A vanadium dioxide film and its preparation method and application

Abstract

The present invention discloses a vanadium dioxide thin film, its preparation method, and application. Vanadium dioxide powder is added to an organic solvent and mixed evenly to form a mixed solution. A polymer additive is then added to the solution and mixed evenly to obtain a suspension. Iodine is added to the suspension and mixed evenly to obtain a vanadium dioxide deposition solution. The vanadium dioxide deposition solution is deposited on a conductive glass substrate using an electrophoretic deposition method, and the obtained film is heat-treated to obtain a vanadium dioxide thin film material. In the present invention, adding a polymer additive to the vanadium dioxide deposition solution can effectively improve the bonding force and adhesion strength between the film and the substrate. The vanadium dioxide film is not easy to fall off after being placed for a long time. The vanadium dioxide film prepared by the electrophoretic deposition method can achieve uniform distribution and uniform doping of the material microstructure.

Description

Technical Field

[0001] The present invention relates to the field of chemical functional materials, and in particular to a vanadium dioxide film and a preparation method and application thereof. Background Art

[0002] Vanadium dioxide is a typical thermotropic phase change material, and its phase transition temperature (T c ~68℃) is closest to room temperature and the resistivity mutation is as high as 2-5 orders of magnitude. Both will undergo a reversible phase transition between the metal phase and the semiconductor phase at 68℃. When the temperature is lower than the phase transition temperature, it has a monoclinic structure and exhibits semiconductor properties. Its resistivity, magnetic susceptibility and transmittance to infrared light are all very high; when it is higher than the phase transition temperature, it has a tetragonal rutile structure and exhibits metallic properties. Its resistivity, magnetic susceptibility and transmittance to infrared light will all decrease, showing obvious infrared switch, electrical switch and magnetic switch characteristics. If further doped with high-valent metal ions, the phase transition temperature can be adjusted without affecting its reversible electrical, magnetic and infrared switch properties. Based on the excellent optical, electrical and magnetic properties of vanadium dioxide, it is expected to be developed and applied to smart windows and energy-saving insulation building materials, photoelectric thermal switches, laser protection and photoelectric storage that meet the requirements of building energy conservation, and has very broad application prospects.

[0003] Research on vanadium dioxide as a functional material has been ongoing for a long time. However, vanadium is a multivalent transition metal element, and the vanadium-oxygen system is a very complex one, forming as many as 13 oxides and vanadium-oxygen solid solutions when reacting with oxygen. Furthermore, vanadium dioxide, which is used as a smart material, is stable only within a very narrow stoichiometric ratio range, making the preparation of phase-pure vanadium dioxide difficult.

[0004] Methods for preparing vanadium dioxide thin films include magnetron sputtering, vacuum evaporation coating, sol-gel, pulsed laser deposition, and hydrothermal synthesis. These methods all have drawbacks: magnetron sputtering, for example, requires high equipment, has difficult-to-control process conditions, and results in high investment costs; vacuum evaporation coating suffers from poor stability, porous and brittle films, numerous defects, and high costs; films prepared by the sol-gel method exhibit poor adhesion to the substrate and are prone to detachment; and pulsed laser deposition, due to the high energy of the pulsed laser, can cause surface defects in the film, limiting its potential for large-scale coating. Summary of the Invention

[0005] In order to solve the problems of poor bonding between the vanadium dioxide film prepared by the prior art and the substrate, low adhesion strength and certain defects on the film surface, a vanadium dioxide film and its preparation method and application are provided.

[0006] A method for preparing a vanadium dioxide thin film, the specific steps are as follows:

[0007] Vanadium dioxide powder is added to an organic solvent and mixed uniformly to form a mixed solution with a concentration of 0.1 g / L to 10 g / L, a polymer additive is added thereto in an amount of 1% to 15% by weight of the vanadium dioxide powder and mixed uniformly to obtain a suspension, and iodine is added to the suspension and mixed uniformly to obtain a vanadium dioxide precipitation solution;

[0008] The vanadium dioxide deposition liquid is deposited on a conductive glass substrate by an electrophoretic deposition method, and the deposited film is a vanadium dioxide film.

