Super-thick silicon carbide ceramic plate and preparation method thereof

Abstract

The invention discloses a super-thick silicon carbide ceramic plate and a preparation method thereof. (1) preparing silicon carbide ceramic powder and an organic additive; (2) mixing and grinding an organic additive and distilled water, respectively adding silicon carbide ceramic powder, ammonia water, ammonium polyacrylate and n-caprylic alcohol, and grinding to obtain silicon carbide granulation powder 1, 2, 3 and 4 slurry; then respectively adding ammonium polyacrylate and n-caprylic alcohol, stirring and granulating, and spraying a release agent to obtain silicon carbide granulation powder 1, 2, 3 and 4; and (3) uniformly distributing the silicon carbide granulation powder in a mold in sequence, carrying out compression molding, demolding and drying, and firing to obtain the super-thick silicon carbide ceramic flat plate. The ultra-thick silicon carbide ceramic plate obtained by the invention has excellent bending strength and compressive strength, solves the problem of cracking in pressing and firing, and meets the use requirements; secondly, the insertion sequences of the powder layers are diversified, so that silicon carbide ceramic plate materials with different thicknesses can be obtained, different use requirements are met, and the wide market prospect is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramics, and in particular relates to an ultra-thick silicon carbide ceramic flat plate and a preparation method thereof. Background Art

[0002] Silicon carbide ceramic materials have good toughness and excellent strength retention rate at high temperature, creep resistance and thermal shock resistance, as well as excellent oxidation resistance and corrosion resistance. They are increasingly widely used in the fields of automobiles, mechanical processing, environmental protection, space technology, information electronics, energy, etc., and have short preparation cycles, low costs, direct molding, no need for a lot of machining, and are environmentally friendly. They have become excellent and irreplaceable structural ceramics in the industrial field. Ultra-thick silicon carbide ceramic materials, as an important category of silicon carbide ceramics, can be used as one of the high-performance bulletproof armor materials due to their high hardness and high elastic modulus. Silicon carbide ceramic bulletproof armor has been increasingly widely used in armor protection fields such as individual equipment, army armored weapon platforms, armed helicopters, and police and civilian special vehicles. Bulletproof armor generally requires silicon carbide ceramics to be 25-30mm thick. In special cases, some even reach more than 60mm, so new requirements are put forward for the thickness and performance of silicon carbide ceramic materials.

[0003] Normally, when the thickness of silicon carbide ceramic material exceeds a certain range, no matter what material it is, during the pressing process, there will be a density difference between the surface and the inside of the green body. In severe cases, the product will crack in the middle during the firing process. The main reason is that during the pressing process, the pressure first acts on the powder particles in contact with the flat surface of the pressure head, and then transmits the pressure to the inside of the mold through this part of the powder particles, and this transmission force will rapidly weaken as the powder particles absorb the force. As the pressure increases, the pressure on the powder particles in contact with the flat surface of the pressure head becomes greater and greater. When the pressure reaches a pressure greater than the pressure that the powder particles can withstand, the powder particles deform and break. At this time, it is more difficult to transmit the pressure to the center of the mold, resulting in a density difference between the surface and the inside of the green body. The greater the pressure, the greater the density difference, which eventually leads to the appearance of cracking.

[0004] At present, there have been some studies on solving the cracking phenomenon of silicon carbide ceramic materials. CN116789454A discloses a silicon carbide ceramic and a preparation method thereof. The preparation method of the silicon carbide ceramic includes: granulation, molding, coating, and sintering. By adding a thermal conductive filler and a polyethylene film to the preparation method at the same time, a low-crack silicon carbide ceramic is obtained; CN111138195A discloses a preparation method of silicon carbide ceramic, by changing the sintering system of the silicon carbide ceramic, wherein the main materials, in parts by weight, include 80 to 92 parts of silicon carbide, 2 to 4 parts of lanthanum oxide, 1 to 3 parts of fumed silica, 1 to 2 parts of aluminum oxide, and 0.5 to 1 part of aluminum diboride, the sintering temperature is significantly reduced, so that the sintering density and mechanical properties of the silicon carbide ceramic are improved. Although the above studies have effectively improved the density of silicon carbide ceramics and reduced the occurrence of cracking, they do not involve the preparation of ultra-thick silicon carbide ceramics, and cannot solve the problem of cracking caused by density differences between different layers during the pressing process of ultra-thick silicon carbide ceramics. At present, no efficient preparation method for ultra-thick silicon carbide ceramic materials has been found. Summary of the invention

