Lab- and Large-Scale Hydrothermal Synthesis of Vanadium Dioxide Thermochromic Powder

Abstract

Vanadium dioxide (VO2) is a phase-change material of great importance due to its thermochromic properties, which make it a potential candidate for energy-saving applications. In this work, a comparative study between VO2 thermochromic films prepared from powders synthesized by either a lab-scale hydrothermal autoclave or a large-scale hydrothermal reactor is presented. In both cases, the as-obtained material, after the hydrothermal step, was subsequently annealed at 700 °C under a nitrogen atmosphere, in order to obtain the monoclinic VO2(M) thermochromic phase. The VO2 powder prepared in the large-scale hydrothermal reactor exhibited a critical transition temperature of 54 °C with a hysteresis width of 9 °C, while for the one prepared in the lab-scale autoclave, the respective values were 62 °C and 5 °C. Despite these differences, the prepared films showed similar thermochromic performance with the lab-scale material displaying a 17% IR (InfraRed), switching at 2000 nm upon heating, and a transmittance solar modulation of 11%, compared to 17% and 9%, respectively, for the large-scale material. Moreover, both films appeared to have similar luminous transmittance of 44% and 46%, respectively, at room temperature (25 °C). These results showcase the potential for scaling up the hydrothermal synthesis of VO2, resulting in films with similar thermochromic performance to those from lab-scale fabrication.

Keywords

• VO₂
• thermochromic
• large-scale synthesis
• hydrothermal