Preparation method of light, high-temperature-resistant carbon aerogel for electromagnetic shielding

Abstract

This invention discloses a method for preparing lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding. A precursor solution is obtained by adding phenolic compounds, polyethylene glycol, formaldehyde, melamine, silica, and ammonia to a reactor and heating to solidify it into an organic gel. The organic gel is then carbonized to obtain carbon aerogel. The carbon aerogel is pulverized and ground, and then activated at high temperature under a carbon dioxide atmosphere. The activated carbon aerogel is mixed uniformly with silicon powder and subjected to high-temperature treatment under a nitrogen atmosphere. The high-temperature treated carbon aerogel is then subjected to a hydrothermal reaction with ferric hydroxide and copper sulfate in deionized water. After washing and drying, a lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding is obtained. The product has advantages such as being lightweight, stable, high-temperature resistant, and high-strength, exhibiting excellent electromagnetic shielding performance and broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of porous carbon material preparation, specifically relating to a method for preparing carbon aerogel material for electromagnetic shielding. Background Technology

[0002] In recent years, with the rapid development of electronic communication technology, various communication devices and wireless networks, while providing numerous conveniences to our daily lives, have also brought serious electromagnetic pollution problems. This not only affects the normal use of electronic products but also has varying degrees of impact on the central nervous system, endocrine system, and visual system. Electromagnetic shielding materials can attenuate electromagnetic waves by reflecting and absorbing them, effectively reducing the harm of electromagnetic radiation to human health. Furthermore, using this method to solve electromagnetic interference problems does not affect the normal operation of circuits, thus eliminating the need for circuit modifications. The development of new, highly efficient electromagnetic shielding materials has broad application prospects.

[0003] Currently, most electromagnetic shielding materials on the market utilize traditional materials and composite systems such as metals, silicon carbide, and magnetic materials. While these materials possess good electromagnetic shielding and wave absorption properties, they still suffer from limitations such as high density, poor corrosion resistance, and single function, restricting their wider application. With the rapid development of science and technology, higher demands are being placed on electromagnetic shielding materials in terms of lightweighting and overall performance. Therefore, developing electromagnetic interference shielding materials with superior performance and lighter weight has become an important research direction.

[0004] To address the aforementioned problems with electromagnetic shielding materials, patent application 202311183882.5 discloses a method for preparing a lightweight carbon aerogel material for electromagnetic shielding, comprising the following steps: adding resorcinol, phloroglucinol, a template agent, and formaldehyde to pure water, stirring to dissolve, and obtaining a precursor solution; adding the precursor solution to white oil containing a surfactant, emulsifying, and then heating in an oil bath to fully react; centrifuging to obtain powder, carbonizing at high temperature, dispersing in oleylamine, and then adding to a stock solution containing nickel acetylacetonate, triphenylphosphine, and oleylamine, reacting at high temperature and cooling, and then adding a mixture of hexane and ethanol to obtain the product; centrifuging and washing to obtain a lightweight, highly electromagnetically shielding carbon aerogel. The lightweight carbon aerogel material for electromagnetic shielding prepared by this invention has advantages such as low density, high efficiency and corrosion resistance, high electromagnetic shielding effectiveness, and high product yield. By controlling the nucleation and growth rate of Ni2P, Ni2P nanoparticles can be uniformly grown on carbon aerogel microspheres. However, experimental tests show that the specific surface area of ​​the lightweight, highly electromagnetically shielded carbon aerogel prepared by this method is only 507–590 m². 2 g -1 The total pore volume ranges from 0.787 to 1.035 cm³. 3 g -1The range is still relatively small, and the richness of the three-dimensional network nanoporous structure still needs to be improved, resulting in high density, poor thermal insulation performance, and electromagnetic shielding effectiveness that also needs further improvement, thus affecting its large-scale industrial application and promotion.

[0005] Carbon aerogels, as multifunctional carbon materials, have attracted widespread attention due to their high specific surface area, excellent electrical conductivity, good stability, and low density. Their rich three-dimensional network of nanopores provides ample space for electromagnetic wave reflection and dissipation, demonstrating their great potential as highly efficient electromagnetic shielding materials and making them a research hotspot for scholars both domestically and internationally. Summary of the Invention

[0006] The purpose of this invention is to address the problems of high density and poor thermal insulation performance of current electromagnetic shielding materials on the market, and to provide a method for preparing lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding.

