Two-dimensional silicon dioxide nanosheet loaded metal wave-absorbing material and preparation method thereof

Abstract

The invention relates to the technical field of electromagnetic wave-absorbing materials, in particular to a two-dimensional silicon dioxide nanosheet loaded metal wave-absorbing material and a preparation method thereof. The specific preparation method comprises the following steps: stirring and mixing silicide and a metal chlorine salt-ethanol solution, and adjusting the topological stripping process of the silicide by using metal chlorine salt to obtain a two-dimensional silicon dioxide nanosheet mixture; and calcining at 400-1000 DEG C, and reducing at 800-1200 DEG C in a reducing atmosphere, so that nano metal particles with a single domain size are uniformly dispersed on the two-dimensional silicon dioxide nanosheet to form a heterostructure, and the two-dimensional silicon dioxide nanosheet loaded metal wave-absorbing material is prepared. According to the invention, the problem of low electromagnetic absorption performance caused by non-uniform dispersion, ex-situ and uncontrollable size of the nano-particles on the two-dimensional material when the two-dimensional material is compounded with the nano-particles in the existing method is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorbing materials, and particularly to a two-dimensional silica nanosheet supported metal wave absorbing material and a preparation method thereof. Background Art

[0002] With the rapid development of modern electronic technology and advanced detection systems, the ability of detectors to explore and track targets has been greatly expanded, resulting in an increasingly serious threat to weapons and equipment in military competition. In order to improve the attack ability, defense ability and survival ability of weapons, enhance their combat effectiveness, and make them difficult to be detected, identified, tracked and attacked by the enemy, stealth technology is very important. Stealth technology refers to using special external structures or surface coatings to reduce the detectable signal characteristics of targets, rendering the enemy's detection systems ineffective. In stealth technology, radar stealth has attracted much attention due to its dominant position in detection technology. Radar stealth technology mainly reduces the radar cross section of targets, making it difficult for them to be detected and tracked by radar detection systems. To achieve this goal, scientists have been continuously exploring various new materials and technologies to improve the stealth performance of weapons and equipment.

[0003] In recent years, two-dimensional materials have shown great application potential in the field of electromagnetic absorption materials due to their high specific surface area, large number of surface-exposed atoms, and excellent mechanical, optical and electronic properties. Among them, silica, as a widely used electromagnetic wave transmission material, has excellent thermal stability, corrosion resistance and cost-effectiveness, making it an ideal choice for preparing electromagnetic absorption materials. By combining nanoparticles with silica, the incident electromagnetic waves can be maximally penetrated to improve the electromagnetic absorption performance of the materials, and the stealth performance of the materials can be improved by improving the impedance matching.

[0004] However, in practical applications, the combination of nanoparticles and silica is still a challenging technical problem. At present, methods for combining nanoparticles with silica, such as sol-gel method, precipitation method, etc., although can achieve the combination of nanoparticles and silica, often have problems of uneven particle size and poor dispersion. The resulting uneven dispersion state will seriously affect the performance of electromagnetic absorption materials. Specifically, the aggregation and uneven distribution of nanoparticles will lead to enhanced scattering and reflection of electromagnetic waves, thereby reducing the electromagnetic absorption efficiency of the materials. In addition, the above methods may also introduce impurities, further affecting the performance of electromagnetic absorption materials. Summary of the Invention

[0005] In order to solve the problems that the combination of current nanoparticles and silica has uneven particle size and poor dispersion, and the resulting uneven dispersion state will seriously affect the performance of electromagnetic absorption materials, the purpose of the present invention is to provide a two-dimensional silica nanosheet supported metal wave absorbing material and a preparation method thereof.

[0006] To achieve the above object, the technical solution of the present invention is as follows.

[0007] The first aspect of the present invention provides a preparation method of a two-dimensional silica nanosheet-supported metal wave-absorbing material, comprising the following steps:

[0008] Stir and mix a silicide with a metal chloride-ethanol solution, and use the metal chloride to regulate the topological exfoliation process of the silicide to obtain a two-dimensional silica nanosheet mixture; then calcine at 400 °C to 1000 °C, and then reduce at 800 °C to 1200 °C in a reducing atmosphere, so that nano-metal particles with single-domain size are uniformly dispersed on the two-dimensional silica nanosheets to form a heterostructure, thereby obtaining a two-dimensional silica nanosheet-supported metal wave-absorbing material.

