One-step chemical synthesis method of W-VO2 (M) nanoparticles and application of W-VO2 (M) nanoparticles in thermochromic intelligent window

Abstract

The invention belongs to the technical field of building glass and coating materials thereof, and discloses a one-step chemical synthesis method of W-VO2 (M) nano-particles and application of the W-VO2 (M) nano-particles in thermochromic smart windows.The method comprises the steps that firstly, ammonium metavanadate, hydrazine hydrate and ammonium metatungstate serve as raw materials, tungsten-doped M-phase vanadium dioxide nano-particles are chemically synthesized through a one-step hydrothermal method, and the tungsten-doped M-phase vanadium dioxide nano-particles are prepared; the obtained W-VO2 (M) nanoparticles are high in crystallinity, small in particle size (10-40nm), high in purity and low in phase change temperature; then, by taking a polyvinylpyrrolidone material as a parent material, uniformly distributing the W-VO2 (M) nanoparticles in PVP (Polyvinyl Pyrrolidone) to form a uniformly dispersed thin film; according to the application of the W-VO2 (M) nanoparticles in the thermochromic intelligent window, not only can high visible light transmittance be obtained, but also the solar energy regulation and control capability of the W-VO2 (M) nanoparticles can be improved, and the application of the W-VO2 (M) nanoparticles in the fields of the thermochromic intelligent window and radiation refrigeration is further promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of architectural glass and its coating materials, and specifically, relates to a method for preparing tungsten-doped M-phase vanadium dioxide (W-VO2(M)) nanoparticles in one step based on a chemical synthesis method, and application of the prepared M-phase vanadium dioxide (W-VO2(M)) nanoparticles in thermochromic smart windows. Background Art

[0002] The "2022 Global Construction Industry Status Analysis Report" points out that building energy consumption accounts for nearly one-third of the world's total energy consumption, and will grow at an annual rate of 1.3% in the next three decades. Windows are an indispensable part of building enclosure structures and have the functions of lighting and ventilation. However, ordinary glass cannot regulate the transmittance of sunlight and has a high thermal emissivity, resulting in a large amount of heat loss and serious energy loss. Therefore, by improving the visible light transmittance and modulation ability of architectural glass in the solar spectrum band, regulating the heat exchange between architectural glass and the outside world, and reducing heating and cooling energy consumption, it will help reduce building operation energy consumption and help achieve the country's "dual carbon" goals.

[0003] In order to reduce the operating energy consumption of architectural glass, researchers have proposed the concept of "smart windows". This structure can achieve dynamic control of light by responding to external stimuli. According to different external stimulus sources, smart windows are divided into four types: photochromic smart windows, gas-chromic smart windows, electrochromic smart windows and thermochromic smart windows. Among them, thermochromism refers to the phenomenon that the transmittance of the film changes in response to the ambient temperature. After the external temperature of thermochromic semiconductor materials changes, the color of the film itself will not change much, but its transmittance in the near-infrared band will suddenly change near the critical temperature. Most solar radiation is concentrated in the near-infrared band. Therefore, this type of material can meet the energy-saving needs while ensuring the lighting effect, and use temperature as an external stimulus without additional stimulus energy consumption. Among many inorganic thermochromic materials, the phase transition temperature of M-phase vanadium dioxide (VO2(M)) is the closest to room temperature, and has a very large application prospect.

[0004] VO2(M) nanoparticles undergo a transition from semiconductor phase to metallic phase at ~68°C, and their carrier concentration increases suddenly. Due to their unique optical regulation properties before and after the phase transition and the localized surface plasmon resonance absorption characteristics of the metallic state, they have become thermochromic smart window functional materials with broad application prospects in the field of building energy conservation. However, VO2(M) nanoparticles are easy to aggregate and have a high phase transition temperature. How to prepare VO2(M) nanoparticles with high dispersion, low phase transition temperature, easy production, and good optical properties through simple and inexpensive methods has become a research hotspot. W doping is an effective method to reduce the phase transition temperature of VO2(M). By adjusting the W doping ratio, VO2(M) nanoparticles with different phase transition temperatures can be obtained. At a suitable doping ratio, the phase transition temperature can be reduced to room temperature.

