Preparation of carbon bowls with artificially manufactured fully impedance-matched natural capture nets

Abstract

The application belongs to the field of non-metallic element carbon material and electromagnetic wave absorbing material, and particularly relates to preparation of a carbon bowl with a completely impedance-matched natural capture net manufactured artificially. SiO2@SiO2 / C carbon spheres are obtained by calcining SiO2@SiO2 / phenolic resin microspheres; then, SiO2 is removed by etching with an etching solution; in the etching process, the carbon shell is subjected to the double action of gas in the shell and liquid outside the shell; when the SiO2 core is etched, the external solution cannot enter the inside of the sphere in time, so the internal pressure is reduced to form a pressure difference; when the pressure difference is greater than the strength that the carbon shell can bear, the carbon shell gradually concaves inward, and finally a carbon bowl with a completely impedance-matched natural capture net manufactured artificially is obtained. The application provides a new idea for the research of light-weight broadband electromagnetic wave absorbing carbon material, and the electromagnetic wave absorbing performance of the carbon material meets the requirements of thinness, lightness, wideband and strength.

Description

Technical Field

[0001] This invention belongs to the field of non-metallic carbon materials and electromagnetic wave absorbing materials, specifically the preparation of a carbon bowl with an artificially manufactured, perfectly impedance-matched natural trapping net. Background Technology

[0002] The rapid development of the 5G smart era has driven the development and application of electromagnetic waves in fields such as radar detection, consumer electronics, and artificial intelligence micro-devices. However, it has also generated significant electromagnetic pollution, even seriously threatening human health and national defense security. Therefore, there is an urgent need to develop high-performance electromagnetic wave absorbing materials. Excellent electromagnetic wave absorbing materials should possess comprehensive characteristics such as high reflection loss, wide effective absorption bandwidth, thin thickness, light weight, and adaptability to practical application environments. Carbon materials are widely studied and applied due to their advantages of light weight, excellent conductivity, and good environmental stability.

[0003] Despite significant progress in the research and application of carbon materials in the field of electromagnetic wave absorption, several challenges remain, such as extremely high electrical conductivity, a single loss mechanism, and poor impedance matching performance. These issues limit the application and development of microwave-absorbing carbon materials. Current research utilizes morphology engineering as an effective strategy for adjusting the electromagnetic parameters of carbon materials. To date, various morphologies of carbonaceous absorbing materials have been developed, including hollow structures, core / yolk shell structures, and porous structures, to achieve superior microwave absorption capabilities. Among these, the unique hollow bowl-shaped structure has been widely applied in catalysis, energy storage, pollutant capture, and drug delivery.

[0004] Compared to traditional hollow spherical particles, hollow bowl-shaped carbon materials possess lower symmetry and a looser structure. Furthermore, the air layer within the carbon bowl exhibits perfect impedance matching with free space. These characteristics contribute to the excellent electromagnetic wave absorption performance of the carbon bowl. However, the preparation of hollow bowl-shaped carbon materials with superior absorption properties remains challenging. The literature [Chemistry of Materials 2021, 33, 1789-1798] used hollow bowl-shaped sulfonated polystyrene microspheres as templates and 2-methylimidazole, methanol, and cobalt salts as raw materials to prepare hollow bowl-shaped nitrogen-doped cobalt / carbon composite materials via pyrolysis, achieving a minimum reflection loss... RL min =-42.30dB, maximum effective absorption bandwidth EAB max=5.10 GHz (f=12.90-18.00GHz). The literature [ACS Applied Materials & Interfaces 2020, 12, 18952-18963] prepared Fe3O4 nanoparticles / N-doped carbon layered hollow microspheres, with a filling amount of 10 wt%, achieving a minimum reflection loss of 5.10 GHz (f=12.90-18.00GHz). RL min =-60.30dB, maximum effective absorption bandwidth EAB max =6.40GHz (f=7.20-13.60GHz).

