NiFe2O4 / Ni3Fe-coated MC biomass derived wave-absorbing material constructed based on heterojunction strategy

Abstract

The invention discloses a biomass-derived porous carbon loaded NiFe2O4 / Ni3Fe wave-absorbing material constructed on the basis of a heterojunction strategy and a preparation method of the biomass-derived porous carbon loaded NiFe2O4 / Ni3Fe wave-absorbing material. The preparation method comprises the following steps: firstly, growing a Ni-Fe precursor on a biomass derived porous carbon material through a hydrothermal method, then heating the biomass derived porous carbon material to 300 DEG C in a muffle furnace to obtain a Ni-Fe intermediate, and finally reducing the Ni-Fe intermediate in an Ar / H2 (10% H2) atmosphere for 2 hours to obtain the wave-absorbing material with NiFe2O4 / Ni3Fe loaded on the porous carbon material, namely NiFe2O4 / Ni3Fe-coated MC. NiFe2O4 / Ni3Fe has a good heterogeneous interface, and an ideal interface polarization effect is provided for electromagnetic wave absorption; meanwhile, the porous structure ensures that incident electromagnetic waves can form multiple reflections in the material, so that the material has the advantages of relatively thin matching thickness, effective absorption bandwidth and the like while showing good microwave absorption performance, and has a wide application prospect in the technical field of electromagnetic wave absorption.

Description

Technical Field

[0001] The present invention belongs to the technical fields of the preparation of nanocomposites and electromagnetic wave absorption, and specifically relates to the preparation and application of a NiFe2O4 / Ni3Fe@MC biomass-derived wave-absorbing material constructed based on a heterojunction strategy. Background Art

[0002] Nowadays, in view of the continuous development of electronic technology, especially since society has entered the information age, various electronic devices are developing towards integration and miniaturization. The wide application of electronic products has improved people's quality of life and living standards. While people enjoy the convenience it brings, the problem of electromagnetic pollution has become increasingly prominent. Therefore, preparing suitable wave-absorbing materials to prevent electromagnetic waves from interfering with the normal operation of precision electronic devices and reducing the impact of electromagnetic waves on the intrinsic magnetic field of the human body has become a crucial research topic. Electromagnetic wave absorption materials aim to absorb incident electromagnetic waves to the greatest extent and convert them into other types of energy, thereby reducing reflected waves and transmitted waves.

[0003] Biomass-derived materials have a high specific surface area, a complex conductive network, and abundant pores and defects. The complex multi-scale pores form multiple reflection paths and extensive surface porosity, contributing to the gradient impedance matching of the entire material. Effectively reducing the surface reflection of electromagnetic waves and enhancing the ability of microwave absorption. For this reason, relying on its complex porous structure, electromagnetic waves can be subjected to multi-stage reflection and scattering within the material. Secondly, a complex conductive network is formed through the porous structure, increasing the conductive loss of electromagnetic waves. Finally, the porous structure introduces a large number of gas-solid interfaces, promoting interfacial polarization and further improving electromagnetic wave attenuation. However, the impedance mismatch caused by too high conductivity and single dielectric loss makes carbon materials still not ideal. As the intrinsic electromagnetic loss performance of the material increases, its interfacial impedance will show serious mismatch, ultimately resulting in the emergence of reflection surges. Strategies such as introducing magnetic materials or combining interfacial polarization have been proposed to improve the impedance matching performance. The composite of carbon materials with high dielectric constants and magnetic alloys and compounds such as Fe and Ni has received great attention. This method can make full use of the advantages of each component material in electromagnetic wave absorption, and at the same time avoid the problem of impedance imbalance through reasonable optimization. Nickel ferrite (NiFe2O4) has good chemical stability and excellent electromagnetic parameters, and is a very promising electromagnetic absorption material. The reasons for interfacial polarization usually include heterojunctions (interfaces between components with different dielectric properties), defects in the lattice structure, and different phase interfaces of materials, providing us with a new perspective. Therefore, finely controlled hierarchical pores play a crucial role in electromagnetic wave attenuation. Using an adjustable morphological structure, combining magnetic / dielectric components with porous carbon materials enables the porous carbon materials to have appropriate impedance matching and cooperative magnetic loss, thereby realizing the preparation of broadband electromagnetic wave materials. Summary of the Invention

[0004] The object of the present invention is to provide a preparation method of NiFe2O4 / Ni3Fe@MC biomass-derived microwave absorbing material constructed based on the heterojunction strategy. The specific invention content is as follows:

[0005] 1. Using the biomass-derived porous carbon material as a carrier, through hydrothermal method, muffle furnace calcination and Ar / H2 reduction method, a microwave absorbing material NiFe2O4 / Ni3Fe@MC composed of NiFe2O4 / Ni3Fe nanoparticles in-situ grown on the biomass-derived porous carbon material is obtained, and it is prepared by the following method:

[0006] (1) Cut the wood material into rectangular block materials of equal size, then soak it in alcohol to remove impurities, finally wash it with deionized water, and place it in an environment of 60 °C for drying. Then, under Ar atmosphere, carbonize it at 900 °C for 2 h with a heating rate of 2 °C / min. After completion, rinse it with alcohol and deionized water to remove residual impurities;

