A silicone composite material for improving high-temperature wave-transmitting performance by in-situ oxygen release decarburization and a preparation method thereof

Abstract

The present application relates to a kind of by in-situ oxygen removal carbon improves high temperature wave-transparent performance of organic silicon composite material and preparation method thereof, select methyl organosilicon resin (i.e. silicon-oxygen bond (Si-O) is main chain, methyl (CH3) is side chain high molecular compound) as precursor, select toluene and ethanol according to (4-5):1 Proportion mixed as solvent, by mixing preparation resin solution, and in resin solution according to certain proportion mixed addition cerium salt with acetylacetone cerium salt;Resin solution is compounded with fiber preform by vacuum impregnation process, by impregnation-curing, obtain the organic silicon composite material with good dielectric property.Compared with prior art, the composite material of the present application has the function of stable dielectric property at high temperature, and can be applied to missile radar antenna cover material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic wave-transparent materials, in particular to an organic silicon composite material for improving high-temperature wave-transparent performance by in-situ oxygen release and carbon removal and a preparation method thereof. BACKGROUND

[0002] In the field of aerospace technology, the material performance of the radar radome is crucial to the system performance. Fiber-reinforced organic silicon resin composite materials are widely used in practical applications due to their mature preparation process, low cost, and short cycle. However, when flying at high Mach numbers, the ordinary resin-based composite materials are prone to decomposition of a large number of organic groups at high temperatures, resulting in a large number of free carbon or carbon compounds, which changes the electromagnetic properties of the material, leading to large fluctuations in the dielectric constant and loss tangent, affecting the quality and accuracy of radar signal transmission. Therefore, it is urgent to research and develop fiber-reinforced organic silicon resin composite materials with stable dielectric properties at high temperatures, which is related to the reliability and survivability of aerospace systems and is of great significance to the development of future hypersonic aircraft.

[0003] Patent CN103387748A discloses an organic-inorganic hybrid resin and a high-temperature wave-transparent composite material and a preparation method thereof. The hybrid resin has better temperature resistance, with a decomposition temperature in air and nitrogen higher than 500℃, and a resin residual weight higher than 70% after 1h oxidation at 500℃ in air. Compared with existing inorganic resins, the quartz fiber-reinforced composite material prepared from the hybrid resin has good mechanical properties, with a room temperature bending strength higher than 300MPa and a high-temperature bending strength of 150MPa at 500℃. The composite material has excellent dielectric properties in the range of 1-12GHz from room temperature to 500℃, with a dielectric constant lower than 3.25 and a dielectric loss lower than 0.012, which can meet the application requirements of high-temperature short-time aircraft such as missiles and rockets, and has a good application prospect in the field of high-temperature wave-transparent materials. However, its dielectric constant and dielectric loss still cannot meet the requirements of high-level radome materials. SUMMARY

[0004] The purpose of the present application is to provide an organic silicon composite material for improving high-temperature wave-transparent performance by in-situ oxygen release and carbon removal and a preparation method thereof, which has the characteristics of stable dielectric properties at high temperatures.

[0005] The purpose of the present application can be achieved by the following technical solution: a preparation method of an organic silicon composite material for improving high-temperature wave-transparent performance by in-situ oxygen release and carbon removal, comprising the following steps:

[0006] S1: taking a methyl organic silicon resin (a high molecular compound with a silicon-oxygen bond (Si-O) as the main chain and a methyl group (CH3) as the side chain) as the precursor, selecting a mixture of benzene solvent and ethanol as the solvent, preparing a resin solution by mixing, and adding cerium octanoate salt and cerium acetylacetone salt into the resin solution;

[0007] S2: compositing the resin solution and the fiber preform through a vacuum impregnation process;

[0008] S3: performing a step-variable temperature curing treatment on the composite material after the vacuum impregnation process, to obtain the silicone composite material.

[0009] The silicone composite material with good dielectric properties is obtained through impregnation-curing.

[0010] In the present application, the methyl silicone resin is selected as the precursor, which has a significant advantage in dielectric properties. The cross-linked network formed after curing and the ceramic structure generated by high-temperature pyrolysis have low dielectric constant (usually < 3.5) and low dielectric loss factor (stable at high frequency), which are suitable for high-frequency electronic devices and insulating materials. At the same time, during high-temperature pyrolysis, methyl escapes in the form of small molecules (such as methane), and the carbon residue is low, which avoids the generation of conductive carbon black and ensures the high insulation of the composite material.

