Attapulgite-based heterogeneous composite wave-absorbing material, preparation method and application thereof

Abstract

The application provides a hetero-composite wave-absorbing material based on attapulgite, a preparation method and application thereof. The wave-absorbing material is prepared by acid activation and high-frequency ultrasonic stirring to disperse attapulgite in a deionized water system to form an attapulgite emulsion, and the well-dispersed attapulgite fibers are uniformly coated with a carbon layer on the surface through hydrothermal stirring and high-temperature carbonization; then, a flower-like NiCo2O4 is grown in situ on the carbon-coated attapulgite to construct a hetero-interface, the carbon-coated attapulgite is used as a dielectric loss material, the flower-like NiCo2O4 is used as a magnetic loss material, through hetero-structure design, the carbon layer can inhibit the skin effect caused by the cross-linked flower-like NiCo2O4, so as to amplify the magnetic response behavior of the NiCo2O4; the hetero-interface formed between the two can significantly enhance the interface polarization, realize impedance matching, significantly improve the microwave absorption performance, and overcome the defects of impedance mismatch and structure design existing in the prior art magnetic-dielectric synergistic wave-absorbing material.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorption technology, specifically relating to a heterogeneous composite absorbing material based on attapulgite, its preparation method, and its application. Background Technology

[0002] With the advent of the 5G communication era, the emergence of various electronic and electrical devices has brought tremendous convenience to human life. However, high-power electrical equipment and highly integrated electronic devices generate a large amount of electromagnetic waves during operation, and the resulting electromagnetic radiation pollution has become a new type of pollution source affecting people's health in the communication era. Furthermore, electromagnetic waves can also seriously affect the normal operation of highly sensitive equipment commonly used in civilian or military fields. Therefore, severe electromagnetic radiation pollution has created an urgent need for the design of high-performance electromagnetic wave absorbing materials.

[0003] Electromagnetic wave absorbing materials are generally composed of absorbing agents and transmitting materials. The transmitting material forms the matrix of the absorbing material, acting as a channel for electromagnetic wave propagation; the absorbing agent absorbs electromagnetic radiation. Absorbing agents can be classified into resistive, dielectric, and magnetic dielectric types according to their material loss mechanisms. A single loss mechanism cannot provide excellent electromagnetic wave absorption performance. Therefore, most widely used absorbing agents currently employ a magnetic-dielectric synergistic system. The dielectric part typically includes carbon materials such as carbon nanotubes, carbon fibers, and graphene. Due to their low density, high dielectric constant, and excellent conductivity, they can absorb electromagnetic waves through dielectric polarization relaxation loss. When combined with magnetic materials (such as iron, cobalt, nickel alloys, and their oxides), the magnetic materials further attenuate electromagnetic waves through resonance and hysteresis losses, thus achieving a synergistic enhancement of the material's absorption performance. However, the impedance mismatch problem in the magnetic-dielectric synergistic system and the composite method of the magnetic-dielectric materials severely limit its application in the field of electromagnetic wave absorption.

[0004] Alumina and silica ceramics were first used as oxide ceramics in wave-transmitting materials. Attapulgite, a natural fibrous aluminosilicate mineral, is similar in composition to these two, thus exhibiting good wave-transmitting properties. Addressing the impedance mismatch and structural design deficiencies in existing magnetic-dielectric synergistic wave-absorbing materials, a method combining attapulgite with carbon materials to achieve optimal impedance matching has been proposed, but there are currently few reports on this technology. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned shortcomings of existing technologies by providing a heterogeneous composite microwave absorbing material based on attapulgite, its preparation method, and its applications. A highly dispersed attapulgite emulsion is prepared using high-frequency ultrasonic stirring. Glucose is then combined with the attapulgite in the emulsion via hydrothermal stirring. A carbon precursor is coated onto the surface of the attapulgite, and carbon-coated attapulgite is prepared by high-temperature carbonization. Flower-like NiCo2O4 is then grown in situ on the surface of the carbon-coated attapulgite through hydrothermal reaction and high-temperature annealing, resulting in a high-performance heterogeneous microwave absorbing material. This material utilizes a heterogeneous interface design to improve the impedance mismatch problem present in existing magnetic-dielectric synergistic systems, thereby enhancing the material's microwave absorption performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first objective of this invention is to provide a method for preparing a heterogeneous composite microwave absorbing material based on attapulgite, comprising the following specific steps:

