One-Step Hydrothermal Synthesis, Thermochromic and Infrared Camouflage Properties of Vanadium Dioxide Nanorods.

Vanadium dioxide (VO 2 ) has attracted interest from researchers because it undergoes a metal-insulator phase transition (MIT), which is accompanied by a reversible and remarkable change in both electrical and optical properties. VO 2 exhibits numerous polymorphs and thus it is essential to control the growth of specific monoclinic VO 2 (M) and rutile VO 2 (R) phases. In this study, we developed a cost-effective and facile method for preparing VO 2 nanorods with a highly crystalline monoclinic phase by one-step hydrothermal synthesis, in which only V 2 O 5 and H 2 C 2 O 4 are used as raw materials. The phase evolution of VO 2 during the hydrothermal process was studied. The obtained VO 2 nanorods were thoroughly mixed with fluorocarbon resin and homogeneous emulsifier in an ethanol solution to obtain a VO 2 dispersion. To prepare VO 2 films, screen printing was performed with a stainless steel screen mesh mask on glasses or fabric substrate. The VO 2 coating had good thermochromic performance; the infrared transmittance change was greater than 20% @1.5 μm whilst keeping the visible transmittance greater than 50%. Meanwhile, the polyester base coating on the fabric had an emissivity change of up to 22%, which provides a solution for adaptive IR camouflage.