Graphene / silicon carbide wave-absorbing material and preparation method thereof

Abstract

The invention discloses a graphene / silicon carbide wave-absorbing material and a preparation method thereof. A continuous silicon carbide fiber bundle / continuous silicon carbide fiber cloth is used as a growth substrate, and the surface of the continuous silicon carbide fiber bundle / continuous silicon carbide fiber cloth is coated with a graphene coating layer which is tightly combined, uniform, continuous and controllable in layer number through a chemical vapor deposition method, so that preparation of the dielectric-adjustable, high-mechanical-strength and high-temperature-resistant graphene / silicon carbide composite material is achieved.

Description

Technical Field

[0001] The invention belongs to the field of wave absorbing materials, and in particular relates to a graphene / silicon carbide wave absorbing material and a preparation method thereof. Background Art

[0002] With the rapid progress of hypersonic aircraft and combat weapons, the field has put forward higher temperature resistance and "thin, light, wide and strong" requirements for radar absorbing components. Fighter jets, cruise missiles and other aerial weapons and equipment, especially tail nozzles, are subject to the dual effects of aerodynamic heat and power combustion heat. The operating temperature of their components can reach over 1500℃, and they have strong reflection of radar waves, which has become a key factor affecting the stealth performance of new weapons and equipment.

[0003] At present, according to the different forms of absorbing materials, absorbing materials can be divided into coated absorbing materials, patch absorbing materials and structural absorbing materials. Coated absorbing materials generally lead to a significant increase in the mass of the protected part, and at the same time, they have poor anti-scouring ability and a short service life in extreme environments. Therefore, the application of coated absorbing materials is greatly limited; patch absorbing materials have certain requirements on the shape and size of the protected part, and will also increase the mass of the protected part. They are also not suitable for electromagnetic protection under certain harsh conditions.

[0004] It can be seen from the contents disclosed in the prior art CN103725080A and CN105172267A that the current absorbing composite material systems are mostly resin-based composite materials, and the absorbers used are mostly magnetic, dielectric, and conductive absorbers. When used at high temperatures of thousands of degrees, traditional resin-based absorbing composite materials face matrix failure, and the magnetic absorber loses its absorbing properties due to exceeding the Curie temperature, resulting in a sharp decline in the absorbing performance of the composite material.

[0005] At present, the preparation of high-temperature resistant broadband wave-absorbing composite materials mainly starts from the resistivity control of fibers, interfaces and ceramic matrices. As the commonly used preparation methods of patents CN102180695A, CN102218868A, CN115764328A and CN110105070A, different types of silicon carbide fibers with different resistivities are used as wave-transmitting layers, wave-absorbing layers and reflective layers, or the resistivity of different matrices is controlled by adding multiple components. The entire component requires different types of silicon carbide fibers, which has high material costs and poor thermal matching. Delamination and other defects are easily generated during the preparation process. The addition of multiple components will also affect the high temperature resistance and mechanical properties of the fiber. But more importantly, the surface of silicon carbide fiber lacks a protective layer. When the temperature reaches above 1500°C, the sublimation of Si atoms is difficult to control, which brings devastating damage to the weapon components and even the whole.

[0006] Patent application CN107675488A uses the method of graphene oxidation and reduction to coat graphene on the surface of silicon carbide fiber, but the surface graphene has little interaction with the silicon carbide substrate and poor quality, and cannot be used as an effective functional layer of silicon carbide fiber; at the same time, some researchers generate graphene on the surface of silicon carbide fiber by high temperature annealing, but the graphene is loose and porous and cannot protect the silicon carbide core. The chemical vapor deposition method can coat high-quality graphene on the surface of silicon carbide, as in patent CN110323126B, researchers use laser-assisted chemical vapor deposition to in-situ generate atomically flat cubic silicon carbide on a single crystal silicon substrate and then coat it with graphene. Although the laser can provide additional energy for heating the silicon substrate, it will also bring about problems such as complex processes and equipment, and high temperature, low pressure or vacuum helps Si sublimation, which has limitations. It can be seen that this method cannot meet the growth and coating of graphene layers on the surface of silicon carbide fibers with more complex surface structures and compositions. Summary of the invention

