Three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material and preparation method thereof

Abstract

The invention discloses a three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material and a preparation method thereof, and belongs to the technical field of insulating materials, the material is composed of 18%-22% of a three-dimensional whisker network reinforced phase, 70%-76% of a silicon oxide-aluminum oxide composite mesoporous matrix, 3%-5% of an anti-condensation functional component and 0.5%-1.5% of an interface coupling agent KH550, the mesoporous matrix is in bimodal pore size distribution, and the anti-condensation component is a composite system of fluorosilane and double nanoparticles. According to the preparation method, material performance optimization is achieved through the synergistic steps of in-situ whisker network construction, sol-gel compounding, ALD transition layer deposition, radiation crosslinking, plasma modification and the like. The dielectric strength of the obtained material is larger than or equal to 27 kV / mm, the compression strength is larger than or equal to 4.2 MPa, the 72-hour condensation inhibition rate in the 95% RH environment is larger than or equal to 96%, the high-humidity 3000-hour dielectric attenuation rate is smaller than or equal to 4%, and the material can tolerate the salt mist extreme environment, is suitable for long-acting insulation protection of electrical equipment in the high-humidity and strong-corrosion scenes such as ocean platforms and chemical industrial parks and has remarkable industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of insulating materials technology, specifically relating to a three-dimensional whisker network-reinforced mesoporous composite anti-condensation insulating material and its preparation method. Background Technology

[0002] Mesoporous insulating materials, with their high specific surface area, low dielectric constant, and low thermal conductivity, have irreplaceable application value in fields such as power equipment insulation and high-frequency electronic packaging. However, existing mesoporous insulating materials are difficult to adapt to complex high-humidity service environments: First, their mechanical properties are weak. The mesoporous structure leads to high brittleness and poor impact resistance, making them prone to microcracks during processing or service, directly causing a decline in insulation reliability. Second, they lack anti-condensation capabilities. In high-humidity environments, the mesoporous channels easily absorb water vapor and form condensation, causing the material's breakdown strength to drop sharply by more than 30%, inducing insulation failure accidents. Third, their performance synergy is poor. Although traditional reinforcement methods (such as single-particle filling and short fiber doping) can slightly improve mechanical properties, they will destroy the integrity of the mesoporous structure, causing insulation performance and anti-condensation effect to mutually restrict each other, making it impossible to achieve simultaneous optimization of multiple properties.

[0003] In existing technologies, whiskers, as one-dimensional reinforcements, have been attempted for use in the modification of composite materials due to their advantages of high specific strength and high modulus. However, they have obvious limitations: for example, the publicly disclosed mesoporous titanium dioxide whisker molding materials only focus on catalytic performance and have no anti-condensation function design. Moreover, the whiskers are in a dispersed state and do not form a continuous network, resulting in limited mechanical reinforcement effect (compressive strength ≤2.5MPa). Although the use of mullite whiskers to reinforce silica aerogel improves mechanical properties, the mesoporous structure is simple (single pore size distribution), which cannot control the water vapor adsorption-desorption balance. Furthermore, without interface modification design, the whiskers are easy to peel off from the matrix, resulting in poor service stability in high humidity environments.

[0004] Most existing anti-condensation technologies rely on hydrophobic surface coatings, which have weak adhesion to the substrate and are prone to peeling, failing to achieve long-term anti-condensation effects. Furthermore, the coating materials have poor compatibility with mesoporous insulation systems, easily clogging the mesoporous channels and compromising the material's inherent insulation properties. Therefore, developing a composite system that retains the excellent insulation and thermal insulation properties of mesoporous materials, enhances mechanical properties through a three-dimensional whisker network, and integrates long-term anti-condensation, corrosion resistance, and self-healing functions is key to solving the insulation challenges in high-humidity and complex environments. To this end, an improved design of a three-dimensional whisker network-reinforced mesoporous composite anti-condensation insulation material and its preparation method were developed. Summary of the Invention

[0005] To address the aforementioned shortcomings in the existing technology, this invention provides a three-dimensional whisker network-reinforced mesoporous composite anti-condensation insulating material and its preparation method to solve the problems mentioned in the background technology.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for preparing a three-dimensional whisker network-reinforced mesoporous composite anti-condensation insulating material includes the following steps:

[0008] (1) Mix SiC whiskers and mullite whiskers at a mass ratio of 2~3:1, clean them with 5%~8% dilute hydrochloric acid at 80℃ using ultrasonic cleaning, wash them with deionized water until neutral, vacuum dry them, add deionized water and dispersant, disperse them with ultrasonication, and then ball mill them to form a suspension.

[0009] (2) Add a temperature control agent to the suspension, stir evenly and then inject into the mold. Use a gradient freezing process to keep it warm, and then apply a pressure of 5~8MPa at -20℃ for 2~3h. Finally, freeze dry to remove the ice crystal template to obtain the whisker skeleton.

[0010] (3) Prepare materials according to the molar ratio of SiO2 to Al2O3 of 3~5:1, use tetraethyl orthosilicate as silicon source, aluminum isopropoxide as aluminum source, ethanol as solvent and hydrochloric acid as catalyst, control the molar ratio of water to tetraethyl orthosilicate of 4~6:1, stir and hydrolyze at 30~40℃ for 4~6h, add methyl methacrylate monomer and initiator, stir to complete in-situ polymerization to obtain composite sol;

[0011] (4) Vacuum impregnate the whisker skeleton with the composite sol, add the anti-condensation functional component and the interface coupling agent, ultrasonically disperse for 20 min, adjust the pH to 8-9 with ammonia water, and react at 50℃ for 3 h; then put it into the atomic layer deposition equipment, using trimethylaluminum and deionized water as precursors, and deposit a 5-10 nm Al2O3 transition layer at 50℃ to obtain the composite gel system.

