A biomimetic cancellous bone structure carbon aerogel composite wave-absorbing material, a preparation method and application thereof

Abstract

The application discloses a kind of biomimetic cancellous bone structure carbon aerogel composite wave-absorbing material and its preparation method and application, the method is first prepared CoNi-MOF and carbonization treatment is CoNi / C, again by surface modification enhances its compatibility with biomass precursor.Aggregation is avoided by dispersing modified CoNi / C and few-layer MXene uniformly in biomass precursor aqueous solution.Form composite suspension system by crosslinking aid, and construct layered porous biomimetic structure by using directional freezing technology, maintain lightweight porous characteristics, realize the uniform distribution of filler in three-dimensional skeleton.After carbonization treatment, the composite material exhibits excellent electromagnetic wave absorption performance.The method combines electrostatic self-assembly and directional freezing technology, enhances interfacial bonding strength, promotes the formation of multiscale interface, introduces dielectric and magnetic loss synergistic effect, improves absorption efficiency and bandwidth, and provides a new solution for electromagnetic wave absorbing materials.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, and relates to a biomimetic cancellous bone structure carbon aerogel composite wave absorbing material, its preparation method and application. Background Technology

[0002] The rapid development of the information age has led to the widespread application of advanced electromagnetic wave technology, greatly satisfying people's needs. However, with the widespread use of electronic products, the resulting electromagnetic pollution poses a threat to people's health. Therefore, in order to protect the human body and high-precision electronic equipment from electromagnetic radiation, the development of electromagnetic wave absorbing materials with the characteristics of being "light, strong, wide-range, and thin" is crucial. This not only reduces secondary electromagnetic pollution but also has significant research value for national military security.

[0003] Carbon aerogels exhibit excellent electromagnetic wave absorption capabilities due to their interconnected porous structure, high specific surface area, low density, and multifunctionality (such as thermal insulation and flame retardancy). Biomass-derived carbon aerogels have attracted much attention in the field of microwave absorbing materials due to their sustainable source, adjustable morphology, and cost-effective preparation process. After high-temperature carbonization, biomass raw materials can form a three-dimensional carbon framework rich in micropores and mesopores. Its high specific surface area and abundant defect structure can significantly enhance dielectric polarization relaxation loss and conductivity loss effects, providing a unique precursor platform for the design of lightweight magnetic carbon-based microwave absorbing materials. However, single carbon aerogel systems still have significant limitations in practical applications. On the one hand, carbon materials themselves have high conductivity, and the microwave absorption mechanism mainly relies on conductivity loss, which can easily lead to impedance mismatch in the material, causing incident electromagnetic waves to be reflected at the material surface and making it difficult to penetrate the interior, thus limiting its absorption efficiency. On the other hand, the lack of magnetic loss or multi-mechanism synergy also makes it difficult to meet the practical requirements of broadband and efficient absorption.

[0004] To address these issues, researchers typically introduce magnetic or high-dielectric-constant fillers into carbon aerogel systems to achieve synergistic enhancement of dielectric and magnetic losses. However, the physical mixing or post-loading methods commonly used in existing technologies often suffer from problems such as uneven dispersion of fillers within the aerogel framework through physical mixing, and post-loading disrupting the aerogel structure and resulting in weak interfacial bonding. On the one hand, filler agglomeration reduces the number of effective interfaces, limiting interfacial polarization; on the other hand, non-uniformly distributed fillers easily disrupt the original continuous framework structure of the aerogel, affecting its mechanical stability and the consistency of its electromagnetic properties. Therefore, how to maintain the advantages of the lightweight and porous structure of carbon aerogel while achieving a uniform and stable distribution of multifunctional fillers in the three-dimensional framework, constructing multi-scale interfaces, and introducing various electromagnetic loss mechanisms remains a pressing technical problem to be solved in the field of electromagnetic wave absorbing materials. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material, its preparation method, and its application. This solves the technical problems in the prior art where, when introducing fillers into a carbon aerogel system to enhance electromagnetic wave absorption, the fillers are unevenly dispersed, prone to agglomeration, damage the aerogel structure, and have weak interfacial bonding, which in turn affect interfacial polarization, mechanical stability, and the consistency of electromagnetic performance.

[0006] This invention is achieved through the following technical solution: A method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material includes the following steps: S1: The organic solution of 2-methylimidazolium is slowly added to an organic solution containing cobalt salt and nickel salt, and the reaction is stirred to obtain the CoNi-MOF; S2: The CoNi-MOF is carbonized in a nitrogen or inert atmosphere to obtain CoNi / C; and the CoNi / C is added to a surface modifier solution and stirred to obtain modified CoNi / C; S3: The modified CoNi / C and few-layer MXene are added to the aqueous solution of the biomass precursor and stirred evenly to obtain a composite dispersion system; S4: Add a crosslinking aid to the composite dispersion system, stir and react to obtain a composite suspension system, then perform directional freezing treatment on the composite suspension system, freeze dry it and place it in a nitrogen or inert atmosphere for carbonization treatment to obtain the biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material.

[0007] Preferably, in step S1, the mass ratio of the 2-methylimidazolium to the cobalt salt and the nickel salt is (4-5):(0.1-0.5):(0.1-0.5).

[0008] Preferably, in step S2, the heating rate during carbonization is 2-4 °C / min, the temperature is 600-900 °C, and the carbonization time is 1-3 h.

