Nano vanadium dioxide composite material as well as preparation method and application thereof

Abstract

The invention belongs to the field of nano composite materials, and particularly discloses a nano vanadium dioxide composite material and a preparation method and application thereof.The nano vanadium dioxide composite material is characterized in that nano VO2 particles are modified through a CuS-modified TiO2 material, the CuS-modified TiO2 material accounts for 20%-80% of the mass of the whole nano vanadium dioxide composite material, and the CuS-modified TiO2 material accounts for 20%-30% of the mass of the whole nano vanadium dioxide composite material. The CuS modified TiO2 material is used for reducing the phase transition temperature of VO2 and keeping the sunlight transmittance to reach 10.3%-16.4% at the same time. Copper chloride dihydrate is adopted as a copper source, an ammonium sulfide solution is adopted as a sulfur source, CuS is deposited on the surface of nano TiO2 through a chemical deposition method under the conditions of high temperature and high pressure, and then the nano VO2 composite powder is prepared through mechanical compounding. The nano vanadium dioxide composite material disclosed by the invention has relatively low phase change temperature, relatively good sunlight modulation capability and relatively stable structure and performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nanocomposites, and more particularly relates to a nanometer vanadium dioxide composite material, a preparation method and application thereof. BACKGROUND

[0002] Vanadium dioxide (VO2) is a typical thermochromic material, which has a very fast reversible metal-insulator transition speed and a transition temperature of 68℃, which is close to room temperature. The optical properties of VO2 include visible light transmittance and solar light modulation capacity (ΔTsol), wherein the solar light modulation capacity (ΔTsol) of VO2 thin film is as follows: below the phase transition temperature, VO2 exhibits a high infrared transmittance insulating monoclinic M phase, allowing more infrared light to pass through and increasing the indoor temperature; when the temperature is higher than the phase transition temperature, it exhibits a low infrared transmittance rutile R phase, reducing the infrared transmittance and reducing the indoor temperature. At the same time, the visible light transmittance (T 550nm ) of VO2 is usually above 40%, which can achieve the condition of light transmittance. Such phase transition characteristics make VO2 have broad application prospects in the fields of smart windows, thermochromic coatings, infrared modulation devices and thermal management.

[0003] However, for smart windows, the phase transition temperature of VO2 is much higher than the comfortable temperature of human body, which becomes the primary bottleneck limiting its practical application. In order to reduce the phase transition temperature of VO2, domestic and foreign scholars have proposed various strategies: (1) “element doping”: such as W, Mo doping can reduce the phase transition temperature to 30 ~ 40 ℃, but doping easily leads to the decrease of solar light modulation capacity of vanadium dioxide; (2) “stress engineering”: by introducing compressive strain through interface lattice mismatch, the phase transition temperature is reduced by about 15℃, but the process is complex; (3) “nanostructure design”: such as preparing VO2 nanowires / quantum dots, using size effect to control the phase transition temperature, but the stability is insufficient. Although these methods have made progress, it is difficult to simultaneously consider low temperature phase transition, high light modulation rate and long-term stability.

[0004] Therefore, it is necessary to develop a new type of nanometer vanadium dioxide composite material, which requires a lower phase transition temperature, a better solar light modulation capacity, and a stable structure and performance. SUMMARY

[0005] In view of the defects of the prior art, the purpose of the present application is to provide a nanometer vanadium dioxide composite material, a preparation method and application thereof, which are designed by formula, and are intended to provide a nanometer vanadium dioxide composite material with a lower phase transition temperature, a better solar light modulation capacity, and a stable structure and performance, which can also simultaneously consider low temperature phase transition, high light modulation rate and long-term stability.

[0006] To achieve the above object, in a first aspect, the application provides a nano vanadium dioxide composite material, which uses CuS modified TiO2 material to modify nano VO2 particles, wherein the CuS modified TiO2 material accounts for 20% to 80% of the mass of the entire nano vanadium dioxide composite material, the CuS modified TiO2 material is used to reduce the phase transition temperature of VO2 while maintaining the solar light transmittance to 10.3% to 16.4%, the nano VO2 particle size is 40 nm to 80 nm, and the size of the CuS modified TiO2 material is 100 nm to 400 nm.

[0007] In the above inventive concept, CuS and TiO2 are used to modify nano VO2 particles at the same time in terms of component design, which can reduce the phase transition temperature of VO2 and balance the adverse effect of CuS on light transmittance, so that the nano vanadium dioxide composite material has high light transmittance and low phase transition temperature. Moreover, the addition of CuS and TiO2 is not independent, but CuS is used to modify TiO2. Compared with independent modification, such a processing method has more stable modification effect.

[0008] Further, the CuS modified TiO2 material is in a sheet layer shape, and the VO2 nano particles are distributed on the edges and surfaces of the CuS modified TiO2 material sheet layer.

[0009] Further, the phase transition temperature is 45℃ to 50℃, and the visible light transmittance is not less than 45.4%.

[0010] According to a second aspect of the application, a method for preparing the nano vanadium dioxide composite material is also provided, which comprises the following steps: S1: CuCl2·2H2O and polyvinylpyrrolidone are dissolved in deionized water to obtain a mixed solution, S2: TiO2 is added to the mixed solution, and stirring is continued to obtain a dispersion solution, S3: (NH4)2S solution is added to the dispersion solution, the concentration of the (NH4)2S solution is 20% to 26%, and stirring is continued to obtain a dark brown suspension, S4: The dark brown suspension is transferred to a reaction kettle, and ultrapure water is added to obtain a precursor solution, ultrasonic stirring is performed on the precursor solution, and then high-temperature and high-pressure hydrothermal reaction is carried out in a sealed state, the reaction temperature is 175℃ to 185℃, and the reaction time is 11h to 13h, S5: The product obtained by hydrothermal reaction in step S4 is first subjected to centrifugal washing, and then vacuum drying is performed to obtain CuS modified TiO2 material, S6: mechanically compounding the M-phase VO2 nano-powder and the CuS-modified TiO2 material obtained in step S5 to form a nano-VO2 composite material.

[0011] Further, the CuCl2·2H2O, (NH 4)2 The ratio of the S solution, the TiO2 and the CuS-modified TiO2 material is (0.09g~0.11g):(0.65ml~0.75ml):(0.04g~0.06g).

[0012] Further, the particle size of the TiO2 in step S2 is 80 nm~120 nm.

[0013] Further, in step S5, the temperature of the vacuum drying is 45℃~55℃, and the reaction time is 5h~7h.

[0014] Further, in step S6, the M-phase VO2 nano-powder is freshly prepared and used in time to prevent agglomeration.

[0015] Further, step S6 comprises the following sub-steps: S61: dissolving the freshly prepared and used in time M-phase VO2 nano-powder in anhydrous ethanol, and continuously stirring to ensure uniform dispersion, S62: weighing the CuS-modified TiO2 material and adding it into the M-phase VO2 nano-powder, mixing at high speed, then adding polyvinylpyrrolidone, and continuously stirring to make it fully mixed and uniform, to obtain a final mixed solution, S63: centrifuging and washing the product of the final mixed solution, and then vacuum drying to obtain a nano-VO2 composite material.

[0016] Further, in sub-step S62, the mass of the CuS-modified TiO2 material is 20%~80% of the mass of the M-phase VO2 nano-powder, and the mass of the added polyvinylpyrrolidone is 18%~22% of the total mass of the final mixed solution, In sub-step S63, the centrifuging and washing time is 8min~12min, the temperature of the vacuum drying is 75℃~85℃, and the reaction time is 5h~7h.

[0017] According to the third aspect of the present application, there is also provided the use of the nano-VO2 composite material as described above in the preparation of intelligent windows, thermochromic coatings and infrared control devices.