[0011] The cerium octoate salt and the acetylacetone salt added in the resin solution can be decomposed into cerium oxide at high temperature, so as to release oxygen combined with carbon ions produced by the decomposition of organic groups, thereby generating gas, which is beneficial to maintaining the dielectric properties of the material. In addition, compared with directly adding cerium oxide, cerium octoate salt and cerium acetylacetone acetate are more easily dissolved in organic solution. The cerium octoate salt and cerium acetylacetone acetate added in the resin solution are decomposed into cerium oxide at high temperature, which is distributed in the form of nanoparticles in the composite material. Compared with directly added cerium oxide particles, it has a larger specific surface area, which is more beneficial to the in-situ oxygen release function and the removal of free carbon / carbon compounds. Compared with adding cerium octoate / acetone acetate alone, adding cerium octoate and cerium acetylacetone acetate in the resin solution can more effectively inhibit the formation of free carbon, reduce dielectric loss, and improve dielectric stability. The synergistic effect of the two optimizes the microstructure of the material, reduces defects and impurities, further improves the dielectric properties, and in a high-temperature environment, the good chemical stability of the two helps to maintain the dielectric properties of the material.

[0012] Preferably, the methyl silicone resin in step S1 has the following structural formula:

[0013] [-O-Si(CH3)2-O-Si(CH3)2-] n

[0014] n is 100-10000.

[0015] Preferably, the benzene solvent in step S1 includes toluene and xylene.

[0016] Preferably, the mass ratio of toluene to ethanol in step S1 is (4-5):1.

[0017] Preferably, step S1 adds cerium octoate salt and cerium acetylacetone salt in a total mass fraction of 2-10% in the resin solution.

[0018] Further preferably, the mass ratio of cerium octoate salt and cerium acetylacetone salt is 1:(0.5-2).

[0019] Preferably, the vacuum impregnation process of step S1 comprises:

[0020] The fiber preform is placed in the mold (vacuum container), vacuumed to 0.05-0.1 MPa, and kept in a vacuum state for a period of time to allow the resin solution to fully penetrate into the interior of the fiber preform.

[0021] Further preferably, step S3 places the mold after the vacuum impregnation process into an oven for stepwise temperature curing treatment, and then takes out the cured composite material from the mold to obtain the organic silicon composite material with good dielectric properties.

[0022] Preferably, the stepwise temperature curing treatment of step S3 comprises:

[0023] The temperature rising rate during the curing process is not less than 1°C / min, and the highest curing temperature is not more than 160°C.

[0024] Further preferably, the initial temperature rising rate is set to 3-5°C / min, the temperature is raised to 80-100°C for 2-3h, and the final temperature rising rate is 1-3°C / min, and the temperature is raised to 120-160°C for 4-5h.

[0025] Preferably, the mass ratio of the resin solution to the fiber preform is (3-5):1.

[0026] Preferably, the fiber preform is selected from quartz fiber, alumina fiber, and silicon nitride fiber.

[0027] An organic silicon composite material with improved high-temperature wave-transparent performance by in-situ oxygen release and carbon removal, prepared by the above preparation method.

[0028] An application of the above organic silicon composite material, the organic silicon composite material is used for a radar antenna cover.

[0029] Preferably, the organic silicon composite material is used for a radar antenna cover of a space vehicle and a missile.

[0030] The resin-based composite material prepared by the application can maintain stable dielectric properties under high-temperature conditions, and can be applied to a radar antenna cover of a space vehicle and a missile.

[0031] Compared with the prior art, the application has the following beneficial effects:

[0032] 1. The cerium octoate salt and acetylacetone salt added in the resin solution can decompose into cerium oxide at high temperature, thereby releasing oxygen and carbon ions produced by the decomposition of organic groups to form gas, which is beneficial to maintaining the dielectric properties of the material; in addition, compared with directly adding cerium salt, cerium octoate salt and cerium acetylacetone acetate are more easily dissolved in organic solution; and the cerium octoate salt and cerium acetylacetone acetate added in the resin solution decompose into cerium oxide at high temperature, which is distributed in the form of nanoparticles in the composite material, has a larger specific surface area compared with directly added cerium oxide particles, and is more beneficial to in-situ oxygen release function and removal of free carbon / carbon compounds. Simultaneous addition of cerium acetylacetone acetate and cerium octoate in the resin solution can more effectively inhibit the formation of free carbon, reduce dielectric loss, and improve dielectric stability compared with separate addition of cerium octoate / acetylacetone cerium, the synergistic effect of the two optimizes the microstructure of the material, reduces defects and impurities, further improves the dielectric properties, and in a high temperature environment, the good chemical stability of the two helps to maintain the dielectric properties of the material, thereby reducing interface reflection loss and improving the wave transmittance of the material.