[0007] In the entire components of combat weapons such as fighter jets, existing technologies require different types of silicon carbide fibers, which have high material costs and poor thermal matching. Delamination and other defects are easily produced during the preparation process. Adding multiple components will also affect the high temperature resistance and mechanical properties of the fiber. But more importantly, the surface of silicon carbide fiber lacks a protective layer. When the temperature reaches above 1500°C, the sublimation of Si atoms is difficult to control, which brings devastating damage to weapon components and even the entire weapon. However, it is difficult to coat the surface of silicon carbide fiber with high-quality graphene.

[0008] Structural absorbing materials with integrated structure and function can be used as the main body of the component, thus effectively avoiding the above problems, and therefore have received widespread attention. Structural absorbing materials with integrated structure and function are developed on the basis of thermal structural materials. Compared with the latter, on the basis of thermal and mechanical performance constraints alone, the requirements for electromagnetic absorbing performance are added. Therefore, the high temperature resistance, mechanical and dielectric properties of the component matrix are required to be higher, resulting in greater difficulties in design, material selection, preparation and performance testing. However, there is currently no technical means for preparing high-quality functional layers on the surface of silicon carbide fibers, and it is difficult to break through the bottleneck of high temperature resistance and absorbing performance of continuous silicon carbide fiber composite materials. Therefore, the present invention aims to develop a new generation of structural and functional integrated absorbing materials that are resistant to higher temperatures, thereby improving the penetration capability, survivability and combat effectiveness of weapons and equipment, which has very important practical significance.

[0009] In order to overcome the problems in the prior art, the present invention provides a graphene / silicon carbide absorbing material with integrated structure and function, and the preparation method thereof comprises the following steps:

[0010] S1, performing a degumming treatment on the silicon carbide fiber;

[0011] S2. growing a graphene layer on the surface of the silicon carbide fiber after the glue is removed.

[0012] By adopting the technical solution of the present invention, the preparation of graphene / silicon carbide absorbing materials with integrated structure and function is realized, and the problem of separation of supporting components and functional components in the prior art is overcome.

[0013] According to a specific embodiment of the present invention, step S1 specifically includes: immersing the silicon carbide fiber in a solvent, ultrasonically treating, washing, and drying;

[0014] Wherein, the solvent is one or more of acetone, ethyl acetate, toluene and xylene;

[0015] The power of ultrasound is 50-100W, the temperature is room temperature, and the time is 5-20 minutes;

[0016] Washing is done with distilled water;

[0017] The drying temperature is 80-120°C.

[0018] According to a specific embodiment of the present invention, step S2 specifically includes: growing a graphene layer on the surface of the silicon carbide fiber after the debonding by chemical vapor deposition.

[0019] According to a specific embodiment of the present invention, the temperature of chemical vapor deposition is 1000-1200°C, specifically 1000°C, 1050°C, 1100°C, 1200°C.

[0020] The present invention controls the temperature of chemical vapor deposition at 1000-1200° C. When the chemical vapor deposition temperature is lower than 1000° C., the carbon layer on the fiber surface has low crystallinity and is amorphous carbon. When the temperature is higher than 1200° C., the surface is coated with graphene. However, the high temperature causes a serious decrease in the intrinsic mechanical strength of the silicon carbide fiber, and the tensile strength of the single fiber must not be lower than 2GPa.

[0021] According to a specific embodiment of the present invention, the processing time of chemical vapor deposition is 10 to 300 minutes, specifically 10 minutes, 20 minutes, 50 minutes, 100 minutes, 180 minutes, 200 minutes, 250 minutes, and 300 minutes.

[0022] The present invention controls the processing time of chemical vapor deposition to 10 to 300 minutes. When the chemical vapor deposition time is less than 10 minutes, the graphene is not completely coated. When the chemical vapor deposition time is more than 300 minutes, the thickness of the graphene on the surface of the silicon carbide fiber exceeds 30 nm, and the silicon carbide fiber cannot be used as an electromagnetic wave absorbing layer material.

