A method for preparing a large-size silicon nitride ceramic

Abstract

The present application relates to a kind of preparation methods of large size silicon nitride ceramics, the preparation method includes the following steps: first mixed sintering aid and dispersant, obtain first mixed powder;Second mixed silicon nitride powder and first mixed powder, obtain second mixed powder;Third mixed binder solution and second mixed powder, obtain silicon nitride slurry;Spray granulation is carried out using silicon nitride slurry, obtain spherical powder;Spherical powder is molded after cold isostatic pressing, obtain silicon nitride green body;Silicon nitride green body is degreased and hot isostatic pressing, obtain the large size silicon nitride ceramic of the present application provides preparation method can realize the preparation of large size silicon nitride ceramic, and process is simple, easy to mass production, and the density of the obtained large size silicon nitride ceramic is high, uniformity is good and performance is excellent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic products, and relates to a preparation method of a ceramic product, in particular to a preparation method of large-size silicon nitride ceramic. BACKGROUND

[0002] The silicon nitride ceramic has excellent properties such as high temperature resistance, wear resistance, high strength, high toughness, corrosion resistance, high hardness and light specific gravity, and has wide application and development prospect in the fields of aerospace, chemical metallurgy, mechanical processing and nuclear industry.

[0003] In the prior art, the preparation process of the silicon nitride ceramic includes but is not limited to flow casting, dry pressing and injection molding. Among them, the flow casting is suitable for preparing thin plate type ceramic and is widely used in the preparation of heat dissipation and packaging materials; the injection molding is mainly used for preparing small-size silicon nitride ceramic parts with complex structure; the dry pressing is suitable for small and medium-sized plate or disc ceramic parts; therefore, the flow casting, dry pressing and injection molding are not conducive to the preparation of large-size silicon nitride ceramic.

[0004] The sintering method mainly includes normal pressure sintering, gas pressure sintering and hot pressing and hot isostatic pressing sintering. The normal pressure sintering, also known as pressureless sintering, is to sinter the silicon nitride green body at 1700-1800 DEG C under normal pressure N2, and the sintered product has poor density and is difficult to prepare high-performance products; the gas pressure sintering generally uses high pressure N2 sintering of not more than 10 MPa, and due to the poor penetration of N2, when preparing large-size products, the N2 in the core is difficult to completely remove, so as to form a porous structure inside, resulting in poor consistency of the internal and external performance of the large-size material; the hot isostatic pressing sintering applies pressure in the sintering process, and promotes the densification of the material by high temperature and high pressure, but the existing technology has not studied the preparation of large-size silicon nitride ceramic by hot pressing sintering.

[0005] Therefore, it is necessary to provide a preparation method of high-performance large-size silicon nitride ceramic to realize the smooth preparation of large-size silicon nitride ceramic. SUMMARY

[0006] The application aims to provide a preparation method of large-size silicon nitride ceramic, which can realize the preparation of large-size silicon nitride ceramic, has simple process, is easy to mass produce, and has high density, good uniformity and excellent performance.

[0007] To achieve the application purpose, the application adopts the following technical scheme:

[0008] The application provides a preparation method of large-size silicon nitride ceramic, characterized by comprising the following steps:

[0009] (1) first mixing sintering aids and dispersants to obtain a first mixed powder;

[0010] (2) second mixing silicon nitride powder and the first mixed powder to obtain a second mixed powder;

[0011] (3) third mixing a binder solution and the second mixed powder to obtain a silicon nitride slurry;

[0012] (4) spray granulation using the silicon nitride slurry to obtain a spherical powder;

[0013] (5) cold isostatic pressing of the spherical powder after molding to obtain a silicon nitride green body;

[0014] (6) debinding and hot isostatic pressing of the silicon nitride green body to obtain the large-size silicon nitride ceramic.

