A preparation method of a cobalt-nickel / graphite phase carbon nitride / reduced graphene oxide composite aerogel wave-absorbing material

Abstract

The application discloses a preparation method of a cobalt-nickel / graphitic carbon nitride / reduced graphene oxide composite aerogel wave-absorbing material. First, cobalt-nickel magnetic nano metal particles and graphitic carbon nitride are obtained through a solvothermal and thermal polymerization method; then, the cobalt-nickel magnetic nano metal particles and the graphitic carbon nitride are mixed with graphene oxide through a one-pot hydrothermal method to obtain a composite hydrogel; finally, the composite hydrogel is subjected to freeze drying and thermal annealing treatment to obtain the cobalt-nickel / graphitic carbon nitride / reduced graphene oxide composite aerogel. The composite aerogel further improves the impedance matching performance of graphene by introducing the graphitic carbon nitride, and the multiple reflection and scattering are enhanced by the porous network structure inside the aerogel, so that the composite aerogel exhibits excellent electromagnetic wave absorption performance.

Description

Technical Field

[0001] This invention relates to a method for preparing a cobalt-nickel / graphite-phase carbon nitride / reduced graphene oxide composite aerogel microwave absorbing material, belonging to the field of microwave absorbing functional materials. Background Technology

[0002] The widespread use of wireless communication and digital devices, while bringing convenience to people's lives, has also caused electromagnetic pollution. Therefore, the preparation of flexible, lightweight electromagnetic wave absorbing materials with strong absorption capacity, wide absorption bandwidth, and high absorbability has become a major research focus. Three-dimensional graphene aerogel structures formed by assembling graphene sheets possess an interconnected porous network structure, characterized by high specific surface area, high porosity, high compressibility, ultra-low density, and tunable conductivity. This not only reduces graphene aggregation and agglomeration but also lowers the dielectric constant of graphene and increases interfacial polarization. Similarly, the presence of the porous structure significantly reduces material density, enhances multiple reflections and scattering, improves impedance matching performance, and enhances electromagnetic wave absorption performance.

[0003] However, single-component graphene aerogels still have shortcomings in terms of broadband absorption and strong microwave attenuation. Introducing graphitic carbon nitride can effectively adjust the high dielectric constant of reduced graphene oxide, improving the impedance matching performance of the composite material. Furthermore, the addition of a cobalt-nickel alloy allows for synergistic effects between magnetic loss-type absorbing materials and dielectric loss-type graphene. The numerous pores and attachment sites in the graphene aerogel facilitate the loading of magnetic nanoparticles, solving the inherent problems of easy aggregation and difficulty in dispersion of magnetic nanoparticles. Magnetic nanomaterials can also optimize the structure and properties of graphene at the nanoscale. The composite aerogel exhibits optimized conductivity loss, interfacial polarization / dipole polarization, and magnetic loss, demonstrating excellent electromagnetic wave absorption performance. Summary of the Invention

[0004] The purpose of this invention is to propose a method for preparing a cobalt-nickel / graphite-phase carbon nitride / reduced graphene oxide composite aerogel microwave absorbing material. Cobalt-nickel magnetic metal nanoparticles and graphite-phase carbon nitride are obtained through solvothermal and thermal polymerization methods, respectively. Subsequently, the cobalt-nickel magnetic metal nanoparticles, graphite-phase carbon nitride, and graphene oxide are mixed and reacted using a one-pot hydrothermal method to obtain a hydrogel of the composite material. Finally, freeze-drying and thermal annealing are performed to obtain the cobalt-nickel / graphite-phase carbon nitride / reduced graphene oxide composite aerogel. This composite aerogel further improves the impedance matching performance of graphene by introducing graphite-phase carbon nitride and synergizes magnetic and dielectric loss mechanisms. Simultaneously, the porous network structure within the aerogel enhances multiple reflections and scattering, exhibiting excellent electromagnetic wave absorption performance.

