High-density recrystallized silicon carbide member and preparation method thereof

Abstract

The invention provides a preparation method of a high-density recrystallized silicon carbide component, which comprises the following steps: taking primary sintering molded high-porosity silicon carbide ceramic as a matrix for secondary sintering molding, designing a secondary sintering molding formula according to a primary sintering result, and selecting silicon carbide particles capable of penetrating into pores as a ceramic raw material for secondary sintering molding, so as to prepare the high-density recrystallized silicon carbide component. According to the present invention, the silicon carbide component is subjected to secondary sintering, such that the silicon carbide component can be completely filled into the primary sintering matrix, and the sintering temperature design is combined so as to leave the finer pores after the secondary sintering, such that the porosity and the pore size of the silicon carbide component are substantially reduced, the defect of the high porosity of the silicon carbide component prepared through the recrystallization method is overcome, and the density of the obtained silicon carbide component can achieve 2.75-3.1 g / cm < 3 >;

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic material preparation, and in particular to a high-density recrystallized silicon carbide component and a preparation method thereof. Background Art

[0002] As a high-performance, high-temperature-resistant material, silicon carbide ceramic not only possesses excellent physical and chemical properties but also demonstrates exceptional stability and reliability in a variety of extreme environments. Therefore, it is suitable for the manufacture of high-temperature furnace tubes. Silicon carbide used in high-temperature furnace tubes typically requires high density, thermal shock resistance, and purity. Currently, reaction sintering and liquid-phase sintering are commonly used.

[0003] Compared with silicon carbide ceramics obtained by other sintering methods, recrystallized silicon carbide (R-SiC) has high purity and operating temperature. When the density of R-SiC is increased to a certain level, it has excellent thermal properties and purity, which is very suitable for the extreme environment of high-temperature furnace tubes.

[0004] However, R-SiC sintering usually cannot achieve a high enough density, generally between 2.5 and 2.6 g / cm3, and it is difficult to exceed 2.6 g / cm 3 For example, Chinese patent publication number CN115340385A discloses a micron-sized silicon carbide porous ceramic with controllable pore size and a preparation method thereof. The silicon carbide prepared by recrystallization has a pore size of 1 to 10 μm and a porosity of 40 to 65%, that is, a density of only 1.12 to 1.92 g / cm 3 , it is difficult to meet the demand for materials such as high-temperature furnace tubes.

[0005] The main reasons for the above situation include: (1) No sintering aids. During the recrystallization sintering process, since no sintering aids are added, the densification is completed by the diffusion and recrystallization of silicon carbide itself, which makes it difficult for the grain growth and densification to proceed simultaneously when the material is sintered at high temperature; (2) Pore problem. During the recrystallization sintering process, the residual pores in the material are difficult to eliminate, especially the pores with smaller pore sizes, which are not easy to eliminate even under high-temperature sintering conditions, resulting in limited sintering density; (3) Sintering temperature and time limitations. In order to avoid excessive grain growth, relatively low sintering temperatures and short sintering times are usually selected, which limits the densification process. Although some studies have increased the density to 2.7 g / cm3 or even higher by using higher temperatures (about 2500°C) or very long sintering times (tens of hours), this is often accompanied by significant grain growth, resulting in a decrease in the mechanical properties of the material.

[0006] Therefore, the difficulty of breaking through the bottleneck of 2.6g / cm3 in the density of recrystallized sintered silicon carbide has become a long-term problem in the silicon carbide field. Summary of the Invention

[0007] The present invention aims to solve the problem that it is difficult to obtain a density higher than 2.6g / cm by sintering recrystallized silicon carbide. 3 The present invention provides a high-density recrystallized silicon carbide component and its preparation method. Through secondary molding and secondary sintering, as well as the design of secondary molding particle size and content, the density of the obtained silicon carbide component can reach 2.75-3.1g / cm 3 .

