Ternary core-shell composite structure microsphere wave-absorbing agent as well as preparation method and application thereof

Abstract

The invention discloses a ternary core-shell composite structure microsphere wave-absorbing agent as well as a preparation method and application thereof. The ternary core-shell composite structure microsphere comprises an inner core, an outer shell and a cavity positioned between the inner core and the outer shell, wherein the inner core is micron-sized magnetic metal or alloy; the shell is composed of continuous-phase carbon and conductive particles serving as a dispersed phase. A rich interface can be introduced into the egg yolk type cavity structure of the composite microsphere, multiple scattering and dissipation of incident electromagnetic waves are achieved, meanwhile, the carbon shell layer serves as a dielectric layer and can effectively restrain electron transfer between magnetic metal, the filling amount of large magnetic particles is increased through compounding of the conductive particles and the carbon thin layer, the magnetic loss is reserved, and meanwhile the magnetic performance of the composite microsphere is improved. According to the present invention, the interface polarization and dipole polarization effects are increased, the dielectric loss is improved, the impedance matching level of the material is optimized, the easily oxidized magnetic metal core is isolated from the external environment, and the environmental stability of the magnetic metal is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of wave absorbing materials, and in particular relates to a ternary core-shell composite structure microsphere wave absorbing agent and a preparation method and application thereof. Background Art

[0002] The rapid development of microwave technology has brought huge demands and opportunities for the research and application of absorbing materials. Absorbers are the core and key of absorbing materials, so their research and development have attracted a lot of attention, and the design and controllable preparation of new absorbers are in the ascendant. In order to meet the increasingly high performance requirements, researchers are increasingly focusing on heterogeneous composite absorbers with dual (multiple) electromagnetic wave loss mechanisms. Among them, composite materials of magnetic metals and carbon have attracted more and more attention in the design of high-performance electromagnetic wave absorbers (absorbers) due to their magnetic properties, conductive (dielectric) properties and macroscopic structures that are easy to tailor. In this type of composite absorber, magnetic metals have high saturation magnetization and conductivity, and can consume the energy of incident electromagnetic waves through magnetic loss and leakage conduction loss; while carbon materials can greatly regulate dielectric and conductivity according to their degree of graphitization and microstructure, which provides the possibility of achieving optimized impedance matching and dielectric, leakage conductance and other losses. More importantly, the combination of magnetic metals and carbon materials at the microscopic scale can also introduce a large number of interfaces into the composite material system. These interfaces have very different conductivity and dielectric properties. On the one hand, this can realize the scattering and reflection of the incident electromagnetic waves, increase the transmission path of the electromagnetic waves, and help to give full play to the loss capacity of the absorber; on the other hand, it can realize the accumulation and relaxation of space charges in the interface area in the alternating electromagnetic field, thereby losing electromagnetic wave energy through polarization relaxation.

[0003] Ferromagnetic microwave absorbing materials have always been an important research direction of electromagnetic microwave absorbing materials. Their unique magnetic loss mechanism makes them an indispensable part of the microwave absorbing family. However, their defects such as poor impedance matching performance, high density, narrow absorption band, thick matching thickness, and poor weather resistance make it difficult to meet the requirements of actual use. Carbon materials have the advantages of light weight, high temperature resistance, corrosion resistance, excellent dielectric loss ability, etc. However, their high dielectric properties make it difficult to use them alone due to poor impedance matching. Therefore, coating carbon materials on ferromagnetic metal materials to form a unique core-shell structure can effectively regulate the impedance matching performance and enhance the mechanical properties, thereby optimizing the comprehensive performance of the microwave absorber. In view of the fact that magnetic metal micro-nanoparticles usually need to form composites with matrix materials such as polymers during application, and at the same time, in order to increase the magnetic loss of the microwave absorber, researchers have currently designed three-layer core-shell composite carbon spheres. The multi-component core-shell coating structure changes the combination state of magnetic metals, adjusts from a dispersed type to a spherical shell distribution, improves the magnetic loss, optimizes the impedance matching performance, and at the same time forms rich heterogeneous interfaces. In addition to changing the combination distribution state, increasing the magnetic loss can also be achieved by increasing the size of magnetic particles to increase the magnetic permeability. Compared with nano-metal particles, micron-sized metal particles have a larger saturation magnetization intensity and stronger magnetic loss, and free electrons inside the metal can form currents under high-frequency alternating magnetic fields, endowing them with dielectric loss performance at the same time.

