Double-shell hollow chain-like carbon nanomaterials, and preparation method and application thereof

Abstract

The application discloses a kind of double-shell hollow chain-like carbon nanomaterials and its preparation method and application, belong to material technical field, including the following steps: step one, phenolic compound and aldehyde compound are added in basic solution and are synthesized phenolic aldehyde resin ball in condensation polymerization reaction;Step two, etching agent is added in the solution obtained in step one, and hollow phenolic aldehyde resin ball is obtained by centrifugation;Step three, hollow phenolic aldehyde resin ball obtained in step two is placed again in basic solution containing phenolic compound and aldehyde compound and is carried out condensation polymerization reaction;Step four, etching agent is added in the solution obtained in step three, and precursor is obtained by centrifugation, ultrasonic;Step five, precursor is pyrolyzed, and double-shell hollow chain-like carbon nanomaterial is obtained.The preparation method of the application has the advantages of high efficiency, convenient and safe, and the carbon component of the double-shell hollow chain-like carbon nanomaterial prepared has the advantages of lightweight and dielectric adjustable.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, and relates to a microwave absorbing material, particularly a double-shell hollow chain-like carbon nanomaterial, its preparation method, and its application. Background Technology

[0002] In the upcoming 5G era, while emerging electromagnetic applications such as the Internet of Things, VR / AR, autonomous driving, and telemedicine will bring convenience to people's lives, they will also bring more electromagnetic pollution. Electromagnetic wave absorbing materials, or simply absorbing materials, act as a relay station for electromagnetic energy, converting electromagnetic energy radiated from the outside into heat energy for dissipation. However, high cost and large filling volume are practical application challenges that continue to restrict the promotion and development of absorbing materials.

[0003] Carbon-based materials are representative of dielectric materials, possessing advantages such as lightweight and tunable dielectric properties, perfectly meeting the "thin and light" application requirements in the microwave absorption field. Simultaneously, carbon materials exhibit stable chemical properties, making them a viable alternative for microwave absorption applications in harsh environments requiring corrosion resistance and thermal conductivity. Furthermore, carbon materials are widely available; over 90% of biomass materials on Earth can be derived from carbon, which helps reduce production costs. Therefore, whether considering the trend towards lighter electronic devices or the demanding environmental requirements of defense and military applications, carbon-based materials are an ideal choice for future microwave absorption materials.

[0004] Constructing hollow structures on carbon-based materials is beneficial for further enhancing lightweight properties and can significantly reduce powder filling rates, thereby lowering application costs. Simultaneously, hollow structures can induce additional properties such as enhanced wave reflection, suppression of eddy currents, and improved impedance matching, making them highly suitable for electromagnetic wave absorption. Furthermore, other structures derived from hollow structures, such as multi-shell structures and hollow porous structures, are considered to have even greater wave absorption potential. Currently, the fabrication of hollow structures is typically template-dependent, generally requiring hard templates such as SiO2 or PS, or soft templates such as PVP or vesicles as the internal structural support. This process is complex, cumbersome, and carries a high degree of risk. An efficient, convenient, and safe method for fabricating hollow structures is lacking. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a double-shell hollow chain carbon nanomaterial, its preparation method, and its application. A hollow structure is obtained through a simple method, and based on this, a double-shell hollow chain carbon nanomaterial is obtained, which has certain value for microstructure design and practical application of carbon materials.

[0006] To achieve the above objectives, this invention provides a method for preparing double-shell hollow chain-like carbon nanomaterials, characterized by the following steps: Step 1, adding phenolic compounds and aldehyde compounds to an alkaline solution for a condensation reaction to synthesize phenolic resin spheres; Step 2, adding an etchant to the solution obtained in Step 1 and centrifuging to obtain hollow phenolic resin spheres; Step 3, placing the hollow phenolic resin spheres obtained in Step 2 back into an alkaline solution containing phenolic compounds and aldehyde compounds for a condensation reaction; Step 4, adding an etchant to the solution obtained in Step 3, centrifuging and sonicating to obtain a precursor; Step 5, pyrolyzing the precursor to obtain double-shell hollow chain-like carbon nanomaterials.

[0007] Furthermore, the present invention provides a method for preparing a double-shelled hollow chain-like carbon nanomaterial, which may also have the following characteristics: wherein the phenolic compound is 3-aminophenol; the aldehyde compound is an aqueous formaldehyde solution; the alkaline solution is an aqueous ammonia solution with a pH of 9-11; and the etching agent is acetone.

