Methods for preparing vanadium dioxide composite powders, vanadium dioxide powder slurry, and vanadium dioxide coating for intelligent temperature control

Abstract

A vanadium dioxide coating for intelligent temperature control is formed by mixing a vanadium dioxide powder slurry, a polymer emulsion, and coating additives, and then coating the mixture onto a substrate. The vanadium dioxide powdery slurry comprises vanadium dioxide composite powders and a dispersion medium, the composite powders comprising vanadium dioxide nanopowders having a chemical composition of V.sub.1xM.sub.xO.sub.2, and the surface of the vanadium dioxide nanopowders being attached to organic modified long-chain molecules, wherein M is a doped element, and 0x0.5. Through using the vanadium dioxide powders and the slurry thereof having an organic modified surface, the coating has higher visible light transmittance, can almost completely screen ultraviolet rays, and simultaneously intelligently adjust infrared rays.

Claims

1. A method for preparing vanadium dioxide composite powders, comprising the following processes: process (1) dispersing vanadium nanopowders with a chemical composition of V.sub.1xM.sub.xO.sub.2 into a dispersion medium A to obtain a mixture A; process (2) adding dispersion-assisting agents and organic modifiers for forming organic modifying long-chain molecules on a surface of the vanadium dioxide nanopowders into the mixture A and mixing by stirring to obtain a mixture B; and process (3) drying the mixture B to obtain the vanadium dioxide composite powders, the surfaces of which are grafted with organic modifying long-chain molecules; wherein M represents doping elements; 0x0.5; the organic modifying long-chain molecules are 0.150 wt % of the vanadium dioxide nanopowders; the organic modifying long-chain molecules are functionalized organic long chains, or long-chain alkyls; and the functionalized organic long chains are polyacrylic acid groups, polyvinyl alcohol groups, epoxy groups, long-chain alkylamino groups, halogenated long-chain alkyls, and/or carboxylated long-chain alkyls.

2. The method for preparing vanadium dioxide composite powders according to claim 1, wherein the organic modifying long-chain molecules are 110 wt % of the vanadium dioxide nanopowders.

3. The method for preparing vanadium dioxide composite powders according to claim 1, wherein the length of the organic modifying long-chain molecules is 0.1 nm100 nm.

4. The method for preparing vanadium dioxide composite powders according to claim 1, wherein the vanadium dioxide powders are rutile vanadium dioxide powders, with a phase transition temperature adjustable in a range of 2070 C.

5. The method for preparing vanadium dioxide composite powders according to claim 1, wherein a particle size of the vanadium dioxide composite powders is 200 nm or less.

6. The method for preparing vanadium dioxide composite powders according to claim 1, wherein the dispersion medium A in process (1) is ethanol, isopropanol, chloroform, dimethylformamide, dimethyl sulfoxide, dichloroethane, and/or acetone.

7. The method for preparing vanadium dioxide composite powders according to claim 1, wherein in process (2), a weight ratio between the vanadium dioxide nanopowders and the dispersion medium A is 1:11:20.

8. The method for preparing vanadium dioxide composite powders according to claim 1, wherein the organic modifiers added in process (2) are stearic acid, polyacrylic acid, silane coupling agents, aluminate coupling agents, and/or titanate coupling agents.

9. The method for preparing vanadium dioxide composite powders according to claim 1, wherein an addition amount of the organic modifiers is 0.055 wt % of the mixture A.

10. A method for preparing vanadium dioxide composite powders, comprising the following processes: process (1) dispersing vanadium nanopowders with a chemical composition of V.sub.1xM.sub.xO.sub.2 into a dispersion medium A to obtain a mixture A; process (2) adding dispersion-assisting agents and organic modifiers for forming organic modifying long-chain molecules on a surface of the vanadium dioxide nanopowders into the mixture A and mixing by stirring to obtain a mixture B; and process (3) drying the mixture B to obtain the vanadium dioxide composite powders, the surfaces of which are grafted with organic modifying long-chain molecules; wherein M represents doping elements; 0x0.5; the organic modifying long-chain molecules are 0.150 wt % of the vanadium dioxide nanopowders; and in process (2), the dispersion-assisting agents are one or more agents selected from the group consisting of polyvinyl alcohol, polyvinylpyrrolidone, organically modified polysiloxane dipropylene glycol monomethyl ether solution, silicone surfactants, and/or fluorosurfactants.

11. The method for preparing vanadium dioxide composite powders according to claim 10, wherein an addition amount of the dispersion-assisting agents is 0.022 wt % of the mixture A.