[0033] 2. The methyl organosilicon resin as a precursor has significant advantages in dielectric properties, and the crosslinked network formed after curing and the ceramic structure generated by high temperature pyrolysis have low dielectric constant (usually <3.5) and low dielectric loss factor (stable at high frequency), which are suitable for high frequency electronic devices and insulating materials; at the same time, during high temperature pyrolysis, methyl is released in the form of small molecules (such as methane), and the carbon residue is low, which avoids the generation of conductive carbon black and ensures the high insulation of the composite material.

[0034] 3. By selecting a mixture of toluene and ethanol as a solvent, the dielectric properties (reducing dielectric constant and loss), material processability (enhancing solubility, dispersibility and adjusting evaporation rate), material density (reducing surface tension to reduce interface defects) and other mechanisms can be optimized, which can effectively reduce the reflection and energy loss of electromagnetic waves in the material, while taking into account environmental friendliness (reducing benzene toxicity) and process adaptability.

[0035] 4. The dielectric constant is less than 2.4 and the dielectric loss is less than 0.027 at 1000℃, which can meet the requirements of high level radome materials. DETAILED DESCRIPTION

[0036] The embodiments of the present application are described in detail below, and the following embodiments are implemented on the premise of the technical solutions of the present application, detailed implementation methods and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0037] The application discloses a kind of through in-situ oxygen removal carbon improves high temperature wave-transparent performance of organic silicon composite material and preparation method thereof.Select methyl organosilicon resin (i.e. silicon-oxygen bond (Si-O) is main chain, methyl (CH3) is side chain high molecular compound) as precursor, select toluene and ethanol as solvent, prepare resin solution by mixing, and add cerium octanoate salt and cerium acetylacetone salt in resin solution according to certain proportion;Resin solution is compounded with fiber preform by vacuum impregnation process, and by impregnation-curing, obtain the organic silicon composite material with good dielectric property.Compared with prior art, the composite material of the application has the function of stable dielectric property at high temperature, and can be applied to missile radar antenna cover material.

[0038] The application will be described in detail below with specific examples.

[0039] Unless otherwise specified, the reagents, methods, instruments and equipment used in the application 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.

[0040] In the following examples and comparative examples, the methyl organosilicon resin has the following structural formula:

[0041] [-O-Si(CH3)2-O-Si(CH3)2-] n

[0042] n is 6000.

[0043] Example 1

[0044] Step 1: methyl organosilicon resin is used as precursor, toluene and ethanol are mixed according to the ratio of 4:1 as solvent, and resin solution is prepared by mixing;

[0045] Step 2: the mass fraction of cerium octanoate salt and cerium acetylacetone salt is set to 2%, and the mass ratio of cerium octanoate salt to cerium acetylacetone salt is 1:1.

[0046] Step 3: 2.5D quartz fiber preform is selected as reinforcing material.

[0047] Step 4: the quartz fiber preform is placed in a vacuum container, vacuumed to 0.05 MPa, and kept in vacuum state for a period of time, so that the resin fully penetrates into the interior of the quartz fiber preform.

[0048] Step 5: the mold after completing the vacuum impregnation process is placed in an oven for stepwise temperature curing treatment, and the organic silicon composite material with good dielectric property is obtained. The initial heating rate is set to 3℃ / min, the temperature is raised to 80℃ and kept for 2h, and the final heating rate is 1℃ / min, the temperature is raised to 120℃ and kept for 4h.

[0049] Example 2

[0050] Step 1: Select methyl silicone resin as the precursor, select toluene and ethanol mixed in a ratio of 5:1 as the solvent, and prepare the resin solution by mixing;

[0051] Step 2: Set the mass fraction of cerium octoate and cerium acetylacetone salt to 6%, and the mass ratio of cerium octoate to cerium acetylacetone salt to 1:0.5.

