CN1693211A - Composite doped vanadium dioxide nanopowder material and preparation method thereof - Google Patents

Abstract

A composite doped vanadium dioxide nano-powder material, the molecular formula is V _1-x M _x O _2-y Z _y , where 0<x≤0.08, 0<y≤0.1, M is a doped metal element, Z is a doped non-metallic element. The preparation method uses V ₂ O ₅ and oxalic acid as basic raw materials, and the process steps are the preparation of the precursor and the thermal decomposition of the precursor in sequence. The precursor is solid vanadyl oxalate doped with metal elements and non-metal elements, and the doped solid vanadyl oxalate is thermally decomposed under vacuum conditions to obtain composite doped vanadium dioxide nanopowder material. This vanadium dioxide nano-powder material can not only reduce the phase transition temperature to 25-30°C, but also improve other physical properties, such as increasing the transmittance of visible light. The preparation process is simple and pollution-free, is beneficial to environmental protection and the health of operators, and is easy to control the quality of the vanadium dioxide nanometer powder material.

Description

Composite doped vanadium dioxide nanopowder material and preparation method thereof

Technical field

The invention belongs to a vanadium dioxide nanometer powder material and a preparation method thereof, in particular to a composite doped vanadium dioxide nanometer powder material and a preparation method thereof.

Background technique

VO ₂ is a typical phase-change compound, which undergoes a first-order phase transition at around 68°C. With the phase transition, the resistivity, magnetic susceptibility, optical refractive index, transmittance, and reflectance undergo a sudden change, and the phase transition process is reversible. of. Experiments have proved that doping can change the phase transition temperature of VO ₂ and expand the application field of VO ₂ . Therefore, the research on doped VO ₂ and its preparation method has very important value.

The Chinese patent application with the application number 95196132.2 discloses a vanadium dioxide particle and its preparation method. The vanadium dioxide particle includes two types: undoped and doped, and the doped vanadium dioxide particle is only doped with a metal ion The method adopts industrial ammonium hexa-vanadate (AHV) or ammonium hexa-vanadate (AHV) ammonium prepared from ammonium metavanadate (AMV) as a precursor, and obtains non- Doped vanadium dioxide particles, or doped vanadium dioxide particles obtained by pyrolysis after doping in the above precursor. Its pyrolysis is carried out at a temperature of about 400° C. and 650° C. and a heating rate of at least 100° C./minute, and the gas generated by the pyrolysis is kept within a certain range and in direct contact with the reaction medium for at least 1/2 hour, preferably for 1 hour. The problems in the above-mentioned technical scheme are: 1, the raw material contains ammonium, so the content of ammonium must be controlled to ensure accurate _VO structure, which brings difficulties to process control; 2, the heating rate of the precursor pyrolysis is at least 100 ℃/min, so the power of the heating furnace is large, which increases the cost of the equipment; 3. The particle size of the prepared vanadium dioxide particles is micron (size less than 5 microns), and only one kind of metal ion is doped in the doped vanadium dioxide particles , so the application is limited.

The Chinese patent application with the application number 00117321.9 discloses a vanadium dioxide nanopowder material and its preparation method. The vanadium dioxide nanopowder material includes two types: undoped and doped. The powder material is doped with Cr or Mo or W, and the steps of the method are: 1) using H ₂ C ₂ O ₄ ·2H ₂ O and N ₂ H ₄ ·2HCl to reduce V ₂ O ₅ in hydrochloric acid medium to prepare VOCl ₂ ; 2) react the prepared VOCl ₂ solution with (NH ₄ ) ₂ CO ₃ or NH ₄ HCO ₃ to prepare vanadyl (IV) basic ammonium carbonate precursor, and ultrasonically crush the precursor in absolute ethanol to Particle size ≤ 2μm; 3) Thermally decompose the prepared precursor in an inert atmosphere or an atmosphere containing an inert atmosphere to obtain VO ₂ powder at a heating temperature of 350-700°C. By doping Cr, Mo, W in the precursor, the vanadium dioxide nano-powder doped with Cr, Mo, W is obtained. The doped vanadium dioxide nanopowder material provided by the above-mentioned technical scheme only contains one kind of metal ion, and the process steps are relatively complicated. Because the raw material uses hydrochloric acid and ammonia-containing substances, it will have adverse effects on the environment and the health of the operator. .

