Silver nanoparticle enhanced foam carbon electromagnetic shielding composite material and preparation method

Abstract

The application discloses a preparation method of a silver nanoparticle reinforced foam carbon electromagnetic shielding composite material, and specifically comprises the following steps: step 1, preparation of foam carbon; and step 2, preparation of an Ag nanoparticle / foam carbon composite material. The material solves the problems of insufficient conductive performance and weak electromagnetic shielding capacity of the foam carbon composite material in the prior art. The application further discloses the silver nanoparticle reinforced foam carbon electromagnetic shielding composite material.

Description

Technical Field

[0001] This invention belongs to the field of new materials, specifically relating to a silver nanoparticle-reinforced foamed carbon electromagnetic shielding composite material, and also to a method for preparing the silver nanoparticle-reinforced foamed carbon electromagnetic shielding composite material. Background Technology

[0002] Among various forms of carbon materials, such as fibrous, tubular, spherical, sheet-like, and granular, carbon foam possesses a specific porous structure, in which most macropores are interconnected, forming an open-cell structure. Due to this porous structure, they exhibit novel characteristics, such as a large geometrical surface area, which are related to the fundamental properties of carbon materials, such as light weight, high thermal stability, hydrophobic surface properties, and high thermal and electrical conductivity. By controlling its structure from graphite to amorphous and its nanostructure from oriented to non-oriented, its thermal and electrical conductivity can be altered over a relatively wide range. In carbon foam, in addition to controlling the structure and nanostructure within the macroporous carbon walls, its properties can also be controlled through the pore structure. Compared to carbon materials with other morphologies, this structure and nanostructure offer greater tolerance in controlling volumetric properties.

[0003] Foamed carbon is a three-dimensional, lightweight, functional carbon material composed of pores and pore walls, prepared from carbon-rich materials through processes such as foaming, curing, carbonization, and graphitization. Due to its superior properties, such as thermal insulation, shock absorption, and gas filtration, foamed carbon materials have attracted widespread attention. Based on its excellent performance characteristics, it has great potential application value in fields such as thermal insulation materials, high-quality sandwich materials, energy storage electrode materials, electromagnetic shielding materials, and microwave absorbing materials. However, the conductivity and electromagnetic shielding effectiveness of foamed carbon alone cannot meet current requirements; therefore, materials with higher conductivity and electromagnetic shielding effectiveness are needed to meet application requirements. Summary of the Invention

[0004] The first objective of this invention is to provide a silver nanoparticle-reinforced foamed carbon electromagnetic shielding composite material, which solves the problems of insufficient conductivity and weak electromagnetic shielding ability of foamed carbon in the prior art.

[0005] The second objective of this invention is to provide a method for preparing a silver nanoparticle-reinforced carbon foam electromagnetic shielding composite material.

[0006] The first technical solution adopted in this invention is a method for preparing silver nanoparticle-reinforced carbon foam electromagnetic shielding composite material, specifically including the following steps:

[0007] Step 1, Preparation of foamed charcoal;

[0008] Step 2, Preparation of Ag nanoparticle / foamed carbon composite material.

[0009] The invention is further characterized in that,

[0010] Step 1 is implemented in the following steps:

[0011] Melamine foam was placed in a tube furnace and purged with nitrogen for 20-30 minutes for heat treatment. After cooling to room temperature, the sample was removed to obtain foamed carbon. Deionized water and concentrated nitric acid (65%-68% by volume) were mixed in a volume ratio of 7-8:1 to obtain a mixed solution. The heat-treated foamed carbon was placed in the mixed solution and loaded into a reaction vessel. It was then kept at 110-120℃ in a drying oven for 90-120 minutes. After removal, it was washed with deionized water until the aqueous solution was neutral. It was then ultrasonically vibrated in anhydrous ethanol for 5-10 minutes and then dried in a constant temperature drying oven at 60-70℃ for 1-2 days.