[0009] The present invention mainly uses metal chloride to regulate the topological exfoliation process of silicide to form two-dimensional nanosheet materials. At the same time, through high-temperature reduction treatment, metal particles grow in-situ on the two-dimensional nanosheet materials, and finally obtain two-dimensional SiO 2 A heterostructure loaded with uniformly dispersed and nano-sized particles, which solves the problem that the existing method of compounding two-dimensional materials with nanoparticles has uneven dispersion, non-in-situ growth, and uncontrollable size of nanoparticles on two-dimensional materials, resulting in low electromagnetic absorption performance.

[0010] In the present invention, the reduction temperature is 800 °C to 1200 °C. Excessively high reduction temperature will cause agglomeration and even sintering; while too low reduction temperature will have more impurities and incomplete reduction.

[0011] Preferably, the size of the nano-metal particles is 10 nm to 20 nm; the size of the two-dimensional silica nanosheets is 1 μm to 50 μm, and the thickness is 20 nm to 200 nm.

[0012] Preferably, the metal chloride is at least one of cobalt chloride, iron chloride, nickel chloride, chromium chloride, and copper chloride.

[0013] Based on the confinement strategy, the present invention uses metal chloride. On the one hand, it is used to regulate the intercalation and exfoliation process of silicide. On the other hand, through high-temperature reduction treatment and temperature adjustment, metal ions are transformed into nano-metal particles with single-domain size and grow in-situ on two-dimensional nanosheet materials. Thus, the formed two-dimensional SiO 2 A heterostructure loaded with uniformly dispersed and nano-sized particles can effectively regulate electromagnetic parameters and obtain excellent electromagnetic absorption performance.

[0014] Metal nanoparticles, such as Fe, Co, Ni, Cu, etc., have good conductivity and nano-size effect, and can provide high-efficiency conductance loss and magnetic loss.

[0015] Preferably, the silicide is at least one of calcium silicide, magnesium silicide, iron silicide, copper silicide, and chromium silicide.

[0016] In the present invention, the silicide is mainly used as a raw material for forming two-dimensional silica nanosheets. The topological exfoliation process of the silicide is regulated by a metal chloride salt to form two-dimensional silica nanosheets. Due to the significant advantages of two-dimensional silica nanosheets, such as fully exposed active sites, a high specific surface area, a large number of surface-exposed atoms, excellent mechanical and electronic properties, etc., the electromagnetic parameters can be effectively regulated, and excellent electromagnetic absorption performance can be obtained.

[0017] Preferably, the mass ratio of the silicide to the metal chloride salt is 1:0.1 - 3.0.

[0018] In the present invention, as the content of the metal chloride salt increases, the doped metal particles increase, the conductivity increases, and the dielectric constant increases; when the content of the metal chloride salt is too low, the doping amount is too small, and the influence on the conductivity and dielectric parameters is very small; when the content of the metal chloride salt is too high, agglomeration is likely to occur, as well as excessive conductivity.

[0019] Preferably, the reducing atmosphere is a reducing gas or a mixture of a reducing gas and a protective gas; the reducing gas is hydrogen or carbon monoxide gas; the protective gas is nitrogen or argon gas.

[0020] Preferably, in the metal chloride-ethanol solution, the dosage ratio of the metal chloride salt to ethanol is 0.25 g - 6 g:100 mL.

[0021] Preferably, the temperature of the stirring and mixing is 50°C - 90°C. The time of the stirring and mixing is 2 h - 10 h.

[0022] In the present invention, as the temperature of the stirring and mixing increases, the dissolution rate accelerates, and the stirring time can be correspondingly shortened; when the temperature exceeds 90°C, the temperature is too high, which is likely to cause uneven reactions; when the temperature exceeds 100°C, it will boil directly; when the temperature is too low, the dissolution is too slow, and there will be precipitates.

[0023] Preferably, after the stirring and mixing, it further includes washing with ethanol and water, centrifuging, collecting the centrifuged precipitate, and drying to obtain a two-dimensional silica nanosheet mixture.

[0024] Preferably, the number of washing times is 1 - 5 times; the rotation speed of centrifugation is 5000 - 10000 revolutions per minute, and the time of centrifugation is 5 - 30 minutes.

[0025] Preferably, the drying temperature is 50°C - 100°C, and the drying time is 12 h - 24 h.

[0026] The second aspect of the present invention provides a two-dimensional silica nanosheet-supported metal wave-absorbing material prepared by the preparation method described in the first aspect.

