A graphite article silicon carbide coating and method of making the same

Abstract

The application discloses a graphite piece silicon carbide coating and a preparation method thereof in the technical field of inorganic non-metallic materials. The method comprises the following steps: firstly, surface polishing, cleaning and drying pretreatment are performed on the graphite piece; then, a solution containing phosphine azine functionalized silazane and boron-silicon calamine compound is sprayed on the pretreated graphite piece and dried and solidified to form a surface modification layer; finally, the surface modified graphite piece is placed in a chemical vapor deposition device to deposit a silicon carbide coating under specific temperature, pressure and atmosphere. The method effectively promotes the uniform nucleation and crystallization of the silicon carbide coating through unique surface modification treatment, significantly improves the compactness, uniformity and bonding force of the coating and the substrate. The obtained coated graphite piece has excellent thermal corrosion resistance, oxidation resistance and mechanical properties, the service life and service frequency in a semiconductor epitaxial device are significantly improved, the whole preparation process is environmentally friendly, and the method is suitable for coating treatment of large graphite substrates.

Description

Technical Field

[0001] This invention relates to the field of inorganic non-metallic materials technology, specifically to a silicon carbide coating for graphite parts and its preparation method. Background Technology

[0002] Graphite substrates, due to their excellent thermal stability, good thermal and electrical conductivity, and high mechanical strength, play an indispensable role in the semiconductor industry, especially in high-temperature epitaxial growth processes, and are often used to manufacture key components such as wafer trays and heaters. However, in the high-temperature and harsh process environment, exposed graphite materials face severe challenges: on the one hand, their porous structure easily adsorbs impurities, leading to semiconductor product contamination; on the other hand, graphite undergoes chemical corrosion and oxidative volatilization when in contact with reactive gases (such as silicon-containing or oxygen-containing atmospheres) at high temperatures, which not only shortens the lifespan of the components themselves, but the resulting particulate matter and impurities also seriously affect the crystal quality of the epitaxial layer and the device yield. Therefore, applying a high-performance protective coating to the graphite substrate to isolate it from direct contact with the harsh environment has become a key technical approach to improve the reliability of semiconductor equipment and product quality.

[0003] Currently, the main technical routes for applying silicon carbide coatings to graphite parts include slurry sintering and direct chemical vapor deposition (DCV). While slurry sintering has lower equipment requirements, the resulting coatings often lack density, exhibiting micropores and weak adhesion between the coating and the substrate. Furthermore, the decomposition of organic binders during high-temperature processing can introduce impurities, affecting the coating's purity and corrosion resistance. DCV can achieve higher purity and denser silicon carbide coatings, but it also faces significant technical bottlenecks: due to the differences in crystal structure and thermal expansion coefficients between graphite and silicon carbide, gaseous precursors struggle to achieve uniform, high-density heterogeneous nucleation on pure graphite surfaces. This leads to uneven initial coating growth, resulting in island-like growth or stress concentration, ultimately affecting the overall consistency, adhesion, and thermal shock resistance of the coating. In addition, existing pretreatment technologies (such as simple carbon source embedding or single reagent coating) have limited effect on improving nucleation effect and are difficult to achieve uniform and effective treatment of large or complex-shaped graphite substrates, which restricts the widespread application of high-performance coated graphite products in the field of high-end semiconductor manufacturing.

[0004] In order to overcome the above technical obstacles, the industry urgently needs an innovative preparation method, which not only inherits the high purity and high density advantages of chemical vapor deposition technology, but also fundamentally solves the core problem of the difficulty of uniform and firm nucleation of silicon carbide on the surface of graphite. The ideal method should be able to build an effective transition layer between the graphite substrate and the subsequent deposited silicon carbide coating. The transition layer should be able to significantly reduce the nucleation barrier and provide sufficient and uniformly distributed active reaction sites, thereby guiding the regular epitaxial growth of silicon carbide crystals. At the same time, the preparation process should have good process compatibility, environmental friendliness, and be able to adapt to the processing needs of graphite substrates of different sizes to meet the extreme pursuit of performance and reliability of key consumables in the semiconductor industry. The present application arises in this technical background. SUMMARY

[0005] The purpose of the present application is to provide a graphite piece silicon carbide coating and a preparation method thereof, which solves the technical problems of uneven nucleation and weak adhesion of silicon carbide on the surface of graphite in the existing chemical vapor deposition process.

