阅读说明：本技术 一种提钒溶液制备钛钨共掺杂二氧化钒粉体的方法 (Method for preparing titanium-tungsten co-doped vanadium dioxide powder by using vanadium extraction solution ) 是由 尹翔鹭 杨晓 高荣荣 曾泽华 刘天豪 于 2021-07-16 设计创作，主要内容包括：本发明公开了一种提钒溶液制备钛钨共掺杂二氧化钒粉体的方法,其包括：a、向提钒溶液中加入酸溶液,调节pH值；b、测定提钒溶液中的钒离子浓度,加入还原剂；c、向所述步骤b得到的溶液中加入钨化合物和钛化合物,进行水热反应,分离得到沉淀；d、将所述步骤c得到的沉淀洗涤、干燥后得到钛钨共掺杂二氧化钒粉体。本发明的方法,采用提钒溶液作为钒源,有效降低了成本,通过钨元素掺杂降低了二氧化钒相变温度,同时以钛元素掺杂提高了二氧化钒的光学性质和稳定性,促进了二氧化钒在相变节能领域中的广泛应用。(The invention discloses a method for preparing titanium-tungsten co-doped vanadium dioxide powder by using a vanadium extraction solution, which comprises the following steps: a. adding an acid solution into the vanadium extraction solution, and adjusting the pH value; b. measuring the concentration of vanadium ions in the vanadium extraction solution, and adding a reducing agent; c. b, adding a tungsten compound and a titanium compound into the solution obtained in the step b, carrying out hydrothermal reaction, and separating to obtain a precipitate; d. and c, washing and drying the precipitate obtained in the step c to obtain the titanium-tungsten co-doped vanadium dioxide powder. According to the method, the vanadium extraction solution is used as a vanadium source, so that the cost is effectively reduced, the phase change temperature of vanadium dioxide is reduced by doping tungsten, the optical property and stability of vanadium dioxide are improved by doping titanium, and the vanadium dioxide is promoted to be widely applied in the field of phase change energy conservation.)

1. A method for preparing titanium-tungsten co-doped vanadium dioxide powder by using a vanadium extraction solution is characterized by comprising the following steps:

a. adding an acid solution into the vanadium extraction solution, and adjusting the pH value;

b. measuring the concentration of vanadium ions in the vanadium extraction solution, and adding a reducing agent;

c. b, adding a tungsten compound and a titanium compound into the solution obtained in the step b, carrying out hydrothermal reaction, and separating to obtain a precipitate;

d. and c, washing and drying the precipitate obtained in the step c to obtain the titanium-tungsten co-doped vanadium dioxide powder.

2. The method for preparing titanium-tungsten co-doped vanadium dioxide powder from the vanadium extraction solution according to claim 1, wherein in the step a, the vanadium extraction solution is a pentavalent vanadium solution.

3. The method for preparing the titanium-tungsten co-doped vanadium dioxide powder from the vanadium extraction solution according to claim 2, wherein the vanadium extraction solution is at least one selected from a sodium vanadium extraction solution, a calcified vanadium extraction solution or a failed vanadium battery positive electrolyte.

4. The method for preparing titanium-tungsten co-doped vanadium dioxide powder from the vanadium extraction solution according to claim 1, wherein in the step a, the acid solution is hydrochloric acid or sulfuric acid, and the pH value is adjusted to 1-5.

5. The method for preparing titanium-tungsten co-doped vanadium dioxide powder from the vanadium extraction solution according to claim 1, wherein in the step b, the reducing agent is at least one selected from hydrazine hydrate, hydrazine hydrochloride, oxalic acid, ascorbic acid, phenethylamine, glycerol, ethanol or sodium bisulfite; the molar ratio of the vanadium ions to the reducing agent is 0.5-3.

6. The method for preparing titanium-tungsten co-doped vanadium dioxide powder from the vanadium extraction solution according to claim 1, wherein in the step c, the tungsten compound is at least one selected from ammonium tungstate, tungsten oxide or tungstic acid, and the titanium compound is at least one selected from titanium tetrachloride, titanyl sulfate, titanium oxide or titanic acid.

