Preparation method of high-efficiency thermal insulation and wave absorption integrated light carbon-based nano aerogel

Abstract

This invention discloses a method for preparing a high-efficiency, lightweight carbon-based nano-aerogel integrating heat insulation and microwave absorption. The method includes ultrasonically dispersing a certain amount of graphene oxide and then adding it to a solution containing a chitosan crosslinking agent. A chitosan crosslinking agent-modified graphene oxide aerogel is obtained through a liquid-phase self-assembly reaction and freeze-drying. A series of two-dimensional metal-organic framework (MOF) nanoarrays with different metal ratios are in-situ grown within the modified graphene oxide aerogel via a liquid-phase reaction to obtain a composite aerogel of MOFs and graphene oxide. This composite aerogel is then subjected to high-temperature pyrolysis at a certain temperature to obtain the lightweight, heat-insulating and microwave-absorbing carbon-based nano-aerogel material. The carbon-based nano-aerogel material provided by this invention has a simple preparation process, a short preparation cycle, and is easy for industrial production. The prepared carbon-based nano-aerogel has the advantages of low density, wide absorption bandwidth, strong absorption capacity, and good heat insulation performance.

Description

Technical Field

[0001] This invention belongs to the field of composite microwave absorbing materials technology, specifically relating to a method for preparing a lightweight, high-efficiency heat insulation and microwave absorbing integrated carbon-based nano-aerogel material. Background Technology

[0002] The rapid development of flexible electronic devices has led to increasingly prominent issues such as electromagnetic radiation and interference, seriously affecting the normal operation of equipment and the secure transmission of information, and posing potential threats to human health. In particular, the continuous upgrading of 5G communication and IoT technologies, and the development of electronic devices towards portability, integration, intelligence, and refinement, have increased the demand for stable information transmission, placing higher requirements on their anti-electromagnetic interference capabilities. In the military field, the continuous development of radar detection systems, electronic countermeasures technologies, and precision-guided weapons poses a significant threat to the survivability of various military equipment and the penetration capabilities of weapon systems. Therefore, improving the stealth capabilities of weaponry is of great significance for enhancing the defensive capabilities of naval, land, and air weapons. Electromagnetic wave absorbing or shielding materials, especially flexible electromagnetic wave absorbing materials, can convert electromagnetic wave energy into other forms of energy, weaken the intensity of electromagnetic waves, prevent electromagnetic information leakage, cut off electromagnetic wave propagation, and suppress the radiation and interference of harmful electromagnetic waves; reducing the target signal of military equipment such as aircraft and ships, thereby achieving stealth. Therefore, the research and design of flexible electromagnetic wave absorbing materials has significant scientific and technological and application value. Furthermore, the integrated high-speed operation of portable electronic devices poses a fire risk due to thermal runaway caused by prolonged operation. Long-term exposure to such an environment could also cause serious health hazards. Additionally, the thermal effect exhibited by electromagnetic absorbing materials after absorbing electromagnetic waves can disrupt the operation of electronic devices and hinder the infrared stealth capabilities of military equipment. Therefore, it is necessary to design materials with thermal insulation features to prevent heat-generating components such as microprocessors from harming other components or human health, or to achieve infrared stealth. Thus, the development of lightweight, thin, wide-bandgap, high-absorption, and flexible integrated microwave absorbing and thermal insulating materials is of paramount importance to adapt to the application environments of portable electronic devices and multiple stealth materials. Summary of the Invention

[0003] This invention proposes a method for preparing lightweight and efficient integrated thermal insulation and microwave absorption carbon-based nano-aerogels using chitosan crosslinking agent-modified graphene oxide as a framework, through in-situ growth of MOF nanoarrays on its surface via liquid-phase reaction, and further through high-temperature pyrolysis. This method is simple, has a short preparation cycle, and is easy to industrialize. The prepared carbon-based nano-aerogels have the advantages of low density, wide absorption bandwidth, strong absorption capacity, and good thermal insulation performance.