[0018] It can be understood that the beneficial effects of the above-mentioned first aspect to third aspect are as follows: (1) The nano VO2 composite material of the present application is added with CuS and TiO2 in component design, can utilize the light-heat conversion capacity of the light-heat material CuS to indirectly reduce the phase change reaction temperature of VO2, the phase change temperature of the modified M-phase nano VO2 is 61℃~63℃, and the phase change temperature of the modified M-phase nano VO2 is 45℃~50℃. Specifically, the light-heat effect of CuS on VO2 can drive VO2 to trigger phase change at a lower environmental temperature, and the phase change of VO2 is no longer triggered by electricity or external heating, which is more energy-saving. In addition, the LSPR effect of CuS is utilized to expand the spectrum control range to the visible-near infrared band in cooperation with the phase change of VO2, specifically in the range of 780-2500nm, which has the benefit of enhancing the near-infrared absorption capacity of the CuS-TiO2 / VO2 composite system. In addition, the high visible light transmittance of TiO2 is utilized to improve the visible light transmittance of VO2 to meet the general environmental light transmittance requirement, that is, the visible light transmittance is greater than 40%. Under the premise of sacrificing little sunlight regulation capacity, the visible light transmittance of the nano VO2 composite material is greatly improved. The component design of the present application maintains the excellent phase change characteristics and thermochromic performance of VO2, reduces the phase change temperature while maintaining good sunlight regulation capacity, so that VO2 can be more widely applied to intelligent windows, thermochromic coatings, infrared regulation devices and thermal management fields.

[0019] (2) The method of the present application has simple preparation process, does not involve expensive equipment and materials, has strong process controllability, and the nano VO2 composite material prepared has excellent comprehensive performance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a flow chart of the preparation method of the nano vanadium dioxide composite material provided by the present application; Figure 2 is the performance test of the M-phase VO2 nano powder prepared in Example 1, Figure 2 the content (a) in the table is the XRD test result, Figure 2 the content (b) in the table is the DSC test result of the prepared VO2, Figure 2 the content (c) in the table is the field emission scanning electron microscope (SEM) test of the prepared VO2, Figure 2 the content (d) in the table is the transmittance test of the prepared VO2 thin film sample using an ultraviolet-visible-near infrared spectrometer (UV-3600); Figure 3 is the FTIR spectrum of the CuS-TiO2 nano powder and CuS powder in Example 2; Figure 4 the content (a) in the table and Figure 4 the content (b) in the table is the SEM image of the CuS nano powder prepared by hydrothermal method with 30,000 times magnification, Figure 4Content (c) in the middle of the figure Figure 4 Content (d) in the middle of the figure is a SEM image of CuS-TiO2 nanopowder prepared by hydrothermal method, magnified by 30000 times; Content (a) in Fig. 5 is a UV-Vis-NIR transmittance spectrum of CuS sample and CuS-TiO2 sample prepared in the embodiment, and content (b) in Fig. 5 is a comparison photograph of sample S1 with one layer of coating and sample S2 with two layers of coating; Figure 6 Content (a) in the middle of the figure is an XRD analysis diagram of samples CuS-TiO2 / VO2, VO2-CuS and CuS prepared in the embodiment; Figure 7 Content (a) in the middle of the figure is an XRD analysis diagram of samples CuS-TiO2 / VO2, VO2-CuS and CuS prepared in the embodiment; Figure 8 Content (a) in the middle of the figure is an XRD analysis diagram of samples CuS-TiO2 / VO2, VO2-CuS and CuS prepared in the embodiment; Figure 8 Content (b) in the middle of the figure is an XRD analysis diagram of CuS-TiO2 nanopowder, pure CuS and pure TiO2; Figure 9 Content (a) and content (b) in the middle of the figure are optical performance diagrams of CuS / VO2 and CuS-TiO2 / VO2 prepared in different mass ratios; Figure 10 Content (a) in the middle of the figure is an infrared thermal imaging diagram of a plurality of sample films, wherein, Figure 10 Content (a) in the middle of the figure is an infrared thermal imaging diagram of a plurality of sample films, wherein, Figure 10 Content (b) in the middle of the figure is a comparison diagram of different component films under the same test condition, Figure 10 Content (c) in the middle of the figure is an infrared thermal imaging diagram of a plurality of sample films, wherein, Figure 10 Content (d) in the middle of the figure is also a comparison diagram of different component films under the same test condition, Figure 10 Content (a) in the middle of the figure is an infrared thermal imaging diagram of a plurality of sample films, wherein, Figure 10 Content (c) in the middle of the figure is a test of ViO2 film sample under different test conditions, the temperature is similar but not completely the same. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0022] The embodiments of the present application are implemented on the premise of the technical scheme of the present application, and detailed implementation modes and processes are given, but the protection scope of the present application is not limited to the following embodiments. The process parameters not specified in the following embodiments are usually according to the conventional conditions.

[0023] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as implicitly included in the meaning of the range. The ranges format is only to simplify disclosure and provides support in the disclosure of 'open ended' numbers which implies any number falling within the range. However, the disclosure should be read to include the first and second endpoints of the ranges, as well as every number or value therebetween. For values which are less than one, one of ordinary skill in the art will understand that the value is to be one unit and 4 / 5, and so forth, as these values nearest the endpoints of the ranges and still falls within the range.

[0024] The present application provides a CuS-TiO2 / VO2 nanocomposite capable of simultaneously improving the visible light transmittance of VO2 and indirectly reducing its phase transition temperature and a preparation method thereof, the core key steps of which are as follows: Step one: preparation of M-phase VO2 nanomaterial: (1) A certain amount of ammonium metavanadate was weighed into a beaker containing deionized water, a magnetic stirrer was placed, and uniform stirring was performed at room temperature to obtain a milky white mixed solution.

[0025] (2) A certain amount of monosalt hydrazine was dissolved in deionized water and stirred until completely dissolved to obtain a monosalt hydrazine solution. The monosalt hydrazine solution was added dropwise to the ammonium metavanadate suspension, and it was observed that the suspension turned gray black and finally turned brown yellow. The brown yellow solution was continuously stirred.

[0026] (3) The brown yellow solution was transferred to a fume hood, and a certain amount of concentrated hydrochloric acid was removed by a pipette under the condition of appropriate speed stirring. The concentration of the concentrated hydrochloric acid was 38 wt%, and it was slowly added dropwise. The reaction was violent, and the mixture slowly turned from brown yellow to gray green, accompanied by the generation of a large amount of bubbles. Until the mixture turned into a blue clear solution, the stirring was continued.

[0027] (4) Ammonia water was taken as a precipitating agent, and the concentration of the ammonia water was 28 wt%. The clear blue solution was quickly added to the ammonia water, and the clear blue solution gradually turned into a brown yellow earthy suspension. The solution gradually became viscous, and the pH was adjusted to 8.0. The stirring was continued, and the deionized water was used for centrifugal washing after a period of time.

[0028] (5) The brown yellow earthy precipitate was transferred to the inner liner of a 100 ml reaction kettle PPL, and a certain amount of ultrapure water was added to obtain a precursor. The stirring was uniform, the volume of the precursor was adjusted to 80% of the volume of the PPL liner, and the PPL liner was placed in a metal reaction kettle after ultrasonic treatment for 30 min. The hydrothermal reaction was performed to obtain a black product. The hydrothermal temperature was 270°C, and the hydrothermal time was 1440 min (i.e. 24 h). It is worth noting that in order to prevent danger, the PPL liner can be taken out only after the metal reaction kettle is completely cooled to room temperature.