7. The method for preparing titanium-tungsten co-doped vanadium dioxide powder from the vanadium extraction solution according to claim 1, wherein in the step c, the tungsten element and the titanium element are respectively 0.5-30% of the total molar amount of the vanadium element.

8. The method for preparing titanium-tungsten co-doped vanadium dioxide powder from the vanadium extraction solution as recited in claim 1, wherein in the step c, the hydrothermal reaction temperature is 240-350 ℃, and the reaction time is 5-72 h; and/or in the step d, the washing is to wash the precipitate with deionized water, ethanol and deionized water respectively, and the drying is vacuum drying or freeze drying.

9. Titanium-tungsten co-doped vanadium dioxide powder, characterized by being prepared by the method of any one of claims 1 to 8.

10. The titanium-tungsten co-doped vanadium dioxide powder according to claim 9, wherein the molar content of titanium or tungsten atoms is 0.5-30% of the molar content of vanadium atoms.

Technical Field

The invention belongs to the technical field of temperature-induced phase change materials, and particularly relates to a method for preparing titanium-tungsten co-doped vanadium dioxide powder by using a vanadium extraction solution.

Background

Vanadium dioxide is one of ideal materials in the field of temperature-induced phase change energy conservation due to the obvious difference of the transmittance of the vanadium dioxide to near infrared light before and after phase change. The vanadium dioxide can not be widely applied due to the defects of high temperature-induced phase transition temperature (68 ℃), poor stability, low visible light transmittance and weak near infrared light regulation and control capability. To address these shortcomings, researchers have proposed numerous solutions, including elemental doping, recombination techniques, introducing defects, structural manipulation, ordered arrays, and the like. Among them, element doping is considered to be the simplest and most efficient method for lowering the phase transition temperature of vanadium dioxide. The phase transition temperature of the vanadium dioxide can be reduced to 20-30 ℃ by doping high valence elements such as Nb, Mo, W, Ta and the like. The larger the element doping ratio, the lower the phase transition temperature. However, elemental doping can lead to distortion damage of the vanadium dioxide crystal structure, which leads to a reduction in optical properties. In addition, since tetravalent vanadium is easily oxidized into pentavalent vanadium, vanadium dioxide is easily changed into vanadium pentoxide to lose phase transition properties. The method effectively improves the stability and optical property of vanadium dioxide, and reduces the phase transition temperature, which is a difficult problem in current research.

Researchers have proposed a multi-element co-doping technology to improve the properties of vanadium dioxide, CN109721102A discloses doping of chromium and tungsten elements, CN103525369A discloses doping of molybdenum and tungsten elements, and CN109502643A discloses doping of boron and magnesium elements. However, these methods have disadvantages such as large energy consumption and low efficiency, and the stability is not improved. For example, CN103525369A discloses a method for preparing molybdenum-tungsten co-doped vanadium dioxide powder, which comprises performing hydrothermal reaction on a precursor at 180-200 ℃ for 5-8 days, and then performing heat preservation at 600-800 ℃ for 2-4 h to obtain molybdenum-tungsten co-doped vanadium dioxide powder. The method has long time consumption and large energy consumption, and is not beneficial to large-scale preparation. At present, vanadium dioxide powder is mainly prepared by using vanadium pentoxide, ammonium metavanadate, vanadyl sulfate and the like as raw materials, and the raw materials are complex in preparation process and high in price, so that the production cost of vanadium dioxide is greatly increased. How to effectively reduce the cost is also a difficult point of current research. Therefore, the existing co-doped vanadium dioxide preparation technology still needs to be improved and developed.

Disclosure of Invention

The present invention is based on the discovery and recognition by the inventors of the following facts and problems: at present, the preparation cost of the doped vanadium dioxide is high, and the preparation method is complex, long in time consumption and large in energy consumption, and is not beneficial to large-scale production. Meanwhile, the stability, optical performance and phase transition temperature of vanadium dioxide are very difficult to regulate and control.

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the embodiment of the invention provides a method for preparing titanium-tungsten co-doped vanadium dioxide powder by using a vanadium extraction solution, the vanadium extraction solution is used as a vanadium source, the cost is effectively reduced, the phase transition temperature of vanadium dioxide is reduced by doping high-valence element tungsten, the optical property of vanadium dioxide is improved by doping titanium, and the stability of vanadium dioxide is improved under the protection of Ti doping elements.

