CN103708558A - CsxWOyFz powder and preparation method thereof - Google Patents

Abstract

The invention provides a Cs _x WO _y F _z powder and a preparation method thereof. The preparation method of the Cs _x WO _y F _z powder includes the following steps: mixing a tungstic acid solution with a fluorine source solution, adding an organic acid to form WO ₃ - F composite sol; add Cs ₂ CO ₃ solution to WO ₃ -F composite sol to form Cs-WO _{3 -F} composite sol; Heat reaction for 1 to 3 days; centrifuge the reactants in sequence, wash with water, wash with alcohol and dry to prepare Cs _x WO _y F _z powder. The preparation method of the invention does not require high-temperature hydrogen reduction, has simple process, low cost and low toxicity, and is favorable for large-scale production and practical application. The Cs _x WO _y F _z powder prepared by the invention has excellent visible light transmission and near-infrared shielding properties, and has broad application prospects in light transmission and heat shielding of building and automobile window glass.

Description

CsxWOyFz powder and preparation method thereof

technical field

The invention relates to material preparation technology, in particular to a Cs _x WO _y F _z powder and a preparation method thereof.

Background technique

Modern industrial production and human life consume a lot of energy and produce a lot of carbon dioxide. It is well known that too much carbon dioxide can lead to the greenhouse effect, an increase in global temperature. In summer, when electricity consumption reaches its peak, the use of air conditioners to cool indoor temperatures accounts for more than half of the average household's daytime electricity consumption. Therefore, how to reduce the use of air conditioners is a key point in promoting an environmentally friendly society.

According to reports, during the daytime in summer, the heat entering the room from openings such as windows accounts for 73% of the total heat. The heat introduced from the window mainly comes from sunlight, so to block the heat from entering through the window, it is necessary to block the heat of the sun. Visible light and infrared rays are related to lighting and heat shielding in sunlight, while near-infrared rays (wavelength 780-2500nm) have most of the heat in sunlight. If the amount of transmission is reduced, the heat shielding effect can be greatly improved.

At present, transparent heat-shielding materials are in great demand in the thermal insulation of automobiles and building window glass. Materials such as precious metals, carbon black rubber, rare earth hexaboride, and indium tin oxide (ITO) have the function of shielding near-infrared rays, and can be used for light transmission and heat shielding of automobile and building window glass. However, these materials all have disadvantages to varying degrees. According to reports, films containing noble metals or carbon black compounds have relatively low permeability to visible light; and rare earth hexaborides can only shield infrared rays of specific wavelengths, and the synthesis of rare earth hexaborides requires high temperature (1500 ° C) and vacuum environment; indium tin oxide (ITO) film is a well-known transparent conductive film with thermal radiation and heat insulation properties, but it can only shield infrared rays with a wavelength greater than 1500nm. In addition, indium is an expensive rare metal. Studies in recent years have found that Cs _x WO ₃ tungsten bronze has excellent near-infrared absorption properties, can absorb infrared rays less than 1500nm, and has high visible light transmittance, so it has a good transparent and heat-shielding function.

Patent CN102145980A reports a transparent heat insulating material, which is tungsten oxide co-doped with alkali metal and halogen, with a general formula of M _x WO _3-y A _y , wherein M is at least one metal element of the alkali metal group, and W is Tungsten, O is oxygen, A is a halogen element, and 0<x≤1, 0<y≤0.5; the patent also discloses its preparation method: using high-temperature hydrogen reduction method to obtain M _x WO _3-y A _y , the preparation process It is as follows: first prepare the precursors of cesium source, fluorine source, and tungsten oxide, and then obtain fluorine-doped cesium tungsten bronze by high-temperature reduction under hydrogen. Difficult to achieve mass production.

Contents of the invention

The purpose of the present invention is to propose a preparation method of Cs _x WO _y F _z powder to realize the reaction condition Mild, easy to implement the advantages of industrialization.