[0009] The organic solvent is a mixed solvent of one or more of methanol, ethanol, isopropanol or acetone or a mixed solvent with water.

[0010] The polymer additive is polyvinyl pyrrolidone, polyvinyl chloride or triethanolamine.

[0011] The concentration of elemental iodine in the vanadium dioxide deposition solution is 0.5 mmol / L to 3 mmol / L.

[0012] The conductive glass substrate adopts an ITO conductive glass substrate, an FTO conductive glass substrate or a sapphire glass substrate.

[0013] The electrophoretic deposition method adopts a constant voltage cathode electrophoretic deposition method, with a conductive glass substrate as the cathode and a graphite sheet as the anode. The electrode spacing is 20mm to 30mm, the deposition voltage is 5V to 50V, and the deposition time is 1min to 7min.

[0014] A vanadium dioxide film is prepared by the above-mentioned method for preparing the vanadium dioxide film.

[0015] A method for preparing a vanadium dioxide thin film material comprises heat-treating the above-mentioned vanadium dioxide thin film to obtain the vanadium dioxide thin film material.

[0016] The heat treatment is to dry the vanadium dioxide film in a vacuum drying oven at 15° C. to 85° C. for 10 minutes to 60 minutes.

[0017] The vanadium dioxide thin film material comprises a conductive glass substrate and a vanadium dioxide thin film deposited on the conductive glass substrate.

[0018] Compared with the prior art, the present invention has the beneficial effect of adding a polymer additive to the vanadium dioxide deposition solution, and using the electrophoretic deposition method to prepare the vanadium dioxide film based on this, achieving uniform distribution and uniform doping of the material microstructure. The obtained vanadium dioxide film is uniform, and the thickness of the vanadium dioxide film can be controlled by the deposition time. The thickness is controllable within a large range, and deposition at room temperature can avoid phase change of the material under high temperature conditions.

[0019] The vanadium dioxide thin film material prepared by the method of the present invention has a relatively sharp characteristic peak in the X-ray diffraction spectrum, indicating that the crystal form is relatively complete; the surface of the vanadium dioxide thin film is relatively flat under a low-magnification SEM morphology microscope, showing relatively good density, and the degree of aggregation of particles on the surface of the vanadium dioxide thin film sample is reduced under a high-magnification microscope, and there are no obvious small particles; the addition of a polymer additive to the vanadium dioxide deposition solution affects the morphology of the vanadium dioxide thin film material, and can effectively improve the bonding force and adhesion strength between the film and the substrate. The vanadium dioxide film does not fall off after being placed for a long time, and the vanadium dioxide film is well bonded to the conductive glass substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the accompanying drawings:

[0021] Figure 1 This is the X-ray diffraction pattern of the indium tin oxide / vanadium dioxide composite film prepared in Example 1 of the present invention.

[0022] Figure 2(a) is a scanning electron photograph of the surface of the indium tin oxide / vanadium dioxide composite film prepared in Example 1 of the present invention at a magnification of 5000 times; Figure 2(b) is a scanning electron photograph of the surface of the indium tin oxide / vanadium dioxide composite film prepared in Example 1 of the present invention at a magnification of 20,000 times.

[0023] Figure 3(a) is a scanning electron photograph of the surface of the tin dioxide / vanadium dioxide composite film prepared in Example 2 of the present invention at a magnification of 500 times; Figure 3(b) is a scanning electron photograph of the surface of the tin dioxide / vanadium dioxide composite film prepared in Example 2 of the present invention at a magnification of 20,000 times.

[0024] Figure 4(a) is a scanning electron photograph of the surface of the indium tin oxide / vanadium dioxide composite film prepared in Example 4 of the present invention at a magnification of 1000 times; Figure 4(b) is a scanning electron photograph of the surface of the indium tin oxide / vanadium dioxide composite film prepared in Example 4 of the present invention at a magnification of 20,000 times. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings:

[0026] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. The specific implementation manner of the present invention is not limited to the embodiments listed below, but also includes any combination of the various specific implementation manners.