[0012] In step 1, the heat treatment process is as follows: heating to 1000℃-1100℃ and holding for 1h-2h; the process of cooling to room temperature is as follows: the first stage is heating to 400℃ and holding for 50min-60min, the second stage is heating to 1000℃-1100℃ and holding for 50min-60min, the heating rate of the first and second stages is 2℃ / min-5℃ / min; then cooling to 200℃ at a cooling rate of 2℃ / min-5℃ / min.

[0013] Step 2 is implemented in the following steps:

[0014] Step 2.1: Weigh AgNO3 and PVP separately and place them in deionized water to obtain a mixed solution. The concentration of AgNO3 in the mixed solution is 0.85 g / L-3.4 g / L, and the concentration of PVP is 100 g / L. Stir to fully dissolve, then sonicate for 10 min-20 min, and then stir for 20 min-30 min to obtain the reaction mother liquor.

[0015] Step 2.2: Place the acidified carbon foam from Step 1 into the reaction mother liquor obtained in Step 2.1, sonicate for 30-40 minutes, then place it in a forced-air drying oven at 200-220℃ for 8-10 hours. Remove the carbon foam, wash it with deionized water until the liquid in the beaker is clear, and then freeze-dry it under vacuum for 40-42 hours to obtain an Ag nanoparticle / carbon foam composite material with a thickness of 1-5 mm. The prepared silver nanoparticles have a purity of up to 99.99% and a size of 90-100 nm. The prepared Ag nanoparticle / carbon foam composite material has an electrical conductivity of up to 234.80 S / m and a porosity of up to 95%.

[0016] In step 2.1, the Mw of PVP is 1000~1300000.

[0017] The second technical solution adopted in this invention is a silver nanoparticle-reinforced foamed carbon electromagnetic shielding composite material, which is prepared by the above-described method.

[0018] The beneficial effects of this invention are:

[0019] This invention provides a method for preparing typical three-dimensional network open-cell foamed carbon via direct carbonization. Then, using a hydrothermal reduction method, spherical silver nanoparticles with uniform morphology and a particle size of 100 nm are readily and quickly prepared, utilizing the weak reducing properties of PVP and its role as a surfactant. These silver nanoparticles possess excellent conductivity and, due to their nanoscale size, exhibit a size effect resulting in high surface energy and good catalytic performance. Finally, the silver nanoparticles are attached to the foamed carbon using a hydrothermal reduction method to prepare a silver nanoparticle / foamed carbon composite material. On one hand, the addition of PVP ensures uniform dispersion of the silver nanoparticles within the foamed carbon matrix; on the other hand, the synergistic optimization between the dielectric loss of the foamed carbon and the conductivity of the silver nanoparticles improves the reflection and absorption losses of the composite system, resulting in a foamed carbon composite material with high electromagnetic shielding effectiveness. This invention addresses the problems of insufficient conductivity and weak electromagnetic shielding capabilities of existing foamed carbon technologies. Attached Figure Description

[0020] Figure 1 The image shows the XRD pattern of the foamed carbon composite material prepared in Example 1.

[0021] Figure 2 The image shows a 1050× magnification SEM image of the Ag nanoparticle / carbon foam composite material prepared in Example 1.

[0022] Figure 3 The image shows a 3500× magnification SEM image of the Ag nanoparticle / carbon foam composite material prepared in Example 1.