[0052] Step 3: Select orthogonal three-way quartz fiber preform as reinforcing material.

[0053] Step 4: Put the quartz fiber preform into the vacuum container, vacuum to 0.1 MPa, and keep the vacuum state for a period of time, so that the resin fully penetrates into the interior of the quartz fiber preform.

[0054] Step 5: Put the mold after completing the vacuum impregnation process into the oven for stepwise temperature curing treatment to obtain an organic silicon composite material with good dielectric properties. Set the initial heating rate to 3℃ / min, heat to 90℃ for 2h, and finally heat at a rate of 3℃ / min, heat to 140℃ for 4h.

[0055] Example 3

[0056] Step 1: Select methyl silicone resin as the precursor, select toluene and ethanol mixed in a ratio of 4:1 as the solvent, and prepare the resin solution by mixing;

[0057] Step 2: Set the mass fraction of cerium octoate and cerium acetylacetone salt to 10%, and the mass ratio of cerium octoate to cerium acetylacetone salt to 1:2.

[0058] Step 3: Select alumina fiber preform as reinforcing material.

[0059] Step 4: Put the quartz fiber preform into the vacuum container, vacuum to 0.05 MPa, and keep the vacuum state for a period of time, so that the resin fully penetrates into the interior of the quartz fiber preform.

[0060] Step 5: Put the mold after completing the vacuum impregnation process into the oven for stepwise temperature curing treatment to obtain an organic silicon composite material with good dielectric properties. Set the initial heating rate to 3℃ / min, heat to 100℃ for 2h, and finally heat at a rate of 3℃ / min, heat to 160℃ for 4h.

[0061] Comparative Example 1

[0062] Step 1: Select methyl silicone resin as the precursor, select toluene and ethanol mixed in a ratio of 4:1 as the solvent, and prepare the resin solution by mixing;

[0063] Step 2: Select 2.5D quartz fiber preform as reinforcing material.

[0064] Step 3: Put the quartz fiber preform into the vacuum container, vacuum to 0.05 MPa, and keep the vacuum state for a period of time, so that the resin fully penetrates into the interior of the quartz fiber preform.

[0065] Step 4: Put the mold after completing the vacuum impregnation process into the oven for stepwise temperature curing treatment, and obtain the organic silicon composite material with good dielectric properties. Set the initial heating rate to 3℃ / min, heat to 80℃ for 2h, and finally heat at a rate of 1℃ / min, heat to 120℃ for 4h.

[0066] Comparative Example 2

[0067] Step 1: Take methyl silicone resin as precursor, select toluene and ethanol mixed according to the proportion of 5:1 as solvent, prepare resin solution by mixing;

[0068] Step 2: Set the mass fraction of cerium octoate to 2%.

[0069] Step 3: Select orthogonal three-way quartz fiber preform as reinforcing material.

[0070] Step 4: Put the quartz fiber preform into the vacuum container, vacuum to 0.1 MPa, and keep the vacuum state for a period of time, so that the resin fully penetrates into the interior of the quartz fiber preform.

[0071] Step 5: Put the mold after completing the vacuum impregnation process into the oven for stepwise temperature curing treatment, and obtain the organic silicon composite material with good dielectric properties. Set the initial heating rate to 3℃ / min, heat to 90℃ for 2h, and finally heat at a rate of 3℃ / min, heat to 140℃ for 4h.

[0072] Comparative Example 3

[0073] Step 1: Take methyl silicone resin as precursor, select toluene and ethanol mixed according to the proportion of 4:1 as solvent, prepare resin solution by mixing;

[0074] Step 2: Set the mass fraction of cerium oxide to 10%.

[0075] Step 3: Select alumina fiber preform as reinforcing material.

[0076] Step 4: Put the quartz fiber preform into the vacuum container, vacuum to 0.05 MPa, and keep the vacuum state for a period of time, so that the resin fully penetrates into the interior of the quartz fiber preform.

[0077] Step 5: Put the mold after completing the vacuum impregnation process into the oven for step curing treatment to obtain the organic silicon composite material with good dielectric properties. Set the initial temperature rising speed to 3℃ / min, heat to 100℃ for 2h, and finally heat to 160℃ for 4h at a speed of 3℃ / min.