[0004] In addition, introducing a hollow structure into the microwave absorber is an important way to achieve the lightweight of the microwave absorber and even the final microwave absorbing composite material. At present, there have been a large number of studies on the construction of hollow structures in micro-nano microwave absorbers, and the chemical composition and structure of materials can also be greatly regulated. However, there are still problems in the forming and performance regulation of the current hollow structures, such as complex and time-consuming preparation processes, inability to prepare in large quantities and efficiently, and difficulties in hierarchical design and coordinated regulation of structure and performance, which restrict the batch preparation and application development of lightweight microwave absorbers. On the other hand, micron-sized particles will inevitably cause the skin effect, reducing the depth of electromagnetic waves entering the metal interior. Summary of the Invention

[0005] Aiming at the above problems, the present invention coats a yolk-shaped cavity dielectric material on the surface of micron-sized particles to reduce the influence of the skin effect, and at the same time introduces a conductive material doped therein. This can not only reduce the weakening effect of amorphous carbon on the dielectric parameters, but also the heterogeneous interfaces among the three can improve the interfacial loss and conductance loss of the material, reduce the density of the material, meet the synergistic effect of magnetism-dielectric-conductivity, and design a microsphere microwave absorber with a ternary core-shell composite structure.

[0006] The first object of the present invention is to provide a microsphere with a ternary core-shell composite structure.

[0007] The second object of the present invention is to provide a preparation method of a microsphere with a ternary core-shell composite structure.

[0008] The third object of the present invention is to provide a wave absorbing agent.

[0009] The fourth object of the present invention is to provide an application of a ternary core-shell composite structure microsphere.

[0010] To achieve the first object, the present invention adopts the following technical solutions:

[0011] A ternary core-shell composite structure microsphere, comprising a core, a shell and a cavity located between the core and the shell; the core is a micron-sized magnetic metal particle or alloy particle, the shell comprises a continuous phase and a dispersed phase, the continuous phase comprises a carbon layer, and the dispersed phase comprises conductive particles.

[0012] Further, the density of the composite structure microsphere is 3.0 - 10.0 g / cm 3 .

[0013] Further, the diameter of the composite structure microsphere is 0.2 - 50 μm, preferably 0.5 - 20 μm.

[0014] Further, the diameter of the micron-sized magnetic metal or alloy core in the composite structure microsphere is 0.2 - 49 μm, preferably 0.5 - 18 μm; the thickness of the shell is 50 - 500 nm, preferably 80 - 400 nm; the cavity is filled with air, and the thickness of the cavity is 0.1 - 5 μm.

[0015] Further, the metal content (content of magnetic particles) in the composite structure microsphere is 30 - 95 wt%, preferably 50 - 80 wt%.

[0016] Further, the micron-sized magnetic metal or alloy core is composed of metal particles and / or metal alloy particles.

[0017] Further, the material of the metal particles of the micron-sized magnetic metal core is selected from one of iron, cobalt and nickel, or a binary alloy formed by two of them, or a ternary alloy formed by three of them. Preferably, metal cobalt particles and alloys, and the proportion of metal components in the alloy is controllable.

[0018] Further, the material of the conductive particles is selected from one of silver, tin and copper, or a binary alloy formed by two of them, or a ternary alloy formed by three of them. Preferably, the conductive particles are silver particles.

[0019] Further, the carbon in the shell is obtained by carbonizing water-soluble organic molecules.