[0023] Figure 4 The image shows a 2500× magnification SEM image of the Ag nanoparticle / carbon foam composite material prepared in Example 1. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0025] This invention provides a method for preparing a silver nanoparticle-reinforced carbon foam electromagnetic shielding composite material, specifically including the following steps:

[0026] Step 1, Preparation of foamed charcoal;

[0027] Step 1 is implemented in the following steps:

[0028] Melamine foam was placed in a tube furnace and purged with nitrogen for 20-30 minutes for heat treatment. After cooling to room temperature, the sample was removed to obtain foamed carbon. Deionized water and concentrated nitric acid (65%-68% by volume) were mixed in a volume ratio of 7-8:1 to obtain a mixed solution. The heat-treated foamed carbon was placed in the mixed solution and loaded into a reaction vessel. It was then kept at 110-120℃ in a drying oven for 90-120 minutes. After removal, it was washed with deionized water until the aqueous solution was neutral. It was then ultrasonically vibrated in anhydrous ethanol for 5-10 minutes and then dried in a constant temperature drying oven at 60-70℃ for 1-2 days.

[0029] In step 1, the heat treatment process is as follows: heating to 1000℃-1100℃ and holding for 1h-2h; the process of cooling to room temperature is as follows: the first stage is heating to 400℃ and holding for 50min-60min, the second stage is heating to 1000℃-1100℃ and holding for 50min-60min, the heating rate of the first and second stages is 2℃ / min-5℃ / min; then cooling to 200℃ at a cooling rate of 2℃ / min-5℃ / min.

[0030] Step 2, Preparation of Ag nanoparticle / foamed carbon composite material.

[0031] Step 2 is implemented in the following steps:

[0032] Step 2.1: Weigh AgNO3 and PVP (Mw = 1000-1300000) separately and place them in deionized water to obtain a mixed solution. The concentration of AgNO3 in the mixed solution is 0.85 g / L-3.4 g / L, and the concentration of PVP is 100 g / L. Stir to fully dissolve, then sonicate for 10-20 min, and stir for another 20-30 min to obtain the reaction mother liquor. In Step 2.1, the Mw of PVP is 1000-1300000.

[0033] Step 2.2: Place the acidified foamed carbon from Step 1 into the reaction mother liquor obtained in Step 2.1, sonicate for 30-40 minutes, then place it in a forced-air drying oven at 200-220℃ for 8-10 hours. Remove the foamed carbon, wash it with deionized water until the liquid in the beaker is clear, and then freeze-dry it under vacuum for 40-42 hours to obtain an Ag nanoparticle / foamed carbon composite material with a thickness of 1-5 mm.

[0034] The present invention also provides a silver nanoparticle-reinforced carbon foam electromagnetic shielding composite material, which is prepared by the above method.

[0035] Example 1

[0036] The preparation method of silver nanoparticle-reinforced carbon foam electromagnetic shielding composite material specifically includes the following steps:

[0037] Step 1, Preparation of foamed charcoal;

[0038] Step 1 is implemented in the following steps:

[0039] Melamine foam was placed in a tube furnace and purged with nitrogen for 20 minutes for heat treatment. After cooling to room temperature, the sample was removed to obtain foamed carbon. Deionized water and 65% concentrated nitric acid were mixed in a volume ratio of 7:1 to obtain a mixed solution. The heat-treated foamed carbon was placed in the mixed solution and loaded into a reaction vessel. It was kept at 110°C for 90 minutes in a drying oven. After removal, it was washed with deionized water until the aqueous solution was neutral. It was then ultrasonically vibrated in anhydrous ethanol for 5-10 minutes and placed in a constant temperature drying oven at 60°C for 1 day.

[0040] In step 1, the heat treatment process is as follows: heat to 1000℃ and hold for 1 hour; the process of heat treatment to cooling to room temperature is as follows: in the first stage, heat up to 400℃ and hold for 50 minutes; in the second stage, heat up to 1000℃ and hold for 50 minutes; the heating rate in the first and second stages is 2℃ / min; then cool down to 200℃ at a cooling rate of 2℃ / min.

[0041] Step 2, Preparation of Ag nanoparticle / foamed carbon composite material.