[0005] In summary, on the one hand, there are few reports on the preparation of bowl-shaped absorbing carbon materials. Even the successfully synthesized bowl-shaped nanoparticles are mainly metals or metal oxides, which are difficult to mass-produce and hinder practical applications due to poor stability. The difficulty in preparing bowl-shaped absorbing carbon materials lies mainly in the difficulty of controlling the synthesis of small-scale materials with weak symmetry. Therefore, research on single-carbon materials with bowl-shaped structures is crucial for the development of absorbing materials. On the other hand, the current enhancement effect of bowl-shaped structures on electromagnetic wave absorption performance is not significant, making it difficult to meet the requirements of excellent electromagnetic wave absorbing materials that are "thin, light, wide, and strong". Summary of the Invention

[0006] To address the current technical challenge of fabricating bowl-shaped, high-quality microwave-absorbing carbon materials, this invention provides a simplified fabrication process for carbon bowls with an artificially manufactured, fully impedance-matched natural trapping mesh. This process is simple to operate, operates under mild conditions, is low-cost, and is easily scalable for industrial mass production. Furthermore, the porous hollow carbon bowls prepared by this process exhibit adjustable dielectric parameters and electromagnetic wave absorption properties.

[0007] This invention is achieved through the following technical solution: a simplified preparation process for a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net, comprising the following steps:

[0008] ① Prepare a mixed solution of alcohol, water and catalyst with a pH of 7-14;

[0009] ② Add the template agent to the mixed solution prepared in step ①, and stir at 5~50℃ for 5~240 min to obtain a homogeneous mixed system;

[0010] ③ Add phenolic and aldehyde substances to the homogeneous mixture in step ②, stir for 4~48h and then centrifuge. Dry the obtained precipitate at 40~60℃ to obtain SiO2@SiO2 / phenolic resin microspheres.

[0011] ④ The SiO2@SiO2 / phenolic resin microspheres obtained in step ③ are calcined at a certain temperature and in a certain atmosphere for a certain time to obtain SiO2@SiO2 / C carbon spheres;

[0012] ⑤ The SiO2@SiO2 / C carbon spheres obtained in step ④ are placed in an etching solution at 20~80℃ to etch and remove SiO2. During the etching process, the carbon shell is subjected to the dual effects of gas inside the shell and liquid outside the shell. Etching ions in the liquid outside the shell enter the interior of the carbon sphere through capillary pores or through mesopores formed after etching of SiO2 embedded in the carbon shell and etch the SiO2 core. After etching, the external solution cannot enter the interior of the sphere in time, so the internal pressure decreases and a pressure difference ΔP is formed. When the pressure difference ΔP is greater than the strength that the carbon shell can withstand, the carbon shell gradually indents inward and evolves into a bowl-shaped structure when the etching is completed. After washing, filtration and drying, a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net is obtained.

[0013] As a further improvement to the technical solution of the present invention, in step ①, the alcohol is one or a mixture of two or more of ethanol, methanol, and ethylene glycol; the volume ratio of the alcohol to water is 2~8:1; and the catalyst is one or a mixture of two or more of NaOH, KOH, and NH3•H2O.

[0014] As a further improvement to the technical solution of the present invention, in step ②, the template agent is one or a mixture of two of tetraethyl or tetrapropyl silicate; the volume ratio of the template agent to alcohol and water is 1~3:40.

[0015] As a further improvement to the technical solution of the present invention, in step ③, the phenolic substance is one or a mixture of two or more of resorcinol, phloroglucinol, 3-aminophenol, and phenol; the aldehyde substance is one or a mixture of two of formaldehyde and acetaldehyde; and the molar ratio of the phenolic substance to the aldehyde substance is 1:2.

[0016] As a further improvement to the technical solution of the present invention, in step ④, the calcination temperature is 400~700℃ and the calcination time is 0.5~2h; the atmosphere is one or a mixture of two or more of argon, nitrogen, ammonia and hydrogen.