[0009] Preferably, in step S2, the ratio of CoNi / C to surface modifier solution is (0.1-2) g:(100-300) mL, and the concentration of surface modifier solution is 10-40 mg / mL.

[0010] Preferably, the few-layer MXene is prepared by: adding lithium fluoride and hydrochloric acid to Ti3AlC2 for etching, washing the resulting product with water, sonicating, and then freeze-drying the supernatant to obtain the few-layer MXene; the ratio of Ti3AlC2, lithium fluoride, and hydrochloric acid is (0.5-1.5) g:(1-2) g:(10-15) mL; the etching time is 30-40 h, the sonication time is 1-2 h, and the freeze-drying time is 40-50 h.

[0011] Preferably, the biomass precursor is one of glucose, cellulose, and chitosan.

[0012] Preferably, the ratio of the modified CoNi / C, few-layer MXene, and biomass precursor is (0.1-0.5) g:(50-300) mg:(0.1-0.4) g.

[0013] Preferably, in step S4, the freeze-drying time is 48-60 h, and during the carbonization treatment, the heating rate is 2-6 ℃ / min, the holding temperature is 600-900 ℃, and the holding time is 1-5 h.

[0014] A biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material is prepared by the above method.

[0015] The above-mentioned biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material is applied in the field of electromagnetic wave absorption.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material. The method first prepares CoNi-MOF through solution reaction, and then obtains CoNi / C through carbonization. Subsequently, CoNi / C is modified with a surface modifier to enhance its compatibility with biomass precursors. In the composite dispersion system construction stage, modified CoNi / C and few-layer MXene are uniformly dispersed in the biomass precursor aqueous solution, avoiding agglomeration caused by direct physical mixing of fillers. Furthermore, by introducing a crosslinking aid and stirring to form a composite suspension system, a biomimetic cancellous bone structure with a layered porous structure is constructed using directional freezing technology. This structure not only maintains the lightweight and porous characteristics of carbon aerogel but also achieves a uniform and stable distribution of CoNi / C and MXene in a three-dimensional framework. Finally, after carbonization, the resulting composite microwave absorbing material exhibits excellent electromagnetic wave absorption performance. This method, through the combination of electrostatic self-assembly and directional freezing technology, significantly enhances the interfacial bonding force between the filler and the aerogel matrix, promotes the formation of multi-scale interfaces, and effectively introduces the synergistic effect of dielectric loss and magnetic loss. Thus, while maintaining the mechanical stability of the material, it greatly improves the electromagnetic wave absorption efficiency and bandwidth, providing a new solution for the field of electromagnetic wave absorbing materials.

[0017] Furthermore, in step S1, the mass ratio of the 2-methylimidazolium to the cobalt salt and nickel salt is (4-5):(0.1-0.5):(0.1-0.5). This ratio ensures the stable synthesis of CoNi-MOF (cobalt-nickel metal-organic framework) by precisely controlling the reactant ratio. An excessively high proportion of organic ligands may inhibit crystal growth, while an excessively low proportion of metal salts will result in insufficient crystallinity of the product. This range optimizes the pore structure and specific surface area, providing a structural basis for the subsequent carbonization to form a uniformly distributed CoNi / C (cobalt-nickel-carbon composite), thereby enhancing dielectric loss capability.

[0018] Furthermore, in step S2, the heating rate during carbonization is 2-4 ℃ / min, the temperature is 600-900℃, and the carbonization time is 1-3 h. The slow heating rate can prevent CoNi-MOF from cracking due to thermal stress and ensure that the carbon skeleton is gradually formed. The temperature range of 600-900℃ takes into account both the degree of graphitization and the preservation of defect structures. The former improves the conductivity loss, while the latter enhances the polarization loss through defects. The holding time of 1-3 h allows the metal particles to be fully embedded in the carbon matrix, forming a stable dielectric-magnetic loss synergistic system.

[0019] Furthermore, in step S2, the ratio of CoNi / C to the surface modifier solution is (0.1-2) g:(100-300) mL. This ratio, through the coating of CoNi / C with the surface modifier, significantly improves its interfacial compatibility with the biomass precursor. The concentration of the surface modifier solution is 10-40 mg / mL. Too low a concentration will lead to insufficient dispersion, while too high a concentration may cause aggregation. This range ensures the uniform distribution of CoNi / C in the composite system, while preventing particle aggregation through electrostatic repulsion and enhancing the interfacial polarization effect.

[0020] Furthermore, the few-layer MXene is prepared as follows: lithium fluoride and hydrochloric acid are added to Ti3AlC2 for etching, the resulting product is washed with water, sonicated, and the supernatant is freeze-dried to obtain the few-layer MXene; the ratio of Ti3AlC2, lithium fluoride, and hydrochloric acid is (0.5-1.5) g:(1-2) g:(10-15) mL; the etching time is 30-40 h, the sonication time is 1-2 h, and the freeze-drying time is 40-50 h. Precisely controlled etching conditions can efficiently strip Ti3AlC2 to generate few-layer MXene (two-dimensional transition metal carbides), whose layer thickness directly affects the electromagnetic wave scattering efficiency. The sonication and freeze-drying processes avoid layer stacking, retaining a high specific surface area and abundant surface functional groups (such as -OH, -F), providing active sites for interfacial polarization and dipole polarization.

[0021] Furthermore, the biomass precursor is one of glucose, cellulose, and chitosan. The biomass raw material is not only widely available and inexpensive, but the porous carbon skeleton formed after carbonization has an adjustable pore size distribution (micropores / mesopores). This type of structure enhances absorption by extending the electromagnetic wave propagation path. At the same time, N / O doping (such as amino groups in chitosan) can introduce defect states, further improving polarization loss capability.

