High-performance repairing method for surface of photovoltaic / semiconductor thermal field carbon-carbon product

Abstract

The invention discloses a high-performance repairing method for the surface of a photovoltaic / semiconductor thermal field carbon-carbon product, and belongs to the field of single crystal furnace thermal field materials in the photovoltaic / semiconductor field. Comprising the following steps: 1) carrying out pre-oxidation treatment on a to-be-repaired defect to enable the defect to be concave-convex; 2) selecting crystalline flake graphite as a restoration carbon source and silicon powder as a restoration silicon source, dissolving the crystalline flake graphite and the silicon powder in an adhesive, and uniformly stirring to obtain restoration slurry; (3) coating the concave-convex defect part with the repairing slurry, then carrying out flame jet treatment, and repeating coating and jet treatment until the defect part is completely repaired; and (4) high-temperature heat treatment is conducted, grinding and polishing treatment is conducted after cooling, and repairing is completed. The carbon-carbon product restoration body repaired by the method is chemically bonded with a parent body, the binding force is large, and the carbon-carbon product restoration body is not prone to cracking due to cyclic thermal shock; the flake graphite can better enable the restoration body to be consistent with the parent body in ground color; the service life of the repaired carbon-carbon product in the photovoltaic / semiconductor crystal pulling process can be further prolonged.

Description

Technical Field

[0001] The present invention belongs to the field of single crystal furnace thermal field materials in the photovoltaic / semiconductor field, and specifically relates to a high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products. Background Art

[0002] Carbon-carbon composite materials provide crucial support for photovoltaic / semiconductor thermal field systems and are widely used as crucible rims, insulation tubes, guide tubes, crucibles, and support rings. During the production and use of carbon-carbon products, surface defects such as pits are common due to improper handling (bumps, scratches, etc.) or accelerated corrosion (localized corrosion leading to increased stress concentration). Because the surface activity at these defects is high, silicon vapor during the crystal pulling process can accelerate surface corrosion, reducing the product's service life.

[0003] To address defects such as surface pits on carbon-carbon products, two methods are currently commonly used. One is to apply graphite emulsion and then dry the graphite emulsion; the disadvantage of this method is that the bonding between the substrate and the repair graphite is poor, and the graphite repair body automatically falls off due to thermal stress during the calcination process. Another method is to use carbon powder and resin to bond and then use chemical vapor deposition to seal the holes. For example, Chinese invention patent publication number CN115028475A discloses a method for repairing carbon-carbon thermal field products. The carbon slag generated during the mechanical processing of the carbon-carbon thermal field product is dried and passed through a 100-mesh sieve. The sieve residue is taken to obtain carbon powder. The carbon powder, resin, and diluent are stirred and mixed to obtain a coating; the coating is applied to the defects of the carbon-carbon thermal field product, dried, finely ground, and then subjected to chemical vapor deposition. Compared with the previous method, the bonding strength after repair of this method is improved, but the bond between the restoration and the matrix is still physical, and the bonding strength is still relatively weak; at the same time, in order to repair, the deposition of carbon-carbon products as a whole is costly, and on the other hand, dense positions will lead to the formation of more carbon black due to the deposition process, requiring additional polishing and other processes, and the surface color difference at the junction of the restoration and the matrix is large. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products to solve the problems of poor bonding between the traditional matrix and the repair body, large surface color difference, and easy cracking due to cyclic thermal shock.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products, comprising the following steps: 1) Pre-oxidation treatment is performed on the defects on the surface of the carbon-carbon product to be repaired, so that the defects appear concave and convex; 2) Select flake graphite as the carbon source of the restoration and silicon powder as the silicon source of the restoration, dissolve the flake graphite and silicon powder in the adhesive, and stir evenly to obtain a restoration slurry; 3) Apply the repair slurry to the concave and convex defects, and then use flame spraying to treat them. Repeat the coating and spraying process until the defects are completely repaired. 4) The carbon-carbon product treated in step 3) is then subjected to high-temperature heat treatment, and after cooling, is ground and polished to complete high-performance repair of the surface of the photovoltaic / semiconductor thermal field carbon-carbon product.

[0006] Preferably, the particle size of the flake graphite is 100-300 mesh; the particle size of the silicon powder is 100-300 mesh.

[0007] Preferably, the mass ratio of flake graphite to silicon powder is 1:(1.2-1.8).

[0008] Preferably, in step 2), the adhesive is prepared from polyvinyl alcohol and water to form a viscous liquid with a viscosity of 200-800 mPa·s; flake graphite and silicon powder are dissolved in the adhesive and stirred until the viscosity of the system rises to 2000-4000 mPa·s.

