Organic wave-transparent composite material for improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal and preparation method of organic wave-transparent composite material

Abstract

The invention relates to an organic wave-transparent composite material for improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal and a preparation method thereof.The organic wave-transparent composite material is prepared by selecting polymethyl ethoxy siloxane (PMES) as a precursor, trifunctional rigid silane as a cross-linking agent, polymethyl ethoxy siloxane (PMES), trifunctional rigid silane, a solvent ethanol and a catalyst through a hydrothermal method. The preparation method comprises the following steps: preparing an organic silicon resin solution by mixing, and adding ceric nitrate into the resin solution; an organic silicon resin solution is compounded with a quartz fiber preform through an RTM (Resin Transfer Molding) process, and the organic wave-transparent composite material with good dielectric properties is obtained through dipping, curing and drying. Compared with the prior art, the composite material has the function of stable dielectric property at high temperature, and can be applied to missile radar radome materials.

Description

Technical Field

[0001] The present invention relates to the technical field of organic wave-transmitting materials, and in particular to an organic wave-transmitting composite material capable of improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal, and a preparation method thereof. Background Art

[0002] In the field of aerospace technology, the radome is a critical component, and its material properties have a decisive impact on the overall effectiveness of the system. Organic wave-transmitting composite materials have gained widespread recognition and adoption in practical applications due to their relatively mature preparation processes, low cost control, and short production cycles. However, when aircraft perform high-Mach number missions, the shortcomings of conventional resin-based composites become apparent. Under high temperatures, the organic groups within the resin matrix are prone to chemical decomposition, producing free carbon or carbon compounds. These decomposition products significantly alter the material's electromagnetic properties, causing fluctuations in key parameters such as the dielectric constant and loss tangent, which in turn affects the transmission quality and accuracy of radar signals. Therefore, in-depth research and development of organic wave-transmitting composite materials that can maintain stable dielectric properties under high-temperature conditions has become a top priority in this field. This not only affects the reliability and survivability of aerospace systems but also has significant implications for the development of future hypersonic vehicles.

[0003] Patent CN 118931205A discloses a nanoporous silicone resin-based composite material that integrates thermal insulation and wave transmission, as well as its preparation method and application. The composite material comprises a matrix and a reinforcement phase, wherein the matrix comprises nanoporous silicone resin and the reinforcement phase comprises a fiber preform. The raw materials for the nanoporous silicone resin include polysiloxane, silane monomer / silane prepolymer, and an alkaline catalyst. The nanoporous silicone resin imparts excellent ablation resistance, thermal insulation, and low dielectric properties to the composite material. At high temperatures, the composite material undergoes an in-situ ceramicization reaction at the molecular scale, effectively hindering the formation of continuous carbon pathways. This results in a wave transmittance exceeding 90% in the 2-18 GHz band from room temperature to 1200°C, making it suitable for use as a high-temperature thermal insulation and wave transmission integrated material in applications such as aircraft radomes and antenna windows. However, its dielectric constant and dielectric loss still fall short of the requirements for high-performance radome materials. Summary of the Invention

[0004] The purpose of the present invention is to provide an organic wave-transmitting composite material and a preparation method thereof that improves high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal, and has the characteristics of stable dielectric properties at high temperatures.

[0005] The object of the present invention can be achieved by the following technical solution: A method for preparing an organic wave-transmitting composite material based on high-temperature oxygen release and carbon removal to improve high-temperature dielectric loss stability, comprising the following steps:

[0006] S1: Selecting polymethylethoxysiloxane (PMES) as a precursor and trifunctional rigid silane as a crosslinking agent, polymethylethoxysiloxane (PMES), trifunctional rigid silane, a solvent, and a catalyst are mixed to prepare a silicone resin solution, and cerium nitrate salt is added to the silicone resin solution;

[0007] S2: Compounding the silicone resin solution with the quartz fiber preform through an RTM impregnation process;

[0008] S3: performing a stepwise temperature curing treatment on the composite material after the RTM impregnation process, and then performing ultrasonic drying at normal pressure to obtain the organic wave-transmitting composite material.

[0009] The invention obtains an organic wave-transmitting composite material with good dielectric properties through impregnation-curing-drying.

[0010] Preferably, the polymethylethoxysiloxane in step S1 is polymethylethoxysiloxane obtained by graft copolymerization of siloxane.

