Largely Lowered Transition Temperature of a VO₂/Carbon Hybrid Phase Change Material with High Thermal Emissivity Switching Ability and Near Infrared Regulations

Abstract

Vanadium oxide (VO2) as a phase changing material possesses abrupt infrared (IR) transmission and thermal emissivity changing during the metal–insulator transition across transition temperature (τc) of 68 °C. However, the high τc, moderate IR transmission and emissivity regulating ability limits its applications in various fields. A VO2/carbon hybrid phase change material fabricated via homemade plasma enhanced chemical vapor deposition is reported. The material shows a best reported thermal emissivity contrast (0.44) among the experimental values, a largely lowered τc (45 °C), promising a near IR‐regulation ability with enhanced photothermal effect in smart windows applications. The theoretical calculation results proved that the improvement of emissivity contrast is due to the hybridization of carbon. This work provides a new approach to synthesize VO2 hybrid materials, which have wide applications in camouflage, sensing, and smart windows.

A Simplified Approach for Obtaining Optical Properties of VO2 Thin Films, and Demonstration of Infrared Shape‐Shifting Devices

“…Figure b shows the , where a similar drop in emissivity from 0.83 to 0.4 is observed across the phase transition. A similar emissivity drop of 0.44 was measured on VO 2 /carbon composites, which is in agreement to the observed drop in the present devices. In order to see the effects of an added layer of SiO 2 above the VO 2 , emissivity measurements were performed for a similar device where the SiO 2 over the VO 2 window was not removed.…”

A Thermal Radiation Modulation Platform by Emissivity Engineering with Graded Metal–Insulator Transition

“…Therefore, much less IR energy is absorbed when VO 2 undergoes the phase transition and becomes metallic. [ 6–9 ] According to the Kirchhoff's law of radiation, [ 10 ] the spectral emissivity, ε(λ), is equal to absorptivity in the IR regime. When averaged for thermal radiation, an abrupt drop [ 11 ] in the integrated emissivity (ε int ) and hence thermal radiance is thus expected for VO 2 at T = T MIT , as schematically illustrated in Figure a, and experimentally measured and shown in Figure S1, Supporting Information.…”

Smart Materials for Dynamic Thermal Radiation Regulation

“…Moreover, VO 2 can be modified by carbon to construct VO 2 /Carbon hybrid structures to realize similar functions with a lower τ c of 45 °C and an excellent Δε of 0.44 at 8–13 µm. [ 37 ] The creative hybrid structures provided new insights for promoting the performance of VO 2 based adaptive dynamic thermal regulation devices and may provide new avenues for the doping or modifying process (Figure 4C).…”