12. A method for preparing a vanadium dioxide powder slurry, comprising the process (1), process (2), and process (3) of the method for preparing vanadium dioxide composite powders as claimed in claim 1, further comprising: process (4) dispersing the vanadium dioxide composite powders obtained in process (3) into a dispersion medium B to obtain the vanadium dioxide powder slurry.

13. The method for preparing the vanadium dioxide powder slurry according to claim 12, wherein the dispersion medium B is one or more solvents selected from the group consisting of deionized water, ethanol, propanol, isopropanol, ethyl acetate, toluene, and butanone.

14. The method for preparing the vanadium dioxide powder slurry according to claim 12, wherein a weight ratio between the vanadium dioxide composite powders and the dispersion medium B is 1:11:1000.

15. The method for preparing the vanadium dioxide powder slurry according to claim 13, wherein the weight ratio between the vanadium dioxide composite powders and the dispersion medium B is 1:101:100.

16. A method for preparing a vanadium dioxide coating for dual temperature control, comprising the process (1), process (2), process (3), and process (4) of the method for preparing the vanadium dioxide composite powder slurry as claimed in claim 12, further comprising: process (5) mixing the vanadium dioxide powder slurry obtained in process (4), a polymer emulsion, and coating additives together to form a mixture and coating the mixture on a substrate to form the vanadium dioxide coating for dual temperature control.

17. The method for preparing the vanadium dioxide coating for dual temperature control according to claim 16, wherein the polymer emulsion is an aqueous dispersion or an emulsion of polymer resin; and the polymer resin is one or more resins selected from the group consisting of polyacrylic acid resins, polyester resins, polyurethane resins, silicone resins, alkyd resins, and epoxy resins.

18. The method for preparing the vanadium dioxide coating for dual temperature control according to claim 16, wherein the coating additives include coalescing agents, wetting-assisting agents, defoaming agents, thickening agents, and/or levelling agents.

19. The method for preparing the vanadium dioxide coating for dual temperature control according to claim 16, wherein the mixture is coated on the substrate by spraying, blade coating, brush coating, curtaining, or roller coating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a transmission electron microscopy (TEM) image of vanadium dioxide powders without their surface being organically modified;

(2) FIG. 2 is a transmission electron microscopy (TEM) image of vanadium dioxide powders with their surface having been organically modified;

(3) FIG. 3 is a high/low temperature graph of a vanadium dioxide coating for intelligent temperature control in an example of the present application, which is made from the vanadium dioxide composite powders and the slurry thereof of the present invention;

(4) FIG. 4 is a high/low temperature graph of a vanadium dioxide coating for intelligent temperature control made from vanadium dioxide powders without being organically modified.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(5) Hereinafter, the present invention will be further described with the following embodiment with reference to the drawings.

(6) The preparation method of the vanadium dioxide composite powders comprises the following processes: dispersing vanadium dioxide nanopowders into a dispersion medium to obtain a mixture A; adding dispersion-assisting agents and organic modifiers for forming organic modifying long-chain molecules on a surface of the vanadium dioxide nanopowders into the mixture A, stirring until fully, evenly mixed to obtain a mixture B; and drying the mixture B to obtain the organically modified vanadium dioxide composite powders.

(7) With regard to the above preparation method of the vanadium dioxide composite powders, specifically, 0.150 wt % of the vanadium dioxide powders and 5099 wt % of the dispersion medium are stirred at high speed to be dispersed and mixed, and ultrasonically dispersed to obtain a mixture, then dispersion-assisting agents and organic modifiers are added to the mixture, and the resulting mixture is stirred at a constant temperature in the range of 0200 C., and dispersed by means of ultrasound, sanding, or ball-milling, etc. Then they are centrifugation precipitated and the precipitates are dried under a vacuum at a certain temperature to obtain organically modified vanadium dioxide composite powders.

(8) In the process of mixing the vanadium dioxide nanopowders and the dispersion medium, the weight ratio between them may be 1:11:20, preferably 1:11:10, more preferably 1:21:5. An insufficient weight ratio will reduce the probability of contact between vanadium dioxide nanopowders and the dispersion medium, while a long dispersion time and a large amount of modifier will be required; while an excessive weight ratio will do harm to full dispersion and wetting of the powders in the dispersion medium, affecting the effect of the subsequent modification.