Contents of Invention

The purpose of the present invention is to overcome the deficiencies in the prior art, to provide a composite doped vanadium dioxide nano-powder material and its preparation method, to improve the performance of vanadium dioxide nano-powder, increase the vanadium dioxide nano-powder Type, the method not only simplifies the process, is conducive to environmental protection, but also is easy to control quality.

The composite doped vanadium dioxide nanopowder material of the present invention has a molecular formula of V _1-x M _x O _2-y Z _y , where 0<x≤0.08, 0<y≤0.1, and M is doped Metal element, Z is a doped non-metal element. The doped metal element M can be W, Mo, Nb, Cr, etc., and the doped non-metallic element can be F, but the test shows that the composite doped vanadium dioxide nanopowder formed by the co-doping of Mo and F, W and F The material can not only reduce the phase transition temperature, but also increase the transmittance of visible light.

The preparation method of the composite doped vanadium dioxide nano powder material of the present invention uses V ₂ O ₅ and oxalic acid (H ₂ C ₂ O ₄ 2H ₂ O) as basic raw materials, and the process steps are the preparation of the precursor and the precursor The thermal decomposition of the body, the specific technical scheme is as follows:

One, the preparation method of the vanadium dioxide nano-powder material of doping Mo, F

1. Preparation of precursor

Using V ₂ O ₅ , oxalic acid, MoO ₃ and NH ₄ F as raw materials, the formula of V ₂ O ₅ , MoO ₃ and NH ₄ F is calculated by weight percentage: V ₂ O ₅ 88-98%, MoO ₃ 1-6 %, NH ₄ F 1-6%; the weight ratio of V ₂ O ₅ to oxalic acid is 1:1-3.

First, mix the V ₂ O ₅ and MoO ₃ in the above ratio evenly, put them into a container, heat them to a molten state under normal pressure (the temperature is 800°C to 900°C), and then pour the melt into a container filled with water. in the reaction vessel and stirred (the amount of water added is not strictly required, so as to disperse the V ₂ O ₅ and MoO ₃ melts), then add the oxalic acid and NH ₄ F in the above solution and continue Stir until the reduction reaction is completed (the reduction reaction is completed to obtain a blue liquid without precipitation, generally 2 to 4 hours), after the reduction reaction is completed, the obtained solution is evaporated to dryness to obtain a solution doped with Mo and F ions vanadyl oxalate solid precursor.

2. Thermal decomposition of precursors

Pulverize the obtained vanadyl oxalate precursor and put it into a heating furnace, heat it at a speed of 3-10 °C/min under normal pressure to 250 °C-300 °C, and start vacuuming at a speed of 3-10 °C under vacuum conditions. Heat at a speed of ℃/min to 350℃～500℃, keep warm for 20～40 minutes, turn off the power supply of the heating furnace, keep the vacuum in the furnace, let the decomposition products cool down to room temperature to obtain Mo and F doped vanadium dioxide nanopowder Material;

Or crush the obtained vanadyl oxalate precursor and heat it to 150°C-250°C in a heating furnace (the heating rate is not strictly required, it can be 5-15°C/min) and keep it warm for 20-30 minutes, and then vacuumize. Heating to 350-500°C at a rate of 3-10°C/min under certain conditions, keeping the temperature for 20-40 minutes, then turning off the power supply of the heating furnace, keeping the vacuum in the furnace, allowing the decomposition products to cool to room temperature to obtain Mo and F-doped Vanadium dioxide nano powder material;

Or pulverize the obtained vanadyl oxalate precursor and put it into the heating furnace, heat it to 350°C-500°C at a speed of 3-10°C/min under vacuum conditions, turn off the power supply of the heating furnace after keeping the temperature for 20-40 minutes, and keep the furnace The vacuum degree inside is allowed to cool the decomposition product to room temperature to obtain Mo and F doped vanadium dioxide nanopowder material.

Two, the preparation method of vanadium dioxide nanopowder material doped with W and F

1. Preparation of precursor

Using V ₂ O ₅ , oxalic acid, N ₅ H ₃₇ W ₆ O ₂₄ and NH ₄ F as raw materials, the formula of V ₂ O ₅ and N ₅ H ₃₇ W ₆ O ₂₄ and NH ₄ F is calculated by weight percentage: V ₂ O ₅ 88-98%, N ₅ H ₃₇ W ₆ O ₂₄ 1-6%, NH ₄ F 1-6%; the weight ratio of V ₂ O ₅ to oxalic acid is 1:1-3.

