Ice and frost formation on surfaces afflicts various energy and transportation industries worldwide, causing economic losses in billions of dollars annually. Most techniques to prevent frost and ice formation on surfaces rely heavily on heating or liquid chemicals that need to be reapplied over and over again because they easily wash away. Even advanced anti-icing materials have problems functioning under conditions of high humidity and subzero conditions when frost and ice formation go into overdrive. Latest research from the University of Illinois at Chicago (UIC) and ESPCI Paris show that certain materials known as phase-switching liquids (PSLs), hold promise as next-generation anti-icing materials. PSLs can delay ice and frost formation up to 300 times longer than traditional anti-icing coatings, and some of them are even better at delaying the formation of frost than state-of-the-art coatings not yet available on the market. These findings are published in the journal Advanced Materials (DOI:10.1002/adma.201807812).
“Ice and frost pose hazards to people and reduce functionality of many technologies, especially those related to energy and transportation, so we have been interested for long time to find out possible ways to overcome their harmful effects, and in phase-switching liquids we found one such excellent candidate” said Sushant Anand, assistant professor mechanical and industrial engineering at UIC.
In a nutshell, PSLs are a subset of phase change materials that have melting points higher than the freezing point of water (0 degrees Celsius), they would be solids at a range of temperatures close to that at which water freezes. “At sub-zero temperatures, all PSLs turn solid. So on a winter day, you could coat a surface where you don’t want icing with a PSL material and it would remain there much longer than most deicing liquids which demand frequent reapplication,” said Rukmava Chatterjee, a doctoral student at UIC and the first author of the paper.
In their current research, Anand and Chatterjee cooled a range of PSLs to -15 degrees Celsius, rendering them all solid. Under high humidity conditions, they noticed that the solidified PSLs melted directly underneath and in the immediate vicinity of water droplets condensing on the PSLs. “It turns out that PSLs are extremely adept at trapping this released heat,” Anand said. “This quality, combined with the fact that condensed water droplets become extremely mobile on these cooled PSLs means that the formation of ice is significantly delayed.”
In further experiments, the researchers found that PSLs have a wide range of optical transparencies, can self-repair after being scratched and also can purge liquid-borne contaminants making them excellent candidates for next-generation multifunctional materials.
Further information: Rukmava Chatterjee et al, Delaying Ice and Frost Formation Using Phase‐Switching Liquids, Advanced Materials (2019). DOI: 10.1002/adma.201807812.
Material provided by University of Illinois Chicago.