[0005] The present invention discloses a method for preparing a cobalt-nickel / graphitic carbon nitride / reduced graphene oxide composite aerogel microwave absorbing material, comprising the following steps:

[0006] Step 1: Preparation of cobalt-nickel alloy

[0007] 1a. Add 1 mmol of cobalt acetate and nickel acetate, 0.5 g of polypyrrolidone and 0.4 g of sodium hydroxide to 40 ml of ethylene glycol and stir at 40 °C for 20 min to obtain a mixed solution.

[0008] 1b. Transfer the above solution to a hydrothermal reactor and react at 200°C for 9 hours. Cool to room temperature, wash repeatedly with deionized water and ethanol until neutral, and dry under vacuum to obtain a cobalt-nickel alloy.

[0009] Step 2: Preparation of graphitic carbon nitride

[0010] A certain amount of melamine was placed in a crucible and then placed in a muffle furnace. The heating time was controlled at 104 min and the heating rate was 5℃ / min. The mixture was then calcined at 550℃ for 4 h and removed when cooled to room temperature.

[0011] Step 3: Preparation of cobalt-nickel / graphite-phase carbon nitride / reduced graphene oxide composite aerogel microwave absorbing material

[0012] 3a. A certain amount of graphene oxide powder is added to deionized water and ultrasonically stirred to obtain a graphene oxide dispersion. The cobalt-nickel alloy obtained in step 1 and the graphitic carbon nitride obtained in step 2 are added to the dispersion and ultrasonically mixed to obtain a mixed solution.

[0013] 3b. The obtained mixed solution is transferred to a hydrothermal reactor and reacted at a certain temperature for a period of time. Then it is repeatedly rinsed with deionized water and ethanol. Finally, it is freeze-dried and heat-annealed to obtain the composite aerogel microwave absorbing material.

[0014] In step 3a, the concentration of the graphene oxide dispersion is 2–5 mg / mL.

[0015] In step 3a, the mass ratio of graphene oxide to graphitic carbon nitride is (3-1):1, and the mass ratio of graphene oxide to cobalt-nickel alloy is (1.5-0.75):1.

[0016] In step 3b, the reaction temperature is 180℃~200℃ and the reaction time is 12~18h.

[0017] In step 3b, freeze drying specifically involves freeze drying at -50°C for 48 hours.

[0018] In step 3b, the thermal annealing specifically involves reacting at 230°C for 2 hours in a tube furnace under a nitrogen atmosphere.

[0019] This invention effectively modulates the high dielectric constant of reduced graphene oxide by introducing graphitic carbon nitride, thereby improving the impedance matching performance of the composite material. Furthermore, the introduction of cobalt-nickel magnetic metal nanoparticles with high magnetic permeability further enhances the impedance matching performance. Moreover, the cobalt-nickel particles and layered graphitic carbon nitride adhere to the three-dimensional porous reduced graphene oxide composite aerogel, forming an 0D / 2D / 3D structure that significantly enhances interfacial reflection and scattering. This results in excellent electromagnetic wave absorption performance in the composite aerogel material even with low filler content.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention uses three-dimensional graphene aerogel as the substrate material. Compared with graphene sheets, it reduces the stacking and agglomeration of graphene, lowers the dielectric constant of graphene, increases the interfacial polarization of the material, and enhances multiple reflections and scattering.

[0022] 2. This invention introduces graphitic carbon nitride to adjust the high dielectric constant of graphene, which significantly improves the impedance matching performance of the composite material and further enhances its wave absorption performance.

[0023] 3. This invention incorporates a cobalt-nickel alloy, a magnetic loss material, to synergize magnetic and dielectric loss mechanisms, thereby optimizing the final ternary 0D / 2D / 3D composite aerogel in terms of conductivity loss, interfacial polarization / dipole polarization, and magnetic loss.

