An oxidation-resistant composite material of carbon-carbon crucible and a preparation method and application thereof

Abstract

The application discloses an oxidation-resistant composite material of carbon-carbon crucible and a preparation method and application thereof, and relates to the technical field of oxidation-resistant composite materials. The composite material takes a polysilazane precursor and a polysilicon nitride precursor as core components, is compounded in a specific proportion, and can add inorganic fillers such as silicon carbide and boron nitride as needed. Through the synergistic complementation of the two, the composite material has good matrix wettability, high-temperature resistance and thermal shock resistance, can form a dense protective layer and realize micro-crack self-healing. The preparation method is completed through steps such as step-by-step synthesis of the precursor, mixing under inert gas protection, addition of filler dispersion and the like. In application, the surface of the crucible is treated, the composite material is coated, pre-solidification is carried out, and ceramicization treatment is carried out in inert gas, so that an oxidation-resistant composite coating is formed on the surface of the crucible. The composite material effectively blocks the erosion of oxygen, solves the problems of easy cracking and peeling of the existing coating, significantly prolongs the service life of the carbon-carbon crucible, and is suitable for harsh scenes such as crystal growth and high-temperature sintering.

Description

Technical Field

[0001] This application relates to the technical field of antioxidant composite materials, and in particular to an antioxidant composite material for a carbon-carbon crucible, its preparation method, and its application. Background Technology

[0002] Currently, carbon-carbon crucibles hold an irreplaceable position in high-end manufacturing due to their superior high-temperature strength, extremely low coefficient of thermal expansion, and excellent thermal shock resistance. They are widely used in scenarios with stringent requirements for container performance, such as crystal growth, high-temperature sintering, and precious metal smelting. Especially in the preparation of precision devices such as semiconductor materials and optical crystals, their excellent high-temperature resistance effectively ensures the stability of the preparation environment and improves product purity and yield. However, carbon-carbon crucibles have a core weakness: instability in high-temperature aerobic environments. As the temperature rises, the oxidation reaction intensifies dramatically, accompanied by combustion. This process rapidly erodes the crucible's matrix structure, leading to a significant decrease in structural strength and loss of toughness. Ultimately, this results in crucible cracking, deformation, or even breakage and failure. This not only severely shortens the crucible's lifespan and increases material costs in the production process but may also cause material leakage, production interruptions, and even safety hazards due to crucible failure. This has become a key technical bottleneck restricting its large-scale application in high-temperature aerobic environments.

[0003] To address this core issue, the industry commonly employs a protective method of preparing antioxidant coatings on the surface of carbon-carbon crucibles. These coatings isolate oxygen from the carbon-carbon matrix, thereby inhibiting oxidation reactions. Common coating types include silicon-based coatings, ceramic coatings, and metal composite coatings. Among these, polysilazane (PSZ) ceramic precursors have become one of the most widely researched and applied coating materials due to their excellent temperature resistance, high ceramic yield, and superior oxidation resistance. Upon pyrolysis, they form a dense ceramic protective layer that can block oxygen penetration to a certain extent. However, in actual industrial production, polysilazane coatings have obvious limitations due to repeated use. Because their coefficient of thermal expansion does not match the carbon-carbon crucible substrate perfectly, thermal stress will be generated between the coating and the substrate during repeated heating and cooling cycles. Over time, microcracks will be generated. Although these microcracks are initially small and difficult to observe directly, they become channels for oxygen diffusion, allowing oxygen to bypass the coating and directly contact the crucible substrate, causing the coating to fail prematurely. After several uses, the surface of the crucible will show obvious macroscopic cracking and peeling, accompanied by oxidation and weight loss, making it unable to meet production requirements.

[0004] Polyborosilazane (PBSZ), as another high-performance ceramic precursor, offers superior high-temperature performance compared to polysilazane. Its SiBCN ceramic phase, formed after pyrolysis, exhibits a stable structure, higher high-temperature stability, and better creep resistance, far exceeding that of ordinary polysilazane systems, making it suitable for higher-temperature applications. However, PBSZ also has its limitations when used alone for film formation. Its wettability to carbon-carbon crucible substrates is poor, and its adhesion to the substrate during low-temperature curing is weaker than that of polysilazane, making it prone to coating peeling from the substrate, which also affects the long-term effectiveness of the protection.

[0005] In the Czochralski process for growing sapphire single crystals, this is also the core process for preparing high-quality sapphire single crystals in the semiconductor and optical device fields. A carbon-carbon crucible is filled with high-purity alumina raw material and placed in a sealed high-temperature furnace. The alumina raw material is first melted completely by gradually increasing the temperature. Then, the Czochralski device is started to slowly pull the seed crystal to grow the sapphire single crystal. The entire crystal growth process takes tens of hours. Although the furnace is mainly protected by inert gas, it is impossible to completely eliminate trace oxygen impurities. There may also be slight gas leakage at the furnace seal, forming a low-temperature oxygen environment. After the crystal growth is completed, it needs to be gradually cooled to room temperature, and the single crystal is taken out. Then, the crucible needs to be filled with raw material again to start the next cycle of heating, cooling and crystal growth. In this environment, the carbon-carbon crucible needs to withstand high temperatures for a long time and undergo repeated temperature cycles from room temperature to high temperature and back to room temperature. The trace oxygen in the furnace will continuously corrode the surface of the crucible. Without long-term and stable coating protection, the carbon-carbon crucible will quickly oxidize, crack and fail. This will not only lead to the interruption of sapphire single crystal growth, resulting in waste of raw materials and increased production costs, but may also cause molten alumina to leak due to crucible breakage, damaging the furnace equipment and causing safety accidents. Summary of the Invention

[0006] The purpose of this application is to provide an antioxidant composite material for carbon-carbon crucibles, its preparation method and application. This antioxidant composite material has excellent antioxidant and thermal shock resistance properties when used in carbon-carbon crucibles, reducing the problems of easy cracking and short lifespan of carbon-carbon crucibles, thereby extending the service life of carbon-carbon crucibles.