[0023] According to a specific embodiment of the present invention, the carrier gas for chemical vapor deposition is one or more of argon and hydrogen, preferably a mixture of hydrogen and argon; the carrier gas flow rate is 100 to 500 sccm, specifically 100 sccm, 200 sccm, 300 sccm, 400 sccm, 500 sccm; the carrier amount is adapted to 1 to 20 dm 3 In a chemical vapor deposition chamber, the gas flow rate can be increased or decreased in proportion to the volume of the chemical vapor deposition chamber.

[0024] The present invention controls the flow rate of the carrier gas to be between 100 and 500 sccm. When the carrier gas flow rate is lower than 100 sccm, the carbon deposition rate is too fast to generate amorphous carbon; when the carrier gas flow rate is higher than 500 sccm, the carbon deposition rate is slower.

[0025] According to a specific embodiment of the present invention, the carbon source for chemical vapor deposition is a gaseous carbon source, and the flow rate of the gaseous carbon source is 5 to 30 sccm; specifically 5 sccm, 10 sccm, 15 sccm, 20 sccm, 25 sccm, 30 sccm; the gaseous carbon source is suitable for 1 to 20 dm 3 In a chemical vapor deposition chamber, the gas flow rate can be increased or decreased in proportion to the volume of the chemical vapor deposition chamber.

[0026] The present invention controls the flow rate of the gaseous carbon source to be between 5 and 30 sccm. When the flow rate of the gaseous carbon source is lower than 5 sccm, the carbon deposition rate is too slow; when the flow rate of the gaseous carbon source is higher than 30 sccm, the carbon deposition rate is faster and amorphous carbon is generated.

[0027] According to a specific embodiment of the present invention, the hydrogen-to-carbon ratio of chemical vapor deposition is 5 to 20:1, specifically 5:1, 10:1, 15:1, and 20:1.

[0028] The present invention controls the hydrogen-carbon ratio to be within the range of 5 to 20:1. Hydrogen can not only act as a carrier gas but also reduce the nucleation density. Moreover, the etching effect of hydrogen is helpful for etching and re-growth of amorphous carbon and graphene defects. When the hydrogen-carbon ratio is less than 5:1, the etching effect of hydrogen is weak and amorphous carbon is easily generated. When the hydrogen-carbon ratio is greater than 20:1, the etching effect of hydrogen is strong and graphene cannot grow.

[0029] According to a specific embodiment of the present invention, the silicon carbide fiber is a continuous silicon carbide fiber tow or a continuous silicon carbide fiber cloth.

[0030] Another object of the present invention is to provide a graphene / silicon carbide absorbing material prepared by the above preparation method.

[0031] Beneficial effects:

[0032] The technical solution of the present invention is to use a continuous silicon carbide fiber bundle or a continuous silicon carbide fiber cloth as a growth substrate, and to coat a tightly bonded, uniformly continuous and controllable number of graphene coating layers on its surface by chemical vapor deposition, thereby realizing the preparation of a graphene / silicon carbide composite material with adjustable dielectric and high mechanical strength. The process is simple and controllable, and the high-quality and continuous graphene coating layer on the surface of the continuous silicon carbide fiber can greatly inhibit the sublimation of Si atoms at high temperatures, thereby improving the mechanical properties of the fiber at high temperatures; the thickness of the graphene layer on the surface of the silicon carbide fiber can be effectively regulated by regulating the growth process, thereby effectively regulating the dielectric properties of the composite fiber; the composite fiber can be gradiently arranged into an absorption layer and a reflection layer, and the absorption layer obtained has a wide absorption bandwidth, and the thermal expansion coefficients between the layers are similar, thereby avoiding cracking caused by thermal mismatch of the layers under high temperature conditions.