[0008] According to a first aspect of the present invention, there is provided a method for preparing a high-density recrystallized silicon carbide component, comprising the following steps:

[0009] S1. Dissolving a first dispersant and a first binder in deionized water, adding a first silicon carbide powder and a second silicon carbide powder, mixing, and ball milling to form a first slurry. The first slurry is then dried, ground, sieved, and dry-pressed to obtain a green body of the desired silicon carbide component; wherein the average particle size D1 of the first silicon carbide powder is larger than the average particle size D2 of the second silicon carbide powder;

[0010] S2, placing the green body obtained in step S1 in an inert atmosphere for recrystallization and sintering to T1, keeping the temperature, and then naturally cooling to room temperature to obtain a matrix of the silicon carbide component;

[0011] S3. Determine the total volume of the third and fourth silicon carbide powders based on the volume V1 and porosity ρ1 of the substrate obtained in step S2, and determine the average particle size of the third silicon carbide powder based on the pore size a1 of the substrate; wherein the average particle size D3 of the third silicon carbide powder is greater than the average particle size D4 of the fourth silicon carbide powder;

[0012] S4, dissolving the second dispersant and the second binder in deionized water, adding the third silicon carbide powder and the fourth silicon carbide powder, mixing and ball milling to form a second slurry, immersing the substrate in the second slurry under vacuum conditions until the second slurry is completely immersed in the substrate, and then drying at room temperature;

[0013] S5. The substrate processed in step S4 is placed in an inert atmosphere for recrystallization and sintering to T2, and then naturally cooled to room temperature after heat preservation to obtain the desired high-density recrystallized silicon carbide component.

[0014] As an optional embodiment, the average particle size D1 of the first silicon carbide is in the range of 20 μm to 100 μm, and the average particle size D2 of the second silicon carbide is in the range of 0.5 μm to 1 μm.

[0015] As an optional embodiment, the mass ratio of the first silicon carbide powder to the second silicon carbide powder is (1-7):1.

[0016] As an optional implementation, the value of T1 is 2100° C. to 2300° C., and the holding time is 2 h to 5 h.

[0017] As an optional embodiment, the total volume of the third silicon carbide powder and the fourth silicon carbide powder is determined based on the volume V1 and porosity ρ1 of the substrate obtained in step S2, and the average particle size of the third silicon carbide powder is determined based on the pore size a1 of the substrate. The principle is as follows:

[0018] The average particle size of the third silicon carbide powder D3≤a1;

[0019] The total powder volume of the third silicon carbide powder and the fourth silicon carbide powder is V1*ρ1.

[0020] As an optional embodiment, the average particle size D3 of the third silicon carbide is in the range of 4 μm to 15 μm, and the average particle size D4 of the fourth silicon carbide is in the range of 0.5 μm to 1 μm.

[0021] As an optional embodiment, the mass ratio of the third silicon carbide powder to the fourth silicon carbide powder is (1-7):1.

[0022] As an optional implementation, the value of T2 is selected according to the following rules:

[0023] When D3 < 10 μm, T2 is 100°C to 150°C lower than T1;

[0024] When D3≥10μm, T2=T1.

[0025] As an optional embodiment, the first dispersant is polyvinyl pyrrolidone or isobutylene maleic anhydride copolymer, accounting for 0.5% to 3% of the total mass of the first silicon carbide powder and the second silicon carbide powder;

[0026] The first binder is one of polyvinyl alcohol and sodium carboxymethyl cellulose or a mixture of the two, accounting for 0.5% to 3% of the total mass of the first silicon carbide powder and the second silicon carbide powder.

[0027] As an optional embodiment, the second dispersant is polyvinyl pyrrolidone or isobutylene maleic anhydride copolymer, accounting for 0.5% to 3% of the total mass of the third silicon carbide powder and the fourth silicon carbide powder;

[0028] The second binder is one of polyvinyl alcohol and sodium carboxymethyl cellulose or a mixture of the two, accounting for 0.5% to 3% of the total mass of the third silicon carbide powder and the fourth silicon carbide powder.

[0029] As an optional embodiment, the solid content of the first slurry is not less than 60 wt %, and the solid content of the second slurry is in the range of 20 wt % to 60 wt %.

[0030] According to a second aspect of the present invention, there is provided a high-density recrystallized silicon carbide component prepared by the above method.

[0031] As an optional embodiment, the density of the high-density recrystallized silicon carbide component is 2.75 g / cm 3 ~3.1g / cm 3 The porosity is 3% to 14%, and the average pore size is 0.5μm to 5μm.