[0029] (6) The black product obtained after the reaction of step (5) is washed with anhydrous ethanol and deionized water alternately, and after vacuum drying, it is fully ground to obtain VO2nanopowder with a particle size of 40 nm to 80 nm and not easy to agglomerate. For example, in this step, the anhydrous ethanol and deionized water are washed alternately 4 times, the centrifuge speed is 8000 r / min, the time is 5 min, the vacuum drying box temperature is set to 70℃, and the drying time is 4 h.

[0030] In the above steps, the stirring speed in step (1) and the subsequent steps can be preferably 1000 r / min, and stirring at room temperature.

[0031] Step two: Preparation of CuS-TiO2nanocomposite (1) Under constant room temperature conditions, an appropriate amount of copper chloride dihydrate (CuCl2·2H2O) and polyvinylpyrrolidone (PVP) are dissolved in an appropriate amount of deionized water, and continuously stirred at high speed for 30 minutes to ensure complete dispersion. Among them, the addition amount of PVP is 10% of the mass of copper chloride dihydrate (CuCl2·2H2O) powder, which ensures uniform dispersion and prevents agglomeration.

[0032] (2) Add an appropriate amount of titanium dioxide (chemical formula TiO2), continue to stir at high speed for 30 minutes to achieve uniform mixing. The added titanium dioxide (TiO2) is 50% of the mass of the copper chloride dihydrate (CuCl2·2H2O) powder.

[0033] (3) A certain volume of (NH4)2S solution is quickly added to the above dispersion, and the solution color is immediately observed to become black. After 30 min of continuous stirring, a dark brown suspension is obtained. Due to the rapid deposition reaction, the (NH4)2S solution is quickly added, and the (NH4)2S solution concentration is 20% to 26%, and the speed of quickly adding the (NH4)2S solution is, for example, 0.2 ml / s.

[0034] (4) The dark brown suspension is transferred to the reaction kettle PPL liner, and an appropriate amount of ultrapure water is added to obtain a precursor, which is stirred uniformly, and the volume of the precursor is adjusted to 80% of the volume of the PPL liner. The PPL liner is placed in a metal reaction kettle and completely sealed, and a hydrothermal reaction is carried out. The reaction temperature is set to 180℃, and the reaction time is 12 h.

[0035] (5) After the hydrothermal reaction is completed, the reactor is naturally cooled to ambient temperature and then removed. Finally, the sample is washed with deionized water and anhydrous ethanol for three times in succession, dried in a vacuum drying oven, and ground to obtain CuS-TiO2 nanocomposite powder. Since the CuS-TiO2 particles prepared by this method are hydrophilic and difficult to centrifuge, the centrifugal speed is 12000 r / min, and the centrifugal time is 30 min; the temperature of the vacuum drying oven is set to 50ºC, and the drying time is 6h.

[0036] Step three: Preparation of CuS-TiO2 / VO2 nanocomposite (1) A certain amount of VO2 nanometer powder is weighed and dissolved in anhydrous ethanol, and continuously stirred at high speed for 24 hours to ensure uniform dispersion. The mass ratio or volume ratio of VO2 nanometer powder to anhydrous ethanol is 0.5g:50ml. The stirring speed is set to 1000r / min to ensure uniform dispersion and prevent agglomeration.

[0037] (2) A certain amount of CuS-TiO2 powder is weighed according to a certain mass ratio and added to the VO2 dispersion, and the mass ratio is CuS-TiO2:VO2=20%~80%. After high-speed stirring and mixing for 12 h, a certain proportion of polyvinylpyrrolidone (PVP) is added for continuous stirring to obtain a uniformly mixed CuS-TiO2 / VO2 / PVP mixture. The added polyvinylpyrrolidone (PVP) is 20% of the total mass of the CuS-TiO2 / VO2 / PVP mixture.

[0038] (3) After the stirring and mixing are completed, the product is washed with deionized water and ethanol for a total of three times, and then dried in a vacuum drying machine. The obtained product is fully ground to prepare CuS-TiO2 / VO2 composite powder. The centrifuge speed is set to 10000 r / min, and the centrifugal time is 10 min; the temperature of the vacuum drying machine is set to 80ºC, and the vacuum drying time is 6h.

[0039] Step four: Preparation of CuS-TiO2 / VO2 nanocomposite thin film (1) The prepared CuS-TiO2 / VO2 nanocomposite powder, polyvinylpyrrolidone (PVP), and anhydrous ethanol are mixed in a 10ml reagent bottle according to a ratio of 0.1g:0.1g:4ml to prepare a slurry. 1mm zirconium oxide grinding beads are added to the bottom of the reagent bottle, and the mixture is quickly stirred on a stirrer at a speed of 1200 r / min for 24h to obtain a uniformly dispersed CuS-TiO2 / VO2 / PVP slurry.

[0040] (2) The uniformly dispersed CuS-TiO2 / VO2 / PVP slurry is allowed to stand for 12h, and the upper clear liquid is taken to prepare a uniform thin film.

[0041] (3) Using a pipette to take an appropriate amount of supernatant of the slurry after standing, slowly drop it onto a 2.5cm*2.5cm glass substrate to prepare a uniform thin film using a small spin coater. The glass substrate should be ultrasonically cleaned with deionized water, acetone, isopropanol, and anhydrous ethanol, and the spin coating parameters are set to two: low speed 800 r / min, acceleration 300 r / min, time 10 s; high speed 2200 r / min, acceleration 400 r / min, time 20 s. The reason for setting two parameters is to make the film more uniform and reduce the generation of defects or voids. 2 2

[0042] (4) After each coating, place it on a heating plate to accelerate the evaporation of anhydrous ethanol, and repeat the above 2-3 times to prepare CuS-TiO2 / VO2 films of different thicknesses. The heating plate temperature is 70℃, and the heating time is 2min.

[0043] The prepared film has good uniformity and low haze, and can better characterize the optical properties of the CuS-TiO2 / VO2 film.

[0044] In terms of material properties, nano-copper sulfide (CuS) and titanium dioxide (TiO2) are highly regarded for their unique photo-thermal properties. Copper sulfide Cu 2-x S (0<x<1) as a key transition metal sulfide, exhibits significant characteristics such as non-toxicity, high chemical stability, and adjustable performance. CuS has a localized surface plasmon resonance effect (LSPR) in the near-infrared region, which can enhance the light-thermal conversion efficiency of the material; while TiO2 not only has excellent photocatalytic stability, its wide bandgap property (~3.2 eV) can also inhibit VO2 oxidation through interface band matching. Based on this, the present application utilizes the localized surface plasmon resonance characteristics of CuS, which can be converted into heat energy through the photo-thermal effect under sunlight, and then help VO2 to realize rapid optical transition at room temperature. By utilizing the high visible light transmittance of TiO2, it helps VO2 to improve the visible light transmittance. Through the combined action of the two, the phase transition behavior of VO2 is no longer triggered by power or external heating, which will be more energy-saving.

