Preparation method of carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance

Abstract

The application discloses a preparation method of carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance and belongs to the electromagnetic shielding material field.The raw materials of the carbon nanotube / silver-doped biomass carbon material include, in terms of weight fractions, 18-22 parts of banana peel, 0.05-0.2 parts of silver nitrate, 0.08-0.12 parts of carbon nanotubes and 1-1.5 parts of pore-forming agents.The application effectively improves the electromagnetic shielding performance through scientific material selection and a process flow of raw material treatment, is easy to form and process, meets environmental protection requirements, is beneficial to realizing the national development of circular economy, and realizes the strategic deployment of efficient utilization of resources and reduction, reuse and resource utilization of waste.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electromagnetic shielding materials, and particularly relates to a preparation method of carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance. BACKGROUND

[0002] With the advent of the information age and the continuous development of science and technology, the development and popularization of electronic product equipment such as smart phones, electric vehicles and smart home appliances is a double-edged sword, which brings great convenience to people's life on the one hand, and on the other hand, it also brings electromagnetic radiation pollution, affecting people's life.

[0003] At present, the carbon-based shielding composite material mainly adds graphene and carbon nanotube composite fillers in the matrix, and realizes the electromagnetic shielding performance by virtue of its excellent electrical conductivity and electromagnetic shielding efficiency, and good synergistic effect. However, such materials have high cost and large mass, causing processing difficulty. This makes them difficult to be applied on a large scale in the field requiring light materials, and in addition, some modification processes use strong oxidants, which will cause environmental pollution and do not meet the green and environmental protection concept. SUMMARY

[0004] The present application provides a preparation method of carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance, which effectively improves the electromagnetic shielding efficiency, is easy to form and process, meets the environmental protection requirements, is beneficial to realize the national development of circular economy, realizes the strategic deployment of efficient utilization of resources and reduction, reuse and resource utilization of waste.

[0005] The preparation method of carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance comprises the following steps:

[0006] Step 1: pretreatment

[0007] The banana peel is cut into small pieces and added into an acetone solution, and ultrasonic treatment is performed for 20-40 min; the treated banana peel is immersed in deionized water and ultrasonic treatment is continued for 10-30 min.

[0008] Step 2: hydrothermal pre-carbonization

[0009] The pretreated banana peel is placed in a polytetrafluoroethylene-lined hydrothermal reactor, a pore-forming agent aqueous solution is added, and after mixing uniformly, hydrothermal pre-carbonization treatment is performed at 170-190 DEG C for 11-13 h; after the reaction is completed, the solution is removed, and a gel-like banana peel is obtained, which is then placed in an oven and dried at a temperature of 50-70 DEG C for 1-3 h.

[0010] Step 3: freeze-drying

[0011] The sample obtained in step 2 is added with silver nitrate solution, and ultrasonic treatment is performed for 20-40 min. After being taken out, the sample is first subjected to freezing treatment at-75℃ to-70℃ for 7-9 h, and then is subjected to vacuum drying treatment in a drying rack of a freeze dryer to obtain a biomass aerogel.

[0012] Step 4: High-temperature carbonization

[0013] The biomass aerogel obtained in step 3 is placed in a tube furnace, and high-temperature carbonization treatment is performed in a nitrogen atmosphere to obtain a silver-doped biomass carbon aerogel.

[0014] Step 5: Ultrasonic mixing

[0015] 0.08-0.12 parts of carbon nanotubes are weighed and added into 20-40 mL of acetone solution to obtain a carbon nanotube-acetone solution. The silver-doped biomass carbon aerogel obtained in step 4 is ground and added into the carbon nanotube-acetone solution, and ultrasonic mixing treatment is performed for 60-100 min.

[0016] Step 6: Vacuum drying

[0017] The sample obtained in step 5 is placed in a drying rack of a freeze dryer for vacuum drying treatment to obtain a carbon nanotube / silver-doped biomass carbon material.

[0018] In step 1, the banana peel is cut into pieces, and the size of each piece is controlled to be 1 cm (length) x 1 cm (width) x 0.3 cm (thickness).

