Preparation method of multi-stage pore broadband wave-absorbing material derived based on hollow graphene foam / metal organic framework
By preparing a multi-stage pore composite material of hollow graphene foam and metal organic frame, the problems of dispersion of the wave absorbing material and insufficient conductive network loss are solved, and ultra-light and wide-band wave absorbing performance are achieved.
Patent Information
- Application Number
- CN202510436214.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-09
- Publication Date
- 2025-08-22
AI Technical Summary
Existing absorbing materials have shortcomings in lightweight, wide band and low fill volume, especially the problems of poor MOF dispersion and insufficient conducting network loss capability.
Hollow graphene foam was prepared by chemical vapor deposition method, and nanoparticles with ZIF-8@ZIF-67 core-shell structure were coated on its surface, and Ni ion exchange-enhanced magnetic coupling network was carried out to form a porous carbon structure embedded in Co/Ni nanoparticles, forming a three-dimensional hybrid composite material with multi-stage pores.
It realizes ultra-light and wide-band wave absorption performance. Composite materials with multi-stage pore structures can effectively absorb electromagnetic waves, have ultra-wide effective absorption bandwidth and excellent impedance matching.
Smart Images
Figure CN120519123A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of functional composite materials, in particular to a method for preparing a broadband wave-absorbing material with multi-level pores derived from hollow graphene foam / metal organic framework. Background Art
[0002] With the rapid development of mobile communications, the Internet of Things, and high-frequency radar systems, electromagnetic radiation pollution and inter-device electromagnetic interference have become global challenges that remain unresolved. Researchers have explored a wide range of absorbing materials. While traditional ferrites and magnetic metals exhibit excellent magnetic loss characteristics, their high density, narrow effective absorption bandwidth, and high content loading requirements severely limit their application in lightweight applications such as aerospace and wearable devices. Therefore, it is crucial to develop new electromagnetic wave absorbing materials that combine lightweight, broadband, and low filler requirements through innovative composition and structure.
[0003] To achieve thin, light, wide, and strong microwave absorbing materials, the development of lightweight materials and composite structures has attracted widespread attention. Compared with traditional microwave absorbing materials, the recently developed carbon-based materials offer a promising approach for fabricating ultrathin, multifunctional, and high-performance microwave absorbing materials due to their large specific surface area, light weight, excellent dielectric properties, high conductivity, and stability under harsh conditions. However, they still suffer from impedance mismatch, easy agglomeration, and difficulty dispersing. Metal-organic frameworks (MOFs), as a new type of microwave absorbing material, have been widely reported due to their strong designability, uniform pores, and the coexistence of dielectric and magnetic losses. However, the matching thickness is large, and MOF particles are prone to agglomeration. A single material generally cannot meet the requirements of wide bandwidth and strong absorption. In recent years, composite approaches have been developed to construct composite absorbers, combining multiple loss mechanisms to compensate for each other's shortcomings and achieve improved microwave absorbing performance. However, problems still exist, such as poor dispersion and easy coating shedding.
[0004] Compared with traditional absorbing coatings, the new generation of absorbing materials has the characteristics of structural and functional integration. The method of supporting functional particles on a continuous carbon matrix developed thereby can effectively solve the problems of poor dispersibility and easy falling off. In recent years, progress has been made in the areas of functional particle-supported carbon fiber non-woven fabrics, carbon fiber fabrics, and interlayers, and porous foam structures (aerogels) have been developed, which utilize multiple reflections and scattering to enhance electromagnetic wave attenuation while reducing material density. For example, a Chinese invention patent (publication number CN119613892A) proposes a PVC structural foam and a preparation method thereof, wherein modified carbon nanotubes with carboxyl or hydroxyl functional groups and conductive carbon black are added to the PVC structural foam system, and the intermolecular force between the modified carbon nanotubes and the conductive carbon black is utilized to coat the conductive carbon black, improve dispersibility, and form a conductive network, thereby solving the problem that the conductive carbon black has poor dispersibility in the PVC structural foam system and the absorbing performance of the carbon nanotubes decreases after modification. In addition, a study (Carbon178(2021)320e331) has grown a bimetallic ZIFs superstructure on cotton fiber cloth, leveraging the coupling effect of highly conductive carbon fiber cloth and hollow Co3O4 to achieve an effective absorption bandwidth of 11.6 GHz and a minimum reflection loss of -36 dB. However, the network structures used in the above work are mostly composed of graphene oxide or turbostratic carbon fibers, which have problems such as insufficient conductivity loss and poor interface bonding, which limit their application. Summary of the Invention
[0005] The purpose of the present invention is to provide a method for preparing a broadband absorbing material with multi-level pores derived from hollow graphene foam / metal organic framework, aiming to solve the problems of poor dispersibility of MOF and insufficient loss capacity of conductive network.