[0004] I. Preparation of Integrated Thermal Insulation and Microwave Absorption Carbon-Based Nanoaerogel (CoNC / rGO)

[0005] A method for preparing a highly efficient, lightweight carbon-based nano-aerogel integrating heat insulation and microwave absorption includes the following steps:

[0006] 1) The graphene oxide dispersion and chitosan solution were mixed evenly and reacted at 20~80℃ for 2~24h. After freeze-drying, chitosan-modified graphene oxide aerogel was obtained.

[0007] The mass ratio of graphene oxide to chitosan is 1:1 to 1:4.

[0008] 2) Chitosan-modified graphene oxide aerogel was immersed in a mixed solution of metal salt and organic ligand to obtain graphene oxide composite aerogel loaded with MOF nanosheet array.

[0009] The metal salt is one or a combination of two of nickel nitrate, cobalt nitrate, and zinc nitrate, and the organic ligand is one of terephthalic acid, tribenzoic acid, or 2-methylimidazole. Preferably, the metal salt is a combination of cobalt nitrate and zinc nitrate, wherein Co is the dominant organic ligand. 2+ / Zn 2+ Based on the molar ratio, the molar ratio of cobalt nitrate to zinc nitrate is 1:3 to 3:1; the organic ligand is 2-methylimidazole.

[0010] The mass ratio of the metal salt to the organic ligand is 2:1 to 1:6.

[0011] The mass ratio of the chitosan-modified graphene oxide aerogel to the metal salt is 1:20 to 1:15.

[0012] 3) The graphene oxide composite aerogel loaded with MOF nanosheet arrays is heated to 500-1000℃ at a rate of 1-10℃ / min for high-temperature pyrolysis to obtain the lightweight carbon-based nano-aerogel material integrating heat insulation and microwave absorption. The inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0013] The preparation process of three-dimensional honeycomb porous CoNCrGO aerogel is as follows: Figure 1 As shown in Figure a. First, chitosan (CS) was selected as a crosslinking agent. The interaction between GO nanosheets was enhanced through hydrogen bonds between the amino and hydroxyl groups in CS and the oxygen-containing functional groups on the surface of graphene oxide (GO). Figure 1 b). Subsequently, the obtained CS and GO mixed slurry was transferred to a plastic mold and freeze-dried to obtain a three-dimensional porous CS-GO aerogel. Then, the prepared CS-GO was immersed in a solution containing Zn. 2+ / Co 2+ZIF-L was grown in situ on the CS-GO aerogel framework in a mixed solution of ZIF-L and organic ligands, and then freeze-dried to obtain CS-GO / ZIF-L aerogel. Finally, after carbonization, a three-dimensional vertically ordered porous carbon aerogel (CoNC / rGO aerogel) with uniformly distributed ZIF-L derivatives was obtained.

[0014] II. Structural Characterization of Integrated Thermal Insulation and Wave Absorption Carbon-Based Nanoaerogels

[0015] Taking the CoNC / rGO-1 / 1 nanoaerogel prepared in the embodiments of the present invention as an example:

[0016] like Figure 2 As shown, placing CoNC / rGO-1 / 1 aerogel on dandelion flower clusters did not cause stem deformation, confirming that CoNC / rGO-1 / 1 has significant lightweight properties. Figure 2 a). Scanning electron microscopy (SEM) characterization of CS-GO / ZIF-L and CoNC / rGO aerogels revealed that ZIF-L nanosheet arrays were uniformly and vertically distributed on the surface of graphene nanosheets, forming a hierarchical structure. Figure 2 be). Figure 2 TEM images of CoNC / rGO-1 / 1 in fi further confirm that after high-temperature pyrolysis, cobalt ions in ZIF-L are transformed into metallic cobalt nanoparticles and loaded into the ZIF-L-derived carbon framework. High-resolution transmission electron microscopy (HR-TEM) images show that the graphene nanosheets exhibit a short-range ordered amorphous structure on the substrate. Figure 2 j). In Figure 2 In m, the HR-TEM image shows a high-resolution interplanar spacing of 0.25 nm, corresponding to the (111) crystal plane of metallic Co.