[0005] The present invention discloses an ultra-thick silicon carbide ceramic flat plate and a preparation method thereof. The prepared silicon carbide granulated powders of different particle strengths are uniformly distributed in a mold in sequence, pressed, molded, demolded, and dried, and then fired into an ultra-thick silicon carbide ceramic flat plate. The present invention makes the pressure transmission in the deformation, crushing, and densification process of the silicon carbide granulated powder smoother and more reasonable; secondly, adding a mixed powder layer between different powder layers can effectively reduce the density difference between different powder layers, and effectively solve the cracking problem of the ultra-thick ceramic flat plate material during the pressing and firing process.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing an ultra-thick silicon carbide ceramic plate, the method comprising the following steps:

[0008] (1) Preparation of silicon carbide ceramic powder: Silicon carbide powder, carbon black, boron carbide and graphite powder are uniformly mixed to prepare silicon carbide ceramic powder;

[0009] (2) Preparation of organic additives: dextrin, polyvinyl alcohol, polyethylene glycol and glycerol are uniformly mixed to prepare organic additives;

[0010] (3) Preparation of silicon carbide granulated powders 1, 2, 3, and 4:

[0011] a: the organic additive prepared in step (2) and distilled water are mixed and ground thoroughly, and then the silicon carbide ceramic powder, ammonia water, ammonium polyacrylate and n-octanol prepared in step (1) are added respectively and ground evenly to obtain slurries of silicon carbide granulated powders 1, 2, 3 and 4;

[0012] b: adding ammonium polyacrylate and n-octanol to the slurry prepared in step (a), stirring and granulating, spraying the granulated powder with a release agent, sodium tripolyphosphate, while stirring, so that the release agent is evenly attached to the surface of the granulated powder, to prepare silicon carbide granulated powders 1, 2, 3, and 4;

[0013] (4) Distributing: Distribute the silicon carbide granulated powder prepared in step (3) evenly in the mold in the order of granulated powder 4, 3, 2, 1, 2, 3, 4;

[0014] (5) Pressing and firing: After pressing, demolding and drying, it is fired into an ultra-thick silicon carbide ceramic plate.

[0015] Furthermore, in step (1), the mass ratio of silicon carbide powder, carbon black, boron carbide and graphite powder is 100:1-2:6-9:1-3.

[0016] Furthermore, in step (2), the mass ratio of dextrin, polyvinyl alcohol, polyethylene glycol and glycerol is 40:8-20:8-20:5-40.

[0017] Furthermore, the amounts of organic additives added to the silicon carbide granulated powders 1, 2, 3, and 4 slurries in step (3) a are 2-3.5 parts, 2.5-4.5 parts, 3.2-5.5 parts, and 4.1-7.5 parts, respectively, in parts by weight; the amounts of distilled water, silicon carbide ceramic powder, ammonia water, ammonium polyacrylate, and n-octanol added are 100-120 parts, 90-110 parts, 0.5-2 parts, 1-5 parts, and 0.3-1 parts, respectively, in parts by weight; the sufficient grinding time is 1-3 hours; and the continued grinding time is 30-50 hours.

[0018] Furthermore, in step (3) b, the amounts of ammonium polyacrylate and n-octanol added are 0.1-0.5% and 0.01-1% of the total volume of the slurry, respectively; and the stirring time is 4-8h.

[0019] Furthermore, the thickness of each layer of the silicon carbide granulated powder in step (4) is 3-4 mm.

