Method for preparing porous light thin film by using MXene powder and MXene slurry

Abstract

The invention discloses a method for preparing a porous light thin film by using MXene powder and MXene slurry, which comprises the following steps: step 1, mixing MXene dispersion liquid with absolute ethyl alcohol, and carrying out spray drying on the mixed liquid to obtain hollow microsphere MXene powder; 2, weighing MXene powder, adding the MXene powder into the MXene slurry, and uniformly mixing the MXene powder and the MXene slurry; and step 3, taking the MXene composite slurry, coating the surface of the hydrophilic film with the MXene composite slurry, and stripping after the MXene composite slurry is naturally dried to obtain the porous light MXene film. The light porous film prepared from the MXene slurry and the MXene powder internally contains a large number of MXene hollow spheres (the diameter is 5-10 microns), the density is 0.1 g / cm < 3 >, the porosity is 95%, the morphology of the hollow microspheres does not change after water is added, and the spherical morphology can be kept in the film processing process.

Description

Technical Field

[0001] The present invention relates to a method for preparing an MXene film, and more particularly to a method for preparing a porous lightweight MXene film using MXene powder and MXene slurry. Background Art

[0002] MXene materials are two-dimensional transition metal carbides or nitrides, which have advantages such as high electrical conductivity, large specific surface area, and excellent electrochemical properties. The MXene film processed from MXene materials has excellent electrical conductivity and mechanical flexibility, and is an excellent electromagnetic shielding material. However, the MXene film prepared by filtering or coating the MXene dispersion has a dense layered structure between layers and a relatively large density, close to 4 g / cm 3 , which greatly limits the application of MXene films in lightweight electromagnetic shielding fields such as aerospace. Therefore, lightweight porous MXene films have been developed to significantly reduce the density of the film without affecting its original electromagnetic shielding performance. Currently, the main methods for preparing lightweight porous MXene films are: (1) the sacrificial template method, by introducing a template agent and removing it by calcination later to obtain a porous structure; (2) the method of foaming with a foaming agent, adding a hydrazine-based foaming agent and performing heat treatment under high pressure to foam the MXene film to obtain a porous structure; (3) obtaining hollow MXene microspheres by low-temperature spray drying, but the stability of these microspheres in water is poor, and it is difficult to maintain the microsphere structure during processing and will decompose into two-dimensional sheet structures in water (CN119158282A); (4) adding a pore-forming agent and retaining the porous structure of the sample by supercritical drying or freeze-drying. However, the above preparation methods have problems such as complex processes, the introduced template agents, foaming agents, etc. affecting the performance of MXene films, and high process costs and low efficiency for processes such as calcination and freeze-drying. Developing a method for preparing lightweight porous MXene films is very important for lightweight electromagnetic shielding fields such as aerospace without affecting the electromagnetic shielding performance of MXene films. Summary of the Invention

[0003] To solve the problems of complex preparation process, easy oxidation, and low porosity of lightweight porous MXene films, the present invention provides a method for preparing porous lightweight films using MXene powder and MXene slurry. By controlling the ethanol content, dehydration drying of the MXene dispersion can be achieved by spray drying a relatively high-concentration MXene dispersion at 120 °C, obtaining MXene powder with a hollow microsphere morphology. The microspheres are composed of pure MXene, without any impurities and oxidation, and can maintain their spherical morphology in water and during processing. Mixing them into the MXene slurry, coating, and drying can obtain a lightweight porous MXene film. Since the film contains a large number of hollow microspheres inside, with regular morphology and high porosity, it has excellent electromagnetic shielding performance.

[0004] The object of the present invention is achieved through the following technical solutions:

[0005] A method for preparing a porous lightweight film using MXene powder and MXene slurry, comprising the following steps:

[0006] Step 1. Preparation of MXene powder:

[0007] First, mix an MXene dispersion with a concentration of 18 - 22 mg / mL and absolute ethanol in a volume ratio of 2.5 - 3:1, and mix them evenly by magnetic stirring. Control the magnetic stirring time to be 1 - 5 minutes and the rotation speed to be 200 - 800 revolutions per minute. Then, spray dry the mixed solution through a spray dryer. After a drying process of 10 - 12 minutes, obtain MXene powder in the form of hollow microspheres. Control the drying temperature to be 120 - 130 °C and the feed rate to be 800 - 1000 mL / h.

[0008] Step 2. Preparation of MXene composite slurry:

[0009] Weigh the MXene powder obtained in Step 1 and add it to an MXene slurry with a concentration of 45 - 50 mg / mL. Among them, add 6 - 8 g of MXene powder to every 100 mL of MXene slurry, and mix them evenly by magnetic stirring. Control the magnetic stirring time to be 5 - 10 minutes and the rotation speed to be 200 - 800 revolutions per minute.