The method for preparing titanium-tungsten co-doped vanadium dioxide powder by using the vanadium extraction solution comprises the following steps:

a. adding an acid solution into the vanadium extraction solution, and adjusting the pH value;

b. measuring the concentration of vanadium ions in the vanadium extraction solution, and adding a reducing agent;

c. b, adding a tungsten compound and a titanium compound into the solution obtained in the step b, carrying out hydrothermal reaction, and separating to obtain a precipitate;

d. and c, washing and drying the precipitate obtained in the step c to obtain the titanium-tungsten co-doped vanadium dioxide powder.

According to the advantages and technical effects brought by the method for preparing the titanium-tungsten co-doped vanadium dioxide powder by using the vanadium extraction solution, 1, the method provided by the embodiment of the invention takes the vanadium extraction solution as a vanadium source, so that the raw materials are easy to obtain, the cost is low, and the production cost is reduced; 2. according to the method provided by the embodiment of the invention, the titanium-tungsten co-doped vanadium dioxide powder is synthesized in situ by adopting a hydrothermal method in one step, so that the process is simple, the large-scale production is easy, the controllability is strong, and the efficiency is high; 3. in the method of the embodiment of the invention, the high-valence element tungsten is doped, so that the phase transition temperature of the vanadium dioxide is reduced, and meanwhile, the optical property of the vanadium dioxide is improved by doping the titanium element; 4. in the method provided by the embodiment of the invention, titanium and tungsten are codoped, the particle size is small, the dispersibility is good, the prepared codoped vanadium dioxide is low in phase change temperature, and the codoped vanadium dioxide has excellent sunlight regulation and control capability, light transmittance and stability, and is beneficial to wide application of the vanadium dioxide in the field of phase change energy conservation.

According to the method for preparing the titanium-tungsten co-doped vanadium dioxide powder by using the vanadium extraction solution, in the step a, the vanadium extraction solution is a pentavalent vanadium solution.

According to the method for preparing the titanium-tungsten co-doped vanadium dioxide powder by using the vanadium extraction solution, the vanadium extraction solution is selected from at least one of a sodium vanadium extraction solution, a calcification vanadium extraction solution or a failure vanadium battery positive electrolyte.

According to the method for preparing the titanium-tungsten co-doped vanadium dioxide powder by using the vanadium extraction solution, in the step a, the acid solution is hydrochloric acid or sulfuric acid, and the pH value is adjusted to 1-5.

According to the method for preparing the titanium-tungsten co-doped vanadium dioxide powder by using the vanadium extraction solution, in the step b, the reducing agent is selected from at least one of hydrazine hydrate, hydrazine hydrochloride, oxalic acid, ascorbic acid, phenethylamine or sodium bisulfite; the molar ratio of the vanadium ions to the reducing agent is 0.5-3.

According to the method for preparing the titanium-tungsten co-doped vanadium dioxide powder from the vanadium extraction solution, in the step c, the tungsten compound is at least one selected from ammonium tungstate, tungsten oxide and tungstic acid, and the titanium compound is at least one selected from titanium tetrachloride, titanyl sulfate, titanium oxide and titanic acid.

According to the method for preparing the titanium-tungsten co-doped vanadium dioxide powder by using the vanadium extraction solution, in the step c, the tungsten element and the titanium element are respectively 0.5-30% of the molar weight of the vanadium element.

According to the method for preparing the titanium-tungsten co-doped vanadium dioxide powder by using the vanadium extraction solution, in the step c, the hydrothermal reaction temperature is 240-350 ℃, and the reaction time is 5-72 h; and/or in the step d, the washing is to wash the precipitate with deionized water, ethanol and deionized water respectively, and the drying is vacuum drying or freeze drying.

The embodiment of the invention also provides titanium-tungsten co-doped vanadium dioxide powder which is prepared by the method provided by the embodiment of the invention.