[0017] like Figure 3 As shown, the SEM images reveal the microstructure of the series of CS-GO / ZIF-L aerogel samples. The results indicate that, despite varying Co contents, the prepared CS-GO / ZIF-L aerogels all maintain similar morphologies, namely, the ZIFL nanosheet array is vertically and uniformly distributed on the surface of the graphene nanosheets. Figure 3 a, 3c, 3e, 3g, 3i). After calcination at 700℃, the microstructure of different CS-GO / ZIF-L components changed significantly. Specifically, the ZIFL derivatives in CoNC / rGO-1 / 0, CoNC / rGO-3 / 1, and CoNC / rGO-1 / 1 maintained their original nanosheet morphology but underwent some shrinkage ( Figure 3 b, 3d, and 3f). The microstructure of the ZIF-L derivatives in CoNC / rGO-1 / 3 and CoNC / rGO-0 / 1 aerogels was significantly disrupted and aggregated. Figure 3 These findings highlight the significant influence of the metal ratio in ZIF-L on the final aerogel microstructure and structure during pyrolysis.

[0018] like Figure 4 As shown, the phase structure and component transitions of the CoNC / rGO aerogel were characterized by XRD. Figure 4 In a, a broad diffraction peak centered at 26.5° corresponds to the (002) crystal plane of graphitic carbon, indicating the presence of amorphous carbon in the aerogel. Furthermore, distinct diffraction peaks were detected at 44.3°, 51.3°, and 75.8°, attributed to the (111), (200), and (220) crystal planes of cubic cobalt. The diffraction peak intensities with increasing cobalt content indicate higher crystallinity and phase purity. Therefore, amorphous carbon and graphitic carbon coexist in the aerogel.

[0019] The degree of graphitization of carbon materials directly affects their electrical conductivity, playing a crucial role in determining their electromagnetic wave absorption performance. For example... Figure 4 As shown in b, the CoNC / rGO aerogel at 1356 cm⁻¹ -1 and 1577cm -1 Significant peaks were observed at the locations, corresponding to disordered carbon (D peak) and graphitized carbon (G peak) in the carbon materials, respectively. The intensity ratio of the D peak to the G peak (I0) was used. D / I G The graphitization degree was characterized by the presence of cobalt particles. The results showed that the graphitization degree of CoNC / rGO-1 / 0 and CoNC / rGO-3 / 1 with different cobalt contents was very similar, indicating that the addition of cobalt particles had the least impact on the intrinsic conductivity of the carbon framework. Compared with other samples, CoNC / rGO-1 / 0 and CoNC / rGO-3 / 1 had relatively high graphitization degrees.

[0020] The N2 adsorption and desorption curves of CoNC / rGO aerogel at 77K show a type IV isotherm. Figure 4 c). The BET specific surface areas of CoNC / rGO-1 / 0, CoNC / rGO-1 / 1, CoNC / rGO-3 / 1, CoNC / rGO-1 / 3, and NC / rGO are 82.8 m². 2 ·g -1 81.3 m 2 ·g -1 42.4 m 2 ·g -1 80.1 m 2 ·g -1 and 49.1 m 2 ·g -1 The pore size distribution curve shows that the pore size is around 3.7 nm, confirming the presence of mesoporous pores in the CoNC / rGO aerogel. Figure 4 d).

[0021] III. Performance Evaluation of Integrated Thermal Insulation and Wave Absorption Carbon-Based Nanoaerogel

[0022] 1. Absorption performance

[0023] The microwave absorption performance of the prepared lightweight carbon aerogel integrating microwave absorption and thermal insulation was tested using a vector network analyzer (VNA, N5230, Agilent Technologies, USA). The results are as follows: Figure 5 As shown, CoNC / rGO-3 / 1 and CoNC / rGO-1 / 1 exhibit the best microwave absorption performance. Specifically, CoNC / rGO-3 / 1, with a thickness of 1.8 mm, has an effective absorption bandwidth of 5.04 GHz and a maximum reflection loss of -56.6 dB at a thickness of 2.4 mm. CoNC / rGO-1 / 1, with a thickness of 1.8 mm, has an effective absorption bandwidth of 4.56 GHz and a maximum reflection loss of -58.1 dB at a thickness of 3.1 mm. Moreover, compared with chitosan-crosslinked graphene aerogels calcined under the same conditions, the microwave absorption performance of CoNC / rGO-3 / 1 and CoNC / rGO-1 / 1 is significantly improved. Furthermore, as shown in Table 1, compared with related aerogel materials in the prior art, the lightweight carbon-based aerogels involved in the embodiments of the present invention simultaneously possess thin thickness, low loading, strong absorption, and a wide effective absorption bandwidth.