[0027] Advantages of the present invention:

[0028] 1. The present invention mainly uses metal chlorides to regulate the topological exfoliation process of silicides to form two-dimensional nanosheet materials. At the same time, through high-temperature reduction treatment, metal particles are in-situ grown on the two-dimensional nanosheet materials, and finally two-dimensional SiO 2 heterostructures loaded with uniformly dispersed and nano-sized particles are obtained, solving the problem that the existing method of compounding silica with nanoparticles has uneven dispersion of nanoparticles on silica, resulting in low electromagnetic absorption performance.

[0029] 2. Thanks to the magnetic-dielectric synergistic effect and the regulation of the particle size of nano-metal particles at different temperatures, the absorption intensity and absorption bandwidth can be effectively improved. The two-dimensional silica nanosheet-supported metal wave-absorbing material prepared by the present invention has excellent electromagnetic properties, with a maximum absorption intensity of -51.6 dB and an effective absorption width of 4.6 GHz. Description of the Drawings

[0030] Figure 1 is the morphology diagram of the two-dimensional silica nanosheet-supported nano-cobalt composite material prepared in Example 1.

[0031] Figure 2 is the morphology diagram of the two-dimensional silica nanosheet-supported nano-cobalt composite material prepared in Example 2.

[0032] Figure 3 is the X-ray diffraction pattern of the two-dimensional silica nanosheet-supported nano-cobalt composite materials prepared in Examples 2 to 4.

[0033] Figure 4 is the TEM electron micrograph of the two-dimensional silica nanosheet-supported nano-cobalt composite material prepared in Example 1.

[0034] Figure 5 is the electromagnetic absorption performance diagram of the two-dimensional silica nanosheet-supported nano-cobalt composite materials with different thicknesses. Detailed Embodiments

[0035] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further describes the present invention in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] As a widely used electromagnetic wave transmission material, silica has excellent thermal stability, corrosion resistance and cost-effectiveness. It can maximize the penetration of incident electromagnetic waves and improve the stealth performance of materials by improving impedance matching. However, how to combine nanoparticles with silica and achieve uniform dispersion of nanoparticles on silica to improve the electromagnetic absorption performance of materials is an important direction in the current research of stealth materials.

[0038] When designing efficient electromagnetic absorption materials, the spatial confinement strategy is an efficient and promising method, which lays the foundation for the development of advanced electromagnetic absorption materials. By regulating the growth of nanoparticles in a limited space, it is possible to rationally adjust the particle size and optimize the configuration at the atomic level, thereby endowing the material with physicochemical properties including electron transfer ability and atomic configuration in the limited space. These properties are significantly different from those in bulk materials, providing new ideas for the development of high-performance electromagnetic absorption materials.

[0039] The present invention proposes a novel confinement strategy to develop a two-dimensional nano-metal / silica heterostructure, in which the in-situ grown metal particles have nano-sizes, which helps to enhance the electromagnetic loss through strong surface anisotropy. This advanced wave-absorbing material with remarkable electromagnetic absorption ability and broadband width provides a general strategy for the synthesis of other two-dimensional composites with controllable structures.

[0040] A preparation method of a two-dimensional silica nanosheet-supported nano-cobalt composite material includes the following steps:

[0041] Step 1: Dissolve metal chloride in ethanol and form a metal chloride-ethanol solution after magnetic stirring for a period of time. The metal chloride is at least one of cobalt chloride, iron chloride, nickel chloride, chromium chloride and copper chloride. The dosage ratio of the metal chloride to ethanol is 0.25 g to 6 g: 100 mL, and the stirring time is 0.5 h to 2 h.

[0042] Step 2: Add a silicide raw material to the above solution, fully stir and mix at a certain temperature, rinse several times with ethanol and ultrapure water, and then centrifuge to collect the obtained mixture. The silicide is at least one of calcium silicide, magnesium silicide, iron silicide, copper silicide and chromium silicide. The mass ratio of the silicide to the metal chloride is 1: 0.1 to 3. The reaction temperature is 50 °C to 90 °C, the stirring time is 2 h to 10 h, the centrifugation time is 5 min to 30 min, and the rotation speed is 5000 rpm to 10000 rpm.

[0043] Step 3: Dry the product obtained in Step 2 under vacuum to obtain two-dimensional silicon nanosheets. The drying temperature is 50 °C to 100 °C, and the drying time is 12 h to 24 h.

