramic matrix composite material.

[0032] Figure 5 This is a photograph of a silicon carbide ceramic matrix composite material. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] To more clearly illustrate the technical solution and advantages of the present invention, the present invention will be further described below in conjunction with embodiments.

[0035] The materials and reagents used in this invention can be purchased directly from the market or synthesized in-house, and there are no restrictions on the specific models.

[0036] Example 1

[0037] (1) Take 50g of liquid polycarbosilane and place it in a ceramic crucible, and put the ceramic boat into a vacuum drying oven. After sealing, first evacuate to -0.1MPa and maintain for 1h to fully remove air from the precursor. Then, fill the drying oven with argon to atmospheric pressure. Repeat the evacuation and argon filling operation three times to ensure that the reaction atmosphere is an oxygen-free environment. Heat to 300℃ at a uniform heating rate of 2℃ / min and hold at this temperature for 3h to complete the crosslinking and curing. After the program is completed, cool naturally to room temperature and take out the cured polycarbosilane precursor block.

[0038] (2) After the above-mentioned solidified block is initially crushed, it is placed in a ball mill jar with zirconia grinding balls at a mass ratio of 1:10, and 50 mL of deionized water is added. The mixture is ball-milled at 300 rpm for 6 hours. The ball-milled slurry is dried in a forced-air drying oven at 80°C for 3 hours, and then sieved using a 200-mesh standard sieve. The powder passing through the sieve is collected to obtain polycarbosilane precursor powder with uniform particle size.

[0039] (3) Weigh 10g of precursor powder and 1.5g of silicon carbide whiskers (600nm in diameter and 15μm in length), place them in a beaker, and add 30mL of anhydrous ethanol. First, use magnetic stirring (200 rpm, 30min) for preliminary mixing and dispersion. Then, place the beaker in an ultrasonic processor and ultrasonically blend and disperse at a frequency of 20kHz and a power of 800W for 30min to ensure that the whiskers are uniformly dispersed in the precursor powder. Dry the uniformly mixed slurry at 80℃ for 2h to obtain a mixed powder of silicon carbide whiskers and precursor.

[0040] (4) Establish a cylindrical geometric model with a diameter of 8 mm and a height of 35 mm, and process the model file using slicing software. Use polylactic acid as raw material and fused deposition modeling technology to print the required sacrificial template.

[0041] (5) Weigh 10g of mixed powder and divide it into two equal portions, each weighing 5g. First, add the first portion of mixed powder into a rectangular mold (the inner cavity of the mold is 30mm long, 14mm wide, and 10mm high), pre-press it flat with the mold head, place the sacrificial template in the middle of the mold, and fix the sacrificial template with powder. Add the second portion of mixed powder and pre-press it flat with the mold head. Place the mold in a hot press and hot press it for 60min at 80℃ and 100MPa. Demold to obtain a dense rectangular blank containing a sacrificial template.

[0042] (6) The billet is placed in a tube furnace and subjected to three evacuation and argon purging operations to replace the air in the furnace. Then, a programmed pyrolysis is performed under an argon atmosphere (flow rate 100 mL / min): the temperature is uniformly increased to 400℃ at a rate of 1℃ / min and held for 2 hours. Then, the temperature is uniformly increased to 1200℃ at a rate of 1℃ / min and held for 3 hours. Figure 2 As shown, a silicon carbide ceramic matrix composite material with a channel structure was obtained.

[0043] Figure 3 The X-ray diffraction (XRD) pattern of the silicon carbide ceramic matrix composite material prepared in Example 1 is shown. The test pattern was compared with the standard diffraction card (PDF#39-1196) for silicon carbide. Significant characteristic diffraction peaks appeared at approximately 35.6°, 60.0°, and 71.8°, corresponding to the (111), (220), and (311) crystal planes of the β-SiC crystal structure, respectively. The main diffraction peaks are clear and have high intensity, showing good agreement with the standard card, indicating that the polycarbosilane precursor was successfully transformed into a well-crystallized ceramic phase after pyrolysis at 1200℃. No obvious impurity peaks (such as residual polylactic acid decomposition products) were detected in the pattern, proving that the pyrolysis process described in this invention can achieve complete removal of the organic sacrificial template and high-purity conversion of the ceramic matrix.

[0044] Example 2

[0045] It is basically the same as Example 1, except that the mass of silicon carbide whiskers in step (3) is 1g, and the other steps and parameters remain unchanged.

[0046] Example 3

[0047] The process is basically the same as in Example 1, except that the diameter of the sacrificial template prepared in step (4) is 3 mm. Other steps and parameters remain unchanged, such as... Figure 4 As shown, a silicon carbide ceramic matrix composite material with a channel structure was obtained.

[0048] Example 4

[0049] It is basically the same as Example 1, except that the temperature of hot pressing in step (5) is 90°C, while the other steps and parameters remain unchanged.

[0050] Example 5

[0051] It is basically the same as Example 1, except that the hot pressing pressure in step (5) is 90MPa, while the other steps and parameters remain unchanged.

[0052] Example 6

[0053] It is basically the same as Example 1, except that the heating rate in step (6) is 1.5℃, while the other steps and parameters remain unchanged.

[0054] Comparative Example 1

[0055] The process is basically the same as in Example 1, except that the sacrificial template described in step (4) is not used. Other steps and parameters remain unchanged, such as... Figure 5 As shown, a complete silicon carbide ceramic matrix composite material without channel structure was obtained.

