CN108298582A - One kind is by VO2The preparation method of hollow ball and film that nanoscale twins surround - Google Patents

Abstract

The invention discloses a method for preparing a hollow sphere surrounded by _VO2 nanosheets and a thin film. In the present invention, the vanadium precursor, ethylene glycol, and reducing agent are added to a certain proportion of ethanol and water mixed liquid, and then the mixed liquid is transferred to a reaction kettle for hydrothermal reaction. After the end, the product is centrifugally washed and dried to obtain The powder sample, heat-treated in an inert atmosphere, can obtain a hollow sphere powder composed of _VO2 nanosheets. The thin films prepared using _VO2 nanosheet hollow spheres exhibit excellent optical properties and sensitivity. First, the _VO2 nanosheets are uniformly distributed vertically on the surface of the hollow sphere, which significantly improves the dispersion of the nanosheets and the porosity of the film, significantly improves the transmittance and modulation ability of the film to visible light, and reduces the phase change hysteresis width . It is of great value for the application of VO ₂ in the field of smart glass.

Description

A method for preparing hollow spheres surrounded by VO2 nanosheets and thin films

【Technical field】

The invention relates to a preparation method of _VO2 nanosheet hollow spheres used for smart window glass, which belongs to the field of smart materials and is also closely related to the fields of energy and environmental protection.

【Background technique】

Vanadium dioxide (VO ₂ ) crystals usually undergo a structural transformation from a monoclinic phase (P2 ₁ /c, low temperature phase) to a tetragonal phase (P4 ₂ /mnm, high temperature phase) at a relatively low temperature (68°C). , and with the insulator-to-metal phase transition (MIT) process, its resistivity and optical properties change suddenly, especially, its infrared transmittance decreases sharply with the increase of temperature, and this process is completely reversible. The regulation effect of VO ₂ on light before and after the phase transition just meets the requirements of smart windows. In terms of function, smart windows can sense and respond to external stimuli such as light, heat, and electricity to effectively control the light intensity passing through the glass and indoor light and temperature. When the ambient temperature is lower than the phase transition temperature (T _c ), _VO2 behaves as an insulator phase with high infrared light transmittance, and the temperature gradually increases. When the temperature rises to _Tc , _VO2 transforms into a metal phase, which has a strong reflection effect on infrared light, and the infrared transmittance decreases rapidly, and its passive feedback can maintain the indoor temperature level.

At present, the energy crisis has become the biggest problem facing mankind, and energy is mainly used in construction, industry and transportation. Among them, building energy consumption has surpassed industry and transportation, accounting for 41% of total energy consumption, and air conditioning and heating accounted for 50% of building energy consumption. If VO ₂ is applied to smart windows to replace air conditioners, it will save a lot of energy. Therefore, the research on VO ₂ thin films becomes very valuable and meaningful. At present, there are still some difficulties in the application of VO ₂ smart windows. On the one hand, the visible light transmittance of VO ₂ films is low, and there is a trade-off relationship with the light modulation ability of the film. For example: by reducing the film thickness When the visible light transmittance is increased, the light modulation ability of the film drops sharply. Seriously restricting the practical application of VO ₂ in the field of smart windows. Experimental and calculation results show that small particle size can improve the optical properties of the film. At present, the minimum size can reach 20-30nm, but it is difficult to prepare particles smaller than 20nm, and small particles are prone to serious aggregation. In addition, the hysteresis of small particles The width is usually large, ie the sensitivity is low. Aiming at these problems, the present invention discloses a method for preparing _VO2 nanosheet hollow sphere structure. Experimental results show that the _VO2 nanosheet hollow sphere not only balances visible light transmittance and light modulation ability, but also significantly enhances its sensitivity.

【Content of invention】

The object of the present invention is to overcome the shortcoming of above-mentioned prior art, provide a kind of preparation method of hollow sphere and thin film surrounded by VO _nano sheet. The invention combines the hydrothermal reaction and heat treatment process to obtain a hollow sphere structure composed of _VO2 nanosheets, and the hollow sphere powder is made into a thin film material by a spin coating method.

In order to achieve the above object, the present invention adopts the following technical solutions to achieve:

A method for preparing hollow spheres surrounded by VO _nanosheets , comprising the following steps:

1) Configure a mixed solution of ethanol and deionized water, dissolve the vanadium precursor into the mixed solution, and process the mixed solution with a cell pulverizer to obtain a mixed solution A;

2) Add ethylene glycol to the mixed solution A obtained in step 1), add a reducing agent after the magnetically stirred solution is uniform, continue to stir and then transfer it to a high-pressure reactor for hydrothermal reaction to obtain a reaction solution. The clear liquid is poured out to obtain the reaction product;

3) The reaction product obtained in step 2) is centrifugally cleaned with deionized water and absolute ethanol respectively, and then dried in a vacuum oven to obtain a powder product;

4) The powder product obtained in step 3) is heat-treated under an inert atmosphere to obtain powder B, which is a hollow sphere surrounded by VO _nanosheets .

