CN1359865A

CN1359865A - Prosess for depositing gas-induced allochroic WO3 film on substrate

Info

Publication number: CN1359865A
Application number: CN 01130015
Authority: CN
Inventors: 沈辉; 庄琳; 徐雪青
Original assignee: Guangzhou Institute of Energy Conversion of CAS
Current assignee: Guangzhou Institute of Energy Conversion of CAS
Priority date: 2001-12-03
Filing date: 2001-12-03
Publication date: 2002-07-24

Abstract

The invention provides a method for depositing WO ₃ aerochromic film on a substrate. The method uses tungsten powder and hydrogen peroxide as main raw materials, adopts tungsten powder peroxidized polytungstic acid method to deposit WO ₃ sol, and adds volatile The sol of polytungstic acid is obtained by distillation under reduced pressure, and palladium, platinum and other transition metal compounds are used as catalysts to form a coating solution, which is deposited on the substrate by dip-caoting. Colorless and transparent WO ₃ aerochromic film. The method is simple in process and low in cost; the deposited sol can be stable for more than two months; the formed film has better aerochromic properties; and the hardness and adhesion to the substrate are greatly enhanced compared with the prior art.

Description

Deposition of gas-induced discoloration WO on substrate3Method for making thin film

The present invention relates to a process, in particular to a process for depositing gasochromic WO on a substrate₃A method of making a thin film.

The gasochromic phenomenon refers to a color development effect of absorbing light waves with certain wavelength by a reversible reaction of a material after the material is contacted with reaction gas. The german Fraunhofer institute adopts an electron beam evaporation method to deposit a tungsten trioxide film with a thickness of about 1 micron on a flat glass, and plates a platinum catalyst layer with a thickness of 2.5-3.5nm on the tungsten trioxide film, a piece of coated glass (the tungsten trioxide film is arranged on the inner side) and another piece of flat glass are made into a gasochromic device, hydrogen and argon mixed gas (the hydrogen concentration is within a safety limit range, such as less than 1-5 percent) is introduced into the device, the coated glass turns blue, the average light transmittance of the device in a visible light region is reduced to 18 percent, air is introduced into the device, the light transmittance of the device is recovered, wherein the coloring response time is 10-20 seconds, and the fading response time is 1-. There are problems in that the cost is high and it is inconvenient to produce in a large area. Zayat et al deposited a platinum-doped tungsten trioxide film about 100nm thick on a glass substrate using ion exchange, and the light transmittance of the device in the colored state at 550 nm was reduced to 50-55%. The method has the advantages of low cost and the disadvantages of short sol stabilizing time, low film hardness and poor adhesive force.

The invention aims to deposit a gas-induced discoloration WO with higher hardness and stronger adhesive force on a substrate₃A method of making a thin film.

The object of the invention can be achieved by the following measures: deposition of WO on a substrate₃A method of producing a gasochromic film, characterized by comprising the steps of:

a) tungsten powder (purity 99.8%) and H₂O₂Mixing and reacting until the tungsten powder is completely dissolved;

b) unreacted H₂O₂Removing with platinum net, filtering to remove lower precipitate to obtain shallow precipitate

Yellow transparent WO₃Sol;

c) adding solvent with strong volatility into the concentrated sol to obtain poly-tungsten

A sol of an acid;

d) doping transition metal compounds such as palladium, platinum and the like as a catalyst;

e) with WO incorporating sol stabilisers and catalysts₃The sol is a coating liquid, and the sol is a coating liquid,

depositing on a glass substrate by dip-coating to obtain colorless film

Ming WO₃A gasochromic film;

f) and (5) drying.

The object of the invention is also achieved by the following measures: adding SiO after step (c) or step (d)₂Solution or ethyl orthosilicate in ethanol, SiO added₂To WO₃The molar ratio of (A) to (B) is 2-4: 1. The drying in the step (f) is carried out by natural drying or heat treatment at 150 ℃ for 1 hour. The concentration of the polytungstic acid prepared in the step (a) is 1.0-1.2M. The solvent with strong volatility added in the step (c) is ethanol or acetone, and the volume ratio of the ethanol or the acetone to the sol is 1-4: 1. The step (c) is carried out by adopting the following method: adding ethanol or acetone to 1-2 times of original sol volume, and vacuum distilling and concentrating the sol to 1-2 times. The step (c) can also be carried out by the following method: distilling the sol under reduced pressure for 3-5 times, adding ethanol to make the volume ratio of ethanol to sol be 24: 1, and distilling under reduced pressure to 1-2 times of original sol concentration. Using palladium chloride (PdCl)₂) Solutions or potassium chloroplatinite (K)₂PtCl₄) The solution is used as a catalyst, the molar ratio of K2PtCl4 to WO3 is 1-5%, and the molar ratio of PdCl2 to WO3 is 0.1-2.5%. The material of the substrate may be glass or ceramic. When soda-lime glass is used as a substrate, a barrier layer film is coated on the substrate in advance, and the barrier layer film is SiO₂Film or AL₂O₃A film.