[0019] In step 2, the pore-forming agent aqueous solution is prepared by dissolving 1-1.5 parts of the pore-forming agent in 20-30 parts of water.

[0020] In step 3, the silver nitrate solution is prepared by dissolving 0.05-0.2 parts of silver nitrate solid particles in 8-10 mL of water.

[0021] In step 3, the parameters of the vacuum drying treatment are set as follows: the chamber vacuum is controlled to be 2-5 Pa, the cold trap temperature is-75℃ to-70℃, the sample temperature is-60℃ to-50℃, and the vacuum drying time is 14-16 h.

[0022] In step 4, the parameters of the high-temperature carbonization treatment are set as follows: the temperature is increased at a rate of 2-3℃ / min from 40-60℃, the temperature is maintained at 440-450℃ for 100-140 min, and then the temperature is increased at a rate of 2-3℃ / min to 680-720℃, and the temperature is maintained for 120-180 min.

[0023] In step 6, the parameters of the vacuum drying treatment are set as follows: the control chamber vacuum is 2-5 Pa, the cold trap temperature is set to -75 to -70 DEG C, the sample temperature is -60 to -50 DEG C, and the vacuum drying time is 14-16 h.

[0024] In the preparation process, the raw materials are composed of the following mass fractions:

[0025] The banana peel is 18-22 parts, silver nitrate is 0.05-0.2 parts, carbon nanotubes are 0.08-0.12 parts, and the pore-forming agent is 1-1.5 parts.

[0026] The pore-forming agent is one of potassium hydroxide or sodium hydroxide.

[0027] Firstly, the banana peel, as a biomass material, can be converted into activated carbon with a porous structure by hydrothermal carbonization, and has a high specific surface area and rich pore structure. Next, the incorporation of metal elements can significantly improve the electrical conductivity and electromagnetic properties of the material. Metals are good conductors and can effectively absorb and reflect electromagnetic waves. By incorporating metals during the carbonization of banana peel, a metal-carbon composite material can be formed, which has potential application value in the field of electromagnetic shielding. Further, coating carbon nanotubes (CNTs) on the surface of the metal-carbon composite material can further enhance its electromagnetic shielding performance. Carbon nanotubes are widely used in electromagnetic shielding and conductive materials due to their unique structure and excellent electrical and mechanical properties. The high aspect ratio and electrical conductivity of carbon nanotubes enable them to effectively absorb and scatter electromagnetic waves, thereby enhancing the electromagnetic shielding effect of the material.

[0028] The carbon nanotube / silver-doped biomass carbon material of the present application can effectively suppress electromagnetic interference, has the characteristics of low density and high porosity, can significantly reduce the structure weight, and maintains good mechanical properties and stability. At the same time, it has the advantage of environmental protection, among which the natural biomass material is used as the precursor, not only the cost is low, the source is rich, but also the environmental pollution in the preparation process is small, which meets the requirements of green development; in addition, due to its multi-level and multi-layer pore structure, this complex pore structure helps to prolong the propagation path of electromagnetic waves, and effectively converts electromagnetic wave energy into heat energy through multiple reflection, interface polarization, conduction loss and dipole polarization mechanisms, thereby realizing high-efficiency shielding effect, which can be used in the fields of electronics, automobiles, aerospace and communication, effectively suppressing electromagnetic interference and ensuring the stability and safety of electronic equipment.

[0029] Compared with the prior art, the beneficial effects of the present application are as follows:

[0030] The application provides a preparation method of carbon nanotube / silver-doped biomass carbon material with good electromagnetic shielding performance, and the material is used as a filling body of a shielding material, so that the synthesized product is light in quality and raw materials are widely available; in addition, the material has a multistage and multilayer pore structure, which helps to prolong the propagation path of electromagnetic waves and realizes high-efficiency shielding effect through multiple reflection, interface polarization and other mechanisms BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The electromagnetic shielding efficiency-frequency change graph of the carbon nanotube / silver-doped biomass carbon material prepared in Example 1 is shown in the figure, and it can be seen that in the Ku band (12-18 GHz) frequency range, the electromagnetic shielding efficiency of the composite material is-28.51 dB to-33.99 dB, which has good electromagnetic shielding effect.

