A structurally stable hollow microsphere microwave absorber, its preparation method and application

Abstract

This invention discloses a structurally stable hollow microsphere microwave absorbing agent, comprising an internal cavity and a composite spherical shell enclosing the cavity. By mass percentage, the composite spherical shell comprises, from the inside out, 15-70 wt% silicate glass shells, 1-6 wt% silica shells, 10-60 wt% silver shells, and 5-30 wt% ferrite shells. This composite hollow microsphere is formed by a combination of room-temperature aqueous solution reduction and heat treatment, a rapid and efficient preparation method suitable for electromagnetic wave absorption. This invention also discloses the preparation method and applications of this hollow microsphere microwave absorbing agent.

Description

Technical Field

[0001] This invention relates to the field of powder materials technology. More specifically, it relates to a structurally stable hollow microsphere microwave absorber, its preparation method, and its applications. Background Technology

[0002] In today's society, lightweighting of various equipment is becoming an important trend in technological development. Lightweighting can usually be achieved through structural design and the use of lightweight materials. Compared to the various limitations of structural design, lightweighting of key materials in equipment is a more effective and easier route to achieve lightweighting. However, given the molecular and atomic characteristics of materials, creating novel molecular structures to reduce the density of materials is difficult and has a clear ceiling. In contrast, using hollow or porous structures is a simpler and more feasible solution for achieving material lightweighting. Among various hollow structures, the strategy of constructing hollow micron-sized spherical structures and introducing them as lightweight fillers into composite material systems has unique advantages: First, spherical structures have good flowability and stacking properties, which is conducive to achieving efficient and high-proportion filling of hollow microspheres; second, for applications subjected to external loads, spherical structures are conducive to effectively dispersing the load and avoiding significant stress concentration, thus maintaining strength while reducing density; third, the micron size is conducive to the composite of hollow microspheres with the matrix and the utilization of size effects, while avoiding the common drawbacks of agglomeration and difficulty in dispersing smaller nanoparticles.

[0003] More importantly, constructing hollow microspheres using micron-scale spherical structures allows for the functionalization of these composite materials through shell design. Combined with the aforementioned mechanical stability of the spherical structure, this approach can reduce material density while endowing it with new functions, achieving a synergy of lightweighting, functionalization, and mechanical support capabilities. This provides possibilities for integrated structure-function design of materials. The hollow core of the microspheres provides low density and thermal insulation, but other properties depend more on the choice of shell material. For electromagnetic functional shells, metals and ferrites have attracted considerable attention due to their easily controllable crystal forms and chemical compositions. However, these two types of materials generally suffer from high density, failing to meet the lightweight development requirements of advanced materials. Therefore, researchers have designed and developed various hollow structures using metals and ferrites to reduce density. The construction of hollow structures mainly relies on template assistance or specific physicochemical reaction processes, which suffers from low efficiency and high requirements for material chemical composition. In recent years, there have been some reports on the preparation of composite hollow microspheres using preformed carriers. However, hollow microsphere materials still suffer from problems such as poor structural stability (including chemical and physical structural stability), simple composition, and difficulty in functional control. In addition, further research is needed on methods for preparing hollow microspheres that are economically viable and suitable for mass production. Summary of the Invention

[0004] To address the current problems of poor structural stability (including chemical and physical structural stability), simple composition, and difficulty in functional control of hollow microspheres, this invention provides a structurally stable hollow microsphere microwave absorber, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] On one hand, the present invention provides a structurally stable hollow microsphere absorbing agent, the absorbing agent being composed of an internal cavity and a composite spherical shell that encloses and seals the cavity; by mass percentage, the composite spherical shell comprises, from the inside out, 15-70 wt% silicate glass spherical shell, 1-6 wt% silica spherical shell, 10-60 wt% silver spherical shell and 5-30 wt% ferrite spherical shell.

[0007] Furthermore, the density of the microwave absorbing agent is 0.5-1.8 g / cm³. 3 The average diameter is 5-70 μm. It can be understood that the average diameter here represents the diameter of the outer surface of the hollow microsphere absorber.

[0008] Furthermore, the ferrite spherical shell is obtained by heat treatment of the precursor solution in air.

[0009] Furthermore, the chemical formula of the ferrite is A. x B y ·Fe2O4, wherein A and B are each independently selected from one of nickel, cobalt, manganese, zinc, copper, and magnesium, and 0≤x≤1, 0≤y≤1, and x+y=1.

[0010] In another aspect, the present invention provides a method for preparing the hollow microsphere absorbing agent as described above, comprising the following steps:

[0011] Hollow microspheres made of silicate glass were acid-washed to obtain hollow microspheres with silicate glass-silica shells.

