A composite coating for growing large-diameter single-crystalline silicon and a preparation method thereof

Abstract

The present invention belongs to the technical field of single-crystal silicon coating, and particularly relates to a composite coating for large-diameter single-crystal silicon growth and a preparation method thereof. Among them, the composite coating for large-diameter single-crystal silicon growth comprises the following raw materials: 70-90 parts of ceramic composite, 5-15 parts of carbon fiber cloth, and 5-15 parts of CeO₂; silane coupling agent is used to modify TaC to achieve chemical metallurgical bonding with MoSi₂, and the ceramic composite is prepared, enhancing the interfacial bonding. The CeO₂ pre-coating and the carbon fiber cloth construct a three-dimensional reinforcement system of "chemical bonding-mechanical interlocking-gradient thermal buffer". The high-strength network of the carbon fiber cloth and the refined ceramic grains of CeO₂ form a synergistic toughening mechanism, which not only bridges the crack propagation through the fibers but also improves the hardness through grain boundary strengthening. Combining with the vitreous protective film on the surface of the carbon fiber, the oxidation process is significantly delayed.

Description

Technical Field

[0001] The present invention belongs to the technical field of single-crystal silicon coating, and particularly relates to a composite coating for growing large-diameter single-crystal silicon and a preparation method thereof. Background Art

[0002] Single-crystal silicon is a key material in the semiconductor and solar energy industries and is widely used in the manufacturing of integrated circuits, solar cells and other fields. With the progress of technology and the growth of market demand, the demand for large-diameter single-crystal silicon is increasing day by day. Large-diameter single-crystal silicon can provide higher production efficiency and better crystal quality, thereby reducing waste in the slicing process and improving the performance of the final product. Currently, in the process of growing large-diameter single-crystal silicon, factors such as high-temperature environment (about 1400 °C), chemical erosion of silicon melt, thermal stress and mechanical stress pose extremely high requirements on the surface coating of the growth container (such as quartz crucible, graphite crucible).

[0003] The traditional coating technology has the following problems: a single ceramic coating is prone to phase transformation or decomposition at high temperature for a long time, resulting in structural damage; metal coatings (such as Mo, W) may form silicides when contacting with silicon melt, contaminating the silicon crystal; mechanical stability defects: the coating is prone to cracking or peeling due to thermal stress, introducing impurity particles; multi-layer composite coatings still have problems such as low interfacial bonding strength and single functionality. In view of the above problems, the present invention aims to provide a composite coating with high temperature resistance, chemical stability and high mechanical strength, reducing thermal stress through interfacial gradient transition, enhancing the interfacial bonding force, solving the problems of easy cracking, peeling and contamination of the coating in the growth of large-diameter single-crystal silicon, and improving the comprehensive properties such as high temperature resistance and corrosion resistance of the coating to extend its service life. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a composite coating for large-diameter single-crystal silicon growth and a preparation method thereof. The ceramic composite / carbon fiber cloth / CeO₂ composite coating prepared by the spraying and laying combination method significantly improves the comprehensive performance of the coating through multiphase synergistic action and gradient interface design: in the gradient interface, the CeO₂ pre-coating forms a mechanical interlocking structure with the carbon fiber cloth and generates a stable interface phase, effectively alleviating the thermal expansion difference between the ceramic and the substrate, enhancing the interlayer bonding force and suppressing the concentration of thermal stress; the high-strength network of the carbon fiber cloth and the refined ceramic grains of CeO₂ form a synergistic toughening mechanism, which not only enhances the hardness by fiber bridging crack propagation but also through grain boundary strengthening; the composite oxide film formed by the sintering of CeO₂ and silica sol forms a dense protective layer at high temperature, combined with the vitreous protective film on the surface of the carbon fiber, significantly delaying the oxidation process. In addition, the high melting point and corrosion resistance of the ceramic composite itself, the lightweight and high thermal conductivity of the carbon fiber, and the oxygen vacancy regulation and catalytic activity of CeO₂ jointly endow the coating with excellent high-temperature stability, chemical compatibility, and the ability to purify the single-crystal silicon growth environment, realizing the multi-dimensional optimization of the composite coating for large-diameter single-crystal silicon growth.

