A core-shell structure hollow carbon sphere@MoSe2 / MoO2 microwave absorbing material and a preparation method thereof

Abstract

The application relates to design and preparation of a novel microwave absorption material of hollow carbon sphere@MoSe2 / MoO2 with a core-shell structure. The material has a hollow core-shell structure, wherein the inner core of the core-shell structure is a hollow carbon sphere, the outer shell is MoSe2 / MoO2 nanosheet, and the whole material constitutes a spherical layered core-shell structure. The hollow carbon sphere@MoSe2 / MoO2 microwave absorption material of the application exhibits excellent electromagnetic wave loss capacity in a frequency range of 2.0-18.0 GHz. The hollow carbon sphere@MoSe2 / MoO2 microwave absorption material with multiple components and rich heterojunction interfaces is prepared by using a functionalized hollow carbon sphere as a template, growing MoSe2 nanosheet on the surface of the template, and then annealing under argon-hydrogen mixed gas and placing in an air environment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of microwave absorption material design and development, and particularly relates to the design and preparation thereof. BACKGROUND

[0002] In today's society, the widespread application of various electronic and electrical products has led to increasingly serious electromagnetic pollution problems, and therefore it is urgent to design and synthesize effective anti-radiation materials. Microwave absorption materials are essentially a kind of functional materials that absorb electromagnetic waves and convert them into heat or other forms of energy, thereby weakening the effect of electromagnetic waves. Carbon materials have always been considered as a kind of microwave absorption materials with great potential, including carbon fibers, carbon nanotubes, graphene and the like, which have the characteristics of light weight, high chemical stability and strong dielectric loss. However, like other single-component microwave absorption materials, the single loss mechanism and poor impedance matching characteristics of carbon materials seriously limit their performance in wave absorption and related applications in this field.

[0003] Since the birth of graphene, two-dimensional materials have attracted the attention of many researchers. Moreover, numerous studies have shown that materials with hierarchical structures can make full use of the advantages of each component material and effectively maximize the performance of the material, so transition metal dichalcogenides with two-dimensional morphology have also attracted the research interest of many researchers. SUMMARY

[0004] The purpose of the present application is to provide a design and preparation process of a novel hollow carbon sphere@MoSe2 / MoO2 composite material with core-shell structure, which has a simple synthesis process and excellent performance.

[0005] The present inventors have designed and synthesized a novel microwave absorption material of hollow carbon sphere@MoSe2 / MoO2 with core-shell structure. The hollow structure involved not only effectively reduces the density of the material, but also provides a good interface, which is very conducive to the loss of electromagnetic waves. After being combined with molybdenum diselenide / molybdenum dioxide, the composite material effectively overcomes the shortcomings of single loss mechanism and poor impedance matching, and forms multiple interfaces, greatly improving the loss capacity of electromagnetic waves. The present application has obvious innovation in method and design, and the designed sample shows very good microwave absorption performance, providing detailed scientific basis for the development of new lightweight high-performance electromagnetic wave absorption materials.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] One of the technical solutions of the present application provides a design idea and synthesis process of a novel hollow carbon sphere@MoSe2 / MoO2 composite material with core-shell structure, and the preparation process thereof includes the following steps:

[0008] (1) A certain amount of styrene is dispersed in a suitable amount of anhydrous ethanol, a certain amount of polyvinylpyrrolidone is added, and a uniform solution is stirred. Argon is introduced, and azobisisobutyronitrile is added. After polymerization, separation and drying, polystyrene microspheres are obtained;

[0009] (2) A certain amount of polystyrene microspheres is ultrasonically dispersed in a suitable amount of Tris-HCl buffer solution, and a certain amount of dopamine hydrochloride is added. After stirring for a period of time, the resulting polymerization product is centrifuged and dried to obtain polystyrene microspheres coated with polydopamine;

[0010] (3) The polystyrene microspheres coated with polydopamine are calcined under argon protection to obtain hollow carbon spheres;

[0011] (4) A certain amount of hollow carbon spheres is ultrasonically dispersed in a suitable amount of nitric acid solution, and then transferred to a reaction kettle. After maintaining at a specific temperature for a period of time, the resulting product is separated, washed and dried to obtain functionalized hollow carbon spheres;

[0012] (5) A certain amount of selenium powder is dispersed in hydrazine hydrate, and then sodium molybdate dihydrate, functionalized hollow carbon spheres and deionized water are added. After ultrasonic dispersion for a period of time, the mixed solution is transferred to a reaction kettle and maintained at a specific temperature for a period of time. The resulting product is separated, washed and dried to obtain MoSe2-coated hollow carbon spheres;

[0013] (6) The MoSe2-coated hollow carbon spheres are annealed under argon-hydrogen mixed gas, cooled to room temperature and placed in an air environment for a period of time to obtain the target product.