[0042] Step 2 is implemented in the following steps:

[0043] Step 2.1: Weigh AgNO3 and PVP separately and place them in deionized water to obtain a mixed solution. The concentration of AgNO3 in the mixed solution is 0.85 g / L and the concentration of PVP is 100 g / L. Stir to fully dissolve, then sonicate for 10 min, and then stir for 20 min to obtain the reaction mother liquor. In Step 2.1, the Mw of PVP is 1000-130000.

[0044] Step 2.2: Place the acidified foamed carbon from Step 1 into the reaction mother liquor obtained in Step 2.1, sonicate for 30 min, then place it in a forced-air drying oven at 200℃ for 8 hours. Remove the foamed carbon, wash it with deionized water until the water in the beaker is clear, and freeze-dry it under vacuum for 40 h to obtain an Ag nanoparticle / foamed carbon composite material with a thickness of 1 mm.

[0045] Parameter 1: The electrical conductivity of the foamed carbon prepared in step 1 of Example 1 is 18.48 S / m;

[0046] Parameter 2: The density of the foamed charcoal in step 1 of Example 1 is 0.2 g / cm³.3 .

[0047] Parameter 3: The purity of the silver nanoparticles attached to the Ag nanoparticle / carbon foam composite material prepared in step 2 of Example 1 is ≥99.99%;

[0048] Parameter 4: The size of the silver nanoparticles attached to the Ag nanoparticle / carbon foam composite material prepared in step 2 of Example 1 is 90 nm;

[0049] Parameter 5: The Ag nanoparticle / carbon foam composite material prepared in step 2 of Example 1 has the highest electrical conductivity of 234.80 S / m;

[0050] Parameter 6: The porosity of the Ag nanoparticle / carbon foam composite material prepared in step 2 of Example 1 is 90%;

[0051] Parameter 7: The electromagnetic shielding effectiveness of the Ag nanoparticle / foamed carbon composite material prepared in step 2 of Example 1 is 25.36 dB.

[0052] Figure 1 The XRD pattern of the prepared carbon foam composite material clearly shows the (002) crystal plane of the dispersed graphitized carbon, and four peaks (111), (200), (220) and (311) belonging to Ag in the range of 10 to 80°, indicating that Ag nanoparticles were successfully attached to the carbon foam. Figure 2-4 SEM images of the foamed carbon composite materials prepared by this invention at different magnifications. Figure 2-4 The images clearly show that a large number of particles are attached to the ridges where the foamed carbon connects to the ligaments, and the particles are evenly distributed. This indicates that the foamed carbon has a good adsorption effect on Ag nanoparticles, and the foamed carbon does not affect the crystal growth of Ag nanoparticles.

[0053] Example 2

[0054] The preparation method of silver nanoparticle-reinforced carbon foam electromagnetic shielding composite material specifically includes the following steps:

[0055] Step 1, Preparation of foamed charcoal;

[0056] Step 1 is implemented in the following steps:

[0057] Melamine foam was placed in a tube furnace and purged with nitrogen for 30 minutes for heat treatment. After cooling to room temperature, the sample was removed to obtain foamed carbon. Deionized water and concentrated nitric acid with a volume concentration of 68% were mixed at a volume ratio of 8:1 to obtain a mixed solution. The heat-treated foamed carbon was placed in the mixed solution, loaded into a reaction vessel, and kept at 120°C for 120 minutes in a drying oven. After removal, it was washed with deionized water until the aqueous solution was neutral, and then ultrasonically vibrated in anhydrous ethanol for 10 minutes. Finally, it was placed in a constant temperature drying oven and dried at 70°C for 2 days.

[0058] In step 1, the heat treatment process is as follows: heat to 1100℃ and hold for 2 hours; the process of heat treatment to cooling to room temperature is as follows: in the first stage, heat up to 400℃ and hold for 60 minutes; in the second stage, heat up to 1100℃ and hold for 60 minutes; the heating rate in the first and second stages is 5℃ / min; then the temperature is cooled down to 200℃ at a cooling rate of 5℃ / min.

