Conductive composite material and preparation method and application thereof

Abstract

The invention discloses a conductive composite material as well as a preparation method and application thereof. The structure of the composite material comprises a plurality of conductive hollow microspheres and a connecting material for connecting the conductive hollow microspheres, wherein the conductive hollow microsphere is composed of a glass hollow microsphere and a conductive metal spherical shell layer coating the glass hollow microsphere; and the connecting material is metal copper. In the conductive composite material, on one hand, a new electromagnetic wave scattering and loss mechanism can be introduced through the cavities of the conductive hollow microspheres, and the density is reduced, and on the other hand, conductive paths among the microspheres can be improved through the metal connecting material copper among the conductive hollow microspheres, and the conductive and electromagnetic shielding performance is improved.

Description

Technical Field

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

[0002] Metal materials are abundant in nature, and their crystal structure lends them to easily manipulated microstructures and macromorphologies through doping. Combined with their inherent electrical and magnetic (or combined electromagnetic) properties, metals offer unique performance advantages and vast application prospects in electrical and magnetic conductivity, as well as electromagnetic absorption and shielding. In applications, metallic electromagnetic functional materials are often combined with a matrix (usually a polymer) as fillers to meet the requirements of shape, environmental adaptability, and mechanical properties in addition to their electromagnetic functionality. In addition to their common dependence on chemical composition and microstructure, the effectiveness of electromagnetically functional metal materials, unlike other functional applications, is significantly dependent on their macroscopic morphology and structure. This is because electromagnetic functionality typically requires the construction of interconnected or interactive networks, and the formation of these networks is highly dependent on the material's macroscopic dimensions, aspect ratio, and other external features. Therefore, researchers often leverage micro- and nanoscale two-dimensional (e.g., sheet-like) or one-dimensional (e.g., rod-like, wire-like) structural designs to effectively construct electromagnetic functional networks while maintaining a low loading of the electromagnetic functional material. The above structural design can not only reduce the cost by reducing the amount of metal materials used, but also reduce the overall density of the composite material system, thereby achieving lightweight electromagnetic functional composite materials to a certain extent.

[0003] Because metal materials have significantly higher densities than commonly used polymer matrices, the addition level of metal fillers must be maintained at a certain level to ensure the formation of an electromagnetically functional network. Furthermore, even at lower addition levels, the density of the composite material is higher than that of the polymer matrix, making further lightweighting difficult. Therefore, designing metal materials into hollow structures is an effective approach to maintaining electromagnetic functionality while minimizing density. Among hollow metal structures, hollow spherical structures (hollow microspheres) have garnered significant attention from researchers and developers. This is due to their ease of rapid and efficient molding, resulting in economical synthesis processes. Furthermore, their ease of flow and dispersion allows for extensive control of their addition and proportion within the matrix. Furthermore, their spherical shape facilitates stress dissipation during composite preparation and application, preventing damage to the hollow structure and the resulting performance degradation. More importantly, through appropriate preparation process conditions and system design, hollow metal spherical structures can achieve densities significantly lower than those of most matrices. This means that the addition of these fillers not only does not increase the matrix density, but can actually further reduce it, resulting in electromagnetically functional composite materials with even lower densities than the matrix material.

[0004] However, as mentioned above, the realization of electromagnetic functionality requires the construction of a reasonable network structure, and the good dispersibility of the spherical shape facilitates the formation of a uniform mixture of metal hollow microspheres and the matrix. While this is beneficial for improving the structural uniformity and mechanical strength of the composite material, it is not conducive to the formation of an electromagnetic functional network, thus restricting the coordinated optimization of density, functionality, and mechanical strength of electromagnetic functional composite materials based on metal hollow microspheres. Summary of the Invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide a conductive composite material and a preparation method and application thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In one aspect, the present invention provides a conductive composite material, wherein the structure of the composite material comprises a plurality of conductive hollow microspheres and a connecting material connecting the conductive hollow microspheres;

[0008] The conductive hollow microspheres are composed of glass hollow microspheres and a conductive metal shell layer covering the glass hollow microspheres.

[0009] The connecting material is metallic copper.