[0007] (2) Weigh 8 mmol of NH4F and 16 mmol of CH4N2O and dissolve them in 70 mL of distilled water. Weigh 4-8 mmol of nickel nitrate hexahydrate and iron nitrate nonahydrate according to a molar ratio of 3:2, dissolve them in the above solution, and transfer them to a reaction kettle. At the same time, immerse the porous carbon material prepared in step (1) into the reaction kettle for hydrothermal reaction. The reaction temperature is 140 °C and the reaction time is 4 h. Then wash and dry the product to obtain the NiFe precursor loaded on the porous carbon material;

[0008] (3) Put the product of step (2) into a muffle furnace, heat it to the set temperature and keep it warm for 1 h. After the product cools to room temperature, take it out to obtain the NiFe intermediate;

[0009] (4) Put the product of step (3) into a tube furnace, heat it to the set temperature in an Ar / H2 (10% H2) atmosphere, keep it warm for 2 h and then cool it to room temperature to obtain the biomass-derived microwave absorbing material NiFe2O4 / Ni3Fe@MC.

[0010] 2. The biomass-derived microwave absorbing material NiFe2O4 / Ni3Fe@MC has a minimum reflection loss of -62.235 dB when the thickness is only 2.42 mm, and shows excellent electromagnetic wave absorption characteristics.

[0011] The NiFe2O4 / Ni3Fe@MC biomass-derived microwave absorbing material disclosed by the present invention constructed based on the heterojunction strategy has the following advantages compared with the prior art:

[0012] (1) The heterojunction composed of NiFe2O4 and Ni3Fe can induce the directional arrangement of dipoles at the heterojunction interface, induce the directional distribution of space charges, trigger interfacial polarization, and thus enhance the microwave absorption ability of the material;

[0013] (2) The high-frequency magnetic field component induces periodic spins inside the activated magnetic microspheres to a certain extent. Its stray magnetic field maintains corresponding dynamic changes, affecting the mutual inductance generated by adjacent microsphere magnets and showing magneto-coupling interaction;

[0014] (3) The biomass-derived carbon-based porous framework, due to its natural hierarchical porous structure, is conducive to the multiple reflections of incident electromagnetic waves inside it. The existence of multiple reflections promotes the dissipation of electromagnetic wave energy. Brief Description of the Drawings

[0015] Figure 1 SEM images of the biomass-derived wave-absorbing material NiFe2O4 / Ni3Fe@MC prepared in Example 1, (a) 50μm, (b) 10μm;

[0016] Figure 2 TEM and HETEM images of the biomass-derived wave-absorbing material NiFe2O4 / Ni3Fe@MC prepared in Example 1, (a) 200nm, (b) 5nm;

[0017] Figure 3 XRD pattern of the biomass-derived wave-absorbing material NiFe2O4 / Ni3Fe@MC prepared in Example 1;

[0018] Figure 4 XPS spectra of the biomass-derived wave-absorbing material NiFe2O4 / Ni3Fe@MC prepared in Example 1, (a) Fe spectrum, (b) Ni spectrum;

[0019] Figure 5 Reflection loss of the biomass-derived wave-absorbing material NiFe2O4 / Ni3Fe@MC prepared in Example 1, (a) dot line graph, (b) two-dimensional graph, (c) three-dimensional graph;

[0020] Figure 6 (a) C0 curve, (b) Z in / Z0 curve of the biomass-derived wave-absorbing material NiFe2O4 / Ni3Fe@MC prepared in Example 1. Detailed Description of the Specific Embodiments

[0021] The following further elaborates on the present invention in detail with specific embodiments, but these embodiments do not limit the scope of the present invention in any way.

[0022] Example 1

[0023] The preparation method of the biomass-derived microwave absorbing material NiFe2O4 / Ni3Fe@MC in this embodiment includes the following steps:

[0024] (1) Cut the wood material into rectangular block materials of equal size, then soak it in alcohol to remove impurities, finally wash it with deionized water, and place it in an environment of 60 °C for drying. Subsequently, under an Ar atmosphere, carbonize at 900 °C for 2 h with a heating rate of 2 °C / min. After completion, rinse with alcohol and deionized water to remove residual impurities;

[0025] (2) Weigh 8 mmol of NH4F and 16 mmol of CH4N2O and dissolve them in 70 mL of distilled water. Weigh 5 mmol of nickel nitrate hexahydrate and iron nitrate nonahydrate according to a molar ratio of 3:2, dissolve them in the above solution, and transfer them to a reaction kettle. At the same time, immerse the porous carbon material prepared in step (1) into the reaction kettle for hydrothermal reaction. The reaction temperature is 140 °C, the reaction time is 4 h, and then wash and dry the product to obtain the NiFe precursor loaded on the porous carbon material;

[0026] (3) Put the product of step (2) into a muffle furnace, heat it to the set temperature and keep it warm for 1 h. After the product cools to room temperature, take it out to obtain the NiFe intermediate;

[0027] (4) Put the product of step (3) into a tube furnace, heat it to the set temperature in an Ar / H2 (10% H2) atmosphere, keep it warm for 2 h and then cool it to room temperature to obtain the biomass-derived microwave absorbing material NiFe2O4 / Ni3Fe@MC.

