Silicon nitride composite ceramic material for insulating support, and preparation method therefor

Abstract

The present disclosure belongs to the technical field of silicon nitride composite ceramic materials, and relates to a silicon nitride composite ceramic material for insulating support, and a preparation method therefor, overcoming defects of silicon nitride ceramic materials such as low toughness and inadequate temperature stability of volume resistivity. The preparation method of the present disclosure comprises: mixing raw materials to obtain a mixed powder, wherein a silicon nitride powder comprises a first silicon nitride powder and a second silicon nitride powder, the average particle size D50 of the first silicon nitride powder is 0.1-0.5 µm, the average particle size D50 of the second silicon nitride powder is 0.7-1.2 µm, and the mass ratio of the first silicon nitride powder to the second silicon nitride powder is (1-2):1; pressing and forming same into a green ceramic body; under a nitrogen atmosphere, keeping the temperature at 1550-1650ºC for 2-4 h; keeping the temperature at 1780-1850ºC for 2-4 h; lowering the temperature to 1200-1400ºC and maintaining said temperature for 2-4 h. The silicon nitride composite ceramic material has relatively high toughness and resistivity temperature stability.

Description

Silicon nitride composite ceramic material for insulating support and preparation method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure is based on and claims the priority of Chinese patent application with application number 202410376318.3 and application date March 29, 2024. The entire contents of the Chinese patent application are hereby introduced into this disclosure in their entirety. Technical Field

[0003] The present disclosure belongs to the technical field of silicon nitride composite ceramic materials, and particularly relates to a silicon nitride composite ceramic material for insulating support and a preparation method thereof. Background Art

[0004] High-voltage direct current (HVDC) transmission is an important means of high-voltage, large-capacity, long-distance power transmission and grid interconnection in my country, and is of great significance to the development of my country's energy landscape. Gas-insulated metal-enclosed transmission lines have the advantages of large transmission capacity, small footprint, high operational stability, and environmental friendliness. Buried directly underground or in tunnels, they can solve power transmission problems in special geographical environments and are an effective alternative to overhead transmission lines and cables. Basin and post insulators are the most critical insulating structures of gas-insulated equipment. Compared with the insulating gas, their insulation strength is relatively low, making them the insulation weak point of gas-insulated equipment. In recent years, basin and post insulator surface flashover failures have frequently occurred under high pressure, strong electric fields, and large temperature gradients.

[0005] Silicon nitride ceramics have the advantages of excellent insulation properties, high hardness, high strength, and low thermal expansion coefficient. They have great potential for application in gas-insulated equipment. However, their toughness is relatively insufficient. In high-seismic intensity areas such as southeastern Tibet, there is a risk of fracture under the combined action of electric fields and temperature fields. In addition, their resistivity is unstable at the service temperature of gas-insulated equipment (60-100 degrees Celsius), which will cause electric field distortion. Therefore, there is an urgent need to develop silicon nitride ceramic materials with high toughness and low temperature drift for the service environment of ultra-high voltage gas-insulated equipment.

[0006] Summary of the Invention

[0007] The embodiments of the present disclosure provide a silicon nitride composite ceramic material for insulating support and a preparation method thereof.

[0008] Therefore, the technical problem to be solved by the embodiments of the present disclosure is to overcome the defects of low toughness and insufficient volume resistivity temperature stability of silicon nitride ceramic materials used in ultra-high voltage gas insulation equipment in the prior art, thereby providing a silicon nitride composite ceramic material for insulation support with high toughness, high resistivity and temperature stability and a preparation method thereof.

[0009] To this end, the embodiments of the present disclosure provide the following technical solutions.