[0020] To achieve the second object, the present invention adopts the following technical solutions:

[0021] A preparation method of a ternary core-shell composite structure microsphere, comprising the following steps:

[0022] Prepare magnetic metal-metal oxide microspheres by a hydrothermal method; perform high-temperature reduction heat treatment on the magnetic metal-metal oxide microspheres to obtain magnetic metal microspheres;

[0023] Coat a silica layer on the surface of the magnetic metal microspheres to obtain silica-coated magnetic microspheres;

[0024] Directively assist in assembling conductive particles-carbon spherical shells on the surface of the silica-coated magnetic microspheres to obtain a precursor of a quaternary composite structure microsphere;

[0025] Heat-treat the precursor of the quaternary composite structure microsphere in a reducing or inert gas;

[0026] Soak the heat-treated precursor of the quaternary composite structure microsphere in an alkali solution to remove the silica layer, obtaining a ternary core-shell composite structure microsphere absorbent.

[0027] Further, preparing the magnetic metal-metal oxide microspheres comprises the following steps:

[0028] Sequentially mix an ion source salt solution with a complexing agent, a reducing agent, and a pH regulator, perform a hydrothermal reaction, and perform a series of filtration, washing, and drying treatments to prepare micro-nano-sized magnetic metal-metal oxide microspheres.

[0029] Further, the ion source salt is selected from sulfates, nitrates, chlorides, or organic acid salts, and the concentration is 0.01-5 mol / L.

[0030] Further, the complexing agent includes one of sodium potassium tartrate, ammonium sulfate, and EDTA, and the concentration is 0.01-4 mol / L.

[0031] Further, the reducing agent is an organic or inorganic reducing agent capable of reducing the corresponding metal ions to metal elements.

[0032] Further, the pH of the pH regulator is preferably 9-11, the concentration is 0.1-10 mol / L, and the pH regulator includes inorganic bases and organic bases, and inorganic bases are preferably selected.

[0033] Further, the temperature of the hydrothermal reaction is 120-200 °C, and more preferably 130-150 °C.

[0034] Further, the time of the hydrothermal reaction is 6-12 h, preferably 8-10 h.

[0035] Further, the temperature of the high-temperature reduction heat treatment is 450 - 850 °C, the heating rate is 1 - 5 °C, and the heat preservation time is 1 - 4 h.

[0036] Further, the reducing atmosphere used in the high-temperature reduction heat treatment is a hydrogen / argon mixed atmosphere.

[0037] Further, the preparation of the silica-coated magnetic microspheres includes the following steps:

[0038] Disperse the magnetic metal microspheres in a concentrated ammonia water solution, slowly add tetraethyl orthosilicate to the reaction solution after stirring, stir at room temperature, and then separate and collect the sample, and prepare the silica-coated magnetic microspheres through a series of filtration, washing, and drying processes.

[0039] Further, the ratio of the magnetic metal microspheres, the reaction solution, and tetraethyl orthosilicate is 3 g : 500 mL : 5 mL.

[0040] Further, the stirring time for stirring at room temperature is 4 - 10 hours.

[0041] Further, the preparation steps of the concentrated ammonia water solution are as follows: Mix absolute ethanol and deionized water evenly according to a mass ratio of 4 : 1, and then add 2% by mass of concentrated ammonia water (25 wt.%) to the mixed solution and stir to mix evenly.

[0042] Further, the preparation of the microsphere precursor with a quaternary composite structure includes the following steps:

[0043] Fully mix the carbon source and the conductive metal salt solution, then add the silica-coated magnetic microsphere particles, and obtain the microsphere precursor with a quaternary composite structure through a series of processes such as stirring, washing, filtering, and drying.

[0044] Further, the mass ratio of the microspheres, the carbon source, the conductive metal salt, and water is (1 - 6) : (5 - 50) : (0.05 - 5) : (10 - 80).

[0045] Further, the carbon source includes one or more of glucose, fructose, sucrose, maltose, starch, and citric acid, and sucrose is further preferred.

