Biomass derived carbon loaded Fe3O4 composite wave-absorbing material and preparation method thereof

Abstract

The invention discloses a biomass derived carbon loaded Fe3O4 composite wave-absorbing material and a preparation method thereof, and belongs to the technical field of electromagnetic wave absorbing materials.The biomass derived carbon loaded Fe3O4 composite wave-absorbing material is prepared by the steps that biomass is subjected to high-temperature carbonization after being cleaned and dried, and a biomass carbon precursor is obtained; mixing the biomass carbon precursor with a ferric salt solution, and drying to obtain a mixture; placing the mixture in a tubular furnace for annealing treatment, and then naturally cooling to obtain the biomass derived carbon loaded Fe3O4 composite wave-absorbing material. According to the biomass-derived carbon-loaded Fe3O4 composite wave-absorbing material and the preparation method thereof, Fe3O4 particles are uniformly loaded on the surface of biomass carbon, impedance matching is effectively improved, and electromagnetic wave absorption performance is remarkably improved by introducing magnetic loss and enhancing interface polarization, so that the electromagnetic wave absorption performance is improved. The composite material has good conductivity and a synergistic effect of multiple loss mechanisms, and excellent performances of thin thickness, light weight, strong absorption and wide bandwidth are realized.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic wave absorbing materials technology, and in particular to a biomass-derived carbon-supported Fe3O4 composite absorbing material and its preparation method. Background Technology

[0002] The rapid development and commercialization of electronic devices and microwave technology have brought serious electromagnetic interference and radiation problems. To address or reduce these issues, researchers have begun to design electromagnetic wave absorbing materials. These materials require high absorption intensity, a wide absorption frequency range, thin absorption thickness, and low bulk density, posing significant challenges to their design. However, their complex manufacturing processes, active chemical states, large weight, and high cost make them unsuitable for large-scale applications. Carbonaceous materials, with their large specific surface area, high electrical conductivity, and low density, are attracting increasing attention. Graphene, a typical carbonaceous material, exhibits excellent performance in many applications. However, due to its high electrical conductivity and low elemental impedance matching, coupled with its high manufacturing cost, graphene is far from commercially viable in electromagnetic wave absorption. Generally, good electromagnetic wave absorption performance requires excellent attenuation characteristics, but only absorbing materials that simultaneously meet these requirements can truly solve the problem of electromagnetic pollution.

[0003] To address these issues, existing technologies have also made efforts, such as the Chinese invention patent 201910052035.2, "A Hollow Carbon Nanoparticle and a Microwave Absorbing Material Prepared Therefrom," which discloses a method for preparing a microwave absorbing material from a biomass carbon source. This method involves ultrasonically treating the biomass carbon source with acetone and alcohol, then drying and ball milling the biomass carbon source, followed by sequentially adding redistilled water, acetone, and alcohol to further refine the biomass carbon source. After drying, the material is annealed to obtain nano-biomass carbon particles.

[0004] However, a closer analysis of the invention revealed that while it uses relatively economical biomass carbon as the electromagnetic wave absorbing material, the single carbon material suffers from poor impedance matching. Good impedance matching is crucial for electromagnetic wave absorbing materials; therefore, a composite process that optimizes the impedance matching of biomass carbon is needed to solve the aforementioned technical problem. Summary of the Invention

[0005] The purpose of this invention is to provide a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material and its preparation method. Fe3O4 particles are uniformly loaded on the surface of biomass carbon, which effectively improves impedance matching. By introducing magnetic loss and enhancing interfacial polarization, the electromagnetic wave absorption performance is significantly improved. The composite material has both good conductivity and the synergistic effect of multiple loss mechanisms, achieving excellent performance of thin thickness, light weight, strong absorption and wide bandwidth, providing a new idea for the development of high-performance microwave absorbing materials.