[0027] Unless otherwise specified, the experimental methods used in the following embodiments are all conventional methods. The size of the substrate in the following scheme is the size under laboratory conditions, and is not a specific limitation on the size of the substrate in the technical solution of the present invention. The size of the substrate in actual processing can be determined according to actual needs, and the scheme of the present invention is also applicable.

[0028] Unless otherwise specified, the experimental drugs and reagents in the following examples can be obtained through commercial channels.

[0029] The specific steps include:

[0030] Step (1), cleaning of the substrate: ultrasonically cleaning a conductive glass substrate (size 20 mm × 20 mm × 1.1 mm) with acetone for 10 min to 15 min, ultrasonically cleaning with anhydrous ethanol for 10 min to 20 min, and ultrasonically cleaning with deionized water for 20 min to 30 min, and then drying with a hair dryer for later use; the conductive glass substrate is ITO conductive glass, FTO conductive glass, or sapphire glass.

[0031] Step (2): the components of the vanadium dioxide deposition liquid include vanadium dioxide powder, a polymer additive, and an organic solvent; the vanadium dioxide powder is added to a mixed solvent of one or more strongly polar organic solvents such as methanol, ethanol, isopropanol, or acetone, or a mixed solvent with water to form a 0.1 g / L to 10 g / L mixed liquid, and the mixture is continuously stirred at a stirring rate of 200 r / min to 500 r / min for 30 min to 100 min; a polymer additive selected from one of polyvinyl pyrrolidone (PVP), polyvinyl chloride (PVC), or triethanolamine (TEA) that can be used as a binder / dispersant / film-forming agent to improve the adhesion of the membrane base is added, with a weight percentage of 1% to 15% of the weight of the vanadium dioxide powder, and the polymer additive can be added in stages at a stirring rate of 200 r / min to 500 r / min for 30 min to 100 min; 0.5 mmol / L to 3 mmol / L of iodine is added and ultrasonically dispersed for 30 min to 80 min to obtain the vanadium dioxide deposition liquid.

[0032] Step (3) uses the vanadium dioxide deposition solution obtained in step (2) to prepare a vanadium dioxide thin film by electrophoretic deposition on a conductive glass substrate using a two-electrode device. The conductive glass substrate uses an ITO conductive glass substrate, an FTO conductive glass substrate, or a sapphire glass substrate. A constant voltage cathode electrophoretic deposition method is used, and the two electrodes are graphite and a conductive glass substrate, respectively. The conductive glass substrate serves as the cathode, and the graphite sheet (larger than the conductive glass substrate) serves as the anode. The spacing between the electrode pieces is 20 mm to 30 mm, the deposition voltage is 5 V to 50 V, and the deposition time is 1 min to 7 min.

[0033] Step (4), film drying: When the vanadium dioxide film is heat-treated, it is dried in a vacuum drying oven at 15°C to 85°C for 10 minutes to 60 minutes.

[0034] Example 1

[0035] The method for preparing the vanadium dioxide thin film and thin film material of this embodiment includes the following steps:

[0036] Step (1), cleaning of the substrate: an ITO conductive glass substrate with a size of 20 mm × 20 mm × 1.1 mm was ultrasonically cleaned with acetone for 15 min, anhydrous ethanol for 15 min, and deionized water for 25 min, and then dried with a hair dryer for later use.

[0037] Step (2), preparation of a vanadium dioxide deposition liquid: weighing 0.21 g of vanadium dioxide powder and placing it into 210 mL of acetone solvent to prepare a suspension with a concentration of 1.0 g / L and continuously stirring at a stirring rate of 400 r / min for 50 min; adding 10% by weight of polyvinylpyrrolidone (PVP) thereto at a stirring rate of 400 r / min for 80 min; adding 0.080 g of iodine and ultrasonically dispersing it for 60 min to obtain a vanadium dioxide deposition liquid.