[0017] As a further improvement to the technical solution of the present invention, the specific surface area of ​​the carbon bowl is 685.43~814.94 m². 2 g -1 The pore size is 9.21~9.82 nm, and the total pore volume is 1.41~1.62 cm³. 3 g -1 The defect level is 1.91~2.54; the oxygen content is 6.77~20.36 at.%.

[0018] As a further improvement to the technical solution of the present invention, the maximum impedance matching bandwidth of the carbon bowl is as high as 7.54 GHz, which is 1.68 times higher than that of the carbon ball with a completely impedance-matched natural trapping net without artificial manufacturing.

[0019] As a further improvement to the technical solution of the present invention, the minimum reflection loss of the carbon bowl can reach -64.38dB, and the maximum effective absorption bandwidth can reach 7.24GHz.

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

[0021] 1) This invention enables the preparation of carbon bowls with uniform particle size and stable morphology, exhibiting a fully impedance-matched natural trapping network, through a simple process. The related equipment is simple, the production cost is low, and it is suitable for large-scale industrial production.

[0022] 2) This invention provides a novel approach to the research of lightweight broadband absorbing carbon materials. The electromagnetic wave absorption performance of the prepared carbon bowl meets the requirements of "thin, light, wide, and strong". The carbon bowl with artificially manufactured, fully impedance-matched natural trapping mesh has a maximum impedance matching bandwidth of up to 7.54 GHz, which is 1.68 times higher than that of a carbon ball without artificially manufactured, fully impedance-matched natural trapping mesh; the minimum reflection loss can reach -64.38 dB, and the maximum effective absorption bandwidth can reach 7.24 GHz.

[0023] 3) The carbon bowl with a fully impedance-matched natural trapping net, obtained by this invention, has a specific surface area of ​​685.43~814.94 m². 2 g -1 The pore size is 9.21~9.82 nm, and the total pore volume is 1.41~1.62 cm³. 3 g -1 With a defect level of 1.91~2.54 and an oxygen content of 6.77~20.36 at.%, it has adjustable dielectric properties and can be widely used in catalysis, energy storage, pollutant capture and drug delivery. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 Scanning electron microscope images of carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 and carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1.

[0027] Figure 2 Transmission electron microscope images of carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 and carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1.

[0028] Figure 3 Raman curves of carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 and carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1.

[0029] Figure 4 The specific surface area curves are for the carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 and the carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1.

[0030] Figure 5 The pore size distribution diagrams are shown for the carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 and the carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1.

[0031] Figure 6 X-ray photoelectron spectroscopy (XPS) curves of carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 and carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1.

[0032] Figure 7 The RL-f curves are shown for the carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 and the carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1.

[0033] Figure 8 The impedance matching performance (|Z|) curves of the carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 and the carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1 are shown. Detailed Implementation

[0034] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0035] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0036] This invention provides a specific embodiment of a simplified preparation process for a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net, comprising the following steps:

[0037] ① Prepare a mixed solution of alcohol, water and catalyst with a pH of 7-14;

[0038] ② Add the template agent to the mixed solution prepared in step ①, and stir at 5~50℃ for 5~240 min to obtain a homogeneous mixed system;

[0039] ③ Add phenolic and aldehyde substances to the homogeneous mixture in step ②, stir for 4~48h and then centrifuge. Dry the obtained precipitate at 40~60℃ to obtain SiO2@SiO2 / phenolic resin microspheres.

[0040] ④ The SiO2@SiO2 / phenolic resin microspheres obtained in step ③ are calcined at a certain temperature and in a certain atmosphere for a certain time to obtain SiO2@SiO2 / C carbon spheres;

[0041] ⑤ The SiO2@SiO2 / C carbon spheres obtained in step ④ are placed in an etching solution at 20~80℃ to etch and remove SiO2. During the etching process, the carbon shell is subjected to the dual effects of gas inside the shell and liquid outside the shell. Etching ions in the liquid outside the shell enter the interior of the carbon sphere through capillary pores or through mesopores formed after etching of SiO2 embedded in the carbon shell and etch the SiO2 core. After etching, the external solution cannot enter the interior of the sphere in time, so the internal pressure decreases and a pressure difference ΔP is formed. When the pressure difference ΔP is greater than the strength that the carbon shell can withstand, the carbon shell gradually indents inward and evolves into a bowl-shaped structure when the etching is completed. After washing, filtration and drying, a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net is obtained.