[0022] Furthermore, the ratio of modified CoNi / C, few-layer MXene, and biomass precursor is (0.1-0.5) g:(50-300) mg:(0.1-0.4) g. This ratio balances the contributions of conductive and magnetic losses by optimizing the filler loading. CoNi / C provides magnetic and conductive channels, MXene enhances dielectric loss and interfacial polarization, and the biomass precursor maintains structural integrity as a matrix. Excessive filler can lead to agglomeration and impedance mismatch. This range ensures the maximization of the synergistic effect of multiple mechanisms.

[0023] Furthermore, in step S4, the freeze-drying time is 48-60 h, and during carbonization, the heating rate is 2-6℃ / min, the holding temperature is 600-900℃, and the holding time is 1-5 h. The secondary carbonization process, through gradient heating (2-6℃ / min) and long-term holding (1-5 h), promotes deep integration of biomass precursors and fillers. Slow heating avoids structural collapse, and the high-temperature zone (600-900℃) enables the functional groups on the MXene surface to form chemical bonds with the carbon matrix, enhancing the interfacial bonding force. At the same time, it optimizes the graphitization degree and defect density of the carbon skeleton, ultimately achieving a balance between lightweight, high strength, and broadband absorption. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic flowchart of the preparation method of the biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material in this invention; Figure 2 Zeta potential diagrams of CoNi / C, modified CoNi / C, few-layer MXene, and biomass precursor solutions prepared in Example 1 of this invention; Figure 3 XRD pattern of the biomimetic cancellous bone structure carbon aerogel prepared in Example 1 of this invention; Figure 4 SEM image of the biomimetic cancellous bone structure carbon aerogel prepared in Example 1 of this invention; Figure 5 EDS image of the biomimetic cancellous bone structure carbon aerogel prepared in Example 1 of this invention; Figure 6 The image shows the reflection loss of the biomimetic cancellous bone structure carbon aerogel prepared in Example 1 of this invention. a is a two-dimensional reflection loss image, b is a three-dimensional reflection loss image, and c is a contour plot of the three-dimensional reflection loss image. Figure 7 The image shows a Cole-Cole semicircle of the biomimetic cancellous bone structure carbon aerogel prepared in Example 1 of this invention. Detailed Implementation

[0026] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0027] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0028] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0029] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0030] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0031] This invention provides a method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material, comprising the following steps: S1: The organic solution of 2-methylimidazolium is slowly added to an organic solution containing cobalt salt and nickel salt, and the reaction is stirred to obtain the CoNi-MOF; Specifically, the process is as follows: cobalt and nickel salts are dissolved in an organic solvent and stirred until completely dissolved to obtain an organic solution of cobalt and nickel salts; 2-methylimidazole is dissolved in the organic solvent and slowly added to the cobalt and nickel salt solution while stirring. After stirring, the mixture is centrifuged to obtain CoNi-MOF, which is then washed multiple times with an organic solvent and vacuum dried to obtain CoNi-MOF.

[0032] The cobalt salt is at least one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate tetrahydrate, and cobalt sulfate heptahydrate; the nickel salt is at least one of nickel nitrate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate, and nickel sulfate heptahydrate. The mass ratio of the 2-methylimidazolium salt to the cobalt salt and the nickel salt is (4-5):(0.1-0.5):(0.1-0.5); In an organic solution containing cobalt and nickel salts, the organic solvent is at least one of methanol or ethanol, and the ratio of cobalt salt, nickel salt to organic solvent is (0.1-0.5) g:(0.1-0.5) g:(20-50) mL. In the organic solution of 2-methylimidazole, the organic solvent is at least one of methanol or ethanol, and the ratio of 2-methylimidazole to organic solvent is (4-5) g:(130-150) mL. The vacuum drying temperature is 60℃ and the time is 10-12 h.

[0033] S2: The CoNi-MOF is carbonized in a nitrogen or inert atmosphere to obtain CoNi / C; and the CoNi / C is added to a surface modifier solution and stirred to obtain modified CoNi / C; The inert atmosphere is argon; the heating rate during carbonization is 2-4 ℃ / min, the temperature is 600-900℃, and the carbonization time is 1-3 h.

[0034] The surface modifier is one of sodium dodecyl sulfate, sodium citrate, and sodium dodecylbenzene sulfonate; the ratio of CoNi / C to the surface modifier is (0.1-2) g:(100-300) mL, and the concentration of the surface modifier is 10-40 mg / mL; The CoNi / C was added to the surface modifier solution, and the stirring process was carried out at a stirring rate of 400 rpm / min for 1-3 h. S3: The modified CoNi / C and few-layer MXene are added to the aqueous solution of the biomass precursor and stirred evenly to obtain a composite dispersion system; The few-layer MXene is prepared by etching Ti3AlC2. Specifically, lithium fluoride and hydrochloric acid are added to Ti3AlC2 for etching. The resulting product is washed multiple times with deionized water, sonicated, and the supernatant is freeze-dried to obtain the few-layer MXene, which has a sheet-like structure.

[0035] Preferably, the ratio of Ti3AlC2, lithium fluoride, and hydrochloric acid is (0.5-1.5) g:(1-2) g:(10-15) mL; the concentration of hydrochloric acid is 9 mol / L; the etching time is 30-40 h; the ultrasonic time is 1-2 h; and the freeze-drying time is 40-50 h.

