Preparation method of mullite whisker modified silicon carbide porous ceramic

Abstract

The invention belongs to the technical field of porous ceramics, and relates to a preparation method of mullite whisker modified silicon carbide porous ceramics. The preparation method comprises the following steps: adding kaolin, silicon carbide, aluminum oxide, aluminum fluoride and molybdenum trioxide into a ball-milling tank for primary ball-milling, then adding a pore-forming agent for secondary ball-milling to obtain ceramic slurry, drying to obtain a solid material, grinding and sieving to obtain mixed powder, then carrying out dry-pressing molding to obtain a green body, and carrying out heat preservation on the green body at 1050-1200 DEG C for 1-4 hours to obtain the porous ceramic. And sintering at 1250-1450 DEG C for 0.5-3 hours to obtain the mullite whisker modified silicon carbide porous ceramic. Pores of the prepared silicon carbide porous ceramic are mainly formed by interlocking mullite whiskers, the pores are of mutually communicated open pore structures, the open porosity is 30-60%, the average pore size is 10-1000 nm, the length-diameter ratio of the whiskers is 10-30, and the bending strength is larger than or equal to 50 MPa.

Description

Technical Field

[0001] This invention belongs to the field of porous ceramics technology and relates to a method for preparing silicon carbide porous ceramics modified with mullite whiskers. Background Technology

[0002] Silicon carbide porous ceramics possess excellent mechanical properties, gas permeability, oxidation resistance, chemical stability, and high-temperature resistance, making them ideal materials for components in the semiconductor field such as porous ceramic suction cups, ceramic filter membranes, and diesel particulate filters (DPFs). The highly interconnected, small-pore structure contributes to good gas permeability, filtration accuracy, and mechanical strength.

[0003] Oxide-bonded porous silicon carbide ceramics have a lower sintering temperature and a significant cost advantage compared to reaction sintering, recrystallization sintering, or atmospheric pressure sintering of silicon carbide porous ceramics. However, conventionally introduced oxides (such as silicon oxide) have a significantly different coefficient of thermal expansion than silicon carbide, leading to thermal stress and relatively lower strength. Mullite has a similar coefficient of thermal expansion to silicon carbide, and when mullite is in whisker form, it can enhance its reinforcing and toughening effects, giving silicon carbide porous ceramics good thermal shock resistance, making it an ideal secondary bonding material. Currently, whisker introduction methods are still not perfect; directly adding whiskers greatly increases costs and makes the process more complicated. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, the present invention aims to provide a method for preparing mullite whisker-modified porous silicon carbide ceramics, thereby overcoming the shortcomings of the prior art.

[0005] One objective of this invention is achieved through the following technical solution:

[0006] A method for preparing mullite whisker-modified porous silicon carbide ceramics, the method comprising the following steps:

[0007] S1. Kaolin, silicon carbide, alumina, aluminum fluoride, and molybdenum trioxide are added to a ball mill jar, and then a binder solution is added for the first ball milling. After that, a pore-forming agent is added for the second ball milling to obtain a ceramic slurry.

[0008] S2. Dry the ceramic slurry to obtain a solid material; grind and sieve the solid material to obtain a mixed powder;

[0009] S3. The mixed powder is dry-pressed to obtain a green body;

[0010] S4. The green body is held at 1050-1200℃ for 1-4 hours, and then sintered at 1250-1450℃ for 0.5-3 hours to obtain mullite whisker-modified silicon carbide porous ceramic.

[0011] Preferably, kaolin, silicon carbide, alumina, aluminum fluoride, and molybdenum trioxide are all in powder form. Preferably, the average particle size of kaolin is 5–50 μm, more preferably 10–40 μm, for example, 10, 15, 20, 25, 30, 35, or 40 μm. Preferably, the average particle size of silicon carbide is 5–50 μm, more preferably 10–40 μm, for example, 10, 15, 20, 25, 30, 35, or 40 μm. Preferably, the average particle size of alumina is 1–10 μm, more preferably 1.5–10 μm, for example, 1.5, 2, 2.5, 3, 3.5, or 4 μm. The average particle size of aluminum fluoride is 0.1–1 μm, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 μm. The average particle size of molybdenum trioxide is 0.1–1 μm, for example, it can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 μm.

[0012] Preferably, the mass ratio of silicon carbide, kaolin, alumina, molybdenum trioxide, and aluminum fluoride is 60–85:0.5–15:10–25:2–12:3–12. More preferably, the mass ratio of silicon carbide, kaolin, alumina, molybdenum trioxide, and aluminum fluoride is 65–80:3–12:10–20:2–10:3–12.