[0012] (5) The composite gel system was allowed to stand at 60°C for 8-12 hours to gel, and then aged at 70°C with an ethanol-deionized water mixture for 24 hours; cross-linking was completed by γ-ray irradiation to obtain a wet gel.

[0013] (6) Dry the wet gel at 40~50℃ and 8~10MPa for 6~8h; then treat it with plasma at 100~150W power in an argon atmosphere for 5~10min to obtain the dry composite material;

[0014] (7) A three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material was obtained by calcining dry composite material using a gradient calcination process.

[0015] Furthermore, the gradient freezing process described in step (2) involves gradually reducing the temperature from -5℃ to -20℃ at a rate of 1℃ / min and holding the temperature for 4 hours.

[0016] The freeze-drying process conditions are -50℃ drying for 8 to 12 hours;

[0017] The temperature control agent is CaF2, and the amount added is 1.5% to 2.5% of the whisker mass.

[0018] Furthermore, in step (3), the amount of methyl methacrylate monomer added is 1% to 2% of the total mass of the sol.

[0019] Furthermore, the initiator is benzoyl peroxide, and the amount added is 0.3% to 0.5% of the monomer mass.

[0020] Furthermore, the dispersant is tetramethylammonium hydroxide, and the amount of dispersant added is 0.5% to 1% of the whisker mass.

[0021] Furthermore, in step (5), the dose of γ-ray irradiation is 50~80kGy, and the irradiation time is 1~2h.

[0022] Further, the gradient calcination process in step (7) is as follows: heating rate of 2℃ / min for 20~200℃ and holding for 2h, heating rate of 5℃ / min for 3h for 200~600℃ and holding for 2h for 600~700℃ and cooling with the furnace.

[0023] Furthermore, the anti-condensation functional component in step (4) is a composite system composed of perfluorooctyltriethoxysilane, nano-TiO2 and nano-ZnO in a mass ratio of 5~7:2~3:1.

[0024] Further, the interfacial coupling agent mentioned in step (4) is γ-aminopropyltriethoxysilane.

[0025] This invention also provides a three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material, prepared by the above-described preparation method, comprising the following components by mass percentage: 18%–22% three-dimensional whisker network reinforcing phase, 70%–76% silica-alumina composite mesoporous matrix, 3%–5% anti-condensation functional component, and 0.5%–1.5% interfacial coupling agent; the three-dimensional whisker network reinforcing phase is a continuous interconnected network formed by combining SiC whiskers and mullite whiskers at a mass ratio of 2–3:1; the silica-alumina composite mesoporous matrix has a SiO2 to Al2O3 molar ratio of 3–5:1, exhibiting a bimodal pore size distribution; the anti-condensation functional component is a composite system composed of perfluorooctyltriethoxysilane, nano-TiO2, and nano-ZnO at a mass ratio of 5–7:2–3:1, with perfluorooctyltriethoxysilane in situ grafted onto the whisker surface and mesoporous pore walls; the interfacial coupling agent is γ-aminopropyltriethoxysilane.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. This solution has the following significant differences: The addition of nano-ZnO and KH550 constructs a triple synergistic system of "hydrophobicity-photocatalysis-interface enhancement," solving the problems of single component and weak interfacial bonding in existing technologies; through bi-whisker size gradation and mesoporous bi-peak distribution, an integrated structure of "rigid framework-flexible interface-functional channels" is formed, breaking through the bottleneck of "mutual repulsion between mechanical enhancement and mesoporous retention" in existing technologies, simultaneously achieving multi-functional integration such as anti-condensation, corrosion resistance, self-healing, flame retardancy, and wide-temperature stability, extending to complex scenarios such as oceans and salt spray, unlike existing patents which only have adaptability to high-humidity environments; in terms of environmental protection, low-toxicity fluorosilanes and biodegradable MMA monomers are selected, and there are no harmful gas emissions during calcination, aligning with the trend of green preparation;

[0028] 2. This solution integrates cross-domain processes to form a dedicated workflow, which improves efficiency by more than 25% compared to the traditional "step-by-step preparation" process. It eliminates the need for additional post-processing steps (such as secondary coating or interface repair) and reduces production costs by 18% to 22%. The precise matching of various process parameters (such as the temperature synergy between low-temperature pressure and freeze-drying, and the time adaptation between radiation cross-linking and aging) solves the problems of poor process integration and large performance fluctuations in existing technologies. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the preparation process of the three-dimensional whisker network-reinforced mesoporous composite anti-condensation insulating material of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this application. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0032] Most existing anti-condensation technologies rely on hydrophobic surface coatings, which have weak adhesion to the substrate and are prone to peeling, failing to achieve long-term anti-condensation effects. Furthermore, the coating materials have poor compatibility with mesoporous insulation systems, easily clogging the mesoporous channels and compromising the material's inherent insulation properties. Therefore, developing a composite system that retains the excellent insulation and thermal insulation properties of mesoporous materials, enhances mechanical properties through a three-dimensional whisker network, and integrates long-term anti-condensation, corrosion resistance, and self-healing functions is key to solving the insulation challenges in high-humidity and complex environments.

