Magnetic composite foam as well as preparation method and application thereof

Abstract

The invention discloses magnetic composite foam as well as a preparation method and application thereof. The composite foam structurally comprises a plurality of hollow composite microspheres and a connecting material for connecting the hollow composite microspheres, wherein the hollow composite microsphere is composed of a glass hollow microsphere and a magnetic metal spherical shell layer coating the glass hollow microsphere; the binder is composed of a carbon matrix and metal particles dispersed in the carbon matrix. In the structure of the magnetic composite foam, the inter-spherical connection structure and composition of the double-spherical-shell magnetic metal hollow microspheres are designed, and a magnetic metal hollow microsphere-carbon-metal particle composite structure can be formed through connection of amorphous carbon-metal composite materials among the hollow microspheres; the macroscopic conductivity and the microscopic loss capability of the composite structure can be regulated and controlled by utilizing dielectric and conductive characteristics of carbon and metal, and light weight is realized by utilizing a large-proportion cavity.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and more specifically to a magnetic composite foam and a preparation method and application thereof. Background Art

[0002] Magnetic metals have both electrical conductivity and magnetism, and also have easily controllable chemical composition (alloy ratio), degree of crystallization and macroscopic morphology, which also makes it possible to control their electromagnetic properties over a large range. Therefore, magnetic metals are widely used in the adjustment of electromagnetic parameters of composite materials to construct electromagnetic wave absorption and shielding composite materials (electromagnetic functional composite materials) suitable for different forms and application scenarios. With the rapid development of new electronic materials and the increasing requirements for material applications, whether for electromagnetic wave stealth or the control of electromagnetic interference and biological damage, dissipating electromagnetic wave energy through absorption mechanisms is a more effective way, and the realization of the absorption mechanism is inseparable from high-performance electromagnetic wave absorbers (absorbers). In order to obtain the expected electromagnetic wave loss effect, absorbers usually account for a higher proportion in electromagnetic functional composite materials, and their density and electromagnetic properties have also become the key to restricting the overall density and functionality of electromagnetic functional composite materials. Since the density adjustment space of the matrix material itself is limited, the lightweight design of the absorber is the decisive factor in achieving the lightweight of electromagnetic functional composite materials. Given that the density of magnetic metals is much higher than that of the matrix materials (typically polymers) of electromagnetic functional composites, hollow structures have been widely incorporated into the design of magnetic metal absorbers to reduce density and improve overall performance. Magnetic metal absorbers with hollow microsphere structures have attracted particular research interest due to their high stability and ease of achieving large-scale filling and dispersion within the matrix.

[0003] Similar to other magnetic metal absorbers with different morphologies, magnetic metals designed as hollow microspheres still face the challenge of high conductivity and the tendency to form a conductive network when filled at a high ratio. This conductive network presents a double-edged sword for absorbers. On the one hand, in electromagnetically functional composite materials where absorption is essential, the excessively high conductivity resulting from the formation of a conductive network hinders impedance matching. This results in incident electromagnetic waves being largely reflected at the composite surface, preventing them from entering the material and fully utilizing the material's loss capacity to absorb the electromagnetic wave energy. On the other hand, moderate conductivity allows incident waves to dissipate through leakage conduction losses, contributing to improved overall absorption performance. However, current methods of directly compounding hollow magnetic metal microspheres with a matrix present difficulties in effectively controlling the connectivity between the microspheres and, further, in modulating their macroscopic conductivity and loss capacity. Specifically, at excessively high microsphere ratios, contact between the microspheres forms, and the inherent high conductivity of the magnetic metal leads to excessively high conductivity and poor matching in the composite material. In contrast, at lower filling ratios, the high dispersion afforded by the spherical shape of the magnetic metal hollow microspheres results in uniform coating and dispersion of the microspheres. This isolation between the microspheres leads to excessively low macroscopic conductivity in the composite. While this facilitates the entry of incident electromagnetic waves into the composite, it prevents the enhanced losses through leakage conduction. Therefore, controlling the distribution and connectivity of magnetic metal hollow microsphere absorbers within the composite to achieve macroscopic conductivity regulation is a potential approach to improving the effectiveness of this type of absorber. However, the design of a controllable magnetic metal hollow microsphere distribution and connectivity structure, as well as methods for their efficient implementation, remain unresolved. Summary of the Invention

[0004] Based on the above facts, the purpose of the present invention is to provide a magnetic composite foam and a preparation method and application thereof, so as to at least solve the above technical problems.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] In one aspect, the present invention provides a magnetic composite foam, wherein the composite foam structure comprises a plurality of hollow composite microspheres and a connecting material connecting the hollow composite microspheres;

[0007] The hollow composite microspheres are composed of glass hollow microspheres and a magnetic metal shell layer covering the glass hollow microspheres.

[0008] The connecting material consists of a carbon matrix and metal particles dispersed in the carbon matrix.

[0009] That is, the hollow composite microspheres are composed of a hollow core, a glass shell layer and a magnetic metal shell layer arranged in sequence from the inside out, wherein the glass shell layer and the magnetic metal shell layer are both continuous and closed shell layers.

[0010] Furthermore, the material of the magnetic metal spherical shell layer 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.

[0011] Furthermore, the material of the carbon matrix is ​​carbon.

[0012] Furthermore, the metal particles are selected from one of iron, cobalt, silver, copper and nickel, or a binary alloy formed by two of them, or a ternary alloy formed by three of them.