[0014] Further, in step (1), the addition amounts of styrene, anhydrous ethanol, polyvinylpyrrolidone and azobisisobutyronitrile are in the ratio of (20-60) mL: 450 g: 5 g: (1-10) g, wherein the average molecular weight of polyvinylpyrrolidone is K28-32; the stirring time is 25-35 min, the polymerization temperature is 60-70 ℃, and the polymerization time is 15-17 h.

[0015] Further, in step (2), the addition amounts of polystyrene, dopamine hydrochloride and Tris-HCl buffer solution are in the ratio of 500 mg: (200-1000) mg: 200 mL, wherein the pH of the Tris-HCl buffer solution is 8-9; the ultrasonic time is 25-30 min, the polymerization temperature is 25-30 ℃, and the polymerization time is 23-25 h.

[0016] Further, in step (3), the calcination temperature is 750-850 ℃, the time is 1-3 h, and the heating rate is 5 ℃ / min.

[0017] Further, in step (4), the hollow carbon sphere and the nitric acid solution are added in a ratio of 100 mg: 50 mL, wherein the concentration of the nitric acid solution is (1-5) mol / L; the ultrasonic time is 5-10 min, the functionalization required temperature is 90-110 ℃, and the holding time is 11-13 h.

[0018] Further, in step (5), the selenium powder, hydrazine hydrate, sodium molybdate dihydrate, the functionalized hollow carbon sphere and deionized water are added in a ratio of 237 mg: 5 mL: 363 mg: (40-60) mg: 30 mL; the stirring time is 5-7 h, the ultrasonic time is 20-30 min, the hydrothermal setting temperature is 170-190 ℃, and the holding time is 11-13 h.

[0019] Further, in step (6), the concentration of hydrogen is 10%, the annealing temperature is 550-650 ℃, the time is 1-3 h, and the heating rate is 5 ℃ / min.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] The present application utilizes the stronger electronegativity of oxygen, and realizes the synthesis of the hollow carbon sphere@MoSe2 / MoO2 by functionalizing the hollow carbon sphere and high-temperature treatment of the hollow carbon sphere@MoSe2 under argon-hydrogen mixed gas. Because of the construction of the rich heterojunction interface and the introduction of metallic MoO2, the polarization loss and the conduction loss ability of the material are improved, so that the hollow carbon sphere@MoSe2 / MoO2 exhibits excellent electromagnetic wave absorption performance.

[0022] (1) The novel microwave absorption material of the core-shell structure of the hollow carbon sphere@MoSe2 / MoO2 provided by the present application has the advantages of wide bandwidth, low matching thickness and wide frequency response. In a low thickness of 1.97 mm, it can realize a wide bandwidth of 5.80 GHz. This type of composite material exhibits excellent electromagnetic wave absorption performance in the entire test frequency band: S (2-4 GHz), C (4-8 GHz), X (8-12 GHz), Ku (12-18 GHz).

[0023] (2) The synthesis process and method of the present application are novel, simple, and easy to synthesize other types of novel core-shell structure of hollow carbon sphere-based composite materials.

[0024] (3) The inner and outer shell material microstructure parameters in the present application can be adjusted to effectively realize the adjustment and optimization of the electromagnetic parameters of the material, so as to obtain adjustable and excellent electromagnetic wave absorption performance. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 (a) X-ray diffraction patterns and (b) Raman spectra of hollow carbon spheres@MoSe2 and hollow carbon spheres@MoSe2 / MoO2 microwave absorbing materials;

[0026] Figure 2 Scanning electron microscope images of the samples: (a1), (a2) Hollow carbon spheres @MoSe2; (b1), (b2) Hollow carbon spheres @MoSe2 / MoO2;

[0027] Figure 3 Transmission electron microscopy (TEM) images of the samples: (a) Hollow carbon spheres @MoSe2; (b) Hollow carbon spheres @MoSe2 / MoO2;

[0028] Figure 4 The variation curves of reflection loss values ​​of the samples: (a) Hollow carbon spheres@MoSe2; (b) Hollow carbon spheres@MoSe2 / MoO2. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0030] The following are examples of the present invention. Unless otherwise specified, the raw materials or processing techniques are conventional commercially available materials or conventional processing techniques in the art.