According to the advantages and technical effects brought by the titanium and tungsten co-doped vanadium dioxide powder disclosed by the embodiment of the invention, the phase transition temperature of vanadium dioxide is reduced by doping with high-valence element tungsten, and meanwhile, the optical property and stability of vanadium dioxide are improved by doping with titanium element, so that the vanadium dioxide is beneficial to wide application in the field of phase transition energy conservation.

According to the titanium-tungsten co-doped vanadium dioxide powder provided by the embodiment of the invention, the molar content of titanium or tungsten atoms accounts for 0.5-30% of the molar content of vanadium atoms.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

The method for preparing titanium-tungsten co-doped vanadium dioxide powder by using the vanadium extraction solution comprises the following steps:

a. adding an acid solution into the vanadium extraction solution, and adjusting the pH value, wherein the acid solution is preferably hydrochloric acid or sulfuric acid, and the pH value is preferably controlled to be 1-5;

b. measuring the concentration of vanadium ions in the vanadium extraction solution, and adding a reducing agent, wherein the reducing agent is preferably at least one selected from hydrazine hydrate, hydrazine hydrochloride, oxalic acid, ascorbic acid, phenethylamine or sodium bisulfite; the molar ratio of the vanadium ions to the reducing agent is 0.5-3;

c. adding a tungsten compound and a titanium compound into the solution obtained in the step b to perform hydrothermal reaction, preferably, the reaction temperature is 240-350 ℃, the reaction time is 5-72h, and separating to obtain a precipitate;

d. and c, washing and drying the precipitate obtained in the step c to obtain the titanium-tungsten co-doped vanadium dioxide powder.

According to the method for preparing the titanium-tungsten co-doped vanadium dioxide powder by using the vanadium extraction solution, the vanadium extraction solution is used as a vanadium source, so that the raw materials are easy to obtain, the cost is low, and the production cost is reduced; according to the method provided by the embodiment of the invention, the titanium-tungsten co-doped vanadium dioxide powder is synthesized in situ by adopting a hydrothermal method in one step, so that the process is simple, the large-scale production is easy, the controllability is strong, and the efficiency is high; in the method of the embodiment of the invention, the high-valence element tungsten is doped, so that the phase transition temperature of the vanadium dioxide is reduced, and meanwhile, the optical property of the vanadium dioxide is improved by doping the titanium element; in the method provided by the embodiment of the invention, titanium and tungsten are codoped, the particle size is small, the dispersibility is good, the prepared codoped vanadium dioxide is low in phase change temperature, and the codoped vanadium dioxide has excellent sunlight regulation and control capability, light transmittance and stability, and is beneficial to wide application of the vanadium dioxide in the field of phase change energy conservation.

According to the method for preparing the titanium-tungsten co-doped vanadium dioxide powder by using the vanadium extraction solution, in the step a, the vanadium extraction solution is a pentavalent vanadium solution, and preferably, the vanadium extraction solution is at least one of a sodium vanadium extraction solution, a calcified vanadium extraction solution or a failed vanadium battery positive electrolyte. The vanadium extraction solution adopted by the embodiment of the invention has low price, and effectively reduces the production cost for preparing the vanadium dioxide powder.

According to the method for preparing the titanium-tungsten co-doped vanadium dioxide powder from the vanadium extraction solution, in the step c, the tungsten compound is at least one selected from ammonium tungstate, tungsten oxide and tungstic acid, and the titanium compound is at least one selected from titanium tetrachloride, titanyl sulfate, titanium oxide and titanic acid. Preferably, the tungsten element and the titanium element are respectively 0.5 to 30 percent of the molar amount of the vanadium element, and more preferably 1 to 10 percent. In the embodiment of the invention, the doping dosage of the tungsten element and the titanium element is optimized, the phase transition temperature of the vanadium dioxide powder is effectively reduced, and the solar light regulation and control capability, the light transmittance and the stability are excellent.

According to the method for preparing the titanium-tungsten co-doped vanadium dioxide powder by using the vanadium extraction solution, in the step d, the washing and drying methods are not particularly limited, preferably, the washing is to wash the precipitate with deionized water, ethanol and deionized water respectively, and the drying is vacuum drying or freeze drying.