[0024] 4. The properties of the composite aerogel prepared by this invention can be controlled by changing the ratio of graphitic carbon nitride, cobalt-nickel magnetic particles, and graphene oxide, thereby achieving effective absorption of electromagnetic waves in different frequency bands. Attached Figure Description

[0025] Figure 1 A schematic diagram of the preparation process of the obtained cobalt-nickel / graphite phase carbon nitride / reduced graphene oxide composite aerogel;

[0026] Figure 2 This is a photograph of the cobalt-nickel / graphite-phase carbon nitride / reduced graphene oxide composite aerogel obtained in Example 1.

[0027] Figure 3 This is a SEM image of the cobalt-nickel / graphite phase carbon nitride / reduced graphene oxide composite aerogel obtained in Example 1.

[0028] Figure 4 The complex permittivity (ε) of the cobalt-nickel / graphite-phase carbon nitride / reduced graphene oxide composite aerogel obtained in Example 1 in the 2–18 GHz frequency band is given. r =ε′-jε″), complex permeability (μ) r =μ′-jμ″) and reflection loss (RL);

[0029] Figure 5 The complex permittivity (ε) of the cobalt-nickel / graphite-phase carbon nitride / reduced graphene oxide composite aerogel obtained in Example 2 is given in the 2–18 GHz frequency band. r =ε′-jε″), complex permeability (μ) r =μ′-jμ″) and reflection loss (RL);

[0030] Figure 6 The complex permittivity (ε) of the cobalt-nickel / graphite-phase carbon nitride / reduced graphene oxide composite aerogel obtained in Example 3 is given in the 2–18 GHz frequency band. r =ε′-jε″), complex permeability (μ) r =μ′-jμ″) and reflection loss (RL);

[0031] Figure 7 The complex permittivity (ε) of the cobalt-nickel / graphite-phase carbon nitride / reduced graphene oxide composite aerogel obtained in Example 4 is given in the 2–18 GHz frequency band. r =ε′-jε″), complex permeability (μ) r =μ′-jμ″) and reflection loss (RL);

[0032] Figure 8 The complex permittivity (ε) of the cobalt-nickel / graphite-phase carbon nitride / reduced graphene oxide composite aerogel obtained in Example 5 is given in the 2–18 GHz frequency band. r =ε′-jε″), complex permeability (μ) r =μ′-jμ″) and reflection loss (RL); Detailed Implementation

[0033] Example 1:

[0034] 1. Add 0.5 mmol of cobalt acetate, 0.5 mmol of nickel acetate, 0.5 g of polypyrrolidone and 0.4 g of sodium hydroxide to 40 ml of ethylene glycol. Stir at 40 °C for 20 min and then transfer to a hydrothermal reactor. React at 200 °C for 9 h. After cooling to room temperature, wash repeatedly with deionized water and ethanol until neutral, and then vacuum dry to obtain a cobalt-nickel alloy.

[0035] 2. Place a certain amount of melamine into a crucible, then place it into a muffle furnace, control the heating time to be 104 min, the heating rate to be 5℃ / min, and calcine at 550℃ for 4 h. Remove it when it cools down to room temperature.

[0036] 3. Add 20mg of graphene oxide powder to 10ml of deionized water, ultrasonically disperse at 30℃ for 30min, add 20mg of cobalt-nickel alloy and 20mg of graphitic carbon nitride, and mix thoroughly by ultrasonication to obtain a mixed solution.

[0037] 4. Transfer the above mixed solution to a hydrothermal reactor and react at 200°C for 12 hours. After cooling to room temperature, wash the product repeatedly with deionized water and ethanol.

[0038] 5. The obtained cobalt-nickel / graphite phase carbon nitride / reduced graphene oxide hydrogel was freeze-dried at -50℃ for 48h to obtain an aerogel, and finally reacted in a tube furnace at 230℃ for 2h under nitrogen atmosphere protection.