[0010] Step 3. Preparation of porous lightweight film:

[0011] Take the MXene composite slurry obtained in Step 2, coat it on the surface of a hydrophilic film, and peel it off after natural drying to obtain a porous lightweight MXene film.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] 1. The lightweight porous film prepared from MXene slurry and MXene powder contains a large number of MXene hollow spheres (with a diameter of 5 - 10 μm), has a density of 0.1 g / cm 3 , has a porosity of 95%, and the morphology of the hollow microspheres does not change after adding water, and can maintain a spherical morphology during the film processing.

[0014] 2. The preparation time of the lightweight MXene film is within 30 minutes, and the preparation efficiency is high.

[0015] 3. No chemical reagents need to be added to create pores in the MXene powder and the porous lightweight film.

[0016] 4. The lightweight MXene film is prepared by directly coating a mixed slurry, and the hollow microspheres can be evenly distributed, which is crucial in lightweight electromagnetic shielding fields such as aerospace.

[0017] 5. The MXene powder used in the present invention can be stored at room temperature for 1 year without oxidation and decomposition, which is beneficial for storage and transportation.

[0018] 6. The porous lightweight film prepared by the present invention achieves an electromagnetic shielding of 70 dB in the X - band, and has good electromagnetic shielding performance. Description of the Drawings

[0019] Figure 1 is the scanning electron microscope (SEM) image of the hollow microsphere MXene powder prepared in Example 1;

[0020] Figure 2 is the SEM image of the wrinkled flaky MXene powder prepared in Example 2;

[0021] Figure 3 is the SEM image of the wrinkled flaky MXene powder prepared in Example 3;

[0022] Figure 4 is the X - ray photoelectron spectroscopy (XPS) spectrum of the MXene film prepared in Example 4;

[0023] Figure 5 is the electromagnetic shielding performance diagram of the MXene film prepared in Example 4;

[0024] Figure 6 is the cross - section SEM image of the lightweight porous MXene film prepared in Example 1;

[0025] Figure 7 is the electromagnetic shielding performance diagram of the lightweight porous MXene film prepared in Example 1. Detailed Description of the Invention

[0026] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be covered by the protection scope of the present invention.

[0027] The present invention provides a method for preparing a porous lightweight film using MXene powder and MXene slurry, and the method includes the following steps:

[0028] Step 1: Preparation of MXene powder:

[0029] First, an MXene dispersion (18 - 22 mg / mL) and absolute ethanol are mixed at a volume ratio of 2.5 - 3:1, and are uniformly mixed by magnetic stirring for 1 - 5 minutes (200 - 800 revolutions per minute). Then, the parameters of the spray dryer are set as follows: the feed rate is 800 - 1000 mL / h, the drying temperature is 120 - 130 °C, the nozzle diameter is 1 mm, the nozzle pressure is 1.8 - 2.2 bar, and the ventilation volume is 300 - 350 m 3 / h. Finally, the mixed liquid is spray-dried by a spray dryer, and through a drying process of 10 - 12 minutes, MXene powder in the form of hollow microspheres is obtained.

[0030] Ordinary spray drying needs to be carried out at a temperature above 200 °C, and the obtained powder is in the form of wrinkled flakes. At the same time, the surface functional groups of MXene will be severely lost at 200 °C, resulting in a decline in its performance. In this step, the MXene dispersion after adding ethanol can be instantaneously dehydrated and dried at 120 °C without loss of the surface functional groups of MXene, ensuring its original performance. The introduction of ethanol makes the spray droplets form a temperature gradient during the evaporation process. Due to the Marangoni effect, the fluctuating MXene flakes self-assemble into hollow microspheres in the area where the surface is exposed to water. The diameter of the microspheres is 5 - 10 μm, and the morphology will not change after adding water, and the spherical morphology can be maintained during the film processing.

[0031] Step 2: Preparation of MXene composite slurry:

[0032] Weigh the MXene powder obtained in Step 1 and add it to the MXene slurry, and mix it evenly by magnetic stirring for 5 - 10 minutes (200 - 800 revolutions per minute), where: 6 - 8 g of MXene powder is added to every 100 mL of MXene slurry (45 - 50 mg / mL).

[0033] Step 3: Preparation of porous lightweight film:

[0034] Take the MXene composite slurry obtained in Step 2, coat it on the surface of a hydrophilic film with a thickness of 0.5 - 1.5 mm, and after natural drying, peel it off to obtain a porous lightweight MXene film.

[0035] Example:

[0036] Example 1:

[0037] Step 1: Preparation of MXene powder: Mix MXene dispersion (20 mg / mL) and absolute ethanol in a volume ratio of 3:1, with a total volume of 200 mL. Mix evenly by magnetic stirring for 5 minutes (500 revolutions per minute). The parameters of the spray dryer are set as follows: feeding rate 1000 mL / h, drying temperature 120 °C, nozzle diameter 1 mm, nozzle pressure 2 bar, and ventilation volume 330 m 3 / h. Spray-dry the mixed solution through the spray dryer. After a drying process of 10 - 12 minutes, obtain the MXene powder in the form of hollow microspheres ( Figure 1 ).

