Method for in-situ synthesis of carbon nanotube / metal-based high-temperature-resistant wave-absorbing material and application thereof

Abstract

The application discloses a method for in-situ synthesis of carbon nanotube / metal-based high-temperature-resistant wave-absorbing material and application, and the method comprises the following steps: S1, uniformly dispersing powder or fiber of metal material in carbon source solution, wherein the metal material is metal or metal oxide; S2, filtering or depositing the dispersion liquid to obtain a solid, and drying the solid to obtain a composite raw material; S3, pyrolyzing the composite raw material at 600-1400 DEG C under inert condition; and S4, washing and redispersing the pyrolysis product with acid or alkali, and depositing and drying the product to obtain a product. The in-situ synthesis method can significantly enhance the binding force between metal and carbon nanotubes, can be combined with other materials to form a coating for preparing a coating, can form a film or a textile by itself, can resist high temperature of 200-300 DEG C for a long time, has a wide wave-absorbing frequency band, high acid and alkali corrosion resistance, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials technology, specifically to a method and application for in-situ synthesis of carbon nanotube / metal-based high-temperature resistant microwave absorbing materials. Background Technology

[0002] Electromagnetic wave technology has immense application value in various fields, but the accompanying threat of electromagnetic pollution is also increasing. The industrial sector has increasingly higher requirements for electromagnetic wave absorption or shielding materials, especially in applications such as stealth, electromagnetic shielding, or anechoic chambers. Carbon nanotubes (CNTs) possess advantages such as high dielectric loss, high thermodynamic stability, and low density, making them a promising emerging microwave absorbing material. Metal or alloy powders and ferrites are already widely used as metal-based microwave absorbing materials. Common methods both domestically and internationally involve preparing carbon nanotube / nano-metal-based composite microwave absorbers through chemical plating modification and hybridization with ferromagnetic materials, showing superior prospects compared to single-component carbon nanotubes. However, these methods suffer from drawbacks such as insufficient direct bonding between components, leading to inadequate protection of the nano-metal; furthermore, the high preparation cost hinders industrial-scale promotion.

[0003] To address the above issues, we propose an in-situ synthesis method that can prepare carbon nanotube / metal or metal oxide composite materials on a large scale. Summary of the Invention

[0004] This invention provides a method for preparing and applying in-situ synthesized carbon nanotube / metal-based high-temperature resistant microwave absorbing materials, overcoming the defects in existing technologies such as poor material bonding leading to insufficient protection of nano-metals and affecting material performance.

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

[0006] A method for in-situ synthesis of carbon nanotube / metal-based high-temperature resistant microwave absorbing materials includes the following steps:

[0007] S1. The powder or fiber of a metallic material is uniformly dispersed in a carbon source solution, wherein the metallic material is a metal or a metal oxide;

[0008] S2. After filtering or settling the dispersion, a solid is obtained, which is then dried to obtain the composite raw material;

[0009] S3. Under inert conditions, the composite raw materials are pyrolyzed at 600-1400℃;

[0010] S4. The pyrolysis product is washed with acid or alkali solution and redispersed, and the precipitate is dried to obtain the product.

[0011] Furthermore, the metal is selected from one metal chosen from Fe, Co, Ni, Mn, Cu, Ag, and Zn, or a composite metal chosen from two of them; the metal oxide is selected from at least one oxide chosen from Fe, Co, Ni, Mn, Cu, Ag, and Zn.

[0012] Furthermore, the powder or fiber is in the micron to nanometer range.

[0013] Furthermore, the carbon source is cellulose or synthetic fiber.

[0014] Furthermore, in step S1, a surfactant or dispersant is used to disperse the metal material in the carbon source solution.

[0015] Furthermore, in step S1, the mass ratio of metal element to carbon element is (0.01-1):1.

[0016] Furthermore, in step S4, a sulfur-containing polymer is added before drying.

[0017] Furthermore, the product obtained in step S4 is redispersed and steps S2 to S4 are repeated to obtain the product of multiple reactions.