(9) In the surface modification of vanadium dioxide nanopowders, the organic modifiers may be stearic acid, polyacrylic acid, silane coupling agents, aluminate coupling agents, titanate coupling agents, etc., preferably silane coupling agents with macromolecular long chains. The amount of organic modifiers added to the mixture may be 0.055 wt %, preferably 0.12 wt %. If the content of the organic modifying long-chain molecules is too low, complete cladding for the surface of the powders will not be realized; on the other hand, if the content of the organic modifying long-chain molecules is too high, the organic molecules will tangle with each other, having a bad influence on the dispersion effect. By means of coupling agents, the surface of vanadium dioxide can be grafted with organic long-chain molecules, thereby greatly improving the chemical stability and dispersibility of vanadium dioxide powders. In addition, the dispersion-assisting agents may be one or more agents selected from the group consisting of polyvinyl alcohol, polyvinylpyrrolidone, organically modified polysiloxane dipropylene glycol monomethyl ether solution, silicone surfactants, fluorosurfactant, and other known dispersion-assisting agents in the art. The dispersion-assisting agents are mainly used for lowering the surface tension and improving the solvent wettability of the powder surface, thereby improving the dispersion effect. The amount of the dispersion-assisting agents added to the mixture may be 0.022 wt %, preferably 0.051 wt %. Adding a tiny amount is enough for achieving the desired dispersion effect. On the contrary, adding too much will affect the process of surface modification for the powders.

(10) With regard to the preparation method of the vanadium dioxide powder slurry, specifically, 0.150 wt % of vanadium dioxide powders and 4099 wt % of dispersion medium are mixed and stirred at high speed for pre-dispersion, then dispersion-assisting agents are added to the mixture, and the resulting mixture is stirred at high speed to obtain an evenly mixed vanadium dioxide powder slurry. Further, the slurry can be evenly mixed in a manner such as ultrasound, ball-milling, and/or sanding.

(11) In the present invention, in both of the process for preparing vanadium dioxide composite powders and the process for preparing a composite powder slurry, the rotating speed of stirring may be 10003000 rad/min. The power of ultrasound may be 505000 W, and the frequency of ultrasound may be 21 KHz. Further, the rotating speed of a ball mill may be 102000 rad/min. Further, the rotating speed of a sand mill may be 102000 rad/min. The sanding medium may be ZrO.sub.2 balls, and the particle size of the sanding medium may be 0.02 mm50 mm. A sanding medium with a small size is preferred.

(12) The vanadium dioxide coating for intelligent temperature control of the present invention is formed by mixing the vanadium dioxide powder slurry of the present invention, a polymer emulsion, and coating additives together to form a mixture and coating the mixture on a substrate. Specifically, 2080 wt % of a polymer emulsion is added to 1060 wt % of the vanadium dioxide powder slurry of the present invention, and then coating additives such as wetting-assisting agents, coalescing agents, leveling agents, defoaming agents, and/or thickening agents totaled to 0.015 wt % is added, and the resulting mixture is stirred at high speed for an appropriate time to obtain a mixed liquid (coating material) for forming a coating. The coating can be coated on a substrate in a manner such as spraying, blade coating, brush coating, curtaining, or roller coating. The substrate may be either a plastic film made from a material such as polypropylene (PP), polyethylene (PE), polyamide (PA), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), etc., or a fiber or a woven bag made from these materials.

(13) The coalescing agents among the coating additives may be one or more additives selected from the group consisting of ethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol methyl etheracetate, propylene glycol monobutyl ether, ethylene glycol propyl ether, and dipropyl ether.

(14) The wetting-assisting agents among the coating additives may be one or more additives selected from the group consisting of dodecyl sulfates, dodecyl sulfonates, polyvinyl alcohol, polyvinylpyrrolidone, organosilicon compounds, and organofluorine compounds.

(15) The defoaming agents among the coating additives may be one or more additives selected from the group consisting of dimethicone, ether ester compounds, modified mineral oil, glycerol ethoxylate, micromolecular metallorganics, and modified organosilicon polymers.

(16) The leveling agents among the coating additives may be one or more additives selected from the group consisting of 2-butoxyethanol, cellulose acetate butyrate, polyacrylates, silicone oil, and modified organosilicon compounds.

(17) The thickening agents among the coating additives may be cellulose thickening agents, polyethylene wax, fumed silica, polyacrylic acid thickening agents, or associative polyurethane thickening agents.

(18) Furthermore, 0.22% of ultraviolet absorbents, such as benzophenone and derivatives thereof, 2-hydroxyphenyl benzotriazole and derivatives thereof, aromatic ester compounds, or hydroxyphenyl s-triazine and derivatives thereof may be added to the coating material.

(19) Hereinafter, the present invention will be described more specifically with examples.

(20) It should be understood that the embodiments described in detail above and the examples below are only for illustration of the present invention, and do not limit the scope of the present invention. The raw materials and reagents used can be obtained through purchase of commercially available starting materials or synthesized by conventional chemical transforming methods. All professional and scientific terms used herein have the same meaning with those familiar to a person skilled in the art, unless otherwise defined or explained. Moreover, any method or material equal or similar to the content recorded can be applied to the present invention. Other aspects of the present invention will be readily understood by a person skilled in the art due to the disclosure herein.