[0007] To achieve the above-mentioned objectives of this invention, the following technical solution is adopted for the preparation method of a lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding:

[0008] (1) Phenolic compounds, polyethylene glycol, formaldehyde, melamine, silicon dioxide and ammonia were added to the reactor in sequence and heated in a water bath to mix thoroughly to obtain a precursor solution;

[0009] The phenolic compound is one, any two, or three of phenol, resorcinol, and phloroglucinol; the molar ratio of the phenolic compound to formaldehyde is 1:1 to 1:3; the amount of polyethylene glycol is 0.5% to 5% of the total mass of the phenolic compound and formaldehyde; the amount of melamine is 1% to 20% of the total mass of the phenolic compound and formaldehyde; the amount of silica is 5% to 40% of the total mass of the phenolic compound and formaldehyde; the amount of ammonia is 0.05% to 1% of the total mass of the phenolic compound and formaldehyde; and the water bath heating temperature is 40 to 65°C.

[0010] (2) The precursor solution was continuously stirred and heated in a water bath to solidify the reaction and obtain an organic gel. The organic gel was then dried in a forced-air drying oven. The water bath heating conditions were 70-95℃ for 5-15 hours.

[0011] (3) The dried organic gel was carbonized in a tube furnace to obtain carbon aerogel; the carbonization conditions were 700-1000℃ for 2-6 hours under a nitrogen atmosphere.

[0012] (4) The carbon aerogel is crushed and ground, and activated at high temperature in a carbon dioxide atmosphere; the high temperature activation conditions are 800-1000℃ for 9-15 hours.

[0013] (5) The activated carbon aerogel is mixed evenly with a certain proportion of silicon powder and subjected to high temperature treatment under a nitrogen atmosphere; the mass ratio of carbon aerogel to silicon powder is 1:0.2 to 1:0.8; the high temperature treatment conditions are 1300℃ to 1700℃ for 1 to 5 hours.

[0014] (6) The carbon aerogel after high temperature treatment, iron hydroxide and copper sulfate are added to deionized water in a mass ratio of 1:(1~3):(0.2~1.5) and stirred evenly. The mixture is then transferred to a hydrothermal reactor at a temperature of 130~170℃ for hydrothermal reaction for 18~30h. After washing and drying, a lightweight and high temperature resistant carbon aerogel for electromagnetic shielding is obtained.

[0015] Preferably, in step (1), the molar ratio of the phenolic compound to formaldehyde is 1:2 to 1:3; the phenolic compound is resorcinol, or a mixture of any one or two of resorcinol, phenol, and phloroglucinol.

[0016] Further, in step (1), the phenolic compound is resorcinol, the molar ratio of resorcinol to formaldehyde is 1:(1.7-2.3), the amount of polyethylene glycol is 0.8%-1.2% of the total mass of resorcinol and formaldehyde, the amount of melamine is 17%-23% of the total mass of resorcinol and formaldehyde, the amount of silica is 17%-23% of the total mass of resorcinol and formaldehyde, and the amount of ammonia is 0.05%-0.07% of the total mass of resorcinol and formaldehyde.

[0017] Preferably, in step (3), the carbonization temperature is 820℃~880℃ and the carbonization time is 3.5~4.5h.

[0018] Preferably, in step (4), the activation temperature is 900℃~950℃ and the activation time is 9~12h.

[0019] Preferably, in step (5), the mass ratio of carbon aerogel to silicon powder is 1:0.2 to 1:0.5; the high temperature treatment conditions are 1400℃ to 1600℃ for 1.8 to 2.5 hours.

[0020] Preferably, in step (6), the mass ratio of carbon aerogel, ferric hydroxide, and copper sulfate is 1:(1-2):(0.2-1); the amount of deionized water is 13-17 times the total mass of carbon aerogel, ferric hydroxide, and copper sulfate.

[0021] Furthermore, in step (1), the water bath heating temperature is 48℃~55℃; in step (2), the water bath heating temperature is 80℃~90℃; and in step (6), the hydrothermal reaction temperature is 155℃~165℃.

[0022] Compared with existing processes, the present invention, by adopting the above technical solution, has the following beneficial effects:

[0023] (1) In this invention, polyethylene glycol is used as a soft template for pore formation, and carbon dioxide is used for secondary pore formation, so that the carbon aerogel has a rich microporous and mesoporous structure. It has the advantages of being lightweight, stable, high temperature resistant, and high strength, which makes it have good electromagnetic shielding effect and a wider range of applications.

