A light-weight core-shell structure urchin-like NiO / Ni@CNTs composite wave-absorbing material and a preparation method thereof

Abstract

The application not only provides a simple and efficient preparation method of a core-shell structure urchin-like NiO / Ni@CNTs composite wave-absorbing material, but also synthesizes a novel core-shell structure urchin-like NiO / Ni@CNTs composite wave-absorbing material by combining a chemical bath deposition method and a catalytic chemical vapor deposition method. The proposed method and sample have the advantages of low cost, simple process, mass production, generalization, adjustable electromagnetic parameters of the prepared sample and the like. Due to the unique urchin-like morphology and the rich interface and adjustable electromagnetic properties brought by the multi-component structure, the impedance matching property and the loss capacity of the material are effectively improved through the interface engineering and the matching characteristic optimization strategy, so that the designed sample can exhibit very excellent electromagnetic wave absorption performance under a relatively thin matching thickness.

Description

Technical Field

[0001] This invention specifically relates to the design and preparation of a novel lightweight core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material, belonging to the field of inorganic electromagnetic wave absorbing materials technology. Background Technology

[0002] With the rapid development of electronic industry technology, people hope to develop high-performance electromagnetic wave absorbing materials with characteristics such as low density, wide frequency band, strong absorption, thin thickness, and strong chemical stability.

[0003] Carbon materials such as carbon foam (CF), graphene (G), and carbon nanotubes (CNTs) are among the most promising high-performance electromagnetic wave absorbing materials due to their low density, high dielectric loss capacity, and good chemical stability. However, the high conductivity, simple loss mechanism, and poor matching characteristics of pure carbon materials greatly hinder the improvement of their overall electromagnetic wave absorption performance. Therefore, constructing novel carbon-based composite microwave absorbing materials through structural and compositional optimization has become a research hotspot. Summary of the Invention

[0004] The purpose of this invention is to provide a simple and widely applicable process for the mass synthesis of novel lightweight core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing materials with excellent electromagnetic wave absorption performance.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material, comprising the following steps:

[0006] 1) Add NiSO4·6H2O to deionized water and stir for 5-10 minutes to fully dissolve it until the liquid is clear; then add K2S2O8 to deionized water and stir for 5-10 minutes to fully dissolve it until the liquid is clear; then add both solutions together to a large beaker and add NH3·H2O, stir continuously to mix evenly and react fully, then let stand to allow the solution to separate into layers, take off the lower precipitate, and after multiple centrifugations, washing and drying, the final product is flower-shaped NiOOH intermediate 1;

[0007] 2) Calcine the intermediate 1 obtained from the above reaction in an air atmosphere to obtain the flower-like NiO intermediate 2.

[0008] 3) Place intermediate 2 in a tube furnace and, under an argon atmosphere, use acetylene as the carbon source. After high-temperature calcination, acetylene is catalytically decomposed on the surface of NiO nanoflowers, and carbon nanotubes are grown in situ. The resulting product is the target product, a core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material.

[0009] In step 1, the molar ratio of K2S2O8 and NiSO4·6H2O is 1:3-6, and the amount of NH3·H2O added is 6-12 mL.

[0010] The amount of NH3·H2O added in step 1 is preferably 10 mL, and the molar ratio of K2S2O8 and NiSO4·6H2O in step 1 is 1:5.

[0011] The calcination temperature in step 2 is 380℃~420℃, and the calcination time is 2h~3h.

[0012] The preferred calcination temperature in step 2 is 400℃, and the preferred calcination time is 2h.

[0013] The calcination temperature in step 3 is 450℃~550℃, the calcination time is 2~3h, the flow rate of acetylene is 20mL / min, and the introduction time is 5~20min.

[0014] The preferred calcination temperature in step 3 is 500℃, and the preferred acetylene introduction time is 10 min.

[0015] Beneficial effects of the present invention

[0016] This invention proposes a simple and scalable process for synthesizing a novel lightweight core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material. Due to its unique urchin-like morphology and tunable composition, the electromagnetic wave absorption performance is greatly improved through interface engineering and matching characteristic optimization strategies, providing a scientific basis for the development of lightweight high-performance electromagnetic wave absorbing materials.

[0017] Specifically, this invention proposes a novel lightweight core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material and its preparation method. This method is low-cost, simple, and mass-producible. The electromagnetic parameters of the prepared sample are adjustable, achieving excellent electromagnetic wave absorption performance even with a relatively thin matching thickness. Furthermore, we provide an effective approach to simultaneously utilize interface engineering and impedance matching strategies to enhance the electromagnetic wave absorption performance of the material, providing a scientific basis for the development of lightweight, high-performance electromagnetic wave absorbing materials.