[0006] The present application achieves the above-mentioned purpose by the following technical solutions:

[0007] A preparation method of a graphite piece silicon carbide coating, characterized in that the steps include:

[0008] S1, polishing the surface of the cut graphite piece with diamond polishing paste, and then ultrasonic cleaning in acetone solvent; then drying the cleaned graphite piece in an oven at 110-130℃ to obtain a pretreated graphite piece;

[0009] S2, spraying a solution containing phosphine functionalized silazane and boron-silicon calamine compound on the pretreated graphite piece, and then drying and curing to obtain a surface-modified graphite piece;

[0010] S3, placing the surface-modified graphite piece in the reaction chamber of a chemical vapor deposition device; introducing a silicon-containing reaction source, a carbon-containing reaction source and a carrier gas into the reaction chamber to deposit a SiC coating on the surface of the surface-modified graphite piece; after deposition, cooling to room temperature in an argon atmosphere.

[0011] In the present application, the preparation reaction mechanism of the silicon carbide coating of the graphite piece is to build an efficient active transition layer between the graphite matrix and the silicon carbide coating through a unique surface modification treatment. In the pretreatment stage, the phosphazene functionalized silazane, with its cyclic phosphazene structure and silane functional group, chemically anchors the graphite surface during the dry curing process, forming an organic-inorganic hybrid network with a nano-scale porous structure; at the same time, the boron element in the boron-silicon calamine compound can be partially decomposed under heat treatment conditions, and the active boron species generated can effectively adjust the energy state of the graphite surface. The synergistic effect of the two modified substances builds a uniform transition layer rich in active sites such as silicon, boron and nitrogen on the graphite surface. After entering the chemical vapor deposition stage, the transition layer provides an ideal nucleation template for silicon carbide deposition, and its active sites can significantly reduce the decomposition activation energy of gaseous precursors such as trichlorosilane and ethylene, promoting the preferential formation and orderly arrangement of carbon-silicon bonds. Under the condition of precise control of temperature and pressure, the silicon source and carbon source in the gas phase react heterogeneously on the surface of the active transition layer, and the silicon carbide crystals nucleate and grow vertically on the graphite surface in an epitaxial growth mode. The boron element in the modified layer can also enter the silicon carbide lattice by solid solution, playing a role in refining the grain size and adjusting the growth orientation of the crystal, while the nitrogen element helps to fill the lattice vacancies, ultimately forming a high-quality silicon carbide coating with consistent crystal form, firm interface bonding, uniform thickness and dense structure, thereby significantly improving the overall performance and service life of the coating.

[0012] According to the preferred embodiment of the present application, in step S2, the mass concentration of the phosphazene functionalized silazane is 1-10%, and the mass concentration of the boron-silicon calamine compound is 0.5-5%; the temperature of the dry curing treatment is 150-400℃.

[0013] According to the preferred embodiment of the present application, in step S3, the temperature of the surface deposition is 1250-1550℃, and the reaction pressure is 100-5000Pa; the silicon-containing reaction source is trichlorosilane, the carbon-containing reaction source is ethylene, and the carrier gas is hydrogen.

[0014] According to the preferred embodiment of the present application, the preparation method of the phosphazene functionalized silazane comprises: A1, dissolving hexachlorocyclotriphosphazene in anhydrous tetrahydrofuran under a dry argon atmosphere, and cooling to -8~-10℃; under stirring, dropwise adding a mixed solution formed by dissolving aminopropyltriethoxysilane and triethylamine in anhydrous tetrahydrofuran; after dropwise addition is completed, warming to room temperature and continuing to stir; A2, heating to 64-66℃ and continuing to react; after the reaction is completed, cooling to room temperature, concentrating the filtrate by vacuum filtration to obtain a crude product; dissolving the crude product in n-hexane and purifying by silica gel column chromatography to collect the fraction.

[0015] In the present application, the synthesis of phosphazene functionalized silazane is based on the nucleophilic substitution reaction between cyclic phosphazene skeleton and amino silane and the subsequent intramolecular rearrangement process. The core mechanism starts from the nucleophilic attack of the primary amino group in the amino propyl triethoxysilane molecule on the chlorine atom of the phosphorus atom in the hexachlorocyclotriphosphazene molecule. Under the condition of low temperature and triethylamine as an acid binding agent, this nucleophilic substitution reaction can be orderly carried out, and three chlorine atoms on each phosphazene ring are gradually replaced by three amino propyl triethoxysilane molecules to form an intermediate connected by nitrogen-phosphorus-nitrogen bonds. This process strictly controls the selectivity and functionality of the reaction, avoiding the generation of branched or crosslinked by-products. Subsequently, under the condition of heating reflux, the silazane functional groups in the molecule and between molecules undergo hydrolysis condensation reaction, and the triethoxysilane group is partially hydrolyzed to form silicon hydroxyl, and further condensed with adjacent silicon hydroxyl or ethoxyl to form a hybrid structure with a cyclic phosphazene core and a partially crosslinked siloxane shell. The key to the whole reaction process is to ensure high functional group conversion rate of the phosphazene ring and controllable condensation of the silane chain by accurately controlling the dropping speed, temperature and molar ratio of the reactants, and finally to obtain a target compound with clear molecular structure, high thermal stability of phosphazene ring and reactivity of silazane.