(21) FIG. 1 is a TEM image of vanadium dioxide powders without their surfaces being organically modified; referring to FIG. 1, as for the morphology of the vanadium dioxide nanopowders without being organically modified, the powders are of a particle size ranging from 10100 nm, and present in the form of agglomerated particles. However, the particles are loose.

(22) FIG. 2 is a TEM image of vanadium dioxide powders with their surfaces having been organically modified; referring to FIG. 2, as for the morphology of vanadium dioxide powders with their surfaces having been organically modified, the powders are of a particle size ranging from 10100 nm, which is slightly larger than that of the particles without being organically modified due to the organic group-cladding for the powder surface. However, the powders are dispersed.

(23) FIG. 3 is a high/low temperature graph of a vanadium dioxide coating for intelligent temperature control in an example of the present application (Example 1), which is made from the vanadium dioxide composite powders and the slurry thereof of the present invention; referring to FIG. 3, as for the coating in the example (Example 1), the visible light transmittance is 53.3% at a low temperature, while 51.8% at a high temperature, the sun light transmittance is 57% at a low temperature, while 43.6% at a high temperature, the phase-transition temperature is 40 C., the high/low temperature solar energy regulation efficiency can reach 13.4%, the high/low temperature infrared integral regulation is 24.2%, and the high/low temperature transmittance difference at IR 1500 nm can reach 36.8%.

(24) FIG. 4 is a high/low temperature graph of a vanadium dioxide coating for intelligent temperature control made from vanadium dioxide powders without being organically modified (Comparative Example 6), which has the following differences compared to a coating made from organically modified vanadium dioxide powders (FIG. 3): the high temperature curve is lower than the low temperature curve in the visible light region due to the bad dispersibility of the vanadium dioxide powders without being organically modified, while in the case that modified vanadium dioxide powders are used as starting material, the high temperature curve is higher than the low temperature curve in the visible light region; and the visible light transmittance and infrared control performance thereof are lower than the coating made from organically modified vanadium dioxide powders (FIG. 3).

EXAMPLE 1

(25) (1) Surface Organic Modification of Vanadium Dioxide Nanopowders

(26) Ingredients and the amounts thereof are as follows: Vanadium dioxide nanopowders (doped with W, particle size: 20100 nm), 20 g; Ethanol (dispersion medium), 80 g; Silane coupling agent (with polyvinyl alcohol group, organic modifier), 1 g; and Polyvinylpyrrolidone (dispersion-assisting agent), 0.05 g. The vanadium dioxide nanopowders and dispersion medium are stirred and mixed at a speed of 1500 rad/min for 30 min, and dispersed under ultrasound for 30 min, then the dispersion-assisting agent and silane coupling agent are added to the mixture, and the resulting mixture is stirred in a high-speed stirrer at 70 C. for 2 h, then centrifugation precipitated, and the precipitates are dried under vacuum at 60 C. to obtain the organic silane coupling agent modified vanadium dioxide composite powders.

(27) (2) Preparation of Vanadium Dioxide Composite Powder Slurry

(28) Ingredients and the amounts thereof are as follows: Vanadium dioxide composite powders prepared in Step (1) of the present example, 4 g; Deionized water, 95.5 g; and Modified acrylic acid dispersion agent, 0.5 g. The organically modified nanopowders are added to deionized water, and the resulting mixture is stirred at high speed for 5 min for pre-dispersion, then the dispersion agent is added and dispersed under ultrasound for 60 min, then stirred in a high-speed stirrer for 2 h to obtain a vanadium dioxide composite powder slurry. The main performance of vanadium dioxide composite powders and the slurry thereof are shown in Table

(29) (3) Preparation of Vanadium Dioxide Coating for Intelligent Temperature Control

(30) Raw materials and the weight percentages thereof are as follows: Polymer emulsion (polyurethane emulsion): 40%; Vanadium dioxide composite powder slurry prepared in Step (2) of the present example (solid content: 4%): 30%; Deionized water: 28%; Coalescing agent (propylene glycol monobutyl ether): 0.5%; Wetting-assisting agent (polyvinyl alcohol): 0.2%; Leveling agent (polyacrylates): 0.25%; Defoaming agent (modified organosilicon compound): 0.25%; Thickening agent (cellulose thickening agents): 0.4%; and Ultraviolet absorbent (hydroxyphenyl s-triazine derivates): 0.5%. The acrylic acid emulsion and deionized water are added to the vanadium dioxide composite powder slurry, then the wetting-assisting agent, coalescing agent, leveling agent, defoaming agent, ultraviolet absorbent, and thickening agent are added, and the resulting mixture is stirred at a speed of 1500 rad/min for 1 h to obtain a water-based vanadium dioxide coating material for intelligent temperature control. The obtained coating material is coated on PET by roller coating, wherein the thickness of the coating layer is controlled at 3.5 m. The basic performances of the coating for intelligent temperature control are shown in Table 2.

