Ceramic carbon fiber sizing agent, preparation method thereof and composite material

Abstract

This invention relates to the field of carbon fiber composite materials, specifically to a ceramicized carbon fiber sizing agent, its preparation method, and the resulting composite material. The ceramicized carbon fiber sizing agent comprises the following components in parts by weight: 20-35 parts polycarbosilane, 2-5 parts nonionic emulsifier, 0.5-1.5 parts adhesion promoter, 0.1-0.5 parts leveling agent, and 60-75 parts deionized water. The composite material is obtained by sizing PAN-based carbon fibers using the above sizing agent. The water-based polycarbosilane sizing agent provided by this invention can be stored for a long time without stratification or agglomeration. When used to sizing PAN-based carbon fibers, after high-temperature ceramicization treatment, it completely transforms into a high-purity β-SiC ceramic matrix with a ceramic conversion rate ≥98%. The resulting composite material forms a uniform and dense film, with N and S contents below the detection limit. No N release is observed under simulated operating conditions of 2300℃ for 5 days, making it suitable for semiconductor production.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber composite materials, and more specifically, to ceramicized carbon fiber sizing agents, their preparation methods, and composite materials. Background Technology

[0002] The growth of SiC semiconductor crystals requires extremely stringent control of impurities in the thermal environment, especially prohibiting the precipitation of nitrogen (N). Otherwise, defects such as dislocations and microtubes will form in the SiC crystal, significantly reducing device yield and electrical performance. Currently, the carbon fiber materials used in semiconductor thermal insulation felts face the core technical bottleneck of nitrogen residue release under high-temperature conditions. While PAN-based carbon fibers offer superior mechanical properties and controllable costs, their molecular chains contain nitrogen. Even after purification at 2200℃, residual nitrogen remains, posing a risk of nitrogen release under the extreme conditions of 2300℃ for 5 days during SiC production. This makes them unsuitable for high-end semiconductor thermal environment scenarios.

[0003] Existing carbon fiber sizing agents are mostly epoxy resin and polyurethane systems, which can only achieve fiber protection at room temperature. They completely decompose and carbonize at temperatures above 2000℃, failing to form a stable structure and potentially introducing additional impurities, thus failing to address the issue of impurity release under high-temperature conditions. Currently, there is a lack of a dedicated sizing agent on the market that can uniformly form a film to protect carbon fibers at room temperature, transform them into a high-purity ceramic matrix after purification at 2200℃, while simultaneously suppressing nitrogen release and preventing the introduction of sulfur impurities. This makes it difficult to meet the high-purity, high-temperature resistance, and low-impurity requirements of semiconductor SiC thermal field materials.

[0004] Polycarbosilane (PCS), as a classic SiC ceramic precursor, has the characteristic of generating high-purity β-SiC ceramics through high-temperature pyrolysis. However, it is an oily polymer and is difficult to directly emulsify in water to form a stable sizing emulsion. Furthermore, its adhesion to the carbon fiber surface and the uniformity of film formation need to be optimized.

[0005] Based on this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide an aqueous polycarbosilane emulsion that can be used for sizing carbon fibers. Using it to sizing PAN-based carbon fibers can yield a composite material that does not release nitrogen at high temperatures.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a ceramicized carbon fiber sizing agent, comprising the following components in parts by weight: 20-35 parts polycarbosilane, 2-5 parts nonionic emulsifier, 0.5-1.5 parts adhesion promoter, 0.1-0.5 parts leveling agent, and 60-75 parts deionized water.

[0008] In an optional embodiment, the nonionic emulsifier is selected from one or two of fatty alcohol polyoxyethylene ether and polyethylene glycol fatty acid ester; Optionally, the adhesion promoter is vinyltrimethoxysilane.

[0009] Optionally, the leveling agent is polydimethylsiloxane diol.

[0010] Secondly, the present invention provides a method for preparing the above-mentioned ceramicized carbon fiber sizing agent, comprising the following steps: S1: Mix polycarbosilane, emulsifier, adhesion promoter and leveling agent in the specified ratio to obtain an oil phase mixture; S2: Add deionized water to the oil phase mixture and disperse it evenly to obtain a ceramicized carbon fiber sizing agent.