[0015] The preparation method provided by the present application can realize the preparation of large-size silicon nitride ceramics, and has the advantages of simple process, easy mass production, high density, good uniformity and excellent performance of the obtained large-size silicon nitride ceramics. The preparation method provided by the present application realizes the uniform mixing of silicon nitride powder, sintering aids, dispersants and binders through first mixing, second mixing and third mixing in sequence, so that the composition of the silicon nitride slurry is uniform, and the size and composition of the obtained spherical powder are uniform. Then, by strictly controlling the conditions of cold isostatic pressing, debinding and hot isostatic pressing, the large-size silicon nitride ceramic with high density, good uniformity and excellent performance is obtained.

[0016] In the present application, "large size" refers to a length of more than 1.5 meters.

[0017] Preferably, the first mixing of step (1) is carried out in anhydrous ethanol.

[0018] Preferably, the sintering aids of step (1) include any one or a combination of at least two of Y2O3, CaF2 or MgO, and typical but non-limiting combinations include a combination of Y2O3 and CaF2, a combination of CaF2 and MgO, a combination of Y2O3 and MgO, or a combination of Y2O3, CaF2 and MgO, preferably a combination of Y2O3 and CaF2.

[0019] Preferably, the sintering aids of step (1) are a combination of Y2O3 and CaF2, and the mass ratio of Y2O3 to CaF2 is (2-4):1, for example, it can be 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0020] Preferably, the sintering aid of step (1) is used in an amount of 1-5 wt% of the silicon nitride powder, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt% or 5 wt%, but is not limited to the listed values, other unlisted values within the range of values are also applicable.

[0021] Preferably, the dispersant of step (1) comprises any one or a combination of at least two of herring oil, castor oil or triolein, typical but non-limiting combinations include a combination of herring oil and castor oil, a combination of castor oil and triolein, a combination of herring oil and triolein, or a combination of herring oil, castor oil and triolein.

[0022] Preferably, the dispersant of step (1) is used in an amount of 0.5-3 wt% of the silicon nitride powder, for example, it can be 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt% or 3 wt%, but is not limited to the listed values, other unlisted values within the range of values are also applicable.

[0023] Preferably, the second mixing of step (2) is performed in anhydrous ethanol.

[0024] Preferably, the silicon nitride powder of step (2) has an average particle size of 0.6-1.2 μm, for example, it can be 0.6 μm, 0.8 μm, 1 μm or 1.2 μm, but is not limited to the listed values, other unlisted values within the range of values are also applicable.

[0025] Preferably, the third mixing of step (3) is performed in anhydrous ethanol.

[0026] Preferably, the binder solution of step (3) is an ethanol solution of a binder.

[0027] Preferably, the binder of step (3) is used in an amount of 2 wt%-6 wt% of the silicon nitride powder, for example, it can be 2 wt%, 3 wt%, 4 wt%, 5 wt% or 6 wt%, but is not limited to the listed values, other unlisted values within the range of values are also applicable.

[0028] Preferably, the binder comprises polyvinyl butyral.

[0029] Preferably, the spherical powder of step (4) has an average particle size of 60-120 μm, for example, it can be 60 μm, 80 μm, 90 μm, 100 μm or 120 μm, but is not limited to the listed values, other unlisted values within the range of values are also applicable.

[0030] Preferably, the pressure of the cold isostatic pressing in step (5) is 200-250 MPa, for example, it can be 200 MPa, 210 MPa, 220 MPa, 230 MPa, 240 MPa or 250 MPa, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0031] Preferably, the time of the cold isostatic pressing in step (5) is 5-10 min, for example, it can be 5 min, 6 min, 8 min, 9 min or 10 min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0032] Preferably, the temperature of the debinding in step (6) is 500-600℃, for example, it can be 500℃, 520℃, 550℃, 580℃ or 600℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0033] The present application avoids the adverse effects of debinding on the density and component uniformity of the silicon nitride green body by debinding at a specific temperature, thereby ensuring the density and component uniformity of the large-size silicon nitride ceramic obtained after hot isostatic pressing.