In order to achieve the above purpose, the technical solution adopted in the present invention is: a preparation method of Cs _x WO _y F _z powder, in which 0.1≤x≤0.5, 2≤y≤3.25 in the Cs _x WO _y F _z powder, 0<Z≤1.0;

The preparation method of the Cs _x WO _y F _z powder comprises the following steps:

(1) Mix tungstic acid solution and fluorine source solution according to F/W molar ratio of 0.11~1, add organic acid to form WO ₃ -F composite sol;

(2) Add Cs ₂ CO ₃ solution to the WO ₃ -F composite sol, so that the Cs/W molar ratio is 0.1 to 0.5, forming a Cs-WO ₃ -F composite sol;

(3) Put the Cs-WO ₃ -F composite sol in an autoclave, and conduct a hydrothermal reaction at 180-200°C for 1-3 days;

(4) The reactants were centrifuged, washed with water, washed with alcohol and dried in sequence to obtain Cs _x WO _y F _z powder.

Further, the molar ratio of the organic acid to W in step (1) is: 4.0-8.0.

Further, in step (1), organic acid is added, and the stirring is continued for 0.5-2 hours until the solution becomes clear, and a WO ₃ -F composite sol is formed.

Further, the fluorine source is hydrofluoric acid or sodium fluoride.

Further, when the fluorine source is hydrofluoric acid: the preparation of the fluorine source solution includes the following steps: adding HF acid to deionized water and diluting to 0.20-0.50 mol/L; when the fluorine source is sodium fluoride: Sodium fluoride is added into deionized water, so that the concentration of NaF solution is 0.20-0.50 mol/L.

Further, the organic acid is one or more of oxalic acid, citric acid, tartaric acid and ascorbic acid.

Further, the preparation of the tungstic acid solution includes the following steps: using a cation exchange resin to convert sodium tungstate into tungstic acid, and the concentration of the tungstic acid solution is 0.25-0.75 mol/L.

Further, the concentration of Cs ₂ CO ₃ is 0.2-0.9 mol/L, preferably 0.33 mol/L. .

Another object of the present invention is to provide a Cs _x WO _y F _z powder prepared by the above preparation method, wherein 0.1≤x≤0.5, 2≤y≤3.25, 0<Z≤1.0.

Further, the Cs _x WO _y F _z powder is more than 80% rod-shaped Cs _x WO _y F _z .

The preparation method of Cs _x WO _y F _z powder of the present invention is scientific and reasonable, and has the following advantages compared with the prior art:

1. The mixing order of the materials is reasonable. The first mixing of the tungstic acid solution and the fluorine source solution of the present invention helps to promote the incorporation of fluoride ions into the tungsten oxide lattice; The complexation reaction of citric acid and tungstic acid will affect the incorporation of fluoride ions;

2. The introduction of fluorine source by hydrothermal reaction can further increase the carrier concentration in the Cs _x WO _y F _z tungsten bronze structure and regulate its forbidden band width; and the formation of rod-shaped Cs _x WO _y F _z particles can be induced during the synthesis process , the rod-shaped Cs _x WO _y F _z powder in the Cs _x WO _y F _z powder prepared by the preparation method of the present invention is greater than 80%. Due to the electronic vibration perpendicular to and parallel to the rod length direction, the rod-shaped structure produces horizontal and vertical plasma Resonance is conducive to improving the absorption of near-infrared light waves;

3. The present invention uses organic acid as a reducing agent and an inducing agent, and can reduce W ⁶⁺ to W ⁵⁺ in a hydrothermal system to create oxygen vacancies, and the appearance of oxygen vacancies is conducive to the incorporation of F atoms and Cs atoms ; At the same time, the organic acid also acts as a complexing agent in the precursor solution, which is conducive to the formation of a stable WO ₃ -F sol;

4. The present invention has mild reaction conditions, does not require high-temperature hydrogen reduction, and reduces unsafe factors in the production process;

5. The preparation process of the present invention has low toxicity, and the raw materials used, except for the fluorine source, are not volatile raw materials and can be directly contacted;

Compared with the pure cesium tungsten bronze powder, the fluorine-doped cesium tungsten bronze powder has better transparent heat-shielding function. This is because in this method, F ^- ions improve the performance of cesium tungsten bronze powder from three aspects: 1. Inducing the cesium tungsten bronze powder to form a rod-shaped morphology and improving near-infrared absorption; 2. Doping cesium tungsten bronze oxygen vacancies to improve 3. Doping cesium tungsten bronze oxygen vacancies increases carrier concentration and improves near-infrared absorption.