[0006] In order to achieve the above technical objectives, the technical solution of the present invention is:
[0007] A method for preparing a broadband absorbing material with multi-level pores derived from hollow graphene foam / metal-organic frameworks. The broadband absorbing material is composed of a composite of macroporous hollow graphene foam and porous carbon derived from a cavity metal-organic framework. First, a hollow graphene foam with a macroporous structure is prepared by chemical vapor deposition and then etched from an original nickel skeleton. Subsequently, nanoparticles with a ZIF-8@ZIF-67 core-shell structure are coated on the surface of the foam and a magnetic Ni ion exchange is performed to enhance the magnetic coupling network. The Zn cores are then carbonized and evaporated at high temperature to obtain a porous carbon structure embedded with Co / Ni nanoparticles. This results in a three-dimensional hybrid composite material with a multi-level pore structure. After combined packaging, the composite material forms an ultralight, broadband absorbing material.
[0008] The method for preparing a broadband absorbing material with multi-level pores derived from a hollow graphene foam / metal organic framework comprises preparing the hollow graphene foam by chemical vapor deposition, followed by etching with a hydrochloric acid-ethanol mixed solution to remove the template, wherein the volume ratio of the hydrochloric acid-ethanol mixed solution is 1:4-10; the obtained graphene foam has a pore size of 200-500 μm, a porosity of 95-99%, a number of graphene layers of 1-10, and a density of 1.25-3.35 mg / cm 3 .
[0009] The method for preparing a broadband absorbing material with multi-level pores derived from a hollow graphene foam / metal-organic framework is described. The ZIF-8@ZIF-67 core-shell structure is grown and prepared by chemical vapor deposition, hydrothermal synthesis, or sol-gel method. The metal-organic framework particle size is 300 to 700 nm, and the molar ratio of ZIF-8 to ZIF-67 is 1:0.5 to 1.5.
[0010] The method for preparing the broadband wave absorbing material with multi-level pores derived from hollow graphene foam / metal organic framework is characterized in that magnetic Ni ion exchange enhances magnetic loss capability, wherein the molar ratio of Ni and Co ions is 1:0.5-1.5.
[0011] The method for preparing a broadband absorbing material with multi-level pores derived from hollow graphene foam / metal organic frameworks is as follows: when Co / Ni nanoparticles are embedded in a porous carbon structure, the carbonization temperature is 800-1000°C, the holding time is 1-3 hours, the heating rate is 3-8°C / min, and the inert atmosphere is one of argon or nitrogen.
[0012] The method for preparing a broadband absorbing material with multi-level pores derived from hollow graphene foam / metal organic framework comprises a multi-level pore structure including micropores and mesopores of 0.5 to 30 nm formed by carbonization of organic ligands of the metal organic framework, cavities of 400 to 700 nm generated by volatilization of the Zn element, and a connected macroporous graphene skeleton of 200 to 500 μm.
[0013] The method for preparing a broadband absorbing material with multi-level pores derived from hollow graphene foam / metal organic framework is as follows: the three-dimensional hybrid composite material with a multi-level pore structure is combined and packaged using one of polydimethylsiloxane, paraffin wax, and epoxy resin as a filling matrix, and the mass fraction of the filling matrix is 80-95%.
[0014] The method for preparing a broadband absorbing material with multi-level pores derived from hollow graphene foam / metal organic framework, wherein the mass fractions of the hollow graphene foam, the cavity metal organic framework and the flexible matrix are 1-15wt%, 1-10wt% and 80-95wt% respectively.
[0015] The method for preparing the broadband absorbing material with multi-level pores derived from hollow graphene foam / metal organic framework is described. The broadband absorbing material is used as a broadband electromagnetic wave absorbing material in the preparation of radar stealth coatings, electromagnetic shielding devices or 5G communication equipment.
