Silicon carbide / graphene composite material and preparation method thereof

Abstract

The invention discloses a silicon carbide / graphene composite material and a preparation method thereof, the composite material is of a three-dimensional network structure generated through in-situ reaction of multilayer graphene and silicon powder, silicon carbide nanowires in the structure are distributed on graphene sheets, the length of the silicon carbide nanowires is 1-5 microns, the diameter of the silicon carbide nanowires is 50-100 nm, and the silicon carbide nanowires are in a beta-SiC crystal form. The material is prepared through a carbon thermal reduction method, specifically, silicon carbide nanowires grow on the surface of graphene in situ, so that electromagnetic parameters and impedance matching characteristics of the material are optimized. The prepared composite material has the characteristics of light weight, high specific surface area, good dielectric loss and the like, and shows good broadband wave-absorbing performance in the frequency band of 2-18 GHz, the minimum reflection loss can reach-23.535 dB, and the effective absorption bandwidth reaches 1.498 GHz. The method is simple in process, low in energy consumption and suitable for large-scale production, and has wide application prospects in the fields of stealth technology, electromagnetic shielding and the like.

Description

Technical Field

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

[0002] With the rapid development of electronic information technology, the application of absorbing materials in fields such as communications, radar, and stealth technology is becoming increasingly widespread. Silicon carbide (SiC) has become a promising absorbing material due to its excellent high-temperature and corrosion resistance, good mechanical properties, and electromagnetic wave absorption performance. Graphene, a two-dimensional material with excellent conductivity, strength, and lightweight, can effectively enhance its electromagnetic wave absorption performance. Existing technology indicates that silicon carbide is widely used in absorbing materials due to its dielectric loss properties, but it suffers from poor impedance matching and a narrow absorption bandwidth. Graphene, due to its high specific surface area and conductivity, can enhance electromagnetic loss, but it also suffers from poor impedance matching and a single absorption mechanism. Therefore, combining silicon carbide and graphene to achieve the synergistic effect of multiple mechanisms makes the composite material more efficient in absorbing electromagnetic waves and exhibits excellent absorption performance across a wider frequency range.

[0003] Prior art discloses a nanowire array-modified graphene honeycomb-reinforced nano-aerogel thermal insulation and wave-absorbing composite material. The composite material consists of a graphene honeycomb, silicon carbide / hafnium carbide nanowire arrays, and graphene-crosslinked carbon hollow sphere aerogel. The nanowire arrays (diameter 50-80 nm, height 2-5 μm) are vertically grown within the pores of the graphene honeycomb via chemical liquid deposition. The aerogel is produced using a sol-gel process (density 40-50 mg / cm³, specific surface area 650-800 m² / g). This material exhibits lightweight, high strength, excellent thermal insulation, and superior wave-absorbing properties. Its key advantages include: a silicon carbide coating reinforces the honeycomb matrix, a discontinuous coating blocks heat conduction, an ordered nanowire array synergistically enhances thermal insulation and wave absorption, and a porous aerogel structure inhibits heat transfer. However, the invention's complex preparation process and high energy consumption make it unsuitable for widespread industrial production.

[0004] A technology for preparing a core-shell silicon carbide-porous carbon nano-absorbent material has also been proposed. This material, based on silicon carbide nanowires and coated with a porous carbon layer, appears as a gray-black powder. During the preparation process, the pore structure of the porous carbon can be precisely controlled by adjusting the heat treatment time, thereby optimizing the material's dielectric and absorption properties. Experiments have shown that when this material is compounded with paraffin wax at a 10% mass ratio, an effective absorption bandwidth of 7.16 GHz (reflection loss <-10 dB) can be achieved at a thickness of 2.69 mm. This technology offers the advantages of a stable preparation process and ease of large-scale production. However, the silicon carbide nanowire raw material used is difficult to prepare, and the porous carbon coating requires uniform dispersion and pyrolysis, which can easily lead to uneven coating. The production process is sensitive to process parameters, making pore control difficult. The multi-step process involves multiple high-temperature treatments, and the total energy consumption may be higher than the single-step high-temperature reaction of the carbothermal reduction method.

[0005] A method for preparing epitaxial graphene on silicon carbide is disclosed. The specific steps include: 1) pre-depositing silicon atoms on the inner wall of a specialized container with an escape hole; 2) placing a silicon carbide substrate in the container and heating it to a first temperature to sublime the pre-deposited silicon to form silicon vapor; 3) further heating the container to a second temperature to encourage silicon atoms on the substrate surface to sublime and escape through the escape hole, thereby achieving graphene growth. This method increases the silicon vapor pressure within the container by pre-depositing silicon atoms, enabling initial graphene growth at a higher temperature, thereby increasing the crystal domain area, improving crystal quality and uniformity, and enabling the production of products of various specifications. However, the process is complex, requiring precise control of the two heating processes and the silicon vapor pressure, making it difficult to operate; it also requires high equipment requirements; the processing of the specialized container (such as the design of the escape hole) increases costs; and it also limits scalability.

