Preparation method of vanadium dioxide

Abstract

The invention relates to the field of preparation of VO2 through liquid phase precipitation, in particular to a preparation method of vanadium dioxide. The invention provides a method for synthesizing vanadium dioxide powder by using vanadium-containing leachate, and aims to solve the problems of large powder particle size, non-uniform distribution, agglomeration, high cost and low reaction efficiency in the traditional preparation method, reduce the preparation cost and the powder particle size of vanadium dioxide and improve the preparation efficiency. An ultrasonic spray drying mode is adopted in the whole process to assist the synthesis process, the particle size of the powder can be further reduced and the particle size distribution of the powder can be improved by utilizing the ultrasonic effect, meanwhile, the crystallization process is rapidly realized in high-temperature airflow by utilizing micro-droplets formed by high-frequency spray, the uniformity and phase change performance of the vanadium dioxide powder can be improved, and the preparation process is simple. Controllable synthesis of powder granularity and morphology is realized; and the method is simple, the production cost is low, large-batch production is easy to realize, and the powder is small in particle size and uniform in distribution.

Description

Technical Field

[0001] The invention relates to the field of preparing VO2 by liquid phase precipitation, in particular to a method for preparing vanadium dioxide. Background Art

[0002] Vanadium dioxide is a type of vanadium oxide, and there are many crystal forms, among which VO2 (A), VO2 (B) and VO2 (R) can all be transformed into VO2 (M). Light, heat, electricity, stress, etc. can all induce phase changes in VO2 (M), accompanied by huge changes in crystal structure, resistivity, optics and other properties. When the phase change occurs, its crystal structure changes from monoclinic phase to tetragonal rutile phase, and the resistivity changes by more than 3 orders of magnitude, from semiconductor before the phase change to metal. In terms of optical properties, it also changes from high transmittance of infrared light to high reflectivity before and after the phase change. Due to the unique phase change properties and excellent performance of VO2, it has been applied in smart glass, optical storage, laser radiation protection film, lithium battery electrodes and other fields in recent years. In addition, VO2 can also be widely used in other aspects, such as antistatic coatings, nonlinear and linear resistor materials, high-sensitivity temperature sensors, adjustable microwave switch devices, infrared light modulation materials. As a functional material, VO2 has high potential application value and broad application prospects.

[0003] The main preparation methods of VO2 powder include thermal decomposition, chemical precipitation, sol-gel, laser-induced vapor deposition, hydrothermal synthesis, etc., but all of them have some shortcomings. In the thermal decomposition method, the redox reaction is intense, and it is inevitable that vanadium oxides of other valence states will exist in the prepared powder. The hydrothermal method and microwave hydrothermal method have simple processes, the prepared powder has high purity, controllable shape and size, and low degree of agglomeration, but the process control is difficult and it is difficult to achieve industrialization. The sol-gel method has simple processes, high powder purity, good experimental repeatability, but long reaction cycle and high energy consumption. Although the chemical precipitation method has a simple preparation process, the prepared powder has a large and uneven particle size. In addition, the above preparation methods mostly use high-purity vanadium raw materials for preparation, which greatly increases the preparation cost. Therefore, the key to the preparation of vanadium dioxide powder is that the raw materials should be cheap and pollution-free, the preparation process is simple, the method is stable and highly repeatable, and the prepared powder particle size should be small and uniform.

[0004] "Method for preparing monodisperse M-phase vanadium dioxide nanoparticles, CN104071843A" Vanadium pentoxide, dihydrated oxalic acid and water are mixed in proportion, a surfactant is added and stirred to obtain a precursor solution, a hydrothermal reaction is used for preparation, solid-liquid separation and washing are performed to obtain vanadium dioxide powder, and the powder is subjected to nitrogen heat treatment to obtain M-phase vanadium dioxide nanoparticles. The powder prepared by this invention has a small particle size and good dispersibility, but the cost is high, the process flow is long and it is not easy to achieve industrial production. "A method for preparing rutile phase vanadium dioxide ultrafine nanopowder, CN109319838A" uses ammonia water and an acidic tetravalent vanadium solution to react to obtain a suspension, which is sealed, heat-insulated and stirred to obtain a colloidal suspension, which is then separated from the solid and liquid and cleaned to obtain a hydrated vanadium hydroxide colloid, which is then dried and sintered in a protective atmosphere to obtain rutile phase vanadium dioxide ultrafine nanopowder. The rutile phase vanadium dioxide particles prepared by the process method of the invention have high purity, small size and uniformity, but the process is too complicated and costly, separation is difficult, and it is not easy to achieve large-scale production.