[0012] The hollow microspheres of the silicate glass-silica spherical shell are subjected to surface activation treatment;

[0013] Metallic silver is coated onto the surface of the hollow microspheres with the above-mentioned surface-activated silicate glass-silica shell to obtain hollow microspheres with silicate glass-silica-silver shells.

[0014] Ferrite is coated onto the surface of the hollow microspheres with silicate glass-silicon oxide-silver spherical shells to obtain the hollow microsphere microwave absorbing agent.

[0015] Furthermore, the pickling treatment method is as follows:

[0016] The silicate glass hollow microspheres were sequentially immersed in flotation solution and acid washing solution to obtain the product.

[0017] Furthermore, the silicate glass hollow microspheres can be commercially available or prepared using methods known in the art. There are no particular limitations on the structural dimensions of the silicate glass hollow microspheres, as they are suitable for the purposes of this invention, and the thickness of the silicate shell can be 0.3-2 μm.

[0018] Furthermore, the flotation solution is water or ethanol or a mixture of the two in any proportion.

[0019] Furthermore, the pickling solution used in the pickling treatment is an aqueous solution of acid; the concentration of the pickling solution is 0.2-1 mol / L; and the acid is selected from inorganic acids.

[0020] Furthermore, the acid is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0021] Furthermore, the surface activation treatment method is as follows: the hollow microspheres of the silicate glass-silica spherical shell are sequentially immersed in a surface treatment solution and an activation solution.

[0022] Furthermore, the surface treatment solution is a coupling agent solution with a concentration of 3-40 g / L.

[0023] Furthermore, the coupling agent solution is an ethanol solution of the coupling agent, an aqueous solution of the coupling agent, or an ethanol-water solution of the coupling agent, wherein ethanol and water are mixed in any proportion.

[0024] Furthermore, the coupling agent is selected from at least one of 3-aminopropyltriethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-mercaptopropyltrimethoxysilane.

[0025] Furthermore, the activating solution is a stannous chloride solution with a concentration of 1-50 g / L.

[0026] Furthermore, the concentration of the hollow microspheres of the silicate glass-silica spherical shell in both the surface treatment solution and the activation solution is 20-300 g / L, preferably 50-200 g / L.

[0027] Furthermore, the method of coating metallic silver onto the surface of the hollow microspheres of the surface-activated silicate glass-silica spherical shell includes:

[0028] The hollow microspheres of the surface-activated silicate glass-silica spherical shell are mixed with silver salt solution, reducing agent and complexing agent, reacted, filtered and dried to obtain the final product.

[0029] Furthermore, the reducing agent is an organic or inorganic reducing agent that can reduce the corresponding silver ions to elemental silver, such as at least one of sodium hypophosphite, glucose, formaldehyde, sodium borohydride, potassium borohydride, and hydrazine hydrate.

[0030] Furthermore, the amount of the reducing agent added is 10-200 g / L.

[0031] Furthermore, the complexing agent is a complexing agent that can assist the reduction reaction, such as ammonia.

[0032] Furthermore, the silver salt solution is a nitrate solution, preferably an aqueous solution of nitrate.

[0033] Furthermore, the concentration of the silver salt solution is 5-50 g / L, such as 10-30 g / L.

[0034] Furthermore, the ratio of the hollow microspheres of the surface-activated silicate glass-silica spherical shell to the silver salt solution is 5-100 g / L, preferably 10-60 g / L.

[0035] Furthermore, the reaction temperature is 0-50℃ and the time is 3-30 min.

[0036] Furthermore, the method of coating the surface of the hollow microspheres having a silicate glass-silicon oxide-silver spherical shell with ferrite includes:

[0037] The hollow microspheres with silicate glass-silicon oxide-silver shells are mixed with a solution containing metal salts, organic additives and water, and then heat-treated.

[0038] Furthermore, the metal salt is an organic or inorganic salt of a metal.

[0039] Furthermore, the metal in the metal salt is selected from two or more of the following: iron salt, cobalt salt, nickel salt, copper salt, zinc salt, molybdenum salt, and manganese salt.

[0040] Furthermore, the organic additive is selected from one or more of citric acid, glycine, sucrose, malic acid, tartaric acid, chitosan, cellulose, and starch.

[0041] Furthermore, the concentration of the metal salt is 300-800 g / L.

[0042] Furthermore, the concentration of the organic additive is 200-600 g / L.

[0043] Furthermore, the mass concentration of the hollow microspheres with silicate glass-silica-silver sphere shells added is 0.2-1.0 g / mL.

[0044] Furthermore, the heat treatment temperature is 300-750℃, the time is 5-30 min, and the reaction atmosphere is air.

