College Park, MD (July 27, 2010) -- Earth's climate is strongly influenced by the presence of particles of different shapes and origins -- in the form of dust, ice and pollutants -- that find their way into the lowest portion of the atmosphere, the troposphere. There, water adsorbed on the surface of these particles can freeze at higher temperatures than pure water droplets, triggering rain and snow.
Researchers at Spain's Centre d'Investigaci en Nanocincia i Nanotecnologia (CIN2) have studied the underlying mechanisms of water condensation in the troposphere and found a way to make artificial materials to control water condensation and trigger ice formation at room temperature. Described in the Journal of Chemical Physics, which is published by the American Institute of Physics, their work may lead to new additives for snowmaking, improved freezer systems, or new coatings that help grow ice for skating rinks.
"Several decades ago, scientists predicted that materials with crystal faces exhibiting a structure similar to that of hexagonal ice, the form of all natural snow and ice on Earth, would be an ideal agent to induce freezing and trigger rain," explains Dr. Albert Verdaguer. "This explanation has since proven to be insufficient."
The research team chose to study barium fluoride (BaF2), a naturally occurring mineral, also known as "Frankdicksonite," as an option. They examined water adsorption on BaF2 (111) surfaces under ambient conditions using different scanning force microscopy modes and optical microscopy to zoom in on the role atomic steps play in the structure of water films, which can affect the stabilization of water bilayers and, ultimately, condensation.
Despite having the desired hexagonal structure, BaF2 turned out to be a poor ice-nucleating material. But oddly enough, other researchers had discovered that when the mineral's surface has defects, its condensation efficiency is enhanced.
|Contact: Jason Socrates Bardi|
American Institute of Physics