A carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance, preparation method and application thereof

Abstract

The present invention discloses a carbon dot carbon nanotube composite film with high conductivity and high electromagnetic shielding performance, a preparation method and application, and belongs to the technical field of electromagnetic shielding materials. The present invention mixes sodium carboxymethyl cellulose and sodium lignin sulfonate and sinters them to obtain a carbon dot solution; the carbon dot solution and the carbon nanotube dispersion are mixed evenly, and vacuum filtered after ultrasonic treatment. The obtained film is washed with acetone several times and then dried to obtain a carbon dot carbon nanotube composite film. Experiments have shown that the carbon dot carbon nanotube electromagnetic shielding material prepared by this method has excellent mechanical properties, electrical conductivity and electromagnetic shielding effectiveness.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic shielding materials, and in particular relates to a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance, a preparation method and an application thereof. Background Art

[0002] The rapid development of electronic information technology has brought convenience to life, but also caused the problem of electromagnetic wave pollution. In recent years, conductive polymer composites have shown obvious advantages due to their flexibility and light weight, and have great application potential in the field of electromagnetic interference shielding. However, the mechanical properties and conductivity of traditional conductive polymer composites are relatively weak, which limits their development. Since their discovery, carbon nanotubes have good application prospects in the fields of composite materials and conductive materials due to their excellent mechanical properties and conductivity. However, carbon nanotubes (CNTs) are easy to agglomerate and have poor dispersion, which limits their application in various aspects.

[0003] Therefore, how to further improve the conductivity, mechanical properties and electromagnetic shielding performance of the material has become a difficult problem in existing technology. Summary of the invention

[0004] In view of the above technical problems, the present invention proposes a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance, a preparation method and application thereof.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance comprises the following steps:

[0007] Mixing sodium carboxymethyl cellulose and sodium lignin sulfonate with water and firing the mixture to obtain a carbon dot solution;

[0008] Ultrasonic mixing the carbon dot solution and the carbon nanotube solution to obtain a mixed solution;

[0009] The mixed solution is vacuum filtered, and the obtained film is washed with acetone and dried to obtain a carbon dot-carbon nanotube composite film.

[0010] Furthermore, the mass ratio of the sodium carboxymethyl cellulose to the sodium lignin sulfonate is 1:0.5.

[0011] Furthermore, the mixed firing refers to reacting at 180° C. for 8 hours.

[0012] Furthermore, the concentration of the carbon dot solution is 10 mg / mL.

[0013] Furthermore, the mass ratio of the carbon dot solution to the carbon nanotube solution is 1:0.43, and the concentration of the carbon nanotube solution is 5 mg / mL.

[0014] Furthermore, the ultrasonic treatment time is 30 minutes.

[0015] Furthermore, the drying refers to drying at 80° C. for 8 hours.

[0016] The present invention also provides a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance, which is prepared by the above preparation method.

[0017] The present invention also provides an application of the carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance as an electromagnetic shielding material.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects:

[0019] The present invention mixes sodium carboxymethyl cellulose and sodium lignin sulfonate and sintering them to obtain a carbon dot solution; the carbon dot solution and the carbon nanotube dispersion are mixed evenly, and after ultrasonic treatment, vacuum filtration is performed, and the obtained film is washed with acetone for several times and then dried to obtain a carbon dot carbon nanotube composite film. The mechanical properties of the film are greatly improved, which is attributed to the large-area graphite π conjugated structure. When the lignin sulfonate is combined with the CMC chain and carbonized, the π-π bridge between the carbon dot and the CNT greatly limits the slippage of the CNT during the stretching process and inhibits the expansion of the crack. At the same time, the carbonized lignin sulfonate chain has an effect on plastic deformation, thereby greatly improving the mechanical properties of the film. Experiments have proved that the carbon dot carbon nanotube electromagnetic shielding material prepared by the method has excellent mechanical properties, electrical conductivity and electromagnetic shielding effectiveness. DETAILED DESCRIPTION

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0022] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0023] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0024] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0025] A method for preparing a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance comprises the following steps:

[0026] (1) mixing sodium carboxymethyl cellulose and sodium lignin sulfonate with water, and mixing and firing them in a pressure bottle to obtain a carbon dot solution;

[0027] (2) ultrasonically mixing the carbon dot solution and the carbon nanotube solution to obtain a mixed solution;

[0028] (3) The mixed solution is vacuum filtered, and the obtained film is washed with acetone and dried to obtain a carbon dot-carbon nanotube composite film.