Description of drawings

Fig. 1 is the XPS spectrogram of W4f in the cesium tungsten bronze of embodiment 4;

Fig. 2 is the XPS spectrogram of F1s in the cesium tungsten bronze of embodiment 4;

Fig. 3 is the SEM picture of the fluorine-doped cesium tungsten bronze of different fluorine additions, and wherein a, b and c are respectively the SEM picture of comparative example 1, embodiment 3 and embodiment 4 fluorine-doped cesium tungsten bronze;

Fig. 4 is the TEM picture of the fluorine-doped cesium tungsten bronze of different fluorine addition amounts, wherein a, b, c and d are respectively the TEM picture of comparative example 1, embodiment 1, embodiment 3 and embodiment 4 fluorine-doped cesium tungsten bronze ;

Fig. 5 is the visible-near-infrared transmission spectrum of the fluorine-doped cesium tungsten bronze film of different fluorine addition amount;

Fig. 6 is the ultraviolet-visible diffuse reflection spectrum of the fluorine-doped cesium tungsten bronze film of different fluorine additions and the ultraviolet-visible absorption spectrum of the fluorine-doped cesium tungsten bronze of different fluorine additions;

Fig. 7 is the visible-near-infrared transmission spectrum diagram of the fluorine-doped cesium tungsten bronze thin film of different fluorine sources adding sequence, wherein a and b are respectively the visible-near-infrared transmission of the fluorine-doped cesium tungsten bronze thin film in embodiment 1 and comparative example 2 spectrum.

Detailed ways

This example discloses a preparation method of Cs _x WO _y F _z powder with visible light transmission and near-infrared shielding functions. In the Cs _x WO _y F _z powder, 0.1≤x≤0.5, 2≤y≤3.25, 0<Z≤1.0;

The preparation method of the Cs _x WO _y F _z powder is hydrothermal synthesis, specifically comprising the following steps:

(1) Mix tungstic acid solution and fluorine source solution according to the F/W molar ratio of 0.11~1, and keep stirring for 0.5~2h, add organic acid to form WO ₃ -F composite sol, and prolong the stirring time is conducive to the formation of fluoride ions fully incorporated;

The preparation of the tungstic acid solution comprises the following steps: washing the hydrochloric acid-activated cation exchange resin with water to neutrality, then slowly passing the sodium tungstate through the cation exchange resin, and finally obtaining a light yellow tungstic acid solution. The concentration of the tungstic acid solution is 0.25-0.75 mol/L, preferably the concentration of the tungstic acid solution is 0.5 mol/L.

The fluorine source in the present invention is hydrofluoric acid or sodium fluoride. Hydrofluoric acid and sodium fluoride are dissolved in water to generate hydrogen ions, fluoride ions, sodium ions and fluoride ions, respectively. The hydrogen ions and sodium ions have a smaller ionic radius, so they will not enter the tungsten bronze structure. Other fluorine sources, such as ammonium fluoride, calcium fluoride, etc., will incorporate ammonia ions or calcium ions into the tungsten bronze structure during the hydrothermal process. When the fluorine source is hydrofluoric acid: the preparation of the fluorine source solution includes the following steps: adding HF acid to deionized water and diluting it to 0.20-0.50 mol/L, placing it in a plastic bottle for storage, wherein the optimal concentration of HF acid If the concentration of HF acid is too low, the output of cesium tungsten bronze will be too low; if the concentration of HF acid is too high, it will excessively corrode the crystal of cesium tungsten bronze, causing tungsten defects and reducing near-infrared absorption. When the fluorine source is sodium fluoride: adding sodium fluoride to deionized water, so that the concentration of NaF solution is 0.20-0.50 mol/L, wherein the optimum concentration of NaF solution is 0.22 mol/L. The doping of fluorine source can increase the carrier concentration in the Cs _x WO _y F _z tungsten bronze structure and regulate its forbidden band width. The present invention improves the carrier concentration of cesium tungsten bronze by doping fluorine atoms, which not only improves the surface plasmon Bulk resonance strength, and the bandgap width of cesium tungsten bronze is increased, thereby increasing the transmittance of visible light. The fluorine source added in the present invention can not only replace the oxygen ions in cesium tungsten bronze (Cs _x WO ₃ ) with F ions during the synthesis process to increase the carrier concentration of the particles, but also the fluorine ions play a role in the growth of the crystal. Induction. In Comparative Example 1, no fluorine source was added to the precursor liquid, and the cesium tungsten bronze crystals were small irregular grains. With the addition of the fluorine source, the morphology of the cesium tungsten bronze grains changes into nanorods, and the nanorods mean that the Cs _x WO _y F powder is a rod-shaped material with a diameter of micronano scale. Due to the longitudinal ion oscillation as well as the transverse ion oscillation, the rod-like morphology has been confirmed to have better light wave absorption performance.

