A method for preparing a reduced graphene oxide film having a low infrared emissivity

Abstract

The application discloses a preparation method of a reduced graphene oxide film with low infrared emissivity, and comprises the following steps: (1) preparing a graphene oxide dispersion liquid containing thioacetamide; (2) vacuum filtering the graphene oxide dispersion liquid containing thioacetamide to obtain a nitrogen and sulfur co-doped graphene oxide film; and (3) air-drying the graphene oxide film and calcining the air-dried graphene oxide film in an inert atmosphere to obtain a reduced graphene oxide film. The reduced graphene oxide film prepared by the method has excellent shielding performance and low infrared emissivity, and the infrared emissivity in the 3-5 mu m wave band can be as low as 0.398.

Description

Technical Field

[0001] This invention relates to a method for preparing a reduced graphene oxide film with low infrared emissivity. Background Technology

[0002] Currently, infrared-guided missiles and infrared detection systems operate primarily in the 3–5 μm and 8–14 μm bands. Infrared radiation from targets in these two bands is a key source of threat and challenge. To improve target survivability, infrared camouflage is necessary. Reducing a target's infrared radiation characteristics generally involves two methods: lowering the target's surface temperature and reducing its surface infrared emissivity. Among these, using low-infrared-emissivity materials is one of the main measures currently employed. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a method for preparing reduced graphene oxide films with low infrared emissivity.

[0004] Technical solution: The method for preparing reduced graphene oxide thin film according to the present invention includes the following steps:

[0005] (1) Prepare a graphene oxide dispersion containing thioacetamide;

[0006] (2) The graphene oxide dispersion containing thioacetamide was vacuum filtered to obtain a nitrogen-sulfur co-doped graphene oxide film. During vacuum-assisted filtration, the film needs to be completely dried to prevent it from falling off the filter paper.

[0007] (3) The graphene oxide film was air-dried and then calcined in an inert atmosphere to obtain a reduced graphene oxide film.

[0008] In step (1), the concentration of thioacetamide in the graphene oxide dispersion is 0.025–0.2 mmol / mL.

[0009] In step (1), the concentration of graphene oxide in the graphene oxide dispersion is 2 mg / mL.

[0010] In step (2), the nitrogen-sulfur co-doped graphene oxide film containing filter paper obtained by vacuum filtration is naturally air-dried for 24 hours. After air-drying, it is soaked in an ethanol aqueous solution (the volume ratio of ethanol to water in the ethanol aqueous solution is 95:5 to 99:1) for 1 minute, and the nitrogen-sulfur co-doped graphene oxide film naturally falls off the filter paper.

[0011] In step (3), the nitrogen-sulfur co-doped graphene oxide film is calcined under an argon atmosphere.

[0012] In step (3), the calcination temperature is 700-750℃, the holding time is 2-2.5h, and the heating rate is 5-5.5℃ / min.

[0013] In step (3), the thickness of the reduced graphene oxide film is 30 μm.

[0014] Graphene oxide films are heat-treated in an argon atmosphere to obtain reduced graphene oxide, which significantly improves the electrical conductivity of the film. At the same time, heteroatoms can effectively increase the defect level of the reduced graphene oxide film, further enhancing its electrical conductivity and thus reducing its infrared emissivity.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The reduced graphene oxide film prepared by the method of the present invention has excellent shielding performance and low infrared emissivity, with an infrared emissivity as low as 0.398 in the 3-5 μm band. Attached Figure Description

[0016] Figure 1 SEM images of the reduced graphene oxide films prepared in Examples 1-4;

[0017] Figure 2 X-ray diffraction patterns of the reduced graphene oxide films prepared in Examples 1-4;

[0018] Figure 3 The Raman spectra of the reduced graphene oxide films prepared in Examples 1-4 are shown below.

[0019] Figure 4 The XPS spectra of the reduced graphene oxide films prepared in Examples 1-4 are shown below.

[0020] Figure 5 The conductivity data are for the reduced graphene oxide films prepared in Examples 1-4.

[0021] Figure 6 The electromagnetic shielding performance of the reduced graphene oxide films prepared in Examples 1-4;

[0022] Figure 7 The infrared emissivity is that of the reduced graphene oxide films prepared in Examples 1-4. Detailed Implementation

[0023] Example 1

[0024] The present invention provides a method for preparing a low infrared emissivity reduced graphene oxide film, comprising the following steps:

[0025] (1) Add 0.5 mmol of solid thioacetamide to 20 mL of graphene oxide dispersion and stir for 10 min until completely dissolved; the concentration of graphene oxide in the graphene oxide dispersion is 2 mg / mL.

[0026] (2) Vacuum-assisted filtration of graphene oxide dispersion containing thioacetamide (first check whether the connection between the Buchner funnel and the filtration flask is tight and whether the connection port of the vacuum pump is leaking; then, place the filter membrane on the filtration flask and add deionized water to wet the filter membrane, slightly open the vacuum valve to make the filter paper and the funnel tightly connected; turn on the vacuum pump switch, pour in the graphene oxide dispersion containing thioacetamide, and start filtration), and let the nitrogen-sulfur co-doped graphene oxide film containing the filter paper naturally dry for 24 hours. After air drying, soak it in an ethanol aqueous solution (the volume ratio of ethanol to water in the ethanol aqueous solution is 99:1) for 1 minute. The nitrogen-sulfur co-doped graphene oxide film will naturally fall off the filter paper to obtain the nitrogen-sulfur co-doped graphene oxide film.