[0033] This invention provides a three-dimensional whisker network-reinforced mesoporous composite anti-condensation insulating material. The material comprises a three-dimensional through-type whisker network, a silica-alumina composite mesoporous matrix, in-situ grafted anti-condensation functional components, and an interfacial coupling agent. The total mass percentage of each component is 100%. The specific composition is as follows:

[0034] Three-dimensional whisker network reinforcement phase: 18%–22%, composed of silicon carbide (SiC) whiskers and mullite whiskers in a mass ratio of 2–3:1; wherein the SiC whiskers have a diameter of 0.5–2 μm and an aspect ratio of 30–50, and bear the load-bearing function of the skeleton; the mullite whiskers have a diameter of 0.1–0.8 μm and an aspect ratio of 20–40, and fill the gaps between the SiC whiskers. The two overlap to form a continuous and interconnected network with an overlap rate of ≥95%.

[0035] Mesoporous matrix phase: 70%–76%, a composite mesoporous system of SiO2 and Al2O3 molar ratio of 3–5:1. The mesopore size exhibits a bimodal distribution—the first characteristic pore size is 4–10 nm (accounting for 60%–70% of the pore volume), used to regulate dielectric properties; the second characteristic pore size is 20–50 nm (accounting for 30%–40% of the pore volume), used to regulate water vapor adsorption-desorption balance; total porosity is 40%–60%, and specific surface area is 180–300 m² / g.

[0036] The anti-condensation functional component is 3%–5%, which is a composite system composed of perfluorooctyltriethoxysilane (fluorosilane modifier), nano-TiO2 and nano-ZnO in a mass ratio of 5–7:2–3:1. Fluorosilane is grafted in situ onto the surface of whiskers and the walls of mesopores to form a long-lasting hydrophobic layer. Nano-TiO2 (particle size 5–15 nm) and nano-ZnO (particle size 8–20 nm) are synergistically dispersed in the mesopores, possessing photocatalytic self-cleaning, micro-scratch repair and antibacterial functions, thus constructing a "hydrophobic-photocatalytic" synergistic anti-condensation system.

[0037] Interface coupling agent: 0.5% to 2%, γ-aminopropyltriethoxysilane (KH550), used to improve the compatibility of whiskers, mesoporous matrix and anti-condensation components, strengthen the interfacial bonding strength and avoid interfacial delamination during service.

[0038] The proportion of the mesoporous matrix phase was adjusted to match other components to ensure that the total proportion of the three-dimensional whisker network reinforcement phase and functional additives did not exceed 32%, thus avoiding excessive components that could cause the mesoporous structure to collapse. The key performance indicators of the optimized material are as follows:

[0039] Dielectric strength ≥27kV / mm, volume resistivity ≥5×10¹ 4Ω·cm, compressive strength ≥4.2MPa, flexural strength ≥2.8MPa; condensation inhibition rate ≥96% after 72h at 25℃ and 95% relative humidity, no condensation formation under sudden temperature change (25℃→5℃, 95%RH); dielectric strength decay rate ≤4% after 3000h continuous service in high humidity environment (95%RH), no corrosion signs after 1000h in 5% salt spray environment, dielectric strength decay ≤3%; thermal conductivity adjustable to 0.065~0.078W / (m·K), dielectric constant stable at 2.5~3.2 (1MHz), oxygen index ≥32% (UL94 V-0 flame retardant), dimensional change rate ≤0.3% after 100 cycles in a wide temperature range of -40~120℃.

[0040] This solution has the following significant differences: ① In terms of composition, it adds nano-ZnO and KH550 to construct a triple synergistic system of "hydrophobicity-photocatalysis-interface strengthening", solving the problems of single composition and weak interfacial bonding in existing technologies; ② In terms of structure, it forms an integrated structure of "rigid framework-flexible interface-functional pores" through double whisker size gradation and mesoporous bimodal distribution, breaking through the bottleneck of "mutual exclusion between mechanical enhancement and mesoporous retention" in existing technologies; ③ In terms of performance, it simultaneously achieves multi-functional integration such as anti-condensation, anti-corrosion, self-healing, flame retardancy, and wide temperature range stability, extending to complex scenarios such as oceans and salt spray, which is different from the single high-humidity environment adaptability of existing patents; ④ In terms of environmental protection, it selects low-toxicity fluorosilanes and biodegradable MMA monomers, and there are no harmful gas emissions during calcination, which is in line with the trend of green preparation.

[0041] This invention also provides a method for preparing the above-mentioned three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material.

[0042] This material employs an integrated preparation process of "in-situ whisker network construction - sol-gel composite - in-situ modification - cross-domain process synergy," integrating five cross-domain technologies: ceramic cryogenic casting, metal powder metallurgy, polymer crosslinking, semiconductor ALD, and optical thin film modification. The specific steps are as follows:

[0043] Whisker pretreatment: SiC whiskers and mullite whiskers are mixed in proportion and placed in dilute hydrochloric acid with a mass fraction of 5% to 8%. They are ultrasonically cleaned at 80°C for 2 hours to remove surface impurities and oxide layers. They are then washed with deionized water until neutral and vacuum dried at 120°C for 4 hours for later use.

[0044] Preparation of whisker dispersion: The pretreated composite whiskers were added to deionized water, and 0.5% to 1% of the whisker mass of dispersant (tetramethylammonium hydroxide) was added. The mixture was ultrasonically dispersed for 30 min, and then placed in a planetary ball mill and ball-milled at 300 rpm for 2 h to form a uniform and stable whisker suspension.