The organic acid used in the present invention is one or more of oxalic acid, citric acid, tartaric acid and ascorbic acid. The molar ratio of the organic acid to W is 4.0-8.0, preferably the molar ratio of the organic acid to W is 6.05. Add an organic acid, and continue stirring for 0.5-2 hours until the solution is clear, and a WO ₃ -F composite sol is formed. The organic acid is a reducing agent and an inducing agent, which can reduce W ⁶⁺ to W ⁵⁺ in a hydrothermal system to create oxygen vacancies, and the appearance of oxygen vacancies is conducive to the incorporation of F atoms and Cs atoms; at the same time, The organic acid also acts as a complexing agent in the precursor solution, which is beneficial to the formation of a stable WO ₃ -F sol.

(2) Add Cs ₂ CO ₃ solution to the WO ₃ -F composite sol, so that the Cs/W molar ratio is 0.1 to 0.5 to form a Cs-WO ₃ -F composite sol; the Cs ₂ CO ₃ concentration is 0.2 to 0.5 0.9mol/L, the preferred concentration is 0.33mol/L. (3) Put the Cs-WO ₃ -F composite sol in a closed autoclave, and conduct a hydrothermal reaction at 180-200°C for 1-3 days; preferably, the reaction temperature and time are 190°C for 3 days.

(4) The reactants were centrifuged, washed with water, washed with alcohol and dried in sequence to obtain Cs _x WO _y F _z powder. Specifically: after the hydrothermal reaction is completed, pour off the supernatant, collect the powder, centrifuge, wash three times with deionized water and three times with absolute ethanol; dry the washed powder at 60°C under normal pressure, A fluorine-doped cesium tungsten bronze Cs _x WO _y F _z powder was obtained.

The hydrothermal synthesis method does not require high-temperature hydrogen reduction, the process is simple, the cost is low, and the toxicity is small, which is conducive to large-scale production and practical application.

The carrier concentration plays a decisive role in the near-infrared shielding performance. The doping of fluorine element in the tungsten bronze improves the carrier concentration of the cesium tungsten bronze and enhances its conductivity at the same time. The rod-shaped Cs _x WO _y F _z powder in the Cs _x WO _y F _z powder prepared by the above preparation method is greater than 80%. The rod-shaped fluorine-doped cesium tungsten bronze powder Cs _x WO _y F _z has excellent visible light transmission and near-infrared shielding properties, and has broad application prospects in the light transmission and heat shielding of building and automobile window glass.

The present invention is further described below in conjunction with embodiment:

In the following examples, unless otherwise specified, in the determination of the performance parameters of the prepared fluorine-doped cesium tungsten bronze (Cs _x WO _y F _z ):

(1) The microscopic morphology of fluorine-doped cesium tungsten bronze powder particles was observed by JEOL JSM-6460LV scanning electron microscope (SEM).

(2) The morphology and structure of fluorine-doped cesium tungsten bronze crystals were observed by JEOL JEM-2100 transmission electron microscope (TEM).

(3) The surface chemical composition of the synthesized fluorine-doped cesium tungsten bronze was analyzed by VG ESCALAB MK2 X-ray photoelectron spectrometer (XPS), using Al Kα rays.

(4) The optical properties of the fluorine-doped cesium tungsten bronze film in the wavelength range of 300nm to 2500nm were characterized by a lambda 950 ultraviolet-visible-near-infrared spectrophotometer produced by Perkin Elmer. The specific preparation method of the fluorine-doped cesium tungsten bronze film: disperse 0.3g of fluorine-doped cesium tungsten bronze powder in water, add PVA solution after ultrasonic vibration, heat and stir in a water bath, and obtain fluorine-doped cesium tungsten bronze coating. It is coated on a glass sheet by roller coating to obtain a fluorine-doped cesium tungsten bronze film. The calculation method of near-infrared shading rate is: near-infrared shading rate=100-near-infrared transmittance; the calculation method of heat insulation index is: heat insulation index=(visible light transmittance+near-infrared shading rate)×100.