[0010] In the technical solution of the present invention, copper is used as the connecting material. On the one hand, it can play a good connecting role, and on the other hand, it helps to form the electromagnetic functional network. Compared with using other metals as connecting materials, copper has better effects and a simpler and gentler preparation process.

[0011] In the technical solution of the present invention, metallic copper is deposited on the surface of the conductive hollow microspheres and between the conductive hollow microspheres, thereby achieving mutual connection between the conductive hollow microspheres.

[0012] Furthermore, the connecting material contains a plurality of through holes, which are conducive to the formation of an electromagnetic functional network, thereby synergistically optimizing the density, functionality and mechanical strength of the conductive composite material.

[0013] Furthermore, the apparent density of the conductive composite material is 0.15-0.7 g / cm 3 , the porosity is 85-97% and the open porosity is 45-55%.

[0014] Furthermore, the conductive composite material comprises, by weight percentage, 30-55 wt % of glass hollow microspheres, 10-35 wt % of conductive metal spherical shell layers, and 25-50 wt % of a connecting material.

[0015] Furthermore, the material of the conductive metal spherical shell layer is one selected from iron, cobalt, silver, copper and nickel, or a binary alloy formed by two of them, or a ternary alloy formed by three of them.

[0016] In another aspect, the present invention provides a method for preparing the conductive composite material as described above, comprising the following steps:

[0017] Performing surface activation pretreatment on the glass hollow microspheres to obtain activated glass hollow microspheres;

[0018] Coating a conductive metal on the surface of the activated glass hollow microspheres;

[0019] The obtained microspheres are subjected to welding treatment using a connecting material to obtain the conductive composite material.

[0020] Furthermore, the activation pretreatment method comprises the following steps:

[0021] The glass hollow microspheres are dispersed in treatment liquids A and B in sequence to obtain activated glass hollow microspheres.

[0022] Furthermore, the solute of the treatment liquid A is a coupling agent, such as KH550, and the solvent is anhydrous ethanol and / or distilled water, preferably a mixture of anhydrous ethanol and distilled water in a volume ratio of 1:1-3:1.

[0023] Furthermore, the density of the glass hollow microspheres is 0.1-0.9 g / cm 3 , preferably 0.30 g / cm 3 .

[0024] Furthermore, in the treatment liquid A, the concentration of the solute is 10-15 g / L, preferably 12 g / L.

[0025] Furthermore, the dispersion concentration of the glass hollow microspheres in the treatment liquid A is 0.04-0.08 g / ml.

[0026] Furthermore, the treatment liquid B comprises a noble metal salt, an acid and water, wherein the concentration of the noble metal salt in the treatment liquid B is 0.002-0.2 mol / L, preferably 0.005-0.1 mol / L, and more preferably 0.008 mol / L.

[0027] Furthermore, the noble metal salt is selected from palladium chloride.

[0028] Furthermore, the acid is selected from hydrochloric acid. In the treatment solution B, the concentration of the acid is preferably 0.2-0.8 mol / L, preferably 0.5 mol / L.

[0029] Furthermore, the activation pretreatment temperature is 10-50° C., preferably 40-50° C., and the time is 30-60 min.

[0030] The activation pretreatment mentioned above allows the subsequent reduction reaction of copper ions to occur. Compared with other activation pretreatment methods (such as silver activation), this method is simple and easy to implement, and has good effects.

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

[0032] The activated glass hollow microspheres are dispersed in a treatment solution C containing conductive metal ions, and stirred in a water bath, filtered, dried and agglomerates are screened out in sequence to obtain the product.

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

[0034] Furthermore, the conductive metal ion source salt is selected from sulfates, nitrates, chlorides or organic acid salts of conductive metals (exemplary examples include one or more of silver nitrate, copper sulfate, cobalt sulfate and nickel sulfate), and the concentration of the conductive metal ion source salt in the treatment solution C is 10-70 g / L, preferably 20-50 g / L.

[0035] Furthermore, 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 temperature of the water bath stirring is 5-85°C.