[0018] This invention prepares a novel lightweight core-shell structured urchin-shaped NiO / Ni@CNTs composite microwave absorbing material. By changing the acetylene pyrolysis time and temperature, the electromagnetic parameters of the material can be effectively adjusted, resulting in a microwave absorbing material with excellent impedance matching characteristics. The novel lightweight core-shell structured NiO / Ni@CNTs composite microwave absorbing material prepared in this invention possesses a unique three-dimensional urchin-like morphology, providing numerous interfaces for multiple reflections and scattering of electromagnetic waves. Simultaneously, it enhances polarization loss and conduction loss capabilities, thereby enhancing the material's electromagnetic wave absorption effect. Results demonstrate that this novel lightweight core-shell structured urchin-shaped NiO / Ni@CNTs composite microwave absorbing material exhibits excellent electromagnetic wave absorption performance, achieving an effective absorption bandwidth of 5.60 GHz with a matching thickness of only 1.82 mm. Furthermore, by adjusting the thickness, it exhibits excellent electromagnetic wave absorption performance across the entire S-Ku band, making it suitable for military stealth applications. Attached Figure Description

[0019] Figure 1 XRD patterns of intermediate 1 and NiO / Ni@CNTs of the novel lightweight core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material synthesized according to the method of the present invention;

[0020] Figure 2 SEM and TEM images of Example 1 of the novel lightweight core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material synthesized according to the method of the present invention;

[0021] Figure 3 SEM and TEM images of Example 2 of the novel lightweight core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material synthesized according to the method of the present invention;

[0022] Figure 4 The microwave absorption performance diagrams of the novel lightweight core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material synthesized according to the method of the present invention are shown in Examples 1 and 2.

[0023] Figure 5 The curves show the three-dimensional variation of reflection loss, frequency, and thickness of the synthesized core-shell structured urchin-like NiO / Ni@CNTs. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] A core-shell structured, urchin-like NiO / Ni@CNTs composite microwave absorbing material was prepared through the following steps:

[0027] (I) Preparation of flower-shaped NiOOH intermediate 1 by chemical bath deposition method;

[0028] Add 50 mmol NiSO4·6H2O to deionized water and stir for 10 min to dissolve completely, obtaining solution A. Then add 10 mmol K2S2O8 to deionized water and stir for 10 min to dissolve completely, obtaining solution B. Add both solutions together to a large beaker and add 10 mL NH3·H2O, stirring constantly to mix thoroughly and allow the mixture to react for a period of time. Then allow the solution to stand to separate into layers. Take the lower precipitate, wash it three times each with deionized water and ethanol, and dry it overnight at 100°C. The final product is flower-shaped NiOOH intermediate 1.

[0029] (ii) The intermediate 1 obtained from the above reaction is placed in a muffle furnace and calcined in an air atmosphere at a temperature of 400°C for 2 hours. The resulting powder is the flower-shaped NiO intermediate 2.

[0030] (III) Place intermediate 2 in a tube furnace and heat it to 450℃ under an argon atmosphere. At the same time, close the argon valve and open the acetylene valve. Control the acetylene flow rate to 20mL / min and the flow time to 10min. After 10min, close the acetylene valve and open the argon valve. Continue to keep it at the temperature for 2h. After high-temperature calcination, the acetylene is catalytically decomposed on the surface of NiO nanoflowers, and carbon nanotubes are grown in situ. The product obtained is the target product, the core-shell structured sea urchin-like NiO / Ni@CNTs composite microwave absorbing material.

[0031] Example 2

[0032] The difference between Example 2 and Example 1 is that the pyrolysis temperature in step 3) is 500℃.

[0033] (iv) The test results are as follows:

[0034] Figure 1 The XRD patterns of the intermediate 2NiO nanoflowers and NiO / Ni@CNTs show that the prepared samples can be well matched with the diffraction peaks of NiO and Ni, respectively. The broad peak at around 25° in the NiO / Ni@CNTs pattern is amorphous graphitic carbon, which proves the formation of CNTs.

[0035] Figure 2The images show SEM and TEM images of the NiO / Ni@CNTs sample prepared in Example 1. As can be seen from the images, CNTs were successfully grown on the surface of the flower-like NiO. The black NiO / Ni nanoparticles can be clearly observed at the tips of the carbon nanotubes. The synthesized sample exhibits a typical core-shell structure with a three-dimensional sea urchin-like morphology. The relevant test results well demonstrate that the process proposed in this application can realize the large-area synthesis of core-shell structured sea urchin-like NiO / Ni@CNTs composites.