[0011] In an optional embodiment, in S1, after mixing, the mixture is stirred at 40~50°C; Optionally, in S2, deionized water is added dropwise to the oil phase mixture 2 to 5 times at 40 to 50°C.

[0012] Thirdly, the present invention provides a method for preparing a surface-ceramized carbon fiber composite material, comprising the following steps: S1: Take the above-mentioned carbon fiber sizing agent and dilute it to a solid content of 2% to 3%; S2: Sizing of PAN-based carbon fibers to a sizing rate of 0.5-1.5%, followed by pre-baking and drying; S3: Pyrolytic ceramization is carried out under an inert gas atmosphere to obtain the surface-ceramized carbon fiber composite material.

[0013] In an optional implementation, in S2, the pre-baking is: Pre-drying with heat-setting rollers at 130-150℃; Optionally, the drying process is as follows: Dry at 130–200℃.

[0014] In an optional implementation, the pyrolytic ceramization includes the following steps: The sizing PAN-based carbon fibers were heated to 2100-2300℃ at a rate of 3-5℃ / min under an inert gas atmosphere and held at that temperature for 2-4 hours to complete the pyrolytic ceramization.

[0015] Fourthly, the present invention provides a surface-ceramized carbon fiber composite material prepared by the above-described preparation method.

[0016] Fifthly, the present invention provides the above-mentioned ceramicized carbon fiber sizing agent, or the composite material prepared by the above-mentioned preparation method, or the application of the above-mentioned surface ceramicized carbon fiber composite material in semiconductor thermal field insulation.

[0017] Sixthly, the present invention provides a semiconductor thermal insulation felt, comprising the above-mentioned surface-ceramized carbon fiber composite material. The present invention has the following beneficial effects: This invention provides an aqueous polycarbosilane sizing agent that can be stored for a long time without stratification or agglomeration. When used to sizing PAN-based carbon fibers, after high-temperature ceramicization treatment, it is completely transformed into a high-purity β-SiC ceramic matrix with a ceramic conversion rate of ≥98%. The resulting composite material film is uniform and dense, with N and S contents below the detection limit. No N release is observed under simulated working conditions of 2300℃×5 days, making it perfectly suitable for semiconductor production. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0019] In a first aspect, the present invention provides a ceramicized carbon fiber sizing agent, comprising the following components in parts by weight: 20-35 parts polycarbosilane, 2-5 parts nonionic emulsifier, 0.5-1.5 parts adhesion promoter, 0.1-0.5 parts leveling agent, and 60-75 parts deionized water.

[0020] The ceramicized carbon fiber sizing agent provided by this invention is an aqueous emulsion of ceramic precursor with polycarbosilane as the core. The emulsion has uniform particle size, does not separate or agglomerate after being stored at room temperature for 3 months, and can quickly spread into a film on the surface of carbon fiber matrix at room temperature.

[0021] In an optional embodiment, the nonionic emulsifier is selected from one or two of fatty alcohol polyoxyethylene ether and polyethylene glycol fatty acid ester; Optionally, the adhesion promoter is vinyltrimethoxysilane.

[0022] Optionally, the leveling agent is polydimethylsiloxane diol.

[0023] Optionally, the polycarbosilane is a high-purity polycarbosilane with a purity of 99.99% or higher and a number-average molecular weight of 800-1500.

[0024] Optionally, the nonionic emulsifier has an HLB value of 10 to 13.

[0025] Secondly, the present invention provides a method for preparing the above-mentioned ceramicized carbon fiber sizing agent, comprising the following steps: S1: Mix polycarbosilane, emulsifier, adhesion promoter and leveling agent in the specified ratio to obtain an oil phase mixture; S2: Add deionized water to the oil phase mixture and disperse it evenly to obtain a ceramicized carbon fiber sizing agent.

[0026] In an optional embodiment, in S1, after mixing, the mixture is stirred at 40~50°C.

[0027] Optionally, the stirring specifically includes: Rotate the engine at 300–500 r / min, heat to 40–50℃, and stir at a constant temperature for 30 min to ensure the mixture is evenly dispersed.