[0009] Preferably, in step 3), the coating thickness of the repair slurry at the defect is 0.5-2 mm.

[0010] Preferably, in step 3), the flame spraying temperature is 1300° C. and the spraying time is 1 min.

[0011] Preferably, in step 4), the high temperature treatment is performed in an argon atmosphere at a temperature of 1800-2200° C. for 2 hours.

[0012] More preferably, the heating rate during the high temperature treatment is 50-90° C. / h.

[0013] Further preferably, in step 1), the pre-oxidation treatment is to perform flame spraying treatment on the defective area with a flame at 1000-1200° C. for 1 minute.

[0014] Further preferably, in step 4), the protruding structure at the defect is ground and polished using 400-mesh SiC sandpaper.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products. First, the defects are pre-oxidized to eliminate impurities, and the surface after pre-oxidation has a microscopic concave-convex structure that facilitates later chemical bonding. In particular, the present invention uses flake graphite as the carbon source for the repair body. The color of flake graphite is consistent with the color of high-performance carbon-carbon products, both of which are dark silver. Silicon powder is used as the silicon source for the repair body (silicon is a non-impurity element in the photovoltaic and semiconductor fields), and is dissolved in an adhesive to prepare a repair slurry, mainly for chemical bonding with flake graphite and parent carbon. The repair slurry is then applied to the pits and flame sprayed, and the coating and spraying cycles are repeated until the repair is complete. Finally, the product is subjected to high-temperature heat treatment to chemically react the silicon powder, flake graphite and parent carbon, and the surface of the product is polished to obtain a high-performance repaired carbon-carbon product. The carbon-carbon product repaired with this method is chemically bonded to the parent material, resulting in strong bonding and resistance to cracking during cyclic thermal shock. The flake graphite ensures that the repaired material maintains the same color as the parent material. Furthermore, the repaired carbon-carbon product's service life during photovoltaic / semiconductor crystal pulling processes is further extended. Combined with these advantages, the carbon-carbon product repaired with this method offers excellent economic and social benefits in the photovoltaic thermal field.

[0016] Furthermore, the present invention uses water-soluble thick polyvinyl alcohol as an adhesive. No impurities remain after the decomposition of the polyvinyl alcohol. A certain proportion of silicon powder and flake graphite are poured into the thick polyvinyl alcohol, and the repair slurry is obtained after stirring. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Comparative photos of the carbon-carbon product before and after surface repair in Example 1 of the present invention; Figure 2 This is a comparison chart of the mechanical properties of the carbon-carbon product after surface repair according to Example 1 of the present invention and after traditional repair. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0020] The present invention is described in further detail below with reference to the accompanying drawings: The present invention discloses a high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products, which uses a combination of slurry coating and heat treatment to repair the surface of photovoltaic / semiconductor carbon-carbon products, specifically comprising the following steps: First, pre-oxidation treatment: Use a flame gun to pre-oxidize the defects to remove impurities, etc., and the surface microscopic concave-convex structure after pre-oxidation is convenient for later chemical bonding; Next, prepare the repair slurry: flake graphite is used as the carbon source for the restoration. The color of flake graphite is consistent with that of high-performance carbon-carbon products, both being dark silver. Silicon powder is used as the silicon source for the restoration (silicon is a non-impurity element in the photovoltaic and semiconductor fields), mainly to chemically bond with the flake graphite and the parent carbon. Thick polyvinyl alcohol soluble in water is used as the adhesive. After decomposition, no impurities remain. A certain proportion of silicon powder and flake graphite are poured into the thick polyvinyl alcohol and stirred to obtain the repair slurry. Next, coating treatment: apply the repair slurry to the pit, and use a flame gun to spray to evaporate the water and alcohol, and repeat this cycle until the repair is complete; Afterwards, high temperature sintering reaction: the product is subjected to high temperature heat treatment to chemically react silicon powder, flake graphite and matrix carbon; Finally, post-processing of grinding and polishing: polishing the surface of the product can obtain high-performance repaired carbon-carbon products.

