Composite foam as well as preparation method and application thereof

Abstract

The invention discloses composite foam as well as a preparation method and application thereof. The structure of the composite foam comprises a metal material which is selected from a metal simple substance or a metal alloy; the hollow glass microspheres and the reinforcing filler are dispersed in the metal material; wherein all the hollow glass microspheres are embedded in the metal material. In the composite foam, a composite cavity is formed by using the preformed hollow glass microspheres and stacking gaps among the microspheres, so that the density of the composite foam is reduced, and the strength and functionality of the composite foam are also ensured; connection enhancement of the preformed hollow microspheres is synchronously achieved through the metal material deposition process, and the process is convenient and efficient through connection of the reinforcing filler and the hollow microspheres.

Description

A composite foam, its preparation method and application Technical Field

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

[0002] Constructing hollow structures and achieving multi-component composite materials is a crucial approach to enhancing the functionality and lightweighting of advanced materials. Related research and technological development are increasingly becoming a focus for scientific researchers, technology developers, and product designers. Compared to material selection and composition design, hollow structures can more effectively reduce material density. Especially for the construction of functional networks in materials, the rational combination of hollow structures and effective functional components can significantly reduce the amount of functional components used while lowering density, thus improving economic value and resource utilization efficiency. However, the introduction of hollow structures inevitably introduces irregular, non-homogeneous regions into the material. When the material bears external loads, these regions are prone to stress concentration, significantly increasing localized stress. Furthermore, these hollow regions, lacking sufficient load-bearing material, form mechanically weak areas, easily inducing crack generation and propagation, leading to a decline in the material's mechanical properties. Insufficient mechanical strength not only limits the application of such lightweight materials in environments requiring certain loads, but even as purely functional materials, their low mechanical strength results in poor structural stability. For advanced functional materials, their functionality depends not only on the chemical composition of the material, but also significantly on the structure at different scales. Therefore, the stability of the structure determines the stability of the functionality to a certain extent.

[0003] For improving the mechanical strength (strengthening stability) of hollow structural materials, constructing hollow structures using pre-formed hollow microspheres with high-strength spherical shells is an effective method. On the one hand, the large proportion of cavities in hollow microspheres can lead to high porosity and consequently low density; on the other hand, the spherical shape helps to maximize the dispersion of stress generated by external loads, avoiding the generation and propagation of microcracks caused by severe stress concentration (an important mechanism of material structural failure). However, the spherical shape of hollow microspheres is a double-edged sword. As mentioned above, for mechanical strength, the spherical shape is beneficial for stress dispersion; but for functionality, the point contact between spherical structures is often a significant factor leading to poor functional connections between spheres (such as conductive connections and the resulting conductive networks). To maximize the advantages and minimize the disadvantages, researchers have explored ways to enhance the functional connections between hollow microspheres. The methods employed include: matching hollow microspheres of different sizes and optimizing the functional network (increasing connection points) by filling and reinforcing the spaces between microspheres of varying sizes; designing the outer shell of the hollow microspheres as a functional shell and designing its structural units as anisotropic structures to increase the contact area between the spheres and optimize the functional network; and targeted reinforcement of the inter-sphere connection areas, such as by depositing functional materials to optimize the functional network. Although these attempts can produce some optimization effects, significant shortcomings remain in terms of process implementation difficulty, cost-effectiveness, and the synergistic optimization of structural strength and functionality. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a composite foam, its preparation method and application.

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

[0006] On one hand, the present invention provides a composite foam, wherein the structure of the composite foam includes:

[0007] Metallic materials, selected from elemental metals or metal alloys; and

[0008] Several hollow glass microspheres and reinforcing fillers dispersed in the metallic material;

[0009] Each hollow glass microsphere is embedded in the metal material.

[0010] Furthermore, the composite foam has a block structure.

[0011] Furthermore, the composite foam contains spherical closed pores and irregular open pores.

[0012] In this composite foam, spherical closed pores are introduced by hollow glass microspheres, while irregular open pores are formed by the voids between hollow micro-accumulations. Reinforcing fillers are also filled into the voids between the hollow micro-accumulations, and the functional spherical shell structure of the hollow glass microspheres, the connection between the microspheres, and the connection between the microspheres and the reinforcing fillers are achieved in one step through a metal material deposition process. This composite foam reduces density by utilizing the cavities inside and between the microspheres; furthermore, it achieves high mechanical strength (structural stability) and electromagnetic functionality through the combination of pre-formed closed spherical shells, metal shells, and reinforcing fillers.

[0013] Furthermore, the apparent density of the composite foam is 0.1-0.6 g / cm³. 3 The porosity is 70-93%, and the open porosity is 45-55%.

[0014] Furthermore, by mass percentage, the composite foam structure comprises: 25-55% hollow glass microspheres, 20-60% metallic materials, and 4-35% reinforcing fillers.