(5) The optical absorption properties of fluorine-doped cesium tungsten bronze in the range of 190nm to 1100nm were characterized by a lambda35 ultraviolet-visible spectrophotometer produced by Perkin Elmer. Specific test method: with BaCl ₂ as the background, the powder is pressed on the BaCl ₂ sheet, and its absorbance is tested. The bandgap width is obtained through the intercept line, the specific method: the absorbance and the corresponding wavelength are converted by the formula (αhν) ² =A(hν-E _g ), the curve is made, the intercept line of the curve is obtained, and finally the intercept line is obtained in the light The value on the energy axis is the forbidden band width.

Comparative example 1

Take the insulation material with Cs:W (molar ratio)=0.33:1 prepared in a 200ml autoclave as an example

Add 6.60g of sodium tungstate Na ₂ WO ₄ into 40ml of deionized water to prepare a 0.5mol/L transparent sodium tungstate solution. Then pass 40ml of sodium tungstate solution through the activated cation exchange resin to obtain light yellow tungstic acid liquid A1 with a pH of 1-1.5. Take 25.4g of citric acid and add directly into the A1 solution, keep stirring until the solution is clear, then add deionized water until the volume of the solution is 100ml, and obtain the solution A3. Take 1.076g of cesium carbonate and add it into 10ml of deionized water to obtain solution C1. The C1 solution was slowly added to the A3 solution to obtain the precursor solution A4. The A4 solution was transferred to a polytetrafluoroethylene-lined autoclave, and reacted at 190° C. for 3 days. After the reaction is completed, the powder is collected and washed three times with water and three times with alcohol. Finally, it was dried at 60°C to obtain Cs _0.33 WO _y powder.

Comparative example 2

Take a 200ml autoclave to prepare a thermal insulation material with Cs:W:F (molar ratio)=0.33:1:0.11 as an example (the order of adding materials is different from that in Examples 1-5)

Add 6.60g of sodium tungstate Na ₂ WO ₄ into 40ml of deionized water to prepare a 0.5mol/L transparent sodium tungstate solution. Then pass 40ml of sodium tungstate solution through the activated cation exchange resin to obtain light yellow tungstic acid liquid A1 with a pH of 1-1.5. Take 1ml of analytical pure hydrofluoric acid solution and add it to 102ml of deionized water to prepare 0.22mol/L hydrofluoric acid solution B1. Take 25.4g of citric acid and add directly into the A1 solution, and keep stirring until the solution is clear to obtain the mixed solution A2. Add 10ml of the B1 solution into the A2 solution, continue to stir for 30-60 minutes, and then add deionized water until the volume of the solution is 100ml to obtain the solution A3. Take 1.076g of cesium carbonate and add it into 10ml of deionized water to obtain solution C1. The C1 solution was slowly added to the A3 solution to obtain the precursor solution A4. The A4 solution was transferred to a polytetrafluoroethylene-lined autoclave, and reacted at 190° C. for 3 days. After the reaction is completed, the powder is collected and washed three times with water and three times with alcohol. Finally, dry at 60°C to obtain Cs _0.33 WO _y F _0.11 powder.

Example 1

Take the insulation material with Cs:W:F (molar ratio)=0.33:1:0.11 prepared in a 200ml autoclave as an example

Add 6.60g of sodium tungstate Na ₂ WO ₄ into 40ml of deionized water to prepare a 0.5mol/L transparent sodium tungstate solution. Then pass 40ml of sodium tungstate solution through the activated cation exchange resin to obtain light yellow tungstic acid liquid A1 with a pH of 1-1.5. Take 1ml of analytical pure hydrofluoric acid solution and add it to 102ml of deionized water to prepare 0.22mol/L hydrofluoric acid solution B1. Add 10ml of the B1 solution into the A1 solution, and keep stirring for 30-60 minutes to obtain the mixed solution A2. Take 25.4g of citric acid and add directly into the A2 solution, keep stirring until the solution is clear, then add deionized water until the volume of the solution is 100ml, and obtain the solution A3. Take 1.076g of cesium carbonate and add it into 10ml of deionized water to obtain solution C1. The C1 solution was slowly added to the A3 solution to obtain the precursor solution A4. The A4 solution was transferred to a polytetrafluoroethylene-lined autoclave, and reacted at 190° C. for 3 days. After the reaction is completed, the powder is collected and washed three times with water and three times with alcohol. Finally, it was dried at 60°C to obtain Cs _0.33 WO _y F _0.11 powder. The fluorine source added in this embodiment can improve the visible light transmittance and near-infrared shielding performance of the cesium tungsten bronze from the aspects of carrier concentration, band gap, and morphology.