A further improvement of the present invention is:

In step 1), the volume ratio of ethanol to deionized water is (1-6):1, the concentration of the vanadium precursor in the solution is 0.025-0.1mol/L, and the mixed solution is treated with a cell pulverizer to fully dissolve the vanadium precursor , to obtain a mixed solution A; the vanadium precursor is a vanadium salt containing +5 valence vanadium, including: ammonium metavanadate (NH ₄ VO ₃ ), sodium metavanadate (NaVO ₃ ), sodium pyrovanadate (Na ₄ V ₂ O ₇ ).

The volume of ethylene glycol in step 2) is 2.5% to 14.5% of the volume of the mixed solution A, and the concentration of the reducing agent in the solution is 0.064 to 0.128mol/L; the lining of the autoclave is polytetrafluoroethylene, and the autoclave The filling degree is 50-80%, the temperature of hydrothermal reaction is 180-220℃, and the reaction time is 20-28h;

The reducing agent is selected from reducing acids, including formic acid (H ₂ CO ₂ ), oxalic acid (H ₂ C ₂ O ₄ ), lactic acid (C ₃ H ₆ O ₃ ), and malic acid (C ₄ H ₆ O ₅ ).

The reaction liquid in step 3) was washed with deionized water and absolute ethanol respectively by centrifugation for 3 times, wherein the volume ratio of the reaction product to the deionized water was 1: (10-15), and the volume ratio of the reaction product to the deionized ethanol was The volume ratio is 1: (5-10); when drying in a vacuum oven, the drying temperature is 50-100°C, and the drying time is 7-12 hours.

Step 4) The heat treatment temperature is 300-450° C., and the time is 1-3 hours.

A hollow sphere surrounded by _VO nanosheets, the diameter of the hollow sphere is 400-2000nm, the outer surface of the hollow sphere is attached with a nanosheet, the length of the nanosheet is 50-100nm, the width is 30-60nm, and the thickness is 5~7nm.

A kind of VO The preparation method of _thin film is characterized in that, comprises the following steps:

(1) Disperse powder B into deionized water, add dispersant and polyurethane, and perform magnetic stirring at room temperature to obtain compound C;

(2) The composite C was spin-coated on the surface of quartz glass or polyethylene terephthalate and dried to obtain the target film.

Step (1) Adding dispersant and polyurethane in a volume ratio of 1: (10-20), stirring magnetically at room temperature for 3-5 hours.

In step (2), the drying temperature is 80-100° C., and the drying time is 1-2 minutes.

A kind of _VO2 thin film, described _VO2 thin film is a kind of thin film prepared by hollow spheres surrounded by _VO2 nano-sheets, wherein the diameter of the hollow spheres is 400-2000nm, and the outer surface of the hollow spheres is attached with nano-sheets, nano-sheets The layer length is 50-100 nm, the width is 30-60 nm, and the thickness is 5-7 nm.

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

The invention combines the hydrothermal reaction and heat treatment process to obtain a hollow sphere structure composed of _VO2 nanosheets, and the hollow sphere powder is made into a thin film material by a spin coating method. In the preparation process of the present invention, a cell pulverizer is selected to fully dissolve the vanadium precursor, ethylene glycol is used as a part of the solvent, and the amount of ethylene glycol is limited, so that the nanosheets are aggregated into a spherical structure; an appropriate amount of reducing dose is added, A hollow sphere structure surrounded by nanosheets was obtained; VO _monoclinic phase was obtained after heat treatment. The uniform vertical distribution of nanosheets on the surface of hollow spheres not only improves the dispersion of nanosheets, but also significantly increases the porosity.

The thin film prepared by the invention, the hollow _VO2 nanosheet layer not only balances the visible light transmittance and light modulation ability, but also significantly enhances its sensitivity, and is suitable for application in the field of smart windows. According to the statistics of the optical properties of films with different thicknesses, it is found that as the film thickness decreases (from 7.8 μm to 2.6 μm), the visible light transmittance increases significantly, from 50% to 87.2%, and maintains a high light transmittance. Modulation ability (when the thickness of the film is 2.6 μm, the light adjustment ability is 5.2%), it can be seen that the film prepared by the present invention plays a role in balancing visible light transmittance and light modulation ability.

【Description of drawings】

Fig. 1 (a) is the hollow sphere SEM photograph before heat treatment of the present invention;

Fig. 1 (b) is the hollow sphere TEM photograph before heat treatment of the present invention;

Fig. 1 (c) is the XRD collection of illustrative plates after heat treatment of the present invention;

Fig. 1 (d) is the SEM photograph after heat treatment of the present invention;

Fig. 2 (a) is the light transmittance of films with different thicknesses at 20°C and 90°C of the present invention;

Fig. 2 (b) is the statistical diagram of the optical performance of the film of different thicknesses of the present invention;

Fig. 3 is the DSC curve after heat treatment of the present invention.