[0016] The design idea of the present invention is:
[0017] Focusing on the key issues of poor dispersibility and insufficient loss capacity of traditional MOF system absorbing materials, the present invention proposes a broadband absorbing material with multi-level pores derived from hollow graphene foam / metal organic framework. The present invention utilizes chemical vapor deposition to prepare and then etches the original nickel skeleton to obtain a hollow graphene foam with a macroporous structure. Subsequently, nanoparticles with a core-shell structure of ZIF-8@ZIF-67 are coated on its surface and Ni ion exchange is performed to enhance the magnetic coupling network. The Zn core is then carbonized and directionally etched to obtain a porous carbon structure embedded with Co / Ni nanoparticles, ultimately obtaining a three-dimensional hybrid composite material with a multi-level pore structure. After combined packaging, an ultra-light, broadband absorbing material is formed. The composite material has both light weight and broadband absorption, which is mainly attributed to the following points: the multi-level pore structure between the graphene foam and MOF promotes multiple reflections of electromagnetic waves while reducing material density, the efficient graphene conductive network promotes conductivity loss, and the magnetic Ni ion exchange promotes low-frequency loss and improves impedance matching, which helps to achieve broadband absorption. The synergistic effect of the above aspects can give full play to the advantages of graphene's efficient conductive network porous MOF and significantly improve the wave absorption performance of the composite material.
[0018] Compared with the prior art, the advantages and beneficial effects of the present invention are:
[0019] 1. This invention combines a highly efficient graphene conductive network with a porous MOF. The three-dimensional graphene network improves the MOF's dispersibility and reduces conductivity losses. Simultaneously, the multi-level pore structure of the two facilitates multiple reflections of electromagnetic waves and reduces material density. Furthermore, the magnetic Ni ion exchange effect helps form a highly efficient magnetic coupling network, promoting low-frequency loss and improving impedance matching, resulting in an ultra-wide effective absorption bandwidth for the absorbing material.
[0020] 2. The present invention uses graphene foam prepared by chemical vapor deposition as a conductive network. On the one hand, compared with the currently widely reported graphene oxide network, it has stronger conductivity loss and is a lighter and more efficient three-dimensional network structure. On the other hand, its size, conductivity, and pore structure can be controlled by changing the reaction substrate, reaction time, etc., so that it has adjustable wave absorption performance.
[0021] 3. The present invention grows MOF particles on a three-dimensional graphene network. The ZIF-8@ZIF-67 core-shell MOF particles can control the core-shell size and thickness by changing the growth conditions, and then directional etching of the internal Zn atoms at high temperature to achieve controllable MOF pore size and achieve optimal wave absorption performance.
[0022] 4. The present invention utilizes magnetic Ni ion exchange to form a magnetic coupling network to enhance the absorption capacity of the composite material at low frequencies. In addition, the enhanced magnetic loss helps to optimize impedance matching, so that the composite material has ultra-wideband electromagnetic wave absorption capacity. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 This is a flow chart for preparing the broadband absorbing material with multi-level pores according to Examples 1 and 2.
[0024] Figure 2 Scanning electron micrographs and (d) XRD patterns of (a) ZIF-8, (b) ZIF-67, and (c) ZIF-8@ZIF-67 prepared in Example 1. In Figure (d), the abscissa 2θ represents the diffraction angle (degrees), and the ordinate Intensity represents the relative intensity (au).
[0025] Figure 3 (a)-(b) are scanning electron microscope images of different scales of the multi-level porous broadband absorbing material prepared in Example 1.
[0026] Figure 4 This is a two-dimensional projection diagram of the reflection loss of the broadband absorbing material with multi-level pores prepared in Example 1. In the figure, the horizontal axis Frequency is the frequency (GHz), and the vertical axis Thickness is the thickness (mm).
[0027] Figure 5 This is the reflection loss / impedance matching-frequency curve of the multi-level pore broadband absorbing material prepared in Example 1. In the figure, the horizontal axis Frequency is the frequency (GHz), the upper vertical axis Reflection Loss represents the reflection loss (dB), and the lower vertical axis | Z in / Z0| represents impedance matching.
[0028] Figure 6 (a)-(b) are scanning electron microscope images of different scales of the multi-level porous broadband absorbing material prepared in Example 2.