[0027] (3) The obtained nitrogen-sulfur co-doped graphene oxide film was placed in a tube furnace for calcination; the calcination temperature was 700℃, the holding time was 2h, and the heating rate was 5℃ / min to obtain reduced graphene oxide film-1.

[0028] Example 2

[0029] The preparation method of Example 2 is exactly the same as that of Example 1, except that the amount of thioacetamide added in step (1) is 1.0 mmol, and reduced graphene oxide film-2 is prepared.

[0030] Example 3

[0031] The preparation method of Example 3 is exactly the same as that of Example 1, except that the amount of thioacetamide added in step (1) is 2.0 mmol, and the reduced graphene oxide film-3 is prepared.

[0032] Example 4

[0033] The preparation method of Example 4 is exactly the same as that of Example 1, except that the amount of thioacetamide added in step (1) is 4.0 mmol, and the reduced graphene oxide film-4 is prepared.

[0034] Figure 1 These are SEM images of the reduced graphene oxide films prepared in Examples 1-4 at a depth of 40 μm. Figure 1 It can be seen that as the content of thioacetamide increases, the reduced graphene oxide sheets begin to detach from the surface. This is due to the reduction of oxygen-containing functional groups and the lattice distortion caused by diatomic doping. Figure 1It can also be seen that the surface of the reduced graphene oxide sheet is rough because the film loses oxygen-containing functional groups during the calcination process, resulting in a curved and rough film surface.

[0035] Figure 2 The XRD patterns of the reduced graphene oxide films prepared in Examples 1-4 are shown below. Figure 2 As can be seen, the characteristic peak (002) shifts to a lower angle as the amount of nitrogen and sulfur doping increases, indicating that heteroatomic nitrogen and sulfur have been successfully incorporated; according to the Bragg equation, the interplanar spacing decreases as the amount of thioacetamide added increases.

[0036] Figure 3 The images show the Raman spectra of the reduced graphene oxide films prepared in Examples 1-4. Figure 3 As can be seen, the Raman characteristic peak is at ~1350 cm⁻¹. -1 and ~1580cm -1 These correspond to D-band and G-band respectively; the intensity ratio of D-band and G-band (I) D / I G From this perspective, as the content of thioacetamide increases, I D / I G The gradually increasing ratio indicates that the doping of diatoms improves the defect level of the thin film, thereby improving the conductivity of the thin film.

[0037] Figure 4 The XPS spectra of the reduced graphene oxide films prepared in Examples 1-4 are shown below. Figure 4 It can be seen that the reduced graphene oxide film contains carbon, sulfur, nitrogen and oxygen elements, indicating that nitrogen and sulfur elements were successfully incorporated into the film. The doping of these two elements is beneficial to improving the defect level of the film, thereby improving its conductivity.

[0038] Figure 5 The conductivity of the reduced graphene oxide films prepared in Examples 1-4 is given by... Figure 5 It can be seen that the film conductivity gradually increases with the increase of thioacetamide content. This is because the amount of nitrogen and sulfur doped gradually increases. The introduction of nitrogen is to provide active sites, which facilitates the substitution of sulfur in the interior of carbon rather than at the edge of carbon. This can further enhance the defect level of the film and improve the conductivity of the film.

[0039] Figure 6 To assess the electromagnetic shielding performance of the reduced graphene oxide films prepared in Examples 1-4, from... Figure 6 It can be seen that the electromagnetic shielding performance gradually improves with the increase of thioacetamide content, indicating that the introduced heteroatoms can effectively improve the electromagnetic shielding performance of the film.

[0040] Figure 7For the infrared emissivity testing of the reduced graphene oxide films prepared in Examples 1-4, from... Figure 7 It can be seen that the products obtained in Examples 1-4 have low infrared emissivity (<0.5) in the 3-5 μm wavelength range; this indicates that heat treatment of the thin film and the introduction of nitrogen and sulfur co-doping can effectively improve the conductivity of the thin film, thereby reducing the infrared emissivity. With the increase of thioacetamide content, the infrared emissivity of the thin film continuously decreases, reaching a minimum of 0.398. When the doping amount reaches a certain level, further increasing the thioacetamide content will not reduce the infrared emissivity, because with continuous increase in the amount introduced, the doping amount will reach saturation, and the infrared emissivity will remain almost unchanged (from 0.404 to 0.398).

Claims

1. A method for preparing a reduced graphene oxide film with low infrared emissivity, characterized in that, Includes the following steps: (1) Add 4.0 mmol of solid thioacetamide to 20 mL of graphene oxide dispersion and stir for 10 min until completely dissolved; the concentration of graphene oxide in the graphene oxide dispersion is 2 mg / mL. (2) The graphene oxide dispersion containing thioacetamide was vacuum-assisted filtered, and the nitrogen-sulfur co-doped graphene oxide film containing filter paper was naturally air-dried for 24 hours. After air-drying, it was immersed in an ethanol aqueous solution for 1 minute. The nitrogen-sulfur co-doped graphene oxide film naturally detached from the filter paper to obtain a nitrogen-sulfur co-doped graphene oxide film. The mixing volume ratio of ethanol and water in the ethanol aqueous solution was 99:

1. (3) The obtained nitrogen-sulfur co-doped graphene oxide film was placed in a tube furnace for calcination; the calcination temperature was 700℃, the holding time was 2h, and the heating rate was 5℃ / min to obtain a reduced graphene oxide film; the thickness of the reduced graphene oxide film was not higher than 30μm. The reduced graphene oxide film obtained by the above method has an infrared emissivity of 0.398 in the 3~5μm wavelength range.

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