A co-doped mesoporous carbon sphere wave-absorbing material, a preparation method and use thereof

Abstract

The application belongs to the technical field of electromagnetic wave absorbing materials, and particularly relates to a co-doped mesoporous carbon sphere wave absorbing material, a preparation method and an application. The preparation method comprises the following steps: aniline is added into a colloidal silica hydrochloric acid solution and uniformly mixed to obtain a mixed solution; then, ammonium persulfate hydrochloric acid solution is added into the mixed solution and uniformly mixed; drying is performed to obtain a precursor; the precursor is calcined under a protective atmosphere to obtain an intermediate; then, the intermediate and a sodium hydroxide solution are mixed, heated, and treated to obtain the co-doped mesoporous carbon sphere wave absorbing material. The calcination method comprises the following steps: the precursor is heated to 250-350 DEG C under a protective atmosphere and then heated to 700-900 DEG C for calcination. The co-doped mesoporous carbon sphere wave absorbing material has excellent wave absorbing performance.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to a co-doped mesoporous carbon sphere absorbing material, its preparation method, and its applications. Background Technology

[0002] The advancement of the information age has spurred the development of electronic communication and radar detection technologies. Electromagnetic waves, as the most effective carrier of information, have become inseparable from people's lives. While innovations in electromagnetic wave-related technologies allow people to enjoy their positive effects, they also expose them to a series of health threats. In the military field, the demands of modern warfare have made stealth technology a strategic priority for military development in various countries. Therefore, to reduce or eliminate electromagnetic pollution harmful to human health and the environment, and to enhance military countermeasures capabilities, the development and application of high-performance electromagnetic absorbing materials have become an important strategy for solving this problem.

[0003] In recent years, microwave absorbing materials have gradually developed towards being lightweight, thin, wide-bandwidth, and having strong absorption capabilities. Carbon materials possess low density, good stability, excellent conductivity, and the ability to attenuate electromagnetic waves. Mesoporous carbon spheres not only possess these advantages but also have an extremely high specific surface area and numerous porous active sites, allowing electromagnetic waves to undergo multiple reflections and absorptions within the material, thus achieving excellent reflection loss. Furthermore, the simple preparation method, compared to composite materials with cumbersome manufacturing processes, provides the possibility of mass production.

[0004] Chinese patent application publication number CN 105820796 A describes a method for preparing a porous carbon sphere composite microwave absorbing material loaded with a magnetic alloy. This method utilizes the high specific surface area and strong adsorption of porous carbon spheres to introduce a mixed precursor solution into the pores of the carbon spheres through capillary action and combine it with hydrophilic oxygen-containing functional groups. However, the diameter of the carbon spheres is too large and the pores are not uniform. Summary of the Invention

[0005] The purpose of this invention is to provide a co-doped mesoporous carbon sphere microwave absorbing material, its preparation method, and its application. The co-doped mesoporous carbon sphere microwave absorbing material has excellent microwave absorption performance.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solutions.

[0007] This invention provides a method for preparing co-doped mesoporous carbon sphere microwave absorbing material. Aniline is added to a colloidal silica hydrochloric acid solution and mixed thoroughly to obtain a mixed solution. Then, an ammonium persulfate hydrochloric acid solution is added to the mixed solution and mixed thoroughly. The mixture is dried to obtain a precursor. The precursor is calcined under a protective atmosphere to obtain an intermediate. The intermediate is then mixed with a sodium hydroxide solution, heated, and treated to obtain the co-doped mesoporous carbon sphere microwave absorbing material. The calcination method involves heating the precursor to 250-350°C under a protective atmosphere and holding it thereafter, then heating it to 700-900°C for calcination.

[0008] Preferably, the molar concentration of the sodium hydroxide solution is 0.8-1.2 mol / L, and the weight-to-volume ratio of the intermediate to the sodium hydroxide solution is 1-1.5 g: 70-80 mL.

