A research team from the Cockrell School of Engineering at The University of Texas has developed a thin electrochromic plastic coating for windows that not only saves on heating and cooling bills, but can also turn opaque or tinted by the flick of a switch.
Whilst industrial chemists have long been able to manufacture coatings that can tint glass with a switch, for many years these films required a constant electrical current. That said, recently a research team from Cambridge University developed a ‘smart glass’ that, according to online journal Popular Mechanics, “can switch back and forth between transparency and opaqueness while…only needing power when making the switch.”
But as the new design from Texas is a thin film that coats the surface (rather than being built into the glass), production costs are significantly reduced and the film is useable on all sorts of surface, such as sunroofs or even curved glass.
The online journal Popular Mechanics outlined the many advantages the discovery has over older methods, stating, “Other types of electrochromic plastic do exist, but are very bulky and require high temperatures to manufacture. This new process produces a thin, flexible material without resorting to high temperatures. The new material is also twice as energy-efficient. The result is a flexible, low-cost plastic sheet that can be applied to any window or any surface, no matter what the shape of the surface is. These sheets can then control the amount of sunlight entering the building, keeping rooms cool in the summer and warm in the winter.”
The online journal Science Daily reports on the chemical structure of the new material, explaining how, “The new electrochromic material, like its high-temperature processed counterpart, has an amorphous structure, meaning the atoms lack any long-range organization as would be found in a crystal. However, the new process yields a unique local arrangement of the atoms in a linear, chain-like structure. Whereas conventional amorphous materials produced at high temperature have a denser three-dimensionally 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.”
Delia Milliron, an associate professor in the McKetta Department of Chemical Engineering, explained how her team was able to make the discovery, stating that, “There’s relatively little insight into amorphous materials and how their properties are impacted by local structure. 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.”
The research was published in the journal Nature Materials, where they, “report on a room-temperature solution process to fabricate electrochromic films of niobium oxide glass (NbOx) and ‘nanocrystal-in-glass’ composites (that is, tin-doped indium oxide (ITO) nanocrystals embedded in NbOx glass) via acid-catalysed condensation of polyniobate clusters.”
Coating manufacturers, architects and plastics producers are showing a lot of interest over this project due to the triple advantage of its lower production cost, stylish yet practical application and cost saving impact on fuel bills. Others have already highlighted how the coating could be turned on or off via a timer or other automatic switch, say for a time of day when sunlight hits a part of the building or to turn a window opaque at sunset.
Meanwhile the researchers are continuing their work, hoping to use their understanding of amorphous materials to refine this and other film coatings. As Milliron says, “We want to see if we can marry the best performance with this new low-temperature processing strategy.”
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