[0008] Step S1: The raw attapulgite ore is soaked in hydrochloric acid and thermally activated to obtain acid-activated attapulgite;

[0009] Step S2: The acid-activated attapulgite obtained in step S1 is mixed with deionized water, and a uniform and highly dispersible attapulgite emulsion is obtained by using a high-frequency ultrasonic synthesizer.

[0010] Step S3: Add glucose to the attapulgite emulsion obtained in step S2, and coat the surface of the attapulgite with carbon precursor through the first hydrothermal stirring reaction. After the reaction is completed, collect the brown powder product, wash it with deionized water or anhydrous ethanol, and dry it to obtain carbon precursor coated attapulgite.

[0011] Step S4: The carbon precursor-coated attapulgite is converted into carbon-coated attapulgite by high-temperature carbonization.

[0012] Step S5: The precursor NiCo2(OH)6 is grown in situ on the carbon-coated attapulgite using liquid phase deposition to obtain carbon-coated attapulgite@NiCo2(OH)6.

[0013] Step S6: Carbon-coated attapulgite@NiCo2(OH)6 is annealed at high temperature in air atmosphere to obtain carbon-coated attapulgite@NiCo2O4.

[0014] Furthermore, in step S1, the grade of the attapulgite ore is greater than 80%, and the particle size is less than 200 mesh; the hydrochloric acid soaking and thermal activation process includes: hydrochloric acid soaking, solid-liquid separation, washing, and drying; wherein the H+ concentration of the hydrochloric acid solution is 2-6 mol / L, the soaking is carried out by stirring, the stirring speed is 600-1200 r / min, the soaking temperature is 60-90℃, and the soaking time is 30-120 min.

[0015] Furthermore, in step S2, the ultrasonic power is 500-800W, the ultrasonic time is 8-12h, the stirring speed is 400-1000r / min, and the mass fraction of attapulgite in the attapulgite emulsion is 0.8wt%-1.2wt%.

[0016] Furthermore, in step S3, the mass-to-volume ratio of glucose to attapulgite emulsion is (2-3.6) g: 50 mL; the first hydrothermal reaction temperature is 180-200 °C, and the hydrothermal reaction time is 18-24 h.

[0017] Furthermore, in step S4, the high-temperature carbonization temperature is 700–900℃, the high-temperature carbonization heating rate is 5–10℃ / min, the high-temperature carbonization time is 1–4h, and the high-temperature carbonization atmosphere is an inert gas.

[0018] Further, in step S5, the liquid phase deposition process is as follows: carbon-coated attapulgite, NiCl2·6H2O, Co(NO3)2·6H2O, NH4F and hexamethylenetetramine are dissolved in deionized water, and a mixed suspension is obtained by stirring. The mixed suspension is then subjected to a second hydrothermal synthesis, wherein the second hydrothermal temperature is 120-150℃ and the synthesis time is 6-12h. After the reaction is completed, the pink powder product is collected, washed with deionized water or anhydrous ethanol, and dried to obtain carbon-coated attapulgite@NiCo2(OH)6.

[0019] Furthermore, by weight parts,

[0020] Carbon-coated attapulgite: 0.5–1.5 parts;

[0021] NiCl2·6H2O: 2-4 parts;

[0022] Co(NO3)2·6H2O: 3-6 parts;

[0023] NH4F: 3-6 parts;

[0024] Hexamethylenetetramine: 0.3–0.6 parts;

[0025] Deionized water: 300-500 parts.

[0026] Furthermore, the feature is that in step S6, the annealing temperature is 350-500°C, the annealing heating rate is 1-5°C / min, and the annealing time is 2-4h.

[0027] A second objective of this invention is to provide a heterogeneous composite microwave absorbing material based on attapulgite prepared by the above method.