[0005] Therefore, in view of the problems of large particle size, uneven distribution, serious agglomeration, complex preparation process, high production cost and low preparation efficiency in the current vanadium dioxide preparation methods, developing an efficient and low-cost synthesis technology for nano vanadium dioxide is an urgent problem to be solved in the application of VO2 in the field of functional materials. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is a method for preparing vanadium dioxide. The method for preparing vanadium dioxide provided by the present invention can prepare vanadium dioxide powder with small particle size and uniform distribution, and the process is simple and the production cost is low.

[0007] The present invention provides a method for preparing vanadium dioxide, comprising the following steps:

[0008] S1) independently passing the vanadium-containing raw material solution, the precipitant solution and the dispersant solution into the same reaction chamber through ultrasonic spraying to react, thereby obtaining a vanadium dioxide precursor; the frequency of the ultrasonic spraying is 25 kHz to 120 kHz;

[0009] S2) heat-treating the vanadium dioxide precursor obtained in step S1) to obtain vanadium dioxide.

[0010] The present invention firstly passes a vanadium-containing raw material liquid, a precipitant solution and a dispersant solution independently through ultrasonic spraying into the same reaction chamber for reaction to obtain a vanadium dioxide precursor; specifically, the vanadium-containing raw material liquid, the precipitant solution and the dispersant solution are respectively uniformly transported to three ultrasonic spray heads through a pump, and the three are respectively ultrasonically sprayed into the same reaction chamber for reaction, and a vanadium dioxide precursor is obtained after the spraying is completed. The temperature of the reaction of the present invention is 120°C to 160°C, and the reaction time is 0.5 h to 2 h. The present invention adopts synchronous atomization and mixing of raw and auxiliary material solutions to realize the transformation of the existence form and valence state of vanadium ions in one step, and at the same time promotes the formation of sol-gel in the reaction process, and combines the effects of spraying and sol-gel to significantly enhance the control of particle size and uniformity in the precursor synthesis process.

[0011] The molar ratio of the precipitant in the precipitant solution of the present invention to the vanadium in the vanadium-containing raw material solution is 1:(2-10); the molar ratio of the dispersant in the dispersant solution to the vanadium in the vanadium-containing raw material solution is 1:(1.5-5). The volume ratio of the precipitant solution, the dispersant solution and the vanadium-containing raw material solution of the present invention is (4-1):(2-0.5):1.

[0012] The pH of the vanadium-containing raw material liquid of the present invention is 1 to 5. In certain embodiments of the present invention, the pH of the vanadium-containing raw material liquid is adjusted by a pH adjusting agent. The vanadium-containing raw material liquid of the present invention is a vanadium-containing raw material vanadium extraction leaching solution, which has low raw material cost and can reduce preparation cost. In certain embodiments of the present invention, the pH of the vanadium-containing raw material vanadium extraction leaching solution is adjusted by a pH adjusting agent, and the vanadium-containing leaching solution after pH adjustment is filtered to obtain the vanadium-containing raw material liquid.

[0013] The precipitant in the precipitant solution of the present invention is selected from one or more mixtures of ammonium carbonate, sodium carbonate, sodium hydroxide or sodium bicarbonate. The dispersant in the dispersant solution of the present invention is selected from citric acid and an acid catalyst, and the acid catalyst is selected from one or more mixtures of nitric acid, acetic acid and hydrochloric acid. The molar ratio of citric acid to acid catalyst of the present invention is (2-4):1.

[0014] After obtaining the vanadium dioxide precursor, the obtained vanadium dioxide precursor is heat-treated to obtain vanadium dioxide. Specifically, the obtained vanadium dioxide precursor is heat-treated in an inert gas atmosphere, wherein the inert gas is selected from one or more of helium, neon, argon or nitrogen. In certain embodiments of the present invention, the obtained vanadium dioxide precursor is ground and placed in a heat treatment chamber, and the vacuum degree in the heat treatment chamber is first pumped to 10 -3 mbar~10 -5mbar, and then heat-treating the obtained vanadium dioxide precursor in an inert gas atmosphere. The heat treatment temperature of the present invention is 300°C to 700°C, and the heat treatment time is 1 h to 4 h.

