Silicon nitride coating and preparation method and application thereof

Abstract

The invention relates to a silicon nitride coating and a preparation method and application thereof.The silicon nitride coating comprises a main material and a reinforcing material, the main material comprises silicon nitride powder, the reinforcing material comprises silicon carbide powder and boron nitride powder, and the preparation method of the silicon nitride coating comprises the steps that 1, the main material, the reinforcing material and a solvent are mixed, a mixed coating is obtained; the main body material comprises silicon nitride powder, and the reinforcing material comprises silicon carbide powder and boron nitride powder; and (2) spraying the mixed coating onto a substrate, and curing to obtain the silicon nitride coating. According to the silicon nitride coating provided by the invention, specific components are adopted, the silicon nitride powder is used as a main body material, the silicon carbide powder and the boron nitride powder are used as reinforcing materials, and the silicon nitride powder, the silicon carbide powder and the boron nitride powder cooperate with one another, so that the strength and the adhesive force of the silicon nitride coating are jointly improved, and cracking of the coating is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and in particular to a silicon nitride coating and a preparation method and application thereof. Background Art

[0002] When semiconductor and photovoltaic equipment are depositing films for their products, they often deposit corresponding films inside the equipment containers. As the use time accumulates, the deposits become thicker and thicker. At this time, both the deposits themselves and the equipment containers will be affected by factors such as thermal stress, and will crack, fall off, break, and other problems. In addition to improving the quality of the equipment container itself, the service life of the equipment is often increased by adding protective coatings. Conventional high-temperature coatings often face many problems and it is difficult to protect the equipment from damage by deposits for a long time.

[0003] Silicon carbide coating is a conventional high-temperature resistant ceramic with a high melting temperature. CN117510236A discloses a method for preparing silicon carbide coating with methylsilane, which uses methylsilane as a precursor of silicon carbide coating and forms a dense silicon carbide polycrystalline film through the CVD / CVI process. The crystal growth and film formation efficiency are high and almost defect-free, and it is a good SiC coating CVD / CVI deposition raw material. However, the silicon carbide coating prepared by the above conventional precursor method and conventional raw materials often faces technical problems such as cracking and the coating performance cannot be fully demonstrated.

[0004] Silicon nitride coating has excellent high temperature stability, high strength, self-lubrication and heat shock resistance, and is a good choice for protecting base materials such as quartz. Generally, silicon nitride is formed at a high temperature of 1200°C by SiH4 and NH3 using the CVD method. For example, CN101567419A discloses a method for forming a silicon nitride film with good insulation properties as a protective film for MTJ elements, using a CVD device to make a film forming device and using SiH4, NH3 and N2 as film forming gases to form a silicon nitride film only on the entire surface including the MTJ element part. However, the CVD method used has high requirements for equipment and process, low preparation efficiency, and is relatively expensive. In addition, the silicon nitride coating obtained by SiH4 and NH3 at a high temperature of 1200°C has poor density, the coating is easy to crack, the barrier ability is weak, the strength is poor, and the performance cannot be improved.

[0005] In addition to density as a key property of the coating, the expansion coefficient and wettability of the coating are also crucial. If the expansion coefficient of the coating itself varies greatly, it will easily destroy its own strength. If the coating is not wet enough or the connecting bond energy is too weak, it will cause the coating to have poor adhesion on the substrate and easy to fall off.

[0006] Therefore, in view of the defects of the coating in the prior art, providing a silicon nitride coating that is not easy to crack, has high strength and strong adhesion has become a problem that needs to be solved urgently. Summary of the invention

[0007] In order to solve the above technical problems, the purpose of the present invention is to provide a silicon nitride coating and a preparation method and application thereof. The silicon nitride coating provided by the present invention adopts a specific composition, with silicon nitride powder as the main material, silicon carbide powder and boron nitride powder as reinforcing materials, and the strength and adhesion of the silicon nitride coating are jointly improved through the mutual synergy between silicon nitride powder, silicon carbide powder and boron nitride powder, and the cracking phenomenon of the coating is effectively avoided.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a silicon nitride coating, wherein the silicon nitride coating comprises a main material and a reinforcing material, wherein the main material comprises silicon nitride powder, and the reinforcing material comprises silicon carbide powder and boron nitride powder.

[0010] The silicon nitride coating provided by the present invention uses silicon nitride powder as the main material, and is doped with silicon carbide powder and boron nitride powder as reinforcing materials. The silicon nitride powder has the advantages of high-temperature stability, high strength, self-lubrication and heat shock resistance, and is a good choice as a coating material; the silicon carbide powder serves as a reinforcing agent for adjusting the formula, and can generate a connection for the overall system of the coating. The cubic crystal form of the silicon carbide powder can make up for the hexagonal crystal form of silicon nitride, so that the silicon carbide powder and the silicon nitride powder can complement each other in performance. The performance of the silicon nitride coating can be assisted and enhanced through the differentiated mechanical properties of the silicon carbide powder and the main material, and the actual performance of the silicon nitride coating is promoted to be closer to the theoretical value; the boron nitride powder has a layered structure and high chemical stability, can eliminate the internal stress of the coating, promote the self-slip ability of the coating during shrinkage, and make the coating not easy to crack. The non-connected wrapping structure formed can improve the impact resistance of the coating.

[0011] The silicon nitride coating provided by the present invention adopts a specific composition, with silicon nitride powder as the main material, and silicon carbide powder and boron nitride powder as reinforcing materials. Through the mutual synergy between silicon nitride powder, silicon carbide powder and boron nitride powder, the strength and adhesion of the silicon nitride coating are jointly improved, and the cracking phenomenon of the coating is effectively avoided.

[0012] Preferably, the silicon nitride coating further comprises a connecting material.

[0013] Preferably, the connecting material comprises polysilazane.

[0014] The present invention adopts polysilazane as a connecting material in connecting powders in the silicon nitride coating, can realize the connection of powders under a relatively low temperature and a relatively simple preparation environment, and at the same time, improves the quality of the silicon nitride coating, and has excellent economic value.

[0015] Preferably, the polysilazane includes any one of polymethylsilazane, polymethylvinylsilazane or polymethylphenylsilazane, or a combination of at least two thereof.

[0016] In the silicon nitride coating of the present invention, the type of polysilazane used as the connecting material will affect the quality and performance of the coating.

[0017] In a second aspect, the present invention provides a method for preparing the silicon nitride coating as described in the first aspect, the preparation method comprising:

[0018] (1) mixing a main material, a reinforcing material and a solvent to obtain a mixed coating; the main material comprises silicon nitride powder, and the reinforcing material comprises silicon carbide powder and boron nitride powder;

[0019] (2) Spraying the mixed coating onto the substrate and curing it to obtain the silicon nitride coating.