Example 2

Take the insulation material with Cs:W:F (molar ratio)=0.33:1:0.28 prepared in a 200ml autoclave as an example

Add 6.60g of sodium tungstate Na ₂ WO ₄ into 40ml of deionized water to prepare a 0.5mol/L transparent sodium tungstate solution. Then pass 40ml of sodium tungstate solution through the activated cation exchange resin to obtain light yellow tungstic acid liquid A1 with a pH of 1-1.5. Take 1ml of analytical pure hydrofluoric acid solution and add it to 102ml of deionized water to prepare 0.22mol/L hydrofluoric acid solution B1. Add 25.5ml of the B1 solution into the A1 solution, and keep stirring for 30-60 minutes to obtain the mixed solution A2. Take 25.4g of citric acid and add directly into the A2 solution, keep stirring until the solution is clear, then add deionized water until the volume of the solution is 100ml, and obtain the solution A3. Take 1.076g of cesium carbonate and add it into 10ml of deionized water to obtain solution C1. The C1 solution was slowly added to the A3 solution to obtain the precursor solution A4. The A4 solution was transferred to a polytetrafluoroethylene-lined autoclave, and reacted at 190° C. for 3 days. After the reaction is completed, the powder is collected and washed three times with water and three times with alcohol. Finally, dry at 60°C to obtain Cs _0.33 WO _y F _0.28 powder. In this embodiment, by doping fluorine atoms to increase the carrier concentration of the cesium tungsten bronze, not only the intensity of the surface plasmon resonance is increased, but also the band gap of the cesium tungsten bronze is increased, thereby increasing the transmittance of visible light.

Example 3

Take the insulation material with Cs:W:F (molar ratio)=0.33:1:0.45 prepared in a 200ml autoclave as an example

Add 6.60g of sodium tungstate Na ₂ WO ₄ into 40ml of deionized water to prepare a 0.5mol/L transparent sodium tungstate solution. Then pass 40ml of sodium tungstate solution through the activated cation exchange resin to obtain light yellow tungstic acid liquid A1 with a pH of 1-1.5. Take 1ml of analytical pure hydrofluoric acid solution and add it to 102ml of deionized water to prepare 0.22mol/L hydrofluoric acid solution B1. Add 41ml of the B1 solution into the A1 solution, and keep stirring for 30-60 minutes to obtain the mixed solution A2. Take 25.4g of citric acid and add directly into the A2 solution, keep stirring until the solution is clear, then add deionized water until the volume of the solution is 100ml, and obtain the solution A3. Take 1.076g of cesium carbonate and add it into 10ml of deionized water to obtain solution C1. The C1 solution was slowly added to the A3 solution to obtain the precursor solution A4. The A4 solution was transferred to a polytetrafluoroethylene-lined autoclave, and reacted at 190° C. for 3 days. After the reaction is completed, the powder is collected and washed three times with water and three times with alcohol. Finally, dry at 60°C to obtain Cs _0.33 WO _y F _0.45 powder. In this embodiment, by doping fluorine atoms to increase the carrier concentration of the cesium tungsten bronze, not only the intensity of the surface plasmon resonance is increased, but also the band gap of the cesium tungsten bronze is increased, thereby increasing the transmittance of visible light.

Example 4

Take the insulation material with Cs:W:F (molar ratio)=0.33:1:0.79 prepared in a 200ml autoclave as an example

Add 6.60g of sodium tungstate Na ₂ WO ₄ into 40ml of deionized water to prepare a 0.5mol/L transparent sodium tungstate solution. Then pass 40ml of sodium tungstate solution through the activated cation exchange resin to obtain light yellow tungstic acid liquid A1 with a pH of 1-1.5. Take 2ml of analytical pure hydrofluoric acid solution and add it to 98ml of deionized water to prepare 0.45mol/L hydrofluoric acid solution B1. Add 35ml of the B1 solution into the A1 solution, and keep stirring for 30-60 minutes to obtain the mixed solution A2. Take 25.4g of citric acid and add directly into the A2 solution, keep stirring until the solution is clear, then add deionized water until the volume of the solution is 100ml, and obtain the solution A3. Take 1.076g of cesium carbonate and add it into 10ml of deionized water to obtain solution C1. The C1 solution was slowly added to the A3 solution to obtain the precursor solution A4. The A4 solution was transferred to a polytetrafluoroethylene-lined autoclave, and reacted at 190° C. for 3 days. After the reaction is completed, the powder is collected and washed three times with water and three times with alcohol. Finally, it was dried at 60°C to obtain Cs _0.33 WO _y F _0.79 powder. In this embodiment, by doping fluorine atoms to increase the carrier concentration of the cesium tungsten bronze, not only the intensity of the surface plasmon resonance is increased, but also the band gap of the cesium tungsten bronze is increased, thereby increasing the transmittance of visible light.

