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KR-102960687-B1 - MANUFACTURING METHOD OF VO2 NANOSHEETS AND VO2 FILMS USING THE SAME

KR102960687B1KR 102960687 B1KR102960687 B1KR 102960687B1KR-102960687-B1

Abstract

The present invention relates to a method for producing VO2 nanosheets by etching and heat-treating vanadium carbide, and producing a VO2 film by coating the nanosheets onto a substrate. According to the present invention, a uniform VO2 film can be manufactured by coating VO2 nanosheets on various 3D curved and flexible substrates, and as the uniformity increases, light scattering suppression and phase transition efficiency increase, thereby improving visible light transmittance and IR shielding efficiency.

Inventors

  • 안기석
  • 이선숙
  • 명성
  • 송우석
  • 임순민
  • 강세원
  • 김진
  • 지슬기

Assignees

  • 한국화학연구원

Dates

Publication Date
20260507
Application Date
20230926

Claims (20)

  1. Step of etching vanadium carbide with an etching solution; A step of peeling off the above-mentioned etched vanadium carbide with a peeling solution; A step of freeze-drying the exfoliated vanadium carbide; and A step of preparing VO2 nanosheets by heat-treating the freeze-dried vanadium carbide at 300 to 550 ℃ in an oxygen atmosphere; A method for manufacturing VO2 nanosheets including
  2. In Article 1, A method for preparing VO2 nanosheets, wherein the above vanadium carbide is a compound represented by the following chemical formula 1. [Chemical Formula 1] V n+1 C n (M) The above M is an element belonging to groups 13 and 14, including Al and Ge, and The above n is an integer from 1 to 3.
  3. In Article 1, A method for manufacturing VO2 nanosheets in which the above etching solution is in a weight ratio of 0.1 to 100 with respect to vanadium carbide.
  4. In Paragraph 3, A method for manufacturing VO2 nanosheets, wherein the etching solution is a 30 to 75 wt% aqueous hydrofluoric acid solution.
  5. In Article 1, A method for manufacturing VO2 nanosheets, wherein the etching temperature is room temperature to 100 ℃.
  6. In Article 1, A method for manufacturing VO2 nanosheets, wherein the etching time is 1 hour to 120 hours.
  7. In Article 1, A method for manufacturing VO2 nanosheets in which the exfoliating solution is in a weight ratio of 0.1 to 100 with respect to the etched vanadium carbide.
  8. In Article 7, A method for preparing VO2 nanosheets, wherein the exfoliating solution is an aqueous solution comprising one or more selected from the group of quaternary ammonium salts including quaternary ammonium hydroxide and quaternary ammonium halide.
  9. In Paragraph 8, A method for preparing VO2 nanosheets, wherein the exfoliating solution is a 20 to 80 wt% aqueous solution of TBAOH (Tetrabutylammonium hydroxide).
  10. In Article 1, A method for manufacturing VO2 nanosheets, wherein the exfoliation time is 1 hour to 48 hours.
  11. In Article 1, A method for preparing VO2 nanosheets by dispersing the exfoliated vanadium carbide in distilled water to a concentration of 0.1 to 2 mg/mL.
  12. In Paragraph 11, A method for manufacturing VO2 nanosheets by ultrasonically exfoliating vanadium carbide dispersed in the above distilled water for 5 minutes to 1 hour.
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  17. In Article 1, A method for manufacturing VO2 nanosheets, wherein the freeze-drying temperature is -20 to -200 ℃.
  18. In Article 1, A method for manufacturing VO2 nanosheets in which the pressure of the freeze-drying is 0 to 200 Torr.
  19. In Article 1, A method for preparing VO2 nanosheets, wherein the freeze-drying time is 40 to 60 hours per 50 mL of aqueous solution of the exfoliated vanadium carbide.
  20. In Article 1, A method for manufacturing VO2 nanosheets in which the oxygen atmosphere is 1 to 5 sccm.

Description

Manufacturing Method of VO2 Nanosheets and VO2 Films Using the Same The present invention relates to a method for producing VO2 nanosheets by etching and heat-treating vanadium carbide, and producing a VO2 film by coating the nanosheets onto a substrate. Currently, 50% of the energy consumed in buildings is used to maintain indoor temperature. To reduce this energy consumption, smart windows are needed that can actively regulate incoming sunlight based on the indoor temperature. A smart window refers to a window that can reduce energy loss and provide a comfortable environment for users by freely adjusting the transmittance of incoming light. In high-temperature environments, solar transmittance decreases to block the entry of external energy into the interior, while in low-temperature environments, solar transmittance increases, allowing for the control of external energy entry at will. Vanadium dioxide ( VO₂ ) exhibits a metal-insulator transition (MIT) at around 68°C. Due to this phase transition, VO₂ possesses thermochromic properties that allow for the control of infrared (IR) transmittance, making it a promising base material for smart windows. However, while high-quality VO₂ films can be manufactured using chemical vapor deposition, the process is costly, the substrates to which they can be applied are limited due to high-temperature conditions, and there are particular limitations in curved surface deposition. As an alternative technology, VO2 is being developed in the form of nanoparticles and manufactured as a water-dispersible coating agent; however, due to the small particle size, it is difficult to achieve a uniform coating, and problems arise such as reduced visible light transmittance and IR shielding efficiency. Accordingly, methods for coating water-dispersible VO2 using Dip, Flow, and Spray methods are currently being developed to apply it more easily and simply to various types of substrates. FIG. 1 is a conceptual diagram showing the VO2 nanosheet of the present invention and a method for manufacturing a VO2 film containing the same. Figure 2 shows the composition of VO2 nanosheets according to the heat treatment temperature. Figure 3 shows the structure of the VO2 film according to the heat treatment temperature of the VO2 nanosheet. Figure 4 shows the optical properties of VO2 nanosheets according to the heat treatment temperature. Figure 5 shows the phase transition efficiency of VO2 nanosheets according to the heat treatment temperature. Figure 6 shows the visible light transmittance and IR shielding efficiency of VO2 nanosheets. Figure 7 shows a demonstration of large-area coating of a VO2 film. Figure 8 shows the thermal shielding performance of a smart window with a VO2 film applied. The embodiments described in this specification may be modified in various different forms, and the technology according to one embodiment is not limited to the embodiments described below. Furthermore, the embodiments of one embodiment are provided to more fully explain the present disclosure to those with average knowledge in the relevant technical field. Unless otherwise defined, technical and scientific terms used herein have the meanings commonly understood by those with ordinary knowledge in the technical field to which this invention pertains, and descriptions of known functions and configurations that may unnecessarily obscure the essence of the present invention are omitted in the following description and accompanying drawings. Additionally, the singular form used in this specification and the appended claims may be intended to include the plural form unless specifically indicated otherwise in the context. Furthermore, in this specification and the appended claims, terms such as "first," "second," etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another. Furthermore, in this specification and the appended claims, when a part such as a film (layer), region, or component is described as being located “on,” “on top,” “on the upper,” “under,” “on the lower,” or “on the lower” of another part, this includes not only cases where a part is in contact with another part, but also cases where another part exists between the two parts. Furthermore, terms such as “approximately,” “substantially,” etc., as used in this specification and the appended claims, are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosure in which precise or absolute values are mentioned to aid in understanding this specification and the appended claims. In addition, as used in this specification and the appended claims, “room temperature” means a constant temperature, usually 20±5 ℃. Additionally, numeric ranges used in this specification include lower and upper limits and all values within the range, increments logically de