Keeping the house cool on a warm day requires either the use of window coverings or expensive air conditioning. However, new technology may allow for both a cooler house and a clear view of the outdoors.
A recent study published in the Journal of Physical Chemistry Letters explores the use of the chemical vanadium oxide as a means to produce a window coating that would allow for temperature-dependant absorption of infrared light into a room.
The study was conducted by Sabajir Banerjee, Ph.D., an associate professor in the department of chemistry, Sambandamurthy Ganapathy, Ph.D., an associate professor in the department of physics, and several of their graduate students. The team explored the effects of "doping" vanadium oxide to lower the temperature at which it takes on its properties of reflecting infrared light.
The chemical reflects infrared light when temperatures are higher and it keeps rooms cool. On the other hand, at lower temperatures, the vanadium oxide coating allows the infrared waves to penetrate and heat the room naturally.
"[Doping] vanadium oxide has been known as a strategy to depress the temperature [at which vanadium oxide] goes from one phase to another," Banerjee said. "What we found is that including [chemicals] in the right ratio has a much amplified effect."
Banerjee and his students are interested in "solid-state chemistry." When combined with oxygen, vanadium takes on a temperature-dependant property of being able to change how it absorbs infrared light. The compound does not change from a solid to a liquid, but rather from a solid with one set of physical properties to a solid with a different set of properties, according to Banerjee.
Vanadium, which is a naturally abundant substance, has a transition temperature of 153 degrees Fahrenheit. By doping the vanadium oxide with chemicals such as tungsten and working on a nanomaterial-sized level, the scientists were able to lower the transition temperature to below 10 degrees Fahrenheit, which is well below room temperature.
"Since we've been able to control the size [of the vanadium oxides]…they reveal these new properties," said Christopher Patridge, a Ph.D. candidate in the department of chemistry who worked on the study. "When you make [the samples] really small, you can make them perfectly. [Any impurities] vacate the material."
By controlling the size of the compound and using it as a coating on wires, the technology can extend beyond the use of window coatings, and can be used in computer circuits, according to Patridge.
The technology is not yet industry-ready.
"We are interested in moving on to the discovery of other and better materials that may show enhanced effects," Banerjee said. "The vanadium oxide showed massive change of the properties that are on four or five orders of magnitude [of difference]. But some of [Patridge's newer experiments] show a 1 million-fold change of properties."
Banerjee and his team have been working on this project for over four years. In January, Banerjee received funding for the project when he awarded the Cottrell Scholar Award from the Research Corporation for Science Advancement. The $75,000 award was given to only 11 scholars in the U.S., and recognized work both in research and in the classroom. He also received a National Science Foundation CAREER award, the foundation's most prestigious award for junior investigators.
Beyond the realm of window coatings and computers, Banerjee believes that vanadium oxide can be used in night-vision instruments as well as missile guidance systems, although the technology is not expected to be ready for common industrial use for another few years.
"[Vanadium oxide coatings] could help reduce heating costs and fuel prices in winter and air conditioning electric costs in the summer," said Danielle Turner, a junior biology major.
This new technology in "smart windows" will help make more energy efficient housing a possibility.
Email: news@ubspectrum.com
Photo: Courtesy of Laron Fomby