[0029] In the following preferred embodiment of the present invention, step (1), the mass ratio of sodium carboxymethyl cellulose to sodium lignin sulfonate is 1:0.5. The mixed firing refers to reacting at 180° C. for 8 hours. The concentration of the obtained carbon dot solution is 10 mg / mL.

[0030] In step (2) of the following preferred embodiment of the present invention, the mass ratio of the carbon dot solution to the carbon nanotube solution is 1:0.43, the concentration of the carbon nanotube solution is 5 mg / mL, and the ultrasonic treatment time is 30 min.

[0031] In step (3) of the following preferred embodiment of the present invention, the drying refers to drying at 80° C. for 8 hours.

[0032] The above preparation method can be used to prepare a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance.

[0033] The carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance can be applied to electromagnetic shielding materials.

[0034] The raw materials used in the present invention are all purchased from the market.

[0035] The technical solution of the present invention is further illustrated by the following embodiments.

[0036] Example 1

[0037] (1) 0.2 g sodium carboxymethyl cellulose and 0.1 g sodium lignin sulfonate were mixed, 30 mL water was added to dissolve, and the mixture was fired at 180 °C for 8 h in a pressure bottle to obtain a carbon dot solution with a concentration of 10 mg / mL;

[0038] (2) Add 6 mL of 5 mg / mL carbon nanotube solution to 7 mL of 10 mg / mL carbon dot solution, mix, sonicate for 30 min, and vacuum filter to obtain a membrane;

[0039] (3) The obtained film was washed several times with acetone and dried at 80°C for 8 h to obtain a carbon dot-carbon nanotube composite film.

[0040] Comparative Example 1

[0041] (1) Dissolve 0.3 g of sodium carboxymethyl cellulose in 30 mL of water and calcine at 180 °C for 8 h in a pressure bottle to obtain a carbon dot solution with a concentration of 10 mg / mL;

[0042] (2) Add 6 mL of 5 mg / mL carbon nanotube solution to 7 mL of 10 mg / mL carbon dot solution, mix, sonicate for 30 min, and vacuum filter to obtain a membrane;

[0043] (3) The obtained film was washed several times with acetone and dried at 80°C for 8 h to obtain a carbon dot-carbon nanotube composite film.

[0044] Comparative Example 2

[0045] (1) 0.3 g of sodium lignin sulfonate was dissolved in 30 mL of water and calcined at 180 °C for 8 h in a pressure bottle to obtain a carbon dot solution with a concentration of 10 mg / mL;

[0046] (2) Add 6 mL of 5 mg / mL carbon nanotube solution to 7 mL of 10 mg / mL carbon dot solution, mix, sonicate for 30 min, and vacuum filter to obtain a membrane;

[0047] (3) The obtained film was washed several times with acetone and dried at 80°C for 8 h to obtain a carbon dot-carbon nanotube composite film.

[0048] Comparative Example 3

[0049] (1) 0.3 g of sodium lignin sulfonate was dissolved in 30 mL of water and calcined at 180 °C for 8 h in a pressure bottle to obtain a sodium lignin sulfonate carbon dot solution with a concentration of 10 mg / mL;

[0050] (2) 1 mL of 10 mg / mL sodium lignin sulfonate carbon dot solution, 7 mL of 10 mg / mL sodium carboxymethyl cellulose solution, and 6 mL of 5 mg / mL carbon nanotube solution were mixed, ultrasonicated for 30 min, and vacuum filtered to obtain a membrane;

[0051] (3) The obtained film was washed several times with acetone and dried at 80°C for 8 h to obtain a carbon dot-carbon nanotube composite film.

