Composite electromagnetic functional hollow microsphere as well as preparation method and application thereof

Abstract

The invention discloses a composite electromagnetic functional hollow microsphere as well as a preparation method and application thereof. The hollow microsphere comprises a hollow glass core, and a magnetic metal spherical shell layer, a connecting metal layer and a conductive metal spherical shell layer which are sequentially arranged on the hollow glass core from inside to outside, wherein the connecting metal layer is made of nickel or nickel-phosphorus alloy. According to the hollow microsphere, the problem that an electric and magnetic composite electromagnetic functional material cannot realize synergistic enhancement of low density and mechanical strength on the basis of electric and magnetic dual response by utilizing component and structural design is solved.

Description

Technical Field

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

[0002] Electromagnetic waves have become a significant source of pollution affecting production, daily life, and public health. To address this issue, highly conductive metal-based materials are widely used in the design of electromagnetic shielding materials and structures. Compared to metal plates or meshes, polymer-based composites using metal micro / nanomaterials as fillers offer advantages such as low density, good designability, ease of molding and processing, and lower cost. To meet the increasing design requirements for lightweight high-end equipment and materials, researchers have long been committed to achieving high conductivity at lower filler fractions by improving the aspect ratio and shape anisotropy of metal micro / nano fillers. This is because the density of metal materials is much higher than that of the polymer matrix; reducing the metal filler ratio not only reduces density but also reduces the amount of expensive metal micro / nanomaterials used, saving costs. However, since high electromagnetic shielding performance depends on the effective construction of the conductive network, it is difficult to reduce the proportion of metal fillers to a very low level. On the other hand, even at low addition ratios, the high density of the metal material itself results in a composite material with a density higher than that of the polymer matrix, making it impossible to further reduce the density of the electromagnetic shielding composite material. In addition, some researchers have tried to combine metals with other low-density materials. While this can produce composite structures with a density lower than that of the metal itself, it is still difficult to significantly reduce the density because the density of most materials is still higher than that of the polymer matrix.

[0003] Therefore, constructing hollow structures made of metal or containing metal is a promising approach to significantly reduce density while maintaining high conductivity. However, such hollow structures still present the following problems. First, the presence of cavities, while reducing density, also leads to severe stress concentration, resulting in poor stability. During polymer matrix composite processes, lower structural stability can cause the hollow structure to break during mixing and molding, negating its low-density advantage. Second, generally, efficient electromagnetic wave shielding requires high conductivity to shield electric field energy or magnetic shielding of magnetic field energy. Electric field shielding is more effective at high frequencies, while magnetic field shielding plays a greater role at low frequencies. Simple mixing of magnetic and conductive fillers can easily lead to component segregation during the formulation and curing of resin-based composite materials, and the presence of magnetic components can also affect the overall conductivity of the composite material. Therefore, designing and preparing heterogeneous composite electromagnetic shielding materials that combine low density, conductivity, and magnetic properties is a development direction with significant economic and technological value. Furthermore, if the mechanical strength of the hollow structure can be considered while achieving heterogeneous component composites, its practical effectiveness will be greatly improved. Because if the hollow structure collapses or breaks due to low mechanical strength during use, the advantage of low density will be lost.

[0004] However, while current electromagnetic shielding fillers that combine magnetic and conductive properties can achieve both electrical and magnetic responses through the combination of magnetic and conductive components, they still fall short in achieving synergistic control of low density and mechanical strength through rational design of composition and structure. Summary of the Invention

[0005] To address the above problems, one objective of this invention is to provide a composite electromagnetic functional hollow microsphere, its preparation method, and its applications. This hollow microsphere overcomes the limitation of electro-magnetic composite electromagnetic functional materials, which cannot achieve synergistic enhancement of low density and mechanical strength based on both electrical and magnetic responses through component and structural design.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a composite electromagnetic functional hollow microsphere, wherein the hollow microsphere comprises:

[0008] Hollow glass core, and

[0009] From the inside out, a magnetic metal spherical shell layer, a connecting metal layer, and a conductive metal spherical shell layer are sequentially disposed on the core of the hollow glass; wherein, the connecting metal layer is made of nickel or a nickel-phosphorus alloy.

[0010] It is understandable that in this hollow microsphere, the glass layer, the magnetic metal shell layer, the connecting metal layer, and the conductive metal shell layer are all continuous layered structures.

[0011] Furthermore, the magnetic metal spherical shell layer is made of cobalt or a cobalt-phosphorus alloy.

[0012] Furthermore, the conductive metal spherical shell layer is made of copper.

[0013] Furthermore, based on mass percentage, the composite electromagnetic functional hollow microspheres comprise:

[0014] The structure consists of 35-60% hollow glass core, 15-35% magnetic metal shell layer, 5-15% connecting metal layer and 10-30% conductive metal shell layer.

[0015] Furthermore, the density of the hollow microspheres is 0.55-1.4 g / cm³. 3 .

[0016] Furthermore, in the hollow glass core of the hollow microsphere, the diameter of the cavity portion is 10-70 micrometers.

[0017] Furthermore, in the structure of the composite electromagnetic functional hollow microsphere, a transition layer is formed between the magnetic metal shell layer and the connecting metal layer, and / or a transition layer is formed between the connecting metal layer and the conductive metal shell layer.

[0018] The transition layer formed between the magnetic metal shell layer and the connecting metal layer is made of an alloy (e.g., a nickel-cobalt alloy) formed between the magnetic metal shell layer and the metal in the connecting metal layer; the transition layer formed between the connecting metal layer and the conductive metal shell layer is made of an alloy (e.g., a copper-nickel alloy) formed between the metal in the connecting metal layer and the metal in the conductive metal shell layer.