【Detailed ways】

The invention discloses a method for preparing a hollow sphere surrounded by _VO2 nanosheets and a thin film. In order to illustrate the present invention more clearly, the present invention will be further described below in conjunction with the examples.

Technical scheme of the present invention is as follows:

Step 1: combining hydrothermal method and heat treatment to obtain a hollow sphere structure surrounded by VO _nanosheets ;

1) Prepare a mixed solution of ethanol and deionized water, the volume ratio of ethanol to deionized water is (1-6):1; add vanadium precursor to the mixed solution, and the concentration of vanadium precursor after dissolution is 0.025-0.1mol /L,; process the mixed solution with a cell pulverizer, so that the vanadium precursor is fully dissolved in the mixed solution, and a mixed solution A is obtained;

2) Add ethylene glycol to the mixed solution A. The volume of ethylene glycol accounts for 2.5-14.5% of the volume of the mixed solution A. After magnetically stirring the solution, add a reducing agent. The concentration of the reducing agent in the solution is 0.064-0.128mol/ L, continue magnetic stirring to make the reaction fully, transfer the stirred reaction solution to a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal reaction, the filling degree of the high-pressure reactor is 50-80%, and the hydrothermal reaction The temperature is 180-220° C., the reaction time is 20-28 hours, natural cooling is obtained to obtain a reaction liquid layered up and down, and the supernatant in the reaction liquid is poured out to obtain a reaction product.

Among them, vanadium precursors are vanadium salts containing +5-valent vanadium, specifically: ammonium metavanadate (NH ₄ VO ₃ ), sodium metavanadate (NaVO ₃ ), sodium pyrovanadate (Na ₄ V ₂ O ₇ ), etc.; the reducing agent is a reducing acid, such as formic acid (H ₂ CO ₂ ), oxalic acid (H ₂ C ₂ O ₄ ), lactic acid (C ₃ H ₆ O ₃ ), malic acid (C ₄ H ₆ O ₅ )Wait.

3) Centrifuge and wash the reaction product three times with deionized water and absolute ethanol respectively. The volume ratio to absolute ethanol is 1: (5-10); and then dried in a vacuum oven at a drying temperature of 50-100°C and a drying time of 7-12 hours to finally obtain a powder product.

4) heat-treat the powder product under an inert atmosphere at a temperature of 300-450° C. for 1-3 hours to obtain the target product: a powder with a hollow sphere structure surrounded by VO _nanosheets , the length of which is 50-100nm, the width is 30-60nm, the thickness is 5-7nm, and the size of the hollow spherical structure is 400-2000nm.

Step 2: using the spin coating method to make the obtained hollow sphere powder into a thin film;

5) Disperse the hollow spherical structure powder obtained in step 1 into deionized water, add dispersant and polyurethane, stir magnetically at room temperature for 3-5 hours, and obtain compound C, wherein the volume ratio of dispersant and polyurethane is 1:(10～ 20);

6) The compound C is spin-coated on the surface of quartz glass or polyethylene terephthalate (PET), and dried at 80-100° C. for 1-2 minutes to obtain the target film.

In the present invention, ethanol promotes the formation of nanosheets; ethylene glycol makes the nanosheets gather into a loose spherical structure; the reducing acid induces the internal dissolution of the spheres to form a hollow sphere structure, and the gas produced by the reaction is formed by the hollow spheres. The inside overflows to the outside of the sphere, which promotes the vertical distribution of nanosheets on the surface of the hollow sphere. This structure not only improves the dispersion of the nanosheets, but also increases the porosity of the hollow sphere surface.

Figure 1(a) is the SEM photo of the hollow spheres obtained before heat treatment, and Figure 1(b) is the corresponding TEM photo. It can be seen that the nanosheets are evenly embedded on the surface of the hollow spheres, which not only improves the dispersion of the nanosheets, but also has a large inter-sheet porosity. Figure 1(c) is the XRD pattern after heat treatment at 450°C for 2 hours. It can be seen that all peaks correspond to monoclinic VO ₂ (JCPDSCard No. 43-1051), indicating that the nanosheets prepared by this method have high purity. Figure 1(d) is the SEM photo after heat treatment at 450°C for 2 hours. It can be seen that the surface morphology of the sample has not changed after heat treatment.

