Integrated Thin-Film Smart Coatings with Dynamically-Tunable Thermo-Optical Characteristics

This paper presents experimental results regarding a new approach to smart radiator devices (SRD) employing a smart, integrated thin-film structure based on V_1-x-yM_xN_yO_n that can be applied to existing thermal blankets such as Kapton or to thermal radiators such as Al. The smart coating facilitates thermal control by dynamically modifying the thermo-optic characteristics of the underlying substrate in response to the ambient temperature and/or a control voltage. This methodology has significant advantages over competitive technologies in terms of weight, cost, structural simplicity, and integration with the space structure. The effective emissivity of the film/substrate structure can be reduced dynamically by changing the behavior of the smart coating from insulator to metallic. High quality VO₂ films have been prepared using a hybrid reactive laser ablation technique. These films can exhibit high transmittance in the insulating state, exceeding 75% from the NIR to beyond 12 μm, and correspondingly high reflectance in the metallic state. Additional dopants, M and N, are employed to tailor the metal-insulator transition characteristics, providing control of the transition temperature, slope and hysteresis.