[0007] Firstly, the antioxidant composite material for a carbon-carbon crucible and its preparation method provided in this application adopt the following technical solution: An antioxidant composite material for a carbon-carbon crucible includes the following raw materials: a polyborosilazane precursor and a polysilazane precursor; wherein the mass ratio of the polyborosilazane precursor to the polysilazane precursor is (1-9):(9-1). The general structural formula of the polyborosilazane precursor is: ; In this structure, R is an aliphatic or aromatic group; The general structural formula of the polysilazane precursor is: ; Wherein, R1 is any one of H, aliphatic or aromatic groups, R2 is any one of H, aliphatic or aromatic groups, R3 is any one of H, aliphatic or aromatic groups, and R4 is any one of H, aliphatic or aromatic groups.

[0008] By employing the above-mentioned technical solution, a carbon-carbon crucible antioxidant composite material prepared using polyborosilazane precursors in a specific mass ratio range achieves excellent protective effects through the synergistic complementarity of the two precursors. Polysilazane possesses excellent matrix wettability and adhesion, penetrating deep into the pores of the carbon-carbon crucible surface to form a stable bond, enhancing the adhesion between the coating and the substrate and effectively avoiding the problem of easy peeling of coatings in existing technologies. Polyborosilazane, on the other hand, can transform into a highly stable ceramic phase at high temperatures, endowing the coating with excellent high-temperature resistance and self-healing ability, filling microscopic defects that may occur during use. The combination of the two in a reasonable mass ratio leverages the bonding and penetration advantages of polysilazane while also enhancing the high-temperature resistance and structural stability of the coating. This results in a better match between the thermal expansion coefficients of the composite coating and the carbon-carbon crucible substrate, significantly improving thermal shock resistance and reducing the likelihood of cracking during repeated heating and cooling cycles, thus fundamentally blocking oxygen permeation channels. The coating formed by this composite system is dense and structurally stable, effectively preventing oxygen from contacting the substrate for extended periods and avoiding high-temperature oxidation failure of the carbon-carbon materials, thus significantly extending the service life of the crucible. Furthermore, the flexibility of this mass ratio range allows for adaptation to different operating conditions; the protective effect can be optimized by adjusting the ratio. Leveraging the properties of the two precursors, the coating possesses both high toughness and density, achieving effective protection without complex processes. This provides a reliable guarantee for the stable application of carbon-carbon crucibles in harsh environments involving high temperatures and repeated thermal cycling.

[0009] Optionally, the mass ratio of the polyborosilazane precursor to the polysilazane precursor is (3-7):(7-3).

[0010] By adopting the above technical solution, at this ratio, the flexible bonding properties of polysilazane and the high-temperature reinforcing properties of polyborosilicate are balanced, ensuring that the core performance is not weakened due to the low proportion of any one component, nor is the combined advantage insufficient due to the high proportion of any one component. Polysilazane can fully wet the pores of the carbon-carbon crucible matrix, strengthening the bond between the coating and the substrate, while polyborosilicate can be sufficiently converted into a high-temperature resistant ceramic phase, giving the coating reliable high-temperature stability and self-healing ability. The composite coating formed by the two achieves a better match with the substrate in terms of thermal expansion coefficient, further improving thermal shock resistance and making it less prone to cracking during repeated thermal cycling. At the same time, the coating has better density, which can more effectively block oxygen erosion. This balanced ratio gives the coating strong adhesion, excellent crack resistance, and long-lasting oxidation resistance, making it suitable for most harsh application scenarios and providing more stable and controllable protective effects.

[0011] Optionally, the antioxidant composite material of the carbon-carbon crucible further includes inorganic fillers; the inorganic fillers are any one or more selected from silicon carbide, silicon nitride, boron nitride, titanium nitride, zirconium oxide, zirconium silicate, mullite, alumina, fumed silica, copper chromate black, titanium dioxide, aluminum oxide, talc, barium sulfate, and inorganic bentonite; the content of the inorganic fillers in the antioxidant composite material used for the carbon-carbon crucible is 5-40 wt%.

[0012] By adopting the above technical solution, adding specific types of inorganic fillers to the antioxidant composite material of carbon-carbon crucibles can form a highly efficient synergistic effect with polyborosilazane and polysilazane precursors, significantly optimizing the protective effect. These inorganic fillers themselves possess excellent high-temperature resistance, structural stability, and erosion resistance. After being integrated into the composite material, they can directly improve the overall mechanical strength and wear and corrosion resistance of the coating, effectively resisting physical erosion and chemical corrosion under high-temperature environments. Different types of inorganic fillers can play complementary roles. Some fillers can fill the tiny voids formed during the curing and ceramization process of the precursor, further densifying the coating structure and reducing the probability of oxygen penetration; some fillers can adjust the thermal expansion characteristics of the coating, making it more compatible with the carbon-carbon crucible matrix, reducing internal stress during thermal cycling, and helping to alleviate coating cracking problems. At the same time, the introduction of inorganic fillers can enrich the functional role of the coating. Depending on the needs of the application scenario, selecting single or multiple filler combinations can flexibly enhance the coating's specific properties such as creep resistance, thermal shock resistance, or resistance to extreme atmospheres, broadening the application range of the composite material. In addition, the multi-component composite system formed by the filler and the two precursors can enable the coating to maintain a more stable structural morphology at high temperatures, slow down the aging and failure rate, and the synergistic effect with the precursors further extends the service life of the carbon-carbon crucible, making the protection effect more comprehensive and longer-lasting.

