A multi-component hollow microsphere with a double-shell hollow structure, its preparation method and application

Abstract

This invention discloses a multi-component hollow microsphere with a double-shell hollow structure. The hollow microsphere has a core-shell structure, with a hollow core and a double-shell structure comprising an inner shell and an outer shell. The inner shell is composed of carbon. The outer shell includes a continuous phase and a dispersed phase dispersed within the continuous phase. The continuous phase is composed of amorphous carbon, and the dispersed phase is composed of metallic silver particles and iron oxide particles. This invention addresses the current challenges in the molding and performance control of high-performance microwave absorbers, such as difficulties in hierarchical design and synergistic control, the inability to efficiently balance impedance matching and loss capability, and complex fabrication processes. This invention also discloses the preparation method and applications of this multi-component hollow microsphere.

Description

Technical Field

[0001] This invention relates to the field of functional materials. More specifically, it relates to a multi-component hollow microsphere with a double-shell hollow structure, its preparation method, and its applications. Background Technology

[0002] The widespread use of electronic devices generates a large amount of electromagnetic waves, which permeate every corner of people's lives, posing a significant threat to the normal operation of precision instruments and human health. Therefore, electromagnetic wave absorbing and shielding materials are widely used for electromagnetic wave protection. For localized electromagnetic shielding, electromagnetic protection within the protected area can be achieved by using highly conductive or highly magnetically permeable materials to block electromagnetic waves outside the protected area. However, in this type of protection, the direct reflection of electromagnetic waves on the surface of the protective material, while protecting the internal area from impact, causes serious secondary pollution. These continuously reflected and superimposed electromagnetic waves can cause even more severe effects. In contrast, using high-performance electromagnetic wave absorbing materials to convert the energy of incident electromagnetic waves into other forms (such as heat) for dissipation is a more effective method for electromagnetic wave control.

[0003] In light of this, researchers have devoted considerable effort to high-performance electromagnetic wave absorbing materials (absorbents), developing various electromagnetic wave absorbers with different chemical compositions and loss mechanisms, such as magnetic metals, iron oxides, conductive metals, conductive polymers, and functional ceramics. Unlike shielding materials that directly reflect electromagnetic waves, electromagnetic wave absorbing materials need to balance impedance matching and loss capability (comprehensive electromagnetic properties). The purpose of impedance matching is to ensure that incident electromagnetic waves penetrate as much as possible into the interior of the absorbing material, rather than causing secondary pollution due to direct reflection from the surface area. Simultaneously, if electromagnetic waves entering the interior of the absorbing material cannot be effectively dissipated within the material, they will further penetrate the material, resulting in the inability to achieve electromagnetic wave shielding or absorption. Therefore, the design of absorbing agents that balance impedance matching and loss capability is crucial for developing high-performance electromagnetic wave absorbing materials. Currently, researchers have made some progress in controlling the comprehensive electromagnetic properties of absorbing agents through the design of chemical composition and structure. However, current challenges in the molding and performance control of high-performance absorbing agents include difficulties in hierarchical design and synergistic control, the inability to efficiently balance impedance matching and loss capability, and complex preparation processes, which restrict the mass production and application development of high-performance absorbing agents. Summary of the Invention

[0004] Based on the above problems, this invention provides a multi-component hollow microsphere with a double-shell hollow structure, its preparation method and application, so as to at least solve the problems that still exist in the molding and performance regulation of current high-performance microwave absorbers, such as difficulties in hierarchical design and synergistic regulation, inefficiency in impedance matching and loss capacity, and complex preparation process.

[0005] On the one hand, the present invention provides a multi-component hollow microsphere with a double-shell hollow structure, wherein the hollow microsphere has a core-shell structure, the core is a cavity, and the shell is a double-shell structure, including an inner spherical shell and an outer spherical shell;

[0006] The inner spherical shell is composed of carbon.

[0007] The outer spherical shell includes a continuous phase and a dispersed phase dispersed in the continuous phase. The continuous phase is composed of amorphous carbon, and the dispersed phase is composed of metallic silver particles and iron oxide particles.

[0008] In this hollow microsphere, the cavity structure and heterogeneous components within the shell can introduce abundant interfaces, enabling multiple scattering and dissipation of incident electromagnetic waves. Furthermore, the electromagnetic waves are dissipated through mechanisms such as interfacial polarization, dielectric properties, leakage conductance, and magnetic loss of the silver particles, iron oxide particles, and carbon materials, thereby enhancing the wave absorption performance.