[0032] It can be seen from the above technical solutions of the present invention that the preparation method of the high-density recrystallized silicon carbide component proposed by the present invention uses a high-porosity silicon carbide ceramic part formed by primary sintering as a matrix for secondary sintering, and designs a secondary sintering molding formula based on the results of the primary sintering, and selects silicon carbide particles that can penetrate into the pores as the ceramic raw material for secondary sintering molding, so that they can be fully filled into the silicon carbide matrix sintered once, and then combined with the sintering temperature design, after the secondary sintering, smaller pores are left, which greatly reduces the porosity and pore size of the molded part, overcomes the disadvantage of high porosity of silicon carbide components prepared by the recrystallization method, and the obtained silicon carbide component has a density of 2.75 to 3.1 g / cm 3 The high density improves the strength of silicon carbide components. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a SEM image of the silicon carbide component of Example 1 of the present invention.

[0034] Figure 2 This is a SEM image of the silicon carbide component of Example 2 of the present invention.

[0035] Figure 3 This is a SEM image of the silicon carbide component of Example 3 of the present invention. DETAILED DESCRIPTION

[0036] In order to better understand the technical content of the present invention, specific embodiments are given and described below with reference to the accompanying drawings.

[0037] Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to be comprehensive. It should be understood that the various concepts and embodiments described above, as well as those described in more detail below, can be implemented in any of a number of ways.

[0038] Recrystallization is a process in which small particles undergo evaporation-condensation recrystallization under the protection of an atmosphere at a temperature above 2100°C and a certain pressure. A sintered body is formed by particle symbiosis at the contact point of large particles. The evaporation of small particles will cause a certain amount of pores.

[0039] Based on this, the present invention provides a method for preparing high-density recrystallized silicon carbide components, designs a secondary sintering molding, uses the primary sintered material as the matrix of particle grading, and through the secondary sintering molding, allows finer particles to enter the pores of the primary sintering molding, and the finer pores left after the secondary sintering, thereby reducing the porosity.

[0040] An exemplary method for preparing a high-density recrystallized silicon carbide component according to the present invention comprises:

[0041] First, the raw material formula for primary sintering is designed to determine the mass percentage of each component in the raw material. After the raw material is made into the green body of the required silicon carbide component, it is placed in an inert atmosphere for recrystallization and primary sintering to obtain a density of <2.6g / cm 3 The substrate of the silicon carbide component.

[0042] Then, a second formula design is carried out according to the volume, porosity and pore size of the matrix. The volume of the secondary raw material is determined in combination with the volume and porosity of the matrix. The particle size of the secondary raw material is determined according to the pore size of the matrix. The raw materials learned from the secondary sintering are made into slurry.

[0043] The matrix obtained by the primary sintering was immersed in the slurry, dried and placed in an inert atmosphere for secondary recrystallization sintering to obtain a density of 2.75-3.1 g / cm 3 High-density recrystallized silicon carbide components.

[0044] As an optional example, the average particle size D1 of the first silicon carbide is in the range of 20 μm to 100 μm, and the average particle size D2 of the second silicon carbide is in the range of 0.5 μm to 1 μm.

[0045] As an optional example, the mass ratio of the first silicon carbide powder to the second silicon carbide powder is (1-7):1.

[0046] As an optional example, the value of T1 is 2100° C. to 2300° C., and the holding time is 2 h to 5 h.

[0047] As an optional example, the total volume of the third silicon carbide powder and the fourth silicon carbide powder is determined based on the volume V1 and porosity ρ1 of the matrix, and the average particle size of the third silicon carbide powder is determined based on the pore size a1 of the matrix. The principle is as follows:

[0048] The average particle size of the third silicon carbide powder is D3≤a1, and particularly preferably 4 μm≤D3≤a1.

[0049] If D3>a1, the particles of the secondary prepared silicon carbide raw material cannot enter the primary sintered product, and thus the density cannot be improved.

[0050] The total powder volume of the third silicon carbide powder and the fourth silicon carbide powder is V1*ρ1;

[0051] Furthermore, the total mass of the third silicon carbide powder and the fourth silicon carbide powder can be obtained according to the total volume of the powder, which is 3.2*V1*ρ1, where 3.2 is the density of silicon carbide, g / cm 3 .

