Preparation method of lightweight reduced graphene oxide-silicon dioxide electromagnetic wave absorbing material

Abstract

The invention relates to a preparation method of a lightweight reduced graphene oxide-silicon dioxide electromagnetic wave absorbing material. The invention belongs to the technical field of electromagnetic wave absorbing materials. The invention solves the problems that the impedance of the existing reduced graphene oxide is mismatched, the density of the modified reduced graphene oxide composite wave-absorbing material is increased and the preparation method is complicated. The method comprises the following steps: performing chemical crosslinking on graphene oxide, silicon dioxide and a silane coupling agent to obtain a precursor; and drying and sintering the precursor. The material prepared in the invention has good impedance matching and abundant interface polarization and relaxation effects, can effectively reduce the reflection loss value of electromagnetic waves and increase the effective absorption bandwidth of the electromagnetic waves, and has excellent electromagnetic wave absorption performance. When the thickness of the material is only 1.5 mm, the RL of the material can reach-54.08 dB, and when the thickness of the material is 1.7 mm, the effective absorption bandwidth of the material can reach 5.12 GHz. In addition, the density of the material is only 0.083 g / cm < 3 >, the process is simple, and stable batch production can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic wave absorbing materials, and specifically relates to a method for preparing a lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material. Background Art

[0002] Excessive electromagnetic radiation not only affects human health, but also affects the normal operation of instruments and equipment. The application of electromagnetic wave absorbing materials can effectively reduce the problem of electromagnetic radiation. Electromagnetic wave absorbing materials can effectively consume electromagnetic waves by converting electromagnetic waves into heat energy or other forms of energy. Therefore, electromagnetic wave absorbing materials play an increasingly important role in modern production and life. With the development of miniaturization of electronic devices and lightweight weapon systems, "thin thickness", "lightweight", "wide absorption" and "strong absorption" have become the inevitable requirements of new electromagnetic wave absorbing materials. Reduced graphene oxide, as a dielectric loss material, can lose electromagnetic waves through mechanisms such as reflection, scattering and interface polarization. At the same time, it has the advantages of low density and good chemical stability. It is a very potential absorbing material. Although reduced graphene oxide has received widespread attention in the field of electromagnetic wave absorption, its impedance mismatch characteristics are not conducive to the absorption of electromagnetic waves, and its actual application effect as a absorbing material alone is not ideal. Although the composite of reduced graphene oxide and magnetic materials can improve the absorbing performance of the material and improve impedance matching, the density of traditional magnetic metal materials is often large, which increases the density of the composite absorbing material, which does not meet the requirements of lightweight and low density for new absorbing materials. Summary of the invention

[0003] The purpose of the present invention is to solve the problems of impedance mismatch of existing reduced graphene oxide, increased density of modified reduced graphene oxide composite absorbing materials and complicated preparation methods, and to provide a method for preparing a lightweight reduced graphene oxide @ silicon dioxide (rGO@SiO2) electromagnetic wave absorbing material.

[0004] A method for preparing a lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material is achieved by the following steps:

[0005] 1. Weigh graphene oxide, silicon dioxide and silane coupling agent, and then add them into a mechanical dispersion device in sequence, and then add a solvent and stir to complete a sufficient chemical cross-linking reaction to obtain a precursor;

[0006] 2. The above precursor is filtered and dried, and then placed in an atmosphere at 500-1000° C. for 6-16 hours to obtain a lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material, thereby completing the preparation method.

[0007] Furthermore, the graphene oxide, silicon dioxide and silane coupling agent described in step 1 are weighed in a mass ratio of (1-3):(0.5-4):(2-6).

[0008] Furthermore, the graphene oxide described in step 1 is in a solution state, and its pH is 1 to 5, and the solid content is one or more of the compositions in the range of 1% to 30%.

[0009] Furthermore, the silicon dioxide described in step 1 is one or a combination of crystalline silicon dioxide, amorphous silicon dioxide, synthetic silicon dioxide, and nano silicon dioxide.

[0010] Furthermore, the silane coupling agent described in step 1 is one or a combination of aminosilane, epoxysilane, acrylic silane, nitrosilane, silane olefin, mercaptan silane, isocyanate silane, and phenyl silane.