[0020] Furthermore, the order of inserting the silicon carbide granulated powder in step (4) can also be: inserting a mixed powder layer of 40-60vol% silicon carbide granulated powder 4 and 40-60vol% silicon carbide granulated powder 3 in the middle of silicon carbide granulated powder 4, 3 and / or silicon carbide granulated powder 3, 4; and / or inserting a mixed powder layer of 40-60vol% silicon carbide granulated powder 3 and 40-60vol% silicon carbide granulated powder 2 in the middle of silicon carbide granulated powder 3, 2 and / or silicon carbide granulated powder 2, 3; and / or inserting a mixed powder layer of 40-60vol% silicon carbide granulated powder 2 and 40-60vol% silicon carbide granulated powder 1 in the middle of silicon carbide granulated powder 2, 1 and / or silicon carbide granulated powder 1, 2.

[0021] Furthermore, the order of inserting the silicon carbide granulated powder in step (4) can also be: inserting 60-70 vol% silicon carbide granulated powder 4 and 30-40 vol% silicon carbide granulated powder 3 in the middle of silicon carbide granulated powder 4, 3 and / or silicon carbide granulated powder 3, 4, and two mixed powder layers of 30-40 vol% silicon carbide granulated powder 4 and 60-70 vol% silicon carbide granulated powder 3; and / or inserting 60-70 vol% silicon carbide granulated powder 3 in the middle of silicon carbide granulated powder 3, 2 and / or silicon carbide granulated powder 2, 3. Silicon granulated powder 3 and 30-40vol% silicon carbide granulated powder 2, and two mixed powder layers of 30-40vol% silicon carbide granulated powder 3 and 60-70vol% silicon carbide granulated powder 2; and / or 60-70vol% silicon carbide granulated powder 2 and 30-40vol% silicon carbide granulated powder 1 are inserted between silicon carbide granulated powders 2, 1 and / or silicon carbide granulated powders 1, 2, and two mixed powder layers of 30-40vol% silicon carbide granulated powder 2 and 60-70vol% silicon carbide granulated powder 1 are inserted.

[0022] Furthermore, in step (5), the pressing pressure is 50-120 MPa; the drying temperature is 80-120° C., and the time is 6-12 h; the firing temperature is 2100-2200° C., and the firing time is 3-6 h.

[0023] The invention provides an ultra-thick silicon carbide ceramic flat plate.

[0024] Technical principle: The present invention prepares silicon carbide granulated powders with different particle strengths, and then evenly distributes the silicon carbide granulated powder with the highest particle strength in the outermost layer of the mold through a distributor, while the silicon carbide granulated powder with the lowest particle strength is evenly distributed in the innermost layer of the mold. During the pressing process, the external pressure can be effectively transmitted to the center of the mold, so that the silicon carbide granulated powder in the central layer is first deformed, crushed and densified. As the pressure increases, the silicon carbide granulated powder in the outer layer is deformed, crushed and densified in turn, and finally the entire ultra-thick silicon carbide ceramic flat body is evenly densified; secondly, adding a mixed powder layer between different powder layers can effectively reduce the cracking phenomenon caused by density difference between different powder layers. The pressing mechanism is as follows: Figure 1 shown.

[0025] Beneficial effects:

[0026] The present invention distributes the prepared silicon carbide granulated powder in an appropriate order according to the different particle strengths, so that the pressure transmission during the deformation, crushing and densification of the silicon carbide granulated powder is smoother and more reasonable; secondly, adding a mixed powder layer between different powder layers can effectively reduce the cracking phenomenon caused by the density difference between different powder layers, and effectively solve the cracking problem of ultra-thick silicon carbide ceramic flat plate materials during the pressing and firing process. The obtained ultra-thick silicon carbide ceramic flat plate has excellent bending strength and compressive strength, which meets the use requirements. Secondly, the insertion order of the powder layer of the present invention is diverse, and silicon carbide ceramic flat plate materials of different thicknesses can be obtained to meet different use requirements, and have broad market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a state diagram of silicon carbide granulated powder with different particle strengths in the mold during the pressing process of this scheme;