Figure 2(a) shows the light transmittance of films with different thicknesses at 20°C and 90°C, and the test wavelength range is 250-2500nm, and Figure 2(b) shows the statistical results of optical properties of films with different thicknesses. Visible light transmittance (T-vis) is the transmittance at a wavelength of 700nm; the near-infrared light modulation capability (ΔT _2500nm ) in Figure 2(b) is defined as the difference in transmittance at 20°C and 90°C at a wavelength of 2500nm; T-vis _L and T-vis _H are the visible light transmittance at 20 and 90°C, respectively; ΔT _sol is the solar light modulation ability, which is calculated by the following formula:

where λ is the wavelength, is the solar radiation spectrum, T(λ, 20°C), and T(λ, 90°C) are the light transmittance at 20°C and 90°C in the 250-2500nm band, respectively. It can be seen that when the film thickness decreases from 7.8 μm to 2.6 μm, the visible light transmittance (T-vis) increases from 50% to 87.2%, and maintains a high light modulation ability (ΔT when the film thickness is 2.6 μm _sol is 5.2%), it can be seen that the film prepared by the present invention balances visible light transmittance and light modulation ability.

Figure 3 shows the DSC curve after heat treatment. It can be seen that the hysteresis width of VO ₂ nanosheet hollow spheres is 9.3°C, which is much smaller than that of nanoparticles (>20°C), which significantly improves the phase transition sensitivity of VO ₂ .

Example 1:

1) Configure a mixed solution of ethanol and deionized water with a volume ratio of 4:1, and add ammonium metavanadate, the concentration of ammonium metavanadate in the solution is 0.05mol/L; crush the mixed solution with a cell pulverizer, and make The vanadium precursor is fully dissolved in the mixed solution to obtain solution A;

2) After adding ethylene glycol, stir magnetically until the solution is uniform, the volume of ethylene glycol accounts for 3% of the volume of the mixed solution A, add oxalic acid (H ₂ C ₂ O ₄ ), the concentration of oxalic acid in the solution is 0.1mol/L, Continue to stir until the reaction is complete, then transfer to a polytetrafluoroethylene-lined autoclave for hydrothermal reaction, with a filling degree of 70%, hydrothermal reaction at 200°C for 24 hours, and natural cooling to obtain a reaction solution. The supernatant was poured out to obtain the reactant;

3) Wash the reactants three times with deionized water and absolute ethanol respectively, wherein the volume ratio of the reaction solution to deionized water is 1:10, and the volume ratio of the reaction solution to absolute ethanol is 1:8; after washing The reaction solution was dried at 70° C. for 10 h to obtain a powdery product;

4) heat-treating the powdered product at 450° C. for 2 h under an argon atmosphere to obtain a hollow spherical structure powder surrounded by VO _nanosheets ;

5) Disperse the hollow sphere structure powder into deionized water, add the dispersant and polyurethane into the deionized water at a volume ratio of 1:10, and stir magnetically at room temperature for 4 hours to obtain a composite;

6) The composite is spin-coated on a glass substrate, and dried at 100° C. for 2 minutes to prepare a thin film.

The hollow sphere structure powder surrounded by _VO2 nanosheets prepared in this example has a nanosheet length of 50-100 nm, a width of 30-60 nm, a thickness of 5-7 nm, and a size of the hollow sphere structure of 400-2000 nm. .

Example 2:

1) Configure a mixed solution of ethanol and deionized water with a volume ratio of 3:1, and add ammonium metavanadate, and the concentration of ammonium metavanadate in the solution is 0.025mol/L; crush the mixed solution with a cell pulverizer to make The vanadium precursor is fully dissolved in the mixed solution to obtain solution A;

2) After adding ethylene glycol, stir magnetically until the solution is uniform, the volume of ethylene glycol accounts for 5% of the volume of the mixed solution A, add oxalic acid (H ₂ C ₂ O ₄ ), the concentration of oxalic acid in the solution is 0.064mol/L, After continuing to stir until the reaction is complete, transfer to a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal reaction. The filling degree is 60%, and the hydrothermal reaction is carried out at 190°C for 26 hours. Cool naturally to obtain a reaction solution. The supernatant was poured out to obtain the reactant;

3) Wash the reactant three times with deionized water and absolute ethanol respectively, wherein the volume ratio of the reaction solution to deionized water is 1:12, and the volume ratio of the reaction solution to absolute ethanol is 1:5; after washing The reaction solution was dried at 50°C for 8 hours to obtain a powdery product;

4) heat-treating the powdered product at 300° C. for 1 h under an argon atmosphere to obtain a hollow spherical structure powder surrounded by VO _nanosheets ;

5) Disperse the hollow sphere structure powder into deionized water, add the dispersant and polyurethane into the deionized water at a volume ratio of 1:15, and stir magnetically at room temperature for 5 hours to obtain a composite;

6) The composite is spin-coated on a glass substrate, and dried at 90° C. for 1 min to prepare a thin film.