[0037] The temperature of the water bath stirring can be controlled according to the selection of the conductive metal in the specific conductive metal ion source salt. For example, when the conductive metal is copper or silver, the temperature of the water bath stirring can be 5-room temperature, room temperature, or 5-85°C. When the conductive metal is nickel or cobalt, the water bath stirring is preferably carried out at a temperature of 50-85°C.

[0038] Furthermore, the dispersed concentration of the activated glass hollow microspheres in the treatment liquid C is 1 g / (60-180) ml.

[0039] Furthermore, the welding method comprises the following steps:

[0040] The obtained microspheres were dispersed in water and filtered, and the treatment liquid D was added to the filter cake for welding and drying.

[0041] Preferably, the microspheres are dispersed in water at a concentration of 0.03-0.1 g / mL.

[0042] Preferably, the treatment solution D is an aqueous solution containing 0.1 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 5 ml / L formaldehyde solution.

[0043] Preferably, the amount of the microspheres added to the treatment solution D is 0.004-0.01 g / mL.

[0044] By the treatment in the specific treatment liquid D, the obtained conductive composite material has high porosity, open porosity and higher electromagnetic shielding effectiveness.

[0045] In general, in the preparation method of the conductive composite material of the present invention, by controlling various materials, the obtained conductive composite material has a stable structure, low density and good electromagnetic shielding performance.

[0046] Preferably, the welding process is performed at room temperature. Unlike traditional welding, this technical solution utilizes a chemical reaction method for welding, which can be performed at room temperature. In this technical solution, through the rational design of the microspheres and the reaction solution, a chemical reduction reaction occurs on the microsphere surfaces and at the contact points between the microspheres, depositing metal and achieving connection between the conductive hollow microspheres.

[0047] Furthermore, the treatment liquid D can be used once or recycled, and the number of recycling times is not more than 6 times.

[0048] In another aspect, the present invention provides a microwave shielding material, which is prepared from the conductive composite material as described above.

[0049] Furthermore, the application of microwave shielding materials can be used as one of the following materials: military stealth field, electromagnetic radiation protection of radio and television transmitters, microwave darkroom materials, and electromagnetic shielding materials in buildings or radio communication equipment.

[0050] In another aspect, the present invention provides use of the conductive composite material as described above in the preparation of a microwave shielding or conductive device.

[0051] The beneficial effects of the present invention are as follows:

[0052] In the conductive composite material provided by the present invention, on the one hand, new electromagnetic wave scattering and loss mechanisms can be introduced through the cavity of the conductive hollow microspheres, resulting in a decrease in density. On the other hand, the conductive path between the microspheres can be improved by the metal connecting material copper between the conductive hollow microspheres, thereby enhancing the conductive and electromagnetic shielding performance.

[0053] In the method for preparing the conductive composite material provided by this invention, through the rational design of the microspheres and the reaction solution, a chemical reduction reaction occurs on the microsphere surfaces and at the contact points between the microspheres, depositing metal and connecting the conductive hollow microspheres. This results in a conductive composite material with a stable structure, low density, and excellent electromagnetic shielding effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0055] Figure 1 The flowchart of the preparation of the conductive composite material of the present invention is shown.

[0056] Figure 2 A schematic structural diagram of the conductive composite material of the present invention is shown.

[0057] Figure 3 A low-magnification scanning electron microscope (SEM) image of the conductive composite material obtained in Example 1 is shown. DETAILED DESCRIPTION

[0058] 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.

[0059] In this embodiment, the preparation process of the exemplary conductive composite material is as follows: Figure 1 As shown, the schematic structural diagram of an exemplary conductive composite material is shown in FIG. Figure 2 shown.

[0060] Example 1

[0061] A preparation method of a conductive composite material is as follows:

[0062] 1) Preparation of hollow microspheres A: 50g of glass hollow microspheres (density 0.30g / cm 3 ) was dispersed in 1000 ml of solution A: 12 g / L silane coupling agent KH550, in a 2:1 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 750 ml of solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, in water; stirred at 40°C for 30 min, filtered, dried at 50°C, and sieved to remove agglomerated particles to obtain hollow microspheres A;

[0063] 2) Preparation of Conductive Hollow Microspheres: Hollow microspheres A obtained in step 1) were dispersed at a ratio of 1 g / 68 mL in a metal assembly reaction solution C containing 30 g / L nickel sulfate, 50 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate as a water solvent. The pH was adjusted to ≈ 9.0 with concentrated aqueous ammonia. The reaction was stirred at 60°C. After the reaction was complete, the solution was filtered to obtain hollow microspheres B.

