Composite material with wave absorbing or scattering properties and preparation method thereof

Abstract

The present application relates to the field of composite materials, and discloses a composite material with wave-absorbing or scattering properties and a preparation method thereof. The preparation method comprises the following steps: subjecting rare earth materials and carbon nanotubes to interfacial polarization pretreatment to enhance their surface active sites; mixing the rare earth materials and carbon nanotubes that have undergone the interfacial polarization pretreatment with a polyacrylonitrile suspension, and subjecting them to ultrasonic vibration treatment to form a composite material precursor; under the action of an electric field, orienting and paving the conductive fibers and the composite material precursor, and curing to form the composite material with wave-absorbing or scattering properties. The new material of the present application is composed of two or more component materials, which are compounded together through a dedicated preparation process, and has both wave-absorbing and scattering properties. It not only achieves broadband absorption and geometric scattering, but also has the characteristics of lightweight.

Description

Technical Field

[0001] The present application relates to the field of broadband absorption and lightweight composite materials made of carbon nanotubes, carbon fibers and nano rare earth fillers, and more specifically, to a composite material with wave absorbing or scattering properties and a preparation method thereof. Background Art

[0002] Currently, in the research and process design and preparation of materials with either microwave-absorbing or scattering properties, microwave-absorbing materials are generally prioritized. Specifically, carbon-based materials, ceramic materials, and metal-based composites are often selected. These materials have distinct properties, such as carbon-based materials (high dielectric loss but poor high-temperature stability), ceramic materials (high-temperature resistance and oxidation resistance, but high cost), and metal-based composites (such as barium ferrite and nickel-zinc ferrite, which exhibit significant magnetic loss but may reflect electromagnetic waves). Using each of these materials individually can have significant advantages and disadvantages. Scattering composites typically include metals and metamaterials, such as laminated structures of metal foil and resin, which enhance scattering through interfacial reflection, or artificially designed subwavelength structures in metamaterials to achieve extraordinary electromagnetic response. Consequently, the variety of materials with both microwave-absorbing and scattering properties is severely limited, hindering the development of the growing multifunctional advanced materials industry.

[0003] Therefore, it is particularly important to develop new materials composed of two or more component materials, which are compounded together through a special preparation process, to meet the requirements of composite materials with both absorption and scattering properties, to achieve novel composite materials with broadband absorption, geometric scattering and lightweight characteristics. Summary of the Invention

[0004] In view of the shortcomings of existing material selection and technology, the present invention aims to provide a composite material with wave absorbing or scattering properties and a preparation method thereof.

[0005] In order to achieve the above-mentioned invention objectives, this application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a method for preparing a composite material having wave absorbing or scattering properties, comprising the following steps:

[0007] The rare earth materials and carbon nanotubes are subjected to interfacial polarization pretreatment to enhance their surface active sites;

[0008] Mixing the rare earth material and carbon nanotubes that have undergone the interfacial polarization pretreatment with a polyacrylonitrile suspension, and subjecting the mixture to ultrasonic vibration treatment to form a composite material precursor;

[0009] Under the action of the electric field, the conductive fibers and the composite material precursor are oriented, arranged, and laid flat, and then solidified to form the composite material with wave absorbing or scattering properties.

[0010] Preferably, the interface polarization pretreatment refers to a step of performing interface polarization on the rare earth material and the carbon nanotubes by using plasma technology by regulating gas pressure, power, time, gas type, gas flow and surface cleaning.

[0011] Preferably, the step of interface polarization pretreatment is:

[0012] A medium-low gas pressure method is used, with the pressure controlled at 10~20Pa, to produce deep grooves on the material surface, enhance surface defect density or oxygen vacancies; high-energy electrons and ions generated by RF power of 100~200W are used to promote surface atomic sputtering and defect formation; the processing time is controlled within 1 minute, and the gas is selected as ultra-high purity argon with a purity of ≥99.999% and an argon flow rate of 10~20sccm. Cleaning, removal of residual particles or reaction by-products, and drying are performed.

[0013] Preferably, after the rare earth material is subjected to interfacial polarization pretreatment, the rare earth material is further processed: the rare earth material subjected to the interfacial polarization pretreatment is mixed with a solvent and mechanically stirred to form a stable suspension.

