A method for preparing a lightweight carbon aerogel material for electromagnetic shielding

Abstract

The application discloses a preparation method of carbon aerogel material for light electromagnetic shielding, and comprises the following steps: adding resorcinol, phloroglucinol, a template agent and formaldehyde into pure water, stirring and dissolving to obtain a precursor solution; adding the precursor solution into white oil containing a surfactant, emulsifying, heating in an oil bath and fully reacting; centrifugal separation to obtain powder, high-temperature carbonization, dispersion in oleylamine, addition into a stock solution containing nickel acetylacetonate, triphenylphosphine and oleylamine, high-temperature reaction and cooling, addition of a mixture of hexane and ethanol to obtain a product; centrifugal separation and washing to obtain light high-electromagnetic-shielding carbon aerogel. The carbon aerogel material for light electromagnetic shielding prepared by the method has the advantages of small density, high efficiency, corrosion resistance, high electromagnetic shielding efficiency, high product yield and the like, and by controlling the nucleation and growth rate of Ni2P, the Ni2P nanoparticles can be uniformly grown on the carbon aerogel microspheres, and the method is suitable for application in large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electromagnetic shielding material preparation, and particularly relates to a carbon aerogel material for electromagnetic shielding and a preparation method thereof. BACKGROUND

[0002] In recent years, with the rapid development of electronic information technology, the popularity of various communication equipment and wireless networks has provided great help to social development and people's daily life. However, the pollution caused by electromagnetic radiation is also increasingly serious, and electromagnetic radiation is harmful to complex electronic equipment, communication systems with high frequency requirements, and even people's health. Using electromagnetic shielding materials to block the propagation of electromagnetic energy in the area to be shielded can effectively reduce the harm of electromagnetic radiation, and using this method to solve electromagnetic interference problems will not affect the normal operation of the circuit, so the circuit does not need to be modified.

[0003] At present, the common electromagnetic shielding materials on the market are mostly traditional materials such as ferrite, metal, silicon carbide and their composites. Although these materials have good electromagnetic shielding and wave absorption performance, high density, poor corrosion resistance, and single function limit their application.

[0004] With the rapid development of science and technology, the performance and lightweight of electromagnetic shielding materials in the fields of aerospace, wireless communication, intelligent electronic equipment and the like are required to be higher. Chinese patent ZL202011514369.6 discloses an electromagnetic shielding composite material and a preparation method thereof. The provided electromagnetic shielding composite material comprises a fabric substrate, graphene aerogel on the surface of the fabric substrate, and water-based polyurethane. The water-based polyurethane is filled in the pores of the graphene aerogel and at the interface between the fabric substrate and the graphene aerogel. In the electromagnetic shielding composite material, the graphene aerogel itself has a porous conductive network structure, which is beneficial to avoid the aggregation of carbon materials, and is uniformly dispersed, thereby reducing the amount of conductive carbon materials and improving the utilization rate of carbon materials; the water-based polyurethane is a filling material for the graphene aerogel and an adhesive between the graphene aerogel and the substrate, which improves the material bonding strength of the electromagnetic shielding composite material. However, the main raw material of the electromagnetic shielding composite material is graphene aerogel, the time of each preparation process is long, the vacuum freeze-drying conditions are harsh, it is difficult to be used in large-scale industrial production, and the cost of raw materials is very high. SUMMARY

[0005] The present application aims at the problems of high density, poor corrosion resistance of electromagnetic shielding materials prepared by the prior art, and the problems of high cost of raw materials, long manufacturing period, harsh process conditions, and difficulty in large-scale industrial production, and provides a preparation method of light-weight carbon aerogel material for electromagnetic shielding, which has small density, high efficiency, corrosion resistance, high electromagnetic shielding efficiency, and is suitable for large-scale industrial production.

[0006] To solve the above problems, the present application provides a preparation method of light-weight carbon aerogel material for electromagnetic shielding, which adopts the following process:

[0007] S1: Preparation of carbon aerogel microspheres

[0008] (1) A certain amount of resorcinol, phloroglucinol and polyethylene glycol are added to a certain amount of pure water, heated and stirred until completely dissolved, then heating is stopped and stirring is continued until room temperature is reached, and then formaldehyde aqueous solution is added and stirred uniformly to prepare a solution precursor;

[0009] In this step, the molar ratio of resorcinol to phloroglucinol is preferably 1:5-15, the amount of polyethylene glycol is preferably 0.5%-5% of the total mass of resorcinol, phloroglucinol and formaldehyde, and the molar ratio of the total amount of resorcinol and phloroglucinol to formaldehyde is preferably 1:1.5-3; the density of the prepared solution precursor should be controlled in the range of 0.3-0.8 g / mL; and the polyethylene glycol is preferably polyethylene glycol 2000;

[0010] In this step, the heating temperature is generally controlled in the range of 20-60℃, and 50-60℃ is preferred.