[0046] Further, the conductive metal salt includes silver salt and copper salt.

[0047] Further, the temperature of the heat treatment is 200 - 600 °C, the heating rate is 1 - 5 °C, and the heat preservation time is 2 - 5 h.

[0048] Further, the reducing atmosphere used in the heat treatment is a hydrogen / argon mixed atmosphere.

[0049] Further, the lye is an aqueous sodium hydroxide solution with a concentration of 3.6 M and a treatment time of 35 hours.

[0050] To achieve the above-mentioned third object, the present invention adopts the following technical solution:

[0051] An absorber, comprising the ternary core-shell composite structure microspheres described in the first object above.

[0052] Further, the absorber further contains paraffin wax, and the volume ratio of the ternary core-shell composite structure microspheres to paraffin wax is 30-90%.

[0053] To achieve the above-mentioned fourth object, the present invention also protects the application of the ternary core-shell composite structure microspheres described in the first object above in microwave absorption, catalysis, adsorption or wastewater treatment.

[0054] Further, the application as an absorbing material can be used as one of the following materials: in the field of military stealth, electromagnetic radiation protection of radio and television transmitting stations, microwave anechoic chamber materials, building absorbing materials or electromagnetic shielding materials in radio communication equipment.

[0055] The ternary core-shell composite structure microspheres of the present invention include a micron-sized magnetic metal or alloy inner core, and the continuous phase carbon and conductive particles as the dispersed phase in the outer yolk-shaped cavity spherical shell structure. Its advantages and beneficial effects are as follows:

[0056] 1. The continuous phase carbon spherical shell in the composite structure microspheres provided by the present invention can effectively block the excessive migration of electrons between magnetic metals. The introduction of conductive particles can further increase the interfacial polarization and dipole polarization effects, and at the same time improve the environmental stability of magnetic metals. The design of the cavity can introduce a rich interface while adjusting the density, realizing multiple scattering and dissipation of incident electromagnetic waves.

[0057] 2. The combination of the micron-sized magnetic metal or alloy inner core and the conductive particle-carbon spherical shell in the composite structure microspheres provided by the present invention realizes the combination of electrical loss and magnetic loss. The combination of conductive particles-carbon spherical shell can increase the filling amount of magnetic metal particles in the absorbing material, and while retaining the magnetic loss, it can improve the dielectric loss and optimize the impedance matching level of the material.

[0058] 3. In the preparation method of the composite structure microspheres provided by the present invention, the structural size of the micron-sized magnetic metal or alloy inner core can be regulated by the type and dosage of the metal source and the heat treatment temperature, and then its electromagnetic properties can be regulated.

[0059] 4. In the preparation method of the composite structure microspheres provided by the present invention, its functionality can be regulated by the composition and structure design of the conductive metal-carbon spherical shell and the thickness of the cavity. Description of the Drawings

[0060] Figure 1 It is the preparation flow chart of the ternary core-shell composite structure microsphere microwave absorber described in the present invention.

[0061] Figure 2 It is the schematic structural diagram of the ternary core-shell composite structure microsphere microwave absorber described in the present invention.

[0062] Figure 3 It is the scanning electron microscope (SEM) photograph of the composite structure microsphere microwave absorber obtained in Example 1.

[0063] Figure 4 It is the transmission electron microscope (TEM) photograph of the composite structure microsphere microwave absorber obtained in Example 1. Detailed implementation manners

[0064] The present invention will be further illustrated by the following examples, but these examples are not intended to limit the protection scope of the present invention.