[0013] Optionally, the method for preparing the antioxidant composite material of the carbon-carbon crucible includes the following steps: S1. Mix vinyl-containing chlorosilane, boron reagent and first solvent, and stir at -20~0℃ to obtain boron-containing mixed solution; S2. Mix the boron-containing mixed solution, methyl-containing dichlorosilane, inhibitor, and amine source from step S1, heat, stir, and distill under reduced pressure to obtain the polyborosilicate precursor. S3. Mix vinyl-containing dichlorosilane, methyl-containing dichlorosilane, a second solvent and liquid ammonia, stir at -20~0℃, filter and rotary evaporate to obtain polysilazane precursor; S4. Add the polyborosilicate precursor to the first solvent and stir to obtain the polyborosilicate precursor preparation solution. S5. Add the polysilazane precursor to the second solvent and stir magnetically to obtain the polysilazane preparation solution. S6. In an inert gas atmosphere, the polyborosilazane precursor preparation solution from step S4 is mixed with the polysilazane preparation solution from step S5. The mixture is then stirred in a water bath at room temperature to obtain a hybrid resin solution. S7. Add inorganic filler to the hybrid resin solution prepared in step S4 and disperse it evenly to obtain the antioxidant composite material of carbon-carbon crucible.

[0014] By adopting the above technical solution, firstly, the stepwise synthesis of the polyborosilazane precursor allows for precise control of the precursor's structure and purity, ensuring its compatibility with the polysilazane precursor and laying the foundation for the synergistic effect of subsequent components. Dissolving the two precursors in an organic solvent ensures complete dissolution and system stability, avoiding component agglomeration or performance degradation caused by inappropriate solvents. Mixing the precursors under inert gas protection effectively isolates impurities such as oxygen, and combined with the mild conditions of room temperature water bath stirring, promotes the uniform fusion of the two precursors, forming a structurally homogeneous hybrid resin system, fully leveraging the high-temperature resistance and bonding advantages of polyborosilazane. Subsequent addition of inorganic fillers and ensuring uniform dispersion allows the fillers to tightly bond with the hybrid resin, further filling system voids and optimizing the coating structure. The entire preparation method is mild and easily controllable, ensuring the full performance of each component while precisely controlling the mixing and dispersion process to form a dense and stable composite material system. The final composite material slurry, after coating, forms a coating with strong adhesion and uniform structure, and has excellent thermal shock resistance, oxidation resistance and self-healing ability. At the same time, the standardization and repeatability of the process are conducive to large-scale production, ensuring stable and consistent product performance.

[0015] Optionally, the mass ratio of the vinyl-containing chlorosilane to the boron reagent is (1-3):(1-3).

[0016] By adopting the above technical solution, the mass ratio of vinyl chlorosilane to boron reagent within this range ensures that the two are fully integrated and synergistically act during the reaction. This ratio prevents the two raw materials from losing functionality due to an excessively low proportion of one component, nor from causing incomplete reaction or performance redundancy due to an excessively high proportion. Vinyl chlorosilane provides sufficient reactive sites, while boron reagent effectively introduces boron. The reaction of the two in this ratio results in a uniform and stable polyborosilicate structure, retaining suitable reactivity while fully endowing it with the characteristic of forming a stable ceramic phase at high temperatures. This ensures that the composite material ultimately possesses excellent high-temperature resistance and achieves excellent protective effects after being combined with polyborosilicate.

[0017] Optionally, the mass ratio of the methyl-containing dichlorosilane, the inhibitor, and the amine source is (1-3):(0.001-0.003):(1-15).

[0018] By employing the above technical solution, the precise synergy of methyl-containing dichlorosilane, inhibitor, and amine source within this mass ratio range can be achieved, ensuring the efficient synthesis and stable performance of the polyborosilazane precursor. The methyl-containing dichlorosilane constitutes the majority of the mixture, providing reaction sites and laying the foundation for a stable precursor structure. The inhibitor, present in trace amounts, effectively regulates the reaction rate, preventing over-polymerization without inhibiting the reaction process due to excessive dosage. The appropriately proportioned amine source fully leverages cross-linking, promoting the formation of the target polymer structure while avoiding excessive residue that could lead to performance degradation. Reacting these three components in this ratio ensures a stable and controllable synthesis process, resulting in a polyborosilazane with a uniform structure, reliable purity, and superior high-temperature resistance and compatibility for subsequent compounding, providing a foundation for carbon-carbon crucible protection.

[0019] Optionally, the inhibitor is any one or more of hydroquinone, triethylamine, 2,6-di-tert-butyl-p-cresol pyridine, triphenylphosphine, tetrabutyl titanate, and zirconium acetylacetonate.