[0045] Furthermore, the method also includes heat treatment followed by sieve dispersion, wherein the sieve dispersion method is to gently grind and press the heat-treated product on a 50-300 mesh standard sieve.

[0046] In another aspect, the present invention provides the application of the hollow microsphere microwave absorbing agent described above in microwave absorption, catalysis, and wastewater treatment.

[0047] Furthermore, in the field of microwave absorption, it can be used as an electromagnetic wave absorber to form composite materials with a matrix material; when making composite materials, the volume fraction of the hollow microsphere microwave absorber of the present invention is between 20% and 90%.

[0048] The beneficial effects of this invention are as follows:

[0049] This hollow microsphere consists of an internal cavity and a composite shell that encloses the cavity. The multi-layered structure reduces defects in the shell and improves mechanical stability. Simultaneously, the abundant interfaces between the heterogeneous shells enhance electromagnetic functionality, enabling multiple scattering and dissipation of electromagnetic waves. Furthermore, the internal cavity not only reduces the overall density of the hollow microsphere but also extends the transmission path of electromagnetic waves through multiple scattering, further enhancing dissipation. This composite hollow microsphere is manufactured using a combination of room-temperature aqueous solution reduction and heat treatment, a rapid and efficient method well-suited for applications in electromagnetic wave absorption. Attached Figure Description

[0050] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0051] Figure 1 A schematic diagram of the structure of the silicate glass-silicon oxide-silver-ferrite composite hollow microspheres of the present invention is shown.

[0052] Figure 2 A schematic diagram showing the preparation process of the silicate glass-silicon oxide-silver-ferrite composite hollow microspheres described in the invention is shown.

[0053] Figure 3 The image shown is a low-magnification scanning electron microscope (SEM) image of the silicate glass-silicon oxide-silver-ferrite composite hollow microspheres obtained in Example 2.

[0054] Figure 4 The image shown is a high-magnification scanning electron microscope (SEM) image of the silicate glass-silicon oxide-silver-ferrite composite hollow microspheres obtained in Example 2. Detailed Implementation

[0055] 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.

[0056] Example 1

[0057] Silicate glass-silicon oxide-silver-ferrite composite hollow microspheres (the schematic diagram of which is shown below) Figure 1 The preparation process is as shown below, with the specific implementation plan as follows (see schematic diagram of the specific preparation process). Figure 2 As shown):

[0058] Using a density of 0.30 g / cm³ 3 Commercial silicate glass hollow microspheres.

[0059] The first step, flotation of silicate glass hollow microspheres: Silicate glass hollow microspheres are mixed with water at a volume ratio of 1:4, stirred, allowed to stand and separate into layers, and the upper floating microspheres are taken and filtered.

[0060] The second step is acid washing of silicate glass hollow microspheres: Add silicate glass hollow microspheres to 0.1 mol / L hydrochloric acid aqueous solution at a ratio of 0.1 g / mL, stir at room temperature for 10 min, filter, dry and set aside for use.

[0061] The third step is the surface treatment of silicate glass hollow microspheres: the acid-washed silicate glass hollow microspheres are added to a treatment solution containing 20 g / L 3-aminopropyltriethoxysilane (the solvent is ethanol and water in a volume ratio of 1:1) at a ratio of 0.5 g / mL (0.5 g microspheres per 1 mL of solution). The solution is stirred in a water bath at 40 °C for 20 min, filtered, and dried for later use.

[0062] Step 4, activation treatment of silicate glass hollow microspheres: The microspheres obtained in step 2 are treated in a 15 g / L stannous chloride solution at a ratio of 50 g / L, stirred at room temperature, filtered, dried and ready for use.

[0063] Fifth step: Add 1g of the microspheres obtained in the fourth step to 50mL of a solution containing 20g / L silver nitrate and 10g / L ammonia. Then, add 1.5g of hydrazine hydrate dropwise while stirring. React at room temperature with stirring. After the reaction is complete, filter and dry for later use.

[0064] Step 6: Weigh 16g of ferric nitrate, 6g of cobalt nitrate, and 25g of citric acid into a 100mL beaker, add 8g of deionized water, heat in a 35℃ water bath, and stir magnetically until completely dissolved to obtain a dark brown solution; mix the microspheres obtained in step 5 with the above solution at a ratio of 0.5g / mL. Then treat in air at 600℃ for 15min, and disperse through a 120-mesh sieve to obtain silicate glass-silicon oxide-silver-ferrite composite hollow microspheres.

[0065] The silicate glass-silicon oxide-silver-ferrite composite hollow microspheres obtained in this embodiment have a density of 0.56 g / cm³. 3 The average particle size is 45.9 micrometers, and the mass percentages of glass, silicon dioxide, silver and ferrite are 48%, 4%, 30% and 18%, respectively.

