Variable Absorptance and Emittance Devices for Thermal Control

Variable absorptance (α) and variable emittance (ε) devices were developed and tested by electrochemical and optical methods for thermal control applications. A unique concept was investigated whereby a highly reflective metal was reversibly deposited on UV/vis/near-infrared (Mylar) and long-wavelength infrared (ZnSe) transparent substrates. Copper was ultimately chosen as a reflective metal due to its desirable optical characteristics, relatively low toxicity, and well-explored electrochemical deposition/stripping phenomena. Dramatically enhanced current densities were obtained by the presence of catalytic, inert metals (Pt, Au, Pd) on the Mylar and ZnSe substrates (working electrodes). Devices functioned by reversible electrochemical transfer of metal (Cu) between the working electrode and Cu/Kapton counter electrode that were sandwiched around 0.1 M Cu(BF4)2/0.1 M LiBF4/propylene carbonate, radiation-absorbing, redox-active electrolyte by application of