[0009] Furthermore, the hollow microspheres have a particle size of 5-40 μm and a cavity diameter of 3-30 μm.

[0010] Furthermore, the thickness of the inner spherical shell is 0.5-2 μm; the thickness of the outer spherical shell is 0.2-1 μm.

[0011] Furthermore, the particle size of the metallic silver particles is 5-100 nm, and their mass percentage in the hollow microspheres is 5-20 wt%.

[0012] The iron oxide particles have a particle size of 8-70 nm and a mass percentage of 5-20 wt% in the hollow microspheres.

[0013] Furthermore, in the outer spherical shell, the metallic silver particles and iron oxide particles are transformed from the thermal decomposition of the initially added metallic nitrate, and the carbon in the outer spherical shell is obtained by carbonization from a water-soluble small molecule carbon source.

[0014] Furthermore, in the inner spherical shell, carbon is obtained by the pyrolysis and carbonization of phenolic microspheres.

[0015] Furthermore, the water-soluble small molecule carbon source includes, but is not limited to, one or more of citric acid, starch, sucrose, glucose, and dopamine.

[0016] In another aspect, the present invention provides a method for preparing multi-component hollow microspheres as described above, comprising the following steps:

[0017] Provide carbon hollow microspheres;

[0018] The provided carbon hollow microspheres are mixed with sol and dried to obtain a mixed gel, wherein the sol is obtained by mixing nitrates of metallic silver and iron, water-soluble small molecule carbon source and deionized water;

[0019] The mixed gel was heat-treated in an inert atmosphere to obtain the multi-component hollow microspheres.

[0020] In this method, pre-dissolving other components besides the microspheres into a sol can ensure uniform dispersion and mixing of the components, and also prevent the hollow microspheres from breaking during the dispersion process. In addition, carbon microspheres can adsorb components such as water and metal salts. If they are not uniformly dispersed beforehand, it is easy for the components to be adsorbed unevenly on the surface of the microspheres.

[0021] Furthermore, the carbon hollow microspheres are obtained by heat-treating phenolic resin hollow microspheres. Phenolic microspheres are inexpensive and readily available, and have a high residual carbon content after carbonization, which facilitates the maintenance of the hollow microsphere structure. Compared with other resins, carbonization results in better processing stability, lower cost, and easier molding.

[0022] Furthermore, the phenolic resin hollow microspheres are heat-treated at a temperature of 700-1500℃ for 1-12 hours under an inert or reducing atmosphere.

[0023] The mixed gel is heat-treated in an inert atmosphere at a temperature of 350-500℃ for 2-10 hours.

[0024] Furthermore, the mass ratio of the carbon hollow microspheres to the sol is 1:2 to 1:8.

[0025] In the sol, the total mass ratio of silver and iron nitrates to the mass ratio of water-soluble small molecule carbon source and deionized water is 3:2:3; the mass ratio of silver nitrates to iron nitrates is 1:3.

[0026] Furthermore, the inert atmosphere is nitrogen or argon.

[0027] Furthermore, the powder obtained by heat treatment of the mixed gel in an inert atmosphere and subsequent cooling can be sieved to remove large particles and achieve dispersion.

[0028] In another aspect, the present invention provides the application of the multi-component hollow microspheres described above as a microwave absorbing agent.

[0029] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0030] The beneficial effects of this invention are as follows:

[0031] The multi-component hollow composite microspheres with a double-shell structure provided by this invention achieve stepwise control of the shell structure and composition through the stepwise molding of the inner carbon shell and the outer multi-component composite shell. The degree of crystallization is generated by different heat treatment temperatures, thereby regulating the electromagnetic function.

[0032] The multi-component hollow composite microspheres with a double-shell structure provided by this invention can simultaneously achieve the dispersion and assembly of metallic silver particles and iron oxide nanoparticles on the surface of the micron-sized shells. This not only prevents the agglomeration of nanoparticles, but also facilitates the use of microwave absorbing agents due to their macroscopic micron-sized spherical shape.

[0033] The multi-component hollow composite microspheres with a double-shell structure provided by this invention have abundant heterogeneous interfaces between the double-shell layers and inside the outer shell, which can effectively enhance the absorption capacity of electromagnetic waves.