Example 3:

1) Configure a mixed solution of ethanol and deionized water with a volume ratio of 2:1, and add ammonium metavanadate, the concentration of ammonium metavanadate in the solution is 0.03mol/L; use a cell pulverizer to pulverize the mixed solution to make The vanadium precursor is fully dissolved in the mixed solution to obtain solution A;

2) After adding ethylene glycol, stir magnetically until the solution is uniform. The volume of ethylene glycol accounts for 10% of the volume of the mixed solution A. Add formic acid (H ₂ CO ₂ ), the concentration of formic acid in the solution is 0.07mol/L, and continue stirring After the reaction is complete, transfer to a polytetrafluoroethylene-lined autoclave for hydrothermal reaction, the filling degree is 50%, hydrothermal reaction at 185°C for 22 hours, and natural cooling to obtain the reaction liquid, and the supernatant in the reaction liquid The liquid is poured out to obtain the reactant;

3) The reactants were washed three times with deionized water and absolute ethanol respectively, wherein the volume ratio of the reaction solution to deionized water was 1:15, and the volume ratio of the reaction solution to absolute ethanol was 1:10; after cleaning The reaction solution was dried at 80°C for 9h to obtain a powdery product;

4) heat-treating the powdered product at 320° C. for 2 h under an argon atmosphere to obtain a hollow spherical structure powder surrounded by VO _nanosheets ;

5) Disperse the hollow sphere structure powder into deionized water, add the dispersant and polyurethane into the deionized water at a volume ratio of 1:10, and stir magnetically at room temperature for 3 hours to obtain a composite;

6) The composite is spin-coated on a glass substrate, and dried at 80° C. for 2 minutes to prepare a thin film.

Example 4:

1) Configure a mixed solution of ethanol and deionized water with a volume ratio of 1:1, and add ammonium metavanadate, the concentration of ammonium metavanadate in the solution is 0.04mol/L; use a cell pulverizer to pulverize the mixed solution to make The vanadium precursor is fully dissolved in the mixed solution to obtain solution A;

2) After adding ethylene glycol, stir magnetically until the solution is uniform, the volume of ethylene glycol accounts for 2.5% of the volume of the mixed solution A, add oxalic acid (H ₂ C ₂ O ₄ ), the concentration of oxalic acid in the solution is 0.08mol/L, Continue to stir until the reaction is fully transferred to a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal reaction, the filling degree is 80%, hydrothermal reaction at 182 ° C for 20 hours, and natural cooling to obtain a reaction solution. The supernatant was poured out to obtain the reactant;

3) The reactants were washed three times with absolute ethanol and deionized water respectively, wherein the volume ratio of the reaction solution to deionized water was 1:11, and the volume ratio of the reaction solution to absolute ethanol was 1:7; after cleaning The reaction solution was dried at 60°C for 7h to obtain a powdery product;

4) heat-treating the powdered product at 360° C. for 2 h under an argon atmosphere to obtain a hollow spherical structure powder surrounded by VO _nanosheets ;

5) Disperse the hollow sphere structure powder into deionized water, add the dispersant and polyurethane into the deionized water at a volume ratio of 1:20, and stir magnetically at room temperature for 4 hours to obtain a composite;

6) The composite is spin-coated on a glass substrate, and dried at 85° C. for 2 minutes to prepare a thin film.

Example 5:

1) Configure a mixed solution of ethanol and deionized water with a volume ratio of 5:1, and add ammonium metavanadate, and the concentration of ammonium metavanadate in the solution is 0.045mol/L; crush the mixed solution with a cell pulverizer to make The vanadium precursor is fully dissolved in the mixed solution to obtain solution A;

2) After adding ethylene glycol, stir magnetically until the solution is uniform, the volume of ethylene glycol accounts for 7% of the volume of the mixed solution A, add oxalic acid (H ₂ C ₂ O ₄ ), the concentration of oxalic acid in the solution is 0.095mol/L, Continue to stir until the reaction is fully transferred to a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal reaction, the filling degree is 55%, hydrothermal reaction at 188 ° C for 21 hours, and natural cooling to obtain a reaction solution. The supernatant was poured out to obtain the reactant;

3) The reactants were washed three times with deionized water and absolute ethanol respectively, wherein the volume ratio of the reaction solution to deionized water was 1:13, and the volume ratio of the reaction solution to absolute ethanol was 1:6; after cleaning The reaction solution was dried at 55°C for 12 hours to obtain a powdery product;

4) heat-treating the powdered product at 400° C. for 3 h under an argon atmosphere to obtain a hollow spherical structure powder surrounded by VO _nanosheets ;

5) Disperse the hollow sphere structure powder into deionized water, add the dispersant and polyurethane into the deionized water at a volume ratio of 1:15, stir magnetically at room temperature for 5 hours, and obtain a composite;

6) The composite is spin-coated on a glass substrate, and dried at 95° C. for 2 minutes to prepare a thin film.

