Preparation method of carbon cage-in-cage / carbon-coated nickel composite material with infrared stealth performance, and product and application thereof

Abstract

The application discloses a preparation method of carbon-cage-in-cage / carbon-coated nickel composite material with infrared stealth performance, and the obtained product and application, and steps are as follows: nickel microspheres are prepared; the nickel microspheres and urea are calcined under an inert atmosphere to obtain NC / Ni composite material; the NC / Ni composite material is placed in dilute hydrochloric acid for acid etching to obtain the carbon-cage-in-cage / carbon-coated nickel composite material. The obtained composite material is a carbon-coated nickel modified carbon microcage-in-nanocage structure, the application has simple process, can accurately control the structure of the carbon-cage-in-cage, and effectively solves the shortcoming that the nickel element is easy to agglomerate, has good electric conductivity, electromagnetic wave absorption performance and low infrared emissivity, and has wide application value in the fields of infrared stealth and electromagnetic wave absorption.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of carbon cage / carbon-coated nickel composite material with infrared stealth performance, and also relates to a product obtained by the method and application of the product in the field of electromagnetic wave absorption and infrared, and belongs to the technical field of nanomaterial preparation and application. BACKGROUND

[0002] With the rapid development of wireless communication devices and power transmission technology, electromagnetic radiation and pollution problems are becoming increasingly serious, which may interfere with the operation of devices and endanger human health. Microwave absorbing materials can effectively absorb electromagnetic energy through dielectric loss or magnetic loss, and are one of the effective means to solve electromagnetic radiation and pollution. So far, various electromagnetic wave absorbing materials, including metal oxides, conductive polymers and ceramics, have been widely studied. In practical applications, the absorber not only needs to have strong absorption and wide bandwidth, but also needs to be light in weight. Among various candidate materials, carbon materials have attracted great attention due to their high electrical conductivity, large specific surface area, light weight and strong chemical stability. However, pure carbon materials have certain limitations. Their high electrical conductivity leads to skin effect, resulting in impedance mismatch, which increases microwave reflection instead of absorption. In addition, the single loss mechanism of pure carbon materials usually limits the absorption bandwidth to below 4 GHz, making it difficult to achieve strong absorption in a wide frequency range.

[0003] The latest progress in electromagnetic wave absorbing materials shows that the addition of magnetic components, including ferromagnetic metals, oxides and alloys, in carbon materials significantly enhances the wideband absorption by improving impedance matching and introducing dielectric loss and magnetic loss. In particular, hollow structure materials show great prospects as microwave absorbing materials, as their large internal cavities and double-sided surfaces result in lower reflection loss (RL) than blocky materials. The large cavities not only reduce the overall weight of the absorber, but also facilitate multiple reflections and scattering of electromagnetic waves, increasing the effective path length and extending the absorption bandwidth. In addition, the double-sided surface provides multiple uniform heterogeneous interfaces, which produces a strong interfacial polarization effect, thereby improving the dielectric loss and further improving the overall absorption efficiency. Unfortunately, traditional manufacturing methods, such as high-temperature pyrolysis, solvothermal method and solid template method, often result in undesirable problems, including nanoparticle aggregation and microstructure collapse. Therefore, achieving precise control over the interfacial properties and optimizing the synergistic effect between dielectric and magnetic properties are crucial for the development of lightweight, wideband and high-performance microwave absorbers.

[0004] With the advancement of infrared and radar detection technology, traditional single-band stealth materials have been unable to meet the needs of modern warfare. Therefore, the development of radar / infrared compatible stealth materials has become a top priority. SUMMARY

[0005] In view of the deficiencies of carbon materials in electromagnetic wave absorption, infrared stealth and the like, the application provides a preparation method of carbon cage-in-cage / carbon-coated nickel composite material with infrared stealth performance and the obtained product, the method is simple in process, the structure of the carbon material is optimized by introducing magnetic carbon-coated nickel nanoparticles and constructing cage-in-cage structure, the obtained composite material is stable in structure, has good electric conductivity, electromagnetic wave absorption performance and low infrared emissivity, and has wide application value in the fields of infrared stealth and electromagnetic wave absorption.

[0006] The specific technical scheme of the application is as follows:

[0007] A preparation method of carbon cage-in-cage / carbon-coated nickel composite material, the method comprises the following steps:

[0008] (1) preparing nickel microspheres;

[0009] (2) calcining the nickel microspheres and urea under an inert atmosphere to obtain an NC / Ni composite material;

[0010] (3) etching the NC / Ni composite material in dilute hydrochloric acid to obtain the carbon cage-in-cage / carbon-coated nickel composite material, namely NC / Ni (Hollow structure).