[0044] Step 4: Calcinate the dried powder obtained in Step 3 in air at different temperatures, and finally reduce it in a high-temperature reducing atmosphere to obtain the final product of metal particles supported on two-dimensional silica nanosheets. The calcination temperature is 400°C to 1000°C, and the calcination time is 2h to 8h. The high-temperature reduction temperature is 800°C to 1200°C, and the reduction time is 1h to 5h. The reducing gas is high-purity H 2 , CO, N 2 / H 2 , Ar / H 2 , and CO / N 2 any one of them.

[0045] The technical solutions of the present invention will be further described below through specific examples.

[0046] In the following examples, unless otherwise specified, the methods are all conventional methods; the reagents and materials, unless otherwise specified, can all be purchased on the market.

[0047] Example 1

[0048] A preparation method of a two-dimensional silica nanosheet-supported nano-cobalt composite material, comprising the following steps:

[0049] Step 1, dissolve 0.5 g of CoCl 2 in 50 mL of ethanol, and after magnetic stirring for 0.5 hour, obtain an ethanol solution of CoCl 2 .

[0050] Step 2, add 1.2 g of CaSi 2 to the ethanol solution of CoCl 2 , stir well at 70°C for 5 hours, rinse three times with ethanol and ultrapure water respectively, then centrifuge for 5 minutes at a rotation speed of 8000 revolutions per minute, collect the obtained precipitate, and dry it in vacuum at 80°C for 12 hours to obtain two-dimensional silicon composite nanosheet powder.

[0051] Step 3, calcinate the two-dimensional silicon composite nanosheet powder obtained in S2 in air at 600°C for 2 hours, and finally reduce it in an N 2 / H 2 atmosphere at 800°C for 3 hours, where the hydrogen flow rate is 60 mL / min and the nitrogen flow rate is 240 mL / min, to obtain a two-dimensional silica nanosheet-supported nano-cobalt composite material.

[0052] Example 2

[0053] A preparation method of a two-dimensional silica nanosheet-supported nano-cobalt composite material, which is different from Example 1 in that the calcination temperature is 950°C. The specific method includes the following steps:

[0054] Step 1, Dissolve 0.5 g of CoCl 2 in 50 mL of ethanol. After magnetic stirring for 0.5 hours, an ethanol solution of CoCl 2 is obtained.

[0055] Step 2, Add 1.2 g of CaSi 2 to the ethanol solution of CoCl 2 . Stir well at 70 °C for 5 hours, rinse three times with ethanol and ultrapure water respectively, then centrifuge for 5 minutes at a speed of 8000 revolutions per minute. Collect the obtained precipitate and dry it under vacuum at 80 °C for 12 hours to obtain two-dimensional silicon composite nanosheet powder.

[0056] Step 3, Calcinate the two-dimensional silicon composite nanosheet powder obtained in S2 in air at 950 °C for 2 hours, and finally reduce it in an N 2 / H 2 atmosphere at 800 °C for 3 hours, where the hydrogen flow rate is 60 mL / min and the nitrogen flow rate is 240 mL / min, to obtain a two-dimensional silica nanosheet-supported cobalt nanocomposite.

[0057] Example 3

[0058] A method for preparing a two-dimensional silica nanosheet-supported cobalt nanocomposite, which is different from Example 1 in that the calcination temperature is 800 °C. The specific method includes the following steps:

[0059] Step 1, Dissolve 0.5 g of CoCl 2 in 50 mL of ethanol. After magnetic stirring for 0.5 hours, an ethanol solution of CoCl 2 is obtained.

[0060] Step 2, Add 1.2 g of CaSi 2 to the ethanol solution of CoCl 2 . Stir well at 70 °C for 5 hours, rinse three times with ethanol and ultrapure water respectively, then centrifuge for 5 minutes at a speed of 8000 revolutions per minute. Collect the obtained precipitate and dry it under vacuum at 80 °C for 12 hours to obtain two-dimensional silicon composite nanosheet powder.

[0061] Step 3, Calcinate the two-dimensional silicon composite nanosheet powder obtained in S2 in air at 800 °C for 2 hours, and finally reduce it in an N 2 / H 2 atmosphere at 800 °C for 3 hours, where the hydrogen flow rate is 60 mL / min and the nitrogen flow rate is 240 mL / min, to obtain a two-dimensional silica nanosheet-supported cobalt nanocomposite.