[0028] Figure 2 This is a state diagram of silicon carbide granulated powder in a mold during the pressing process under a conventional scheme;

[0029] Figure 3 The prepared ultra-thick silicon carbide ceramic plate. DETAILED DESCRIPTION

[0030] The following will combine the contents in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] A method for preparing ultra-thick silicon carbide ceramics comprises the following steps:

[0033] (1) Preparation of silicon carbide ceramic powder: Silicon carbide powder, carbon black, boron carbide, and graphite powder are uniformly mixed in a mass ratio of 100:1.5:8:2 to prepare silicon carbide ceramic powder;

[0034] (2) Preparation of organic additives: dextrin, polyvinyl alcohol, polyethylene glycol, and glycerol are uniformly mixed in a mass ratio of 40:15:13:10 to prepare an organic additive;

[0035] (3) Preparation of silicon carbide granulated powder 1: Add 2.5 parts of organic additives and 110 parts of distilled water into a ball mill and grind for 2 hours to fully dissolve the organic additives and mix them evenly; then add 100 parts of silicon carbide ceramic powder, 1 part of ammonia water, 3 parts of ammonium polyacrylate, and 0.5 parts of n-octanol and continue grinding for 40 hours; transfer the slurry to a stirring barrel, add 0.3% ammonium polyacrylate and 0.1% n-octanol to the total volume of the slurry and stir for 6 hours; use a spray granulator to granulate, then put the granulated powder into a mixer and spray the release agent sodium tripolyphosphate while stirring, so that the release agent is evenly attached to the surface of the granulated powder to prepare a low-strength silicon carbide granulated powder 1 for later use;

[0036] (4) Preparation of silicon carbide granulated powder 2: Add 4 parts of organic additives and 110 parts of distilled water into a ball mill and grind for 2 hours to fully dissolve and mix the organic additives; then add 100 parts of silicon carbide ceramic powder, 1 part of ammonia water, 3 parts of ammonium polyacrylate, and 0.5 parts of n-octanol and continue grinding for 40 hours; transfer the slurry to a stirring barrel, add 0.3% ammonium polyacrylate and 0.1% n-octanol to the total volume of the slurry and stir for 6 hours; use a spray granulator to granulate, then put the granulated powder into a mixer and spray the release agent sodium tripolyphosphate while stirring, so that the release agent is evenly attached to the surface of the granulated powder to prepare medium-strength silicon carbide granulated powder 2 for use;

[0037] (5) Preparation of silicon carbide granulated powder 3: Add 5 parts of organic additives and 110 parts of distilled water into a ball mill and grind for 2 hours to fully dissolve the organic additives and mix them evenly; then add 100 parts of silicon carbide ceramic powder, 1 part of ammonia water, 3 parts of ammonium polyacrylate, and 0.5 parts of n-octanol and continue grinding for 40 hours; transfer the slurry to a stirring barrel, add 0.3% ammonium polyacrylate and 0.1% n-octanol to the total volume of the slurry and stir for 6 hours; use a spray granulator to granulate, then put the granulated powder into a mixer and spray the release agent sodium tripolyphosphate while stirring, so that the release agent is evenly attached to the surface of the granulated powder to prepare medium-strength silicon carbide granulated powder 3 for use;

[0038] (6) Preparation of silicon carbide granulated powder 4: Add 6.5 parts of organic additives and 110 parts of distilled water into a ball mill and grind for 2 hours to fully dissolve the organic additives and mix them evenly; then add 100 parts of silicon carbide ceramic powder, 1 part of ammonia water, 3 parts of ammonium polyacrylate, and 0.5 parts of n-octanol and continue grinding for 40 hours; transfer the slurry to a stirring barrel, add 0.3% ammonium polyacrylate and 0.1% n-octanol to the total volume of the slurry and stir for 6 hours; use a spray granulator to granulate, then put the granulated powder into a mixer and spray the release agent sodium tripolyphosphate while stirring, so that the release agent is evenly attached to the surface of the granulated powder to prepare high-strength silicon carbide granulated powder 4 for use;

[0039] (7) Distribution: The silicon carbide granulated powder is loaded into the distributor cylinder in the order of granulated powder 4, granulated powder 3, granulated powder 2, granulated powder 1, granulated powder 2, granulated powder 3, and granulated powder 4, and evenly distributed in the mold from the bottom of the mold through the distributor. The thickness of each layer is 3 mm, and there are 7 layers in total, with a size of 360 mm×360 mm×21 mm.