Put V ₂ O ₅ , N ₅ H ₃₇ W ₆ O ₂₄ , NH ₄ F and oxalic acid into the reaction vessel, add water and stir at 40-70°C under normal pressure (the amount of water added is not strictly required, It is advisable that the raw materials in the reaction vessel are flooded), until the reduction reaction is completed (the reduction reaction is completed to obtain a blue liquid without precipitation, generally 2 to 4 hours), after the reduction reaction is completed, the obtained solution After evaporating to dryness, a solid vanadyl oxalate precursor doped with W and F ions is obtained.

2. Thermal decomposition of precursors

Pulverize the obtained vanadyl oxalate precursor and put it into a heating furnace, heat it at a rate of 3-10 °C/mm under normal pressure to 250 °C-300 °C and start vacuuming, and continue to vacuum at a rate of 3-10 °C under vacuum conditions. Heating at a rate of 10°C/min to 350°C-500°C, keeping the temperature for 20-40 minutes, then turning off the power supply of the heating furnace, keeping the vacuum in the furnace, allowing the decomposition products to cool to room temperature to obtain vanadium dioxide nanopowder doped with W and F body material;

Or crush the obtained vanadyl oxalate precursor and heat it to 150°C-250°C in a heating furnace (the heating rate is not strictly required, it can be 5-15°C/min) and keep it warm for 20-30 minutes, and then vacuumize. Heating to 350°C-500°C at a rate of 3-10°C/min under certain conditions, keeping the temperature for 20-40 minutes, then turning off the power supply of the heating furnace, keeping the vacuum in the furnace, allowing the decomposition products to cool to room temperature to obtain W and F-doped Vanadium dioxide nano powder material;

Or pulverize the obtained vanadyl oxalate precursor and put it into a heating furnace, heat it to 350 ° C ~ 500 ° C at a speed of 3 ~ 10 ° C / min under vacuum conditions, and turn off the power supply of the heating furnace after keeping the temperature for 20 ~ 40 minutes. The vacuum degree in the furnace allows the decomposition products to cool down to room temperature to obtain vanadium dioxide nanopowder materials doped with W and F.

Above-mentioned two kinds of preparation methods have all adopted following technical measures:

1. The raw material V ₂ O ₅ used is industrial grade or chemical reagent grade.

2. The surfactant polyethylene glycol can be added in the precursor preparation step, and the amount of polyethylene glycol added is 2-5% (percentage by weight) of the total weight of V ₂ O ₅ and oxalic acid.

3. In the thermal decomposition step of the precursor, the vacuum degree in the heating furnace is controlled at 20-60Pa.

4. Annealing the composite doped vanadium dioxide nano-powder material obtained by thermal decomposition. The annealing process is to heat up to 400°C-600°C for 1-4 hours under vacuum conditions (vacuum degree is 10-20Pa), and then Cool to room temperature under vacuum.

The present invention has the following beneficial effects:

1. The Mo-F, W-F composite doped vanadium dioxide nanopowder material can not only reduce the phase transition temperature (down to about 25-30°C), but also increase the transmittance of visible light, thus expanding the application field , adding new varieties to vanadium dioxide nanopowder materials.

2. The particle size of the obtained composite doped vanadium dioxide nanopowder is less than 50nm, and the powder particles are nearly spherical, with good uniformity and high purity.

3. Since oxalic acid is used as the V ₂ O ₅ reducing agent, there is no pollution, which is beneficial to environmental protection and the health of operators, and it is easy to control the quality of vanadium dioxide nano-powder material.

4. The reduction reaction of V ₂ O ₅ and oxalic acid can directly obtain the precursor—doped vanadyl oxalate, thus simplifying the process flow of precursor preparation.

5. The thermal decomposition temperature of the precursor is low, and the decomposition time is short, which is beneficial to energy saving.

6. The thermal decomposition and heating speed of the precursor is slow, so the power requirement of the heating furnace is small, and the investment in equipment can be reduced.

7. Adding a surfactant in the precursor preparation step is beneficial to the pulverization of the precursor and improving the dispersibility of the nanopowder.