[0005] The present invention provides a composite coating for large-diameter single-crystal silicon growth, and the composite coating for large-diameter single-crystal silicon growth is prepared from the following raw materials in parts by weight: 70-90 parts of ceramic composite, 5-15 parts of carbon fiber cloth, 5-15 parts of CeO₂, and 30-60 parts of silica sol;

[0006] The ceramic composite is prepared from the following raw materials in the following weight ratio: TaC:MoSi₂:zirconia microspheres:silane coupling agent:acetone = 2-3:1:3:0.04:1-3;

[0007] The preparation method of the ceramic composite specifically includes the following steps:

[0008] A1, weigh TaC, soak TaC in absolute ethanol, ultrasonically clean for 15 min to remove surface oil stains and impurities, then filter, and dry in an oven at 80 °C for 2 h to obtain TaC powder;

[0009] A2, add the silane coupling agent to the solution of absolute ethanol and deionized water, the volume ratio of deionized water to absolute ethanol is 1:10, and the volume ratio of the silane coupling agent to the solution is 1:10, stir evenly, and adjust the pH to 4-5 with glacial acetic acid to promote hydrolysis to form a mixed solution;

[0010] A3, add the TaC powder to the mixed solution prepared in step A2, stir at room temperature for 2-4 h, then filter and wash, dry at 60 °C first, then put it into a vacuum oven, heat-treat for 1 h, set the temperature to 120 °C, and naturally cool to obtain modified TaC;

[0011] A4. Put the modified TaC and zirconia microspheres into a ball mill and start ball milling. Then add MoSi2 and acetone and carry out ball milling and mixing at a rotation speed of 300 rpm for a set time of 12 h to fully mix and refine the powder to form a mixed powder.

[0012] A5. Pour the mixed powder into a mold and press it into a green compact at 100 - 500 MPa. Put the green compact into a high-temperature furnace for sintering. Starting from room temperature, heat it up at a rate of 5 °C / min to 1600 - 2000 °C, hold it at 1600 - 2000 °C for 3 h, and then cool it to room temperature to obtain a ceramic composite.

[0013] Further, the silane coupling agent is KH-550 (γ-aminopropyltriethoxysilane) or KH-560 (γ-glycidoxypropyltrimethoxysilane).

[0014] The present invention also provides a preparation method for a composite coating for growing large-diameter single crystal silicon, which specifically includes the following steps:

[0015] S1. Weigh CeO2 and 10 - 30 parts of silica sol and add them to deionized water. The mass ratio of CeO2 to deionized water is 1:5. Stir for 30 min to form a uniform CeO2 dispersion. Use the CeO2 dispersion for spraying to obtain a CeO2 pre-coating. Control the spraying pressure at 0.2 - 0.3 MPa, the spraying distance at 15 - 20 cm, and the spraying thickness of each layer at 20 - 30 μm. After spraying each layer, put the pretreated substrate into an oven at 80 °C and dry it for 10 min. Repeat spraying 3 times to make the total thickness of the CeO2 pre-coating reach 50 - 80 μm.

[0016] S2. Immerse the carbon fiber cloth in a 3% ammonium nitrate solution for 30 min, then wash it with deionized water, dry it, and cut it to obtain a pretreated carbon fiber cloth. Lay the pretreated carbon fiber cloth flat on the CeO2 pre-coating and press it to form a carbon fiber cloth pre-coating.

[0017] S3. Weigh the ceramic composite and 20 - 30 parts of silica sol and add them to deionized water for batching. The mass ratio of the ceramic composite to deionized water is 3:1 to form a slurry with a viscosity of 500 - 800 mPa·s. Use the slurry to spray above the carbon fiber cloth pre-coating prepared in step S2 with a thickness of 400 - 600 µm to obtain a composite coating precursor. Control the spraying pressure at 10 - 15 MPa, the nozzle diameter at 1.5 mm, and the moving speed of the spraying machine at 50 mm / s. Control the spraying thickness of each layer at 100 - 150 μm. After spraying each layer, first leave it to dry at room temperature for 30 min, and then put it into an oven and dry it at 120 °C for 1 h. Repeat spraying 4 times to make the total thickness of the ceramic composite coating reach 400 - 600 μm.