[0066] Example 2

[0067] The specific implementation scheme for the preparation of silicate glass-silicon oxide-silver-ferrite composite hollow microspheres is as follows:

[0068] A density of 0.38 g / cm³ was used. 3 Commercial silicate glass hollow microspheres.

[0069] The first step is flotation of silicate glass hollow microspheres: Silicate glass hollow microspheres are mixed with water at a volume ratio of 1:3, stirred, allowed to stand and separate into layers, and the upper floating microspheres are taken and filtered.

[0070] The second step is acid washing of silicate glass hollow microspheres: Add silicate glass hollow microspheres to 0.2 mol / L hydrochloric acid aqueous solution at a ratio of 0.13 g / mL, stir at room temperature for 10 min, filter, dry and set aside for use.

[0071] The third step is the surface treatment of silicate glass hollow microspheres: the acid-washed silicate glass hollow microspheres are added to a treatment solution containing 20 g / L 3-aminopropyltriethoxysilane (the solvent is ethanol and water in a volume ratio of 1:1) at a ratio of 0.7 g / mL (0.5 g microspheres per 1 mL of solution). The mixture is stirred in a water bath at 40 °C for 20 min, filtered, and dried for later use.

[0072] Step 4, activation treatment of silicate glass hollow microspheres: The microspheres obtained in step 2 are treated in a 15 g / L stannous chloride solution at a ratio of 60 g / L, stirred at room temperature, filtered, dried and ready for use.

[0073] Fifth step: Add 1g of the microspheres obtained in the fourth step to 100mL of a solution containing 20g / L silver nitrate and 10g / L ammonia. Then, add 3g of hydrazine hydrate dropwise while stirring. React at room temperature with stirring. After the reaction is complete, filter and dry for later use.

[0074] Step 6: Weigh 16g of ferric nitrate, 6g of cobalt nitrate, and 25g of citric acid into a 100mL beaker, add 8g of deionized water, heat in a 35℃ water bath, and stir magnetically until completely dissolved to obtain a dark brown solution; mix the microspheres obtained in Step 5 with the above solution at a ratio of 0.5g / mL. Then treat in air at 600℃ for 15min, and disperse through a 120-mesh sieve to obtain silicate glass-silica-silver-ferrite composite hollow microspheres. The low-magnification SEM images and high-magnification SEM images are shown below. Figure 3 and Figure 4 As shown.

[0075] The silicate glass-silicon oxide-silver-ferrite composite hollow microspheres obtained in this embodiment have a density of 0.95 g / cm³. 3 The average particle size is 42.6 micrometers, and the mass percentages of glass, silicon dioxide, silver and ferrite are 39%, 5%, 42% and 14%, respectively.

[0076] Example 3

[0077] The specific implementation scheme for the preparation of silicate glass-silicon oxide-silver-ferrite composite hollow microspheres is as follows:

[0078] A density of 0.46 g / cm³ was used. 3 Commercial silicate glass hollow microspheres.

[0079] The first step is flotation of silicate glass hollow microspheres: Silicate glass hollow microspheres are mixed with water at a volume ratio of 1:3, stirred, allowed to stand and separate into layers, and the upper floating microspheres are taken and filtered.

[0080] The second step is acid washing of silicate glass hollow microspheres: Add silicate glass hollow microspheres to 0.1 mol / L hydrochloric acid aqueous solution at a ratio of 0.5 g / mL, stir at room temperature for 5 min, filter, dry and set aside for use.

[0081] The third step is the surface treatment of silicate glass hollow microspheres: the acid-washed silicate glass hollow microspheres are added to a treatment solution containing 20 g / L 3-aminopropyltriethoxysilane (the solvent is ethanol and water in a volume ratio of 1:1) at a ratio of 1 g / mL (0.5 g microspheres per 1 mL of solution). The mixture is stirred in a water bath at 40 °C for 20 min, filtered, and dried for later use.

[0082] Step 4, activation treatment of silicate glass hollow microspheres: The microspheres obtained in step 2 are treated in a 15 g / L stannous chloride solution at a ratio of 90 g / L, stirred at room temperature, filtered, dried and ready for use.

[0083] Fifth step: Add 1g of the microspheres obtained in the fourth step to 20mL of a solution containing 30g / L silver nitrate and 13g / L ammonia. Then, add 0.8g of hydrazine hydrate dropwise while stirring. React at room temperature with stirring. After the reaction is complete, filter and dry for later use.

[0084] Step 6: Weigh 16g of ferric nitrate, 6g of cobalt nitrate, and 25g of citric acid into a 100mL beaker, add 8g of deionized water, heat in a 35℃ water bath, and stir magnetically until completely dissolved to obtain a dark brown solution; mix the microspheres obtained in Step 5 with the above solution at a ratio of 1g / mL. Then treat in air at 600℃ for 15min, and disperse through a 120-mesh sieve to obtain silicate glass-silicon oxide-silver-ferrite composite hollow microspheres.