[0062] Example 4

[0063] A preparation method of a two-dimensional silica nanosheet-supported nano-cobalt composite material, which is different from Example 1 in that the calcination temperature is 400 °C. The specific method includes the following steps:

[0064] Step 1, dissolve 0.5 g of CoCl 2 in 50 mL of ethanol, and after magnetic stirring for 0.5 hours, obtain an ethanol solution of CoCl 2 .

[0065] Step 2, add 1.2 g of CaSi 2 to the ethanol solution of CoCl 2 , stir well at 70 °C for 5 hours, wash three times with ethanol and ultrapure water respectively, then centrifuge for 5 minutes at a rotation speed of 8000 revolutions per minute, collect the obtained precipitate, and dry it in vacuo at 80 °C for 12 hours to obtain two-dimensional silicon composite nanosheet powder.

[0066] Step 3, calcine the two-dimensional silicon composite nanosheet powder obtained in S2 in air at 400 °C for 2 hours, and finally reduce it in an N 2 / H 2 atmosphere at 800 °C for 3 hours, where the hydrogen flow rate is 60 mL / min and the nitrogen flow rate is 240 mL / min, to obtain a two-dimensional silica nanosheet-supported nano-cobalt composite material.

[0067] Example 5

[0068] A preparation method of a two-dimensional silica nanosheet-supported nano-cobalt composite material, which is different from Example 1 in that the calcination temperature is 1000 °C. The specific method includes the following steps:

[0069] Step 1, dissolve 0.5 g of CoCl 2 in 50 mL of ethanol, and after magnetic stirring for 0.5 hours, obtain an ethanol solution of CoCl 2 .

[0070] Step 2, add 1.2 g of CaSi 2 to the ethanol solution of CoCl 2 , stir well at 70 °C for 5 hours, wash three times with ethanol and ultrapure water respectively, then centrifuge for 5 minutes at a rotation speed of 8000 revolutions per minute, collect the obtained precipitate, and dry it in vacuo at 80 °C for 12 hours to obtain two-dimensional silicon composite nanosheet powder.

[0071] Step 3, calcine the two-dimensional silicon composite nanosheet powder obtained in S2 in air at 1000 °C for 2 hours, and finally reduce it in an N 2 / H 2Reduce in the atmosphere for 3 hours, with a hydrogen flow rate of 60 mL / min and a nitrogen flow rate of 240 mL / min, to obtain a two-dimensional silica nanosheet-supported nano-cobalt composite material.

[0072] Example 6

[0073] A method for preparing a two-dimensional silica nanosheet-supported nano-cobalt composite material, comprising the following steps:

[0074] Step 1, dissolve 0.12 g of CoCl 2 in 50 mL of ethanol, and after magnetic stirring for 0.5 hour, obtain an ethanol solution of CoCl 2 .

[0075] Step 2, add 1.2 g of CaSi 2 to the ethanol solution of CoCl 2 to make the mass ratio of the silicide to the metal chloride salt 1:0.1. Stir well at 50 °C for 10 hours, rinse three times with ethanol and ultrapure water respectively, then centrifuge for 30 minutes at a rotation speed of 5000 revolutions per minute, collect the obtained precipitate, and dry it in vacuum at 100 °C for 12 hours to obtain two-dimensional silicon composite nanosheet powder.

[0076] Step 3, calcine the two-dimensional silicon composite nanosheet powder obtained in S2 in air at 600 °C for 2 hours, and finally reduce it in an N 2 / H 2 atmosphere for 1 hour, with a hydrogen flow rate of 60 mL / min and a nitrogen flow rate of 240 mL / min, to obtain a two-dimensional silica nanosheet-supported nano-cobalt composite material.

[0077] Example 7

[0078] A method for preparing a two-dimensional silica nanosheet-supported nano-cobalt composite material, comprising the following steps:

[0079] Step 1, dissolve 3.6 g of CoCl 2 in 50 mL of ethanol, and after magnetic stirring for 0.5 hour, obtain an ethanol solution of CoCl 2 .

[0080] Step 2, add 1.2 g of CaSi 2 to the ethanol solution of CoCl 2 to make the mass ratio of the silicide to the metal chloride salt 1:3. Stir well at 90 °C for 2 hours, rinse three times with ethanol and ultrapure water respectively, then centrifuge for 20 minutes at a rotation speed of 10000 revolutions per minute, collect the obtained precipitate, and dry it in vacuum at 50 °C for 24 hours to obtain two-dimensional silicon composite nanosheet powder.