[0018] S4. High-temperature sinter the composite coating precursor. Starting from room temperature, raise the temperature to 600 °C at a heating rate of 5 °C / min, hold at 600 °C for 1 h, then continue to raise the temperature to 1400 °C at a rate of 5 °C, hold at 1400 °C for 5 h, and cool to room temperature with the furnace to obtain the composite coating for large-diameter single-crystal silicon growth.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0020] The present invention adopts a method combining spraying and laying, and uses a ceramic composite, carbon fiber cloth, and CeO2 to jointly prepare a composite coating for the growth of large-diameter single-crystalline silicon. The chemical metallurgical bonding between TaC and MoSi2 is realized through the modification of TaC with a silane coupling agent, breaking through the problem of weak interfacial bonding of ceramic composite materials. The dual interfacial design of the CeO2 pre-coating and the carbon fiber cloth constructs a three-dimensional reinforcement system of "chemical bonding - mechanical interlocking - gradient thermal buffering". Treating TaC with a silane coupling agent, the -SiOH generated by the hydrolysis of the silane coupling agent condenses with the surface hydroxyl groups of TaC to form Si-O-Ta. At the same time, the amino group at the other end reacts with the Si-O bond of MoSi2 to form an interpenetrating network structure at the TaC-MoSi2 interface, increasing the interfacial bonding strength by 3 times, effectively inhibiting phase separation and interfacial debonding; the modification of the silane coupling agent reduces the surface energy of TaC particles, inhibits agglomeration, and makes it more evenly dispersed in substances such as MoSi2 during ball milling. Combining acetone as a dispersant ensures the uniform distribution of each component, facilitating the formation of a uniform microstructure. The surface hydroxyl groups hydrolyzed from CeO2 nanoparticles condense with the surface hydroxyl groups of the carbon fiber cloth to form ether bonds, and the Si-OH of the silica sol forms Si-O-C bonds with the C-OH of the carbon fiber cloth. Coupled with the defect sites formed by the surface oxidation of the carbon fiber, it promotes the formation of Ce-O-C bonds, greatly enhancing the bonding strength between the carbon fiber cloth and the ceramic layer and realizing efficient interlayer load transfer; CeO2 nanoparticles are embedded in the pores of the carbon fiber cloth to form mechanical interlocking and sinter with the silica sol to generate a Ce2Si2O7 interface phase, constructing a thermal expansion gradient buffer structure between the graphite matrix and the ceramic layer, realizing the continuous matching of the thermal expansion coefficients, effectively alleviating the thermal expansion difference between the ceramic and the matrix, inhibiting the concentration of thermal stress, and preventing the coating from cracking due to thermal mismatch. The high-strength carbon fiber cloth forms a physical barrier on the crack propagation path, and the toughness of the coating is improved through the fiber pull-out energy dissipation mechanism. CeO2 nanoparticles form a pinning effect in the ceramic layer, inhibiting abnormal grain growth. Combining with zirconia microspheres during ball milling reduces the average grain size and increases the grain boundary area, and greatly improves the hardness of the coating through grain boundary strengthening, forming a structure of rigidity and flexibility and breaking through the mechanical property limitations of single materials. The dense Ce2Si2O7 glassy film blocks the oxygen ion diffusion path from both chemical barrier and physical barrier aspects. Using the silica sol precursor to in-situ generate a SiO2 protective film on the carbon fiber surface improves the antioxidant performance; the coating inherits the high melting point of TaC and the self-healing property of MoSi2, forming a dynamically balanced SiO2 protective layer in the high-temperature melt, increasing the service life of the coating. Description of the Drawings

[0021] Figure 1 SEM image of the composite coating for the growth of large-diameter single-crystalline silicon prepared by the present invention;

[0022] Figure 2 Thermal conductivity diagram of the composite coating for the growth of large-diameter single-crystalline silicon prepared by the present invention. Detailed implementation mode

[0023] In order to enable those skilled in the art to better understand the technical solutions of the present invention and make the above features, objectives, and advantages of the present invention clearer and easier to understand, the present invention will be further described below in conjunction with embodiments. The embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0024] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the present invention. The preferred implementation methods and materials described herein are only for demonstration purposes and cannot limit the content of this application.

[0025] In the following embodiments, unless otherwise specified, they are all conventional methods; the materials used in the following embodiments, unless otherwise specified, the raw materials are all new materials purchased from the market.

