Scientists come up with novel way to freeze water into a solid

February 21st, 2009 - 3:10 pm ICT by ANI  

Washington, Feb 21 (ANI): An interdisciplinary team of scientists and engineers has suggested a novel way to freeze water into a solid, not by cooling but by confining it to narrow spaces less than one-millionth of a millimeter wide.

A deeper understanding of how thin films of water behave in nanometer-sized spaces may help advance numerous scientific endeavors, including the development of new energy sources, pharmaceuticals and self-cleaning surfaces.

Water has long been known for its quirky physical properties, including its ability to expand when cooled and to flow with increasing ease when compressed.

While this behavior on a large scale has been the subject of much research, the effect of nano-confinement on waters physical properties and transitions between the gas, liquid and solid phases is largely unknown.

This research suggests the idea that phase transitions can be controlled by understanding the effects of confinement and interaction with a surface, said team member Pablo Debenedetti, vice dean of Princeton Universitys School of Engineering and Applied Science.

In their investigation, the researchers used computers to simulate the movement of water molecules trapped between two hypothetical plates.

The plates in the scenario were hydrophobic, or water-fearing, meaning they repel water much like the surface of a leaf.

When the distance between the two plates was narrowed to roughly the width of three water molecules, the simulations demonstrated a previously unknown phase of water consisting of a layer of mobile water sandwiched between two layers of frozen water adjacent to each plate.

The layers were each one-molecule thick and, in the simulated environment, remained at room temperature.

The ice sandwich phase persisted throughout the length of the simulation, some two nanoseconds long.

Though brief by most standards, this is a long period of time as simulations go, indicating that the phase would persist indefinitely without the middle layer freezing, if conditions were kept stable, according to Debenedetti.

When the density of the system was reduced, the three-layer phase transitioned into two layers of fluid - again, still at room temperature.

According to H. Eugene Stanley, professor and director of the Center for Polymer Studies at Boston University, Phenomenologically, their findings are very striking. In particular, the observation that a tri-layered system, with two frozen layers sandwiching a fluid intermediate layer, can exist as an equilibrium state because of confinement is very exciting.

This is the perfect example of confined water, where a molecular-level understanding will have considerable practical applications, Debenedetti said. (ANI)

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