[0013] For electromagnetic wave stealth, the incident electromagnetic wave cannot be directly reflected back (otherwise it will be received and detected by the radar), so the conductivity cannot be too good (impedance matching is required). A good match is to let the electromagnetic wave come in as early as possible, and then consume the electromagnetic wave energy through the loss capacity of the material; in this technical solution, through the selection of metal particles in the connecting material and its mixing with the carbon matrix, the material has a better electromagnetic shielding effect.

[0014] The composite foam comprises, by weight percentage, 40-57% hollow glass microspheres, 30-35% magnetic metal shells, 4-6% carbon matrix, and 8-11% metal particles. By controlling the selection and content of the components in the composite foam, the preparation process is simplified, while the composite material achieves both density and strength, as well as electromagnetic shielding performance.

[0015] Furthermore, the connecting material includes a plurality of through-holes. It is understood that the connecting material connecting the hollow composite microspheres includes through-holes, and the through-holes are located between the hollow composite microspheres in the connecting material. The presence of through-holes reduces density, increases interfacial polarization, improves compatibility, and facilitates electromagnetic wave penetration into the material, reducing losses during transmission.

[0016] Furthermore, the apparent density of the composite foam is 0.15-0.55 g / cm 3 , the porosity is 87-97%, and the open porosity is 46-54%.

[0017] In the present invention, the three-dimensional connection structure of magnetic metal hollow microspheres is designed, and the distribution and connection state of the hollow composite microspheres in the composite material are controlled to achieve the regulation of the macroscopic conductivity of the composite material, and the improvement of the electromagnetic wave absorption capacity is achieved by means of the balanced design of the material's conductivity, dielectricity and magnetism. Specifically, lightweight and high-strength double-shell magnetic metal hollow microspheres are first prepared, and the adsorption of the precursor sol on the microsphere surface and the enrichment between the microspheres are achieved by utilizing the adsorption effect and the capillary action principle between the hollow microspheres. After post-processing, the heterogeneous components are synergistically decomposed, carbonized and reduced to form a hollow microsphere inter-sphere connection network with the carbon-metal composite material as the connector. The electromagnetic properties of the connector are regulated by the enrichment and decomposition conditions to achieve the regulation of the conductivity and dielectric properties of the connection structure.

[0018] In another aspect, the present invention provides a method for preparing the composite foam as described above, the method comprising the following steps:

[0019] Performing surface activation pretreatment on the glass hollow microspheres to obtain activated glass hollow microspheres;

[0020] Coating a magnetic metal on the surface of the activated glass hollow microspheres;

[0021] The obtained microspheres are subjected to a connection treatment to obtain the composite foam.

[0022] Furthermore, the activation pretreatment method comprises the following steps:

[0023] The glass hollow microspheres are dispersed in treatment solution A and treatment solution B in sequence to obtain the activated glass hollow microspheres. Furthermore, the density of the glass hollow microspheres is 0.1-0.9 g / cm 3 , an exemplary range is 0.1-0.6 g / cm 3 .

[0024] Furthermore, the solute of the treatment solution A is a coupling agent, such as KH550, etc., and the concentration of the solute is preferably 10-15 g / L, more preferably 12 g / L.

[0025] Preferably, the solute of the treatment liquid A is a coupling agent, and the solvent is anhydrous ethanol, distilled water, or a mixture of the two in any proportion. Preferably, the volume ratio of anhydrous ethanol to distilled water is 1:1-3:1.

[0026] Preferably, the treatment solution B contains a noble metal salt, an acid and water, wherein the concentration of the noble metal salt in the treatment solution B is 0.002-0.2 mol / L, preferably 0.005-0.05 mol / L, more preferably 0.005-0.01 mol / L, more preferably 0.008 mol / L, etc.

[0027] Furthermore, in the treatment solution B, the noble metal salt includes but is not limited to palladium chloride.

[0028] Furthermore, in the treatment liquid B, the acid includes but is not limited to hydrochloric acid. In the treatment liquid B, the concentration of the acid includes but is not limited to 0.3-0.6 mol / L, preferably 0.5 mol / L.

[0029] Preferably, the temperature of the activation pretreatment is 10-50°C.

[0030] Furthermore, the activation pretreatment method further includes stirring, dispersing and drying steps after the glass hollow microspheres are sequentially dispersed in treatment liquid A and treatment liquid B, wherein the stirring temperature is 10-50°C, preferably 40-50°C, and the stirring time is 30-60 minutes.

[0031] Furthermore, the method of coating the surface of activated glass hollow microspheres with magnetic metal comprises the following steps:

[0032] The activated glass hollow microspheres are dispersed in a treatment solution C containing magnetic metal ions, and the process is followed by stirring in a water bath, filtering, drying and screening out agglomerates to obtain the obtained product.

[0033] Preferably, the treatment solution C is an aqueous solution obtained by mixing a magnetic metal ion source salt, a stabilizer, a reducing agent, a pH regulator and water.

[0034] Preferably, the magnetic metal ion source salt is selected from sulfates, nitrates, chlorides or organic acid salts of magnetic metals (exemplary magnetic metal ion source salts include but are not limited to one or more selected from nickel sulfate, cobalt sulfate, and ferrous ammonium sulfate), and the concentration of the magnetic metal ion source salt in the treatment solution C is 10-70 g / L.

[0035] Preferably, the stabilizer is selected from ammonium sulfate and / or potassium sodium tartrate, and the concentration of the stabilizer in the treatment solution C is 20-100 g / L.

[0036] Preferably, the stirring temperature of the water bath is 55-80°C.

