Vanadium dioxide coating with high latent heat and preparation method thereof

Abstract

The invention discloses a preparation method of a high-latent-heat vanadium dioxide coating, which comprises the following steps: dispersing vanadium dioxide nano-powder with the mass fraction of 10-40% in acetone, then adding tetrabutyl titanate according to the molar ratio of vanadium to titanium of 1: (0.05-0.6), then adding sodium carbonate accounting for 0.001% of the total mass of the solution, and stirring uniformly to obtain the high-latent-heat vanadium dioxide coating. Shearing the solution by adopting a high-speed shearing machine; placing the obtained mixed solution in vacuum for defoaming, then placing the mixed solution in a reducing atmosphere for calcining, and then washing and drying to obtain modified vanadium dioxide nano powder; the modified vanadium dioxide nano powder is dispersed in deionized water, then PVP is added, stirring is conducted, and the vanadium dioxide coating is obtained. Vanadium dioxide is modified through bridging titanium compounds such as tetrabutyl titanate, the latent heat value of vanadium dioxide in the phase change process is greatly increased, the vanadium dioxide can absorb and release more heat during phase change, and the efficiency of the material in thermal management and energy storage application is improved.

Description

Technical Field

[0001] The invention relates to the field of functional nanomaterials, and in particular to a vanadium dioxide coating with high latent heat characteristics and a preparation method thereof. Background Art

[0002] Vanadium dioxide (VO2) has attracted widespread attention in the fields of smart materials and energy-saving technologies in recent years due to its unique phase change properties. VO2 undergoes a phase transition from semiconductor to metal at around 68°C, accompanied by significant changes in physical properties such as optics and electricity. Therefore, it has important potential in applications such as smart windows, energy-saving glass, and thermal regulation materials. However, the phase transition temperature of VO2 itself is relatively high, and the latent heat value exhibited during the phase change process is relatively low, which to a certain extent limits its practical application. In order to improve the performance of VO2, existing technologies attempt to improve its phase transition temperature and latent heat characteristics by doping with other metal elements or compounds.

[0003] Existing doping technologies usually use different metal elements (such as tungsten, molybdenum, chromium, etc.) doped into the VO2 lattice to adjust the phase transition temperature of VO2. This type of doping can indeed effectively reduce the phase transition temperature of VO2, allowing it to undergo phase transition at a temperature more suitable for practical applications. However, these doping technologies have the following shortcomings:

[0004] The preparation process is complex: During the doping process, the proportion and distribution of the doping elements need to be precisely controlled to avoid the negative impact of lattice distortion on the VO2 phase change performance. Any improper process will lead to unstable material performance.

[0005] Limited doping efficiency: The addition of doped metal elements can only slightly reduce the phase transition temperature of VO2, and the doping concentration cannot be too high, otherwise it will destroy the crystal structure of VO2 and cause the material performance to deteriorate. Therefore, the regulation range of doping technology is limited and cannot adapt to a wide range of application scenarios.

[0006] Insufficient improvement in latent heat value: Although doping technology has made some progress in regulating the phase transition temperature of VO2, the effect of improving the latent heat value is limited. In many applications that require high latent heat properties, doped VO2 still cannot meet the needs of heat energy absorption and release.

[0007] Stability issues: After the doping elements are introduced into the VO2 crystal structure, with the long-term use of the material, the doping elements may gradually migrate or precipitate from the lattice, causing the material performance to deteriorate and reducing the long-term stability of the material.

[0008] Therefore, although the existing doping technology has solved the problem of high phase transition temperature of VO2 to some extent, it still has great limitations in increasing the latent heat value of VO2, simplifying the preparation process and improving the stability of materials, and cannot meet the growing application needs of intelligent energy-saving materials and thermal regulation materials. Therefore, it is urgent to develop a new, simple and efficient VO2 modification method that can significantly improve its latent heat characteristics, while reducing the phase transition temperature, and adapt to more application scenarios. Summary of the invention

[0009] The purpose of the present invention is to provide a high latent heat vanadium dioxide coating and a preparation method thereof, which has simple steps, is easy to operate, has low cost, high latent heat and low phase change temperature.

[0010] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0011] In a first aspect, the present invention provides a high latent heat vanadium dioxide coating and a preparation method thereof, comprising the following steps:

[0012] Step 1, dispersing vanadium dioxide nanopowder in acetone, the mass fraction of vanadium dioxide is 10-40%, then adding tetrabutyl titanate in a ratio of vanadium to titanium of 1:0.05-0.6, then adding sodium carbonate of 0.001% of the total mass of the solution, and shearing the solution with a high-speed shearing machine;

[0013] Step 2, placing the mixed solution obtained in step 1 under vacuum to remove bubbles, then placing it in a reducing atmosphere at 200-400° C. for calcination, and then washing and drying to obtain modified vanadium dioxide nanopowder;

[0014] Step three, dispersing the modified vanadium dioxide nanopowder in deionized water with a mass fraction of 0.5-5%, then adding 0.05-2% PVP by mass of the dispersion, stirring, and obtaining a vanadium dioxide coating.