EXAMPLE 2

(31) (1) Surface Organic Modification of Vanadium Dioxide Nanopowders

(32) Ingredients and the amounts thereof are as follows: Vanadium dioxide nanopowders (without doped element, particle size: 2060 nm), 10 g; Ethanol (dispersion medium), 90 g; Silane coupling agent (with long-chain alkylamino group, organic modifier), 1 g; and Polyvinyl alcohol (dispersion-assisting agent), 0.05 g. The vanadium dioxide nanopowders and dispersion medium are stirred and mixed at a speed of 1500 rad/min for 30 min, and dispersed under ultrasound for 30 min, then the dispersion-assisting agent and stearic acid are added to the mixture, and the resulting mixture is stirred in a high-speed stirrer at 60 C. for 2 h, then centrifugation precipitated, and the precipitates are dried under vacuum at 60 C. to obtain long-chain alkylamino group modified vanadium dioxide composite nanopowders.

(33) (2) Preparation of Vanadium Dioxide Composite Powder Slurry

(34) Ingredients and the amounts thereof are as follows: Vanadium dioxide composite powders prepared in Step (1) of the present example, 5 g; Deionized water, 94.5 g; and Polyacrylate dispersion agent, 0.05 g. The organically modified nanopowders are added to deionized water, and the resulting mixture is stirred at high speed for 10 min for pre-dispersion, then the dispersion agent is added and dispersed under ultrasound for 30 min, then stirred in a high-speed stirrer for 1 h to obtain a vanadium dioxide composite powder slurry. The main performance of vanadium dioxide composite powders and the slurry thereof are shown in Table

(35) (3) Preparation of Vanadium Dioxide Coating for Intelligent Temperature Control

(36) Raw materials and the weight percentages thereof are as follows: Polymer emulsion (polyurethane emulsion): 60%; Vanadium dioxide composite powder slurry prepared in Step (2) of the present example (solid content: 5%): 30%; Deionized water: 8.5%; Coalescing agent (propylene glycol monobutyl ether): 0.25%; Wetting-assisting agent (polyvinyl alcohol): 0.1%; Leveling agent (polyacrylates): 0.15%; Defoaming agent (modified organosilicon compound): 0.25%; Thickening agent (associative polyurethane thickening agents): 0.35%; and Ultraviolet absorbent (2-hydroxyphenyl benzotriazole derivates): 0.4%. The acrylic acid emulsion and deionized water are added to the vanadium dioxide composite powder slurry then the wetting-assisting agent, coalescing agent, leveling agent, defoaming agent, ultraviolet absorbent, and thickening agent are added, and the resulting mixture is stirred at a speed of 1500 rad/min for 1 h to obtain vanadium dioxide coating material for intelligent temperature control. The obtained coating material is coated on PET by roller coating, wherein the thickness of the coating layer is controlled at 2.5 m. The basic performances of the coating for intelligent temperature control are shown in Table 2.

EXAMPLE 3

(37) (1) Surface Organic Modification of Vanadium Dioxide Nanopowders

(38) Ingredients and the amounts thereof are as follows: Vanadium dioxide nanopowders (doped with W, particle size: 20100 nm), 15 g; Isopropanol (dispersion medium), 85 g; Silane coupling agent (with epoxy group, organic modifier), 1 g; and Organically modified polysiloxane dipropylene glycol monomethyl ether solution (dispersion-assisting agent), 0.08 g. The vanadium dioxide nanopowders and dispersion medium are stirred and mixed at a speed of 1000 rad/min for 20 min, and dispersed under ultrasound for 60 min, then the dispersion-assisting agent and silane coupling agent are added, and the resulting mixture is stirred in a high-speed stirrer at 80 C. for 2 h, then centrifugation precipitated, and the precipitates are dried under vacuum at 60 C. to obtain vanadium dioxide composite nanopowders grafted with epoxy group on surface.

(39) (2) Preparation of Vanadium Dioxide Composite Powder Slurry

(40) Ingredients and the amounts thereof are as follows: Vanadium dioxide composite powders prepared in Step (1) of the present example, 1.5 g; Deionized water, 98 g; and Modified polyester dispersion agent, 0.5 g. The organically modified nanopowders are added to deionized water, and the resulting mixture is stirred at high speed for 5 min for pre-dispersion, then the dispersion agent is added and dispersed under ultrasound for 20 min, then stirred in a high-speed stirrer for 1 h to obtain a vanadium dioxide composite powder slurry. The main performance of vanadium dioxide composite powders and the slurry thereof are shown in Table 1.