[0037] Preferably, the amount of the activated glass hollow microspheres added to the treatment solution C is 0.004-0.012 g / mL.

[0038] Furthermore, the method for connecting the obtained microspheres comprises the following steps:

[0039] The obtained microspheres are dispersed in the treatment liquid D, stirred evenly, the excess treatment liquid D is filtered out under normal pressure, dried, and heat-treated under a reducing atmosphere to obtain the composite foam.

[0040] Furthermore, the treatment solution D is a mixture of metal salt, carbon source, and water in a mass ratio of 7-10:4-8:4-7. Preferably, the mass ratio is (8-12):6:5, and more preferably (9-11):6:5. In this case, the overall performance of the obtained material is better.

[0041] Furthermore, the metal salt in the treatment solution D is a water-soluble nitrate or organic acid salt of nickel, iron or cobalt. Exemplary metal salts include, but are not limited to, one or more of nickel nitrate, cobalt nitrate, iron nitrate, and the like.

[0042] Preferably, the carbon source in the treatment solution D is an organic carbon source, selected from one or more of citric acid, starch, sucrose and tartaric acid.

[0043] Preferably, the amount of the microspheres added to the treatment solution D is 0.02-0.2 g / mL.

[0044] Preferably, the heat treatment is carried out in a hydrogen / argon mixed atmosphere at a temperature of 500-700° C. for 1-4 hours.

[0045] In another aspect, the present invention provides a microwave absorbing or shielding material, which is prepared from the composite foam as described above.

[0046] In another aspect, the present invention provides use of the composite foam as described above in the preparation of a microwave absorbing or shielding device.

[0047] Furthermore, the application in the preparation of microwave absorbing or shielding material devices can be used as one of the following materials: military stealth field, electromagnetic radiation protection of broadcasting and television transmitters, microwave darkroom materials, electromagnetic shielding materials in buildings or radio communication equipment.

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

[0049] The magnetic composite foam structure provided by the present invention can provide a new approach to the construction of macroscopic three-dimensional materials for composite electromagnetic functional hollow microspheres. In the structure of this magnetic composite foam, the inter-sphere connection structure and composition of the double-shell magnetic metal hollow microspheres are designed. By connecting the amorphous carbon-metal composite material between the hollow microspheres, a magnetic metal hollow microsphere-carbon-metal particle composite structure can be formed. The dielectric and conductive properties of carbon and metal can be used to regulate the macroscopic conductivity and microscopic loss capacity of the composite structure, and a large-scale cavity can be used to achieve lightweighting. In addition, the magnetic metal shells in this structure realize magnetic loss, and the glass shells realize mechanical support. The composite welding material between the spheres realizes the improvement of matching, dielectric loss, and overall electromagnetic function. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0051] Figure 1 A flow chart for preparing an exemplary glass-metal-carbon composite foam material according to the present invention is shown.

[0052] Figure 2 A schematic structural diagram of an exemplary glass-metal-carbon composite foam material in the present invention is shown.

[0053] Figure 3 A scanning electron microscope image of the glass-metal-carbon composite foam material obtained in Example 1 is shown. DETAILED DESCRIPTION

[0054] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the following detailed description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0055] In a specific embodiment of the present invention, the schematic diagram of the preparation process of an exemplary glass-metal-carbon composite foam material is as follows: Figure 1 As shown; the structural schematic diagram of an exemplary glass-metal-carbon composite foam material is shown Figure 2 shown.

[0056] Example 1

[0057] The preparation of glass-metal-carbon composite foam material comprises the following steps:

[0058] 1) Preparation of activated glass hollow microspheres: 50g of glass hollow microspheres (density 0.30g / cm 3 ) was dispersed in 1000 ml of treatment solution A: 12 g / L silane coupling agent KH550, the solvent being a mixture of anhydrous ethanol and water in a volume ratio of 2:1; then dispersed in 750 ml of treatment solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, the solvent being water, stirred at 40° C. for 30 min, filtered, dried at 50° C., and sieved to remove agglomerated particles to obtain activated glass hollow microspheres;

[0059] 2) The activated glass hollow microspheres obtained in step 1) were dispersed in a magnetic metal assembly treatment solution C at a ratio of 1 g / 140 mL. The reaction solution was a water solvent containing 25 g / L nickel sulfate, 40 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate. The pH was adjusted to 9.5 with concentrated ammonia water. The reaction was stirred at 70° C. After the reaction was completed, the solution was filtered to obtain magnetic metal (metal 1)-glass hollow microspheres.

[0060] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed in the treatment liquid D at a ratio of 1 g / 10 mL. The reaction solution was mixed with nickel nitrate, citric acid and water in a mass ratio of 9:6:5, stirred evenly at room temperature, and the excess treatment liquid D was filtered out under normal pressure. The filter cake was then removed, dried, and heat treated at 700 ° C in a hydrogen / argon mixed atmosphere for 3 h to obtain a glass-metal-carbon composite foam material in which the microspheres were connected by a carbon-metal (metal 2) composite material.

[0061] The apparent density of the glass-metal-carbon composite foam material obtained in this example is 0.28 g / cm 3 , the porosity is 91.8%, the open porosity is 50.5%, and its SEM image is as follows Figure 3 As shown; the mass fractions of glass, carbon, metal 1 and metal 2 are 50.6%, 4.9%, 35.4% and 9.1% respectively; the optimized electromagnetic wave optimal reflection loss value (RL minimum value) at a thickness of 2mm is -23.2dB, and the effective absorption bandwidth is 5.6GHz (9.8-15.4GHz).