[0034] Preferably, the time of the debinding in step (6) is 1-5 h, for example, it can be 1 h, 2 h, 3 h, 4 h or 5 h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0035] Preferably, the debinding in step (6) comprises sequentially performing a first heat treatment, a second heat treatment, a third heat treatment and a fourth heat treatment.

[0036] Preferably, the temperature of the first heat treatment is 900-1200℃, and the time is 1-3 h.

[0037] The temperature of the first heat treatment is 900-1200℃, for example, it can be 900℃, 1000℃, 1100℃, 1200℃ or 1300℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0038] The time of the first heat treatment is 1-3 h, for example, it can be 1 h, 1.5 h, 2 h, 2.5 h or 3 h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0039] Preferably, the temperature of the second heat treatment is 1300-1500℃, and the time is 1-3 h.

[0040] The temperature of the second heat treatment is 1300-1500℃, for example, it can be 1300℃, 1350℃, 1400℃, 1450℃ or 1500℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0041] The time of the second heat treatment is 1-3h, for example, it can be 1h, 1.5h, 2h, 2.5h or 3h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0042] Preferably, the temperature of the third heat treatment is 1600-1700℃, and the time is 2-4h.

[0043] The temperature of the third heat treatment is 1600-1700℃, for example, it can be 1600℃, 1630℃, 1650℃, 1680℃ or 1700℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0044] The time of the third heat treatment is 2-4h, for example, it can be 2h, 2.5h, 3h, 3.5h or 4h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0045] Preferably, the temperature of the fourth heat treatment is 1750-1850℃, and the time is 2-6h.

[0046] The temperature of the fourth heat treatment is 1750-1850℃, for example, it can be 1750℃, 1780℃, 1800℃, 1820℃ or 1850℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0047] The time of the fourth heat treatment is 2-6h, for example, it can be 2h, 3h, 4h, 5h or 6h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0048] Preferably, the pressure of the hot isostatic pressing in step (6) is 180-250MPa, for example, it can be 180MPa, 200MPa, 210MPa, 240MPa or 250MPa, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0049] As a preferred technical solution of the preparation method of the present application, the preparation method comprises the following steps:

[0050] (1) mixing the first mixed sintering aid and the dispersant in the powder mixing barrel to obtain a first mixed powder;

[0051] The first mixing is carried out in anhydrous ethanol.

[0052] The sintering aid includes any one or a combination of at least two of Y2O3, CaF2 or MgO, and the amount is 1-5wt% of the silicon nitride powder;

[0053] The dispersant includes any one or a combination of at least two of herring oil, castor oil or triolein, and the amount is 0.5-3wt% of the silicon nitride powder;

[0054] (2) The silicon nitride powder with an average particle size of 0.6-1.2μm is added into the first mixed powder to perform second mixing, and the second mixed powder is obtained;

[0055] (3) The binder solution is added into the second mixed powder to perform third mixing, and the silicon nitride slurry is obtained;

[0056] The binder solution is an ethanol solution of the binder, and the amount of the binder is 2wt%-6wt% of the silicon nitride powder;

[0057] The binder includes polyvinyl butyral;

[0058] (4) The spray granulation is performed using the silicon nitride slurry, and the spherical powder with an average particle size of 60-120μm is obtained;

[0059] (5) The spherical powder is loaded into a mold to perform cold isostatic pressing, and the silicon nitride green body is obtained;

[0060] The pressure of the cold isostatic pressing is 200-250MPa, and the time is 5-10min;

[0061] (6) The silicon nitride green body is subjected to debinding and hot isostatic pressing, and the large-size silicon nitride ceramic is obtained;

[0062] The temperature of the debinding is 500-600℃, and the time is 1-5h;

[0063] The hot isostatic pressing includes first, second, third and fourth heat treatments performed in sequence; the temperature of the first heat treatment is 900-1200℃, and the time is 1-3h; the temperature of the second heat treatment is 1300-1500℃, and the time is 1-3h; the temperature of the third heat treatment is 1600-1700℃, and the time is 2-4h; and the temperature of the fourth heat treatment is 1750-1850℃, and the time is 2-6h;

[0064] The pressure of the hot isostatic pressing is 180-250MPa.