[0005] The main preparation methods of W-VO2(M) nanoparticles include liquid phase method, solid phase method, gel sol method and thermal decomposition method. Among them, the liquid phase method can change the physicochemical properties of the substance under high temperature and high pressure to obtain nanoparticles with small particle size, high crystallinity and complete crystal morphology. By changing the reaction time, reaction temperature, pH value and other parameters of the reaction system, the morphology, crystal type, size, etc. of the product can be adjusted, thereby preparing W-VO2(M) nanopowders with good performance.

[0006] Patent application document CN116102063B discloses a method for preparing VO2(M) nanoparticles by thermal decomposition of vanadyl sulfate, including preparing vanadium acetate powder using vanadyl sulfate; and preparing M-phase vanadium dioxide powder using vanadyl acetate powder. However, this method requires a subsequent high-temperature annealing process, which is complicated and has a high phase transition temperature, and cannot meet the actual application requirements of smart windows.

[0007] Patent application document CN112125338A provides a method for synthesizing nano VO2(M) by solvothermal method, wherein an organic solvent (one of toluene, tetrahydrofuran, dioxane, N,N-dimethylformamide or dimethyl sulfoxide), vanadyl acetate and morphology modifier oleic acid are mixed evenly to form a uniform solution, and then reacted at 130-260°C for 4-24h. However, the method is cumbersome, and the organic solvent involved in the experiment is highly toxic (highly toxic and carcinogenic), the nanopowder particles formed are large in size (50-100nm), and the phase transition temperature is high, which is not conducive to improving the modulation ability of smart windows. Summary of the invention

[0008] The technical problem to be solved by the present invention is that the VO2(M) nanoparticles prepared by the existing hydrothermal method have large particle size, complicated preparation method (secondary annealing), high phase transition temperature, and cannot meet the application requirements of thermochromic smart windows with high dispersion and high particle size requirements. Tungsten-doped M-phase vanadium dioxide (W-VO2(M)) nanoparticles that meet the requirements are prepared by a simple one-step hydrothermal method, and polyvinyl pyrrolidone (PVP) material is used as the matrix material to uniformly distribute the VO2(M) nanoparticles in PVP to form a uniformly dispersed thin film. The application of the tungsten-doped M-phase vanadium dioxide (W-VO2(M)) nanoparticles in thermochromic smart windows can not only obtain high visible light transmittance, but also increase its solar energy regulation capability.

[0009] According to one aspect of the present invention, there is provided a W-VO2(M) nanoparticle, using NH4VO3 as a vanadium source, N2H4·H2O as a reducing agent, (NH4)6H2W 12 O 40 xH2O was used as W source to synthesize W-VO2(M); it was obtained by a one-step chemical synthesis method according to the following steps:

[0010] S1, NH4VO3 and (NH4)6H2W 12 O 40 xH2O is dissolved in deionized water and heated to boiling under magnetic stirring, then N2H4·H2O is added to the solution, and the solution is kept boiling and stirred evenly to obtain a mixed solution;

[0011] S2. Adjust the volume of the mixed solution obtained in S1 with deionized water, stir it evenly and pour it into a high-temperature and high-pressure reactor to make the filling degree of the high-temperature and high-pressure reactor 60%-80%; react at 260-280°C for 30-48h, wait for the high-temperature and high-pressure reactor to cool to room temperature, wash the reaction product for multiple times, collect the precipitate by centrifugation, and dry it to obtain W-VO2(M) nanoparticles with a W doping amount of 1.0-3.0%, wherein the W doping amount refers to the molar ratio of W / (V+W).