[0062] Example 2

[0063] The preparation of glass-metal-carbon composite foam material comprises the following steps:

[0064] 1) Preparation of activated glass hollow microspheres: 50g of glass hollow microspheres (density 0.32g / cm 3 ) was dispersed in 1000 ml of treatment solution A: 12 g / L silane coupling agent KH550, the solvent being a mixture of anhydrous ethanol and water in a volume ratio of 2:1; then dispersed in 750 ml of treatment solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, the solvent being water, stirred at 40° C. for 30 min, filtered, dried at 50° C., and sieved to remove agglomerated particles to obtain activated glass hollow microspheres;

[0065] 2) The activated glass hollow microspheres obtained in step 1) were dispersed in a magnetic metal assembly treatment solution C at a ratio of 1 g / 200 mL. The reaction solution was a water solvent containing 25 g / L nickel sulfate, 40 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate. The pH was adjusted to 9.5 with concentrated ammonia water. The reaction was stirred at 70° C. After the reaction was completed, the solution was filtered to obtain magnetic metal (metal 1)-glass hollow microspheres.

[0066] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed in the treatment liquid D at a ratio of 1 g / 10 mL. The reaction solution was mixed with nickel nitrate, citric acid and water in a mass ratio of 9:6:5, stirred evenly at room temperature, and the excess treatment liquid D was filtered out under normal pressure. The filter cake was then removed, dried, and heat treated at 550 ° C in a hydrogen / argon mixed atmosphere for 4 h to obtain a glass-metal-carbon composite foam material in which the microspheres were connected by a carbon-metal (metal 2) composite material.

[0067] The apparent density of the glass-metal-carbon composite foam material obtained in this example is 0.34 g / cm 3 The porosity is 92.0%, the open porosity is 51.2%; the mass fractions of glass, carbon, metal 1 and metal 2 are 43.9%, 4.2%, 43.9% and 8.0% respectively; the optimized electromagnetic wave optimal reflection loss value (RL minimum value) at a thickness of 2mm is -31.4dB, and the effective absorption bandwidth is 5.2GHz (10-15.2GHz).

[0068] Example 3

[0069] The preparation of glass-metal-carbon composite foam material comprises the following steps:

[0070] 1) Preparation of activated glass hollow microspheres: 50g of glass hollow microspheres (density 0.38g / cm 3 ) was dispersed in 1000 ml of treatment solution A: 12 g / L silane coupling agent KH550, the solvent being a mixture of anhydrous ethanol and water in a volume ratio of 2:1; then dispersed in 750 ml of treatment solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, the solvent being water, stirred at 40° C. for 30 min, filtered, dried at 50° C., and sieved to remove agglomerated particles to obtain activated glass hollow microspheres;

[0071] 2) The activated glass hollow microspheres obtained in step 1) were dispersed in a magnetic metal assembly treatment solution C at a ratio of 1 g / 100 mL. The reaction solution was a water solvent containing 26.8 g / L cobalt sulfate, 40 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate. The pH was adjusted to ≈ 10 with concentrated aqueous ammonia. The reaction was stirred at 70° C. After the reaction was completed, the solution was filtered to obtain magnetic metal (metal 1)-glass hollow microspheres.

[0072] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed in the treatment liquid D at a ratio of 1 g / 10 mL. The reaction solution was mixed with nickel nitrate, citric acid and water in a mass ratio of 9:6:5, stirred evenly at room temperature, and the excess treatment liquid D was filtered out under normal pressure. The filter cake was then removed, dried, and heat treated at 700 ° C in a hydrogen / argon mixed atmosphere for 3 h to obtain a glass-metal-carbon composite foam material in which the microspheres were connected by a carbon-metal (metal 2) composite material.

[0073] The apparent density of the glass-metal-carbon composite foam material obtained in this example is 0.33 g / cm 3 The porosity is 91.0%, the open porosity is 48.3%; the mass fractions of glass, carbon, metal 1 and metal 2 are 56.3%, 5.4%, 28.2% and 10.1% respectively; the optimized electromagnetic wave optimal reflection loss value (RL minimum value) at a thickness of 2mm is -27.5dB, and the effective absorption bandwidth is 6.0GHz (9.5-15.5GHz).

[0074] Example 4

[0075] The preparation of glass-metal-carbon composite foam material comprises the following steps:

[0076] 1) Preparation of activated glass hollow microspheres: 50g of glass hollow microspheres (density 0.40g / cm 3 ) was dispersed in 1000 ml of treatment solution A: 12 g / L silane coupling agent KH550, the solvent being a mixture of anhydrous ethanol and water in a volume ratio of 2:1; then dispersed in 750 ml of treatment solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, the solvent being water, stirred at 40° C. for 30 min, filtered, dried at 50° C., and sieved to remove agglomerated particles to obtain activated glass hollow microspheres;

[0077] 2) The activated glass hollow microspheres obtained in step 1) were dispersed in a magnetic metal assembly treatment solution C at a ratio of 1 g / 140 mL. The reaction solution was a water solvent containing 26.8 g / L cobalt sulfate, 40 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate. The pH was adjusted to 10.5 with concentrated aqueous ammonia. The reaction was stirred at 70° C. After the reaction was completed, the solution was filtered to obtain magnetic metal (metal 1)-glass hollow microspheres.