[0015] Preferably, the vanadium dioxide nanopowder, tetrabutyl titanate, sodium carbonate and PVP are all commercially available powders with a purity greater than 98%.

[0016] Preferably, in step 1, the shear rate is 1440 rpm to 28000 rpm, and the shear time is 20 to 60 min.

[0017] Preferably, in step 2, the reducing atmosphere comprises nitrogen and hydrogen, wherein the proportion of hydrogen in the total gas volume is 5-15%, and the calcination time is 1-5 hours.

[0018] Preferably, in step 2, ethanol and deionized water are used for washing 1 to 3 times respectively, the drying temperature is 40 to 60° C., and the drying time is 2 to 4 hours.

[0019] Preferably, in step three, the stirring rate is 500-800 rpm, and the stirring time is 2-6 h.

[0020] In a second aspect, the present invention provides a high latent heat vanadium dioxide coating prepared by the above preparation method.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. Significantly improve the latent heat value: VO2 is modified by bridging titanium compounds such as tetrabutyl titanate, which greatly improves the latent heat value of vanadium dioxide during the phase change process, allowing it to absorb and release more heat during the phase change, thereby improving the efficiency of the material in thermal management and energy storage applications.

[0023] 2. Lower the phase change temperature: By introducing titanium compounds for modification, the phase change temperature of VO2 is effectively adjusted, so that it can undergo phase change at a temperature below 68°C, which is more suitable for application in daily environments, especially in low-temperature phase change applications such as smart energy-saving glass and temperature control equipment.

[0024] 3. Simple preparation process: The preparation method of the present invention adopts conventional wet chemical modification and calcination process. The process is simple and easy to control, and does not require high temperature and high pressure conditions, which significantly reduces the production cost of the material and is suitable for large-scale industrial production.

[0025] 4. High material stability: The structural stability of the VO2 coating material is significantly enhanced through the modification of the bridging titanium compound. During long-term use, it is not easy for the migration of doping elements or the degradation of material properties to occur, thus ensuring the long-term stability of the coating in terms of optical, electrical and thermal properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a bar chart comparing the minimum phase transition temperatures of the coatings prepared in Examples 1, 2, 3 and the comparative example. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1

[0029] Take 10g of vanadium dioxide nanopowder, add it to 100mL of acetone, stir evenly, and prepare a dispersion with a mass fraction of vanadium dioxide of 10%. According to the molar ratio of vanadium to titanium of 1:0.1, add tetrabutyl titanate, and then add sodium carbonate, the mass of sodium carbonate is 0.001% of the total mass of the solution. Use a high-speed shearing machine, the shear rate is 1440rpm, and the shearing time is 30 minutes. After the sheared solution is vacuum degassed, it is calcined at 300℃ for 3 hours in a reducing atmosphere (5% hydrogen and 95% nitrogen). After calcination, wash it twice with ethanol and deionized water respectively, dry it at 50℃ for 3 hours, and obtain the modified vanadium dioxide nanopowder. The modified nanopowder is dispersed in deionized water with a mass fraction of 1%, PVP is added, and stirred at a stirring rate of 600rpm for 2 hours to obtain a coating solution.

[0030] Example 2

[0031] Take 40g of vanadium dioxide nanopowder, add it to 100mL of acetone, stir evenly, and prepare a dispersion with a mass fraction of vanadium dioxide of 40%. According to the molar ratio of vanadium to titanium of 1:0.6, tetrabutyl titanate is added, and then sodium carbonate is added, and the mass of sodium carbonate is 0.001% of the total mass of the solution. A high-speed shearing machine is used, the shear rate is 28000rpm, and the shearing time is 60 minutes. After the sheared solution is vacuum degassed, it is calcined at 400℃ for 5 hours in a reducing atmosphere (10% hydrogen and 90% nitrogen). After calcination, it is washed three times with ethanol and deionized water respectively, and dried at 60℃ for 4 hours to obtain the modified vanadium dioxide nanopowder. The modified nanopowder is dispersed in deionized water with a mass fraction of 5%, PVP is added, and stirred at a stirring rate of 800rpm for 6 hours to obtain a coating solution.