[0028] In an optional embodiment, in step S2, deionized water is added dropwise to the oil phase mixture 2 to 5 times at a temperature of 40 to 50°C.

[0029] Optionally, the specific method of joining is as follows: The deionized water was slowly added dropwise to the oil phase mixture in three separate drops, with each dropwise interval of 10 min. After the addition was completed, the rotation speed was increased to 1000-1500 r / min, and high-speed shear emulsification was carried out for 40-60 min.

[0030] In an optional embodiment, the emulsion particle size after dispersion is 100~300 nm.

[0031] In an optional implementation, after S2, the mixture is cooled to room temperature and passed through a 1000-mesh filter cloth to remove agglomerated particles, thus obtaining a ceramicized carbon fiber sizing agent.

[0032] Thirdly, the present invention provides a method for preparing a surface-ceramized carbon fiber composite material, comprising the following steps: S1: Take the above-mentioned carbon fiber sizing agent and dilute it to a solid content of 2%~3%; S2: Sizing of PAN-based carbon fibers to a sizing rate of 0.5-1.5%, followed by pre-baking and drying; S3: Pyrolytic ceramization is carried out under an inert gas atmosphere to obtain the surface-ceramized carbon fiber composite material.

[0033] In an optional implementation, in S2, the pre-baking is: Pre-drying with heat-setting rollers at 130-150℃; Optionally, the drying process is as follows: The carbon fiber is dried at 130–200℃. After drying, the carbon fiber sizing agent forms a continuous and dense protective film on the carbon fiber surface.

[0034] The above sizing rate is calculated as follows: (dry weight of fiber after sizing - dry weight of original fiber before sizing) / dry weight of original fiber before sizing × 100%.

[0035] In an optional implementation, the pyrolytic ceramization includes the following steps: The sizing PAN-based carbon fibers were heated to 2100-2300℃ at a rate of 3-5℃ / min under an inert gas atmosphere and held at that temperature for 2-4 hours to complete the pyrolytic ceramization.

[0036] In the surface-ceramized carbon fiber composite material prepared by the above method, the carbon fiber sizing agent is completely converted into β-SiC ceramic matrix. The test results show no N or S impurities remaining, and no N element is released after long-term heat preservation at 2300℃, which meets the high purity requirements of semiconductor SiC thermal field materials.

[0037] Fourthly, the present invention provides a surface-ceramized carbon fiber composite material prepared by the above-described preparation method.

[0038] Fifthly, the present invention provides the above-mentioned ceramicized carbon fiber sizing agent, or the composite material prepared by the above-mentioned preparation method, or the application of the above-mentioned surface ceramicized carbon fiber composite material in semiconductor thermal field insulation.

[0039] Sixthly, the present invention provides a semiconductor thermal insulation felt, comprising the above-mentioned surface-ceramized carbon fiber composite material. Example 1 (1) The carbon fiber sizing agent components provided in this embodiment are: 25 parts high-purity polycarbosilane, 3 parts fatty alcohol polyoxyethylene ether, 0.8 parts vinyltrimethoxysilane, 0.2 parts polydimethylsiloxane diol, and 71 parts deionized water.

[0040] (2) Preparation of carbon fiber sizing agent S1: Add polycarbosilane, emulsifier, adhesion promoter and leveling agent to the reaction vessel, stir at 400 r / min, and keep at 45℃ for 30 min to mix evenly; S2: Add deionized water in 3 drops, and after the addition is complete, stir and shear at 1200 r / min for 50 min. Pass the mixture through a 1000-mesh filter cloth to obtain the ceramicized carbon fiber sizing agent.

[0041] (3) Carbon fiber sizing S1: Dilute the ceramicized carbon fiber sizing agent to a solid content of 2.5%; S2: PAN-based carbon fiber felt is continuously impregnated and sized, with the sizing rate precisely controlled at 1.0%; it is then pre-dried on a 140℃ heat-setting roller and dried in a 160℃ continuous drying oven. S3: Ceramization at 2200℃ for 3 hours under argon atmosphere.