[0078] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed in the treatment liquid D at a ratio of 1 g / 10 mL. The reaction solution was mixed with nickel nitrate, citric acid and water in a mass ratio of 9:6:5, stirred evenly at room temperature, and the excess treatment liquid D was filtered out under normal pressure. The filter cake was then removed, dried, and heat treated at 700 ° C in a hydrogen / argon mixed atmosphere for 2 h to obtain a glass-metal-carbon composite foam material in which the microspheres were connected by a carbon-metal (metal 2) composite material.

[0079] The apparent density of the glass-metal-carbon composite foam material obtained in this example is 0.37 g / cm 3The porosity is 90.6% and the open porosity is 50.8%; the mass fractions of glass, carbon, metal 1 and metal 2 are 50.3%, 4.9%, 35.6% and 9.2% respectively; the optimized electromagnetic wave optimal reflection loss value (RL minimum value) at a thickness of 2mm is -33.7dB, and the effective absorption bandwidth is 6.2GHz (9.7-15.9GHz).

[0080] Example 5

[0081] The preparation of glass-metal-carbon composite foam material comprises the following steps:

[0082] 1) Preparation of activated glass hollow microspheres: 50g of glass hollow microspheres (density 0.50g / cm 3 ) was dispersed in 1000 ml of treatment solution A: 12 g / L silane coupling agent KH550, the solvent being a mixture of anhydrous ethanol and water in a volume ratio of 2:1; then dispersed in 750 ml of treatment solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, the solvent being water, stirred at 40° C. for 30 min, filtered, dried at 50° C., and sieved to remove agglomerated particles to obtain activated glass hollow microspheres;

[0083] 2) The activated glass hollow microspheres obtained in step 1) were dispersed in a magnetic metal assembly treatment solution C at a ratio of 1 g / 105 mL. The reaction solution was a water solvent containing 15 g / L nickel sulfate, 15 g / L cobalt sulfate, 50 g / L sodium hypophosphite, 80 g / L potassium sodium tartrate, and 50 g / L ammonium sulfate. The pH was adjusted to 9.5 with concentrated aqueous ammonia. The reaction was stirred at 65°C. After the reaction was completed, the solution was filtered to obtain magnetic metal (metal 1)-glass hollow microspheres.

[0084] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed in the treatment liquid D at a ratio of 1 g / 10 mL. The reaction solution was mixed with cobalt nitrate, citric acid and water in a mass ratio of 9:6:5, stirred evenly at room temperature, and the excess treatment liquid D was filtered out under normal pressure. The filter cake was then removed, dried, and heat treated at 700 ° C in a hydrogen / argon mixed atmosphere for 3 h to obtain a glass-metal-carbon composite foam material in which the microspheres were connected by a carbon-metal (metal 2) composite material.

[0085] The apparent density of the glass-metal-carbon composite foam material obtained in this example is 0.43 g / cm 3 The porosity is 87.9% and the open porosity is 52.1%; the mass fractions of glass, carbon, metal 1 and metal 2 are 53.3%, 5.1%, 32.0% and 9.6% respectively; the optimized electromagnetic wave optimal reflection loss value (RL minimum value) at a thickness of 2mm is -35.1dB, and the effective absorption bandwidth is 5.7GHz (9.9-15.6GHz).

[0086] Example 6

[0087] The preparation of glass-metal-carbon composite foam material comprises the following steps:

[0088] 1) Preparation of activated glass hollow microspheres: 50g of glass hollow microspheres (density 0.15g / cm 3 ) was dispersed in 1000 ml of treatment solution A: 12 g / L silane coupling agent KH550, the solvent being a mixture of anhydrous ethanol and water in a volume ratio of 2:1; then dispersed in 750 ml of treatment solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, the solvent being water, stirred at 40° C. for 30 min, filtered, dried at 50° C., and sieved to remove agglomerated particles to obtain activated glass hollow microspheres;

[0089] 2) The activated glass hollow microspheres obtained in step 1) were dispersed in a magnetic metal assembly treatment solution C at a ratio of 1 g / 135 mL. The reaction solution was a water solvent containing 15 g / L nickel sulfate, 15 g / L cobalt sulfate, 50 g / L sodium hypophosphite, 80 g / L potassium sodium tartrate, and 50 g / L ammonium sulfate. The pH was adjusted to 9.5 with concentrated aqueous ammonia. The reaction was stirred at 60° C. After the reaction was completed, the solution was filtered to obtain magnetic metal (metal 1)-glass hollow microspheres.

[0090] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed in a treatment solution D at a ratio of 1 g / 10 mL. The reaction solution was prepared by mixing nickel nitrate, citric acid, and water in a mass ratio of 9:6:5. The mixture was stirred evenly at room temperature, and the excess treatment solution D was filtered out under normal pressure. The filter cake was then removed, dried, and heat treated at 700 ° C in a hydrogen / argon mixed atmosphere for 1 h to obtain a glass-metal-carbon composite foam material in which the microspheres were connected by a carbon-metal (metal 2) composite material.

[0091] The apparent density of the glass-metal-carbon composite foam material obtained in this example is 0.15 g / cm 3 The porosity is 95.1%, the open porosity is 49.4%; the mass fractions of glass, carbon, metal 1 and metal 2 are 48.2%, 4.6%, 38.5% and 8.7% respectively; the optimized electromagnetic wave optimal reflection loss value (RL minimum value) at a thickness of 2mm is -26.2dB, and the effective absorption bandwidth is 6.5GHz (9.6-16.1GHz).