Embodiment 6:

1) Configure a mixed solution of ethanol and deionized water with a volume ratio of 6:1, and add sodium pyrovanadate, the concentration of sodium pyrovanadate in the solution is 0.055mol/L; use a cell pulverizer to pulverize the mixed solution to make The vanadium precursor is fully dissolved in the mixed solution to obtain solution A;

2) After adding ethylene glycol, stir magnetically until the solution is uniform, the volume of ethylene glycol accounts for 9% of the volume of the mixed solution A, add oxalic acid (H ₂ C ₂ O ₄ ), the concentration of oxalic acid in the solution is 0.128mol/L, Continue to stir until the reaction is fully transferred to a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal reaction, the filling degree is 65%, hydrothermal reaction at 192 ° C for 25 hours, and natural cooling to obtain a reaction solution. The supernatant was poured out to obtain the reactant;

3) The reactants were washed three times with deionized water and absolute ethanol respectively, wherein the volume ratio of the reaction solution to deionized water was 1:12, and the volume ratio of the reaction solution to absolute ethanol was 1:8; after cleaning The reaction solution was dried at 100°C for 11 hours to obtain a powdery product;

4) heat-treating the powdered product at 380° C. for 2 h under an argon atmosphere to obtain a hollow spherical structure powder surrounded by VO _nanosheets ;

5) Disperse the hollow sphere structure powder into deionized water, add the dispersant and polyurethane into the deionized water at a volume ratio of 1:12, and stir magnetically at room temperature for 3 hours to obtain a composite;

6) The composite is spin-coated on a PET substrate, and dried at 82° C. for 2 minutes to prepare a thin film.

Embodiment 7:

1) Configure a mixed solution of ethanol and deionized water with a volume ratio of 5:1, and add sodium metavanadate (NaVO ₃ ), the concentration of sodium metavanadate in the solution is 0.06mol/L; crush it with a cell pulverizer Mix the solution so that the vanadium precursor is fully dissolved in the mixed solution to obtain solution A;

2) After adding ethylene glycol, stir magnetically until the solution is uniform. The volume of ethylene glycol accounts for 8.5% of the volume of the mixed solution A. Add lactic acid (C ₃ H ₆ O ₃ ), the concentration of lactic acid in the solution is 0.09mol/L, Continue to stir until the reaction is complete, transfer to a polytetrafluoroethylene-lined high-pressure reactor for hydrothermal reaction, the filling degree is 75%, hydrothermal reaction at 198 ° C for 27 hours, and naturally cool to obtain a reaction solution. The supernatant was poured out to obtain the reactant;

3) The reactants were washed three times with deionized water and absolute ethanol respectively, wherein the volume ratio of the reaction solution to deionized water was 1:13, and the volume ratio of the reaction solution to absolute ethanol was 1:9; after cleaning The reaction solution was dried at 95°C for 8 hours to obtain a powdery product;

4) heat-treating the powdered product at 420° C. for 2 h under an argon atmosphere to obtain a hollow spherical structure powder surrounded by VO _nanosheets ;

5) Disperse the hollow sphere structure powder in deionized water, add the dispersant and polyurethane into the deionized water at a volume ratio of 1:11, and stir magnetically at room temperature for 3 hours to obtain a composite;

6) The composite is spin-coated on a PET substrate, and dried at 88° C. for 2 minutes to prepare a thin film.

Embodiment 8:

1) Configure a mixed solution of ethanol and deionized water with a volume ratio of 4:1, and add ammonium metavanadate, the concentration of ammonium metavanadate in the solution is 0.1mol/L; use a cell pulverizer to pulverize the mixed solution to make The vanadium precursor is fully dissolved in the mixed solution to obtain solution A;

2) After adding ethylene glycol, stir magnetically until the solution is uniform. The volume of ethylene glycol accounts for 10% of the volume of the mixed solution A. Add oxalic acid (H ₂ C ₂ O ₄ ), the concentration of oxalic acid in the solution is 0.105mol/L, Continue to stir until the reaction is fully transferred to a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal reaction, the filling degree is 53%, hydrothermal reaction at 195 ° C for 23 hours, and natural cooling to obtain a reaction solution. The supernatant was poured out to obtain the reactant;

3) The reactants were washed three times with deionized water and absolute ethanol respectively, wherein the volume ratio of the reaction solution to deionized water was 1:10, and the volume ratio of the reaction solution to absolute ethanol was 1:10; after cleaning The reaction solution was dried at 90°C for 7h to obtain a powdery product;

4) heat-treating the powdered product at 430° C. for 3 h under an argon atmosphere to obtain a hollow spherical structure powder surrounded by VO _nanosheets ;

5) Disperse the hollow sphere structure powder into deionized water, add the dispersant and polyurethane into the deionized water at a volume ratio of 1:16, and stir magnetically at room temperature for 4 hours to obtain a composite;

6) The composite is spin-coated on a PET substrate, and dried at 92° C. for 2 minutes to prepare a thin film.