[0019] Specifically, the nickel in the connecting metal layer can form an alloy with the magnetic cobalt in the inner magnetic metal shell layer, or with the conductive copper in the outer conductive metal shell layer. This invention has found that if the materials of each layer are replaced (for example, replacing the material of the magnetic metal layer with another magnetic metal, or the material of the conductive metal shell layer with another conductive metal), or if the bonding order of the layers is changed, the compatibility and ease of alloy formation (solid solubility) between the metals will differ, making it impossible to obtain hollow microspheres with a stable structure and good electromagnetic shielding effect.

[0020] In this hollow microsphere, the cavity results in low density, and the glass shell serves as a carrier for the metal shell. The cobalt, nickel, and copper shells not only impart functionalities such as electrical, magnetic, and electromagnetic wave absorption but also enhance the structural stability (mechanical strength) of the hollow microsphere. The composite of the multi-component components and multi-layered shells in this electromagnetically functional hollow microsphere imparts electrical and magnetic responses, achieving a combination of electrical and magnetic losses in electromagnetic waves.

[0021] In another aspect, the present invention provides a method for preparing the composite electromagnetic functional hollow microspheres as described above, the method comprising the following steps:

[0022] Active seed nuclei were modified on the surface of hollow glass microspheres;

[0023] A magnetic metal layer, a connecting metal layer, and a conductive metal layer are sequentially coated onto the hollow glass microspheres modified with active seed cores.

[0024] Heat treatment is performed to obtain the composite electromagnetic functional hollow microspheres.

[0025] In this invention, the hollow glass microspheres can be obtained commercially or prepared using methods already disclosed in the art. The suitable particle size of the hollow glass microspheres is 10.5-72 micrometers, and the diameter of their cavities is preferably 10-70 micrometers. The suitable density of the hollow glass microspheres is 0.3-0.6 g / cm³. 3 Preferably, it is 0.3-0.5 g / cm³. 3 .

[0026] Furthermore, the method for modifying the surface of hollow glass microspheres with active seed cores includes the following steps:

[0027] The hollow glass microspheres were sequentially dispersed in an aqueous solution of stannous chloride and an aqueous solution of palladium chloride, and then filtered, dried, and sieved to obtain the final product.

[0028] Preferably, the concentration of the hollow glass microspheres in the aqueous solutions of stannous chloride and palladium chloride is 40-60 g / L, more preferably 40-50 g / L.

[0029] Preferably, the concentration of stannous chloride in the aqueous solution is 0.05-0.4 mol / L. Exemplary concentrations of stannous chloride include, but are not limited to, 0.05-0.2 mol / L, 0.05-0.15 mol / L, 0.05-0.12 mol / L, 0.12-0.2 mol / L, 0.12-0.15 mol / L, 0.15-0.2 mol / L, 0.06 mol / L, 0.12 mol / L, 0.15 mol / L, and 0.2 mol / L.

[0030] Preferably, the concentration of palladium chloride in the aqueous solution is 0.002-0.02 mol / L. Exemplary examples include, but are not limited to, 0.005-0.01 mol / L, 0.005 mol / L, and 0.01 mol / L.

[0031] Preferably, the dispersion temperature of the hollow glass microspheres in the aqueous solutions of stannous chloride and palladium chloride is 10-50°C, and the dispersion time is 20-60 min. Exemplarily, the dispersion temperature is 30-50°C, 30-40°C, 40°C, etc. Exemplarily, the dispersion time is 20-30 min, 30 min-1 h, 30 min, etc.

[0032] Furthermore, the method for coating a magnetic metal layer includes the following steps:

[0033] The hollow glass microspheres modified with active seed cores are dispersed in an aqueous solution containing magnetic metal ion salts, and then stirred in a water bath, filtered, dried, and sieved to remove agglomerates to obtain the final product.

[0034] Preferably, the concentration of the hollow glass microspheres modified with active seed cores in the aqueous solution is 0.005-0.02 g / mL. Exemplary examples include, but are not limited to, 0.007-0.017 g / mL, 0.007-0.013 g / mL, 0.007-0.01 g / mL, 0.007-0.008 g / mL, 0.008-0.017 g / mL, 0.008-0.013 g / mL, 0.008-0.01 g / mL, 0.01-0.017 g / mL, 0.01-0.013 g / mL, and 0.013-0.017 g / mL.

[0035] Preferably, the magnetic metal ion salt is selected from sulfates, nitrates, or chlorides of magnetic metals. An exemplary magnetic metal ion salt is cobalt sulfate.

[0036] Preferably, the concentration of the magnetic metal ion salt in the aqueous solution is 15-60 g / L. For example, the concentration of the magnetic metal ion salt in the aqueous solution includes, but is not limited to, 20-30 g / L, 24-28 g / L, etc.

[0037] Preferably, the aqueous solution further contains a stabilizer, a reducing agent, and a pH adjuster.

[0038] Preferably, the stabilizer is selected from ammonium sulfate and / or potassium sodium tartrate, and the concentration of the stabilizer in the aqueous solution is 20-100 g / L. For example, the concentration of the stabilizer in the aqueous solution is 30-60 g / L, 40-60 g / L, 50-60 g / L, 40-50 g / L, 50 g / L, etc.

[0039] Preferably, the reducing agent is selected from sodium borohydride and / or sodium hypophosphite, and the concentration of the reducing agent in the aqueous solution is 25-40 g / L.

[0040] Preferably, the pH adjuster is selected from inorganic bases, and the addition of pH makes the pH of the aqueous solution 8.5-10, preferably 10.