[0011] (2) The prepared solution precursor is poured into white oil containing a surfactant, and emulsified by an emulsifier, and the emulsified suspension is continuously stirred while water bath reaction to obtain a slurry containing gel microspheres;

[0012] In this step, the amount of surfactant is preferably 0.5%-3% of the volume of white oil, and the volume ratio of precursor to white oil is preferably in the range of 1:3-15, and preferably 1:6-10;

[0013] In this step, the temperature of the water bath process is preferably 30-70℃, and 50-70℃ is preferred, the reaction time is 6-15h, and the stirring speed is 100-500r / min.

[0014] (3) The prepared slurry is subjected to solid-liquid separation and washing, and then dried at room temperature to obtain aerogel microspheres.

[0015] (4) The carbon aerogel microspheres obtained after drying are carbonized in a tube furnace to obtain carbon aerogel microspheres;

[0016] The carbonization temperature in this step is generally 750-1050°C, preferably 750-950°C, and the carbonization time is generally 2-6h.

[0017] S2: Preparation of mixed stock solution A

[0018] (5) Acetylacetone nickel, triphenylphosphine, and oleylamine are added to a reaction container according to a set ratio, heated to a set T1 temperature, stirred, and at the same time, N2 is introduced for a period of time, and then the temperature is continuously increased to T2 to obtain mixed stock solution A;

[0019] In this step, the molar ratio of acetylacetone nickel to triphenylphosphine is preferably 1:1-5, and the molar ratio of acetylacetone nickel to oleylamine is preferably 1:4-12; the T1 temperature is generally 25°C-65°C, preferably 25°C-40°C; and the T2 is generally 80°C-130°C.

[0020] S3: Preparation of carbon aerogel material product for electromagnetic shielding

[0021] (6) The carbon aerogel microspheres prepared in step (4) are added to a set amount of oleylamine to obtain mixture B;

[0022] In this step, the mass ratio of carbon aerogel microspheres to oleylamine in mixture B is preferably 1:100-400.

[0023] (7) Mixture B is injected into mixed stock solution A of step (5), stirred for a period of time, then the temperature is increased and stirred for a period of time, then cooled to room temperature, a mixture of hexane and ethanol is added to precipitate the black product, and the product is purified by centrifuge separation-washing-precipitation-centrifuge separation cycle, and then vacuum dried to obtain carbon aerogel material product Ni2P / CA for electromagnetic shielding;

[0024] In step (7), the mass ratio of carbon aerogel microspheres to acetylacetone nickel is generally 1:1-30, preferably 1:8-25; and in the mixture of hexane and ethanol, the volume ratio of hexane to ethanol is generally 1:0.5-1.5, preferably 1:0.8-1.3;

[0025] In step (7), the mass ratio of acetylacetone nickel to carbon aerogel microspheres is generally 1:4-20, preferably 1:5-10.

[0026] In step (7), the stirring time before temperature increase is 5-25 min, and the temperature after temperature increase is preferably controlled in the range of 200-400°C.

[0027] Compared with the prior art, the preparation method of the carbon aerogel material for light electromagnetic shielding has the following beneficial effects:

[0028] (1) The carbon aerogel is used as a multifunctional carbon material in the present application, and has the advantages of high specific area, high conductivity, high stability, low density and the like, and meanwhile, the carbon aerogel has a rich three-dimensional network nano-pore structure inside, which can provide sufficient internal reflection space for electromagnetic waves.

[0029] (2) A small-size Ni2P grown on the carbon aerogel microspheres is designed as an electromagnetic wave absorber in the present application, and a layer of Ni2P is wrapped on the surface of the carbon aerogel microspheres with a rich mesoporous structure, high conductivity, high stability and low density, so as to prepare a light and efficient electromagnetic shielding material with corrosion resistance.