[0006] As shown in the aforementioned patents, traditional methods for preparing composites of silicon carbide and graphene often present significant technical challenges, including complex preparation, demanding equipment, and difficulty in in-situ graphene production. Therefore, there is an urgent need to develop a novel silicon carbide / graphene composite material and its preparation method to enhance its microwave absorption performance. Summary of the Invention

[0007] In order to overcome the above shortcomings, the present invention provides a silicon carbide / graphene composite material and a preparation method thereof.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is: A silicon carbide / graphene composite material is formed by an in-situ reaction between multilayer graphene and silicon powder to form a three-dimensional network structure. In this structure, silicon carbide nanowires are distributed on graphene flakes. The silicon carbide nanowires are 1-5 μm in length, 50-100 nm in diameter, and exhibit a β-SiC crystal form.

[0009] A method for preparing a silicon carbide / graphene composite material comprises the following steps: (1) Graphene and silicon powder are placed in a porcelain boat in a molar ratio of 1:1 to 5, and the graphene is evenly covered with silicon powder. After sealing, the boat is moved into the reaction zone of a tubular furnace; (2) After evacuation, introduce inert gas at a flow rate of 100-150 mL / min; (3) The tube furnace is heated to 1300-1500°C, kept warm for 2-3 hours, and cooled to obtain a silicon carbide / graphene composite material with a three-dimensional network structure.

[0010] Further optimization, the vacuum degree of the vacuum pumping in step (2) is 10 -2 ~10 -4 Pa.

[0011] Further optimization, the inert gas in step (2) is argon or hydrogen.

[0012] Further optimization is performed in step (3) by adopting staged temperature increase under inert gas protection during the sintering process: a. Heating from 50°C to 650°C at a rate of 6-10°C / min; b. Continue to increase the temperature to 650~1500℃ at a rate of 4~5℃ / min.

[0013] Further optimization is performed, in step (3), after keeping warm, the temperature is lowered to 1000° C. at a rate of 10° C. / min, and then naturally cooled.

[0014] The beneficial effects of the present invention are: 1. The present invention adopts a carbothermal reduction method to prepare silicon carbide / graphene composite powder, which has a simple process, high yield and high purity, and is suitable for large-scale production; 2. During the sintering process, the heating rate is high during the low-temperature stage (50-650°C), which inhibits particle agglomeration and favors the formation of fine SiC nuclei. During the high-temperature stage (650-1500°C), the heating rate is slowed to promote directional growth of SiC nanowires and avoid coarsening caused by rapid reactions. Slow cooling effectively mitigates the difference in thermal expansion coefficients between SiC and graphene, preventing interfacial cracking and stabilizing the β-SiC crystal form. 3. Set the molar ratio of graphene to silicon powder to 1:1-5. Excess silicon can maintain the silicon vapor concentration during the reaction and compensate for silicon volatilization losses, avoiding incomplete reaction due to insufficient silicon. It also prevents excessive graphene from forming a continuous conductive network, which can cause electromagnetic waves to be reflected rather than absorbed by the surface. 4. The composite material has good wave absorption performance. In the 2-18GHz frequency band, when the material coating thickness is 7.5mm, the product has the maximum effective absorption bandwidth EAB max=1.498GHz, when the material coating thickness is 8mm, the product has the minimum reflection loss RL min =-23.535dB; In summary, the present invention can be widely used in the fields of electromagnetic shielding, stealth technology, etc. Compared with traditional methods, the present invention solves the technical problems of complex preparation process and low purity, and has important application value in the electronics, new energy and other industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the SEM image of silicon carbide / graphene composite powder; Figure 2 is the SEM image of silicon carbide nanowires; Figure 3 XRD image of silicon carbide / graphene composite powder; Figure 4 This is a two-dimensional graph of electromagnetic wave reflection loss at different matching thicknesses in the frequency range of 2GHz to 18GHz. DETAILED DESCRIPTION

[0016] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is described in detail below in conjunction with specific embodiments. The following embodiments are implemented based on the technical solutions of the present invention, and provide detailed implementation methods and specific operating procedures. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the following embodiments.

[0017] Example 1 (1) Weigh 0.47 g of high-purity silicon powder and spread it evenly in a porcelain boat, and evenly cover it with 0.02 g of multilayer graphene (the molar ratio of graphene to silicon powder is 1:1).