(41) (3) Preparation of Vanadium Dioxide Coating for Intelligent Temperature Control

(42) Raw materials and the weight percentages thereof are as follows: Polymer emulsion (acrylic acid emulsion): 45%; Vanadium dioxide composite powder slurry prepared in Step (2) of the present example (solid content: 1.5%): 45%; Deionized water: 5%; Coalescing agent (diphenyl ether): 0.5%; Wetting-assisting agent (organosilicon compound): 0.2%; Leveling agent (modified organosilicon compound): 0.25%; Defoaming agent (micromolecular metallorganics): 0.25%; Thickening agent (associative polyurethane thickening agents): 0.8%; and Ultraviolet absorbent (2-hydroxyphenyl benzotriazole derivates): 0.5%. The acrylic acid emulsion and deionized water are added to the vanadium dioxide composite powder slurry, then the wetting-assisting agent, coalescing agent, leveling agent, defoaming agent, ultraviolet absorbent, and thickening agent are added, and the resulting mixture is stirred at a speed of 2500 rad/min for 3 h to obtain vanadium dioxide coating material for intelligent temperature control. The obtained coating material is coated on PET by spraying, wherein the thickness of the coating layer is controlled at 6.5 m. The basic performances of the coating for intelligent temperature control are shown in Table 2.

EXAMPE 4

(43) (1) Surface Organic Modification of Vanadium Dioxide Nanopowders

(44) Ingredients and the amounts thereof are as follows: Vanadium dioxide nanopowders (doped with Mo, particle size: 20100 nm), 25 g; Isopropanol (dispersion medium), 75 g; Titanate coupling agent (with epoxy group, organic modifier), 1 g; and Polyvinyl alcohol (dispersion-assisting agent), 0.15 g. The vanadium dioxide nanopowders and dispersion medium are stirred and mixed at a speed of 1500 rad/min for 20 min, and dispersed under ultrasound for 60 min, then the dispersion-assisting agent and titanate coupling agent are added to the mixture, and the resulting mixture is stirred in a high-speed stirrer at 80 C. for 2 h, then centrifugation precipitated, and the precipitates are dried under vacuum at 70 C. to obtain vanadium dioxide composite nanopowders grafted with epoxy groups on their surface.

(45) (2) Preparation of Vanadium Dioxide Composite Powder Slurry

(46) Ingredients and the amounts thereof are as follows: Vanadium dioxide composite powders prepared in Step (1) of the present example, 3 g; Deionized water, 96.95 g; and Modified acrylic acid dispersion agent, 0.05 g. The organically modified nanopowders are added to deionized water, and the resulting mixture is stirred at high speed for 5 min for pre-dispersion, then the dispersion agent is added and dispersed under ultrasound for 30 min, then stirred in a high-speed stirrer for 1 h to obtain a vanadium dioxide and doped vanadium dioxide nanopowder slurry. The main performance of vanadium dioxide composite powders and the slurry thereof are shown in Table 1.

(47) (3) Preparation of Vanadium Dioxide Coating for Intelligent Temperature Control

(48) Raw materials and the weight percentages thereof are as follows: Polymer emulsion (acrylic acid emulsion): 50%; Vanadium dioxide composite powder slurry prepared in Step (2) of the present example (solid content: 3%): 30%; Deionized water: 18.5%; Coalescing agent (ethylene glycol monobutyl ether): 0.2%; Wetting-assisting agent (organosilicon compound): 0.05%; Leveling agent (cellulose acetate butyrate): 0.2%; Defoaming agent (modified mineral oil): 0.35%; Thickening agent (polyacrylic acid thickening agents): 0.2%; and Ultraviolet absorbent (benzophenone derivates): 0.5%. The acrylic acid emulsion and deionized water are added to the vanadium dioxide composite powder slurry, then the wetting-assisting agent, coalescing agent, leveling agent, defoaming agent, ultraviolet absorbent, and thickening agent are added, and the resulting mixture is stirred at a speed of 2500 rad/min for 2 h to obtain a vanadium dioxide coating material for intelligent temperature control. The obtained coating material is coated on PET by roller coating, wherein the thickness of the coating layer is controlled at 2.5 m. The basic performances of the coating for intelligent temperature control are shown in Table 2.

