A graphene / silicon carbide composite material and its preparation method and application in electromagnetic shielding equipment

Abstract

The present invention relates to a graphene / silicon carbide composite material, its preparation method, and its application in electromagnetic shielding equipment. The graphene / silicon carbide composite material is obtained by compounding multiple layers of graphene and silicon carbide grains. The silicon carbide grains are evenly distributed to form a thin film, and the multiple layers of graphene are densely packed on the surface and between the grain boundaries of the silicon carbide grains, forming a large number of nanoscale graphene / silicon carbide heterogeneous structures. The graphene / silicon carbide composite material provided by the present invention has high electrical conductivity, good electromagnetic shielding performance and high-temperature oxidation resistance. At a thickness of 0.45 mm, its electromagnetic shielding effectiveness is 74.2 dB, and its heat resistance index T is 0.1. HRI =330.13℃, which ensures the stability of the composite material in harsh environments and has good application prospects in fields such as electromagnetic shielding equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of shielding equipment or components for electric or magnetic fields, and specifically relates to a graphene / silicon carbide composite material, a preparation method thereof, and an application thereof in electromagnetic shielding equipment. Background Art

[0002] Due to the rapid development of communication technology and the widespread use of electronic devices, electromagnetic radiation pollution has become an increasingly serious social problem. It is harmful to precision electronics, information security, and even human health. With the rise of portable and wearable smart devices, the development of fabric-based flexible electromagnetic interference shielding materials will be greatly promoted. Integrating conductive materials on fabrics is an effective method for preparing flexible electromagnetic shielding materials. Currently, common conductive materials for modifying fabrics include conductive polymers, metal nanomaterials, MXenes, etc. However, conductive polymers have low conductivity and are easily decomposed at high temperatures. Metal nanomaterials are unstable at high temperatures, and MXenes will inevitably oxidize under ambient conditions. In addition, most textiles are easily ignited and cause fires at high temperatures. Therefore, it is crucial to find stable and efficient conductive materials to improve the high-temperature stability of conductive textiles while ensuring the functionality of conductive textiles.

[0003] SiC has good high-temperature and oxidation resistance, but its electrical conductivity is poor. Carbon materials, on the other hand, have high electrical conductivity but are susceptible to oxidation at high temperatures. Therefore, combining highly conductive carbonaceous materials with SiC to create C / SiC composites with high electrical conductivity and high temperature stability is beneficial for their application in electromagnetic shielding in high-temperature environments.

[0004] Traditional C / SiC composites are synthesized by mixing graphene oxide (GO) with SiC powder and then sintering. However, this sintering process often produces defects, significantly reducing the intrinsic conductivity of the graphene oxide. This new method combines high-quality graphene and SiC at the micro / nanoscale, promoting electromagnetic wave interface attenuation while also ensuring high conductivity and high-temperature resistance. Its application as a flexible, multifunctional device is of great significance and value. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art and provide a graphene-silicon carbide composite material, a preparation method thereof, and an application in electromagnetic shielding equipment. The graphene / silicon carbide composite material has a rich nanoscale graphene / silicon carbide heterostructure, and the multiple reflections and interface polarization at the interface improve the electromagnetic shielding performance of the composite material. At the same time, the composite material also has extremely high conductivity and high-temperature stability, and has good application prospects in the field of electromagnetic shielding equipment.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0007] Provided is a graphene / silicon carbide composite material, which is obtained by compounding multilayer graphene and silicon carbide grains. The silicon carbide grains are evenly distributed to form a thin film, and the multilayer graphene is densely filled on the surface and between the grain boundaries of the silicon carbide grains to form a large number of nanoscale graphene / silicon carbide heterostructures.

[0008] According to the above solution, the number of layers of the multi-layer graphene is 3 to 20.

[0009] According to the above scheme, the silicon carbide grains are (111) oriented and have a grain size of 10 to 30 nm.

[0010] According to the above solution, the thickness of the graphene / silicon carbide composite material is 1 to 5 μm.

[0011] The present invention also includes a method for preparing the above-mentioned graphene / silicon carbide composite material, which specifically comprises the following steps:

[0012] 1) Place the cleaned substrate into the deposition chamber of the laser chemical vapor deposition equipment and adjust the position of the substrate so that it is within the laser coverage range;

[0013] 2) Evacuate the deposition chamber to below 10 Pa, introduce H2 and a carrier gas containing the precursor, adjust the deposition pressure and stabilize it for 5 minutes;

[0014] 3) Turn on the laser to irradiate the substrate, heat the substrate surface to the deposition temperature for deposition, and turn off the precursor, carrier gas and laser in sequence after the deposition is completed. When the substrate temperature drops to 150°C, turn off H2, and then evacuate to below 20 Pa, cool the substrate to room temperature, and obtain a graphene / silicon carbide composite material on the substrate surface.