[0092] Example 7

[0093] The preparation of glass-metal-carbon composite foam material comprises the following steps:

[0094] 1) Preparation of activated glass hollow microspheres: 50g of glass hollow microspheres (density 0.22g / cm 3) was dispersed in 1000 ml of treatment solution A: 12 g / L silane coupling agent KH550, the solvent being a mixture of anhydrous ethanol and water in a volume ratio of 2:1; then dispersed in 750 ml of treatment solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, the solvent being water, stirred at 40° C. for 30 min, filtered, dried at 50° C., and sieved to remove agglomerated particles to obtain activated glass hollow microspheres;

[0095] 2) The activated glass hollow microspheres obtained in step 1) were dispersed in a magnetic metal assembly treatment solution C at a ratio of 1 g / 200 mL. The reaction solution was a water solvent containing 25 g / L nickel sulfate, 40 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate. The pH was adjusted to 9.5 with concentrated ammonia water. The reaction was stirred at 70° C. After the reaction was completed, the solution was filtered to obtain magnetic metal (metal 1)-glass hollow microspheres.

[0096] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed in the treatment liquid D at a ratio of 1 g / 10 mL. The reaction solution was mixed with ferric nitrate, citric acid and water in a mass ratio of 11:6:5, stirred evenly at room temperature, and the excess treatment liquid D was filtered out under normal pressure. The filter cake was then removed, dried, and heat treated at 700 ° C in a hydrogen / argon mixed atmosphere for 4 h to obtain a glass-metal-carbon composite foam material in which the microspheres were connected by a carbon-metal (metal 2) composite material.

[0097] The apparent density of the glass-metal-carbon composite foam material obtained in this example is 0.24 g / cm 3 The porosity is 92.9% and the open porosity is 47.3%; the mass fractions of glass, carbon, metal 1 and metal 2 are 46.0%, 4.4%, 41.4% and 8.3% respectively; the optimized electromagnetic wave optimal reflection loss value (RL minimum value) at a thickness of 2mm is -24.8dB, and the effective absorption bandwidth is 6.6GHz (9.7-16.3GHz).

[0098] Example 8

[0099] The preparation of glass-metal-carbon composite foam material comprises the following steps:

[0100] 1) Preparation of activated glass hollow microspheres: 50g of glass hollow microspheres (density 0.20g / cm 3 ) was dispersed in 1000 ml of treatment solution A: 12 g / L silane coupling agent KH550, the solvent being a mixture of anhydrous ethanol and water in a volume ratio of 2:1; then dispersed in 750 ml of treatment solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, the solvent being water, stirred at 40° C. for 30 min, filtered, dried at 50° C., and sieved to remove agglomerated particles to obtain activated glass hollow microspheres;

[0101] 2) The activated glass hollow microspheres obtained in step 1) were dispersed in a magnetic metal assembly treatment solution C at a ratio of 1 g / 225 mL. The reaction solution was a water solvent containing 15 g / L nickel sulfate, 16 g / L ammonium ferrous sulfate, 50 g / L sodium hypophosphite, 90 g / L potassium sodium tartrate, and 50 g / L ammonium sulfate. The pH was adjusted to 10.5 with concentrated ammonia water. The reaction was stirred at 70° C. After the reaction was completed, the solution was filtered to obtain magnetic metal (metal 1)-glass hollow microspheres.

[0102] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed in a treatment solution D at a ratio of 1 g / 10 mL. The reaction solution was prepared by mixing nickel nitrate, citric acid, and water in a mass ratio of 9:6:5. The mixture was stirred evenly at room temperature, and the excess treatment solution D was filtered out under normal pressure. The filter cake was then removed, dried, and heat treated at 550° C. in a hydrogen / argon mixed atmosphere for 3 h to obtain a glass-metal-carbon composite foam material in which the microspheres were connected by a carbon-metal (metal 2) composite material.

[0103] The apparent density of the glass-metal-carbon composite foam material obtained in this example is 0.21 g / cm 3 The porosity is 93.8%, the open porosity is 51.1%; the mass fractions of glass, carbon, metal 1 and metal 2 are 43.7%, 4.2%, 44.2% and 7.9% respectively; the optimized electromagnetic wave optimal reflection loss value (RL minimum value) at a thickness of 2mm is -25.6dB, and the effective absorption bandwidth is 6.4GHz (9.8-16.2GHz).

[0104] Example 9

[0105] The preparation of glass-metal-carbon composite foam material comprises the following steps:

[0106] 1) Preparation of activated glass hollow microspheres: 50g of glass hollow microspheres (density 0.46g / cm 3 ) was dispersed in 1000 ml of treatment solution A: 12 g / L silane coupling agent KH550, the solvent being a mixture of anhydrous ethanol and water in a volume ratio of 2:1; then dispersed in 750 ml of treatment solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, the solvent being water, stirred at 40° C. for 30 min, filtered, dried at 50° C., and sieved to remove agglomerated particles to obtain activated glass hollow microspheres;

[0107] 2) The activated glass hollow microspheres obtained in step 1) were dispersed in a magnetic metal assembly treatment solution C at a ratio of 1 g / 150 mL. The reaction solution was a water solvent containing 25 g / L nickel sulfate, 40 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate. The pH was adjusted to 9.0 with concentrated ammonia water. The reaction was stirred at 60° C. After the reaction was completed, the solution was filtered to obtain magnetic metal (metal 1)-glass hollow microspheres.

[0108] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed in the treatment liquid D at a ratio of 1 g / 10 mL. The reaction solution was mixed with cobalt nitrate, citric acid and water in a mass ratio of 9:6:5, stirred evenly at room temperature, and the excess treatment liquid D was filtered out under normal pressure. The filter cake was then removed, dried, and heat treated at 600 ° C in a hydrogen / argon mixed atmosphere for 3 h to obtain a glass-metal-carbon composite foam material in which the microspheres were connected by a carbon-metal (metal 2) composite material.