[0041] Preferably, the water bath stirring temperature is 60-85℃ and the time is 20-50 minutes, preferably 20-30 minutes. Exemplary examples include, but are not limited to, 60-70℃, 65-70℃, 60-65℃, 60℃, and 65℃.

[0042] Furthermore, the method for covering the connecting metal layer includes the following steps:

[0043] The hollow glass microspheres coated with a magnetic metal layer are dispersed in an aqueous solution containing an ionic salt of a connecting metal, and then stirred in a water bath, filtered, dried, and sieved to remove agglomerates to obtain the final product.

[0044] Preferably, the concentration of hollow glass microspheres coated with a magnetic metal layer in the aqueous solution is 0.015-0.06 g / mL. For example, the concentration of hollow glass microspheres coated with magnetic metal ionic salts in the aqueous solution includes, but is not limited to, 0.017-0.052 g / mL, 0.017-0.033 g / mL, 0.017-0.028 g / mL, 0.017-0.025 g / mL, 0.017-0.023 g / mL, 0.023-0.052 g / mL, 0.023-0.033 g / mL, 0.023-0.028 g / mL, 0.023-0.025 g / mL, 0.025-0.052 g / mL, 0.025-0.033 g / mL, 0.025-0.028 g / mL, 0.028-0.052 g / mL, 0.028-0.033 g / mL, etc.

[0045] Preferably, the ionic salt of the linking metal is selected from the sulfate, nitrate, or chloride of the linking metal. An exemplary ionic salt of the linking metal is nickel sulfate.

[0046] Preferably, the concentration of the metal-linked ion salt in the aqueous solution is 10-50 g / L. Exemplarily, the concentration of the metal-linked ion salt in the aqueous solution includes, but is not limited to, 10-30 g / L, 20-30 g / L, 21 g / L, etc.

[0047] Preferably, the aqueous solution further contains a stabilizer, a reducing agent, and a pH adjuster.

[0048] Preferably, the stabilizer is selected from ammonium sulfate and / or potassium sodium tartrate, and the concentration of the stabilizer in the aqueous solution is 30-90 g / L, more preferably 40-60 g / L, 50 g / L, etc.

[0049] Preferably, the reducing agent is selected from sodium borohydride and / or sodium hypophosphite, and the concentration of the reducing agent in the aqueous solution is 25-40 g / L.

[0050] Preferably, the pH adjuster is selected from inorganic bases, and the addition of pH makes the pH of the aqueous solution 8-10, more preferably 8.5-9.2.

[0051] Preferably, the water bath stirring temperature is 50-75℃ and the time is 20-50 min, more preferably 20-30 min. More preferably, the water bath stirring temperature is 60-70℃, 60-65℃, 60℃, 65℃, etc.

[0052] Furthermore, the method for coating a conductive metal layer includes the following steps:

[0053] The hollow glass microspheres coated with the connecting metal layer are dispersed in an aqueous solution containing an ionic salt of conductive metal, and then stirred in a water bath, filtered, dried, and sieved to remove agglomerates to obtain the final product.

[0054] Preferably, the concentration of hollow glass microspheres coated with the connecting metal layer in the aqueous solution is 0.02-0.06 g / mL.

[0055] Preferably, the ionic salt of the conductive metal is selected from the sulfate, nitrate or chloride of the conductive metal, such as copper sulfate.

[0056] Preferably, the concentration of the conductive metal ion salt in the aqueous solution is 15-55 g / L. For example, the concentration of the conductive metal ion salt in the aqueous solution includes, but is not limited to, 25-50 g / L.

[0057] Preferably, the aqueous solution further contains a stabilizer, a reducing agent, and a pH adjuster.

[0058] Preferably, the stabilizer is selected from sodium potassium tartrate, and the concentration of the stabilizer in the aqueous solution is 50-120 g / L.

[0059] Preferably, the reducing agent is selected from formaldehyde, and the concentration of the reducing agent in the aqueous solution is 3-10 ml / L, preferably 5 ml / L.

[0060] Preferably, the pH adjuster is selected from inorganic bases and has a concentration of 0.4-8 mol / L.

[0061] Preferably, the water bath stirring temperature is 5-35℃ and the time is 20-40 minutes, preferably 20 minutes. Exemplarily, the water bath stirring temperature is room temperature, such as 15-25℃.

[0062] Furthermore, the heat treatment is carried out in a hydrogen / argon mixed atmosphere, a nitrogen atmosphere, or an argon atmosphere.

[0063] Further, the heat treatment temperature is 400-750℃, and the time is 0.5-5 hours. For example, the heat treatment temperature includes, but is not limited to, 400-650℃, 400-550℃, 550-750℃, 550-650℃, 550-600℃, 600-750℃, 600-650℃, 650-750℃, 400℃, 550℃, 600℃, 650℃, and 750℃. Through heat treatment, the uniformity and density of each metal layer are improved, and a transition layer alloy is formed.

[0064] Furthermore, the heat treatment method is as follows: the temperature is increased to 400-750℃ at a rate of 5-10℃ / min (preferably 10℃ / min), and held at this temperature for 0.5-5 hours, and then naturally cooled to room temperature.

[0065] In the above preparation method, by selecting raw materials, controlling their concentration and reaction temperature in the coating method of each layer structure, and combining specific heat treatment conditions, a transition layer that promotes the bonding strength between each metal layer structure is formed, giving the hollow microsphere a stable structure and good electromagnetic shielding effect.

[0066] Cobalt spherical shells were obtained through nucleus-assisted in-situ reduction and deposition; nickel spherical shells were obtained through in-situ reduction and deposition under the catalysis of cobalt; and copper spherical shells were obtained through directional assembly under the catalysis of nickel. To improve performance, heat treatment was also introduced during the preparation of these electromagnetically functional hollow microspheres to enhance functionality and mechanical strength.