[0042] In this invention, the pressure difference ΔP = pressure of the liquid outside the carbon shell − gas pressure inside the carbon shell.

[0043] In one embodiment of the present invention, in step ①, the alcohol is one or a mixture of two or more of ethanol, methanol, and ethylene glycol; the volume ratio of the alcohol to water is 2~8:1; and the catalyst is one or a mixture of two or more of NaOH, KOH, and NH3•H2O.

[0044] In another embodiment of the present invention, in step ②, the template agent is one or a mixture of two of tetraethyl or tetrapropyl silicate; the volume ratio of the template agent to alcohol-water (total volume of alcohol and water) is 1 to 3:40.

[0045] In one embodiment of the present invention, in step ③, the phenolic substance is one or a mixture of two or more of resorcinol, phloroglucinol, 3-aminophenol, and phenol; the aldehyde substance is one or a mixture of two of formaldehyde and acetaldehyde; and the molar ratio of the phenolic substance to the aldehyde substance is 1:2.

[0046] In another embodiment of the present invention, in step ④, the calcination temperature is 400~700℃ and the calcination time is 0.5~2h; the atmosphere is one or a mixture of two or more of argon, nitrogen, ammonia and hydrogen.

[0047] The carbon bowls prepared using the simplified preparation process of the carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets described in this invention have a specific surface area of ​​685.43~814.94 m². 2 g -1 The pore size is 9.21~9.82 nm, and the total pore volume is 1.41~1.62 cm³. 3 g -1 The defect level is 1.91~2.54; the oxygen content is 6.77~20.36 at.%.

[0048] The carbon bowl prepared by the simplified preparation process of the carbon bowl with artificially manufactured, fully impedance-matched natural trapping net described in this invention has a maximum impedance matching bandwidth of up to 7.54 GHz, which is 1.68 times higher than that of the corresponding carbon ball without artificially manufactured, fully impedance-matched natural trapping net.

[0049] The carbon bowl prepared by the simplified preparation process of the carbon bowl with a fully impedance-matched natural trapping net described in this invention can achieve a minimum reflection loss of -64.38dB and a maximum effective absorption bandwidth of 7.24GHz.

[0050] The specific embodiments of the present invention will be described in detail below. Example 1

[0051] A simplified fabrication process for a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net includes the following steps:

[0052] ① Prepare a mixed solution of 80 mL anhydrous ethanol, 20 mL water and 3 mL ammonia (NH3•H2O), and control the pH value of the mixed solution to 10;

[0053] ② Add 5.19 mL of tetraethyl orthosilicate to the mixed solution prepared in step ①, stir at 30°C for 30 min to obtain a homogeneous mixed system;

[0054] ③ Add 0.4 g of resorcinol and 0.56 mL of 37% formaldehyde solution (molar ratio 1:2) to the homogeneous mixed solution in step ②, continue stirring for 24 h, then centrifuge and separate the precipitate. Dry the precipitate at 60 °C to obtain SiO2@SiO2 / phenolic resin microspheres.

[0055] ④ The SiO2@SiO2 / phenolic resin microspheres obtained in step ③ are calcined at 600℃ for 2 hours in an argon atmosphere to obtain SiO2@SiO2 / C carbon spheres;

[0056] ⑤ The SiO2@SiO2 / C carbon spheres obtained in step ④ were placed in a NaOH solution at 40℃ for 40 hours to remove SiO2. During the etching process, the carbon shell was subjected to the dual effects of the gas inside the shell and the liquid outside the shell. The etching ions in the liquid outside the shell entered the interior of the carbon sphere through capillary pores or through the mesopores formed after the SiO2 embedded in the carbon shell was etched, and etched the SiO2 core. After etching, the external solution could not enter the interior of the sphere in time, so the internal pressure decreased, forming a pressure difference ΔP. When ΔP was greater than the strength that the carbon shell could withstand, the carbon shell gradually sank inward, and when the etching was completed, it evolved into a bowl-shaped structure. After washing, filtration and drying, a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net was obtained.