[0018] (2) Cover the porcelain boat in step (1) with a lid and carefully push it into the center of the tube furnace. Let argon flow in at 100 mL / min and sinter to 1300°C in the circulating argon. The heating rate from 50 to 650°C is 6°C / min, and the heating rate from 650 to 1300°C is 4°C / min. Keep at 1300°C for 3 h, and then cool to 1000°C at a rate of 10°C / min.

[0019] (3) Finally, the sample was taken out after cooling; the generated SiC accounted for 66.1% of the product. The coaxial method was used to test the electromagnetic wave reflection loss. The sample was prepared into a ring structure with an inner diameter of 3.04mm, an outer diameter of 7mm, and a thickness of 2mm. The powder and paraffin were evenly mixed in a mass ratio of 3:7 and then pressed into shape. The absorption performance of the coating at different thicknesses was measured in the 2~18GHz frequency band as shown in Table 1. When the coating thickness was 8mm, the RL min =-5.262dB.

[0020] Table 1 Absorption properties of different coating thicknesses at 1300℃ with C:Si=1:1 Example 2 (1) Weigh 0.47 g of high-purity silicon powder and spread it evenly in a porcelain boat, and evenly cover it with 0.02 g of multilayer graphene.

[0021] (2) Cover the porcelain boat prepared in step (1) with a lid and carefully push it into the center of the tube furnace. Let argon flow in at a rate of 100 mL / min and sinter to 1350°C in the circulating argon. The heating rate from 50 to 650°C is 6°C / min, and the heating rate from 650 to 1350°C is 4°C / min. Keep at 1350°C for 3 h, and then cool to 1000°C at a rate of 10°C / min.

[0022] (3) Finally, the sample was taken out after cooling; the generated SiC accounted for 81.3% of the product. The coaxial method was used to test the electromagnetic wave reflection loss. The sample was prepared into a ring structure with an inner diameter of 3.04mm, an outer diameter of 7mm, and a thickness of 2mm. The powder and paraffin were evenly mixed in a mass ratio of 3:7 and then pressed into shape. The absorption performance at different coating thicknesses was measured in the 2~18GHz frequency band as shown in Table 2; when the coating thickness was 8mm, it had EAB max =0.155GHz, RL min =-9.532dB.

[0023] Table 2 Absorption properties of different coating thicknesses at C:Si=1:1 and 1350℃ Example 3 (1) Weigh 0.47 g of high-purity silicon powder and spread it evenly in a porcelain boat, and evenly cover it with 0.02 g of multilayer graphene.

[0024] (2) Cover the porcelain boat in step (1) with a lid and carefully push it into the center of the tube furnace. Let argon flow in at 100 mL / min and sinter to 1400°C in the circulating argon. The heating rate from 50 to 650°C is 6°C / min, and the heating rate from 650 to 1400°C is 4°C / min. Keep at 1400°C for 3 h, and then cool to 1000°C at a rate of 10°C / min.

[0025] (3) Finally, the sample was taken out after cooling; the generated SiC accounted for 94.2% of the product. The coaxial method was used to test the electromagnetic wave reflection loss. The sample was prepared into a ring structure with an inner diameter of 3.04mm, an outer diameter of 7mm, and a thickness of 2mm. The powder and paraffin were evenly mixed in a mass ratio of 3:7 and then pressed into shape. The absorption performance at different coating thicknesses was measured in the 2~18GHz frequency band as shown in Table 3; when the coating thickness was 7.5mm, the EAB max =1.498GHz, RL when the coating thickness is 8mm min =-23.535dB (as attached Figure 4 ).

[0026] Table 3 Absorption properties of different coating thicknesses at C:Si=1:1 at 1400℃ Example 4 (1) Weigh 0.2 g of high-purity silicon powder and spread it evenly in a porcelain boat, and evenly cover it with 0.02 g of multilayer graphene (the molar ratio of graphene to silicon powder is 1:4).

[0027] (2) Cover the porcelain boat in step (1) with a lid and carefully push it into the center of the tube furnace. Let argon flow in at 100 mL / min and sinter to 1400°C in the circulating argon. The heating rate from 50 to 650°C is 6°C / min, and the heating rate from 650 to 1400°C is 4°C / min. Keep at 1400°C for 3 h, and then cool to 1000°C at a rate of 10°C / min.

[0028] (3) Finally, the sample was taken out after cooling; the generated SiC accounted for 87.1% of the product. The coaxial method was used to test the electromagnetic wave reflection loss. The sample was prepared into a ring structure with an inner diameter of 3.04mm, an outer diameter of 7mm, and a thickness of 2mm. The powder and paraffin were evenly mixed in a mass ratio of 3:7 and then pressed into shape. The absorption performance at different coating thicknesses was measured in the 2~18GHz frequency band as shown in Table 4; when the coating thickness was 7.5mm, the EAB max =1.600GHz, RL when coating thickness is 8mm min =-15.307dB.