[0014] Preferably, the mixing of the rare earth material pretreated by the interfacial polarization with a solvent and forming a stable suspension by mechanical stirring refers to adding 100 mL of ethanol, 100 mL of deionized water and 50 g of the rare earth material pretreated by the interfacial polarization into a barrel, and stirring at a speed of 150~220 r / min at room temperature to form a stable suspension.

[0015] Preferably, the polyacrylonitrile suspension refers to a solution obtained by mixing 5 g of polyacrylonitrile powder with 200 mL of 95% ethanol.

[0016] Preferably, in the composite material precursor, the amounts of rare earth material, carbon nanotubes and polyacrylonitrile suspension are 250g:80g:200g.

[0017] Preferably, under the action of the electric field, the conductive fibers and the composite material precursor are oriented and laid flat, and solidified to form the composite material with absorbing or scattering properties, which means that the conductive fibers are radially arranged on the glass plane of the material synthesis operating table, the two ends of the conductive fibers are pressed with metal materials, one end of the metal material is connected to the positive wire and the other end is connected to the negative wire, and the metal and wire parts are sealed with step-type quartz above the metal material, and then the composite material precursor is laid flat on the conductive fibers and swept back and forth. After the sweep is completed, the power is turned on and the orientation is carried out. After the end, the composite material with absorbing or scattering properties is obtained.

[0018] Preferably, the conductive fibers are carbon fibers.

[0019] In a second aspect, the present application provides a composite material having wave absorbing or scattering properties prepared by the preparation method.

[0020] In summary, this application has the following beneficial effects:

[0021] This application utilizes the low density and high dielectric loss characteristics of carbon nanotubes and carbon fibers, rationally proportioning their components to achieve excellent conductivity loss and polarization relaxation loss (e.g., impedance matching and attenuation mechanisms), as well as chemical stability. Nano-lanthanum oxide and nano-rare earth materials are then used as fillers in the carbon nanotubes and carbon fibers to leverage polarization relaxation and interfacial effects caused by electronic structure and lattice distortion, thereby regulating the dielectric properties of the composite material and enabling interaction between the carbon and rare earth materials. This results in a process flow and method for preparing a composite material with microwave-absorbing or scattering properties. The metal-organic framework material produced using this process exhibits multiple functions, including microwave-absorbing and scattering properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 :Process flow chart;

[0023] Figure 2 : test sample;

[0024] Figure 3 : Test results show that the return loss is less than -7dB at 10GHz in the X-band;

[0025] Figure 4 : Test results show that the reflection loss is less than -14dB at 38GHz in the X-band. DETAILED DESCRIPTION

[0026] The technical solutions and effects of the present application are further described in detail below with reference to the embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain the invention, rather than to limit the invention.

[0027] Example

[0028] A composite material with wave absorbing or scattering properties is prepared by the following preparation method:

[0029] Using the interface polarization method:

[0030] The first step is to select one or more lanthanum oxide or related rare earth materials for interface polarization. During the polarization, plasma technology is used, and the operation is performed by regulating gas pressure, power, time, gas type, gas flow rate and surface cleaning. The specific steps are as follows: a medium-low gas pressure method is used, and the pressure is controlled at 10~20Pa. The effect produced is high bombardment energy, which causes deep grooves on the surface of the rare earth material and enhances the surface defect density or oxygen vacancies; high-energy electrons and ions generated by radio frequency power of 100~200W are used to promote surface atomic sputtering and defect formation. The processing time is controlled within 1 minute. The gas is selected as ultra-high purity argon with a purity of ≥99.999% and an argon flow rate of 10~20 sccm. The main feature of the plasma is low density but high energy, which is suitable for deep etching or defect induction of the processed material; deionized water is used to rinse to remove residual particles or reaction by-products, and the material is vacuum-dehydrated and dried to become A material for standby use;

[0031] In the second step, carbon nanotubes are used for interfacial polarization. The same steps and technical means as above are used for polarization. The difference is that they are soaked in ethanol during cleaning and frozen after being taken out as material B. The purpose of freezing is to prevent carbon nanotubes from agglomerating and affecting the polarization treatment effect.