[0013] The binder may be one or more of polyvinyl alcohol, polyvinyl butyral, epoxy resin, etc. Preferably, the concentration of the binder solution is 1 to 10 wt%, and the binder is 0.1 to 2 wt% of the mass of the matrix raw material. The total mass of silicon carbide, kaolin, alumina, molybdenum trioxide, and aluminum fluoride is the mass of the matrix raw material.

[0014] Preferably, a solvent and grinding balls are further added to the ball mill jar for ball milling. The types of solvent and grinding balls are not specifically limited; any substance that can serve as a solvent or grinding ball during the ball milling process can be used. Examples of solvents include anhydrous ethanol, water, toluene, acetone, etc.; examples of grinding balls include silicon carbide microspheres, zirconia beads, steel balls, etc. Preferably, the solvent accounts for 8–30 wt% of the matrix raw material; the mass of the grinding balls is 0.5–5 times the mass of the matrix raw material.

[0015] Preferably, the pore-forming agent is polymethyl methacrylate (PMMA) with an average particle size of 15–50 μm, more preferably 20–40 μm. The mass of the pore-forming agent is 2–15 wt% of the matrix raw material.

[0016] Preferably, the first ball milling time is 2 to 5 hours, the second ball milling time is 0.5 to 2 hours, and the ball mill speed is 200 to 400 r / min.

[0017] Preferably, the drying temperature in step S2 is 40–80°C, and the drying time is 2–10 h.

[0018] Preferably, the grinding in step S2 is carried out in an agate grinding body, and the sieve is 40 to 80 mesh.

[0019] Preferably, the dry pressing pressure in step S3 is 20-50 MPa, and the holding time is 20-120 s.

[0020] Preferably, step S4 includes: placing the green blank into a crucible, heating it to 750-900°C at a rate of 0.5-2.5°C / min in an air atmosphere, then heating it to 1050-1200°C at a rate of 3-7°C / min and holding it at that temperature for 1-4 hours, and then heating it to 1250-1450°C at a rate of 3-7°C / min and holding it at that temperature for 0.5-3 hours.

[0021] The second objective of this invention is achieved through the following technical solution:

[0022] A mullite whisker-modified silicon carbide porous ceramic is prepared by the above-described preparation method.

[0023] Preferably, the pores of the silicon carbide porous ceramic are mainly generated by the interlocking of mullite whiskers, and the pores are interconnected open-pore structures with an open porosity of 30-60%, more preferably 35-60%; the average pore diameter is 10-1000 nm, more preferably 10-800 nm.

[0024] Preferably, the aspect ratio of the mullite whiskers in the silicon carbide porous ceramic is 10 to 30, and more preferably 15 to 30.

[0025] Preferably, the flexural strength of the silicon carbide porous ceramic is ≥50MPa.

[0026] The third objective of this invention is achieved through the following technical solution:

[0027] Application of mullite whisker-modified silicon carbide porous ceramics in semiconductor vacuum chucks and filter materials.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This invention uses kaolin, silicon carbide, alumina, aluminum fluoride, and molybdenum trioxide as raw materials to grow mullite whiskers in situ, thereby preparing a mullite whisker-silicon carbide porous ceramic material.

[0030] 2. The selection of raw material components and proportions in this invention is conducive to the high-quality growth of mullite whiskers; and the invention further increases the mullite matrix required for the growth of mullite whiskers by first performing heat preservation treatment at 1050-1200℃ before sintering, thereby achieving the growth of high-quality mullite whiskers with a high aspect ratio of 10-30.

[0031] 3. By selecting appropriate raw materials and preparation methods, this invention enables the preparation of high-performance mullite-silicon carbide porous ceramic materials at a lower temperature (1250-1450℃) compared to previous technologies.

[0032] 4. The in-situ mullite whiskers of this invention grow well, which can effectively modify pores and adjust pore size to obtain ceramic materials with an average pore size of 10-1000nm, thereby greatly improving the filtration accuracy of the material; and the reinforcing and toughening effect of mullite whiskers makes the flexural strength of the ceramic ≥50MPa.