[0064] 3) The hollow microspheres B were dispersed in water at a ratio of 1 g / 20 mL, stirred for 10 minutes, and then filtered. A welding reaction solution D was then added to the filter cake at a ratio of 1 g / 100 mL of the initial hollow microspheres B. The reaction solution contained 0.1 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 5 ml / L formaldehyde. The mixture was reacted at room temperature. The filtered filtrate was repeatedly added to the filter cake and the reaction was repeated for 5 cycles. The filter cake was then removed and dried to obtain a conductive composite material.

[0065] The apparent density of the conductive composite material obtained in this embodiment is 0.28 g / cm 3 , the porosity is 92.7%, the open porosity is 50.5%, and its SEM image is as follows Figure 3 As shown; the mass fractions of glass, metal 1, and connector (metal 2) are 52.6%, 21.1%, and 26.3%, respectively; the electromagnetic shielding effectiveness at a thickness of 2.5 mm is 57-68 dB.

[0066] Example 2

[0067] A preparation method of a conductive composite material is as follows:

[0068] 1) Preparation of hollow microspheres A: 50g of glass hollow microspheres (density 0.35g / cm 3 ) was dispersed in 1000 ml of solution A: 12 g / L silane coupling agent KH550, in a 2:1 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 750 ml of solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, in water; stirred at 40°C for 30 min, filtered, dried at 50°C, and sieved to remove agglomerated particles to obtain hollow microspheres A;

[0069] 2) Preparation of Conductive Hollow Microspheres: Hollow microspheres A obtained in step 1) were dispersed at a ratio of 1 g / 130 mL in a metal assembly reaction solution C containing 30 g / L nickel sulfate, 50 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate as a water solvent. The pH was adjusted to ≈ 9.5 with concentrated aqueous ammonia. The reaction was stirred at 65°C. After the reaction was complete, the solution was filtered to obtain hollow microspheres B.

[0070] 3) The hollow microspheres B were dispersed in water at a ratio of 1 g / 20 mL, stirred for 10 minutes, and then filtered. A welding reaction solution D was then added to the filter cake at a ratio of 1 g / 140 mL of the initial hollow microspheres B. The reaction solution contained 0.1 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 5 ml / L formaldehyde. The reaction was carried out at room temperature. The filtered filtrate was repeatedly added to the filter cake and the reaction was repeated for 5 cycles. The filter cake was removed and dried to obtain a conductive composite material.

[0071] The apparent density of the conductive composite material obtained in this embodiment is 0.42 g / cm 3 The porosity is 90.7%, the open porosity is 51.2%; the mass fractions of glass, metal 1, and connector (metal 2) are 40.3%, 31.5%, and 28.2%, respectively; the electromagnetic shielding effectiveness at a thickness of 2.5mm is 67-80dB.

[0072] Example 3

[0073] A preparation method of a conductive composite material is as follows:

[0074] 1) Preparation of hollow microspheres A: 50g of glass hollow microspheres (density 0.40g / cm 3 ) was dispersed in 1000 ml of solution A: 12 g / L silane coupling agent KH550, in a 2:1 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 750 ml of solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, in water; stirred at 40°C for 30 min, filtered, dried at 50°C, and sieved to remove agglomerated particles to obtain hollow microspheres A;

[0075] 2) Preparation of Conductive Hollow Microspheres: Hollow microspheres A obtained in step 1) were dispersed at a ratio of 1 g / 90 mL in a metal assembly reaction solution C containing 30 g / L cobalt sulfate, 50 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate as a water solvent. The pH was adjusted to ≈10.5 with concentrated aqueous ammonia. The reaction was stirred at 60°C. After the reaction was complete, the solution was filtered to obtain hollow microspheres B.