[0109] The apparent density of the glass-metal-carbon composite foam material obtained in this example is 0.44 g / cm 3 The porosity is 87.9% and the open porosity is 50.6%; the mass fractions of glass, carbon, metal 1 and metal 2 are 49.1%, 4.7%, 37.3% and 8.8% respectively; the optimized electromagnetic wave optimal reflection loss value (RL minimum value) at a thickness of 2mm is -35.8dB, and the effective absorption bandwidth is 4.7GHz (10.2-14.9GHz).

[0110] Example 10

[0111] The preparation of glass-metal-carbon composite foam material comprises the following steps:

[0112] 1) Preparation of activated glass hollow microspheres: 50g of glass hollow microspheres (density 0.35g / cm 3 ) was dispersed in 1000 ml of treatment solution A: 12 g / L silane coupling agent KH550, the solvent being a mixture of anhydrous ethanol and water in a volume ratio of 2:1; then dispersed in 750 ml of treatment solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, the solvent being water, stirred at 40° C. for 30 min, filtered, dried at 50° C., and sieved to remove agglomerated particles to obtain activated glass hollow microspheres;

[0113] 2) The activated glass hollow microspheres obtained in step 1) were dispersed in a magnetic metal assembly treatment solution C at a ratio of 1 g / 160 mL. The reaction solution was a water solvent containing 25 g / L nickel sulfate, 40 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate. The pH was adjusted to 9.0 with concentrated aqueous ammonia. The reaction was stirred at 65° C. After the reaction was completed, the solution was filtered to obtain magnetic metal (metal 1)-glass hollow microspheres.

[0114] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed in the treatment liquid D at a ratio of 1 g / 10 mL. The reaction solution was mixed with nickel nitrate, citric acid and water in a mass ratio of 9:6:5, stirred evenly at room temperature, and the excess treatment liquid D was filtered out under normal pressure. The filter cake was then removed, dried, and heat treated at 500 ° C in a hydrogen / argon mixed atmosphere for 3 h to obtain a glass-metal-carbon composite foam material in which the microspheres were connected by a carbon-metal (metal 2) composite material.

[0115] The apparent density of the glass-metal-carbon composite foam material obtained in this example is 0.35 g / cm 3 The porosity is 90.2%, the open porosity is 49.2%; the mass fractions of glass, carbon, metal 1 and metal 2 are 48.2%, 4.6%, 38.5% and 8.7% respectively; the optimized electromagnetic wave optimal reflection loss value (RL minimum value) at a thickness of 2mm is -39.3dB, and the effective absorption bandwidth is 4.9GHz (10.1-15GHz).

[0116] Comparative Example 1

[0117] The preparation of glass-metal-carbon composite foam material comprises the following steps:

[0118] 1) Preparation of activated glass hollow microspheres: 50g of glass hollow microspheres (density 0.32g / cm 3 ) was dispersed in 1000 ml of treatment solution A: 12 g / L silane coupling agent KH550, the solvent being a mixture of anhydrous ethanol and water in a volume ratio of 2:1; then dispersed in 750 ml of treatment solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, the solvent being water, stirred at 40° C. for 30 min, filtered, dried at 50° C., and sieved to remove agglomerated particles to obtain activated glass hollow microspheres;

[0119] 2) The activated glass hollow microspheres obtained in step 1) were dispersed in a magnetic metal assembly treatment solution C at a ratio of 1 g / 200 mL. The reaction solution was a water solvent containing 25 g / L nickel sulfate, 40 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate. The pH was adjusted to 9.5 with concentrated ammonia water. The reaction was stirred at 70° C. After the reaction was completed, the solution was filtered to obtain magnetic metal (metal 1)-glass hollow microspheres.

[0120] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed in the treatment liquid D at a ratio of 1 g / 10 mL. The reaction solution was mixed with nickel nitrate, citric acid and water in a mass ratio of 23:7:10, stirred evenly at room temperature, and the excess treatment liquid D was filtered out under normal pressure. The filter cake was then removed, dried, and heat treated at 550 ° C in a hydrogen / argon mixed atmosphere for 4 h to obtain a glass-metal-carbon composite foam material in which the microspheres were connected by a carbon-metal (metal 2) composite material.

[0121] The apparent density of the glass-metal-carbon composite foam material obtained in this comparative example is 0.34 g / cm 3 The porosity is 92.0%, the open porosity is 51.2%; the mass fractions of glass, carbon, metal 1 and metal 2 are 41.4%, 3.1%, 41.3% and 14.2% respectively (the metal content in the connecting material is too much); the optimized electromagnetic wave optimal reflection loss value (RL minimum value) at a thickness of 2mm is -20.2dB, and the effective absorption bandwidth is 1.3GHz (12.6-13.9GHz).

[0122] Comparative Example 2

[0123] The preparation of glass-metal-carbon composite foam material comprises the following steps:

[0124] 1) Preparation of activated glass hollow microspheres: 50g of glass hollow microspheres (density 0.32g / cm 3 ) was dispersed in 1000 ml of treatment solution A: 12 g / L silane coupling agent KH550, the solvent being a mixture of anhydrous ethanol and water in a volume ratio of 2:1; then dispersed in 750 ml of treatment solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, the solvent being water, stirred at 40° C. for 30 min, filtered, dried at 50° C., and sieved to remove agglomerated particles to obtain activated glass hollow microspheres;

[0125] 2) The activated glass hollow microspheres obtained in step 1) were dispersed in a magnetic metal assembly treatment solution C at a ratio of 1 g / 200 mL. The reaction solution was a water solvent containing 25 g / L nickel sulfate, 40 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate. The pH was adjusted to 9.5 with concentrated ammonia water. The reaction was stirred at 70° C. After the reaction was completed, the solution was filtered to obtain magnetic metal (metal 1)-glass hollow microspheres.