[0045] In-situ construction of a three-dimensional whisker network: CaF2 temperature control agent (1.5%–2.5% of whisker mass) was added to the whisker suspension, stirred evenly, and then transferred to a cryogenic casting mold; a gradient freezing process was adopted (gradually decreasing from -5℃ to -20℃ at a cooling rate of 1℃ / min), and the temperature was held for 4 hours to induce the directional growth of ice crystals and the overlap of whiskers; a low-temperature thermoforming process from the field of metal powder metallurgy was introduced, and a pressure of 5–8 MPa was applied at -20℃ for 2 hours to improve the density of whisker overlap; subsequently, the ice crystal template was removed by freeze-drying at -50℃ for 12 hours, resulting in a three-dimensional SiC-mullite bi-whisker network framework with an overlap rate of ≥95%, continuous and interconnected structure, and excellent density. This framework can form a stable support structure by virtue of the size distribution advantage of coarse whiskers bearing the load and fine whiskers filling the gaps, effectively avoiding structural collapse during subsequent sol filling and drying processes, laying the core foundation for the preservation of mesoporous structure and performance synergy; this process replaces the traditional centrifugal separation process and completely solves the problem of network loosening caused by single freeze-drying.

[0046] Preparation of mesoporous matrix sol: Tetraethyl orthosilicate (TEO2) was used as the silicon source, aluminum isopropoxide (APO2) as the aluminum source, ethanol as the solvent, and hydrochloric acid as the hydrolysis catalyst. The mixture was prepared with SiO2 to Al2O3 in a molar ratio of 3-5:1. Deionized water (water to TEO2 molar ratio of 4-6:1) was added, and the mixture was stirred at 30-40°C for 4-6 hours for hydrolysis. During this period, methyl methacrylate (MMA) monomer (1%-2% of the total mass of the sol) and trace amounts of benzoyl peroxide initiator (0.3%-0.5% of the mass of MMA) were added. The mixture was stirred for another hour to form an "inorganic sol-organic polymer" composite precursor through in-situ polymerization. This yielded a transparent, uniform, and highly stable silica-alumina composite sol. This sol combines the insulating and heat-resistant properties of the inorganic phase with the bonding and flexibility of the organic phase, and can fully penetrate and fill the gaps in the whisker network.

[0047] Composite and in-situ modification: The whisker network framework was immersed in the composite sol and vacuum impregnated for 30-45 min to ensure the sol fully filled the gaps in the network; a preset ratio of fluorosilane modifier, nano TiO2, nano ZnO and interfacial coupling agent KH550 were added and ultrasonically dispersed for 20 min; ammonia was added to adjust the pH to 8-9 and the reaction was carried out at 50℃ for 3 h to allow fluorosilane to be grafted in-situ onto the whiskers and sol molecular chains; subsequently, the composite system was placed in an atomic layer deposition (ALD) device, and a 5-10 nm Al2O3 transition layer was deposited at 50℃ using trimethylaluminum and deionized water as precursors to enhance the grafting stability of hydrophobic components and the corrosion resistance of the material;

[0048] Gelation, aging, and radiation crosslinking: The above-mentioned mixture was placed in a sealed container and allowed to stand at 60°C for 8–12 hours to complete gelation, resulting in a wet gel with a uniform structure and no obvious pore defects. The whisker network and mesoporous sol in the wet gel were tightly bonded. The wet gel was then immersed in a mixed solution of ethanol and deionized water (volume ratio 1:1) and aged at 70°C for 24 hours, with the solution being changed 3 times during the process to thoroughly remove unreacted monomers, catalysts, and impurities, while further enhancing the stability of the gel network structure. After aging, a gamma-ray radiation crosslinking process from the field of polymer materials was introduced, using 50–80 kGy gamma rays to irradiate for 1–2 hours, causing the organic polymer chains to form a dense crosslinked network, significantly strengthening the whisker-matrix interface bonding force and preventing interface delamination during service. This process replaces traditional chemical crosslinking, leaves no additional reagent residues, and does not negatively affect the insulation performance of the material.

[0049] Supercritical drying and plasma modification: The aged and cross-linked wet gel is placed in a supercritical drying device with CO2 as the drying medium, and the temperature is controlled at 40~50℃ and the pressure at 8~10MPa for 6~8h to remove the solvent in the pores while preserving the integrity of the mesoporous structure. After drying, the plasma surface modification process in the field of optical thin films is introduced. Under an argon atmosphere, the plasma is treated with 100~150W power for 5~10min to activate the mesoporous pore walls and material surface, thereby increasing the fluorosilane grafting density by 30% and further enhancing the hydrophobic durability.

[0050] Gradient calcination and shaping: The modified material is placed in a muffle furnace and calcined under a gradient temperature in an air atmosphere: 20~200℃ (heating rate 2℃ / min) for 2h to remove residual organic matter, 200~600℃ (heating rate 5℃ / min) for 3h to promote the shaping of the mesoporous structure, and 600~700℃ (heating rate 2℃ / min) for 2h to strengthen the fusion between the Al2O3 transition layer and the matrix; after cooling to room temperature in the furnace, perfluorohexylethylene is used as the monomer and treated for 15min in an argon / helium mixed atmosphere (volume ratio 1:1), at 80℃ and 120W power to form a 50~80nm dense fluorocarbon polymer layer on the material surface, further improving the hydrophobic and anti-corrosion performance; finally, a three-dimensional whisker network reinforced mesoporous composite anti-condensation insulation material with mechanical reinforcement, long-term anti-condensation, corrosion resistance, self-healing and wide temperature range stability is obtained. The comprehensive performance of the material meets the long-term insulation requirements of power equipment in high humidity and strong corrosion environments.

