A new smart window material when incorporated into windows, sunroofs, or even curved glass surfaces, will have the ability to control both heat and light from the sun. Delia Milliron, an associate professor in the McKetta Department of Chemical Engineering, and her team’s advancement is a new low-temperature process for coating the new smart material on plastic, which makes it easier and cheaper to apply than conventional coatings made directly on the glass itself. The team demonstrated a flexible electrochromic device, ie a small electric charge (~4 volts) can lighten or darken the material and control the transmission of heat-producing, near-infrared radiation. Such smart windows are aimed at saving on cooling and heating bills for homes and businesses.
Milliron and her team’s low-temperature process generates a material with a unique nanostructure, which doubles the efficiency of the coloration process compared with a coating produced by a conventional high-temperature process. It can switch between clear and tinted more quickly, using less power.
Linear structural model of chemically condensed niobium oxide determined by combined experimental and theoretical approach (green balls represent Nb while red balls represent O).
The new electrochromic material, like its high-temperature processed counterpart, has an amorphous structure. However, the new process yields a unique local arrangement of atoms in a linear, chain-like structure. Whereas conventional amorphous materials produced at high temperature have a denser 3D bonded structure, the researchers’ new linearly structured material, made of chemically condensed niobium oxide, allows ions to flow in and out more freely. As a result, it is twice as energy efficient as the conventionally processed smart window material. “There’s relatively little insight into amorphous materials and how their properties are impacted by local structure,” Milliron said. “But, we were able to characterize with enough specificity what the local arrangement of the atoms is, so that it sheds light on the differences in properties in a rational way.”
Determining the atomic structure for amorphous materials is far more difficult than for crystalline materials, which have an ordered structure. In this case, the researchers were able to use a combination of techniques and measurements to determine an atomic structure that is consistent in both experiment and theory.
The knowledge gained here could inspire deliberate engineering of amorphous materials for other applications such as supercapacitors that store and release electrical energy rapidly and efficiently. The Milliron lab’s next challenge is to develop a flexible material using their low-temperature process that meets or exceeds the best performance of electrochromic materials made by conventional high-temperature processing.
http://news.utexas.edu/2016/08/22/researchers-invent-cheaper-flexible-smart-windows
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