Spherical biomass derived carbon electromagnetic wave-absorbing material and preparation method thereof

Abstract

The invention discloses a spherical biomass derived carbon electromagnetic wave-absorbing material and a preparation method thereof, and belongs to the technical field of electromagnetic wave-absorbing materials.The method comprises the steps that in an inert atmosphere, dried chlorella is subjected to high-temperature treatment, and chlorella derived carbon is obtained; the preparation method comprises the following steps: dissolving trivalent iron salt in deionized water at room temperature, adding chlorella derived carbon, uniformly dispersing, adding bivalent iron salt, uniformly dispersing, adding ammonia water, heating to 60-80 DEG C, stirring, cooling to room temperature, standing at room temperature, collecting a product, and cleaning to obtain the spherical biomass derived carbon electromagnetic wave-absorbing material. The spherical biomass derived carbon electromagnetic wave-absorbing material prepared by the invention has the advantages of regular shape, excellent wave-absorbing performance and wide effective absorption range, and the preparation method is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic absorbing materials, and in particular to a spherical biomass-derived carbon electromagnetic absorbing material and a preparation method thereof. Background Art

[0002] With the rapid development of science and technology, the use of electronic and electrical devices has exploded, posing a significant challenge to the speed of information processing. The operating frequencies of electronic devices are gradually shifting towards the microwave band. With the use of these devices, electromagnetic radiation and interference have become new sources of pollution, following water pollution, air pollution, and noise pollution. Furthermore, absorbing materials are gaining increasing attention in military applications, with their applications in weaponry stealth and electromagnetic radiation protection gradually moving towards strong broadband absorption properties. To overcome the hazards of electromagnetic radiation and effectively utilize "stealth" capabilities on the battlefield, research into materials for electromagnetic shielding and absorption holds great value.

[0003] Research on electromagnetic absorbing materials primarily encompasses dielectric and magnetic materials. While these materials have been extensively studied both domestically and internationally, the vast majority of these materials, such as ferrites and metal powders, exhibit irregular shapes, limiting their applications. Therefore, the search for new, regularly shaped absorbing materials and the development of their preparation methods have become a key focus for scientists.

[0004] Pure carbon-based absorbing materials offer advantages such as light weight, corrosion resistance, and high-temperature resistance. However, their high electrical conductivity can lead to excessive reflection, resulting in poor absorption performance and a narrow absorption bandwidth. By introducing magnetic electromagnetic wave absorbing materials, impedance matching can be adjusted to achieve magneto-electric co-absorption. Therefore, developing a carbon-based absorbing material with a regular structure and excellent absorption performance has important scientific significance and application prospects.

[0005] An electromagnetic absorber with a regular shape can be formulated by connecting naturally regularly shaped biomass carbon and ferroferric oxide magnetic absorbing material through electrostatic adsorption.

[0006] Chinese patent CN113429933A discloses a ferroferric oxide / biomass porous carbon composite absorber and its preparation method. The patent involves washing and drying a biomass carbon source, then soaking the dried biomass carbon source in an iron source solution to absorb iron ions. The soaked biomass carbon source is then washed, dried, and calcined to produce the ferroferric oxide / biomass porous carbon composite absorber. However, this method involves a two-step calcination process: the first step produces biomass-derived carbon, followed by a second calcination under vacuum. This results in a long product preparation cycle, high vacuum equipment requirements, and high finished product costs. Any improper operation can easily lead to the decomposition of the ferroferric oxide, significantly reducing its absorbent properties. Summary of the Invention