[0028] A third objective of this invention is to provide the application of the above-mentioned heterogeneous composite absorbing material based on attapulgite in the preparation of electromagnetic radiation protection equipment.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] (1) This invention provides a heterogeneous composite microwave absorbing material based on attapulgite, its preparation method, and its application. This microwave absorbing material utilizes the excellent wave transmission properties of the natural fibrous aluminosilicate mineral attapulgite. The attapulgite is decomposed into an attapulgite emulsion in a deionized water system through acid activation and high-frequency ultrasonic stirring. The well-dispersed attapulgite fibers are uniformly coated with a carbon layer on their surface through hydrothermal stirring and high-temperature carbonization, which can effectively adjust the dielectric constant of the composite material. Simultaneously, the carbon layer on the attapulgite surface has extremely strong electronegativity, which is beneficial for the in-situ growth of uniform, controllable, and consistent magnetic metal materials on its surface. Therefore, carbon-coated attapulgite has significant advantages in constructing a magnetic-dielectric synergistic microwave absorbing system using it as a matrix material.

[0031] (2) This invention constructs a heterogeneous interface by in-situ growing magnetic flower-shaped NiCo2O4 on carbon-coated attapulgite, using carbon-coated attapulgite as the dielectric loss material and magnetic flower-shaped NiCo2O4 as the magnetic loss material. Through the heterogeneous structure design, the carbon layer can suppress the skin effect caused by the cross-linked flower-shaped NiCo2O4, thereby amplifying the magnetic response behavior of NiCo2O4. At the same time, the heterogeneous interface formed between the carbon layer and NiCo2O4 significantly enhances the interfacial polarization, resulting in good impedance matching. In addition, the rich porous structure of the composite material can enhance the multiple reflection loss of electromagnetic waves inside the material. Combined with the strong magnetic loss of magnetic flower-shaped NiCo2O4 and the synergistic effect between multiple loss mechanisms, the electromagnetic wave attenuation capability of the composite material is significantly enhanced, overcoming the impedance mismatch and structural design defects of existing magnetic-dielectric synergistic microwave absorbing materials. Through the heterogeneous structure design, a heterogeneous interface is constructed between the carbon dielectric and the magnetic material. The synergistic effect of the magnetic-dielectric heterogeneous interface can induce dielectric polarization relaxation and magnetic response enhancement, further achieving impedance matching and significantly improving microwave absorption performance.

[0032] (3) The microwave absorbing material provided by the present invention has an effective absorption bandwidth (frequency range with reflection loss less than -10dB) of 3.92GHz in the 218GHz range when the thickness is 2.6mm (better than the effective absorption bandwidth of carbon nanotubes of 3GHz), and reaches a minimum reflection loss value of -51.36dB at 11.6GHz when the thickness is 2.8mm (better than most magnetic-dielectric synergistic microwave absorbing materials). The microwave absorbing material has superior microwave absorption performance.

[0033] (4) The carbon-coated attapulgite@NiCo2O4 heterostructure composite microwave absorbing material provided by the present invention overcomes the defects in impedance mismatch and structural design of existing magnetic-dielectric synergistic microwave absorbing materials, promotes the design of high-performance electromagnetic wave absorbing materials, and is of great significance for realizing electromagnetic interference shielding of high-end electronic devices.

[0034] (5) The raw materials for the preparation of the absorbing material of the present invention are widely available and the preparation method is simple, making it very suitable for industrial production. It can be applied to the field of electromagnetic wave absorption, specifically to the absorption of electromagnetic radiation pollution caused by civilian household devices such as mobile phones, Bluetooth, wireless routers and military equipment such as radar and satellites, as well as the manufacture of personal electromagnetic radiation protection equipment. Attached Figure Description

[0035] Figure 1 The particle size distribution diagram is shown for the attapulgite emulsion prepared in Example 1.

