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CAMP: Wetting transitions: from helium to water to mercury

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Milton Cole, Pennsylvania State University
When
31 March 2015 from 3:30 PM to 4:30 PM
Where
339 Davey Laboratory
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If one looks at a leaf of a plant after a rain, one sees water droplets of varying sizes. What determines this behavior? The answer, known in principle for two centuries, involves the surface tension of the water itself, as well as surface tensions at the water-leaf interface. At the microscopic level, the “wetting” behavior depends on the interaction between two water molecules compared to that between a water molecule and the leaf.

My group has been studying the problem of wetting transitions on various surfaces. This transition is a two-dimensional analog of the familiar three-dimensional vapor-liquid transition, i.e. there is a line of first-order transitions in the P-T plane, ending with a critical point. The phenomenon can involve liquids as varied as superfluid helium, mercury and water, interacting with a wide variety of surfaces. The common characteristic is a very weak attractive interaction between the adsorbed molecules and the surface in question. As discussed in the talk, this transition has been predicted and seen for the absolutely least attractive interaction in nature. The system in question may surprise you!

Among the recent results presented will be evidence for the first wetting phase transition for water. We predicted this in 2004 [2,4] and it was recently observed in Taborek’s group at UC Irvine [3]

 

Reference:

1. S. M. Gatica and M. W. Cole, "To wet or not to wet: that is the question", J. Low Temp. Phys., 157, 111-136 (2009)

2. S. M. Gatica, Xiongce Zhao, J. K. Johnson and M. W. Cole, “Wetting transition of water on graphite and other surfaces”, J. Phys. Chem. B108, 11704-11708 (2004)

3. S. R. Friedman, M. Khalil and P. Taborek, Wetting transition in water, Phys. Rev. Lett. 111, 226101 (2013)

4. Hye-Young Kim, Maria Cristina dos Santos and Milton W. Cole, Wetting transitions of water on graphite and graphene, J. Phys. Chem A118, 8237 (2014)

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