[0056] The density and apparent porosity of the silicon carbide ceramic matrix composites prepared in the embodiments and comparative examples of the present invention are shown in the table below:

[0057] Table 1

[0058]

[0059] Comparing Comparative Example 1 with Examples 1-6, it can be seen that although the present invention introduces a sacrificial template during the preparation process and forms a macroscopic channel structure through decomposition in the subsequent pyrolysis stage, the apparent porosity of the resulting composite material does not show a significant increase. In particular, Example 4, with optimized process, has an apparent porosity of 14.6%, which is only 1.5% higher than that of Comparative Example 1. This proves that the process route adopted in the present invention can effectively avoid the loose matrix structure caused by gas retention, and ensures that the ceramic matrix maintains a high degree of densification while successfully achieving in-situ channel construction.

[0060] Comparing the data from Examples 1, 4, and 5, it is evident that temperature and pressure during the hot pressing process are key factors affecting density. The sample formed under hot pressing conditions at 90°C in Example 4 exhibited the highest density (2.45 g / cm³). 3 The sample with the lowest apparent porosity (14.6%) was the best among all channel-containing samples, indicating that appropriately increasing the molding temperature is beneficial to the flow of the polycarbosilane precursor powder, allowing it to more tightly encapsulate the silicon carbide whiskers and sacrificial template. In Example 5, reducing the hot-pressing pressure to 90 MPa resulted in an increase in apparent porosity to 16.9%, with a corresponding decrease in density. This demonstrates that using higher molding pressure during the molding stage helps improve the material's density.

[0061] Comparing Example 1 and Example 6, it can be seen that Example 6 used a relatively fast heating rate (1.5℃ / min), its apparent porosity (16.4%) was higher than that of Example 1 (1℃ / min), and its density decreased to 2.19 g / cm³. 3 This indicates that within the rate range (1~2℃ / min) defined by this invention, a relatively slow heating rate is more conducive to the smooth escape of gas molecules, thereby minimizing the generation of micropores inside the matrix and obtaining a denser ceramic matrix.

[0062] Comparing Example 1 and Example 2, it can be seen that in Example 1, where the silicon carbide whisker content is higher (1.5g), the material density (2.38g / cm³) is lower. 3 Example 2 (2.26 g / cm³) was superior to Example 2 (2.26 g / cm³) which had a lower whisker content (1 g). 3 This indicates that, under good dispersion conditions, an appropriate amount of silicon carbide whiskers helps to suppress the volume shrinkage of the matrix during the ceramization process, thereby achieving higher density.

[0063] These data demonstrate that the technical solution of the present invention has good universality, and can flexibly adjust the process parameters and structural design within a limited range according to actual application needs, while maintaining good molding quality.

[0064] It should be noted that the above embodiments and descriptions are merely specific examples to help understand the technical solutions of the present invention, and are not intended to limit the present invention. Those skilled in the art should understand that the shape of the sacrificial template is not limited to the cylinder used in the foregoing embodiments. Depending on the function and structural design of the channels required for the final composite material, the sacrificial template can be manufactured in various geometric shapes. All such changes and adaptations to the shape of the sacrificial template based on the core concept of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for preparing a silicon carbide ceramic matrix composite material for in-situ channel construction, characterized in that: The method includes the following steps: Step 1: Crosslink and cure the liquid-phase polycarbonylsilane precursor to obtain a cured block; Step 2: The solidified block is ball-milled and sieved to obtain precursor powder; Step 3: Mix the precursor powder with silicon carbide whiskers to obtain a mixed powder; Step 4: Prepare the sacrificial template; Step 5: The sacrificial template and mixed powder are filled into the mold, hot-pressed, and demolded to obtain the original blank; Step 6: The original green body is subjected to pyrolysis treatment to remove the sacrificial template and transform the mixed powder into ceramic, thereby obtaining a silicon carbide ceramic matrix composite material with an internal channel structure.

2. The method according to claim 1, characterized in that: In step one, the molecular weight of the polycarbosilane is 1050~1600; the cross-linking and curing are carried out in an inert gas atmosphere, with a heating rate of 2~3℃ / min, and the temperature is uniformly raised to 300~350℃ and then held for 2~4 hours.

3. The method according to claim 1, characterized in that: In step two, the ball milling time is 6-8 hours, the rotation speed is 300-350 rpm, and the sieve used for sieving is 200-300 mesh.

4. The method according to claim 1, characterized in that: In step three, the diameter of the silicon carbide whiskers is 400~600 nm and the length is 10~15 μm; the mass ratio of the precursor powder to the silicon carbide whiskers is 10:1~1.

5.

5. The method according to claim 1, characterized in that: In step four, the sacrificial template is prepared by additive manufacturing technology, and its raw material is a thermoplastic polymer material that can be completely removed by pyrolysis without residue.

6. The method according to claim 1 or 5, characterized in that: In step four, the shape of the sacrificial template is flexibly designed and customized according to the structure of the required channel.

7. The method according to claim 1, characterized in that: In step five, the hot pressing temperature is 80~90℃, the pressure is 90~100 MPa, and the holding time is 60~90 min.

8. The method according to claim 1, characterized in that: In step five, the filling sequence is as follows: fill part of the mixed powder, place the sacrificial template in the preset position, compact and fix it with the mixed powder, and fill the remaining mixed powder.

9. The method according to claim 1, characterized in that: In step six, the pyrolysis treatment is carried out under an inert gas atmosphere, specifically including: (1) Heat the temperature at a constant rate of 1~2℃ / min to 300~400℃ and keep it at that temperature for 1~2h; (2) Heat the temperature at a constant rate of 1~2℃ / min to 1000~1200℃ and keep it warm for 3~4h.

10. A silicon carbide ceramic matrix composite material for in-situ channel construction, characterized in that: The composite material is prepared by the method described in any one of claims 1 to 9.

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