[0032] Example 3

[0033] Take 20g of vanadium dioxide nanopowder, add it to 100mL of acetone, stir evenly, and prepare a dispersion with a mass fraction of vanadium dioxide of 20%. According to the molar ratio of vanadium to titanium of 1:0.2, tetrabutyl titanate is added, and then sodium carbonate is added, and the mass of sodium carbonate is 0.001% of the total mass of the solution. A high-speed shearing machine is used, the shear rate is 20000rpm, and the shearing time is 45 minutes. After the sheared solution is vacuum degassed, it is calcined at 350℃ for 4 hours in a reducing atmosphere (7% hydrogen and 93% nitrogen). After calcination, it is washed three times with ethanol and deionized water respectively, and dried at 55℃ for 3 hours to obtain the modified vanadium dioxide nanopowder. The modified nanopowder is dispersed in deionized water with a mass fraction of 3%, PVP is added, and stirred at a stirring rate of 700rpm for 4 hours to obtain a coating solution.

[0034] Comparative Example

[0035] Without adding tetrabutyl titanate, take 20g of vanadium dioxide nanopowder, add it to 100mL acetone, stir evenly, and prepare a dispersion with a mass fraction of vanadium dioxide of 20%. Add sodium carbonate, the mass of sodium carbonate is 0.001% of the total mass of the solution. Use a high-speed shearing machine, the shear rate is 20000rpm, and the shearing time is 45 minutes. After the sheared solution is vacuum degassed, it is calcined at 350℃ for 4 hours in a reducing atmosphere (7% hydrogen and 93% nitrogen). After calcination, wash it three times with ethanol and deionized water respectively, dry it at 55℃ for 3 hours, and obtain unmodified vanadium dioxide nanopowder. Disperse the unmodified nanopowder in deionized water with a mass fraction of 3%, add PVP, and stir it at a stirring rate of 600rpm for 4 hours to obtain a coating solution.

[0036] Figure 1 It is a bar chart comparing the minimum phase transition temperatures of the coatings prepared in Examples 1, 2, 3 and the comparative example.

[0037] like Figure 1 As shown, Examples 1, 2, and 3 effectively reduce the phase transition temperature after bridging with titanium, indicating that the latent heat of phase transition of the material is increased, while the comparative example is a conventional mixing method, and the final coating phase transition temperature is high. In summary, the material prepared by the method provided by the present invention has high latent heat and low phase transition temperature, and is therefore very suitable for use as a temperature control coating.

[0038] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a high latent heat vanadium dioxide coating, characterized in that: The modification of vanadium dioxide by bridging titanium compound comprises the following steps: Step 1, dispersing vanadium dioxide nanopowder in acetone, the mass fraction of vanadium dioxide is 10-40%, then adding tetrabutyl titanate in a ratio of vanadium to titanium of 1:0.05-0.6, then adding sodium carbonate of 0.001% of the total mass of the solution, and shearing the solution with a high-speed shearing machine; Step 2, placing the mixed solution obtained in step 1 under vacuum to remove bubbles, then placing it in a reducing atmosphere at 200-400° C. for calcination, and then washing and drying to obtain modified vanadium dioxide nanopowder; Step three, dispersing the modified vanadium dioxide nanopowder in deionized water with a mass fraction of 0.5-5%, then adding 0.05-2% PVP by mass of the dispersion, stirring, and obtaining a vanadium dioxide coating.

2. The method for preparing a high latent heat vanadium dioxide coating according to claim 1, characterized in that: The vanadium dioxide nanopowder, tetrabutyl titanate, sodium carbonate and PVP are all commercially available powders with a purity greater than 98%.

3. The method for preparing a high latent heat vanadium dioxide coating according to claim 1, characterized in that: In step 1, the shear rate is 1440 rpm to 28000 rpm, and the shear time is 20 to 60 min.

4. The method for preparing a high latent heat vanadium dioxide coating according to claim 1, characterized in that: In step 2, the reducing atmosphere comprises nitrogen and hydrogen, wherein the proportion of hydrogen in the total gas volume is 5-15%, and the calcination time is 1-5 hours.

5. The method for preparing a high latent heat vanadium dioxide coating according to claim 1, characterized in that: In step 2, ethanol and deionized water are used for washing 1 to 3 times respectively, the drying temperature is 40 to 60° C., and the drying time is 2 to 4 hours.

6. The method for preparing a high latent heat vanadium dioxide coating according to claim 1, characterized in that: In step three, the stirring rate is 500-800 rpm, and the stirring time is 2-6 hours.

7. A high latent heat vanadium dioxide coating prepared by the preparation method according to any one of claims 1 to 6.

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