[0011] Further, the nickel microspheres can be prepared by the method disclosed in the prior art, for example, can be obtained by hydrothermal reaction. In a specific embodiment of the application, a preparation method of nickel microspheres is provided, which specifically comprises the following steps: uniformly mixing nickel chloride hexahydrate, methanol and water, then adding hydrazine hydrate under stirring, uniformly mixing, then heating to react, collecting the product after reaction, and washing to obtain nickel microspheres.

[0012] Further, in the preparation process of the above nickel microspheres, the reactants are nickel chloride hexahydrate and hydrazine hydrate, and the solvents are methanol and deionized water. In the mixture formed by nickel chloride hexahydrate, hydrazine hydrate, methanol and water, the concentration of nickel chloride hexahydrate is 0.023 g / mL-0.025 g / mL; the concentration of hydrazine hydrate (in the form of a solution, the concentration is 80 wt%) is 0.036 mL / mL-0.039 mL / mL; the concentration of methanol is 0.24 mL / mL-0.25 mL / mL; and the concentration of water is the remaining part except for nickel chloride hexahydrate, hydrazine hydrate and methanol. The addition amount of hydrazine hydrate can be adjusted to control the morphology of the nickel microspheres. Experiments show that the addition amount of hydrazine hydrate has a great influence on the morphology and performance of the final product, is the key to the composition and morphology of the final product, and is also the key to the electromagnetic wave absorption performance of the composite material. Preferably, the addition amount of hydrazine hydrate is 0.038 mL / mL.

[0013] Further, in the preparation of the nickel microspheres, the hydrazine hydrate is preferably added under strong stirring. After the hydrazine hydrate is mixed uniformly, the mixture is heated to 100°C for reaction, and the reaction time is 2-4h.

[0014] Further, in step (2), the mass ratio of the nickel microspheres to urea is 1:3-6, for example, 1:3, 1:4, 1:5, or 1:6.

[0015] Further, in step (2), the inert atmosphere is provided by nitrogen, argon or other inert gases, and the inert gas is continuously introduced into the system during the reaction, and the amount of the inert gas introduced is 30-40mL / min.

[0016] Further, in step (2), the nickel microspheres and urea are calcined, and the urea generates gaseous nitrogen and carbon source, forming a carbon layer on the surface of the nickel microspheres, and the nickel microspheres are decomposed into a plurality of nanoparticles, which enter the carbon layer or the inside of the carbon layer to form a carbon-coated nickel microsphere, forming an NC / Ni composite material. The calcination is carried out in two stages, and the calcination program is as follows: first, the temperature is raised to 350-450°C, for example, 350°C, 400°C, or 450°C, and the calcination is carried out for 1-1.5h; then, the temperature is raised to 500-650°C, for example, 500°C, 550°C, 600°C, or 650°C, and the calcination is carried out for 1.5-2h. The temperature rising rate during the calcination is preferably 1-5°C / min, for example, 1°C / min, 2°C / min, 3°C / min, 4°C / min, or 5°C / min.

[0017] Further, in step (3), the concentration of the dilute hydrochloric acid is 0.9-1.1mol / L, and the acid etches the exposed or partially exposed nickel in the NC / Ni composite material. The acid treatment temperature is 85-95°C, for example, 85°C, 90°C, or 95°C. The treatment time is generally 3-12h, for example, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, or 12h. It has been found that the reaction time has certain influence on the morphology of the final product and the electromagnetic wave absorption performance of the composite material, and the preferred reaction time is 10h.

[0018] The present application uses nickel microspheres as a template and catalyst, realizes the decomposition of nickel spheres and the coating of carbon layer through gradient pyrolysis, and then etches the exposed or partially exposed nickel core through hydrochloric acid heat treatment to obtain NC / Ni(HS) composite material with special appearance and excellent performance. During the gradient pyrolysis, the nickel microspheres and urea are placed in an inert gas environment for calcination. In the calcination process, the nickel microspheres act as catalysts and templates to catalyze the formation of a uniform carbon layer on the surface of the urea. In the subsequent hydrochloric acid heat treatment, the nickel that is not coated or partially coated with carbon is etched to form the carbon cage / carbon-coated nickel composite material-NC / Ni(HS). In the composite material, multiple carbon nanocages are confined in a micron cage, and many carbon-coated nickel nanoparticles are embedded in the carbon shell and cage of the carbon nanocage. The carbon micron cage and carbon nanocage are both porous structures, and the etching degree of nickel can be accurately controlled by controlling the etching time to form a special hollow structure. The excellent structure of the carbon cage solves the problem of high electrical conductivity of carbon materials, and the nickel nanoparticles are coated with a dense carbon layer. The carbon-coated nickel nanoparticles are uniform in size and do not agglomerate, which solves the problem of nickel nanoparticle agglomeration and easy oxidation, and greatly improves the electromagnetic wave absorption and infrared stealth performance of carbon materials.