[0038] Step (3), using the vanadium dioxide deposition solution prepared in step (2) to prepare a vanadium dioxide thin film: a constant voltage cathode electrophoretic deposition method is used, with a graphite sheet (larger than the conductive glass substrate) as the anode and an ITO conductive glass substrate as the cathode for electrophoretic deposition to prepare the vanadium dioxide thin film, the spacing between the electrodes is 25 mm, the deposition voltage is 30 V, and the deposition time is 2 min.

[0039] Step (4), film drying: When the vanadium dioxide film is heat-treated, it is dried in a vacuum drying oven at 40° C. for 40 minutes.

[0040] The X-ray diffraction pattern and SEM morphology of the indium tin oxide / vanadium dioxide composite film prepared in this embodiment are as follows: Figure 1 , as shown in Figure 2(a) and Figure 2(b). Figure 1 It can be seen that the peak position of the film prepared in this example is consistent with the vanadium dioxide standard card (JCPDS: 82-0661). Overall, the sample surface is smooth and well bonded to the ITO conductive glass substrate. The film does not fall off after being placed for a long time. Figure 1 The main characteristic peaks of the film are relatively sharp, indicating good crystallinity and a relatively complete crystal structure. The SEM images in Figures 2(a) and 2(b) show that the film surface is relatively flat and free of holes at low magnification, demonstrating good compactness. High magnification reveals low aggregation of particles on the film surface, with no visible small particles.

[0041] Example 2

[0042] The method for preparing the vanadium dioxide thin film and thin film material of this embodiment includes the following steps:

[0043] Step (1), cleaning of the substrate: an FTO conductive glass substrate with a size of 20 mm × 20 mm × 1.1 mm was ultrasonically cleaned with acetone for 15 min, anhydrous ethanol for 15 min, and deionized water for 25 min, and then dried with a hair dryer for later use.

[0044] Step (2), preparation of a vanadium dioxide deposition liquid: weighing 1.0 g of vanadium dioxide powder and placing it into 100 mL of acetone solvent to prepare a suspension with a concentration of 10 g / L and continuously stirring at a stirring rate of 350 r / min for 45 minutes; adding 6% by weight of polyvinyl chloride (PVC) thereto at a stirring rate of 350 r / min for 80 minutes; adding 0.025 g of iodine and ultrasonically dispersing it for 75 minutes to obtain a vanadium dioxide deposition liquid.

[0045] Step (3), using the vanadium dioxide deposition solution prepared in step (2) to prepare a vanadium dioxide thin film: a constant voltage cathode electrophoretic deposition method is adopted, with a graphite sheet (larger than the conductive glass substrate) as the anode and an FTO conductive glass substrate as the cathode for electrophoretic deposition to prepare the vanadium dioxide thin film, the spacing between the electrodes is 30 mm, the deposition voltage is 25 V, and the deposition time is 2.5 min.

[0046] Step (4), film drying: When the vanadium dioxide film is heat-treated, it is dried in a vacuum drying oven at 55° C. for 50 minutes.

[0047] The SEM morphologies of the tin dioxide / vanadium dioxide composite thin film prepared in this example are shown in Figures 3(a) and 3(b). The film sample adheres well to the FTO conductive glass substrate and does not detach even after prolonged exposure. The images show a smooth surface and good density at low magnification. At higher magnification, the film sample exhibits a sparse distribution of increasing particle size and distinct particle boundaries.

[0048] Example 3

[0049] The method for preparing the vanadium dioxide thin film and thin film material of this embodiment includes the following steps:

[0050] Step (1), cleaning of the substrate: an ITO conductive glass substrate with a size of 20 mm × 20 mm × 1.1 mm was ultrasonically cleaned with acetone for 15 min, anhydrous ethanol for 15 min, and deionized water for 25 min, and then dried with a hair dryer for later use.