[0011] Furthermore, the solvent in step 1 is water and / or anhydrous ethanol.

[0012] Furthermore, the drying temperature in step 2 is 40-70°C.

[0013] Furthermore, in step 2, the atmosphere sintering is performed in an argon, helium or vacuum atmosphere, and the sintering heating rate is 5-10° C. / min.

[0014] Advantages of the present invention:

[0015] The present invention adopts a simple method to uniformly disperse silicon dioxide on the surface of graphene oxide by chemical cross-linking, and then obtains a lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material in which silicon dioxide is uniformly distributed on the surface of reduced graphene oxide through simple thermal reduction. The absorbing material prepared in this way solves the problems of impedance mismatch when reduced graphene oxide is applied to the field of microwave absorption and density increase after reduced graphene oxide is composited with metal materials, which is of great benefit to the flexible design of lightweight absorbing materials.

[0016] Mechanism of the present invention: A new type of lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material is prepared by uniformly combining reduced graphene oxide with a higher dielectric constant and light silicon dioxide with a lower dielectric constant. Since silicon dioxide is difficult to be evenly dispersed on the surface of reduced graphene oxide, it cannot effectively play a role in regulating the impedance matching of reduced graphene oxide. We evenly combine silicon dioxide and the precursor of reduced graphene oxide (graphene oxide) by chemical crosslinking, and then make silicon dioxide evenly distributed on the surface of reduced graphene oxide by in-situ synthesis through heat treatment. Due to the low dielectric constant of silicon dioxide, the wave transmission characteristics, it can effectively reduce the dielectric constant and attenuation constant of the absorbing material, and effectively improve the impedance matching of the material. And because silicon dioxide is evenly distributed on the surface and the middle of the lamella of reduced graphene oxide, it can also prevent the folding and agglomeration of reduced graphene oxide, enhance the interface polarization of the absorbing material, and further enhance the absorbing performance of the absorbing material. In addition, since silicon dioxide also has the characteristics of light weight, the density of the modified absorbing material is very light. Through multi-component design and structural regulation, lightweight reduced graphene oxide@silica electromagnetic wave absorption material has excellent wave absorption performance.

[0017] The lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorption material prepared in the present invention has good impedance matching, rich interface polarization and relaxation effects, can effectively reduce the reflection loss value of electromagnetic waves, increase the effective absorption bandwidth of electromagnetic waves, and has excellent electromagnetic wave absorption performance. When the thickness of the reduced graphene oxide @ silicon dioxide electromagnetic wave absorption material is only 1.5mm, its reflection loss (RL) can reach -54.08dB, and when the thickness is 1.7mm, its effective absorption bandwidth can reach 5.12GHz. In addition, the density of the reduced graphene oxide @ silicon dioxide electromagnetic wave absorption material is only 0.083g / cm 3 , and because of its simple preparation process, it can be stably produced in batches, so it has more practical application significance.

[0018] The present invention is suitable for the preparation of lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a scanning electron microscope image of the lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material in the embodiment;

[0020] Figure 2 is a transmission electron microscope image of the lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material in the embodiment;

[0021] Figure 3 is a Raman image of the lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material in the embodiment;

[0022] Figure 4 This is an XPS graph of the lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material in the embodiment;

[0023] Figure 5 is an impedance matching diagram of reduced graphene oxide in the embodiment;

[0024] Figure 6 is an impedance matching diagram of the lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material in the embodiment;

[0025] Figure 7 is a graph showing the microwave absorption performance of reduced graphene oxide in the embodiment;

[0026] Figure 8 This is a graph showing the wave absorption performance of the lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material in the embodiment. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0028] Specific implementation method 1: This implementation method is a method for preparing a lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material, which is achieved by the following steps:

[0029] 1. Weigh graphene oxide, silicon dioxide and silane coupling agent, and then add them into a mechanical dispersion device in sequence, and then add a solvent and stir to complete a sufficient chemical cross-linking reaction to obtain a precursor;

[0030] 2. The above precursor is filtered and dried, and then placed in an atmosphere at 500-1000° C. for 6-16 hours to obtain a lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material, thereby completing the preparation method.

[0031] The sufficient chemical cross-linking reaction in step 1 of this embodiment is to conduct a sufficient chemical cross-linking reaction between graphene oxide and silicon dioxide through a silane coupling agent.