[0051] Post-treatment modification (optional): For extreme salt spray environment requirements, the material is placed in an ALD device to deposit a 10~15nm SiO2 sealing layer, then impregnated with fluorinated silane ethanol sol (2% by mass), and dried at 60℃ for 3h to form a "ALD sealing + in-situ hydrophobic" double protective layer, which further improves the dielectric stability in salt spray environment by 10%.

[0052] This solution integrates cross-domain processes to form a dedicated workflow, which improves efficiency by more than 25% compared to the traditional "step-by-step preparation" process. It eliminates the need for additional post-processing steps (such as secondary coating or interface repair) and reduces production costs by 18% to 22%. The precise matching of various process parameters (such as temperature coordination between low-temperature pressure and freeze-drying, and time adaptation between radiation cross-linking and aging) solves the problems of poor process integration and large performance fluctuations in existing technologies.

[0053] Example 1

[0054] The ingredients are formulated according to the following mass percentages: SiC whiskers 12.6%, mullite whiskers 5.4% (total 20%, mass ratio 2.33:1), silica-alumina composite mesoporous matrix 73.2%, perfluorooctyltriethoxysilane 2.8%, nano TiO2 1.2%, nano ZnO 0.4% (anti-condensation components total 4.4%, mass ratio 7:3:1), KH550 0.8%, total mass percentage 100%.

[0055] Preparation steps:

[0056] Whisker pretreatment: SiC whiskers (diameter 1μm, aspect ratio 40) and mullite whiskers (diameter 0.5μm, aspect ratio 30) were mixed, 7% dilute hydrochloric acid was added, ultrasonic cleaning was performed at 80℃ for 2h, washed with deionized water until neutral, and vacuum dried at 120℃ for 4h.

[0057] Dispersion preparation: Add the composite whiskers to deionized water, add 0.8% tetramethylammonium hydroxide, sonicate for 30 min, and then ball mill at 300 rpm for 2 h to form a uniform suspension;

[0058] Network construction: 2% CaF2 was added, stirred evenly, and then injected into a mold. The mixture was subjected to gradient freezing from -5℃ to -20℃ (1℃ / min) and kept at that temperature for 4 hours. Subsequently, a pressure of 6MPa was applied at -20℃ for 2 hours, followed by freeze drying at -50℃ for 12 hours to obtain a three-dimensional SiC-mullite bicrystalline whisker network framework with an overlap rate of 96% and a dense and non-loose structure, which provides stable support for subsequent sol filling and performance synergy.

[0059] Sol preparation: Tetraethyl orthosilicate and aluminum isopropoxide were mixed in a molar ratio of 4:1, with ethanol as solvent, hydrochloric acid as catalyst, and water to tetraethyl orthosilicate in a molar ratio of 5:1. The mixture was hydrolyzed at 35°C for 5 hours. 1.5% MMA monomer and 0.4% benzoyl peroxide initiator were added, and the mixture was stirred for another hour to form a composite sol.

[0060] Composite modification and ALD treatment: Whisker framework was vacuum impregnated with sol for 40 min, then perfluorooctyltriethoxysilane, nano-TiO2 (10 nm particle size), nano-ZnO (15 nm particle size) and KH550 were added, and the mixture was sonicated for 20 min; the pH was adjusted to 8.5 with ammonia, and the reaction was carried out at 50 °C for 3 h; the mixture was then transferred to an ALD device to deposit an 8 nm Al2O3 transition layer (trimethylaluminum and water were alternately introduced, and the cycle was repeated 20 times).

[0061] Gel aging and radiation crosslinking: gelation was achieved by standing at 60℃ for 10 h, aging in an ethanol-water mixture at 70℃ for 24 h (with the solution changed 3 times), and crosslinking was completed by irradiation with 60 kGy gamma rays for 1.5 h.

[0062] Drying and plasma modification: supercritical CO2 drying at 45℃ and 9MPa for 7h, followed by plasma treatment at 120W power in an argon atmosphere for 8min;

[0063] Gradient calcination: Hold at 20~200℃ (2℃ / min) for 2h, hold at 200~600℃ (5℃ / min) for 3h, hold at 600~700℃ (2℃ / min) for 2h, and then cool with the furnace.

[0064] The resulting material properties are: dielectric strength 30 kV / mm, volume resistivity 1.5 × 10¹ 5 Ω·cm, compressive strength 5.2MPa, flexural strength 3.1MPa; condensation inhibition rate of 98% in 25℃, 95%RH environment for 72h, no condensation during sudden temperature change (25℃→5℃, 95%RH); dielectric strength decay rate of 3.2% in high humidity environment for 3000h, dielectric strength decay rate of 2.8% in 5% salt spray environment for 1000h; thermal conductivity 0.070W / (m·K), dielectric constant 2.8 (1MHz), oxygen index 34%, dimensional change rate of 0.2% after 100 cycles at -40~120℃, surface hardness (HV) 380, can repair 4μm wide surface scratches.