[0016] According to the preferred embodiment of the present application, in step A1, the molar ratio of hexachlorocyclotriphosphazene, amino propyl triethoxysilane and triethylamine is 1:3:3; the stirring time is 12-14h.

[0017] According to the preferred embodiment of the present application, in step A2, the reaction time is 24-26h.

[0018] According to the preferred embodiment of the present application, the preparation method of the boron-silicon calamine composite comprises: B1, dissolving 1,4-bis(4-hydroxyphenyl) benzene and triisopropyl borate in toluene, adding p-toluenesulfonic acid; heating and refluxing, and continuously reacting; after the reaction is completed, cooling to room temperature to obtain an acid ester compound; B2, placing the acid ester compound, hydrogenated trimethoxysilane and tris(triphenylphosphine) rhodium chloride in a high-pressure reaction kettle, adding anhydrous dichloromethane; replacing the air in the reaction kettle with argon, and then filling with argon; heating to 58-62℃, and continuously stirring and reacting; after the reaction is completed, cooling to room temperature, and filtering through a diatomite pad; adding triphenylphosphine to the filtrate, filtering, and then concentrating the filtrate by a rotary evaporator to obtain a crude product; dissolving the crude product in dichloromethane, and purifying by neutral alumina column chromatography to collect the fraction.

[0019] According to the preferred embodiment of the present application, the "calamite" refers to a rod-like liquid crystal structure unit contained in the boron-silicon calamite composite, which is derived from 1,4-bis(4-hydroxyphenyl)benzene used in the preparation process. The compound has a typical rigid linear structure (i.e. "calamite" structure, meaning rod-like molecule), which is bonded to boron and silicon elements through chemical reaction in the composite as a skeleton component, forming a boron-silicon organic-inorganic hybrid material with specific orientation and enhanced performance.

[0020] In the present application, the construction of the boron-silicon calamite composite involves a step-by-step ester exchange reaction and transition metal catalyzed hydrosilylation reaction, which is a delicate molecular assembly process. First, one molar equivalent of linear bisphenol compound undergoes ester exchange reaction with three molar equivalents of triisopropyl borate under acid catalysis. p-Toluenesulfonic acid as a catalyst provides protons to activate the alkoxy group of borate, making it more susceptible to nucleophilic attack by the phenolic hydroxyl group, thereby removing isopropyl alcohol and forming a borate cyclic intermediate centered on a boron atom and connected to two aromatic rings through boron-oxygen bonds. This step constructs the rigid skeleton and boron-oxygen heterocyclic structure of the molecule. Subsequently, the borate intermediate undergoes hydrosilylation reaction with excess hydridotrimethylsilane in the presence of rhodium catalyst. Tris(triphenylphosphine)rhodium chloride first adds to the silicon-hydrogen bond to form an active rhodium hydride species; this species then inserts into the carbon-carbon double bond at a specific position in the aromatic ring of the borate intermediate, undergoing hydrosilylation to covalently connect the hydrogen-containing trimethoxysilane group to the aromatic skeleton through a carbon-silicon bond. After the reaction is complete, triphenylphosphine is added to quench and precipitate the residual rhodium catalyst in the system, ensuring the purity of the product.

[0021] According to the preferred embodiment of the present application, in step B1, the molar ratio of 1,4-bis(4-hydroxyphenyl)benzene to triisopropyl borate is 1:3; the reaction is continuously stirred for 18-20h.

[0022] According to the preferred embodiment of the present application, in step B2, the reaction is continuously stirred for 36-40h.

[0023] The present application also provides a graphite piece silicon carbide coating prepared according to the preparation method of the graphite piece silicon carbide coating.

[0024] The present application has the following advantages:

[0025] The present application significantly improves the comprehensive performance of the final silicon carbide coating by introducing phosphazene functionalized silazane and boron-silicon calamine compound to modify the surface of the graphite matrix before chemical vapor deposition, thereby successfully constructing an efficient active transition layer. The transition layer greatly improves the nucleation process of silicon carbide on the graphite surface, provides a large number of uniformly distributed active sites, and guides the ordered epitaxial growth of silicon carbide crystals. The technical effect is first reflected in the optimization of the microstructure of the coating. The prepared silicon carbide coating has extremely high density, excellent thickness uniformity, and significantly enhanced bonding force between the coating and the substrate. The crystal consistency of the coating is finely controlled, and the porosity is significantly reduced, thereby exhibiting excellent high-temperature oxidation resistance and thermal corrosion resistance, effectively blocking the invasion of external corrosive media and the volatilization of the internal graphite matrix, and providing long-term and effective protection for the graphite piece.