[0015] Furthermore, the metallic element is selected from one or more of cobalt, copper, and nickel.

[0016] Furthermore, the metal alloy is selected from alloys formed from two or three of cobalt, copper, and nickel.

[0017] Furthermore, the reinforcing filler is selected from one or more of the following: silver nanowires, silver nanosheets, a mixture of silver nanosheets and copper-plated carbon nanotubes in a 1:1 mass ratio, copper-plated carbon nanotubes, and carbon nanotubes. Compared with other reinforcing fillers such as glass fiber, silica, and alumina, these reinforcing fillers in this invention not only provide mechanical reinforcement but also enhance electrical conductivity and electromagnetic functionality. Moreover, unlike spherical reinforcing fillers, their anisotropic shape is beneficial for enhancing the conductive network.

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

[0019] Surface treatments were performed on the glass hollow microspheres and the reinforcing filler, respectively.

[0020] Surface-treated hollow glass microspheres and surface-treated reinforcing fillers are mixed to obtain a mixture, and the mixture is subjected to metal deposition treatment to obtain a composite foam intermediate.

[0021] The composite foam intermediate is subjected to heat treatment to obtain the composite foam.

[0022] Furthermore, the density of the hollow glass microspheres is 0.11-0.6 g / cm³. 3 .

[0023] Furthermore, the method for surface treatment of hollow glass microspheres includes the following steps:

[0024] The glass hollow microspheres were first dispersed in a silane coupling agent solution, then dispersed in a noble metal salt solution and stirred to react. After filtration and drying, the surface-treated glass hollow microspheres were obtained.

[0025] The reinforcing filler is first dispersed in a silane coupling agent solution, then dispersed in a noble metal salt solution and stirred to react. After filtration and drying, the surface-treated reinforcing filler is obtained.

[0026] Furthermore, in the silane coupling agent solution, the solvent is water and / or anhydrous ethanol.

[0027] Furthermore, in the silane coupling agent solution, the solvent is a mixture of anhydrous ethanol and water in a volume ratio of 2:1 to 1:2. For example, the volume ratio of anhydrous ethanol to water includes, but is not limited to, 1:(0.5-1), 1:(1-2), etc.

[0028] Further, the concentration of the silane coupling agent in the silane coupling agent solution is 10-20 g / L. For example, the concentration of the silane coupling agent in the silane coupling agent solution includes, but is not limited to, 12-18 g / L, 12-15 g / L, 12-14 g / L, 14-18 g / L, 14-15 g / L, 15-18 g / L, etc.

[0029] Furthermore, in the silane coupling agent solution, the silane coupling agent is selected from KH550.

[0030] Furthermore, the concentration of the noble metal salt in the noble metal salt solution is 0.002-0.2 mol / L. Exemplary concentrations of precious metal salts include 0.003-0.015 mol / L, 0.003-0.009 mol / L, 0.003-0.008 mol / L, 0.003-0.007 mol / L, 0.003-0.005 mol / L, 0.005-0.015 mol / L, 0.005-0.009 mol / L, 0.005-0.008 mol / L, 0.005-0.007 mol / L, 0.007-0.015 mol / L, 0.007-0.009 mol / L, 0.007-0.008 mol / L, 0.008-0.015 mol / L, 0.008-0.009 mol / L, and 0.009-0.015 mol / L.

[0031] Furthermore, the precious metal salt is palladium chloride.

[0032] Furthermore, in the noble metal salt solution, the solute is a mixture of water and concentrated sulfuric acid at a volume ratio of 100:1.

[0033] Further, the temperature of the stirring reaction is 20-60℃, and the time is 20-60 min. For example, the temperature of the stirring reaction includes, but is not limited to, 40-50℃. For example, the time of the stirring reaction includes, but is not limited to, 20-50 min, 20-40 min, 20-30 min, 30-50 min, 30-40 min, 40-50 min, etc.

[0034] Furthermore, the addition ratio of the glass hollow microspheres to the silane coupling agent solution is 1g:(10-40)mL.

[0035] Furthermore, the addition ratio of the hollow glass microspheres to the noble metal salt solution is 1g:(10-70)mL.

[0036] Furthermore, the ratio of the reinforcing filler to the silane coupling agent solution and the noble metal salt solution is (20-140) g / L.

[0037] Furthermore, the ratio of the reinforcing filler to the noble metal salt solution is (30-150) g / L.

[0038] Furthermore, the method for preparing the composite foam intermediate includes the following steps:

[0039] The mixture is dispersed in water, mixed well, and then filtered to obtain a filter cake.

[0040] Under vacuum filtration, the aqueous solution containing the metal ion source salt is added to the filter cake to carry out the reaction. The filtrate obtained by vacuum filtration is added back to the filter cake. The vacuum filtration is repeated 1-8 times. The filter cake is then removed and dried to obtain a hollow microsphere welded structure intermediate.