[0081] Step 3: The two-dimensional silicon composite nanosheet powder obtained in S2 is calcined in air at 800 °C for 2 hours, and finally reduced in an N 2 / H 2 atmosphere at 800 °C for 5 hours, where the hydrogen flow rate is 60 mL / min and the nitrogen flow rate is 240 mL / min, to obtain a two-dimensional silica nanosheet-supported cobalt nanocomposite material.

[0082] The two-dimensional silica nanosheet-supported cobalt nanocomposite material prepared in the above examples is tested and analyzed.

[0083] Test 1: Morphology analysis and transmission electron microscopy analysis.

[0084] The morphology of the two-dimensional silica nanosheet-supported cobalt nanocomposite materials prepared in Examples 1 to 5 is analyzed, and some morphology diagrams are as shown in Figure 1 and Figure 2 shown.

[0085] It can be seen from the morphology diagrams that the silica carrier presents an obvious two-dimensional nanosheet structure, and cobalt nanoparticles are loaded on the surface.

[0086] The two-dimensional silica nanosheet-supported cobalt nanocomposite materials prepared in Examples 1 to 5 are analyzed by transmission electron microscopy, and some TEM electron micrographs are as shown in Figure 4 shown. The full English name of transmission electron microscope is Transmission Electron Microscope, abbreviated as TEM.

[0087] Table 1 Influence of different calcination temperatures

[0088]

[0089] It can be seen from Table 1 combined with Figure 1 , Figure 2 and Figure 4 that uniformly distributed cobalt nanoparticles are loaded on the surface of the two-dimensional silica nanosheets, and the particle size range of the cobalt nanoparticles is 10 nm to 20 nm. The size range of the two-dimensional silica nanosheets is 1 μm to 50 μm, and the thickness is 20 nm to 200 nm. And with the increase of the calcination temperature, the size of the metal nanoparticles will gradually increase and the agglomeration will also increase.

[0090] Test 2: X-ray diffraction analysis.

[0091] The two-dimensional silica nanosheet-supported cobalt nanocomposite materials prepared in Examples 1 to 5 are analyzed by X-ray diffraction. Some results are as shown in Figure 3 shown. Among them, Co-2DSiO 2 (950 °C), Co-2DSiO 2(800 °C), Co-2DSiO 2 (400 °C) are the two-dimensional silica nanosheet-supported nano-cobalt composites prepared in Example 2, Example 3, and Example 4 respectively. Co-2DSiO 2 is the powder of two-dimensional silicon composite nanosheets before calcination. Si: PDF#75-0589; SiO 2 : PDF#46-1045; Co (Hexagonal): PDF#89-4308; Co (Cubic): PDF#15-0806 are the standard X-ray diffraction patterns of Si, SiO 2 , Co (hexagonal crystal system), and Co (cubic crystal system) respectively.

[0092] It can be analyzed from the X-ray diffraction pattern that the two-dimensional silica nanosheet-supported nano-cobalt composite mainly contains silica and elemental cobalt after annealing at different temperatures. And with the increase of the annealing temperature, the crystal form of elemental cobalt becomes stronger, and at the same time, silica appears, which is caused by the oxidation of Si at high temperature.

[0093] Test 3: Analysis of electromagnetic absorption performance.

[0094] The electromagnetic absorption performance of the two-dimensional silica nanosheet-supported nano-cobalt composites prepared at different calcination temperatures was analyzed, and the results are shown in Table 2. The test was carried out at a thickness of 2.5 mm.

[0095] Table 2 Influence of calcination temperature on electromagnetic absorption performance

[0096] Calcination temperature Maximum absorption intensity Effective absorption width 600℃ -45.2 dB 3.2 GHz 950℃ -32.5 dB 1.6 GHz 800℃ -42.3 dB 4.2 GHz 400℃ -51.6 dB 4.6 GHz 1000℃ -35.3 dB 2.6 GHz

[0097] As shown in the results of Table 2, when the calcination temperature is between 400 °C and 800 °C, the maximum absorption intensity reaches -42.3 dB to -51.6 dB, and at the calcination temperature of 400 °C, the two-dimensional silica nanosheet-supported nano-cobalt composite has the strongest electromagnetic absorption ability. With the further increase of the calcination temperature, the maximum absorption intensity further decreases to -32.5 dB and -35.3 dB, indicating that too high a calcination temperature may lead to a weakening of the electromagnetic absorption ability of the material.