[0026] Embodiment 1: This embodiment provides a composite coating for the growth of large-diameter single-crystalline silicon. The composite coating for the growth of large-diameter single-crystalline silicon is prepared from the following raw materials in parts by weight: 70 parts of ceramic composite, 5 parts of carbon fiber cloth, 5 parts of CeO₂, and 30 parts of silica sol;

[0027] The ceramic composite is prepared from the following raw materials in weight ratio: TaC:MoSi₂:zirconia microspheres:silane coupling agent:acetone = 2 - 3:1:3:0.04:1 - 3;

[0028] The preparation method of the ceramic composite specifically includes the following steps:

[0029] A1. Weigh 5 parts of TaC, soak TaC in absolute ethanol, ultrasonically clean for 15 min to remove surface oil stains and impurities, then filter, and dry in an 80 °C oven for 2 h to obtain TaC powder;

[0030] A2. Add KH-550 to a solution of absolute ethanol and deionized water. The volume ratio of deionized water to absolute ethanol is 1:10, and the volume ratio of KH-550 to the solution is 1:10. Stir evenly, and adjust the pH to 4 - 5 with glacial acetic acid to promote hydrolysis to form a mixed solution;

[0031] A3. Add the TaC powder to the mixed solution prepared in step A2, stir at room temperature for 2 h, filter and wash, dry in a 60 °C oven, then put it into a vacuum oven, heat-treat for 1 h, set the temperature to 120 °C, and cool naturally to obtain modified TaC;

[0032] A4. Put the modified TaC and zirconia microspheres into a ball mill and start ball milling. Then add MoSi2 and acetone and carry out ball milling and mixing at a rotation speed of 300 rpm for a set time of 12 h to achieve sufficient mixing and refinement, forming a mixed powder.

[0033] A5. Pour the mixed powder into a mold and press it into a green compact at 100 MPa. Put the green compact into a high-temperature furnace for sintering. Starting from room temperature, heat it up to 1600 °C at a rate of 5 °C / min, hold it at 1600 °C for 3 h, and then cool it to room temperature to obtain a ceramic composite.

[0034] This embodiment also provides a preparation method for a composite coating for growing large-diameter single-crystalline silicon, specifically including the following steps:

[0035] S1. Select a quartz crucible as the substrate to be coated, soak the quartz crucible in acetone for 15 min for cleaning to remove oil and impurities, then rinse it with deionized water and dry it to obtain a pretreated substrate.

[0036] S2. Weigh 5 parts of CeO2 and 10 parts of silica sol and add them to deionized water. The mass ratio of CeO2 to deionized water is 1:5. Stir for 30 min to form a uniform CeO2 dispersion. Use the CeO2 dispersion to spray the pretreated substrate to obtain a CeO2 pre-coating. Control the spraying pressure at 0.2 MPa, the spraying distance at 15 cm, and the thickness of each sprayed layer at 20 μm. After spraying each layer, put the sprayed pretreated substrate into an oven at 80 °C and dry it for 10 min. Repeat spraying 3 times to make the total thickness of the CeO2 pre-coating reach 50 μm.

[0037] S3. Soak 5 parts of carbon fiber cloth in a 3% ammonium nitrate solution for 30 min, then wash it with deionized water, dry it, and cut it to obtain pretreated carbon fiber cloth. Lay the pretreated carbon fiber cloth flat on the CeO2 pre-coating and press it to form a carbon fiber cloth pre-coating.

[0038] S4. Weigh 70 parts of the ceramic composite and 20 parts of silica sol and add them to deionized water for batching. The mass ratio of the ceramic composite to deionized water is 3:1 to form a slurry with a viscosity of 500 mPa·s. Use the slurry to spray above the carbon fiber cloth pre-coating prepared in step S3 with a thickness of 400 µm to obtain a composite coating precursor. Control the spraying pressure at 10 MPa, the nozzle diameter at 1.5 mm, and the moving speed of the spraying machine at 50 mm / s. Control the thickness of each sprayed layer at 100 - 150 μm. After spraying each layer, first leave it to dry at room temperature for 30 min, then put it into an oven and dry it at 120 °C for 1 h. Repeat spraying 4 times to make the total thickness of the ceramic composite coating reach 400 μm.

[0039] S5. Subject the composite coating precursor to high-temperature sintering. Starting from room temperature, raise the temperature to 600 °C at a heating rate of 5 °C / min, hold at 600 °C for 1 h, then continue to raise the temperature to 1400 °C at a rate of 5 °C, hold at 1400 °C for 5 h, and cool to room temperature in the furnace to obtain the composite coating for large-diameter single-crystal silicon growth.

[0040] Example 2: This example provides a composite coating for large-diameter single-crystal silicon growth, which is prepared from the following raw materials in parts by weight: 80 parts of ceramic composite, 10 parts of carbon fiber cloth, 10 parts of CeO2, and 40 parts of silica sol.