[0015] According to the above scheme, the substrate in step 1) is carbon cloth, graphite paper or graphite felt.

[0016] According to the above scheme, the precursor in step 2) is one or more of hexamethyldisilane (HMDS), methyltrichlorosilane (MTS), silicon chloride, methane, and propane.

[0017] According to the above scheme, in step 2), the purity of H2 is above 99 vol%, the flow rate is 500-2000 sccm, the carrier gas is Ar with a purity of above 99 vol%, the flow rate is 25-50 sccm, and the precursor flow rate is 3-3 sccm.

[0018] According to the above scheme, the deposition pressure in step 2) is 200-3000 Pa.

[0019] According to the above scheme, the deposition temperature in step 3) is 1400-1300° C., and the deposition time is 10-30 min.

[0020] The present invention also includes the application of the above-mentioned graphene / silicon carbide composite material in electromagnetic shielding equipment, such as aircraft electronic equipment and space protective clothing.

[0021] The present invention also includes the use of the above-mentioned graphene / silicon carbide composite material in a Joule heat sensor or a pressure sensor. The Joule heat sensor or the pressure sensor can be used as a multifunctional material to prepare personal smart medical fabrics with functions such as body temperature regulation and motion detection.

[0022] This method uses laser chemical vapor deposition to prepare a graphene / silicon carbide composite material. By adjusting deposition process parameters to control the degree of precursor decomposition, the graphene content and its distribution within the silicon carbide matrix are regulated. The resulting coating exhibits high-quality graphene with few defects, resulting in high electrical conductivity. Furthermore, the graphene and silicon carbide form a nanoscale heterostructure, and multiple reflections and interfacial polarization at the interface enhance the composite's electromagnetic shielding performance.

[0023] The beneficial effects of the present invention are as follows: 1. The graphene / silicon carbide composite material provided by the present invention has high electrical conductivity, good electromagnetic shielding performance and high temperature oxidation resistance. At a thickness of 0.45 mm, its electromagnetic shielding effectiveness is 74.2 dB, and its heat resistance index T HRI =330.13°C, which ensures the stability of the composite material in harsh environments and has good application prospects in the fields of electromagnetic shielding equipment. 2. The preparation method of the present invention is simple, time-saving and reproducible. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 XRD and Raman spectra of the graphene / silicon carbide composite materials prepared in Examples 1-2 and Comparative Example 1 of the present invention;

[0025] Figure 2 Field emission scanning microscope images of the surface and cross section of the coating material prepared in Comparative Example 1;

[0026] Figure 3 This is a field emission scanning microscope image of the graphene / silicon carbide composite material prepared in Example 1;

[0027] Figure 4 This is a transmission electron microscope image of the graphene / silicon carbide composite material prepared in Example 1;

[0028] Figure 5 A comparison chart of the electrical conductivity and electromagnetic shielding effectiveness of the graphene / silicon carbide composite materials prepared in Examples 1-2 and Comparative Example 1;

[0029] Figure 6 This is a Joule heat performance test diagram of the coated fabric in Example 1;

[0030] Figure 7 This is a test diagram of the piezoresistive performance of the coated fabric prepared in Example 2;

[0031] Figure 8 Graphs of thermogravimetric tests of the coated fabrics and the original carbon cloth substrate prepared in Examples 1-2 and Comparative Example 1. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings.

[0033] Comparative Example 1

[0034] A silicon carbide coating material, the preparation method thereof has the following specific steps:

[0035] 1) Place a cleaned carbon cloth substrate (30 mm × 20 mm × 0.3 mm) into the deposition chamber of the laser chemical vapor deposition equipment and adjust the position of the substrate so that it is within the laser coverage range;

[0036] 2) The deposition chamber was evacuated to below 10 Pa, and dilution gas H2 and carrier gas Ar containing the precursor HMDS were introduced. The H2 purity was 99.999 vol%, the H2 flow rate was 500 sccm, the Ar purity was 99.999 vol%, the Ar flow rate was 25 sccm, and the HMDS flow rate was 3 sccm. The deposition pressure was adjusted to 500 Pa and stabilized for 5 minutes.