[0085] The silicate glass-silicon oxide-silver-ferrite composite hollow microspheres obtained in this embodiment have a density of 0.64 g / cm³. 3 The average particle size is 21.1 micrometers, and the mass percentages of glass, silicon dioxide, silver and ferrite are 65%, 3%, 24% and 8%, respectively.

[0086] Example 4

[0087] The specific implementation scheme for the preparation of silicate glass-silicon oxide-silver-ferrite composite hollow microspheres is as follows:

[0088] A density of 0.20 g / cm³ was used. 3 Commercial silicate glass hollow microspheres.

[0089] The first step is flotation of silicate glass hollow microspheres: Silicate glass hollow microspheres are mixed with water at a volume ratio of 1:5, stirred, allowed to stand and separate into layers, and the upper floating microspheres are taken and filtered.

[0090] The second step is acid washing of silicate glass hollow microspheres: Add silicate glass hollow microspheres to 0.2 mol / L hydrochloric acid aqueous solution at a ratio of 0.1 g / mL, stir at room temperature for 10 min, filter, dry and set aside for use.

[0091] The third step is the surface treatment of silicate glass hollow microspheres: the acid-washed silicate glass hollow microspheres are added to a treatment solution containing 20 g / L 3-aminopropyltriethoxysilane (the solvent is ethanol and water in a volume ratio of 1:1) at a ratio of 0.3 g / mL (0.5 g microspheres per 1 mL of solution). The solution is stirred in a water bath at 40 °C for 20 min, filtered, and dried for later use.

[0092] Step 4, activation treatment of silicate glass hollow microspheres: The microspheres obtained in step 2 are treated in a 30 g / L stannous chloride solution at a ratio of 30 g / L, stirred at room temperature, filtered, dried and ready for use.

[0093] Fifth step: Add 1g of the microspheres obtained in the fourth step to 200mL of a solution containing 30g / L silver nitrate and 15g / L ammonia. Then, add 6g of hydrazine hydrate dropwise while stirring. React at room temperature with stirring. After the reaction is complete, filter and dry for later use.

[0094] Step 6: Weigh 16g of ferric nitrate, 6g of nickel nitrate, and 25g of citric acid into a 100mL beaker, add 8g of deionized water, heat in a 35℃ water bath, and stir magnetically until completely dissolved to obtain a dark brown solution; mix the microspheres obtained in Step 5 with the above solution at a ratio of 0.3g / mL. Then treat in air at 600℃ for 15min, and after the reaction, disperse through a 120-mesh sieve to obtain silicate glass-silicon oxide-silver-ferrite composite hollow microspheres.

[0095] The silicate glass-silicon oxide-silver-ferrite composite hollow microspheres obtained in this embodiment have a density of 1.07 g / cm³. 3 The average particle size is 66.8 micrometers, and the mass percentages of glass, silicon oxide, silver, and ferrite are 16%, 1.4%, 56%, and 26.6%, respectively.

[0096] Example 5

[0097] The specific implementation scheme for the preparation of silicate glass-silicon oxide-silver-ferrite composite hollow microspheres is as follows:

[0098] Using a density of 0.30 g / cm³ 3 Commercial silicate glass hollow microspheres.

[0099] The first step, flotation of silicate glass hollow microspheres: Silicate glass hollow microspheres are mixed with water at a volume ratio of 1:4, stirred, allowed to stand and separate into layers, and the upper floating microspheres are taken and filtered.

[0100] The second step is acid washing of silicate glass hollow microspheres: Add silicate glass hollow microspheres to a 0.15 mol / L hydrochloric acid aqueous solution at a ratio of 0.1 g / mL, stir at room temperature for 10 min, filter, dry and set aside for later use.

[0101] The third step is the surface treatment of silicate glass hollow microspheres: the acid-washed silicate glass hollow microspheres are added to a treatment solution containing 20 g / L 3-aminopropyltriethoxysilane (the solvent is ethanol and water in a volume ratio of 1:1) at a ratio of 0.5 g / mL (0.5 g microspheres per 1 mL of solution). The solution is stirred in a water bath at 40 °C for 20 min, filtered, and dried for later use.

[0102] Step 4, activation treatment of silicate glass hollow microspheres: The microspheres obtained in step 2 are treated in a 15 g / L stannous chloride solution at a ratio of 50 g / L, stirred at room temperature, filtered, dried and ready for use.