[0029] Figure 7 This is a two-dimensional projection diagram of the reflection loss of the broadband absorbing material with multi-level pores prepared in Example 2. In the figure, the horizontal axis Frequency is the frequency (GHz), and the vertical axis Thickness is the thickness (mm).
[0030] Figure 8 This is the reflection loss / impedance matching-frequency curve of the multi-level pore broadband absorbing material prepared in Example 2. In the figure, the horizontal axis Frequency is the frequency (GHz), the upper vertical axis Reflection Loss represents the reflection loss (dB), and the lower vertical axis | Z in / Z0| represents impedance matching. DETAILED DESCRIPTION
[0031] To facilitate understanding of the present invention, the present invention will be described in more detail below with reference to the relevant drawings. The accompanying drawings provide preferred embodiments of the present invention. The accompanying drawings provide preferred embodiments of the present invention. The above are merely preferred embodiments of the present invention and do not limit the scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied to other related technical fields, are also included in the scope of patent protection of the present invention.
[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification are intended only to describe specific embodiments and are not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0033] In practice, the present invention proposes a method for preparing a broadband absorbing material with hierarchical pores derived from hollow graphene foam / metal-organic frameworks. The broadband absorbing material with a hierarchical pore structure is composed of a composite of macroporous hollow graphene foam and porous carbon derived from a metal-organic framework (MOF). First, a macroporous hollow graphene foam is prepared by chemical vapor deposition and then etched from a pristine nickel skeleton. This is then coated with ZIF-8@ZIF-67 core-shell nanoparticles and subjected to Ni ion exchange to enhance the magnetic coupling network. The Zn cores are then carbonized and evaporated at high temperature to form a hollow carbon nanocage structure (HCN@Co / Ni) embedded with Co / Ni nanoparticles. Ultimately, a three-dimensional hybrid composite material (GrF@HCN@Co / Ni) with a hierarchical pore structure is obtained. These composite materials are then packaged together to form an ultralight, broadband absorbing material.
[0034] Among them, ZIF-8 (zeolitic imidazolate framework material-8) is a three-dimensional porous metal-organic framework (MOF) structure formed by zinc ions (Zn2+) and dimethylimidazole (2-MIM) through coordination bonds, and ZIF-67 (zeolitic imidazolate framework material-67) is a three-dimensional porous metal-organic framework (MOF) structure formed by cobalt ions (Co2+) and dimethylimidazole (2-MIM) through coordination bonds. In addition, HCN refers to a hollow carbon nanocage structure.
[0035] The present invention is further described below with reference to specific embodiments, but the invention is not limited to the embodiments.
[0036] Example 1
[0037] like Figure 1 As shown in the figure, this embodiment is a broadband absorbing material with a multi-level pore structure. It is prepared by chemical vapor deposition and then etching the original nickel skeleton to obtain a hollow graphene foam (GrF) with a macroporous structure. Then, ZIF-8@ZIF-67 core-shell structure nanoparticles are coated on its surface to form GrF@ZIF-8 and GrF@ZIF-8@ZIF-67 in sequence, and Ni ion exchange (Ni 2 + exchange) to enhance the magnetic coupling network, and then high-temperature carbonization (pyrolysis) to evaporate the Zn core to obtain a hollow carbon nanocage structure (HCN@Co / Ni) embedded with Co / Ni nanoparticles, resulting in a three-dimensional hybrid composite material (GrF@HCN@Co / Ni) with a multi-level pore structure. After combination and packaging, it forms an ultra-light, broadband absorbing material. The specific preparation and assembly methods are as follows:
[0038] (1) Three-dimensional hollow graphene foam was prepared by chemical vapor deposition, and then the template was removed by etching with a mixed solution of hydrochloric acid and ethanol (volume ratio of 1:5). The resulting graphene foam had a pore size of 350 μm, a porosity of 97%, 6 graphene layers, and a density of 2.25 mg / cm 3 .