The invention adopts a tungsten powder peroxidation poly-tungstic acid method to deposit tungsten trioxide sol, and then makes the deep gel form a film on a substrate. The reaction can be represented by the following formula:

the concentration of the prepared polytungstic acid sol is moderate. If the concentration is too low, the film thickness is too thin and the film coloring degree is low (the film coloring degree is proportional to the film thickness). If the concentration is too high, the tungsten trioxide will gel during the reaction. The sol concentration is preferably 1.0 to 1.2M.

The solvent with strong volatility in the step (c) can adopt ethanol or acetone.

The sol concentration in step (c) may be carried out by distillation under reduced pressure.

Said step (c) is generally carried out by the following method: adding ethanol or acetone into the sol to 1-2 times of the original sol volume, carrying out reduced pressure distillation and concentration on the sol by 1-2 times, and repeating the operation for 2-4 times to achieve the required sol concentration. In this case, the sol can be stable for several months.

Said improvement of step (c) is: distilling the sol under reduced pressure for 3-5 times, adding ethanol to make the volume ratio of ethanol to sol be 24: 1, and distilling under reduced pressure to 1-2 times of original sol concentration. In this case, the sol can be stable for several months, even a year.

The ethanol or acetone can not only improve the stability of the sol, but also improve the uniformity of the film. When the film is formed by the pulling method, when the volatility of the solvent in the sol is low, the film is not uniformly formed, and in order to improve the volatility of the solvent, the content of water is reduced, and the content of volatile solvents such as ethanol or acetone is increased. The method of adding the sol into ethanol or acetone and distilling the sol under reduced pressure can better improve the film forming uniformity of the sol. However, this method generally only increases the volume ratio of ethanol or acetone to water in the sol to 6 to 9. When the humidity of the outside air is high or when a barrier layer film is arranged on the glass substrate, the sol film formation is still uneven. To further increase the solvent volatility, the volume ratio of ethanol or acetone to water is increased. The preferred method of the invention is: adding ethanol into the concentrated sol to ensure that the volume ratio of the ethanol to the water is 24: 1, and then distilling under reduced pressure to reach the required concentration.

The catalyst can adopt palladium chloride (PdCl)₂) Solutions or potassium chloroplatinite (K)₂PtCl₄) And (3) solution.

When potassium chloroplatinite (K)₂PtCl₄) When preparing an aqueous or alcoholic solution as catalyst, K₂PtCl₄To WO₃The molar ratio of (A) is 1-5%. When palladium chloride(PdCl)₂) When the PdCl is prepared into aqueous solution or alcohol solution and is added as a catalyst, PdCl₂To WO₃The molar ratio of (A) is 1-5%.

The film forming method adopts a drawing coating method. The dip coating method has the advantage of facilitating large-area film formation. The pulling speed is 75mm/min-300 mm/min.

To WO₃The film can be dried naturally or by heat treatment. When heat treatment is used to dry WO₃In the case of thin films, the temperature of the heat treatment is generally about 150 ℃ and the time of the heat treatment is 40min to 1 h.

To further enhance WO₃The hardness and adhesion of the film to the substrate, a further improvement of the invention, is found in WO₃Adding SiO into the sol₂Sol or ethyl orthosilicate in ethanol to obtain WO₃-SiO₂And (3) compounding the film. The specific process is that SIO2 solution or ethyl orthosilicate ethanol solution is added after the step (c) or the step (d) of the method of the invention, and the WO prepared by the method₃-SiO₂After the composite film is subjected to heat treatment at the temperature of 150-To an enhancement. When using an ethanol solution containing ethyl orthosilicate, the amount of ethyl orthosilicate is such that WO is added₃With SiO₂The molar ratio is 2-4: 1, and the adding amount of the ethanol is to ensure that the tetraethoxysilane is miscible with the water.

The substrate material of the present invention may be glass or ceramic.

When soda-lime glass is used as a substrate material, sodium ions and calcium ions in the glass substrate can migrate into the film in the heat treatment process of the film, sodium tungstate crystals are formed in the film and precipitated, and theappearance of the film is affected. To solve this problem, a barrier film may be previously coated on a glass substrate. The barrier film comprises SiO₂Film of Al₂O₃A film. SiO2₂The film deposition method is that a certain amount of ethyl orthosilicate and ethanol are mixed, the mixture is magnetically stirred for 10min, the mixed solution of the ethanol and 0.1NHCl is added while stirring, the PH is adjusted to 2-3 by 17 percent HCl, the mixture is stirred and reacts for 2h at room temperature, wherein the molar ratio of the ethyl orthosilicate, the ethanol and the water is 1: 10: 2-4, and the coating liquid is formed. And coating the substrate material with the coating solution to form a barrier layer film.