[0011] In this invention, polymethylethoxysiloxane (PMES), derived from grafted polysiloxane, is used as a precursor. Its backbone structure is a silicon-oxygen (Si-O) bond, resulting in a lower dielectric constant in the material, helping to improve wave transmission performance. The hydrophobic groups introduced by the grafted polysiloxane reduce the hydroxyl content on the surface and within the material, thereby lowering dielectric loss. The use of trifunctional rigid silane-crosslinked polymethylethoxysiloxane reduces residual methyl groups and lowers the carbon content of the composite material. Its high degree of crosslinking reduces polar groups, lowering polarization and dielectric loss, effectively improving wave transmission performance.

[0012] The cerium nitrate salt added to the resin solution decomposes into cerium oxide at high temperature, thereby releasing oxygen and combining with the free carbon / carbon compounds produced by the decomposition of organic groups to generate CO2 gas, thereby reducing the free carbon / carbon compound content of the composite material during high-temperature service, which is beneficial to maintaining the dielectric properties of the material; in addition, compared with directly adding cerium oxide, the cerium nitrate salt is more soluble in organic solutions; and the cerium nitrate salt added to the resin solution decomposes into cerium oxide at high temperature and is distributed in the composite material as nanoparticles. Compared with directly added cerium oxide particles, it has a larger specific surface area and is more conducive to the in-situ oxygen release function and the removal of free carbon / carbon compound combinations.

[0013] Preferably, the polymethylethoxysiloxane in step S1 has the following structural formula:

[0014] -O-Si(CH3)2-O-Si(CH3)(OCH2CH3)-O-Si(CH3)2-O-

[0015] The degree of polymerization is 5-200.

[0016] Preferably, in step S1, cerium nitrate with a mass fraction of 2 to 10% is added to the silicone resin solution.

[0017] Preferably, the mass ratio of the polymethylethoxysiloxane (PMES), trifunctional rigid silane, solvent and catalyst in step S1 is 1:(0.3-0.5):(1-3):(0.02-0.5).

[0018] Preferably, the trifunctional rigid silane is phenyltrimethoxysilane, phenyltriethoxysilane, or vinyltrimethoxysilane.

[0019] Preferably, the solvent in step S1 is ethanol.

[0020] Preferably, the catalyst in step S1 is sodium hydroxide or tetramethylammonium hydroxide.

[0021] Preferably, the mass ratio of the silicone resin solution to the quartz fiber preform in step S2 is (3-5):1.

[0022] Preferably, the RTM impregnation process in step S2 includes: clamping the quartz fiber preform in a mold, evacuating the pressure to 0.01 MPa-0.05 MPa, and sucking the silicone resin solution into the mold by vacuum impregnation to fully impregnate the quartz fiber preform.

[0023] Further preferably, in step S3, the mold after the RTM impregnation process is placed in an oven for step temperature curing treatment, and then the cured composite material is taken out of the mold for ultrasonic drying at normal pressure to obtain the organic wave-transmitting composite material with good dielectric properties.

[0024] Preferably, the stepwise temperature-varying curing process in step S3 includes:

[0025] The heating rate during the curing process is set to be no less than 1°C / min, and the maximum curing temperature is set to be no more than 120°C.

[0026] More preferably, the initial heating rate is set at 3-5°C / min, the temperature is raised to 60-80°C and kept warm for 2-3 hours, and the final heating rate is set at 1-2°C / min, the temperature is raised to 90-110°C and kept warm for 4-5 hours.

[0027] Preferably, the ultrasonic normal pressure drying process in step S3 includes:

[0028] First, keep the temperature at 10-40°C for 120-180 hours, and then keep the temperature at 80-100°C for 10-20 hours.

[0029] Preferably, the ultrasonic power of the normal pressure ultrasonic drying process in step S3 is 40 to 60 kHz.

[0030] An organic wave-transmitting composite material capable of improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal is prepared by the above-mentioned preparation method.

[0031] An application of the organic wave-transmitting composite material is to use the organic wave-transmitting composite material in a radar antenna cover.

[0032] Preferably, the organic wave-transparent composite material is used for aerospace radar radomes and missile radar radomes.

[0033] The resin-based composite material prepared by the present invention can still maintain stable dielectric properties under high temperature conditions and can be applied to aerospace vehicle radar antenna covers and missile radar antenna covers.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The cerium nitrate salt added to the resin solution of the present invention decomposes into cerium oxide at high temperature, thereby releasing oxygen and combining with the free carbon / carbon compound produced by the decomposition of organic groups to generate CO2 gas, thereby reducing the free carbon / carbon compound content of the composite material during high-temperature service, which is beneficial to maintaining the dielectric properties of the material. In addition, compared with directly adding cerium oxide, the cerium nitrate salt is more soluble in organic solutions. Moreover, the cerium nitrate salt added to the resin solution decomposes into cerium oxide at high temperature and is distributed in the composite material as nanoparticles. Compared with directly added cerium oxide particles, it has a larger specific surface area and is more conducive to the in-situ oxygen release function and the removal of free carbon / carbon compound combinations.