[0037] 3) Turn on the laser to irradiate the carbon cloth substrate with a laser wavelength of 1000 nm, heat the substrate surface to 1300°C for deposition, and deposit for 20 minutes;

[0038] 4) After the deposition is completed, HMDS, carrier gas Ar and laser are turned off in sequence. When the substrate temperature shows 150°C, H2 is turned off, the vacuum is evacuated to below 20 Pa, and the substrate is cooled to room temperature to obtain a silicon carbide coating material on the substrate surface.

[0039] The XRD and Raman spectra of the coating material prepared in this comparative example are as follows Figure 1 As shown in the figure, it can be seen that the coating material prepared in this comparative example is a pure silicon carbide coating. The field emission scanning microscope imaging of the surface and cross section of the coating material prepared in this comparative example is shown in FIG. Figure 2 As shown, the carbon fiber surface is wrapped by a SiC layer with hexagonal symmetrical pyramids and columnar cross-sections, which is a typical (111) oriented SiC structure.

[0040] Example 1

[0041] A graphene / silicon carbide composite material, the preparation method of which comprises the following specific steps:

[0042] 1) Place a cleaned carbon cloth substrate (30 mm × 20 mm × 0.3 mm) into the deposition chamber of the laser chemical vapor deposition equipment and adjust the position of the substrate so that it is within the laser coverage range;

[0043] 2) The deposition chamber was evacuated to below 10 Pa, and dilution gas H2 and carrier gas Ar containing the precursor HMDS were introduced. The H2 purity was 99.999 vol%, the H2 flow rate was 500 sccm, the Ar purity was 99.999 vol%, the Ar flow rate was 25 sccm, and the HMDS flow rate was 3 sccm. The deposition pressure was adjusted to 500 Pa and stabilized for 5 minutes.

[0044] 3) Turn on the laser to irradiate the carbon cloth substrate with a laser wavelength of 1000 nm, heat the substrate surface to 1400°C for deposition, and deposit for 20 minutes;

[0045] 4) After the deposition is completed, HMDS, carrier gas Ar and laser are turned off in sequence. When the substrate temperature shows 150° C., H2 is turned off, the vacuum is evacuated to below 20 Pa, and the substrate is cooled to room temperature to obtain a graphene / silicon carbide composite material on the substrate surface.

[0046] The XRD and Raman spectra of the coating material prepared in this example are as follows Figure 1 As shown in the figure, the coating material prepared in this embodiment is composed of graphene / silicon carbide, and the I D / I G It is 0.137, indicating that graphene has fewer defects and high quality.

[0047] Figure 3 Field emission scanning microscope images of the surface and cross-section of the graphene / silicon carbide composite material prepared in this example show that the coating is deposited on the carbon fiber surface in an irregular sand dune shape, and the thickness of the coating wrapped around the carbon fiber surface is 1 to 5 μm.

[0048] Figure 4 This is a transmission electron microscope image of the graphene / silicon carbide composite material prepared in this embodiment. Figure 4 As can be seen from (a) and (b), the spacing between the two lattice fringes is 0.252nm and 0.334nm, corresponding to the 3C-SiC (111) plane and the graphene (0001) plane, respectively. Graphene shows a high degree of order, indicating a high degree of graphitization. Figure 4 (c)-(e) Figure 3(b) is an enlarged view of the corresponding box position. It can be seen from the figure that multilayer graphene (N = 3 to 20) is distributed on the surface and between the grain boundaries of SiC grains, respectively. Figure 4 As shown in (c) and (d). Figure 4 (e) It can be seen that the graphene / silicon carbide heterostructure inside the composite material is assembled at the nanoscale, with a grain size of 10 to 30 nm and good dispersion.

[0049] Example 2

[0050] A graphene / silicon carbide composite material, the preparation method of which comprises the following specific steps:

[0051] 1) Place the cleaned carbon cloth substrate into the deposition chamber of the laser chemical vapor deposition equipment and adjust the position of the substrate so that it is within the laser coverage range;

[0052] 2) The deposition chamber was evacuated to below 10 Pa, and dilution gas H2 and carrier gas Ar containing the precursor HMDS were introduced. The H2 purity was 99.999 vol%, the H2 flow rate was 500 sccm, the Ar purity was 99.999 vol%, the Ar flow rate was 25 sccm, and the HMDS flow rate was 3 sccm. The deposition pressure was adjusted to 500 Pa and stabilized for 5 minutes.