[0024] (2) In this invention, melamine is used as a nitrogen source to dope carbon aerogel, and high temperature treatment is combined to improve its graphitization degree, which effectively improves the conductivity of carbon aerogel.

[0025] (3) Silicon carbide materials are produced by reacting silicon dioxide, silicon powder, and carbon at high temperature, while FeOOH is loaded onto the surface and pores of carbon aerogel using a hydrothermal method. Both are excellent electromagnetic shielding materials. This further improves the electromagnetic shielding effect of carbon aerogel materials while avoiding the problem of high density.

[0026] (4) The experimental results show that, through synergistic optimization and adjustment of the raw material ratio and process parameters in each step, the technical performance of the final prepared carbon aerogel for electromagnetic shielding is as follows: electrical conductivity 251-280 S / cm, tap density 0.41-0.48 g / cm³. 3 The electromagnetic shielding effectiveness is 73.1–75.6 dB for the 8.2–12.4 GHz range. Detailed Implementation

[0027] The present invention will now be described in detail with reference to specific embodiments. These illustrative embodiments and descriptions are used to explain the invention but are not intended to limit it. Based on the embodiments of the present invention, any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the invention should be included within the scope of protection of the present invention.

[0028] Example 1

[0029] The raw materials used in the preparation of the precursor in this embodiment are: resorcinol, polyethylene glycol, formaldehyde, melamine, silica, and ammonia water. The molar ratio of resorcinol to formaldehyde is 1:2. The amount of polyethylene glycol is 1% of the total mass of resorcinol and formaldehyde, the amount of melamine is 20% of the total mass of resorcinol and formaldehyde, the amount of silica is 20% of the total mass of resorcinol and formaldehyde, and the amount of ammonia water is 0.05% of the total mass of resorcinol and formaldehyde.

[0030] Resorcinol, polyethylene glycol, formaldehyde, melamine, etc. are stirred and dissolved under 50℃ water bath conditions, and then ammonia and silicon dioxide are added and mixed thoroughly to prepare a precursor solution.

[0031] The precursor solution was heated in a water bath at 85°C for 13 hours under continuous magnetic stirring to obtain a blocky organic gel.

[0032] After drying the block-shaped organic gel by blowing air, it was carbonized at 850°C for 4 hours in a tube furnace under a nitrogen atmosphere to obtain carbon aerogel.

[0033] The obtained carbon aerogel was crushed and ground into fine powder, and then activated at 920°C for 10 hours under a carbon dioxide atmosphere.

[0034] The activated carbon aerogel was mixed evenly with silicon powder at a mass ratio of 1:0.2 and kept at 1500℃ for 2 hours under a nitrogen atmosphere.

[0035] The carbon aerogel treated at high temperature, iron hydroxide, and copper sulfate in a ratio of 1:2:1 were added sequentially to 15 times their total mass of deionized water, stirred evenly, and then transferred to a hydrothermal reactor. The mixture was hydrothermally reacted at 160°C for 20 hours. After washing and drying, the carbon aerogel for electromagnetic shielding was obtained.

[0036] Example 2

[0037] The raw materials used in the preparation of the precursor in this embodiment are: resorcinol, phloroglucinol, polyethylene glycol, formaldehyde, melamine, silica, and ammonia. The molar ratio of resorcinol to phloroglucinol is 10:1, the molar ratio of resorcinol to formaldehyde is 1:2, the amount of polyethylene glycol is 0.5% of the total mass of resorcinol and formaldehyde, the amount of melamine is 10% of the total mass of resorcinol and formaldehyde, the amount of silica is 40% of the total mass of resorcinol and formaldehyde, and the amount of ammonia is 1% of the total mass of resorcinol and formaldehyde.

[0038] Resorcinol, phloroglucinol, polyethylene glycol, formaldehyde, melamine, etc. are stirred and dissolved under 40℃ water bath conditions, and then ammonia and silicon dioxide are added and mixed thoroughly to prepare a precursor solution.

[0039] The precursor solution was heated in a water bath at 70°C for 15 hours under continuous magnetic stirring to obtain a blocky organic gel.

[0040] After drying the blocky organic gel by blowing air, carbon aerogel was obtained by carbonizing it at 1000℃ for 2 hours in a tube furnace under a nitrogen atmosphere.