[0020] The preparation method of the silicon nitride coating provided by the present invention is simple, low-cost, and has low equipment requirements. In addition, through the synergistic effect of using silicon nitride powder as the main material and silicon carbide powder and boron nitride powder as reinforcing materials, combined with the spraying process and curing process after mixing, a silicon nitride coating with high strength, strong adhesion and not easy to crack is prepared.

[0021] Preferably, based on the total mass of the mixed raw materials in step (1) being 100wt%, the added amount of the silicon nitride powder is 45-50wt%, for example, 45wt%, 46wt%, 47wt%, 48wt%, 49wt% or 50wt%.

[0022] In the preparation method of the silicon nitride coating provided by the present invention, by optimizing the addition amount of silicon nitride powder, cracking of the coating is further reduced, and the strength and stability of the silicon nitride coating are greatly improved.

[0023] Preferably, based on the total mass of the mixed raw materials in step (1) being 100wt%, the added amount of the silicon carbide powder is 3-7wt%, for example, 3wt%, 4wt%, 5wt%, 6wt% or 7wt%.

[0024] In the preparation method of the silicon nitride coating of the present invention, the addition amount of silicon carbide powder is optimized to ensure the auxiliary enhancement effect on the actual effect of the silicon nitride coating, and at the same time, the quality of the coating can be effectively improved.

[0025] Preferably, based on the total mass of the mixed raw materials in step (1) as 100wt%, the added amount of the boron nitride powder is 0.5-3wt%, for example, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt% or 3wt%, etc., preferably 1-3wt%.

[0026] The present invention further optimizes the amount of boron nitride powder added in the preparation method of the silicon nitride coating, which can ensure the self-slip ability of the coating during shrinkage, avoid cracking of the coating, and at the same time improve the strength of the coating.

[0027] Preferably, the particle size of the silicon nitride powder is 1200-8000 mesh, for example, 1200 mesh, 2000 mesh, 3000 mesh, 4000 mesh, 5000 mesh, 6000 mesh, 7000 mesh or 8000 mesh.

[0028] Preferably, the particle size of the silicon carbide powder is 2000-4000 mesh, for example, 2000 mesh, 2200 mesh, 2400 mesh, 2600 mesh, 2800 mesh, 3000 mesh, 3200 mesh, 3400 mesh, 3600 mesh, 3800 mesh or 4000 mesh.

[0029] Preferably, the particle size of the boron nitride powder is 1000-2000 mesh, for example, 1000 mesh, 1200 mesh, 1400 mesh, 1600 mesh, 1800 mesh or 2000 mesh.

[0030] In the present invention, further selecting silicon nitride powder, silicon carbide powder and boron nitride powder with appropriate particle sizes can avoid the occurrence of coating defects and reduced coating strength caused by excessively large or small particle sizes.

[0031] Preferably, the solvent in step (1) comprises a first solvent and a second solvent.

[0032] In the method for preparing the silicon nitride coating provided by the present invention, the first solvent and the second solvent are compounded with each other to adjust the dispersion of the powder and the film-forming agent, and to promote the curing speed of the coating during the film-forming process.

[0033] Preferably, the first solvent includes any one of trimethylbenzene, ethyl lactate or acetone, or a combination of at least two thereof.

[0034] Preferably, the second solvent comprises any one of xylene, ethyl acetate or tetrahydrofuran, or a combination of at least two thereof.

[0035] Preferably, based on the total mass of the mixed raw materials in step (1) being 100wt%, the amount of the first solvent added is 8-12wt%, for example 8wt%, 9wt%, 10wt%, 11wt% or 12wt%, etc.

[0036] Preferably, based on the total mass of the mixed raw materials in step (1) being 100wt%, the amount of the second solvent added is 4-6wt%, for example 4wt%, 4.5wt%, 5wt%, 5.5wt% or 6wt%, etc.

[0037] The present invention improves the wettability of the coating during the preparation process by optimizing the contents of the first solvent and the second solvent, thereby improving the adhesion of the coating to the substrate during use and preventing the coating from falling off.

[0038] Preferably, the mixed raw materials in step (1) also include connecting materials.

[0039] Preferably, based on the total mass of the mixed raw materials in step (1) as 100wt%, the amount of the connecting material added is 24-35wt%, for example, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt% or 35wt%, etc.

[0040] If the content of the film-forming agent in the present invention is too much or too little, the strength of the silicon nitride coating will be reduced and the coating performance will be affected.

[0041] Preferably, the mixed raw materials in step (1) further include any one of a dispersant, a defoamer or a leveling agent, or a combination of at least two of them, preferably a dispersant, a defoamer and a leveling agent.

[0042] The mixed raw materials of the silicon nitride coating provided by the present invention further include dispersants, defoamers and leveling agents, which are used in combination with the main material and the reinforcing material in a solvent. The dispersant promotes the complete combination and uniform dispersion of the film-forming agent, the solvent and the powder material; the defoamer can promote the release of bubbles generated during the mixing of the raw materials, thereby avoiding defects in the coating during the film preparation process; and the addition of the leveling agent can make the coating smoother, thereby avoiding defects in the spraying process.

[0043] Preferably, based on the total mass of the mixed raw materials in step (1) being 100wt%, the added amount of the dispersant is 0.5-2wt%, for example 0.5wt%, 1wt%, 1.5wt% or 2wt%.

[0044] Preferably, the dispersant includes any one of Tech-596 dispersant, Tech-5044 dispersant or Tech-5204 dispersant, or a combination of at least two thereof.

[0045] Preferably, based on the total mass of the mixed raw materials in step (1) as 100wt%, the added amount of the defoaming agent is 0.1-0.5wt%, for example, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt% or 0.5wt%.

[0046] Preferably, the defoaming agent includes any one of Tech-353 defoaming agent, Tech-210A defoaming agent or Tech-330 defoaming agent, or a combination of at least two thereof.

[0047] Preferably, based on the total mass of the mixed raw materials in step (1) being 100wt%, the added amount of the leveling agent is 0.05-0.2wt%, such as 0.05wt%, 0.1wt%, 0.15wt% or 0.2wt%.

[0048] Preferably, the leveling agent includes Tech-38101 leveling agent and / or Tech-UV2725 leveling agent.

[0049] Preferably, the substrate in step (2) is also washed and dried before spraying.

[0050] In the present invention, the material of the substrate in step (2) is not specifically limited, including but not limited to quartz glass, alumina ceramics or metal materials, and those skilled in the art can select according to their needs.

[0051] Preferably, the washing is performed by flushing with a spray gun.

[0052] In the present invention, there is no specific limitation on the washing solvent, including but not limited to ethanol or water, etc. Those skilled in the art can select it according to needs.

[0053] Preferably, the spraying thickness in step (2) is 20-50 μm, for example, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm.