[0032] Figure 2 The electromagnetic shielding efficiency-frequency change graph of the carbon nanotube / silver-doped biomass carbon material prepared in Example 2 is shown in the figure, and it can be seen that in the Ku band (12-18 GHz) frequency range, the electromagnetic shielding efficiency of the composite material is-21.37 dB to-25.87 dB, which has good electromagnetic shielding effect.

[0033] Figure 3 The electromagnetic shielding efficiency-frequency change graph of the carbon nanotube / silver-doped biomass carbon material prepared in Example 3 is shown in the figure, and it can be seen that in the Ku band (12-18 GHz) frequency range, the electromagnetic shielding efficiency of the composite material is-38.14 dB to-42.35 dB, which can shield more than 99% of electromagnetic waves, and has excellent electromagnetic shielding effect.

[0034] Figure 4 The electromagnetic shielding efficiency-frequency change graph of the carbon nanotube / silver-doped biomass carbon material prepared in Example 4 is shown in the figure, and it can be seen that in the Ku band (12-18 GHz) frequency range, the electromagnetic shielding efficiency of the composite material is-22.59 dB to-28.39 dB, and the electromagnetic shielding efficiency is more than 20 dB, which can shield 99% of electromagnetic waves, and has good electromagnetic shielding effect.

[0035] Figure 5 The microscopic characterization graph of the carbon nanotube / silver-doped biomass carbon material prepared in Example 4 under a scanning electron microscope is shown in the figure. Figure 5 It can be seen that the prepared material has obvious pore structure, low density and light weight effect, and the pore structure helps to prolong the propagation path of electromagnetic waves, and effectively converts electromagnetic wave energy into heat energy through multiple reflection mechanism, so as to realize high-efficiency shielding effect. DETAILED DESCRIPTION

[0036] The advantages and features of the present application will be more clearly understood from the following detailed description of the preferred embodiments of the present application, so as to make the scope of protection of the present application more clearly defined.

[0037] Example 1

[0038] The raw materials of the carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance in this embodiment include, by weight fraction: banana peel 20 parts, silver nitrate particles 0.064 parts, carbon nanotubes 0.1 parts, and pore-forming agent 1 part.

[0039] The banana peel is cut into pieces, each piece being 1 cm (long) x 1 cm (wide) x 0.3 cm (thick) in size.

[0040] The pore-forming agent is potassium hydroxide.

[0041] The preparation process of the carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance in this embodiment is as follows:

[0042] (1) Pretreatment

[0043] 20 parts of banana peel are weighed and cut into small pieces, each piece being 1 cm (long) x 1 cm (wide) x 0.3 cm (thick) in size. The cut banana peel is placed in a beaker, and a banana peel-acetone mixed solution of 70 ml is configured. The treated banana peel is immersed in deionized water, and a banana peel-deionized water mixed solution of 70 ml is configured. The treated banana peel is subjected to ultrasonic treatment for 20 min.

[0044] (2) Hydrothermal pre-carbonization treatment

[0045] The pretreated banana peel in step (1) is placed in a polytetrafluoroethylene-lined hydrothermal reactor. 1 part of potassium hydroxide is dissolved in 20 parts of water to prepare a potassium hydroxide aqueous solution. The pore-forming agent aqueous solution is mixed with the banana peel, and the mixture is subjected to hydrothermal pre-carbonization treatment at a temperature of 180°C for 12 h. Then, the solution is poured out to obtain a gel-like banana peel treated by the potassium hydroxide aqueous solution, which is placed in an oven and dried at 60°C for 2 h.

[0046] (3) Freeze-drying treatment

[0047] a. 0.064 parts of silver nitrate particles are weighed and dissolved in 10 ml of water to prepare a silver nitrate solution. After stirring for 2 min, the sample prepared in step (2) is added and subjected to ultrasonic treatment for 30 min.

[0048] b. The sample obtained in a is subjected to freezing treatment at a temperature of -74.5°C for 8 h.

[0049] c. The freeze-treated sample was placed in a freeze-drying machine drying rack for vacuum drying treatment, the chamber vacuum was controlled at 2 Pa, the cold trap temperature was -74℃, the sample temperature was -56℃, and the vacuum drying time was 15 h, to obtain the biomass aerogel.