[0126] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed in the treatment liquid D at a ratio of 1 g / 10 mL. The reaction solution was mixed with nickel nitrate, citric acid and water in a mass ratio of 4:18:12, stirred evenly at room temperature, and the excess treatment liquid D was filtered out under normal pressure. The filter cake was then removed, dried, and heat treated at 550° C. in a hydrogen / argon mixed atmosphere for 4 h to obtain a glass-metal-carbon composite foam material in which the microspheres were connected by a carbon-metal (metal 2) composite material.

[0127] The apparent density of the glass-metal-carbon composite foam material obtained in this example is 0.34 g / cm 3 The porosity is 92.0%, the open porosity is 51.2%; the mass fractions of glass, carbon, metal 1 and metal 2 are 44.2%, 8.3%, 44.5% and 3% respectively (the carbon matrix content in the connecting material is too much); the optimized electromagnetic wave optimal reflection loss value (RL minimum value) at a thickness of 2mm is -9.4dB, and there is no effective absorption bandwidth (RL is less than -10dB).

[0128] Performance testing:

[0129] The electromagnetic properties of the products prepared in the above embodiments were tested using the following methods: apparent density was obtained by measuring size and weight; porosity was obtained by measuring true density; and transmission parameters were tested using a vector network analyzer to analyze shielding performance.

[0130] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A magnetic composite foam, characterized in that: The composite foam structure includes a plurality of hollow composite microspheres and a connecting material connecting the hollow composite microspheres; The hollow composite microspheres are composed of glass hollow microspheres and a magnetic metal shell layer covering the glass hollow microspheres. The connecting material consists of a carbon matrix and metal particles dispersed in the carbon matrix.

2. The composite foam according to claim 1, characterized in that The connecting material contains a plurality of through holes.

3. The composite foam according to claim 1 or 2, characterized in that The apparent density of the composite foam is 0.15-0.55 g / cm 3 , the porosity is 87-97%, and the open porosity is 46-54%.

4. The composite foam according to claim 1, wherein Calculated by weight percentage, the composite foam contains 40-57 wt% of glass hollow microspheres, 30-35 wt% of magnetic metal spherical shells, 4-6 wt% of carbon matrix and 8-11 wt% of metal particles.

5. The composite foam according to claim 1, wherein The material of the magnetic metal spherical shell layer 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; and / or The metal particles are selected from one of iron, cobalt, silver, copper and nickel, or a binary alloy formed by two of them, or a ternary alloy formed by three of them.

6. The method for preparing a composite foam according to any one of claims 1 to 5, wherein: The steps include: Performing surface activation pretreatment on the glass hollow microspheres to obtain activated glass hollow microspheres; Coating a magnetic metal on the surface of the activated glass hollow microspheres; The obtained microspheres are subjected to a connection treatment to obtain the composite foam.

7. The preparation method according to claim 6, characterized in that The method for coating the surface of activated glass hollow microspheres with magnetic metal comprises the following steps: The activated glass hollow microspheres are dispersed in a treatment solution C containing magnetic metal ions, and stirred in a water bath, filtered, dried, and agglomerates are removed by screening in sequence to obtain the product; Preferably, the treatment solution C is an aqueous solution obtained by mixing a magnetic metal ion source salt, a stabilizer, a reducing agent, a pH regulator and water; Preferably, the magnetic metal ion source salt is selected from sulfates, nitrates, chlorides or organic acid salts of magnetic metals, and the concentration of the magnetic metal ion source salt in the treatment solution C is 10-70 g / L; Preferably, the stabilizer is selected from ammonium sulfate and / or potassium sodium tartrate, and the concentration of the stabilizer in the treatment solution C is 20-100 g / L; Preferably, the temperature of the water bath stirring is 55-80°C; Preferably, the amount of the activated glass hollow microspheres added to the treatment solution C is 0.004-0.012 g / mL.

8. The preparation method according to claim 6, characterized in that The method for connecting the obtained microspheres comprises the following steps: Dispersing the obtained microspheres in the treatment liquid D, stirring evenly, filtering out the excess treatment liquid D under normal pressure, drying, and heat-treating under a reducing atmosphere to obtain the composite foam; Preferably, the treatment solution D is a mixture of metal salt, carbon source and water in a mass ratio of 7-10:4-8:4-7; Preferably, the metal salt in the treatment solution D is a water-soluble nitrate or organic acid salt of nickel, iron or cobalt; Preferably, the carbon source in the treatment solution D is an organic carbon source, selected from one or more of citric acid, starch, sucrose and tartaric acid; Preferably, the amount of the microspheres added to the treatment solution D is 0.02-0.2 g / mL; Preferably, the heat treatment is carried out in a hydrogen / argon mixed atmosphere at a temperature of 500-700° C. for 1-4 hours.

9. A microwave absorbing or shielding material, characterized in that: The composite foam is prepared from the composite foam according to any one of claims 1 to 5.

10. Use of the composite foam according to any one of claims 1 to 5 in the preparation of a microwave absorbing or shielding device.

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