[0033] The present invention provides experimental conditions for quickly coating high-quality graphene on the surface of silicon carbide fibers with more complex structures and compositions, while having little effect on the intrinsic properties of the fibers. Compared with the prior art, such as coating graphene on the surface of silicon carbide fibers by oxidation-reduction of graphene, generating graphene on the surface of silicon carbide fibers by high-temperature annealing, etc., the graphene / silicon carbide absorbing material prepared by the present invention can withstand high temperatures above 1500°C, has good mechanical property retention, and has a wide absorbing frequency band. Furthermore, the chemical vapor deposition method can be used to achieve high-quality and low-cost preparation of graphene / silicon carbide fiber composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a process flow chart of preparing the graphene / silicon carbide absorbing material of the present invention;

[0035] Figure 2 is a SEM image of the silicon carbide fiber after the debonding treatment of Example 1;

[0036] Figure 3 This is a SEM image of the graphene / silicon carbide absorbing material prepared in Example 1;

[0037] Figure 4 is a TEM image of the graphene / silicon carbide absorbing material prepared in Example 1;

[0038] Figure 5 The Raman spectra of the silicon carbide fiber after debonding and the prepared graphene / silicon carbide absorbing material in Example 1 are shown;

[0039] Figure 6 The electromagnetic wave reflection loss of the silicon carbide fiber after debonding and the prepared graphene / silicon carbide absorbing material in Example 1;

[0040] Figure 7This is a test chart of the tensile strength of the silicon carbide fiber after debonding in Example 1 and the prepared graphene / silicon carbide absorbing material after high-temperature treatment. DETAILED DESCRIPTION

[0041] The following further exemplifies the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples in a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values ​​​​exemplified below.

[0042] Example 1

[0043] The preparation process flow chart of the graphene / silicon carbide absorbing material of the present invention is as follows: Figure 1 As shown, the specific preparation process of Example 1 is as follows:

[0044] Related indicators of continuous silicon carbide fiber cloth: plain weave, fiber single filament tensile strength is 3.4GPa, fiber bundle is circular cross-section silicon carbide fiber.

[0045] Step 1: Immerse the continuous silicon carbide fiber cloth in acetone, perform ultrasound at 100W for 10 minutes, then wash with distilled water, and bake at 100°C for 10 minutes to remove moisture, thereby completing the removal of impurities such as colloid on the surface of the silicon carbide fiber.

[0046] Step 2: Connect argon gas to the gas inlet, introduce 300sccm argon gas, the system is at normal pressure, the heating rate is 10℃ / min, the system temperature rises from 20℃ to 1100℃, introduce 100sccm hydrogen gas, maintain for 10min, then introduce 10sccm methane gas, and the growth time is 180min. After the growth is completed, turn off the heating program to cool down the chemical vapor deposition chamber, turn off methane and hydrogen, wait until the temperature drops to room temperature, turn off argon gas, and obtain a well-grown sample.

[0047] Figure 2 This is the SEM image of the silicon carbide fiber after the debonding treatment of Example 1. Figure 2 It can be seen that the surface cleanliness of the silicon carbide fiber after debonding by the solvent removal method is relatively high, and there is no glue layer attached, indicating that this process can effectively remove the glue on the fiber surface;

[0048] Figure 3 This is the SEM image of the graphene / silicon carbide absorbing material prepared in Example 1. Figure 3 It can be seen that after chemical vapor deposition of silicon carbide fiber, the surface is covered with a tightly bound and continuous graphene layer;

[0049] Figure 4 TEM image of the graphene / silicon carbide absorbing material prepared in Example 1. Figure 4 It can be seen that the graphene layer is tightly combined with the silicon carbide fiber substrate, and the graphene has high crystallinity. The continuous layered structure can be clearly observed. The average thickness of graphene is 12.3nm, which can effectively inhibit the sublimation of Si atoms under high temperature conditions, so that the fiber can withstand higher temperatures.