[0054] The present invention further optimizes the spraying thickness, and can ensure that the obtained silicon nitride coating has excellent quality and strong performance.

[0055] Preferably, the spraying equipment in step (2) is a spray gun.

[0056] Preferably, the caliber of the spray gun is 0.5-1 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm.

[0057] In the process of preparing the silicon nitride coating of the present invention, selecting a suitable spray gun is helpful to improve the preparation quality of the coating.

[0058] Preferably, after the spraying in step (2), the substrate sprayed with the mixed coating is also rotated.

[0059] After spraying is completed, the present invention continuously rotates the substrate coated with the coating paint, which helps to improve the uniformity of the paint on the substrate.

[0060] Preferably, the linear speed of the rotation is 0.4-0.8 m / s, such as 0.4 m / s, 0.5 m / s, 0.6 m / s, 0.7 m / s or 0.8 m / s.

[0061] Preferably, the rotation time is 20-40 min, such as 20 min, 25 min, 30 min, 35 min or 40 min.

[0062] Preferably, the curing in step (2) is carried out under a nitrogen atmosphere and / or an inert atmosphere.

[0063] Preferably, the curing in step (2) includes a first curing stage, a second curing stage, a third curing stage and a fourth curing stage which are performed successively.

[0064] In the preparation method provided by the present invention, the curing process is optimized. In the first curing stage, the organic solvent is removed. In the second curing stage, the film-forming agent is cured. In the third curing stage, some unstable groups in the coating are removed. In the fourth curing stage, the film-forming agent bonds the powder materials together to form a continuous and dense coating. The process setting from the first curing stage to the fourth curing stage can avoid the generation of gas in the coating due to an overly fast curing process, and can prevent the organic components in the coating from volatilizing incompletely, thereby affecting the performance of the resulting coating.

[0065] Preferably, the temperature of the first curing stage is 80-120°C, for example, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, etc.

[0066] Preferably, the heating time of the first curing stage is 8-16 min, for example, 8 min, 10 min, 12 min, 14 min or 16 min.

[0067] Preferably, the insulation time of the first curing stage is 30-60 min, for example, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0068] Preferably, the temperature of the second curing stage is 160-200°C, for example, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C or 200°C.

[0069] Preferably, the heating time of the second curing stage is 8-16 min, for example, 8 min, 10 min, 12 min, 14 min or 16 min.

[0070] Preferably, the insulation time of the second curing stage is 20-40 min, for example, 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, 32 min, 34 min, 36 min, 38 min or 40 min, etc.

[0071] Preferably, the temperature of the third curing stage is 550-650°C, for example, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C or 650°C.

[0072] Preferably, the heating time of the third curing stage is 80-120 min, for example, 80 min, 85 min, 90 min, 95 min, 100 min, 105 min, 110 min, 115 min or 120 min.

[0073] Preferably, the insulation time of the third curing stage is 60-90 min, for example, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min or 90 min.

[0074] Preferably, the temperature of the fourth curing stage is 950-1100°C, for example, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, 1050°C, 1060°C, 1070°C, 1080°C, 1090°C or 1100°C, etc.

[0075] Preferably, the heating time of the fourth curing stage is 60-90 min, for example, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min or 90 min.

[0076] Preferably, the insulation time of the fourth curing stage is 20-30 min, for example, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min.

[0077] As a preferred technical method of the present invention, the preparation method comprises:

[0078] (I) Based on the total mass of the mixed raw materials as 100wt%, a main material of silicon nitride powder with a content of 45-50wt%, a reinforcing material composed of silicon carbide powder with a content of 3-7wt% and boron nitride powder with a content of 0.5-3wt%, a connecting material with a content of 24-35wt%, a dispersant with a content of 0.5-2wt%, a defoamer with a content of 0.1-0.5wt%, a leveling agent with a content of 0.05-0.2wt%, a first solvent with a content of 8-12wt% and a second solvent with a content of 4-6wt% are mixed to obtain a mixed coating; wherein the particle size of the silicon nitride powder is 1200-8000 mesh, the particle size of the silicon carbide powder is 2000-4000 mesh, and the particle size of the boron nitride powder is 1000-2000 mesh;

[0079] washing and drying the substrate to obtain the pretreated substrate;

[0080] (II) using a spray gun with a caliber of 0.5-1 mm, spraying the mixed coating onto the pretreated substrate to a thickness of 20-50 μm, and then rotating the sprayed substrate at a linear speed of 0.4-0.8 m / s for 20-40 min to obtain the substrate coated with the mixed coating;

[0081] (III) Drying the substrate coated with the mixed coating, and then placing the dried substrate coated with the mixed coating in a nitrogen atmosphere and / or an inert atmosphere for curing, first heating from room temperature to 80-120°C within 8-16 minutes, keeping the temperature for 30-60 minutes to perform a first curing stage, then heating to 160-200°C within 8-16 minutes, keeping the temperature for 20-40 minutes to perform a second curing stage, then heating again to 550-650°C within 80-120 minutes, keeping the temperature for 60-90 minutes to perform a third curing stage, then heating to 950-1100°C within 60-90 minutes, keeping the temperature for 20-30 minutes to perform a fourth curing stage, and finally obtaining the silicon nitride coating.

[0082] In the present invention, "room temperature" refers to a temperature of 25±5°C, for example, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C, etc.

[0083] In a third aspect, the present invention provides an application of the silicon nitride coating as described in the first aspect, wherein the silicon nitride coating is applied in the semiconductor or photovoltaic field.

[0084] The silicon nitride coating provided by the present invention is suitable for any application field that can be thought of by those skilled in the art.

[0085] Compared with the prior art, the present invention has at least the following beneficial effects:

[0086] (1) In the silicon nitride coating provided by the present invention, silicon nitride powder is used as the main material, and silicon carbide powder and boron nitride powder as reinforcing materials are doped. Silicon nitride powder has the advantages of high temperature stability, high strength, self-lubrication and heat shock resistance, and is a good choice as a coating material; silicon carbide powder is used as a reinforcing agent for adjusting the formula, and its cubic crystal form can make up for the hexagonal silicon nitride. The mechanical properties of silicon carbide powder and the main material are differentiated and can also assist in strengthening the silicon nitride coating, and promote the actual performance of the silicon nitride coating to be closer to the theoretical value; boron nitride powder has a layered structure, high chemical stability, can eliminate the internal stress of the coating, promote the self-slip ability of the coating during shrinkage, avoid cracking of the coating, and the non-connected package structure formed improves the impact resistance of the coating. Through the mutual synergy between silicon nitride powder, silicon carbide powder and boron nitride powder, the strength and adhesion of the silicon nitride coating are jointly improved, and the cracking phenomenon of the coating is effectively avoided.