[0032] Material A is further processed by adding 100 mL of ethanol, 100 mL of deionized water, and 50 g of material A to a barrel at room temperature of 25°C. A stable suspension (abbreviated as material A1, material A1 being the rare earth material in the composite precursor) is formed by high-speed stirring. The speed range is set between 150 and 220 r / min. Lanthanum oxide is dissolved / dispersed in ethanol and deionized water by a physical and chemical method to introduce hydroxyl (-OH) groups on the surface of the material, thereby changing the surface properties of the material to make it hydrophilic, chemically reactive, or biocompatible. The oxygen atoms on the surface of lanthanum oxide (La2O3) can react with water or hydroxyl radicals to generate La-OH groups. The surface reconstruction hydroxylation induces surface atomic rearrangement, forming more active sites (such as defects or active centers). In terms of chemical reaction enhancement, the hydroxyl groups can serve as anchoring sites for further grafting of functional molecular materials. After hydroxylation of lanthanum oxide, the interfacial bonding strength with the carbon material and the resin matrix is ​​enhanced.

[0033] To prepare Material C, take 200 mL of 95% high-concentration ethanol and 5 g of PAN powder, thoroughly stir them with ultrasound to soften and swell the polyacrylonitrile particles, then strengthen the ultrasound to allow high-frequency vibration to further refine the particles to the micron or even nanometer level until a uniform suspension is formed for later use. Material C is the polyacrylonitrile suspension in the composite material precursor.

[0034] Materials A, B, and C were further synthesized and processed. 80 g of material B (carbon nanotubes) was thawed and poured directly into an ultrasonic oscillation barrel. The previously prepared material A1 (250 g) and material C (200 g) were then added and ultrasonically oscillated for about 15 minutes until a stable paste-like viscous substance was formed, which was then used to prepare the metal-organic framework material.

[0035] The synthesis process of composite materials is to arrange carbon fibers radially on the glass surface of the material synthesis operating table (a track is set under the synthesis operating table as a moving device, which is divided into three areas, consisting of a fiber laying table, a slurry sweeping and orientation arrangement table and a drying and flattening table). The size is customized according to needs. The two ends of the carbon fibers are pressed with metal materials, one end of the metal material is connected to the positive wire and the other end is connected to the negative wire. The metal and wire parts are sealed with a step-type quartz on the top of the metal material. Then, the ABC synthetic material is spread flat on the carbon fibers and swept back and forth. After the sweep is completed, the power is turned on (voltage 12-24 volts, time 1-2 minutes) to drive the hydroxylated carbon nanotubes by electric charge and induce them to be oriented, forcing different metals and organic ligands to meet the requirements of precisely controlling the structure and function of the composite materials. The above paving process can be repeated according to the special requirements of the material until the composite material with the designed parameters is achieved. After the sweep and orientation arrangement are completed, the platform moves to the drying and flattening area and the material is taken up by the receiving device (refer to Figure 1 Process flow chart). Accordingly, the metal-organic framework material produced by this process possesses multiple functions, namely, a composite material with wave-absorbing or scattering properties.

[0036] Performance testing

[0037] Experimental Materials:

[0038] The composite material with wave absorbing or scattering properties obtained in the above embodiment is used as the test material. Test sample 1, according to the requirements of GJB 2038A-2011: the sample is square, the surface roughness is not greater than 6.4 μm, the recommended size is: 180*180*4 mm, and the operating frequency range is: 1 GHz-40 GHz.

[0039] Experimental conditions, results, and data analysis:

[0040] According to the relevant provisions of GJB 2038A-2011 "Test Method for Reflectivity of Radar Absorbing Materials", this test method is: the bow method, the sample is fixed on a toothed bracket, the test system composition is shown in the military standard bow test method 6.2.1 test system composition diagram, and the test steps are shown in 6.5.

[0041] The above method was used to test the (S21-dB) data of the material surface B1 and the back surface B2. The measured data of the B1 surface were: the reflectivity (S21-dB) in the frequency range of 6GHz-18GHz was -2.2dB, -7.3dB, and -3.7dB, among which the reflectivity was -7.3dB at the frequency of 11GHz, which was the lowest value. When the frequency was above 18GHz, the reflectivity fluctuated between -2 and -3.5dB. The measured data of the B2 surface test were: the reflectivity (S21-dB) in the frequency range of 6GHz-28GHz was between -2dB and -8.5, and the reflectivity was -8dB, -14.1dB, and -13dB at the frequency of 28GHz-40GHz. Among them, the reflectivity was -14.1dB at the frequency of 38GHz, which was the lowest value.