[0050] (4) High-temperature carbonization treatment

[0051] The biomass aerogel obtained in step (3) was placed in a tube furnace for high-temperature carbonization treatment in a nitrogen atmosphere, the carbonization temperature was: 50℃, the temperature was raised at a rate of 2℃ / min, and the temperature was kept at 450℃ for 120 min, then the temperature was continuously raised at a rate of 2℃ / min to 700℃, and kept for 150 min; to obtain the silver-doped biomass carbon aerogel.

[0052] (5) Ultrasonic mixing treatment

[0053] a. 0.1 parts of carbon nanotubes were weighed and added to 30 ml of acetone solution to obtain a carbon nanotube-acetone solution.

[0054] b. The silver-doped biomass carbon aerogel obtained in (4) was ground and broken and placed in the carbon nanotube-acetone solution obtained in a for ultrasonic mixing treatment for 80 min.

[0055] (6) Vacuum drying treatment

[0056] The sample treated in step (5) was placed in a freeze-drying machine drying rack for vacuum drying treatment for 15 h, wherein the chamber vacuum was set to 2 Pa, the cold trap temperature was set to -74℃, and the sample temperature was -57.4℃, and in the process of low-temperature vacuum drying, mechanically cross-linked carbon nanotubes were produced, and the silver-doped biomass carbon was fixed therein, to obtain the carbon nanotube / silver-doped biomass carbon material.

[0057] The carbon nanotube / silver-doped biomass carbon material prepared above was tested for electromagnetic shielding performance by a vector network analyzer by a coaxial method, and the electromagnetic shielding performance in the Ku band (12-18 GHz) was -28.51 dB to -33.99 dB.

[0058] Example 2:

[0059] The raw materials of the carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance in this example included, by weight fraction: banana peel 20 parts, silver nitrate particles 0.064 parts, carbon nanotubes 0.1 parts, and pore-forming agent 1 part.

[0060] The banana peel was cut into pieces, each piece being 1 cm (long) x 1 cm (wide) x 0.3 cm (thick) in size.

[0061] The pore-forming agent was sodium hydroxide.

[0062] The preparation process of the carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance in this embodiment is as follows:

[0063] (1) Pretreatment

[0064] 20 parts of banana peels were weighed, cut into small pieces with a size of 1 cm (length) x 1 cm (width) x 0.3 cm (thickness), and placed in a beaker. A banana peel-acetone mixed solution 70 ml was configured, and ultrasonic treatment was performed for 30 min. The treated banana peels were immersed in deionized water again, a banana peel-deionized water mixed solution 70 ml was configured, and ultrasonic treatment was performed for 20 min.

[0065] (2) Hydrothermal pre-carbonization treatment

[0066] The pretreated banana peels in step (1) were placed in a polytetrafluoroethylene-lined hydrothermal reactor, and 1 part of sodium hydroxide was dissolved in 20 parts of water to prepare a sodium hydroxide aqueous solution. The pore-forming agent aqueous solution was mixed with the banana peels, and hydrothermal pre-carbonization treatment was performed at a temperature of 180℃ for 12 h. Then, the solution was poured out to obtain a gel-like banana peel after sodium hydroxide aqueous solution hydrothermal treatment, which was placed in an oven and dried at 60℃ for 2 h.

[0067] (3) Freeze-drying treatment

[0068] a. 0.064 parts of silver nitrate particles were weighed and dissolved in 10 ml of water to prepare a silver nitrate solution. After stirring for 2 min, the sample prepared in step (2) was added and ultrasonic treatment was performed for 30 min.

[0069] b. The sample obtained in a was frozen at a temperature of -74.5℃ for 8 h.

[0070] c. The frozen sample was placed in a freeze-drying machine drying rack for vacuum drying treatment. The chamber vacuum was controlled at 2 Pa, the cold trap temperature was -74℃, the sample temperature was -56℃, and the vacuum drying time was 15 h. Biomass aerogel was obtained.