[0059] Step 2, Preparation of Ag nanoparticle / foamed carbon composite material.

[0060] Step 2 is implemented in the following steps:

[0061] Step 2.1: Weigh AgNO3 and PVP separately and place them in deionized water to obtain a mixed solution. The concentration of AgNO3 in the mixed solution is 3.4 g / L and the concentration of PVP is 100 g / L. Stir to fully dissolve, then sonicate for 20 min, and stir for another 30 min to obtain the reaction mother liquor. In Step 2.1, the Mw of PVP is 1000-130000.

[0062] Step 2.2: Place the acidified foamed carbon from Step 1 into the reaction mother liquor obtained in Step 2.1, sonicate for 40 min, and then place it in a forced-air drying oven at 220℃ for 10 h. Remove the foamed carbon, wash it with deionized water until the water in the beaker is clear, and then freeze-dry it under vacuum for 42 h to obtain an Ag nanoparticle / foamed carbon composite material with a thickness of 5 mm.

[0063] Example 3

[0064] The preparation method of silver nanoparticle-reinforced carbon foam electromagnetic shielding composite material specifically includes the following steps:

[0065] Step 1, Preparation of foamed charcoal;

[0066] Step 1 is implemented in the following steps:

[0067] Melamine foam was placed in a tube furnace and purged with nitrogen for 25 minutes for heat treatment. After cooling to room temperature, the sample was removed to obtain foamed carbon. Deionized water and 66% concentrated nitric acid were mixed at a volume ratio of 7.5:1 to obtain a mixed solution. The heat-treated foamed carbon was placed in the mixed solution and loaded into a reaction vessel. The mixture was kept at 115°C for 100 minutes in a drying oven. After removal, the mixture was washed with deionized water until the aqueous solution was neutral. It was then ultrasonically vibrated in anhydrous ethanol for 8 minutes and dried in a constant temperature drying oven at 65°C for 1.5 days.

[0068] In step 1, the heat treatment process is as follows: heat to 1050℃ and hold for 1.5h; the process of heat treatment to cooling to room temperature is as follows: in the first stage, heat up to 400℃ and hold for 45min; in the second stage, heat up to 1050℃ and hold for 45min; the heating rate in the first and second stages is 3℃ / min; then cool down to 200℃ at a cooling rate of 3℃ / min.

[0069] Step 2, Preparation of Ag nanoparticle / foamed carbon composite material.

[0070] Step 2 is implemented in the following steps:

[0071] Step 2.1: Weigh AgNO3 and PVP separately and place them in deionized water to obtain a mixed solution. The concentration of AgNO3 in the mixed solution is 2.55 g / L and the concentration of PVP is 100 g / L. Stir to fully dissolve, then sonicate for 15 min, and stir for another 15 min to obtain the reaction mother liquor. In Step 2.1, the Mw of PVP is 1000-130000.

[0072] Step 2.2: Place the acidified foamed carbon from Step 1 into the reaction mother liquor obtained in Step 2.1, sonicate for 30-40 minutes, and then place it in a forced-air drying oven at 210℃ for 9 hours. Remove the foamed carbon, wash it with deionized water until the water in the beaker is clear, and then freeze-dry it under vacuum for 41 hours to obtain an Ag nanoparticle / foamed carbon composite material with a thickness of 4 mm.

[0073] Measurements and analyses showed that the porosity of the composite materials was basically consistent, ranging from 90% to 95%. Measurements and analyses also confirmed that silver nanoparticles were successfully loaded onto the carbon foam matrix in all embodiments. The density of the composite materials ranged from 0.4 to 0.6 g / cm³. 3 .

[0074] The electromagnetic parameters of the composite material in the Ku band (12-18 GHz) were measured using a network vector analyzer. The total electromagnetic shielding effectiveness was calculated and the results are shown in Table 1. The conductivity data of the corresponding material is also recorded in Table 1.

