SiC-coated CoSe2-VSe nano composite material and preparation method thereof

Abstract

The invention discloses a preparation method of a SiC (at) CoSe2-VSe wave-absorbing material containing a large amount of Se vacancies. The preparation method comprises the following steps: loading a cobalt precursor on the surface of a SiC nanowire through a hydrothermal method, calcining by using a muffle furnace to prepare a SiC-coated Co3O4 nano composite material, converting cobalt oxide into cobalt selenide through a hydrothermal method, putting the product into a reductive KBH4 solution, and regulating and controlling a vacancy to obtain the SiC-coated CoSe2-VSe wave-absorbing material. CoSe2 is added, so that the material has good impedance matching, a CoSe2 nanosheet is formed on the SiC nanowire, a phase interface is also generated in the structure, and extra charges and dipoles are introduced into all defects and interfaces, so that the dielectric loss is enhanced, dipole polarization is generated by taking various defect structures as dipole centers, and the dielectric loss is reduced. The device plays an important role in attenuation of incident electromagnetic waves. Due to the synergistic effect of the multiple losses, the designed SiC-coated CoSe2 nano composite material with the vacancy has excellent electromagnetic wave absorption performance. A good foundation is provided for development of SiC-based materials, and a good design thought is provided for preparation of electromagnetic wave absorbing materials. Various problems caused by current electromagnetic pollution can be well solved due to the excellent performance of the composite material, and the composite material has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of nanocomposite materials and electromagnetic wave absorption technology, and specifically relates to a SiC@CoSe2-V nanocomposite containing a large number of Se vacancies. Se Method for preparing nanocomposite materials. Background Art

[0002] In today's information age, an increasing number of technological products are influencing people's lives. With the widespread adoption of technologies like 5G, the Internet of Things, and autonomous driving, electromagnetic wave frequency bands are becoming increasingly dense, leading to increasingly significant electromagnetic interference (EMI) and electromagnetic radiation issues. This interference not only affects the normal operation of electronic devices, but excessive exposure to electromagnetic waves can also pose potential risks to human health. Given this reality, the development of ideal "thin, light, wide, and strong" absorbing materials to effectively absorb electromagnetic waves and thus reduce electromagnetic pollution has become a crucial research topic and a current hot topic.

[0003] SiC nanowires are a semiconductor material widely recognized for their exceptional optical, electromagnetic, and mechanical properties. They are also attracting significant attention as a direct electromagnetic wave absorber due to their superior performance and simple, controllable preparation methods. SiC is a typical dielectric material with no magnetic loss. SiC nanowires exhibit extensive dipole and interface polarization. Surface defects generate localized dipoles, which undergo relaxation polarization under an alternating electric field, converting electromagnetic energy into other forms of energy, such as heat. The high aspect ratio and large surface area of the nanowire form expose more active sites, and the randomly arranged three-dimensional grid structure causes multiple losses and scattering of electromagnetic waves between pores and interfaces, enhancing the material's microwave absorption capacity. However, the single loss mechanism of SiC nanowires also limits their effective electromagnetic wave absorption. When used alone, they lack good impedance matching, have a narrow absorption bandwidth, and fall short of ideal electromagnetic wave absorption. To improve the impedance matching performance of absorbing materials, researchers have proposed combining them with other materials. This strategy significantly enhances absorbing performance through synergistic effects, fully utilizing the advantages of various materials in electromagnetic absorption, optimizing impedance matching, enhancing interfacial polarization effects, and making the material's structure more flexible. Among various absorbing materials, transition metal selenides have become a research hotspot in the field due to their low cost, abundant reserves, high capacity, and good conductivity. Co3O4 is a typical magnetic loss microwave absorbing material, but the absorption width is narrow after being compounded with SiC nanowires, and it is difficult to achieve a balance between RL and EAB. Cobalt diselenide (CoSe2) is a typical pyrite-type metal transition metal chalcogenide compound with good electrical and dielectric properties, and has both semiconductor and metal-like properties. Its high carrier mobility can significantly enhance conductive loss, and it also has good stability and can adapt to more complex environments. Compared with Co3O4 materials, the magnetic loss of CoSe2 materials is almost negligible, mainly through the mechanism of dielectric loss, but more vacancies can be controlled. After compounding, multiple mechanisms can be enhanced and impedance matching can be optimized to achieve the preparation of ideal electromagnetic absorbing materials. Summary of the Invention