[0040] (8) Pressing and sintering: The powder layer obtained in step (7) is pressed at a pressure of 70 MPa, and after demolding, it is dried at a temperature of 80°C for 6 hours; after drying, it is fired at a temperature of 2100°C for 3.5 hours to obtain an ultra-thick silicon carbide ceramic plate.

[0041] Example 2

[0042] A method for preparing ultra-thick silicon carbide ceramics comprises the following steps:

[0043] (1) Distribution: The silicon carbide granulated powder prepared in Example 1 is loaded into the distributor cylinder in the order of granulated powder 4, granulated powder 3, granulated powder 2, granulated powder 1, granulated powder 2, granulated powder 3, and granulated powder 4, and evenly distributed in the mold from the bottom of the mold through the distributor, wherein a mixed powder layer of 50 vol% silicon carbide granulated powder 4 and 50 vol% silicon carbide granulated powder 3 is inserted between silicon carbide granulated powders 4 and 3 and silicon carbide granulated powders 3 and 4, respectively, each layer is 3 mm thick, a total of 9 layers, and the size is 360 mm×360 mm×27 mm;

[0044] (2) Pressing and firing: The powder layer obtained in step (1) is pressed at a pressure of 90 MPa, and after demolding, it is dried at a temperature of 90°C for 7 hours. After drying, it is fired at a temperature of 2130°C for 4 hours to obtain an ultra-thick silicon carbide ceramic plate.

[0045] Example 3

[0046] A method for preparing ultra-thick silicon carbide ceramics comprises the following steps:

[0047] (1) Distribution: The silicon carbide granulated powder prepared in Example 1 is loaded into the distributor cylinder in the order of granulated powder 4, granulated powder 3, granulated powder 2, granulated powder 1, granulated powder 2, granulated powder 3, and granulated powder 4, and evenly distributed in the mold from the bottom of the mold through the distributor, wherein a mixed powder of 66 vol% silicon carbide granulated powder 4 and 34 vol% silicon carbide granulated powder 3 and 34 vol% silicon carbide granulated powder 4 are inserted in the middle of silicon carbide granulated powders 4 and 3 and granulated powders 3 and 4, respectively. Two mixed powder layers of granular powder 4 and 66vol% silicon carbide granulated powder 3; a mixed powder of 66vol% silicon carbide granulated powder 3 and 34vol% silicon carbide granulated powder 2, and two mixed powder layers of 34vol% silicon carbide granulated powder 3 and 66vol% silicon carbide granulated powder 2 are inserted between silicon carbide granulated powder 3, 2 and granulated powder 2, 3, respectively, each layer is 3mm thick, a total of 15 layers, and the size is 360mm×360mm×45mm;

[0048] (2) Pressing and sintering: The powder layer obtained in step (1) is pressed at a pressure of 110 MPa, and after demolding, it is dried at a temperature of 115°C for 10 hours. After drying, it is fired at a temperature of 2180°C for 5.5 hours to obtain an ultra-thick silicon carbide ceramic plate.

[0049] Comparative Example 1

[0050] A method for preparing silicon carbide ceramics comprises the following steps:

[0051] (1) Distribution: The medium-strength granulated powder 3 prepared in Example 1 is loaded into the distributor cylinder and evenly distributed in the mold from the bottom of the mold through the distributor, with a size of 360 mm × 360 mm × 21 mm;

[0052] (2) Pressing and sintering: The powder layer obtained in step (1) is pressed at a pressure of 70 MPa, and after demolding, it is dried at a temperature of 80°C for 6 hours; after drying, it is fired at a temperature of 2100°C for 3.5 hours to obtain a silicon carbide ceramic flat plate.