[0026] Secondly, the preparation method exhibits significant advantages in process compatibility and environmental friendliness. The method has strong adaptability to the size and shape of the graphite matrix and can be successfully applied to uniform coating treatment of large-size workpieces such as large wafers and complex crucibles, effectively expanding the application range of coated graphite products in the semiconductor manufacturing field. The entire process is carried out in a low-pressure environment, and the reaction source and modifier used do not involve highly toxic and highly polluting substances. The process emissions are mainly nitrogen and water vapor, almost no harmful by-products to the environment, and meet the strict requirements of modern industry for green manufacturing. At the same time, by accurately controlling the key parameters such as deposition temperature, pressure, and gas flow, the production process has high repeatability and stability, laying a solid technical foundation for building an automated and efficient production line.

[0027] Finally, the technical effect of the present application is directly reflected in the service life and reliability of the coated graphite products. The silicon carbide coated graphite piece prepared by the present application has significantly improved core performance indicators under extremely harsh working conditions such as semiconductor epitaxial equipment. DETAILED DESCRIPTION

[0028] The following further describes the present application, and it is necessary to point out here that the following detailed description is only used to further illustrate the present application, and cannot be understood as limiting the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0029] The main related equipment and material suppliers are as follows:

[0030] The trichlorosilane is purchased from Wuxi Audecheng Chemical Co., Ltd.

[0031] The ethylene is purchased from Nanjing Yaojiang Trade Co., Ltd.

[0032] The hydrogen was purchased from Liaoning Kunlun Hanxing Hydrogen Energy Technology Co., Ltd.

[0033] The hexachlorotriphosphazine was purchased from Shanghai Aladdin Biochem Technology Co., Ltd.

[0034] The aminopropyl triethoxysilane was purchased from Hubei Xinlantian New Material Co., Ltd.

[0035] The triethylamine was purchased from Jinan Rennyu Chemical Co., Ltd.

[0036] The 1,4-bis(4-hydroxyphenyl)benzene was purchased from Xi'an Ruixi Biological Technology Co., Ltd.

[0037] The triisopropyl borate was purchased from Jinan Mingwei Chemical Co., Ltd.

[0038] The p-toluenesulfonic acid was purchased from Dezhou Hongqiao Chemical Co., Ltd.

[0039] The hydrogenated trimethoxysilane was purchased from Chengdu Kelin'en Chemical Technology Co., Ltd.

[0040] The tris(triphenylphosphine)rhodium(I) chloride was purchased from Shanghai Likai Chemical Technology Co., Ltd.

[0041] The triphenylphosphine was purchased from Shandong Hongchuan Chemical Co., Ltd.

[0042] Example 1: Preparation of phosphonazine-functionalized silazane: Under a dry argon atmosphere, 1.84 g of hexachlorocyclotriphosphonazine was dissolved in 50 mL of anhydrous tetrahydrofuran and cooled to -9 °C. While stirring, a mixed solution of 4.97 g of aminopropyltriethoxysilane and 3.04 g of triethylamine dissolved in 30 mL of anhydrous tetrahydrofuran was added dropwise. After the addition was complete, the temperature was raised to room temperature and stirring was continued for 13 h. The mixture was then heated to 65 °C and reacted for 25 h. After the reaction was complete, the mixture was cooled to room temperature, and the filtrate was concentrated by vacuum filtration to obtain the crude product. The crude product was dissolved in 20 mL of n-hexane and purified by silica gel column chromatography. The target fraction was collected to obtain the phosphonazine-functionalized silazane. Preparation of borosilicate caramitrile complex: 2.5 g of 1,4-bis(4-hydroxyphenyl)benzene and 3.6 g of triisopropyl borate were dissolved in 40 mL of toluene, and 0.1 g of p-toluenesulfonic acid was added; the mixture was heated to reflux and reacted for 19 h; after the reaction was completed, it was cooled to room temperature to obtain the ester compound; all the ester compound was placed in a high-pressure reactor with 1.5 g of hydrogenated trimethoxysilane and 0.05 g of tris(triphenylphosphine)rhodium chloride (I), and 30 mL of anhydrous dichloromethane was added; the air in the reactor was replaced with argon, and then argon was introduced to 0.5 MPa; the mixture was heated to 60 °C and stirred continuously for 38 h; after the reaction was completed, it was cooled to room temperature and filtered through a diatomaceous earth pad; 0.1 g of triphenylphosphine was added to the filtrate, and after filtration, the filtrate was concentrated by rotary evaporation to obtain the crude product; the crude product was dissolved in 15 mL of dichloromethane and purified by neutral alumina column chromatography, and the target fraction was collected to obtain the borosilicate caramitrile complex. Preparation of silicon carbide coating on graphite parts: A 100mm×100mm×10mm graphite part was polished with diamond polishing paste, then ultrasonically cleaned in 200mL acetone for 30min; subsequently, the cleaned graphite part was dried in an oven at 120℃ for 1.5h to obtain a pretreated graphite part; 0.5g of phosphazine-functionalized silazane and 0.1g of borosilicate caramelite composite were weighed and dissolved in 9.4g of deionized water to form a spraying solution; the solution was then sprayed onto the pretreated graphite part using a spraying process. The graphite part was then dried and cured at 200℃ for 1 hour to obtain a surface-modified graphite part. The surface-modified graphite part was placed in the reaction chamber of a chemical vapor deposition (CVD) apparatus. Trichlorosilane (a silicon-containing reaction source) with a flow rate of 10 sccm, ethylene (a carbon-containing reaction source) with a flow rate of 5 sccm, and hydrogen (a carrier gas) with a flow rate of 200 sccm were introduced into the reaction chamber. Under the conditions of a surface deposition temperature of 1400℃ and a reaction pressure of 1 kPa, a silicon carbide coating was deposited on the surface of the surface-modified graphite part for 3 hours. After deposition, the part was cooled to room temperature under an argon atmosphere.