Example 5

Take the insulation material with Cs:W:F (molar ratio)=0.33:1:1 prepared in a 200ml autoclave as an example

Add 6.60g of sodium tungstate Na ₂ WO ₄ into 40ml of deionized water to prepare a 0.5mol/L transparent sodium tungstate solution. Then pass 40ml of sodium tungstate solution through the activated cation exchange resin to obtain light yellow tungstic acid liquid A1 with a pH of 1-1.5. Take 2ml of analytical pure hydrofluoric acid solution and add it to 98ml of deionized water to prepare 0.45mol/L hydrofluoric acid solution B1. Add 44ml of the B1 solution into the A1 solution, and keep stirring for 30-60 minutes to obtain the mixed solution A2. Take 25.4g of citric acid and add directly into the A2 solution, keep stirring until the solution is clear, then add deionized water until the volume of the solution is 100ml, and obtain the solution A3. Take 1.076g of cesium carbonate and add it into 10ml of deionized water to obtain solution C1. The C1 solution was slowly added to the A3 solution to obtain the precursor solution A4. The A4 solution was transferred to a polytetrafluoroethylene-lined autoclave, and reacted at 190° C. for 3 days. After the reaction is completed, the powder is collected and washed three times with water and three times with alcohol. Finally, dry at 60°C to obtain Cs _0.33 WO _y F _1.0 powder. In this embodiment, by doping fluorine atoms to increase the carrier concentration of the cesium tungsten bronze, not only the intensity of the surface plasmon resonance is increased, but also the band gap of the cesium tungsten bronze is increased, thereby increasing the transmittance of visible light.

Fig. 1 is the XPS spectrogram of W4f in the cesium tungsten bronze of embodiment 4, as shown in Fig. 1, the spectral peaks at 34.87eV, 37.02eV and 36.17eV, 38.32eV respectively correspond to W ⁵⁺ and W ⁶⁺ , illustrating that The prepared Cs _0.33 WO _y F _0.79 contains a certain amount of W ⁵⁺ . Figure 2 is the XPS spectrum of F1s in cesium tungsten bronze in Example 4. The spectrum shown in Figure 2 shows that part of F in Cs _0.33 WO _y F _0.79 exists in the state of F ^- ions, and part of it exists in the state of FWO bonding.

Figure 3 is the SEM image of fluorine-doped cesium tungsten bronze with different fluorine additions. It can be seen from the figure that with the increase of fluorine addition, the number of rod-shaped particles in the synthesized fluorine-doped cesium tungsten bronze powder increases, indicating that the addition of fluorine has an effect on rod-shaped particles. Particle growth has a certain inductive effect.

Figure 4 is a TEM image of fluorine-doped cesium tungsten bronze with different fluorine additions. It can be seen more clearly from the figure that the rod-shaped particles in the synthesized fluorine-doped cesium tungsten bronze powder increase with the increase of fluorine doping, further It shows that the incorporation of fluorine is beneficial to the formation of rod-shaped particles.

Figure 5 is the visible-near-infrared transmission spectrum of fluorine-doped cesium tungsten bronze films with different fluorine additions. It can be seen from the figure that as the fluorine doping increases, the visible light transmittance increases, and the near-infrared shielding performance first increases and then decreases; The Cs _0.33 WO _y F _0.45 powder dispersion synthesized when the fluorine doping amount z=0.45 has the best near-infrared shielding performance, and the visible light transmittance is better than that of the sample without fluorine doping.

Fig. 6 is the ultraviolet-visible diffuse reflectance spectrum of the fluorine-doped cesium tungsten bronze film of different fluorine additions and the ultraviolet-visible absorption spectrum of the fluorine-doped cesium tungsten bronze of different fluorine additions; The tape width increases.