[0008] Furthermore, the present invention provides a method for preparing a double-shelled hollow chain-like carbon nanomaterial, which may also have the following characteristics: wherein the concentration of the formaldehyde aqueous solution is 37%; in step one, the ratio of 3-aminophenol to formaldehyde aqueous solution is 0.05-0.2g:0.05-0.2ml; in step three, the ratio of 3-aminophenol to formaldehyde aqueous solution is 0.1-0.3g:0.1-0.3ml; and the mass ratio of 3-aminophenol in step one to 3-aminophenol in step three is 0.1:0.15.

[0009] Furthermore, the present invention provides a method for preparing double-shell hollow chain carbon nanomaterials, which may also have the following characteristics: in steps one and three, the reaction time of the polycondensation reaction is 25 to 30 minutes.

[0010] Furthermore, the present invention provides a method for preparing double-shell hollow chain-like carbon nanomaterials, which may also have the following characteristics: wherein the ratio of acetone in step two to 3-aminophenol in step one is 0.05-0.2g:10-30ml; and the ratio of acetone in step four to 3-aminophenol in step three is 0.1-0.3g:20-40ml.

[0011] Furthermore, the present invention provides a method for preparing double-shell hollow chain-like carbon nanomaterials, which may also have the following characteristics: in steps two and four, the etching agent reaction time is 25-30 min.

[0012] Furthermore, the present invention provides a method for preparing a double-shell hollow chain-like carbon nanomaterial, which may also have the following feature: in step four, the ultrasonic treatment frequency is 35-40KHz.

[0013] Furthermore, the present invention provides a method for preparing double-shell hollow chain-like carbon nanomaterials, which may also have the following characteristics: in step five, the pyrolysis is carried out in an inert gas; the pyrolysis procedure is as follows: heating from room temperature to 900-1100°C at a heating rate of 5°C / min, holding at that temperature for 5-7 hours, and then naturally cooling to room temperature after the holding period.

[0014] The present invention also provides a double-shell hollow chain carbon nanomaterial prepared by the above preparation method.

[0015] The present invention also provides the application of the above-mentioned double-shell hollow chain carbon nanomaterials in microwave absorption.

[0016] The beneficial effects of this invention are as follows: This invention provides a

[0017] I. The preparation method of the present invention adopts the kinetics of phenolic molecule synthesis, and utilizes the difference in internal / external cross-linking degree caused by the spontaneous aggregation of small phenolic molecules into spheres in an alkaline environment. The internal low cross-linking degree components are dissolved by a suitable organic solvent, avoiding the disadvantages of using hard template or soft template methods such as time consumption, complicated steps, and dangerous acid and alkali etching solvents.

[0018] II. The preparation method of this invention employs interfacial polymerization dynamics regulation. Conventional nanomaterial preparation methods require the application of high-frequency ultrasound to a liquid medium, utilizing the generated microjets to create thousands of instantaneous impacts on the nanomaterial surface for dispersion. This invention utilizes latent interfacial polymerization dynamics to induce hollow phenolic nanomaterials to autonomously assemble into chains, using these chains as a matrix for a second layer of coating.

[0019] Third, the preparation method of the present invention is characterized by high efficiency, convenience and safety. It takes only 1 hour from synthesis to obtaining the hollow structure and only 2 hours to obtain the double-shell hollow chain structure.

[0020] IV. In the double-shell hollow chain carbon nanomaterials prepared by the method of this invention, the double-shell hollow chain structure reduces the material density and increases the volume ratio at the same mass, which is beneficial for optimizing the carrier migration model and thus enhancing electrical conductivity loss. At the same time, the double-shell hollow chain structure increases the specific surface area, providing more carbon-air heterogeneous interfaces, attracting charges of different electronegativity to accumulate and collide at the interface, thereby causing interfacial polarization and converting electromagnetic energy into heat energy for dissipation.

[0021] V. The carbon components of the double-shell hollow chain carbon nanomaterials prepared by the method of the present invention have the advantages of being lightweight and having tunable dielectric properties.

[0022] VI. The double-shell hollow chain carbon nanomaterials prepared by the method of the present invention, when fully stirred with paraffin at a filling amount of 15wt% and molded into a coaxial ring with an outer diameter of 7.00mm and an inner diameter of 3.04mm, exhibit an effective absorption bandwidth of 5.1GHz at a thickness of 1.59mm, which is far superior to solid carbon nanomaterials. Attached Figure Description

[0023] Figure 1 This is a TEM image of the double-shell hollow chain-like carbon nanomaterial in the embodiment;

[0024] Figure 2 The XRD results are for the solid carbon nanomaterials in the comparative example and the double-shell hollow chain carbon nanomaterials in the embodiment.