[0007] The purpose of the present invention is to provide a spherical biomass-derived carbon electromagnetic absorbing material and a preparation method thereof. The prepared spherical biomass-derived carbon electromagnetic absorbing material has the advantages of regular shape, excellent absorbing performance, and a wide effective absorption range, and the preparation method is simple.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions: A method for preparing a spherical biomass-derived carbon electromagnetic absorbing material comprises: subjecting dried Chlorella to a high-temperature treatment in an inert atmosphere to obtain Chlorella-derived carbon; dissolving a trivalent iron salt in deionized water at room temperature, adding the Chlorella-derived carbon, and evenly dispersing the mixture; adding a divalent iron salt, and evenly dispersing the mixture; adding ammonia water, heating the mixture to 60-80° C., stirring the mixture, and then cooling the mixture to room temperature. The mixture is allowed to stand at room temperature, and the product is collected and washed to obtain the spherical biomass-derived carbon electromagnetic absorbing material. The inert atmosphere is a nitrogen atmosphere or an argon atmosphere; The drying temperature of the dried chlorella is 70-80° C. The high temperature treatment is to raise the temperature to 600-800°C at a heating rate of 4-6°C / min and keep the temperature at 600-800°C for 110-130 minutes; The trivalent iron salt is ferric chloride; The divalent iron salt is ferrous sulfate; The concentration of the ammonia solution is 28-30%; The ratio of ferric salt to deionized water is 0.5g:9.5-10.5mL; The mass ratio of Chlorella-derived carbon to ferric salt is 0.2-0.6:0.48-0.52; The mass ratio of Chlorella-derived carbon to ferrous salt is 0.2-0.6:0.28-0.32; The ratio of Chlorella-derived carbon to ammonia water is 0.2-0.6 g: 2-7.5 mL; After heating to 60-80℃, the stirring time is 60-70min; The resting time at room temperature is 4-4.5h; The product was collected by a strong magnet and washed with deionized water.

[0009] A spherical biomass-derived carbon electromagnetic absorbing material obtained by the above-mentioned preparation method.

[0010] The present invention discloses the following technical effects: (1) The present invention obtains a spherical biomass-derived carbon electromagnetic absorbing material with a regular shape and a rough surface by a co-precipitation method, and then composites the chlorella-derived carbon material obtained by high-temperature treatment with ferroferric oxide to finally obtain a spherical biomass-derived carbon electromagnetic absorbing material. The obtained spherical biomass-derived carbon electromagnetic absorbing material has good absorbing performance. When electromagnetic waves are incident on the interior of the nano-scale spheres, the ferroferric oxide magnetic nanoparticles embedded in the carbon matrix realize impedance matching regulation and conductivity loss between the carbon matrix and the material. In addition, the electromagnetic waves can be synergistically absorbed through the polarization loss and hysteresis loss at the interface between the two. The ferroferric oxide nanoparticles deposited on the surface enhance the interface polarization loss, play a role in regulating impedance matching, and further enhance the electromagnetic loss performance. At the same time, the construction of low-thickness absorbing devices is achieved through the micro-nano spherical structure, which makes its application range wider and has good prospects. (2) The spherical biomass-derived carbon electromagnetic absorbing material prepared by the present invention is mixed with paraffin wax and then made into a 3 mm thick coaxial ring through a mold. The best absorbing performance is achieved when the spherical biomass-derived carbon electromagnetic absorbing material accounts for 50%, the minimum reflection loss RL value is -50.535 dB, and the effective absorption bandwidth is 2.46 GHz. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a scanning electron microscope image of the spherical biomass-derived carbon electromagnetic absorbing material of Example 1; Figure 2 Graphs showing the electromagnetic wave absorption performance of the spherical biomass-derived carbon electromagnetic absorbing materials of Examples 1-3 and Comparative Examples 1-6; In the figure, Figure 2 a is a graph showing the electromagnetic wave absorption performance of the spherical biomass-derived carbon electromagnetic absorbing material obtained in Example 1; Figure 2 b is a graph showing the electromagnetic wave absorption performance of the spherical biomass-derived carbon electromagnetic absorbing material obtained in Example 2; Figure 2 c is a graph showing the electromagnetic wave absorption performance of the spherical biomass-derived carbon electromagnetic absorbing material obtained in Example 3; Figure 2 d is a graph showing the electromagnetic wave absorption performance of the spherical biomass-derived carbon electromagnetic absorbing material obtained in Comparative Example 1; Figure 2e is a graph showing the electromagnetic wave absorption performance of the spherical biomass-derived carbon electromagnetic absorbing material obtained in Comparative Example 2; Figure 2 f is a graph showing the electromagnetic wave absorption performance of the spherical biomass-derived carbon electromagnetic absorbing material obtained in Comparative Example 3; Figure 2 g is a graph showing the electromagnetic wave absorption performance of the spherical biomass-derived carbon electromagnetic absorbing material obtained in Comparative Example 4; Figure 2 h is a graph showing the electromagnetic wave absorption performance of the spherical biomass-derived carbon electromagnetic absorbing material obtained in Comparative Example 5; Figure 2 i is a graph showing the electromagnetic wave absorption performance of the spherical biomass-derived carbon electromagnetic absorbing material obtained in Comparative Example 6. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0013] Example 1 The Chlorella was dried at 80°C and then heat-treated in a tubular furnace. The heat treatment atmosphere was N2. The temperature was increased at a heating rate of 5°C / min, and the temperature was stopped at 700°C and kept at this temperature for 2 hours to obtain Chlorella-derived carbon.