[0036] Figure 2 Scanning electron microscope image of carbon-coated attapulgite prepared in Example 3;

[0037] Figure 3 The XRD pattern of carbon-coated attapulgite@NiCo2O4-2 prepared in Example 7;

[0038] Figure 4 XPS high-resolution spectra of Co 2p, Ni 2p, and O 1s of carbon-coated attapulgite@NiCo2O4-2 prepared in Example 7;

[0039] Figure 5 Scanning electron microscope images of Co 2p, Ni 2p, and O 1s of carbon-coated attapulgite@NiCo2O4-2 prepared in Example 7;

[0040] Figures 6-9 The electromagnetic wave absorption parameters of carbon-coated attapulgite@NiCo2O4-0.5, carbon-coated attapulgite@NiCo2O4-1, carbon-coated attapulgite@NiCo2O4-2 and carbon-coated attapulgite@NiCo2O4-3 prepared in Examples 5, 6, 7 and 8, respectively, were obtained by coaxial method testing.

[0041] Figures 10-13 For carbon-coated attapulgite@NiCo2O4-0.5, carbon-coated attapulgite@NiCo2O4-1, carbon-coated attapulgite@NiCo2O4-2, and carbon-coated attapulgite@NiCo2O4-3 prepared in Examples 5, 6, 7, and 8, respectively, the reflection loss values ​​of the samples were simulated and calculated based on the relative complex permittivity and permeability under different given absorber thicknesses, combined with transmission line theory, and the corresponding three-dimensional surface plots were plotted. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the specific embodiments and accompanying drawings are described in further detail below. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0043] In some embodiments of the present invention, the method for calculating the reflection loss value of the heterogeneous composite microwave absorbing material sample based on attapulgite can be referred to in the literature "Multi-interfacial TiO2 / carbon fibers encapsulated with needle-like FeCo2O4 for excellent microwave absorption" by Chen Li. a Lianwen Deng a Jun He b Sen Peng a,c Shengxiang Huang a Leilei Qiu a,* The URL is https: / / doi.org / 10.1016 / j.apsusc.2023.157417.

[0044] Example 1

[0045] The preparation method of the attapulgite emulsion provided in this embodiment has the following steps:

[0046] Step S1: Weigh 10g of raw attapulgite ore (ATP) and place it in a beaker containing 100mL of 2mol / L hydrochloric acid solution. Place the beaker in an 80℃ constant temperature water bath, stir, sonicate, and acid wash in a water bath for 60min. Then, clean it to neutrality by filtration, dry it, and grind it to obtain acid-activated attapulgite.

[0047] Step S2: Weigh 1.5g of acid-activated attapulgite and 186mL of deionized water into a three-necked flask, and ultrasonically stir for 10h at room temperature using a high-frequency ultrasonic synthesizer. The ultrasonic power is 700W and the stirring rate is 500r / min. After ultrasonic stirring, an attapulgite emulsion with a mass fraction of 0.8wt% is obtained.

[0048] Example 2

[0049] The preparation method of carbon-coated attapulgite provided in this embodiment has the following steps:

[0050] The attapulgite emulsion prepared in Example 1 was used.

[0051] Step S3: Weigh 2.0 g of glucose and 50 mL of attapulgite emulsion with a mass fraction of 0.8 wt% into an 80 mL polytetrafluoroethylene liner, transfer to a hydrothermal stirred reactor and hydrothermally stir at 180 °C for 18 h at a stirring rate of 500 r / min. After the reaction is completed, collect the brown powder product, wash with deionized water or anhydrous ethanol, and dry to obtain carbon precursor-coated attapulgite.

[0052] Step S4: The carbon precursor-coated attapulgite is transferred to a tube furnace and carbonized at 700°C for 2 hours in a nitrogen atmosphere at a heating rate of 5°C / min to obtain carbon-coated attapulgite.

[0053] Example 3

[0054] The preparation method of carbon-coated attapulgite provided in this embodiment has the following steps:

[0055] The attapulgite emulsion prepared in Example 1 was used.