[0071] (4) High-temperature carbonization treatment

[0072] The biomass aerogel obtained in step (3) was placed in a tube furnace for high-temperature carbonization treatment in a nitrogen atmosphere. The carbonization temperature was: 50℃, the temperature was raised at a rate of 2℃ / min, and the temperature was maintained at 450℃ for 120 min. Then, the temperature was raised to 700℃ at a rate of 2℃ / min, and the temperature was maintained for 150 min. Silver-doped biomass carbon aerogel was obtained.

[0073] (5) Ultrasonic mixing treatment

[0074] a. Take 0.1 parts of carbon nanotubes and add them to 30 ml of acetone solution to obtain a carbon nanotube-acetone solution.

[0075] b. Grind the silver-doped biomass carbon aerogel obtained in (4) and place it in the carbon nanotube-acetone solution obtained in a for ultrasonic mixing treatment for 80 min.

[0076] (6) Vacuum drying treatment

[0077] Place the sample obtained by the treatment in step (5) in a freeze dryer drying rack for vacuum drying treatment for 15 h, wherein the chamber vacuum is set to 2 Pa, the cold trap temperature is set to -74°C, and the sample temperature is -57.4°C. In the process of low-temperature vacuum drying, mechanically cross-linked carbon nanotubes are produced, and the silver-doped biomass carbon is fixed therein, obtaining a carbon nanotube / silver-doped biomass carbon material.

[0078] The carbon nanotube / silver-doped biomass carbon material prepared above has an electromagnetic shielding performance of -21.37 dB to -25.87 dB in the Ku band (12-18 GHz) as measured by a vector network analyzer using the coaxial method.

[0079] Example 3:

[0080] The raw materials for the carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance in this example include, by weight fraction: banana peel 20 parts, silver nitrate particles 0.128 parts, carbon nanotubes 0.1 parts, and pore-forming agent 1 part.

[0081] The banana peel is cut into pieces, each with a size of 1 cm (length) x 1 cm (width) x 0.3 cm (thickness).

[0082] The pore-forming agent is potassium hydroxide.

[0083] The preparation process of the carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance in this example is as follows:

[0084] (1) Pretreatment

[0085] Take 20 parts of banana peel and cut it into small pieces, each with a size of 1 cm (length) x 1 cm (width) x 0.3 cm (thickness). Place the cut banana peel in a beaker and prepare a banana peel-acetone mixed solution of 70 ml, and ultrasonically treat for 30 min. Then immerse the treated banana peel in deionized water and prepare a banana peel-deionized water mixed solution of 70 ml, and ultrasonically treat for another 20 min.

[0086] (2) Hydrothermal pre-carbonization treatment

[0087] The pretreated banana peel in step (1) was placed in a polytetrafluoroethylene-lined hydrothermal reactor, and 1 part of potassium hydroxide was dissolved in 20 parts of water to prepare a potassium hydroxide aqueous solution. The pore-forming agent aqueous solution was mixed with the banana peel, and the mixture was subjected to hydrothermal pre-carbonization treatment at a temperature of 180°C for 12 hours. Then, the solution was removed to obtain a gel-like banana peel after hydrothermal treatment with potassium hydroxide aqueous solution, which was placed in an oven and dried at 60°C for 2 hours.

[0088] (3) Freeze-drying treatment

[0089] a. 0.128 parts of silver nitrate particles were weighed and dissolved in 10 ml of water to prepare a silver nitrate solution. After stirring for 2 minutes, the prepared sample in step (2) was added and subjected to ultrasonic treatment for 30 minutes.

[0090] b. The sample obtained in a was frozen at a temperature of -74.5°C for 8 hours.

[0091] c. The frozen sample was placed in a freeze-drying machine drying rack for vacuum drying treatment. The chamber vacuum was controlled at 2 Pa, the cold trap temperature was -74°C, the sample temperature was -56°C, and the vacuum drying time was 15 hours. A biomass aerogel was obtained.

[0092] (4) High-temperature carbonization treatment

[0093] The biomass aerogel obtained in step (3) was placed in a tube furnace for high-temperature carbonization treatment in a nitrogen atmosphere. The carbonization temperature was: starting at 50°C, increasing at a rate of 2°C / min, holding at 450°C for 120 minutes, then continuing to increase at a rate of 2°C / min to 700°C, holding for 150 minutes. A silver-doped biomass carbon aerogel was obtained.