[0041] Further, in the mixture, the mass ratio of surface-treated hollow glass microspheres to surface-treated reinforcing filler is (1-10):1. More exemplary mass ratios include, but are not limited to, (1-7):1, (1-5):1, (1-3.5):1, (1-2.5):1, (2.5-10):1, (2.5-7):1, (2.5-5):1, (2.5-3.5):1, (3.5-10):1, (3.5-7):1, (3.5-5):1, (5-10):1, (5-7):1, (7-10):1, etc.

[0042] Furthermore, the aqueous solution containing the metal ion source salt contains 10-80 g / L of metal ion source salt, 20-100 g / L of stabilizer, 20-100 g / L of reducing agent, and pH adjuster, wherein the amount of pH adjuster added is such that the pH of the aqueous solution of the metal ion source salt is 8.5-11.

[0043] Furthermore, the metal ion source salt is selected from one or more soluble salts of cobalt, copper, and nickel. For example, the metal ion source salt includes, but is not limited to, one or more selected from copper sulfate, cobalt sulfate, and nickel sulfate.

[0044] Furthermore, the reducing agent is selected from sodium hypophosphite, etc.

[0045] Furthermore, the stabilizer is selected from one or more of EDTA, ammonium sulfate, and sodium potassium tartrate.

[0046] Furthermore, the reaction temperature is 10-80°C. For example, the reaction temperature is room temperature (20-25°C)-80°C, room temperature, 70-80°C, 70°C, or 80°C.

[0047] Furthermore, the ratio of the surface-treated glass hollow microspheres to the aqueous solution containing the metal ion source salt is 1g:(50-250)mL.

[0048] Furthermore, the heat treatment method includes the following steps:

[0049] Heat treatment is carried out in a reducing or inert atmosphere at a temperature of 300-600℃ for 1-12 hours.

[0050] Furthermore, the heat treatment temperature is 400-600℃, and the time is 4-12 hours.

[0051] Furthermore, the reducing atmosphere is a mixture of hydrogen and argon in a volume ratio of 1:19.

[0052] In another aspect, the present invention provides the application of the composite foam described above in microwave shielding.

[0053] The beneficial effects of this invention are as follows:

[0054] In the composite foam of this invention, by designing the structure and controlling the components in each layer, a stable structure and excellent microwave shielding effect are achieved. In this composite foam, pre-formed hollow glass microspheres and the gaps between them form a composite cavity, reducing the density of the composite foam while ensuring its strength and functionality. The connection and reinforcement of the pre-formed hollow microspheres are simultaneously achieved through the metal material deposition process, and the connection between the filler and the hollow microspheres is strengthened through a convenient and efficient process.

[0055] In this invention, the method for preparing composite foam revolves around constructing a hollow composite foam using pre-formed hollow microspheres. The composition and structure of the foam are designed and optimized, and a metal composite foam can be obtained through a low-temperature reaction. A closed cavity is constructed using pre-formed hollow glass spheres, and further metallization and enhanced inter-sphere connections are achieved through chemical reduction and in-situ deposition of metal. More importantly, specific reinforcing fillers are preferably introduced, and their efficient connection with the hollow microspheres is achieved through a metal deposition process to enhance functionality. The preparation method used in this invention constructs composite foam through a one-step metal reduction deposition process. This not only optimizes performance through reinforcing fillers and strengthening connection points but also avoids the high-temperature and complex processing involved in traditional preparation methods, making it convenient and efficient. It can provide a new approach for constructing composite porous structures based on hollow microspheres. Attached Figure Description

[0056] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0057] Figure 1 shows a schematic diagram of an exemplary composite foam in this invention.

[0058] Figure 2 shows a schematic diagram of the preparation process of an exemplary composite foam in this invention.

[0059] Figure 3 shows a SEM image of the composite foam obtained in Example 1. Detailed Implementation

[0060] 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.

[0061] In an embodiment of the present invention, an exemplary structural schematic diagram of hollow microsphere foam is shown in Figure 1.

[0062] Example 1

[0063] The preparation method of composite foam is shown in Figure 2, and specifically includes the following steps:

[0064] 1) Preparation of microsphere intermediates and modification of reinforcing fillers: 30g of glass hollow microspheres (density 0.31g / cm³) were prepared. 3The following were dispersed in 500 ml of solution A: silane coupling agent KH550 12 g / L, solvent is a 1:1 volume mixture of anhydrous ethanol and distilled water; then dispersed in 600 ml of solution B: palladium chloride 0.008 mol / L, solvent is a solution prepared by water and concentrated hydrochloric acid at a volume ratio of 100:1. The mixture was stirred at 40 °C for 30 min, filtered, dried at 50 °C, and the agglomerated particles were removed by sieving to obtain microsphere intermediates.