[0056] Step S3: Weigh 2.8g of glucose and 50mL of attapulgite emulsion with a mass fraction of 0.8wt% into an 80mL polytetrafluoroethylene liner, transfer to a hydrothermal stirred reactor and hydrothermally stir at 180℃ for 18h at a stirring rate of 500r / min. After the reaction is completed, collect the brown powder product, wash with deionized water or anhydrous ethanol, and dry to obtain carbon precursor-coated attapulgite.

[0057] Step S4: The carbon precursor-coated attapulgite is transferred to a tube furnace and carbonized at 700°C for 2 hours in a nitrogen atmosphere at a heating rate of 5°C / min to obtain carbon-coated attapulgite.

[0058] Example 4

[0059] The preparation method of carbon-coated attapulgite provided in this embodiment has the following steps:

[0060] The attapulgite emulsion prepared in Example 1 was used.

[0061] Step S3: Weigh 3.6g of glucose and 50mL of attapulgite emulsion with a mass fraction of 0.8wt% into an 80mL polytetrafluoroethylene liner, transfer to a hydrothermal stirred reactor and hydrothermally stir at 180℃ for 18h at a stirring rate of 500r / min. After the reaction is completed, collect the brown powder product, wash with deionized water or anhydrous ethanol, and dry to obtain carbon precursor-coated attapulgite.

[0062] Step S4: The carbon precursor-coated attapulgite is transferred to a tube furnace and carbonized at 700°C for 2 hours in a nitrogen atmosphere at a heating rate of 5°C / min to obtain carbon-coated attapulgite.

[0063] Example 5

[0064] This embodiment provides a method for preparing carbon-coated attapulgite@NiCo2O4-0.5, a heterogeneous composite microwave absorbing material based on attapulgite, with the following steps:

[0065] The carbon-coated attapulgite prepared in Example 3 was used.

[0066] In step S5, 0.24 g NiCl2·6H2O, 0.58 g Co(NO3)2·6H2O, 0.06 g NH4F and hexamethylenetetramine were weighed and dissolved in 50 ml of deionized water. Then, 0.30 g of carbon-coated attapulgite was added and stirred for 1 h. The mixed suspension was then poured into a 100 ml polytetrafluoroethylene liner and transferred to a stainless steel reactor. The reactor was placed in a 120 °C oven for 6 h for hydrothermal synthesis. After the reaction was completed, the pink powder product was collected, washed with deionized water or anhydrous ethanol, and dried.

[0067] Step S6: Place the dried pink powder product in a ceramic crucible, transfer it to a muffle furnace, and anneal it at 350°C for 2 hours with a heating rate of 5°C / min to obtain carbon-coated attapulgite@NiCo2O4-0.5.

[0068] Example 6

[0069] This embodiment provides a method for preparing carbon-coated attapulgite@NiCo2O4-1, a heterogeneous composite microwave absorbing material based on attapulgite, with the following steps:

[0070] The carbon-coated attapulgite prepared in Example 3 was used.

[0071] In step S5, 0.24 g NiCl2·6H2O, 0.58 g Co(NO3)2·6H2O, 0.06 g NH4F and hexamethylenetetramine were weighed and dissolved in 50 ml of deionized water. Then, 0.15 g of carbon-coated attapulgite was added and stirred for 1 h. The mixed suspension was then poured into a 100 ml polytetrafluoroethylene liner and transferred to a stainless steel reactor. The reactor was placed in a 120 °C oven for 6 h for hydrothermal synthesis. After the reaction was completed, the pink powder product was collected, washed with deionized water or anhydrous ethanol, and dried.

[0072] Step S6: Place the dried pink powder product in a ceramic crucible, transfer it to a muffle furnace, and anneal it at 350°C for 2 hours with a heating rate of 5°C / min to obtain carbon-coated attapulgite@NiCo2O4-1.

[0073] Example 7

[0074] This embodiment provides a method for preparing carbon-coated attapulgite@NiCo2O4-2, a heterogeneous composite microwave absorbing material based on attapulgite, with the following steps:

[0075] The carbon-coated attapulgite prepared in Example 3 was used.