[0010] In a first aspect, an embodiment of the present disclosure provides a method for preparing a silicon nitride composite ceramic material for insulating support, comprising the following steps:

[0011] mixing silicon nitride powder, a sintering aid, and a binder to obtain a mixed powder;

[0012] The silicon nitride powder includes a first silicon nitride powder and a second silicon nitride powder; the average particle size D of the first silicon nitride powder 50 (D 50 The particle size corresponding to the cumulative particle size distribution percentage of the sample reaching 50% is 0.1 to 0.5 microns (μm); the average particle size of the second silicon nitride powder D 50 The mass ratio of the first silicon nitride powder to the second silicon nitride powder is (1-2):1;

[0013] Pressing the mixed powder into a shape to obtain a ceramic body;

[0014] Sintering is carried out in a protective atmosphere;

[0015] The sintering in a protective atmosphere comprises:

[0016] In nitrogen atmosphere, keep at 1550-1650℃ for 2-4 hours;

[0017] Heat to 1780-1850℃ and keep warm for 2-4h;

[0018] Cool down to 1200-1400℃ and keep warm for 2-4h.

[0019] In one embodiment, the silicon nitride powder, the sintering aid, and the binder are mixed to obtain a mixed powder that satisfies at least one of the following conditions:

[0020] The mass ratio of the silicon nitride powder to the sintering aid is (84-94):(6-16);

[0021] The binder is 1 to 2 wt.% (weight percentage) of the silicon nitride powder;

[0022] The binder comprises at least one of polyvinyl butyral or polyvinyl alcohol;

[0023] The silicon nitride powder has an α-phase content of ≥95 wt.%.

[0024] In one embodiment, the sintering aid includes yttrium oxide (Y2O3), aluminum oxide (Al2O3) and silicon dioxide (SiO2);

[0025] The mass ratio of Y2O3, Al2O3 and SiO2 is (3-5):(3-5):2.

[0026] In one embodiment, at least one of the following conditions is met:

[0027] In a nitrogen atmosphere, the temperature is increased at a rate of 10 to 15 degrees Celsius per minute (°C / min) to 1200 to 1300°C, then increased at a rate of 3 to 5°C / min to 1550 to 1650°C, and kept at this temperature for 2 to 4 hours;

[0028] The heating rate is 5-10℃ / min;

[0029] The cooling rate is 5-10℃ / min;

[0030] After the insulation is completed, the temperature is lowered to room temperature at 10-15℃ min.

[0031] In one embodiment, the press forming includes dry pressing and cold isostatic pressing.

[0032] In one embodiment, the dry pressing pressure is 50-100 MPa.

[0033] In one embodiment, the cold isostatic pressing pressure is 200-250 MPa.

[0034] In one embodiment, the step of pressing the mixed powder into a shape to obtain a ceramic body further comprises the step of degreasing the ceramic body;

[0035] In one embodiment, the degreasing treatment is carried out by keeping the temperature at 450-550° C. for 8-10 hours.

[0036] In one embodiment, the mixing of silicon nitride powder, a sintering aid, and a binder to obtain a mixed powder comprises: mixing the silicon nitride powder, the sintering aid, and the binder according to a proportion, and ball milling the mixture to obtain a mixed powder;

[0037] In one embodiment, the ball milling media for ball milling comprises silicon nitride balls and / or zirconium oxide balls;

[0038] In one embodiment, the size of the ball milling medium is 2 to 5 mm, and the ball-to-material ratio is controlled to be (3 to 4):1;

[0039] In one embodiment, the dispersion medium for ball milling is anhydrous ethanol;

[0040] In one embodiment, the ball milling speed is 200-400 revolutions per minute (r / min).

[0041] In a second aspect, an embodiment of the present disclosure provides a silicon nitride composite ceramic material for insulating support prepared according to the preparation method.

[0042] The technical solution of the embodiment of the present disclosure has the following advantages:

[0043] 1. The preparation method of the silicon nitride composite ceramic material for insulating support according to the embodiment of the present disclosure comprises: mixing silicon nitride powder, a sintering aid and a binder to obtain a mixed powder; the silicon nitride powder comprises a first silicon nitride powder and a second silicon nitride powder; the average particle size D of the first silicon nitride powder is 50 The average particle size of the second silicon nitride powder is 0.1 to 0.5 μm; 50 The silicon nitride powder is 0.7 to 1.2 μm; the mass ratio of the first silicon nitride powder to the second silicon nitride powder is (1 to 2):1; the mixed powder is pressed into shape to obtain a ceramic body; and sintered in a protective atmosphere; the sintering in a protective atmosphere comprises: in a nitrogen atmosphere, keeping warm at 1550 to 1650° C. for 2 to 4 hours; heating to 1780 to 1850° C. for 2 to 4 hours; cooling to 1200 to 1400° C. for 2 to 4 hours.