[0004] The purpose of the present invention is to provide a SiC@CoSe2-V containing a large number of Se vacancies Se A method for preparing a high-efficiency electromagnetic wave absorbing material, the specific invention content is as follows:

[0005] 1. Using SiC nanowires as carriers, the hydrothermal method and muffle furnace calcination were used multiple times to synthesize SiC@CoSe2 nanocomposites. The materials were then regulated to create vacancies in a reducing solution to finally obtain SiC@CoSe2-V Se The absorbing material is prepared by the following method:

[0006] (1) Cut the carbon fiber cloth loaded with SiC nanowires into 3 cm × 4 cm pieces and soak it in a 3 mol / L NaOH aqueous solution for 2 hours to remove some impurities such as SiO2, increase surface activity, and introduce a large number of functional groups. After soaking, remove the carbon cloth and rinse it with deionized water until the pH value is about 7 to ensure that the residual NaOH is washed away. Then rinse it with anhydrous ethanol and finally place the treated carbon fiber cloth in an oven for drying.

[0007] (2) Dissolve 4.5 mmol Co(NO3)2·6H2O, 4 mmol NH4F, and 20 mmol CO(NH2)2 in 45 mL of deionized water and stir for 20 min to ensure complete dissolution. The solution is then transferred to a 100 mL reactor and pretreated carbon cloth loaded with SiC nanowires is added. The reaction is continued at 110°C for 3 h. After completion, the product is calcined in a muffle furnace to obtain a SiC@Co3O4 nanocomposite.

[0008] (3) Weigh a certain amount of NaOH and Se powder and dissolve them in 35 mL of deionized water to prepare a solution of a certain concentration. Place the solution in a reactor and perform a hydrothermal reaction at 220 °C for 24 h to ensure that the reaction proceeds fully.

[0009] (4) The SiC@Co3O4 material obtained in step (2) was placed in the solution obtained in step (3) and placed in a reactor again for hydrothermal reaction. The oven temperature was kept at 220°C for 12 hours to obtain a SiC@CoSe2 nanocomposite material.

[0010] (5) The SiC@CoSe2 nanocomposite material obtained in step (4) is placed in a 0.1 mol / L KBH4 solution, and a reduction reaction is performed to control vacancies to obtain the nanocomposite absorbing material SiC@CoSe 2- V Se .

[0011] 2. Nanocomposite absorber SiC@CoSe 2- V Se When the thickness is 1.90mm, the minimum reflection loss reaches -50.23dB, and when the thickness is 2.03mm, the EAB is 7.84GHz, showing excellent electromagnetic wave absorption performance.

[0012] The present invention discloses a SiC@CoSe2-V containing a large number of Se vacancies Se High-efficiency electromagnetic wave absorbing materials have the following advantages:

[0013] (1) The three-dimensional conductive network constructed by SiC nanowires is conducive to multiple reflections and scattering of incident electromagnetic waves, and provides a good channel for the migration and jumping of surface electrons, thereby enhancing conductive losses;

[0014] (2) The formation of CoSe2 nanosheets on SiC nanowires will produce phase interfaces in the structure, thereby introducing additional charges and dipoles, which will enhance the dielectric loss;

[0015] (3) The appearance of selenium vacancies gives the material a higher specific surface area and porosity, which allows for more effective reflection, scattering, and absorption of incident electromagnetic waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The absorbing material SiC@CoSe prepared in Example 1 2- V Se SEM image of .