[0065] Compared with the prior art, the present application has the following beneficial effects:

[0066] The preparation method can realize preparation of large-size silicon nitride ceramics, and has the advantages of simple process, easy mass production, high density, good uniformity and excellent performance of the obtained large-size silicon nitride ceramics; the preparation method realizes uniform mixing of silicon nitride powder, sintering aids, dispersants and binders through first mixing, second mixing and third mixing in sequence, so that the composition of the silicon nitride slurry is uniform, and the size and composition of the obtained spherical powder are uniform; and then through strict control of the conditions of cold isostatic pressing, debinding and hot isostatic pressing, the large-size silicon nitride ceramics with high density, good uniformity and excellent performance are obtained. DETAILED DESCRIPTION

[0067] The technical solutions of the present application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as specific limitations on the present application.

[0068] The length of the large-size silicon nitride ceramic obtained in the embodiment is 2m, which is only used to clearly illustrate the technical solutions of the present application, and should not be regarded as a further limitation on the present application.

[0069] Embodiment 1

[0070] The embodiment provides a preparation method of large-size silicon nitride ceramic, which comprises the following steps:

[0071] (1) mixing sintering aids and dispersants in a powder mixing barrel to obtain first mixed powder;

[0072] The first mixing is carried out in anhydrous ethanol;

[0073] The sintering aid is Y2O3, and the amount is 3wt% of the silicon nitride powder;

[0074] The dispersant is glycerol trioleate, and the amount is 2wt% of the silicon nitride powder;

[0075] (2) adding silicon nitride powder with an average particle size of 1μm into the first mixed powder to carry out second mixing, and obtaining second mixed powder;

[0076] (3) adding a binder solution into the second mixed powder to carry out third mixing, and obtaining silicon nitride slurry;

[0077] The binder solution is an ethanol solution of a binder, and the amount of the binder is 4wt% of the silicon nitride powder;

[0078] The binder comprises polyvinyl butyral;

[0079] (4) using the silicon nitride slurry to carry out spray granulation to obtain spherical powder with an average particle size of 90μm;

[0080] (5) the spherical powder is subjected to cold isostatic pressing to obtain a silicon nitride green body;

[0081] The pressure of the cold isostatic pressing is 220 MPa, and the time is 8 min;

[0082] (6) the silicon nitride green body is subjected to debinding and hot isostatic pressing to obtain the large-size silicon nitride ceramic;

[0083] The temperature of the debinding is 550 ℃, and the time is 3 h;

[0084] The hot isostatic pressing comprises sequentially performed first heat treatment, second heat treatment, third heat treatment and fourth heat treatment; the temperature of the first heat treatment is 1100 ℃, and the time is 2 h; the temperature of the second heat treatment is 1400 ℃, and the time is 2 h; the temperature of the third heat treatment is 1650 ℃, and the time is 3 h; and the temperature of the fourth heat treatment is 1800 ℃, and the time is 4 h;

[0085] The pressure of the hot isostatic pressing is 210 MPa.

[0086] Embodiment 2

[0087] The embodiment provides a preparation method of a large-size silicon nitride ceramic, and the preparation method comprises the following steps:

[0088] (1) a first mixed sintering aid and a dispersing agent are mixed in a powder mixing barrel to obtain a first mixed powder;

[0089] The first mixing is performed in anhydrous ethanol;

[0090] The sintering aid is Y2O3, and the amount is 1 wt% of the silicon nitride powder;

[0091] The dispersing agent is glycerol trioleate, and the amount is 0.5 wt% of the silicon nitride powder;

[0092] (2) the first mixed powder is added with silicon nitride powder with an average particle size of 1.2 μm to perform second mixing to obtain a second mixed powder;

[0093] (3) the second mixed powder is added with a binder solution to perform third mixing to obtain a silicon nitride slurry;

[0094] The binder solution is an ethanol solution of a binder, and the amount of the binder is 6 wt% of the silicon nitride powder;

[0095] The binder comprises polyvinyl butyral;

[0096] (4) spray granulation is performed using the silicon nitride slurry to obtain spherical powder with an average particle size of 120 μm;

[0097] (5) the spherical powder is subjected to cold isostatic pressing to obtain a green body of silicon nitride;

[0098] The pressure of the cold isostatic pressing is 200 MPa, and the time is 10 min.