[0044] The disclosed embodiment uses silicon nitride powder as the main raw material, and obtains a bimodal particle size distribution powder by particle grading of powders of different particle sizes. During the high-temperature sintering process, the bimodal particle size powder is easy to rearrange the particles, and is easy to form self-toughening bimodal particle size β-phase columnar crystals when the α-phase silicon nitride (α-Si3N4) powder is transformed into the β-phase silicon nitride (β-Si3N4) powder, thereby improving the fracture toughness of the silicon nitride composite ceramic material.

[0045] After achieving initial densification at 1550-1650°C, the temperature is raised to 1780-1850°C and then maintained to further promote the growth and densification of β-phase columnar crystals. The temperature is then lowered to 1200-1400°C and maintained to promote grain boundary phase recrystallization and improve the temperature stability of the resistivity of the silicon nitride composite ceramic. This ensures that the silicon nitride composite ceramic material of the disclosed embodiments maintains a high resistivity at the service temperature of gas-insulated equipment (60-100°C), thus preventing electric field distortion at the service temperature.

[0046] 2. The sintering aids of the disclosed embodiments include Y2O3, Al2O3, and SiO2; the ratio of Y2O3, Al2O3, and SiO2 is (3-5):(3-5):2. The addition of the Y2O3, Al2O3, and SiO2 ternary composite sintering aid can form a liquid phase during the sintering process, promoting the rearrangement and phase transformation of α-phase silicon nitride powder particles, lowering the sintering temperature, and achieving densification of the silicon nitride ceramic.

[0047] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, rather than limiting the present disclosure. Other features and aspects of the present disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings herein are incorporated into and constitute a part of the specification. These drawings illustrate embodiments consistent with the present disclosure and, together with the specification, are used to explain the technical solutions of the embodiments of the present disclosure.

[0049] FIG1 is a flowchart illustrating a method for preparing a silicon nitride composite ceramic material for insulating support provided by an embodiment of the present disclosure;

[0050] FIG2 is a flowchart showing a method for preparing another silicon nitride composite ceramic material for insulating support provided by an embodiment of the present disclosure;

[0051] FIG3 shows a flowchart of a method for preparing another silicon nitride composite ceramic material for insulating support provided by an embodiment of the present disclosure;

[0052] FIG4 shows a scanning electron microscope photograph of a product provided in an embodiment of the present disclosure;

[0053] FIG5 shows a scanning electron microscope photograph of another product provided in an embodiment of the present disclosure;

[0054] FIG6 shows an X-ray diffraction (XRD) pattern of the product of Preparation Method 1 and Comparative Example 3 provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0055] Various exemplary embodiments, features, and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0056] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0057] The term "and / or" herein simply describes an association relationship between associated objects, indicating that three relationships can exist. For example, "A and / or B" can represent the existence of three situations: A alone, A and B simultaneously, and B alone. Furthermore, the term "at least one" herein refers to any combination of at least two of any one or more of a plurality of items. For example, "at least one of A, B, and C" can represent any one or more elements selected from the set consisting of A, B, and C.

[0058] In addition, numerous specific details are provided in the following detailed description to better illustrate the present disclosure. Those skilled in the art will appreciate that the present disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art are not described in detail in order to highlight the main points of the present disclosure.

[0059] In the related art, the polyvinyl alcohol in the following examples and comparative examples was purchased from Kemp (Xiamen) New Materials Co., Ltd. with a purity of >99%; the first silicon nitride powder was SN-E10 from Ube, Japan; and the second silicon nitride powder was SN-E05 from Ube, Japan.

[0060] The present disclosure provides a method for preparing a silicon nitride composite ceramic material for insulating support. FIG1 is a flowchart of the method for preparing a silicon nitride composite ceramic material for insulating support provided by the present disclosure. As shown in FIG1 , the preparation method includes steps 101 to 103:

[0061] Step 101: 45 g of the first silicon nitride powder, 45 g of the second silicon nitride powder, 5 g of Y2O3, 3 g of Al2O3, 2 g of SiO2 and 1.8 g of polyvinyl alcohol are mixed and ball-milled to obtain a mixed powder.