[0012] According to another aspect of the present invention, a one-step chemical synthesis method of W-VO2(M) nanoparticles is provided, using NH4VO3 as a vanadium source, N2H4·H2O as a reducing agent, (NH4)6H2W 12 O 40 xH2O was used as W source to synthesize W-VO2(M); the steps were as follows:

[0013] S1, NH4VO3 and (NH4)6H2W 12 O 40xH2O is dissolved in deionized water and heated to boiling under magnetic stirring, then N2H4·H2O is added to the solution, and the solution is kept boiling and stirred evenly to obtain a mixed solution;

[0014] S2. Adjust the volume of the mixed solution obtained in S1 with deionized water, stir it evenly and pour it into a high-temperature and high-pressure reactor to make the filling degree of the high-temperature and high-pressure reactor 60%-80%; react at 260-280°C for 30-48h, wait for the high-temperature and high-pressure reactor to cool to room temperature, wash the reaction product for multiple times, collect the precipitate by centrifugation, and dry it to obtain W-VO2(M) nanoparticles with a W doping amount of 1.0-3.0%, wherein the W doping amount refers to the molar ratio of W / (V+W).

[0015] In the above-mentioned W-VO2(M) nanoparticles and preparation method thereof:

[0016] Furthermore, the molar ratio of NH4VO3 to N2H4·H2O in S1 is 8:(1-3).

[0017] Preferably, the drying in S2 is carried out in an oven at 60° C. for 12 h.

[0018] According to another aspect of the present invention, a thermochromic smart window is provided, which is obtained by the following preparation method:

[0019] (1) placing the W-VO2(M) nanoparticles in anhydrous ethanol and performing ultrasonic dispersion for later use;

[0020] (2) adding PVP as a dispersant to the dispersion obtained in step (1), stirring after ultrasonication, and standing for later use;

[0021] (3) Applying the upper layer solution of the W-VO2(M) & PVP dispersion obtained in step (2) to the surface of the pretreated glass substrate to obtain a thermochromic smart window.

[0022] According to another aspect of the present invention, there is provided an application of the above-mentioned W-VO2(M) nanoparticles in a thermochromic smart window, which is carried out according to the following steps:

[0023] (1) placing W-VO2(M) nanoparticles in anhydrous ethanol and ultrasonically dispersing them for later use;

[0024] (2) adding PVP as a dispersant to the dispersion obtained in step (1), stirring after ultrasonication, and standing for later use;

[0025] (3) Applying the upper layer solution of the W-VO2(M) & PVP dispersion obtained in step (2) to the surface of the pretreated glass substrate to obtain a thermochromic smart window.

[0026] In the application of the above-mentioned W-VO2(M) nanoparticles in thermochromic smart windows, and in the thermochromic smart windows prepared using the W-VO2(M) nanoparticles:

[0027] The pretreatment in step (3) includes: firstly, ultrasonically cleaning the glass substrate in an acetone solution, then ultrasonically cleaning the glass substrate in anhydrous ethanol, and finally ultrasonically cleaning the glass substrate in deionized water, and then drying the glass substrate for later use.

[0028] The coating in step (3) includes: firstly dropping the upper layer of W-VO2(M)&PVP solution onto the surface of the pretreated glass substrate, then using a spin coater to spin coat, first at a low speed, then at a high speed, and finally drying for use.

[0029] The beneficial effects of the present invention are:

[0030] The present invention provides a preparation method of W-VO2(M) nanoparticles by using ammonium metavanadate, hydrazine hydrate and ammonium metatungstate as raw materials and chemically synthesizing them by a one-step hydrothermal method. The obtained W-VO2(M) nanoparticles have high crystallinity, small particle size (10-40nm), high purity and low phase transition temperature. The thermochromic smart window made by using the W-VO2(M) nanoparticles prepared by the present invention can maintain a high near-infrared solar modulation rate in addition to its high visible light transmittance, further promoting the application of W-VO2(M) nanoparticles in the field of thermochromic smart windows and radiation refrigeration, and promoting the reduction of building operation energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of SEM of W-VO2(M) nanoparticles prepared according to an embodiment of the present invention; (a) SEM schematic diagram; (b) particle size statistics.