[0025] Figure 3 The electromagnetic parameters are those of the solid carbon nanomaterial in the comparative example and the double-shell hollow chain carbon nanomaterial in the embodiment.

[0026] Figure 4 The comparison shows the two-dimensional microwave absorption properties of solid carbon nanomaterials and double-shell hollow chain carbon nanomaterials in the examples.

[0027] Figure 5 The reflection loss curve of the double-shell hollow chain carbon nanomaterial in the embodiment is shown at a thickness of 1.59 mm. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments.

[0029] Example

[0030] This embodiment provides a double-shell hollow chain-like carbon nanomaterial, the preparation method of which includes the following steps:

[0031] Step 1: Pour 30ml of deionized water into a 100ml volumetric beaker, and add 25% ammonia solution dropwise until the pH reaches 10; add 0.1g of 3-aminophenol to the solution and stir magnetically until completely dissolved; add 0.1ml of 37% formaldehyde solution dropwise, react for 30min, and synthesize phenolic resin balls.

[0032] Step 2: Add 30 ml of acetone and react for 30 min; centrifuge the solution at 10,000 rpm without sonication to obtain hollow phenolic resin balls.

[0033] Step 3: Place the centrifuged product in 45 ml of deionized water, and add 25% ammonia solution dropwise until the pH reaches 10; add 0.15 g of 3-aminophenol to the mixed solution and stir until completely dissolved; add 0.15 ml of 37% formaldehyde solution dropwise and react for 30 min.

[0034] Step 4: Add 45 ml of acetone and react for 30 min; centrifuge the solution at 10,000 rpm and then disperse it using 40 kHz ultrasonic frequency; dry the obtained product overnight in a 60 ℃ oven to obtain the precursor.

[0035] Step 5: Place the precursor powder in an Ar atmosphere and heat it from room temperature to 1000℃ at a heating rate of 5℃ / min. Hold it at 1000℃ for 6 hours. After the holding period, allow it to cool naturally to room temperature to obtain a double-shell hollow chain carbon nanomaterial.

[0036] Comparative Example

[0037] This embodiment provides a double-shell hollow chain-like carbon nanomaterial, the preparation method of which includes the following steps:

[0038] Step 1: Pour 30ml of deionized water into a 100ml volumetric beaker, and add 25% ammonia solution dropwise until the pH reaches 10; add 0.1g of 3-aminophenol to the solution and stir magnetically until completely dissolved; add 0.1ml of 37% formaldehyde solution dropwise, react for 30min, and synthesize phenolic resin balls.

[0039] Step 2: Centrifuge the solution at 10,000 rpm and then disperse it using 40 kHz ultrasonic frequency; dry the resulting product overnight in a 60°C oven to obtain the precursor.

[0040] Step 3: Place the precursor powder in an Ar atmosphere and heat it from room temperature to 1000℃ at a heating rate of 5℃ / min. Hold it at 1000℃ for 6 hours. After the holding period, allow it to cool naturally to room temperature to obtain solid carbon nanomaterials.

[0041] The double-shell hollow chain-like carbon nanomaterials of the example were subjected to TEM testing, and the results are as follows: Figure 1 As shown in the TEM image, the sample consists of an internal hollow chain and an external second shell. The internal cavity size is approximately 160 nm, and the outer diameter of the internal particles is approximately 340 nm. Significant voids exist between the hollow chain and the second shell, indicating that acetone still etched the low molecular weight fraction during the second round of phenolic growth.

[0042] The double-shell hollow chain-like carbon nanomaterials of the examples and the solid carbon nanomaterials of the comparative examples were subjected to XRD tests, and the results are as follows: Figure 2 As shown in the XRD patterns, both carbon materials exhibit significant (002) and (004) bulging crystal planes, indicating that the matrix composition is amorphous carbon. The peak diffraction intensities show almost no difference, attributed to the similar thermal driving forces exerted on the phenolic precursors at the same carbonization temperature, resulting in similar carbon crystallinity.

[0043] Electromagnetic parameters of the double-shell hollow chain carbon nanomaterials of the embodiment and the solid carbon nanomaterials of the comparative example were tested. The test samples were prepared by mixing the double-shell hollow chain carbon nanomaterial powder with paraffin wax at a filling amount of 15 wt% and molding it into a coaxial ring with an outer diameter of 7.00 mm and an inner diameter of 3.04 mm. The results are as follows. Figure 3 As shown, the dielectric parameter of solid carbon nanomaterials is lower than that of double-shell hollow chain carbon nanomaterials, indicating that the latter has stronger dielectric properties. Due to the almost identical properties of the amorphous carbon matrix, the difference in dielectric properties mainly stems from the difference in structure. Under the same mass ratio filling model, the hollow structure of the double-shell hollow chain carbon nanomaterials makes them lighter, while the chain structure facilitates long-range carrier migration. The double shell provides more interfaces, collectively contributing to both conductivity and polarization losses. Furthermore, due to their non-magnetic nature, the real and imaginary parts of the permeability are close to 1 and 0, respectively, indicating that the contribution of magnetic losses is very weak.