[0062] In one embodiment, the α-phase content in the first silicon nitride powder and the second silicon nitride powder is ≥ 95 wt.%. The average particle size D of the first silicon nitride powder 50 The average particle size of the second silicon nitride powder is 0.3 μm. 50 1.0μm.

[0063] In one embodiment, the ball milling medium is silicon nitride balls, which are 3 mm and 5 mm in size and are mixed in a mass ratio of 1:1. The ball-to-material ratio is controlled to be 3:1. The ball milling speed is 300 r / min, and the dispersion medium is anhydrous ethanol.

[0064] Step 102: dry-press the mixed powder obtained in step 101 at 50 MPa for 300 seconds, and then cold-isostatically press at 250 MPa for 300 seconds to obtain a ceramic body.

[0065] In one embodiment, the ceramic body is subjected to a degreasing treatment: the ceramic body is kept at 500° C. for 10 hours.

[0066] Step 103: raising the temperature of the degreased ceramic body to 1200° C. at a rate of 10° C. / min in a nitrogen atmosphere, and then raising the temperature to 1650° C. at a rate of 5° C. / min, and keeping the temperature for 2 hours;

[0067] Then increase the temperature to 1825℃ at a rate of 5℃ / min and keep it at this temperature for 3h;

[0068] Then the temperature was lowered to 1300°C at 5°C / min and kept at this temperature for 3h;

[0069] Then the temperature was lowered to room temperature at 10°C / min.

[0070] The present disclosure also provides a method for preparing a silicon nitride composite ceramic material for insulating support. FIG2 is a flowchart of another method for preparing a silicon nitride composite ceramic material for insulating support provided by the present disclosure. As shown in FIG2, the preparation method includes steps 201 to 203:

[0071] Step 201: 42 g of the first silicon nitride powder, 42 g of the second silicon nitride powder, 8 g of Y2O3, 4.8 g of Al2O3, 3.2 g of SiO2 and 1.68 g of polyvinyl alcohol are mixed and ball-milled to obtain a mixed powder.

[0072] In one embodiment, the α-phase content in the first silicon nitride powder and the second silicon nitride powder is ≥ 95 wt.%. The average particle size D of the first silicon nitride powder 50 The average particle size of the second silicon nitride powder is 0.3 μm. 50 1.0μm.

[0073] In one embodiment, the ball milling medium is silicon nitride balls, which are 3 mm and 5 mm in size and are mixed in a mass ratio of 1:1. The ball-to-material ratio is controlled to be 3:1. The ball milling speed is 300 r / min, and the dispersion medium is anhydrous ethanol.

[0074] Step 202: dry-press the mixed powder obtained in step 201 at 80 MPa for 300 seconds, and then cold-isostatically press at 200 MPa for 300 seconds to obtain a ceramic body.

[0075] In one embodiment, the ceramic body is subjected to a degreasing treatment: the ceramic body is kept at 550° C. for 8 hours.

[0076] Step 203: raising the temperature of the degreased ceramic body to 1300° C. at a rate of 15° C. / min in a nitrogen atmosphere, then raising the temperature to 1600° C. at a rate of 3° C. / min, and keeping the temperature for 3 hours;

[0077] Then increase the temperature to 1800℃ at a rate of 5℃ / min and keep it at this temperature for 4h;

[0078] Then the temperature was lowered to 1200°C at 5°C / min and kept at this temperature for 3h;

[0079] Then the temperature was lowered to room temperature at 10°C / min.

[0080] The present disclosure also provides a method for preparing a silicon nitride composite ceramic material for insulating support. FIG3 is a flowchart of another method for preparing a silicon nitride composite ceramic material for insulating support provided by the present disclosure. As shown in FIG3, the preparation method includes steps 301 to 303:

[0081] Step 301: 47 g of the first silicon nitride powder, 47 g of the second silicon nitride powder, 3 g of Y2O3, 1.8 g of Al2O3, 1.2 g of SiO2 and 1.88 g of polyvinyl alcohol are mixed and ball-milled to obtain a mixed powder.