[0065] Example 1

[0066] This example provides a preparation method of a ternary core-shell composite structure microsphere microwave absorber, and its preparation process is as Figure 1 shown, and the structure of the prepared ternary core-shell composite structure microsphere is as Figure 2 shown. The specific implementation scheme is as follows:

[0067] In the first step, 2.25 mL of 1.00 mol / L cobalt sulfate solution is added to 6.00 mL of 1.00 mol / L sodium potassium tartrate solution, and they are quickly stirred and mixed. Then, 4.50 mL of 80% hydrazine hydrate solution is added to the mixed solution, and they are stirred and mixed. Next, 3.00 mL of 10.00 mol / L sodium hydroxide aqueous solution is added to the mixed solution, and the volume is fixed to 30.00 mL with a measuring cylinder, and they are stirred evenly. Finally, it is poured into a 50.00 mL polytetrafluoroethylene liner and loaded into a stainless steel autoclave, and heated at 140 °C for 10 hours. The obtained sample is denoted as magnetic metal microsphere cobalt particles (Co-650). The magnetic metal microsphere Co particles prepared in the above process are placed in a tube furnace and reduced in H 2 / Ar atmosphere at 650 °C for 3 hours. This operation is to improve the crystallinity of the cobalt particles and remove the surface oxide layer.

[0068] In the second step, 3.5 g of magnetic metal particles are added to 350 mL of ethanol / water solution (volume ratio 4:1), and then 5.0 mL of ammonia water is added. After ultrasonic treatment for 30 minutes, while mechanically stirring, 5 mL of tetraethyl orthosilicate is slowly added dropwise to the reaction solution, and stirring is maintained at 30 °C for 8 hours. Then, the sample is collected by magnetic separation, washed with distilled water and ethanol, and finally dried in a constant temperature oven at 60 °C to obtain silica-coated magnetic metal microspheres.

[0069] In the third step, 28.00 g of sucrose is dissolved in 40.00 g of deionized water, magnetically stirred for 10 minutes, then 0.12 g of silver nitrate is added and stirred until completely dissolved. Then, 2.00 g of the obtained microsphere particles are added to the solution, and mechanical stirring is carried out for 30 minutes. Finally, the mixed solution is filtered and washed, and dried in an oven at 60 °C to obtain a microsphere precursor of the quaternary composite structure.

[0070] In the fourth step, the obtained microsphere precursor of the quaternary composite structure is placed in a tubular furnace and kept at 300 °C under H 2 / Ar atmosphere for 3 hours;

[0071] In the fifth step, the microsphere precursor of the quaternary composite structure obtained in the fourth step is added to a 3.6 M aqueous sodium hydroxide solution and soaked for 35 hours to remove the silica layer, obtaining microspheres of the ternary core-shell composite structure.

[0072] Figure 3 Figure (13) is a scanning electron microscope (SEM) photograph of the composite structure microsphere absorbent obtained in this example. Figure 4 Figure (15) is a transmission electron microscope (TEM) photograph of the composite structure microsphere absorbent obtained in this example, where Amorphouscarbon represents amorphous carbon.

[0073] Example 2

[0074] This example provides a preparation method of a ternary core-shell composite structure microsphere absorbent, and its preparation process is as Figure 1 shown, and the structure of the prepared ternary core-shell composite structure microspheres is as Figure 2 shown. The specific implementation scheme is as follows:

[0075] In the first step, 4.00 mL of 1.00 mol / L cobalt sulfate solution is added to 8.00 mL of 1.00 mol / L sodium potassium tartrate solution, and rapidly stirred and mixed. Then, 9.00 mL of 80% hydrazine hydrate solution is added to the mixed solution and stirred and mixed. Then, 3.00 mL of 20.00 mol / L aqueous sodium hydroxide solution is added, and the volume is fixed to 60.00 mL with a measuring cylinder and stirred evenly. Finally, it is poured into a 100.00 mL polytetrafluoroethylene inner liner and loaded into a stainless steel reaction kettle, and heated at 140 °C for 10 hours. The obtained sample is denoted as magnetic metal microsphere cobalt particles. The magnetic metal microsphere Co particles prepared in the above process are placed in a tubular furnace and reduced in H2 / Ar atmosphere at 650 °C for 3 hours. This operation is to improve the crystallinity of the cobalt particles and remove the surface oxide layer.