[0019] The NC / Ni(HS) composite material obtained by the present application has excellent electrical conductivity, electromagnetic wave absorption performance, low infrared emissivity, and stable structure, and has good application prospects in the field of electromagnetic wave absorption and infrared stealth, overcoming the shortcomings of pure carbon materials in these fields. Therefore, the NC / Ni(HS) composite material prepared by the present application is also within the scope of protection of the present application.

[0020] The present application also provides the application of the NC / Ni(HS) composite material as a microwave absorber.

[0021] The present application also provides the application of the NC / Ni(HS) composite material in the field of electromagnetic wave absorption, which can be used as an electromagnetic wave absorbing material.

[0022] The present application also provides the application of the NC / Ni(HS) composite material in the field of infrared stealth, which can be used as an infrared stealth material.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] (1) The present application combines hydrothermal reaction, gradient pyrolysis and hydrochloric acid etching to prepare the NC / Ni(HS) composite material, and the preparation process is simple and easy to operate.

[0025] (2) The NC / Ni(HS) composite material with cage-in-cage structure is prepared, the removal degree of exposed nickel is controlled by hydrochloric acid thermal etching, the hollow degree of the composite material can be accurately controlled, and the problems of small specific surface area and large density of nickel microspheres are effectively solved; the nickel nanoparticles are coated by the dense carbon layer, the problems of nickel nanoparticle agglomeration and easy oxidation are well solved, the active sites are more, and the performance is excellent.

[0026] (3) The NC / Ni(HS) composite material prepared in the application is carbon microcage coated with carbon-coated nickel modified nanocage structure, has good conductivity and stable structure, and through experiments, it is found that the performance is significantly improved compared with pure nickel microspheres; due to the stable structure and low infrared emissivity, it has wide application prospects in infrared stealth.

[0027] (4) The NC / Ni(HS) composite material prepared in the application has strong thermal stability, excellent conductivity and electromagnetic wave absorption performance, and has wide application prospects in electromagnetic wave absorption. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a scanning electron microscope graph of the sample of the application, (a) nickel microspheres, (b) NC / Ni, (c) NC / Ni(HS)-3, (d) NC / Ni(HS)-5, (e) NC / Ni(HS)-7, (f) NC / Ni(HS)-10.

[0029] Figure 2 It is a transmission electron microscope graph of the sample of the application, (a) nickel microspheres, (b) NC / Ni.

[0030] Figure 3 It is a transmission electron microscope graph of the sample of the application, (a) NC / Ni(HS)-3, (b) NC / Ni(HS)-5, (c) NC / Ni(HS)-7, (d) NC / Ni(HS)-10, (e) high-resolution graph of carbon-coated nickel nanoparticles, (f) element surface distribution graph.

[0031] Figure 4 It is an electromagnetic parameter graph of nickel microspheres and NC / Ni, (a) dielectric real part of complex dielectric constant, (b) dielectric imaginary part of complex dielectric constant, (c) magnetic guide real part of complex magnetic permeability, (d) magnetic guide imaginary part of complex magnetic permeability.

[0032] Figure 5 It is an electromagnetic parameter graph of NC / Ni(HS), (a) dielectric real part of complex dielectric constant, (b) dielectric imaginary part of complex dielectric constant, (c) magnetic guide real part of complex magnetic permeability, (d) magnetic guide imaginary part of complex magnetic permeability.

[0033] Figure 6 It is an electromagnetic wave absorption performance graph of nickel microspheres (a) and NC / Ni (b).

[0034] Figure 7 Electromagnetic wave absorption performance graph of NC / Ni(HS), (a) NC / Ni(HS)-3, (b) NC / Ni(HS)-5, (c) NC / Ni(HS)-7, (d) NC / Ni(HS)-10.