[0041] The obtained carbon aerogel was crushed and ground into fine powder, and then activated at 1000℃ for 9 hours under a carbon dioxide atmosphere.

[0042] The activated carbon aerogel was mixed evenly with silicon powder at a mass ratio of 1:0.8 and kept at 1700℃ for 1 hour under a nitrogen atmosphere.

[0043] The carbon aerogel after high-temperature treatment, iron hydroxide, and copper sulfate in a ratio of 1:1:0.2 were added sequentially to 15 times their total mass of deionized water, stirred evenly, and transferred to a hydrothermal reactor. The mixture was then hydrothermally reacted at 130°C for 30 hours. After washing and drying, the carbon aerogel for electromagnetic shielding was obtained.

[0044] Example 3

[0045] The raw materials used to prepare the precursor in this embodiment are: resorcinol, phenol, polyethylene glycol, formaldehyde, melamine, silica, and ammonia. The molar ratio of resorcinol to phenol is 10:1, the molar ratio of resorcinol to formaldehyde is 1:3, the amount of polyethylene glycol is 5% of the total mass of resorcinol and formaldehyde, the amount of melamine is 1% of the total mass of resorcinol and formaldehyde, the amount of silica is 5% of the total mass of resorcinol and formaldehyde, and the amount of ammonia is 0.05% of the total mass of resorcinol and formaldehyde.

[0046] Resorcinol, phenol, polyethylene glycol, formaldehyde, melamine, etc. are stirred and dissolved under a 65℃ water bath, and then ammonia and silicon dioxide are added and mixed thoroughly to prepare a precursor solution.

[0047] The precursor solution was heated in a water bath at 95°C for 5 hours under continuous magnetic stirring to obtain a blocky organic gel.

[0048] After drying the blocky organic gel by blowing air, carbon aerogel was obtained by carbonizing it at 700°C for 6 hours in a tube furnace under a nitrogen atmosphere.

[0049] The obtained carbon aerogel was crushed and ground into fine powder, and then activated at 800°C for 15 hours under a carbon dioxide atmosphere.

[0050] The activated carbon aerogel was mixed evenly with silicon powder at a mass ratio of 1:0.2 and kept at 1400℃ for 3 hours under a nitrogen atmosphere.

[0051] The carbon aerogel after high-temperature treatment, iron hydroxide, and copper sulfate in a ratio of 1:1:0.2 were added sequentially to 15 times their total mass of deionized water, stirred evenly, and transferred to a hydrothermal reactor. The mixture was then hydrothermally reacted at 150°C for 20 hours. After washing and drying, the carbon aerogel for electromagnetic shielding was obtained.

[0052] Example 4

[0053] The raw materials used in the preparation of the precursor in this embodiment are: resorcinol, phenol, phloroglucinol, polyethylene glycol, formaldehyde, melamine, silica, and ammonia. The molar ratio of resorcinol to phenol and phloroglucinol is 10:1:1, the molar ratio of resorcinol to formaldehyde is 1:2, the amount of polyethylene glycol is 1% of the total mass of resorcinol and formaldehyde, the amount of melamine is 15% of the total mass of resorcinol and formaldehyde, the amount of silica is 10% of the total mass of resorcinol and formaldehyde, and the amount of ammonia is 0.1% of the total mass of resorcinol and formaldehyde.

[0054] Resorcinol, phenol, phloroglucinol, polyethylene glycol, formaldehyde, melamine, etc. are stirred and dissolved under a 65℃ water bath, and then ammonia and silicon dioxide are added and mixed thoroughly to prepare a precursor solution.

[0055] The precursor solution was heated in a water bath at 80°C for 14 hours under continuous magnetic stirring to obtain a blocky organic gel.

[0056] After drying the block-shaped organic gel by blowing air, it was carbonized at 850°C for 4 hours in a tube furnace under a nitrogen atmosphere to obtain carbon aerogel.

[0057] The obtained carbon aerogel was crushed and ground into fine powder, and then activated at 800°C for 15 hours under a carbon dioxide atmosphere.

[0058] The activated carbon aerogel was mixed evenly with silicon powder at a mass ratio of 1:0.4 and kept at 1500℃ for 3 hours under a nitrogen atmosphere.

[0059] The carbon aerogel treated at high temperature, iron hydroxide, and copper sulfate in a ratio of 1:2:0.7 were added sequentially to 15 times their total mass of deionized water, stirred evenly, and transferred to a hydrothermal reactor. The mixture was then hydrothermally reacted at 150°C for 20 hours. After washing and drying, the carbon aerogel for electromagnetic shielding was obtained.