[0045] Figure 1 ​​This is a flowchart of the preparation method of the nano-vanadium dioxide composite material provided in this application. As shown in the figure, in the preparation method of the CuS-TiO2 / VO2 nanocomposite material of this invention, copper chloride dihydrate (CuCl2·2H2O) is used as the copper source and ammonium sulfide (NH4)2S solution is used as the S source. Under high temperature and high pressure conditions, CuS is further deposited on the surface of nano-TiO2 by chemical deposition, and CuS-TiO2 heterojunction composite material is obtained by epitaxial growth. Then, CuS-TiO2 / VO2 composite nanopowder is prepared by mechanical composite method. The actual engineering preparation method includes: preparing M-phase VO2 nanopowder by one-step hydrothermal method; epitaxially growing CuS on the surface of TiO2 by chemical deposition under high temperature and high pressure conditions to form CuS-TiO2 heterojunction composite material; combining the prepared M-phase VO2 nanopowder and CuS-TiO2 powder by simple mechanical composite method to form CuS-TiO2 / VO2 composite powder; and finally preparing CuS-TiO2 / VO2 thin film by spin coating method. By mechanically combining VO2 nanomaterials with CuS-TiO2 nanomaterials, the excellent photothermal conversion capability of CuS is utilized to indirectly reduce the phase transition temperature of VO2, while the light transmittance of TiO2 is significantly improved to enhance the visible light transmittance of VO2. This allows the composite material to be better controlled to meet the light conditions required at room temperature.

[0046] The embodiments of this application are described below with reference to the accompanying drawings.

[0047] Example 1 In this embodiment, M-phase VO2 nanopowder was prepared.

[0048] The method for preparing small-sized, uniformly sized M-phase VO2 nanoparticles in this example is as follows, specifically including the following steps: (1) Weigh 4.5g of ammonium metavanadate and place it in a 250ml beaker. Add 50ml of deionized water and place it on a magnetic stirrer. Stir evenly at room temperature for 1h to obtain a milky white mixture. The stirring speed of the stirrer is 1000 r / min.

[0049] (2) Weigh 1.0g of hydrazine monohydrochloride into a 10ml reagent bottle, add 10ml of deionized water, stir until completely dissolved, and then add dropwise to the ammonium metavanadate suspension. Observe that the suspension turns gray-black and finally turns brown-yellow. Continue stirring for 40min at a stirring speed of 1000 r / min.

[0050] (3) The mixed solution was transferred to a fume hood, and concentrated hydrochloric acid, about 10-12 ml, with a concentration of 38 wt%, was slowly added dropwise by pipette under stirring. The reaction was violent, and the mixed solution slowly changed from brown yellow to grass green, accompanied by a large amount of bubble generation. The mixed solution became a blue clear solution, and there was no black precipitate at the bottom of the cup. Then the stirring was continued for 1 h.

[0051] (4) Ammonia water was taken as a precipitant, and the amount was 13-15 ml. 10 ml of the ammonia water was quickly added, and then the ammonia water was slowly added. It was observed that the clear blue solution gradually changed to a brown yellow suspension, and the solution gradually became viscous. The pH of the solution was adjusted to 8.0 by slowly adding the ammonia water, and the stirring was continued for 2 h to obtain a suspension.

[0052] (5) The suspension in the above (4) was washed twice by centrifugation with deionized water at a speed of 8000 r / min for 5 min. The brown yellow precipitate after centrifugation was transferred to a 100 ml PPL inner liner of a reaction kettle, and a proper amount of ultrapure water was added to obtain a precursor. The volume of the precursor was adjusted to 80% of the volume of the PPL inner liner, and the PPL inner liner was placed in a metal reaction kettle after ultrasonic treatment for 30 min. The hydrothermal reaction was carried out at a hydrothermal temperature of 270℃ for 1440 min (24 h).

[0053] (6) The black product obtained after the reaction in step (5) was washed 4 times by centrifugation with anhydrous ethanol and deionized water. After vacuum drying at a temperature of 70℃ for 4 h, the M-phase VO2 nanopowder was obtained by grinding.

[0054] Figure 2 The performance tests of the M-phase VO2 nanopowder prepared in this embodiment were carried out according to the contents of (a), (b) and (c) in the following table. Figure 2 According to the XRD characterization of the content (a) in the table, strong diffraction peaks appeared at 27.9°, 37.0° and 55.6°, which corresponded to the (110), (101) and (211) crystal faces of the standard card JPCDS #71-2362, respectively. According to the principle of three strong peaks, it was proved that the successfully prepared M-phase VO2 nanoparticles were indeed M-phase VO2 nanoparticles. Figure 2 The content (b) in the table is the DSC test of the prepared VO2. According to the results, the M-phase VO2 particles prepared in this experiment were small in size and uniform in size. Due to the small size effect, the phase transition temperature of VO2 was 62.28℃, which was lower than the phase transition temperature 68℃ of ordinary VO2. Figure 2 The content (c) in the table is the field emission scanning electron microscope (SEM) test of the prepared VO2. It can be seen from the figure that the VO2 particles are small and spherical, uniform in size, and the particle size is 40-80 nm. Figure 2The content (d) is that the prepared VO2 thin film sample is tested by using a UV-visible near infrared spectrometer (UV-3600), and it is found that the visible light transmittance of the VO2 thin film prepared in the experiment is 45%, the solar light adjusting capacity ΔTsol is 18.0, the optical performance is good, and the color is relatively deep.

[0055] Example 2 In this embodiment, CuS-TiO2 nanopowder is prepared.

[0056] The specific method for preparing CuS-TiO2 nanopowder in this embodiment is as follows: (1) Under the condition of constant room temperature, 0.1 g of copper chloride dihydrate (CuCl2·2H2O) and polyvinylpyrrolidone (PVP) are weighed and dissolved in 30 ml of deionized water, and high-speed continuous stirring is performed for 30 min to ensure sufficient dispersion.

[0057] (2) 0.05 g of titanium dioxide (TiO2) is added to the mixed solution in step (1), and high-speed stirring is continued for 30 min to achieve uniform mixing.

[0058] (3) 0.7 ml of ammonium sulfide solution is quickly added to the above dispersion, and the solution color is observed to immediately turn black. After 30 min of continuous stirring, a dark brown suspension is generated.

[0059] (4) The dark brown suspension is transferred to the inner liner of the reaction kettle PPL with a capacity of 100 ml, and an appropriate amount of ultrapure water is added to obtain a precursor. After uniform stirring, the volume of the precursor is adjusted to 80% of the volume of the PPL inner liner. After ultrasonic treatment for 30 min, the PPL inner liner is placed in a metal reaction kettle and completely sealed for hydrothermal reaction. The reaction kettle containing the sample is placed in a constant temperature air drying oven with a set temperature of 180°C for hydrothermal treatment, and the duration is 12 hours.

[0060] (5) After the hydrothermal reaction is completed, the sample is taken out after natural cooling to ambient temperature at room temperature, and the sample is subjected to centrifugal washing with deionized water and anhydrous ethanol for three times in succession. Since the CuS-TiO2 particles prepared by this method are hydrophilic and not easy to separate, the centrifugal speed is set to 12000 r / min, and the centrifugal time is 30 min. Then, the CuS-TiO2 particles are obtained by vacuum drying at 50°C in a vacuum drying oven for 6 h. Figure 3 The FTIR spectra of the CuS-TiO2 nanopowder and CuS powder in Example 2 are shown in the figure. It can be seen from the figure that the absorption peaks of the powders appear at 3420 cm -1 , 2358.9 cm -1 , 1628 cm -1 , 1385 cm -11028 cm -1 604 cm -1 Nearby. 3420-3439 cm -1 The absorption band is a characteristic vibration of the hydroxyl group (-OH), at 2358.9 cm⁻¹. -1 This is an asymmetric stretching vibration of carbon dioxide in the air, 1628-1645 cm. -1 The strong C=O absorption originating from the lactam group in the PVP side chain, via the bending mode of HOH at 1000 cm⁻¹, is achieved. -1 The formation of CuS nanoparticles was observed below, which consisted of 1385.4 cm⁻¹ nanoparticles. -1 As demonstrated in the adsorption band of TiO2-S, 1028-1090 cm⁻¹ -1 The corresponding absorption peaks for the stretching vibrations of CuS are 604.3–648.3 cm⁻¹. -1 This corresponds to the absorption peak of the Ti-O-Ti stretching vibration of TiO2. 1090 cm⁻¹ -1 The nearby peaks indicate the presence of SO stretching, suggesting that CuS binds to the TiO2 surface by constructing SO groups.