The embodiment of the invention also provides titanium-tungsten co-doped vanadium dioxide powder which is prepared by the method provided by the embodiment of the invention. Preferably, the molar content of the titanium or tungsten element atoms is 0.5-30% of the molar content of the vanadium element atoms.

According to the titanium-tungsten co-doped vanadium dioxide powder disclosed by the embodiment of the invention, the high-valence element tungsten is doped, so that the phase change temperature of the vanadium dioxide is reduced, and meanwhile, the titanium element is doped, so that the optical property and stability of the vanadium dioxide are improved, and the titanium-tungsten co-doped vanadium dioxide powder is beneficial to wide application of the vanadium dioxide in the field of phase change energy conservation.

The present invention will be described in detail below with reference to examples and the accompanying drawings.

Example 1

Measuring 70mL of vanadium extraction solution, and adjusting the pH value to 2 by using 10% hydrochloric acid solution by mass fraction; the concentration of pentavalent vanadium ions is 40g/L determined by potentiometric titration, namely the total molar amount of vanadium ions is 0.055 mol. 4mL of hydrazine hydrate (the mass fraction is 85 percent) is slowly added into the solution, namely the molar weight of the reducing agent hydrazine hydrate is 0.068mol, the molar ratio of vanadium ions to the reducing agent is 0.81, and the solution turns blue; sequentially adding 0.42g of ammonium tungstate and 0.21g of titanium tetrachloride solution into the vanadium solution, and uniformly mixing by using ultrasonic waves; transferring the mixed solution into a hydrothermal reaction kettle with the volume of 100 mL; then carrying out hydrothermal reaction for 15h at 280 ℃; after natural cooling, performing high-speed centrifugal separation on the solution; then cleaning the solid precipitate with ethanol and deionized water; and (3) freeze-drying the solid to obtain 2 at% Ti and 3 at% W co-doped vanadium dioxide powder, wherein the doping percentages of Ti and W are calculated by taking the molar weight of V atoms in the product as a base number.

FIG. 1 is a DSC curve of the titanium-tungsten co-doped vanadium dioxide prepared in example 1.

FIG. 2 shows the transmission spectra of the titanium-tungsten co-doped vanadium dioxide prepared in example 1 at 10 ℃ and 80 ℃.

As shown in the figure, the phase transition temperature of the titanium-tungsten co-doped vanadium dioxide prepared in example 1 is 29.1 ℃.

According to the formula Ti ═ phi | (λ)T (λ)/[ integral ] (λ) and Δ Tsol ═ Tsol (T < Tc) -Tsol (T ═ Tsol>Tc), where T represents the transmittance, i represents lum or sol, λ represents the wavelength,as a function of the visual perception of the human eye,represents the solar radiation spectrum,. DELTA.T, at an atmospheric mass of 1.5_solIndicating the solar light control ability, Tc indicates the phase transition temperature. The visible light transmittance is calculated to be 40%, and the sunlight regulation and control rate is about 14%.

The stability test is carried out under the conditions that the temperature is 60 ℃ and the humidity is 80% R.H, after 1000 hours, the sunlight regulation and control capability can be kept to be 90.3% of the original capability, and the stability is excellent.

Example 2

Measuring 70mL of vanadium extraction solution, and adjusting the pH value to 2 by using 10% hydrochloric acid solution by mass fraction; the concentration of pentavalent vanadium ions is 40g/L determined by potentiometric titration, namely the total molar amount of vanadium ions is 0.055 mol. 4mL of hydrazine hydrate (the mass fraction is 85 percent) is slowly added into the solution, namely the molar weight of the reducing agent hydrazine hydrate is 0.068mol, the molar ratio of vanadium ions to the reducing agent is 0.81, and the solution turns blue; sequentially adding 0.28g of ammonium tungstate and 0.10g of titanium tetrachloride solution into the vanadium solution, and uniformly mixing by using ultrasonic waves; transferring the mixed solution into a hydrothermal reaction kettle with the volume of 100 mL; then carrying out hydrothermal reaction for 15h at 280 ℃; after natural cooling, performing high-speed centrifugal separation on the solution; then cleaning the solid precipitate with ethanol and deionized water; and (4) freeze-drying the solid to obtain 1% Ti and 2% W co-doped vanadium dioxide powder.