[0024] Table 1 Comparison of electromagnetic wave absorption performance of different absorbing materials in the prior art

[0025]

[0026] 2. Thermal insulation performance

[0027] Figure 6 Infrared thermographic image of CoNC / rGO-3 / 1 nanoaerogel prepared according to an embodiment of the present invention. Figure 6 It can be seen that after the aerogel is placed on a hot table at 100℃ and 250℃ and heated for 1 hour, the surface temperature of the aerogel can be maintained at about 76.7℃ and 191℃ respectively, indicating that the aerogel has good thermal insulation performance.

[0028] Based on the above-mentioned excellent performance, this integrated heat insulation and wave absorption carbon-based nano-aerogel has potential application prospects in aerospace, flexible smart wearable electronic products and other fields. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the synthesis route of the lightweight carbon-based nano-aerogel that integrates heat insulation and wave absorption according to the present invention.

[0030] Figure 2In the image, (a) is a digital photograph of the CoNC / rGO-1 / 1 nanoaerogel prepared in the embodiment of the present invention, (bc) is a SEM image of CS-GO / ZIFL-1 / 1, (de) is a SEM image of CoNC / rGO-1 / 1, (fi) is a TEM image of CoNC / rGO-1 / 1, and (jm) is an HR-TEM image.

[0031] Figure 3 SEM images of a series of CS-GO / ZIFL and CoNC / rGO nanoaerogels prepared for embodiments of the present invention are shown, wherein: (a) is CS-GO / ZIFL-1 / 0, (b) is CoNC / rGO-1 / 0, (c) is CS-GO / ZIFL-3 / 1, (d) is CoNC / rGO-3 / 1, (e) is CS-GO / ZIFL-1 / 1, (f) is CoNC / rGO-1 / 1, (g) is CS-GO / ZIFL-1 / 3, (h) is CoNC / rGO-1 / 3, (i) is CS-GO / ZIFL-0 / 1, and (j) is NC / rGO.

[0032] Figure 4 (a) is the X-ray diffraction pattern of the CoNC / rGO nanoaerogel prepared in the embodiment of the present invention, (b) is the Raman spectrum, (c) is the N2 adsorption-desorption isotherm, and (d) is the pore size distribution.

[0033] Figure 5 The reflection loss diagrams of the CoNC / rGO nanoaerogels prepared in the embodiments of the present invention are shown, wherein: (a) CoNC / rGO-1 / 0, (b) CoNC / rGO-3 / 1, (c) CoNC / rGO-1 / 1, (d) CoNC / rGO-1 / 3, (e) CoNC / rGO-0 / 1, and (f) rGO-CS.

[0034] Figure 6 Infrared thermograph of CoNC / rGO-3 / 1 nanoaerogel prepared in an embodiment of the present invention. Detailed Implementation

[0035] The present invention will be further explained and described below with reference to specific embodiments. Example

[0036] (1) Synthesis of chitosan-modified graphene oxide aerogel (CS-GO)

[0037] 200 mg of chitosan powder was dissolved in 6 mL of 2% acetic acid aqueous solution and magnetically stirred for 2 h to prepare a chitosan solution. Graphene oxide was prepared by liquid-phase exfoliation-oxidation. Then, 50 mg of graphene oxide was dispersed in 4 mL of deionized water and ultrasonically dispersed for 1 h to prepare a graphene oxide dispersion. The chitosan solution and graphene oxide dispersion were mixed and reacted magnetically at 30 °C for 5 h. The mixture was then freeze-dried to prepare a chitosan-modified graphene oxide aerogel.