[0052] If the total mass of the silicon carbide raw material powder is greater than 3.2*V1*ρ1, the powder prepared by the secondary molding is too much, and it is not easy to prepare a low-solid content slurry that can be impregnated; but if it is less than 3.2*V1*ρ1, the mass is too small, and there will not be enough powder to enter the pores of the primary sintering, and the pore blocking effect cannot be achieved.

[0053] As an optional example, the average particle size D3 of the third silicon carbide is in the range of 4 μm to 15 μm, and the average particle size D4 of the fourth silicon carbide is in the range of 0.5 μm to 1 μm.

[0054] As an optional example, the mass ratio of the third silicon carbide powder to the fourth silicon carbide powder is (1-7):1.

[0055] As an optional example, the value of T2 is selected according to the following rules:

[0056] When D3 < 10 μm, T2 is 100°C to 150°C lower than T1;

[0057] When D3≥10μm, T2=T1.

[0058] Selecting the sintering temperature according to the particle size of D3 can, on the one hand, prevent the small-sized silicon carbide grains from growing during the secondary sintering and reducing the strength of the material, and on the other hand, reduce the sintering cost.

[0059] As an optional example, the first dispersant is polyvinyl pyrrolidone or isobutylene maleic anhydride copolymer, accounting for 0.5% to 3% of the total mass of the first silicon carbide powder and the second silicon carbide powder;

[0060] The first binder is one of polyvinyl alcohol and sodium carboxymethyl cellulose or a mixture of the two, accounting for 0.5% to 3% of the total mass of the first silicon carbide powder and the second silicon carbide powder.

[0061] As an optional example, the second dispersant is polyvinyl pyrrolidone or isobutylene maleic anhydride copolymer, accounting for 0.5% to 3% of the total mass of the third silicon carbide powder and the fourth silicon carbide powder;

[0062] The second binder is one of polyvinyl alcohol and sodium carboxymethyl cellulose or a mixture of the two, accounting for 0.5% to 3% of the total mass of the third silicon carbide powder and the fourth silicon carbide powder.

[0063] As an optional example, the solid content of the first slurry is not less than 60 wt %, and the solid content of the second slurry is in the range of 20 wt % to 60 wt %.

[0064] In a typical example, a method for preparing a high-density recrystallized silicon carbide component is provided, comprising the following specific steps:

[0065] Step 1. Design of raw material formula 1

[0066] The raw materials are composed of silicon carbide coarse powder, silicon carbide fine powder, and organic substances such as a dispersant and a binder. The average particle size D1 of the silicon carbide coarse powder is 20 μm to 100 μm, and the average particle size D2 of the silicon carbide fine powder is in the range of 0.5 μm to 1 μm.

[0067] The dispersant is polyvinyl pyrrolidone or isobutylene maleic anhydride copolymer; the binder is polyvinyl alcohol or sodium carboxymethyl cellulose or a mixture of the two;

[0068] The mass ratio of silicon carbide coarse powder to silicon carbide fine powder is (1-7):1; the mass ratio of dispersant and binder to powder is 0.5-3%.

[0069] Step 2: Green Forming of Silicon Carbide Components

[0070] Using the raw materials determined in step 1, a dispersant and a binder are dissolved in a deionized water mixture, and then coarse silicon carbide powder and fine silicon carbide powder are added. After mixing, the mixture is ball-milled for 12 to 24 hours to form a uniform first slurry, wherein the solid content of the silicon carbide raw material powder in the first slurry is not less than 60 wt %;

[0071] The first slurry is dried at 50-80°C for 4-8 hours, and the obtained solid is ground into a dry powder. After passing through a 100-mesh sieve, the dry powder is placed in a mold and dry-pressed at a pressure of 10-100 MPa to obtain a green body of the desired silicon carbide component.

[0072] Step 3: Sintering once to obtain the matrix of the silicon carbide component

[0073] The green body prepared in step 2 is placed in an inert atmosphere and recrystallized and sintered to T1. After keeping the temperature for 2 to 5 hours, it is naturally cooled to room temperature to obtain a matrix of the silicon carbide component; wherein the value of T1 is 2100°C to 2300°C.