[0042] The test results show that the B1 surface material is suitable for low-frequency wave absorption (the optimal frequency range is 11GHz), and the B2 quilt cover material is suitable for medium and high-frequency wave absorption (the optimal frequency range is 38GHz).

[0043] Note: Figure 3 、 Figure 4 In the figure, the red line represents relatively low frequency and the blue line represents relatively high frequency, which is only used to distinguish the relationship between relatively high and relatively low.

[0044] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing a composite material having wave absorbing or scattering properties, characterized in that: The following steps are involved: The rare earth materials and carbon nanotubes are subjected to interfacial polarization pretreatment to enhance their surface active sites; Mixing the rare earth material and carbon nanotubes that have undergone the interfacial polarization pretreatment with a polyacrylonitrile suspension, and subjecting the mixture to ultrasonic vibration treatment to form a composite material precursor; Under the action of an electric field, the conductive fibers and the composite material precursor are oriented, arranged, and laid flat, and solidified to form the composite material having wave absorbing or scattering properties; The interface polarization pretreatment refers to the step of performing interface polarization on rare earth materials and carbon nanotubes by using plasma technology and regulating gas pressure, power, time, gas type, gas flow and surface cleaning.

2. The method for preparing a composite material having wave absorbing or scattering properties according to claim 1, characterized in that: The steps of the interface polarization pretreatment are: A medium-low gas pressure method is used, with the pressure controlled at 10~20Pa, to produce deep grooves on the material surface, enhance surface defect density or oxygen vacancies; high-energy electrons and ions generated by RF power of 100~200W are used to promote surface atomic sputtering and defect formation; the processing time is controlled within 1 minute, and the gas is selected as ultra-high purity argon with a purity of ≥99.999% and an argon flow rate of 10~20sccm. Cleaning, removal of residual particles or reaction by-products, and drying are performed.

3. The method for preparing a composite material having wave absorbing or scattering properties according to claim 1, characterized in that: After the rare earth material is subjected to the interface polarization pretreatment, the rare earth material is further processed: the rare earth material subjected to the interface polarization pretreatment is mixed with a solvent and a stable suspension is formed by mechanical stirring.

4. The method for preparing a composite material having wave absorbing or scattering properties according to claim 3, characterized in that: The mixing of the rare earth material pretreated by the interfacial polarization with a solvent and forming a stable suspension by mechanical stirring refers to adding 100 mL of ethanol, 100 mL of deionized water and 50 g of the rare earth material pretreated by the interfacial polarization into a barrel, and stirring at a speed of 150~220 r / min at room temperature to form a stable suspension.

5. The method for preparing a composite material having wave absorbing or scattering properties according to claim 1, wherein: The polyacrylonitrile suspension refers to a suspension obtained by mixing 5 g of polyacrylonitrile powder with 200 mL of 95% ethanol and performing ultrasonic dispersion.

6. The method for preparing a composite material having wave absorbing or scattering properties according to claim 1, characterized in that: In the composite material precursor, the amounts of rare earth material, carbon nanotubes and polyacrylonitrile suspension are 250g:80g:200g.

7. The method for preparing a composite material having wave absorbing or scattering properties according to claim 1, characterized in that: The conductive fibers and the composite material precursor are oriented and laid out under the action of an electric field, and solidified to form the composite material with absorbing or scattering properties. This means that the conductive fibers are radially arranged on a glass plane of a material synthesis operating table, both ends of the conductive fibers are pressed with metal materials, one end of the metal material is connected to a positive electrode wire and the other end is connected to a negative electrode wire, and the metal and wire parts are sealed with stepped quartz above the metal material. Then, the composite material precursor is laid out on the conductive fibers and swept back and forth. After the sweep is completed, the power is turned on and the fibers are oriented and arranged. After the sweep is completed, the composite material with absorbing or scattering properties is obtained.

8. The method for preparing a composite material having wave absorbing or scattering properties according to claim 7, characterized in that: The conductive fibers are carbon fibers.

9. A composite material with wave absorbing or scattering properties prepared by the preparation method according to any one of claims 1 to 8.

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