[0067] On another front, the present invention provides the application of the composite electromagnetic functional hollow microspheres described above in microwave absorption or shielding.

[0068] Furthermore, as a microwave absorbing or shielding material, it can be used as one of the following: in the field of military stealth, electromagnetic radiation protection for radio and television transmitters, microwave anechoic chamber materials, and electromagnetic shielding materials in buildings or radio communication equipment.

[0069] The beneficial effects of this invention are as follows:

[0070] The hollow microspheres provided in this invention feature a cavity in the core that provides low density and an electromagnetic wave transmission path, a cobalt shell that provides magnetic properties, an outer copper shell that provides conductivity, and a nickel connecting layer that connects the cobalt and copper shells through interfacial alloying, enhancing mechanical strength and functionality. These hollow microspheres provide magnetic and electrical losses through the magnetic and conductive metal shell layers, and mechanical support through the glass shell. Furthermore, the interface design between the magnetic, connecting, and conductive metals provides functional and mechanical reinforcement. Macroscopically, these composite microspheres exhibit a single microsphere structure with a large internal cavity. Besides their low density, the overall microsphere structure, when combined with a polymer matrix, ensures uniform distribution of components within the shell, preventing segregation. Attached Figure Description

[0071] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0072] Figure 1 A schematic diagram of the structure of the composite electromagnetic functional hollow microsphere of the present invention is shown.

[0073] Figure 2 This diagram illustrates a preparation process for the composite electromagnetic functional hollow microspheres of the present invention.

[0074] Figure 3 The image shown is a scanning electron microscope image of the composite electromagnetic functional hollow microsphere in Embodiment 1 of the present invention. Detailed Implementation

[0075] 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.

[0076] Performance testing:

[0077] The electromagnetic properties of the products prepared in each embodiment were tested. The test method was as follows:

[0078] Apparent density is obtained by measuring size and weight;

[0079] Porosity is obtained by measuring true density;

[0080] The transmission parameters were tested using a vector network analyzer (test frequency 8-12GHz, sample thickness 2.5mm) to analyze its shielding performance.

[0081] Electromagnetic parameters were tested using a vector network analyzer (test frequency 2-18GHz) to analyze its wave absorption performance.

[0082] Example 1

[0083] Composite electromagnetic functional hollow microspheres (its structural schematic diagram is shown below) Figure 1 The preparation of (as shown in the figure) is illustrated in the schematic diagram below. Figure 2 As shown, the specific steps are as follows:

[0084] 1) Preparation of glass hollow microspheres with surface-modified active seed cores:

[0085] Hollow glass microspheres (density 0.32 g / cm³) 3 The particles were sequentially dispersed in treatment solution A (a 0.2 mol / L aqueous solution of stannous chloride) and treatment solution B (a 0.005 mol / L aqueous solution of palladium chloride) at an addition ratio of 50 g / L. The reaction conditions in treatment solutions A and B were both 40 °C with stirring for 30 min. After filtration, drying at 50 °C, and sieving to remove agglomerated particles, glass hollow microspheres with surface-modified active seed cores were obtained.

[0086] 2) The glass hollow microspheres with surface-modified active seed cores obtained in step 1) were dispersed at an addition amount of 0.017 g / mL in treatment solution C containing 28 g / L cobalt sulfate, 30 g / L sodium hypophosphite, and 50 g / L potassium sodium tartrate, and pH≈10 (adjusted with ammonia). The mixture was stirred in a water bath at 65℃ for 30 min, filtered, and dried to obtain magnetic metal-glass hollow microspheres.

[0087] 3) Disperse the magnetic metal-glass hollow microspheres obtained in step 2) at an addition amount of 0.025 g / mL in treatment solution D containing 21 g / L nickel sulfate, 30 g / L sodium hypophosphite, 50 g / L potassium sodium tartrate, and pH≈9 (adjusted with ammonia). Stir the reaction in a water bath at 60℃ for 20 min, filter, and dry to obtain the connected metal-magnetic metal-glass hollow microspheres.

[0088] 4) The connected metal-magnetic metal-glass hollow microspheres obtained in step 3) were dispersed at an addition amount of 0.03 g / mL in treatment solution E containing 0.15 mol / L copper sulfate, 90 g / L potassium sodium tartrate, 0.5 mol / L sodium hydroxide, and 5 mL / L formaldehyde. The mixture was reacted at room temperature for 20 min, then filtered and dried to obtain the conductive metal-connected metal-magnetic metal-glass hollow microsphere intermediate.

[0089] 5) The conductive metal-connecting metal-magnetic metal-glass hollow microsphere intermediate obtained in step 4) was dispersed in a flowing hydrogen-argon mixed atmosphere (hydrogen volume percentage of 5%), heated to 650℃ at 10℃ / min and held at that temperature for 2 hours, and then naturally cooled to room temperature to obtain the composite electromagnetic functional hollow microspheres. Its scanning electron microscope image is shown below. Figure 3 As shown.

[0090] The density of the composite electromagnetic functional hollow microspheres obtained in this embodiment is 0.59 g / cm³. 3 The diameter of the core cavity is 43 micrometers; the mass fractions of the glass sphere, magnetic metal sphere, connecting sphere, and conductive metal sphere are 52.6%, 15.8%, 10.5%, and 21.1%, respectively.