FIG. 3 is a DSC curve of the titanium tungsten co-doped vanadium dioxide prepared in example 2.

FIG. 4 shows the transmission spectra of the titanium-tungsten-codoped vanadium dioxide prepared in example 2at 10 ℃ and 80 ℃.

As shown in the figure, the phase transition temperature of the titanium-tungsten co-doped vanadium dioxide prepared in the example 2 is 32 ℃. The visible light transmittance is 43 percent and the sunlight regulation and control rate is about 14.7 percent.

The stability test was performed in the same manner as in example 1, and the solar light control ability was maintained at 83.6% after 1000 hours in a high-temperature high-humidity environment.

Example 3

Measuring 70mL of vanadium extraction solution, and adjusting the pH value to 2 by using 10% hydrochloric acid solution by mass fraction; the concentration of pentavalent vanadium ions is 40g/L determined by potentiometric titration, namely the total molar amount of vanadium ions is 0.055 mol. 4mL of hydrazine hydrate (the mass fraction is 85 percent) is slowly added into the solution, namely the molar weight of the reducing agent hydrazine hydrate is 0.068mol, the molar ratio of vanadium ions to the reducing agent is 0.81, and the solution turns blue; sequentially adding 0.14g of ammonium tungstate and 0.10g of titanium tetrachloride solution into the vanadium solution, and uniformly mixing by using ultrasonic waves; transferring the mixed solution into a hydrothermal reaction kettle with the volume of 100 mL; then carrying out hydrothermal reaction for 15h at 280 ℃; after natural cooling, performing high-speed centrifugal separation on the solution; then cleaning the solid precipitate with ethanol and deionized water; and (4) freeze-drying the solid to obtain 1% Ti and 1% W co-doped vanadium dioxide powder.

FIG. 5 is a DSC curve of the titanium tungsten co-doped vanadium dioxide prepared in example 3.

FIG. 6 shows the transmission spectra of the titanium-tungsten-codoped vanadium dioxide prepared in example 3at 10 ℃ and 80 ℃.

As shown in the figure, the phase transition temperature of the titanium-tungsten co-doped vanadium dioxide prepared in the example 3 is 43.5 ℃. The visible light transmittance is 45% and the sunlight regulation and control rate is about 13.2% through calculation.

The stability test was performed in the same manner as in example 1, and the solar light control ability was maintained at 82.4% after 1000 hours in a high-temperature high-humidity environment.

Example 4

Measuring 70mL of vanadium extraction solution, and adjusting the pH value to 2 by using 10% hydrochloric acid solution by mass fraction; the concentration of pentavalent vanadium ions is 40g/L determined by potentiometric titration, namely the total molar amount of vanadium ions is 0.055 mol. 4mL of hydrazine hydrate (the mass fraction is 85 percent) is slowly added into the solution, namely the molar weight of the reducing agent hydrazine hydrate is 0.068mol, the molar ratio of vanadium ions to the reducing agent is 0.81, and the solution turns blue; sequentially adding 0.07g of ammonium tungstate and 0.05g of titanium tetrachloride solution into the vanadium solution, namely, the molar weight of tungsten element is 0.064mol, and the molar weight of titanium element is 0.032mol, and uniformly mixing by using ultrasonic waves; transferring the mixed solution into a hydrothermal reaction kettle with the volume of 100 mL; then carrying out hydrothermal reaction for 15h at 280 ℃; after natural cooling, performing high-speed centrifugal separation on the solution; then cleaning the solid precipitate with ethanol and deionized water; and (3) freeze-drying the solid to obtain 0.5% Ti and 0.5% W co-doped vanadium dioxide powder.

FIG. 7 is a DSC curve of the titanium tungsten co-doped vanadium dioxide prepared in example 4.

FIG. 8 shows the transmission spectra of the titanium-tungsten-codoped vanadium dioxide prepared in example 4 at 10 ℃ and 80 ℃.

As shown in the figure, the phase transition temperature of the titanium-tungsten co-doped vanadium dioxide prepared in the example 4 is 54.5 ℃. The visible light transmittance is calculated to be 30%, and the sunlight regulation and control rate is about 12.7%.