[0103] Fifth step: Add 1g of the microspheres obtained in the fourth step to 100mL of a solution containing 30g / L silver nitrate and 10g / L ammonia. Then, add 3g of hydrazine hydrate dropwise while stirring. React at room temperature with stirring. After the reaction is complete, filter and dry for later use.

[0104] Step 6: Weigh 16g of ferric nitrate, 6g of zinc nitrate, 10g of citric acid, and 15g of sucrose into a 100mL beaker, add 8g of deionized water, heat in a 35℃ water bath, and stir magnetically until completely dissolved to obtain a dark brown solution; mix the microspheres obtained in Step 5 with the above solution at a ratio of 0.2g / mL. Then treat in air at 600℃ for 15min, and disperse through a 120-mesh sieve to obtain silicate glass-silicon oxide-silver-ferrite composite hollow microspheres.

[0105] The silicate glass-silicon oxide-silver-ferrite composite hollow microspheres obtained in this embodiment have a density of 1.18 g / cm³. 3 The average particle size is 47.7 micrometers, and the mass percentages of glass, silicon dioxide, silver and ferrite are 21%, 3%, 40% and 36%, respectively.

[0106] Example 6

[0107] The specific implementation scheme for the preparation of silicate glass-silicon oxide-silver-ferrite composite hollow microspheres is as follows:

[0108] Using a density of 0.30 g / cm³ 3 Commercial silicate glass hollow microspheres.

[0109] The first step, flotation of silicate glass hollow microspheres: Silicate glass hollow microspheres are mixed with water at a volume ratio of 1:4, stirred, allowed to stand and separate into layers, and the upper floating microspheres are taken and filtered.

[0110] The second step is acid washing of silicate glass hollow microspheres: Add silicate glass hollow microspheres to a 0.15 mol / L hydrochloric acid aqueous solution at a ratio of 0.1 g / mL, stir at room temperature for 10 min, filter, dry and set aside for later use.

[0111] The third step is the surface treatment of silicate glass hollow microspheres: the acid-washed silicate glass hollow microspheres are added to a treatment solution containing 20 g / L 3-aminopropyltriethoxysilane (the solvent is ethanol and water in a volume ratio of 1:1) at a ratio of 0.5 g / mL (0.5 g microspheres per 1 mL of solution). The solution is stirred in a water bath at 40 °C for 20 min, filtered, and dried for later use.

[0112] Step 4, activation treatment of silicate glass hollow microspheres: The microspheres obtained in step 2 are treated in a 15 g / L stannous chloride solution at a ratio of 50 g / L, stirred at room temperature, filtered, dried and ready for use.

[0113] Fifth step: Add 1g of the microspheres obtained in the fourth step to 100mL of a solution containing 30g / L silver nitrate and 10g / L ammonia. Then, add 3g of hydrazine hydrate dropwise while stirring. React at room temperature with stirring. After the reaction is complete, filter and dry for later use.

[0114] Step 6: Weigh 16g ferric nitrate, 5g copper nitrate, 10g citric acid, and 15g sucrose into a 100mL beaker, add 8g deionized water, heat in a 35℃ water bath, and stir magnetically until completely dissolved to obtain a dark brown solution; mix the microspheres obtained in Step 5 with the above solution at a ratio of 0.6g / mL. Then treat in air at 600℃ for 15min, and disperse through a 120-mesh sieve to obtain silicate glass-silicon oxide-silver-ferrite composite hollow microspheres.

[0115] The silicate glass-silicon oxide-silver-ferrite composite hollow microspheres obtained in this embodiment have a density of 0.92 g / cm³. 3 The average particle size is 46.4 micrometers, and the mass percentages of glass, silicon dioxide, silver and ferrite are 28%, 4%, 54% and 14%, respectively.

[0116] Comparative Example 1

[0117] The specific implementation scheme for the preparation of silicate glass-silicon oxide-silver composite hollow microspheres is as follows:

[0118] Using a density of 0.30 g / cm³ 3 Commercial silicate glass hollow microspheres.

[0119] The first step, flotation of silicate glass hollow microspheres: Silicate glass hollow microspheres are mixed with water at a volume ratio of 1:4, stirred, allowed to stand and separate into layers, and the upper floating microspheres are taken and filtered.

[0120] The second step is acid washing of silicate glass hollow microspheres: Add silicate glass hollow microspheres to a 0.15 mol / L hydrochloric acid aqueous solution at a ratio of 0.1 g / mL, stir at room temperature for 10 min, filter, dry and set aside for later use.

[0121] The third step is the surface treatment of silicate glass hollow microspheres: the acid-washed silicate glass hollow microspheres are added to a treatment solution containing 20 g / L 3-aminopropyltriethoxysilane (the solvent is ethanol and water in a volume ratio of 1:1) at a ratio of 0.5 g / mL (0.5 g microspheres per 1 mL of solution). The solution is stirred in a water bath at 40 °C for 20 min, filtered, and dried for later use.