[0021] The flake graphite used in the present invention was purchased from Nanjing Geruifa Carbon Materials Co., Ltd. The specific embodiments are as follows: Example 1 A high-performance repair method for the surface of photovoltaic / semiconductor thermal field carbon / carbon products, comprising the following steps: 1) Pre-oxidation: First, use a 1000℃ flame gun to flame spray the defect for 1 minute to eliminate impurities in the defect. After pre-oxidation, the microstructure of the defect is concave and convex, which is convenient for chemical bonding with the repair slurry in the later stage. 2) Prepare the slurry: 300-mesh flake graphite was selected as the carbon source for the restoration. The color of flake graphite is consistent with that of high-performance carbon products, both being dark silver. Because silicon is a non-impurity element in the photovoltaic and semiconductor industries, 300-mesh silica powder was selected as the silicon source for the restoration. Using an electronic balance, weigh the flake graphite powder and silica powder in a mass ratio of 1:1.2 into an agate mortar. Then, thoroughly mix the mixture in the mortar and pestle. Stir for 1 hour before setting aside. Weigh 8g of polyvinyl alcohol into a beaker and slowly add deionized water, stirring with a glass rod until the liquid viscosity reaches approximately 200mPa·s. Then, slowly pour the silica powder and flake graphite powder mixed in the mortar into the beaker and stir thoroughly with a glass rod until the viscosity reaches 2000mPa·s. The restoration slurry is now ready for use.

[0022] 3) Coating: Use a brush to apply the repair slurry to the surface of the pit defect to a thickness of approximately 1mm. A thicker, looser, and less dense coating will cause cracking. Then, flame spray with a 1300°C flame gun for 1 minute to fully evaporate the surface solvent. Repeat the brushing and flame spraying process until the pit surface is completely repaired. Stop coating.

[0023] 4) Sintering reaction treatment: Place the product repaired in step 3) in a graphitization furnace and react at a high temperature of 1800℃ for 2 hours under an argon atmosphere at a heating rate of 50℃ / h. After the treatment is completed, turn off the power and cool down.

[0024] 5) Grinding and polishing: Use a special angle grinder to grind the protruding hard SiC block, and then use 400-grit SiC sandpaper to grind and polish its surface. At this point, the repair is complete.

[0025] Example 2 A high-performance repair method for the surface of photovoltaic / semiconductor thermal field carbon / carbon products, comprising the following steps: 1) Pre-oxidation: First, use a 1200℃ flame gun to flame spray the defect for 1 minute to eliminate impurities in the defect. After pre-oxidation, the microstructure of the defect is concave and convex, which is convenient for chemical bonding with the repair slurry in the later stage. 2) Prepare the slurry: 200-mesh flake graphite is used as the carbon source for the restoration. The color of flake graphite is consistent with that of high-performance carbon products, both being dark silver. Because silicon is a non-impurity element in the photovoltaic and semiconductor industries, 200-mesh silica powder is used as the silicon source for the restoration. Using an electronic balance, weigh the flake graphite powder and silica powder in a mass ratio of 1:1.5 into an agate mortar. Then, thoroughly mix the powders in the mortar and stir for 1 hour before setting aside. Weigh 8g of polyvinyl alcohol into a beaker and slowly add deionized water, stirring with a glass rod until the liquid viscosity reaches approximately 500mPa·s. Then, slowly pour the silica powder and flake graphite powder mixed in the mortar into the beaker and stir thoroughly with a glass rod until the viscosity reaches 3000mPa·s. The restoration slurry is now ready for use.

[0026] 3) Coating: Use a brush to apply the repair slurry to the surface of the pit defect to a thickness of approximately 2 mm. A thicker, looser, and less dense coating will cause subsequent cracking. Then, flame spray with a 1300°C flame gun for one minute to fully evaporate the surface solvent. Repeat the brushing and flame spraying process until the pit surface is completely repaired. Stop coating.

[0027] 4) Sintering reaction treatment: Place the product repaired in step 3) in a graphitization furnace and react at a high temperature of 2000℃ for 2 hours under an argon atmosphere at a heating rate of 70℃ / h. After the treatment is completed, turn off the power and cool down.

[0028] 5) Grinding and polishing: Use a special angle grinder to grind the protruding hard SiC block, and then use 400-grit SiC sandpaper to grind and polish its surface. At this point, the repair is complete.

[0029] Example 3 A high-performance repair method for the surface of photovoltaic / semiconductor thermal field carbon / carbon products, comprising the following steps: 1) Pre-oxidation: First, use a 1100℃ flame gun to flame spray the defect for 1 minute to eliminate impurities in the defect. After pre-oxidation, the microstructure of the defect is concave and convex, which is convenient for chemical bonding with the repair slurry in the later stage. 2) Prepare the slurry: 100-mesh flake graphite was selected as the carbon source for the restoration. The color of flake graphite is consistent with that of high-performance carbon products, both being dark silver. Because silicon is a non-impurity element in the photovoltaic and semiconductor industries, 300-mesh silica powder was selected as the silicon source for the restoration. Using an electronic balance, weigh the flake graphite powder and silica powder in a mass ratio of 1:1.8 into an agate mortar. Then, thoroughly mix the powders in the mortar and pestle. Stir for 1.8 hours before use. Weigh 8g of polyvinyl alcohol into a beaker and slowly add deionized water, stirring with a glass rod until the liquid viscosity reaches approximately 800mPa·s. Then, slowly pour the silica powder and flake graphite powder mixed in the mortar into the beaker and stir thoroughly with a glass rod until the viscosity reaches 4000mPa·s. The restoration slurry is now ready for use.