[0033] 5. This invention uses PMMA with an average particle size of 15-50 μm as a pore-forming agent to ensure that the ceramic material has a high porosity and meets the requirements of gas permeability and filtration performance. Attached Figure Description

[0034] Figure 1 SEM image of the cross section of the mullite whisker-modified silicon carbide porous ceramic material prepared in Example 1;

[0035] Figure 2 SEM image of the cross section of the mullite whisker-modified silicon carbide porous ceramic material prepared in Example 2;

[0036] Figure 3 SEM image of the cross section of the mullite whisker-modified silicon carbide porous ceramic material prepared in Example 3;

[0037] Figure 4 SEM image of the cross section of the mullite whisker-modified silicon carbide porous ceramic material prepared in Example 4;

[0038] Figure 5 SEM image of the cross section of the mullite whisker-modified silicon carbide porous ceramic material prepared in Example 5;

[0039] Figure 6 The XRD pattern of the mullite whisker-modified silicon carbide porous ceramic prepared in Example 1;

[0040] Figure 7 SEM image of the silicon carbide ceramic prepared in Comparative Example 1;

[0041] Figure 8 SEM image of the silicon carbide ceramic prepared in Comparative Example 2;

[0042] Figure 9 SEM image of the silicon carbide ceramic prepared in Comparative Example 3;

[0043] Figure 10 The image shows a SEM image of the silicon carbide ceramic prepared in Comparative Example 4. Detailed Implementation

[0044] The technical solution of the present invention will be further described and illustrated below with reference to specific embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of helping to understand the present invention and are not intended to limit the specific scope of the present invention. Furthermore, the accompanying drawings used herein are merely for better illustrating the content disclosed in the present invention and do not limit the scope of protection. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used in the art, and the methods used in the embodiments are all conventional methods in the art.

[0045] In the following examples and comparative examples:

[0046] The average particle size of silicon carbide powder is 20 μm, the average particle size of kaolin powder is 20 μm, the average particle size of alumina powder is 5 μm, the average particle size of aluminum fluoride powder is 500 nm, the average particle size of molybdenum trioxide powder is 500 nm, and the average particle size of the pore-forming agent polymethyl methacrylate (PMMA) is 25 μm.

[0047] Example 1

[0048] The method for preparing the mullite-modified silicon carbide ceramic material in this embodiment includes the following steps:

[0049] S1. Silicon carbide powder, kaolin powder, alumina powder, molybdenum trioxide powder, and aluminum fluoride powder are mixed in a mass ratio of 75:5:20:8:9 and added to a ball mill jar as the matrix raw material. 5wt% polyvinyl alcohol aqueous solution (polyvinyl alcohol mass is 1wt% of the matrix raw material mass), 15wt% anhydrous ethanol (matrix raw material mass), and silicon carbide microspheres (silicon carbide microspheres mass is 1.2 times the matrix raw material mass) are then added and mixed for the first ball milling for 3.5 hours. Subsequently, PMMA equivalent to 3wt% of the matrix mass is added as a pore-forming agent, and a second ball milling is performed for 0.5 hours at a ball mill speed of 300 r / min to obtain a ceramic slurry.

[0050] S2. Place the ceramic slurry in a constant temperature drying oven and dry it at 60°C for 6 hours to obtain a solid material. Place the solid material in an agate grinding wheel for grinding and then sieve it through a 60-mesh screen to obtain a mixed powder.

[0051] S3. The mixed powder is dry-pressed at 30 MPa for 30 seconds to obtain a green body.

[0052] S4. Place the green body into an alumina crucible and heat it to 850°C at a rate of 2°C / min under an air atmosphere. Then heat it to 1200°C at a rate of 5°C / min and hold it for 120 min. Then heat it to 1400°C at a rate of 5°C / min and hold it for 120 min to obtain mullite whisker-reinforced silicon carbide porous ceramic.

[0053] Depend on Figure 1 As can be seen, mullite whiskers grow on the surface of the mullite whisker-reinforced porous silicon carbide ceramic material prepared in this embodiment. The mullite whiskers achieve good growth and have a high aspect ratio. Furthermore, large-sized pores are not visible in the figure. The pores are mainly generated by the interlocking of mullite whiskers, resulting in small and uniform pore diameters.

[0054] Figure 6 The XRD pattern of the silicon carbide porous ceramic shows that the main components of the sample are silicon carbide, mullite, and silicon dioxide.

[0055] The mullite whisker-reinforced silicon carbide porous ceramic material prepared in this embodiment has a porosity of 39%, an average pore diameter of 330 nm, and a whisker aspect ratio of 17.5. This indicates that the ceramic material has high filtration accuracy.

[0056] The flexural strength of the mullite whisker-reinforced silicon carbide porous ceramic material prepared in this embodiment is 53 MPa.