[0041] The ceramic composite is prepared from the following raw materials in weight ratio: TaC:MoSi2:zirconia microspheres:silane coupling agent:acetone = 2 - 3:1:3:0.04:1 - 3.

[0042] The preparation method of the ceramic composite specifically includes the following steps:

[0043] A1. Weigh 60 parts of TaC, soak TaC in absolute ethanol, ultrasonically clean for 15 min to remove surface oil stains and impurities, then filter, and dry in an 80 °C oven for 2 h to obtain TaC powder.

[0044] A2. Add KH-550 to the solution of absolute ethanol and deionized water. The volume ratio of deionized water to absolute ethanol is 1:10, and the volume ratio of the silane coupling agent to the solution is 1:10. Stir evenly, adjust the pH to 5 with glacial acetic acid to promote hydrolysis, and form a mixed solution.

[0045] A3. Add the TaC powder to the mixed solution prepared in step A2, stir at room temperature for 3 h, filter and wash, dry in a 60 °C oven, then put it into a vacuum oven, perform heat treatment for 1 h at a temperature of 120 °C, and cool naturally to obtain modified TaC.

[0046] A4. Put the modified TaC and zirconia microspheres into a ball mill to start ball milling, then add MoSi2 and acetone, perform ball milling and mixing at a rotation speed of 300 rpm for a set time of 12 h to make them fully mixed and refined to form a mixed powder.

[0047] A5. Pour the mixed powder into a mold, press it into a compact at 400 MPa, put the compact into a high-temperature furnace for sintering, raise the temperature from room temperature to 1800 °C at a rate of 5 °C / min, hold at 1800 °C for 3 h, and cool to room temperature to obtain the ceramic composite.

[0048] This example also provides a preparation method of the composite coating for large-diameter single-crystal silicon growth, which specifically includes the following steps:

[0049] S1, Select a quartz crucible as the substrate to be coated. Immerse the quartz crucible in acetone for 15 min for cleaning to remove oil and impurities, then rinse with deionized water and dry to obtain a pretreated substrate;

[0050] S2, Weigh 10 parts of CeO2 and 20 parts of silica sol and add them to deionized water. The mass ratio of CeO2 to deionized water is 1:5. Stir for 30 min to form a uniform CeO2 dispersion. Use the CeO2 dispersion to spray the pretreated substrate to obtain a CeO2 pre - coating. Control the spraying pressure at 0.3 MPa, the spraying distance at 20 cm, and the thickness of each sprayed layer at 25 μm. After spraying each layer, put the sprayed pretreated substrate into an oven at 80 °C and dry for 10 min. Repeat spraying 3 times to make the total thickness of the CeO2 pre - coating reach 60 μm;

[0051] S3, Immerse 10 parts of carbon fiber cloth in a 3% ammonium nitrate solution for 30 min, then wash with deionized water, dry, and cut to obtain pretreated carbon fiber cloth. Lay the pretreated carbon fiber cloth flat on the CeO2 pre - coating and press it to form a carbon fiber cloth pre - coating;

[0052] S4, Weigh 80 parts of ceramic composite and 20 parts of silica sol, add them to deionized water for batching. The mass ratio of the ceramic composite to deionized water is 3:1 to form a slurry with a viscosity of 600 mPa·s. Use the slurry to spray above the carbon fiber cloth pre - coating prepared in step S3 with a thickness of 500 µm to obtain a composite coating precursor. Control the spraying pressure at 15 MPa, the nozzle diameter at 1.5 mm, and the moving speed of the spraying machine at 50 mm / s. Control the thickness of each sprayed layer at 120 μm. After spraying each layer, first leave it to dry at room temperature for 30 min, then put it into an oven and dry at 120 °C for 1 h. Repeat spraying 4 times to make the total thickness of the ceramic composite coating reach 500 μm;

[0053] S5, Perform high - temperature sintering on the composite coating precursor. From room temperature, raise the temperature to 600 °C at a heating rate of 5 °C / min, hold at 600 °C for 1 h, then continue to raise the temperature to 1400 °C at a rate of 5 °C, hold at 1400 °C for 5 h, and cool to room temperature with the furnace to obtain a composite coating for large - diameter single - crystal silicon growth.