8. The source of raw materials is wide and easy to obtain, which is convenient for industrial production.

Description of drawings

Fig. 1 is a graph of X-ray diffraction (XRD) analysis results of vanadium dioxide nanopowder material doped with N ₅ H ₃₇ W ₆ O ₂₄ 2%, NH ₄ F 3%.

Detailed ways

Example 1: Preparation of Mo-F composite doped vanadium dioxide nanopowder material

The first group: select industrial grade V ₂ O ₅ , the formula of V ₂ O ₅ and MoO ₃ , NH ₄ F is calculated by weight percentage: V ₂ O ₅ 98%, MoO ₃ 1%, NH ₄ F 1%; V The weight ratio of ₂ O ₅ to oxalic acid is 1:1.

(1) Preparation of precursor

First, mix the V ₂ O ₅ and MoO ₃ in the ratio evenly and put them into a container, heat them to 800°C under normal pressure to form a molten state, then pour the melt into a reaction container filled with water and carry out Stir (the amount of water added is not strictly required, so as to disperse the V ₂ O ₅ and MoO ₃ melt), then add the oxalic acid and NH ₄ F in the above solution to the above solution and continue to stir until the reduction reaction Until a blue liquid without precipitation is obtained (the whole process is about 3 hours), after the reduction reaction is completed, the obtained solution is evaporated to dryness at 90°C to obtain a solid precursor of vanadyl oxalate doped with Mo and F ions.

(2) Thermal decomposition of precursors

Put the obtained vanadyl oxalate precursor into a tubular heating furnace after pulverization, and start vacuuming when it is heated to 250 °C at a rate of 3 °C/min under normal pressure, and the vacuum degree is controlled at 55 Pa. Heat at a rate of ℃/min to 350 ℃, keep the temperature for 40 minutes, turn off the power of the heating furnace, keep the vacuum in the furnace, let the decomposition product cool to room temperature and obtain the Mo-F composite doped vanadium dioxide nanopowder material. The particle size of the Mo-F compound doped vanadium dioxide nanometer powder is ≤40nm, and the phase transition temperature is 55°C.

The second group: use chemical reagent grade V ₂ O ₅ , the formula of V ₂ O ₅ and MoO ₃ , NH ₄ F is calculated by weight percentage: V ₂ O ₅ 95%, MoO ₃ 3%, NH ₄ F 2%; The weight ratio of V ₂ O ₅ to oxalic acid is 1:1.5.

(1) Preparation of precursor

Firstly, mix the V ₂ O ₅ and MoO ₃ in the ratio evenly and put them into a container, heat them to 850°C under normal pressure to form a molten state, then pour the melt into a reaction container filled with water and carry out Stir (the amount of water added is not strictly required, so as to disperse the V ₂ O ₅ and MoO ₃ melt), and then add the oxalic acid, NH ₄ F, V ₂ O ₅ and total oxalic acid to the above solution. 3% polyethylene glycol by weight and continue stirring until the completion of the reduction reaction to obtain a blue liquid without precipitation (about 3 hours in the whole process). After the completion of the reduction reaction, the obtained solution was evaporated to dryness at 80° C. Vanadyl oxalate solid precursor with Mo and F ions.

(2) Thermal decomposition of precursors

After pulverizing the obtained vanadyl oxalate precursor, heat it in a tubular heating furnace at 10°C/min to 150°C for 30 minutes, then put it into the tubular heating furnace, and heat it at a speed of 5°C/min under a vacuum of 45Pa. Heating to 400°C, keeping the temperature for 30 minutes, then turning off the power supply of the heating furnace, keeping the vacuum in the furnace, allowing the decomposition products to cool to room temperature to obtain the Mo-F composite doped vanadium dioxide nanopowder material. The particle size of the Mo-F compound doped vanadium dioxide nanometer powder is ≤40nm, and the phase transition temperature is 40°C.

The third group: use chemical reagent grade V ₂ O ₅ , the formula of V ₂ O ₅ and MoO ₃ , NH ₄ F is calculated by weight percentage: V ₂ O ₅ 92%, MoO ₃ 3%, NH ₄ F 5%; The weight ratio of V ₂ O ₅ to oxalic acid is 1:2.