[0038] (2) Synthesis of graphene oxide composite aerogel supported on MOF nanosheet array

[0039] Different molar ratios of Co(NO3)2·6H2O and Zn(NO3)2·6H2O (see Table 2) and 1.301 g of 2-methylimidazole were dissolved in 40 mL of deionized water. The metal solution was then rapidly added to the 2-methylimidazole solution, and after stirring for a few minutes, the chitosan-modified graphene oxide aerogel was immersed in the mixed solution. After standing at room temperature for 4 h, the aerogel was removed and freeze-dried to obtain chitosan-modified graphene oxide aerogel loaded with MOF nanoarrays. Different samples were labeled CS-GO / ZIFL-1 / 0, CS-GO / ZIFL-3 / 1, CS-GO / ZIFL-1 / 1, CS-GO / ZIFL-1 / 3, and CS-GO / ZIFL-0 / 1, respectively.

[0040] Table 2. Content ratio of Zn(NO3)2•6H2O and Co(NO3)2•6H2O in different ZIF-Ls

[0041]

[0042] (3) Preparation of lightweight carbon-based nano-aerogel materials

[0043] The CS-GO / ZIFL-1 / 0, CS-GO / ZIFL-3 / 1, CS-GO / ZIFL-1 / 1, CS-GO / ZIFL-1 / 3 and CS-GO / ZIFL-0 / 1 obtained in step (2) were placed in a tube furnace and calcined at 700°C under nitrogen protection at a heating rate of 2°C / min to obtain CoNC / rGO aerogels. The different aerogels were labeled as CoNC / rGO-1 / 0, CoNC / rGO-3 / 1, CoNC / rGO-1 / 1, CoNC / rGO-1 / 3 and NC / rGO, respectively.

[0044] Structural characterization and performance evaluation are described above.

Claims

1. A method for preparing a high-efficiency heat insulation and microwave absorption integrated lightweight carbon-based nano-aerogel, characterized in that, Includes the following steps: 1) The graphene oxide dispersion and chitosan solution were mixed evenly and reacted at 20~80℃ for 2~24h. After freeze-drying, chitosan-modified graphene oxide aerogel was obtained. 2) The chitosan-modified graphene oxide aerogel was immersed in a mixed solution of metal salt and organic ligand, stirred at room temperature for 10-12 h, centrifuged to collect the precipitate, washed and dried to obtain graphene oxide composite aerogel loaded with MOF nanosheet array. The metal salt is a combination of cobalt nitrate and zinc nitrate, and the organic ligand is 2-methylimidazole; with Co 2+ / Zn 2+ Based on the molar ratio, the molar ratio of cobalt nitrate to zinc nitrate is greater than 1:3 and not greater than 3:1; 3) The graphene oxide composite aerogel loaded with MOF nanosheet arrays was heated to 500~1000℃ under an inert atmosphere at a rate of 1~10℃ / min to carry out high-temperature pyrolysis, thereby obtaining the lightweight carbon-based nano-aerogel material that integrates heat insulation and wave absorption.

2. The preparation method of the high-efficiency heat insulation and microwave absorption integrated lightweight carbon-based nano-aerogel as described in claim 1, characterized in that: In step 1), the mass ratio of graphene oxide to chitosan is 1:4 to 4:

1.

3. The preparation method of the high-efficiency heat insulation-wave absorption integrated lightweight carbon-based nano-aerogel as described in claim 1, characterized in that: In step 2), the mass ratio of the metal salt to the organic ligand is 2:1 to 1:

6.

4. The preparation method of the high-efficiency heat insulation and microwave absorption integrated lightweight carbon-based nano-aerogel as described in claim 1, characterized in that: In step 2), the mass ratio of the chitosan-modified graphene oxide aerogel to the metal salt is 1:20 to 1:

15.

5. The preparation method of the high-efficiency heat insulation and microwave absorption integrated lightweight carbon-based nano-aerogel as described in claim 1, characterized in that: In step 3), the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

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