[0076] In step S5, 0.24 g NiCl2·6H2O, 0.58 g Co(NO3)2·6H2O, 0.06 g NH4F and hexamethylenetetramine were weighed and dissolved in 50 ml of deionized water. Then, 0.075 g of carbon-coated attapulgite was added and stirred for 1 h. The mixed suspension was then poured into a 100 ml polytetrafluoroethylene liner and transferred to a stainless steel reactor. The reactor was placed in a 120 °C oven for 6 h for hydrothermal synthesis. After the reaction was completed, the pink powder product was collected, washed with deionized water or anhydrous ethanol, and dried.

[0077] Step S6: Place the dried pink powder product in a ceramic crucible, transfer it to a muffle furnace, and anneal it at 350°C for 2 hours with a heating rate of 5°C / min to obtain carbon-coated attapulgite@NiCo2O4-2.

[0078] Example 8

[0079] This embodiment provides a method for preparing carbon-coated attapulgite@NiCo2O4-3, a heterogeneous composite microwave absorbing material based on attapulgite, with the following steps:

[0080] The carbon-coated attapulgite prepared in Example 3 was used.

[0081] In step S5, 0.24 g NiCl2·6H2O, 0.58 g Co(NO3)2·6H2O, 0.06 g NH4F and hexamethylenetetramine were weighed and dissolved in 50 ml of deionized water. Then, 0.05 g of carbon-coated attapulgite was added and stirred for 1 h. The mixed suspension was poured into a 100 ml polytetrafluoroethylene liner and transferred to a stainless steel reactor. The reactor was placed in a 120 °C oven for 6 h for hydrothermal synthesis. After the reaction was completed, the pink powder product was collected, washed with deionized water or anhydrous ethanol, and dried.

[0082] Step S6: Place the dried pink powder product in a ceramic crucible, transfer it to a muffle furnace, and anneal it at 350°C for 2 hours with a heating rate of 5°C / min to obtain carbon-coated attapulgite@NiCo2O4-3.

[0083] like Figure 1 The image shows the particle size distribution of the attapulgite emulsion prepared in Example 1. Figure 1 It can be seen that the particle size distribution of attapulgite in the emulsion formed after acid activation treatment and high-frequency ultrasonic stirring treatment gradually becomes uniform, and the average particle size D 50 At approximately 660 nm, the attapulgite is partially unbound, which helps to coat a uniform carbon layer later.

[0084] like Figure 2 The image shown is a scanning electron microscope image of carbon-coated attapulgite prepared in Example 3. Figure 2 It can be seen that successfully coating the surface of attapulgite fibers with a carbon layer can effectively adjust the dielectric constant of the composite material; at the same time, the carbon layer on the surface of attapulgite has extremely strong electronegativity, which is more conducive to the in-situ growth of uniform, controllable, and consistent magnetic metal oxides on its surface.

[0085] like Figure 3 The image shown is the XRD pattern of carbon-coated attapulgite@NiCo2O4-2 prepared in Example 7. Figure 3 It can be seen that, by comparing with the standard cards of attapulgite (PDF:31-0783) and NiCo2O4 (PDF:20-0781), the diffraction peaks observed in carbon-coated attapulgite@NiCo2O4-2 correspond to the diffraction peaks shown in the NiCo2O4 standard card; at the same time, weak diffraction peaks of attapulgite can also be observed in carbon-coated attapulgite@NiCo2O4-2, indicating that highly crystalline magnetic NiCo2O4 has been successfully grown on carbon-coated attapulgite.

