Highly efficient energy-saving windows with high solar modulation properties (ΔTsol) are the everlasting pursuit of research for industrial applications in the smart window field. Hybridization is an effective means of improving both ΔTsoland luminous transmittance (Tlum). In this paper, hybrid thermochromic films were synthesized using tungsten-doped VO2nanoparticles (NPs) and starch derivatives. Thermoresponsive 2-hydroxy-3-butoxypropyl starch (HBPS) was prepared with a low critical solution temperature (LCST) varying from 32 to 21 °C by the substitution of reactive groups. The hybrid film was obtained by dispersing W-doped VO2NPs in HBPS hydrogels, which exhibiting remarkable solar modulation property (ΔTsol= 34.3%) with a high average luminous transmittance (Tlum, average= 53.9%).Keywords:W-doped VO2(M) NPs;starch derivative;inorganic and organic hybrid film;thermochromism;smart window
Nan Shen,Shi Chen,Run Shi,Shuzhang Niu,Abbas Amini,Chun Cheng
The critical challenge for the practical applications of VO2-based smart windows is to nucleate and propagate the phase transformation in the ambient condition while maintaining a balance between solar energy regulation and visible light transmittance. Doping proves effective in the modification of the thermochromic performance in VO2 but always causes unfavorable degradation accompanied with the significant reduction of phase transition temperature. Joule heating has been introduced in VO2-based devices to activate the metal–insulator transition (MIT) at ambient temperature. A synergy between these two strategies is necessary to achieve a well-balanced performance of VO2 films at the appropriate temperature. Here, we systematically investigate the thermochromic properties of tungsten (W)-doped VO2 composite films with Joule heating triggered MIT. The phase transition temperature of VO2 is effectively decreased by 21.6 °C per at. % W, and the balanced luminous transmittance (Tlum = 50.8%) and solar energy modulation ability (ΔTsol = 11.4%) are achieved at 0.6 at. % W doping. Importantly, as a synergetic result of W doping and hysteresis behavior of MIT in VO2, the optimal infrared blocking performance can be retained at a reduced cost of energy consumption and at the ambient temperature down to 47 °C. This is comparable to the glass window temperature in the summer in subtropical and tropical regions. This result suggests quite low and even zero energy consumption to maintain the optimal infrared blocking performance of VO2 films. This study provides a practical and advanced setup for operable and efficient smart windows in ambient conditions.
Aerogel materials have shown tremendous vistas in electromagnetic interference (EMI) of intelligentized electronics and armaments. However, it is challenging to simultaneously achieve self-enhanced shielding performance and release the accumulation thermal. Herein, an intelligent tunable shielding composite was demonstrated through synergistic dynamic interactions between Ti 3 C 2 T x and tungsten doped VO 2 (WVO 2 ), tactfully transforming the accumulation thermal energy to superiority for enhanced shielding. Additionally, the performances of meticulously engineered Ti 3 C 2 T x -WVO 2 composite from thermal conversion to enhanced electromagnetic shielding have been hierarchically dissected. The composite possessed highly sensitive and dynamically tunable shielding performance (Δ SE = 13.9 dB, X-band = 8–12 GHz) and high-efficiency thermal management characteristic by virtue of three-dimensional porous Ti 3 C 2 T x skeleton, the phase transition of WVO 2 and energy transformation between Ti 3 C 2 T x and WVO 2 . Furthermore, the composite provides excellent shielding performance (EMI SE = 42.8 dB). Therefore, this Ti 3 C 2 T x -WVO 2 composite can be a potential candidate in both EMI shielding and tunable shielding fields.
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