[0032] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that the graphene oxide, silicon dioxide and silane coupling agent in step 1 are weighed in a mass ratio of (1-3):(0.5-4):(2-6). Other steps and parameters are the same as those in specific embodiment 1.

[0033] The graphene oxide in step 1 of this embodiment is in a solution state, and the dry weight is taken and weighed according to the mass ratio.

[0034] Specific implementation method 3: This implementation method is different from specific implementation method 2 in that the graphene oxide, silicon dioxide and silane coupling agent in step 1 are weighed in a mass ratio of 2:2:6. Other steps and parameters are the same as those in specific implementation method 2.

[0035] Specific embodiment 4: This embodiment is different from specific embodiment 1 in that the graphene oxide described in step 1 is in a solution state, with a pH of 1 to 5 and a solid content of one or more of 1% to 30%. Other steps and parameters are the same as those in specific embodiment 1.

[0036] In this embodiment, when the graphene oxide is a composition, the components are mixed in any ratio.

[0037] Specific embodiment 5: This embodiment is different from specific embodiment 1 in that the silicon dioxide described in step 1 is one or a combination of crystalline silicon dioxide, amorphous silicon dioxide, synthetic silicon dioxide, and nano silicon dioxide. Other steps and parameters are the same as those in specific embodiment 1.

[0038] When the silicon dioxide in this embodiment is a composition, the components are mixed in any ratio.

[0039] Specific embodiment 6: This embodiment is different from specific embodiment 1 in that the silane coupling agent described in step 1 is one or a combination of aminosilane, epoxysilane, acrylic silane, nitrosilane, silane olefin, mercaptan silane, isocyanate silane, and phenyl silane. Other steps and parameters are the same as those in specific embodiment 1.

[0040] When the silane coupling agent is a composition in this embodiment, the components are mixed in any ratio.

[0041] Specific embodiment 7: This embodiment differs from specific embodiment 1 in that the solvent in step 1 is water and / or anhydrous ethanol. The other steps and parameters are the same as those in specific embodiment 1. The amount of solvent added in the embodiment is such that the solvent liquid level can completely disperse the raw materials in the equipment.

[0042] Specific implementation example eight: This implementation example is different from specific implementation example one in that the drying temperature in step two is 40-70° C. The other steps and parameters are the same as those in specific implementation example one.

[0043] Specific embodiment 9: This embodiment differs from specific embodiment 1 in that the atmosphere sintering in step 2 is argon, helium or vacuum, and the sintering temperature rise rate is 5-10°C / min. Other steps and parameters are the same as those in specific embodiment 1.

[0044] Specific implementation method 10: This implementation method is different from the specific implementation method 1 in that in step 2, the material is sintered in an atmosphere at 700° C. for 6 hours. The other steps and parameters are the same as those in the specific implementation method 1.

[0045] The beneficial effects of the present invention are verified by the following examples:

[0046] Example:

[0047] A method for preparing a lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material is achieved by the following steps:

[0048] 1. Weigh graphene oxide, silicon dioxide and silane coupling agent, and then add them into a mechanical dispersion device in sequence, and then add a solvent and stir to complete a sufficient chemical cross-linking reaction to obtain a precursor;

[0049] 2. The above precursor is filtered and dried, and then placed in an atmosphere for sintering at 700° C. for 6 hours to obtain a lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material, thereby completing the preparation method.

[0050] The equipment used in this embodiment is an electric heating blast drying oven and a tubular furnace.

[0051] The graphene oxide described in step 1 of this embodiment is 66.67 grams (dry weight 2 grams), a graphene oxide solution with a solid content of 3% and a pH value of 1;

[0052] The silicon dioxide described in step 1 is 2 g of synthetic silicon dioxide, and the powder size is nanometer scale;

[0053] The silane coupling agent described in step 1 is 6g of silane olefin (Si69) type silane coupling agent;

[0054] The solvent in step 1 is a mixture of water and anhydrous ethanol; the volume ratio of water to anhydrous ethanol is 3:1; the amount of solvent added is until the solvent liquid level can completely disperse the raw materials in the equipment.

[0055] The drying temperature in step 2 is 60°C.