[0029] Table 4 Absorption properties of different coating thicknesses at C:Si=1:4 at 1400℃ Example 5 (1) Weigh 0.47 g of high-purity silicon powder and spread it evenly in a porcelain boat, and evenly cover it with 0.02 g of multilayer graphene.

[0030] (2) Cover the porcelain boat in step (1) with a lid and carefully push it into the center of the tube furnace. Let argon flow in at 100 mL / min and sinter to 1400°C in the circulating argon. The heating rate from 50 to 1400°C is 6°C / min. Keep at 1400°C for 3 h and then cool to 1000°C at a rate of 10°C / min.

[0031] (3) Finally, the sample was taken out after cooling; the generated SiC accounted for 83.2% of the product. The coaxial method was used to test the electromagnetic wave reflection loss. The sample was prepared into a ring structure with an inner diameter of 3.04mm, an outer diameter of 7mm, and a thickness of 2mm. The powder and paraffin were evenly mixed in a mass ratio of 3:7 and then pressed into shape. The absorption performance of the coating at different thicknesses was measured in the 2~18GHz frequency band as shown in Table 5; when the coating thickness was 8mm, it had EAB max =1.024GHz, RL min =-15.095dB.

[0032] Table 5 Absorption performance of different coating thicknesses when C:Si=1:1 and sintering to 1400℃ without setting temperature gradient Example 6 (1) Weigh 0.47 g of high-purity silicon powder and spread it evenly in a porcelain boat, and evenly cover it with 0.02 g of multilayer graphene.

[0033] (2) Cover the porcelain boat in step (1) with a lid and carefully push it into the center of the tube furnace. Let argon flow in at 100 mL / min and sinter to 1400°C in the circulating argon. The heating rate from 50 to 650°C is 6°C / min, and the heating rate from 650 to 1400°C is 4°C / min. Keep at 1400°C for 3 h, and then cool naturally to room temperature.

[0034] (3) Finally, the sample was taken out after cooling; the generated SiC accounted for 87.9% of the product. The coaxial method was used to test the electromagnetic wave reflection loss. The sample was prepared into a ring structure with an inner diameter of 3.04mm, an outer diameter of 7mm, and a thickness of 2mm. The powder and paraffin were evenly mixed in a mass ratio of 3:7 and then pressed into shape. The absorption performance at different coating thicknesses was measured in the 2~18GHz frequency band as shown in Table 6. When the coating thickness was 7.5mm, EAB max =1.183GHz, RL when the coating thickness is 8mm min =-16.670dB.

[0035] Table 6 Absorption performance of different coating thicknesses when C:Si=1:1, 1400℃, sintered and naturally cooled to room temperature The above shows and describes the main features, methods of use, basic principles, and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and improvements may be made to the present invention based on actual circumstances without departing from the spirit and scope of the present invention. Such changes and improvements are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A silicon carbide / graphene composite material, characterized in that: A three-dimensional network structure is generated by in-situ reaction between multilayer graphene and silicon powder. Silicon carbide nanowires in the structure are distributed on the graphene sheets. The silicon carbide nanowires are 1-5 μm in length, 50-100 nm in diameter, and present a β-SiC crystal form.

2. The method for preparing a silicon carbide / graphene composite material according to claim 1, wherein: The specific steps include: (1) Graphene and silicon powder are placed in a porcelain boat in a molar ratio of 1:1 to 5, and the graphene is evenly covered with silicon powder. After sealing, the boat is moved into the reaction zone of a tubular furnace; (2) After vacuuming, introduce inert gas at a flow rate of 100-150 mL / min; (3) The tube furnace is heated to 1300-1500°C, kept warm for 2-3 hours, and then naturally cooled to room temperature to obtain a silicon carbide / graphene composite material with a three-dimensional network structure.

3. The method for preparing a silicon carbide / graphene composite material according to claim 2, wherein: The inert gas in step (2) is argon or hydrogen.

4. The method for preparing a silicon carbide / graphene composite material according to claim 2, wherein: During the sintering process in step (3), the temperature is raised in stages under the protection of an inert gas: a. Heating from 50°C to 650°C at a rate of 6-10°C / min; b. Continue to increase the temperature to 650~1500℃ at a rate of 4~5℃ / min.

5. The method for preparing a silicon carbide / graphene composite material according to claim 2, wherein: The vacuum degree of the vacuum pumping in step (2) is 10 -2 ~10 -4 Pa.

6. The method for preparing a silicon carbide / graphene composite material according to claim 2, wherein: In step (2), the inert gas is argon or hydrogen.

7. The method for preparing a silicon carbide / graphene composite material according to claim 2, wherein: After the heat preservation in step (3), the temperature is lowered to 1000°C at a rate of 10°C / min, and then naturally cooled.

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