[0061] Figure 4 Content (a) and Figure 4 Content (b) is a SEM image of CuS nanoparticles prepared by hydrothermal processing, magnified 30,000 times. It can be seen that the microstructure of the sample is plate-like, with the size of a single plate being approximately 100~300 nm, and there is slight aggregation between the plates. Figure 4 Content (c) and Figure 4 The content (d) is a SEM image of CuS-TiO2 nanoparticles prepared by hydrothermal processing, magnified 30,000 times. As can be seen from the figure, the microstructure of CuS-TiO2 is a layered structure with overlapping layers, and the size is 100nm~400nm.

[0062] Figure 5 (a) shows the UV-Vis-NIR transmittance spectra of CuS sample, CuS-TiO2 sample prepared in this embodiment, wherein CuS-TiO2-S1 is a sample of one layer of spin coating, and CuS-TiO2-S2 is a sample of two layers of spin coating. As can be seen from the figure, under the same conditions, the CuS prepared in this experiment has a lower near-infrared light transmittance (the near-infrared light wavelength is 780-2500 nm, and the transmittance at 2000 nm is taken as the near-infrared transmittance for qualitative analysis), which means that it has a higher near-infrared light absorption capacity. The visible light transmittance of the CuS thin film is relatively low, only about 45% (the visible light wavelength is 380-780 nm, and the transmittance at 550 nm is taken as the visible light transmittance for qualitative analysis), compared with the CuS-TiO2 nanometer powder, the thin film prepared by the CuS-TiO2 nanometer powder has a better near-infrared light absorption capacity, and its visible light transmittance can reach 78%, greatly improving the defect of low visible light transmittance of pure CuS thin film, while retaining the characteristics of strong near-infrared absorption of CuS. Figure 5 (b) is a photograph of the sample S1 of one layer of spin coating and the sample S2 of two layers of spin coating. As can be seen by comparison, the sample of one layer of spin coating is more transparent.

[0063] Example 3 This embodiment describes the preparation of CuS-TiO2 / VO2 nanocomposite material, and the specific method is as follows: (1) 0.5g of VO2 nanometer powder is weighed and dissolved in 50ml of anhydrous ethanol in advance, and the stirring speed is set to 1000r / min, and the high-speed stirring is continued for 24 hours to ensure uniform dispersion.

[0064] (2) According to the mass ratio of CuS-TiO2 to VO2 being 2:5, 0.2g of CuS-TiO2 powder is weighed and added to the VO2 dispersion liquid, and after high-speed stirring and mixing for 12h, 0.1g of polyvinylpyrrolidone (PVP) is added for continuous stirring.

[0065] (3) After completing the stirring and mixing, the product should be centrifuged three times alternately using deionized water and ethanol, the centrifuge speed is set to 10000r / min, and the centrifugation time is 10min. After drying in a vacuum drying machine, the vacuum drying machine temperature is set to 80℃, and vacuum drying is carried out for 6h. The obtained product is fully ground to prepare CuS-TiO2 / VO2 composite powder.

[0066] Figure 6The X-ray diffraction (XRD) analysis graphs of the samples of CuS-TiO2 / VO2, VO2-CuS, and CuS prepared in the present embodiment are shown in FIG. 1. Through analysis of the diffraction graphs, it is revealed that the CuS-TiO2 / VO2 composite powder prepared by the mechanical compounding technique is compared with the standard CuS comparison card (JCPDS No. 79-2321), and the characteristic peaks appearing at 2θ = 31.79°, 32.85°, 47.94°, 52.73°, and 59.34° correspond to the (006), (110), (110), (108), and (116) crystal planes of monoclinic CuS, respectively. In comparison with the standard comparison card JCPDS No. 82-0661 of VO2(M), the characteristic peaks appearing at 2θ = 27.80°, 36.98°, 42.08°, and 52.93° correspond to the (011), (-211), (-212), and (121) crystal planes of monoclinic VO2, respectively. It is shown that the crystal structure of the original powder VO2(M) is not damaged in the process of preparing the composite powder, and both of the two raw materials can exhibit their respective inherent functional properties. The XRD test proves the realization and effectiveness of the preparation of the composite powder from the attribution level.

[0067] Figure 7 For the typical morphological characteristics of the CuS-TiO2 / VO2 composite material in the present embodiment, two significant characteristics can be observed: ① the substrate material CuS-TiO2 presents a typical sheet-like structure, with a horizontal size of 600-800 nm, and a large number of wrinkle structures exist on the surface thereof; and ② the VO2 nanoparticles (particle size 50-80 nm) are deposited in a heterogeneous nucleation manner preferentially at the edge and surface defect sites of the CuS-TiO2 sheet, forming a stable structure.

[0068] Among them, the VO2 particles can be clearly observed to present a microspherical morphology after magnification, with a particle size distribution range of 80-150 nm, and there is a little aggregation phenomenon in the sample. In the hydrothermal reaction process (reaction temperature 270°C, duration 24 h), the high-pressure environment accelerates the Ostwald ripening process, leading to the dissolution of small-size particles and recrystallization on the surface of large particles. At the same time, the strong hydrogen bond interaction between the hydroxyl (-OH) groups (confirmed by FTIR analysis) remaining on the surface of the nanoparticles is a key factor for inducing the non-directional adsorption between the particles.

[0069] In view of the characteristics of the VO2 nanoparticles synthesized by the one-step hydrothermal method, such as small particle size, high specific surface area, and significant surface activation energy, it is inevitable that there is a little aggregation phenomenon, and aggregation is also a common problem of nanomaterials. In the mechanical mixing process, an appropriate amount of surfactant PVP is added, aiming to improve the steric hindrance effect between the nanoparticles, so as to enhance the dispersity of the nanoparticles in the substrate solution.

[0070] Example 4 This embodiment illustrates the method for preparing CuS-TiO2 / VO2 uniform thin film: (1) The prepared CuS-TiO2 / VO2 composite powder, polyvinylpyrrolidone (PVP) and anhydrous ethanol are prepared into a slurry in a 10 ml reagent bottle according to the ratio of 0.1 g:0.1 g:4 ml, 1 mm zirconium oxide ball milling beads are added to the bottom of the reagent bottle, and the reagent bottle is placed on a stirrer for rapid stirring. The stirring speed is 1200 r / min, and the continuous stirring is carried out for 24 h.

[0071] (2) The uniformly dispersed CuS-TiO2 / VO2 slurry obtained in step (1) is allowed to stand for 12 h, and the upper clear liquid is taken to prepare a uniform thin film.

[0072] (3) An appropriate amount of the upper clear liquid of the slurry after standing in step (2) is taken by using a pipette, and is slowly added to a 2.5 cm*2.5 cm glass substrate, and a small-sized spin coater is used to prepare a uniform thin film. The glass substrate is ultrasonically cleaned with deionized water, acetone, isopropyl alcohol and anhydrous ethanol, and the spin coating parameters are set as follows: low speed 800 r / min, acceleration 300 r / min 2 , time 10 s; high speed 2200 r / min, acceleration 400 r / min 2 , time 20 s.

[0073] (4) After each coating, the heating plate is used to accelerate the volatilization of anhydrous ethanol, and the above steps 2-3 are repeated to prepare CuS-TiO2 / VO2 thin films with different thicknesses. The temperature of the heating plate in step (4) is 70℃, and the heating time is 2 min.