[0017] Figure 2 The absorbing material SiC@CoSe prepared in Example 1 2- V Se TEM and HRTEM images.

[0018] Figure 3 The absorbing material SiC@CoSe prepared in Example 1 2- V Se XRD pattern of .

[0019] Figure 4 The absorbing material SiC@CoSe prepared in Example 1 2- V Se XPS spectrum of .

[0020] Figure 5 The absorbing material SiC@CoSe prepared in Example 1 2- V Se reflection loss.

[0021] Figure 6 The absorbing material SiC@CoSe prepared in Example 1 2- V Se electromagnetic parameters. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to specific examples, but these examples are not intended to limit the scope of the present invention in any way.

[0023] Example 1

[0024] The electromagnetic wave absorbing material SiC@CoSe2-V containing a large number of Se vacancies described in this embodiment SeThe preparation method comprises the following steps:

[0025] (1) Cut the carbon fiber cloth loaded with SiC nanowires into 3 cm × 4 cm pieces and soak it in a 3 mol / L NaOH aqueous solution for 2 hours to remove some impurities such as SiO2, increase surface activity, and introduce a large number of functional groups. After soaking, remove the carbon cloth and rinse it with deionized water until the pH value is about 7 to ensure that the residual NaOH is washed away. Then rinse it with anhydrous ethanol and finally place the treated carbon fiber cloth in an oven for drying.

[0026] (2) Dissolve 4.5 mmol Co(NO₃)₂·6H₂O, 4 mmol NH₄F, and 20 mmol CO(NH₂)₂ in 45 mL of deionized water and stir for 20 min to ensure complete dissolution. The solution is then transferred to a 100 mL reactor and reacted at 110°C for 3 h. The product is then placed in a muffle furnace and heated at 300°C for 2 h to obtain a SiC@Co₃O₄ nanocomposite.

[0027] (3) Weigh 3 g of NaOH and 0.4 g of Se powder and dissolve them in 35 mL of deionized water to prepare a solution of a certain concentration. Place the solution in a reactor and perform a hydrothermal reaction at 220 °C for 24 h to ensure that the reaction proceeds fully.

[0028] (4) The SiC@Co3O4 material obtained in step (2) was placed in the solution obtained in step (3) and placed in a reactor again for hydrothermal reaction. The oven temperature was kept at 220°C for 12 hours to obtain a SiC@CoSe2 nanocomposite material.

[0029] (5) The SiC@CoSe2 nanocomposite material obtained in step (4) is placed in a 0.1 mol / L KBH4 solution to perform a reduction reaction to modulate Se vacancies to obtain the nanocomposite absorbing material SiC@CoSe 2- V Se .

[0030] The SEM images of the absorbing material at different magnifications are shown in the accompanying drawings of the specification. Figure 1 As shown in Figure 2, CoSe2 nanosheets are uniformly grown on the surface of SiC nanowires, increasing the average diameter of SiC nanowires to about 1.5 μm. Figure 2 It can be seen that the nanosheets are clearly fixed on the surface of the SiC nanowires. The marked lattice spacing of the nanosheets is 0.190nm, 0.260nm, 0.290nm and 0.373nm, which can be assigned to the (211), (111), (101) and (110) crystal planes of the CoSe2 phase respectively. The multiple bright and dark points in the figure are the Se vacancies generated during the reduction process. Figure 3XRD shows that the diffraction peaks at 23.8°, 29.0°, 30.8°, 34.5°, 36.0°, 40.4°, 44.0°, 47.7°, 50.2°, 53.5°, 56.9°, and 63.3° correspond to the (110), (011), (101), (111), (120), (210), (121), (211), (002), (031), (131), and (122) crystal planes of orthorhombic CoSe2 (JCPDS No. 53-0449), respectively. The absence of a large number of other additional peaks also indicates that CoSe2 has a high degree of crystallinity. This result proves the presence of CoSe2 in the sample and its structural characteristics have been effectively verified. Figure 4 The XPS spectrum shows the surface state and chemical valence state of the material.