[0122] Step 4, activation treatment of silicate glass hollow microspheres: The microspheres obtained in step 2 are treated in a 15 g / L stannous chloride solution at a ratio of 50 g / L, stirred at room temperature, filtered, dried and ready for use.

[0123] Fifth step: Add 1g of the microspheres obtained in the fourth step to 130mL of a solution containing 30g / L silver nitrate and 10g / L ammonia. Then, add 3g of hydrazine hydrate dropwise while stirring. React at room temperature with stirring. After the reaction is complete, filter and dry for later use.

[0124] The silicate glass-silicon oxide-silver-ferrite composite hollow microspheres obtained in this embodiment have a density of 0.94 g / cm³. 3 The average particle size is 46.4 micrometers, and the mass percentages of glass, silicon oxide, silver and ferrite are 28%, 4% and 68% respectively (excluding ferrite, with silver on the outermost side).

[0125] Comparative Example 2

[0126] The specific implementation scheme for the preparation of silicate glass-silicon oxide-ferrite-silver composite hollow microspheres is as follows:

[0127] Using a density of 0.30 g / cm³ 3 Commercial silicate glass hollow microspheres.

[0128] The first step, flotation of silicate glass hollow microspheres: Silicate glass hollow microspheres are mixed with water at a volume ratio of 1:4, stirred, allowed to stand and separate into layers, and the upper floating microspheres are taken and filtered.

[0129] The second step is acid washing of silicate glass hollow microspheres: Add silicate glass hollow microspheres to a 0.15 mol / L hydrochloric acid aqueous solution at a ratio of 0.1 g / mL, stir at room temperature for 10 min, filter, dry and set aside for later use.

[0130] Third, weigh 16g of ferric nitrate, 5g of copper nitrate, 10g of citric acid, and 15g of sucrose into a 100mL beaker, add 8g of deionized water, heat in a 35℃ water bath, and stir magnetically until completely dissolved to obtain a dark brown solution; mix the microspheres obtained in step five with the above solution at a ratio of 0.6g / mL. Then treat in air at 600℃ for 15min, and disperse through a 120-mesh sieve to obtain silicate glass-silica-ferrite composite hollow microspheres.

[0131] Fourth step: Add the silicate glass-silica-ferrite composite hollow microspheres obtained in the third step to a treatment solution containing 20 g / L 3-aminopropyltriethoxysilane (the solvent is ethanol and water in a volume ratio of 1:1) at a ratio of 0.5 g / mL (0.5 g microspheres per 1 mL of solution). Stir in a water bath at 40 °C for 20 min, filter, and dry for later use.

[0132] Fifth, the microspheres obtained in the fourth step are treated in a 15 g / L stannous chloride solution at a ratio of 50 g / L, stirred at room temperature, filtered, dried and ready for use.

[0133] Step 6: Add 1g of the microspheres obtained in step 4 to 70mL of a solution containing 30g / L silver nitrate and 10g / L ammonia. Then, add 3g of hydrazine hydrate dropwise while stirring. React at room temperature with stirring. After the reaction is complete, filter and dry for later use.

[0134] The silicate glass-silicon oxide-ferrite-silver composite hollow microspheres obtained in this embodiment have a density of 0.92 g / cm³. 3 The average particle size is 46.4 micrometers, and the mass percentages of glass, silicon oxide, ferrite and silver are 28%, 4%, 14% and 54% respectively (silver is on the outside of the ferrite (silver is on the outermost side)).

[0135] The performance parameters of the hollow composite microspheres prepared in the above embodiments are shown in Table 1 below. Wherein:

[0136] Performance testing:

[0137] Density and strength testing of silicate glass-silicon oxide-silver-ferrite composite hollow microspheres:

[0138] Density was tested using Archimedes' principle. Strength was evaluated using isostatic pressing, referring to the patent "A method for determining the isostatic pressing strength of hollow glass microspheres" (201410196976.0), with a loading pressure of 25 MPa and a constant pressure time of 3 min.

[0139] Electromagnetic property testing of hollow composite microspheres and lightweight functional composite materials using them as fillers:

[0140] (1) Electromagnetic performance test of hollow composite microspheres: Hollow composite microspheres were mixed with paraffin to prepare coaxial rings (the mass fraction of hollow microspheres in the sample is shown in Table 1). The inner diameter of the ring was 3 mm, the outer diameter was 7 mm, and the thickness was 2 mm. The electromagnetic parameters were then tested using a vector network analyzer to analyze its electromagnetic performance. The effective absorption bandwidth is the frequency range with a reflection loss ≤ -10 dB.