[0065] 2) The reinforcing filler (silver nanowires) was dispersed in solutions A and B at addition amounts of 50 g / L and 40 g / L respectively, under the same reaction conditions as the microsphere intermediate preparation process in step 1), to obtain the modified reinforcing filler;

[0066] 3) Preparation of composite foam intermediate (i.e., the metal deposition step in Figure 2): The microsphere intermediates obtained in steps 1) and 2) and the reinforcing filler are added to water in proportions of 20 g / L and 2 g / L, respectively. The mixture is ultrasonically dispersed for 30 min, then stirred for 10 min and filtered. Then, under vacuum filtration, treatment solution C is added to the wet filter cake at a ratio of 1 g / 190 mL to the microsphere intermediate. The solvent of the treatment solution is water, 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. The reaction is carried out at room temperature. The filtrate is repeatedly added to the filter cake and the reaction is repeated 5 times. The filter cake is then removed, dried, and the composite foam intermediate is obtained.

[0067] 4) Preparation of composite foam (i.e., the heat treatment step in Figure 2): The composite foam intermediate obtained in step 3) is heat-treated in a reducing atmosphere (hydrogen to argon in a volume ratio of 1:19) at a temperature of 450℃ for 8 hours to obtain the target product, composite foam. The SEM image of this composite foam is shown in Figure 3.

[0068] Performance testing:

[0069] The electromagnetic properties of the obtained composite foam were tested. The test method was as follows:

[0070] Apparent density is obtained by measuring size and weight; porosity is obtained by measuring true density.

[0071] Transmission parameters were tested using a vector network analyzer (test frequency 8-12GHz), and its shielding performance (thickness 2.3mm) was analyzed.

[0072] Uniaxial compressive strength was tested using a universal testing machine.

[0073] The apparent density of the composite foam obtained in this embodiment is 0.30 g / cm³. 3The porosity is 92.8%, and the open porosity is 53.6%; the mass fractions of glass, metal, and reinforcing filler are 46.5%, 48.8%, and 4.7%, respectively.

[0074] The composite foam has an electromagnetic shielding effectiveness of 63-75 dB and a compressive strength of 2301 kPa.

[0075] Example 2

[0076] The preparation of composite foam specifically includes the following steps:

[0077] 1) Preparation of microsphere intermediates and modification of reinforcing fillers: 30g of hollow glass microspheres (density 0.32g / cm³) were prepared. 3 The following were dispersed in 500 ml of solution A: silane coupling agent KH550 12 g / L, solvent was a 2:1 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 600 ml of solution B: palladium chloride 0.009 mol / L, solvent was a solution prepared by water and concentrated hydrochloric acid in a 100:1 volume ratio, stirred at 40 °C for 40 min, filtered, dried at 50 °C, and sieved to remove agglomerated particles to obtain microsphere intermediates;

[0078] 2) The reinforcing filler (silver nanowires) was added to solutions A and B at amounts of 40 g / L and 60 g / L respectively, under the same reaction conditions as the microsphere intermediate preparation process in step 1), to obtain the modified reinforcing filler;

[0079] 3) Preparation of composite foam intermediate: The microsphere intermediates obtained in steps 1) and 2) and the reinforcing filler were added to water in proportions of 20 g / L and 4 g / L, respectively. The mixture was ultrasonically dispersed for 30 min, then stirred for 10 min and filtered. Then, under vacuum filtration, treatment solution C was added to the wet filter cake at a ratio of 1 g / 160 mL to the microsphere intermediate. The solvent of the treatment solution was water, 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. The reaction was carried out at room temperature. The filtrate was repeatedly added to the filter cake and the reaction was repeated 6 times. The filter cake was then removed, dried, and the composite foam intermediate was obtained.

[0080] 4) Preparation of composite foam: The composite foam intermediate obtained in step 3) is heat-treated in a reducing atmosphere (volume ratio of hydrogen to argon 1:19) at a temperature of 550°C for 4 hours to obtain the target product composite foam.

[0081] The apparent density of the composite foam obtained in this embodiment is 0.31 g / cm³. 3 The porosity is 92.4%, and the open porosity is 51.9%; the mass fractions of glass, metal, and reinforcing filler are 47.6%, 42.5%, and 9.9%, respectively.

[0082] The composite foam has an electromagnetic shielding effectiveness of 70-88 dB and a compressive strength of 2057 kPa.