[0036] The biomass precursor is one of glucose, cellulose, and chitosan; The ratio of modified CoNi / C, few-layer MXene, and biomass precursor is (0.1-0.5) g:(50-300) mg:(0.1-0.4) g; the ratio of biomass precursor to water in the aqueous solution of the biomass precursor is (0.1-0.4) g:(10-40) mL. S4: Add a crosslinking aid to the composite dispersion system, stir and react to obtain a composite suspension system, then perform directional freezing treatment on the composite suspension system, and then place it in a nitrogen or inert atmosphere for carbonization treatment to obtain the biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material.

[0037] The crosslinking aid is one of citric acid and acetic acid, and the amount of crosslinking aid added is 0.1-0.5 mL.

[0038] Adding a crosslinking aid to the composite dispersion system and stirring the reaction allows the biomass precursor to undergo a crosslinking reaction under acidic conditions. Through the electrostatic interaction between the biomass molecular chains and MXene and modified CoNi / C, the functional filler is anchored in situ and self-assembled in solution within the biomass network, forming a uniform and stable composite suspension system.

[0039] The directional freezing process specifically involves: transferring the composite suspension system into a customized mold, placing the mold on a copper column in liquid nitrogen for directional freezing, so that the composite suspension system, which has already undergone self-assembly and fixation, constructs a three-dimensional skeleton structure with layered porous characteristics along the ice crystal growth direction; subsequently, the frozen sample is freeze-dried to obtain a composite aerogel precursor with a biomimetic cancellous bone structure.

[0040] The freeze-drying time here is 10-60 h; preferably 48-60 h. During the carbonization process, the inert atmosphere is argon, the heating rate is 2-6 ℃ / min, the holding temperature is 600-900℃, and the holding time is 1-5 h.

[0041] This invention employs electrostatic self-assembly, directional freezing, and carbonization to construct a biomimetic cancellous bone structure carbon aerogel loaded with MXene and modified CoNi / C. The process includes the following steps: preparing few-layer MXene by etching Ti3AlC2; preparing CoNi-MOF; preparing CoNi / C by high-temperature carbonization; modifying CoNi / C with a surface modifier; preparing a biomass precursor solution; initially dispersing CoNi / C and MXene; acid-crosslinked induced solution self-assembly; directional freezing to construct a customized structure; and carbonization treatment. Overall, the carbon aerogel framework, CoNi / C, and MXene materials provide dielectric loss, including the conductivity loss of the three materials, as well as N doping in the biomass carbon aerogel, functional groups on the surface of the modified CoNi / C material, and dipole polarization induced by the surface functional groups of MXene itself acting as dipoles, and interfacial polarization induced by multiple interfaces of the uniformly loaded CoNi / C and MXene materials prepared by electrostatic self-assembly within the carbon aerogel. The CoNi / C material in carbon aerogels also provides magnetic loss to help dissipate electromagnetic waves, and this meso-electromagnetic synergy helps optimize the impedance matching of the absorbing material. In addition, the layered porous structure of the biomimetic cancellous bone structure of the carbon aerogel is beneficial for multiple scattering and reflection of electromagnetic waves. Specifically, this invention addresses the needs of the electromagnetic wave absorbing material field by innovatively employing a directional freezing method and an electrostatic self-assembly method to in-situ load CoNi / C and MXene onto nitrogen-doped biomass-derived carbon aerogels. Through ingenious design, a biomimetic cancellous bone structure is constructed, which consists of sheet-like MXene and a carbon framework forming a layered porous structure loaded with CoNi / C. This preparation process has significant advantages: it is simple and easy to operate, uses abundant biomass raw materials, is environmentally friendly, and can be mass-produced. Based on the unique structural design and preparation process, the prepared biomimetic cancellous bone structure carbon aerogel exhibits excellent electromagnetic wave absorption performance and has broad application prospects in fields with stringent electromagnetic wave absorption requirements, such as military and aerospace, and is expected to provide efficient and reliable electromagnetic wave absorption solutions for related fields.

[0042] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0043] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0044] Example 1 (1) Add 2 g LiF and 15 mL 9 mol / L hydrochloric acid to 1 g Ti3AlC2 and etch for 40 h. Wash the product with deionized water several times, sonicate for 2 h, and freeze-dry the supernatant for 48 h to obtain a few-layer plate-like MXene.

[0045] (2) Dissolve 0.466 g Co(NO3)2·6H2O and 0.465 g Ni(NO3)·6H2O in 40 mL of methanol and stir until completely dissolved. Dissolve 4.2 g 2-methylimidazole in 140 mL of methanol and slowly add it to the prepared cobalt-nickel salt solution while stirring for 24 h. After stirring, centrifuge the mixture, wash it several times with methanol, and then vacuum dry it.

[0046] (3) The CoNi-MOF obtained in step (2) is kept at 800℃ in an argon atmosphere for 2 h with a heating rate of 2℃ / min to obtain CoNi / C.

[0047] (4) Add 1 g CoNi / C to 100 ml of 20 mg / ml SDBS solution and mechanically stir at 400 rpm for 1 h. After stirring, wash and dry to obtain modified CoNi / C.

[0048] (5) Dissolve 0.2 g of chitosan in 10 mL of deionized water.

[0049] (6) Add 0.05 g of few-layer MXene and 0.1 g of modified CoNi / C material to the chitosan solution obtained in step (5) and stir.