[0009] Preferably, the intermediate and sodium hydroxide solution are mixed and then heated to a temperature of 95-105°C.

[0010] Preferably, the intermediate and sodium hydroxide solution are mixed, heated, and then washed until neutral (pH 6.5-7.5) and dried at 55-65°C to obtain a co-doped mesoporous carbon sphere microwave absorbing material.

[0011] Preferably, the colloidal silica hydrochloric acid solution comprises colloidal silica and hydrochloric acid aqueous solution, wherein the molar concentration of the hydrochloric acid aqueous solution is 0.8-1.2 mol / L, and the weight-to-volume ratio of colloidal silica to hydrochloric acid solution is 1 g: 2.5-3.5 mL.

[0012] Preferably, aniline is added to the colloidal silica hydrochloric acid solution and mixed evenly at a temperature of 0-5°C, and ammonium persulfate hydrochloric acid solution is added to the mixed solution and mixed evenly at a temperature of 0-5°C.

[0013] The weight-to-volume ratio of colloidal silica to aniline is 15-25 g: 1 ml.

[0014] Preferably, the ammonium persulfate hydrochloric acid solution comprises ammonium persulfate and hydrochloric acid aqueous solution, wherein the molar concentration of the hydrochloric acid aqueous solution is 0.8-1.2 mol / L, and the weight-volume ratio of ammonium persulfate to hydrochloric acid aqueous solution is 2-3 g: 10-15 mL.

[0015] Preferably, the drying temperature for obtaining the precursor is 80°C;

[0016] The heating rate when the temperature is raised to 250-350℃ is 4-6℃ / min, and the heating rate when the temperature is raised to 700-900℃ is 4-6℃ / min; the calcination method is to heat the precursor to 300℃ under a protective atmosphere and hold it there, and then heat it to 800℃ for calcination.

[0017] This invention provides a co-doped mesoporous carbon sphere absorbing material prepared by the aforementioned method. The co-doped mesoporous carbon sphere absorbing material has a size of 180-280 nm, a pore size of 5.7-6.1 nm, and a specific surface area of ​​350-620 m². 2 / g.

[0018] This invention provides an application of the co-doped mesoporous carbon sphere absorbing material in absorbing electromagnetic waves.

[0019] The beneficial effects of this invention are that the co-doped mesoporous carbon spheres of this invention have the characteristics of being lightweight, having a wide bandwidth, and strong absorption compared to traditional microwave absorbing materials, and have excellent microwave absorption performance solely due to their hierarchical pore structure; the preparation method of this invention is simple and low-cost, requires no complex synthesis equipment, and can be mass-produced on a large scale.

[0020] This invention utilizes carbon nanospheres as the basic unit, and adjusts the pore structure, graphitization degree, and nitrogen content by controlling the carbonization temperature. The co-doped mesoporous carbon sphere material of this invention exhibits excellent microwave absorption performance at thin-matched thicknesses due to its larger specific surface area, ordered mesoporous carbon structure, ideal impedance matching, different polarization processes, and conduction losses.

[0021] This invention involves sequentially adding a mixture of aniline, ammonium persulfate, and hydrochloric acid to a colloidal silica hydrochloric acid solution. Compared to directly mixing aniline with colloidal silica in hydrochloric acid, this method allows for better control of the polymerization process, promotes nitrogen doping, results in more uniform dispersion, and enhances microwave absorption performance. This application significantly reduces the amount of aniline used and employs a strong base instead of a strong acid for etching, leading to more uniform etching and a substantial improvement in microwave absorption performance. Attached Figure Description

[0022] Figure 1 The X-ray diffraction patterns are of the NOCS absorbing materials prepared in Examples 1-3 of this invention.

[0023] Figure 2 Scanning electron microscope images of the NOCS absorbing materials prepared in Examples 1-3 of this invention.

[0024] Figure 3 Raman spectroscopy results of NOCS absorbing materials prepared in Examples 1-3 of this invention.