[0050] Figure 5 The Raman spectra of the silicon carbide fiber and the prepared graphene / silicon carbide absorbing material of Example 1 are shown in FIG. Figure 5 It can be seen that after the silicon carbide fiber is coated with graphene, the 2D intensity increases and the D peak intensity decreases significantly, which proves that the preparation process of the present invention can achieve high-quality and rapid coating of graphene on the surface of silicon carbide fiber;

[0051] Figure 6 is the electromagnetic wave reflection loss of the silicon carbide fiber and the prepared graphene / silicon carbide absorbing material of Example 1, Figure 6 It can be seen that when the sample thickness is 3 mm, the absorption band width below -10 dB of the silicon carbide fiber sample not coated with graphene is 0, while when coated with a graphene layer with an average thickness of 12.3 nm by chemical vapor deposition, the absorption band width below -10 dB can reach 8.5 GHz, including two bands of 4.4 to 6.6 GHz and 10.2 to 16.5 GHz. The minimum RL value is at 13.4 GHz, which can reach -37.1 dB.

[0052] Figure 7 This is a high temperature resistance test diagram of the silicon carbide fiber and the prepared graphene / silicon carbide absorbing material of Example 1. Figure 7 It can be seen that when the fiber is kept at 1500℃ and Ar atmosphere for 1h for high temperature resistance test, the maximum load of silicon carbide fiber is 0.227N and the tensile strength is 1.72GPa, while the maximum load of graphene silicon carbide fiber is 0.328N and the tensile strength is 2.96GPa.

[0053] Example 2

[0054] Other conditions are the same as those in Example 1, except that: argon flow rate is 400 sccm, hydrogen flow rate is 100 sccm, methane flow rate is 5 sccm, growth temperature is 1200° C., and growth time is 300 min.

[0055] Example 3

[0056] The other conditions are the same as those in Example 1, except that: the argon flow rate is 50 sccm, the hydrogen flow rate is 150 sccm, the methane flow rate is 30 sccm, the growth temperature is 1000° C., and the growth time is 10 min.

[0057] Example 4

[0058] The other conditions are the same as those in Example 1, except that: the argon flow rate is 50 sccm, the hydrogen flow rate is 50 sccm, the ethylene flow rate is 5 sccm, the growth temperature is 1100° C., and the growth time is 20 min.

[0059] Comparative Example 1

[0060] The other conditions are the same as those in Example 1, except that the chemical vapor deposition stage is omitted.

[0061] Comparative Example 2

[0062] Other conditions are the same as those in Example 1, except that the chemical vapor deposition temperature is increased to 1250°C.

[0063] Comparative Example 3

[0064] Other conditions are the same as those in Example 1, except that the chemical vapor deposition temperature is reduced to 950°C.

[0065] Comparative Example 4

[0066] The other conditions are the same as those in Example 1, except that the chemical vapor deposition process uses only argon as a carrier gas, without using hydrogen, and the argon flow rate is 50 sccm.

[0067] Comparative Example 5

[0068] Other conditions are the same as those in Example 1, except that the chemical vapor deposition process uses a carrier gas flow rate of 600 sccm, including 300 sccm of argon and 300 sccm of hydrogen.

[0069] Comparative Example 6

[0070] The other conditions are the same as those in Example 1, except that the chemical vapor deposition process uses a methane flow rate of 1 sccm and the deposition time of the chemical vapor deposition process is 400 min.

[0071] Comparative Example 7

[0072] Other conditions are the same as those in Example 1, except that the chemical vapor deposition process uses a methane flow rate of 50 sccm and the chemical vapor deposition process deposition time is 10 min.

[0073] Comparative Example 8

[0074] The other conditions are the same as those in Example 3, except that the deposition time of the chemical vapor deposition process is 5 minutes.