[0032] Figure 2 Schematic diagram of XRD of W-VO2(M) nanoparticles prepared according to an embodiment of the present invention.

[0033] Figure 3 This is a high and low temperature transmission spectrum of the thermochromic cooling smart window film prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and drawings.

[0035] Step 1: Raw material selection

[0036] The present invention adopts commercial ammonium metavanadate (NH4VO3) as vanadium source, hydrazine hydrate (N2H4·H2O, 80%) as reducing agent, PVP (K30) as dispersant, ammonium metatungstate ((NH4)6H2W 12 O 40 ·xH2O, 99%) was used as W source for the synthesis of W-VO2(M).

[0037] Step 2: Preparation of hydrothermal reaction solution precursor

[0038] Take 4g of NH4VO3 and an appropriate amount of (NH4)6H2W 12 O 40 ·xH2O was dissolved in 40 ml of deionized water and heated to boiling under magnetic stirring. Then, 0.42 ml of 80% by volume N2H4·H2O was added to the solution. The solution was kept boiling and stirred evenly to form a brown-black solution.

[0039] Step 3: Chemical synthesis reaction

[0040] The solution was adjusted to 80 ml with deionized water, stirred evenly, and poured into a 100 ml high temperature and high pressure reactor, and reacted at 280° C. for 36 hours. In the present invention, the filling degree of the high temperature and high pressure reactor is 60%-80%.

[0041] After the reactor was cooled to room temperature, the black precipitate was washed alternately with ethanol and deionized water for multiple times, the precipitate was collected by centrifugation, and dried in an oven at 60° C. for 12 h to obtain W-VO2(M) nanoparticles with a doping ratio of 1.0 at %.

[0042] Step 4: Slide cleaning

[0043] This experiment uses a commercial glass slide as the substrate, with a size of 2.0×2.0 cm and a thickness of 5 mm. First, the glass slide substrate is ultrasonically cleaned in an acetone solution for 15 minutes, then ultrasonically cleaned in anhydrous ethanol for 15 minutes, and finally ultrasonically cleaned in deionized water for 15 minutes, and then dried for use.

[0044] Step 5: Preparation of W-VO2(M) nanoparticle solution

[0045] 50 mg of W-VO2(M) nanoparticles were poured into a screw-cap bottle containing 5 ml of anhydrous ethanol, and ultrasonically dispersed at 60°C for 30 min for later use.

[0046] Step 6: Preparation of W-VO2(M) & PVP solution

[0047] In order to further form a highly dispersed W-VO2(M) nanoparticle solution, 1 g of polyvinyl pyrrolidone PVP(K30) was added to the above solution, and ultrasonication was continued for 1 h. Finally, the solution was stirred for 3 h using a magnetic stirrer and then allowed to stand for 24 h for use.

[0048] During the whole experiment, the solution was sealed with a screw-cap bottle to prevent ethanol evaporation.

[0049] Step 7: Preparation of W-VO2(M) & PVP composite film

[0050] Use a pipette to measure 100 μL of the supernatant of the W-VO2(M)&PVP solution and drop it on the surface of the glass slide substrate pretreated in step 4, then use a gel coater to spin coat it, first at a low speed of 800 r / min for 10 s, then at a high speed of 2000 r / min for 20 s, and finally dry it at 60°C for use.