[0036] 2. This invention uses polymethylethoxysiloxane (PMES), derived from grafted polysiloxane, as a precursor. Its main chain structure is a silicon-oxygen (Si-O) bond, resulting in a lower dielectric constant in the material, which helps improve wave transmission performance. The hydrophobic groups introduced by the grafted polysiloxane reduce the hydroxyl content on the surface and within the material, thereby lowering dielectric loss. The use of trifunctional rigid silane-crosslinked polymethylethoxysiloxane reduces residual methyl groups and lowers the carbon content of the composite material. Its high degree of crosslinking reduces polar groups, lowering polarization and dielectric loss, effectively improving wave transmission performance.

[0037] 3. The present invention optimizes the uniformity and density of the resin cross-linked network, reduces internal stress and pore defects, and effectively eliminates residual polar small molecules (such as moisture and solvents) through step-by-step temperature curing treatment, significantly reducing the imaginary part of the dielectric constant (loss factor) and inhibiting dipole relaxation loss at high frequencies; through ultrasonic normal pressure drying treatment, the cavitation effect can be used to accelerate solvent volatilization, reduce microcracks and pores caused by thermal stress, promote orderly arrangement of resin molecular chains, reduce residual solvent and interface polarization, thereby reducing dielectric loss and improving material homogeneity, especially making the dielectric constant more stable at high frequencies.

[0038] 4. The present invention uses ethanol as a solvent and sodium hydroxide or tetramethylammonium hydroxide as a catalyst, which can effectively promote the condensation of silanols to form a uniform and dense Si-O-Si cross-linked network, reduce residual polar groups (such as Si-OH) and solvent micropores, significantly reduce the dielectric constant and loss, and avoid the interference of acidic byproducts on the transmission characteristics, thereby achieving better electromagnetic wave transmittance and signal fidelity at high frequencies.

[0039] 5. The dielectric constant of the present invention is less than 2.2 and the dielectric loss is less than 0.025 at 1000°C, which can meet the requirements of high-level antenna cover materials. DETAILED DESCRIPTION

[0040] The embodiments of the present invention are described in detail below. The following embodiments are implemented based on the technical solutions of the present invention, and provide detailed implementation methods and specific operating processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0041] An organic wave-transmitting composite material that improves high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal, and its preparation method. Polymethylethoxysiloxane (PMES) is selected as a precursor, trifunctional rigid silane is selected as a crosslinker, and polymethylethoxysiloxane (PMES), trifunctional rigid silane, solvent ethanol, and a catalyst are mixed to prepare an organic silicone resin solution. Cerium nitrate salt is added to the resin solution; the organic silicone resin solution is compounded with a quartz fiber preform through an RTM process, and an organic wave-transmitting composite material with excellent dielectric properties is obtained through impregnation-curing-drying. Compared with the existing technology, the composite material of the present invention has the function of stable dielectric properties at high temperatures and can be used as a missile radar antenna cover material.

[0042] The following describes the details in conjunction with specific embodiments.

[0043] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0044] In the following examples and comparative examples, polymethylethoxysiloxane has the following structural formula:

[0045] -O-Si(CH3)2-O-Si(CH3)(OCH2CH3)-O-Si(CH3)2-O-

[0046] The degree of polymerization is 100.

[0047] Example 1

[0048] Step 1: Select polymethylethoxysiloxane (PMES) as a precursor and phenyltrimethoxysilane as a crosslinker, and prepare a silicone resin solution by mixing polymethylethoxysiloxane (PMES), trifunctional rigid silane, solvent ethanol, and tetramethylammonium hydroxide in a mass ratio of 1:0.3:2:0.02.

[0049] Step 2: Set the mass fraction of cerium nitrate to 2%.

[0050] Step 3: The quartz fiber preform is clamped in a mold, and the vacuum is drawn to 0.01 MPa. The organic silicone resin solution is absorbed into the mold by vacuum impregnation to fully impregnate the quartz fiber preform.

[0051] Step 4: Place the mold after the RTM impregnation process in an oven for step-by-step temperature curing treatment; set the initial heating rate to 3°C / min, heat to 60°C and keep warm for 2 hours, and the final heating rate to 1°C / min, heat to 90°C and keep warm for 4 hours.

[0052] Step 5: The cured composite material is taken out of the mold and dried at 40 kHz ultrasonically at normal pressure to obtain an organic wave-transmitting composite material with good dielectric properties.