[0074] Step 4: Design of raw material formula 2

[0075] Formula 2 is designed based on the volume V1, porosity ρ1, and pore size a1 of the matrix. In Formula 2, the average particle size D3 of the coarse silicon carbide powder is larger than the average particle size D4 of the fine silicon carbide powder, and D3 ≤ a1. The sum of the masses (g) of the coarse silicon carbide powder and the fine silicon carbide powder is 3.2*V1*ρ1, where 3.2 is the density of silicon carbide, g / cm 3 ;

[0076] The average particle size D3 of the coarse silicon carbide powder is in the range of 4 μm to 15 μm, and the average particle size D4 of the fine silicon carbide powder is in the range of 0.5 μm to 1 μm.

[0077] The mass ratio of silicon carbide coarse powder to silicon carbide fine powder is (1-7):1; the same dispersant and binder as those in formula 1 are used in formula 2, and the mass ratio of the dispersant and binder to the powder is 0.5-3%.

[0078] Step 5: Secondary molding of the substrate

[0079] Using the raw materials determined in step 4, the dispersant and the binder are dissolved in a deionized water mixture, and then the coarse silicon carbide powder and the fine silicon carbide powder are added. After mixing, the mixture is ball-milled for 12 to 24 hours to form a uniform second slurry, wherein the solid content of the silicon carbide raw material powder in the second slurry is not higher than 60 wt%;

[0080] The substrate is immersed in the second slurry for 1 to 10 minutes. Vacuuming is required during the process to ensure that the slurry is completely immersed in the substrate. The immersed substrate is dried at room temperature for 12 to 24 hours.

[0081] Step 6: Secondary sintering to obtain high-density recrystallized silicon carbide components

[0082] The substrate impregnated and dried in step 5 is placed in an inert atmosphere and sintered again at a high temperature, with the highest sintering temperature reaching T2. After holding the temperature for 2 to 5 hours, the substrate is cooled to room temperature to obtain the desired high-density recrystallized silicon carbide component.

[0083] The selection rule of T2 is: when D3 is less than 10 μm, T2 is 100°C to 150°C lower than T1; when D3 is greater than or equal to 10 μm, T2 is equal to T1.

[0084] In another exemplary embodiment of the present invention, a high-density recrystallized silicon carbide component prepared by the above method is also provided, wherein the density of the silicon carbide component is 2.75 g / cm 3 ~3.1g / cm 3 The porosity is 3% to 14%, the average pore size is 0.5 μm to 5 μm, the porosity is particularly preferably 4% to 8%, and the average pore size is preferably 2 μm to 4 μm.

[0085] The obtained silicon carbide components have high density, high purity and high temperature resistance. The corresponding silicon carbide material can meet the material requirements of high-temperature sintering furnace tubes, and also has great application potential in the links of semiconductor preparation that have requirements for purity and temperature resistance.

[0086] For better understanding, the present invention is further described below with reference to several specific examples, but the preparation process is not limited thereto, and the content of the present invention is not limited thereto.

[0087] Unless otherwise specified, the materials in the examples were prepared according to existing methods or directly purchased from the market.

[0088] Example 1

[0089] [One-step molding and sintering]

[0090] Silicon carbide coarse powder D1 with an average particle size of 50 μm, silicon carbide fine powder with a size of 1 μm, and a coarse powder / fine powder mass ratio of 5 were selected as silicon carbide raw material powder.

[0091] Polyvinyl pyrrolidone and polyvinyl alcohol accounting for 0.5 wt% and 1 wt% of the total mass of silicon carbide coarse and fine powder respectively are mixed with the raw material powder and ball milled for 12 hours to form a uniform slurry, wherein the solid content of the powder is 75 wt%.

[0092] The slurry was dried at 80°C for 4 h, and the obtained solid was ground into a dry powder. After passing through a 100-mesh sieve, the dry powder was placed in a Φ5 cm mold and dry-pressed at a pressure of 100 MPa to obtain a green body with a thickness of 3 mm.

[0093] The green body was placed in an inert atmosphere and recrystallized and sintered to 2200°C. After holding for 2 hours, it was naturally cooled to room temperature to obtain silicon carbide component A. The test showed that its porosity was 40%, the average pore size was 10 μm, and the volume after sintering was 5.4 cm 3 .

[0094] Example 2

[0095] [Secondary molding and sintering]

[0096] The silicon carbide component A in Example 1 was used as the silicon carbide component to be molded at one time.