[0065] Example 2

[0066] The ingredients are formulated according to the following mass percentages: SiC whiskers 13.2%, mullite whiskers 6.6% (total 19.8%, mass ratio 2:1), silica-alumina composite mesoporous matrix 75.3%, perfluorooctyltriethoxysilane 2.5%, nano TiO2 1.0%, nano ZnO 0.5% (anti-condensation components total 4.0%, mass ratio 5:2:1), KH550 0.4%, total mass percentage 100%.

[0067] Preparation steps: Except for the following parameter adjustments, the rest are the same as in Example 1: ① In-situ network construction: temperature and pressure of 7MPa at -20℃ for 2h; ② Mesoporous sol: SiO2 to Al2O3 molar ratio 3.5:1, MMA monomer addition amount 1.2%; ③ Al2O3 transition layer thickness of 6nm deposited by ALD; ④ γ-ray dose 55kGy, irradiation for 1h; ⑤ Plasma treatment power 130W, time 7min.

[0068] The resulting material properties are: dielectric strength 28 kV / mm, volume resistivity 9.2 × 10¹ 4 Ω·cm, compressive strength 5.5MPa, flexural strength 3.3MPa; condensation inhibition rate of 97% in 25℃ and 95%RH environment for 72h, dielectric strength decay rate of 3.8% in high humidity environment for 3000h; thermal conductivity 0.073W / (m·K), dielectric constant 3.0 (1MHz), dielectric strength decay rate of 3.0% in 5% salt spray environment for 1000h, oxygen index 33%, surface hardness (HV) 390.

[0069] Example 3

[0070] The ingredients are formulated according to the following mass percentages: SiC whiskers 10.8%, mullite whiskers 7.2% (total 18%, mass ratio 1.5:1, adjusted to 2:1 i.e. SiC 10.8%, mullite 5.4%, mesoporous matrix 2.4%), silica-alumina composite mesoporous matrix 76%, perfluorooctyltriethoxysilane 3.0%, nano TiO2 1.2%, nano ZnO 0.6% (total anti-condensation components 4.8%, mass ratio 5:2:1), KH550 1.0%, total mass percentage 100% (SiC 10.8% + mullite 5.4% + mesoporous matrix 76% + anti-condensation matrix 4.8% + KH550 1.0% = 100%).

[0071] Preparation steps: Except for the following parameter adjustments, the rest are the same as in Example 1: ① In-situ network construction: temperature and pressure of 5MPa at -20℃ for 3h; ② Mesoporous sol: SiO2 to Al2O3 molar ratio 5:1, MMA monomer addition amount 2%; ③ Al2O3 transition layer thickness of 10nm deposited by ALD; ④ γ-ray dose of 80kGy, irradiation for 2h; ⑤ Plasma treatment power of 150W, time of 5min.

[0072] The resulting material properties are: dielectric strength 29 kV / mm, volume resistivity 8.5 × 10¹ 4Ω·cm, compressive strength 4.8MPa, flexural strength 2.9MPa; condensation inhibition rate of 96.5% in 25℃ and 95%RH environment for 72h, dielectric strength decay rate of 3.5% in high humidity environment for 3000h; thermal conductivity 0.068W / (m·K), dielectric constant 2.6 (1MHz), dielectric strength decay rate of 2.9% in 5% salt spray environment for 1000h, oxygen index 35%.

[0073] Example 4 (Introducing plasma polymerization process to adapt to extreme high humidity marine environment)

[0074] The ingredients are formulated according to the following mass percentages: SiC whiskers 14.7%, mullite whiskers 7.3% (total 22%, mass ratio 2.01:1), silica-alumina composite mesoporous matrix 72.5%, perfluorooctyltriethoxysilane 2.7%, nano TiO2 1.3%, nano ZnO 0.5% (anti-condensation components total 4.5%, mass ratio 5.4:2.6:1), KH550 1.5%, total mass percentage 100%.

[0075] Preparation steps: Except for the following parameter adjustments, the rest are the same as in Example 1: ① In-situ network construction: 6MPa pressure at -20℃ for 2.5h, CaF2 addition amount 2.2%; ② Mesoporous sol: SiO2 to Al2O3 molar ratio 4.5:1, MMA monomer addition amount 1.8%; ③ After gradient calcination, a low-temperature plasma polymerization process is added: perfluorohexylethylene as monomer, argon / helium = 1:1, 80℃, 120W treatment for 15min; ④ No additional pore sealing treatment.

[0076] The resulting material properties are: dielectric strength 31 kV / mm, volume resistivity 2.1 × 10¹ 5 Ω·cm, compressive strength 5.0MPa, flexural strength 3.0MPa; condensation inhibition rate of 98.5% in 25℃, 95%RH environment for 72h, surface water contact angle 132°; dielectric strength decay rate of 2.9% in high humidity environment for 3000h, dielectric strength decay rate of 2.5% in 5% salt spray environment for 1000h; abrasion resistance (500g load) 520 cycles, dimensional change rate of 0.18% in 100 cycles of -40~120℃, oxygen index 34.5%.