[0042] Test results: The prepared sizing agent emulsion showed no stratification or agglomeration after standing at room temperature for 3 months, and the emulsion particle size was uniform; the ceramic conversion rate was 98.5%, the N content was <0.1ppm, and no N element was released after holding at 2300℃ for 5 days, which meets the high purity requirements of semiconductor thermal field.

[0043] Example 2 (1) The carbon fiber sizing agent components provided in this embodiment are: 30 parts high-purity polycarbosilane, 4 parts polyethylene glycol fatty acid ester, 1.0 part vinyltrimethoxysilane, 0.3 parts polydimethylsiloxane diol, and 64.7 parts deionized water.

[0044] (2) Preparation of carbon fiber sizing agent It is basically the same as Example 1, except that in S2, the rotational speed is 1400 r / min; (3) Carbon fiber sizing It is basically the same as Example 1, except that in S2, the ceramicization is maintained for 4 hours.

[0045] Test results: The prepared sizing agent emulsion showed no stratification or agglomeration after standing at room temperature for 3 months, and the emulsion particle size was uniform; the ceramic conversion rate was 99.1%, there was no N or S residue, and the high temperature stability was excellent.

[0046] Example 3 (1) The carbon fiber sizing agent components provided in this embodiment are: 28 parts high-purity polycarbosilane, 2 parts fatty alcohol polyoxyethylene ether + 2 parts polyethylene glycol fatty acid ester, 1.2 parts vinyltrimethoxysilane, 0.4 parts polydimethylsiloxane diol, and 64.4 parts deionized water.

[0047] (2) Preparation of carbon fiber sizing agent The process is basically the same as in Example 1, except that in S2, the rotation speed is 1300 r / min and the high-speed shear emulsification is carried out for 55 min. (3) Carbon fiber sizing The process is basically the same as in Example 1, except that in S3, the sizing rate is precisely controlled at 1.2%, and the ceramicization is carried out after 3.5 hours of heat treatment.

[0048] Test results: The prepared sizing agent emulsion showed no stratification or agglomeration after standing at room temperature for 3 months, and the emulsion particle size was uniform; after pyrolysis, the β-SiC ceramic conversion rate was 98.8%, with no N or S residue, and excellent high-temperature stability.

[0049] Comparative Example 1 PAN-based carbon fiber felt was treated with conventional epoxy resin sizing agent. After purification at 2200℃, the sizing layer was completely decomposed and carbonized. After holding at 2300℃, the nitrogen release was measured to be 12 ppm, which could not meet the stringent requirement of zero nitrogen release in SiC production.

[0050] Comparative Example 2 Based on the formulation and process of Example 1, the high-purity polycarbosilane in the carbon fiber sizing agent was adjusted to 15 parts, while the remaining components, preparation, sizing, and ceramicization processes were completely identical.

[0051] Test results: The emulsion was too thin, and slight stratification occurred after standing at room temperature for 15 days; the average particle size was 357 nm, with uneven particle size distribution; the surface tension was 41.6 mN / m, indicating poor fiber spreadability. Sizing effect: The sizing film was thin and discontinuous, with localized sizing leakage. Ceramicization performance: The β-SiC ceramic conversion rate was only 82.3%; the nitrogen content was 0.35 ppm; significant nitrogen release was detected after holding at 2300℃ for 5 days, failing to meet the requirements for semiconductor use.

[0052] Comparative Example 3 Based on the formulation and process of Example 1, the high-purity polycarbosilane was adjusted to 40 parts, while the remaining components, preparation, sizing, and ceramicization processes were completely identical.

[0053] Test results: The emulsion has poor stability and agglomeration and precipitation occurred after standing at room temperature for 7 days.

[0054] Comparative Example 4 Based on Example 1, the formulation and process were identical, with 1.8 parts of vinyltrimethoxysilane and 0.3 parts of polydimethylsiloxane diol, and the remaining components, preparation, sizing, and ceramicization processes were completely consistent.

[0055] Test results: The film adhesion was too strong, and after drying, the carbon fiber bundles became hard, less flexible, and more brittle, making them easy to break and unable to be used to make thermal insulation felt.