[0097] For secondary molding, the average particle size D3 of silicon carbide coarse powder is 10 μm, the average particle size D4 of silicon carbide fine powder is 0.5 μm, and the mass ratio of coarse powder to fine powder is 5 as the silicon carbide raw material powder. According to the volume and porosity of silicon carbide structural part A, the total mass of the secondary molded silicon carbide powder is 6.9 g.

[0098] Polyvinyl pyrrolidone and polyvinyl alcohol accounting for 0.5 wt% and 1 wt% of the total mass of silicon carbide coarse and fine powder respectively were mixed with the raw material powder and ball milled for 12 hours to form a uniform slurry, wherein the solid content of the powder was 60 wt%.

[0099] The silicon carbide component A (obtained in Example 1) was immersed in the slurry for 10 minutes, and vacuum was applied during the process to ensure that the slurry was completely immersed in the silicon carbide component A.

[0100] The impregnated silicon carbide component A was dried at room temperature for 24 hours, recrystallized and sintered to 2200° C. in an inert atmosphere, kept at this temperature for 2 hours, and then naturally cooled to room temperature to obtain a silicon carbide component B.

[0101] Example 3

[0102] [Secondary molding and sintering]

[0103] The silicon carbide component A in Example 1 was used as the silicon carbide component to be molded at one time.

[0104] For secondary molding, the average particle size D3 of silicon carbide coarse powder is 5μm, the average particle size D4 of silicon carbide fine powder is 0.5μm, and the mass ratio of coarse powder / fine powder is 6 as the silicon carbide raw material powder. According to the volume and porosity of silicon carbide component A, the total mass of the secondary molded silicon carbide powder is 6.9g.

[0105] Polyvinyl pyrrolidone and polyvinyl alcohol accounting for 1 wt% and 1 wt% of the total mass of silicon carbide coarse and fine powder respectively were mixed with the raw material powder and ball-milled for 12 hours to form a uniform slurry, wherein the solid content of the powder was 60 wt%.

[0106] The silicon carbide component A (obtained in Example 1) was immersed in the slurry for 10 minutes, and vacuum was applied during the process to ensure that the slurry was completely immersed in the silicon carbide component A.

[0107] The impregnated silicon carbide component A was dried at room temperature for 24 hours, then recrystallized and sintered to 2100° C. in an inert atmosphere, kept warm for 2 hours, and then naturally cooled to room temperature to obtain a silicon carbide component C.

[0108] SEM

[0109] The samples of Examples 1-3 were subjected to SEM testing, and the results were as follows: Figure 1-3 shown.

[0110] As can be seen from the figure, by designing secondary molding and combining it with formula design, the pore size and porosity after secondary sintering are smaller, and as the secondary molding particles are refined, the pore size and porosity after secondary sintering also decrease.

[0111] Performance Testing

[0112] The porosity and average pore size of the material were tested by mercury intrusion method, and the strength of the material was tested by three-point bending method. The results are shown in the following table.

[0113] Porosity% Average pore size μm <![CDATA[Density g / cm 3 > Strength MPa Example 1 40 10 1.91 20 Example 2 8 4 2.93 65 Example 3 4 2 3.07 200

[0114] As can be seen from the table above, the silicon carbide component prepared by the method of the present invention has a lower porosity and pore size, and the strength of the material is improved by reducing the porosity and pore size, and the corresponding density is higher, which can reach 2.9g / cm 3 As the secondary molding particles become finer, the strength of the silicon carbide components is greatly improved.

[0115] While the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for preparing a high-density recrystallized silicon carbide component, characterized in that: The following steps are involved: S1, dissolving a first dispersant and a first binder in deionized water, adding a first silicon carbide powder and a second silicon carbide powder, mixing and ball milling to form a first slurry, then drying, grinding, sieving and dry pressing the first slurry to obtain a green body of the desired silicon carbide component; wherein the average particle size D1 of the first silicon carbide powder is greater than the average particle size D2 of the second silicon carbide powder; S2, placing the green body obtained in step S1 in an inert atmosphere for recrystallization and sintering to T1, keeping the temperature and then naturally cooling to room temperature to obtain a matrix of the silicon carbide component; S3, determining the total volume of the third silicon carbide powder and the fourth silicon carbide powder according to the volume V1 and the porosity ρ1 of the matrix obtained in step S2, and determining the average particle size of the third silicon carbide powder according to the pore size a1 of the matrix; wherein the average particle size D3 of the third silicon carbide powder is greater than the average particle size D4 of the fourth silicon carbide powder; S4, dissolving the second dispersant and the second binder in deionized water, adding the third silicon carbide powder and the fourth silicon carbide powder, mixing and ball milling to form a second slurry, immersing the substrate in the second slurry under vacuum conditions until the second slurry is completely immersed in the substrate, and then drying at room temperature; S5, placing the substrate processed in step S4 in an inert atmosphere for recrystallization and sintering to T2, keeping the temperature and then naturally cooling to room temperature to obtain the desired high-density recrystallized silicon carbide component.