[0099] (6) the green body of silicon nitride is subjected to debinding and hot isostatic pressing to obtain the large-size silicon nitride ceramic;

[0100] The temperature of the debinding is 500 DEG C, and the time is 5 h.

[0101] The hot isostatic pressing comprises sequentially performed first heat treatment, second heat treatment, third heat treatment and fourth heat treatment; the temperature of the first heat treatment is 1200 DEG C, and the time is 1 h; the temperature of the second heat treatment is 1500 DEG C, and the time is 1 h; the temperature of the third heat treatment is 1700 DEG C, and the time is 2 h; and the temperature of the fourth heat treatment is 1850 DEG C, and the time is 2 h.

[0102] The pressure of the hot isostatic pressing is 250 MPa.

[0103] Embodiment 3

[0104] The embodiment provides a preparation method of a large-size silicon nitride ceramic, and the preparation method comprises the following steps:

[0105] (1) a first mixed sintering aid and a dispersing agent are mixed in a powder mixing barrel to obtain a first mixed powder;

[0106] The first mixing is performed in anhydrous ethanol.

[0107] The sintering aid is Y2O3, and the amount is 5 wt% of the silicon nitride powder;

[0108] The dispersing agent is glyceryl trioleate, and the amount is 3 wt% of the silicon nitride powder;

[0109] (2) the first mixed powder is added with silicon nitride powder with an average particle size of 0.6 μm to perform second mixing to obtain a second mixed powder;

[0110] (3) a binder solution is added to the second mixed powder to perform third mixing to obtain a silicon nitride slurry;

[0111] The binder solution is an ethanol solution of a binder, and the amount of the binder is 2 wt% of the silicon nitride powder;

[0112] The binder comprises polyvinyl butyral.

[0113] (4) spray granulation is performed by using the silicon nitride slurry to obtain spherical powder with an average particle size of 60 μm;

[0114] (5) the spherical powder is molded by cold isostatic pressing to obtain a green body of silicon nitride;

[0115] The pressure of the cold isostatic pressing is 250 MPa, and the time is 5 min.

[0116] (6) the green body of silicon nitride is subjected to debinding and hot isostatic pressing to obtain the large-size silicon nitride ceramic;

[0117] The temperature of the debinding is 600 DEG C, and the time is 1 h.

[0118] The hot isostatic pressing comprises sequentially performed first heat treatment, second heat treatment, third heat treatment and fourth heat treatment; the temperature of the first heat treatment is 900 DEG C, and the time is 3 h; the temperature of the second heat treatment is 1300 DEG C, and the time is 3 h; the temperature of the third heat treatment is 1600 DEG C, and the time is 4 h; and the temperature of the fourth heat treatment is 1750 DEG C, and the time is 6 h.

[0119] The pressure of the hot isostatic pressing is 180 MPa.

[0120] Example 4

[0121] The example provides a preparation method of a large-size silicon nitride ceramic, wherein, except that the sintering aid is Y2O3 and CaF2 with a mass ratio of 2:1, the rest is the same as in example 1.

[0122] Example 5

[0123] The example provides a preparation method of a large-size silicon nitride ceramic, wherein, except that the sintering aid is Y2O3 and CaF2 with a mass ratio of 4:1, the rest is the same as in example 1.

[0124] Example 6

[0125] The example provides a preparation method of a large-size silicon nitride ceramic, wherein, except that the temperature of the debinding is 480 DEG C, the rest is the same as in example 1.

[0126] Example 7

[0127] The example provides a preparation method of a large-size silicon nitride ceramic, wherein, except that the temperature of the debinding is 620 DEG C, the rest is the same as in example 1.