[0087] (2) In the present invention, polysilazane is used as a connecting material in connecting powders in the silicon nitride coating, which can achieve powder connection at a relatively low temperature and in a relatively simple preparation environment. At the same time, the quality of the silicon nitride coating is improved, and it has excellent economic value.

[0088] (3) The preparation method of the silicon nitride coating provided by the present invention is simple, low-cost, and has low equipment requirements. In addition, through the synergistic effect of using silicon nitride powder as the main material and silicon carbide powder and boron nitride powder as reinforcing materials, combined with the spraying process and curing process after mixing, a silicon nitride coating with high strength, strong adhesion and not easy to crack is prepared.

[0089] (4) The mixed raw materials of the silicon nitride coating provided by the present invention further include dispersants, defoamers and leveling agents, which are used in combination with the main material and the reinforcing material in a solvent. The dispersant promotes the complete combination and uniform dispersion of the film-forming agent, the solvent and the powder material; the defoamer can promote the release of bubbles generated during the mixing of the raw materials, thereby avoiding the occurrence of defects in the coating during the film preparation process; and the addition of the leveling agent can make the coating smoother and reduce the occurrence of defects during the spraying construction. DETAILED DESCRIPTION

[0090] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0091] The various types of dispersants, defoamers and leveling agents used in the following examples are all commercially available from Taige Additives.

[0092] Example 1

[0093] This embodiment provides a method for preparing a silicon nitride coating, and the specific preparation process is as follows:

[0094] (I) Based on the total mass of the mixed raw materials as 100wt%, 47wt% of silicon nitride powder, 6wt% of silicon carbide powder, 2wt% of boron nitride powder, 28wt% of polymethylsilazane, 1.5wt% of Tech-596 dispersant, 0.3wt% of Tech-353 defoamer, 0.2wt% of Tech-38101 leveling agent and a mixed solvent consisting of 10wt% of trimethylbenzene and 5wt% of xylene are mixed to obtain a mixed coating; wherein the particle size of the silicon nitride powder is 3000 mesh, the particle size of the silicon carbide powder is 3000 mesh, and the particle size of the boron nitride powder is 1500 mesh.

[0095] The inner wall of the quartz tube is washed with a spray gun containing anhydrous ethanol, and after drying, a pretreated inner wall of the quartz tube is obtained.

[0096] (II) The mixed coating obtained in step (I) is uniformly sprayed onto the inner wall of the pretreated quartz tube using a spray gun with a diameter of 0.8 mm, and the spraying thickness is 35 μm. Then, the inner wall of the quartz tube after spraying is rotated at a linear speed of 0.6 m / s for 30 min to obtain the inner wall of the quartz tube coated with the mixed coating.

[0097] (III) The inner wall of the quartz tube coated with the mixed coating obtained in step (II) is dried, and then placed in a sintering furnace for curing under a nitrogen atmosphere, firstly heating from 25°C to 100°C within 10 minutes, keeping the temperature for 50 minutes, then heating to 180°C within 12 minutes, keeping the temperature for 30 minutes, then heating to 600°C within 100 minutes, keeping the temperature for 80 minutes, then heating to 1000°C within 80 minutes, keeping the temperature for 25 minutes, and finally preparing a silicon nitride coating on the surface of the inner wall of the quartz tube.

[0098] Example 2

[0099] This embodiment provides a method for preparing a silicon nitride coating, and the specific preparation process is as follows:

[0100] (I) Based on the total mass of the mixed raw materials as 100wt%, 45wt% of silicon nitride powder, 7wt% of silicon carbide powder, 1wt% of boron nitride powder, 32wt% of polymethylsilazane, 0.5wt% of Tech-5044 dispersant, 0.4wt% of Tech-210A defoamer, 0.1wt% of Tech-38101 leveling agent, 9wt% of acetone and 5wt% of tetrahydrofuran are mixed with a mixed solvent to obtain a mixed coating; wherein the particle size of the silicon nitride powder is 1200 mesh, the particle size of the silicon carbide powder is 4000 mesh, and the particle size of the boron nitride powder is 1000 mesh.

[0101] The inner wall of the quartz tube is washed with a spray gun containing anhydrous ethanol, and after drying, a pretreated inner wall of the quartz tube is obtained.

[0102] (II) The mixed coating obtained in step (I) is uniformly sprayed onto the inner wall of the pretreated quartz tube using a spray gun with a diameter of 0.5 mm, and the spraying thickness is 20 μm. Then, the inner wall of the quartz tube after spraying is rotated at a linear speed of 0.4 m / s for 20 min to obtain the inner wall of the quartz tube coated with the mixed coating.

[0103] (III) The inner wall of the quartz tube coated with the mixed coating obtained in step (II) is dried, and then placed in a sintering furnace for curing under a nitrogen atmosphere, firstly heating from 25°C to 80°C within 8 minutes, keeping the temperature for 60 minutes, then heating to 200°C within 16 minutes, keeping the temperature for 20 minutes, then heating to 550°C within 80 minutes, keeping the temperature for 90 minutes, then heating to 1100°C within 90 minutes, keeping the temperature for 20 minutes, and finally preparing a silicon nitride coating on the surface of the inner wall of the quartz tube.

[0104] Example 3

[0105] This embodiment provides a method for preparing a silicon nitride coating, and the specific preparation process is as follows:

[0106] (I) Based on the total mass of the mixed raw materials as 100wt%, 50wt% of silicon nitride powder, 3wt% of silicon carbide powder and 3wt% of boron nitride powder, 24wt% of polymethylsilazane, 1.5wt% of Tech-5204 dispersant, 0.3wt% of Tech-330 defoamer, 0.2wt% of Tech-38101 leveling agent and a mixed solvent consisting of 12wt% of ethyl lactate and 6wt% of ethyl acetate are mixed to obtain a mixed coating; wherein the particle size of the silicon nitride powder is 5000 mesh, the particle size of the silicon carbide powder is 2000 mesh, and the particle size of the boron nitride powder is 2000 mesh.

[0107] The inner wall of the quartz tube is washed with a spray gun containing anhydrous ethanol, and after drying, a pretreated inner wall of the quartz tube is obtained.

[0108] (II) using a spray gun with a diameter of 1 mm, the mixed coating obtained in step (I) is evenly sprayed onto the inner wall of the pretreated quartz tube, and the spraying thickness is 50 μm. Then, the inner wall of the quartz tube after spraying is rotated at a linear speed of 0.8 m / s for 40 min to obtain the inner wall of the quartz tube coated with the mixed coating.