[0030] (3) In the synthesis process, the nucleation and growth rate of the Ni2P can be controlled, so that the Ni2P nanoparticles can be uniformly grown on the carbon aerogel microspheres.

[0031] (4) The size and coverage range of the Ni2P on the carbon aerogel microspheres can be adjusted by adjusting the reaction conditions, so as to obtain a higher yield, which is very beneficial to adjusting the application performance. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 SEM diagram of the carbon aerogel material Ni2P / CA for light electromagnetic shielding prepared by the method of the present application in Example 1;

[0033] Figure 2 SEM diagram of the carbon aerogel material Ni2P / CA for light electromagnetic shielding prepared by the method of the present application in Example 2. DETAILED DESCRIPTION

[0034] In order to describe the present application, the preparation method of the carbon aerogel material for light electromagnetic shielding of the present application will be further described in detail in combination with examples. However, the present application is not limited to the examples.

[0035] Example 1

[0036] The raw materials used for configuring the precursor in this embodiment are: resorcinol, phloroglucinol, formaldehyde and polyethylene glycol 2000, the molar ratio of resorcinol to phloroglucinol is 8:1, the molar ratio of formaldehyde to the total amount of resorcinol and phloroglucinol is 1:0.5, and the total mass ratio of polyethylene glycol 2000 to resorcinol, phloroglucinol and formaldehyde is 0.015:1.

[0037] After the resorcinol, phloroglucinol and polyethylene glycol are dissolved by stirring at 60 DEG C, the formaldehyde solution is added and continuously stirred to be uniform, and a precursor solution with a density of 0.5 g / ml is configured.

[0038] The precursor solution was poured into 15# white oil containing 0.5% by volume of Span 80, emulsified at low speed for 5 min with an emulsifier, and then poured into a three-necked flask. The suspension was prepared by stirring at 200 r / min in an oil bath at 60℃ for 14 h. The volume ratio of the precursor to white oil was 1:8.

[0039] The suspension was centrifuged and repeatedly washed with dichloromethane to obtain a powder without agglomeration. The powder dried at room temperature was carbonized in a tube furnace at 850℃ for 4 h to obtain carbon aerogel microspheres.

[0040] Nickel acetylacetonate, triphenylphosphine, and oleylamine in a molar ratio of 2:5:15 were added to a three-necked flask, and the temperature was raised to 100℃ while stirring and purging with N2 for 30 min. Then the temperature was raised to 300℃ at a rate of 5℃ / min, and the mixture was kept at 300℃ for 30 min. After cooling to room temperature, a mixture of hexane and ethanol in a volume ratio of 1:1 was added to produce black precipitates. The volume ratio of the mixture to the original solution was 1:1.

[0041] The mixture liquid (mixture B) of carbon aerogel and oleylamine was added to the above-mentioned original solution. The mass ratio of carbon aerogel to oleylamine was 1:120, and the mass ratio of carbon aerogel to nickel acetylacetonate was 1:10. After stirring for 10 min, the temperature was raised to 300℃ at a rate of 5℃ / min, and the mixture was kept at 300℃ for 30 min. After cooling to room temperature, a mixture of hexane and ethanol in a volume ratio of 1:1 was added to produce black precipitates. The volume ratio of the mixture to the original solution was 1:1.

[0042] The black precipitates obtained after centrifugation were washed with ethanol and pure water several times and then dried in vacuum to obtain Ni2P / CA-1.

[0043] Example 2

[0044] The raw materials for preparing the precursor in this example included resorcinol, phloroglucinol, formaldehyde, and polyethylene glycol 2000. The molar ratio of resorcinol to phloroglucinol was 5:1. The molar ratio of formaldehyde to the total amount of resorcinol and phloroglucinol was 1:0.5. The total mass ratio of polyethylene glycol 2000 to resorcinol, phloroglucinol, and formaldehyde was 0.005:1.

[0045] After the resorcinol, phloroglucinol, and polyethylene glycol were dissolved by stirring at 60℃, the formaldehyde solution was added and stirred uniformly to prepare a precursor solution with a density of 0.4 g / ml.

[0046] The precursor solution was poured into 15# white oil containing 0.5% by volume of Span 80, emulsified at low speed for 5 min with an emulsifier, and then poured into a three-necked flask. The suspension was prepared by stirring at 200 r / min in an oil bath at 60℃ for 14 h. The volume ratio of the precursor to white oil was 1:8.