[0038] Step 2: Preparation of MXene composite slurry:

[0039] Take 100 mL of MXene dispersion, obtain MXene slurry (100 mg / mL) by high-speed centrifugation for 30 minutes (10000 revolutions per minute), and dilute it with deionized water to 50 mg / mL. Weigh 1.5 g of the obtained MXene powder, add it to 20 mL of MXene slurry (50 mg / mL), and mix evenly by magnetic stirring for 10 minutes (500 revolutions per minute) to obtain a viscous composite slurry.

[0040] Step 3: Preparation of porous lightweight film:

[0041] Evenly coat the composite slurry on the surface of the PET film with a thickness of 1 mm. After drying, peel it off to obtain a lightweight porous MXene film with a porous structure between layers, containing a large number of MXene microspheres, and the electromagnetic shielding performance in the X-band is 70 dB ( Figure 6 and Figure 7 ).

[0042] Example 2:

[0043] The difference between this example and Example 1 is that the MXene dispersion and absolute ethanol are mixed in a volume ratio of 1:3. In this example, a wrinkled flaky MXene powder is obtained, which cannot be used to process a lightweight porous MXene film ( Figure 2 ).

[0044] Example 3:

[0045] The difference between this example and Example 1 is that the concentration of the MXene dispersion is 1 mg / mL. In this example, a wrinkled flaky MXene powder is obtained, which cannot be used to process a lightweight porous MXene film ( Figure 3 ).

[0046] Example 4:

[0047] The difference between this example and Example 1 is that the drying temperature is 220 °C. In this example, MXene powder of hollow microspheres with oxidation is obtained. The electromagnetic shielding performance of the processed lightweight MXene film deteriorates. After testing, the electromagnetic shielding performance of the film in the X-band is 50 dB( Figure 4 and Figure 5 ).

[0048] Example 5:

[0049] The difference between this example and Example 1 is that 1.5 g of the obtained MXene powder is weighed and added to 20 mL of MXene dispersion (5 mg / mL), and mixed evenly by magnetic stirring for 10 minutes (500 revolutions per minute). After standing, the mixed solution shows a layering phenomenon, and the powder floats on the upper layer of the solution.

[0050] Example 6:

[0051] The difference between this example and Example 1 is that 0.2 g of the obtained MXene powder is weighed and added to 20 mL of MXene slurry (5 mg / mL), and mixed evenly by magnetic stirring for 10 minutes (500 revolutions per minute). A viscous mixed slurry is obtained, which can be evenly coated on the surface of the PET film to obtain a relatively dense film, not a lightweight porous film, with a density of 3.2 g / cm 3 .

[0052] From the above examples, it can be concluded that by using the method provided by the present invention, hollow microsphere MXene powder is obtained by spray drying, and then mixed with MXene slurry to prepare a porous lightweight film. The lightweight MXene film processed from this slurry has high porosity, low density and excellent electromagnetic shielding performance.

Claims

1. A method for preparing a porous lightweight film using MXene powder and MXene slurry, characterized in that The method includes the following steps: Step 1: Preparation of MXene powder: First, mix the MXene dispersion with a concentration of 18 - 22 mg / mL and absolute ethanol in a volume ratio of 2.5 - 3:1, and mix them evenly by magnetic stirring. Control the time of magnetic stirring to be 1 - 5 minutes and the rotation speed to be 200 - 800 revolutions per minute; Then, spray-dry the mixed solution through a spray dryer. After a drying process of 10 - 12 minutes, obtain the MXene powder in the form of hollow microspheres. Control the drying temperature to be 120 - 130 °C and the feed rate to be 800 - 1000 mL / h; Step 2: Preparation of MXene composite slurry: Weigh the MXene powder obtained in Step 1 and add it to the MXene slurry with a concentration of 45 - 50 mg / mL. Among them: add 6 - 8 g of MXene powder to every 100 mL of MXene slurry, and mix them evenly by magnetic stirring. Control the time of magnetic stirring to be 5 - 10 minutes and the rotation speed to be 200 - 800 revolutions per minute; Step 3: Preparation of porous lightweight film: Take the MXene composite slurry obtained in Step 2, coat it on the surface of the hydrophilic film, and peel it off after natural drying to obtain the porous lightweight MXene film.

2. The method for preparing a porous lightweight film using MXene powder and MXene slurry according to claim 1, wherein In the first step, the parameters of the spray dryer are set as follows: the feeding rate is 800 - 1000 mL / h, the drying temperature is 120 - 130 °C, the nozzle diameter is 1 mm, the nozzle pressure is 1.8 - 2.2 bar, and the ventilation volume is 300 - 350 m 3 / h.

3. The method for preparing a porous lightweight film using MXene powder and MXene slurry according to claim 1, characterized in that In the said Step 1, the diameter of the hollow microspheres is 5 - 10 μm.

4. The method for preparing a porous lightweight film using MXene powder and MXene slurry according to claim 1, characterized in that In the said Step 3, the thickness of the MXene film is 0.5 - 1.5 mm.

Images