[0076] 3) The hollow microspheres B were dispersed in water at a ratio of 1 g / 20 mL, stirred for 10 minutes, and then filtered. A welding reaction solution D was then added to the filter cake at a ratio of 1 g / 140 mL of the initial hollow microspheres B. The reaction solution contained 0.1 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 5 ml / L formaldehyde. The reaction was carried out at room temperature. The filtered filtrate was repeatedly added to the filter cake and the reaction was repeated for 5 cycles. The filter cake was removed and dried to obtain a conductive composite material.

[0077] The apparent density of the conductive composite material obtained in this embodiment is 0.43 g / cm 3 The porosity is 89.7%, the open porosity is 48.7%; the mass fractions of glass, metal 1, and connector (metal 2) are 47.6%, 23.8%, and 28.6%, respectively; the electromagnetic shielding effectiveness at a thickness of 2.5mm is 60-71dB.

[0078] Example 4

[0079] A preparation method of a conductive composite material is as follows:

[0080] 1) Preparation of hollow microspheres A: 50g of glass hollow microspheres (density 0.50g / cm 3 ) was dispersed in 1000 ml of solution A: 12 g / L silane coupling agent KH550, in a 2:1 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 750 ml of solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, in water; stirred at 40°C for 30 min, filtered, dried at 50°C, and sieved to remove agglomerated particles to obtain hollow microspheres A;

[0081] 2) Preparation of Conductive Hollow Microspheres: Hollow microspheres A obtained in step 1) were dispersed at a ratio of 1 g / 75 mL in a metal assembly reaction solution C containing 30 g / L cobalt sulfate, 50 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate as a water solvent. The pH was adjusted to ≈10.5 with concentrated aqueous ammonia. The reaction was stirred at 60°C. After the reaction was complete, the solution was filtered to obtain hollow microspheres B.

[0082] 3) The hollow microspheres B were dispersed in water at a ratio of 1 g / 20 mL, stirred for 10 minutes, and then filtered. A welding reaction solution D was then added to the filter cake at a ratio of 1 g / 160 mL of the initial hollow microspheres B. The reaction solution contained 0.1 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 5 ml / L formaldehyde. The reaction was carried out at room temperature. The filtered filtrate was repeatedly added to the filter cake and the reaction was repeated for 5 cycles. The filter cake was then removed and dried to obtain a conductive composite material.

[0083] The apparent density of the conductive composite material obtained in this embodiment is 0.53 g / cm 3 The porosity is 87.6%, the open porosity is 51.1%; the mass fractions of glass, metal 1, and connector (metal 2) are 45.5%, 18.2%, and 36.4%, respectively; the electromagnetic shielding effectiveness at a thickness of 2.5mm is 62-72dB.

[0084] Example 5

[0085] A preparation method of a conductive composite material is as follows:

[0086] 1) Preparation of hollow microspheres A: 50g of glass hollow microspheres (density 0.20g / cm 3 ) was dispersed in 1000 ml of solution A: 12 g / L silane coupling agent KH550, in a 2:1 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 750 ml of solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, in water; stirred at 40°C for 30 min, filtered, dried at 50°C, and sieved to remove agglomerated particles to obtain hollow microspheres A;

[0087] 2) Preparation of Conductive Hollow Microspheres: Hollow microspheres A obtained in step 1) were dispersed at a ratio of 1 g / 125 mL in a metal assembly reaction solution C containing 30 g / L cobalt sulfate, 50 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate as a water solvent. The pH was adjusted to ≈10.0 with concentrated aqueous ammonia. The reaction was stirred at 65°C. After the reaction was complete, the solution was filtered to obtain hollow microspheres B.

[0088] 3) The hollow microspheres B were dispersed in water at a ratio of 1 g / 20 mL, stirred for 10 minutes, and then filtered. A welding reaction solution D was then added to the filter cake at a ratio of 1 g / 175 mL of the initial hollow microspheres B. The reaction solution contained 0.1 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 5 ml / L formaldehyde. The reaction was carried out at room temperature. The filtered filtrate was repeatedly added to the filter cake and the reaction was repeated for 5 cycles. The filter cake was then removed and dried to obtain a conductive composite material.