[0109] (III) The inner wall of the quartz tube coated with the mixed coating obtained in step (II) is dried, and then placed in a sintering furnace for curing under a nitrogen atmosphere, firstly heating from 25°C to 120°C within 16 minutes, keeping the temperature for 30 minutes, then heating to 160°C within 8 minutes, keeping the temperature for 30 minutes, then heating to 650°C within 80 minutes, keeping the temperature for 60 minutes, then heating to 950°C within 60 minutes, keeping the temperature for 20 minutes, and finally preparing a silicon nitride coating on the inner wall of the quartz tube.

[0110] Example 4

[0111] The difference between this embodiment and embodiment 1 is that: in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 40wt%, the amount of silicon carbide powder added is 7wt%, the amount of boron nitride powder added is 3wt%, the amount of polymethylsilazane added is 31wt%, the amount of Tech-596 dispersant added is 1.3wt%, the amount of Tech-353 defoamer added is 0.5wt%, the amount of Tech-38101 leveling agent added is 0.2wt%, the amount of trimethylbenzene organic solvent added is 11wt%, and the amount of xylene organic solvent added is 6wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0112] Example 5

[0113] The difference between this embodiment and embodiment 1 is that: in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 55wt%, the amount of silicon carbide powder added is 3wt%, the amount of boron nitride powder added is 1wt%, the amount of polymethylsilazane added is 27wt%, the amount of Tech-596 dispersant added is 1.5wt%, the amount of Tech-353 defoamer added is 0.3wt%, the amount of Tech-38101 leveling agent added is 0.2wt%, the amount of trimethylbenzene organic solvent added is 8wt%, and the amount of xylene organic solvent added is 4wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0114] Example 6

[0115] The difference between this embodiment and embodiment 1 is that: in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 50wt%, the amount of silicon carbide powder added is 2wt%, the amount of boron nitride powder added is 3wt%, the amount of polymethylsilazane added is 28wt%, the amount of Tech-596 dispersant added is 1.5wt%, the amount of Tech-353 defoamer added is 0.3wt%, the amount of Tech-38101 leveling agent added is 0.2wt%, the amount of trimethylbenzene organic solvent added is 10wt%, and the amount of xylene organic solvent added is 5wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0116] Example 7

[0117] The difference between this embodiment and embodiment 1 is that: in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 46wt%, the amount of silicon carbide powder added is 8wt%, the amount of boron nitride powder added is 1wt%, the amount of polymethylsilazane added is 28wt%, the amount of Tech-596 dispersant added is 1.5wt%, the amount of Tech-353 defoamer added is 0.3wt%, the amount of Tech-38101 leveling agent added is 0.2wt%, the amount of trimethylbenzene organic solvent added is 10wt%, and the amount of xylene organic solvent added is 5wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0118] Example 8

[0119] The difference between this embodiment and embodiment 1 is that: in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 48wt%, the amount of silicon carbide powder added is 6.5wt%, the amount of boron nitride powder added is 0.5wt%, the amount of polymethylsilazane added is 28wt%, the amount of Tech-596 dispersant added is 1.5wt%, the amount of Tech-353 defoamer added is 0.3wt%, the amount of Tech-38101 leveling agent added is 0.2wt%, the amount of trimethylbenzene organic solvent added is 10wt%, and the amount of xylene organic solvent added is 5wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0120] Example 9

[0121] The difference between this embodiment and embodiment 1 is that: in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 45.5wt%, the amount of silicon carbide powder added is 4.5wt%, the amount of boron nitride powder added is 5wt%, the amount of polymethylsilazane added is 28wt%, the amount of Tech-596 dispersant added is 1.5wt%, the amount of Tech-353 defoamer added is 0.3wt%, the amount of Tech-38101 leveling agent added is 0.2wt%, the amount of trimethylbenzene organic solvent added is 10wt%, and the amount of xylene organic solvent added is 5wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0122] Example 10

[0123] The difference between this embodiment and embodiment 1 is that in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 50wt%, the amount of silicon carbide powder added is 7wt%, the amount of boron nitride powder added is 3wt%, the amount of polymethylsilazane added is 20wt%, the amount of Tech-596 dispersant added is 1.5wt%, the amount of Tech-353 defoamer added is 0.3wt%, the amount of Tech-38101 leveling agent added is 0.2wt%, the amount of trimethylbenzene organic solvent added is 12wt%, and the amount of xylene organic solvent added is 6wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0124] Embodiment 11

[0125] The difference between this embodiment and embodiment 1 is that in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 45wt%, the amount of silicon carbide powder added is 3wt%, the amount of boron nitride powder added is 1wt%, the amount of polymethylsilazane added is 38wt%, the amount of Tech-596 dispersant added is 0.5wt%, the amount of Tech-353 defoamer added is 0.3wt%, the amount of Tech-38101 leveling agent added is 0.2wt%, the amount of trimethylbenzene organic solvent added is 8wt%, and the amount of xylene organic solvent added is 4wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0126] Example 12

[0127] The difference between this embodiment and embodiment 1 is that in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 47wt%, the amount of silicon carbide powder added is 6wt%, the amount of boron nitride powder added is 2wt%, the amount of polymethylsilazane added is 28wt%, the amount of Tech-596 dispersant added is 1.5wt%, the amount of Tech-353 defoamer added is 0.3wt%, the amount of Tech-38101 leveling agent added is 0.2wt%, the amount of trimethylbenzene organic solvent added is 6wt%, and the amount of xylene organic solvent added is 9wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0128] Example 13

[0129] The difference between this embodiment and embodiment 1 is that: in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 47wt%, the amount of silicon carbide powder added is 6wt%, the amount of boron nitride powder added is 2wt%, the amount of polymethylsilazane added is 28wt%, the amount of Tech-596 dispersant added is 1.5wt%, the amount of Tech-353 defoamer added is 0.3wt%, the amount of Tech-38101 leveling agent added is 0.2wt%, the amount of trimethylbenzene organic solvent added is 14wt%, and the amount of xylene organic solvent added is 1wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0130] Embodiment 14

[0131] The difference between this embodiment and embodiment 1 is that in the method for preparing the silicon nitride coating provided in this embodiment, the first solvent is omitted and only xylene with a content of 15 wt % is used as the organic solvent. The rest of the contents and parameters are the same as those in embodiment 1.

[0132] Embodiment 15

[0133] The difference between this embodiment and embodiment 1 is that in the method for preparing the silicon nitride coating provided in this embodiment, the second solvent is omitted and only trimethylbenzene with a content of 15 wt % is used as the organic solvent. The rest of the contents and parameters are the same as those in embodiment 1.