[0035] Figure 8 Infrared emissivity graph of NC / Ni(HS)-10; wherein, (a) infrared emissivity of the sample at 3-5 μm at different temperatures; (b) infrared emissivity of the sample at 8-14 μm at different temperatures; (c) infrared emissivity contrast graph; (d) infrared emissivity curve with wavelength. DETAILED DESCRIPTION

[0036] The application will be described in detail below with specific examples, but the purpose and purpose of these exemplary embodiments are only used to exemplify the application, and do not constitute any form of any limitation on the actual protection scope of the application, nor limit the protection scope of the application.

[0037] Example 1 Preparation of NC / Ni(HS) composite material

[0038] (1) Synthesis of nickel microspheres

[0039] 500 mg of nickel chloride hexahydrate was dissolved in a mixed solution containing 5 mL of methanol and 15 mL of ionized water, and under strong magnetic stirring, after mixing uniformly, 800 μL of hydrazine hydrate (concentration 80 wt%) was added to the above mixed solution, and after mixing uniformly under strong magnetic stirring, the mixed solution was transferred to an autoclave, and reacted at 100°C for 3h, then cooled to room temperature, and the black powder was collected with a magnet, washed with ultrapure water and ethanol three times, and dried under vacuum at 70°C to obtain nickel microspheres.

[0040] (2) Preparation of NC / Ni by gradient pyrolysis method

[0041] 100 mg of nickel microspheres and 500 mg of urea were spread on a porcelain boat and transferred into a tube furnace, and the urea was located at the gas inlet end of the tube furnace, and argon was introduced into the tube furnace at a flow rate of 40 mL / min. Two-stage calcination method was used. First, the temperature was raised to 400°C at a rate of 2°C / min and calcined for 1h. Then, continue to raise the temperature to 550°C at a rate of 2°C / min and calcine for 2h, and the obtained product is NC / Ni composite material.

[0042] (3) Preparation of NC / Ni(HS) composite material by hydrochloric acid thermal etching method

[0043] The obtained NC / Ni composite material was immersed in 1M HCl and reacted in an oil bath at 90℃ for 3h, 5h, 7h, and 10h, respectively, to obtain NC / Ni(HS) composite materials. Based on the reaction time, the products were named NC / Ni(HS)-3, NC / Ni(HS)-5, NC / Ni(HS)-7, and NC / Ni(HS)-10, respectively.

[0044] Nickel microspheres play several key roles in the preparation of NC / Ni(HS): (1) as a catalyst, catalyzing the growth of highly graphitized nitrogen-doped carbon (NC) layers on the nickel surface; (2) as a template, helping to form a hollow structure by etching the nickel core; and (3) as a nickel source, incorporating nickel nanoparticles into the nitrogen-doped carbon shell through a solid-state diffusion process. A composite material consisting of a nitrogen-doped carbon shell and a nickel core was prepared by urea pyrolysis. Finally, a well-structured hollow NC / Ni(HS) composite material was obtained by selectively etching the exposed or partially exposed nickel core. Scanning electron microscopy and transmission electron microscopy images show that the original nickel exhibits a distinct microsphere morphology, characterized by a solid structure and numerous nanosheets on the surface. Figure 1 a and Figure 2 a). The metallic properties and large surface area of ​​nickel facilitate the decomposition of urea, generating gaseous nitrogen and a carbon source, which then transforms into a nitrogen-doped graphitized carbon layer. The NC / Ni intermediate retains the same morphological characteristics as the original nickel. Figure 1 b). The carbon shell uniformly coating the particle surface has a thickness of approximately 20 nm. Figure 2 b). During the acid etching process, the etched edges gradually became highly visible with increasing etching time. As expected, the microcage size of the sample did not change significantly before and after acid etching. After the acid removed the metallic nickel core, NC / Ni was converted to NC / Ni(HS) ( Figure 1 c- Figure 1 f). The NC / Ni(HS) sample exhibits a cage-like structure, composed of numerous small nanocage carbon chambers as subunits. Figure 3 a- Figure 3 d). Highly ordered striations of graphitic carbon were observed in high-resolution transmission (p). Figure 3 The presence of e1 indicates high crystallinity. Furthermore, the absence of clearly aggregated nickel nanoparticles on the carbon layer suggests good dispersion of nickel within the carbon lattice. Figure 3 e2 shows a lattice spacing of 0.20 nm, corresponding to the (111) plane of nickel. High-angle annular dark-field scanning transmission electron microscopy (HAADF) and elemental plane distribution images ( Figure 3 f) This observation is further confirmed, showing that C, Ni and N elements are uniformly distributed throughout the NC / Ni(HS) matrix.