EXAMPLE 5

(49) (1) Surface Organic Modification of Vanadium Dioxide Nanopowders

(50) Ingredients and the amounts thereof are as follows: Vanadium dioxide nanopowders (doped with W, particle size: 20100 nm), 5 g; Isopropanol (dispersion medium), 95 g; Aluminate coupling agent (with long-chain alkylamino group, organic modifier), 0.7 g; and Polyvinylpyrrolidone (dispersion-assisting agent), 0.04 g. The vanadium dioxide nanopowders and dispersion medium are stirred and mixed at a speed of 1500 rad/min for 20 min, and dispersed under ultrasound for 60 min, then the dispersion-assisting agent and aluminate coupling agent are added to the mixture, and the resulting mixture is stirred in a high-speed stirrer at 80 C. for 2 h, then centrifugation precipitated, and the precipitates are dried under vacuum at 60 C. to obtain vanadium dioxide nanopowders grafted with long-chain alkyl groups on their surface.

(51) (2) Preparation of Vanadium Dioxide Composite Powder Slurry

(52) Ingredients and the amounts thereof are as follows: Vanadium dioxide composite powders prepared in Step (1) of the present example, 4 g; Deionized water, 95.5 g; and Modified polyurethane dispersion agent, 0.5 g. The organically modified nanopowders are added to deionized water, and the resulting mixture is stirred at high speed for 5 min for pre-dispersion, then the dispersion agent is added and dispersed under ultrasound for 60 min, then stirred in a high-speed stirrer for 2 h to obtain a vanadium dioxide composite powder slurry. The main performance of vanadium dioxide composite powders and the slurry thereof are shown in Table 1.

(53) (3) Preparation of Vanadium Dioxide Coating for Intelligent Temperature Control

(54) Raw materials and the weight percentages thereof are as follows: Polymer emulsion (polyurethane emulsion): 70%; Vanadium dioxide composite powder slurry prepared in Step (2) of the present example (solid content: 4%): 20%; Deionized water: 8.5%; Coalescing agent (propylene glycol monobutyl ether): 0.5%; Wetting-assisting agent (polyvinyl alcohol): 0.2%; Leveling agent (polyacrylates): 0.25%; Defoaming agent (modified organosilicon compound): 0.25%; and Thickening agent (cellulose thickening agents): 0.4%. The acrylic acid emulsion and deionized water are added to the vanadium dioxide composite powder slurry, then the wetting-assisting agent, coalescing agent, leveling agent, defoaming agent, ultraviolet absorbent, and thickening agent are added, and the resulting mixture is stirred at a speed of 1500 rad/min for 1 h to obtain water-based vanadium dioxide coating material for intelligent temperature control. The obtained coating material is coated on PET by blade coating, wherein the thickness of the coating layer is controlled at 5.5 m. The basic performances of the coating for intelligent temperature control are shown in Table 2.

COMPARATIVE EXAMPLE 6

(55) (1) The unmodified vanadium dioxide nanopowders used in Step (1) of the above Example 1, 4 g; Deionized water, 95.5 g; and Modified acrylic acid dispersion agent, 0.5 g; The unmodified nanopowders are added to deionized water, and the resulting mixture is stirred at high speed for 5 min for pre-dispersion, then the dispersion agent is added and dispersed under ultrasound for 60 min, then stirred in a high-speed stirrer for 2 h to obtain a vanadium dioxide powder slurry. The main performance of vanadium dioxide powders and the slurry thereof are shown in Table 1;

(56) (2) The prepared slurry in Step (1) of the present comparative example is used, and the raw materials are prepared as follows.

(57) Raw materials and the weight percentages thereof are as follows: Polymer emulsion (polyurethane emulsion): 40%; Vanadium dioxide composite powder slurry prepared in Step (1) of the present comparative example (solid content: 4%): 30%; Deionized water: 28%; Coalescing agent (propylene glycol monobutyl ether): 0.5%; Wetting-assisting agent (polyvinyl alcohol): 0.2%; Leveling agent (polyacrylates): 0.25%; Defoaming agent (modified organosilicon compound): 0.25%; Thickening agent (cellulose thickening agents): 0.4%; and Ultraviolet absorbent (hydroxyphenyl s-triazine derivates): 0.5%; The acrylic acid emulsion and deionized water are added to the vanadium dioxide powder slurry, then the wetting-assisting agent, coalescing agent, leveling agent, defoaming agent, ultraviolet absorbent, and thickening agent are added, and the resulting mixture is stirred at a speed of 1500 rad/min for 1 h to obtain a water-based vanadium dioxide coating material for intelligent temperature control. The obtained coating material is coated on PET by roller coating, wherein the thickness of the coating layer is controlled at 5.5 m. The basic performances of the coating for intelligent temperature control are shown in Table 2.