[0091] The composite electromagnetic functional hollow microspheres have a survival rate of 81.2% at 35 MPa; their optimized electromagnetic wave reflection loss is -52.3 dB, and their effective absorption bandwidth is 4.2 GHz (4.8-9 GHz); their electromagnetic shielding effectiveness is 59-71 dB.

[0092] Example 2

[0093] The specific steps for preparing composite electromagnetic functional hollow microspheres are as follows:

[0094] 1) Preparation of glass hollow microspheres with surface-modified active seed cores: Glass hollow microspheres (density 0.35 g / cm³) were prepared. 3 The particles were sequentially dispersed in treatment solution A (a stannous chloride aqueous solution with a concentration of 0.15 mol / L) and treatment solution B (a palladium chloride aqueous solution with a concentration of 0.01 mol / L) at an addition ratio of 50 g / L. The reaction conditions were: stirring at 40℃ for 30 min, followed by filtration, drying at 50℃, and sieving to remove agglomerated particles, yielding glass hollow microspheres with surface-modified active seed cores.

[0095] 2) The glass hollow microspheres with surface-modified active seed cores obtained in step 1) were dispersed at an addition amount of 0.01 g / mL in treatment solution C containing 28 g / L cobalt sulfate, 30 g / L sodium hypophosphite, 50 g / L potassium sodium tartrate, and pH≈9.5 (adjusted with ammonia). The mixture was stirred in a water bath at 65℃ for 30 min, filtered, and dried to obtain magnetic metal-glass hollow microspheres.

[0096] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed at an addition amount of 0.028 g / mL in treatment solution D containing 21 g / L nickel sulfate, 30 g / L sodium hypophosphite, 50 g / L potassium sodium tartrate, and pH≈9.2 (adjusted with ammonia). The mixture was stirred in a water bath at 60℃ for 20 min, filtered, and dried to obtain the connected metal-magnetic metal-glass hollow microspheres.

[0097] 4) The connected metal-magnetic metal-glass hollow microspheres obtained in step 3) were dispersed at an addition amount of 0.046 g / mL in treatment solution E containing 0.15 mol / L copper sulfate, 100 g / L potassium sodium tartrate, 0.5 mol / L sodium hydroxide, and 5 mL / L formaldehyde. The mixture was reacted at room temperature for 20 min, then filtered and dried to obtain the conductive metal-connected metal-magnetic metal-glass hollow microsphere intermediate.

[0098] 5) The conductive metal-connecting metal-magnetic metal-glass hollow microsphere intermediate obtained in step 4) is dispersed in a flowing hydrogen-argon mixed atmosphere (hydrogen volume percentage is 5%), heated to 550°C at 10°C / min and held at that temperature for 4 hours, and then naturally cooled to room temperature to obtain the composite electromagnetic functional hollow microsphere.

[0099] The density of the composite electromagnetic functional hollow microspheres obtained in this embodiment is 0.69 g / cm³. 3 The diameter of the core cavity is 41 micrometers; the mass fractions of the glass sphere, magnetic metal sphere, connecting sphere, and conductive metal sphere are 50.0%, 25.0%, 10.0%, and 15.0%, respectively.

[0100] The composite electromagnetic functional hollow microspheres have a survival rate of 86.5% at 35 MPa; their optimized electromagnetic wave reflection loss is -56.8 dB, and their effective absorption bandwidth is 4.5 GHz (4.6-9.1 GHz); their electromagnetic shielding effectiveness is 60-73 dB.

[0101] Example 3

[0102] The specific steps for preparing composite electromagnetic functional hollow microspheres are as follows:

[0103] 1) Preparation of glass hollow microspheres with surface-modified active seed cores: Glass hollow microspheres (density 0.39 g / cm³) were prepared. 3 The particles were sequentially dispersed in treatment solution A (a stannous chloride aqueous solution with a concentration of 0.12 mol / L) and treatment solution B (a palladium chloride aqueous solution with a concentration of 0.005 mol / L) at an addition ratio of 50 g / L. The reaction conditions were: stirring at 40℃ for 30 min, followed by filtration, drying at 50℃, and sieving to remove agglomerated particles, yielding glass hollow microspheres with surface-modified active seed cores.

[0104] 2) The glass hollow microspheres with surface-modified active seed cores obtained in step 1) were dispersed at an addition amount of 0.008 g / mL in treatment solution C containing 28 g / L cobalt sulfate, 30 g / L sodium hypophosphite, 50 g / L potassium sodium tartrate, and pH≈9 (adjusted with ammonia). The mixture was stirred in a water bath at 65℃ for 30 min, filtered, and dried to obtain magnetic metal-glass hollow microspheres.

[0105] 3) Disperse the magnetic metal-glass hollow microspheres obtained in step 2) at an addition amount of 0.017 g / mL in treatment solution D containing 21 g / L nickel sulfate, 30 g / L sodium hypophosphite, 50 g / L potassium sodium tartrate, and pH≈8.5 (adjusted with ammonia). Stir the reaction in a water bath at 60℃ for 20 min, filter, and dry to obtain the connected metal-magnetic metal-glass hollow microspheres.

[0106] 4) The connected metal-magnetic metal-glass hollow microspheres obtained in step 3) were dispersed at an addition amount of 0.034 g / mL in treatment solution E containing 0.10 mol / L copper sulfate, 80 g / L potassium sodium tartrate, 0.5 mol / L sodium hydroxide, and 5 mL / L formaldehyde. The mixture was reacted at room temperature for 20 min, then filtered and dried to obtain the conductive metal-connected metal-magnetic metal-glass hollow microsphere intermediate.