[0015] The vanadium dioxide obtained by the preparation method of vanadium dioxide of the present invention is a vanadium dioxide nanopowder, and the powder particle size is small and the distribution is uniform. The specific reaction principle of the preparation method of vanadium dioxide of the present invention is: the existence form of vanadium ions in the vanadium-containing raw material liquid is converted into the required existence form of vanadium ions by pH adjustment, the precipitant, the composite dispersant solution and the vanadium-containing solution are atomized by a high-frequency ultrasonic spray head, and the tiny liquids generated by the three nozzles collide and mix in the reaction chamber. During the droplet mixing process, the precipitant will cause the pH of the vanadium-containing solution to change, and the dispersant plays a role in promoting the reduction of pentavalent vanadium and the formation and dispersion of sol-gel. The precursor is initially crystallized and dried in the reaction chamber through the intervention of high temperature, and the precursor particles with smaller particle size and better uniformity are prepared. Finally, the crystal form conversion is completed by heat treatment to prepare the vanadium dioxide nanopowder. The sol-gel method can realize the uniform mixing of raw materials in the liquid phase, and form a stable sol system through hydrolysis and condensation chemical reactions, which is helpful for the control of the particle size and uniformity of the powder. Ultrasonic spray drying can convert solutions into tiny droplets. Through the simultaneous atomization and mixing of raw and auxiliary material solutions, it can effectively improve the uniformity and ultrafineness of the precursor synthesis process, and achieve precise control of material morphology, structure and performance. The principle of ultrasonic spray drying is to use the high-frequency pressure waves generated by ultrasonic vibration to atomize the solution or slurry into extremely fine droplets. The droplets are sprayed into a high-temperature airflow, quickly evaporating the solvent to obtain uniform and fine powder particles.

[0016] The present invention provides a method for synthesizing vanadium dioxide powder using vanadium-containing leaching solution, aiming to solve the problems of large powder particle size, uneven distribution, agglomeration, high cost and low reaction efficiency in traditional preparation methods, reduce the preparation cost and powder particle size of vanadium dioxide, and improve preparation efficiency. The present invention uses ultrasonic spray drying to assist the synthesis process throughout the process, and can use the ultrasonic effect to further reduce the powder particle size and improve its particle size distribution. At the same time, the micro-droplets formed by high-frequency spraying are used to quickly realize the crystallization process in the high-temperature airflow, which can improve the uniformity and phase change performance of vanadium dioxide powder, and realize the controllable synthesis of powder particle size and morphology; and the process method of the present invention is simple, the production cost is low, and it is easy to realize mass production, and the powder particle size is small and the distribution is uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a SEM image of the vanadium dioxide nanopowder obtained in Example 1;

[0018] Figure 2 This is the SEM image of the vanadium dioxide nanopowder obtained in Comparative Example 1. DETAILED DESCRIPTION

[0019] The present invention discloses a method for preparing vanadium dioxide. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art and they are all considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the method and application of this article without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0020] The present invention will be further described below in conjunction with embodiments:

[0021] Example 1

[0022] The pH of the vanadium-containing leaching solution was tested to be 9.5, and 2 mol / L sodium hydroxide solution was added to adjust the pH to 3. The vanadium-containing solution after pH adjustment was filtered for use. The vanadium concentration was tested to be 22.5 g / L. An ammonium carbonate solution was prepared at a molar ratio of 1:2 to the vanadium concentration of the vanadium-containing solution. A composite dispersant solution was prepared at a molar ratio of 1:1.5 to the vanadium concentration of the vanadium-containing solution. The molar ratio of the composite dispersant citric acid and the acid catalyst nitric acid was 2:1. The prepared precipitant solution and composite dispersant solution were uniformly transported to three ultrasonic spray heads through a pump at a volume ratio of 4:1 and 2:1 to the vanadium-containing solution. During the introduction process, the temperature of the reaction chamber was controlled at 120°C and the ultrasonic frequency was 120 kHZ. After the spraying was completed, a vanadium dioxide precursor was obtained. The vanadium dioxide precursor was ground and placed in a tubular furnace. The vacuum degree in the furnace was first pumped to 10 -5 mbar, and then heat treated at 700℃ for 1.5 h under nitrogen protection. After the reaction is completed, vanadium dioxide nanopowder is obtained. The SEM image of the obtained vanadium dioxide nanopowder is as follows: Figure 1 As shown, Figure 1 This is a SEM image of the vanadium dioxide nanopowder obtained in Example 1. The particle size D50 of the obtained vanadium dioxide nanopowder was 55 nm after testing.