[0039] Example 2:

[0040] 1. Add 0.5 mmol of cobalt acetate, 0.5 mmol of nickel acetate, 0.5 g of polypyrrolidone and 0.4 g of sodium hydroxide to 40 ml of ethylene glycol. Stir at 40 °C for 20 min and then transfer to a hydrothermal reactor. React at 200 °C for 9 h. After cooling to room temperature, wash repeatedly with deionized water and ethanol until neutral, and then vacuum dry to obtain a cobalt-nickel alloy.

[0041] 2. Place a certain amount of melamine into a crucible, then place it into a muffle furnace, control the heating time to be 104 min, the heating rate to be 5℃ / min, and calcine at 550℃ for 4 h. Remove it when it cools down to room temperature.

[0042] 3. Add 30mg of graphene oxide powder to 10ml of deionized water, ultrasonically disperse at 30℃ for 30min, add 20mg of cobalt-nickel alloy and 20mg of graphitic carbon nitride, and mix thoroughly by ultrasonication to obtain a mixed solution.

[0043] 4. Transfer the above mixed solution to a hydrothermal reactor and react at 180°C for 18 hours. After cooling to room temperature, wash the product repeatedly with deionized water and ethanol.

[0044] 5. The obtained cobalt-nickel / graphite phase carbon nitride / reduced graphene oxide hydrogel was freeze-dried at -50℃ for 48h to obtain an aerogel, and finally reacted in a tube furnace at 230℃ for 2h under nitrogen atmosphere protection.

[0045] Example 3:

[0046] 1. Add 0.5 mmol of cobalt acetate, 0.5 mmol of nickel acetate, 0.5 g of polypyrrolidone and 0.4 g of sodium hydroxide to 40 ml of ethylene glycol. Stir at 40 °C for 20 min and then transfer to a hydrothermal reactor. React at 200 °C for 9 h. After cooling to room temperature, wash repeatedly with deionized water and ethanol until neutral, and then vacuum dry to obtain a cobalt-nickel alloy.

[0047] 2. Place a certain amount of melamine into a crucible, then place it into a muffle furnace, control the heating time to be 104 min, the heating rate to be 5℃ / min, and calcine at 550℃ for 4 h. Remove it when it cools down to room temperature.

[0048] 3. Add 20mg of graphene oxide powder to 10ml of deionized water, ultrasonically disperse at 30℃ for 30min, add 20mg of cobalt-nickel alloy and 10mg of graphitic carbon nitride, and mix thoroughly by ultrasonication to obtain a mixed solution.

[0049] 4. Transfer the above mixed solution to a hydrothermal reactor and react at 200°C for 12 hours. After cooling to room temperature, wash the product repeatedly with deionized water and ethanol.

[0050] 5. The obtained cobalt-nickel / graphite phase carbon nitride / reduced graphene oxide hydrogel was freeze-dried at -50℃ for 48h to obtain an aerogel, and finally reacted in a tube furnace at 230℃ for 2h under nitrogen atmosphere protection.

[0051] Example 4:

[0052] 1. Add 0.5 mmol of cobalt acetate, 0.5 mmol of nickel acetate, 0.5 g of polypyrrolidone and 0.4 g of sodium hydroxide to 40 ml of ethylene glycol. Stir at 40 °C for 20 min and then transfer to a hydrothermal reactor. React at 200 °C for 9 h. After cooling to room temperature, wash repeatedly with deionized water and ethanol until neutral, and then vacuum dry to obtain a cobalt-nickel alloy.

[0053] 2. Place a certain amount of melamine into a crucible, then place it into a muffle furnace, control the heating time to be 104 min, the heating rate to be 5℃ / min, and calcine at 550℃ for 4 h. Remove it when it cools down to room temperature.

[0054] 3. Add 30mg of graphene oxide powder to 10ml of deionized water, ultrasonically disperse at 30℃ for 30min, add 40mg of cobalt-nickel alloy and 30mg of graphitic carbon nitride, and mix thoroughly by ultrasonication to obtain a mixed solution.

[0055] 4. Transfer the above mixed solution to a hydrothermal reactor and react at 200°C for 12 hours. After cooling to room temperature, wash the product repeatedly with deionized water and ethanol.