[0020] By employing the above-mentioned technical solution and selecting specific inhibitors such as hydroquinone and triethylamine, the synthesis system of polyborosilazane precursors is highly compatible with them, enabling precise and effective regulation. These inhibitors are stable, do not cause harmful side reactions with the reactants, and do not leave residues that affect the performance of subsequent composite materials. The reaction process can be specifically controlled to ensure the formation of a uniform and stable target structure in the polyborosilazane precursor. Furthermore, the availability and combination of various inhibitors allow for flexible adaptation to different reaction conditions and reactant ratios, making the reaction process easier to control and ensuring consistent precursor performance. Ultimately, the rational selection of these inhibitors lays the foundation for the synergistic effect between the composite material and polysilazane, and for the excellent protective performance of the coating.

[0021] Optionally, the amine source is any one or more of hexamethyldisilazane, liquid ammonia, aliphatic amines, hydrazine, aromatic amines, 1,3-divinyltetramethyldisilazane, and hexamethyldisilazane.

[0022] By employing the above technical solution and selecting specific amine sources such as hexamethyldisilazane and liquid ammonia, the synthesis system of polyborosilazane precursors is highly compatible, exhibiting efficient and stable crosslinking effects. These amine sources possess strong adaptability, precisely providing nitrogen in the reaction to promote the full crosslinking of components such as boron-containing mixed solutions and methyl-containing dichlorosilanes, thus contributing to the formation of structurally regular and stable polyborosilazane precursors. The availability and combination of multiple amine sources allow for flexible adaptation to different reaction conditions and raw material ratios, making the reaction process easier to control and ensuring the consistency and reliability of the precursor. Ultimately, the rational selection of these amine sources lays a solid foundation for the synergistic effect of polyborosilazane and polysilazane, ensuring that the composite coating possesses excellent high-temperature resistance, crack resistance, and oxidation resistance, providing long-term protection for the carbon-carbon crucible.

[0023] Optionally, the heating temperature in step S2 is 100-200℃.

[0024] By adopting the above technical solution, this temperature range is adapted to the reaction requirements of step S2. It can promote the full cross-linking reaction of components such as the boron-containing mixed solution and the methyl-containing dichlorosilane, while avoiding incomplete reaction due to excessively low temperature or side reactions and damage to the product structure due to excessively high temperature. The mild and suitable temperature allows the polyborosilicate precursor to form a uniform and stable structure, ensuring its compatibility with subsequent composites with polysilazines, and laying a solid foundation for the excellent protective performance of the composite material.

[0025] Secondly, the application of the antioxidant composite material of the carbon-carbon crucible provided in this application adopts the following technical solution: The application of an antioxidant composite material for carbon-carbon crucibles in protecting carbon-carbon crucibles includes the following steps: Step 1: Surface treatment of the carbon-carbon crucible substrate; Step 2: Apply the antioxidant composite material for the carbon-carbon crucible to the surface of the carbon-carbon crucible; Step 3: Pre-cure at 80-150℃ for 0.5-2 hours; Step 4: Ceramization treatment in an inert gas to form an anti-oxidation composite coating on the surface of the carbon-carbon crucible.

[0026] By adopting the above technical solutions, surface treatment can remove impurities from the substrate and optimize the surface condition, laying a solid foundation for coating bonding and improving the adhesion and stability of subsequent coatings; slurry application allows the composite material to uniformly cover the crucible surface, ensuring comprehensive protection; mild pre-curing conditions allow the slurry to initially form, avoiding problems such as peeling or sagging during subsequent processing; ceramicization treatment in an inert gas atmosphere can avoid impurity interference and promote the transformation of the composite material into a dense composite coating. The entire process is seamless, ensuring a strong bond between the coating and the substrate, and allowing the coating to fully exhibit the synergistic advantages of thermal shock resistance, crack resistance, and oxidation resistance, effectively blocking oxygen erosion, delaying crucible aging and failure, and significantly extending its service life.

[0027] The core of this application lies in precisely controlling the composite ratio of the two ceramic precursors to fully stimulate their synergistic and complementary effects. Polysilazane, with its excellent matrix wettability, can penetrate deep into the porous structure of the carbon-carbon crucible surface, forming a strong interfacial bond and fundamentally solving the problem of easy peeling of traditional coatings. Meanwhile, polyborosilicate, as a reinforcing and high-temperature resistant phase, can transform into a highly stable SiBCN ceramic phase under high-temperature environments. This phase not only withstands extreme temperatures but also possesses a unique microcrack self-healing ability, actively sealing any minute defects that may arise during use. Furthermore, specific inorganic fillers can be added to the composite material as needed to form a multi-component synergistic system with the two precursors, further densifying the coating structure and adjusting thermal expansion characteristics, resulting in better compatibility between the coating and the carbon-carbon crucible matrix. During preparation and application, precursor mixing under an inert atmosphere, flexible coating methods, and precisely controlled pre-curing and high-temperature ceramicization treatment ensure that the hybrid coating forms a stable structure with high toughness and high density. Ultimately, this composite coating combines thermal shock resistance, strong adhesion, ultra-high temperature stability, and efficient oxygen barrier properties. It is not prone to cracking during repeated thermal cycling, successfully overcoming the performance limitations of traditional coatings and significantly extending the service life of carbon-carbon crucibles.