[0025] Figure 4 The N2 adsorption curves are for the NOCS absorbing materials prepared in Examples 1-3 of this invention.

[0026] Figure 5 The diagram shows the pore size distribution of the NOCS absorbing materials prepared in Examples 1-3 of this invention.

[0027] Figure 6The microwave absorption performance of the NOCS-800 microwave absorbing material prepared in Example 1 of this invention.

[0028] Figure 7 The microwave absorption performance of the NOCS-700 microwave absorbing material prepared in Example 2 of this invention.

[0029] Figure 8 The microwave absorption performance of the NOCS-900 microwave absorbing material prepared in Example 3 of this invention.

[0030] Figure 9 The microwave absorption performance of the microwave absorbing materials in Comparative Examples 1-3 of this invention is shown. Detailed Implementation

[0031] The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] A method for preparing a co-doped mesoporous carbon sphere microwave absorbing material includes the following steps:

[0034] 1. Disperse 20 g of colloidal silica in 60 ml of hydrochloric acid (1 M) and stir for 10 min.

[0035] 2. Add 1 ml of aniline to the mixed solution and stir at 0-5 ℃ for 1 h.

[0036] 3. Add a mixed solution of 2.5 g ammonium persulfate and 12 ml hydrochloric acid (1 M) to the mixed solution in step 2, and stir at a low temperature of 0-5 °C for 12 h.

[0037] 4. The mixture solution was dried in an 80 ℃ drying oven to obtain the green precursor.

[0038] 5. The precursor material is transferred to a tube furnace and heated to 300 °C at a rate of 5 °C / min under a nitrogen atmosphere and held for 3 h. Then, it is heated to 800 °C at a rate of 5 °C / min and calcined for 2 h. After cooling in the furnace, the intermediate is obtained.

[0039] 6. 1.12 g of intermediate material was added to 72 ml of sodium hydroxide (1 M), transferred to a reaction vessel, and heated to 100 °C in an electrically heated drying oven for 18 h. After furnace cooling, the reaction product was filtered, washed with distilled water until neutral, and dried at 60 °C for 12 h to obtain co-doped mesoporous carbon sphere microwave absorbing material, denoted as NOCS-800.

[0040] Example 2

[0041] The difference between Example 2 and Example 1 is that the carbonization temperature in step 4 is changed to 700 °C. Everything else is the same as in Example 1, and it is denoted as NOCS-700.

[0042] Example 3

[0043] The difference between Example 3 and Example 1 is that the carbonization temperature in step 4 is changed to 900 ℃, while the rest is the same as Example 1, and it is denoted as NOCS-900.

[0044] By controlling the carbonization time, the graphitization degree of mesoporous carbonaceous microwave absorbing materials can be effectively adjusted, thereby optimizing the impedance matching effect of the composite microwave absorbing agent and improving its electromagnetic wave loss.

[0045] Figure 1 The X-ray diffraction patterns of NOCS-800, NOCS-700, and NOCS-900 prepared in Examples 1, 2, and 3, respectively, are shown below. Figure 1 It can be seen that Examples 1, 2, and 3 have similar diffraction peaks, all showing a broad peak at 22.7°, corresponding to the (002) crystal plane of graphitized carbon, indicating that the carbon spheres underwent a certain degree of graphitization at high temperature. The XRD patterns of all samples show broad characteristic peaks, meaning that most of the carbon obtained is amorphous carbon.

[0046] Figure 2 The scanning electron microscope (SEM) images of NOCS-800, NOCS-700, and NOCS-900 prepared in Examples 1, 2, and 3, respectively, show that they have uniform size and morphology with a particle size of 180–280 nm.

[0047] Generally speaking, the Raman spectra of carbon materials are in the range of 1000-2000 cm⁻¹. -1 Two peaks will appear, corresponding to defects and graphitization in the carbon material, respectively. The ratio of the defect peak to the graphitization peak represents the degree of graphitization of the carbon material. Figure 3 It can be seen that the graphitization ratios of the mesoporous carbon spheres prepared in Examples 1, 2 and 3 are 0.96, 0.90 and 0.94, respectively, proving that NOCS-800 has the highest degree of graphitization.