[0047] The suspension was centrifuged and repeatedly washed with dichloromethane to obtain a non-agglomerated powder. The powder dried at room temperature was carbonized in a tube furnace at 800℃ for 4h. The carbon aerogel microspheres were obtained after carbonization.

[0048] Nickel acetylacetonate, triphenylphosphine and oleylamine with a molar ratio of 2:7:15 were added into a three-necked flask, and heated and stirred at 40℃ while purging with N2 for 30min, and then the temperature was increased to 100℃ to prepare a mixed stock solution A.

[0049] The mixed solution of carbon aerogel and oleylamine (mixture B) was added into the above stock solution, the mass ratio of carbon aerogel to oleylamine was 1:140, and the mass ratio of carbon aerogel to nickel acetylacetonate was 1:4, and then stirred for 10min, and then the temperature was increased to 300℃ at a rate of 5℃ / min and kept for 30min, and then a mixture of hexane and ethanol was added after cooling to room temperature to produce black precipitates.

[0050] The black precipitates obtained after centrifugation were washed with ethanol and pure water for several times and then vacuum dried to obtain Ni2P / CA-2.

[0051] Example 3

[0052] The raw materials for preparing the precursor in this example included resorcinol, phloroglucinol, formaldehyde and polyethylene glycol 2000, the molar ratio of resorcinol to phloroglucinol was 10:1, the molar ratio of formaldehyde to the total amount of resorcinol and phloroglucinol was 1:0.6, and the total mass ratio of polyethylene glycol 2000 to resorcinol, phloroglucinol and formaldehyde was 0.015:1.

[0053] The resorcinol, phloroglucinol and polyethylene glycol were dissolved by stirring at 60℃, and then formaldehyde solution was added and stirred uniformly to prepare a precursor solution with a density of 0.5g / ml.

[0054] The precursor solution was poured into 15# white oil containing 3% by volume of Span 80, emulsified at low speed for 5min with an emulsifier, and then poured into a three-necked flask, and reacted for 6h under stirring at 200r / min in an oil bath at 70℃ to prepare a suspension; the volume ratio of the precursor to white oil was 1:10.

[0055] The suspension was centrifuged and repeatedly washed with dichloromethane to obtain a non-agglomerated powder. The powder dried at room temperature was carbonized in a tube furnace at 750℃ for 6h. The carbon aerogel microspheres were obtained after carbonization.

[0056] Nickel acetylacetonate, triphenylphosphine and oleylamine with a molar ratio of 2:5:24 were added into a three-necked flask, and heated and stirred at 25℃ while purging with N2 for 30min, and then the temperature was increased to 80℃ to prepare a mixed stock solution A.

[0057] The mixture of carbon aerogel and oleylamine (mixture B) was added to the above solution, the mass ratio of carbon aerogel to oleylamine was 1:100, the mass ratio of carbon aerogel to nickel acetylacetonate was 1:30, and after stirring for 10 min, the temperature was raised to 200℃ at a rate of 5℃ / min and kept for 30 min. After cooling to room temperature, a mixture of hexane and ethanol was added to produce black precipitate.

[0058] After centrifugal separation, the obtained black precipitate was washed with ethanol and pure water several times and vacuum dried to obtain Ni2P / CA-3.

[0059] Example 4

[0060] The raw materials for preparing the precursor in this example were resorcinol, phloroglucinol, formaldehyde, and polyethylene glycol 2000. The molar ratio of resorcinol to phloroglucinol was 15:1, the molar ratio of formaldehyde to the total amount of resorcinol and phloroglucinol was 3:1, and the total mass ratio of polyethylene glycol 2000 to resorcinol, phloroglucinol, and formaldehyde was 0.05:1.

[0061] After stirring and dissolving resorcinol, phloroglucinol, and polyethylene glycol at 60℃, formaldehyde solution was added and stirred uniformly to prepare a precursor solution with a density of 0.5g / ml.

[0062] The precursor solution was poured into 15# white oil containing 1% volume fraction of Span 80, emulsified at low speed for 5 min with an emulsifier, and then poured into a three-necked flask. The suspension was prepared by stirring at 200r / min in an oil bath at 70℃ for 6h. The volume ratio of the precursor to white oil was 1:10.