[0054] Example 3: This example provides a composite coating for large - diameter single - crystal silicon growth. The composite coating for large - diameter single - crystal silicon growth is prepared from the following raw materials in parts by weight: 90 parts of ceramic composite, 15 parts of carbon fiber cloth, 15 parts of CeO2, and 60 parts of silica sol;

[0055] The ceramic composite is prepared from raw materials in the following weight ratios: TaC:MoSi2:zirconia microspheres:silane coupling agent:acetone = 2 - 3:1:3:0.04:1 - 3;

[0056] The preparation method of the ceramic composite specifically includes the following steps:

[0057] A1, Weigh 65 parts of TaC, soak TaC in absolute ethanol, ultrasonically clean for 15 min to remove surface oil stains and impurities, then filter, and dry in an 80 °C oven for 2 h to obtain TaC powder;

[0058] A2, Add KH-560 to a solution of a mixture of absolute ethanol and deionized water. The volume ratio of deionized water to absolute ethanol is 1:10, and the volume ratio of the silane coupling agent to the solution is 1:10. Stir evenly, and adjust the pH to 5 with glacial acetic acid to promote hydrolysis to form a mixed solution;

[0059] A3, Add the TaC powder to the mixed solution prepared in step A2, stir at room temperature for 4 h, filter and wash, dry in a 60 °C oven, then put it into a vacuum oven, perform heat treatment for 1 h, set the temperature to 120 °C, and cool naturally to obtain modified TaC;

[0060] A4, Put the modified TaC and zirconia microspheres into a ball mill to start ball milling, then add MoSi2, and then add acetone, and perform ball milling and mixing at a rotation speed of 300 rpm for a set time of 12 h to make the powder fully mixed and refined to form a mixed powder;

[0061] A5, Pour the mixed powder into a mold, press and form at 500 MPa to form a green compact. Put the green compact into a high-temperature furnace for sintering. From room temperature, heat up to 2000 °C at a rate of 5 °C / min, hold at 2000 °C for 3 h, and cool to room temperature to obtain the ceramic composite.

[0062] This embodiment also provides a preparation method of a composite coating for growing large-diameter single-crystalline silicon, specifically including the following steps:

[0063] S1, Select a quartz crucible as the substrate to be coated, soak the quartz crucible in acetone for cleaning for 15 min to remove oil and impurities, then rinse with deionized water and dry to obtain a pretreated substrate;

[0064] S2. Weigh 15 parts of CeO₂ and 30 parts of silica sol and add them to deionized water. The mass ratio of CeO₂ to deionized water is 1:5. Stir for 30 min to form a uniform CeO₂ dispersion. Use the CeO₂ dispersion to spray the pretreated substrate to obtain a CeO₂ pre-coating. Control the spraying pressure at 0.3 MPa, the spraying distance at 20 cm, and the thickness of each sprayed layer at 30 μm. After spraying each layer, put the sprayed pretreated substrate into an oven at 80 °C and dry for 10 min. Repeat spraying 3 times to make the total thickness of the CeO₂ pre-coating reach 80 μm.

[0065] S3. Immerse 15 parts of carbon fiber cloth in 3% ammonium nitrate solution for 30 min, then wash with deionized water, dry, and cut to obtain pretreated carbon fiber cloth. Lay the pretreated carbon fiber cloth flat on the CeO₂ pre-coating and press it to form a carbon fiber cloth pre-coating.

[0066] S4. Weigh 90 parts of ceramic composite and 30 parts of silica sol and add them to deionized water for batching. The mass ratio of the ceramic composite to deionized water is 3:1 to form a slurry with a viscosity of 800 mPa·s. Use the slurry to spray above the carbon fiber cloth pre-coating prepared in step S3 with a thickness of 600 µm to obtain a composite coating precursor. Control the spraying pressure at 15 MPa, the nozzle diameter at 1.5 mm, and the moving speed of the spraying machine at 50 mm / s. Control the thickness of each sprayed layer at 150 μm. After spraying each layer, first leave it to dry at room temperature for 30 min, then put it into an oven and dry at 120 °C for 1 h. Repeat spraying 4 times to make the total thickness of the ceramic composite coating reach 600 μm.

[0067] S5. Perform high-temperature sintering on the composite coating precursor. From room temperature, raise the temperature to 600 °C at a heating rate of 5 °C / min, hold at 600 °C for 1 h, then continue to raise the temperature to 1400 °C at a rate of 5 °C, and hold at 1400 °C for 5 h, and then cool to room temperature with the furnace to obtain a composite coating for large-diameter single-crystalline silicon growth.

[0068] The difference between Comparative Example 1 and Example 2 is that no ceramic composite is added, and the rest is the same as Example 2.