[0048] The pore structure of the material was characterized using adsorption-desorption curves of N2 at 77 K, and the results are as follows: Figure 4 and Figure 5 As shown. The adsorption curve is a type I curve, proving the presence of a microporous structure. The hysteresis loop in the isotherm curve confirms the existence of a certain proportion of mesopores in the carbon sphere material. Calculations show that the specific surface area of ​​NOCS-700 is 348.2 m². 2 / g, with an average pore size of 6.07nm, and a specific surface area of ​​613.3 m². 2 / g, with an average pore size of 5.77 nm, and a specific surface area of ​​515.8 m². 2 / g, with an average pore size of 5.79 nm.

[0049] The absorption performance of Examples 1-3 is as follows: Figure 6-8 As shown, Figure 6 The reflection loss curves of the NOCS-800 absorbing material prepared in Example 1 at thicknesses of 1.8–3.0 mm are shown. Figure 7 The reflection loss curves of the NOCS-700 absorbing material prepared in Example 2 at thicknesses of 1.8–3.0 mm are shown. Figure 6 The reflection loss curves of the NOCS-900 absorbing material prepared in Example 3 at thicknesses of 1.8–3.0 mm.

[0050] Depend on Figure 6 It can be seen that, with a thickness of 2.85 mm, Example 1 has a minimum reflectivity of -48.19 dB and an effective bandwidth (reflectivity R < -10 dB) of 5.52 GHz at a frequency of 12.5 GHz. Figure 7 It can be seen that Example 2, with a thickness of 3.0 mm, has a minimum reflectivity of -7.57 dB at a frequency of 15.68 GHz. Figure 8 It can be seen that, in Example 3, with a thickness of 2.25 mm, at a frequency of 11.28 GHz, it has a minimum reflectivity of -18.86 dB and an effective bandwidth (reflectivity R < -10 dB) of 3.76 GHz. Figure 6-8 It can be seen that the RL value first increases and then decreases with increasing carbonization temperature. This is because when the pyrolysis temperature is not high enough, the assembled microspheres are not fully carbonized, and the pore structure is not fully opened, resulting in poor microwave absorption performance. Conversely, the graphitized region at higher carbonization temperatures facilitates electron passage through the carbon structure and increases conductive losses. Due to the skin effect, the enhanced conductivity leads to impedance mismatch, thereby reducing microwave absorption performance.

[0051] Comparative Example 1

[0052] A method for preparing a co-doped mesoporous carbon sphere microwave absorbing material includes the following steps:

[0053] 1. Disperse 20 g of colloidal silica and 1 ml of aniline in 72 ml of hydrochloric acid (1 M) and stir at 0-5 ℃ for 70 min.

[0054] 2. Add 2.5 g of ammonium persulfate to the mixed solution from step 2 and stir at a low temperature of 0-5 °C for 12 h.

[0055] The subsequent steps are the same as in Example 1.

[0056] Comparative Example 2

[0057] A method for preparing a co-doped mesoporous carbon sphere microwave absorbing material includes the following steps:

[0058] 1. Disperse 20 g of colloidal silica in 60 ml of hydrochloric acid (1 M) and stir for 10 min.

[0059] 2. Add 5 ml of aniline to the mixed solution and stir at 0-5 °C for 1 h.

[0060] 3. Add the mixed solution of 10g ammonium persulfate and 48 ml hydrochloric acid (1 M) to the mixed solution in step 2, and stir at a low temperature of 0-5℃ for 12 h.

[0061] The subsequent steps are the same as in Example 1.