[0006] To achieve the above objectives, this invention provides a method for preparing a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material, comprising the following steps: Step 1: After cleaning and drying the biomass, it is subjected to high-temperature carbonization to obtain biomass carbon precursor; Step 2: Mix the biomass carbon precursor obtained in Step 1 with an iron salt solution, and dry the mixture to obtain a final product. Step 3: Place the mixture obtained in Step 2 into a tube furnace for annealing, and then allow it to cool naturally to obtain biomass-derived carbon-supported Fe3O4 composite microwave absorbing material.

[0007] Preferably, in step one, the biomass is pine bark, which is ultrasonically cleaned. The cleaning method is as follows: 90-120g of pine bark is placed in a mixed solution of 45mL deionized water and 5mL alcohol and ultrasonically cleaned for 30min, and repeated 3-5 times.

[0008] Preferably, in step one, the product is dried in a drying oven at a temperature of 60°C.

[0009] Preferably, in step two, the iron salt is ferrous sulfate heptahydrate.

[0010] Preferably, the mixing operation in step two is as follows: 200-300 mg of biomass carbon precursor is mixed with 5-8 mL of 0.5-0.8 mol / L iron salt solution in a beaker, the drying temperature is 60℃, the drying time is 12 h, and after drying, the mixture is dry-ground in a mortar and pestle.

[0011] Preferably, in step three, the annealing process is as follows: first, nitrogen gas is introduced for 20-30 minutes, then the temperature is increased to 300-600℃ at a rate of 4-6℃ / min, and the temperature is held for annealing for 2 hours, followed by natural cooling.

[0012] This invention also provides a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material, which is prepared using the preparation method of the biomass-derived carbon-supported Fe3O4 composite microwave absorbing material described above.

[0013] Therefore, the present invention employs the above-mentioned biomass-derived carbon-supported Fe3O4 composite microwave absorbing material and its preparation method, which has the following beneficial effects: (1) The prepared biomass-derived carbon-supported Fe3O4 composite microwave absorbing material is thin, has strong absorption performance, is lightweight, and has a wide effective absorption bandwidth, and can be used as an absorbent in the field of electromagnetic wave absorption. (2) A biomass-derived carbon-loaded Fe3O4 composite microwave absorbing material was prepared using waste pine bark from a wood mill. Fe3O4 particles were uniformly loaded on the surface of the biomass carbon prepared from pine bark. This structure not only effectively improved the impedance matching of the material, but also enhanced the interface polarization effect by introducing a magnetic loss mechanism, thus significantly improving the electromagnetic wave absorption performance of the biomass carbon. (3) The biomass-derived carbon-supported Fe3O4 composite microwave absorbing material prepared by the present invention has excellent microwave absorption performance, with a minimum reflection loss of -55.70dB, an effective absorption bandwidth (EAB) of 5.921GHz, and a matching thickness of only 1.80mm. The material has good conductivity and dielectric loss. At the same time, Fe3O4, as a ferromagnet, introduces magnetic loss, realizing the synergistic effect of multiple loss mechanisms. It meets the design requirements of "thin, wide, light, and strong" microwave absorbing materials, and provides a new idea for the development of high-performance microwave absorbing materials.

[0014] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, embodiments and comparative examples. Attached Figure Description

[0015] Figure 1 A flowchart illustrating a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material and its preparation method provided by the present invention; Figure 2 The images show scanning electron microscope (SEM) images of the biomass-derived carbon-supported Fe3O4 composite microwave absorbing materials (hereinafter referred to as BC / Fe-600 and BC / Fe-300) prepared in Examples 1 and 2 of this invention, and the biomass carbon (hereinafter referred to as BC) prepared in Comparative Example 1. Figure 3 The XRD patterns of BC / Fe-600 and BC / Fe-300 prepared in Examples 1 and 2 of this invention, and the X-ray diffraction energy spectrum of BC prepared in Comparative Example 1; Figure 4 The Raman spectra of BC / Fe-600 and BC / Fe-300 prepared in Examples 1 and 2 of this invention, and the Raman spectrum of BC prepared in Comparative Example 1; Figure 5 The graphs show the reflection loss curves of BC / Fe-600 and BC / Fe-300 prepared in Examples 1 and 2 of the present invention, and the biomass carbon prepared in Comparative Example 1 with a filling degree of 10 wt%. Detailed Implementation