[0069] The difference between Comparative Example 2 and Example 2 is that no carbon fiber cloth is added, and the rest is the same as Example 2.

[0070] The difference between Comparative Example 3 and Example 2 is that no CeO₂ is added, and the rest is the same as Example 2.

[0071] Experimental Example 1: The Vickers microhardness of the composite coating for large-diameter single-crystal silicon growth prepared by the present invention was measured using a micro Vickers hardness tester (HV-1000). The composite coatings for large-diameter single-crystal silicon growth prepared in Examples 1-3 and Comparative Examples 1-3 were used as specimens. The load was set at 1000 gf and the pressure holding time was 10 s. The measurement points were taken every 0.2 mm from the top of the coating to the substrate. Every ten points were taken as a set of data points. The above steps were repeated three times at three different initial positions for each specimen, and the average value was taken. The results were recorded in Table 1.

[0072] Experimental Example 2: According to the test standard of GB / T1040.1-2006, a CMT-4202 universal tensile testing machine of MTS Systems (China) Corporation was used for testing at room temperature. The composite coatings for large-diameter single-crystal silicon growth prepared in Examples 1-3 and Comparative Examples 1-3 were used as specimens, and the tensile rate was set at 5 mm·min -1 . Before the test, the specimens were cut into dumbbell-shaped standard specimens with a cutter (width b = 4.00 ± 0.05 mm, thickness d = 2.00 ± 0.05 mm, original gauge length was 25.00 ± 0.05 mm). The fracture toughness of the samples was recorded. After testing 5 samples in each group, the average value was taken. The results were recorded in Table 1.

[0073] Experimental Example 3: According to the requirements of GB / T 1768-2006 "Test Methods for Wear Resistance of Coatings and Coating Materials", a paint film abrasion meter was used to measure the wear resistance of the coating. The composite coatings for large-diameter single-crystal silicon growth prepared in Examples 1-3 and Comparative Examples 1-3 were used as specimens. The specimens were fixed on the testing machine, a load of 500 g was applied, the standard abrasive CS-10 grinding wheel was selected, the number of revolutions was set at 500 revolutions, and the equipment was started for cyclic friction and wear. After the test, the mass difference of the specimens before and after wear was weighed, and the wear resistance was characterized by the mass loss per unit revolution. The average value was taken after parallel testing 3 times. The mass loss situation, that is, the wear amount results, were recorded in Table 1.

[0074] Experimental Example 4: Corrosion resistance test

[0075] The corrosion resistance of the coating was tested by salt spray test. Specimens were prepared from the composite coatings for large-diameter single-crystal silicon growth prepared in Examples 1-3 and Comparative Examples 1-3. The prepared coating surface was scratched with a scalpel, left standing for 24 h, and then placed in a salt spray test chamber to observe the corrosion behavior. During the test, the corrosion situation of the coating specimens' surface was regularly checked, and the corrosion area was rated according to the national standard GB / T 6464-2002. The corrosion rating of the metal was calculated according to the percentage of the total area occupied by the corrosion defects using the following formula: Rp = 3×(2 - LogA), where Rp is the corrosion rating number and A is the percentage of the total area occupied by the metal corrosion. The corrosion results were recorded as shown in Table 1.

[0076] Table 1

[0077]

[0078] As shown in the results of Table 1, the hardness of the composite coating for large-diameter single-crystalline silicon growth prepared by the present invention reached 665.42 HV. The added ceramic composite significantly enhanced the hardness of the composite coating. The fracture toughness of Examples 1-3 was significantly higher than that of Comparative Examples 1-3. The added carbon fiber interacted with CeO2, effectively improving the toughness of the composite coating for large-diameter single-crystalline silicon growth while maintaining the hardness. The wear amount of the example was as low as 2.16 mg, significantly enhancing the wear resistance. In the corrosion resistance rating, the composite coating for large-diameter single-crystalline silicon growth prepared by the present invention had good corrosion resistance. The present invention realized the comprehensive optimization of the coating hardness, toughness, wear resistance and corrosion resistance, and the performance was significantly better than that of the comparative example.

[0079] Figure 1 This is the microscopic morphology of the surface of the composite coating for large-diameter single-crystalline silicon growth prepared by the present invention. It can be seen that the surface of the coating is flat and dense, and no obvious cracks appear; Figure 2 The thermal conductivity results show that the thermal conductivity of Example 2 was increased to 29.3 W / (m·k), reducing the growth energy consumption, forming a continuous thermal conductivity gradient, reducing the interfacial thermal resistance, ensuring the uniform growth of large-diameter single-crystalline silicon, and increasing the service life of the composite coating.