[0074] The thin films prepared in this embodiment are uniform and have low haze, and can better exhibit the optical properties of the prepared CuS-TiO2 / VO2 thin film.

[0075] The thin films in the present application are all prepared by this method.

[0076] Example 5 This example is a comparative example of Example 2, which is based on Example 2, and explores the influence of different reaction times on the preparation of CuS-TiO2 under the condition that the reaction temperature is unchanged during the hydrothermal reaction.

[0077] The difference between the steps of this example and the steps of Example 2 is that the reaction temperature is kept at 180℃ unchanged during the hydrothermal treatment in step (4), and the reaction time is changed to 6 h, 8 h, 10 h and 12 h respectively, so as to explore the crystallization degree of CuS-TiO2 under different reaction times. The other steps of this example are the same as those of Example 2.

[0078] Figure 8 Content (a) shows the XRD test results of CuS-TiO2 nanopowder prepared under different hydrothermal times. The XRD patterns of samples with reaction times of 6h, 8h, 10h and 12h during hydrothermal treatment are listed. By comparison with the PDF standard card of CuS (JCPDS#79-2321), the prepared CuS-TiO2 nanopowder showed diffraction characteristic peaks at 2θ=27.13°, 27.68°, 29.28°, 31.79°, 32.85°, 47.94°, 52.73° and 59.34°, which correspond to the (004), (101), (102), (103), (006), (110), (110), (108) and (116) crystal planes of CuS, respectively. No other impurity peaks were found. This indicates that the diffraction characteristic peaks of the prepared CuS become sharper with the extension of hydrothermal time, suggesting that the CuS prepared at a hydrothermal time of 12 h has the highest crystallinity, which is beneficial for subsequent experiments.

[0079] Figure 8 Content (b) shows the XRD test results of CuS-TiO2 nanopowder, pure CuS, and pure TiO2. The characteristic peak at 2θ=25.38° corresponds to the characteristics of crystalline TiO2 (PDF#73-1764), which corresponds to the (101) crystal plane of monoclinic TiO2, and its peak value is weakened. The characteristic peaks appearing at 2θ=27.13°, 27.68°, 29.28°, 31.79°, 32.85°, 47.94°, 52.73°, and 59.34° correspond to the (004), (101), (102), (103), (006), (110), (110), (108), and (116) crystal planes of monoclinic CuS, respectively. The above XRD spectra further verify the formation of CuS-TiO2 composite material.

[0080] Example 6 This example is a comparative example of Example 3. Based on Example 3, two sets of comparative experiments were conducted to prepare CuS / VO2 and CuS-TiO2 / VO2 composite materials, respectively, to explore the effect of adding TiO2 on the performance of the composite materials. The optical properties of composite materials with different component ratios were systematically studied (test wavelength range 300nm ~ 2500nm, resolution 1nm).

[0081] (1) Weigh 0.5g of VO2 nanopowder and dissolve it in 50ml of anhydrous ethanol. Set the speed to 1000r / min and stir continuously at high speed for 24 hours to ensure uniform dispersion.

[0082] (2) CuS and CuS-TiO2 powders were weighed according to different mass ratios and added into the V2O3 dispersion liquid, the mass ratio of V2O3 powder to CuS or CuS-TiO2 was 5:1, 5:2, 5:3, 5:4, respectively, and the samples were named as S1, S2, S3, S4, respectively, wherein S0 represents a pure V2O3-based film sample. After high-speed stirring for 12 h, 0.1 g of polyvinylpyrrolidone (PVP) was added and stirring was continued.

[0083] (3) After completing the stirring and mixing, the product should be centrifuged three times by alternately using deionized water and ethanol, the speed of the centrifuge was set to 10000 r / min, the centrifugation time was 10 min, and the vacuum drying machine was used for drying, the temperature of the vacuum drying machine was set to 80℃, vacuum drying was performed for 6 h, and the obtained product was fully ground, thereby preparing CuS / V2O3 and CuS-TiO2 / V2O3 composite powders.

[0084] Table 1 Optical standard performance parameters of CuS modified V2O3 (also represented as CuS / V2O3) composite powder intelligent temperature control coating

[0085] Figure 9 Content (a) and Figure 9 Content (b) in the table is the optical performance spectrum of CuS / V2O3 and CuS-TiO2 / V2O3 prepared by different mass ratios, the solid line represents the transmittance curve obtained by testing at room temperature, and the dotted line represents the transmittance curve obtained by testing in the range of 90~100℃. In the figure, S0 to S4 represent the naming of the samples. The specific results are shown in Tables 1 and 2, wherein, T lum,l represents the average value of visible light transmittance obtained by testing at room temperature, T lum,h represents the average value of visible light transmittance obtained by testing in the range of 90~100℃, T sol,l represents the solar light regulation ability obtained by testing at room temperature, T sol,h represents the solar light regulation ability obtained by testing in the range of 90~100℃, T 550nm represents the visible light transmittance of the sample, ∆T solThe solar light modulation ability of the sample. As shown in Table 1, the pure VO2-based thin film (sample S0) exhibits excellent solar light modulation ability (ΔTsol= 18.0%), which is due to the significant change in free carrier concentration during the phase transition of VO2(M). When the temperature is lower than the phase transition point (Tc≈68℃), VO2 is in a monoclinic semiconductor state, and has high transmittance in the near-infrared waveband (780-2500 nm); while in the high-temperature metal state, the plasmonic resonance effect causes the transmittance of near-infrared light to decrease sharply.

[0086] Table 2 Optical standard performance parameters of CuS-TiO2 / VO2 composite powder intelligent temperature control coating

[0087] Further comparison shows that, in the CuS / VO2 composite material, with the increase of the doping ratio of CuS nano-powder (wherein, from sample S0 to sample S4, the doping ratio of CuS nano-powder in the composite material gradually increases), two significant change trends are presented: one is that the solar light modulation ability linearly decays (ΔTsol decreases from 18.0% to 11.3%), and the decay coefficient is 0.59% / wt%, which is mainly due to the decrease of the effective volume fraction of VO2 in the composite system, resulting in the weakening of the phase transition driven optical switching effect. According to the Maxwell-Garnett effective medium theory calculation, when the CuS doping amount reaches 30 wt%, the light modulation contribution of VO2 decreases to 58.3%; the intrinsic wide-spectrum absorption characteristics of CuS (its absorption rate is >85% in the range of 400-1800 nm) lead to the decrease of the incident light flux available for VO2 modulation.

[0088] The other is that the near-infrared light absorption rate presents a monotonic increasing trend, and the enhancement mechanism includes: the narrow band gap characteristics (Eg≈1.7 eV, calculated by Taucplot method) of CuS promote the intrinsic absorption of photo-generated carriers; the Type-II heterojunction structure (confirmed by UPS band analysis) formed at the CuS-VO2 interface accelerates the spatial separation efficiency of photo-generated electron-hole pairs, and thus the surface plasmonic resonance (LSPR) effect of the CuS / VO2 composite material system is enhanced.

[0089] As shown in Table 2, when TiO2 is introduced to form the ternary composite system CuS-TiO2 / VO2, the material system exhibits a unique optical performance evolution rule: when the mass of CuS-TiO2 composite additive is 0.20 g (sample S2), the system obtains the best comprehensive performance: ΔTsol= 15.4 % (decreased by 14.4 % compared with SO) and T550nm= 54.8 % (increased by 20.7 % compared with SO). The introduction of TiO2 effectively regulates the refractive index matching degree of the system and reduces the interface Fresnel reflection loss; the porous structure of TiO2 provides a dispersion carrier for VO2 nanoparticles; the CuS-TiO2 heterojunction serves as a high-efficiency light-heat conversion unit, and its light-heat conversion efficiency is relatively high, which significantly reduces the phase transition activation energy barrier of VO2 and can reduce the phase transition temperature of VO2. The increase in visible light transmittance is mainly due to the wide band gap characteristic (Eg= 3.2 eV) of TiO2, which reduces the intrinsic absorption in the visible light region.