[0134] Example 16

[0135] The difference between this embodiment and embodiment 1 is that: in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 45.5wt%, the amount of silicon carbide powder added is 6wt%, the amount of boron nitride powder added is 2wt%, the amount of polymethylsilazane added is 28wt%, the amount of Tech-596 dispersant added is 3wt%, the amount of Tech-353 defoamer added is 0.3wt%, the amount of Tech-38101 leveling agent added is 0.2wt%, the amount of trimethylbenzene organic solvent added is 10wt%, and the amount of xylene organic solvent added is 5wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0136] Embodiment 17

[0137] The difference between this embodiment and embodiment 1 is that: in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 47wt%, the amount of silicon carbide powder added is 6wt%, the amount of boron nitride powder added is 2wt%, the amount of polymethylsilazane added is 28wt%, the amount of Tech-596 dispersant added is 0.9wt%, the amount of Tech-353 defoamer added is 1wt%, the amount of Tech-38101 leveling agent added is 0.1wt%, the amount of trimethylbenzene organic solvent added is 10wt%, and the amount of xylene organic solvent added is 5wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0138] Embodiment 18

[0139] The difference between this embodiment and embodiment 1 is that: in the preparation method of the silicon nitride coating provided in this embodiment, based on the total mass of the raw materials mixed in step (I) being 100wt%, the amount of silicon nitride powder added is 47wt%, the amount of silicon carbide powder added is 6wt%, the amount of boron nitride powder added is 2wt%, the amount of polymethylsilazane added is 28wt%, the amount of Tech-596 dispersant added is 1.2wt%, the amount of Tech-353 defoamer added is 0.3wt%, the amount of Tech-38101 leveling agent added is 0.5wt%, the amount of trimethylbenzene organic solvent added is 10wt%, and the amount of xylene organic solvent added is 5wt%. The remaining contents and parameters are the same as those in embodiment 1.

[0140] Embodiment 19

[0141] The difference between this embodiment and embodiment 1 is that in the method for preparing the silicon nitride coating provided in this embodiment, polymethylsilazane is replaced by polymethylvinylsilazane. The rest of the contents and parameters are the same as those in embodiment 1.

[0142] Embodiment 20

[0143] The difference between this embodiment and embodiment 1 is that in the method for preparing the silicon nitride coating provided in this embodiment, polymethylsilazane is replaced by polymethylphenylsilazane. The rest of the contents and parameters are the same as those in embodiment 1.

[0144] Embodiment 21

[0145] The difference between this embodiment and embodiment 1 is that in the method for preparing the silicon nitride coating provided in this embodiment, the second curing stage and the third curing stage are omitted in the curing process of step (III), that is, the temperature is first raised from 25° C. to 100° C. within 10 minutes, kept at this temperature for 50 minutes, and then continued to be raised to 1000° C. within 180 minutes, and kept at this temperature for 25 minutes. The rest of the contents and parameters are the same as those in embodiment 1.

[0146] Comparative Example 1

[0147] The difference between this comparative example and Example 1 is that in the preparation method of the silicon nitride coating provided in this comparative example, the addition of silicon carbide powder is omitted, that is, based on the total mass of the raw materials mixed in step (I) as 100wt%, the addition amount of silicon nitride powder is 50wt%, the addition amount of boron nitride powder is 3wt%, the addition amount of polymethylsilazane is 30wt%, the addition amount of Tech-596 dispersant is 1.5wt%, the addition amount of Tech-353 defoamer is 0.3wt%, the addition amount of Tech-38101 leveling agent is 0.2wt%, the addition amount of trimethylbenzene organic solvent is 10wt%, and the addition amount of xylene organic solvent is 5wt%. The remaining contents and parameters are the same as those in Example 1.

[0148] Comparative Example 2

[0149] The difference between this comparative example and Example 1 is that in the preparation method of the silicon nitride coating provided in this comparative example, the addition of boron nitride powder is omitted, that is, based on the total mass of the raw materials mixed in step (I) as 100wt%, the addition amount of silicon nitride powder is 48wt%, the addition amount of silicon carbide powder is 7wt%, the addition amount of polymethylsilazane is 28wt%, the addition amount of Tech-596 dispersant is 1.5wt%, the addition amount of Tech-353 defoamer is 0.3wt%, the addition amount of Tech-38101 leveling agent is 0.2wt%, the addition amount of trimethylbenzene organic solvent is 10wt%, and the addition amount of xylene organic solvent is 5wt%. The remaining contents and parameters are the same as those in Example 1.

[0150] The silicon nitride coatings provided in the above Examples 1-21 and Comparative Examples 1-2 were tested for bending strength, cracking, and adhesion, and the test process was as follows:

[0151] (1) Bending strength: This bending strength is mainly based on specific circumstances, and the company sets the test plan by itself. A quartz test sample with a length of 100mm±2, a width of 20mm±0.2, and a thickness of 6mm±0.1 and a purity of 99.9999% is selected, and a single side is subjected to 120-mesh sandblasting for standby use; except that the inner wall of the quartz tube of the base material in Example 1-21 and Comparative Example 1-2 is replaced with the above-mentioned quartz test sample, the remaining process parameters are completely the same as the preparation method of the silicon nitride coating provided in Example 1-21 and Comparative Example 1-2, and a silicon nitride coating is prepared on the quartz test sample for testing. A three-point bending test method is used with a span of 6cm. The prepared coating is facing upward, and the downward pressure speed is 0.2mm / min. The bending strength value is read on the computer and recorded as Q, which is recorded as the bending strength of the silicon nitride coating prepared in Example 1-21 and Comparative Example 1-2.

[0152] (2) Cracking: According to GB / B 1766-2008, the crack severity of the silicon nitride coatings provided in Examples 1-21 and Comparative Examples 1-2 was graded, with grade 0 indicating almost no damage and grade 5 indicating very severe damage. The cracking of the coatings was graded from 0 to 5:

[0153] Level 0: No cracking.

[0154] Level 1: Slight cracking, which does not affect the overall performance of the coating.

[0155] Level 2: Moderate cracking, coating performance is reduced.

[0156] Level 3: Severe cracking and significant degradation of coating performance.

[0157] Level 4: Very severe cracking, with the coating almost completely failing.

[0158] Level 5: The coating is completely cracked and completely failed.

[0159] (3) Adhesion: According to GT / B 9286, the adhesion of the silicon nitride coatings provided in Examples 1-21 and Comparative Examples 1-2 is graded, with Grade 0 being the best adhesion and Grade 5 being the worst adhesion. The adhesion of the coatings is graded from 0 to 5:

[0160] Level 0: There is no or little coating peeling off in the scribed area of ​​the coating. This situation indicates that the adhesion between the coating and the substrate is very good, and there is basically no need to worry about the coating peeling off.

[0161] Level 1: Less than or equal to 5% of the coating is peeled off in the scribed area of ​​the coating, and its adhesion is also very ideal, which is suitable for some occasions that require high coating stability.