(1) Preparation of precursor

First, mix the V ₂ O ₅ and MoO ₃ in the ratio evenly and put them into a container, heat them to 900°C under normal pressure to form a molten state, then pour the melt into a reaction container filled with water and carry out Stir (the amount of water added is not strictly required, so as to disperse the V ₂ O ₅ and MoO ₃ melt), and then add the oxalic acid, NH ₄ F, V ₂ O ₅ and total oxalic acid to the above solution. 4% polyethylene glycol by weight and continue to stir until the completion of the reduction reaction to obtain a blue liquid without precipitation (about 2.5 hours in the whole process). Vanadyl oxalate solid precursor with Mo and F ions.

(2) Thermal decomposition of precursors

The obtained vanadyl oxalate precursor was pulverized and put into a tubular heating furnace, heated to 450°C at a speed of 7°C/min under a vacuum of 35Pa, and turned off the power supply of the heating furnace after holding for 25 minutes to maintain the vacuum in the furnace , allowing the decomposition product to cool to room temperature to obtain Mo-F composite doped vanadium dioxide nanopowder material.

(3) Annealing

Raise the temperature to 600°C for 1 hour under the condition of vacuum degree of 10 Pa, turn off the power supply of the heating furnace, keep the vacuum degree in the furnace, and cool to room temperature.

The particle size of the Mo-F compound doped vanadium dioxide nanometer powder is ≤50nm, and the phase transition temperature is 38°C.

The fourth group: select industrial grade V ₂ O ₅ , the formula of V ₂ O ₅ and MoO ₃ , NH ₄ F is calculated by weight percentage: V ₂ O ₅ 90%, MoO ₃ 6%, NH ₄ F 4%; V The weight ratio of ₂ O ₅ to oxalic acid is 1:3.

(1) Preparation of precursor

First, mix the V ₂ O ₅ and MoO ₃ in the ratio evenly and put them into a container, heat them to 900°C under normal pressure to form a molten state, then pour the melt into a reaction container filled with water and carry out Stir (the amount of water added is not strictly required, so as to disperse the V ₂ O ₅ and MoO ₃ melts), then add the oxalic acid and NH ₄ F in the above solution to the above solution and continue to stir until the reduction reaction Until a blue liquid without precipitation is obtained (the whole process is about 2 hours), after the reduction reaction is completed, the obtained solution is evaporated to dryness at 100°C to obtain a solid precursor of vanadyl oxalate doped with Mo and F ions.

(2) Thermal decomposition of precursors

The obtained vanadyl oxalate precursor was pulverized and put into a tubular heating furnace, and heated to 500°C at a rate of 7°C/min under a vacuum of 25Pa, and turned off the power supply of the heating furnace after holding for 20 minutes to maintain the vacuum in the furnace , allowing the decomposition product to cool to room temperature to obtain Mo-F composite doped vanadium dioxide nanopowder material.

(3) Annealing

Raise the temperature to 500°C for 2 hours under the condition of vacuum degree of 10 Pa, turn off the power supply of the heating furnace, keep the vacuum degree in the furnace, and cool to room temperature.

The particle size of the Mo-F compound doped vanadium dioxide nanometer powder is ≤50nm, and the phase transition temperature is 35°C.

Embodiment 2: Preparation of W-F composite doped vanadium dioxide nanopowder material

The first group: select industrial grade V ₂ O ₅ , the formula of V ₂ O ₅ and N ₅ H ₃₇ W ₆ O ₂₄ , NH ₄ F is calculated by weight percentage: V ₂ O ₅ 97%, N ₅ H ₃₇ W ₆ O ₂₄ 1%, NH ₄ F 2%; the weight ratio of V ₂ O ₅ to oxalic acid is 1:1

(1) Preparation of precursor

First put V ₂ O ₅ , N ₅ H ₃₇ W ₆ O ₂₄ , NH ₄ F, oxalic acid, and polyethylene glycol with 2% of the total weight of V ₂ O ₅ and oxalic acid into the reaction vessel and add water at room temperature. Stir under pressure at 40°C (the amount of water added is not strictly required, it is advisable to submerge the raw materials in the reaction vessel), until the reduction reaction is completed and a blue liquid without precipitation is obtained (the whole process is about 3 hours), the reduction reaction After completion, the obtained solution was evaporated to dryness at 90° C. to obtain a solid vanadyl oxalate precursor doped with W and F ions.