[0031] Example 1

[0032] (1) Measure 55 ml of styrene and add it to a three-necked glass flask containing 450 g of anhydrous ethanol. Then add 1 g of polyvinylpyrrolidone and stir for 30 min to form a homogeneous solution. Add 5 g of azobisisobutyronitrile to the homogeneous solution, raise the temperature to 65 °C and maintain it for 16 hours. After cooling, wash, centrifuge, and dry, polystyrene microspheres can be obtained. The entire polymerization process is carried out under argon protection.

[0033] (2) Weigh 500 mg of polystyrene microspheres and add 200 mL of Tris-HCl buffer (preferably pH=8.5). After sonicating for 30 minutes, add 500 mg of dopamine hydrochloride. Stir at 30 °C for 24 h, then centrifuge and dry to obtain polydopamine-coated polystyrene microspheres.

[0034] (3) Polydopamine-coated polystyrene microspheres were placed under argon protection and calcined at 700 °C for 2 h with a heating rate of 5 °C / min to obtain hollow carbon spheres.

[0035] (4) 100 mg hollow carbon spheres were dispersed in 50 mL nitric acid solution (1 mol / L), and after ultrasonic treatment for 10 min, they were transferred into a reaction kettle with a polytetrafluoroethylene liner. The reaction kettle was placed in an oven, and the temperature was set to 100 ℃ for 12 h. After the reaction was completed and the temperature was lowered, the product was separated, dried, and functionalized hollow carbon spheres were obtained;

[0036] (5) 0.237 g of selenium powder was dispersed in 5 mL of hydrazine hydrate, and after stirring for 6 h, 0.363 g of sodium molybdate dihydrate, 50 mg of functionalized hollow carbon spheres, and 30 mL of deionized water were added. After ultrasonic treatment for 30 min, they were transferred into a reaction kettle with a polytetrafluoroethylene liner, and the temperature was set to 180 ℃ for 12 h. After the reaction was completed and the temperature was lowered, the product was separated, washed, and dried to obtain MoSe2-coated hollow carbon spheres;

[0037] (6) The MoSe2-coated hollow carbon spheres were annealed at 600 ℃ for 2 h under argon-hydrogen mixed gas (hydrogen concentration of 10%), and the heating rate was 5 ℃ / min. After the reaction was completed and the temperature was lowered to room temperature, the target product was obtained by placing it in an air environment.

[0038] Example 2

[0039] Without changing other steps, 2 g of azobisisobutyronitrile was added in step (1), and hollow carbon sphere@MoSe2 / MoO2 wave-absorbing materials with smaller diameters were obtained.

[0040] Example 3

[0041] Without changing other steps, 200 mg of dopamine hydrochloride was added in step (2), and hollow carbon sphere@MoSe2 / MoO2 wave-absorbing materials with lower carbon layer thickness were obtained.

[0042] Example 4

[0043] Without changing other steps, the concentration of nitric acid added in step (4) was changed to 5 mol / L, and hollow carbon sphere@MoSe2 / MoO2 wave-absorbing materials with more MoO2 components were obtained.

[0044] Example 5

[0045] Without changing other steps, 60 mg of functionalized hollow carbon spheres was added in step (5), and hollow carbon sphere@MoSe2 / MoO2 wave-absorbing materials with less MoSe2 / MoO2 coating were obtained.

[0046] Comparative Example 1:

[0047] Compared to Example 1, only steps (1) to (5) are different.