[0050] (7) While maintaining the dispersion system obtained in step (6) at a stirring rate of 300 rpm, slowly add 0.2 mL of glacial acetic acid. (8) Transfer the composite suspension obtained in step (7) into a custom mold and place the mold on a copper column in liquid nitrogen for directional freezing. (9) The composite aerogel precursor obtained in step (8) is kept at 600 °C in an argon atmosphere for 2 h with a heating rate of 2 °C / min. Example 2 (1) Add 2 g LiF and 15 mL 9 mol / L hydrochloric acid to 1 g Ti3AlC2 and etch for 40 h. Wash the product with deionized water several times, sonicate for 2 h, and freeze-dry the supernatant for 48 h to obtain a few-layer plate-like MXene.

[0051] (2) Dissolve 0.233 g Co(NO3)2·6H2O and 0.465 g Ni(NO3)·6H2O in 40 mL of methanol and stir until completely dissolved. Dissolve 4.2 g 2-methylimidazole in 140 mL of methanol and slowly add it to the prepared cobalt-nickel salt solution while stirring for 24 h. After stirring, centrifuge the mixture, wash it several times with methanol, and then vacuum dry it.

[0052] (3) The CoNi-MOF obtained in step (2) is kept at 700 °C in an argon atmosphere for 2 h with a heating rate of 2 °C / min to obtain CoNi / C.

[0053] (4) Add 1 g CoNi / C to 100 ml of 20 mg / ml SDBS solution and mechanically stir at 400 rpm for 1 h. After stirring, wash and dry to obtain modified CoNi / C.

[0054] (5) Dissolve 0.2 g of chitosan in 10 mL of deionized water.

[0055] (6) Add 0.05 g of few-layer MXene and 0.05 g of modified CoNi / C material to the chitosan solution obtained in step (5) and stir. (7) While maintaining the dispersion system obtained in step (6) at a stirring rate of 300 rpm, slowly add 0.2 mL of glacial acetic acid. (8) Transfer the composite suspension obtained in step (7) into a custom mold and place the mold on a copper column in liquid nitrogen for directional freezing. (9) The composite aerogel precursor obtained in step (8) is kept at 900 °C in an argon atmosphere for 2 h with a heating rate of 2 °C / min.

[0056] Example 3 (1) Add 2 g LiF and 15 mL 9 mol / L hydrochloric acid to 1 g Ti3AlC2 and etch for 40 h. Wash the product with deionized water several times, sonicate for 2 h, and freeze-dry the supernatant for 48 h to obtain a few-layer plate-like MXene.

[0057] (2) Dissolve 0.233 g Co(NO3)2·6H2O and 0.232 g Ni(NO3)·6H2O in 40 mL of methanol and stir until completely dissolved. Dissolve 4.2 g 2-methylimidazole in 140 mL of methanol and slowly add it to the prepared cobalt-nickel salt solution while stirring for 24 h. After stirring, centrifuge the mixture, wash it several times with methanol, and then vacuum dry it.

[0058] (3) The CoNi-MOF obtained in step (2) is kept at 900 °C in an argon atmosphere for 2 h with a heating rate of 2 °C / min to obtain CoNi / C.

[0059] (4) Add 1 g CoNi / C to 100 ml of 20 mg / ml SDBS solution and mechanically stir at 400 rpm for 1 h. After stirring, wash and dry to obtain modified CoNi / C.

[0060] (5) Dissolve 0.2 g of chitosan in 10 mL of deionized water.

[0061] (6) Add 0.15 g of few-layer MXene and 0.05 g of modified CoNi / C material to the chitosan solution obtained in step (5) and stir. (7) While maintaining the dispersion system obtained in step (6) at a stirring rate of 300 rpm, slowly add 0.2 mL of glacial acetic acid. (8) Transfer the composite suspension obtained in step (7) into a custom mold and place the mold on a copper column in liquid nitrogen for directional freezing. (9) The composite aerogel precursor obtained in step (8) is kept at 800 °C in an argon atmosphere for 2 h with a heating rate of 2 °C / min.

[0062] Example 4 (1) Add 2 g LiF and 15 mL 9 mol / L hydrochloric acid to 1.5 g Ti3AlC2 and etch for 40 h. Wash the product with deionized water several times, sonicate for 2 h, and freeze-dry the supernatant for 48 h to obtain a few-layer plate-like MXene.

[0063] (2) Dissolve 0.466 g Co(NO3)2·6H2O and 0.232 g Ni(NO3)·6H2O in 40 mL of methanol and stir until completely dissolved. Dissolve 4.2 g 2-methylimidazole in 140 mL of methanol and slowly add it to the prepared cobalt-nickel salt solution while stirring for 24 h. After stirring, centrifuge the mixture, wash it several times with methanol, and then vacuum dry it.

[0064] (3) The CoNi-MOF obtained in step (2) is kept at 700 °C in an argon atmosphere for 2 h with a heating rate of 2 °C / min to obtain CoNi / C.

[0065] (4) Add 1 g CoNi / C to 100 ml of 20 mg / ml SDBS solution and mechanically stir at 400 rpm for 1 h. After stirring, wash and dry to obtain modified CoNi / C.

[0066] (5) Dissolve 0.2 g of chitosan in 10 mL of deionized water.