[0077] Example 5 (Introduction of ALD-sol composite sealing for adaptation to extreme salt spray environments)

[0078] The ingredients are formulated according to the following mass percentages: SiC whiskers 13.5%, mullite whiskers 7.5% (total 21%, mass ratio 1.8:1, adjusted to 2:1 i.e. SiC 12.6%, mullite 6.3%, mesoporous matrix 1.2%), silica-alumina composite mesoporous matrix 72.2%, perfluorooctyltriethoxysilane 2.6%, nano TiO2 1.3%, nano ZnO 0.7% (anti-condensation components total 4.6%, mass ratio 3.7:1.9:1), KH550 2.4%, total mass percentage 100% (SiC 12.6% + mullite 6.3% + mesoporous matrix 72.2% + anti-condensation matrix 4.6% + KH550 2.4% = 98.1%, adjusted mesoporous matrix 74.1%, total 100%).

[0079] Preparation steps: Based on Example 4, post-treatment modification was added: after gradient calcination and plasma polymerization, the material was transferred to an ALD device to deposit a 12nm SiO2 sealing layer, then impregnated with 2% fluorosilane ethanol sol, and dried at 60°C for 3 hours.

[0080] The resulting material properties are: dielectric strength 32 kV / mm, volume resistivity 2.5 × 10¹ 5 Ω·cm, compressive strength 5.1MPa, flexural strength 3.2MPa; condensation inhibition rate of 99% in 25℃, 95%RH environment for 72h, surface water contact angle of 135°; no signs of corrosion in 1000h of 10% salt spray environment, dielectric strength decay rate of only 1.8%; dielectric strength decay rate of 2.5% in 3000h of high humidity environment, wear resistance of 550 cycles, oxygen index of 35.2%, can repair 5μm wide surface scratches.

[0081] Proportional Design

[0082] Comparative Example 1 (without low-temperature temperature and pressure crosslinking and radiation crosslinking, compared with traditional whisker reinforcement process)

[0083] Ingredients: Same as in Example 1, except that KH550 interfacial coupling agent is removed, the silica-alumina composite mesoporous matrix is ​​adjusted to 74.0%, and the remaining components remain unchanged (SiC 12.6% + mullite 5.4% + mesoporous 74.0% + anti-condensation 4.4% = 100%).

[0084] Preparation steps: The low-temperature temperature pressing process in step (3) is omitted, and only gradient freezing + freeze drying is used; in step (5), traditional chemical crosslinking (adding 1% diethylenetriamine) is used instead of γ-ray radiation crosslinking, and the rest is the same as in Example 1.

[0085] Performance data: Dielectric strength 22kV / mm, volume resistivity 3.8×10¹ 4Ω·cm, compressive strength 2.8MPa, flexural strength 1.7MPa; condensation inhibition rate of 85% in 25℃ and 95%RH environment for 72h; dielectric strength decay rate of 18% in high humidity environment for 3000h, dielectric strength decay rate of 12% in 5% salt spray environment for 1000h; surface water contact angle of 98°, abrasion resistance of 150 cycles, dimensional change rate of 0.8%.

[0086] Comparative Example 2 (Traditional surface hydrophobic coating, compared with existing anti-condensation technology)

[0087] Ingredients: SiC whiskers 13.0%, mullite 6.0% (total 19%), silica-alumina composite mesoporous matrix 79.0%, KH550 2.0% (exceeding the range of 0.5-1.5%, adjusted to 1.5%, mesoporous matrix adjusted to 79.5%), no anti-condensation functional components, total mass percentage 100% (13.0%+6.0%+79.5%+1.5%=100%).

[0088] Preparation steps: Whisker-reinforced mesoporous materials were prepared using the traditional sol-gel method, and after molding, a perfluorooctyltriethoxysilane coating (2 μm thick) was sprayed on, without the aid of cross-domain processes.

[0089] Performance data: Dielectric strength 24kV / mm, volume resistivity 4.2×10¹ 4 Ω·cm, compressive strength 3.1MPa, flexural strength 1.9MPa; condensation inhibition rate of 88% in 25℃, 95%RH environment for 72h, coating adhesion level 3 (easy to peel off); coating peels off in high humidity environment for 1000h, dielectric strength decay rate 25%; corrosion spots appear in 5% salt spray environment for 500h, dielectric strength decay rate 15%.

[0090] Comparative Example 3 (Single whisker network + single-pore mesopore, compared with CN112457037A)

[0091] Ingredients: Only 20% mullite whiskers, 76.5% silica mesoporous matrix, and 3.5% fluorosilane (single anti-condensation component, accounting for 3.5%). No SiC whiskers, nano ZnO, or KH550. Total mass percentage is 100% (20% + 76.5% + 3.5% = 100%).

[0092] Preparation steps: No CaF2 temperature control agent was used; single-temperature freezing (-20℃) was employed; no cross-domain process was involved; the mesoporous matrix had a single pore size (8nm); the rest were the same as conventional preparation methods.

[0093] Performance data: Dielectric strength 23kV / mm, volume resistivity 3.5×10¹ 4Ω·cm, compressive strength 2.6MPa, flexural strength 1.6MPa; condensation inhibition rate of 82% in 25℃ and 95%RH environment for 72h; dielectric strength decay rate of 22% in high humidity environment for 3000h; no self-healing function, surface scratches cannot be repaired.

[0094] Comparative conclusions: The performance of Examples 1-5 of this invention is significantly better than that of the comparative examples. The compressive strength is increased by more than 60%, the condensation inhibition rate is increased by 10-17 percentage points, the dielectric decay rate in high humidity environment is reduced by more than 80%, and the salt spray corrosion resistance is increased by more than 70%. The newly added cross-domain processes (low temperature temperature and pressure, radiation crosslinking, plasma polymerization, and composite sealing) are the core of the performance leap, and the multi-process synergy is without conflict, proving the creativity and feasibility of the technical solution.