Embodiment 9:

1) Configure a mixed solution of ethanol and deionized water with a volume ratio of 3:1, and add ammonium metavanadate, the concentration of ammonium metavanadate in the solution is 0.09mol/L; crush the mixed solution with a cell pulverizer to make The vanadium precursor is fully dissolved in the mixed solution to obtain solution A;

2) After adding ethylene glycol, stir magnetically until the solution is uniform. The volume of ethylene glycol accounts for 11.5% of the volume of the mixed solution A. Add malic acid (C ₄ H ₆ O ₅ ), and the concentration of malic acid in the solution is 0.11mol/ L, after adding 2ml of ethylene glycol, stir magnetically until the solution is uniform, add 0.005mol of malic acid (C ₄ H ₆ O ₅ ), continue to stir and transfer to a high-pressure reactor lined with polytetrafluoroethylene after the reaction is complete Carrying out hydrothermal reaction, the filling degree is 58%, hydrothermal reaction at 215°C for 28 hours, cooling naturally to obtain the reaction liquid, pouring out the supernatant in the reaction liquid to obtain the reactant;

3) The reactants were washed three times with deionized water and absolute ethanol respectively, wherein the volume ratio of the reaction solution to deionized water was 1:15, and the volume ratio of the reaction solution to absolute ethanol was 1:15; after cleaning The reaction solution was dried at 85°C for 12 hours to obtain a powdery product;

4) heat-treating the powdered product at 410° C. for 1 h under an argon atmosphere to obtain a hollow spherical structure powder surrounded by VO _nanosheets ;

5) Disperse the hollow sphere structure powder into deionized water, add the dispersant and polyurethane into the deionized water at a volume ratio of 1:17, and stir magnetically at room temperature for 5 hours to obtain a composite;

6) The composite is spin-coated on a PET substrate, and dried at 98° C. for 2 minutes to prepare a thin film.

Example 10:

1) Configure a mixed solution of ethanol and deionized water with a volume ratio of 2:1, and add ammonium metavanadate, the concentration of ammonium metavanadate in the solution is 0.8mol/L; crush the mixed solution with a cell pulverizer to make The vanadium precursor is fully dissolved in the mixed solution to obtain solution A;

2) After adding ethylene glycol, stir magnetically until the solution is uniform. The volume of ethylene glycol accounts for 13% of the volume of the mixed solution A. Add oxalic acid (H ₂ C ₂ O ₄ ), the concentration of oxalic acid in the solution is 0.115mol/L, Continue to stir until the reaction is complete, then transfer to a polytetrafluoroethylene-lined autoclave for hydrothermal reaction, with a filling degree of 64%, hydrothermal reaction at 210°C for 22 hours, and natural cooling to obtain a reaction solution. The supernatant was poured out to obtain the reactant;

3) The reactants were washed three times with deionized water and absolute ethanol respectively, wherein the volume ratio of the reaction solution to deionized water was 1:14, and the volume ratio of the reaction solution to absolute ethanol was 1:8; after cleaning The reaction solution was dried at 55°C for 9h to obtain a powdery product;

4) heat-treating the powdered product at 390° C. for 1 h under an argon atmosphere to obtain a hollow spherical structure powder surrounded by VO _nanosheets ;

5) Disperse the hollow sphere structure powder into deionized water, add the dispersant and polyurethane into the deionized water at a volume ratio of 1:18, and stir magnetically at room temperature for 5 hours to obtain a composite;

6) The composite is spin-coated on a PET substrate, and dried at 93° C. for 2 minutes to prepare a thin film.

Example 11:

1) Configure a mixed solution of ethanol and deionized water with a volume ratio of 1:1, and add ammonium metavanadate, the concentration of ammonium metavanadate in the solution is 0.07mol/L; use a cell pulverizer to pulverize the mixed solution to make The vanadium precursor is fully dissolved in the mixed solution to obtain solution A;

2) After adding ethylene glycol, stir magnetically until the solution is uniform, the volume of ethylene glycol accounts for 14.5% of the volume of the mixed solution A, add oxalic acid (H ₂ C ₂ O ₄ ), the concentration of oxalic acid in the solution is 0.12mol/L, After adding 5ml of ethylene glycol, stir magnetically until the solution is uniform, add 0.012mol of oxalic acid (H ₂ C ₂ O ₄ ), continue stirring until the reaction is complete, transfer to a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal Reaction, with a filling degree of 78%, hydrothermal reaction at 180°C for 25 hours, natural cooling to obtain a reaction solution, pouring out the supernatant in the reaction solution to obtain a reactant;

3) The reactants were washed three times with deionized water and absolute ethanol respectively, wherein the volume ratio of the reaction solution to deionized water was 1:10, and the volume ratio of the reaction solution to absolute ethanol was 1:7; after cleaning The reaction solution was dried at 65° C. for 10 h to obtain a powdery product;