[0043] Example 2 was prepared according to the same procedure as Example 1, except that the phosphinazin-functionalized silazane was prepared as follows: 1.84 g of hexachlorocyclotriphosphazene was dissolved in 50 mL of anhydrous tetrahydrofuran under a dry argon atmosphere and cooled to -8 °C; a mixture solution of 4.97 g of aminopropyltriethoxysilane and 3.04 g of triethylamine dissolved in 30 mL of anhydrous tetrahydrofuran was added dropwise under stirring; after the addition was completed, the temperature was raised to room temperature and stirring was continued for 12 h; heating was continued at 64 °C for 24 h; after the reaction was completed, the temperature was cooled to room temperature and the filtrate was concentrated by vacuum filtration to obtain a crude product; the crude product was dissolved in 20 mL of n-hexane and purified by silica gel column chromatography to obtain the phosphinazin-functionalized silazane. The borosilacalmette composite was prepared as follows: 2.5 g of 1,4-bis(4-hydroxyphenyl)benzene and 3.6 g of triisopropyl borate were dissolved in 40 mL of toluene and 0.1 g of p-toluenesulfonic acid was added; heating was continued at reflux for 18 h; after the reaction was completed, the temperature was cooled to room temperature to obtain an ester compound; the entire ester compound was placed in a high-pressure reaction kettle together with 1.5 g of hydrogenated trimethoxysilane and 0.05 g of tris(triphenylphosphine)rhodium(I) chloride and 30 mL of anhydrous dichloromethane was added; the reaction kettle was replaced with argon and then filled with argon to 0.5 MPa; heating was continued at 58 °C for 36 h under stirring; after the reaction was completed, the temperature was cooled to room temperature and filtered through a diatomite pad; 0.1 g of triphenylphosphine was added to the filtrate and filtered; the filtrate was concentrated by a rotary evaporator to obtain a crude product; the crude product was dissolved in 15 mL of dichloromethane and purified by neutral alumina column chromatography to obtain the borosilacalmette composite. The graphite piece silicon carbide coating was prepared as follows: a 100 mm x 100 mm x 10 mm graphite piece was polished with a diamond abrasive paste and then ultrasonically cleaned in 200 mL of acetone solvent for 30 min; the cleaned graphite piece was then dried in an oven at 110 °C for 1 h to obtain a pretreated graphite piece; 1.0 g of the phosphinazin-functionalized silazane and 0.5 g of the borosilacalmette composite were dissolved in 8.5 g of deionized water to form a spraying solution; the pretreated graphite piece was sprayed with the spraying solution by a spraying process and then dried and cured at 150 °C for 1.5 h to obtain a surface-modified graphite piece; the surface-modified graphite piece was placed in a reaction chamber of a chemical vapor deposition apparatus; a silicon-containing reaction source trichlorosilane was introduced into the reaction chamber at a flow rate of 10 seem, a carbon-containing reaction source ethylene was introduced at a flow rate of 5 seem, and a carrier gas hydrogen was introduced at a flow rate of 200 seem; a silicon carbide coating was deposited on the surface of the surface-modified graphite piece at a surface deposition temperature of 1250 °C and a reaction pressure of 100 Pa for 3 h; after the deposition was completed, the temperature was cooled to room temperature under an argon atmosphere.