[0053] Example 2

[0054] Step 1: Select polymethylethoxysiloxane (PMES) as a precursor and phenyltrimethoxysilane as a crosslinker, and prepare a silicone resin solution by mixing polymethylethoxysiloxane (PMES), trifunctional rigid silane, solvent ethanol, and tetramethylammonium hydroxide in a mass ratio of 1:0.3:2:0.02.

[0055] Step 2: Set the mass fraction of cerium nitrate to 6%.

[0056] Step 3: The quartz fiber preform is clamped in a mold, and the vacuum is drawn to 0.03 MPa. The organic silicone resin solution is absorbed into the mold by vacuum impregnation to fully impregnate the quartz fiber preform.

[0057] Step 4: Place the mold after the RTM impregnation process in an oven for step-by-step temperature curing treatment; set the initial heating rate to 4°C / min, heat to 70°C and keep warm for 3 hours, and the final heating rate to 2°C / min, heat to 100°C and keep warm for 5 hours.

[0058] Step 5: The cured composite material is taken out of the mold and dried at 50 kHz ultrasonically at normal pressure to obtain an organic wave-transmitting composite material with good dielectric properties.

[0059] Example 3

[0060] Step 1: Select polymethylethoxysiloxane (PMES) as a precursor and phenyltrimethoxysilane as a crosslinker, and prepare a silicone resin solution by mixing polymethylethoxysiloxane (PMES), trifunctional rigid silane, solvent ethanol, and tetramethylammonium hydroxide in a mass ratio of 1:0.3:2:0.02.

[0061] Step 2: Set the mass fraction of cerium nitrate to 10%.

[0062] Step 3: Clamp the quartz fiber preform in a mold, evacuate to 0.05 MPa, and absorb the silicone resin solution into the mold through vacuum impregnation to fully impregnate the quartz fiber preform.

[0063] Step 4: Place the mold after the RTM impregnation process in an oven for step-by-step temperature curing treatment; set the initial heating rate to 5°C / min, heat to 80°C and keep warm for 3 hours, and the final heating rate to 2°C / min, heat to 110°C and keep warm for 5 hours.

[0064] Step 5: The cured composite material is taken out of the mold and ultrasonically dried at 60 kHz under normal pressure to obtain an organic wave-transmitting composite material with good dielectric properties.

[0065] Comparative Example 1

[0066] Step 1: Select polymethylethoxysiloxane (PMES) as a precursor and phenyltrimethoxysilane as a crosslinker, and prepare a silicone resin solution by mixing polymethylethoxysiloxane (PMES), trifunctional rigid silane, solvent ethanol, and tetramethylammonium hydroxide in a mass ratio of 1:0.3:2:0.02.

[0067] Step 2: The quartz fiber preform is clamped in a mold, vacuumed to 0.01 MPa, and the silicone resin solution is absorbed into the mold by vacuum impregnation to fully impregnate the quartz fiber preform.

[0068] Step 3: Place the mold after the RTM impregnation process in an oven for step-by-step temperature curing treatment; set the initial heating rate to 3°C / min, heat to 60°C and keep warm for 2 hours, and the final heating rate to 1°C / min, heat to 90°C and keep warm for 4 hours.

[0069] Step 4: The cured composite material is taken out of the mold and dried at 40 kHz ultrasonically at normal pressure to obtain an organic wave-transmitting composite material with good dielectric properties.

[0070] Comparative Example 2

[0071] Step 1: Select polymethylethoxysiloxane (PMES) as a precursor and phenyltrimethoxysilane as a crosslinker, and prepare a silicone resin solution by mixing polymethylethoxysiloxane (PMES), trifunctional rigid silane, solvent ethanol, and tetramethylammonium hydroxide in a mass ratio of 1:0.3:2:0.02.

[0072] Step 2: Set the mass fraction of potassium nitrate to 6%.

[0073] Step 3: The quartz fiber preform is clamped in a mold, and the vacuum is drawn to 0.03 MPa. The organic silicone resin solution is absorbed into the mold by vacuum impregnation to fully impregnate the quartz fiber preform.

[0074] Step 4: Place the mold after the RTM impregnation process in an oven for step-by-step temperature curing treatment; set the initial heating rate to 4°C / min, heat to 70°C and keep warm for 3 hours, and the final heating rate to 2°C / min, heat to 100°C and keep warm for 5 hours.

[0075] Step 5: The cured composite material is taken out of the mold and dried at 50 kHz ultrasonically at normal pressure to obtain an organic wave-transmitting composite material with good dielectric properties.

[0076] Table 1 summarizes the properties of the organic wave-transmitting composite materials obtained in Examples 1 to 3 and the resin-based composite materials obtained in Comparative Examples 1 to 2 after carbonization at 1000°C. The dielectric constant was tested according to GBT 32361-2015, and the wave transmittance was tested according to GJB 7954-2012.