[0107] 5) The conductive metal-connecting metal-magnetic metal-glass hollow microsphere intermediate obtained in step 4) is dispersed in a flowing hydrogen-argon mixed atmosphere (hydrogen volume percentage is 5%), heated to 750°C at 10°C / min and held at that temperature for 1 hour, and then naturally cooled to room temperature to obtain the composite electromagnetic functional hollow microsphere.

[0108] The density of the composite electromagnetic functional hollow microspheres obtained in this embodiment is 0.84 g / cm³. 3 The diameter of the core cavity is 39 micrometers; the mass fractions of the glass sphere, magnetic metal sphere, connecting sphere, and conductive metal sphere are 45.5%, 27.3%, 13.8%, and 13.4%, respectively.

[0109] The composite electromagnetic functional hollow microspheres have a survival rate of 86.5% at 35 MPa; their optimized electromagnetic wave reflection loss is -61.7 dB, and their effective absorption bandwidth is 4.6 GHz (4.7-9.3 GHz); their electromagnetic shielding effectiveness is 63-77 dB.

[0110] Example 4

[0111] The specific steps for preparing composite electromagnetic functional hollow microspheres are as follows:

[0112] 1) Preparation of glass hollow microspheres with surface-modified active seed cores: Glass hollow microspheres (density 0.47 g / cm³) were prepared. 3 The particles were sequentially dispersed in treatment solution A (a stannous chloride aqueous solution with a concentration of 0.2 mol / L) and treatment solution B (a palladium chloride aqueous solution with a concentration of 0.005 mol / L) at an addition ratio of 50 g / L. The reaction conditions were: stirring at 40℃ for 30 min, followed by filtration, drying at 50℃, and sieving to remove agglomerated particles, yielding glass hollow microspheres with surface-modified active seed cores.

[0113] 2) The glass hollow microspheres with surface-modified active seed cores obtained in step 1) were dispersed at an addition amount of 0.007 g / mL in treatment solution C containing 24 g / L cobalt sulfate, 30 g / L sodium hypophosphite, 50 g / L potassium sodium tartrate, and pH≈9 (adjusted with ammonia). The mixture was stirred in a water bath at 60℃ for 30 min, filtered, and dried to obtain magnetic metal-glass hollow microspheres.

[0114] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed at an addition amount of 0.033 g / mL in treatment solution D containing 21 g / L nickel sulfate, 30 g / L sodium hypophosphite, 50 g / L potassium sodium tartrate, and pH≈9 (adjusted with ammonia). The mixture was stirred in a water bath at 65℃ for 20 min, filtered, and dried to obtain the connected metal-magnetic metal-glass hollow microspheres.

[0115] 4) The connected metal-magnetic metal-glass hollow microspheres obtained in step 3) were dispersed at an addition amount of 0.025 g / mL in treatment solution E containing 0.1 mol / L copper sulfate, 110 g / L potassium sodium tartrate, 0.5 mol / L sodium hydroxide, and 5 mL / L formaldehyde. The mixture was reacted at room temperature for 20 min, then filtered and dried to obtain the conductive metal-connected metal-magnetic metal-glass hollow microsphere intermediate.

[0116] 5) The conductive metal-connecting metal-magnetic metal-glass hollow microsphere intermediate obtained in step 4) is dispersed in a flowing hydrogen-argon mixed atmosphere (hydrogen volume percentage is 5%), heated to 400℃ at 10℃ / min and held at that temperature for 5h, and then naturally cooled to room temperature to obtain the composite electromagnetic functional hollow microsphere.

[0117] The density of the composite electromagnetic functional hollow microspheres obtained in this embodiment is 1.06 g / cm³. 3 The diameter of the core cavity is 18 micrometers; the mass fractions of the glass sphere, magnetic metal sphere, connecting sphere, and conductive metal sphere are 43.5%, 30.4%, 8.7%, and 17.4%, respectively.

[0118] The composite electromagnetic functional hollow microspheres have a survival rate of 95.8% at 35 MPa; their optimized electromagnetic wave reflection loss is -62.5 dB, and their effective absorption bandwidth is 4.4 GHz (4.8-9.2 GHz); their electromagnetic shielding effectiveness is 65-79 dB.

[0119] Example 5

[0120] The specific steps for preparing composite electromagnetic functional hollow microspheres are as follows:

[0121] 1) Preparation of glass hollow microspheres with surface-modified active seed cores: Glass hollow microspheres (density 0.50 g / cm³) were prepared. 3 The particles were sequentially dispersed in treatment solution A (a stannous chloride aqueous solution with a concentration of 0.06 mol / L) and treatment solution B (a palladium chloride aqueous solution with a concentration of 0.005 mol / L) at an addition ratio of 40 g / L. The reaction conditions were: stirring at 40℃ for 30 min, followed by filtration, drying at 50℃, and sieving to remove agglomerated particles, yielding glass hollow microspheres with surface-modified active seed cores.

[0122] 2) The glass hollow microspheres with surface-modified active seed cores obtained in step 1) were dispersed at an addition amount of 0.007 g / mL in treatment solution C containing 28 g / L cobalt sulfate, 30 g / L sodium hypophosphite, 50 g / L potassium sodium tartrate, and pH≈10 (adjusted with ammonia). The mixture was stirred in a water bath at 65℃ for 30 min, filtered, and dried to obtain magnetic metal-glass hollow microspheres.

[0123] 3) The magnetic metal-glass hollow microspheres obtained in step 2) were dispersed at an addition amount of 0.023 g / mL in treatment solution D containing 21 g / L nickel sulfate, 30 g / L sodium hypophosphite, 50 g / L potassium sodium tartrate, and pH≈9 (adjusted with ammonia). The mixture was stirred in a water bath at 60℃ for 20 min, filtered, and dried to obtain the connected metal-magnetic metal-glass hollow microspheres.