[0048] Characterization and performance testing experiments

[0049] Figure 1 X-ray diffraction (XRD) analysis was performed on the samples prepared in Example 1 and Comparative Example 1. As shown in the figure, the diffraction peaks of the hollow carbon spheres@MoSe2 / MoO2 material in Example 1 at 2θ = 13.6°, 31.6°, 36.5°, 39.1°, and 55.8° correspond to the (003), (101), (104), (015), and (110) crystal planes of MoSe2 (JCPDS Card No. 72-1420), while the diffraction peaks at 2θ = 26.0°, 36.9°, and 53.5° correspond to the (011), (-211), and (-311) crystal planes of MoO2 (JCPDS Card No. 86-0135). For Comparative Example 1, its XRD pattern only matches that of MoSe2 (JCPDS Card No. 72-1420). In addition, we further analyzed the data using Raman spectroscopy and found that the concentrations at 1350 and 1580 cm⁻¹ were... -1 The presence of distinct D and G peaks confirms the presence of carbon. Our XRD and Raman spectroscopy characterizations together demonstrate the successful synthesis of hollow carbon spheres@MoSe2 / MoO2.

[0050] Figure 2 Scanning electron microscope (SEM) images of hollow carbon spheres@MoSe2 and hollow carbon spheres@MoSe2 / MoO2 are shown. a1 and a2 show the microstructure of the hollow carbon spheres@MoSe2 in Comparative Example 1. As shown in Figure a1, the diameter of a single sphere is on the micrometer scale, and the surface is not smooth, indicating that the carbon spheres are coated with MoSe2 nanosheets. A further magnified image in a2 shows that its surface is densely encapsulated by nanosheets. b1 and b2 show the microstructure of the hollow carbon spheres@MoSe2 / MoO2 in Example 1. Figure b1 shows some surface-damaged spheres, revealing the hollow internal morphology, which proves the successful design of the hollow morphology. Furthermore, the magnified image in b2 shows that its morphology is not significantly different from that of Comparative Example 1, indicating that the subsequent argon-hydrogen annealing treatment did not damage the morphology of the precursor.

[0051] Figure 3 This is a transmission electron microscope (TEM) image of the hollow carbon spheres@MoSe2 / MoO2 prepared in Example 1 above. Figure 3 As shown in Figure a, the sample exhibits an overall hollow spherical structure, while from... Figure 3It can be found that the rough folds on the outer surface of b are assembled by many tiny nanosheets, which is consistent with the results observed by scanning electron microscopy, which shows that the process conditions we proposed can be used to prepare hollow carbon sphere@MoSe2 / MoO2 with core-shell structure on a large scale.

[0052] Figure 4 The reflection loss values of the above-mentioned comparative example 1 and example 1 at a thickness of 1.0-10.0 mm and a frequency of 2.0-18.0 GHz are shown in the following table. Figure 4 As shown in comparative example 1, the hollow carbon sphere@MoSe2 sample has a maximum effective bandwidth (reflection loss <-10 dB) of 2.80 GHz at a thickness of 3.30 mm; after step (6), as shown in example 1, the synthesized hollow carbon sphere@MoSe2 / MoO2 has a maximum effective bandwidth of 4.80 GHz at a thickness of 3.30 mm. Figure 4 As shown in comparative example 1, the hollow carbon sphere@MoSe2 sample has a maximum effective bandwidth (reflection loss <-10 dB) of 2.80 GHz at a thickness of 3.30 mm; after step (6), as shown in example 1, the synthesized hollow carbon sphere@MoSe2 / MoO2 has a maximum effective bandwidth of 4.80 GHz at a thickness of 3.30 mm.

[0053] Comparing comparative example 1 with example 1, the wave-absorbing performance of the hollow carbon sphere@MoSe2 / MoO2 sample is greatly improved, and its superior performance is attributed to the construction of a large number of heterojunction surfaces, which is conducive to the optimization of impedance matching and the enhancement of polarization loss; in addition, the introduction of metallic MoO2 enhances the conductive loss capacity, and the morphology of two-dimensional nanosheets can prolong the transmission path of electrons, which can further enhance the conductive loss.

[0054] The above description of the comparative examples and examples is for the convenience of the ordinary skilled person in the art to understand and use the invention. Those skilled in the art can easily modify these examples and apply the general principles described herein to other examples without the need for creative discovery. Therefore, the present application is not limited to the above examples, and those skilled in the art can make improvements and modifications within the scope of the present application without departing from the scope of the present application.