[0053] Comparative Example 2

[0054] A method for preparing silicon carbide ceramics comprises the following steps:

[0055] (1) Distribution: The high-strength granulated powder 4 prepared in Example 1 is loaded into the distributor cylinder and evenly distributed in the mold from the bottom of the mold through the distributor, with a size of 360 mm × 360 mm × 27 mm;

[0056] (2) Pressing and sintering: The powder layer obtained in step (1) is pressed at a pressure of 90 MPa, and after demolding, it is dried at a temperature of 90°C for 7 hours. After drying, it is sintered at a temperature of 2130°C for 4 hours to obtain a silicon carbide ceramic flat plate.

[0057] Comparative Example 3

[0058] A method for preparing silicon carbide ceramics comprises the following steps:

[0059] (1) Distribution: The medium-strength granulated powder 3 prepared in Example 1 is loaded into the distributor cylinder and evenly distributed in the mold from the bottom of the mold through the distributor, with a size of 360 mm × 360 mm × 45 mm;

[0060] (2) Pressing and sintering: The powder layer obtained in step (1) is pressed at a pressure of 110 MPa, and after demolding, it is dried at a temperature of 115°C for 10 hours. After drying, it is sintered at a temperature of 2180°C for 5.5 hours to obtain a silicon carbide ceramic flat plate.

[0061] Test example

[0062] Studies have shown that cracks in silicon carbide ceramics are small in size and few in number, and have high bending strength and compressive strength. The present application indirectly evaluates the crack conditions of the prepared silicon carbide ceramics through bending strength and compressive strength.

[0063] The silicon carbide ceramic plates obtained in Examples 1-3 of the present application and Comparative Examples 1-3 were tested for bending strength and compressive strength.

[0064] Table 1 Test results of silicon carbide ceramic plates of Examples 1-3 and Comparative Examples 1-3

[0065]

[0066]

[0067] As shown in Table 1, the ultra-thick silicon carbide ceramic flat plate obtained by the present invention has excellent bending strength and compressive strength. Under the same initial thickness conditions, the bending strength and compressive strength of the silicon carbide ceramic flat plate obtained by the present invention are better than those using conventional single granulation powder (pressing process such as Figure 2 ) can effectively reduce the occurrence of cracking. Figure 3 The ultra-thick silicon carbide ceramic flat plate is obtained by the present invention.

Claims

1. A method for preparing an ultra-thick silicon carbide ceramic plate, Its characteristics are: The method comprises the following steps: (1) Preparation of silicon carbide ceramic powder: Silicon carbide powder, carbon black, boron carbide and graphite powder are uniformly mixed to prepare silicon carbide ceramic powder; (2) Preparation of organic additives: dextrin, polyvinyl alcohol, polyethylene glycol and glycerol are uniformly mixed to prepare organic additives; (3) Preparation of silicon carbide granulated powders 1, 2, 3, and 4: a: the organic additive prepared in step (2) and distilled water are mixed and ground thoroughly, and then the silicon carbide ceramic powder, ammonia water, ammonium polyacrylate and n-octanol prepared in step (1) are added respectively and ground evenly to obtain slurries of silicon carbide granulated powders 1, 2, 3 and 4; b: adding ammonium polyacrylate and n-octanol to the slurry prepared in step (a), stirring and granulating, spraying the granulated powder with a release agent, sodium tripolyphosphate, while stirring, so that the release agent is evenly attached to the surface of the granulated powder, to prepare silicon carbide granulated powders 1, 2, 3, and 4; (4) Distributing: Distribute the silicon carbide granulated powder prepared in step (3) evenly in the mold in the order of granulated powder 4, 3, 2, 1, 2, 3, 4; (5) Pressing and firing: After pressing, demolding and drying, it is fired into an ultra-thick silicon carbide ceramic plate.