[0056] Comparative Example 5 Based on Example 1, the formulation and process were identical, with 1.0 part of vinyltrimethoxysilane and 0.8 parts of polydimethylsiloxane diol, and the remaining components, preparation, sizing, and ceramicization processes were completely consistent.

[0057] Test results: Excellent leveling properties and normal emulsion state. The film surface is smooth after sizing, but the adhesion between the film and the carbon fiber matrix is ​​insufficient, resulting in localized peeling and detachment after drying.

[0058] Comparative Example 6 Based on Example 1, the formulation and process were used, with pitch-based carbon fiber used as the fiber, and other processes remained unchanged.

[0059] Test results: The surface of pitch-based carbon fiber is highly inert, the slurry spreads poorly, the film formation is discontinuous and uneven, and the pitch-based carbon fiber itself is brittle and cannot be used to make thermal insulation felt.

[0060] Comparative Example 7 Based on Example 1, the formulation and process were used, with viscose-based carbon fiber as the fiber and other processes remaining unchanged.

[0061] Test results: Short-term film formation was normal, but the viscose-based carbon fiber itself had poor thermal stability. During the ceramization process at 2200℃, the carbon fiber matrix underwent severe pyrolysis and pulverization, resulting in structural collapse. It was unable to form a complete composite material and was therefore completely unsuitable for semiconductor thermal insulation applications.

Claims

1. A ceramicized carbon fiber sizing agent, characterized in that, The components include the following parts by mass: 20-35 parts polycarbosilane, 2-5 parts nonionic emulsifier, 0.5-1.5 parts adhesion promoter, 0.1-0.5 parts leveling agent, and 60-75 parts deionized water.

2. The ceramicized carbon fiber sizing agent according to claim 1, characterized in that, The nonionic emulsifier is selected from one or two of fatty alcohol polyoxyethylene ether and polyethylene glycol fatty acid ester; Optionally, the adhesion promoter is vinyltrimethoxysilane. Optionally, the leveling agent is polydimethylsiloxane diol.

3. The method for preparing the ceramicized carbon fiber sizing agent as described in claim 1, characterized in that, Includes the following steps: S1: Mix polycarbosilane, emulsifier, adhesion promoter and leveling agent in the specified ratio to obtain an oil phase mixture; S2: Add deionized water to the oil phase mixture and disperse it evenly to obtain a ceramicized carbon fiber sizing agent.

4. The preparation method according to claim 3, characterized in that, In S1, after mixing, the mixture is stirred at 40~50℃; Optionally, in S2, deionized water is added dropwise to the oil phase mixture 2 to 5 times at 40 to 50°C.

5. A method for preparing a surface-ceramized carbon fiber composite material, characterized in that, Includes the following steps: S1: Take the carbon fiber sizing agent according to claim 1 and dilute it to a solid content of 2% to 3%; S2: Sizing of PAN-based carbon fibers to a sizing rate of 0.5-1.5%, followed by pre-baking and drying; S3: Pyrolytic ceramization is carried out under an inert gas atmosphere to obtain the surface-ceramized carbon fiber composite material.

6. The preparation method according to claim 5, characterized in that, In S2, the pre-baking is: Pre-drying with heat-setting rollers at 130-150℃; Optionally, the drying process is as follows: Dry at 130–200℃.

7. The preparation method according to claim 5, characterized in that, The pyrolytic ceramization includes the following steps: The sizing PAN-based carbon fibers were heated to 2100-2300℃ at a rate of 3-5℃ / min under an inert gas atmosphere and held at that temperature for 2-4 hours to complete the pyrolytic ceramization.

8. The surface-ceramized carbon fiber composite material prepared by the preparation method according to claim 5.

9. The ceramicized carbon fiber sizing agent as described in claim 1, or the composite material prepared by the preparation method as described in claim 5, or the surface ceramicized carbon fiber composite material as described in claim 8, in semiconductor thermal insulation.

10. A semiconductor thermal insulation felt, comprising the surface-ceramized carbon fiber composite material as described in claim 8.