[0083] Example 3

[0084] The preparation of composite foam specifically includes the following steps:

[0085] 1) Preparation of microsphere intermediates and modification of reinforcing fillers: 40g of hollow glass microspheres (density 0.3g / cm³) were prepared. 3 The following were dispersed in 500 ml of solution A: silane coupling agent KH550 15 g / L, solvent is a 2:1 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 600 ml of solution B: palladium chloride 0.015 mol / L, solvent is a solution prepared by water and concentrated hydrochloric acid in a 100:1 volume ratio, stirred at 50 °C for 20 min, filtered, dried at 50 °C, and sieved to remove agglomerated particles to obtain microsphere intermediates;

[0086] 2) The reinforcing filler (silver nanowires) was added to solutions A and B at amounts of 100 g / L and 150 g / L respectively, under the same reaction conditions as the microsphere intermediate preparation process in step 1), to obtain the modified reinforcing filler;

[0087] 3) Preparation of composite foam intermediate: The microsphere intermediates obtained in steps 1) and 2) and the reinforcing filler were added to water in proportions of 10 g / L and 3 g / L, respectively. The mixture was ultrasonically dispersed for 50 min, then stirred for 20 min and filtered. Then, under vacuum filtration, treatment solution C was added to the wet filter cake at a ratio of 1 g / 250 mL to the microsphere intermediate. The solvent of the treatment solution was water, 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. The reaction was carried out at room temperature. The filtrate was repeatedly added to the filter cake and the reaction was repeated 6 times. The filter cake was then removed, dried, and the composite foam intermediate was obtained.

[0088] 4) Preparation of composite foam: The composite foam intermediate obtained in step 3) is heat-treated in a reducing atmosphere (volume ratio of hydrogen to argon 1:19) at a temperature of 550°C for 4 hours to obtain the target product composite foam.

[0089] The apparent density of the composite foam obtained in this embodiment is 0.37 g / cm³. 3 The porosity is 92.1%, and the open porosity is 52.7%; the mass fractions of glass, metal, and reinforcing filler are 36.4%, 52.7%, and 10.9%, respectively.

[0090] The composite foam has an electromagnetic shielding effectiveness of 70-88 dB and a compressive strength of 2450 kPa.

[0091] Example 4

[0092] The preparation of composite foam specifically includes the following steps:

[0093] 1) Preparation of microsphere intermediates and modification of reinforcing fillers: 60g of hollow glass microspheres (density 0.5g / cm³) were prepared. 3 The following were dispersed in 600 ml of solution A: silane coupling agent KH550 18 g / L, solvent was a 1:1 volume mixture of anhydrous ethanol and distilled water; then dispersed in 600 ml of solution B: palladium chloride 0.009 mol / L, solvent was a solution prepared by water and concentrated hydrochloric acid in a 100:1 volume ratio, stirred at 40 °C for 40 min, filtered, dried at 50 °C, and sieved to remove agglomerated particles to obtain microsphere intermediates;

[0094] 2) The reinforcing filler (silver nanosheets) was added to solutions A and B at amounts of 140 g / L and 150 g / L respectively, under the same reaction conditions as the microsphere intermediate preparation process in step 1), to obtain the modified reinforcing filler;

[0095] 3) Preparation of composite foam intermediate: The microsphere intermediates and reinforcing fillers obtained in steps 1) and 2) were added to water in proportions of 30 g / L and 24 g / L, respectively. The mixture was ultrasonically dispersed for 30 min, stirred for 10 min, and then filtered. Under vacuum filtration, treatment solution C was added to the wet filter cake at a ratio of 1 g / 79 mL to the microsphere intermediate. The solvent of the treatment solution was water, containing 40 g / L cobalt sulfate, 60 g / L sodium hypophosphite, 70 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate. The pH was adjusted to approximately 10.8 with concentrated ammonia. The reaction was carried out at 80℃. The filtrate was repeatedly added to the filter cake and the reaction was repeated for 8 rounds. The filter cake was then removed, dried, and the composite foam intermediate was obtained.

[0096] 4) Preparation of composite foam: The composite foam intermediate obtained in step 3) is heat-treated in an inert atmosphere (nitrogen) at a temperature of 600℃ for 12 hours to obtain the target product composite foam.

[0097] The apparent density of the composite foam obtained in this embodiment is 0.52 g / cm³. 3 The porosity is 88.0% and the open porosity is 52.5%; the mass fractions of glass, metal, and reinforcing filler are 43.5%, 21.7%, and 34.8%, respectively.

[0098] The composite foam has an electromagnetic shielding effectiveness of 70-88 dB and a compressive strength of 855 kPa.

[0099] Example 5

[0100] The preparation of composite foam specifically includes the following steps:

[0101] 1) Preparation of microsphere intermediates and modification of reinforcing fillers: 20g of hollow glass microspheres (density 0.22g / cm³) were prepared. 3 The following were dispersed in 600 ml of solution A: silane coupling agent KH550 14 g / L, solvent was a 1:2 volume ratio mixture of anhydrous ethanol and distilled water; then dispersed in 600 ml of solution B: palladium chloride 0.005 mol / L, solvent was a solution prepared by water and concentrated hydrochloric acid at a volume ratio of 100:1. The mixture was stirred at 50 °C for 40 min, filtered, dried at 50 °C, and sieved to remove agglomerated particles to obtain microsphere intermediates.