[0057] Electromagnetic wave absorption performance was tested on the carbon bowl with a fully impedance-matched natural trapping network. The composite material with a filler content of 20 wt% exhibited the best electromagnetic wave absorption performance: minimum reflection loss. RL min =-53.13dB, maximum effective absorption bandwidth EAB max =7.2GHz; it has excellent impedance matching performance when |Z|=0.8~1.2 (equal to or close to 1), and its optimal impedance matching bandwidth reaches 7.54GHz. Example 2

[0058] A simplified fabrication process for a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net includes the following steps:

[0059] The process is exactly the same as in Example 1, except that the calcination temperature in step ④ is 700°C.

[0060] Electromagnetic wave absorption performance was tested on the carbon bowl with a fully impedance-matched natural trapping network. The composite material with a filler content of 10 wt% exhibited the best electromagnetic wave absorption performance: minimum reflection loss. RL min=-64.38dB, maximum effective absorption bandwidth EAB max =7.24GHz; it has excellent impedance matching performance when |Z|=0.8~1.2 (equal to or close to 1), and its optimal impedance matching bandwidth reaches 7.43GHz. Comparative Example 1

[0061] A method for preparing carbon spheres with fully impedance-matched natural trapping nets without artificial fabrication includes the following steps:

[0062] The process is exactly the same as in Example 1, except that the calcination temperature in step ④ is 800°C.

[0063] During the etching process in step ⑤, the carbon shell is subjected to the dual effects of the gas inside the shell and the liquid outside the shell. The etching ions in the liquid outside the shell enter the interior of the carbon sphere through capillary pores or through the mesopores formed after the SiO2 embedded in the carbon shell is etched, and then etch the SiO2 core. After etching, the external solution cannot enter the interior of the sphere in time, so the internal pressure decreases and a pressure difference ΔP is formed. Since the carbon shell obtained by calcination at 800℃ has high mechanical strength, the pressure difference ΔP is less than the strength that the carbon shell can withstand, so that the carbon shell can maintain its original spherical shape. Washing, filtration and drying result in a carbon sphere with a completely impedance-matched natural trapping network without artificial manufacturing.

[0064] Electromagnetic wave absorption performance was tested on the carbon spheres with perfectly impedance-matched natural trapping nets obtained without artificial manufacturing. The composite material with a filler content of 5 wt% exhibited the best electromagnetic wave absorption performance: minimum reflection loss. RL min =-38.94dB, maximum effective absorption bandwidth EAB max =5.22GHz; it has excellent impedance matching performance when |Z|=0.8~1.2 (equal to or close to 1), and its optimal impedance matching bandwidth reaches 4.48GHz.

[0065] The above performance test results are shown below:

[0066] 1) Scanning electron microscope (SEM)

[0067] The morphology and structure of the prepared carbon material were observed by spraying a Pt / Au conductive layer onto the surface and then using a scanning electron microscope (Hitachi SU8010, Tokyo, Japan).

[0068] 2) Transmission electron microscopy (TEM)

[0069] The morphology and structure of the prepared carbon materials were observed using a transmission electron microscope (JEM-2100F, JEOL, Japan).

[0070] 3) Raman

[0071] The degree of defects in the prepared carbon materials was studied using Raman spectroscopy (Renishaw, UK).

[0072] 4) By N2 adsorption-desorption analysis (BET)

[0073] Nitrogen adsorption-desorption isotherms were obtained using a fully automated physical adsorption analyzer (ASAP 2460, USA). Samples were typically degassed under vacuum at 200°C for 6 hours prior to testing. Pore size distribution was calculated using the Barrett-Joyner-Halenda (BJH) method.

