Physics is filled with mysteries. To find a few worth exploring, look no further than an ice cube. At room temperature, of course, the cube will melt before your eyes. But even far below freezing, ice can shift in barely perceptible ways that scientists are still trying to understand. Using imaging tools at the U.S. Department of Energy’s (DOE) Argonne National Laboratory, researchers have detected a phenomenon known as premelting at temperatures far lower than those previously observed.
Premelting is the reason that a patch of ice can be slippery even on a frigid, clear day. Though the spot is frozen, some part at the surface is wet, an idea first posited by Michael Faraday in the mid-1800s. The idea of a premelted, liquid-like layer on ice opens up other longstanding questions about how water transforms from liquid to solid to vapor—and how, under certain conditions, it can be all three at once.
In the recent study, scientists examined ice crystals formed below minus 200 degrees Fahrenheit. The team used Argonne’s Center for Nanoscale Materials (CNM), a DOE Office of Science user facility, to grow and observe the ice nanocrystals, which measured only 10 millionths of a meter across.
Besides what the study reveals about the nature of water at subfreezing temperatures, it demonstrates a method for examining sensitive samples in molecular detail: low-dose, high-resolution transmission electron microscopy (TEM). TEM directs a stream of electrons, which are subatomic particles, at an object. A detector creates an image by picking up how the electrons scatter off the object.
“Some materials are beam-sensitive. When you use an electron beam to image them, they can be changed or destroyed,” said Jianguo Wen, Argonne materials scientist and a lead author on the paper. One example of an electron beam sensitive material is electrolytes, which exchange charged particles in batteries.” Being able to study them in fine detail without disrupting their structure could help in the development of better batteries.
2024-01-05 04:00:03
Article from phys.org rnrn