[0034] The method for preparing multi-component hollow composite microspheres with a double-shell structure provided by this invention employs heat treatment-induced pyrolysis molding, which is characterized by its speed and efficiency. Attached Figure Description

[0035] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0036] Figure 1 The preparation process (a) of the multi-component hollow composite microsphere absorbing agent with a double spherical shell structure and the schematic diagram of the obtained absorbing agent structure (b) are shown.

[0037] Figure 2 The X-ray diffraction (XRD) pattern of the hollow composite microsphere absorbing agent prepared in Example 1 is shown.

[0038] Figure 3 The image shows a scanning electron microscope (SEM) image of the hollow composite microsphere absorbing agent prepared in Example 1.

[0039] Figure 4 The image shows a scanning electron microscope (SEM) image of the hollow composite microsphere absorbing agent prepared in Example 1.

[0040] Figure 5 The electromagnetic wave absorption curve of the hollow composite microsphere absorbing agent prepared in Example 1 is shown. Detailed Implementation

[0041] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] The preparation method of a multi-component hollow composite microsphere microwave absorber with a double-shell structure includes the following steps:

[0044] (1) Phenolic resin hollow microspheres with a particle size of about 12.3 μm were heat-treated at 900 °C for 2 h in a hydrogen-argon mixed gas atmosphere with a volume percentage of 5% hydrogen to obtain hollow microspheres with carbon shells (hollow microsphere A).

[0045] (2) Mix 6g silver nitrate, 18g ferric nitrate nonahydrate, 16g sucrose and 24g water, and stir to dissolve to obtain a sol. Mix the sol with 16g hollow microspheres A obtained in step (1), stir evenly, and then dry at 60℃ to obtain a mixed gel.

[0046] (3) The mixed gel obtained in step (2) was heat-treated at 500°C for 3 hours in a nitrogen atmosphere, cooled and then sieved to disperse, thus obtaining a multi-component hollow composite microsphere absorbing agent with a double shell structure.

[0047] The composite microsphere absorber has an average particle size of 13.0 μm and a hollow cavity diameter of 9 μm; the inner carbon sphere shell thickness is 1.4 μm and the outer composite sphere shell thickness is 0.6 μm; the content of silver particles is 11.9 wt% with a particle size of about 73 nm, and the content of iron oxide particles is 11.7 wt% with a particle size of about 45 nm.

[0048] Example 2

[0049] The preparation method of a multi-component hollow composite microsphere microwave absorber with a double-shell structure includes the following steps:

[0050] (1) Phenolic resin hollow microspheres with a particle size of about 12.3 μm were heat-treated at 1000 °C for 3 h in a hydrogen-argon mixed gas atmosphere with a volume percentage of 5% hydrogen to obtain hollow microspheres with carbon shells (hollow microsphere A).

[0051] (2) Mix 3g silver nitrate, 9g ferric nitrate nonahydrate, 8g starch and 12g water, and stir to dissolve to obtain a sol. Mix the sol with 4g hollow microspheres A obtained in step (1), stir evenly, and then dry at 60℃ to obtain a mixed gel.

[0052] (3) The mixed gel obtained in step (2) was heat-treated at 450°C for 3 hours in a nitrogen atmosphere, cooled and then sieved to disperse, thus obtaining a multi-component hollow composite microsphere absorbing agent with a double shell structure.

[0053] The composite microsphere absorber has an average particle size of 13.8 μm and an average hollow cavity diameter of 9 μm; the inner carbon shell thickness is 1.4 μm and the outer composite shell thickness is 1.0 μm; the silver particle content is 17.1 wt% with a particle size of about 92 nm, and the iron oxide particle content is 16.9 wt% with a particle size of about 69 nm.

[0054] Example 3

[0055] The preparation method of a multi-component hollow composite microsphere microwave absorber with a double-shell structure includes the following steps:

[0056] (1) Phenolic resin hollow microspheres with a particle size of about 6 μm were heat-treated at 1200℃ for 2 h in a hydrogen-argon mixed gas atmosphere with a volume percentage of 5% hydrogen to obtain hollow microspheres with carbon shells (hollow microsphere A).