[0057] Test methods: Porosity was determined using Archimedes' drainage method. Pore size was measured using a pore size analyzer. Whisker length and diameter were measured in SEM images using an Image-Pro Plus 6.0, and the aspect ratio was calculated. Bending strength and three-point bending strength were tested using a universal testing machine at a loading rate of 0.5 mm / min.

[0058] Example 2

[0059] The method for preparing the mullite-modified silicon carbide ceramic material in this embodiment includes the following steps:

[0060] S1. Silicon carbide powder, kaolin powder, alumina powder, molybdenum trioxide powder, and aluminum fluoride powder are mixed in a mass ratio of 75:10:20:8:9 and added to a ball mill jar as the matrix raw material. 8 wt% polyvinyl butyral ethanol solution (the mass of polyvinyl butyral is 1.5 wt% of the matrix raw material mass), 12 wt% anhydrous ethanol of the matrix raw material mass, and silicon carbide microspheres (the silicon carbide microspheres are 1.5 times the mass of the matrix raw material mass) are then added and mixed for the first ball milling for 4 hours. Subsequently, 4 wt% PMMA pore-forming agent of the matrix mass is added and the mixture is ball-milled for a second time for 1 hour. The ball mill speed is 250 r / min to obtain a ceramic slurry.

[0061] S2. Place the ceramic slurry in a constant temperature drying oven and dry it at 80°C for 5 hours to obtain a solid material. Place the solid material in an agate grinding wheel for grinding and then sieve it through an 80-mesh screen to obtain a mixed powder.

[0062] S3. The mixed powder is dry-pressed at 35 MPa for 40 seconds to obtain a green body.

[0063] S4. Place the green body into an alumina crucible and heat it to 800°C at a rate of 1.5°C / min under an air atmosphere. Then heat it to 1100°C at a rate of 4.5°C / min and hold it for 150 min. Then heat it to 1350°C at a rate of 4.5°C / min and hold it for 100 min to obtain mullite whisker-reinforced silicon carbide porous ceramic.

[0064] Depend on Figure 2 As can be seen, mullite whiskers grow on the surface of the mullite whisker-reinforced porous silicon carbide ceramic material prepared in this embodiment. The mullite whiskers achieve good growth and have a high aspect ratio. Furthermore, large-sized pores are not visible in the figure. The pores are mainly generated by the interlocking of mullite whiskers, resulting in small and uniform pore diameters.

[0065] The mullite whisker-reinforced silicon carbide porous ceramic material prepared in this embodiment has a porosity of 35.6%, an average pore diameter of 422 nm, and a whisker aspect ratio of 15.8. This indicates that the ceramic material has high filtration accuracy.

[0066] The flexural strength of the mullite whisker-reinforced silicon carbide porous ceramic material prepared in this embodiment is 54 MPa.

[0067] Example 3

[0068] The method for preparing the mullite-modified silicon carbide ceramic material in this embodiment includes the following steps:

[0069] S1. Silicon carbide powder, kaolin powder, alumina powder, molybdenum trioxide powder, and aluminum fluoride powder are mixed in a mass ratio of 75:5:15:10:10 and added to a ball mill jar as the matrix raw material. 3wt% polyvinyl alcohol aqueous solution (polyvinyl alcohol is 0.5wt% of the matrix raw material mass), 20wt% anhydrous ethanol (the matrix raw material mass), and silicon carbide microspheres (the silicon carbide microspheres are twice the matrix raw material mass) are then added and mixed for the first ball milling for 3 hours. Subsequently, 5wt% PMMA (a pore-forming agent) equivalent to the matrix mass is added, and the second ball milling is carried out for 1.5 hours at a ball mill speed of 350 r / min to obtain a ceramic slurry.

[0070] S2. Place the ceramic slurry in a constant temperature drying oven and dry it at 50°C for 7 hours to obtain a solid material. Place the solid material in an agate grinding wheel for grinding and then sieve it through a 50-mesh screen to obtain a mixed powder.

[0071] S3. The mixed powder is dry-pressed at 50 MPa for 30 seconds to obtain a green body.

[0072] S4. Place the green body into an alumina crucible and heat it to 900°C at a rate of 2.5°C / min under an air atmosphere. Then heat it to 1150°C at a rate of 6°C / min and hold it for 150 min. Then heat it to 1400°C at a rate of 6°C / min and hold it for 120 min to obtain mullite whisker-reinforced silicon carbide porous ceramic.