[0089] The apparent density of the conductive composite material obtained in this embodiment is 0.24 g / cm 3 The porosity is 94.66%, the open porosity is 52.3%; the mass fractions of glass, metal 1, and connector (metal 2) are 38.5%, 26.9%, and 34.6%, respectively; the electromagnetic shielding effectiveness at a thickness of 2.5mm is 69-81dB.

[0090] Example 6

[0091] A preparation method of a conductive composite material is as follows:

[0092] 1) Preparation of hollow microspheres A: 50g of glass hollow microspheres (density 0.15g / cm 3 ) was dispersed in 1000 ml of solution A: 12 g / L silane coupling agent KH550, in a 2:1 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 750 ml of solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, in water; stirred at 40°C for 30 min, filtered, dried at 50°C, and sieved to remove agglomerated particles to obtain hollow microspheres A;

[0093] 2) Preparation of Conductive Hollow Microspheres: Hollow microspheres A obtained in step 1) were dispersed at a ratio of 1 g / 80 mL in a metal assembly reaction solution C containing 20 g / L cobalt sulfate, 20 g / L nickel sulfate, 60 g / L sodium hypophosphite, 90 g / L potassium sodium tartrate, and 60 g / L ammonium sulfate as a water solvent. The pH was adjusted to ≈ 9.0 with concentrated aqueous ammonia. The reaction was stirred at 60° C. After the reaction was complete, the solution was filtered to obtain hollow microspheres B.

[0094] 3) The hollow microspheres B were dispersed in water at a ratio of 1 g / 20 mL, stirred for 10 minutes, and then filtered. A welding reaction solution D was then added to the filter cake at a ratio of 1 g / 200 mL of the initial hollow microspheres B. The reaction solution contained 0.1 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 5 ml / L formaldehyde. The mixture was reacted at room temperature. The filtered filtrate was repeatedly added to the filter cake and the reaction was repeated for 5 cycles. The filter cake was then removed and dried to obtain a conductive composite material.

[0095] The apparent density of the conductive composite material obtained in this embodiment is 0.20 g / cm 3 The porosity is 95.9%, the open porosity is 49.1%; the mass fractions of glass, metal 1, and connector (metal 2) are 38.5%, 23.1%, and 38.4%, respectively; the electromagnetic shielding effectiveness at a thickness of 2.5mm is 72-84dB.

[0096] Example 7

[0097] The preparation of the conductive composite material is as follows:

[0098] 1) Preparation of hollow microspheres A: 50g of glass hollow microspheres (density 0.22g / cm 3 ) was dispersed in 1000 ml of solution A: 12 g / L silane coupling agent KH550, in a 2:1 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 750 ml of solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, in water; stirred at 40°C for 30 min, filtered, dried at 50°C, and sieved to remove agglomerated particles to obtain hollow microspheres A;

[0099] 2) Preparation of Conductive Hollow Microspheres: Hollow microspheres A obtained in step 1) were dispersed at a ratio of 1 g / 120 mL in a metal assembly reaction solution C containing 20 g / L cobalt sulfate, 20 g / L nickel sulfate, 60 g / L sodium hypophosphite, 90 g / L potassium sodium tartrate, and 60 g / L ammonium sulfate as a water solvent. The pH was adjusted to ≈ 9.0 with concentrated aqueous ammonia. The reaction was stirred at 60° C. After the reaction was complete, the solution was filtered to obtain hollow microspheres B.

[0100] 3) The hollow microspheres B were dispersed in water at a ratio of 1 g / 20 mL, stirred for 10 minutes, and then filtered. A welding reaction solution D was then added to the filter cake at a ratio of 1 g / 155 mL of the initial hollow microspheres B. The reaction solution contained 0.1 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 5 ml / L formaldehyde. The reaction was carried out at room temperature. The filtered filtrate was repeatedly added to the filter cake and the reaction was repeated for 5 cycles. The filter cake was then removed and dried to obtain a conductive composite material.

[0101] The apparent density of the conductive composite material obtained in this embodiment is 0.31 g / cm 3 The porosity is 93.5%, the open porosity is 47.8%; the mass fractions of glass, metal 1, and connector (metal 2) are 37.0%, 33.4%, and 29.6%, respectively; the electromagnetic shielding effectiveness at a thickness of 2.5mm is 70-80dB.