[0023] Example 2

[0024] The pH of the vanadium-containing leaching solution was tested to be 9.5, and 2 mol / L sodium hydroxide solution was added to adjust the pH to 1. The vanadium-containing solution after pH adjustment was filtered for use. The vanadium concentration was tested to be 22.5 g / L. A sodium carbonate solution was prepared according to a molar ratio of 1:5 between the concentration and the vanadium concentration of the vanadium-containing solution. A composite dispersant solution was prepared according to a molar ratio of 1:5 between the concentration and the vanadium concentration of the vanadium-containing solution. The molar ratio of the composite dispersant citric acid and the acid catalyst hydrochloric acid was 3:1. The prepared precipitant solution and composite dispersant solution were uniformly transported to three ultrasonic spray heads through a pump at a volume ratio of 2:1 and 1:1 to the vanadium-containing solution. During the introduction process, the temperature of the reaction chamber was controlled at 160°C and the ultrasonic frequency was 25 kHZ. After the spraying was completed, a vanadium dioxide precursor was obtained. The vanadium dioxide precursor was ground and placed in a tubular furnace. The vacuum degree in the furnace was first pumped to 10 -3 mbar, and then heat treated at 500°C for 1h under nitrogen protection, to obtain vanadium dioxide nanopowder after the reaction is completed. The particle size D50 of the obtained vanadium dioxide nanopowder is 80nm.

[0025] Example 3

[0026] The pH of the vanadium-containing leaching solution was tested to be 9.5, and 2 mol / L sodium hydroxide solution was added to adjust the pH to 1. The vanadium concentration was tested to be 22.5 g / L. A sodium hydroxide solution was prepared at a molar ratio of 1:10 to the vanadium concentration of the vanadium-containing solution. A composite dispersant solution was prepared at a molar ratio of 1:5 to the vanadium concentration of the vanadium-containing solution. The molar ratio of the composite dispersant citric acid and the acid catalyst hydrochloric acid was 4:1. The prepared precipitant solution and composite dispersant solution were uniformly transported to three ultrasonic spray heads through a pump at a volume ratio of 1:1 and 0.5:1 to the vanadium-containing solution. During the introduction process, the temperature of the reaction chamber was controlled at 150°C and the ultrasonic frequency was 100 kHz. After the spraying was completed, a vanadium dioxide precursor was obtained. The vanadium dioxide precursor was ground and placed in a tubular furnace. The vacuum degree in the furnace was first pumped to 10 -5 mbar, and then heat treated at 300°C for 4 h under nitrogen protection, to obtain vanadium dioxide nanopowder after the reaction. The particle size D50 of the obtained vanadium dioxide nanopowder was 70 nm.

[0027] Example 4

[0028] The pH of the vanadium-containing leaching solution was tested to be 9.5, and 2 mol / L sodium hydroxide solution was added to adjust the pH to 5. The vanadium concentration was tested to be 30 g / L, and a sodium bicarbonate solution was prepared at a molar ratio of 1:8 to the vanadium concentration of the vanadium-containing solution. A composite dispersant solution was prepared at a molar ratio of 1:4 to the vanadium concentration of the vanadium-containing solution, and the molar ratio of the composite dispersant citric acid and the acid catalyst acetic acid was 3:1. The prepared precipitant solution and composite dispersant solution were uniformly transported to three ultrasonic spray heads through a pump at a volume ratio of 1:1 and 0.5:1 to the vanadium-containing solution, respectively. During the introduction process, the temperature of the reaction chamber was controlled at 140°C, and the ultrasonic frequency was 80 kHZ. After the spraying was completed, a vanadium dioxide precursor was obtained. The vanadium dioxide precursor was ground and placed in a tubular furnace. The vacuum degree in the furnace was first pumped to 10 -3 mbar, and then heat treated at 550°C for 1.5 h under nitrogen protection, to obtain vanadium dioxide nanopowder after the reaction. The particle size D50 of the obtained vanadium dioxide nanopowder was 75 nm.