Fig. 7 is the visible-near-infrared transmission spectrum diagram of the fluorine-doped cesium tungsten bronze film of different fluorine sources adding order, wherein a and b are the visible-near-infrared transmission of fluorine-doped cesium tungsten bronze film in embodiment 1 and comparative example 2 respectively spectrum. It can be seen from the figure that compared with Comparative Example 2, the fluorine-doped cesium tungsten bronze prepared in Example 1 exhibited higher visible light transmittance and near-infrared shielding performance, indicating that it has better light transmission and heat shielding performance.

Table 1 shows the band gap and thermal insulation index of fluorine-doped cesium tungsten bronze (Cs _x WO _y F _z ) with different fluorine doping amounts. It can be seen from Table 1 that the ratio of fluorine-doped cesium tungsten bronze (Cs _x WO _y F _z ) The pure cesium tungsten bronze without fluorine shows high near-infrared shielding rate and thermal insulation index, especially when the fluorine doping amount z=0.45, the synthesized Cs _0.33 WO _y F _0.45 powder dispersion has the best Excellent near-infrared shielding performance and heat insulation performance.

Table 1 Comparative Example 1, Examples 1-5 The bandgap width and thermal insulation index of fluorine-doped cesium tungsten bronze (Cs _x WO _y F _z )

The present invention is not limited to the Cs _x WO _y F _z powder and its preparation method described in the above examples, the change of the molar ratio of each component, the change of the concentration of each solution and the change of reaction conditions are all within the protection scope of the present invention within.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (10)

1. a Cs _xwO _yf _zthe preparation method of powder, is characterized in that, described Cs _xwO _yf _z0.1≤x≤0.5 in powder, 2≤y≤3.25,0 < Z≤1.0;

Described Cs _xwO _yf _zthe preparation method of powder comprises the following steps:

(1), by wolframic acid solution and fluorine source solution, according to F/W mol ratio, be 0.11～1 to mix, add organic acid to form WO ₃-F complex sol;

(2), to WO ₃in-F complex sol, add Cs ₂cO ₃solution, making Cs/W mol ratio is 0.1～0.5, forms Cs-WO ₃-F complex sol;

(3), by Cs-WO ₃-F complex sol is placed in autoclave, and at 180～200 ℃, hydro-thermal reaction is 1～3 day;

(4), by reactant successively centrifugal, washing, alcohol wash and the dry Cs for preparing _xwO _yf _zpowder.

2. Cs according to claim 1 _xwO _yf _zthe preparation method of powder, is characterized in that, described in step (1), the mol ratio of organic acid and W is: 4.0～8.0.

3. Cs according to claim 1 _xwO _yf _zthe preparation method of powder, is characterized in that, step adds organic acid in (1), continues to stir 0.5～2h and clarifies to solution, forms WO ₃-F complex sol.

4. according to Cs described in claim 1 or 2 _xwO _yf _zthe preparation method of powder, is characterized in that, described fluorine source is hydrofluoric acid or Sodium Fluoride.

5. Cs according to claim 4 _xwO _yf _zthe preparation method of powder, is characterized in that, when described fluorine source is hydrofluoric acid: the preparation of fluorine source solution comprises the following steps: add deionized water to be diluted to 0.20～0.50mol/L HF acid; When described fluorine source is Sodium Fluoride: Sodium Fluoride is added to deionized water, and making NaF strength of solution is 0.20～0.50mol/L.

6. according to Cs described in claim 1 or 3 _xwO _yf _zthe preparation method of powder, is characterized in that, described organic acid is one or more in oxalic acid, citric acid, tartrate and xitix.

7. Cs according to claim 1 _xwO _yf _zthe preparation method of powder, is characterized in that, the preparation of described wolframic acid solution comprises the following steps: utilize Zeo-karb that sodium wolframate is converted into wolframic acid, described wolframic acid strength of solution is 0.25～0.75mol/L.

8. Cs according to claim 1 _xwO _yf _zthe preparation method of powder, is characterized in that, described Cs ₂cO ₃concentration is 0.2～0.9mol/L.

9. one kind adopts the Cs that prepared by method described in claim 1～8 any one _xwO _yf _zpowder.

10. Cs according to claim 9 _xwO _yf _zpowder, is characterized in that, wherein bar-shaped Cs _xwO _yf _zpowder is greater than 80%.

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