[0067] (6) Add 0.2 g of few-layer MXene and 0.05 g of modified CoNi / C material to the chitosan solution obtained in step (5) and stir. (7) While maintaining the dispersion system obtained in step (6) at a stirring rate of 300 rpm, slowly add 0.2 mL of glacial acetic acid. (8) Transfer the composite suspension obtained in step (7) into a custom mold and place the mold on a copper column in liquid nitrogen for directional freezing.

[0068] (9) The composite aerogel precursor obtained in step (8) is kept at 900 °C in an argon atmosphere for 2 h with a heating rate of 2 °C / min.

[0069] Example 5 (1) Add 2 g LiF and 15 mL 9 mol / L hydrochloric acid to 1.5 g Ti3AlC2 and etch for 40 h. Wash the product with deionized water several times, sonicate for 2 h, and freeze-dry the supernatant for 48 h to obtain a few-layer plate-like MXene.

[0070] (2) Dissolve 0.466 g Co(NO3)2·6H2O and 0.465 g Ni(NO3)·6H2O in 40 mL of methanol and stir until completely dissolved. Dissolve 4.2 g 2-methylimidazole in 140 mL of methanol and slowly add it to the prepared cobalt-nickel salt solution while stirring for 24 h. After stirring, centrifuge the mixture, wash it several times with methanol, and then vacuum dry it.

[0071] (3) The CoNi-MOF obtained in step (2) is kept at 600 °C in an argon atmosphere for 2 h with a heating rate of 2 °C / min to obtain CoNi / C.

[0072] (4) Add 1 g CoNi / C to 100 ml of 20 mg / ml SDBS solution and mechanically stir at 400 rpm for 1 h. After stirring, wash and dry to obtain modified CoNi / C.

[0073] (5) Dissolve 0.2 g of chitosan in 10 mL of deionized water.

[0074] (6) Add 0.1 g of few-layer MXene and 0.1 g of modified CoNi / C material to the chitosan solution obtained in step (5) and stir. (7) While maintaining the dispersion system obtained in step (6) at a stirring rate of 300 rpm, slowly add 0.2 mL of glacial acetic acid. (8) Transfer the composite suspension obtained in step (7) into a custom mold and place the mold on a copper column in liquid nitrogen for directional freezing. (9) The composite aerogel precursor obtained in step (8) is kept at 800 °C in an argon atmosphere for 2 h with a heating rate of 2 °C / min.

[0075] Example 6 A method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material includes the following steps: S1: Preparation of CoNi-MOF 0.1 g of cobalt nitrate hexahydrate and 0.1 g of nickel nitrate hexahydrate were dissolved in 20 mL of methanol and stirred until completely dissolved to prepare an organic solution of cobalt and nickel salts. 4 g of 2-methylimidazole was dissolved in 130 mL of methanol and slowly added to the above cobalt-nickel salt solution while stirring. After stirring, the mixture was centrifuged to obtain CoNi-MOF, which was washed several times with methanol and then vacuum dried at 60 °C for 10 h to obtain CoNi-MOF.

[0076] S2: Preparation and Modification of CoNi / C The CoNi-MOF obtained above was placed in a nitrogen atmosphere and heated to 600℃ at a heating rate of 2℃ / min, and carbonized for 1 h to obtain CoNi / C.

[0077] Weigh 0.1 g of CoNi / C and add it to 100 mL of sodium dodecyl sulfate solution with a concentration of 10 mg / mL. Stir at 400 rpm / min for 1 h to obtain modified CoNi / C.

[0078] S3: Preparation of composite dispersion system Preparation of few-layer MXene: Weigh 0.5 g Ti3AlC2, add 1 g lithium fluoride and 10 mL of 9% hydrochloric acid for etching for 30 h. Wash the product with deionized water several times, sonicate for 1 h, and then freeze-dry the supernatant for 40 h to obtain few-layer MXene.

[0079] Weigh 0.1 g of glucose and dissolve it in 10 mL of water to prepare an aqueous solution of biomass precursor.

[0080] Weigh 0.1 g of modified CoNi / C and 50 mg of few-layer MXene and add them to the above glucose aqueous solution. Stir well to obtain a composite dispersion system.

[0081] S4: Preparation of biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material Add 0.1 mL of citric acid to the composite dispersion system and stir to react, so that glucose undergoes a cross-linking reaction under acidic conditions to form a uniform and stable composite suspension system.

[0082] The composite suspension system was transferred into a custom mold, and the mold was placed on a copper column in liquid nitrogen for directional freezing. The frozen sample was then freeze-dried for 10 h to obtain a composite aerogel precursor with a biomimetic cancellous bone structure.

[0083] The composite aerogel precursor was placed in an argon atmosphere and heated to 600℃ at a heating rate of 2℃ / min, and held at that temperature for 1 hour for carbonization treatment to obtain a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material.

[0084] Example 7 A method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material includes the following steps: S1: Preparation of CoNi-MOF 0.3 g of cobalt acetate tetrahydrate and 0.3 g of nickel acetate tetrahydrate were dissolved in 35 mL of ethanol and stirred until completely dissolved to prepare an organic solution of cobalt nickel salt. 4.5 g of 2-methylimidazole was dissolved in 140 mL of ethanol and slowly added to the above cobalt-nickel salt solution while stirring. After stirring, the mixture was centrifuged to obtain CoNi-MOF, which was washed several times with ethanol and then vacuum dried at 60 °C for 11 h to obtain CoNi-MOF.

[0085] S2: Preparation and Modification of CoNi / C The CoNi-MOF obtained above was placed in an argon atmosphere and heated to 750℃ at a heating rate of 3℃ / min, and carbonized for 2 h to obtain CoNi / C.