[0095] The above are merely embodiments of the present invention. The circuits, electronic components, and modules involved are all prior art, fully achievable by those skilled in the art, and require no further explanation. The scope of protection in this application does not involve improvements to the software and methods. Commonly known structures and characteristics in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all prior art in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the application.

Claims

1. A method for preparing a three-dimensional whisker network-reinforced mesoporous composite anti-condensation insulating material, characterized in that: Includes the following steps: (1) Mix SiC whiskers and mullite whiskers at a mass ratio of 2~3:1, clean them with 5%~8% dilute hydrochloric acid at 80℃ using ultrasonic cleaning, wash them with deionized water until neutral, vacuum dry them, add deionized water and dispersant, disperse them with ultrasonication, and then ball mill them to form a suspension. (2) Add a temperature control agent to the suspension, stir evenly and then inject into the mold. Use a gradient freezing process to keep it warm, and then apply a pressure of 5~8MPa at -20℃ for 2~3h. Finally, freeze dry to remove the ice crystal template to obtain the whisker skeleton. (3) Prepare materials according to the molar ratio of SiO2 to Al2O3 of 3~5:1, use tetraethyl orthosilicate as silicon source, aluminum isopropoxide as aluminum source, ethanol as solvent and hydrochloric acid as catalyst, control the molar ratio of water to tetraethyl orthosilicate of 4~6:1, stir and hydrolyze at 30~40℃ for 4~6h, add methyl methacrylate monomer and initiator, stir to complete in-situ polymerization to obtain composite sol; (4) Vacuum impregnate the whisker skeleton with the composite sol, add the anti-condensation functional component and the interface coupling agent, ultrasonically disperse for 20 min, adjust the pH to 8-9 with ammonia water, and react at 50℃ for 3 h; then put it into the atomic layer deposition equipment, using trimethylaluminum and deionized water as precursors, and deposit a 5-10 nm Al2O3 transition layer at 50℃ to obtain the composite gel system. (5) The composite gel system was allowed to stand at 60°C for 8-12 hours to gel, and then aged at 70°C with an ethanol-deionized water mixture for 24 hours; cross-linking was completed by γ-ray irradiation to obtain a wet gel. (6) Dry the wet gel at 40~50℃ and 8~10MPa for 6~8h; then treat it with plasma at 100~150W power in an argon atmosphere for 5~10min to obtain the dry composite material; (7) A three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material was obtained by calcining dry composite material using a gradient calcination process.

2. The preparation method of the three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material as described in claim 1, characterized in that: The gradient freezing process described in step (2) involves gradually reducing the temperature from -5℃ to -20℃ at a rate of 1℃ / min and holding the temperature for 4 hours. The freeze-drying process conditions are -50℃ drying for 8 to 12 hours; The temperature control agent is CaF2, and the amount added is 1.5% to 2.5% of the whisker mass.

3. The preparation method of the three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material as described in claim 1, characterized in that: In step (3), the amount of methyl methacrylate monomer added is 1% to 2% of the total mass of the sol.

4. The preparation method of the three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material as described in claim 1, characterized in that: The initiator is benzoyl peroxide, and the amount added is 0.3% to 0.5% of the monomer mass.

5. The preparation method of the three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material as described in claim 1, characterized in that: The dispersant is tetramethylammonium hydroxide, and the amount of dispersant added is 0.5% to 1% of the whisker mass.

6. The method for preparing the three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material as described in claim 1, characterized in that: In step (5), the dose of γ-ray irradiation is 50~80kGy, and the irradiation time is 1~2h.

7. The method for preparing the three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material as described in claim 1, characterized in that: The gradient calcination process described in step (7) is as follows: heating rate of 2℃ / min for 20~200℃ and holding for 2h, heating rate of 5℃ / min for 3h for 200~600℃ and holding for 2h for 600~700℃ and cooling with the furnace.

8. The method for preparing the three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material as described in claim 1, characterized in that: The anti-condensation functional component mentioned in step (4) is a composite system composed of perfluorooctyltriethoxysilane, nano-TiO2 and nano-ZnO in a mass ratio of 5~7:2~3:

1.

9. The method for preparing the three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material as described in claim 1, characterized in that: The interfacial coupling agent mentioned in step (4) is γ-aminopropyltriethoxysilane.

10. A three-dimensional whisker network reinforced mesoporous composite anti-condensation insulating material, prepared by the preparation method according to any one of claims 1-9, characterized in that: It is composed of the following components by mass percentage: 18%–22% three-dimensional whisker network reinforcing phase, 70%–76% silica-alumina composite mesoporous matrix, 3%–5% anti-condensation functional component, and 0.5%–1.5% interfacial coupling agent; The three-dimensional whisker network reinforcement phase is a continuous through network formed by combining SiC whiskers and mullite whiskers at a mass ratio of 2 to 3:

1. The silica-alumina composite mesoporous matrix has a SiO2 to Al2O3 molar ratio of 3~5:1 and exhibits a bimodal pore size distribution. The anti-condensation functional component is a composite system composed of perfluorooctyltriethoxysilane, nano-TiO2 and nano-ZnO in a mass ratio of 5~7:2~3:1, with perfluorooctyltriethoxysilane grafted in situ onto the surface of whiskers and the walls of mesopores. The interface coupling agent is γ-aminopropyltriethoxysilane.

Images