[0044] Example 3, with the exception that the phosphinazin-functionalized silazane was prepared: 1.84 g of hexachlorocyclotriphosphazene was dissolved in 50 mL of anhydrous tetrahydrofuran under a dry argon atmosphere, and cooled to -10 °C; a mixed solution formed by dissolving 4.97 g of aminopropyltriethoxysilane and 3.04 g of triethylamine in 30 mL of anhydrous tetrahydrofuran was added dropwise under stirring; after the dropwise addition was completed, the temperature was raised to room temperature, and stirring was continued for 14 h; heating was performed to 66 °C, and the reaction was continued for 26 h; after the reaction was completed, the temperature was cooled to room temperature, and the filtrate was concentrated by vacuum filtration to obtain a crude product; the crude product was dissolved in 20 mL of n-hexane, and purified by silica gel column chromatography, and the target fraction was collected to obtain the phosphinazin-functionalized silazane. The preparation of the borosilacalmette composite: 2.5 g of 1,4-bis(4-hydroxyphenyl)benzene and 3.6 g of triisopropyl borate were dissolved in 40 mL of toluene, and 0.1 g of p-toluenesulfonic acid was added; heating was performed under reflux, and the reaction was continued for 20 h; after the reaction was completed, the temperature was cooled to room temperature to obtain an ester compound; the entire ester compound was placed in a high-pressure reaction kettle together with 1.5 g of hydrogenated trimethoxysilane and 0.05 g of tris(triphenylphosphine)rhodium(I) chloride, and 30 mL of anhydrous dichloromethane was added; the reaction kettle was replaced with argon, and then filled with argon to 0.5 MPa; heating was performed to 62 °C, and the reaction was continued under stirring for 40 h; after the reaction was completed, the temperature was cooled to room temperature, and filtration was performed through a diatomite pad; 0.1 g of triphenylphosphine was added to the filtrate, and the filtrate was concentrated by a rotary evaporator after filtration to obtain a crude product; the crude product was dissolved in 15 mL of dichloromethane, and purified by neutral alumina column chromatography, and the target fraction was collected to obtain the borosilacalmette composite. The preparation of the graphite piece silicon carbide coating: a graphite piece with a size of 100 mm x 100 mm x 10 mm was polished with a diamond polishing paste, and then ultrasonically cleaned in 200 mL of acetone solvent for 30 min; the cleaned graphite piece was then dried in an oven at 130 °C for 2 h to obtain a pretreated graphite piece; 0.1 g of the phosphinazin-functionalized silazane and 0.05 g of the borosilacalmette composite were dissolved in 9.85 g of deionized water to form a spraying solution; the solution was sprayed onto the pretreated graphite piece by using a spraying process, and then dried and cured at 400 °C for 2 h to obtain a surface-modified graphite piece; the surface-modified graphite piece was placed in a reaction chamber of a chemical vapor deposition device; a silicon-containing reaction source trichlorosilane was introduced into the reaction chamber at a flow rate of 10 sccm, a carbon-containing reaction source ethylene was introduced at a flow rate of 5 sccm, and a carrier gas hydrogen was introduced at a flow rate of 200 sccm, and a silicon carbide coating was deposited on the surface of the surface-modified graphite piece at a surface deposition temperature of 1550 °C and a reaction pressure of 5 kPa for 3 h; after the deposition was completed, the temperature was cooled to room temperature under an argon atmosphere.

[0045] Comparative Example 1

[0046] The preparation method is the same as that in Example 1, except that the preparation of the silicon carbide coating on the graphite piece: a 100 mm x 100 mm x 10 mm graphite piece is polished on the surface with diamond abrasive paste, and then ultrasonic cleaning in 200 mL of acetone solvent for 30 min; then the cleaned graphite piece is dried in a 120°C oven for 1.5 h to obtain a pretreated graphite piece; 0.5 g of phosphazene functionalized silazane is weighed and dissolved in 9.5 g of deionized water to form a spraying solution; the pretreated graphite piece is sprayed with the solution by using a spraying process, and then dried and cured at 200°C for 1 h to obtain a surface-modified graphite piece; the surface-modified graphite piece is placed in the reaction chamber of a chemical vapor deposition device; the reaction chamber is introduced with a silicon-containing reaction source trichlorosilane at a flow rate of 10 sccm, a carbon-containing reaction source ethylene at a flow rate of 5 sccm, and a carrier gas hydrogen at a flow rate of 200 sccm, and a silicon carbide coating is deposited on the surface of the surface-modified graphite piece at a surface deposition temperature of 1400°C and a reaction pressure of 1 kPa for 3 h; after deposition, cooling to room temperature under argon atmosphere.