[0073] Depend on Figure 3 As can be seen, mullite whiskers grow on the surface of the mullite whisker-reinforced porous silicon carbide ceramic material prepared in this embodiment. The mullite whiskers achieve good growth and have a high aspect ratio. Furthermore, large-sized pores are rarely seen in the figure. The main way pores are generated is through the interlocking of mullite whiskers, resulting in small and uniform pore diameters.

[0074] The mullite whisker-reinforced silicon carbide porous ceramic material prepared in this embodiment has a porosity of 37%, an average pore diameter of 874 nm, and a whisker aspect ratio of 16.6. This indicates that the ceramic material has high filtration accuracy.

[0075] The flexural strength of the mullite whisker-reinforced silicon carbide porous ceramic material prepared in this embodiment is 60 MPa.

[0076] Example 4

[0077] The difference between Example 4 and Example 1 is that in Example 4, silicon carbide powder, kaolin powder, alumina powder, molybdenum trioxide powder, and aluminum fluoride powder are mixed in a mass ratio of 75:10:15:12:12, while the rest is the same as in Example 1.

[0078] Figure 4 The image shows a SEM image of the mullite whisker-reinforced porous silicon carbide ceramic material prepared in Example 4. The mullite whiskers achieved good growth and have a high aspect ratio. Furthermore, large-sized pores are rarely seen in the image; the pores are mainly formed by the interlocking of the mullite whiskers, resulting in small and uniform pore diameters.

[0079] The mullite whisker-reinforced silicon carbide porous ceramic material prepared in this embodiment has a porosity of 41%, an average pore diameter of 354 nm, and a whisker aspect ratio of 13.8. This indicates that the ceramic material has high filtration accuracy.

[0080] The flexural strength of the mullite whisker-reinforced silicon carbide porous ceramic material prepared in this embodiment is 52 MPa.

[0081] Example 5

[0082] The difference between Example 5 and Example 1 is that in Example 5, silicon carbide powder, kaolin powder, alumina powder, molybdenum trioxide powder, and aluminum fluoride powder are mixed in a mass ratio of 75:5:17:10:10, while the rest is the same as in Example 1.

[0083] Figure 5 The image shows a SEM image of the mullite whisker-reinforced porous silicon carbide ceramic material prepared in Example 5. The mullite whiskers achieved good growth and have a high aspect ratio. Furthermore, large-sized pores are rarely seen in the image; the pores are mainly formed by the interlocking of the mullite whiskers, resulting in small and uniform pore diameters.

[0084] The mullite whisker-reinforced silicon carbide porous ceramic material prepared in this embodiment has a porosity of 39%, an average pore diameter of 473 nm, and a whisker aspect ratio of 24. This indicates that the ceramic material has high filtration accuracy.

[0085] The flexural strength of the mullite whisker-reinforced silicon carbide porous ceramic material prepared in this embodiment is 50 MPa.

[0086] Comparative Example 1

[0087] The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, silicon carbide powder, kaolin powder, alumina powder, molybdenum trioxide powder, and aluminum fluoride powder are mixed in a mass ratio of 75:0:20:8:9, while the rest is the same as in Example 1.

[0088] Figure 7 The SEM image of the silicon carbide ceramic prepared in Comparative Example 1 shows that the mullite whiskers have a large diameter and a low aspect ratio of only 7.

[0089] The silicon carbide ceramic material prepared in this comparative example has an open porosity of 41.8%, an average pore diameter of 1.1 μm, and a bending strength of only 19.8 MPa.

[0090] Comparative Example 2

[0091] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, step S4 involves placing the green blank into an alumina crucible, heating it to 850°C at a rate of 2°C / min in an air atmosphere, and then heating it to 1400°C at a rate of 5°C / min and holding it at that temperature for 120 min to obtain mullite whisker-reinforced silicon carbide porous ceramic.

[0092] Figure 8 The image shows a SEM image of the silicon carbide ceramic prepared in Comparative Example 2, where well-grown mullite whiskers are barely visible.

[0093] The silicon carbide ceramic material prepared in this comparative example has an open porosity of 39.4%, an average pore diameter of 1.9 μm, and a bending strength of only 15.6 MPa.

[0094] Comparative Example 3

[0095] The difference between Comparative Example 3 and Example 1 is that in Comparative Example 1, silicon carbide powder, kaolin powder, alumina powder, molybdenum trioxide powder, and aluminum fluoride powder were mixed in a mass ratio of 75:25:20:8:9, while the rest was the same as in Example 1.