[0077] Table 1

[0078]

[0079] By comparing Examples 1, 2, and 3, it can be found that when the temperature reaches above the decomposition temperature of cerium nitrate (500° C.), as the content of cerium nitrate increases, the dielectric properties and wave transmittance of the material are significantly improved.

[0080] By comparing Example 1 and Comparative Example 1, it can be found that in the organic wave-transmitting material, the silicone resin solution with cerium nitrate added as a precursor has greatly improved ability to maintain stable dielectric properties at high temperatures compared to the resin solution without cerium nitrate added.

[0081] By comparing Example 2 and Example 3, it can be found that in the organic wave-transmitting material, the composite material prepared by using a silicone resin solution with cerium nitrate added as a precursor has improved ability to maintain stable dielectric properties at high temperatures compared to the composite material prepared by using a resin solution with a small amount of cerium nitrate added.

[0082] By comparing Example 2 and Comparative Example 2, it can be found that among the organic wave-transmitting materials, the composite material prepared using the organic silicone resin solution with the addition of cerium nitrate as a precursor has better dielectric properties and higher wave transmittance than the composite material prepared using the organic silicone resin solution with the addition of potassium nitrate as a precursor.

[0083] The composite material obtained by the present invention has the function of maintaining stable dielectric properties at high temperatures (about 1000°C) and has broad application prospects in aerospace radar antenna covers.

[0084] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing an organic wave-transmitting composite material based on high-temperature oxygen release and carbon removal to improve high-temperature dielectric loss stability, characterized in that: The following steps are involved: S1: Selecting polymethylethoxysiloxane as a precursor and trifunctional rigid silane as a crosslinking agent, the polymethylethoxysiloxane, trifunctional rigid silane, a solvent, and a catalyst are mixed to prepare a silicone resin solution, and cerium nitrate salt is added to the silicone resin solution; S2: Compounding the silicone resin solution with the quartz fiber preform through an RTM impregnation process; S3: performing a stepwise temperature curing treatment on the composite material after the RTM impregnation process, and then performing ultrasonic drying at normal pressure to obtain the organic wave-transmitting composite material.

2. The method for preparing an organic wave-transmitting composite material for improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal according to claim 1, characterized in that: Step S1: adding cerium nitrate salt with a mass fraction of 2 to 10% to the silicone resin solution.

3. The method for preparing an organic wave-transmitting composite material for improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal according to claim 1, characterized in that: The mass ratio of the polymethylethoxysiloxane, trifunctional rigid silane, solvent and catalyst in step S1 is 1:(0.3-0.5):(1-3):(0.02-0.5).

4. The method for preparing an organic wave-transmitting composite material for improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal according to claim 1, characterized in that: The solvent in step S1 is ethanol; The catalyst in step S1 is sodium hydroxide or tetramethylammonium hydroxide.

5. The method for preparing an organic wave-transmitting composite material for improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal according to claim 1, characterized in that: The mass ratio of the silicone resin solution to the quartz fiber preform in step S2 is (3-5):

1.

6. The method for preparing an organic wave-transmitting composite material for improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal according to claim 1, characterized in that: The RTM impregnation process in step S2 includes: closing the quartz fiber preform in a mold, evacuating the mold to 0.01 MPa-0.05 MPa, and sucking the silicone resin solution into the mold by vacuum impregnation to fully impregnate the quartz fiber preform.

7. The method for preparing an organic wave-transmitting composite material for improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal according to claim 6, characterized in that: In step S3, the mold after the RTM impregnation process is placed in an oven for step-by-step temperature curing treatment, and then the cured composite material is taken out of the mold for ultrasonic drying at normal pressure.

8. The method for preparing an organic wave-transmitting composite material for improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal according to claim 1, characterized in that: The stepwise temperature-changing curing process in step S3 includes: Set the initial heating rate to 3-5°C / min, heat to 60-80°C and keep warm for 2-3 hours, and the final heating rate to 1-2°C / min, heat to 90-110°C and keep warm for 4-5 hours.

9. The method for preparing an organic wave-transmitting composite material for improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal according to claim 1, characterized in that: The ultrasonic normal pressure drying process in step S3 includes: First, at 10-40°C for 120-180 hours, then at 80-100°C for 10-20 hours; The ultrasonic power is 40~60kHz.

10. An organic wave-transmitting composite material for improving high-temperature dielectric loss stability based on high-temperature oxygen release and carbon removal, characterized in that: The preparation method according to any one of claims 1 to 9 is used.

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