[0078] Table 1 is a summary of the properties of the fiber-reinforced organic silicon composite material obtained in Examples 1-3 and the resin-based composite material obtained in Comparative Examples 1-3 after carbonization at 800℃. The test method for dielectric constant is GBT 32361-2015, and the test method for wave permeability is GJB 7954-2012.

[0079] Table 1

[0080]

[0081] By comparing Examples 1, 2 and 3, it can be found that when the temperature reaches the decomposition temperature of cerium octoate and cerium acetylacetate, the dielectric properties and wave permeability of the material are obviously improved with the increase of the content of cerium acetylacetate and cerium octoate.

[0082] By comparing Example 1 and Comparative Example 1, it can be found that in the organic wave-transparent material, the function of maintaining stable dielectric properties at high temperature is greatly improved by using the organic silicon resin solution with added cerium acetylacetate and cerium octoate as the precursor, compared with the resin solution without added cerium acetylacetate and cerium octoate.

[0083] By comparing Example 2 and Comparative Example 2, it can be found that in the organic wave-transparent material, the function of maintaining stable dielectric properties at high temperature is greatly improved by using the organic silicon resin solution with added cerium acetylacetate and cerium octoate as the precursor, compared with the resin solution with only a small amount of cerium octoate.

[0084] By comparing Example 3 and Comparative Example 3, it can be found that in the organic wave-transparent material, the function of maintaining stable dielectric properties at high temperature is greatly improved by using the organic silicon resin solution with added cerium acetylacetate and cerium octoate as the precursor, compared with the resin solution with only an equal amount of cerium oxide.

[0085] The material obtained by the present application has the function of maintaining stable dielectric properties at high temperature, and has wide application prospects in aerospace radar radomes.

[0086] The foregoing description of the embodiments has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from practice of the application. As well, the description is presented in the context of the preferred embodiments as a number of alternatives. It is not intended to limit the application to the precise form described.

Claims

1. A method for preparing a silicone composite material with improved high-temperature wave-transparent performance by in-situ oxygen releasing decarburization, characterized in that, The method comprises the following steps: S1: preparing a resin solution by mixing methyl silicone resin as a precursor and a mixture of toluene and ethanol as a solvent, and adding cerium octoate and cerium acetylacetone salt into the resin solution; S2: performing vacuum impregnation process on the resin solution and a fiber preform; S3: performing step-variable temperature curing treatment on the composite material after the vacuum impregnation process to obtain the silicone composite material; In step S1, the total mass fraction of cerium octoate and cerium acetylacetone salt added into the resin solution is 2-10%; The mass ratio of cerium octoate to cerium acetylacetone salt is 1:(0.5-2).

2. The preparation method of the organic silicon composite material for improving high-temperature wave-transparent performance by in-situ oxygen releasing decarburization according to claim 1, characterized in that, The mass ratio of toluene to ethanol in step S1 is (4-5):

1.

3. The method according to claim 1, wherein The vacuum impregnation process in step S1 comprises: placing the fiber preform into a mold, vacuumizing to 0.05-0.1 MPa, and keeping the vacuum state for a period of time to make the resin solution fully penetrate into the fiber preform.

4. The preparation method of the organic silicon composite material for improving high-temperature wave-transparent performance by in-situ oxygen releasing decarburization according to claim 3, characterized in that, In step S3, the mold after the vacuum impregnation process is placed into an oven for step-variable temperature curing treatment, and then the cured composite material is taken out of the mold to obtain the silicone composite material.

5. The method according to claim 1, wherein The step-variable temperature curing treatment in step S3 comprises: setting the temperature rising rate during the curing process to be not less than 1℃ / min, and the highest curing temperature to be not more than 160℃.

6. The method according to claim 5, wherein The step-variable temperature curing treatment in step S3 comprises: setting the initial temperature rising rate to be 3-5℃ / min, rising to 80-100℃ for 2-3h, and finally setting the temperature rising rate to be 1-3℃ / min, rising to 120-160℃ for 4-5h.

7. The method according to claim 1, wherein The mass ratio of the resin solution to the fiber preform is (3-5):1; The fiber preform is selected from quartz fiber, alumina fiber and silicon nitride fiber.

8. A silicone composite material with high-temperature wave-transparent performance improved by in-situ oxygen release decarburization, characterized in that, The silicone composite material is prepared by the method in any one of claims 1-7.

Images