4) heat-treating the powdered product at 310° C. for 2 h under an argon atmosphere to obtain a hollow spherical structure powder surrounded by VO _nanosheets ;

5) Disperse the hollow sphere structure powder in deionized water, add the dispersant and polyurethane into the deionized water at a volume ratio of 1:19, and stir magnetically at room temperature for 4 hours to obtain a composite;

6) The composite is spin-coated on a PET substrate, and dried at 100° C. for 2 minutes to prepare a thin film.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (10)

1. a method for preparing hollow spheres surrounded by VO _nanosheets , characterized in that, comprising the following steps: 1) Configure a mixed solution of ethanol and deionized water, dissolve the vanadium precursor into the mixed solution, and process the mixed solution with a cell pulverizer to obtain a mixed solution A; 2) Add ethylene glycol to the mixed solution A obtained in step 1), stir the solution uniformly with a magnetic force, add a reducing agent, continue to stir and then transfer it to a high-pressure reactor for hydrothermal reaction to obtain a reaction solution. The clear liquid is poured out to obtain the reaction product; 3) The reaction product obtained in step 2) is centrifugally cleaned with deionized water and absolute ethanol respectively, and then dried in a vacuum oven to obtain a powder product; 4) The powder product obtained in step 3) is heat-treated under an inert atmosphere to obtain powder B, which is a hollow sphere surrounded by VO _nanosheets . 2. a kind of method according to claim 1 is surrounded by VO _nanosheets , wherein the volume ratio of ethanol and deionized water in step 1) is (1～6): 1, vanadium The concentration of the precursor in the solution is 0.025-0.1mol/L, and the mixed solution is treated with a cell pulverizer to fully dissolve the vanadium precursor, and a mixed solution A is obtained; the vanadium precursor is selected from vanadium salts containing +5-valent vanadium, including: Ammonium vanadate (NH ₄ VO ₃ ), sodium metavanadate (NaVO ₃ ), sodium pyrovanadate (Na ₄ V ₂ O ₇ ). 3. a kind of by VO according to claim ₁ The method for preparing hollow spheres surrounded by nanosheets is characterized in that the volume of ethylene glycol in step 2) is 2.5～14.5% of the volume of mixed solution A, and the reducing agent The concentration in the solution is 0.064-0.128mol/L; the lining of the autoclave is polytetrafluoroethylene, the filling degree of the autoclave is 50-80%, the temperature of the hydrothermal reaction is 180-220°C, and the reaction time is 20～28h; The reducing agent is selected from reducing acids, including formic acid (H ₂ CO ₂ ), oxalic acid (H ₂ C ₂ O ₄ ), lactic acid (C ₃ H ₆ O ₃ ), and malic acid (C ₄ H ₆ O ₅ ). 4. a kind of by VO according to claim ₁ The method for preparing hollow spheres surrounded by nanosheets, is characterized in that, in step 3), the reaction solution is cleaned 3 times with deionized water and dehydrated alcohol respectively, wherein For each cleaning, the volume ratio of the reaction product to deionized water is 1: (10-15), and the volume ratio of the reaction product to absolute ethanol is 1: (5-10); when drying in a vacuum oven, dry The temperature is 50-100°C, and the drying time is 7-12 hours. 5 . The method for preparing hollow spheres surrounded by VO ₂ nanosheets according to claim 1 , wherein the heat treatment temperature in step 4) is 300-450° C. and the time is 1-3 hours. 6. A kind of hollow sphere surrounded by VO _nanosheets according to any one of the methods of claim 1-5, characterized in that, the diameter of the hollow sphere is 400～2000nm, and the outer surface of the hollow sphere is A nano-sheet layer is attached, and the length of the nano-sheet layer is 50-100 nm, the width is 30-60 nm, and the thickness is 5-7 nm. 7. a kind of VO based on any one of claim 1-5 The preparation method of _the method, is characterized in that, may further comprise the steps: (1) Disperse powder B into deionized water, add dispersant and polyurethane, and perform magnetic stirring at room temperature to obtain compound C; (2) The composite C was spin-coated on the surface of quartz glass or polyethylene terephthalate and dried to obtain the target film. 8. A kind of VO _film preparation method according to claim 7, it is characterized in that, the volume ratio of step (1) adding dispersing agent and polyurethane is 1: (10～20), magnetic stirring 3～5h under normal temperature . 9 . The method for preparing a VO ₂ thin film according to claim 7 , characterized in that, in step (2), the drying temperature is 80-100° C., and the drying time is 1-2 minutes. 10. a kind of according to claim 8 or 9 described _VO film that method makes, it is characterized in that, described _VO film is a kind of film prepared by hollow sphere surrounded by VO _nano sheet, wherein hollow sphere The diameter is 400-2000nm, the outer surface of the hollow sphere is attached with nano-sheets, the length of the nano-sheets is 50-100nm, the width is 30-60nm, and the thickness is 5-7nm.