[0016] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0018] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0019] Example 1 like Figure 1 As shown, this invention provides a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material and its preparation method, comprising the following steps: Step 1: After washing and drying the biomass, it is subjected to high-temperature carbonization to obtain biomass carbon precursor: (1) Washing of biomass: Pine bark is broken into 1cm×1cm pieces. 100g is placed in a mixed solution of 45mL water and 5mL alcohol. After ultrasonic treatment for 30min, the pine bark is taken out and the washing operation is repeated three times. Then it is placed in an oven to dry for more than 12h to obtain clean pine bark.

[0020] (2) Preparation of biomass carbon precursor: 10g of washed pine bark was placed in a corundum crucible and then placed in a tube furnace. Nitrogen gas was first introduced into the tube furnace for 20min, and then the temperature was increased to 700℃ at 5℃ / min. The temperature was held at 700℃ for annealing for 2h, and then naturally cooled. Nitrogen gas was kept in the tube furnace throughout the process. The obtained biomass carbon precursor was ultrasonically washed with a mixture of deionized water and alcohol to remove inorganic salts. It was then dried in an oven for more than 12h, and then ground in a mortar for 30min to obtain the biomass carbon precursor.

[0021] Step 2: Mix the biomass carbon precursor obtained in Step 1 with an iron salt solution, and dry to obtain a mixture: Take 200 mg of biochar precursor and 5 mL of 0.5 M FeSO4·7H2O solution, sonicate for 30 min and stir for 30 min in a beaker, then dry in an oven for 12 h, and grind the mixture in a mortar until homogeneous.

[0022] Step 3: The mixture obtained in Step 2 is placed in a tube furnace for annealing, then naturally cooled, washed, and dried to obtain biomass-derived carbon-supported Fe3O4 composite microwave absorbing material. The mixture obtained in step two was placed in a corundum crucible and then placed in a tube furnace. Nitrogen gas was first introduced into the tube furnace for 20 minutes, and then the temperature was increased to 600°C at a rate of 5°C / min. The temperature was maintained for annealing for 2 hours, followed by natural cooling. Nitrogen gas was maintained throughout the entire process. The final product was a biomass carbon-supported Fe3O4 composite material, named BC / Fe-600.

[0023] Example 2 This invention provides a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material and its preparation method, comprising the following steps: Step 1: After washing and drying the biomass, it is subjected to high-temperature carbonization to obtain biomass carbon precursor: (1) Washing of biomass: Pine bark is broken into 1cm×1cm pieces. 100g is placed in a mixed solution of 45mL water and 5mL alcohol. After ultrasonic treatment for 30min, the pine bark is taken out and the washing operation is repeated three times. Then it is placed in an oven to dry for more than 12h to obtain clean pine bark.

[0024] (2) Preparation of biomass char: 10g of washed pine bark was placed in a corundum crucible and then placed in a tube furnace. Nitrogen gas was first introduced into the tube furnace for 20min, and then the temperature was increased to 700℃ at 5℃ / min. The furnace was then annealed at 700℃ for 2h and then cooled naturally. Nitrogen gas was maintained throughout the process. The obtained biomass char was ultrasonically washed with a mixture of deionized water and alcohol to remove inorganic salts. It was then dried in an oven for more than 12h and then ground in a mortar for 30min to obtain biomass char.

[0025] Step 2: Mix the biomass carbon precursor obtained in Step 1 with an iron salt solution, and dry to obtain a mixture: Take 200 mg of biomass carbon precursor and 5 mL of 0.5 M FeSO4·7H2O solution, sonicate for 30 min and then stir for 30 min in a beaker. After mixing, dry in an oven for 12 h and grind the mixture in a mortar until homogeneous.