[0063] The suspension was centrifugally separated and repeatedly washed with dichloromethane to obtain non-agglomerated powder. The powder dried at room temperature was carbonized in a tube furnace at 750℃ for 6h to obtain carbon aerogel microspheres.

[0064] Nickel acetylacetonate, triphenylphosphine, and oleylamine with a molar ratio of 1:1:4 were added to a three-necked flask. After heating and stirring at 25℃ and purging with N2 for 30 min, the temperature was raised to 80℃ to prepare a mixed solution A.

[0065] The mixture of carbon aerogel and oleylamine (mixture B) was added to the above solution, the mass ratio of carbon aerogel to oleylamine was 1:100, the mass ratio of carbon aerogel to nickel acetylacetonate was 1:10, and after stirring for 5 min, the temperature was raised to 200℃ at a rate of 5℃ / min and kept for 30 min. After cooling to room temperature, a mixture of hexane and ethanol was added to produce black precipitate.

[0066] After centrifugal separation, the obtained black precipitate was washed with ethanol and pure water several times and vacuum dried to obtain Ni2P / CA-4.

[0067] Example 5

[0068] The raw materials used for preparing the precursor in this example are resorcinol, phloroglucinol, formaldehyde, and polyethylene glycol 2000. The molar ratio of resorcinol to phloroglucinol is 8:1, the molar ratio of formaldehyde to the total amount of resorcinol and phloroglucinol is 2:1, and the total mass ratio of polyethylene glycol 2000 to resorcinol, phloroglucinol, and formaldehyde is 0.01:1.

[0069] After the resorcinol, phloroglucinol, and polyethylene glycol are dissolved by stirring at 60℃, formaldehyde solution is added and stirred until uniform to prepare a precursor solution with a density of 0.5 g / ml.

[0070] The precursor solution is poured into 15# white oil containing 1% by volume of Span 80, emulsified at low speed for 5 min using an emulsifier, and then poured into a three-necked flask. The suspension is prepared by stirring at 200 r / min in an oil bath at 60℃ for 13 h. The volume ratio of the precursor to white oil is 1:10.

[0071] The suspension is centrifuged and repeatedly washed with dichloromethane to obtain a powder without agglomeration. The powder dried at room temperature is carbonized in a tube furnace at 950℃ for 2 h to obtain carbon aerogel microspheres.

[0072] Nickel acetylacetonate, triphenylphosphine, and oleylamine in a molar ratio of 1:5:10 are added to a three-necked flask, heated and stirred at 40℃ while purging with N2 for 30 min, and then the temperature is increased to 80℃ to prepare a mixed stock solution A.

[0073] The mixed solution of carbon aerogel and oleylamine (mixture B) is added to the above stock solution. The mass ratio of carbon aerogel to oleylamine is 1:200, and the mass ratio of carbon aerogel to nickel acetylacetonate is 1:5. After stirring for 5 min, the temperature is increased to 400℃ at a rate of 5℃ / min and maintained for 30 min. After cooling to room temperature, a mixture of hexane and ethanol is added to produce black precipitates.

[0074] After centrifugation, the black precipitates are washed with ethanol and pure water several times and vacuum dried to obtain Ni2P / CA-5.

[0075] Example 6

[0076] The raw materials used for preparing the precursor in this example are resorcinol, phloroglucinol, formaldehyde, and polyethylene glycol 2000. The molar ratio of resorcinol to phloroglucinol is 7:1, the molar ratio of formaldehyde to the total amount of resorcinol and phloroglucinol is 2:1, and the total mass ratio of polyethylene glycol 2000 to resorcinol, phloroglucinol, and formaldehyde is 0.02:1.

[0077] The resorcinol, phloroglucinol, and polyethylene glycol were dissolved by stirring at 60°C, and then a formaldehyde solution was added and stirred to obtain a precursor solution having a density of 0.5 g / ml.

[0078] The precursor solution was poured into 15# white oil containing 1% by volume of Span 80, emulsified at low speed for 5 min using an emulsifier, and then poured into a three-necked flask. The suspension was prepared by stirring at 200 r / min in an oil bath at 60°C for 13 h. The volume ratio of the precursor to the white oil was 1:3.

[0079] The suspension was centrifuged and repeatedly washed with dichloromethane to obtain a powder without agglomeration. The powder dried at room temperature was carbonized in a tube furnace at 900°C for 3 h to obtain carbon aerogel microspheres.