[0076] In the second step, 3.5 g of magnetic metal particles are added to 350 mL of an ethanol / water solution (volume ratio 4:1), and then 5.0 mL of ammonia water is added. After ultrasonic treatment for 30 minutes, while mechanically stirring, 5 mL of tetraethyl orthosilicate is slowly added dropwise to the reaction solution. Stirring is maintained at 30 °C for 8 hours. Then, the sample is collected by magnetic separation, washed with distilled water and ethanol, and finally dried in an incubator at 60 °C to obtain silica-coated magnetic metal microspheres.

[0077] In the third step, 28.00 g of sucrose is dissolved in 40.00 g of deionized water, and magnetically stirred for 10 minutes. Then, 0.12 g of silver nitrate is added and stirred until completely dissolved. Next, 2.00 g of the above-obtained microsphere particles are added to the solution, and mechanically stirred for 30 minutes. Finally, the mixed solution is filtered and washed, and dried in an oven at 60 °C to obtain a precursor of a quaternary composite structure microsphere.

[0078] In the fourth step, the obtained precursor of the quaternary composite structure microsphere is placed in a tubular furnace and kept at 300 °C under an H 2 / Ar atmosphere for 3 hours;

[0079] In the fifth step, the precursor of the quaternary composite structure microsphere obtained in the fourth step is added to a 3.6 M aqueous sodium hydroxide solution and soaked for 35 hours to remove the silica layer, obtaining a ternary core-shell composite structure microsphere.

[0080] Example 3

[0081] This example provides a method for preparing a ternary core-shell composite structure microsphere absorbent, and its preparation process is as Figure 1 shown, and the structure of the prepared ternary core-shell composite structure microsphere is as Figure 2 shown. The specific implementation plan is as follows:

[0082] In the first step, 2.25 mL of 1.00 mol / L cobalt sulfate solution is added to 6.00 mL of 1.00 mol / L sodium potassium tartrate solution, and quickly stirred and mixed. Then, 4.50 mL of 80% hydrazine hydrate solution is added to the mixed solution and stirred and mixed. Next, 3.00 mL of 10.00 mol / L aqueous sodium hydroxide solution is added, and the volume is fixed to 30.00 mL with a measuring cylinder and stirred evenly. Finally, it is poured into a 50.00 mL polytetrafluoroethylene liner and placed in a stainless steel autoclave, and heated at 140 °C for 10 hours. The obtained sample is denoted as magnetic metal microsphere cobalt particles (Co-650). The magnetic metal microsphere Co particles prepared in the above process are placed in a tubular furnace and reduced in an H2 / Ar atmosphere at 650 °C for 3 hours. This operation is to improve the crystallinity of the cobalt particles and remove the surface oxide layer.

[0083] Step 2: Add 3.5 g of magnetic metal particles to 350 mL of ethanol / water solution (volume ratio 4:1), then add 8.0 mL of ammonia water, and ultrasonicate for 30 minutes. While mechanically stirring, slowly drop 10.0 mL of tetraethyl orthosilicate into the reaction solution, and stir at 30 °C for 8 hours. Then collect the sample by magnetic separation, wash it with distilled water and ethanol, and finally dry it in an incubator at 60 °C to obtain silica-coated magnetic metal microspheres.

[0084] Step 3: Dissolve 28.00 g of sucrose in 40.00 g of deionized water, stir magnetically for 10 minutes, then add 0.12 g of silver nitrate and stir until completely dissolved. Then add 2.00 g of the above-obtained microsphere particles to the solution, stir mechanically for 30 minutes, and finally filter and wash the mixed solution, and dry it in an oven at 60 °C to obtain the precursor of the quaternary composite structure microspheres.