[0057] (2) Mix 6g silver nitrate, 18g ferric nitrate nonahydrate, 16g sucrose and 24g water, and stir to dissolve to obtain a sol. Mix the sol with 11g hollow microspheres A obtained in step (1), stir evenly, and then dry at 60℃ to obtain a mixed gel.

[0058] (3) The mixed gel obtained in step (2) was heat-treated at 500°C for 3 hours in a nitrogen atmosphere, cooled and then sieved to disperse, thus obtaining a multi-component hollow composite microsphere absorbing agent with a double shell structure.

[0059] The composite microsphere absorber has an average particle size of 7.3 μm and a hollow cavity diameter of 3.7 μm; the inner carbon sphere shell thickness is 1 μm and the outer composite sphere shell thickness is 0.8 μm; the content of silver particles is 17.6 wt% with a particle size of about 87 nm, and the content of iron oxide particles is 17.2 wt% with a particle size of about 64 nm.

[0060] Example 4

[0061] The preparation method of a multi-component hollow composite microsphere microwave absorber with a double-shell structure includes the following steps:

[0062] (1) Phenolic resin hollow microspheres with a particle size of about 12.3 μm were heat-treated at 900 °C for 4 h in an argon atmosphere to obtain hollow microspheres with carbon shells (hollow microsphere A).

[0063] (2) Mix 6g silver nitrate, 18g ferric nitrate nonahydrate, 16g citric acid and 24g water, and stir to dissolve to obtain a sol. Mix the sol with 16g hollow microspheres A obtained in step (1), stir evenly, and then dry at 60℃ to obtain a mixed gel.

[0064] (3) The mixed gel obtained in step (2) was heat-treated at 400°C for 3 hours in a nitrogen atmosphere, cooled and then sieved to disperse, thus obtaining a multi-component hollow composite microsphere absorbing agent with a double shell structure.

[0065] The composite microsphere absorber has an average particle size of 13.2 μm and a hollow cavity diameter of 9 μm; the inner carbon sphere shell thickness is 1.4 μm and the outer composite sphere shell thickness is 0.7 μm; the content of silver particles is 11.7 wt% with a particle size of about 61 nm, and the content of iron oxide particles is 11.3 wt% with a particle size of about 34 nm.

[0066] Example 5

[0067] The preparation method of a multi-component hollow composite microsphere microwave absorber with a double-shell structure includes the following steps:

[0068] (1) Phenolic resin hollow microspheres with a particle size of about 36 μm were heat-treated at 1300 °C for 5 h in an argon atmosphere to obtain hollow microspheres with carbon shells (hollow microsphere A).

[0069] (2) Mix 6g silver nitrate, 18g ferric nitrate nonahydrate, 10g citric acid, 6g sucrose and 24g water, and stir to dissolve to obtain a sol. Mix the sol with 16g hollow microspheres A obtained in step (1), stir evenly, and then dry at 60℃ to obtain a mixed gel.

[0070] (3) The mixed gel obtained in step (2) was heat-treated at 450°C for 8 hours in a nitrogen atmosphere, cooled and then sieved to disperse, thus obtaining a multi-component hollow composite microsphere absorbing agent with a double shell structure.

[0071] The composite microsphere absorber has an average particle size of 13.2 μm and a hollow cavity diameter of 30.4 μm; the inner carbon sphere shell thickness is 2.1 μm and the outer composite sphere shell thickness is 0.6 μm; the content of silver particles is 5.5 wt% with a particle size of about 9 nm, and the content of iron oxide particles is 5.3 wt% with a particle size of about 8 nm.

[0072] Example 6

[0073] The preparation method of a multi-component hollow composite microsphere microwave absorber with a double-shell structure includes the following steps:

[0074] (1) Phenolic resin hollow microspheres with a particle size of about 12.3 μm were heat-treated at 1100 °C for 5 h in an argon atmosphere to obtain hollow microspheres with carbon shells (hollow microsphere A).

[0075] (2) Mix 6g silver nitrate, 18g ferric nitrate nonahydrate, 10g citric acid, 6g sucrose and 24g water, and stir to dissolve to obtain a sol. Mix the sol with 32g hollow microspheres A obtained in step (1), stir evenly, and then dry at 60℃ to obtain a mixed gel.

[0076] (3) The mixed gel obtained in step (2) was heat-treated at 450°C for 8 hours in a nitrogen atmosphere, cooled and then sieved to disperse, thus obtaining a multi-component hollow composite microsphere absorbing agent with a double shell structure.