The stability test was performed in the same manner as in example 1, and the solar light control ability was maintained at 80.1% after 1000 hours in a high-temperature high-humidity environment.

Comparative example 1

Measuring 70mL of vanadium extraction solution, and adjusting the pH value to 2 by using 10% hydrochloric acid solution by mass fraction; the concentration of pentavalent vanadium ions is 40g/L determined by potentiometric titration, namely the total molar amount of vanadium ions is 0.055 mol. 4mL of hydrazine hydrate (the mass fraction is 85 percent) is slowly added into the solution, namely the molar weight of the reducing agent hydrazine hydrate is 0.068mol, the molar ratio of vanadium ions to the reducing agent is 0.81, and the solution turns blue; removing solids in the solution by vacuum filtration to obtain a clear vanadium solution; transferring the vanadium solution into a hydrothermal reaction kettle with the volume of 100 mL; then carrying out hydrothermal reaction for 15h at 280 ℃; after natural cooling, performing high-speed centrifugal separation on the solution; then cleaning the solid precipitate with ethanol and deionized water; and (4) freeze-drying the solid to obtain undoped vanadium dioxide powder.

FIG. 9 shows the DSC curve of undoped vanadium dioxide obtained in comparative example 1, with a phase transition temperature of 67.5 ℃. Thus, pure vanadium dioxide has a high phase transition temperature.

FIG. 10 is a graph showing the transmission spectra at 10 ℃ and 80 ℃ of undoped vanadium dioxide obtained in comparative example 1, respectively. The visible light transmittance is calculated to be 24%, and the sunlight regulation and control rate is about 13.8%.

The stability test was performed in the same manner as in example 1, and the solar light control ability was maintained at 75.1% after 1000 hours in a high-temperature high-humidity environment.

Compared with the examples 1 to 4, the vanadium dioxide prepared by the comparative example 1 without doping titanium and tungsten has high phase transition temperature, low visible light transmittance, weak sunlight regulation and control capability and obviously reduced stability.

Comparative example 2

The difference compared to example 2 is that no titanium tetrachloride was added. Obtaining 2% W doped vanadium dioxide powder.

FIG. 11 is a DSC curve of tungsten doped vanadium dioxide prepared in comparative example 2, with a phase transition temperature of 33 ℃.

FIG. 12 is a graph showing the transmission spectra at 10 ℃ and 80 ℃ of tungsten-doped vanadium dioxide obtained in comparative example 2. The visible light transmittance is calculated to be 22%, and the sunlight regulation and control rate is about 12.3%.

The stability test was performed in the same manner as in example 2, and the solar light control ability was maintained at 79.2% after 1000 hours in a high-temperature high-humidity environment.

Compared with the example 2, the titanium element is not doped, so that the visible light transmittance is reduced, the sunlight control capability is weakened, and the stability is obviously reduced.

Comparative example 3

The difference compared to example 2 is that no ammonium tungstate was added. Obtaining the 1 percent Ti-doped vanadium dioxide powder.

FIG. 13 is a DSC curve of tungsten doped vanadium dioxide prepared in comparative example 3, with a phase transition temperature of 67 ℃.

FIG. 14 is a graph showing the transmission spectra at 10 ℃ and 80 ℃ of tungsten-doped vanadium dioxide obtained in comparative example 3. The visible light transmittance is calculated to be 50%, and the sunlight regulation and control rate is about 15.3%.

The stability test was performed in the same manner as in example 2, and the solar light control ability was maintained at 82.4% after 1000 hours in a high-temperature high-humidity environment.

Compared with the embodiment 2, the vanadium dioxide still has higher phase transition temperature due to the fact that tungsten is not doped in the comparative example 3, the visible light transmittance, the sunlight control capability and the stability are improved due to the fact that titanium is doped in the vanadium dioxide, and the factors for reducing the visible light transmittance and the sunlight control capability are reduced due to the fact that tungsten is not doped in the comparative example 3, so that the visible light transmittance and the sunlight control capability are improved compared with the embodiment 2 after the same amount of titanium is doped.

In the present disclosure, the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" and the like mean that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.