2. The method for preparing a high-density recrystallized silicon carbide component according to claim 1, characterized in that: The average particle size D1 of the first silicon carbide is in the range of 20 μm to 100 μm, and the average particle size D2 of the second silicon carbide is in the range of 0.5 μm to 1 μm.

3. The method for preparing a high-density recrystallized silicon carbide component according to claim 1, characterized in that: The mass ratio of the first silicon carbide powder to the second silicon carbide powder is (1-7):

1.

4. The method for preparing a high-density recrystallized silicon carbide component according to claim 1, characterized in that: The value of T1 is 2100℃~2300℃, and the insulation time is 2h~5h.

5. The method for preparing a high-density recrystallized silicon carbide component according to claim 1, characterized in that: The total volume of the third silicon carbide powder and the fourth silicon carbide powder is determined according to the volume V1 and the porosity ρ1 of the matrix obtained in step S2, and the average particle size of the third silicon carbide powder is determined according to the pore size a1 of the matrix as follows: The average particle size of the third silicon carbide powder is D3≤a1; The total powder volume of the third silicon carbide powder and the fourth silicon carbide powder is V1*ρ1.

6. The method for preparing a high-density recrystallized silicon carbide component according to claim 1, characterized in that: The average particle size D3 of the third silicon carbide is in the range of 4 μm to 15 μm, and the average particle size D4 of the fourth silicon carbide is in the range of 0.5 μm to 1 μm.

7. The method for preparing a high-density recrystallized silicon carbide component according to claim 1, characterized in that: The mass ratio of the third silicon carbide powder to the fourth silicon carbide powder is (1-7):

1.

8. The method for preparing a high-density recrystallized silicon carbide component according to claim 5, characterized in that: The value of T2 is selected according to the following rules: When D3 < 10 μm, T2 is 100℃~150℃ lower than T1; When D3≥10μm, T2=T1.

9. The method for preparing a high-density recrystallized silicon carbide component according to any one of claims 1 to 8, characterized in that: The first dispersant is polyvinyl pyrrolidone or isobutylene maleic anhydride copolymer, accounting for 0.5% to 3% of the total mass of the first silicon carbide powder and the second silicon carbide powder; The first binder is one of polyvinyl alcohol and sodium carboxymethyl cellulose or a mixture of the two, accounting for 0.5% to 3% of the total mass of the first silicon carbide powder and the second silicon carbide powder.

10. The method for preparing a high-density recrystallized silicon carbide component according to any one of claims 1 to 8, characterized in that: The second dispersant is polyvinyl pyrrolidone or isobutylene maleic anhydride copolymer, accounting for 0.5% to 3% of the total mass of the third silicon carbide powder and the fourth silicon carbide powder; The second binder is one of polyvinyl alcohol and sodium carboxymethyl cellulose or a mixture of the two, accounting for 0.5% to 3% of the total mass of the third silicon carbide powder and the fourth silicon carbide powder.

11. The method for preparing a high-density recrystallized silicon carbide component according to any one of claims 1 to 8, characterized in that: The solid content of the first slurry is not less than 60 wt %, and the solid content of the second slurry is in the range of 20 wt % to 60 wt %.

12. A high-density recrystallized silicon carbide component prepared by the method according to any one of claims 1 to 11.

13. The high-density recrystallized silicon carbide component according to claim 12, characterized in that: The density of the high-density recrystallized silicon carbide component is 2.75 g / cm 3 ~3.1g / cm 3 The porosity is 3% to 14%, and the average pore size is 0.5μm to 5μm.

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