[0047] Comparative Example 2

[0048] The preparation method is the same as that in Example 1, except that the preparation of the silicon carbide coating on the graphite piece: a 100 mm x 100 mm x 10 mm graphite piece is polished on the surface with diamond abrasive paste, and then ultrasonic cleaning in 200 mL of acetone solvent for 30 min; then the cleaned graphite piece is dried in a 120°C oven for 1.5 h to obtain a pretreated graphite piece; 0.5 g of phosphazene functionalized silazane is weighed and dissolved in 9.5 g of deionized water to form a spraying solution; the pretreated graphite piece is sprayed with the solution by using a spraying process, and then dried and cured at 200°C for 1 h to obtain a surface-modified graphite piece; the surface-modified graphite piece is placed in the reaction chamber of a chemical vapor deposition device; the reaction chamber is introduced with a silicon-containing reaction source trichlorosilane at a flow rate of 10 sccm, a carbon-containing reaction source ethylene at a flow rate of 5 sccm, and a carrier gas hydrogen at a flow rate of 200 sccm, and a silicon carbide coating is deposited on the surface of the surface-modified graphite piece at a surface deposition temperature of 1400°C and a reaction pressure of 1 kPa for 3 h; after deposition, cooling to room temperature under argon atmosphere.

[0049] Comparative Example 3

[0050] The preparation method is the same as that in Example 1, except that the preparation of the silicon carbide coating on the graphite piece: a 100 mm x 100 mm x 10 mm graphite piece is polished with diamond abrasive paste, and then ultrasonic cleaned in 200 mL of acetone solvent for 30 min; then the cleaned graphite piece is dried in an oven at 120°C for 1.5 h to obtain a pretreated graphite piece; the pretreated graphite piece is directly placed in the reaction chamber of a chemical vapor deposition device; a silicon-containing reaction source trichlorosilane with a flow rate of 10 sccm, a carbon-containing reaction source ethylene with a flow rate of 5 sccm, and a carrier gas hydrogen with a flow rate of 200 sccm are introduced into the reaction chamber, and a silicon carbide coating is deposited on the surface of the graphite piece at a surface deposition temperature of 1400°C and a reaction pressure of 1 kPa for 3 h; after deposition, cooling to room temperature under argon atmosphere.

[0051] Performance test and result analysis

[0052] According to the existing national and industry standards, the following methods are used to test the performance of the silicon carbide coating on the graphite piece prepared in Examples 1-3 and Comparative Examples 1-3 and the preparation method thereof: the samples of Examples 1-3 and Comparative Examples 1-3 are tested as follows: line scanning of the coating cross-section is performed by scanning electron microscopy with an energy dispersive spectrometer to analyze the element distribution and measure the coating thickness, five measurements are taken at different positions for each sample and the average value is taken; the adhesion between the coating and the graphite substrate is tested by scratch method, a diamond indenter is used to load the coating surface at a constant rate to 100 N, and the critical load is determined by the sudden change of acoustic emission signal and friction force; the sample is placed in a high temperature muffle furnace in air atmosphere, and oxidized at 800°C for 1 hour, then taken out and cooled to room temperature, weighed, and the mass change per unit area is calculated to evaluate the oxidation resistance performance; the sample is used as a susceptor tray of an epitaxial growth device, and repeated thermal cycle test is carried out in a semiconductor process chamber, each cycle includes the process of rising from room temperature to 1200°C and holding for 10 minutes and then cooling to room temperature, and the total cycle number before the coating cracks, peels off or fails is recorded to evaluate the service life.

[0053] Table 1: Performance test results of each example and comparative example

[0054]

[0055] As can be seen from Table 1, the present application embodiments 1-3 successfully solve the core technical problems of uneven nucleation and weak adhesion of silicon carbide on the surface of graphite in the chemical vapor deposition process by synergistically using phosphazene functionalized silazane and boron-silicon calamine compound for surface pretreatment. Specifically, the coating thickness uniformity of the embodiments is significantly better than that of the comparative examples, with a fluctuation range controlled within ±5.1%, which is far lower than that of comparative example 1 of ±8.9%, comparative example 2 of ±9.5% and comparative example 3 of ±15.6%, which directly confirms that the active transition layer created by the composite modifier greatly promotes the uniform and dense formation of silicon carbide nuclei. In terms of adhesion, the critical load of the embodiments is as high as 75 N or more, while the critical load of comparative examples 1 and 2 decreases to 55 N and 50 N respectively due to the absence of one key modifier, and the critical load of comparative example 3 without any pretreatment drops to 35 N, highlighting the synergistic effect of the two substances in strengthening the interfacial bonding. In the final performance life test, the thermal cycle times of the embodiments are close to or more than 500 times, the life is more than 1.7 times that of comparative example 3, and the oxidation weight gain is less than half that of comparative examples 1 and 2, which comprehensively shows that the coating prepared by the present application not only has high initial quality, but also has fundamental improvement in long-term stability and reliability during use, completely overcoming the early failure problem of the coating caused by poor nucleation and weak adhesion in the prior art.