[0060] Example 5

[0061] The raw materials used in the preparation of the precursor in this embodiment are: phenol, polyethylene glycol, formaldehyde, melamine, silica, and ammonia water. The molar ratio of phenol to formaldehyde is 1:2. The amount of polyethylene glycol is 1% of the total mass of resorcinol and formaldehyde, the amount of melamine is 20% of the total mass of resorcinol and formaldehyde, the amount of silica is 10% of the total mass of resorcinol and formaldehyde, and the amount of ammonia water is 1% of the total mass of resorcinol and formaldehyde.

[0062] Phenol, polyethylene glycol, formaldehyde, melamine, etc. are dissolved by stirring under a 65℃ water bath, and then ammonia and silicon dioxide are added and mixed thoroughly to prepare a precursor solution.

[0063] The precursor solution was heated in a water bath at 85°C for 13 hours under continuous magnetic stirring to obtain a blocky organic gel.

[0064] After drying the block-shaped organic gel by blowing air, it was carbonized at 850°C for 4 hours in a tube furnace under a nitrogen atmosphere to obtain carbon aerogel.

[0065] The obtained carbon aerogel was crushed and ground into fine powder, and then activated at 900°C for 12 hours under a carbon dioxide atmosphere.

[0066] The activated carbon aerogel was mixed evenly with silicon powder at a mass ratio of 1:0.2 and kept at 1500℃ for 3 hours under a nitrogen atmosphere.

[0067] The carbon aerogel treated at high temperature, iron hydroxide, and copper sulfate in a ratio of 1:2:0.7 were added sequentially to 15 times their total mass of deionized water, stirred evenly, and transferred to a hydrothermal reactor. The mixture was then hydrothermally reacted at 150°C for 20 hours. After washing and drying, the carbon aerogel for electromagnetic shielding was obtained.

[0068] Example 6

[0069] The raw materials used in the precursor preparation of this embodiment are: phenol, phloroglucinol, polyethylene glycol, formaldehyde, melamine, silica, and ammonia. The molar ratio of phenol to phloroglucinol is 8:2, the molar ratio of phenol to formaldehyde is 1:2, the amount of polyethylene glycol is 2% of the total mass of resorcinol and formaldehyde, the amount of melamine is 15% of the total mass of resorcinol and formaldehyde, the amount of silica is 30% of the total mass of resorcinol and formaldehyde, and the amount of ammonia is 1% of the total mass of resorcinol and formaldehyde.

[0070] Phenol, phloroglucinol, polyethylene glycol, formaldehyde, melamine, etc. are stirred and dissolved under 60℃ water bath conditions, and then ammonia and silicon dioxide are added and mixed thoroughly to prepare a precursor solution.

[0071] The precursor solution was heated in a water bath at 85°C for 13 hours under continuous magnetic stirring to obtain a blocky organic gel.

[0072] After drying the block-shaped organic gel by blowing air, it was carbonized at 850°C for 4 hours in a tube furnace under a nitrogen atmosphere to obtain carbon aerogel.

[0073] The obtained carbon aerogel was crushed and ground into fine powder, and then activated at 900°C for 12 hours under a carbon dioxide atmosphere.

[0074] The activated carbon aerogel was mixed evenly with silicon powder at a mass ratio of 1:0.2 and kept at 1500℃ for 3 hours under a nitrogen atmosphere.

[0075] The carbon aerogel treated at high temperature, iron hydroxide, and copper sulfate in a ratio of 1:2:0.7 were added sequentially to 15 times their total mass of deionized water, stirred evenly, and transferred to a hydrothermal reactor. The mixture was then hydrothermally reacted at 150°C for 20 hours. After washing and drying, the carbon aerogel for electromagnetic shielding was obtained.

[0076] Compare with Example 1

[0077] The raw materials used to prepare the precursor in this comparative example are: resorcinol, polyethylene glycol, formaldehyde, melamine, and ammonia water. The molar ratio of resorcinol to formaldehyde is 1:2. The amount of polyethylene glycol is 1% of the total mass of resorcinol and formaldehyde, the amount of melamine is 20% of the total mass of resorcinol and formaldehyde, and the amount of ammonia water is 0.05% of the total mass of resorcinol and formaldehyde.