[0124] 4) The connected metal-magnetic metal-glass hollow microspheres obtained in step 3) were dispersed at an addition amount of 0.033 g / mL in treatment solution E containing 0.15 mol / L copper sulfate, 120 g / L potassium sodium tartrate, 0.5 mol / L sodium hydroxide, and 5 mL / L formaldehyde. The mixture was reacted at room temperature for 20 min, then filtered and dried to obtain the conductive metal-connected metal-magnetic metal-glass hollow microsphere intermediate.

[0125] 5) The conductive metal-connecting metal-magnetic metal-glass hollow microsphere intermediate obtained in step 4) is dispersed in a flowing hydrogen-argon mixed atmosphere (hydrogen volume percentage is 5%), heated to 600℃ at 10℃ / min and held at that temperature for 3h, and then naturally cooled to room temperature to obtain the composite electromagnetic functional hollow microsphere.

[0126] The density of the composite electromagnetic functional hollow microspheres obtained in this embodiment is 1.27 g / cm³. 3 The diameter of the core cavity is 35 micrometers; the mass fractions of the glass sphere, magnetic metal sphere, connecting sphere, and conductive metal sphere are 38.5%, 30.8%, 11.5%, and 19.2%, respectively.

[0127] The composite electromagnetic functional hollow microspheres have a survival rate of 98.5% at 35 MPa; their optimized electromagnetic wave reflection loss is -66.9 dB, and their effective absorption bandwidth is 5.2 GHz (4.7-9.9 GHz); their electromagnetic shielding effectiveness is 70-83 dB.

[0128] Example 6

[0129] The specific steps for preparing composite electromagnetic functional hollow microspheres are as follows:

[0130] 1) Preparation of glass hollow microspheres with surface-modified active seed cores: Glass hollow microspheres (density 0.38 g / cm³) were prepared. 3The particles were sequentially dispersed in treatment solution A (a stannous chloride aqueous solution with a concentration of 0.2 mol / L) and treatment solution B (a palladium chloride aqueous solution with a concentration of 0.005 mol / L) at an addition ratio of 50 g / L. The reaction conditions were: stirring at 40℃ for 30 min, followed by filtration, drying at 50℃, and sieving to remove agglomerated particles, yielding glass hollow microspheres with surface-modified active seed cores.

[0131] 2) The glass hollow microspheres with surface-modified active seed cores obtained in step 1) were dispersed at an addition amount of 0.013 g / mL in treatment solution C containing 28 g / L cobalt sulfate, 30 g / L sodium hypophosphite, 50 g / L potassium sodium tartrate, and pH≈9.5 (adjusted with ammonia). The mixture was stirred in a water bath at 65℃ for 30 min, filtered, and dried to obtain magnetic metal-glass hollow microspheres.

[0132] 3) Disperse the magnetic metal-glass hollow microspheres obtained in step 2) at an addition amount of 0.052 g / mL in treatment solution D containing 21 g / L nickel sulfate, 30 g / L sodium hypophosphite, 50 g / L potassium sodium tartrate, and pH≈9.2 (adjusted with ammonia). Stir the reaction in a water bath at 60℃ for 20 min, filter, and dry to obtain the connected metal-magnetic metal-glass hollow microspheres.

[0133] 4) The connected metal-magnetic metal-glass hollow microspheres obtained in step 3) were dispersed at an addition amount of 0.048 g / mL in treatment solution E containing 0.12 mol / L copper sulfate, 90 g / L potassium sodium tartrate, 0.5 mol / L sodium hydroxide, and 5 mL / L formaldehyde. The mixture was reacted at room temperature for 20 min, then filtered and dried to obtain the conductive metal-connected metal-magnetic metal-glass hollow microsphere intermediate.

[0134] 5) The conductive metal-connecting metal-magnetic metal-glass hollow microsphere intermediate obtained in step 4) is dispersed in a flowing hydrogen-argon mixed atmosphere (hydrogen volume percentage is 5%), heated to 650°C at 10°C / min and held at that temperature for 4 hours, and then naturally cooled to room temperature to obtain the composite electromagnetic functional hollow microsphere.

[0135] The density of the composite electromagnetic functional hollow microspheres obtained in this embodiment is 0.63 g / cm³. 3 The diameter of the core cavity is 39 micrometers; the mass fractions of the glass sphere, magnetic metal sphere, connecting sphere, and conductive metal sphere are 58.8%, 23.5%, 5.9%, and 11.8%, respectively.

[0136] The composite electromagnetic functional hollow microspheres have a survival rate of 90.1% at 35 MPa; their optimized electromagnetic wave reflection loss is -45.3 dB, and their effective absorption bandwidth is 3.9 GHz (5-8.9 GHz); their electromagnetic shielding effectiveness is 52-64 dB.

[0137] 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 composite electromagnetic functional hollow microsphere, characterized in that, The hollow microspheres are composed of: Hollow glass core, and From the inside out, a magnetic metal spherical shell layer, a connecting metal layer, and a conductive metal spherical shell layer are sequentially disposed on the core of the hollow glass; wherein, the connecting metal layer is made of nickel or a nickel-phosphorus alloy.

2. The composite electromagnetic functional hollow microsphere according to claim 1, characterized in that, The magnetic metal spherical shell layer is made of cobalt or a cobalt-phosphorus alloy; and / or The conductive metal spherical shell layer is made of copper; and / or The composite electromagnetic functional hollow microspheres, by mass percentage, comprise the following: The structure consists of 35-60% hollow glass core, 15-35% magnetic metal shell layer, 5-15% connecting metal layer and 10-30% conductive metal shell layer.