[0082] In one embodiment, the α-phase content in the first silicon nitride powder and the second silicon nitride powder is ≥ 95 wt.%. The average particle size D of the first silicon nitride powder 50 The average particle size of the second silicon nitride powder is 0.3 μm. 50 1.0μm.

[0083] In one embodiment, the ball milling medium is silicon nitride balls, which are 3 mm and 5 mm in size and are mixed in a mass ratio of 1:1. The ball-to-material ratio is controlled to be 3:1. The ball milling speed is 300 r / min, and the dispersion medium is anhydrous ethanol.

[0084] Step 302: dry-press the mixed powder obtained in step 301 at 50 MPa for 300 seconds, and then cold-isostatically press at 250 MPa for 300 seconds to obtain a ceramic body.

[0085] In one embodiment, the ceramic body is subjected to a degreasing treatment: the ceramic body is kept at 500° C. for 10 hours.

[0086] Step 303: raising the temperature of the degreased ceramic body to 1200° C. at a rate of 10° C. / min in a nitrogen atmosphere, and then raising the temperature to 1650° C. at a rate of 5° C. / min, and keeping the temperature for 2 hours;

[0087] Then increase the temperature to 1825℃ at a rate of 5℃ / min and keep it at this temperature for 3h;

[0088] Then the temperature was lowered to 1300°C at 5°C / min and kept at this temperature for 3h;

[0089] Then the temperature was lowered to room temperature at 10°C / min.

[0090] Comparative Example 1

[0091] The preparation method of this comparative example is basically the same as that shown in FIG1 , except that the silicon nitride powder used in this comparative example is all the first silicon nitride powder.

[0092] Comparative Example 2

[0093] The preparation method of this comparative example is basically the same as that shown in FIG1 , except that the silicon nitride powder used in this comparative example is all the second silicon nitride powder.

[0094] Comparative Example 3

[0095] This comparative example provides a preparation method of a silicon nitride composite ceramic material, which is basically the same as the preparation method shown in FIG1 , except that, in this comparative example, after cooling to 1300° C., no heat preservation is performed, and the temperature is directly cooled to room temperature at a rate of 10° C. / min.

[0096] Test example

[0097] 1. Figures 4 and 5 are scanning electron microscope images of the product of the preparation method shown in Figure 1 and the product of Comparative Example 1, respectively. It can be seen from Figures 4 and 5 that the grading of powders with different particle sizes is conducive to the formation of uniformly distributed bimodal interlocking structure β-Si3N4 columnar crystals, which is beneficial to improving the fracture toughness of silicon nitride ceramics.

[0098] 2. FIG6 is an XRD pattern of the preparation method shown in FIG1 and the product of Comparative Example 3. As shown in FIG6 , keeping the temperature at 1300° C. can stabilize nitrogen-doped yttrium aluminosilicate (Y2SiAlO5N phase), which is beneficial to improving the temperature stability of the volume resistivity of silicon nitride ceramics.

[0099] 3. The properties of the silicon nitride composite ceramic materials prepared by the preparation methods shown in Figures 1 to 3 and Comparative Examples 1 to 3 were tested. As an example, the test process is:

[0100] Density: The silicon nitride composite ceramic material is ground and polished, and the volume density is measured using the Archimedes drainage method. The density is then calculated using the theoretical density.

[0101] Fracture toughness: Fracture toughness was measured using the single-edge notched beam (SENB) method. Samples were processed into a size of 3×6×30 mm and then artificially notched to simulate the introduction of cracks. The notches were approximately 3 mm deep and 0.2 mm wide. The fracture toughness of the samples was tested on a universal testing machine.

[0102] Volume resistivity: The resistivity test is carried out according to the three-electrode method required by GB / T1410 standard.

[0103] The test results are shown in Table 1.

[0104] Table 1 Properties of silicon nitride composite ceramic materials

[0105] As can be seen from Table 1, the silicon nitride composite ceramic material of the embodiment of the present disclosure has excellent high fracture toughness, high density, and significantly improved resistivity stability, and has broad application scenarios in the field of high-voltage gas power insulation.