[0014] 0.4 g of Chlorella-derived carbon, 0.5 g of ferric chloride, and 0.3 g of ferrous sulfate were weighed using an analytical balance. At room temperature, 10 mL of deionized water was measured using a graduated cylinder and added to a beaker. 0.5 g of ferric chloride was added and dissolved using a glass rod. The 0.4 g of Chlorella-derived carbon was then placed in the beaker and, after uniform dispersion, 0.3 g of ferrous sulfate was added and stirred. The suspension was then dispersed thoroughly using a glass rod to obtain a black suspension. 3 mL of 28% ammonia was then added. The mixture was heated to 70°C and mixed at 70°C. During the stirring process, a red flocculent precipitate first appeared, which then disappeared and turned black. After stirring for 1 hour, the mixture was allowed to stand at room temperature for 4 hours. Finally, the mixture was collected using a strong magnet and washed with deionized water to obtain a spherical biomass-derived carbon electromagnetic absorber with a rough surface.

[0015] This embodiment also provides a spherical biomass-derived carbon electromagnetic absorbing material obtained by the aforementioned preparation method.

[0016] A 3mm-thick coaxial ring was molded by mixing paraffin wax with a spherical biomass-derived carbon electromagnetic absorber, with the spherical biomass-derived carbon absorber comprising 50% of the material. The prepared coaxial ring was measured using a vector network analyzer coaxial method, yielding a minimum return loss (RL) value of -50.535dB and an effective absorption bandwidth of 2.46GHz.

[0017] The spherical biomass-derived carbon electromagnetic absorbing material obtained in this example was analyzed by scanning electron microscopy, and the obtained scanning electron microscopy image is shown in FIG. Figure 1 .

[0018] Example 2 The Chlorella was dried at 80°C and then heat-treated in a tubular furnace. The heat treatment atmosphere was N2. The temperature was increased at a heating rate of 5°C / min, and the temperature was stopped at 700°C and kept at this temperature for 2 hours to obtain Chlorella-derived carbon.

[0019] 0.6 g of Chlorella-derived carbon, 0.5 g of ferric chloride, and 0.3 g of ferrous sulfate were weighed using an analytical balance. At room temperature, 10 mL of deionized water was measured using a graduated cylinder and added to a beaker. 0.5 g of ferric chloride was added and dissolved using a glass rod. The 0.6 g of Chlorella-derived carbon was then placed in the beaker and, after uniform dispersion, 0.3 g of ferrous sulfate was added and stirred. The suspension was then dispersed thoroughly using a glass rod to obtain a black suspension. 3 mL of 28% ammonia was then added. The mixture was heated to 70°C and mixed at 70°C. During the stirring process, a red flocculent precipitate first appeared, which then disappeared and turned black. After stirring for 1 hour, the mixture was allowed to stand at room temperature for 4 hours. Finally, the mixture was collected using a strong magnet and washed with deionized water to obtain a spherical biomass-derived carbon electromagnetic absorber with a rough surface.

[0020] This embodiment also provides a spherical biomass-derived carbon electromagnetic absorbing material obtained by the aforementioned preparation method.