[0077] The composite microsphere absorber has an average particle size of 12.4 μm and a hollow cavity diameter of 9 μm; the inner carbon sphere shell thickness is 1.4 μm and the outer composite sphere shell thickness is 0.3 μm; the content of silver particles is 7.8 wt% with a particle size of about 23 nm, and the content of iron oxide particles is 7.5 wt% with a particle size of about 21 nm.

[0078] Example 7

[0079] The preparation method of a multi-component hollow composite microsphere microwave absorber with a double-shell structure includes the following steps:

[0080] (1) Phenolic resin hollow microspheres with a particle size of about 12.3 μm were heat-treated at 1000 °C for 5 h in an argon atmosphere to obtain hollow microspheres with carbon shells (hollow microsphere A).

[0081] (2) Mix 6g silver nitrate, 18g ferric nitrate nonahydrate, 8g starch, 8g sucrose and 24g water, and stir to dissolve to obtain a sol. Mix the sol with 21.3g hollow microspheres A obtained in step (1), stir evenly, and then dry at 60℃ to obtain a mixed gel.

[0082] (3) The mixed gel obtained in step (2) was heat-treated at 500°C for 8 hours in a nitrogen atmosphere, cooled and then sieved to disperse, thus obtaining a multi-component hollow composite microsphere absorbing agent with a double shell structure.

[0083] The composite microspheres have an average particle size of 12.8 μm and a hollow cavity diameter of 9 μm; the inner carbon shell thickness is 1.4 μm and the outer composite shell thickness is 0.46 μm; the content of silver particles is 11.7 wt% with a particle size of about 63 nm, and the content of iron oxide particles is 10.2 wt% with a particle size of about 47 nm.

[0084] Example 8

[0085] The preparation method of a multi-component hollow composite microsphere microwave absorber with a double-shell structure includes the following steps:

[0086] (1) Phenolic resin hollow microspheres with a particle size of about 12.3 μm were heat-treated at 1400 °C for 5 h in an argon atmosphere to obtain hollow microspheres with carbon shells (hollow microsphere A).

[0087] (2) Mix 6g silver nitrate, 18g ferric nitrate nonahydrate, 5g starch, 5g citric acid, 6g sucrose and 24g water, and stir to dissolve to obtain a sol. Mix the sol with 16g hollow microspheres A obtained in step (1), stir evenly, and then dry at 60℃ to obtain a mixed gel.

[0088] (3) The mixed gel obtained in step (2) was heat-treated at 400°C for 8 hours in a nitrogen atmosphere, cooled and then sieved to disperse, thus obtaining a multi-component hollow composite microsphere absorbing agent with a double shell structure.

[0089] The composite microsphere absorber has an average particle size of 13.2 μm and a hollow cavity diameter of 9 μm; the inner carbon sphere shell thickness is 1.4 μm and the outer composite sphere shell thickness is 0.65 μm; the silver particle content is 11.2 wt% with a particle size of about 45 nm, and the iron oxide particle content is 10.9 wt% with a particle size of about 29 nm.

[0090] Comparative Example 1

[0091] The preparation method of a multi-component hollow composite microsphere microwave absorber with a double-shell structure includes the following steps:

[0092] (1) Phenolic resin hollow microspheres with a particle size of about 12.3 μm were heat-treated at 1000 °C for 5 h in an argon atmosphere to obtain hollow microspheres with carbon shells (hollow microsphere A).

[0093] (2) Mix 6g silver nitrate, 8g starch, 8g sucrose and 24g water, stir and dissolve to obtain a sol. Mix the sol with 16g hollow microspheres A obtained in step (1), stir evenly, and then dry at 60℃ to obtain a mixed gel.

[0094] (3) The mixed gel obtained in step (2) was heat-treated at 500°C for 8 hours in a nitrogen atmosphere, cooled and then sieved to disperse, thus obtaining a multi-component hollow composite microsphere absorbing agent with a double shell structure.

[0095] The composite microsphere absorber has an average particle size of 12.9 μm and a hollow cavity diameter of 9 μm; the inner carbon shell thickness is 1.4 μm and the outer composite shell thickness is 0.54 μm; the silver particle content is 14.7 wt%, the particle size is about 98 nm, and it does not contain iron oxide.