[0102] 2) The reinforcing filler (a mixture of silver nanosheets and copper-plated carbon nanotubes in a 1:1 mass ratio) was added to solutions A and B at amounts of 80 g / L and 90 g / L respectively, under the same reaction conditions as the microsphere intermediate preparation process in step 1), to obtain the modified reinforcing filler.

[0103] 3) Preparation of composite foam intermediate: The microsphere intermediates and reinforcing fillers obtained in steps 1) and 2) were added to water in proportions of 10 g / L and 4 g / L, respectively. The mixture was ultrasonically dispersed for 60 min, then stirred for 30 min and filtered. Then, under vacuum filtration, treatment solution C was added to the wet filter cake at a ratio of 1 g / 200 mL to the microsphere intermediate. The solvent of the treatment solution was water, containing 60 g / L nickel sulfate, 60 g / L sodium hypophosphite, 80 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate. The pH was adjusted to approximately 9.5 with concentrated ammonia. The reaction was carried out at 70℃. The filtrate was repeatedly added to the filter cake and the reaction was repeated 6 times. The filter cake was then removed, dried, and the composite foam intermediate was obtained.

[0104] 4) Preparation of composite foam: The composite foam intermediate obtained in step 3) is heat-treated in an inert atmosphere (nitrogen) at a temperature of 500℃ for 9 hours to obtain the target product composite foam.

[0105] The apparent density of the composite foam obtained in this embodiment is 0.33 g / cm³. 3 The porosity is 93.6% and the open porosity is 54.1%; the mass fractions of glass, metal, and reinforcing filler are 29.4%, 58.8%, and 11.8%, respectively.

[0106] The composite foam has an electromagnetic shielding effectiveness of 80-93dB and a compressive strength of 2530kPa.

[0107] Example 6

[0108] The preparation of composite foam specifically includes the following steps:

[0109] 1) Preparation of microsphere intermediates and modification of reinforcing fillers: 15g of glass hollow microspheres (density 0.14g / cm³) were prepared. 3The following were dispersed in 600 ml of solution A: silane coupling agent KH550 12 g / L, solvent was a 2:1 volume mixture of anhydrous ethanol and distilled water; then dispersed in 1000 ml of solution B: palladium chloride 0.003 mol / L, solvent was a solution prepared by water and concentrated hydrochloric acid in a 100:1 volume ratio, stirred at 40 °C for 30 min, filtered, dried at 50 °C, and sieved to remove agglomerated particles to obtain microsphere intermediates;

[0110] 2) The reinforcing filler (copper-plated carbon nanotubes) was added to solutions A and B at amounts of 70 g / L and 90 g / L respectively, under the same reaction conditions as the microsphere intermediate preparation process in step 1), to obtain the modified reinforcing filler;

[0111] 3) Preparation of composite foam intermediate: The microsphere intermediates obtained in steps 1) and 2) and the reinforcing filler were added to water in proportions of 10 g / L and 3 g / L, respectively. The mixture was ultrasonically dispersed for 120 min, stirred for 30 min, and then filtered. Then, under vacuum filtration, treatment solution C was added to the wet filter cake at a ratio of 1 g / 72 mL to the microsphere intermediate. The solvent of the treatment solution was water, containing 25 g / L cobalt sulfate, 25 g / L nickel sulfate, 70 g / L sodium hypophosphite, 80 g / L potassium sodium tartrate, and 50 g / L ammonium sulfate. The pH was adjusted to approximately 10.3 with concentrated ammonia. The reaction was carried out at 80℃. The filtrate was repeatedly added to the filter cake and the reaction was repeated 7 times. The filter cake was then removed, dried, and the composite foam intermediate was obtained.

[0112] 4) Preparation of composite foam: The composite foam intermediate obtained in step 3) is heat-treated in a reducing atmosphere (volume ratio of hydrogen to argon 1:9) at a temperature of 400℃ for 8 hours to obtain the target product composite foam.

[0113] The apparent density of the composite foam obtained in this embodiment is 0.12 g / cm³. 3 The porosity is 96.8% and the open porosity is 52.7%; the mass fractions of glass, metal, and reinforcing filler are 52.6%, 31.6%, and 15.8%, respectively.

[0114] The composite foam has an electromagnetic shielding effectiveness of 56-68 dB and a compressive strength of 685 kPa.