[0094] (5) Ultrasonic mixing treatment

[0095] a. 0.1 parts of carbon nanotubes were weighed and added to 30 ml of acetone solution to obtain a carbon nanotube-acetone solution.

[0096] b. The silver-doped biomass carbon aerogel obtained in (4) was ground and placed in the carbon nanotube-acetone solution obtained in a for ultrasonic mixing treatment for 80 minutes.

[0097] (6) Vacuum drying treatment

[0098] The sample obtained in step (5) was placed in a freeze-drying machine drying rack for vacuum drying treatment for 15 hours. The chamber vacuum was set to 2 Pa, the cold trap temperature was set to -74°C, and the sample temperature was -57.4°C. During the low-temperature vacuum drying process, mechanically cross-linked carbon nanotubes were produced, and silver-doped biomass carbon was fixed therein, obtaining a carbon nanotube / silver-doped biomass carbon material.

[0099] The carbon nanotube / silver-doped biomass carbon material prepared above was tested for electromagnetic shielding performance by a coaxial method using a vector network analyzer, and the electromagnetic shielding performance in the Ku band (12-18 GHz) was -38.14 dB to -42.35 dB.

[0100] Example 4:

[0101] The raw materials for the carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance in this example included, by weight fraction, banana peel 20 parts, silver nitrate particles 0.128 parts, carbon nanotubes 0.1 parts, and pore-forming agent 1 part.

[0102] The banana peel was cut into pieces, each with a size of 1 cm (length) x 1 cm (width) x 0.3 cm (thickness).

[0103] The pore-forming agent was sodium hydroxide.

[0104] The preparation process for the carbon nanotube / silver-doped biomass carbon material with electromagnetic shielding performance in this example was as follows:

[0105] (1) Pretreatment

[0106] 20 parts of banana peel were weighed out, cut into small pieces each with a size of 1 cm (length) x 1 cm (width) x 0.3 cm (thickness), and placed in a beaker. A banana peel-acetone mixed solution 70 ml was prepared and ultrasonically treated for 30 min. The treated banana peel was then immersed in deionized water, a banana peel-deionized water mixed solution 70 ml was prepared, and ultrasonic treatment was performed again for 20 min.

[0107] (2) Hydrothermal pre-carbonization treatment

[0108] The pretreated banana peel from step (1) was placed in a polytetrafluoroethylene-lined hydrothermal reactor, and 1 part of sodium hydroxide was dissolved in 20 parts of water to prepare a sodium hydroxide aqueous solution. The pore-forming agent aqueous solution was mixed with the banana peel, and hydrothermal pre-carbonization treatment was performed at a temperature of 180°C for 12 h. The solution was then poured off to obtain gelatinous banana peel after sodium hydroxide aqueous hydrothermal treatment, which was placed in an oven and dried at 60°C for 2 h.

[0109] (3) Freeze-drying treatment

[0110] a. 0.128 parts of silver nitrate particles were weighed out, dissolved in 10 ml of water to prepare a silver nitrate solution, and stirred for 2 min before being added to the sample prepared in step (2) for ultrasonic treatment for 30 min.

[0111] b. The sample obtained in a was frozen at a temperature of -74.5°C for 8 h.

[0112] c. The freeze-treated sample was placed in a freeze-drying machine drying rack for vacuum drying treatment, the chamber vacuum was controlled at 2 Pa, the cold trap temperature was -74°C, the sample temperature was -56°C, and the vacuum drying time was 15 h, to obtain a biomass aerogel.

[0113] (4) High-temperature carbonization treatment

[0114] The biomass aerogel obtained in step (3) was placed in a tube furnace for high-temperature carbonization treatment in a nitrogen atmosphere, the carbonization temperature was: 50°C, the temperature was raised at a rate of 2°C / min, and the temperature was kept at 450°C for 120 min, then the temperature was continued to be raised at a rate of 2°C / min to 700°C, and kept for 150 min; to obtain a silver-doped biomass carbon aerogel.