Claims

1. A preparation method of a core-shell structure hollow carbon sphere@MoSe2 / MoO2 microwave absorption material, characterized in that, Comprising the following steps: (1) dispersing styrene in anhydrous ethanol, adding polyvinylpyrrolidone, stirring into a uniform solution, passing argon, adding azobisisobutyronitrile, and then obtaining polystyrene microspheres after polymerization, separation and drying; (2) weighing polystyrene microspheres, ultrasonic dispersion in Tris-HCl buffer solution, adding dopamine hydrochloride, polymerizing under stirring, centrifuging, drying, and then obtaining polystyrene microspheres coated with polydopamine; (3) placing the polystyrene microspheres coated with polydopamine in argon protection and calcining to obtain hollow carbon spheres; (4) ultrasonic dispersion of the hollow carbon spheres in nitric acid solution, then transferring to a reaction kettle for reaction, separating, washing and drying the obtained product to obtain functionalized hollow carbon spheres; (5) dispersing selenium powder in hydrazine hydrate, then adding sodium molybdate dihydrate, functionalized hollow carbon spheres and deionized water, ultrasonic dispersion, then transferring the mixed solution to a reaction kettle for reaction, separating, washing and drying the obtained product to obtain MoSe2-coated hollow carbon spheres; (6) annealing the MoSe2-coated hollow carbon spheres under argon-hydrogen mixed gas, cooling to room temperature and placing in an air environment to obtain the target product.

2. The preparation method of the core-shell structure hollow carbon sphere@MoSe2 / MoO2 microwave absorbing material according to claim 1, characterized in that, In step (1), the adding amount ratio of styrene, anhydrous ethanol, polyvinylpyrrolidone and azobisisobutyronitrile is (20-60) mL: 450 g: 5 g: (1-10) g; the stirring time is 25-35 min, the polymerization temperature is 60-70 ℃, and the polymerization time is 15-17 h.

3. The method for preparing the core-shell structured hollow carbon spheres@MoSe2 / MoO2 microwave absorbing material as described in claim 1, characterized in that, In step (2), the adding amount ratio of polystyrene, dopamine hydrochloride and Tris-HCl buffer solution is 500 mg: (200-1000) mg: 200 mL, wherein the pH of the Tris-HCl buffer solution is 8-9; the ultrasonic time is 25-30 min, the polymerization temperature is 25-30 ℃, and the polymerization time is 23-25 h.

4. The method for preparing the core-shell structured hollow carbon sphere@MoSe2 / MoO2 microwave absorbing material as described in claim 1, characterized in that, In step (3), the calcination temperature is 750-850 ℃, the calcination time is 1-3 h, and the heating rate is 5 ℃ / min.

5. The method for preparing the core-shell structured hollow carbon spheres@MoSe2 / MoO2 microwave absorbing material as described in claim 1, characterized in that, In step (4), the adding amount ratio of hollow carbon spheres and nitric acid solution is 100 mg: 50 mL, wherein the concentration of the nitric acid solution is (1-5) mol / L; the ultrasonic time is 5-10 min, the functionalization reaction temperature is 90-110 ℃, and the reaction holding time is 11-13 h.

6. The method for preparing the core-shell structured hollow carbon spheres@MoSe2 / MoO2 microwave absorbing material as described in claim 1, characterized in that, In step (5), the selenium powder is dispersed in hydrazine hydrate and stirred, wherein the adding amount ratio of selenium powder, hydrazine hydrate, sodium molybdate dihydrate, functionalized hollow carbon spheres and deionized water is 237 mg: 5 mL: 363 mg: (40-60) mg: 30 mL; the stirring time is 5-7 h, the ultrasonic time is 20-30 min, the reaction temperature is 170-190 ℃, and the holding time is 11-13 h.

7. The method for preparing the core-shell structured hollow carbon spheres@MoSe2 / MoO2 microwave absorbing material as described in claim 1, characterized in that, In step (6), the concentration of hydrogen is 10%, the annealing temperature is 550-650 ℃, the time is 1-3 h, and the heating rate is 5 ℃ / min.

8. The hollow carbon sphere@MoSe2 / MoO2 microwave absorbing material with core-shell structure prepared by the preparation method according to any one of claims 1-7.

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