(2) Thermal decomposition of precursors

Put the obtained vanadyl oxalate precursor into a tubular heating furnace after pulverization, and start vacuuming when it is heated to 250 °C at a rate of 3 °C/min under normal pressure, and the vacuum degree is controlled at 55 Pa. Heat at a rate of ℃/min to 350 ℃, keep the temperature for 40 minutes, then turn off the power of the heating furnace, keep the vacuum in the furnace, let the decomposition products cool down to room temperature to obtain W-F composite doped vanadium dioxide nanopowder material.

The particle size of the W-F compound doped vanadium dioxide nanometer powder is ≤40nm, and the phase transition temperature is 37°C.

The second group: use chemical reagent grade V ₂ O ₅ , the formula of V ₂ O ₅ and N ₅ H ₃₇ W ₆ O ₂₄ , NH ₄ F is calculated by weight percentage: V ₂ O ₅ 95%, N ₅ H ₃₇ W ₆ O ₂₄ 2%, NH ₄ F 3%; the weight ratio of V ₂ O ₅ to oxalic acid is 1:1.5.

(1) Preparation of precursor

First, put V ₂ O ₅ , N ₅ H ₃₇ W ₆ O ₂₄ , NH ₄ F and oxalic acid into the reaction vessel, add water and stir at 50°C under normal pressure (the amount of water added is not strictly required, and The raw material in the reaction vessel is preferably submerged), until the reduction reaction is completed to obtain a blue liquid without precipitation (the whole process is about 3 hours), after the reduction reaction is completed, the obtained solution is evaporated to dryness at 80 ° C to obtain the mixed Solid vanadyl oxalate precursor for W and F ions.

(2) Thermal decomposition of precursors

After pulverizing the obtained vanadyl oxalate precursor, heat it to 150°C at a speed of 5°C/min in a tube furnace and keep it for 30 minutes, then heat it to 400°C at a speed of 5°C/min under a vacuum of 45Pa, and keep it warm. After 30 minutes, turn off the power supply of the heating furnace, keep the vacuum in the furnace, and allow the decomposition product to cool to room temperature to obtain the W-F composite doped vanadium dioxide nanopowder material.

(3) Annealing

Raise the temperature to 500°C for 2 hours under the condition of vacuum degree of 10 Pa, turn off the power supply of the heating furnace, keep the vacuum degree in the furnace, and cool to room temperature.

The particle size of the W-F compound doped vanadium dioxide nanometer powder is ≤40nm, and the phase transition temperature is 35°C.

The XRD analysis results of the W-F composite doped vanadium dioxide nanopowder material prepared in this example are shown in Figure 1, which shows that the product obtained by thermal decomposition has a vanadium dioxide crystal structure.

The third group: use chemical reagent grade V ₂ O ₅ , the formula of V ₂ O ₅ and N ₅ H ₃₇ W ₆ O ₂₄ is calculated by weight percentage: V ₂ O ₅ 92%, N ₅ H ₃₇ W ₆ O ₂₄ 4 %, NH ₄ F 4%; the weight ratio of V ₂ O ₅ to oxalic acid is 1:2.

(1) Preparation of precursor

First, put the ratio of V ₂ O ₅ , N ₅ H ₃₇ W ₆ O ₂₄ , NH ₄ F, oxalic acid and polyethylene glycol with 4% of the total amount of V ₂ O ₅ and oxalic acid into the reaction vessel and add water to Stir under pressure at 60°C (the amount of water added is not strictly required, it is advisable to submerge the raw materials in the reaction vessel), until the reduction reaction is completed and a blue liquid without precipitation is obtained (the whole process is about 2.5 hours), the reduction reaction After completion, the obtained solution was evaporated to dryness at 90° C. to obtain a solid vanadyl oxalate precursor doped with W and F ions.

(2) Thermal decomposition of precursors

The obtained vanadyl oxalate precursor was pulverized and put into a tubular heating furnace, heated to 450°C at a speed of 7°C/min under a vacuum of 35Pa, and turned off the power supply of the heating furnace after holding for 25 minutes to maintain the vacuum in the furnace , allowing the decomposition product to cool to room temperature to obtain a W-F composite doped vanadium dioxide nanopowder material.

(3) Annealing

Raise the temperature to 600°C for 1 hour under the condition of vacuum degree of 20 Pa, turn off the power supply of the heating furnace, keep the vacuum degree in the furnace, and cool to room temperature.