[0098] When the calcination temperature is between 400 °C and 800 °C, the effective absorption width reaches 3.2 GHz to 4.6 GHz, and at the calcination temperature of 400 °C, the two-dimensional silica nanosheet-supported nano-cobalt composite has the widest electromagnetic absorption frequency range. When the calcination temperature continues to rise to 950 °C and 1000 °C, the effective absorption width further decreases to 1.6 GHz and 2.6 GHz, indicating that too high a calcination temperature may lead to a narrowing of the electromagnetic absorption frequency range of the material.

[0099] The electromagnetic absorption properties of the two-dimensional silica nanosheet-supported cobalt nanocomposites with different thicknesses were analyzed, and the results are as Figure 5 shown in Table 3.

[0100] Table 3 Influence of thickness on electromagnetic absorption properties

[0101] Thickness Maximum absorption intensity Effective absorption width 1.0 mm -5.2 dB 0 1.5 mm -9.3 dB 0 2.0 mm -17.3 dB 2.4 GHz 2.5 mm -51.6 dB 4.6 GHz 3.0 mm -24.5 dB 5.3 GHz 3.5 mm -17.8 dB 5.1 GHz 4.0 mm -14.5 dB 4.7 GHz 4.5 mm -12.3 dB 1.4 GHz

[0102] As Figure 5 shown, the maximum absorption intensity of the two-dimensional silica nanosheet-supported cobalt nanocomposites is -51.6 dB, the effective absorption width is 4.6 GHz, and the optimal matching thickness is 2.5 mm, showing excellent electromagnetic absorption properties.

[0103] In summary, the above analysis shows that the heterostructure of the two-dimensional silica nanosheet-supported cobalt nanocomposites prepared in the embodiments of the present invention can effectively construct a magnetoelectric synergy system, promote polarization loss and conductance loss, etc., and effectively improve the absorption intensity and absorption bandwidth.

[0104] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a two-dimensional silica nanosheet loaded with a metal absorbing material, characterized in that: The following steps are involved: The silicide is stirred and mixed with a metal chloride-ethanol solution, and the topological exfoliation process of the silicide is regulated by the metal chloride to obtain a two-dimensional silica nanosheet mixture; it is then calcined at 400°C to 1000°C, and then reduced at 800°C to 1200°C in a reducing atmosphere so that single-domain-sized nanometal particles are uniformly dispersed on the two-dimensional silica nanosheet to form a heterogeneous structure, thereby obtaining a two-dimensional silica nanosheet-loaded metal absorbing material.

2. The method for preparing the two-dimensional silica nanosheet-loaded metal absorbing material according to claim 1, characterized in that: The size of the nano metal particles is 10nm to 20nm; The size of the two-dimensional silicon dioxide nanosheet is 1 μm to 50 μm, and the thickness is 20 nm to 200 nm.

3. The method for preparing the two-dimensional silica nanosheet-loaded metal absorbing material according to claim 1, characterized in that: The metal chloride salt is at least one of cobalt chloride, ferric chloride, nickel chloride, chromium chloride and cupric chloride.

4. The method for preparing the two-dimensional silica nanosheet-loaded metal absorbing material according to claim 1, characterized in that: The silicide is at least one of calcium silicide, magnesium silicide, iron silicide, copper silicide and chromium silicide.

5. The method for preparing the two-dimensional silica nanosheet-loaded metal absorbing material according to claim 1, characterized in that: The mass ratio of silicide to metal chloride is 1:0.1-3.

0.

6. The method for preparing the two-dimensional silica nanosheet-loaded metal absorbing material according to claim 1, characterized in that: The reducing atmosphere is a reducing gas or a mixture of a reducing gas and a protective gas; The reducing gas is hydrogen or carbon monoxide; the protective gas is nitrogen or argon.

7. The method for preparing the two-dimensional silica nanosheet-loaded metal absorbing material according to claim 1, characterized in that: In the metal chloride-ethanol solution, the dosage ratio of the metal chloride to ethanol is 0.25g-6g:100mL.

8. The method for preparing a two-dimensional silicon dioxide nanosheet-loaded metal absorbing material according to claim 1, characterized in that: The temperature for stirring and mixing is 50°C to 90°C.

9. A two-dimensional silicon dioxide nanosheet loaded with a metal absorbing material prepared by the preparation method according to any one of claims 1 to 8.

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