[0039] (2) Core-shell ZIF-8@ZIF-67 was prepared by hydrothermal synthesis. The graphene foam was first placed in a hexahydrate zinc nitrate methanol solution (concentration of 0.1 mol / L), and then a dimethylimidazole methanol solution (concentration of 1.2 mol / L) was added. The volume ratio of the hexahydrate zinc nitrate methanol solution to the dimethylimidazole methanol solution was 3:1. ZIF-8 was in situ grown on the surface to form a composite foam. The composite foam was then placed in a hexahydrate cobalt nitrate methanol solution (concentration of 0.1 mol / L), and a dimethylimidazole methanol solution (concentration of 1.2 mol / L) was added. The volume ratio of the hexahydrate cobalt nitrate methanol solution to the dimethylimidazole methanol solution was 3:1. ZIF-8@ZIF-67 was in situ grown on the surface. The obtained MOF particle size was 550-650 nm, where the molar ratio of ZIF-8 to ZIF-67 was 1:1.2. The corresponding scanning electron microscope image is shown in FIG. Figure 2 (a), (b) and (c) are shown, and the corresponding XRD spectra are shown in Figure 2 (d) is shown. Figure 2It can be seen that ZIF-8, ZIF-67, and ZIF-8@ZIF-67 nanoparticles with dodecahedral shapes were successfully synthesized, and the maximum particle size of ZIF-8@ZIF-67 was about 650-850 nm.
[0040] (3) The graphene foam with ZIF-8@ZIF-67 nanoparticles grown on the surface was placed in a nickel nitrate hexahydrate methanol solution (concentration of 0.03 mol / L) for Ni ion exchange to enhance the magnetic loss capacity, where the molar ratio of Ni and Co ions was 1:0.8.
[0041] (4) The graphene foam grown with ZIF-8@ZIF-67 nanoparticles and subjected to Ni ion exchange was placed in a tubular furnace for carbonization treatment, wherein the carbonization temperature was 950°C, the holding time was 2 h, the heating rate was 2°C / min, and the inert atmosphere was argon. A three-dimensional hybrid composite material (GrF@HCN@Co / Ni) with a multi-level pore structure was obtained. The corresponding scanning electron microscope image is shown in FIG. Figure 3 (a) and (b). Figure 3 It can be seen that the carbonized MOF particles are evenly coated on the surface of graphene foam, and the carbonized particles show an obvious cavity structure.
[0042] (5) The obtained hierarchical pore structure includes micropores and mesopores of 2–20 nm formed by carbonization of MOF organic ligands, cavities of 400–450 nm generated by volatilization of Zn elements, and interconnected macroporous graphene skeletons of 350–450 μm.
[0043] (6) The three-dimensional hybrid composite material with a multi-level pore structure is assembled and packaged using paraffin as a filling matrix. The three-dimensional hybrid composite material is placed in melted paraffin under vacuum conditions and vacuumed for 30 minutes to ensure that the paraffin is fully impregnated into the sample. The mass fraction of the filling matrix is 90%.
[0044] (7) After combined packaging, an ultra-light, broadband absorbing material is formed. The mass fractions of the graphene skeleton, the cavity MOF, and the flexible matrix in the obtained molded sample are 7 wt%, 3 wt%, and 90 wt%, respectively.
[0045] (8) Figure 4 As shown in the figure, the performance test of the broadband absorbing material with a multi-level pore structure was carried out to obtain its two-dimensional projection diagram of reflection loss-thickness-frequency. The effective bandwidth of the prepared absorbing material is 7.41GHz (10.59GHz~18.00GHz), and the matching thickness at this time is only 2.4mm, realizing ultra-broadband absorption.
[0046] (9) Figure 5As shown in FIG, the reflection loss / impedance matching-frequency curve of the absorbing material is calculated. When the thickness is 2.9 mm, the minimum reflection loss is -48.4 dB at 11.2 GHz, indicating that more than 99.99% of the electromagnetic waves can be effectively absorbed.
[0047] Example 2
[0048] like Figure 1 As shown in the figure, this embodiment is a broadband absorbing material with a multi-level pore structure. It is prepared by chemical vapor deposition and then etching the original nickel skeleton to obtain a hollow graphene foam (GrF) with a macroporous structure. Then, ZIF-8@ZIF-67 core-shell structure nanoparticles are coated on its surface to form GrF@ZIF-8 and GrF@ZIF-8@ZIF-67 in sequence, and Ni ion exchange (Ni 2 + exchange) to enhance the magnetic coupling network, and then high-temperature carbonization (pyrolysis) to evaporate the Zn core to obtain a hollow carbon nanocage structure (HCN@Co / Ni) embedded with Co / Ni nanoparticles, resulting in a three-dimensional hybrid composite material (GrF@HCN@Co / Ni) with a multi-level pore structure. After combination and packaging, it forms an ultra-light, broadband absorbing material. The specific preparation and assembly methods are as follows:
[0049] (1) Three-dimensional hollow graphene foam was prepared by chemical vapor deposition, and then the template was removed by etching with a mixed solution of hydrochloric acid and ethanol (volume ratio of 1:5). The resulting graphene foam had a pore size of 350 μm, a porosity of 97%, 6 graphene layers, and a density of 2.25 mg / cm 3 .