[0028] In summary, this application includes at least one of the following beneficial technical effects: 1. Compared with existing technologies, this composite material overcomes the performance shortcomings of traditional single coatings through the synergistic complementarity of polyborosilazane and polysilazane. Polysilazane possesses excellent matrix wettability and adhesion, enabling it to penetrate deep into the pores of the carbon-carbon crucible surface to form a stable bond, preventing coating peeling. At high temperatures, polyborosilazane transforms into a stable ceramic phase, endowing the coating with excellent high-temperature resistance and microcrack self-healing ability. The synergistic effect of these two components optimizes the thermal expansion matching between the coating and the substrate, alleviating internal stress generated by repeated thermal cycling, fundamentally preventing coating cracking, and ensuring the long-term stability of the protective structure. 2. Compared with existing technologies, the composite coating combines long-lasting oxidation resistance and penetrating sealing, providing comprehensive and long-lasting protection. The dense, multi-element ceramic layer formed after ceramization effectively blocks oxygen corrosion, and the optional inorganic fillers can further enhance the coating's density and mechanical strength, significantly extending the service life of the carbon-carbon crucible. Simultaneously, the preparation process is mild and easily controllable, and can be adapted to different high-temperature operating conditions by adjusting the precursor ratio, filler type, and coating method. Detailed Implementation

[0029] Unless otherwise specified, all raw materials used in the embodiments and comparative examples of this application are commercially available products: Methyl vinyl dichlorosilane, product number: W8102465000, Anhui Zesheng Technology Co., Ltd.; Dichloromethylsilane, product number: C14738-100ML, Anhui Zesheng Technology Co., Ltd.; Boric acid, product number: M0113414-500g, Anhui Zesheng Technology Co., Ltd.; Boron trichloride, item number: W3200945000, Anhui Zesheng Technology Co., Ltd.; Trimethyl borate, product number: D021612-500ml, Anhui Zesheng Technology Co., Ltd.; Hexamethyldisilazane, product number: D021612-500ml, Anhui Zesheng Technology Co., Ltd.; Silicon carbide, item number: S817584-25g, Shanghai Maclean Biochemical Technology Co., Ltd.; Boron nitride, product number: B887052-25g, Shanghai Maclean Biochemical Technology Co., Ltd.; Zirconia, item number: Z787450-25g, Shanghai Maclean Biochemical Technology Co., Ltd.; Mullite, product number: M970145-50, Shanghai Maclean Biochemical Technology Co., Ltd.; Fumed silica, product number: S818465-500g, Shanghai Maclean Biochemical Technology Co., Ltd. Propylene glycol methyl ether acetate, product number: P799303-500ml, Shanghai Maclean Biochemical Technology Co., Ltd. Example 1

[0030] A method for preparing an antioxidant composite material for a carbon-carbon crucible includes the following steps: 300g of methylvinyldichlorosilane (a vinyl-containing chlorosilane), 150g of boric acid, 150g of boron trichloride, and 120g of anhydrous xylene (the first solvent) were mixed and stirred at 500 rpm for 40 h at -15°C to obtain a boron-containing mixed solution. The above boron-containing mixed solution, 146.7g of dichloromethylsilane (a methyl-containing dichlorosilane), 0.15g of hydroquinone, and 586.8g of hexamethyldisilazane were mixed and heated to 175°C, stirred at 500 rpm for 20 h. First, low-boiling-point byproducts were removed by distillation at 0.08 MPa and 50°C for 3 h, and then by distillation at 0.01 MPa and 155°C for 3 h to obtain a polyborosilicate precursor.

[0031] 300g of methylvinyldichlorosilane (a vinyl-containing chlorosilane), 146.7g of dichloromethylsilane (a methyl-containing dichlorosilane), and 120g of anhydrous n-hexane (a second solvent) were mixed and stirred at 500rpm for 12h under ammonia gas at -15℃ to obtain a polysilazane mixed solution. The solution was filtered, and the filtrate was collected. The filtrate was rotary evaporated at 200rpm for 60min at 50℃ to obtain the polysilazane precursor.

[0032] 70g of polyborosilazane precursor was dissolved in 130g of anhydrous xylene (first solvent), and stirred at 500rpm for 30min to obtain a polyborosilazane precursor preparation solution. 30g of polysilazane precursor was dissolved in 70g of anhydrous n-hexane (second solvent), and magnetically stirred at 500rpm for 1h to obtain a polysilazane preparation solution. Under an argon atmosphere, the polyborosilazane precursor preparation solution and the polysilazane preparation solution were mixed, and stirred at 500rpm for 2h at 25℃ to obtain a hybrid resin solution. 15g of silicon carbide (average particle size 200nm), 5g of boron nitride, and 5g of fumed silica were added to 100g of the hybrid resin solution, dispersed at 3000rpm for 30min, and sonicated at 40kHz for 1h to obtain an antioxidant composite material with a carbon-carbon crucible.

[0033] The application of an antioxidant composite material for a carbon-carbon crucible includes the following steps: The carbon-carbon crucible was polished with 400-grit sandpaper, ultrasonically cleaned with ethanol at 250W power for 12 min, and dried at 90℃ for 1.5 h to obtain a purified carbon-carbon crucible. The purified carbon-carbon crucible was immersed in the antioxidant composite material of the crucible and pulled at a speed of 5 cm / min to check the uniformity of the coating on the surface. The coated carbon-carbon crucible was cured at 120℃ for 1 h to obtain a cured carbon-carbon crucible, and the thickness of the antioxidant composite material on the surface was measured to be 180 μm. Under argon protection, the cured carbon-carbon crucible was ceramicized by heating from 25℃ to 1200℃ at a rate of 2℃ / min, holding at that temperature for 1 h, and then cooling to 25℃. The above immersion, curing, and ceramicization processes were repeated twice to obtain a carbon-carbon crucible with an antioxidant composite material coating. Example 2