The particle size of the W-F compound doped vanadium dioxide nanometer powder is ≤45nm, and the phase transition temperature is 30°C.

The fourth group: select industrial grade V ₂ O ₅ , the formula of V ₂ O ₅ and N ₅ H ₃₇ W ₆ O ₂₄ is calculated by weight percentage: V ₂ O ₅ 88%, N ₅ H ₃₇ W ₆ O ₂₄ 6% , NH ₄ F 6%; the weight ratio of V ₂ O ₅ to oxalic acid is 1:3.

(1) Preparation of precursor

First put V ₂ O ₅ , N ₅ H ₃₇ W ₆ O ₂₄ , NH ₄ F, oxalic acid and polyethylene glycol with 5% of the total weight of V ₂ O ₅ and oxalic acid into the reaction vessel and add water to Stir at 70°C under high pressure (the amount of water added is not strictly required, it is advisable to submerge V ₂ O ₅ and oxalic acid), until the reduction reaction is completed and a blue liquid without precipitation is obtained (the whole process is about 2 hours), and the reduction After the reaction is completed, the obtained solution is evaporated to dryness at 100° C. to obtain a solid vanadyl oxalate precursor doped with W and F ions.

(2) Thermal decomposition of precursors

The obtained vanadyl oxalate precursor was pulverized and put into a tubular heating furnace, and heated to 500°C at a rate of 7°C/min under a vacuum of 25Pa, and turned off the power supply of the heating furnace after holding for 20 minutes to maintain the vacuum in the furnace , allowing the decomposition product to cool to room temperature to obtain a W-F composite doped vanadium dioxide nanopowder material.

The particle size of the W-F compound doped vanadium dioxide nanometer powder is ≤50nm, and the phase transition temperature is 28°C.

Claims (9)