[0029] Comparative Example 1

[0030] The pH of the vanadium-containing leaching solution was tested to be 9.5, and 2 mol / L sodium hydroxide solution was added to adjust the pH to 5. The vanadium concentration was tested to be 30 g / L, and a sodium bicarbonate solution was prepared at a molar ratio of 1:8 to the vanadium concentration of the vanadium-containing solution. A composite dispersant solution was prepared at a molar ratio of 1:4 to the vanadium concentration of the vanadium-containing solution, and the molar ratio of the composite dispersant citric acid and the acid catalyst acetic acid was 3:1. The prepared precipitant solution and composite dispersant solution were mixed at a volume ratio of 1:1 and 0.5:1 with the vanadium-containing solution, and then uniformly transported to the ultrasonic spray head through a pump. During the introduction process, the temperature of the reaction chamber was controlled at 120°C and the ultrasonic frequency was 120 kHZ. After the spraying was completed, a vanadium dioxide precursor was obtained. The vanadium dioxide precursor was ground and placed in a tubular furnace. The vacuum degree in the furnace was first pumped to 10 -5 mbar, and then heat treated at 700℃ for 1.5 h under nitrogen protection. After the reaction is completed, vanadium dioxide nanopowder is obtained. The SEM image of the obtained vanadium dioxide nanopowder is as follows: Figure 2 As shown, Figure 2 This is a SEM image of the vanadium dioxide nanopowder obtained in Comparative Example 1. The particle size D50 of the obtained vanadium dioxide nanopowder was 480 nm after testing.

[0031] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing vanadium dioxide, characterized in that: The following steps are involved: S1) independently passing the vanadium-containing raw material solution, the precipitant solution and the dispersant solution into the same reaction chamber through ultrasonic spraying to react, thereby obtaining a vanadium dioxide precursor; the frequency of the ultrasonic spraying is 25 kHz to 120 kHz; S2) heat-treating the vanadium dioxide precursor obtained in step S1) to obtain vanadium dioxide.

2. The method for preparing vanadium dioxide according to claim 1, characterized in that: In step S1), the reaction temperature is 120°C to 160°C, and the reaction time is 0.5 h to 2 h.

3. The method for preparing vanadium dioxide according to claim 1, characterized in that: In step S1), the molar ratio of the precipitant in the precipitant solution to the vanadium in the vanadium-containing raw material solution is 1:(2-10); the molar ratio of the dispersant in the dispersant solution to the vanadium in the vanadium-containing raw material solution is 1:(1.5-5).

4. The method for preparing vanadium dioxide according to claim 1, characterized in that: In step S1), the volume ratio of the precipitant solution, the dispersant solution and the vanadium-containing raw material solution is (4-1):(2-0.5):

1.

5. The method for preparing vanadium dioxide according to claim 1, characterized in that: In step S1), the pH of the vanadium-containing raw material solution is 1-5.

6. The method for preparing vanadium dioxide according to claim 1, characterized in that: In step S1), the vanadium-containing raw material liquid is a vanadium-extracting leaching liquid of a vanadium-containing raw material.

7. The method for preparing vanadium dioxide according to claim 1, characterized in that: In step S1), the precipitant in the precipitant solution is selected from a mixture of one or more of ammonium carbonate, sodium carbonate, sodium hydroxide or sodium bicarbonate.

8. The method for preparing vanadium dioxide according to claim 1, characterized in that: In step S1), the dispersant in the dispersant solution is selected from citric acid and an acid catalyst; The acid catalyst is selected from a mixture of one or more of nitric acid, acetic acid and hydrochloric acid.

9. The method for preparing vanadium dioxide according to claim 8, characterized in that: The molar ratio of the citric acid to the acid catalyst is (2-4):

1.

10. The method for preparing vanadium dioxide according to claim 1, characterized in that: In step S2), the temperature of the heat treatment is 300° C. to 700° C., and the time of the heat treatment is 1 h to 4 h.

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