[0075] The products prepared in Examples 1-4 and Comparative Examples 1-8 were characterized, and the results are summarized in Table 1:

[0076] Table 1

[0077] Graphene thickness / nm Presence or absence of amorphous carbon Single filament tensile strength / GPa Example 1 12.3 none 3.61 Example 2 3.2 none 2.93 Example 3 1.3 none 3.41 Example 4 6.4 none 3.47 Comparative Example 1 0 none 3.42 Comparative Example 2 12.7 none 1.83 Comparative Example 3 0 have 2.87 Comparative Example 4 0 have 2.32 Comparative Example 5 0 none 1.92 Comparative Example 6 0 none 1.77 Comparative Example 7 0 have 3.11 Comparative Example 8 0 none 3.39

[0078] Through the analysis and comparison of Examples 1-4 and Comparative Examples 1-8, it can be seen that the present application controls the temperature of the chemical vapor phase at 1000-1200°C, the time of chemical vapor deposition at 10-300 min, the carrier gas flow rate at 100-500 sccm, and the gaseous carbon source flow rate at 5-30 sccm, thereby preparing a graphene / silicon carbide absorbing material with moderate graphene thickness, no amorphous carbon, and high single-filament tensile strength.

[0079] The preparation of high-quality graphene silicon carbide composite fibers is limited by the temperature range. When the chemical vapor deposition temperature is lower than 1000°C, the carbon layer on the fiber surface has low crystallinity and is amorphous carbon. When the temperature is higher than 1200°C, the surface is coated with graphene, but high temperature causes the intrinsic mechanical strength of silicon carbide fibers to decrease. The preparation of high-quality graphene silicon carbide composite fibers is limited by the carrier gas flow range. When the carrier gas flow rate is lower than 50sccm, the carbon deposition rate is too fast to generate amorphous carbon. When the carrier gas flow rate is higher than 500sccm, the carbon deposition rate is slower. The preparation of carbon fibers is limited by the range of carbon source flow rate. When the methane flow rate is lower than 5 sccm, the carbon deposition rate is too slow. When the methane flow rate is higher than 30 sccm, the carbon deposition rate is faster and amorphous carbon is generated. In addition, the hydrogen-carbon ratio must be kept between 5 and 20:1. The preparation of high-quality graphene silicon carbide composite fibers is limited by the range of processing time. When the chemical vapor deposition time is lower than 10 minutes, the graphene is not completely coated. When the chemical vapor deposition time is higher than 300 minutes, the graphene thickness on the surface of the silicon carbide fiber exceeds 30 nm, and it cannot be used as an electromagnetic wave absorption layer material.

[0080] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0081] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims

1. A method for preparing a graphene / silicon carbide absorbing material, It is characterized in that The specific steps include: S1, removing glue from silicon carbide fiber; S2. growing a graphene layer on the surface of the silicon carbide fiber after the glue is removed.

2. The preparation method according to claim 1, It is characterized in that Step S1 specifically includes: immersing the silicon carbide fiber in a solvent, ultrasonically treating, washing, and drying; Wherein, the solvent is one or more of acetone, ethyl acetate, toluene and xylene.

3. The preparation method according to claim 1, It is characterized in that Step S2 specifically includes: growing a graphene layer on the surface of the silicon carbide fiber after the debonding by chemical vapor deposition.

4. The preparation method according to claim 3, It is characterized in that The temperature of the chemical vapor deposition is 1000-1200°C.

5. The preparation method according to claim 3, It is characterized in that The processing time of the chemical vapor deposition is 10 to 300 minutes.

6. The preparation method according to claim 3, It is characterized in that The carrier gas for chemical vapor deposition is one or more of argon and hydrogen, preferably a mixed gas of hydrogen and argon.

7. The preparation method according to claim 6, It is characterized in that The carrier gas flow rate is 100-500 sccm.

8. The preparation method according to claim 3, It is characterized in that The carbon source for chemical vapor deposition is a gaseous carbon source, and the flow rate of the gaseous carbon source is 5 to 30 sccm; Preferably, the gaseous carbon source is one or more of methane and ethylene.

9. The preparation method according to claim 1, It is characterized in that The silicon carbide fiber is a continuous silicon carbide fiber tow or a continuous silicon carbide fiber cloth.

10. The graphene / silicon carbide absorbing material prepared by the preparation method according to any one of claims 1 to 9.

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