[0102] Example 8

[0103] The preparation of the conductive composite material is as follows:

[0104] 1) Preparation of hollow microspheres A: 50g of glass hollow microspheres (density 0.38g / cm 3 ) was dispersed in 1000 ml of solution A: 12 g / L silane coupling agent KH550, in a 2:1 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 750 ml of solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, in water; stirred at 40°C for 30 min, filtered, dried at 50°C, and sieved to remove agglomerated particles to obtain hollow microspheres A;

[0105] 2) Preparation of Conductive Hollow Microspheres: Hollow microspheres A obtained in step 1) were dispersed at a ratio of 1 g / 65 mL in a metal assembly reaction solution C containing water, 0.08 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 4.5 ml / L formaldehyde. The reaction was allowed to proceed at room temperature. After the reaction was complete, the solution was filtered to obtain hollow microspheres B.

[0106] 3) The hollow microspheres B were dispersed in water at a ratio of 1 g / 20 mL, stirred for 10 minutes, and then filtered. A welding reaction solution D was then added to the filter cake at a ratio of 1 g / 215 mL of the initial hollow microspheres B. The reaction solution contained 0.1 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 5 ml / L formaldehyde. The reaction was carried out at room temperature. The filtered filtrate was repeatedly added to the filter cake and the reaction was repeated for 5 cycles. The filter cake was then removed and dried to obtain a conductive composite material.

[0107] The apparent density of the conductive composite material obtained in this embodiment is 0.44 g / cm 3 The porosity is 90.2%, the open porosity is 51.4%; the mass fractions of glass, metal 1, and connector (metal 2) are 41.7%, 12.5%, and 45.8%, respectively; the electromagnetic shielding effectiveness at a thickness of 2.5mm is 75-86dB.

[0108] Example 9

[0109] The preparation of the conductive composite material is as follows:

[0110] 1) Preparation of hollow microspheres A: 50g of glass hollow microspheres (density 0.46g / cm 3 ) was dispersed in 1000 ml of solution A: 12 g / L silane coupling agent KH550, in a 2:1 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 750 ml of solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, in water; stirred at 40°C for 30 min, filtered, dried at 50°C, and sieved to remove agglomerated particles to obtain hollow microspheres A;

[0111] 2) Preparation of Conductive Hollow Microspheres: Hollow microspheres A obtained in step 1) were dispersed at a ratio of 1 g / 170 mL in a metal assembly reaction solution C containing 0.08 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 4.5 mL / L formaldehyde as the solvent. The reaction was carried out at room temperature. After the reaction was complete, the solution was filtered to obtain hollow microspheres B.

[0112] 3) The hollow microspheres B were dispersed in water at a ratio of 1 g / 20 mL, stirred for 10 minutes, and then filtered. A welding reaction solution D was then added to the filter cake at a ratio of 1 g / 235 mL of the initial hollow microspheres B. The reaction solution contained 0.1 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 5 ml / L formaldehyde. The reaction was carried out at room temperature. The filtered filtrate was repeatedly added to the filter cake and the reaction was repeated for 5 cycles. The filter cake was then removed and dried to obtain a conductive composite material.

[0113] The apparent density of the conductive composite material obtained in this embodiment is 0.66 g / cm 3 The porosity is 87.0%, the open porosity is 50.9%; the mass fractions of glass, metal 1, and connector (metal 2) are 34.5%, 24.1%, and 41.4%, respectively; the electromagnetic shielding effectiveness at a thickness of 2.5mm is 73-81dB.

[0114] Example 10

[0115] The preparation of the conductive composite material is as follows:

[0116] 1) Preparation of hollow microspheres A: 50g of glass hollow microspheres (density 0.46g / cm 3 ) was dispersed in 1000 ml of solution A: 12 g / L silane coupling agent KH550, in a 2:1 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 750 ml of solution B: 0.5 mol / L hydrochloric acid, 0.008 mol / L palladium chloride, in water; stirred at 40°C for 30 min, filtered, dried at 50°C, and sieved to remove agglomerated particles to obtain hollow microspheres A;

[0117] 2) Preparation of Conductive Hollow Microspheres: Hollow microspheres A obtained in step 1) were dispersed at a ratio of 1 g / 82 mL in a metal assembly reaction solution C containing water as the solvent and 0.12 mol / L silver nitrate (ammonia was added dropwise until colorless). After the hollow microspheres A and metal assembly reaction solution C were uniformly mixed, 4.0 ml / L formaldehyde was added with stirring, and the mixture was reacted at room temperature. After the reaction was complete, the mixture was filtered to obtain hollow microspheres B.