[0106] From the comparison between the preparation method shown in FIG1 and Comparative Example 3, it can be seen that during the sintering process of the silicon nitride composite ceramic material, the temperature stability of its resistivity can be further improved by cooling and then keeping the temperature.

[0107] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications derived therefrom remain within the scope of protection of the present disclosure.

[0108] Those skilled in the art will understand that in the above-mentioned method of the specific implementation method, the writing order of each step does not mean a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic.

[0109] While various embodiments of the present disclosure have been described above, the above descriptions are illustrative, non-exhaustive, and not intended to be limiting of the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to existing technologies, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a silicon nitride composite ceramic material for insulating support, the method comprising: mixing silicon nitride powder, a sintering aid, and a binder to obtain a mixed powder; The silicon nitride powder includes a first silicon nitride powder and a second silicon nitride powder; the average particle size D of the first silicon nitride powder is 50 The average particle size of the second silicon nitride powder is 0.1 to 0.5 μm; 50 The mass ratio of the first silicon nitride powder to the second silicon nitride powder is (1-2):1; Pressing the mixed powder into a shape to obtain a ceramic body; Sintering is carried out in a protective atmosphere; The sintering in a protective atmosphere comprises: In nitrogen atmosphere, keep warm at 1550-1650℃ for 2-4h; Heat to 1780-1850℃ and keep warm for 2-4h; Cool down to 1200-1400℃ and keep warm for 2-4h.

2. The method for preparing the silicon nitride composite ceramic material for insulating support according to claim 1, wherein: The silicon nitride powder, sintering aid and binder are mixed to obtain a mixed powder that satisfies at least one of the following conditions: The mass ratio of the silicon nitride powder to the sintering aid is (84-94):(6-16); The binder is 1-2 wt.% of the mass of silicon nitride powder; The binder comprises at least one of polyvinyl butyral or polyvinyl alcohol; The silicon nitride powder has an α-phase content of ≥95 wt.%.

3. The method for preparing the silicon nitride composite ceramic material for insulating support according to claim 1, wherein: The sintering aids include Y2O3, Al2O3 and SiO2; The mass ratio of Y2O3, Al2O3 and SiO2 is (3-5):(3-5):

2.

4. The method for preparing the silicon nitride composite ceramic material for insulating support according to any one of claims 1 to 3, wherein: The preparation method satisfies at least one of the following conditions: The method of maintaining the temperature at 1550-1650° C. for 2-4 hours under a nitrogen atmosphere includes increasing the temperature to 1200-1300° C. at a rate of 10-15° C. / min under a nitrogen atmosphere, and then increasing the temperature to 1200-1300° C. at a rate of 3-5° C. / min. 1550~1650℃, keep warm for 2~4h; In the step of heating to 1780-1850° C. and keeping the temperature for 2-4 hours, the heating rate is 5-10° C. / min; In the step of cooling to 1200-1400° C. and keeping the temperature for 2-4 hours, the cooling rate is 5-10° C. / min; After the step of cooling to 1200-1400° C. and keeping the temperature for 2-4 hours is completed, the temperature is cooled to room temperature at a rate of 10-15° C. min.

5. The method for preparing the silicon nitride composite ceramic material for insulating support according to any one of claims 1 to 3, wherein: The pressing and molding of the mixed powder to obtain the ceramic body includes dry pressing and cold isostatic pressing.

6. The method for preparing the silicon nitride composite ceramic material for insulating support according to claim 5, wherein: The dry pressing pressure is 50-100 MPa.

7. The method for preparing the silicon nitride composite ceramic material for insulating support according to claim 5, wherein: The cold isostatic pressing pressure is 200-250 MPa.

8. The method for preparing the silicon nitride composite ceramic material for insulating support according to any one of claims 1 to 3, wherein: The step of pressing the mixed powder into a shape to obtain a ceramic body also includes the step of degreasing the ceramic body.

9. The method for preparing the silicon nitride composite ceramic material for insulating support according to claim 8, wherein: The degreasing treatment is carried out by keeping the temperature at 450-550° C. for 8-10 hours.

10. A silicon nitride composite ceramic material for insulating support prepared according to the preparation method according to any one of claims 1 to 9.

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