[0128] Example 8

[0129] The example provides a preparation method of a large-size silicon nitride ceramic, wherein, except that the pressure of the cold isostatic pressing is 180 MPa, the rest is the same as in example 1.

[0130] Example 9

[0131] The embodiment provides a preparation method of large-size silicon nitride ceramic, which is the same as that in the embodiment 1 except that the pressure of cold isostatic pressing is 280 MPa.

[0132] Comparative example 1

[0133] The embodiment provides a preparation method of large-size silicon nitride ceramic, which comprises the following steps:

[0134] (1) mixing a first mixed sintering aid and a dispersing agent in a powder mixing barrel to obtain first mixed powder;

[0135] The first mixing is performed in anhydrous ethanol;

[0136] The sintering aid is Y2O3, and the amount is 3wt% of the silicon nitride powder;

[0137] The dispersing agent is glyceryl trioleate, and the amount is 2wt% of the silicon nitride powder;

[0138] (2) adding silicon nitride powder into the first mixed powder to perform second mixing to obtain second mixed powder;

[0139] (3) adding a binder solution into the second mixed powder to perform third mixing to obtain silicon nitride slurry;

[0140] The binder solution is an ethanol solution of a binder, and the amount of the binder is …wt% of the silicon nitride powder;

[0141] The binder comprises polyvinyl butylal;

[0142] (4) performing spray granulation by using the silicon nitride slurry to obtain spherical powder;

[0143] (5) performing cold isostatic pressing after the spherical powder is loaded into a mold to obtain silicon nitride green body;

[0144] The pressure of the cold isostatic pressing is 220 MPa, and the time is 8 min;

[0145] (6) performing hot isostatic pressing on the silicon nitride green body to obtain the large-size silicon nitride ceramic;

[0146] The temperature of the hot isostatic pressing is 1800 DEG C, and the time is 3 h.

[0147] Performance characterization

[0148] The thermal conductivity and the bending strength of the large-size silicon nitride ceramic obtained in the above embodiment and the comparative example are determined, and the obtained results are shown in Table 1.

[0149] Table 1

[0150] Thermal conductivity (W / (m·K)) Flexural strength (MPa) Example 1 66 873 Example 2 48 956 Example 3 69 830 Example 4 73 980 Example 5 70 927 Example 6 53 632 Example 7 65 815 Example 8 62 756 Example 9 67 850 Comparative Example 1 32 410

[0151] In summary, the preparation method can realize the preparation of large-size silicon nitride ceramics, and the process is simple, easy for mass production, and the obtained large-size silicon nitride ceramics has high density, good uniformity and excellent performance; the preparation method realizes the uniform mixing of silicon nitride powder, sintering aid, dispersant and binder by sequentially performing the first mixing, the second mixing and the third mixing, makes the composition of the silicon nitride slurry uniform, so that the size and composition of the obtained spherical powder are uniform; and then by strictly controlling the conditions of cold isostatic pressing, debinding and hot isostatic pressing, the large-size silicon nitride ceramics with high density, good uniformity and excellent performance is obtained.

[0152] The above merely describes the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for producing a large-sized silicon nitride ceramic having a length of 1.5 m or more, characterized by, The preparation method comprises the following steps: (1) first mixing sintering aids and dispersants to obtain first mixed powder; (2) second mixing silicon nitride powder and the first mixed powder to obtain second mixed powder; (3) third mixing binder solution and the second mixed powder to obtain silicon nitride slurry; (4) spray granulation using the silicon nitride slurry to obtain spherical powder; (5) cold isostatic pressing of the spherical powder after molding to obtain silicon nitride green body; (6) debinding and hot isostatic pressing of the silicon nitride green body to obtain the large-size silicon nitride ceramic; The pressure of the cold isostatic pressing in step (5) is 200-250 MPa; The time of the cold isostatic pressing in step (5) is 5-10 min; The temperature of the debinding in step (6) is 500-600 ℃; The time of the debinding in step (6) is 1-5 h; The hot isostatic pressing in step (6) comprises first heat treatment, second heat treatment, third heat treatment and fourth heat treatment performed in sequence; The temperature of the first heat treatment is 900-1200 ℃, and the time is 1-3 h; The temperature of the second heat treatment is 1300-1500 ℃, and the time is 1-3 h; The temperature of the third heat treatment is 1600-1700 ℃, and the time is 2-4 h; The temperature of the fourth heat treatment is 1750-1850 ℃, and the time is 2-6 h; The pressure of the hot isostatic pressing in step (6) is 180-250 MPa.