[0162] Level 2: More than 5% and less than or equal to 15% of the coating film is peeled off in the scribed area of ​​the coating. Although the adhesion is slightly reduced, it is still within the acceptable qualified range.

[0163] Level 3: More than 15% and less than or equal to 35% of the coating film is peeled off in the scribed area of ​​the coating, indicating that its adhesion performance is medium and the product quality should be inspected and evaluated in time.

[0164] Level 4: More than 35% and less than or equal to 65% of the coating film is peeled off in the scribed area of ​​the coating. At this time, the adhesion is seriously insufficient and in-depth analysis and improvement of the coating process are required.

[0165] Level 5: More than 65% of the coating film is peeled off in the scribe area of ​​the coating.

[0166] The test results are shown in Table 1:

[0167] Table 1

[0168]

[0169]

[0170]

[0171] The test results show that:

[0172] (1) It can be seen from Examples 1 to 3 that the method for preparing the silicon nitride coating provided by the present invention is simple, low-cost, and has low equipment requirements. In addition, by using silicon nitride powder as the main material and silicon carbide powder and boron nitride powder as the reinforcing material, combined with the spraying process and curing process after mixing, a silicon nitride coating with high strength, strong adhesion and not easy to crack can be prepared.

[0173] (2) It can be seen from Example 1 and Examples 4-5 that, while ensuring that the contents of the other raw materials are within a reasonable range, if the amount of silicon nitride powder added in the present invention is too low, the performance of the coating cannot be effectively improved, resulting in a decrease in the flexural strength of the material, and making it more susceptible to damage after external impact, pressure, and bending; if the amount of silicon nitride powder added is too high, it will be more susceptible to damage after external impact, pressure, and bending, and the flexural strength will also be reduced.

[0174] (3) It can be seen from Example 1 and Examples 6-7 that, while ensuring that the contents of the other raw materials are within a reasonable range, if the amount of silicon carbide powder added in the present invention is too low, it will lead to the inability to effectively realize the full effect of the coating-assisted reinforcement, resulting in a significant decrease in the bending strength of the material, and it will be more susceptible to damage after being subjected to external impact, pressure, and bending; if the amount of silicon carbide powder added is too high, it will be more susceptible to damage after being subjected to external impact, pressure, and bending, and the adhesion of the coating will also be slightly reduced.

[0175] (4) It can be seen from Example 1 and Examples 8-9 that, while ensuring that the contents of the other raw materials are within a reasonable range, if the amount of boron nitride powder added in the present invention is too low, the self-slip ability of the coating during shrinkage will decrease, the coating will crack, and the shielding performance of the coating will decrease, and it will not be able to effectively block the damage of the environment to the substrate material; if the amount of boron nitride powder added is too high, the adhesion of the coating to the substrate will decrease, the coating will powder and fall off, and thus lose the ability to protect the substrate.

[0176] (5) It can be seen from Example 1 and Examples 10-11 that, while ensuring that the contents of the other raw materials are within a reasonable range, if the amount of polymethylsilazane added in the present invention is too low, effective connection of the powder cannot be achieved, resulting in a decrease in the performance of the silicon nitride coating, a deterioration in shielding properties, an increase in brittleness, or even powderization and shedding, thereby losing the ability to protect the substrate; if the amount of polymethylsilazane added is too high, problems such as bubbles and collapse will occur during the preparation process, affecting the strength and shielding properties of the coating.

[0177] (6) It can be seen from Example 1 and Examples 12-13 that in the present invention, if the amount of the first solvent added is too low and the amount of the second solvent added is too high, the solvent will evaporate too quickly, the substrate material will not be sufficiently wetted, the coating density will be reduced, and the protective performance will be reduced; if the amount of the first solvent added is too high and the amount of the second solvent added is too low, it will lead to insufficient dissolution ability, powder agglomeration, and defects such as sagging of the coating.

[0178] (7) It can be seen from Example 1 and Examples 14-15 that if the first solvent is omitted in the present invention, the solvent evaporates too quickly, the base material is insufficiently wetted, the coating density is reduced, and the protective performance is significantly reduced; if the second solvent is omitted, the dissolving ability is insufficient, the powder is more likely to agglomerate, and the coating has defects such as sagging.

[0179] (8) It can be seen from Example 1 and Examples 16-18 that if the amount of dispersant added to the mixed raw materials of the coating of the present invention is too high, the viscosity of the coating decreases, the workability deteriorates, and the overall performance of the coating decreases; if the amount of defoamer added is too high, shrinkage holes appear during spraying and curing, and stratification occurs during storage; if the amount of leveling agent added is too high, shrinkage holes appear in the coating and the adhesion decreases. Excessive addition of dispersant, defoamer and leveling agent in the coating of the silicon nitride coating will cause the bending strength of the obtained silicon nitride coating to decrease, the adhesion on the substrate to decrease, and the coating to crack slightly.

[0180] (9) It can be seen from Examples 1 and 19-20 that if the polymethylsilazane in the present invention is replaced by polymethylvinylsilazane or polymethylphenylsilazane, the strength of the silicon nitride coating will decrease, microcracks will occur in the coating, and the adhesion of the coating will be reduced.

[0181] (10) It can be seen from Example 1 and Example 21 that if the second curing stage and the third curing stage are omitted in the present invention, it will lead to over-rapid curing, the formation of pores in the coating, and incomplete volatilization of the organic components, which will affect the strength of the coating. At the same time, it will make the adhesion of the coating on the substrate poor and the coating will crack.

[0182] (11) It can be seen from Example 1 and Comparative Example 1 that if the silicon carbide powder is missing in the silicon nitride coating of the present invention, it is completely unable to assist the silicon nitride coating, resulting in a significant decrease in the flexural strength of the coating, cracking of the coating, and deterioration of the adhesion between the coating and the substrate.

[0183] (12) It can be seen from Example 1 and Comparative Example 2 that if the silicon nitride coating of the present invention lacks boron nitride powder, it cannot eliminate the internal stress of the coating and the self-slip ability of the coating during shrinkage, causing serious cracking of the coating and a decrease in the flexural strength of the coating.

[0184] In summary, the silicon nitride coating provided by the present invention is based on silicon nitride powder as the main material, doped with silicon carbide powder and boron nitride powder as reinforcing materials, and the high temperature stability, high strength, self-lubrication and heat shock resistance advantages of silicon nitride powder are good choices as coating materials; silicon carbide powder is used as a reinforcing agent for adjusting the formula, and the cubic crystal form it has can make up for the silicon nitride of the hexagonal crystal form, and its mechanical properties differentiated from the main material can also assist in strengthening the silicon nitride coating, and promote the actual performance of the silicon nitride coating to be closer to the theoretical value; boron nitride powder has a layered structure, high chemical stability, can eliminate the internal stress of the coating, promote the self-slip ability during the shrinkage process of the coating, avoid the cracking of the coating, and the non-connected package structure formed improves the impact resistance of the coating. Through the mutual coordination between silicon nitride powder, silicon carbide powder and boron nitride powder, the strength and adhesion of the silicon nitride coating are jointly improved, and the cracking phenomenon of the coating is effectively avoided.