[0036] Figure 3 The images show SEM and TEM images of the NiO / Ni@CNTs sample prepared in Example 2. As can be seen from the images, Example 2 is similar to Example 1. The synthesized samples are all composed of CNTs aggregates, exhibiting a typical core-shell structure with a three-dimensional sea urchin-like morphology. In Example 2, the length and aggregation degree of carbon nanotubes in the sample are significantly higher than those in Example 1. The relevant test results well demonstrate that our proposed process can control the growth of carbon nanotubes by adjusting the reaction conditions, thereby enhancing the material's loss capacity and impedance matching characteristics, and optimizing the material's electromagnetic wave absorption performance.

[0037] Figure 4 The graphs show the microwave absorption performance of the NiO / Ni@CNTs samples prepared in Examples 1 and 2. It can be seen that the novel lightweight core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material exhibits excellent microwave absorption performance. Example 1 achieves an effective absorption bandwidth of 6.00 GHz with a matching thickness of only 2.28 mm; Example 2 achieves an effective absorption bandwidth of 5.60 GHz with a matching thickness of only 1.82 mm, and both samples demonstrate excellent electromagnetic wave absorption performance across the entire S-Ku band. These results prove that the process proposed in this application can synthesize a novel lightweight core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material with excellent electromagnetic wave absorption performance, which has great application potential.

[0038] Figure 5The figures show the three-dimensional variation curves of reflection loss, frequency, and thickness for the NiO / Ni@CNTs samples prepared in Examples 1 and 2. The left figure shows Sample 1, prepared under acetylene introduction time of 10 minutes and pyrolysis temperature of 450℃. Its electromagnetic wave absorption capability is RLmin = -21.92dB (i.e., absorption rate > 99.99%) at a matching thickness of 2.62mm; it has an effective absorption bandwidth of 6.00GHz at a matching thickness of 2.28mm. Sample 2, prepared under acetylene introduction time of 10min and pyrolysis temperature of 500℃, achieves an effective absorption bandwidth of 5.60GHz with a matching thickness of only 1.82mm, and RLmin = -29.16dB (i.e., absorption rate approximately 99.999%) at an ultra-thin matching thickness of 1.51mm. The results above show that the process proposed in this application can synthesize a novel lightweight core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material with excellent electromagnetic wave absorption performance, which has great application prospects and value.

[0039] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a core-shell structure urchin-like NiO / Ni@CNTs composite wave-absorbing material, characterized in that, Comprising the following steps: 1) NiSO4.6H2O is added to deionized water, stirred for 5-10 min, and fully dissolved until the liquid is transparent; K2S2O8 is then added to deionized water, stirred for 5-10 min, and fully dissolved until the liquid is transparent; then the two solutions are added together in a large beaker, NH3.H2O is added, and stirred constantly to mix uniformly and fully react, then left to stand to separate the solution into layers, the lower layer precipitate is removed, and after multiple centrifugation, washing, and drying, the final product is the flower-shaped NiOOH intermediate 1; 2) the intermediate 1 obtained from the above reaction is calcined under an air atmosphere, and the obtained product is the flower-shaped NiO intermediate 2; 3) the intermediate 2 is placed in a tube furnace, under an argon atmosphere, with acetylene as the carbon source, after high-temperature calcination, acetylene is catalytically cracked on the surface of the NiO nanoflower, carbon nanotubes are in-situ grown, and the obtained product is the target product, the urchin-shaped NiO / Ni@CNTs composite wave-absorbing material with core-shell structure.

2. The preparation method of the core-shell structure urchin-like NiO / Ni@CNTs composite wave-absorbing material according to claim 1, characterized in that, The molar ratio of K2S2O8 to NiSO4.6H2O in step 1) is 1:3-6.

3. The preparation method of the core-shell structure urchin-like NiO / Ni@CNTs composite wave-absorbing material according to claim 2, characterized in that, The molar ratio of K2S2O8 to NiSO4.6H2O in step 1) is 1:

5.

4. The preparation method of the core-shell structure urchin-like NiO / Ni@CNTs composite wave-absorbing material according to claim 1, characterized in that, The calcination temperature in step 2) is 380-420°C, and the calcination time is 2-3h.

5. The preparation method of the core-shell structure urchin-like NiO / Ni@CNTs composite wave-absorbing material according to claim 4, characterized in that, The calcination temperature in step 2) is preferably 400°C, and the calcination time is preferably 2h.

6. The method for preparing the core-shell structure urchin-like NiO / Ni@CNTs composite wave-absorbing material according to claim 1, characterized in that, The calcination temperature in step 3) is 450-550°C, the calcination time is 2-3h, the flow rate of acetylene is 20mL / min, and the acetylene flow time is 5-20min.

7. The method for preparing a core-shell structured urchin-like NiO / Ni@CNTs composite microwave absorbing material according to claim 1, characterized in that, The calcination temperature in step 3) is preferably 500°C, and the acetylene flow time is preferably 10min.

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