[0080] Nickel acetylacetonate, triphenylphosphine, and oleylamine in a molar ratio of 1:5:15 were added to a three-necked flask, and heated and stirred at 40°C while purging with N2for 30 min. The temperature was then increased to 130°C to obtain a mixed stock solution A.

[0081] The mixed solution of the carbon aerogel and oleylamine (mixture B) was added to the above stock solution. The mass ratio of the carbon aerogel to oleylamine was 1:200, and the mass ratio of the carbon aerogel to nickel acetylacetonate was 1:5. The temperature was increased to 300°C at a rate of 5°C / min and maintained for 30 min. After cooling to room temperature, a mixture of hexane and ethanol was added to produce black precipitates.

[0082] The black precipitates were obtained by centrifugation, washed with ethanol and pure water, and vacuum dried to obtain Ni2P / CA-6.

[0083] Comparative Example 1

[0084] The raw materials for preparing the precursor in this example included resorcinol, phloroglucinol, formaldehyde, and polyethylene glycol 2000. The molar ratio of resorcinol to phloroglucinol was 8:1. The molar ratio of formaldehyde to the total amount of resorcinol and phloroglucinol was 1:0.5. The total mass ratio of polyethylene glycol 2000 to resorcinol, phloroglucinol, and formaldehyde was 0.015:1.

[0085] The resorcinol, phloroglucinol, and polyethylene glycol were dissolved by stirring at 60°C, and then a formaldehyde solution was added and stirred to obtain a precursor solution having a density of 0.5 g / ml.

[0086] The precursor solution was poured into 15# white oil containing 0.5% by volume of Span 80, emulsified at low speed for 5 min using an emulsifier, and then poured into a three-necked flask. The suspension was prepared by stirring at 200 r / min in an oil bath at 60°C for 14 h. The volume ratio of the precursor to the white oil was 1:8.

[0087] The suspension was centrifuged and repeatedly washed with dichloromethane to obtain a non-agglomerated powder. The powder dried at room temperature was carbonized in a tube furnace at 850℃ for 4h. The CA was obtained after carbonization.

[0088] Table 1. Preparation parameters of Ni2P / CA of each example

[0089]

[0090]

[0091] The above only describes the preferred embodiments of the application and is not intended to limit the application. Any modification, equivalent replacement and improvement made within the spirit and principle of the application shall be included in the protection scope of the application.

[0092] The Ni2P / CA-1 and Ni2P / CA-2 prepared in Example 1 and Example 2 were analyzed by transmission electron microscopy, and the results are shown in FIGS. 1 and 2. The Ni2P in the two samples is in the form of small particles of about 4-7nm coated on the surface of the carbon aerogel. The difference between Example 1 and Example 2 is that more carbon aerogel is added in Example 2. By comparing FIGS. 1 and 2, it can be seen that the content of Ni2P particles on the sample Ni2P / CA-1 is higher and the coating range is wider, so the content and coating range of Ni2P particles on the surface of the carbon aerogel can be controlled by adjusting the ratio of nickel acetylacetonate to carbon aerogel. Figure 1 、 Figure 2 Figure 1 、 Figure 2

[0093] The lightweight high electromagnetic shielding carbon aerogel materials prepared in Examples 1-6 and Comparative Example 1 were tested for the following properties:

[0094] Pore structure test: Specific surface area test was used for full pore test, and the results are shown in Table 2;

[0095] Electrical property test: The conductivity of the carbon aerogel was tested using a double electrical measurement four-probe tester, and the results are shown in Table 3;

[0096] Tap density test: The test was carried out according to GB / T 21354-2008, and the results are shown in Table 3;

[0097] Electromagnetic shielding performance test: According to ASTM ES7-83 and ASTM D4935-99, the electromagnetic shielding performance of the biomass-based carbon aerogel in the frequency range of 8.2-12.4GHz (X-band) was measured at room temperature using a vector network analyzer equipped with a coaxial test unit (APC-7 connector). The carbon aerogel was made into a round piece with a diameter of about 13mm and a thickness of 2mm for testing, and the results are shown in Table 3;

[0098] ​​Salt fog resistance test: tested according to GB6458-86, the results are shown in Table 3;

[0099] Table 2 Pore volume and specific surface area of lightweight high electromagnetic shielding carbon aerogels of each example and control

[0100]

[0101] As can be seen from Table 2, the prepared carbon aerogels have high specific surface area and large pore volume, and the rich three-dimensional nanopore structure can effectively alleviate the impedance mismatch of electromagnetic wave propagation at the interface between air and material, and reduce electromagnetic wave reflection. The carbon aerogels prepared by control example 1 without Ni2P coating have the highest specific surface area and pore volume, and the specific surface area and total pore volume decrease after Ni2P coating, indicating that Ni2P also enters the mesopores of the carbon aerogels, effectively increasing the dielectric loss of electromagnetic waves.