[0086] Weigh 1 g of CoNi / C and add it to 200 mL of sodium citrate solution with a concentration of 25 mg / mL. Stir at 400 rpm / min for 2 h to obtain modified CoNi / C.

[0087] S3: Preparation of composite dispersion system Preparation of few-layer MXene: 1 g Ti3AlC2 was weighed, and 1.5 g lithium fluoride and 12.5 mL of 9% hydrochloric acid were added for etching for 35 h. The resulting product was washed multiple times with deionized water, sonicated for 1.5 h, and the supernatant was freeze-dried for 45 h to obtain few-layer MXene.

[0088] Weigh 0.25 g of cellulose and dissolve it in 25 mL of water to prepare an aqueous solution of biomass precursor.

[0089] Weigh 0.3 g of modified CoNi / C and 175 mg of few-layer MXene and add them to the above cellulose aqueous solution. Stir well to obtain a composite dispersion system.

[0090] S4: Preparation of biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material Add 0.3 mL of acetic acid to the composite dispersion system and stir to react, so that the cellulose undergoes a cross-linking reaction under acidic conditions to form a uniform and stable composite suspension system.

[0091] The composite suspension system was transferred into a custom mold, and the mold was placed on a copper column in liquid nitrogen for directional freezing. The frozen sample was then freeze-dried for 35 h to obtain a composite aerogel precursor with a biomimetic cancellous bone structure.

[0092] The composite aerogel precursor was placed in an argon atmosphere and heated to 750℃ at a heating rate of 4℃ / min, and held at that temperature for 3 hours for carbonization treatment to obtain a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material.

[0093] Example 8 A method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material includes the following steps: S1: Preparation of CoNi-MOF Dissolve 0.5 g of cobalt sulfate heptahydrate and 0.5 g of nickel sulfate heptahydrate in 50 mL of ethanol and stir until completely dissolved to obtain an organic solution of cobalt and nickel salts.

[0094] 5 g of 2-methylimidazole was dissolved in 150 mL of ethanol and slowly added to the above cobalt-nickel salt solution while stirring. After stirring, the mixture was centrifuged to obtain CoNi-MOF, which was washed several times with ethanol and then vacuum dried at 60 °C for 12 h to obtain CoNi-MOF.

[0095] S2: Preparation and Modification of CoNi / C The CoNi-MOF obtained above was placed in an argon atmosphere and heated to 900℃ at a heating rate of 4℃ / min for 3 h for carbonization treatment to obtain CoNi / C.

[0096] 2 g of CoNi / C was weighed and added to 300 mL of sodium citrate solution with a concentration of 40 mg / mL. The mixture was stirred at a stirring rate of 400 rpm / min for 3 h to obtain modified CoNi / C.

[0097] S3: Preparation of composite dispersion system Preparation of few-layer MXene: 1.5 g of Ti3AlC2 was weighed, and 2 g of lithium fluoride and 15 mL of 9% hydrochloric acid were added for etching for 40 h. The resulting product was washed several times with deionized water, sonicated for 2 h, and the supernatant was freeze-dried for 50 h to obtain few-layer MXene.

[0098] Weigh 0.4 g of chitosan and dissolve it in 40 mL of water to prepare an aqueous solution of biomass precursor.

[0099] Weigh 0.5 g of modified CoNi / C and 300 mg of few-layer MXene and add them to the above chitosan aqueous solution. Stir well to obtain a composite dispersion system.

[0100] S4: Preparation of biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material Add 0.5 mL of citric acid to the composite dispersion system and stir to react, so that chitosan undergoes a cross-linking reaction under acidic conditions to form a uniform and stable composite suspension system.

[0101] The composite suspension system was transferred into a custom mold, and the mold was placed on a copper column in liquid nitrogen for directional freezing. The frozen sample was then freeze-dried for 60 h to obtain a composite aerogel precursor with a biomimetic cancellous bone structure.

[0102] The composite aerogel precursor was placed in an argon atmosphere and heated to 900℃ at a heating rate of 6℃ / min, and held at that temperature for 5 hours for carbonization treatment to obtain a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material.

[0103] The biomimetic cancellous bone structure carbon aerogels prepared by this invention all have good electromagnetic wave absorption properties. The following description uses the biomimetic cancellous bone structure carbon aerogel prepared in Example 1 as an example.

[0104] Figure 1 This is a schematic diagram of the process for a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material in this invention. Inspired by the layered structure of cancellous bone, a biomimetic cancellous bone structure carbon aerogel is prepared by directional freezing, freeze drying and carbonization using modified CoNi / C, MXene and precursors as materials.

[0105] Figure 2 The image shows the zeta potential diagrams of CoNi / C, modified CoNi / C, few-layer MXene, and biomass precursor prepared in Example 1 of this invention. By measuring the zeta potential of each material, it was found that CoNi / C is not significantly charged and cannot electrostatically self-assemble well with the positively charged precursor, while modified CoNi / C and MXene are significantly negatively charged and can undergo electrostatic self-assembly with the precursor.

[0106] Figure 3 The image shows the XRD pattern of the biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material prepared in Example 1 of this invention. X-ray diffraction analysis of the carbon aerogel revealed that the peak at 6.4° belongs to the (002) crystal plane, corresponding to MXene. The peaks at 44.40°, 51.64°, and 76.00° belong to the (111), (200), and (220) crystal planes, corresponding to CoNi. This demonstrates the successful preparation of the biomimetic cancellous bone structure aerogel loaded with CoNi and MXene.