[0115] Example 7

[0116] The preparation of composite foam specifically includes the following steps:

[0117] 1) Preparation of microsphere intermediates and modification of reinforcing fillers: 40g of hollow glass microspheres (density 0.47g / cm³) were prepared. 3The following were dispersed in 500 ml of solution A: silane coupling agent KH550 12 g / L, solvent was a 2:1 volume mixture of anhydrous ethanol and distilled water; then dispersed in 500 ml of solution B: palladium chloride 0.005 mol / L, solvent was a solution prepared by water and concentrated hydrochloric acid in a 100:1 volume ratio, stirred at 40 °C for 30 min, filtered, dried at 50 °C, and sieved to remove agglomerated particles to obtain microsphere intermediates;

[0118] 2) The reinforcing filler (carbon nanotubes) was added to solutions A and B at amounts of 25 g / L and 35 g / L respectively, under the same reaction conditions as the microsphere intermediate preparation process in step 1), to obtain the modified reinforcing filler;

[0119] 3) Preparation of composite foam intermediate: The microsphere intermediates obtained in steps 1) and 2) and the reinforcing filler were added to water in proportions of 30 g / L and 4.5 g / L, respectively. The mixture was ultrasonically dispersed for 120 min, then stirred for 30 min and filtered. Then, under vacuum filtration, treatment solution C was added to the wet filter cake at a ratio of 1 g / 225 mL to the microsphere intermediate. The solvent of the treatment solution was water, containing 15 g / L cobalt sulfate, 20 g / L nickel sulfate, 50 g / L sodium hypophosphite, 60 g / L potassium sodium tartrate, and 40 g / L ammonium sulfate. The pH was adjusted to approximately 9.8 with concentrated ammonia. The reaction was carried out at 70℃. The filtrate was repeatedly added to the filter cake and the reaction was repeated for 8 rounds. The filter cake was then removed, dried, and the composite foam intermediate was obtained.

[0120] 4) Preparation of composite foam: The composite foam intermediate obtained in step 3) is heat-treated in a reducing atmosphere (volume ratio of hydrogen to argon 1:19) at a temperature of 450°C for 9 hours to obtain the target product composite foam.

[0121] The apparent density of the composite foam obtained in this embodiment is 0.51 g / cm³. 3 The porosity is 88.6% and the open porosity is 53.6%; the mass fractions of glass, metal, and reinforcing filler are 40.8%, 53.1%, and 6.1%, respectively.

[0122] The composite foam has an electromagnetic shielding effectiveness of 63-74 dB and a compressive strength of 3050 kPa.

[0123] Example 8

[0124] The preparation of composite foam specifically includes the following steps:

[0125] 1) Preparation of microsphere intermediates and modification of reinforcing fillers: 30g of glass hollow microspheres (density 0.39g / cm³) were prepared. 3The following were dispersed in 600 ml of solution A: silane coupling agent KH550 15 g / L, solvent was a 1:2 volume mixture of anhydrous ethanol and distilled water; then dispersed in 600 ml of solution B: palladium chloride 0.007 mol / L, solvent was a solution prepared by water and concentrated hydrochloric acid at a volume ratio of 100:1. The mixture was stirred at 50 °C for 50 min, filtered, dried at 50 °C, and the agglomerated particles were removed by sieving to obtain microsphere intermediates.

[0126] 2) The reinforcing filler (carbon nanotubes) was added to solutions A and B at amounts of 20 g / L and 30 g / L respectively, under the same reaction conditions as the microsphere intermediate preparation process in step 1), to obtain the modified reinforcing filler;

[0127] 3) Preparation of composite foam intermediate: The microsphere intermediates obtained in steps 1) and 2) and the reinforcing filler were added to water in proportions of 25 g / L and 2.5 g / L, respectively. The mixture was ultrasonically dispersed for 100 min, then stirred for 40 min and filtered. Then, under vacuum filtration, treatment solution C was added to the wet filter cake at a ratio of 1 g / 155 mL to the microsphere intermediate. The solvent of the treatment solution was water, containing 40 g / L nickel sulfate, 60 g / L sodium hypophosphite, 60 g / L potassium sodium tartrate, and 30 g / L ammonium sulfate. The pH was adjusted to approximately 9.5 with concentrated ammonia. The reaction was carried out at 75℃. The filtrate was repeatedly added to the filter cake and the reaction was repeated 7 times. The filter cake was then removed, dried, and the composite foam intermediate was obtained.

[0128] 4) Preparation of composite foam: The composite foam intermediate obtained in step 3) is heat-treated in an inert atmosphere (nitrogen) at a temperature of 550°C for 5 hours to obtain the target product composite foam.

[0129] The apparent density of the composite foam obtained in this embodiment is 0.39 g / cm³. 3 The porosity is 90.6% and the open porosity is 52.1%; the mass fractions of glass, metal, and reinforcing filler are 45.5%, 50%, and 4.5%, respectively.

[0130] The composite foam has an electromagnetic shielding effectiveness of 58-72 dB and a compressive strength of 2863 kPa.