[0078] Resorcinol, polyethylene glycol, formaldehyde, melamine, etc. were dissolved by stirring under a 50℃ water bath, and then ammonia and silicon dioxide were added and stirred evenly to prepare a precursor solution.

[0079] The precursor solution was heated in a water bath at 85°C for 13 hours under continuous magnetic stirring to obtain a blocky organic gel.

[0080] After drying the block-shaped organic gel by blowing air, it was carbonized at 850°C for 4 hours in a tube furnace under a nitrogen atmosphere to obtain carbon aerogel.

[0081] The obtained carbon aerogel was crushed and ground into fine powder, and then activated at 920°C for 10 hours under a carbon dioxide atmosphere.

[0082] Compare with Example 2

[0083] The raw materials used to prepare the precursor in this comparative example are: resorcinol, polyethylene glycol, formaldehyde, melamine, silica, and ammonia water. The molar ratio of resorcinol to formaldehyde is 1:2. The amount of polyethylene glycol is 1% of the total mass of resorcinol and formaldehyde, the amount of melamine is 20% of the total mass of resorcinol and formaldehyde, the amount of silica is 20% of the total mass of resorcinol and formaldehyde, and the amount of ammonia water is 0.05% of the total mass of resorcinol and formaldehyde.

[0084] Resorcinol, polyethylene glycol, formaldehyde, melamine, etc. were dissolved by stirring under a 50℃ water bath, and then ammonia and silicon dioxide were added and stirred evenly to prepare a precursor solution.

[0085] The precursor solution was heated in a water bath at 85°C for 13 hours under continuous magnetic stirring to obtain a blocky organic gel.

[0086] After drying the block-shaped organic gel by blowing air, it was carbonized at 850°C for 4 hours in a tube furnace under a nitrogen atmosphere to obtain carbon aerogel.

[0087] The obtained carbon aerogel was crushed and ground into fine powder, and then activated at 920°C for 10 hours under a carbon dioxide atmosphere.

[0088] The activated carbon aerogel was mixed evenly with silicon powder at a mass ratio of 1:0.2 and kept at 1500℃ for 2 hours under a nitrogen atmosphere.

[0089] The following performance tests were performed on the lightweight, highly electromagnetically shielded carbon aerogel materials prepared in Examples 1-6 and Comparative Examples 1 and 2:

[0090] Pore ​​structure testing: A specific surface area test was used to perform full-pore testing, and the results are shown in Table 1.

[0091] Electrical performance testing: The conductivity of carbon aerogel was tested using a dual-electrical-measurement four-probe tester, and the results are shown in Table 2.

[0092] Tap density test: The test was conducted according to GB / T 21354-2008, and the results are shown in Table 2.

[0093] Electromagnetic shielding performance testing: Following ASTM ES7-83 and ASTM D4935-99, a vector network analyzer equipped with a coaxial test unit (APC-7 connector) was used to measure the electromagnetic shielding performance of biomass-based carbon aerogel in the frequency range of 8.2–12.4 GHz (X-band) at room temperature. Carbon aerogel was prepared into discs approximately 13 mm in diameter and 2 mm thick for testing.

[0094] Salt spray resistance test: The test was conducted according to GB 6458-86, and the results are shown in Table 2.

[0095]

[0096] As shown in Table 1, the prepared carbon aerogel possesses a high specific surface area and large pore volume. Its abundant three-dimensional nanoporous structure can effectively alleviate the impedance mismatch at the air-material interface and reduce electromagnetic wave reflection. Control Example 1 (without silicon carbide and iron) and Control Example 2 (with silicon carbide but without iron) exhibited higher specific surface area and pore volume under essentially the same formulation as Example 1 and the same activation conditions. The changes in specific surface area and pore volume in Control Example 2 indicate that iron was successfully loaded onto the surface of the carbon aerogel and into its pores, effectively increasing the dielectric loss of electromagnetic waves.

[0097]

[0098] Table 2 shows that the prepared lightweight, highly electromagnetically shielded carbon aerogel possesses high electrical conductivity, low tap density, and good electromagnetic shielding effectiveness. Salt spray resistance testing also demonstrates its excellent corrosion resistance. Although the incorporation of silicon carbide and iron slightly increases the tap density, its shielding performance is significantly improved. For example, Example 1 shows a 40.37% improvement in electromagnetic shielding effectiveness in the 8.2-12.4 GHz range compared to Control Example 1, and a 17.90% improvement compared to Control Example 2.