2. The preparation method according to claim 1, Its characteristics are: The mass ratio of the silicon carbide powder, carbon black, boron carbide and graphite powder in step (1) is 100:1-2:6-9:1-3.

3. The preparation method according to claim 1, Its characteristics are: In step (2), the mass ratio of dextrin, polyvinyl alcohol, polyethylene glycol and glycerol is 40:8-20:8-20:5-40.

4. The preparation method according to claim 1, Its characteristics are: In step (3) a, the amounts of organic additives added to the silicon carbide granulated powders 1, 2, 3, and 4 slurries are 2-3.5 parts, 2.5-4.5 parts, 3.2-5.5 parts, and 4.1-7.5 parts, respectively, in parts by weight; the amounts of distilled water, silicon carbide ceramic powder, ammonia water, ammonium polyacrylate, and n-octanol added are 100-120 parts, 90-110 parts, 0.5-2 parts, 1-5 parts, and 0.3-1 parts, respectively, in parts by weight; the sufficient grinding time is 1-3 hours; and the continued grinding time is 30-50 hours.

5. The preparation method according to claim 1, Its characteristics are: In step (3) b, the amounts of ammonium polyacrylate and n-octanol added are 0.1-0.5% and 0.01-1% of the total volume of the slurry respectively; and the stirring time is 4-8h.

6. The preparation method according to claim 1, Its characteristics are: The thickness of each layer of the silicon carbide granulated powder in step (4) is 3-4 mm.

7. The preparation method according to claim 1, Its characteristics are: The order of inserting the silicon carbide granulated powder in step (4) can also be: inserting a mixed powder layer of 40-60vol% silicon carbide granulated powder 4 and 40-60vol% silicon carbide granulated powder 3 in the middle of silicon carbide granulated powder 4, 3 and / or silicon carbide granulated powder 3, 4; and / or inserting a mixed powder layer of 40-60vol% silicon carbide granulated powder 3 and 40-60vol% silicon carbide granulated powder 2 in the middle of silicon carbide granulated powder 3, 2 and / or silicon carbide granulated powder 2, 3; and / or inserting a mixed powder layer of 40-60vol% silicon carbide granulated powder 2 and 40-60vol% silicon carbide granulated powder 1 in the middle of silicon carbide granulated powder 2, 1 and / or silicon carbide granulated powder 1, 2.

8. The preparation method according to claim 1, Its characteristics are: The order of inserting the silicon carbide granulated powder in step (4) can also be: inserting 60-70 vol% silicon carbide granulated powder 4 and 30-40 vol% silicon carbide granulated powder 3 in the middle of silicon carbide granulated powder 4, 3 and / or silicon carbide granulated powder 3, 4, and two mixed powder layers of 30-40 vol% silicon carbide granulated powder 4 and 60-70 vol% silicon carbide granulated powder 3; and / or inserting 60-70 vol% silicon carbide granulated powder 3 in the middle of silicon carbide granulated powder 3, 2 and / or silicon carbide granulated powder 2, 3. Powder 3 and 30-40vol% silicon carbide granulated powder 2, and two mixed powder layers of 30-40vol% silicon carbide granulated powder 3 and 60-70vol% silicon carbide granulated powder 2; and / or 60-70vol% silicon carbide granulated powder 2 and 30-40vol% silicon carbide granulated powder 1 are inserted between silicon carbide granulated powders 2, 1 and / or silicon carbide granulated powders 1, 2, and two mixed powder layers of 30-40vol% silicon carbide granulated powder 2 and 60-70vol% silicon carbide granulated powder 1.

9. The preparation method according to claim 1, Its characteristics are: In step (5), the pressing pressure is 50-120 MPa; the drying temperature is 80-120° C., and the time is 6-12 h; the firing temperature is 2100-2200° C., and the firing time is 3-6 h.

10. An ultra-thick silicon carbide ceramic flat plate prepared according to the preparation method according to any one of claims 1 to 9.

Images