[0045] Application Example 1

[0046] Applications of NC / Ni(HS) composite materials in electromagnetic wave absorption:

[0047] (1) Add the sample and paraffin to a beaker at a mass ratio of 5:95.

[0048] (2) Place the beaker on a 60°C hot plate to mix the sample with the paraffin wax evenly.

[0049] (3) Place the well-mixed sample and paraffin wax in a mold to obtain a ring with an inner diameter of 3.04 mm, an outer diameter of 7.00 mm, and a thickness of 2.00 mm.

[0050] (4) Place each ring on a vector grid analyzer to measure its electromagnetic parameters.

[0051] The real part (ε′) and imaginary part (ε″) of the complex permittivity represent the ability to store and dissipate electrical energy, respectively. The real part (μ′) and imaginary part (μ″) of the complex permeability represent the magnetic energy storage and dissipation capabilities, respectively. For example... Figure 4 As shown, the ε′ values ​​for Ni and NC / Ni are 3.0 and 2.6, respectively, which are almost constant, while the ε″ value is close to 0, indicating that Ni and NC / Ni have limited ability to absorb electromagnetic energy. According to previous reports, introducing a hollow structure is an effective strategy to improve impedance matching and dielectric loss capabilities. As expected, the ε′ and ε″ values ​​increase rapidly with increasing acid etching time. Figure 5 (a, 5b). Within the frequency range of 2.00–18.00 GHz, the ε′ values ​​of NC / Ni(HS)-3, NC / Ni(HS)-5, NC / Ni(HS)-7, and NC / Ni(HS)-10 vary between 7.3–5.9, 9.0–6.7, 9.5–5.9, and 11.3–5.8, respectively. Simultaneously, the ε″ values ​​of NC / Ni(HS)-3, NC / Ni(HS)-5, NC / Ni(HS)-7, and NC / Ni(HS)-10 vary between 1.0–1.2, 2.4–1.8, 2.9–1.5, and 3.6–2.4, respectively. According to the free electron theory (ε″≈φ / 2πε0f, where φ and ε0 represent conductivity and free-space impedance, respectively), ε″ is positively correlated with φ. A larger φ favors electron migration and hopping, thus increasing conduction losses. Figure 4 c,4d and 5c,5d show the complex permeability curves of the obtained samples. μ′ gradually increases with etching time, which is likely due to the uniform distribution of Ni in the carbon layer. Furthermore, several natural resonance peaks were found in the μ″ curve, which may be caused by losses and magnetic coupling effects.

[0052]

[0053] RL=20lg|(Z in -Z0) / (Zin + Z0) (Equation 2)

[0054] where Z in is the input impedance of the absorber, Z0is the free space impedance, μ r is the relative complex permeability (μ r = μ' - i μ"), ε r is the complex permittivity (ε r = ε' - i ε"), d is the thickness of the absorber, c, f are the speed and frequency of light, respectively.

[0055] The electromagnetic wave absorption performance of a material is usually evaluated using the reflection loss (RL) value (Equations 1 and 2). An RL value less than -10 dB is considered as effective absorption, indicating that more than 90% of the incident electromagnetic wave is absorbed. To highlight the advantages of the NC / Ni(HS) hollow porous structure with Ni site anchoring, the three-dimensional RL maps of the prepared samples were systematically compared. When the filling rate is 4 wt.%, pure Ni microspheres do not exhibit electromagnetic wave absorption performance (no RL≤-10 dB) Figure 6 a), and even with a nitrogen-doped carbon shell, the electromagnetic wave absorption performance is not improved Figure 6 b). Interestingly, with the etching of the Ni core, the electromagnetic wave absorption performance of the sample is significantly improved. Specifically, the RL of NC / Ni(HS)-3 at a thickness of 3.00 mm is -11.26 dB, and the calculated effective bandwidth (EAB) at a thickness of 3.10 mm is 1.52 GHz Figure 7 a). Notably, with the increase of etching time, the electromagnetic wave absorption performance is significantly enhanced, while the matching thickness is also reduced. The minimum RL (RL min ) values of NC / Ni(HS)-5, NC / Ni(HS)-7 and NC / Ni(HS)-10 at thicknesses of 5.00 mm, 3.20 mm and 2.63 nm are -19.37 dB (5.44 GHz), -24.25 dB (8.64 GHz) and -63.67 dB (10.16 GHz) Figure 7 b-7d), respectively, and the maximum EAB (EAB max ) values at a thickness of 2.00 mm are 3.92 GHz, 4.8 GHz and 6.16 GHz, respectively. Compared with NC / Ni(HS)-3, NC / Ni(HS)-10 not only has a reduced matching thickness (from 3.0 to 2.63 mm), but also has enhanced absorption intensity (from -11.26 to -63.67 dB) and a wider EAB (from 1.52 to 6.16 GHz). The RL min and EAB maxThe NC / Ni(HS)-10 shows a clear advantage at thin absorption thickness, outperforming most previously reported carbon-based absorbers. Moreover, by adjusting the etching time, the absorption peak can be tuned from the c-band (4-8 GHz) to the ku-band (12-18 GHz).