[0051] Step (2), preparation of a vanadium dioxide deposition liquid: weighing 0.015 g of vanadium dioxide powder and placing it into 150 mL of acetone solvent to prepare a suspension with a concentration of 0.1 g / L and continuously stirring at a stirring rate of 450 r / min for 30 min; adding 1% by weight of triethanolamine (TEA) thereto at a stirring rate of 450 r / min for 50 min; adding 0.114 g of iodine and ultrasonically dispersing the suspension for 90 min to obtain a vanadium dioxide deposition liquid.

[0052] Step (3), using the vanadium dioxide deposition solution prepared in step (2) to prepare a vanadium dioxide thin film: a constant voltage cathode electrophoretic deposition method is used, with a graphite sheet (larger than the conductive glass substrate) as the anode and an FTO conductive glass substrate as the cathode for electrophoretic deposition to prepare the vanadium dioxide thin film, the spacing between the electrodes is 20 mm, the deposition voltage is 5 V, and the deposition time is 7 min.

[0053] Step (4), film drying: When the vanadium dioxide film is heat-treated, it is dried in a vacuum drying oven at 40° C. for 45 minutes.

[0054] The tin dioxide / vanadium dioxide composite film prepared in this embodiment is well bonded to the FTO conductive glass substrate. Overall, the surface of the film sample is relatively smooth without cracking, and the film is not likely to fall off after being placed for a long time.

[0055] Example 4

[0056] The method for preparing the vanadium dioxide thin film and thin film material of this embodiment includes the following steps:

[0057] Step (1), cleaning of the substrate: an ITO conductive glass substrate with a size of 20 mm × 20 mm × 1.1 mm was ultrasonically cleaned with acetone for 15 min, anhydrous ethanol for 15 min, and deionized water for 25 min, and then dried with a hair dryer for later use.

[0058] Step (2), preparation of a vanadium dioxide deposition liquid: weighing 1.12 g of vanadium dioxide powder and placing it into 200 mL of acetone solvent to prepare a suspension with a concentration of 5.6 g / L and continuously stirring at a stirring rate of 500 r / min for 60 min; adding 15% by weight of polyvinylpyrrolidone (PVP) thereto at a stirring rate of 500 r / min for 80 min; adding 0.100 g of iodine and ultrasonically dispersing the suspension for 65 min to obtain a vanadium dioxide deposition liquid.

[0059] Step (3), using the vanadium dioxide deposition solution prepared in step (2) to prepare a vanadium dioxide thin film: a constant voltage cathode electrophoretic deposition method is used, with a graphite sheet (larger than the conductive glass substrate) as the anode and an ITO conductive glass substrate as the cathode for electrophoretic deposition to prepare the vanadium dioxide thin film, the spacing between the electrodes is 20 mm, the deposition voltage is 50 V, and the deposition time is 1.5 min.

[0060] Step (4), film drying: When the vanadium dioxide film is heat-treated, it is dried in a vacuum drying oven at 40° C. for 45 minutes.

[0061] The SEM morphologies of the indium tin oxide / vanadium dioxide composite film prepared in this example are shown in Figures 4(a) and 4(b). The images show a relatively smooth surface and good compactness at low magnification. High magnification reveals reduced particle aggregation on the film sample surface, with no visible small particles.

[0062] Comparative Example

[0063] The method for preparing the vanadium dioxide thin film and thin film material of this embodiment includes the following steps:

[0064] Step (1), cleaning of the substrate: an ITO conductive glass substrate with a size of 20 mm × 20 mm × 1.1 mm was ultrasonically cleaned with acetone for 15 min, anhydrous ethanol for 15 min, and deionized water for 25 min, and then dried with a hair dryer for later use.

[0065] Step (2), preparation of a vanadium dioxide deposition liquid: weighing 0.19 g of vanadium dioxide powder and placing it in 75 mL of acetone solvent to prepare a suspension with a concentration of 2.5 g / L and continuously stirring at a stirring rate of 400 r / min for 50 min; adding 0.029 g of iodine and ultrasonically dispersing it for 60 min to obtain a vanadium dioxide deposition liquid.