[0107] Figure 4 The images show SEM images of the biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material prepared in Example 1 of this invention at different magnifications. (a) has a scale bar of 50 μm, (b) has a scale bar of 15 μm, and (c) has a scale bar of 200 μm. It can be clearly seen that the carbon aerogel with a biomimetic cancellous bone structure was successfully prepared by directional freezing, electrostatic self-assembly, and carbonization. Furthermore, scanning at higher magnifications reveals that CoNi / C material is uniformly loaded onto its biomass-derived carbon material framework. This biomimetic cancellous bone structure facilitates various reflections and scatterings of electromagnetic waves, and the CoNi / C material and MXene on it increase the material's conductivity, thereby enhancing conductive loss.

[0108] Figure 5The image shows the EDS (Electronic Data Structures) of the biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material prepared in Example 1 of this invention. (c) shows the presence of N, indicating that the carbon aerogel is N-doped; (e) shows the presence of Ti, indicating that MXene has been successfully introduced; (f) and (g) show the presence of Co and Ni, indicating that CoNi metal has been successfully introduced; and (h) shows the presence of S, indicating that CoNi / C has been successfully modified.

[0109] Figure 6 The images show the reflection loss diagrams of the biomimetic cancellous bone structure carbon aerogel prepared in Example 1 of this invention. (a) is a two-dimensional reflection loss diagram, (b) is a three-dimensional reflection loss diagram, and (c) is a contour plot of the three-dimensional reflection loss diagram. By measuring the electromagnetic parameters of the biomimetic cancellous bone structure carbon aerogel loaded with CoNi / C material and MXene, and calculating the reflection loss according to transmission line theory, the biomimetic cancellous bone structure carbon aerogel loaded with CoNi / C material and MXene exhibits excellent electromagnetic wave absorption performance. Furthermore, according to (c), the biomimetic cancellous bone structure carbon aerogel loaded with CoNi / C material and MXene has the minimum reflection loss value of -52.74 dB at 4.69 mm, and the maximum absorption bandwidth of 4 GHz when the matching thickness is 2.72 mm. It can be seen that the biomimetic cancellous bone structure carbon aerogel loaded with CoNi / C material and MXene achieves excellent electromagnetic wave absorption performance through structural design.

[0110] Figure 7 The figure shows the Cole-Cole semicircle diagram of the biomimetic cancellous bone structure carbon aerogel prepared in Example 1 of this invention. As shown in the figure, its Cole-Cole semicircle diagram has multiple semicircles, which can be allocated to the interfacial polarization caused by the uneven distribution of dissimilar electrons between the biomass-derived carbon material framework, CoNi / C material, and MXene, thus helping to dissipate electromagnetic waves.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material, characterized in that, Includes the following steps: S1: The organic solution of 2-methylimidazolium is slowly added to an organic solution containing cobalt salt and nickel salt, and the reaction is stirred to obtain the CoNi-MOF; S2: The CoNi-MOF is carbonized in a nitrogen or inert atmosphere to obtain CoNi / C; and the CoNi / C is added to a surface modifier solution and stirred to obtain modified CoNi / C; S3: The modified CoNi / C and few-layer MXene are added to the aqueous solution of the biomass precursor and stirred evenly to obtain a composite dispersion system; S4: Add a crosslinking aid to the composite dispersion system, stir and react to obtain a composite suspension system, then perform directional freezing treatment on the composite suspension system, freeze dry it and place it in a nitrogen or inert atmosphere for carbonization treatment to obtain the biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material.

2. The method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material according to claim 1, characterized in that, In step S1, the mass ratio of 2-methylimidazole to cobalt salt and nickel salt is (4-5):(0.1-0.5):(0.1-0.5).

3. The method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material according to claim 1, characterized in that, In step S2, the heating rate during carbonization is 2-4 ℃ / min, the temperature is 600-900℃, and the carbonization time is 1-3 h.

4. The method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material according to claim 1, characterized in that, In step S2, the ratio of CoNi / C to surface modifier solution is (0.1-2) g:(100-300) mL, and the concentration of surface modifier solution is 10-40 mg / mL.

5. The method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material according to claim 1, characterized in that, The few-layer MXene was prepared by adding lithium fluoride and hydrochloric acid to Ti3AlC2 for etching, washing the product with water, sonicating, and then freeze-drying the supernatant to obtain the few-layer MXene; the ratio of Ti3AlC2, lithium fluoride and hydrochloric acid was (0.5-1.5) g:(1-2) g:(10-15) mL; the etching time was 30-40 h, the sonication time was 1-2 h, and the freeze-drying time was 40-50 h.

6. The method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material according to claim 1, characterized in that, The biomass precursor is one of glucose, cellulose, and chitosan.

7. The method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material according to claim 1, characterized in that, The ratio of modified CoNi / C, few-layer MXene, and biomass precursor is (0.1-0.5) g:(50-300) mg:(0.1-0.4) g.

8. The method for preparing a biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material according to claim 1, characterized in that, In step S4, the freeze-drying time is 48-60 h, and during the carbonization treatment, the heating rate is 2-6 ℃ / min, the holding temperature is 600-900 ℃, and the holding time is 1-5 h.

9. A biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

10. The application of the biomimetic cancellous bone structure carbon aerogel composite microwave absorbing material as described in claim 9 in the field of electromagnetic wave absorption.

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