The number of layers of thin films formed on the substrate of the present invention may generally be 1 to 3.

The invention being deposited on a substrateGasochromic WO₃The film has the advantage of low cost, the stability time of the deposited sol can reach more than 2 months, the formed film has better gasochromic performance, and the hardness and the adhesive force to the substrate of the film are greatly enhanced compared with the prior art.

FIG. 1 is WO₃The transmission spectrum of the film in a colored and faded state.

The invention will be further described in detail with reference to the following examples:

example one

① mixing W powder (purity 99.8%) and H₂O₂Mixing, stirring until W powder is completely dissolved for about 5-6H, removing unreacted H2O2 from ② with platinum net, and filtering to remove precipitate to obtain light yellow transparent WO₃Addingequal volume of ethanol into ③ sol, distilling, ④ repeating the above steps for 2-3 times, ⑤ adding a certain amount of PdCl₂Alcohol solution of Pd and WO₃The mol percentage of the solution is 1: 125. ⑥, the solution is used as coating liquid, the film is drawn on plate glass, the drawing speed is 75-300mm/min, ⑦ film is naturally dried.

The light transmittance of the film manufactured by the method can be reduced from 80% to 15% at 340nm-1100nm, and the response time of coloring and fading is within 60 s. FIG. 1 shows the transmission spectrum of a film from WO3 in the colored and bleached state.

Example two

This example differs from the first example in that ethyl orthosilicate is added after step ⑥ and the reaction is stirred at room temperature for 2h (WO)₃With SiO₂The molar ratio is 2: 1). The film was dried at 120 ℃ for 1 hour and heat treated at 150 ℃ for about 0.5 hour, the remaining steps being essentially the same as in example one.

EXAMPLE III

The difference between this embodiment and the second embodiment is that the coating is previously coated with SiO₂The film is formed on the glass substrate of the barrier layer film, the heat treatment temperature of the film is 250-360 ℃, and the rest steps are basically the same as the embodiment.

Example four

This example is different from the first example in that step ④ is to add acetone into the sol, the volume ratio of acetone to water is 3: 1, and the rest of the steps are basically the same as the first example.

Claims

1. A method of depositing WO on a substrate _Aerochromic thin film is characterized in that comprising the following steps:

a) Tungsten powder (purity 99.8%) and H ₂ O ₂ mixed reaction until the tungsten powder is completely dissolved

untie;

b) Unreacted H ₂ O ₂ was removed with a platinum mesh, and the lower precipitate was filtered to obtain

Light yellow transparent WO ₃ sol;

c) Add the concentrated sol to a highly volatile solvent to obtain polytungsten

acid sol;

d) Incorporate transition metal compounds such as palladium and platinum as catalysts;

e) taking WO ₃ sol added with sol stabilizer and catalyst as coating liquid,

Deposited on a glass substrate by dip-coating to obtain colorless and transparent

WO ₃ aerochromic film;

f) dry.

2. The method according to claim 1, characterized in that: after step (c) or step (d), SiO ₂ solution or ethanol solution of ethyl orthosilicate is added, and the added SiO ₂ has an effect on WO ₃ The molar ratio is 2-4:1.

3. The method according to claim 1, characterized in that the step (f) is dried naturally or heat treated at 150° C. for 1 hour.

4. The method according to claim 1, characterized in that the concentration of the polytungstic acid prepared in step (a) is between 1.0-1.2M.

5. The method according to claim 1, characterized in that the highly volatile solvent added in step (c) is ethanol or acetone, and the volume ratio of ethanol or acetone to the sol is 1-4:1.

6. The method according to claim 1, characterized in that: the (c) step adopts the following method: add ethanol or acetone to 1-2 times the volume of the original sol, and concentrate the sol by vacuum distillation for 1-2 times .

7, by the described method of claim 1, it is characterized in that: the following method can also be adopted to carry out in (c) step: sol decompression distillation is concentrated 3-5 times, adds ethanol, makes ethanol to sol volume ratio be 24:1, and then distilled under reduced pressure to 1-2 times the concentration of the original sol.

8. The method according to claim 1, characterized in that: when palladium chloride (PdCl ₂ ) solution or potassium chloroplatinite (K ₂ PtCl ₄ ) solution is used as catalyst, the molar ratio of K ₂ PtCl ₄ to WO ₃ The ratio is 1% to 5%, and the molar ratio of PdCl2 to WO ₃ is 0.1% to 2.5%.

9. The method of claim 1, wherein the material of the substrate is glass or ceramics.

10. The method according to claim 1 or 9, characterized in that: when soda-lime glass is used as the substrate, a layer of barrier film is pre-coated on the substrate, and the barrier film is SiO2 film or Al ₂ O ₃ films.