[0096] Figure 9 The image shows a SEM image of the silicon carbide ceramic prepared in Comparative Example 3. This silicon carbide ceramic material has a low mullite whisker aspect ratio of only 5, a porosity of 41%, an average pore diameter of 310 nm, and a flexural strength of only 14 MPa.

[0097] Comparative Example 4

[0098] The difference between Comparative Example 4 and Example 1 is that in Comparative Example 4, step S4 involves placing the green blank into an alumina crucible, heating it to 850°C at a rate of 2°C / min in an air atmosphere, then heating it to 1200°C at a rate of 5°C / min and holding it for 120 min, and then heating it to 1500°C at a rate of 5°C / min and holding it for 120 min to obtain mullite whisker-reinforced silicon carbide porous ceramic.

[0099] Figure 10 The image shows a SEM image of the silicon carbide ceramic prepared in Comparative Example 4. This silicon carbide ceramic material has a low mullite whisker aspect ratio of only 2.5. It exhibits an open porosity of 32%, an average pore diameter of 430 nm, and a flexural strength of only 21 MPa.

[0100] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0101] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0102] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A method for preparing mullite whisker-modified porous silicon carbide ceramics, characterized in that, The preparation method includes the following steps: S1. Kaolin, silicon carbide, alumina, aluminum fluoride, and molybdenum trioxide are added to a ball mill jar, and then a binder solution is added for the first ball milling. After that, a pore-forming agent is added for the second ball milling to obtain a ceramic slurry. S2. Dry the ceramic slurry to obtain a solid material; grind and sieve the solid material to obtain a mixed powder; S3. The mixed powder is dry-pressed to obtain a green body; S4. The green body is held at 1050-1200℃ for 1-4 hours, and then sintered at 1250-1450℃ for 0.5-3 hours to obtain mullite whisker-modified silicon carbide porous ceramic.

2. The method for preparing mullite whisker-modified porous silicon carbide ceramics according to claim 1, characterized in that, Kaolin, silicon carbide, alumina, aluminum fluoride, and molybdenum trioxide are all in powder form. The average particle size of kaolin is 5–50 μm, the average particle size of silicon carbide is 5–50 μm, the average particle size of alumina is 1–10 μm, the average particle size of aluminum fluoride is 0.1–1 μm, and the average particle size of molybdenum trioxide is 0.1–1 μm.

3. The method for preparing mullite whisker-modified porous silicon carbide ceramics according to claim 1 or 2, characterized in that, The mass ratio of silicon carbide, kaolin, alumina, molybdenum trioxide, and aluminum fluoride is 60–85. 0.5～15：10～25：2～12：3～12。 4. The method for preparing mullite whisker-modified porous silicon carbide ceramics according to claim 1, characterized in that, The pore-forming agent is polymethyl methacrylate with an average particle size of 15–50 μm. The mass of the pore-forming agent is 2 to 15 wt% of the mass of the matrix raw material.

5. The method for preparing mullite whisker-modified porous silicon carbide ceramics according to claim 1, characterized in that, The first ball milling time is 2 to 5 hours, the second ball milling time is 0.5 to 2 hours, and the ball mill speed is 200 to 400 r / min.

6. The method for preparing mullite whisker-modified porous silicon carbide ceramics according to claim 1, characterized in that, The drying temperature in step S2 is 40–80°C, and the drying time is 2–10 hours. The dry pressing pressure in step S3 is 20-50 MPa, and the holding time is 20-120 s.

7. The method for preparing mullite whisker-modified porous silicon carbide ceramics according to claim 1, characterized in that, Step S4 includes: placing the green blank into a crucible, heating it to 750-900°C at a rate of 0.5-2.5°C / min in an air atmosphere, then heating it to 1050-1200°C at a rate of 3-7°C / min and holding it at that temperature for 1-4 hours, and then heating it to 1250-1450°C at a rate of 3-7°C / min and holding it at that temperature for 0.5-3 hours.

8. A mullite whisker-modified porous silicon carbide ceramic, characterized in that, It is prepared by the preparation method described in claim 1.

9. A mullite whisker-modified silicon carbide porous ceramic according to claim 8, characterized in that, The pores of silicon carbide porous ceramics are mainly generated by the interlocking of mullite whiskers. The pores are interconnected open pore structures with an open porosity of 30-60% and an average pore diameter of 10-1000 nm. The aspect ratio of mullite whiskers in silicon carbide porous ceramics is 10 to 30. The flexural strength of porous silicon carbide ceramics is ≥50MPa.

10. The application of the mullite whisker-modified silicon carbide porous ceramic as described in claim 8 in semiconductor vacuum chucks and filter materials.

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