[0062] Comparative Example 3

[0063] Compared to Example 1, Comparative Example 3 differs in step 6, where 1.12 g of intermediate material is added to 72 ml of hydrofluoric acid (10% by mass), transferred to a reaction vessel, and heated to 100 °C in an electrically heated drying oven for 18 h. After furnace cooling, the reaction product is filtered, washed with distilled water until neutral, and dried at 60 °C for 12 h to obtain co-doped mesoporous carbon sphere microwave absorbing material. Other steps are the same as in Example 1.

[0064] The absorption performance of comparative examples 1-3 is as follows Figure 9 As shown, it can be seen that when the thickness is 2.85 mm, the minimum reflectivity (-12.53 dB) and effective bandwidth (3.52 GHz) of the optimal material in Comparative Examples 1-3 are significantly lower than the minimum reflectivity (-47.1 dB) and effective bandwidth (4.7 GHz) of Example 1.

[0065] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0066] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A method for preparing a co-doped mesoporous carbon sphere microwave absorbing material, characterized in that, Aniline was added to the colloidal silica hydrochloric acid solution and mixed thoroughly to obtain a mixed solution. Then add the ammonium persulfate hydrochloric acid solution to the mixed solution and mix thoroughly. Drying yields the precursor; The precursor was calcined under a protective atmosphere to obtain the intermediate. Then the intermediate is mixed with sodium hydroxide solution, heated, and processed to obtain co-doped mesoporous carbon sphere microwave absorbing material. The calcination method is to heat the precursor to 300°C under a protective atmosphere and hold it therefore, and then heat it to 800°C for calcination.

2. The preparation method according to claim 1, characterized in that, The molar concentration of the sodium hydroxide solution is 0.8-1.2 mol / L, and the weight-to-volume ratio of the intermediate to the sodium hydroxide solution is 1-1.5 g: 70-80 mL.

3. The preparation method according to claim 1, characterized in that, After mixing the intermediate with the sodium hydroxide solution, the heating temperature is 95-105℃.

4. The preparation method according to claim 1, characterized in that, The intermediate and sodium hydroxide solution are mixed, heated, and then washed until neutral. The mixture is dried at 55-65℃ to obtain co-doped mesoporous carbon sphere microwave absorbing material.

5. The preparation method according to any one of claims 1-4, characterized in that, The colloidal silica hydrochloric acid solution comprises colloidal silica and hydrochloric acid aqueous solution, wherein the molar concentration of hydrochloric acid aqueous solution is 0.8-1.2 mol / L, and the weight-volume ratio of colloidal silica to hydrochloric acid solution is 1 g: 2.5-3.5 mL.

6. The preparation method according to any one of claims 1-4, characterized in that, Aniline was added to the colloidal silica hydrochloric acid solution and mixed thoroughly at a temperature of 0-5℃. Ammonium persulfate hydrochloric acid solution was added to the mixed solution and mixed thoroughly at a temperature of 0-5℃. The weight-to-volume ratio of colloidal silica to aniline is 15-25 g: 1 ml.

7. The preparation method according to any one of claims 1-4, characterized in that, The ammonium persulfate hydrochloric acid solution consists of ammonium persulfate and hydrochloric acid aqueous solution. The molar concentration of the hydrochloric acid aqueous solution is 0.8-1.2 mol / L, and the weight-volume ratio of ammonium persulfate to hydrochloric acid aqueous solution is 2-3 g: 10-15 mL.

8. The preparation method according to claim 1, characterized in that the drying temperature for obtaining the precursor is 80°C; The heating rate when the temperature rises to 300℃ is 4-6℃ / min, and the heating rate when the temperature rises to 800℃ is 4-6℃ / min.

9. A co-doped mesoporous carbon sphere microwave absorbing material obtained by the preparation method according to any one of claims 1-8, characterized in that, The co-doped mesoporous carbon sphere absorbing material has a size of 180-280 nm, a pore size of 5.7-6.1 nm, and a specific surface area of ​​350-620 m². 2 / g.

10. The use of the co-doped mesoporous carbon sphere absorbing material as described in claim 9 in absorbing electromagnetic waves.

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