[0056] 5. The obtained cobalt-nickel / graphite phase carbon nitride / reduced graphene oxide hydrogel was freeze-dried at -50℃ for 48h to obtain an aerogel, and finally reacted in a tube furnace at 230℃ for 2h under nitrogen atmosphere protection.

[0057] Example 5:

[0058] 1. Add 0.5 mmol of cobalt acetate, 0.5 mmol of nickel acetate, 0.5 g of polypyrrolidone and 0.4 g of sodium hydroxide to 40 ml of ethylene glycol. Stir at 40 °C for 20 min and then transfer to a hydrothermal reactor. React at 200 °C for 9 h. After cooling to room temperature, wash repeatedly with deionized water and ethanol until neutral, and then vacuum dry to obtain a cobalt-nickel alloy.

[0059] 2. Place a certain amount of melamine into a crucible, then place it into a muffle furnace, control the heating time to be 104 min, the heating rate to be 5℃ / min, and calcine at 550℃ for 4 h. Remove it when it cools down to room temperature.

[0060] 3. Add 50mg of graphene oxide powder to 10ml of deionized water, ultrasonically disperse at 30℃ for 30min, add 40mg of cobalt-nickel alloy and 40mg of graphitic carbon nitride, and mix thoroughly by ultrasonication to obtain a mixed solution.

[0061] 4. Transfer the above mixed solution to a hydrothermal reactor and react at 200°C for 12 hours. After cooling to room temperature, wash the product repeatedly with deionized water and ethanol.

[0062] 5. The obtained cobalt-nickel / graphite phase carbon nitride / reduced graphene oxide hydrogel was freeze-dried at -50℃ for 48h to obtain an aerogel, and finally reacted in a tube furnace at 230℃ for 2h under nitrogen atmosphere protection.

[0063] Figure 3 (Left) is a SEM image of the cobalt-nickel / graphite phase carbon nitride / reduced graphene oxide composite aerogel obtained in Example 1 above, showing an obvious three-dimensional porous network structure, in which a small number of cobalt-nickel alloy particles and clusters formed by the aggregation of sheet-like graphite phase carbon nitride are distributed. Figure 3 (Right) This is a further magnified view of the composite aerogel structure, where a distinct lamellar structure can be observed. Figure 4 , Figure 5 , Figure 6 The electromagnetic parameters and microwave absorption properties of the composite aerogels (samples 1-3) are shown below. It can be seen that from sample 3 to sample 1, when the cobalt-nickel alloy content in the composite aerogel remains constant, as the content of graphitic carbon nitride increases (i.e., the ratio of added graphitic carbon nitride to graphene oxide approaches 1), the dielectric constant of the composite aerogel gradually decreases, exhibiting better impedance matching performance. This is largely due to the lower dielectric constant of the added graphitic carbon nitride, which can significantly reduce the high dielectric constant of single reduced graphene oxide, thereby improving the impedance mismatch problem. Figure 4It is evident that when the filling amount of sample 1 in paraffin is only 9wt%, the minimum reflection loss of the material reaches -58.06dB at a frequency of 6.01GHz and a thickness of 5.9mm. Furthermore, at a thickness of 7.4mm, the effective absorption bandwidth (RL < -10dB) is 5.96GHz. Figure 5 It is evident that when the paraffin filling amount of sample 2 is only 9wt%, the minimum reflection loss of the material reaches -58.12dB at a frequency of 3.46GHz and a thickness of 7.9mm. At a thickness of 2.6mm, the effective absorption bandwidth (RL < -10dB) is 6.28GHz. Figure 6 It can be seen that when the filling amount of sample 3 in paraffin is only 9wt%, the minimum reflection loss of the material reaches -20.16dB at a frequency of 16.25GHz and a thickness of 2.0mm. At a thickness of 2.3mm, the effective absorption bandwidth (RL < -10dB) is 5.92GHz. Figure 7 When sample 4 had a paraffin filling amount of only 9 wt%, at a frequency of 14.28 GHz and a thickness of 2.4 mm, the material achieved a minimum reflection loss of -56.25 dB. At a thickness of 2.5 mm, the effective absorption bandwidth (RL < -10 dB) was 6.96 GHz, almost covering the entire Ku band (12–18 GHz) and 28% of the X band (8–12 GHz). Figure 8 When the filling amount of sample 5 in paraffin was only 9wt%, the minimum reflection loss of the material reached -26.27dB at a frequency of 3.84GHz and a thickness of 5.9mm. At a thickness of 2.1mm, the effective absorption bandwidth (RL < -10dB) was 6.28GHz. This shows that increasing the concentration of graphene oxide weakens the reduction of the high dielectric constant of the graphitic carbon nitride phase to some extent, resulting in a decrease in impedance matching performance.