[0115] (5) Ultrasonic mixing treatment

[0116] a. 0.1 parts of carbon nanotubes were weighed and added to 30 ml of acetone solution to obtain a carbon nanotube-acetone solution.

[0117] b. The silver-doped biomass carbon aerogel obtained in (4) was ground and broken and placed in the carbon nanotube-acetone solution obtained in a for ultrasonic mixing treatment for 80 min.

[0118] (6) Vacuum drying treatment

[0119] The sample treated in step (5) was placed in a freeze-drying machine drying rack for vacuum drying treatment for 15 h, wherein the chamber vacuum was set to 2 Pa, the cold trap temperature was set to -74°C, and the sample temperature was -57.4°C. During the low-temperature vacuum drying process, mechanically cross-linked carbon nanotubes were produced, and silver-doped biomass carbon was fixed therein, to obtain a carbon nanotube / silver-doped biomass carbon material.

[0120] The carbon nanotube / silver-doped biomass carbon material prepared above was tested for electromagnetic shielding performance by a vector network analyzer by a coaxial method, and the electromagnetic shielding performance in the Ku band (12-18 GHz) was -22.59 dB to -28.39 dB.

[0121] A vector network analyzer was used to test and analyze the electromagnetic shielding performance of the materials prepared in each example in the Ku band (12-18 GHz).

[0122] Figure 1 The electromagnetic shielding performance of the carbon nanotube / silver-doped biomass carbon material prepared in Example 1 varied with frequency, and as shown in the graph, in the Ku band (12-18 GHz) frequency range, the electromagnetic shielding performance of the composite material was -28.51 dB to -33.99 dB, which had good electromagnetic shielding effect.

[0123] Figure 2 The graph shows the electromagnetic shielding effectiveness of the carbon nanotube / silver-doped biomass carbon material prepared in Example 2 as a function of frequency. As can be seen from the graph, the electromagnetic shielding effectiveness of the composite material is -21.37dB to -25.87dB in the Ku band (12-18GHz) frequency range, which has a good electromagnetic shielding effect.

[0124] Figure 3 The graph shows the electromagnetic shielding effectiveness of the carbon nanotube / silver-doped biomass carbon material prepared in Example 3 as a function of frequency. As can be seen from the graph, in the Ku band (12-18GHz) frequency range, the electromagnetic shielding effectiveness of the composite material is -38.14dB to -42.35dB, which can shield more than 99% of electromagnetic waves, and has a relatively excellent electromagnetic shielding effect.

[0125] Figure 4 The graph shows the electromagnetic shielding effectiveness of the carbon nanotube / silver-doped biomass carbon material prepared in Example 4 as a function of frequency. As can be seen from the graph, in the Ku band (12-18GHz) frequency range, the electromagnetic shielding effectiveness of the composite material is -22.59dB to -28.39dB, which is above 20dB. It can shield 99% of electromagnetic waves, and the electromagnetic shielding effect is relatively good.

[0126] Figure 5 The image shows the scanning electron microscope (SEM) micrograph of the carbon nanotube / silver-doped biomass carbon material prepared in Example 4. Figure 5 It can be seen that the prepared material has a distinct porous structure, resulting in low density and lightweight properties. This porous structure helps to extend the propagation path of electromagnetic waves and effectively convert electromagnetic wave energy into heat energy through mechanisms such as multiple reflections, thereby achieving a highly efficient shielding effect.

[0127] To compare the effects of the present invention, performance tests were conducted on the above-mentioned sets of embodiments, and the specific comparison data are shown in Table 1 below:

[0128] Table 1

[0129]

[0130] The performance curves of example 1 and example 3 are observed, wherein the shielding performance of example 1 in the Ku band (12-18GHz) is -28.51dB to -33.99dB, and the shielding performance of example 3 in the Ku band (12-18GHz) is -38.14dB to -42.35dB, and it can be seen that the shielding performance is significantly improved with the increase of the amount of silver nitrate added in the case of potassium hydroxide as the pore-forming agent. The performance curves of example 2 and example 4 are observed, wherein the shielding performance of example 2 in the Ku band (12-18GHz) is -21.37dB to -25.87dB, and the shielding performance of example 4 in the Ku band (12-18GHz) is -22.59dB to -28.39dB, and it can be seen that the shielding performance is significantly improved with the increase of the amount of silver nitrate added in the case of sodium hydroxide as the pore-forming agent. At the same time, it can also be seen from table 1 and the performance diagram that in the process of the experiment, under the condition that the amount of silver nitrate added is the same, the shielding performance of the sample obtained when the pore-forming agent is potassium hydroxide is better than that of the sample obtained when the pore-forming agent is sodium hydroxide