[0026] Step 3: The mixture obtained in Step 2 is placed in a tube furnace for annealing. After annealing, it is cooled, washed, and dried to obtain biomass-derived carbon-supported Fe3O4 composite microwave absorbing material. The mixture obtained in step two was placed in a corundum crucible and then placed in a tube furnace. Nitrogen gas was first introduced into the tube furnace for 20 minutes, and then the temperature was increased to 300°C at a rate of 5°C / min. The mixture was then annealed at 300°C for 2 hours and then allowed to cool naturally. Nitrogen gas was maintained throughout the entire process. The resulting biomass carbon-supported Fe3O4 composite material was named BC / Fe-300.

[0027] Comparative Example 1 Biomass is washed, dried, and then carbonized at high temperature to obtain biomass carbon. (1) Washing of biomass: Pine bark is broken into 1cm×1cm pieces. 100g is placed in a mixed solution of 45mL water and 5mL alcohol. After ultrasonic treatment for 30min, the pine bark is taken out and the washing operation is repeated three times. Then it is placed in an oven to dry for more than 12h to obtain clean pine bark.

[0028] (2) Preparation of biomass char: 10g of washed pine bark was placed in a corundum crucible and then placed in a tube furnace. Nitrogen gas was first introduced into the tube furnace for 20min, and then the temperature was increased to 700℃ at 5℃ / min. The furnace was then annealed at 700℃ for 2h and then cooled naturally. Nitrogen gas was maintained throughout the process. The obtained biomass char was ultrasonically washed with a mixture of deionized water and alcohol to remove inorganic salts. It was then dried in an oven for more than 12h and then ground in a mortar for 30min to obtain biomass char, which was named BC.

[0029] Experimental Example 1: The microstructure of BC / Fe-600 and BC / Fe-300 prepared in Examples 1 and 2, as well as BC prepared in Comparative Example 1, was observed using a scanning electron microscope.

[0030] Depend on Figure 2 It can be seen that, compared to biomass carbon with a smooth surface ( Figure 2 a and Figure 2 b in Figure 2 b in Figure 2 (Enlarged view of 'a' in the image) In the composite material, Fe3O4 particles are attached to the surface of biomass carbon. Figure 2 c and Figure 2 d in Figure 2 d in Figure 2 (Enlarged view of c in the image), and as the temperature increases, reaching 600℃, the Fe3O4 particles attached to the surface of the biomass carbon are uniformly distributed ( Figure 2 e and Figure 2 f in Figure 2 f in Figure 2 (Magnified view of 'e' in the image). This greatly optimizes the impedance matching of biomass carbon, thus making it easier for electromagnetic waves to penetrate the sample.

[0031] Experimental Example 2: The structures of BC / Fe-600 and BC / Fe-300 prepared in Examples 1 and 2, as well as BC prepared in Comparative Example 1, were characterized using X-ray diffraction.

[0032] exist Figure 3 It can be clearly seen that the diffraction peaks of samples BC / Fe-600 and BC / Fe-300 after being loaded with Fe3O4 correspond to the PDF cards of Fe3O4. Clearly, the Fe3O4 magnetic particles have successfully composited with biomass carbon, thereby introducing magnetic loss and enhancing interfacial polarization.

[0033] Experimental Example 3: Raman spectroscopy was used to analyze BC / Fe-600 and BC / Fe-300 prepared in Examples 1 and 2, as well as BC prepared in Comparative Example 1.

[0034] exist Figure 4The ID / IG ratios for samples BC, BC / Fe-300, and BC / Fe-600 were 1.12, 1.15, and 1.14, respectively. The data shows that the graphitization degree of the three samples was roughly the same. This indicates that biomass carbon composite Fe3O4 particles did not significantly enhance the graphitization degree of the carbon material, thus failing to improve electrical conductivity and polarization losses, and exhibited good stability.