[0074] 5) X-ray photoelectron spectroscopy (XPS):

[0075] The elemental composition and state of the prepared carbon materials were studied using X-ray photoelectron spectroscopy (NEXSA, ThermoFisher Scientific, USA).

[0076] 6) Absorption performance: The sample and paraffin are mixed at a certain mass ratio and then pressed into a ring (Φ 外 =7.00mm, Φ 内 =3.04mm), and then the electromagnetic parameters were measured and the absorption performance and impedance matching performance were calculated using a vector network analyzer (Agilent, N5232A, USA) with the coaxial line method.

[0077] Depend on Figure 1 It can be seen that the carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 of the present invention all have typical bowl-shaped morphology. The carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1 have a complete spherical structure.

[0078] Depend on Figure 2 It can be seen that the carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 of this invention all have good bowl-shaped morphology, with the carbon shell concave inward and the interior being a hollow structure. The carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1 have a complete hollow spherical structure.

[0079] Depend on Figure 3 It can be seen that the carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 of this invention and the carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1 have similar compatibility at 1340 and 1590 cm⁻¹. -1 Each of the points has two distinct characteristic peaks, corresponding to the D peak and the G peak, respectively.

[0080] Depend on Figure 4It can be seen that the nitrogen adsorption-desorption isotherms of the carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 of the present invention and the carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1 both exhibit typical Type IV curves with H3 hysteresis loops, indicating that there are a large number of mesopores in the carbon shell.

[0081] Depend on Figure 5 It can be seen that the pore sizes of the carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 of the present invention and the carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1 are 9.13, 11.48 and 7.51 nm, respectively.

[0082] Depend on Figure 6 It can be seen that the carbon bowls with artificially manufactured, fully impedance-matched natural trapping nets prepared in Examples 1-2 of this invention and the carbon spheres without artificially manufactured, fully impedance-matched natural trapping nets prepared in Comparative Example 1 both exhibit characteristic peaks of C1s and O1s, indicating that they are composed of only C and O elements. Furthermore, with increasing calcination temperature, the C1s peak strengthens while the O1s peak decreases; when the calcination temperature increases from 600℃ to 800℃, the oxygen content decreases from 20.36 at% to 6.77 at%.

[0083] Depend on Figure 7 It can be seen that the optimal electromagnetic wave absorption performance of the carbon bowl with a fully impedance-matched natural trapping net prepared in Examples 1-2 of this invention is: minimum reflection loss. RL min =-64.38dB, maximum effective absorption bandwidth EAB max =7.24GHz. The optimal electromagnetic wave absorption performance of the carbon spheres prepared in Comparative Example 1, without any artificially manufactured, fully impedance-matched natural trapping net, is: minimum reflection loss. RL min =-38.94dB, maximum effective absorption bandwidth EAB max =5.22GHz. It can be seen that the minimum reflection loss of the carbon bowl with a fully artificially manufactured impedance-matched natural trapping mesh prepared in this invention is 1.38 times that of the carbon sphere without a fully artificially manufactured impedance-matched natural trapping mesh; the maximum effective absorption bandwidth of the carbon bowl with a fully artificially manufactured impedance-matched natural trapping mesh prepared in this invention is 1.39 times that of the carbon sphere without a fully artificially manufactured impedance-matched natural trapping mesh. This indicates that the absorption performance of the carbon bowl with a fully artificially manufactured impedance-matched natural trapping mesh prepared in this invention is superior to that of the carbon sphere without a fully artificially manufactured impedance-matched natural trapping mesh.

[0084] Depend on Figure 8It can be seen that the optimal impedance matching bandwidth of the carbon bowl with a fully manufactured impedance-matched natural trapping net prepared in Examples 1-2 of the present invention reaches 7.54 GHz; while the optimal impedance matching bandwidth of the carbon sphere without a fully manufactured impedance-matched natural trapping net prepared in Comparative Example 1 is 4.48 GHz. It can be seen that the optimal impedance matching bandwidth of the carbon bowl prepared in this invention is 1.68 times that of the carbon sphere, indicating that the manufactured fully impedance-matched natural trapping net endows the carbon bowl of this invention with superior impedance matching performance compared to the carbon sphere, and thus superior absorption performance compared to the carbon sphere.