[0030] 3) Coating: Use a brush to apply the repair slurry to the surface of the pit defect to a thickness of approximately 1mm. A thicker, looser, and less dense coating will cause cracking. Then, flame spray with a 1300°C flame gun for 1 minute to fully evaporate the surface solvent. Repeat the brushing and flame spraying process until the pit surface is completely repaired. Stop coating.

[0031] 4) Sintering reaction treatment: Place the product repaired in step 3) in a graphitization furnace and react at a high temperature of 2200℃ for 2 hours under an argon atmosphere. The heating rate is 90℃ / h. After the treatment is completed, turn off the power and cool down.

[0032] 5) Grinding and polishing: Use a special angle grinder to grind the protruding hard SiC block, and then use 400-grit SiC sandpaper to grind and polish its surface. At this point, the repair is complete.

[0033] See also Figure 1 Taking the carbon-carbon product repaired in Example 1 as an example, the comparison photos before and after the repair show that the pits at the repair site have been basically eliminated, and the color difference between the mother body and the repaired body at the repair site is small.

[0034] See also Figure 2 , which is a comparison chart of the mechanical properties of the carbon-carbon product repaired by Example 1 of the present invention and the carbon-carbon product repaired by the traditional method (such as the invention patent with publication number CN115028475A). It can be seen that the tensile strength of the carbon-carbon product repaired by the method of the present invention is significantly higher. The traditional method does not involve chemical reaction and is only a physical bonding method, and the bonding strength does not exceed 5MPa.

[0035] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A high-performance repair method for the surface of photovoltaic / semiconductor thermal field carbon-carbon products, characterized in that: The following steps are involved: 1) Pre-oxidation treatment is performed on the defects on the surface of the carbon-carbon product to be repaired, so that the defects appear concave and convex; 2) Select flake graphite as the carbon source of the restoration and silicon powder as the silicon source of the restoration, dissolve the flake graphite and silicon powder in the adhesive, and stir evenly to obtain a restoration slurry; 3) Apply the repair slurry to the concave and convex defects, and then use flame spraying to treat them. Repeat the coating and spraying process until the defects are completely repaired. 4) The carbon-carbon product treated in step 3) is then subjected to high-temperature heat treatment, and after cooling, is ground and polished to complete high-performance repair of the surface of the photovoltaic / semiconductor thermal field carbon-carbon product.

2. The high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products according to claim 1, characterized in that: The particle size of flake graphite is 100-300 mesh; the particle size of silicon powder is 100-300 mesh.

3. The high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products according to claim 1, characterized in that: The mass ratio of flake graphite to silicon powder is 1:(1.2-1.8).

4. The high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products according to claim 1, characterized in that: In step 2), the adhesive is prepared by polyvinyl alcohol and water to form a thick liquid with a viscosity of 200-800 mPa·s; flake graphite and silicon powder are dissolved in the adhesive, and stirring is continued until the viscosity of the system rises to 2000-4000 mPa·s.

5. The high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products according to claim 1, characterized in that: In step 3), the coating thickness of the repair slurry at the defect is 0.5-2 mm.

6. The high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products according to claim 1, characterized in that: In step 3), the flame spraying temperature is 1300°C and the spraying time is 1 min.

7. The high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products according to claim 1, characterized in that: In step 4), the high temperature treatment is performed in an argon atmosphere at a temperature of 1800-2200° C. for 2 hours.

8. The high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products according to claim 7, characterized in that: The heating rate during the high temperature treatment is 50-90 ℃ / h.

9. The high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products according to any one of claims 1 to 8, characterized in that: In step 1), the pre-oxidation treatment is to perform flame spraying treatment on the defective area with a flame at 1000-1200°C for 1 minute.

10. The high-performance surface repair method for photovoltaic / semiconductor thermal field carbon-carbon products according to any one of claims 1 to 8, characterized in that: In step 4), the protruding structure at the defect is ground and polished using 400-grit SiC sandpaper.

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