[0086] like Figure 4 The image shows the high-resolution XPS spectra of Co 2p, Ni 2p, and O1s of carbon-coated attapulgite@NiCo2O4-2 prepared in Example 7. Figure 4 As can be seen from the peak fitting, the high-resolution spectrum of Co 2p exhibits two spin orbital doublets (corresponding to Co 2p and Co 2p respectively). 2+ and Co 3+ The characteristic peaks of Ni 2p and two satellite peaks are observed; the high-resolution spectrum of Ni 2p shows two main peaks at ~855.4 eV and ~872.8 eV, belonging to the 2p characteristic peaks and two satellite peaks, respectively. 1 / 2 and 2p 2 / 3 The electronic configurations of the O 1s electrons are all accompanied by a satellite peak; the characteristic peaks at 529.3, 531.5, and 532.9 eV in the high-resolution spectrum of O 1s correspond to metal-oxygen bonds, defect oxygen, and adsorbed oxygen, respectively. This indicates that magnetic NiCo2O4 was successfully grown on carbon-coated attapulgite, and that NiCo2O4 coexists as a mixed phase, with the atomic ratio of CoII to CoIII being 32.0:40.5, in the Co 2p phase. 3 / 2 The ratio of CoII to CoIII atoms in the peak is 28.7:23.7, which is significant in Co 2p. 1 / 2 The atomic ratio of CoII to CoIII in the peak is 3.3:16.8, and the content ratio of O1, O2 and O3 is 16.9:63.1:19.9.

[0087] like Figure 5 The image shown is a scanning electron microscope image of carbon-coated attapulgite@NiCo2O4-2 prepared in Example 7. Figure 5 It is evident that magnetic NiCo2O4 grows in a flower-like pattern along the surface of carbon-coated attapulgite fibers. This flower-like NiCo2O4 exhibits good magnetic loss characteristics. Furthermore, the heterogeneous interface formed between it and the carbon layer significantly enhances interfacial polarization, resulting in excellent impedance matching. In addition, the pronounced porous structure of carbon-coated attapulgite@NiCo2O4 enhances multiple reflections of electromagnetic waves within the composite material, contributing to improved electromagnetic wave absorption performance.

[0088] like Figure 6 , 7 Figures 8 and 9 show the electromagnetic wave absorption parameters obtained by coaxial method for carbon-coated attapulgite@NiCo2O4-0.5, carbon-coated attapulgite@NiCo2O4-1, carbon-coated attapulgite@NiCo2O4-2, and carbon-coated attapulgite@NiCo2O4-3 prepared in Examples 5, 6, 7, and 8, respectively. As can be seen from the figures, the relative permittivity of the composite absorbing material gradually increases with the increase of the flower-like NiCo2O4 content, especially the imaginary part (ε”) of the permittivity. This indicates that the heterogeneous interface between the magnetic NiCo2O4 and the carbon layer gradually satisfies the interface impedance matching, which is beneficial for enhancing the effective absorption bandwidth.

[0089] like Figure 10 ,11 As shown in Figures 12 and 13, carbon-coated attapulgite@NiCo2O4-0.5, carbon-coated attapulgite@NiCo2O4-1, carbon-coated attapulgite@NiCo2O4-2, and carbon-coated attapulgite@NiCo2O4-3 prepared in Examples 5, 6, 7, and 8, respectively, had their reflection loss values ​​simulated and calculated based on the relative complex permittivity and permeability under different given absorber thicknesses, combined with transmission line theory. The corresponding three-dimensional surface plots were then plotted. As shown in the figure, with the increase of the content of flower-like NiCo2O4, carbon-coated attapulgite@NiCo2O4-2 achieves the best absorption performance in the 2-18 GHz range. When the thickness is 2.6 mm, the effective absorption bandwidth (frequency range with reflection loss less than -10 dB) can reach 3.92 GHz (superior to the effective absorption bandwidth of carbon nanotubes 3 GHz), and when the thickness is 2.8 mm, the minimum reflection loss value of -51.36 dB is reached at 11.6 GHz (superior to most magnetic-dielectric synergistic absorbing materials). The absorption performance of carbon-coated attapulgite@NiCo2O4-3 in the 2-18 GHz range is as follows: when the thickness is 2.7 mm, the effective absorption bandwidth (frequency range with reflection loss less than -10 dB) can reach 3.28 GHz (superior to the effective absorption bandwidth of carbon nanotubes 3 GHz), and when the thickness is 2.7 mm, the minimum reflection loss value of -46.60 dB is reached at 10.3 GHz. The introduction of attapulgite and the design of the magnetic-dielectric heterostructure adjust the complex permittivity of the composite material to a suitable range, ensuring impedance matching of the material. At the same time, the synergistic effect of multiple loss mechanisms gives the composite material superior microwave absorption performance, meeting the requirements of microwave absorbing materials such as "thin, light, wide, and strong".