(58) Referring to Table 1, with regard to the organically modified vanadium dioxide composite powders and the slurry thereof obtained by the methods provided by the present invention, the particle size is significantly smaller than that of the unmodified powders, the BET (Brunauer-Emmett-Teller) specific surface area is larger than that of the unmodified powders, and the stability of the slurry is significantly better than that of the unmodified slurry. It can be seen from the weight-loss data at 300 C. that the surfaces of the nanopowders are grafted with 5 10% of organic long chains by means of the process of surface organic modification, thereby greatly improving the chemical stability and dispersibility of vanadium dioxide powders.

(59) TABLE-US-00001 TABLE 1 Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Modifier Silane Silane Silane Water-based Water-based Unmodified coupling coupling coupling titanate aluminate agent with agent with agent with coupling coupling water-soluble water-soluble water-soluble agent agent long chains long chains long chains Surface group Polyvinyl Long-chain Epoxy Epoxy Long-chain alcohol alkylamino functional functional alkylamino group group group group Dynamic laser scattering 20~100 50~300 20~150 50~150 50~200 20~200 particle size (nm) BET specific surface 60~70 45~55 50~60 50~60 45~55 40~50 area (m.sup.3/g) Powder surface performance Hydrophilic Hydrophilic Hydrophilic Hydrophilic Hydrophilic Hydrophilic Weight-loss at 300 C. 12% 4% 10% 8% 7% 1% Slurry stability after No Slight No No Slight Severe 3-month storage precipitation precipitation precipitation precipitation precipitation precipitation

(60) Referring to Table 2, the coating of the present invention possesses high visible light transmittance, while it almost completely shields ultraviolet rays, accompanied by intelligent regulation for infrared ray of high energy among the sunlight (seen from the high/low temperature infrared transmittance difference), being of transparent and clear appearance, ageing resistance, watertightness, favorable adhesion to substrates, and strong brush resistance; and as compared with the slurry of VO.sub.2 without being organically modified (Comparative Example 6), the coating obtained by the present method is of higher intelligent regulation rate, lower visible light transmittance, and lower haze.

(61) TABLE-US-00002 TABLE 2 (performance test of coating) Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Matrix resin Polyurethane Polyurethane acrylic acid acrylic acid Polyurethane Polyurethane emulsion emulsion emulsion emulsion emulsion emulsion VO.sub.2 particle Organically Organically Organically Organically Organically Unmodified modified modified modified modified modified Coating manner Roller Roller Spraying Roller Blade Blade coating coating coating coating coating Coating thickness 3.5 um 4.5 um 6.5 um 2.5 um 5.5 um 5.5 um Visible light transmittance .sup.53% 38% .sup.55% 65% 45% 30 Infrared High 37.1% 30% 43.5% 35% 38% 35% transmit- temper- tance ature Low 61.3% 47% .sup.70% 55% 58% 45% temper- ature Infrared regulation rate 24.2% 17% 26.5% 20% 20% 10% High/low temperature difference at 1500 nm 36.8% 23% 35.6% 30% 28% 19% Ultraviolet rejection .sup.99% 99% .sup.99% 97% 90% 92% Water-resistance No abnormal- No abnormal- No abnormal- No abnormal- No abnormal- No abnormal- ities for 96 h ities for 96 h ities for 96 h ities for 96 h ities for 96 h ities for 96 h Artificial climate ageing resistance No peeling, No peeling, No peeling, No peeling, No peeling, No peeling, no frothing, no frothing, no frothing, no frothing, no frothing, no frothing, and no crack and no crack and no crack and no crack and no crack and no crack for 1000 h for 1000 h for 1000 h for 1000 h for 1000 h for 1000 h Brush resistance/time 5000 5000 7000 7000 5000 5000 Coating haze .sup.<5% <15% <10% <5% <8% >15% Temperature resistance of coating No No No No No No abnormalities abnormalities abnormalities abnormalities abnormalities abnormalities

INDUSTRIAL APPLICABILITY

(62) The vanadium dioxide composite powers can be applied to preparing a coating or painting for intelligent energy saving. The prepared coating is of high transparency, low haze, and strong ageing resistance, mainly used in flexible materials such as film, braided fabric, etc., in thermal insulation cases such as glass and outer walls, as well as energy conservation and emissions reduction devices such as energy-saving films, energy-saving painting, and solar temperature control devices; or energy information devices such as micro-photoelectric switching devices, thermistors, battery materials, and optical data storage devices. The preparation method of vanadium dioxide composite powders provided by the present invention uses innovative preparation technologies, and the surface modification process by organic modifiers can effectively improve the dispersibility and chemical stability of vanadium dioxide (VO.sub.2) nanopowders and doped vanadium dioxide nanopowders.