[0085] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A simplified fabrication process for a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net, comprising the following steps: ① Prepare a mixed solution of alcohol, water and catalyst with a pH of 7-14; ② Add the template agent to the mixed solution prepared in step ①, and stir at 5~50℃ for 5~240 min to obtain a homogeneous mixed system; ③ Add phenolic and aldehyde substances to the homogeneous mixture in step ②, stir for 4~48h and then centrifuge. Dry the obtained precipitate at 40~60℃ to obtain SiO2@SiO2 / phenolic resin microspheres. ④ The SiO2@SiO2 / phenolic resin microspheres obtained in step ③ are calcined in a certain atmosphere and at a certain temperature for a certain time to obtain SiO2@SiO2 / C carbon spheres; in step ④, the calcination temperature is 400~700℃ and the calcination time is 0.5~2h. ⑤ The SiO2@SiO2 / C carbon spheres obtained in step ④ are placed in an etching solution at 20~80℃ to etch and remove SiO2. During the etching process, the carbon shell is subjected to the dual effects of gas inside the shell and liquid outside the shell. Etching ions in the liquid outside the shell enter the interior of the carbon sphere through capillary pores or through mesopores formed after etching of SiO2 embedded in the carbon shell and etch the SiO2 core. After etching, the external solution cannot enter the interior of the sphere in time, so the internal pressure decreases and a pressure difference ΔP is formed. When the pressure difference ΔP is greater than the strength that the carbon shell can withstand, the carbon shell gradually indents inward, and when the etching is completed, it evolves into a bowl-shaped structure; washing, filtration and drying result in a carbon bowl with a fully impedance-matched natural trapping net that is artificially manufactured.

2. The simplified preparation process of a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net according to claim 1, characterized in that, in step ①, the alcohol is one or a mixture of two or more of ethanol, methanol, and ethylene glycol; the volume ratio of the alcohol to water is 2~8:1; and the catalyst is one or a mixture of two or more of NaOH, KOH, and NH3•H2O.

3. The simplified preparation process of a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net according to claim 1, characterized in that, in step ②, the template agent is one or a mixture of two of tetraethyl or tetrapropyl silicate; the volume ratio of the template agent to alcohol-water is 1~3:

40.

4. A simplified preparation process for a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net according to claim 1, characterized in that, in step ③, the phenolic substance is one or a mixture of two or more of resorcinol, phloroglucinol, 3-aminophenol, and phenol; the aldehyde substance is one or a mixture of two of formaldehyde and acetaldehyde; and the molar ratio of the phenolic substance to the aldehyde substance is 1:

2.

5. The simplified preparation process of a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net according to claim 1, characterized in that the atmosphere is one or a mixture of two or more of argon, nitrogen, ammonia, and hydrogen.

6. A simplified preparation process for a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net, as described in any one of claims 1 to 5, characterized in that the specific surface area of ​​the carbon bowl is 685.43~814.94 m². 2 g −1 The pore size is 9.21~9.82 nm, and the total pore volume is 1.41~1.62 cm³. 3 g -1 The defect level is 1.91~2.54; the oxygen content is 6.77~20.36 at.%.

7. A simplified fabrication process for a carbon bowl with an artificially manufactured, fully impedance-matched natural trapping net, as described in any one of claims 1 to 5, characterized in that the maximum impedance-matching bandwidth of the carbon bowl is up to 7.54 GHz, which is 1.68 times higher than that of a carbon ball without an artificially manufactured, fully impedance-matched natural trapping net.

8. A simplified fabrication process for a carbon bowl with a fully impedance-matched natural trapping net, as described in any one of claims 1 to 5, characterized in that the carbon bowl has a minimum reflection loss of -64.38 dB and a maximum effective absorption bandwidth of 7.24 GHz.

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