[0056] The above-described embodiments only express several embodiments of the present application, which are described in detail and specifically, but should not be understood as limiting the scope of the present application. It should be noted that for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application.

Claims

1. A method of producing a silicon carbide coating on a graphite article, characterized by the steps of The application relates to a surface modification method of graphite, which comprises the following steps: S1, polishing the surface of the cut graphite piece with a diamond polishing paste, then placing the graphite piece into an acetone solvent for ultrasonic cleaning; subsequently drying the cleaned graphite piece in an oven at 110-130 DEG C to obtain a pretreated graphite piece; S2, spraying a solution containing phosphazene functionalized silazane and a boron-silicon calamine compound on the pretreated graphite piece, then performing drying and curing treatment to obtain a surface-modified graphite piece; The preparation method of the phosphazene functionalized silazane comprises the following steps: A1, dissolving hexachlorocyclotriphosphazene in anhydrous tetrahydrofuran under a dry argon atmosphere, and cooling to-8~-10 DEG C; under stirring, dropwise adding a mixed solution formed by dissolving aminopropyltriethoxysilane and triethylamine in anhydrous tetrahydrofuran; after dropwise addition, warming to room temperature, and continuing stirring; A2, heating to 64-66 DEG C, and continuously reacting; after reaction completion, cooling to room temperature, and concentrating the filtrate through vacuum filtration to obtain a crude product; dissolving the crude product in n-hexane, and purifying through silica gel column chromatography to collect a fraction; The preparation method of the boron-silicon calamine compound comprises the following steps: B1, dissolving 1,4-bis(4-hydroxyphenyl)benzene and triisopropyl borate in toluene, and adding p-toluenesulfonic acid; heating to reflux, and continuously reacting; after reaction completion, cooling to room temperature, and obtaining an acid ester compound; B2, placing the acid ester compound, hydrogenated trimethoxysilane and tris(triphenylphosphine)rhodium chloride in a high-pressure reaction kettle, and adding anhydrous dichloromethane; replacing the air in the reaction kettle with argon, and then filling with argon; heating to 58-62 DEG C, and continuously stirring and reacting; after reaction completion, cooling to room temperature, and filtering through a diatomite pad; adding triphenylphosphine to the filtrate, filtering, and then concentrating the filtrate through a rotary evaporator to obtain a crude product; dissolving the crude product in dichloromethane, and purifying through neutral alumina column chromatography to collect a fraction; S3, placing the surface-modified graphite piece in a reaction cavity of a chemical vapor deposition device; introducing a silicon-containing reaction source, a carbon-containing reaction source and a carrier gas into the reaction cavity, and depositing a SiC coating on the surface of the surface-modified graphite piece; after deposition completion, cooling to room temperature under an argon atmosphere.

2. The method of claim 1, wherein In step S2, the mass concentration of the phosphazene functionalized silazane is 1-10%, and the mass concentration of the boron-silicon calamine compound is 0.5-5%; the drying and curing treatment temperature is 150-400 DEG C.

3. The method of claim 1, wherein the graphite article is a graphite electrode. In step S3, the surface deposition temperature is 1250-1550 DEG C, and the reaction pressure is 100-5000 Pa; the silicon-containing reaction source is trichlorosilane, the carbon-containing reaction source is ethylene, and the carrier gas is hydrogen.

4. The method of claim 1, wherein In step A1, the molar ratio of hexachlorocyclotriphosphazene, aminopropyltriethoxysilane and triethylamine is 1:3:3; the continuous stirring time is 12-14 h.

5. The method of claim 1, wherein the graphite article is a graphite electrode. In step A2, the continuous reaction time is 24-26 h.

6. The method of claim 1, wherein In step B1, the molar ratio of 1,4-bis(4-hydroxyphenyl)benzene and triisopropyl borate is 1:3; and the continuous reaction time is 18-20 h.

7. The method of claim 1, wherein the graphite article is a graphite electrode. In step B2, the continuous stirring and reaction time is 36-40 h.

8. A silicon carbide coating for a graphite article, characterized by, The graphite piece silicon carbide coating is prepared according to the method of any one of claims 1-7. The graphite piece silicon carbide coating is prepared according to the method of any one of claims 1-7.

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