2. The production method according to claim 1, characterized by, The first mixing in step (1) is performed in anhydrous ethanol.

3. The preparation method according to claim 1, characterized in that, The sintering aids in step (1) comprise any one or a combination of at least two of Y2O3, CaF2 or MgO.

4. The preparation method according to claim 1, characterized in that, The amount of the sintering aids in step (1) is 1-5 wt% of the silicon nitride powder.

5. The method of claim 1, wherein, The dispersants in step (1) comprise any one or a combination of at least two of herring oil, castor oil or triolein.

6. The method of claim 1, wherein, The amount of the dispersants in step (1) is 0.5-3 wt% of the silicon nitride powder.

7. The method of any one of claims 1-6, wherein, The second mixing in step (2) is performed in anhydrous ethanol.

8. The method of any one of claims 1-6, wherein, The average particle size of the silicon nitride powder in step (2) is 0.6-1.2 μm.

9. The method of any one of claims 1-6, wherein, The third mixing in step (3) is performed in anhydrous ethanol.

10. The method of any one of claims 1-6, wherein, The binder solution in step (3) is an ethanol solution of the binder.

11. The method of any one of claims 1-6, wherein, The amount of the binder in step (3) is 2 wt%-6 wt% of the silicon nitride powder.

12. The method of any one of claims 1-6, wherein, The binder comprises polyvinyl butyral.

13. The method of any one of claims 1-6, wherein, The average particle size of the obtained spherical powder in step (4) is 60-120 μm.

14. The method of claim 1, wherein, The preparation method comprises the following steps: (1) mixing sintering aids and dispersants in a powder mixing barrel to obtain first mixed powder; The first mixing is performed in anhydrous ethanol; The sintering aids comprise any one or a combination of at least two of Y2O3, CaF2 or MgO, and the amount is 1-5 wt% of the silicon nitride powder; The dispersants comprise any one or a combination of at least two of herring oil, castor oil or triolein, and the amount is 0.5-3 wt% of the silicon nitride powder; (2) adding silicon nitride powder with an average particle size of 0.6-1.2 μm into the first mixed powder to perform second mixing to obtain second mixed powder; (3) adding a binder solution into the second mixed powder to perform a third mixing to obtain a silicon nitride slurry; the binder solution is an ethanol solution of a binder, and the amount of the binder is 2wt%-6wt% of the silicon nitride powder; the binder includes polyvinyl butyral; (4) using the silicon nitride slurry to perform spray granulation to obtain a spherical powder with an average particle size of 60-120μm; (5) performing cold isostatic pressing on the spherical powder after the spherical powder is loaded into a mold to obtain a silicon nitride green body; the pressure of the cold isostatic pressing is 200-250MPa, and the time is 5-10min; (6) performing debinding and hot isostatic pressing on the silicon nitride green body to obtain the large-size silicon nitride ceramic; the temperature of the debinding is 500-600℃, and the time is 1-5h; the hot isostatic pressing includes first heat treatment, second heat treatment, third heat treatment and fourth heat treatment performed in sequence; the temperature of the first heat treatment is 900-1200℃, and the time is 1-3h; the temperature of the second heat treatment is 1300-1500℃, and the time is 1-3h; the temperature of the third heat treatment is 1600-1700℃, and the time is 2-4h; the temperature of the fourth heat treatment is 1750-1850℃, and the time is 2-6h; the pressure of the hot isostatic pressing is 180-250MPa.