[0118] 3) The hollow microspheres B were dispersed in water at a ratio of 1 g / 20 mL, stirred for 10 minutes, and then filtered. A welding reaction solution D was then added to the filter cake at a ratio of 1 g / 200 mL of the initial hollow microspheres B. The reaction solution contained 0.1 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 5 ml / L formaldehyde. The mixture was reacted at room temperature. The filtered filtrate was repeatedly added to the filter cake and the reaction was repeated for 5 cycles. The filter cake was then removed and dried to obtain a conductive composite material.

[0119] The apparent density of the conductive composite material obtained in this embodiment is 0.49 g / cm 3 The porosity is 80.3%, the open porosity is 49.2%; the mass fractions of glass, metal 1, and connector (metal 2) are 33.2%, 34.1%, and 32.7% respectively; the electromagnetic shielding effectiveness at a thickness of 2.5mm is 78-87dB.

[0120] Performance testing:

[0121] The electromagnetic properties of the products prepared in the above examples were tested. The testing methods were as follows: apparent density was obtained by measuring size and weight; porosity was obtained by measuring true density; transmission parameters were tested using a vector network analyzer (test frequency 8-12 GHz) to analyze shielding performance.

[0122] 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 conductive composite material, characterized in that: The composite material comprises a plurality of conductive hollow microspheres and a connecting material for connecting the conductive hollow microspheres; The conductive hollow microspheres are composed of glass hollow microspheres and a conductive metal shell layer covering the glass hollow microspheres. The connecting material is metallic copper.

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

3. The conductive composite material according to claim 1 or 2, characterized in that: The apparent density of the conductive composite material is 0.15-0.7 g / cm 3 , the porosity is 85-97% and the open porosity is 45-55%.

4. The conductive composite material according to claim 1, wherein Calculated by weight percentage, the conductive composite material comprises 30-55 wt % of glass hollow microspheres, 10-35 wt % of conductive metal spherical shell layers and 25-50 wt % of connecting materials.

5. The conductive composite material according to claim 1, wherein The material of the conductive metal spherical shell layer is 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 the conductive composite material 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 conductive metal on the surface of the activated glass hollow microspheres; The obtained microspheres are subjected to welding treatment using a connecting material to obtain the conductive composite material.

7. The preparation method according to claim 6, characterized in that The method for coating the surface of the activated glass hollow microspheres with a conductive metal comprises the following steps: The activated glass hollow microspheres are dispersed in a treatment solution C containing conductive 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 conductive metal ion source salt, a stabilizer, a reducing agent, a pH regulator and water; Preferably, the conductive metal ion source salt is selected from sulfates, nitrates, chlorides or organic acid salts of conductive metals, and the concentration of the conductive 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 5-85°C; Preferably, the amount of the activated glass hollow microspheres added to the treatment solution C is 0.005-0.02 g / mL.

8. The preparation method according to claim 6, characterized in that The welding method comprises the following steps: The obtained microspheres were dispersed in water and filtered, and the treatment liquid D was added to the filter cake for welding and drying; Preferably, the microspheres are dispersed in water at a concentration of 0.03-0.1 g / mL; Preferably, the treatment solution D is an aqueous solution containing 0.1 mol / L copper sulfate, 0.08 mol / L potassium sodium tartrate, 0.06 mol / L EDTA, 0.5 mol / L sodium hydroxide, and 5 ml / L formaldehyde solution; Preferably, the amount of the microspheres added to the treatment solution D is 0.004-0.01 g / mL; Preferably, the soldering process is performed at room temperature.

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

10. Use of the microwave shielding material according to claim 9 in the preparation of a microwave absorbing or shielding device.

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