[0050] (2) Core-shell ZIF-8@ZIF-67 was prepared by hydrothermal synthesis. The graphene foam was first placed in a hexahydrate zinc nitrate methanol solution (concentration of 0.1 mol / L), and then a dimethylimidazole methanol solution (concentration of 1.2 mol / L) was added. The volume ratio of the hexahydrate zinc nitrate methanol solution to the dimethylimidazole methanol solution was 3:1. ZIF-8 was in situ grown on its surface to form a composite foam. The composite foam was then placed in a hexahydrate cobalt nitrate methanol solution (concentration of 0.1 mol / L), and a dimethylimidazole methanol solution (concentration of 1.2 mol / L) was added. The volume ratio of the hexahydrate cobalt nitrate methanol solution to the dimethylimidazole methanol solution was 3:1. ZIF-8@ZIF-67 was in situ grown on its surface. The obtained MOF particle size was 550-650 nm, and the molar ratio of ZIF-8 to ZIF-67 was 1:1.5.
[0051] (3) The graphene foam with ZIF-8@ZIF-67 nanoparticles grown on the surface was placed in a nickel nitrate hexahydrate methanol solution (concentration of 0.03 mol / L) for Ni ion exchange to enhance the magnetic loss capacity, where the molar ratio of Ni and Co ions was 1:1.2.
[0052] (4) The graphene foam grown with ZIF-8@ZIF-67 nanoparticles and subjected to Ni ion exchange was placed in a tubular furnace for carbonization treatment, wherein the carbonization temperature was 950°C, the holding time was 2 h, the heating rate was 2°C / min, and the inert atmosphere was argon. The corresponding scanning electron microscopy images are shown in Figure 4. Figure 6 (a) and (b). Figure 6 It can be seen that the carbonized MOF particles are evenly coated on the surface of graphene foam, and more carbon nanotubes grow on the surface of MOF particles.
[0053] (5) The obtained hierarchical pore structure includes micropores and mesopores of 2–20 nm formed by carbonization of MOF organic ligands, cavities of 600–650 nm generated by volatilization of Zn elements, and interconnected macroporous graphene skeletons of 350–450 μm.
[0054] (6) The three-dimensional hybrid composite material with a multi-level pore structure is assembled and packaged using paraffin as a filling matrix. The three-dimensional hybrid composite material is placed in melted paraffin under vacuum conditions and vacuumed for 30 minutes to ensure that the paraffin is fully impregnated into the sample. The mass fraction of the filling matrix is 90%.
[0055] (7) After combined packaging, an ultra-light, broadband absorbing material is formed. The mass fractions of the graphene skeleton, the cavity MOF, and the flexible matrix in the obtained molded sample are 6 wt%, 4 wt%, and 90 wt%, respectively.
[0056] (8) Figure 7 As shown in the figure, the performance test of the broadband absorbing material with a multi-level pore structure was carried out to obtain its two-dimensional projection diagram of reflection loss-thickness-frequency. The effective bandwidth of the prepared absorbing material is 13.6GHz (4.40GHz~18.00GHz), and the matching thickness at this time is only 4.4mm, achieving ultra-broadband absorption, covering the entire Ku and X bands, and part of the C band.
[0057] (9) Figure 8 As shown in the figure, the reflection loss / impedance matching-frequency curve of the absorbing material was calculated. When the thickness is 4.4mm, the minimum reflection loss is -33.6dB at 5.75GHz, indicating that more than 99.9% of electromagnetic waves can be effectively absorbed. In addition, the position of the absorption peak moves to low frequency, which can be widely used in wireless communications and electronic equipment.