[0185] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A silicon nitride coating, characterized in that: The silicon nitride coating comprises a main material and a reinforcing material, wherein the main material comprises silicon nitride powder, and the reinforcing material comprises silicon carbide powder and boron nitride powder.

2. The silicon nitride coating according to claim 1, characterized in that: The silicon nitride coating also includes a connecting material; Preferably, the connecting material comprises polysilazane; Preferably, the polysilazane includes any one of polymethylsilazane, polymethylvinylsilazane or polymethylphenylsilazane, or a combination of at least two thereof.

3. A method for preparing a silicon nitride coating according to claim 1 or 2, characterized in that: The preparation method comprises: (1) mixing a main material, a reinforcing material and a solvent to obtain a mixed coating; the main material comprises silicon nitride powder, and the reinforcing material comprises silicon carbide powder and boron nitride powder; (2) Spraying the mixed coating onto the substrate and curing it to obtain the silicon nitride coating.

4. The preparation method according to claim 3, characterized in that: Based on the total mass of the mixed raw materials in step (1) being 100wt%, the amount of silicon nitride powder added is 45-50wt%; Preferably, based on the total mass of the mixed raw materials in step (1) being 100wt%, the amount of silicon carbide powder added is 3-7wt%; Preferably, based on the total mass of the mixed raw materials in step (1) being 100wt%, the amount of boron nitride powder added is 0.5-3wt%, preferably 1-3wt%; Preferably, the particle size of the silicon nitride powder is 1200-8000 mesh; Preferably, the particle size of the silicon carbide powder is 2000-4000 mesh; Preferably, the particle size of the boron nitride powder is 1000-2000 mesh.

5. The preparation method according to claim 3 or 4, characterized in that: The solvent in step (1) includes a first solvent and a second solvent; Preferably, the first solvent comprises any one of trimethylbenzene, ethyl lactate or acetone, or a combination of at least two thereof; Preferably, the second solvent comprises any one of xylene, ethyl acetate or tetrahydrofuran, or a combination of at least two thereof; Preferably, based on the total mass of the mixed raw materials in step (1) being 100wt%, the amount of the first solvent added is 8-12wt%; Preferably, based on the total mass of the mixed raw materials in step (1) being 100 wt%, the amount of the second solvent added is 4-6 wt%.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The mixed raw materials in step (1) also include connecting materials; Preferably, based on the total mass of the mixed raw materials in step (1) being 100wt%, the amount of the connecting material added is 24-35wt%; Preferably, the mixed raw materials in step (1) further include any one of a dispersant, a defoamer or a leveling agent or a combination of at least two thereof, preferably a dispersant, a defoamer and a leveling agent; Preferably, based on the total mass of the mixed raw materials in step (1) being 100wt%, the amount of the dispersant added is 0.5-2wt%; Preferably, based on the total mass of the mixed raw materials in step (1) being 100wt%, the amount of the defoaming agent added is 0.1-0.5wt%; Preferably, based on the total mass of the mixed raw materials in step (1) being 100 wt%, the amount of the leveling agent added is 0.05-0.2 wt%.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The substrate in step (2) also includes washing and drying before spraying; Preferably, the spraying thickness in step (2) is 20-50 μm; Preferably, after the spraying in step (2), the substrate sprayed with the mixed coating is also rotated; Preferably, the linear speed of the rotation is 0.4-0.8 m / s; Preferably, the rotation time is 20-40 minutes.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The curing in step (2) is carried out under a nitrogen atmosphere and / or an inert atmosphere; Preferably, the curing in step (2) comprises a first curing stage, a second curing stage, a third curing stage and a fourth curing stage which are performed successively; Preferably, the temperature of the first curing stage is 80-120°C; Preferably, the heating time of the first curing stage is 8-16 minutes; Preferably, the holding time of the first curing stage is 30-60 minutes; Preferably, the temperature of the second curing stage is 160-200°C; Preferably, the heating time of the second curing stage is 8-16 minutes; Preferably, the holding time of the second curing stage is 20-40 minutes; Preferably, the temperature of the third curing stage is 550-650°C; Preferably, the heating time of the third curing stage is 80-120 min; Preferably, the heat preservation time of the third curing stage is 60-90 minutes; Preferably, the temperature of the fourth curing stage is 950-1100°C; Preferably, the heating time of the fourth curing stage is 60-90 minutes; Preferably, the heat preservation time of the fourth curing stage is 20-30 minutes.

9. The preparation method according to claim 3, characterized in that: The preparation method comprises: (I) Based on the total mass of the mixed raw materials as 100wt%, a main material of silicon nitride powder with a content of 45-50wt%, a reinforcing material composed of silicon carbide powder with a content of 3-7wt% and boron nitride powder with a content of 0.5-3wt%, a connecting material with a content of 24-35wt%, a dispersant with a content of 0.5-2wt%, a defoamer with a content of 0.1-0.5wt%, a leveling agent with a content of 0.05-0.2wt%, a first solvent with a content of 8-12wt% and a second solvent with a content of 4-6wt% are mixed to obtain a mixed coating; wherein the particle size of the silicon nitride powder is 1200-8000 mesh, the particle size of the silicon carbide powder is 2000-4000 mesh, and the particle size of the boron nitride powder is 1000-2000 mesh; washing and drying the substrate to obtain the pretreated substrate; (II) using a spray gun with a caliber of 0.5-1 mm, spraying the mixed coating onto the pretreated substrate to a thickness of 20-50 μm, and then rotating the sprayed substrate at a linear speed of 0.4-0.8 m / s for 20-40 min to obtain the substrate coated with the mixed coating; (III) Drying the substrate coated with the mixed coating, and then placing the dried substrate coated with the mixed coating in a nitrogen atmosphere and / or an inert atmosphere for curing, first heating from room temperature to 80-120°C within 8-16 minutes, keeping the temperature for 30-60 minutes to perform a first curing stage, then heating to 160-200°C within 8-16 minutes, keeping the temperature for 20-40 minutes to perform a second curing stage, then heating again to 550-650°C within 80-120 minutes, keeping the temperature for 60-90 minutes to perform a third curing stage, then heating to 950-1100°C within 60-90 minutes, keeping the temperature for 20-30 minutes to perform a fourth curing stage, and finally obtaining the silicon nitride coating.

10. An application of the silicon nitride coating according to claim 1 or 2, characterized in that: The silicon nitride coating is used in the semiconductor or photovoltaic fields.

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