[0090] For any points not covered above, existing technologies shall apply.

[0091] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a heterogeneous composite wave-absorbing material based on attapulgite, characterized in that, The method comprises the following specific steps: S1, soaking attapulgite ore with hydrochloric acid and obtaining acid-activated attapulgite through heat activation; S2, mixing the acid-activated attapulgite obtained in step S1 with deionized water, and obtaining uniform and highly dispersed attapulgite emulsion through high-frequency ultrasonic stirring; S3, adding glucose into the attapulgite emulsion obtained in step S2, coating carbon precursor on the surface of attapulgite through first hydrothermal stirring reaction, collecting brown powder product after the reaction, washing with deionized water or anhydrous ethanol, and drying to obtain attapulgite coated with carbon precursor; S4, converting the attapulgite coated with carbon precursor into carbon-coated attapulgite through high-temperature carbonization; S5, growing precursor NiCo2(OH)6 on the carbon-coated attapulgite in situ through liquid deposition to obtain carbon-coated attapulgite@NiCo2(OH)6; S6, annealing the carbon-coated attapulgite@NiCo2(OH)6 in an air atmosphere at high temperature to obtain a carbon-coated attapulgite@NiCo2O4 wave-absorbing material.

2. The production method according to claim 1, wherein In step S1, the attapulgite ore has a grade greater than 80% and a particle size less than 200 mesh; the hydrochloric acid soaking and heat activation process comprises: hydrochloric acid soaking, solid-liquid separation, washing, and drying; wherein the H + The concentration of the hydrochloric acid is 2-6 mol / L, the soaking is carried out in stirring, the stirring speed is 600-1200 r / min, the soaking temperature is 60-90 DEG C, and the soaking time is 30-120 min.

3. The production method according to claim 1, wherein In step S2, the ultrasonic power is 500-800 W, the ultrasonic time is 8-12 h, the stirring speed is 400-1000 r / min, and the mass fraction of attapulgite in the attapulgite emulsion is 0.8 wt%-1.2 wt%.

4. The production method according to claim 1, wherein In step S3, the mass-volume ratio of glucose to attapulgite emulsion is (2-3.6) g:50 mL, the first hydrothermal stirring reaction temperature is 180-200 ℃, and the first hydrothermal stirring reaction time is 18-24 h.

5. The production method according to claim 1, characterized by, In step S4, the high-temperature carbonization temperature is 700-900 ℃, the high-temperature carbonization heating rate is 5-10 ℃ / min, the high-temperature carbonization time is 1-4 h, and the high-temperature carbonization atmosphere is inert gas.

6. The production method according to claim 1, wherein In step S5, the liquid deposition process is as follows: carbon-coated attapulgite, NiCl2·6H2O, Co(NO3)2·6H2O, NH4F and hexamethyleneimine are dissolved in deionized water to obtain a mixed suspension through stirring, and the mixed suspension is subjected to second hydrothermal synthesis at a second hydrothermal temperature of 120-150 ℃ for 6-12 h; after the reaction, the pink powder product is collected, washed with deionized water or anhydrous ethanol, and dried to obtain carbon-coated attapulgite@NiCo2(OH)6.

7. The production method according to claim 6, wherein According to weight fractions, Carbon-coated attapulgite: 0.5-1.5 parts; NiCl2·6H2O: 2-4 parts; Co(NO3)2·6H2O: 3-6 parts; NH4F: 3-6 parts; Hexamethyleneimine: 0.3-0.6 parts; Deionized water: 300-500 parts.

8. The production method according to claim 1, wherein In step S6, the annealing temperature is 350-500 ℃, the annealing heating rate is 1-5 ℃ / min, and the annealing time is 2-4 h.

9. A hetero-composite wave-absorbing material based on attapulgite prepared by the method of any one of claims 1-8.

10. Use of the hetero-composite wave-absorbing material based on attapulgite of claim 9 in the preparation of electromagnetic radiation protection equipment.

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