1. A composite doped vanadium dioxide nanopowder material, characterized in that the molecular formula is V _1-x M _x O _2-y Z _y , where 0<x≤0.08, 0<y≤0.1, M is doped Doped metal elements, Z is doped non-metallic elements. 2. The composite doped vanadium dioxide nanopowder material according to claim 1, characterized in that the doped metal element is Mo, and the doped non-metal element is F. 3. The composite doped vanadium dioxide nanopowder material according to claim 1, characterized in that the doped metal element is W, and the doped non-metal element is F. 4. A method for preparing the composite doped vanadium dioxide nano-powder material according to claim 2, the process steps are successively the preparation of the precursor and the thermal decomposition of the precursor, characterized in that: (1) Preparation of precursor Using V ₂ O ₅ , oxalic acid, MoO ₃ and NH ₄ F as raw materials, the formula of V ₂ O ₅ , MoO ₃ and NH ₄ F is calculated by weight percentage: V ₂ O ₅ 88-98%, MoO ₃ 1-6 %, NH ₄ F 1-6%, the weight ratio of V ₂ O ₅ and oxalic acid is 1:1-3, firstly mix the V ₂ O ₅ and MoO ₃ in the said ratio evenly and put them into the container, Press down and heat to a molten state, then pour the melt into a reaction vessel filled with water and stir, then add the above-mentioned proportion of oxalic acid and NH ₄ F to the above solution and continue to stir until the reduction reaction is completed So far, the amount of water added is sufficient to disperse the molten _V2O5 and _MoO3 . After the reduction reaction is completed, _the obtained solution is evaporated to dryness to obtain a solid precursor of vanadyl oxalate doped with Mo and F ions; (2) Thermal decomposition of precursors Pulverize the obtained vanadyl oxalate precursor and put it into a heating furnace, heat it at a speed of 3-10 °C/min under normal pressure to 250 °C-300 °C and start vacuuming, and continue to vacuum under vacuum conditions at a rate of 3-10 °C/min. Heating at a rate of 10°C/min to 350°C-500°C, keeping the temperature for 20-40 minutes, then turning off the power supply of the heating furnace, keeping the vacuum in the furnace, allowing the decomposition products to cool to room temperature to obtain Mo and F-doped vanadium dioxide nanopowder body material; Or crush the obtained vanadyl oxalate precursor and heat it in a heating furnace to 150°C-250°C for 20-30 minutes, then vacuumize it, and heat it to 350°C-350°C at a speed of 3-10°C/min under vacuum conditions. 500°C, keep warm for 20 to 40 minutes, then turn off the power supply of the heating furnace, keep the vacuum in the furnace, let the decomposition products cool down to room temperature to obtain Mo and F doped vanadium dioxide nanopowder materials; Or pulverize the obtained vanadyl oxalate precursor and put it into a tubular heating furnace, heat it to 350 ° C ~ 500 ° C at a speed of 3 ~ 10 ° C / min under vacuum conditions, and turn off the power supply of the heating furnace after keeping it for 20 ~ 40 minutes. Keeping the vacuum in the furnace, allowing the decomposition product to cool down to room temperature to obtain Mo and F doped vanadium dioxide nanopowder material. 5. A method for preparing the composite doped vanadium dioxide nano-powder material according to claim 3, the process steps are successively the preparation of the precursor and the thermal decomposition of the precursor, characterized in that: (1) Preparation of precursor Using V ₂ O ₅ , oxalic acid, N ₅ H ₃₇ W ₆ O ₂₄ and NH ₄ F as raw materials, the formula of V ₂ O ₅ and N ₅ H ₃₇ W ₆ O ₂₄ and NH ₄ F is calculated by weight percentage: V ₂ O ₅ 88-98%, N ₅ H ₃₇ W ₆ O ₂₄ 1-6%, NH ₄ F 1-6%, the weight ratio of V ₂ O ₅ to oxalic acid is 1:1-3, the Put V ₂ O ₅ , N ₅ H ₃₇ W ₆ O ₂₄ , NH ₄ F and oxalic acid into the reaction vessel, add water and stir at 40-70°C under normal pressure until the reduction reaction is completed. The amount of water added depends on the reaction vessel It is advisable to submerge the raw materials in it. After the reduction reaction is completed, the obtained solution is evaporated to dryness to obtain a solid vanadyl oxalate precursor doped with W and F ions; (2) Thermal decomposition of precursors Pulverize the obtained vanadyl oxalate precursor and put it into a heating furnace, heat it at a speed of 3-10 °C/min under normal pressure to 250 °C-300 °C, and start vacuuming at a speed of 3-10 °C under vacuum conditions. Heat at a speed of ℃/min to 350℃～500℃, keep warm for 20～40 minutes, then turn off the power supply of the heating furnace, keep the vacuum in the furnace, let the decomposition products cool down to room temperature to obtain vanadium dioxide nanopowder doped with W and F Material; Or crush the obtained vanadyl oxalate precursor and heat it in a heating furnace to 150°C-250°C for 20-30 minutes, then vacuumize it, and heat it to 350°C-350°C at a speed of 3-10°C/min under vacuum conditions. 500°C, keep warm for 20 to 40 minutes, then turn off the power supply of the heating furnace, keep the vacuum in the furnace, let the decomposition products cool down to room temperature to obtain vanadium dioxide nanopowder materials doped with W and F; Or pulverize the obtained vanadyl oxalate precursor and put it into the heating furnace, heat it to 350°C-500°C at a speed of 3-10°C/min under vacuum conditions, turn off the power supply of the heating furnace after keeping the temperature for 20-40 minutes, and keep the furnace The vacuum degree inside is allowed to cool down the decomposition products to room temperature to obtain vanadium dioxide nanopowder material doped with W and F. 6. The method for preparing composite doped vanadium dioxide nano-powder material according to claim 4 or 5, characterized in that the process of annealing the vanadium dioxide nano-powder material obtained by thermal decomposition is to raise the temperature under vacuum conditions Keep warm at 400°C-600°C for 1-4 hours, then cool to room temperature under vacuum. 7. The method for preparing composite doped vanadium dioxide nano-powder material according to claim 4 or 5, characterized in that in the thermal decomposition step of the precursor, the vacuum degree in the heating furnace is controlled at 20-60Pa. 8. The method for preparing composite doped vanadium dioxide nano-powder material according to claim 4 or 5, characterized in that in the precursor preparation step, surfactant polyethylene glycol is added, and the amount of polyethylene glycol added It is 2-5% of the total weight of V ₂ O ₅ and oxalic acid. 9. The preparation method of composite doped vanadium dioxide nanopowder material according to claim 4 or 5, characterized in that V ₂ O ₅ is industrial grade or chemical reagent grade.