[0034] The difference between Example 2 and Example 1 is that the 70g and 30g of polyborosilazane precursors in Example 1 are replaced with 60g and 40g of polyborosilazane precursors. Example 3

[0035] The difference between Example 3 and Example 1 is that the 70g polyborosilazane precursor and 30g polysilazane precursor in Example 1 are replaced with 50g polyborosilazane precursor and 50g polysilazane precursor. Example 4

[0036] The difference between Example 4 and Example 1 is that the 70g and 30g of polyborosilazane precursors in Example 1 are replaced with 40g and 60g of polyborosilazane precursors. Example 5

[0037] The difference between Example 5 and Example 1 is that the 70g polyborosilazane precursor and 30g polysilazane precursor in Example 1 are replaced with 30g polyborosilazane precursor and 70g polysilazane precursor. Example 6

[0038] The difference between Example 6 and Example 3 is that 15g of silicon carbide, 5g of boron nitride and 5g of fumed silica in Example 3 are replaced with 10g of nano-zirconia and 10g of mullite powder and 5g of fumed silica. Example 7

[0039] The difference between Example 7 and Example 1 is that a spraying process is used instead of an impregnation process, and the thickness of the antioxidant composite material on the carbon-carbon crucible surface is kept consistent. The spraying is done with propylene glycol methyl ether acetate as a diluent, and the ceramization temperature is 1000℃. Example 8

[0040] The difference between Example 8 and Example 1 is that phenylmethyldichlorosilane was used instead of methylvinyldichlorosilane in the preparation of the polysilazane precursor. After pre-curing, UV curing was performed for 5 minutes, followed by a high-temperature ceramization step. Comparative Example 1

[0041] The difference between Comparative Example 1 and Example 1 is that the 70g and 30g of polyborosilazane precursor in Example 1 are replaced with 20g and 90g of polyborosilazane precursor. Comparative Example 2

[0042] The difference between Comparative Example 2 and Example 1 is that 15g of silicon carbide, 5g of boron nitride, and 5g of fumed silica were not added in Comparative Example 2. Comparative Example 3

[0043] The difference between Comparative Example 3 and Example 5 is that Comparative Example 5 did not contain 15g of silicon carbide, 5g of boron nitride, and 5g of fumed silica. Test case

[0044] Antioxidant and thermal shock resistance: The surface coating was continuously calcined in air at 1550℃, and subjected to a thermal cycling test once daily, holding at 1550℃ for 2 hours and then cooling to 25℃. The coating remained intact, without peeling or flaking, and no changes in weight or mass were observed. The changes in mass before and after the treatment were also calculated.

[0045] Thermal shock resistance: Intermittent thermal shock tests were conducted in an air atmosphere at 1500℃ (rapidly heated to 1500℃ and held for 10 minutes, then removed and quenched in air to 25℃, repeated 100 times). The surface coating remained intact, without peeling or flaking, and the weight change was observed. The mass change before and after the treatment was calculated. The test results are shown in Table 1.

[0046]

[0047] Comparative analysis of Examples 1-5 and Comparative Example 1 revealed that the antioxidant composite material prepared in Example 1 provided the best protection for carbon-carbon crucibles. The difference in performance may be due to variations in the mass ratio of the polyborosilazane precursor to the polysilazane precursor. In Example 1, the coating was dense and smooth, exhibiting strong adhesion to the substrate. After continuous calcination at 1550°C in air, followed by daily thermal cycling at 1550°C for 2 hours and then cooling to room temperature, the crucible remained stable for over 8 months (approximately 240 thermal cycles) before showing only slight oxidation weight gain (<1%), with no visible cracks. The mass ratio of the polyborosilazane precursor to the polysilazane precursor is a key factor affecting the long-term stability of the antioxidant coating on carbon-carbon crucibles, and its core lies in fully leveraging the synergistic effect of the two. Polyborosilazane, as a high-temperature reinforcing phase, can form a stable SiBCN ceramic phase at high temperatures, endowing the coating with excellent high-temperature stability and microcrack self-healing ability, providing core support for protection under long-term high-temperature environments. Meanwhile, polysilazane acts as a flexible binder, penetrating the pores of the carbon-carbon crucible matrix with good wettability, enhancing the bonding strength between the coating and the substrate, while simultaneously alleviating internal stress during thermal cycling and improving the coating's flexibility. When the mass ratio of the two is within a reasonable range, a structurally balanced hybrid network can be formed. This network utilizes the high-temperature resistance of polyborosilazane to block oxygen corrosion, while its flexibility adjusts the thermal expansion matching between the coating and the substrate, preventing cracking and peeling during repeated thermal cycling, thus ensuring oxidation resistance and thermal shock resistance during long-term service. If the proportion of polyborosilazane is too low, the high-temperature self-healing ability and high-temperature stability will be insufficient, making it difficult for the coating to repair micro-cracks caused by thermal cycling, and oxygen can easily penetrate, leading to protective failure. If the proportion of polysilazane is too low, the bonding strength and flexibility between the coating and the substrate will decrease, and the internal stress cannot be effectively released during thermal shock, which can easily cause the coating to crack and weaken the stability of long-term service. Only when the proportions of the two are properly matched can the synergistic advantages be maximized and the coating be ensured to play a stable protective role in the long term.