[0085] Step 4: Place the obtained precursor of the quaternary composite structure microspheres into a tube furnace and keep it at 300 °C under H 2 / Ar atmosphere for 3 hours;

[0086] Step 5: Add the precursor of the quaternary composite structure microspheres obtained in Step 4 to a 3.6 M aqueous sodium hydroxide solution and soak for 35 hours to remove the silica layer and obtain the ternary core-shell composite structure microspheres.

[0087] Example 4

[0088] This example provides a preparation method of a ternary core-shell composite structure microsphere microwave absorber, and its preparation process is as Figure 1 shown, and the structure of the prepared ternary core-shell composite structure microspheres is as Figure 2 shown. The specific implementation plan is as follows:

[0089] Step 1: Add 2.25 mL of 1.00 mol / L cobalt sulfate solution to 6.00 mL of 1.00 mol / L sodium potassium tartrate solution, quickly stir and mix, then add 4.50 mL of 80% hydrazine hydrate solution to the mixed solution, stir and mix, then add 3.00 mL of 10.00 mol / L aqueous sodium hydroxide solution, make up the volume to 30.00 mL with a measuring cylinder, stir evenly, and finally pour it into a 50.00 mL polytetrafluoroethylene inner liner and place it in a stainless steel autoclave, heat at 140 °C for 10 hours, and record the obtained sample as magnetic metal microsphere cobalt particles (Co-650). Place the magnetic metal microsphere Co particles prepared in the above process into a tube furnace and reduce them at 650 °C in H2 / Ar atmosphere for 3 hours. This operation is to improve the crystallinity of the cobalt particles and remove the surface oxide layer.

[0090] In the second step, 3.5 g of magnetic metal particles are added to 350 mL of an ethanol / water solution (volume ratio 4:1), and then 5.0 mL of ammonia water is added. After ultrasonic treatment for 30 minutes, while mechanically stirring, 5 mL of tetraethyl orthosilicate is slowly added dropwise to the reaction solution. Stirring is maintained at 30 °C for 8 hours. Then, the sample is collected by magnetic separation, washed with distilled water and ethanol, and finally dried in an incubator at 60 °C to obtain silica-coated magnetic metal microspheres.

[0091] In the third step, 40.00 g of sucrose is dissolved in 40.00 g of deionized water, and magnetically stirred for 10 minutes. Then, 0.3 g of silver nitrate is added and stirred until completely dissolved. Next, 2.00 g of the microsphere particles obtained above are added to the solution, and mechanically stirred for 30 minutes. Finally, the mixed solution is filtered and washed, and dried in an oven at 60 °C to obtain a precursor of a quaternary composite structure microsphere.

[0092] In the fourth step, the obtained precursor of the quaternary composite structure microsphere is placed in a tubular furnace and kept at 300 °C under an H 2 / Ar atmosphere for 3 hours;

[0093] In the fifth step, the precursor of the quaternary composite structure microsphere obtained in the fourth step is added to a 3.6 M aqueous sodium hydroxide solution and soaked for 35 hours to remove the silica layer, obtaining a ternary core-shell composite structure microsphere.

[0094] The microwave absorbing agents of the ternary core-shell composite structure microspheres prepared in the above examples are dispersed in paraffin, and their microwave absorbing properties are tested. The obtained microwave absorbing properties are shown in Table 1.

[0095] Table 1

[0096]

[0097] The specific embodiments of the present invention disclosed above are intended to help understand the content of the present invention and implement it accordingly. Those of ordinary skill in the art can understand that various substitutions, changes, and modifications are possible without departing from the spirit and scope of the present invention. The present invention should not be limited to the content disclosed in the embodiments of this specification, and the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A ternary core-shell composite microsphere, It is characterized in that It comprises a core, an outer shell and a cavity between the core and the outer shell; the core is a micron-sized magnetic metal particle or alloy particle, the outer shell comprises a continuous phase and a dispersed phase, the continuous phase comprises a carbon layer, and the dispersed phase comprises conductive particles.