Claims

1. A method for preparing a cobalt-nickel / graphite-phase carbon nitride / reduced graphene oxide composite aerogel microwave absorbing material, characterized in that: First, cobalt-nickel magnetic nanoparticles and graphitic carbon nitride were obtained by solvothermal and thermal polymerization methods, respectively. Then, the cobalt-nickel magnetic nanoparticles, graphitic carbon nitride, and graphene oxide were mixed and reacted using a one-pot hydrothermal method to obtain a composite hydrogel. Finally, freeze-drying and thermal annealing were performed to obtain a cobalt-nickel / graphitic carbon nitride / reduced graphene oxide composite aerogel. The composite aerogel further improves the impedance matching performance of graphene by introducing graphitic carbon nitride, and at the same time, the porous network structure inside the aerogel enhances multiple reflections and scattering, exhibiting excellent electromagnetic wave absorption performance. Includes the following steps: Step 1: Preparation of cobalt-nickel alloy 1a. Add 1 mmol of cobalt acetate and nickel acetate, 0.5 g of polypyrrolidone and 0.4 g of sodium hydroxide to 40 ml of ethylene glycol and stir at 40 °C for 20 min to obtain a mixed solution. 1b. The above solution was transferred to a hydrothermal reactor for hydrothermal reaction at a temperature of 200°C for 9 hours. After the reaction was completed, the solution was cooled to room temperature and washed repeatedly with deionized water and ethanol until neutral. The solution was then dried under vacuum to obtain a cobalt-nickel alloy. Step 2: Preparation of graphitic carbon nitride A certain amount of melamine was placed in a crucible, then placed in a muffle furnace, heated to 550°C and calcined for 4 hours, and then removed when cooled to room temperature. Step 3: Preparation of cobalt-nickel / graphite-phase carbon nitride / reduced graphene oxide composite aerogel microwave absorbing material 3a. A certain amount of graphene oxide powder is added to deionized water and ultrasonically stirred to obtain a graphene oxide dispersion. The cobalt-nickel alloy obtained in step 1 and the graphitic carbon nitride obtained in step 2 are added to the dispersion and ultrasonically mixed to obtain a mixed solution. 3b. The obtained mixed solution is transferred to a hydrothermal reactor and reacted at a certain temperature for a period of time. After repeated rinsing with deionized water and ethanol, the solution is finally freeze-dried and heat-annealed to obtain the composite aerogel microwave absorbing material. In step 3a, the mass ratio of graphene oxide to graphitic carbon nitride is (3~1):1, and the mass ratio of graphene oxide to cobalt-nickel alloy is (1.5~0.75):

1. In step 3b, the reaction temperature is 180℃~200℃ and the reaction time is 12~18h.

2. The preparation method according to claim 1, characterized in that: In step 1a, the molar ratio of cobalt acetate to nickel acetate is 1:

1.

3. The preparation method according to claim 1, characterized in that: In step 2, the heating rate is 5℃ / min.

4. The preparation method according to claim 1, characterized in that: In step 3b, the thermal annealing specifically involves reacting at 230°C for 2 hours in a tube furnace under a nitrogen atmosphere.

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