[0035] Experimental Example 4: The samples prepared in Examples 1, 2, and Comparative Example 1 were uniformly mixed with paraffin wax (the filler loading of the samples was 10 wt%). The resulting mixture was compressed into cylindrical test composites with an inner diameter of 3.04 mm, an outer diameter of 7.00 mm, and a thickness of 2.0 mm. The electromagnetic parameters of these samples in the frequency range of 2.0–18.0 GHz were measured using a vector network analyzer (VNA, AV3629D).

[0036] Test results are as follows Figure 5 As shown, where, Figure 5 In the figure, 'a' represents the reflection loss curve of BC prepared in Comparative Example 1. Figure 5 In the figure, b represents the reflection loss curve of BC / Fe-300 prepared in Example 2. Figure 5 In the figure, 'c' represents the reflection loss curve of BC / Fe-600 prepared in Example 1. Figure 5 It is easy to see from 'a' that sample BC exhibits weak reflection loss capability; from Figure 5 As shown in b, the minimum reflection loss of the composite material BC / Fe-300 is -42.23dB, the effective absorption bandwidth is 5.521GHz, and the matching thickness is 1.839mm; Figure 5 As shown in 'c', with the increase of annealing temperature, the composite material BC / Fe-600 exhibits excellent reflection loss performance at 600℃, with a minimum reflection loss value of -55.70dB, an effective absorption bandwidth of 5.921GHz, and a matching thickness of only 1.80mm, which meets the design requirements of "thin, wide, light, and strong" for absorbing materials.

[0037] Therefore, this invention employs the aforementioned biomass-derived carbon-supported Fe3O4 composite microwave absorbing material and its preparation method. Fe3O4 particles are uniformly loaded on the surface of biomass carbon, effectively improving impedance matching. Furthermore, by introducing magnetic loss and enhancing interfacial polarization, the electromagnetic wave absorption performance is significantly improved. The composite material possesses both good conductivity and the synergistic effect of multiple loss mechanisms, achieving excellent performance in terms of thinness, light weight, strong absorption, and wide bandwidth, providing a new approach for the development of high-performance microwave absorbing materials.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material, characterized in that: Includes the following steps: Step 1: After cleaning and drying the biomass, it is subjected to high-temperature carbonization to obtain biomass carbon precursor; Step 2: Mix the biomass carbon precursor obtained in Step 1 with an iron salt solution, and dry the mixture to obtain a final product. Step 3: Place the mixture obtained in Step 2 into a tube furnace for annealing, and then allow it to cool naturally to obtain biomass-derived carbon-supported Fe3O4 composite microwave absorbing material.

2. The preparation method of a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material according to claim 1, characterized in that: In step one, the biomass is pine bark, which is cleaned using ultrasound. The cleaning method is as follows: place 90-120g of pine bark in a mixed solution of 45mL deionized water and 5mL alcohol and clean it with ultrasound for 30min. Repeat 3-5 times.

3. The method for preparing a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material according to claim 1, characterized in that: In step one, the product is dried in a drying oven at a temperature of 60°C.

4. The preparation method of a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material according to claim 1, characterized in that: In step two, the iron salt is ferrous sulfate heptahydrate.

5. The method for preparing a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material according to claim 1, characterized in that: The mixing operation in step two is as follows: 200-300 mg of biomass carbon precursor is mixed with 5-8 mL of 0.5-0.8 mol / L iron salt solution in a beaker, and then placed in a drying oven at 60℃ for 12 h. After drying, the mixture is dry-ground in a mortar and pestle.

6. The preparation method of a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material according to claim 1, characterized in that: In step three, the annealing process is as follows: first, nitrogen gas is introduced for 20-30 minutes, then the temperature is increased to 300-600℃ at a rate of 4-6℃ / min, and the annealing is carried out for 2 hours before natural cooling.

7. A biomass-derived carbon-supported Fe3O4 composite microwave absorbing material, characterized in that: The material was prepared using the method described in any one of claims 1-6 for preparing a biomass-derived carbon-supported Fe3O4 composite microwave absorbing material.

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