[0018] This invention also proposes the application of the above-described in-situ synthesis method in the preparation of microwave absorbing materials. Specifically, the microwave absorbing material is used alone or in combination with other ingredients to prepare coatings or textiles; the ingredients include silicon dioxide, glass powder, dispersant, anti-settling agent, and organosilicon. The resulting coating or film can withstand high temperatures of 200-300℃ for a long time, and has a wide microwave absorption frequency band and high resistance to acid and alkali corrosion.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The in-situ synthesis method provided by the present invention disperses metal-based powder in a carbon source solution and then pyrolyzes it at high temperature to form a carbon nanotube / metal-based high-temperature resistant microwave absorbing material. The preparation method is simple, convenient and low in cost, and the metal-based and carbon nanotubes in the obtained microwave absorbing material have strong bonding force, avoiding the defect of insufficient bonding force affecting microwave absorption performance.

[0021] 2. The microwave absorbing material obtained by the in-situ synthesis method provided by the present invention can be used alone or in combination with other ingredients to prepare coatings or textiles. It can withstand high temperatures of 200-300℃ for a long time, and has a wide microwave absorption frequency band and high resistance to acid and alkali corrosion. Attached Figure Description

[0022] Figure 1 This is a TEM image of the carbon nanotube / metal-based high-temperature absorbing material obtained in Example 1 of the present invention.

[0023] Figure 2This is a TEM image of the carbon nanotube / metal-based high-temperature absorbing material obtained in Example 2 of the present invention.

[0024] Figure 3 This is a TEM image of the carbon nanotube / metal-based high-temperature absorbing material obtained in Example 3 of the present invention.

[0025] Figure 4 This is a schematic diagram showing the electromagnetic wave loss as a function of frequency before and after treatment with concentrated sulfuric acid for the carbon nanotube / metal-based microwave absorbing material obtained in Example 1 of the present invention.

[0026] Figure 5 This is a schematic diagram showing the electromagnetic wave loss as a function of frequency before and after treatment with concentrated sulfuric acid for the carbon nanotube / metal-based microwave absorbing material obtained in Example 2 of the present invention.

[0027] Figure 6 This is a schematic diagram showing the electromagnetic wave loss of the microwave absorbing material obtained in the comparative example of the present invention before and after treatment with concentrated sulfuric acid, as a function of frequency. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0030] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "joining," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] In embodiments of the present invention, a method for in-situ synthesis of carbon nanotube / metal-based high-temperature resistant microwave absorbing materials is provided, comprising the following steps:

[0032] S1. The powder or fiber of a metallic material is uniformly dispersed in a carbon source solution, wherein the metallic material is a metal or a metal oxide;

[0033] S2. After filtering or settling the dispersion, a solid is obtained, which is then dried to obtain the composite raw material;

[0034] S3. Under inert conditions, the composite raw materials are pyrolyzed at 600-1400℃;

[0035] S4. The pyrolysis product is washed with acid or alkali solution and redispersed, and the precipitate is dried to obtain the product.

[0036] The metal is selected from one of the elements Fe, Co, Ni, Mn, Cu, Ag, and Zn, or a composite metal selected from two of them; the metal oxide is selected from at least one of the oxides of Fe, Co, Ni, Mn, Cu, Ag, and Zn.

[0037] The powder or fiber is in the micron to nanometer range; the carbon source is cellulose or synthetic fiber.

[0038] In a preferred embodiment, in step S1, a surfactant or dispersant is used to disperse the metal material in a carbon source solution, such as polypyrrolidone (PVP), sodium dodecylbenzenesulfonate (SDBS), etc.; dispersion can also be carried out by methods such as ultrasound, shear stirring, etc.

[0039] In a preferred embodiment, the mass ratio of metal element to carbon element in step S1 is (0.01-1):1, forming a metal nanotube wire with metal matrix loaded on carbon nanotubes. The amount of metal element added can be adjusted according to cost or required performance.

[0040] In a preferred embodiment, heteroatoms can be introduced in step S3 before pyrolysis and in step S4 before drying to improve the performance of the microwave absorbing material in other aspects. For example, sulfur-containing polymers can be introduced in step S4 before drying to increase the overall performance after coating or film formation.