[0053] 3) Turn on the laser to irradiate the carbon cloth substrate with a laser wavelength of 1000 nm, heat the substrate surface to 1500°C for deposition, and deposit for 20 minutes;

[0054] 4) After the deposition is completed, HMDS, carrier gas Ar and laser are turned off in sequence. When the substrate temperature shows 150° C., H2 is turned off, the vacuum is evacuated to below 20 Pa, and the substrate is cooled to room temperature to obtain a graphene / silicon carbide composite material on the substrate surface.

[0055] The XRD and Raman spectra of the coating material prepared in this example are as follows Figure 1 As shown in the figure, it can be seen that the coating material prepared in this embodiment is composed of graphene / silicon carbide.

[0056] The electrical conductivity and electromagnetic shielding effectiveness of the coatings prepared in Examples 1-2 and Comparative Example 1 were characterized. Figure 5 (a) and (b) show a comparison of the electrical conductivity and electromagnetic shielding effectiveness (EMIS) of Examples 1-2 and Comparative Example 1, respectively. The conductivity of the graphene / silicon carbide composites obtained in Examples 1-2 is significantly higher than that of the pure silicon carbide-coated fabric, increasing from 14.1 S / cm to 27.9 S / cm and 37.5 S / cm, respectively, demonstrating the enhanced conductivity achieved with the introduction of graphene. Correspondingly, the Examples also exhibited a higher EMIS, achieving a 74.2 dB EMIS, significantly higher than the 59 dB achieved with the pure silicon carbide-coated fabric.

[0057] To further investigate the Joule heating performance of the coated fabric with the graphene / silicon carbide composite coating in Example 1, a Fluke infrared thermal imager was used to monitor the Joule heating temperature. The sample was cut into 20 mm x 25 mm pieces and processed into a heater. Copper foil was attached to the upper and lower surfaces of the sample and connected to a DC circuit. To eliminate contact resistance, a nanosilver paste was applied to the junction between the carbon cloth and the copper electrode. The Joule heating performance test of the coated fabric in Example 1 is shown in the figure below. Figure 3 As shown, Figure 3 (a) shows the surface temperature of the fabric over time at different supply voltages. The heater is quite susceptible to the DC voltage. At a low supply voltage (1-3V), the surface temperature rises rapidly from 24.3°C (room temperature) to 34.9°C, 49.2°C, 35.7°C, 35.3°C, and 103.7°C within 20 seconds, demonstrating the heater's rapid response. The fabric temperature then stabilizes and rapidly decreases after the voltage is turned off. Figure 3 (b) shows the surface temperature of the fabric steadily rising and falling with a repetitive driving voltage of 2.5 V over 1300 s and 30 cycles. At a given input voltage, the induced temperature of each pulse has a similar level, which demonstrates the high cycling stability and durability of the fabric as a Joule heater.

[0058] The sensing performance of the coated fabric with graphene / silicon carbide composite material coating in Example 2 was tested using a test system consisting of a computer-controlled stepper motor, a dynamometer, and a constant current source. A constant voltage was applied to the sample, and the pressure and frequency applied by the stepper motor were adjusted. The changes in the sample current at different pressures were recorded to obtain the piezoresistive properties of the fabric. The piezoresistive properties test of the coated fabric prepared in this example is shown in the figure below. Figure 7 As shown, Figure 7 (a) shows the current change (ΔI / I0) of the textile under different pressures. It can be seen that the current change of the fabric has a good linear relationship with the pressure. The fabric shows a 52.93kPa current under a low pressure below 3.1kPa. -1 The sensitivity is high, and under the high pressure of 133kPa, the sensitivity gradually decreases to 0.133kPa -1 . Figure 7(b) shows the IT curve of the fabric under increasing pressure. The voltage was applied three times at the same pressure, with loading and unloading durations of 3 seconds. The fabric exhibited good sensitivity over a wide pressure range (0.59-133 kPa), and the current value remained almost unchanged at the same pressure, demonstrating the wide pressure range, stability, and durability of the fabric as a pressure sensor. The current increases with increasing applied pressure, which is due to the increased contact area between the carbon fibers and the interlaced electrodes, resulting in a decrease in contact resistance. This is because as the applied pressure increases, the contact area between the interlaced electrodes and the carbon fibers increases, the current increases, and the contact resistance decreases.