[0031] The electromagnetic wave absorption performance test of the product is tested and analyzed by vector network analyzer. The product is mixed with paraffin in a certain proportion to make a coaxial ring with an outer diameter of 7mm, an inner diameter of 3mm and a thickness of 2mm. The electromagnetic wave absorption performance test is carried out using the coaxial measurement method. Figure 5 The RL is the wave absorbing performance of the material. It can be seen that when the thickness is 1.90 mm, min It reaches -50.23dB, and when the matching thickness is 2.03mm, the EAB is 7.84GHz, showing excellent electromagnetic wave absorption performance. Figure 6 The electromagnetic parameters of the material are good, and the dielectric loss capacity, attenuation constant and impedance matching are good, which is mainly due to the introduction of CoSe2, which changes the defect structure of the material and the synergistic effect of multiple losses.

Claims

1. A SiC@CoSe2-V with a large number of Se vacancies Se High-efficiency electromagnetic wave absorbing material, characterized in that: The SiC@CoSe2 nanocomposite material was synthesized by repeated hydrothermal method and muffle furnace calcination. The vacancies of the material were then regulated in a reducing solution to finally obtain SiC@CoSe2-V Se The absorbing material is characterized by being prepared by the following method: (1) Cut the carbon fiber cloth loaded with SiC nanowires into 3 cm × 4 cm pieces and soak it in a 3 mol / L NaOH aqueous solution for 2 hours to remove some impurities such as SiO2, increase surface activity, and introduce a large number of functional groups. After soaking, remove the carbon cloth and rinse it with deionized water until the pH value is about 7 to ensure that the residual NaOH is washed away. Then rinse it with anhydrous ethanol and finally place the treated carbon fiber cloth in an oven for drying. (2) Dissolve appropriate amounts of Co(NO₃)₂·6H₂O, NH₄F, and CO(NH₂)₂ in 45 mL of deionized water and stir for 20 min to ensure complete dissolution. The solution is then transferred to a reactor and pretreated carbon cloth loaded with SiC nanowires is added. The reaction is continued at 110°C for 3 h. The product is then calcined in a muffle furnace to obtain a SiC@Co₃O₄ nanocomposite. (3) Weigh a certain amount of NaOH and Se powder and dissolve them in 35 mL of deionized water to prepare a solution of a certain concentration. Place the solution in a reactor and perform a hydrothermal reaction at 220 °C for 24 h to ensure that the reaction proceeds fully. (4) The SiC@Co3O4 material obtained in step (2) is placed in the solution obtained in step (3) and placed in a reactor again for hydrothermal reaction to obtain a SiC@CoSe2 nanocomposite material. (5) The SiC@CoSe2 nanocomposite material obtained in step (4) is placed in a KBH4 solution of a certain concentration, and a reduction reaction is performed to control vacancies to obtain the nanocomposite absorbing material SiC@CoSe 2- V Se .

2. The absorbing material SiC@CoSe2-V according to claim 1 Se , characterized in that, The amounts of solute used in step (2) were 4.5 mmol Co(NO3)2·6H2O, 4 mmol NH4F and 20 mmol CO(NH2)2.

3. The absorbing material SiC@CoSe2-V according to claim 1 Se , characterized in that, In step (2), the material is calcined in a muffle furnace at a temperature of 300° C. for 2 h.

4. The absorbing material SiC@CoSe2-V according to claim 1 Se , characterized in that, The amounts of solute used in step (3) were 3 g NaOH and 0.4 g Se powder.

5. The absorbing material SiC@CoSe2-V according to claim 1 Se , characterized in that, The hydrothermal reaction conditions used in step (4) are 220° C. for 12 h.

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