Claims

1. A method for preparing a lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding, characterized in that... The following steps are to be taken: (1) Phenolic compounds, polyethylene glycol, formaldehyde, melamine, silicon dioxide and ammonia were added to the reactor in sequence and heated in a water bath to mix thoroughly to obtain a precursor solution; The phenolic compound is one, any two, or three of phenol, resorcinol, and phloroglucinol; the molar ratio of the phenolic compound to formaldehyde is 1:1 to 1:3; the amount of polyethylene glycol is 0.5% to 5% of the total mass of the phenolic compound and formaldehyde; the amount of melamine is 1% to 20% of the total mass of the phenolic compound and formaldehyde; the amount of silica is 5% to 40% of the total mass of the phenolic compound and formaldehyde; the amount of ammonia is 0.05% to 1% of the total mass of the phenolic compound and formaldehyde; and the water bath heating temperature is 40 to 65°C. (2) The precursor solution was continuously stirred and heated in a water bath to solidify the reaction and obtain an organic gel. The organic gel was then dried in a forced-air drying oven. The water bath heating conditions were 70-95℃ for 5-15 hours. (3) The dried organic gel was carbonized in a tube furnace to obtain carbon aerogel; the carbonization conditions were 700-1000℃ for 2-6 hours under a nitrogen atmosphere. (4) The carbon aerogel is crushed and ground, and activated at high temperature in a carbon dioxide atmosphere; the high temperature activation conditions are 800-1000℃ for 9-15 hours. (5) The activated carbon aerogel is mixed evenly with a certain proportion of silicon powder and subjected to high temperature treatment under a nitrogen atmosphere; the mass ratio of carbon aerogel to silicon powder is 1:0.2 to 1:0.8; the high temperature treatment conditions are 1300℃ to 1700℃ for 1 to 5 hours. (6) The carbon aerogel after high temperature treatment, iron hydroxide and copper sulfate are added to deionized water in a mass ratio of 1:(1~3):(0.2~1.5) and stirred evenly. The mixture is then transferred to a hydrothermal reactor at a temperature of 130~170℃ for hydrothermal reaction for 18~30h. After washing and drying, a lightweight and high temperature resistant carbon aerogel for electromagnetic shielding is obtained.

2. The method for preparing a lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding as described in claim 1, characterized in that: In step (1), the molar ratio of the phenolic compound to formaldehyde is 1:2 to 1:3; the phenolic compound is resorcinol, or a mixture of any one or two of resorcinol, phenol, and phloroglucinol.

3. The method for preparing a lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding as described in claim 1, characterized in that: In step (1), the phenolic compound is resorcinol, the molar ratio of resorcinol to formaldehyde is 1:(1.7-2.3), the amount of polyethylene glycol is 0.8%-1.2% of the total mass of resorcinol and formaldehyde, the amount of melamine is 17%-23% of the total mass of resorcinol and formaldehyde, the amount of silica is 17%-23% of the total mass of resorcinol and formaldehyde, and the amount of ammonia is 0.05%-0.07% of the total mass of resorcinol and formaldehyde.

4. The method for preparing a lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding as described in claim 1, characterized in that: In step (3), the carbonization temperature is 820℃~880℃ and the carbonization time is 3.5~4.5h.

5. The method for preparing a lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding as described in claim 1, characterized in that: In step (4), the activation temperature is 900℃~950℃ and the activation time is 9~12h.

6. The method for preparing a lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding as described in claim 1, characterized in that: In step (5), the mass ratio of carbon aerogel to silicon powder is 1:0.2 to 1:0.5; the high temperature treatment conditions are 1400℃ to 1600℃ for 1.8 to 2.5 hours.

7. The method for preparing a lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding as described in claim 1, characterized in that: In step (6), the mass ratio of carbon aerogel, ferric hydroxide, and copper sulfate is 1:(1-2):(0.2-1).

8. The method for preparing a lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding as described in claim 1, characterized in that: In step (6), the amount of deionized water is 13 to 17 times the total mass of carbon aerogel, ferric hydroxide, and copper sulfate.

9. The method for preparing a lightweight, high-temperature resistant carbon aerogel for electromagnetic shielding as described in claim 1, characterized in that: In step (1), the water bath heating temperature is 48℃~55℃; in step (2), the water bath heating temperature is 80℃~90℃; in step (6), the hydrothermal reaction temperature is 155℃~165℃.

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