2. The ternary core-shell composite structure microsphere according to claim 1, It is characterized in that The density of the ternary core-shell composite microspheres is 3.0-10.0 g / cm 3 , and the diameter is 0.2-50 μm; the thickness of the outer shell is 50-500 nm; the cavity is filled with air, and the thickness of the cavity is 0.1-5 μm; the material of the inner core is a binary alloy formed by one or two of iron, cobalt and nickel or a ternary alloy formed by the three; the material of the conductive particles is a binary alloy formed by one or two of silver, tin and copper or a ternary alloy formed by the three.

3. A method for preparing ternary core-shell composite structure microspheres, It is characterized in that The following steps are involved: The magnetic metal-metal oxide microspheres are prepared by a hydrothermal method, and the magnetic metal-metal oxide microspheres are subjected to a high-temperature reduction heat treatment to obtain magnetic metal microspheres; Coating a silicon dioxide layer on the surface of the magnetic metal microspheres to obtain silicon dioxide-coated magnetic microspheres; Conductive particles-carbon spherical shells are assembled on the surface of silica-coated magnetic microspheres to obtain a quaternary composite structure microsphere precursor; The quaternary composite structure microsphere precursor is subjected to heat treatment in a reducing or inert gas; The heat-treated quaternary composite structure microsphere precursor is placed in an alkaline solution for soaking treatment to remove the silicon dioxide layer, thereby obtaining a ternary core-shell composite structure microsphere.

4. The method according to claim 3, It is characterized in that The hydrothermal method for preparing magnetic metal-metal oxide microspheres comprises: sequentially mixing an ion source salt solution with a complexing agent, a reducing agent and a pH regulator, performing a hydrothermal reaction, and filtering, washing and drying to obtain micro-nano-sized magnetic metal-metal oxide microspheres.

5. The method according to claim 4, It is characterized in that The ion source salt is selected from sulfate, nitrate, chloride or organic acid salt, and the concentration is 0.01-5mol / L; the complexing agent includes one of potassium sodium tartrate, ammonium sulfate and EDTA, and the concentration is 0.01-4mol / L; the reducing agent is an organic or inorganic reducing agent that can reduce the corresponding metal ions to metal elements; the pH of the pH regulator is 9-11, and the concentration is 0.1-10mol / L; the temperature of the hydrothermal reaction is 120-200℃, and the time is 6-12h; the temperature of the high-temperature reduction heat treatment is 450-850℃, the heating rate is 1-5℃, and the insulation time is 1-4h; the reducing atmosphere used in the high-temperature reduction heat treatment is a hydrogen / argon mixed atmosphere.

6. The method according to claim 3, It is characterized in that The method of coating the surface of the magnetic metal microspheres with a silicon dioxide layer comprises: dispersing the magnetic metal microspheres in a concentrated ammonia solution, slowly adding tetraethyl orthosilicate after stirring, stirring at room temperature, separating and collecting samples, filtering, washing and drying to obtain silicon dioxide coated magnetic microspheres.

7. The method according to claim 3, It is characterized in that The method of directional auxiliary assembly of conductive particles-carbon shells on the surface of silica-coated magnetic microspheres comprises: fully mixing a carbon source with a conductive metal salt solution, adding silica-coated magnetic microsphere particles, stirring, washing, filtering and drying to obtain a quaternary composite structure microsphere precursor.

8. The method according to claim 3, It is characterized in that The temperature for heat-treating the quaternary composite structure microsphere precursor is 200 - 600 °C, the heating rate is 1 - 5 °C, and the heat preservation time is 2 - 5 h; the reducing atmosphere used for the heat treatment is a hydrogen / argon mixed atmosphere; the alkali solution is an aqueous sodium hydroxide solution with a concentration of 3.6 M, and the treatment time is 35 hours.

9. An electromagnetic wave absorber, comprising the ternary core-shell composite structure microspheres described in claim 1 or 2.

10. Use of the ternary core-shell composite structure microspheres described in claim 1 or 2 in microwave absorption, catalysis, adsorption or wastewater treatment.

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