[0090] Figure 10 The infrared thermal imaging map of the infrared light irradiation on the thin film of various samples is shown in FIG. 6. In order to explore whether the introduction of TiO2 has an effect on the light-heat conversion efficiency of the formed ternary composite, a 250 W infrared lamp is used to irradiate the glass sample 20 cm below for 30 s, and an infrared thermal imager is used to record the surface temperature of the glass. By comparing the temperature of the glass sheet within the equivalent light exposure time, the light-heat conversion efficiency of the sample can be evaluated.

[0091] Figure 10 The content (a) in the Figure 10 The content (b) in the Figure 10 As shown in the content (a) in the Figure 10 As shown in the content (b) in the

[0092] Figure 10 The content (c) in the Figure 10 The content (d) in the Figure 10 The content (a) in the Figure 10 The content (b) in the Figure 10 As shown in the content (c) in the Figure 10As shown in content (d), the surface temperature of the CuS-TiO2 / VO2 glass sample under the same irradiation time was 53.8 ℃, which was 43.4 % higher than that of the sample without compounding. Therefore, when irradiated for a short time, the light-heat conversion efficiency of the CuS-TiO2 / VO2 thin film sample was slightly lower than that of CuS / VO2, but the influence on the whole system was small.

[0093] During the long-wave infrared radiation exposure, the enhancement of the heat insulation performance of the CuS-TiO2 / VO2 composite powder was due to the addition of CuS-TiO2, which had high penetration and significant infrared shielding performance. In contrast, under the action of short-time infrared radiation, the improvement of the heat insulation performance was more significant, which indicated that the addition of CuS-TiO2 accelerated the phase change process of the VO2 nanoparticles by exerting its excellent light-heat conversion efficiency, thereby more effectively releasing the heat insulation effect. This strategy provides an effective path for lowering the phase change response temperature of VO2 nanoparticles and expanding the application field of VO2 nanomaterials.

[0094] Example 7 This example is used to prepare a nano vanadium dioxide composite material, which comprises the following steps: S1: CuCl2·2H2O and an appropriate amount of polyvinylpyrrolidone were dissolved in deionized water to obtain a mixed solution. The mass of CuCl2·2H2O was 0.45 g.

[0095] S2: TiO2 was added to the mixed solution, and uniform stirring was continued to obtain a dispersion solution. The particle size of TiO2 was 80 nm ~ 100 nm. The mass of TiO2 was 0.30 g.

[0096] S3: (NH4)2S solution was added to the dispersion solution, the concentration of (NH4)2S solution was 20%, the volume of (NH4)2S solution was 3.25 ml, and stirring was continued to obtain a dark brown suspension.

[0097] S4: The dark brown suspension was transferred to a reaction kettle, and ultrapure water was added to obtain a precursor solution. The precursor solution was subjected to ultrasonic stirring, and then sealed for high-temperature and high-pressure hydrothermal reaction. The reaction temperature was 175 ℃, and the reaction time was 11 h.

[0098] S5: The product obtained by the hydrothermal reaction in step S4 was first subjected to centrifugal washing, and then vacuum drying was performed to obtain a CuS-modified TiO2 material. The temperature of the vacuum drying was 55 ℃, and the reaction time was 5 h.

[0099] S6: The mechanical composite method was used to prepare the nano vanadium dioxide composite material. First, the M-phase VO2 nano powder was dissolved in anhydrous ethanol immediately, and continuous stirring was performed to ensure uniform dispersion. The particle size of the nano VO2 particles was 40 nm to 60 nm. Then, the CuS modified TiO2 material was weighed and added to the M-phase VO2 nano powder. After high-speed stirring and mixing, polyvinylpyrrolidone was added and continued to be stirred to make it fully integrated and uniform. The final mixed solution was obtained. The mass of the CuS modified TiO2 material was 80% of the mass of the M-phase VO2 nano powder, and the mass of the added polyvinylpyrrolidone was 18% of the total mass of the final mixed solution. Finally, the product of the final mixed solution was centrifuged and washed, and then vacuum dried to obtain the nano vanadium dioxide composite material. The centrifugal washing time was 8 min, the vacuum drying temperature was 75°C, and the reaction time was 5 h.

[0100] After component detection, microscopic morphology observation, and light transmittance test, the results showed that the size of the CuS modified TiO2 material was 100 nm to 210 nm. Among them, the CuS modified TiO2 material was in a sheet layer form, and the VO2 nano particles were distributed on the edges and surfaces of the CuS modified TiO2 material sheet layer. The phase transition temperature of the finished nano vanadium dioxide composite material was 45°C, the solar light transmittance reached 16.4%, and the visible light transmittance was not less than 45.4%.

[0101] Example 8 This example was used to prepare a nano vanadium dioxide composite material, which included the same steps as example 7, but the process parameters, material ratios, etc. were different, specifically: S1: The mass of CuCl2·2H2O was 0.55 g.

[0102] S2: The particle size of TiO2 was 90 nm to 120 nm, and the mass of TiO2 was 0.20 g.

[0103] S3: The concentration of (NH4)2S solution was 26%, and the volume of (NH4)2S solution was 3.75 ml.

[0104] S4: The reaction temperature was 185°C, and the reaction time was 13 h.

[0105] S5: The vacuum drying temperature was 45°C, and the reaction time was 7 h.

[0106] S6: The particle size of the nano VO2 particles was 50 nm to 80 nm. The mass of the CuS modified TiO2 material was 20% of the mass of the M-phase VO2 nano powder, and the mass of the added polyvinylpyrrolidone was 22% of the total mass of the final mixed solution. The centrifugal washing time was 12 min, the vacuum drying temperature was 85°C, and the reaction time was 7 h.

[0107] After component detection, microscopic morphology observation, light transmittance test and other tests, the results show that the size of the CuS modified TiO2 material is 120nm-400nm. Among them, the CuS modified TiO2 material is in sheet layer, and the VO2 nanoparticles are distributed on the edge and surface of the CuS modified TiO2 material sheet layer. The phase transition temperature of the finished nano vanadium dioxide composite material is 50℃, the solar light transmittance reaches 10.3%, and the visible light transmittance is not less than 45.4%.

[0108] Example 9 This example is used to prepare a nano vanadium dioxide composite material, which includes the same steps as example 7, except that the process parameters, material ratio and the like are different, specifically: S1: The mass of CuCl2·2H2O is 0.50g.

[0109] S2: The particle size of TiO2 is 100nm-120nm, and the mass of TiO2 is 0.25g.

[0110] S3: The concentration of (NH4)2S solution is 24%, and the volume of (NH4)2S solution is 3.50ml.

[0111] S4: The reaction temperature is 180℃, and the reaction time is 12h.

[0112] S5: The temperature of vacuum drying is 50℃, and the reaction time is 6h.

[0113] S6: The particle size of nano VO2 particles is 40nm-70nm. The mass of CuS modified TiO2 material is 40% of the mass of M-phase VO2 nano powder, and the mass of polyvinylpyrrolidone added is 22% of the total mass of the final mixed solution. The time of centrifugal washing is 10min, the temperature of vacuum drying is 80℃, and the reaction time is 6h.