[0021] A 3mm-thick coaxial ring was molded by mixing paraffin wax with a spherical biomass-derived carbon electromagnetic absorber, with the spherical biomass-derived carbon absorber comprising 50% of the material. The prepared coaxial ring was measured using a vector network analyzer coaxial method, yielding a minimum return loss (RL) value of -44.225dB and an effective absorption bandwidth of 2.4GHz.

[0022] Example 3 The Chlorella was dried at 80°C and then heat-treated in a tubular furnace. The heat treatment atmosphere was N2. The temperature was increased at a rate of 2°C / min until it reached 700°C and the temperature was kept at that temperature for 2 hours to obtain Chlorella-derived carbon.

[0023] Weigh 0.2g of Chlorella-derived carbon, 0.5g of ferric chloride, and 0.3g of ferrous sulfate using an analytical balance. At room temperature, measure 10mL of deionized water using a graduated cylinder. Add 10mL of deionized water to a beaker. Add 0.5g of ferric chloride and stir with a glass rod to dissolve. Then, place 0.2g of Chlorella-derived carbon in the beaker. Once evenly dispersed, add 0.3g of ferrous sulfate and stir. Stir thoroughly with a glass rod to disperse the mixture, resulting in a black suspension. Then, add 3mL of 28% ammonia solution. Heat the mixture to 70°C and mix at 70°C. During stirring, a red, flocculent precipitate first appears, then disappears and turns black. Stir for 1 hour and then allow to stand at room temperature for 4 hours. Finally, collect the mixture using a strong magnet and wash with deionized water to obtain a spherical biomass-derived carbon electromagnetic absorber with a rough surface.

[0024] This embodiment also provides a spherical biomass-derived carbon electromagnetic absorbing material obtained by the aforementioned preparation method.

[0025] A 3mm-thick coaxial ring was molded by mixing paraffin wax with spherical biomass-derived carbon electromagnetic absorbers, with the spherical biomass-derived carbon absorbers comprising 50% of the material. The prepared coaxial ring was measured using a vector network analyzer coaxial method, yielding a minimum return loss (RL) value of -46.107dB and an effective absorption bandwidth of 3.12GHz.

[0026] Comparative Example 1 Same as Example 1, except that the amount of 28% ammonia water added is 2 mL.

[0027] The small amount of ammonia added, in a weakly alkaline environment, resulted in a small amount of ferroferric oxide produced by the coprecipitation of ferrous and ferric iron, making impedance matching difficult. Furthermore, the hysteresis loss capability was low, resulting in poor electromagnetic wave absorption performance compared to Example 1. The measured reflection loss (RL) value of the spherical biomass-derived carbon electromagnetic absorbing material prepared in this comparative example was -23.514 dB, and the effective absorption bandwidth was 2.24 GHz.

[0028] Comparative Example 2 Same as Example 1, except that the amount of 28% ammonia water added is 7.5 mL.

[0029] The high amount of ammonia added, combined with the strong alkaline environment, resulted in the coprecipitation of ferrous and ferric iron, primarily as ferric hydroxide. This made it difficult to achieve impedance matching and optimize hysteresis loss, and also introduced a large amount of ferric hydroxide as an impurity. Consequently, the electromagnetic wave absorption performance was inferior to that of Example 1. The spherical biomass-derived carbon electromagnetic absorber prepared in this comparative example had a measured reflection loss (RL) value of -14.256 dB, and an effective absorption bandwidth of 1.76 GHz.

[0030] Comparative Example 3 Same as Example 2, except that the heat treatment temperature is 600°C.

[0031] After treatment at 600°C, the biomass carbon tube absorbing material has a low carbonization degree, a low dielectric constant, and a small dielectric loss, and its electromagnetic wave absorption performance is poorer than that of Example 2. The reflection loss RL value of the spherical biomass-derived carbon electromagnetic absorbing material prepared in this comparative example was measured to be -38.731 dB, and the effective absorption bandwidth was 4.48 GHz.

[0032] Comparative Example 4 Same as Example 2, except that the heat treatment temperature is 800°C.