[0048] A comparative analysis of Examples 1 and 6 revealed that the antioxidant composite material prepared in Example 1 provided the best protection for the carbon-carbon crucible. The reason for this performance difference may be that the synergistic effect of silicon carbide, boron nitride, and fumed silica used in Example 1 was better than that of nano-zirconia, mullite powder, and fumed silica, thus affecting the protective effect of the antioxidant composite material on the carbon-carbon crucible.

[0049] The carbon-carbon crucible coating prepared in Example 6, after ceramicization, also exhibited a dense and crack-free structure. Intermittent thermal shock tests were conducted in an air atmosphere at 1500°C, and the coating remained crack-free after more than 100 intense thermal shocks, demonstrating excellent thermal shock resistance. The synergistic effect of silicon carbide and boron nitride in Example 1 is superior, primarily due to their compatibility and functional complementarity with the polyborosilicate and polysilazane hybrid resin systems. Silicon carbide possesses excellent high-temperature stability and high hardness, filling the micropores formed during the ceramicization process of the hybrid resin, significantly improving coating density, reducing oxygen permeation channels, and forming a stable structural support with the SiBCN multi-element ceramic phase generated by the hybrid resin. Boron nitride, on the other hand, has good lubricity and a low coefficient of expansion; its layered structure effectively alleviates the internal stress generated during thermal cycling, preventing microcrack initiation. Synergistically, it works with the flexible network structure formed by polysilazane to further optimize the thermal compatibility between the coating and the carbon-carbon crucible substrate. In contrast, while nano-zirconia and mullite powder are also resistant to high temperatures, their chemical compatibility with hybrid resins is slightly weaker, and their functional complementarity is insufficient. Unlike silicon carbide and boron nitride, they cannot synergistically enhance the density of the coating to block oxygen and jointly alleviate thermal stress to improve thermal shock resistance. Therefore, their synergistic gains in antioxidant protection and thermal shock resistance are not as significant as the former.

[0050] Comparative analysis of Examples 1 and 7 revealed that the antioxidant composite material prepared in Example 1 provided the best protection for the carbon-carbon crucible. This difference in performance may be attributed to the superior protective properties of the antioxidant composite material prepared in Example 1. This difference in performance may also be due to the use of an impregnation process in Example 1, the use of the specially prepared antioxidant composite material, and the different ceramization temperatures. The carbon-carbon crucible prepared in Example 7 is suitable for surface protection of large or complex-shaped carbon-carbon structural components. The resulting coating is uniform and exhibits good resistance to high-temperature oxidation. In Example 1, the impregnation process, with its excellent permeability, allowed the specially prepared antioxidant composite material slurry to fully impregnate the pores of the carbon-carbon crucible matrix, strengthening the bond between the coating and the matrix, preventing peeling during thermal cycling, and ensuring uniform coating thickness, thus laying the foundation for protection. This composite material uses polyborosilazane and polysilazane in a 7:3 mass ratio as its core. The former provides high-temperature resistance and self-healing ability, while the latter imparts a flexible network to relieve internal stress. Combined with silicon carbide and boron nitride fillers, it further fills the pores, improves the coating's density, and effectively blocks oxygen penetration. The ceramization process reduces the internal stress generated during heating, preventing coating cracking. With the synergistic effect of these three factors, the coating exhibits both excellent oxidation resistance and thermal shock resistance, fully leveraging the compatibility advantages of the materials and processes.

[0051] Comparative analysis of Examples 1 and 8 revealed that the antioxidant composite materials prepared in Examples 1 and 8 provided comparable protection for carbon-carbon crucibles. This is because UV curing only enhances the mechanical strength of the coating at low temperatures, facilitating subsequent handling and processing, without altering the core composition and structure of the coating. Furthermore, the phenylmethyl-containing polysilazane can still synergize with the polyborosilicate, and in conjunction with subsequent high-temperature ceramicization, both can form a dense, strongly adherent composite coating on the surface of the carbon-carbon crucible, effectively exerting antioxidant and thermal shock resistance effects, thus maintaining consistent protective efficacy.

[0052] Comparative analysis of Example 1 and Comparative Example 2 revealed that the antioxidant composite material prepared in Example 1 provided the best protection for the carbon-carbon crucible. The difference in performance may be due to the absence of filler in Comparative Example 2. Inorganic fillers such as silicon carbide and boron nitride possess high density, excellent high-temperature resistance, and thermal stability, which are crucial for improving the protective performance of the composite material. The absence of such fillers in Comparative Example 2 resulted in insufficient density of the coating's internal structure, failing to effectively block the diffusion of oxygen into the carbon-carbon crucible matrix, leading to a decrease in antioxidant capacity. Furthermore, these inorganic fillers form a rigid support structure within the coating, buffering the internal stress generated by the difference in thermal expansion coefficients between the coating and the carbon-carbon crucible matrix during thermal cycling. Without fillers, the coating is unable to withstand the stress impact caused by sudden temperature changes, easily generating microcracks, thus affecting thermal shock resistance. Moreover, the high-temperature resistance of the fillers cannot enhance the overall structural stability of the coating, ultimately resulting in a less effective protective effect than the experimental group with added fillers.