[0141] (2) Electromagnetic performance test of composite material with hollow composite microspheres as filler: The prepared composite material was processed into a coaxial ring with an inner diameter of 3 mm, an outer diameter of 7 mm, and a thickness of 2 mm. The electromagnetic parameters were then tested using the coaxial method through a vector network analyzer to analyze its electromagnetic performance.

[0142] (3) The saturation magnetization intensity was measured using a vibrating sample magnetometer.

[0143] Table 1 Performance parameters of hollow composite microsphere samples obtained in each embodiment

[0144]

[0145] 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. A structurally stable hollow microsphere microwave absorbing agent, characterized in that, The microwave absorbing agent consists of an internal cavity and a composite spherical shell that encloses the cavity; by mass percentage, the composite spherical shell comprises, from the inside out, 15-70 wt% silicate glass spherical shell, 1-6 wt% silica spherical shell, 10-60 wt% silver spherical shell and 5-30 wt% ferrite spherical shell.

2. The hollow microsphere microwave absorbing agent according to claim 1, characterized in that, The density of the microwave absorber is 0.5-1.8 g / cm³. 3 The average diameter is 5-70 μm.

3. The hollow microsphere microwave absorbing agent according to claim 1, characterized in that, The chemical formula of the ferrite is A. x B y ·Fe2O4, wherein A and B are each independently selected from one of nickel, cobalt, manganese, zinc, copper, and magnesium, and 0≤x≤1, 0≤y≤1, and x+y=1.

4. The method for preparing the hollow microsphere microwave absorbing agent according to any one of claims 1-3, characterized in that, Includes the following steps: Hollow microspheres made of silicate glass were acid-washed to obtain hollow microspheres with silicate glass-silica shells. The hollow microspheres of the silicate glass-silica spherical shell are subjected to surface activation treatment; Metallic silver is coated onto the surface of the hollow microspheres with the above-mentioned surface-activated silicate glass-silica shell to obtain hollow microspheres with silicate glass-silica-silver shells. Ferrite is coated onto the surface of the hollow microspheres with silicate glass-silicon oxide-silver spherical shells to obtain the hollow microsphere microwave absorbing agent.

5. The preparation method according to claim 4, characterized in that, The pickling treatment uses an aqueous solution of acid; the concentration of the pickling solution is 0.2-1 mol / L; and the acid is selected from inorganic acids.

6. The preparation method according to claim 4, characterized in that, The surface activation treatment method is as follows: the hollow microspheres of the silicate glass-silica spherical shell are sequentially immersed in a surface treatment solution and an activation solution.

7. The preparation method according to claim 6, characterized in that, The surface treatment solution is a coupling agent solution with a concentration of 3-40 g / L.

8. The preparation method according to claim 6, characterized in that, The activation solution is a stannous chloride solution with a concentration of 1-50 g / L.

9. The preparation method according to claim 6, characterized in that, The concentration of the hollow microspheres in the silicate glass-silica spherical shell is 20-300 g / L in both the surface treatment solution and the activation solution.

10. The preparation method according to claim 4, characterized in that, The method of coating metallic silver onto the surface of the hollow microspheres of the aforementioned surface-activated silicate glass-silica spherical shell includes: The hollow microspheres of the surface-activated silicate glass-silica spherical shell are mixed with silver salt solution, reducing agent and complexing agent, reacted, filtered and dried to obtain the final product.

11. The preparation method according to claim 10, characterized in that, The silver salt solution is a nitrate solution.

12. The preparation method according to claim 10, characterized in that, The ratio of the hollow microspheres in the surface-activated silicate glass-silica spherical shell to the silver salt solution is 5-100 g / L.

13. The preparation method according to claim 10, characterized in that, The reaction is carried out at a temperature of 0-50℃ for a time of 3-30 minutes.

14. The preparation method according to claim 4, characterized in that, The method of coating the surface of the hollow microspheres having a silicate glass-silicon oxide-silver spherical shell with ferrite includes: The hollow microspheres with silicate glass-silicon oxide-silver shells are mixed with a solution containing metal salts, organic additives and water, and then heat-treated.

15. The preparation method according to claim 14, characterized in that, The metal salt is an organic or inorganic salt of a metal.

16. The preparation method according to claim 14, characterized in that, The metal salt is selected from two or more of the following: iron salt, cobalt salt, nickel salt, copper salt, zinc salt, molybdenum salt, and manganese salt.

17. The preparation method according to claim 14, characterized in that... The heat treatment temperature is 300-750℃, the time is 5-30 minutes, and the reaction atmosphere is air.

18. The application of the hollow microsphere microwave absorbing agent as described in any one of claims 1-3 in microwave absorption, catalysis, and wastewater treatment.

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