[0052] Comparative Example 4

[0053] (1) 0.2 g sodium carboxymethyl cellulose and 0.1 g sodium lignin sulfonate were mixed, 30 mL water was added to dissolve, and the mixture was fired at 180 °C for 8 h in a pressure bottle to obtain a carbon dot solution with a concentration of 10 mg / mL;

[0054] (2) 6 mL of 5 mg / mL carbon nanotube solution was added to 7 mL of 10 mg / mL carbon dot solution, mixed, ultrasonicated for 30 min, and then poured into a glass mold (10 cm × 10 cm × 3 cm). The solution was stored at room temperature to remove moisture, thereby obtaining a film;

[0055] (3) The obtained film was washed several times with acetone and dried at 80°C for 8 h to obtain a carbon dot-carbon nanotube composite film.

[0056] The performance of the products prepared in Example 1 and Comparative Examples 1-4 was tested. The specific test method was as follows: uniaxial tensile measurement was performed using an electronic universal testing machine (Shenzhen Sun God Technology Co., Ltd., China) at a tensile speed of 100 mm / min. The electromagnetic interference shielding performance of the material depends largely on its conductivity. EMI shielding is mainly determined by the reflective SE (SE R ) and absorption SE(SE A ) and the reflection coefficient (R), absorption coefficient (A) and transmission coefficient (T). Such a prominent EMISE can be explained by Simon's formula:

[0057] SE=50+10lg(σ / f)+1.7t(σ×f) 1 / 2

[0058] Where σ is the electrical conductivity (unit: Scm -1 ), f is the electromagnetic wave frequency (in GHz), and t is the thickness of the EMI shielding material (in cm). According to Simon's formula, t and σ of the shielding material are the determining factors of EMISE at a given frequency.

[0059] Specific shielding effectiveness (SSE) is calculated by dividing SE by composite density (d). Taking into account the effect of thickness (t), the absolute effectiveness (SSEt) of the composite is evaluated using the following formula: -1 ):

[0060]

[0061] The results are shown in Table 1.

[0062] Table 1 Performance test results of electromagnetic shielding materials

[0063]

[0064]

[0065] It can be seen from the performance test data in Table 1 that the electromagnetic shielding materials prepared in Example 1 and Comparative Examples 1-4 have excellent mechanical properties, electrical conductivity and electromagnetic shielding effectiveness. The electromagnetic shielding effectiveness of the electromagnetic shielding material prepared in Example 1 is much higher than that of the electromagnetic shielding materials prepared in Comparative Examples 1-4, and it can be used in application fields with high requirements for electromagnetic shielding. This also shows that after adding the carbon dot solution, the various performances of the prepared electromagnetic shielding material can be further improved.

[0066] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance, characterized in that: The following steps are involved: Mixing sodium carboxymethyl cellulose and sodium lignin sulfonate with water, and mixing and firing them in a pressure bottle to obtain a carbon dot solution; Ultrasonic mixing the carbon dot solution and the carbon nanotube solution to obtain a mixed solution; The mixed solution is vacuum filtered, and the obtained film is washed with acetone and dried to obtain a carbon dot-carbon nanotube composite film.

2. The method for preparing a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance according to claim 1, characterized in that: The mass ratio of the sodium carboxymethyl cellulose to the sodium lignin sulfonate is 1:0.

5.

3. The method for preparing a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance according to claim 1, characterized in that: The mixed firing is carried out at 180° C. for 8 hours.

4. The method for preparing a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance according to claim 1, characterized in that: The concentration of the carbon dot solution is 10 mg / mL.

5. The method for preparing a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance according to claim 1, characterized in that: The mass ratio of the carbon dot solution to the carbon nanotube solution is 1:0.43, and the concentration of the carbon nanotube solution is 5 mg / mL.

6. The method for preparing a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance according to claim 1, characterized in that: The ultrasonic treatment time is 30 min.

7. The method for preparing a carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance according to claim 1, characterized in that: The drying refers to drying at 80° C. for 8 hours.

8. A carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the carbon dot-carbon nanotube composite film with high conductivity and high electromagnetic shielding performance as claimed in claim 8 as an electromagnetic shielding material.

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