[0053] Comparative analysis of Example 5 and Comparative Example 3 revealed that the antioxidant composite material prepared in Example 5 provided the best protection for the carbon-carbon crucible. The difference in performance may be attributed to the absence of filler in Comparative Example 3. Inorganic fillers such as silicon carbide and boron nitride are not merely filler components, but rather form a synergistic protective structure with the polyborosilicate and polysilazane hybrid system. The high-temperature resistant SiBCN phase provided by polyborosilicate requires the rigid framework of the filler for more uniform distribution, and the bonding effect of polysilazane further enhances the overall integrity of the coating through the filler particles. Together, these three elements construct a three-dimensional protective network. Comparative Example 3, lacking such fillers, resulted in a coating formed by the hybrid precursor lacking effective structural support. The self-healing effect of polyborosilicate was difficult to fully realize without filler anchoring, failing to promptly seal the micropores generated during thermal cycling. Simultaneously, the complementary thermal properties between the filler and the hybrid system disappeared, reducing the thermal expansion coordination between the coating and the carbon-carbon crucible matrix, and the internal stress generated during thermal shock could not be dispersed and buffered by the filler particles. Furthermore, the synergistic antioxidant effect formed by the high temperature resistance and low oxygen permeability of the filler itself and the barrier effect of the hybrid coating is no longer present, ultimately leading to a significant weakening of the protective performance.

[0054] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An antioxidant composite material for a carbon-carbon crucible, characterized in that, The preparation materials include: polyborosilazane precursor and polysilazane precursor; the mass ratio of the polyborosilazane precursor to the polysilazane precursor is (1-9):(9-1); The general structural formula of the polyborosilazane precursor is: ； In this structure, R is an aliphatic or aromatic group; The general structural formula of the polysilazane precursor is: ； Wherein, R1 is any one of H, aliphatic or aromatic groups, R2 is any one of H, aliphatic or aromatic groups, R3 is any one of H, aliphatic or aromatic groups, and R4 is any one of H, aliphatic or aromatic groups.

2. The antioxidant composite material for the carbon-carbon crucible according to claim 1, characterized in that, The mass ratio of the polyborosilazane precursor to the polysilazane precursor is (3-7):(7-3).

3. The antioxidant composite material for the carbon-carbon crucible according to claim 1, characterized in that, The antioxidant composite material for carbon-carbon crucibles further includes inorganic fillers; the inorganic fillers are any one or more of silicon carbide, silicon nitride, boron nitride, titanium nitride, zirconium oxide, zirconium silicate, mullite, alumina, fumed silica, copper chromate black, titanium dioxide, aluminum oxide, talc, barium sulfate, and inorganic bentonite; the content of the inorganic fillers in the antioxidant composite material for carbon-carbon crucibles is 5-40 wt%.

4. A method for preparing an antioxidant composite material for a carbon-carbon crucible according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Mix vinyl-containing chlorosilane, boron reagent and first solvent, and stir at -20~0℃ to obtain boron-containing mixed solution; S2. Mix the boron-containing mixed solution, methyl-containing dichlorosilane, inhibitor, and amine source from step S1, heat, stir, and distill under reduced pressure to obtain the polyborosilicate precursor. S3. Mix vinyl-containing dichlorosilane, methyl-containing dichlorosilane, a second solvent and liquid ammonia, stir at -20~0℃, filter and rotary evaporate to obtain polysilazane precursor; S4. Add the polyborosilicate precursor to the first solvent and stir to obtain the polyborosilicate precursor preparation solution. S5. Add the polysilazane precursor to the second solvent and stir magnetically to obtain the polysilazane preparation solution. S6. In an inert gas atmosphere, the polyborosilazane precursor preparation solution from step S4 is mixed with the polysilazane preparation solution from step S5. The mixture is then stirred in a water bath at room temperature to obtain a hybrid resin solution. S7. Add inorganic filler to the hybrid resin solution prepared in step S4 and disperse it evenly to obtain the antioxidant composite material of carbon-carbon crucible.

5. The method for preparing the antioxidant composite material of the carbon-carbon crucible according to claim 4, characterized in that, The mass ratio of the vinyl-containing chlorosilane to the boron reagent is (1-3):(1-3).

6. The method for preparing the antioxidant composite material of the carbon-carbon crucible according to claim 4, characterized in that, The mass ratio of the methyl-containing dichlorosilane, the inhibitor, and the amine source is (1-3):(0.001-0.003):(1-15).

7. The method for preparing the antioxidant composite material of the carbon-carbon crucible according to claim 4, characterized in that, The inhibitor is any one or more of hydroquinone, triethylamine, 2,6-di-tert-butyl-p-cresol pyridine, triphenylphosphine, tetrabutyl titanate, and zirconium acetylacetonate.

8. The method for preparing the antioxidant composite material of the carbon-carbon crucible according to claim 4, characterized in that, The amine source is any one or more of hexamethyldisilazane, liquid ammonia, fatty amines, hydrazine, aromatic amines, 1,3-divinyltetramethyldisilazane, and hexamethyldisilazane.

9. The method for preparing the antioxidant composite material of the carbon-carbon crucible according to claim 4, characterized in that, The heating temperature in step S2 is 100-200℃.

10. The application of an antioxidant composite material of the carbon-carbon crucible according to any one of claims 1-3 in protecting the carbon-carbon crucible, characterized in that, Includes the following steps: Step 1: Surface treatment of the carbon-carbon crucible substrate; Step 2: Apply the antioxidant composite material for the carbon-carbon crucible to the surface of the carbon-carbon crucible; Step 3: Pre-cure at 80-150℃ for 0.5-2 hours; Step 4: Ceramization treatment in an inert gas to form an anti-oxidation composite coating on the surface of the carbon-carbon crucible.

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