[0080] In summary, the present invention constructed a ternary composite coating system of ceramic composite / carbon fiber cloth / CeO2 by the spraying and laying combination method. Through the modification of silane coupling agent, the chemical metallurgical bonding of TaC-MoSi2 was realized. The CeO2 pre-coating and the carbon fiber cloth formed a three-dimensional interface of "chemical bonding-mechanical interlocking-gradient thermal buffer", as well as the grain refinement and rigid-flexible coexistence structure of the ceramic layer, breaking through the technical bottlenecks such as weak interfacial bonding, thermal mismatch cracking and insufficient oxidation resistance of traditional coatings. The prepared coating has high thermal conductivity, high hardness and good fracture toughness. Through the collaborative innovation of material design and process, the present invention provides a high-performance solution for large-diameter single-crystalline silicon growth, with significant technological progress and industrial application value.

[0081] The above describes the present invention and its implementation manners. This description is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention, and the actual application is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and design similar ways and embodiments without creative work without departing from the purpose of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A preparation method of a composite coating for growing large-diameter single-crystalline silicon, characterized in that, Specifically, it includes the following steps: S1, Weigh CeO2 and 10 - 30 parts of silica sol, add them to deionized water, stir to form a CeO2 dispersion liquid, and use the CeO2 dispersion liquid for spraying to obtain a CeO2 pre - coating; S2, Immerse the carbon fiber cloth in ammonium nitrate solution, then wash with water, dry, and cut to obtain a pretreated carbon fiber cloth. Lay the pretreated carbon fiber cloth on the CeO2 pre - coating and compact it to form a carbon fiber cloth pre - coating; S3, Weigh the ceramic composite and 20 - 30 parts of silica sol, add them to deionized water for batching to form a slurry, and use the slurry to spray above the carbon fiber cloth pre - coating prepared in step S2 to obtain a composite coating precursor; S4, Subject the composite coating precursor to high - temperature sintering, and cool it to room temperature to obtain a composite coating for large - diameter single - crystal silicon growth; Among them, the CeO2 is 5 - 15 parts by weight, the carbon fiber cloth is 5 - 15 parts by weight, and the ceramic composite is 70 - 90 parts by weight; The ceramic composite is prepared from raw materials in the following weight ratios: TaC:MoSi2:zirconia microspheres:silane coupling agent:acetone = 2 - 3:1:3:0.04:1 - 3; The preparation method of the ceramic composite specifically includes the following steps: A1, Weigh TaC, ultrasonically clean TaC, filter, and dry to obtain TaC powder; A2, Add the silane coupling agent to a solution mixed with anhydrous ethanol and deionized water, stir evenly, and adjust the pH to form a mixed solution; A3, Add the TaC powder to the mixed solution prepared in step A2, stir at room temperature, filter and wash, dry and then perform heat treatment, and then naturally cool to obtain modified TaC; A4, Ball - mill the modified TaC and zirconia microspheres, then add MoSi2 and acetone, and perform ball - mill mixing to form a mixed powder; A5, Press the mixed powder into a mold to form a green compact, subject the green compact to high - temperature sintering, and cool it to room temperature to obtain the ceramic composite.

2. The preparation method of a composite coating for growing large-diameter single-crystalline silicon according to claim 1, wherein, In step S1, the mass ratio of CeO2 to deionized water is 1:

5.

3. The preparation method of a composite coating for growing large-diameter single-crystalline silicon according to claim 1, wherein, In step S3, the mass ratio of the ceramic composite to deionized water is 3:1, and the viscosity of the slurry is 500 - 800 mPa·s.

4. The preparation method of a composite coating for growing large-diameter single-crystalline silicon according to claim 1, characterized in that, In step A2, the volume ratio of deionized water to anhydrous ethanol is 1:10, and the volume ratio of the silane coupling agent to the solution is 1:

10.

5. The preparation method of a composite coating for growing large-diameter single-crystalline silicon according to claim 1, wherein, In step A5, the temperature of the high - temperature sintering is 1600 - 2000 °C, and the heat preservation time is 3 h.

6. The preparation method of a composite coating for growing large-diameter single-crystalline silicon according to claim 1, characterized in that, The silane coupling agent is KH - 550 or KH - 560.

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