[0058] The implementation results show that the present invention can obtain an ultra-light, broadband wave-absorbing composite material based on three-dimensional graphene hybrid. The broadband electromagnetic wave absorbing material can be used to prepare radar stealth coatings, electromagnetic shielding devices or 5G communication equipment.
Claims
1. A method for preparing a broadband microwave absorbing material with multi-level pores derived from hollow graphene foam / metal organic framework, characterized in that: This broadband absorbing material is composed of a composite of macroporous hollow graphene foam and a porous carbon derived from a cavity metal-organic framework. First, a macroporous hollow graphene foam is prepared by chemical vapor deposition and then the original nickel skeleton is etched to obtain a hollow graphene foam. Subsequently, ZIF-8@ZIF-67 core-shell structured nanoparticles are coated on its surface and a magnetic Ni ion exchange is performed to enhance the magnetic coupling network. The Zn core is then carbonized and evaporated at high temperature to obtain a porous carbon structure embedded with Co / Ni nanoparticles, resulting in a three-dimensional hybrid composite material with a multi-level pore structure. After combined packaging, an ultra-light, broadband absorbing material is formed.
2. The method for preparing a broadband microwave absorbing material with multi-level pores derived from hollow graphene foam / metal organic framework according to claim 1, characterized in that: The hollow graphene foam is prepared by chemical vapor deposition, and then the template is etched away using a hydrochloric acid-ethanol mixed solution, where the volume ratio of the hydrochloric acid-ethanol mixed solution is 1:4-10. The resulting graphene foam has a pore size of 200-500 μm, a porosity of 95-99%, 1-10 graphene layers, and a density of 1.25-3.35 mg / cm. 3 .
3. The method for preparing a broadband microwave absorbing material based on multi-level pores derived from hollow graphene foam / metal organic framework according to claim 1, characterized in that: The ZIF-8@ZIF-67 core-shell structure is prepared by chemical vapor deposition, hydrothermal synthesis or sol-gel growth. The metal organic framework particle size is 300-700 nm, and the molar ratio of ZIF-8 to ZIF-67 is 1:0.5-1.
5.
4. The method for preparing a broadband microwave absorbing material based on multi-level pores derived from hollow graphene foam / metal organic framework according to claim 1, characterized in that: Magnetic Ni ion exchange enhances magnetic loss capability, wherein the molar ratio of Ni to Co ions is 1:0.5 to 1.
5.
5. The method for preparing a broadband microwave absorbing material based on multi-level pores derived from hollow graphene foam / metal organic framework according to claim 1, characterized in that: When the Co / Ni nanoparticles are embedded in the porous carbon structure, the carbonization temperature is 800-1000° C., the holding time is 1-3 hours, the heating rate is 3-8° C. / min, and the inert atmosphere is one of argon and nitrogen.
6. The method for preparing a broadband microwave absorbing material based on multi-level pores derived from hollow graphene foam / metal organic framework according to claim 1, characterized in that: The multi-level pore structure includes micropores and mesopores of 0.5 to 30 nm formed by carbonization of organic ligands of the metal organic framework, cavities of 400 to 700 nm generated by volatilization of Zn elements, and interconnected macroporous graphene skeletons of 200 to 500 μm.
7. The method for preparing a broadband microwave absorbing material based on multi-level pores derived from hollow graphene foam / metal organic framework according to claim 1, characterized in that: The three-dimensional hybrid composite material with a multi-level pore structure is packaged by combining one of polydimethylsiloxane, paraffin and epoxy resin as a filling matrix, and the mass fraction of the filling matrix is 80-95%.
8. The method for preparing a broadband microwave absorbing material based on multi-level pores derived from hollow graphene foam / metal organic framework according to claim 7, characterized in that: The mass fractions of the hollow graphene foam, the cavity metal organic framework and the flexible matrix are 1-15wt%, 1-10wt% and 80-95wt% respectively.
9. The method for preparing a broadband microwave absorbing material based on multi-level pores derived from hollow graphene foam / metal organic framework according to claim 1, characterized in that: Broadband absorbing materials are used as broadband electromagnetic wave absorbing materials in the preparation of radar stealth coatings, electromagnetic shielding devices or 5G communication equipment.
Citation Information
Patent Citations
Wave-absorbing PVC structural foam and preparation method thereof
CN119613892A