[0028] From the attached drawings of the specification Figure 1 (a), (b) It can be seen from the SEM pictures at different magnifications that the biomass-derived porous microwave absorbing material has a large-diameter pore structure, which conforms to the natural biological structure. At the same time, the large geometric surface provides an ideal loading area for the active particles; NiFe2O4 / Ni3Fe nanoparticles with a diameter of about 500 nm are evenly loaded on the geometric surface. From the attached Figure 2 (a), (b) In the TEM photos, lattice fringes with two different interplanar spacings can be clearly seen. Among them, the lattice fringe with a d value of 0.155 nm corresponds to the (2 0 5) crystal plane of NiFe2O4, and the lattice fringe with a d value of 0.205 nm corresponds to the (1 11) crystal plane of Ni3Fe. This result confirms the successful preparation of the NiFe2O4 / Ni3Fe heterojunction in the product. At the same time, from the attached Figure 3From the XRD pattern, the characteristic peaks at 18.4°, 30.3°, 35.7°, 37.3°, 43.4°, 47.5°, 53.8°, 57.4° and 62.9° correspond to the (1 1 1), (2 2 0), (3 1 1), (2 2 2), (4 0 0), (3 3 1), (4 2 2), (5 1 1) and (4 4 0) crystal planes of spinel NiFe2O4 (PDF#10 - 0325); the diffraction peak at 44.2° corresponds to the (1 1 1) crystal plane of Ni3Fe (PDF#88 - 1715), and this result confirms the co - existence of NiFe2O4 and Ni3Fe in the product. Attached Figure 4 (a), (b) The XPS spectra characterize the chemical valence states of Fe and Ni elements in the microwave absorbing material, where Ni 0 The presence of the peak proves the successful preparation of Ni3Fe alloy.

[0029] The electromagnetic wave absorption performance of the product was tested and parameter - analyzed using a vector network analyzer. By mixing the product with paraffin in a certain ratio, a coaxial ring with an outer diameter of 7 mm, an inner diameter of 3 mm, and a thickness of 2 mm was made, and the coaxial measurement method was used for the electromagnetic wave absorption performance test. Attached Figure 5 (a), (b), (c) are the microwave absorption performance diagrams of the microwave absorbing material, and it can be obtained that: when the thickness is 2.42 mm, the lowest reflection loss value of the material is RL min =-62.235 dB; when the thickness is 1.83 mm, the maximum effective absorption bandwidth of the material is EAB max =6.72 GHz, showing relatively excellent electromagnetic wave absorption performance. At the same time, from attached Figure 6 (a), (b) The electromagnetic parameters show that the material exhibits relatively excellent impedance matching performance and has an ideal eddy current loss mechanism, which is because the introduction of magnetic particles endows the material with strong magnetic loss ability.

Claims

1. A NiFe2O4 / Ni3Fe@MC biomass-derived microwave absorption material constructed based on a heterojunction strategy, characterized in that, An electromagnetic wave absorbing material composed of NiFe2O4 / Ni3Fe nanoparticles in-situ grown on biomass-derived porous carbon materials is obtained by hydrothermal method, muffle furnace calcination and Ar / H2 reduction method. It is characterized in that it is prepared by the following method: (1) Cut the wood material into rectangular block materials of equal size, then soak it in alcohol to remove impurities, finally wash it with deionized water, and place it in an environment of 60 °C for drying. Then, under an Ar atmosphere, heat it to 900 °C at a heating rate of 2 °C / min, keep it warm for 2 h for carbonization, and after completion, rinse it with alcohol and deionized water to remove residual impurities; (2) Weigh 8 mmol of NH4F and 16 mmol of CH4N2O and dissolve them in 70 mL of distilled water. Weigh an appropriate amount of nickel nitrate hexahydrate and iron nitrate nonahydrate according to a molar ratio of 3:2, dissolve them in the above solution, and transfer them to a reaction kettle. At the same time, immerse the porous carbon material prepared in step (1) in the reaction kettle for hydrothermal reaction. The reaction temperature is 140 °C and the reaction time is 4 h. Then wash and dry the product to obtain the NiFe precursor loaded on the porous carbon material; (3) Put the product of step (2) into a muffle furnace, with a heating rate of 5 °C / min, a holding temperature of 300 °C, and a holding time of 1 h. Take out the product after it cools to room temperature to obtain the NiFe intermediate loaded on the porous carbon material; (4) Put the product of step (3) into a tubular furnace, heat it to 350 °C at a heating rate of 5 °C / min in an Ar / H2 (10% H2) atmosphere, keep it warm for 2 h, and cool it to room temperature to obtain the biomass-derived electromagnetic wave absorbing material NiFe2O4 / Ni3Fe@MC.

2. The biomass-derived microwave absorbing material NiFe2O4 / Ni3Fe@MC according to claim 1, characterized in that, The total molar amount of nickel nitrate hexahydrate and iron nitrate nonahydrate used in step (2) is 4-8 mmol.

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