[0096] Comparative Example 2

[0097] The preparation method of a multi-component hollow composite microsphere microwave absorber with a double-shell structure includes the following steps:

[0098] (1) Phenolic resin hollow microspheres with a particle size of about 12.3 μm were heat-treated at 1000 °C for 5 h in an argon atmosphere to obtain hollow microspheres with carbon shells (hollow microsphere A).

[0099] (2) Mix 18g of ferric nitrate nonahydrate, 8g of starch, 8g of sucrose and 24g of water, and stir to dissolve to obtain a sol. Mix the sol with 16g of hollow microspheres A obtained in step (1), stir evenly, and then dry at 60℃ to obtain a mixed gel.

[0100] (3) The mixed gel obtained in step (2) was heat-treated at 500°C for 8 hours in a nitrogen atmosphere, cooled and then sieved to disperse, thus obtaining a multi-component hollow composite microsphere absorbing agent with a double shell structure.

[0101] The composite microsphere absorber has an average particle size of 13.1 μm and a hollow cavity diameter of 9 μm; the inner carbon shell thickness is 1.4 μm and the outer composite shell thickness is 0.56 μm; the content of iron oxide particles is 14.1 wt%, the particle size is about 67 nm, and it does not contain silver.

[0102] Comparative Example 3

[0103] Example 1 was repeated, except that in step (2), 16g of hollow microspheres A was mixed with 6g of silver nitrate, 18g of ferric nitrate nonahydrate, 16g of sucrose, and 24g of water, stirred evenly, and then dried at 60°C to obtain a mixed gel. The other conditions remained unchanged to prepare the composite microsphere microwave absorber.

[0104] Compared to the microwave absorbers prepared in the above embodiments, this composite microsphere absorber exhibited significantly more microsphere breakage during preparation, and the components were not evenly dispersed. In the following performance tests, its performance was far inferior to that of the embodiments.

[0105] Performance testing:

[0106] The electromagnetic properties of the products prepared in the above embodiments were tested. The test method was as follows: the multi-component hollow composite microspheres (wave-absorbing agent) prepared in each embodiment were mixed with paraffin wax, and the wave-absorbing agent was prepared into coaxial rings with an inner diameter of 3 mm, an outer diameter of 7 mm, and a thickness of 2 mm at a mass ratio of 25%-55% of the mixture. The electromagnetic parameters were then tested using a vector network analyzer, and their electromagnetic properties were analyzed. The results are shown in Table 1.

[0107] Table 1 Performance parameters of samples from each embodiment

[0108]

[0109] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. The application of a multi-component hollow microsphere with a double-shell hollow structure as a microwave absorbing agent, characterized in that, The microwave absorbing agent is a multi-component hollow microsphere with a double-shell hollow structure. The hollow microsphere has a core-shell structure, with the core being a cavity and the shell having a double-shell structure, including an inner spherical shell and an outer spherical shell. The inner spherical shell is composed of carbon. The outer spherical shell includes a continuous phase and a dispersed phase dispersed in the continuous phase. The continuous phase is composed of amorphous carbon, and the dispersed phase is composed of metallic silver particles and iron oxide particles. The method for preparing the hollow microspheres includes the following steps: Provide carbon hollow microspheres; The carbon hollow microspheres were mixed with the sol and dried to obtain a mixed gel, wherein the sol was obtained by mixing silver and iron nitrates, water-soluble small molecule carbon source and deionized water; The mixed gel was heat-treated in an inert atmosphere to obtain the multi-component hollow microspheres; The heat treatment is performed at a temperature of 350-500℃ for 2-10 hours. The hollow microspheres have a particle size of 5-40 μm and a cavity diameter of 3-30 μm; The thickness of the inner spherical shell is 0.5-2 μm; the thickness of the outer spherical shell is 0.2-1 μm. The silver particles have a particle size of 5-100 nm and a mass percentage of 5-20 wt% in the hollow microspheres. The iron oxide particles have a particle size of 8-70 nm and a mass percentage of 5-20 wt% in the hollow microspheres.

2. The application according to claim 1, characterized in that, The mass ratio of the carbon hollow microspheres to the sol is 1:2-1:8; In the sol, the total mass ratio of silver and iron nitrates to the mass ratio of water-soluble small molecule carbon source and deionized water is 3:2:3; the mass ratio of silver nitrates to iron nitrates is 1:3.

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