[0102] Table 3 Performance parameters of lightweight high electromagnetic shielding carbon aerogels of each example and control

[0103]

[0104]

[0105] As can be seen from Table 3, the prepared lightweight high electromagnetic shielding carbon aerogels have high electrical conductivity, low tap density and good electromagnetic shielding effectiveness, and have good corrosion resistance through salt fog resistance test. Although the tap density of the carbon aerogel material coated with Ni2P increases slightly, its shielding performance is greatly improved, for example, the electromagnetic shielding effectiveness of 8.2-12.4 GHz of example 2 is increased by 40.4% compared with the control group.

Claims

1. A method for preparing a carbon aerogel material for electromagnetic shielding, characterized in that... The following process is adopted: S1: Preparation of carbon aerogel microspheres (1) Add resorcinol, phloroglucinol, and polyethylene glycol to a set amount of pure water according to a set ratio, heat and stir until completely dissolved, then stop heating and continue stirring and cool to room temperature, then add formaldehyde aqueous solution and stir evenly to prepare a solution precursor. The heating temperature is 50-60 ℃; the molar ratio of resorcinol to phloroglucinol is 1:5-15, the amount of polyethylene glycol is 0.5%-5% of the total mass of resorcinol, phloroglucinol and formaldehyde, and the molar ratio of the total amount of resorcinol and phloroglucinol to formaldehyde is 1:1.5-3; the density of the solution precursor should be controlled in the range of 0.4-0.8 g / mL; (2) The prepared solution precursor is poured into white oil containing surfactant and emulsified using an emulsifier. The emulsified suspension is continuously stirred while reacting in a water bath to obtain a slurry containing gel microspheres. The surfactant is 0.5%-3% of the volume of white oil, and the volume ratio of precursor to white oil is 1:6-10. The temperature of the water bath process is 50-70 ℃, the reaction time is 6-15 h, and the stirring speed is 100-500 r / min. (3) After solid-liquid separation and washing, the prepared slurry is dried at room temperature to obtain aerogel microspheres; (4) Carbon aerogel microspheres were obtained by carbonizing the dried aerogel microspheres in a tube furnace; the carbonization temperature was 750-1050 ℃ and the carbonization time was 2-6 h. S2: Preparation of Mixed Stock Solution A (5) Add nickel acetylacetone, triphenylphosphine, and oleylamine to a reaction vessel in a set ratio, heat to a set temperature T1, stir and purge with N2 for a period of time, and then continue to raise the temperature to T2 to obtain mixed stock solution A; the molar ratio of nickel acetylacetone to triphenylphosphine is 1:1-5, and the molar ratio of nickel acetylacetone to oleylamine is 1:4-12; the T1 is 25 ℃-65 ℃, and the T2 is 80 ℃-130 ℃; S3: Preparation of carbon aerogel materials for electromagnetic shielding (6) The carbon aerogel microspheres obtained in step (4) are added to a set amount of oleylamine to obtain mixture B; the mass ratio of carbon aerogel microspheres to oleylamine in mixture B is 1:100-400; Mixture B is injected into the original mixture A in step (5). The mass ratio of carbon aerogel microspheres to nickel acetylacetone is controlled at 1:8-25. After stirring for a period of time, the temperature is raised and stirring is continued for a period of time. After cooling to room temperature, a mixture of hexane and ethanol is added to precipitate the black product. The product is purified by centrifugation-washing-precipitation-centrifugation cycle. Then, it is dried under vacuum to obtain the carbon aerogel material product Ni2P / CA for electromagnetic shielding. The volume ratio of hexane to ethanol in the mixture of hexane and ethanol is 1:0.8-1.

3. The mass ratio of nickel acetylacetone to carbon aerogel microspheres is 1:5-10. The stirring time before heating is 5-25 min, and the temperature is controlled in the range of 200-400℃ after heating.

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