[0044] The absorption performance was calculated based on the measured electromagnetic parameters, and the results are as follows: Figure 4 As shown, solid carbon nanomaterials exhibit almost no effective absorption of electromagnetic waves (>10dB) within a thickness range of 1-5mm. In contrast, double-shell hollow chain carbon nanomaterials have an effective absorption range of 3.5-18GHz within a thickness range of 1-5mm, covering the C, X, and Ku bands. Moreover, at a thickness of 1.59mm, the effective absorption bandwidth is 5.1GHz (12.9-18GHz), demonstrating the characteristics of being lightweight, thin, and wide. This superior absorption performance stems from the combined effect of hollow, chain, and double-shell structural factors on dielectric properties. Furthermore, the amorphous carbon matrix composition also contributes to conductivity and polarization.

[0045] In summary, this invention provides a method for preparing double-shell hollow chain carbon nanomaterials by synergistically regulating multiple aspects such as phenolic synthesis kinetics, interfacial polymerization kinetics, and thermodynamics. By comparing the microwave absorption performance with that of solid carbon nanomaterials in a comparative example, it can be seen that the double-shell hollow chain carbon nanomaterials have excellent prospects for microwave absorption applications.

[0046] In this invention, unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, the reagents, materials, and procedures used herein are all widely used in the relevant fields.

[0047] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a double-shelled hollow chain-like carbon nanomaterial, characterized in that: Includes the following steps: Step 1: Phenolic and aldehyde compounds are added to an alkaline solution to carry out a condensation reaction to synthesize phenolic resin balls; Step 2: Add an etchant to the solution obtained in Step 1, centrifuge, and do not perform ultrasonic treatment to obtain hollow phenolic resin balls; Step 3: Place the hollow phenolic resin balls obtained in Step 2 into an alkaline solution containing phenolic and aldehyde compounds again for polycondensation reaction; Step 4: Add an etchant to the solution obtained in Step 3, centrifuge and sonicate to obtain the precursor; the sonication frequency is 35-40 kHz. Step 5: Pyrolyze the precursor to obtain double-shell hollow chain carbon nanomaterials.

2. The method for preparing double-shell hollow chain-like carbon nanomaterials according to claim 1, characterized in that: in, The phenolic compound is 3-aminophenol; The aldehyde compound is an aqueous formaldehyde solution; The alkaline solution is an ammonia solution with a pH of 9-11. The etching agent is acetone.

3. The method for preparing double-shell hollow chain-like carbon nanomaterials according to claim 2, characterized in that: in, The concentration of the formaldehyde aqueous solution is 37%; In step one, the ratio of 3-aminophenol to formaldehyde aqueous solution is 0.05~0.2g : 0.05~0.2ml; In step three, the ratio of 3-aminophenol to formaldehyde aqueous solution is 0.1~0.3g : 0.1~0.3ml; The mass ratio of 3-aminophenol in step one to 3-aminophenol in step three is 0.1:0.

15.

4. The method for preparing double-shell hollow chain-like carbon nanomaterials according to claim 1, characterized in that: in, In both steps one and three, the reaction time for the polycondensation reaction is 25-30 minutes.

5. The method for preparing double-shell hollow chain-like carbon nanomaterials according to claim 2, characterized in that: in, The ratio of acetone used in step two to 3-aminophenol used in step one is 0.05~0.2g : 10~30ml; The ratio of acetone in step four to 3-aminophenol in step three is 0.1~0.3g: 20~40ml.

6. The method for preparing double-shell hollow chain-like carbon nanomaterials according to claim 1, characterized in that: in, In steps two and four, the etching reaction time is 25-30 minutes.

7. The method for preparing double-shell hollow chain-like carbon nanomaterials according to claim 1, characterized in that: in, In step five, the pyrolysis is carried out in an inert gas; The pyrolysis procedure is as follows: heat from room temperature to 900~1100℃ at a heating rate of 5℃ / min, hold at that temperature for 5~7 hours, and then allow to cool naturally to room temperature after the holding period.

8. The double-shell hollow chain-like carbon nanomaterial prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the double-shell hollow chain carbon nanomaterial as described in claim 8 in microwave absorption.

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