[0131] Comparative Example 1

[0132] The preparation of the composite foam material follows the same scheme as in Example 2, except that no reinforcing filler is added.

[0133] The apparent density of the composite foam obtained in this example is 0.3 g / cm³. 3 Porosity 90.6%; Open porosity 52.1%; Glass and metal mass fractions: 52.6% and 47.4% respectively; Electromagnetic shielding effectiveness 62-73dB; Compressive strength 1203kPa.

[0134] 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 foam, characterized in that, The composite foam structure includes: a metallic material selected from elemental metals or metal alloys; and a plurality of hollow glass microspheres and reinforcing fillers dispersed in the metallic material; wherein each hollow glass microsphere is embedded in the metallic material.

2. The composite foam according to claim 1, characterized in that, The apparent density of the composite foam is 0.1-0.6 g / cm³. 3 The porosity is 70-93%, and the open porosity is 45-55%.

3. The composite foam according to claim 1, characterized in that, The composite foam comprises, by weight percentage: 25-55% hollow glass microspheres, 20-60% metallic materials, and 4-35% reinforcing fillers.

4. The composite foam according to claim 1, characterized in that, The elemental metal is selected from one or more of cobalt, copper, and nickel; the metal alloy is selected from alloys formed from two or three of cobalt, copper, and nickel.

5. The composite foam according to claim 1, characterized in that, The reinforcing filler is selected from one or more of the following: silver nanowires, silver nanosheets, a mixture of silver nanosheets and copper-plated carbon nanotubes in a mass ratio of 1:1, copper-plated carbon nanotubes, and carbon nanotubes.

6. The method for preparing composite foam according to any one of claims 1-5, characterized in that, The process includes the following steps: surface treating the glass hollow microspheres and the reinforcing filler respectively; mixing the surface-treated glass hollow microspheres and the surface-treated reinforcing filler to obtain a mixture; performing metal deposition treatment on the mixture to obtain a composite foam intermediate; and heat treating the composite foam intermediate to obtain the composite foam.

7. The preparation method according to claim 6, characterized in that, A method for surface treatment of hollow glass microspheres includes the following steps: dispersing the hollow glass microspheres first in a silane coupling agent solution, then dispersing them in a noble metal salt solution and stirring to react, filtering, and drying to obtain surface-treated hollow glass microspheres; dispersing the reinforcing filler first in a silane coupling agent solution, then dispersing them in a noble metal salt solution and stirring to react, filtering, and drying to obtain surface-treated reinforcing filler; preferably, the solvent in the silane coupling agent solution is water and / or anhydrous ethanol; preferably, the solvent in the silane coupling agent solution is a mixture of anhydrous ethanol and water at a volume ratio of 2:1 to 1:2; preferably, the concentration of the silane coupling agent in the silane coupling agent solution is 10-20 g / L; preferably, The concentration of the noble metal salt in the noble metal salt solution is 0.002-0.2 mol / L; preferably, the solute in the noble metal salt solution is a mixture of water and concentrated sulfuric acid at a volume ratio of 100:1; preferably, the temperature of the stirring reaction is 20-60℃ and the time is 20-60 min; preferably, the addition ratio of the glass hollow microspheres to the silane coupling agent solution is 1 g:(10-40) mL, and the addition ratio of the glass hollow microspheres to the noble metal salt solution is 1 g:(10-70) mL; preferably, the addition ratio of the reinforcing filler to the silane coupling agent solution is (20-140) g / L, and the addition ratio of the reinforcing filler to the noble metal salt solution is (30-150) g / L.

8. The preparation method according to claim 6, characterized in that, The method for preparing the composite foam intermediate includes the following steps: dispersing the mixture in water, mixing it evenly, and then filtering it to obtain a filter cake; while under filtration, adding the aqueous solution containing the metal ion source salt to the filter cake to react, adding the filtered filtrate back to the filter cake, repeating the filtration 1-8 times, removing the filter cake, drying it, and obtaining the hollow microsphere welded structure intermediate; preferably, the aqueous solution containing the metal ion source salt contains 10-80 g / L of metal ion source salt, 20-100 g / L of stabilizer, 20-100 g / L of reducing agent, and pH adjuster, and the amount of pH adjuster added is such that the pH of the aqueous solution of the metal ion source salt is 8.5-11; preferably, the reaction temperature is 10-80℃; preferably, the ratio of the surface-treated glass hollow microspheres to the aqueous solution containing the metal ion source salt is 1 g:(50-250) mL.

9. The preparation method according to claim 6, characterized in that, The heat treatment method includes the following steps: heat treatment is carried out in a reducing atmosphere or an inert atmosphere at a temperature of 300-600℃ for 1-12 hours.

10. The application of the composite foam as described in any one of claims 1-5 in microwave shielding.

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