[0041] In a preferred embodiment, the product obtained in step S4 is redispersed and steps S2 to S4 are repeated to obtain products from multiple reactions, which can increase the loading rate of the metal matrix and obtain a microwave absorbing material with better performance.

[0042] In the microwave absorbing material preparation method provided in the above embodiments, the carbon source forms a graphite-like structure during high-temperature pyrolysis. Simultaneously, the surface of the metal material possesses inherent ionization defects or partial charges, which can directly serve as reaction centers. During continued heating, the reaction centers on the metal surface strongly bond with the carbon material of the carbon-like graphite through coordination and other mechanisms, inducing the sheet-like graphite structure to twist in situ into a tubular structure, thus becoming carbon nanotubes. The metal's reaction centers and surrounding areas are protected by the carbon material, resisting corrosion; the metal reaction centers, being inherently reactive, can form metal-C bonds under high temperatures, resulting in a strong bond.

[0043] When metal oxides are heated in the presence of carbon, they can be reduced to metals. The metal surface contains active sites that can catalyze the curling of carbon structures into nanotubes. These active metal sites strongly bind to the carbon material through coordination or metal-C bonds. Furthermore, as the carbon material curls up, it protects the metal sites and surrounding atoms, thus making this portion of the metal resistant to corrosion.

[0044] Example 1

[0045] (1) A hydrosol was obtained by dissolving sodium carboxymethyl cellulose (CMC) in water.

[0046] (2) FeNi alloy short fibers with a length of 20 μm and a diameter of 1 μm were dispersed in CMC hydrosol with the aid of polypyrrolidone (PVP) dispersant. The mass ratio of CMC:FeNi:PVP was 1:0.1:0.01, and the CMC concentration was 100 g / L. After stirring vigorously for 1 hour, the precipitate was collected by centrifugation, washed with water and methanol, and then air-dried.

[0047] (3) Pyrolysis at 1300℃ for 1 hour under nitrogen protection.

[0048] (4) Take out the pyrolysis black solid, wash and stir with 1 mol / L dilute nitric acid, keep warm at 50°C for half an hour, centrifuge, wash with water and methanol, and dry to obtain the product.

[0049] The product obtained in step (4) was tested by transmission electron microscopy, and the TEM image is shown below. Figure 1 As shown, distinct carbon nanotubes (light-colored tubular) and metal nanotubes (dark-colored tubular) were observed.

[0050] Example 2

[0051] (1) A hydrosol is obtained by dissolving water-soluble wool fibers in water.

[0052] (2) Fe3O4 nanoparticles with a diameter of 20 nm were directly dispersed in the hydrosol. The mass ratio of wool fiber to Fe3O4 was 1:0.1, and the wool fiber concentration was 100 g / L. The mixture was stirred vigorously for 1 hour, centrifuged to collect the precipitate, washed with water and methanol, and then air-dried.

[0053] (3) Pyrolysis at 600℃ for 1 hour under nitrogen protection.

[0054] (4) Take out the pyrolysis black solid, wash and stir with 1 mol / L dilute nitric acid, keep warm at 50°C for half an hour, centrifuge, wash with water and methanol, and dry to obtain the product.

[0055] The product obtained in step (4) was tested by transmission electron microscopy, and the TEM image is shown below. Figure 2 As shown, the TEM image reveals distinct carbon nanotubes (light-colored tubular shapes) and metallic nanoparticles (dark-colored particles).

[0056] Example 3

[0057] (1) A hydrosol is obtained by dissolving water-soluble wool fibers in water.

[0058] (2) Co2O3 micron particles with a diameter of 20 μm were directly dispersed in the hydrosol. The mass ratio of wool fiber to Co2O3 was 1:0.5, and the wool fiber concentration was 100 g / L. The mixture was stirred vigorously for 1 hour, centrifuged to collect the precipitate, washed with water and methanol, and then air-dried.

[0059] (3) Pyrolysis at 600℃ for 1 hour under nitrogen protection.