[0131] It can be seen from the above that the carbon nanotube / silver-doped biomass carbon material prepared by the method has good performance, meets the environmental protection requirements, realizes efficient use of resources, reduction of waste and lightweight design of products, and provides a new technical scheme for the selection of electromagnetic shielding material filler preparation.

Claims

1. A method for preparing carbon nanotube / silver-doped biomass carbon materials with electromagnetic shielding properties, characterized in that... Includes the following steps: Step 1: Preprocessing Cut 18-22 parts by weight of banana peel into small pieces, add them to acetone solution, and sonicate for 20-40 minutes; then immerse the treated banana peel in deionized water and continue sonicating for 10-30 minutes. Step 2: Hydrothermal precarbonization The pretreated banana peels were placed in a hydrothermal reactor lined with polytetrafluoroethylene, and an aqueous solution of a pore-forming agent was added. After mixing evenly, the mixture was subjected to hydrothermal pre-carbonization treatment. After the reaction was completed, the solution was removed to obtain a gel-like banana peel, which was then placed in an oven to dry. Step 3: Freeze-drying Add silver nitrate solution to the sample obtained in step 2, sonicate for 20-40 min, remove and freeze at -75℃ to -70℃ for 7-9 h, then place it on the drying rack of a freeze dryer for vacuum drying to obtain biomass aerogel. Step 4: High-temperature carbonization The biomass aerogel obtained in step 3 is placed in a tube furnace and subjected to high-temperature carbonization in a nitrogen atmosphere to obtain silver-doped biomass carbon aerogel. Step 5: Ultrasonic mixing Weigh 0.08-0.12 parts by mass of carbon nanotubes and add them to acetone to obtain a carbon nanotube-acetone solution; grind and crush the silver-doped biomass carbon aerogel obtained in step 4 and add it to the carbon nanotube-acetone solution, and ultrasonically mix for 60-100 min. Step 6: Vacuum drying The sample obtained in step 5 was placed in the drying rack of a freeze dryer for vacuum drying to obtain carbon nanotube / silver-doped biomass carbon material.

2. The preparation method according to claim 1, characterized in that: In step 2, the pore-forming agent aqueous solution is prepared by dissolving 1-1.5 parts by weight of the pore-forming agent in 20-30 parts by weight of water.

3. The preparation method according to claim 2, characterized in that: The pore-forming agent is either potassium hydroxide or sodium hydroxide.

4. The preparation method according to claim 1, characterized in that: In step 2, the hydrothermal precarbonization treatment is carried out at a temperature of 170-190℃ for 11-13 hours.

5. The preparation method according to claim 1, characterized in that: In step 3, the silver nitrate solution is prepared by dissolving 0.05-0.2 parts by mass of silver nitrate solid particles in 8-10 mL of water.

6. The preparation method according to claim 1, characterized in that: In step 3, the parameters for the vacuum drying process are set as follows: the chamber vacuum is controlled at 2-5 Pa, the cold trap temperature is -75℃ to -70℃, the sample temperature is -60℃ to -50℃, and the vacuum drying time is 14-16 h.

7. The preparation method according to claim 1, characterized in that: In step 4, the parameters for the high-temperature carbonization treatment are set as follows: start heating at 40-60℃, heating rate at 2-3℃ / min, hold at 440-450℃ for 100-140min, and then continue heating at 2-3℃ / min to 680-720℃ and hold for 120-180min.

8. The preparation method according to claim 1, characterized in that: In step 6, the parameters for the vacuum drying process are set as follows: the chamber vacuum is controlled at 2-5 Pa, the cold trap temperature is set to -75℃ to -70℃, the sample temperature is -60℃ to -50℃, and the vacuum drying time is 14-16 h.

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