How two liquids mix at the surface: an atomic view

September 1, 2005
How two liquids mix at the surface: an atomic view

Whenever cream is poured into coffee, these two liquids form a homogeneous mixture, which is difficult to separate again. Other liquids, such as water and oil, do not mix, instead forming emulsions, such as salad dressing.

Image: Schematic representation of atomic-scale demixing observed in BiSn liquid alloy.

In results reported in this week's issue of Physical Review Letters [Phys. Rev. Lett. 95, 106103 (2005)], a collaboration lead by physicists from Harvard University have used x-rays to look at how atoms of two elemental liquids - bismuth and tin - mix together. Despite forming a perfectly miscible alloy in the bulk phase, near the surface the two elements separate into alternating atomic layers.

"The surface demixing is somewhat of a paradox since it occurs due to the strongly enhanced attraction between the atoms of the two components, while for partially miscible mixtures the opposite is true: atoms or molecules are more attracted to their own kind" explains Dr. Oleg Shpyrko, the leading author of the study.

"Surface demixing was predicted in 1950 by Defay and Prigogine, but it eluded experimentalists for more than 50 years: liquids only demix within a nanometer-deep surface region, and there are very few techniques that can probe structure of liquid surfaces on such tiny length scales. As we attempt to understand properties of nanoscale materials where most atoms are near the surface, these and other interfacial effects are expected to play a dominant role."

by Oleg Shpyrko, Argonne National Laboratory
Web address: http://liquids.deas.harvard.edu/oleg/
Email: oshpyrko_AT_anl.gov
Tel: 630-252-7540

Explore further: Graphene on silicon carbide can store energy

Related Stories

Graphene on silicon carbide can store energy

May 23, 2017

By introducing defects into the perfect surface of graphene on silicon carbide, researchers at Linköping University in Sweden have increased the capacity of the material to store electrical charge. This result, which has ...

Stenciling with atoms in 2-D materials possible

May 1, 2017

The possibilities for the new field of two-dimensional, one-atomic-layer-thick materials, including but not limited to graphene, appear almost limitless. In new research, Penn State material scientists report two discoveries ...

Recommended for you

Camera on NASA's Lunar Orbiter survived 2014 meteoroid hit

May 26, 2017

On Oct. 13, 2014 something very strange happened to the camera aboard NASA's Lunar Reconnaissance Orbiter (LRO). The Lunar Reconnaissance Orbiter Camera (LROC), which normally produces beautifully clear images of the lunar ...

The high cost of communication among social bees

May 26, 2017

(Phys.org)—Eusocial insects are predominantly dependent on chemosensory communication to coordinate social organization and define group membership. As the social complexity of a species increases, individual members require ...

Toward mass-producible quantum computers

May 26, 2017

Quantum computers are experimental devices that offer large speedups on some computational problems. One promising approach to building them involves harnessing nanometer-scale atomic defects in diamond materials.

Conch shells spill the secret to their toughness

May 26, 2017

The shells of marine organisms take a beating from impacts due to storms and tides, rocky shores, and sharp-toothed predators. But as recent research has demonstrated, one type of shell stands out above all the others in ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.