[0060] (4) Take out the pyrolysis black solid, wash and stir with 1 mol / L dilute nitric acid, keep warm at 50°C for half an hour, centrifuge, wash with water and methanol, and dry to obtain the product.

[0061] The product obtained in step (4) was tested by transmission electron microscopy, and the TEM image is shown below. Figure 3 As shown, the TEM image also revealed carbon nanotubes (light-colored tubular shapes) and metallic nanoparticles (dark-colored particles).

[0062] Comparative Example

[0063] The pyrolysis step (3) is omitted, and the other steps are the same as in Example 1.

[0064] Test experiment on the effect of hot acid immersion on microwave absorbing materials

[0065] The microwave absorbing materials obtained in Examples 1-3 and the comparative example were subjected to acid treatment by immersing them in concentrated sulfuric acid at 60°C for 1 hour. The electromagnetic wave loss before and after treatment was measured as a function of frequency. The test results of Examples 1-2 are as follows: Figure 4-5 As shown, the test results of the comparative example are as follows: Figure 6 As shown.

[0066] The results of the test in Example 3 showed that the electromagnetic wave loss was considerable after hot acid immersion treatment, combined with Figure 4-5 The changes in the curves demonstrate that the electromagnetic wave loss of the microwave absorbing materials prepared in Examples 1-3 is minimal before and after hot acid treatment, proving that the samples are very stable.

[0067] In the comparative example, Figure 6 The results showed a significant difference in electromagnetic wave loss after hot acid immersion treatment. The reason is that when carbon nanotubes are directly mixed with metal nanomaterials without the formation of metal-C bonds, acid washing is used. The metal nanomaterials are very active and will be completely washed away, leaving only carbon nanotubes.

[0068] Furthermore, the above-mentioned experimental results on the effect of hot acid immersion on microwave absorbing materials Figure 4-5 It is easy to see that the absorbing materials prepared by the methods described in Examples 1-2 have a wide absorption frequency band. The hot acid immersion experiment can be considered an accelerated degradation experiment. The high temperature test results of the coating prepared by the absorbing materials in Examples 1-3 show that it can withstand high temperatures of 300°C for a long time without affecting the shedding of the metal substrate, and has the advantage of stable absorption performance under extreme conditions.

[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for in-situ synthesis of carbon nanotube / metal-based high-temperature resistant microwave absorbing materials, characterized in that, Includes the following steps: S1. The powder or fiber of a metallic material is uniformly dispersed in a carbon source solution, wherein the metallic material is a metal or a metal oxide; S2. After filtering or settling the dispersion, a solid is obtained, which is then dried to obtain the composite raw material; S3. Under inert conditions, the composite raw materials are pyrolyzed at 600-1400℃; S4. The pyrolysis product is washed with acid or alkali solution and redispersed, and the precipitate is dried to obtain the product.

2. The method according to claim 1, characterized in that, The metal is selected from one of the elements Fe, Co, Ni, Mn, Cu, Ag, and Zn, or a composite metal selected from two of them; the metal oxide is selected from at least one of the oxides of Fe, Co, Ni, Mn, Cu, Ag, and Zn.

3. The method according to claim 1, characterized in that, The powder or fiber is in the micron to nanometer range.

4. The method according to claim 1, characterized in that, The carbon source is cellulose or synthetic fiber.

5. The method according to claim 1, characterized in that, In step S1, a surfactant or dispersant is used to disperse the metal material in the carbon source solution.

6. The method according to claim 1, characterized in that, In step S1, the mass ratio of metal element to carbon element is (0.01-1):

1.

7. The method according to claim 1, characterized in that, In step S4, a sulfur-containing polymer is added before drying.

8. The method according to claim 1, characterized in that, The product obtained in step S4 is redispersed, and steps S2 to S4 are repeated to obtain the product of multiple reactions.

9. The application of the method according to any one of claims 1-8 in the preparation of microwave absorbing materials.

10. The application according to claim 9, characterized in that, The microwave absorbing material is used alone or in combination with other ingredients to prepare coatings or textiles; the other ingredients include silicon dioxide, glass powder, dispersant, anti-settling agent, and organosilicon.

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