[0056] Application Example 2

[0057] Application of NC / Ni(HS) composite in the field of infrared stealth:

[0058] The sample was pressed into a circular sheet, and the infrared emissivity was tested in the atmospheric window band using an infrared spectrometer.

[0059] Low infrared emissivity is an important condition for achieving infrared stealth. To demonstrate the infrared stealth performance of NC / Ni(HS)-10, the infrared emissivity of NC / Ni(HS)-10 was tested in the range of 25-400°C. By adjusting the nodal emissivity, the infrared radiation characteristics can be reduced without changing the surface temperature of the material. In the atmospheric environment, infrared radiation of different wavelengths will be attenuated to different degrees. The main working band of the infrared detector is in the atmospheric window region of 3-5 μm and 8-14 μm, which is relatively transparent. Due to its excellent electromagnetic wave performance, NC / Ni(HS)-10 was selected for detailed analysis. Figure 8 a, 8b respectively show the change of infrared emissivity of NC / Ni(HS)-10 with temperature in the 3-5 μm and 8-14 μm bands. From room temperature to 400°C, the infrared emissivity of NC / Ni(HS)-10 increases slightly, with an average emissivity of only 0.76 (3-5 μm) and 0.79 (8-14 μm) Figure 8 c). Figure 8 d shows the curve of infrared emissivity changing with wavelength in more detail. The larger specific surface area of NC / Ni(HS)-10 is beneficial to the internal refraction and absorption of infrared light, thereby reducing the infrared radiation energy emitted by the target, thus reducing the infrared emissivity. The special hollow channel structure enhances the heat preservation performance, reducing the infrared radiation energy density of the sample. The surface of the NC / Ni(HS)-10 sample is smooth, and the particle size is uniform. The surface roughness is positively correlated with the uniformity of particle size and emissivity, which is beneficial to reducing the emissivity. The air space between the shells in the hollow structure acts as a thermal insulation layer, further reducing the infrared radiation energy density.

Claims

1. A method for preparing a carbon cage-in-cage / carbon-coated nickel composite material, characterized in that: The method comprises the following steps: (1) preparing nickel microspheres: uniformly mixing nickel chloride hexahydrate, methanol and water, then adding hydrazine hydrate under stirring, uniformly mixing, and then heating to 100°C for 2-4h, collecting the product after reaction, and washing to obtain nickel microspheres; (2) calcining the nickel microspheres and urea under inert atmosphere to obtain NC / Ni composite material; (3) etching the NC / Ni composite material in dilute hydrochloric acid to obtain carbon cage-in-cage / carbon-coated nickel composite material; In step (2), the mass ratio of nickel microspheres to urea is 1:3-6; In step (2), the nickel microspheres and urea are first heated to 350-450°C under inert atmosphere and calcined for 1-1.5h, and then heated to 500-650°C and calcined for 1.5-2h; In step (3), the concentration of dilute hydrochloric acid is 0.9-1.1mol / L, the etching temperature is 85-95°C, and the etching time is 3-12h.

2. The method of claim 1, wherein: When preparing the nickel microspheres, at least one of the following conditions is included: Condition 1: in the mixture formed by nickel chloride hexahydrate, hydrazine hydrate, methanol and water, the concentration of nickel chloride hexahydrate is 0.023g / mL-0.025g / mL; Condition 2: in the mixture formed by nickel chloride hexahydrate, hydrazine hydrate, methanol and water, the concentration of hydrazine hydrate is 0.036mL / mL-0.039mL / mL; Condition 3: in the mixture formed by nickel chloride hexahydrate, hydrazine hydrate, methanol and water, the concentration of methanol is 0.24mL / mL-0.25mL / mL.

3. The application of carbon cage / carbon-coated nickel composite material in the field of infrared stealth, characterized in that: The carbon cage-in-cage / carbon-coated nickel composite material is prepared according to the preparation method of claim 1 or 2.

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