[0051] according to Figure 1 From the SEM image, we can see that the prepared W-VO2(M) nanoparticles have a good morphology. By calculating 100 particles, the average size of the prepared nanoparticles is 25nm, and they are distributed in the range of 10nm to 40nm. Figure 2 The XRD results show that the W-VO2(M) nanoparticles have a high diffraction peak intensity, which proves that the product has high crystallinity. The film was tested at high and low temperatures in the wavelength range of 300nm to 2500nm by a spectrophotometer. The high and low temperature transmission spectra are shown in the figure below. Figure 3 As shown in the figure, the smart glass can achieve a modulation rate of 9.26% in the near-infrared band (780nm~2500nm) while ensuring a visible light transmittance of 49.82%, meeting the use requirements of smart windows. The above analysis shows that this method can achieve the one-step preparation of W-VO2(M) nanoparticles with small particle size, high crystallinity and good phase change performance.

[0052] The technical solutions disclosed and proposed by the present invention can be realized by those skilled in the art by referring to the contents of this article and appropriately changing the conditions, routes and other links. Although the methods and preparation techniques of the present invention have been described through preferred embodiments, relevant technicians can obviously modify or re-combine the methods and technical routes described herein without departing from the content, spirit and scope of the present invention to realize the final preparation technology. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the spirit, scope and content of the present invention.

Claims

1. A one-step chemical synthesis method of W-VO2(M) nanoparticles, characterized in that: NH4VO3 was used as vanadium source, N2H4·H2O as reducing agent, (NH4)6H2W 12 O 40 xH2O was used as W source to synthesize W-VO2(M); the steps were as follows: S1, NH4VO3 and (NH4)6H2W 12 O 40 xH2O is dissolved in deionized water and heated to boiling under magnetic stirring, then N2H4·H2O is added to the solution, and the solution is kept boiling and stirred evenly to obtain a mixed solution; S2. Adjust the volume of the mixed solution obtained in S1 with deionized water, stir it evenly and pour it into a high-temperature and high-pressure reactor to make the filling degree of the high-temperature and high-pressure reactor 60%-80%; react at 260-280°C for 30-48h, wait for the high-temperature and high-pressure reactor to cool to room temperature, wash the reaction product for multiple times, collect the precipitate by centrifugation, and dry it to obtain W-VO2(M) nanoparticles with a W doping amount of 1.0-3.0%, wherein the W doping amount refers to the molar ratio of W / (V+W).

2. A one-step chemical synthesis method of W-VO2(M) nanoparticles according to claim 1, characterized in that: The molar ratio of NH4VO3 and N2H4·H2O in S1 is 8:(1-3).

3. A one-step chemical synthesis method of W-VO2(M) nanoparticles according to claim 1, characterized in that: The drying in S2 is carried out in an oven at 60°C for 12 h.

4. A W-VO2(M) nanoparticle, characterized in that: The method is obtained by the preparation method described in any one of claims 1 to 3.

5. A use of W-VO2(M) nanoparticles as claimed in claim 4 in thermochromic smart windows, characterized in that: Follow these steps: (1) placing W-VO2(M) nanoparticles in anhydrous ethanol and ultrasonically dispersing them for later use; (2) adding PVP as a dispersant to the dispersion obtained in step (1), stirring after ultrasonication, and standing for later use; (3) Applying the upper layer solution of the W-VO2(M) & PVP dispersion obtained in step (2) to the surface of the pretreated glass substrate to obtain a thermochromic smart window.

6. The use of W-VO2(M) nanoparticles in thermochromic smart windows according to claim 5, characterized in that: The pretreatment in step (3) includes: firstly, ultrasonically cleaning the glass substrate in an acetone solution, then ultrasonically cleaning the glass substrate in anhydrous ethanol, and finally ultrasonically cleaning the glass substrate in deionized water, and then drying the glass substrate for later use.

7. The use of W-VO2(M) nanoparticles in thermochromic smart windows according to claim 5, characterized in that: The coating in step (3) includes: firstly dropping the upper layer solution of W-VO2(M)&PVP dispersion onto the surface of the pretreated glass substrate, then using a coating machine for spin coating, first rotating at a low speed, then rotating at a high speed, and finally drying for use.

8. A thermochromic smart window, characterized in that: Obtained by the use according to any one of claims 5-7.

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