[0059] The thermogravimetric test curves of the coated fabrics and the original carbon cloth substrate prepared in Examples 1-2 and Comparative Example 1 of the present invention are as follows: Figure 3 As shown, Figure 3 (a) and (b) show the TGA and DTG curves of the original carbon cloth and the coated fabric in air environment. It can be seen that all samples have only one degradation step, which corresponds to the oxidation process of the carbon fiber. Compared with the original carbon cloth, the initial temperature of the oxidative decomposition of the coated fabric increases from 400℃ to 700℃, indicating that the graphene / silicon carbide composite coating effectively protects the carbon fiber from oxidation. The heat resistance index T is usually used to measure the heat resistance of the carbon fiber. HRI To measure the heat resistance of the material, T HRI The calculation formula is:

[0060] T HRI =0.49×[T 5％ +0.3×(T 30％ -T 5％ )]

[0061] T 5％ With T 30％ Respectively represent the temperatures corresponding to 5% and 30% mass loss in the TGA curve. Compared with the original carbon cloth, its T HRI The increase from 244.03℃ to 330.13℃ shows a significant improvement in its high-temperature oxidation resistance, which has important application value in the field of textile-based wearable devices.

[0062] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be within the scope of protection of the present invention.

Claims

1. A graphene / silicon carbide composite material, characterized in that: The graphene / silicon carbide composite material is obtained by compounding multilayer graphene and silicon carbide grains. The silicon carbide grains are evenly distributed to form a thin film, and the multilayer graphene is densely filled on the surface and between the grain boundaries of the silicon carbide grains to form a large number of nano-scale graphene / silicon carbide heterogeneous structures. The number of multilayer graphene layers is 6 to 20. The specific steps of its preparation method are as follows: 1) Place the cleaned substrate into the deposition chamber of the laser chemical vapor deposition equipment and adjust the position of the substrate so that it is within the laser coverage range; 2) Evacuate the deposition chamber to below 10 Pa, introduce H2 and a carrier gas containing the precursor, adjust the deposition pressure to 200-3000 Pa, and stabilize for 5 minutes; 3) Turn on the laser to irradiate the substrate, heat the substrate surface to the deposition temperature for deposition, the deposition temperature is 1400-1600°C, the deposition time is 10-60 minutes, and after the deposition is completed, turn off the precursor, carrier gas and laser in sequence. When the substrate temperature drops to 150°C, turn off H2, and then evacuate to below 20Pa, cool the substrate to room temperature, and obtain a graphene / silicon carbide composite material on the substrate surface.

2. The graphene / silicon carbide composite material according to claim 1, characterized in that The silicon carbide grains are oriented in a (111) direction and have a grain size of 10 to 30 nm.

3. The graphene / silicon carbide composite material according to claim 1, characterized in that The thickness of the graphene / silicon carbide composite material is 1 to 5 μm.

4. A method for preparing the graphene / silicon carbide composite material according to any one of claims 1 to 3, characterized in that: The specific steps are as follows: 1) Place the cleaned substrate into the deposition chamber of the laser chemical vapor deposition equipment and adjust the position of the substrate so that it is within the laser coverage range; 2) Evacuate the deposition chamber to below 10 Pa, introduce H2 and a carrier gas containing the precursor, adjust the deposition pressure to 200-3000 Pa, and stabilize for 5 minutes; 3) Turn on the laser to irradiate the substrate, heat the substrate surface to the deposition temperature for deposition, the deposition temperature is 1400-1600°C, the deposition time is 10-60 minutes, and after the deposition is completed, turn off the precursor, carrier gas and laser in sequence. When the substrate temperature drops to 150°C, turn off H2, and then evacuate to below 20Pa, cool the substrate to room temperature, and obtain a graphene / silicon carbide composite material on the substrate surface.

5. The method for preparing the graphene / silicon carbide composite material according to claim 4, wherein: Step 1) The substrate is carbon cloth, graphite paper or graphite felt.

6. The method for preparing the graphene / silicon carbide composite material according to claim 4, wherein: In step 2), the precursor is one or more of hexamethyldisilane, methyltrichlorosilane, silicon chloride, methane, and propane; in step 2), the H2 purity is greater than 99 vol%, the flow rate is 500 to 2000 sccm, the carrier gas is Ar with a purity greater than 99 vol%, the flow rate is 25 to 50 sccm, and the precursor flow rate is 3 to 6 sccm.

7. Use of the graphene / silicon carbide composite material according to any one of claims 1 to 3 in electromagnetic shielding equipment.

8. Use of the graphene / silicon carbide composite material according to any one of claims 1 to 3 in a Joule heat sensor or a pressure sensor.

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