[0033] After 800°C, the dielectric constant of the biomass carbon tube absorbing material is too high, making it difficult for electromagnetic waves to enter, resulting in a skin effect. The reflection loss RL value of the spherical biomass-derived carbon electromagnetic absorbing material prepared in this comparative example was measured to be -31.091dB, and the effective absorbing bandwidth was 2.48GHz.

[0034] Comparative Example 5 Same as Example 3, except that the temperature after adding 28% ammonia water was changed from 70°C to 80°C.

[0035] As the solution temperature increases, the reaction in the system accelerates, and a large amount of iron hydroxide precipitates on the spheres, resulting in poor electromagnetic wave absorption performance compared to Example 3. The reflection loss RL value of the spherical biomass-derived carbon electromagnetic absorbing material prepared in this comparative example was measured to be -19.585 dB, and the effective absorption bandwidth was 2.72 GHz.

[0036] Comparative Example 6 Same as Example 3, except that the temperature after adding 28% ammonia water was changed from 70°C to 60°C.

[0037] Due to the decrease in solution temperature, the reaction rate of the reaction system was too slow to generate a large amount of ferroferric oxide precipitate, and the electromagnetic wave absorption performance was poorer than that of Example 3. The reflection loss RL value of the spherical biomass-derived carbon electromagnetic absorbing material prepared in this comparative example was measured to be -32.782 dB, and the effective absorption bandwidth was 1.2 GHz.

[0038] The electromagnetic wave absorption performance of the spherical biomass-derived carbon electromagnetic wave absorbing materials obtained in Examples 1-3 and Comparative Examples 1-6 is shown in FIG. Figure 2 .

Claims

1. A method for preparing a spherical biomass-derived carbon electromagnetic absorbing material, characterized in that: The method comprises the following steps: subjecting dried chlorella to a high-temperature treatment in an inert atmosphere to obtain chlorella-derived carbon; dissolving a trivalent iron salt in deionized water at room temperature, adding the chlorella-derived carbon, and evenly dispersing the mixture; adding a divalent iron salt, and evenly dispersing the mixture; adding ammonia water, heating the mixture to 60-80°C, stirring the mixture, cooling the mixture to room temperature, allowing the mixture to stand at room temperature, collecting the product, and then washing the product to obtain a spherical biomass-derived carbon electromagnetic absorbing material.

2. The method for preparing the spherical biomass-derived carbon electromagnetic absorbing material according to claim 1, characterized in that: The inert atmosphere is a nitrogen atmosphere or an argon atmosphere; The drying temperature of the dried chlorella is 70-80°C.

3. The method for preparing the spherical biomass-derived carbon electromagnetic absorbing material according to claim 1, characterized in that: The high temperature treatment is to raise the temperature to 600-800°C at a heating rate of 4-6°C / min and keep the temperature at 600-800°C for 110-130 minutes.

4. The method for preparing the spherical biomass-derived carbon electromagnetic absorbing material according to claim 1, characterized in that: The trivalent iron salt is ferric chloride; The divalent iron salt is ferrous sulfate; The concentration of the ammonia water is 28-30%.

5. The method for preparing the spherical biomass-derived carbon electromagnetic absorbing material according to claim 1, characterized in that: The ratio of ferric salt to deionized water is 0.5g:9.5-10.5mL; The mass ratio of Chlorella-derived carbon to ferric salt is 0.2-0.6:0.48-0.52; The mass ratio of Chlorella-derived carbon to ferrous salt is 0.2-0.6:0.28-0.32; The ratio of chlorella-derived carbon to ammonia water is 0.2-0.6 g: 2-7.5 mL.

6. The method for preparing the spherical biomass-derived carbon electromagnetic absorbing material according to claim 1, characterized in that: After heating to 60-80°C, the stirring time is 60-70 minutes; the standing time at room temperature is 4-4.5 hours; The product was collected by a strong magnet and washed with deionized water.

7. A spherical biomass-derived carbon electromagnetic absorbing material obtained by the preparation method according to any one of claims 1 to 6.

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