[0056] The atmosphere sintering in step 2: the atmosphere is vacuum, and the sintering heating rate is 10°C / min.

[0057] The lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material prepared in this embodiment:

[0058] Its scanning electron microscope image, such as Figure 1 As shown, granular silicon dioxide is distributed on the surface of flaky reduced graphene oxide, and the reduced graphene oxide has an obvious layered structure without overlapping and agglomeration.

[0059] Its transmission electron microscopy image is as follows Figure 2 As shown, granular silicon dioxide is distributed on the edge, surface and middle of the reduced graphene oxide.

[0060] The Raman test results are as follows Figure 3 As shown, it can be seen that compared with reduced graphene oxide (rGO), the I D / I G The value increases significantly, indicating that its structural defects increase and silicon dioxide and graphene oxide undergo chemical cross-linking reactions.

[0061] The XPS test results are as follows: Figure 4 As shown, the elemental composition of reduced graphene oxide @ silicon dioxide electromagnetic wave absorption material, the XPS test results clearly show that there are no other impurity elements present.

[0062] The obtained light reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material was prepared in this embodiment and tested. The impedance matching was as follows: Figure 5 and Figure 6 As shown, it can be seen that when the reduced graphene oxide is not combined with silicon dioxide, its impedance matching is very poor (generally the default impedance matching value between 0.8-1.2 is effective impedance matching). When the reduced graphene oxide is combined with silicon dioxide, the impedance matching of the absorbing material is significantly improved.

[0063] Wave absorption performance Figure 7 As shown in Figure 2, it can be seen that when the reduced graphene oxide is not combined with silicon dioxide, the material as a whole has basically no wave absorbing performance; when the reduced graphene oxide is combined with silicon dioxide, Figure 8 As shown, the material exhibits excellent wave absorption performance. When the thickness of the lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorption material is only 1.5mm, its reflection loss (RL) can reach -54.08dB, and when the thickness is 1.7mm, its effective absorption bandwidth can reach 5.12GHz.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material, characterized in that It proceeds as follows:

1. Weigh graphene oxide, silicon dioxide and silane coupling agent, and then add them into a mechanical dispersion device in sequence, and then add a solvent and stir to complete a sufficient chemical cross-linking reaction to obtain a precursor; 2. The above precursor is filtered and dried, and then placed in an atmosphere at 500-1000° C. for 6-16 hours to obtain a lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material, thereby completing the preparation method.

2. The method for preparing a lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material according to claim 1, characterized in that The graphene oxide, silicon dioxide and silane coupling agent described in step 1 are weighed according to a mass ratio of (1-3):(0.5-4):(2-6).

3. The method for preparing a lightweight reduced graphene oxide @ silicon dioxide electromagnetic wave absorbing material according to claim 2, characterized in that The graphene oxide, silicon dioxide and silane coupling agent described in step 1 are weighed in a mass ratio of 2:2:

6.

4. The method for preparing a lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material according to claim 1, characterized in that The graphene oxide described in step 1 is in a solution state, and its pH is 1 to 5, and the solid content is one or more compositions of 1% to 30%.

5. The method for preparing a lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material according to claim 1, characterized in that The silicon dioxide described in step 1 is one or a combination of crystalline silicon dioxide, amorphous silicon dioxide, synthetic silicon dioxide, and nano silicon dioxide.

6. The method for preparing a lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material according to claim 1, characterized in that The silane coupling agent described in step 1 is one or a combination of aminosilane, epoxysilane, acrylic silane, nitrosilane, silane olefin, mercaptan silane, isocyanate silane and phenyl silane.

7. The method for preparing a lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material according to claim 1, characterized in that The solvent in step 1 is water and / or anhydrous ethanol.

8. The method for preparing a lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material according to claim 1, characterized in that The drying temperature in step 2 is 40-70°C.

9. The method for preparing a lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material according to claim 1, characterized in that The atmosphere sintering in step 2: the atmosphere is argon, helium or vacuum, and the sintering heating rate is 5-10°C / min.

10. The method for preparing a lightweight reduced graphene oxide@silicon dioxide electromagnetic wave absorbing material according to claim 1, characterized in that In step 2, the mixture is sintered at 700°C in atmosphere for 6 hours.

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