[0075] Table 1

[0076] Example 1 25.36 215.60 Example 2 27.89 222.30 Example 3 30.26 234.80 Foamed Charcoal 10 18.48

[0077] The method of the present invention can ensure the uniform dispersion of silver nanoparticles in the carbon foam matrix. On the other hand, it can obtain a carbon foam composite material with high electromagnetic shielding performance through the synergistic optimization of the dielectric loss of carbon foam and the conductivity of silver nanoparticles. As can be seen from Table 1, the material of the present invention has higher electromagnetic shielding performance and significantly improved electrical conductivity compared with carbon foam.

[0078] With improved electromagnetic shielding capabilities, the conductivity of this system can reach up to 215.60-234.80 (S / m). Furthermore, the method for preparing foamed carbon electromagnetic shielding composite materials according to this invention features simple manufacturing processes and good stability. The prepared composite material has a purity of 99.99%, a porosity of 90%-95%, and a density of 0.4-0.6 g / cm³. 3 The electromagnetic shielding effectiveness of composite materials in the Ku band can reach up to 25.36-30.26 dB.

Claims

1. A method for preparing silver nanoparticle-reinforced carbon foam electromagnetic shielding composite material, characterized in that, Specifically, the following steps are included: Step 1, Preparation of foamed charcoal; Step 1 is implemented in the following steps: Melamine foam was placed in a tube furnace and purged with nitrogen for 20-30 minutes for heat treatment. After cooling to room temperature, the sample was removed to obtain foamed carbon. Deionized water and concentrated nitric acid (65%-68% by volume) were mixed at a volume ratio of 7-8:1 to obtain a mixed solution. The heat-treated foamed carbon was placed in the mixed solution and loaded into a reaction vessel. The mixture was kept at 110-120℃ for 90-120 minutes in a drying oven. After removal, it was washed with deionized water until the aqueous solution was neutral. Then, it was ultrasonically vibrated in anhydrous ethanol for 5-10 minutes and placed in a constant temperature drying oven at 60-70℃ for 1-2 days. Step 2, Preparation of Ag nanoparticle / foamed carbon composite material; Step 2 is implemented in the following steps: Step 2.1: Weigh AgNO3 and PVP separately and place them in deionized water to obtain a mixed solution. The concentration of AgNO3 in the mixed solution is 0.85 g / L-3.4 g / L, and the concentration of PVP is 100 g / L. Stir to fully dissolve, then sonicate for 10-20 minutes, and then stir for 20-30 minutes to obtain the reaction mother liquor. In Step 2.1, the Mw of PVP is 1000-1300000. Step 2.2: Place the acidified foamed carbon from Step 1 into the reaction mother liquor obtained in Step 2.1, sonicate for 30-40 minutes, then place it in a forced-air drying oven at 200 ℃-220 ℃ for 8-10 hours. Remove the foamed carbon, wash it with deionized water until the liquid in the beaker is clear, and then freeze-dry it under vacuum for 40-42 hours to obtain an Ag nanoparticle / foamed carbon composite material with a thickness of 1 mm-5 mm. The electromagnetic shielding effectiveness of composite materials in the Ku band can reach up to 25.36-30.26 dB.

2. The preparation method of the silver nanoparticle-reinforced carbon foam electromagnetic shielding composite material according to claim 1, characterized in that, In step 1, the heat treatment process is as follows: heating to 1000℃-1100℃ and holding for 1h-2h; the process of cooling to room temperature is as follows: the first stage is heating to 400℃ and holding for 50min-60min, the second stage is heating to 1000℃-1100℃ and holding for 50min-60min, the heating rate of the first and second stages is 2℃ / min-5℃ / min; then cooling to 200℃ at a cooling rate of 2℃ / min-5℃ / min.

3. A silver nanoparticle-reinforced foamed carbon electromagnetic shielding composite material, characterized in that, It is prepared by the method described in any one of claims 1-2.

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