[0066] Step (3), using the vanadium dioxide deposition solution prepared in step (2) to prepare a vanadium dioxide thin film: a constant voltage cathode electrophoretic deposition method is used, with a graphite sheet (larger than the conductive glass substrate) as the anode and an ITO conductive glass substrate as the cathode for electrophoretic deposition to prepare the vanadium dioxide thin film, the spacing between the electrodes is 25 mm, the deposition voltage is 30 V, and the deposition time is 2 min.

[0067] Step (4), film drying: When the vanadium dioxide film is heat-treated, it is dried in a vacuum drying oven at 40° C. for 40 minutes.

[0068] The indium tin oxide / vanadium dioxide composite film prepared in this embodiment has a smooth surface overall, but the film sample has poor bonding strength with the ITO conductive glass substrate, and is prone to peeling and instability at the edges. The film will fall off if left for a long time.

[0069] The vanadium dioxide thin film material prepared by the present invention is prepared by combining an electrophoretic deposition method with vanadium dioxide powder, a polymer additive and an organic solvent as components of a deposition liquid. The addition of the polymer additive to the vanadium dioxide deposition liquid affects the morphology of the vanadium dioxide thin film material, and the film-base bonding strength is better than that of the vanadium dioxide film prepared without adding the additive.

[0070] The present invention first prepares a vanadium dioxide deposition liquid to prepare for the subsequent preparation of a vanadium dioxide thin film material, thereby improving the adhesion between the thin film and the substrate. Then, an electrophoretic deposition method is used to prepare the vanadium dioxide thin film. By combining the advantages of the electrophoretic deposition method, uniform distribution and uniform doping of the material microstructure can be achieved. Deposition is performed at room temperature, and a low deposition temperature can avoid phase change of the material under high temperature conditions. The equipment requirements are simple, the film formation is fast, the film thickness is uniform, and the thickness is controllable within a large range.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art may still modify or make equivalent substitutions to the specific implementations of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A method for preparing a vanadium dioxide thin film, characterized in that: The specific steps are as follows: Vanadium dioxide powder is added to an organic solvent and mixed uniformly to form a mixed solution with a concentration of 0.1 g / L to 10 g / L, a polymer additive is added thereto in an amount of 1% to 15% by weight of the vanadium dioxide powder and mixed uniformly to obtain a suspension, and iodine is added to the suspension and mixed uniformly to obtain a vanadium dioxide precipitation solution; The vanadium dioxide deposition solution is deposited on a conductive glass substrate by an electrophoretic deposition method, and the deposited film is a vanadium dioxide film; The polymer additive is polyvinyl pyrrolidone, polyvinyl chloride or triethanolamine; The concentration of iodine in the vanadium dioxide sediment solution is 0.5mmol / L~3mmol / L; The electrophoretic deposition method adopts a constant voltage cathode electrophoretic deposition method, with a conductive glass substrate as the cathode and a graphite sheet as the anode. The electrode spacing is 20mm~30mm, the deposition voltage is 5V~50V, and the deposition time is 1min~7min.

2. The method for preparing a vanadium dioxide thin film according to claim 1, wherein: The organic solvent is a mixed solvent of one or more of methanol, ethanol, isopropanol or acetone or a mixed solvent with water.

3. The method for preparing a vanadium dioxide thin film according to claim 1, wherein: The conductive glass substrate adopts an ITO conductive glass substrate, an FTO conductive glass substrate or a sapphire glass substrate.

4. A vanadium dioxide thin film, characterized in that The vanadium dioxide thin film is prepared by the preparation method of any one of claims 1 to 3.

5. A method for preparing a vanadium dioxide thin film material, characterized in that: The vanadium dioxide thin film material is obtained by heat-treating the vanadium dioxide thin film according to claim 4.

6. The method for preparing a vanadium dioxide thin film material according to claim 5, characterized in that: The heat treatment is to dry the vanadium dioxide film in a vacuum drying oven at 15°C to 85°C for 10min to 60min.

7. A vanadium dioxide thin film material obtained by the preparation method according to claim 5, characterized in that: The invention comprises a conductive glass substrate and a vanadium dioxide film deposited on the conductive glass substrate.

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