3. The composite electromagnetic functional hollow microsphere according to claim 1, characterized in that, The density of the hollow microspheres is 0.55-1.4 g / cm³. 3 ; and / or The hollow microspheres have a diameter of 10.5-72 micrometers, and the cavity diameter is 10-70 micrometers.

4. The method for preparing composite electromagnetic functional hollow microspheres as described in any one of claims 1-3, characterized in that, The steps include: Active seed nuclei were modified on the surface of hollow glass microspheres; A magnetic metal layer, a connecting metal layer, and a conductive metal shell layer are sequentially coated onto the hollow glass microspheres modified with active seed cores. Heat treatment is performed to obtain the composite electromagnetic functional hollow microspheres.

5. The preparation method according to claim 4, characterized in that, The method for modifying the surface of hollow glass microspheres with active seed cores includes the following steps: The hollow glass microspheres were sequentially dispersed in an aqueous solution of stannous chloride and an aqueous solution of palladium chloride, and then filtered, dried, and sieved to obtain the product. Preferably, the concentration of stannous chloride in the aqueous solution is 0.05-0.4 mol / L; Preferably, the concentration of palladium chloride in the aqueous solution is 0.002-0.02 mol / L; Preferably, the dispersion temperature of the hollow glass microspheres in the aqueous solutions of stannous chloride and palladium chloride is 10-50℃, and the dispersion time is 20-60 min, preferably 30 min.

6. The preparation method according to claim 4, characterized in that, The method for coating a magnetic metal layer includes the following steps: The hollow glass microspheres modified with active seed cores are dispersed in an aqueous solution containing magnetic metal ion salts, and then stirred in a water bath, filtered, dried, and sieved to remove agglomerates to obtain the product. Preferably, the concentration of the hollow glass microspheres modified with active seed cores in the aqueous solution is 0.005-0.02 g / mL; Preferably, the magnetic metal ion salt is selected from the sulfate, nitrate or chloride of magnetic metals, and the concentration of the magnetic metal ion salt in the aqueous solution is 15-60 g / L. Preferably, the aqueous solution further comprises at least one of a stabilizer, a reducing agent, and a pH adjuster; Preferably, the stabilizer is selected from ammonium sulfate and / or potassium sodium tartrate, and the concentration of the stabilizer in the aqueous solution is 20-100 g / L; Preferably, the reducing agent is selected from sodium borohydride and / or sodium hypophosphite, and the concentration of the reducing agent in the aqueous solution is 25-40 g / L; Preferably, the pH adjuster is selected from inorganic bases, and the addition of pH adjuster makes the pH of the aqueous solution 8.5-10; Preferably, the temperature of the water bath stirring is 60-85℃, and the time is 20-50 minutes.

7. The preparation method according to claim 4, characterized in that, The method for covering the connecting metal layer includes the following steps: The hollow glass microspheres coated with a magnetic metal layer are dispersed in an aqueous solution containing an ionic salt of the metal linker, and then stirred in a water bath, filtered, dried, and sieved to remove agglomerates to obtain the product. Preferably, the concentration of hollow glass microspheres coated with a magnetic metal layer in the aqueous solution is 0.015-0.06 g / mL; Preferably, the ionic salt of the connecting metal is selected from the sulfate, nitrate or chloride of the connecting metal, and the concentration of the ionic salt of the connecting metal in the aqueous solution is 10-50 g / L; Preferably, the aqueous solution further contains a stabilizer, a reducing agent, and a pH adjuster; Preferably, the stabilizer is selected from ammonium sulfate and / or potassium sodium tartrate, and the concentration of the stabilizer in the aqueous solution is 30-90 g / L; Preferably, the reducing agent is selected from sodium borohydride and / or sodium hypophosphite, and the concentration of the reducing agent in the aqueous solution is 25-40 g / L; Preferably, the pH adjuster is selected from inorganic bases, and the addition of pH adjuster makes the pH of the aqueous solution 8-10; Preferably, the temperature of the water bath stirring is 50-75℃, and the time is 20-50 minutes.

8. The preparation method according to claim 4, characterized in that, The method for coating a conductive metal layer includes the following steps: The hollow glass microspheres coated with the connecting metal layer are dispersed in an aqueous solution containing an ionic salt of conductive metal, and then stirred in a water bath, filtered, dried, and sieved to remove agglomerates to obtain the product. Preferably, the concentration of hollow glass microspheres coated with the connecting metal layer in the aqueous solution is 0.02-0.06 g / mL; Preferably, the conductive metal ionic salt is selected from the sulfate, nitrate or chloride of the conductive metal, and the concentration of the conductive metal ionic salt in the aqueous solution is 15-55 g / L; Preferably, the aqueous solution further contains a stabilizer, a reducing agent, and a pH adjuster; Preferably, the stabilizer is selected from sodium potassium tartrate, and the concentration of the stabilizer in the aqueous solution is 50-120 g / L; Preferably, the reducing agent is selected from formaldehyde, and the concentration of the reducing agent in the aqueous solution is 3-10 ml / L, preferably 5 ml / L; Preferably, the pH adjuster is selected from inorganic bases; Preferably, the temperature of the water bath stirring is 5-35℃, and the time is 20-40 min, preferably 20 min.

9. The preparation method according to claim 4, characterized in that, The heat treatment is carried out in a hydrogen / argon mixed atmosphere, a nitrogen atmosphere, or an argon atmosphere, at a temperature of 400-750℃ for a time of 0.5-5h.

10. The application of the composite electromagnetic functional hollow microspheres as described in any one of claims 1-3 in microwave absorption or shielding.

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