[0114] After component detection, microscopic morphology observation, light transmittance test and other tests, the results show that the size of the CuS modified TiO2 material is 100nm-400nm. Among them, the CuS modified TiO2 material is in sheet layer, and the VO2 nanoparticles are distributed on the edge and surface of the CuS modified TiO2 material sheet layer. The phase transition temperature of the finished nano vanadium dioxide composite material is 46℃, the solar light transmittance reaches 14.2%, and the visible light transmittance is not less than 45.4%.

[0115] Example 10 This example is used to prepare a nano vanadium dioxide composite material, which includes the same steps as example 7, except that the process parameters, material ratio and the like are different, specifically: S1: The mass of CuCl2·2H2O is 0.49g.

[0116] S2: The particle size of TiO2 is 80 nm ~ 120 nm, and the mass of TiO2 is 0.28 g.

[0117] S3: The concentration of (NH4)2S solution is 25%, and the volume of (NH4)2S solution is 3.40 ml.

[0118] S4: The reaction temperature is 182℃, and the reaction time is 11.5 h.

[0119] S5: The temperature of vacuum drying is 52℃, and the reaction time is 6.5 h.

[0120] S6: The particle size of nano VO2 particles is 40 nm ~ 80 nm. The mass of CuS modified TiO2 material is 27% of the mass of M-phase VO2 nano powder, and the mass of polyvinylpyrrolidone added is 22% of the total mass of the final mixed solution. The time of centrifugal washing is 11 min, the temperature of vacuum drying is 83℃, and the reaction time is 7 h.

[0121] After component detection, microscopic morphology observation, and light transmittance test, the results show that the size of CuS modified TiO2 material is 120 nm ~ 380 nm. Among them, the CuS modified TiO2 material is in a sheet layer shape, and the VO2 nano particles are distributed on the edge and surface of the CuS modified TiO2 material sheet layer. The phase transition temperature of the finished nano vanadium dioxide composite material is 49℃, the solar light transmittance reaches 16.2%, and the visible light transmittance is not less than 45.4%.

[0122] Example 11 This example is used to prepare a nano vanadium dioxide composite material, which includes the same steps as example 7, except that the process parameters, material ratios, etc. are different, specifically: S1: The mass of CuCl2·2H2O is 0.51 g.

[0123] S2: The particle size of TiO2 is 90 nm ~ 120 nm, and the mass of TiO2 is 0.29 g.

[0124] S3: The concentration of (NH4)2S solution is 22%, and the volume of (NH4)2S solution is 3.70 ml.

[0125] S4: The reaction temperature is 179℃, and the reaction time is 12 h.

[0126] S5: The temperature of vacuum drying is 51℃, and the reaction time is 6 h.

[0127] S6: The size of the nano VO2 particles is 40nm-80nm. The mass of the CuS modified TiO2 material is 30% of the mass of the M phase VO2 nano powder, and the mass of the polyvinylpyrrolidone added is 19% of the total mass of the final mixed solution. The centrifugal washing time is 9min, the vacuum drying temperature is 79℃, and the reaction time is 7h.

[0128] Through component detection, microscopic morphology observation, light transmittance test and the like, the results show that the size of the CuS modified TiO2 material is 110nm-380nm. Among them, the CuS modified TiO2 material is in a sheet layer shape, and the VO2 nano particles are distributed on the edges and surfaces of the CuS modified TiO2 material sheet layer. The phase transition temperature of the finished nano vanadium dioxide composite material is 50℃, the solar light transmittance reaches 11.3%, and the visible light transmittance is not less than 45.4%.

[0129] The nano composite material of the application can maintain the optical performance of VO2 and indirectly reduce the phase transition temperature, and can be widely applied in the fields of intelligent windows, thermochromic coatings, infrared regulating devices and thermal management and the like.

[0130] In the application, CuS-TiO2 represents the CuS modified TiO2 material, and CuS-TiO2 / VO2 is the nano vanadium dioxide composite material.

[0131] The above is merely a specific implementation manner of the application, but the protection scope of the application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A nano-vanadium dioxide composite material, characterized in that, The nano-VO2 particles are modified with CuS-modified TiO2 material. The CuS-modified TiO2 material accounts for 20% to 80% of the total mass of the nano-vanadium dioxide composite material. The CuS-modified TiO2 material is used to reduce the phase transition temperature of VO2 while maintaining the solar transmittance of 10.3% to 16.4%. The nano-VO2 particles have a particle size of 40 nm to 80 nm, and the size of the CuS-modified TiO2 material is 100 nm to 400 nm.

2. The nano-vanadium dioxide composite material as described in claim 1, characterized in that, The CuS-modified TiO2 material is in the form of sheets, with VO2 nanoparticles distributed at the edges and surface of the CuS-modified TiO2 material sheets.

3. The nano-vanadium dioxide composite material as described in claim 1, characterized in that, Its phase transition temperature is 45℃ ~ 50℃, and its visible light transmittance is not less than 45.4%.

4. A method for preparing the nano-vanadium dioxide composite material as described in any one of claims 1-3, characterized in that, It includes the following steps: S1: Dissolve CuCl2·2H2O and polyvinylpyrrolidone in deionized water and stir until homogeneous to obtain a mixed solution. S2: Add TiO2 to the mixed solution and continue stirring until homogeneous to obtain a dispersed solution. S3: Add (NH4)2S solution to the dispersion solution. The concentration of (NH4)2S solution is 20%~26%, and continue stirring to obtain a dark brown suspension. S4: Transfer the dark brown suspension to a reaction vessel and add ultrapure water to obtain a precursor solution. Perform ultrasonic stirring on the precursor solution, then seal and conduct a high-temperature, high-pressure hydrothermal reaction at 175℃ ~ 185℃ for 11h ~ 13h. S5: The product obtained from the hydrothermal reaction in step S4 is first centrifuged and washed, then vacuum dried to obtain CuS-modified TiO2 material. S6: Mechanically combine the M-phase VO2 nanopowder and the CuS-modified TiO2 material obtained in step S5 to form a nano-vanadium dioxide composite material.

5. The method as described in claim 4, characterized in that, in, The ratio of CuCl2·2H2O, (NH4)2S solution, and TiO2 is (0.09g~0.11g): (0.65ml~0.75ml): (0.04g~0.06g).

6. The method as described in claim 5, characterized in that, In step S2, the particle size of TiO2 is 80 nm ~ 120 nm. In step S5, the vacuum drying temperature is 45℃ ~ 55℃, and the reaction time is 5h ~ 7h.

7. The method as described in claim 6, characterized in that, In step S6, the M-phase VO2 nanoparticles are freshly prepared and used immediately to prevent agglomeration.

8. The method as described in claim 7, characterized in that, Step S6 includes the following sub-steps: S61: Immediately dissolve the freshly prepared M-phase VO2 nanoparticles in anhydrous ethanol, stirring continuously to ensure uniform dispersion. S62: Weigh out the CuS-modified TiO2 material and add it to the M-phase VO2 nanoparticles. After stirring and mixing, add polyvinylpyrrolidone and continue stirring until it is fully mixed and homogeneous to obtain the final mixed solution. S63: The product of the final mixed solution is first centrifuged and washed, and then vacuum dried to obtain nano-vanadium dioxide composite material.

9. The method as described in claim 8, characterized in that, In sub-step S62, the mass of CuS-modified TiO2 material is 20% to 80% of the mass of M-phase VO2 nanoparticles, and the mass of polyvinylpyrrolidone added is 18% to 22% of the total mass of the final mixed solution. In sub-step S63, the centrifugal washing time is 8 min to 12 min, the vacuum drying temperature is 75℃ to 85℃, and the reaction time is 5 h to 7 h.

10. The application of the nano-vanadium dioxide composite material as described in any one of claims 1-3, characterized in that, It is used to prepare smart windows, thermochromic coatings, and infrared control devices.

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