How MIT scientists kept water solid at 100 degrees Celsius.

Water at sea level is known to start boiling at 100 degrees Celsius (or 212 degrees Fahrenheit).
same time, scientists have long found that when water is confined to a very small space, its boiling and solidification points change somewhat, dropping by about 10 degrees Celsius.
But now, a team of researchers from the Massachusetts Institute of Technology has discovered a completely unexpected change: water can remain solid in a tiny space made up of carbon nanotubes the size of just a few water molecules.
the findings suggest that even very common materials, when tied to a nanoscale (i.e. a billionth of a meter) structure, their behavior changes dramatically.
the discovery could lead to new applications, such as "ice wires" that stabilize at room temperature while maintaining the ice's unique electrical and thermal properties.
study was published in the journal Nature Nanotechnology.
author of this article are Michael Strano, a professor at MIT's Carbon P. Dubbs, a postdoctoral student, Kumar Agrawal, and three other colleagues.
If you limit a liquid to a nanoc cavity, you can actually change its phase-change behavior," says Strano, "i.e. how and when a substance transforms between the liquid phase and the gas phase."
's effect is not surprising, but the magnitude of the change and its direction (i.e., the increase rather than decrease of the solidification point) was completely surprising to the researchers: in one of the team's tests, the water remained solid at 105 degrees Celsius and higher temperatures.
(the exact temperature in the carbon nanotubes is difficult to determine, but in this test the temperature is at least 105 degrees C or more, where the actual temperature can be as high as 151 degrees C).
) "The effect far exceeded everyone's expectations," Strano said.
that the way water changes within tiny carbon nanotubes depends largely on the exact diameter of the nanotubes.
these nanotubes are similar in structure to straws and are made up entirely of carbon atoms, but only a few nanometers in diameter.
"These are really the smallest pipes you can think of," Strano said.
nanotubes used in the experiment were open at both ends and had tanks at the openings at both ends.
researchers found that nanotubes with diameters of 1.05 nanometers and 1.06 nanometers, respectively, had tens of degrees of difference in coagulation points.
this extreme difference was completely unexpected before.
, "When it's small enough, all the speculation fails, and it's really an untapped area, " says Mr. Strano.
early work, Strano noted that "many of the early simulations ended up being completely contradictory" in order to understand the behavior of water and other liquids in such small spaces.
partly because many previous research teams were unable to accurately measure the exact size of their carbon nanotubes, without realizing that small differences in size could lead to very different results.
fact, the most surprising thing is that water is able to get into these tiny pipes.
nanotubes are often considered hydrophobic, or water-free, so in theory, water molecules should be difficult to get into, said Mr. Strano.
he says it's still a bit strange that water can really get into carbon nanotubes.
and his team used an ultra-sensitive imaging system called vibration spectroscopy to track the movement of water inside nanotubes, enabling the first detailed measurement of their behavior.
team can detect not only the presence of water in carbon nanotubes, but also the state of water.
we can tell that water is present in carbon nanotubes in gaseous, liquid or solid form, " he said.
Although water is bound to exist in solid form under certain conditions, the team has tried to avoid calling water in this state "ice" because the term implies that water has a particular crystalline structure, but they are not sure that such a structure can exist in such a limited space.
"It's not necessarily ice, but it's an ice-like state," strano said, "because the solid water doesn't melt until it's much higher than the normal boiling point of the water, so it should be very stable at room temperature."
says this nature makes it possible to have many potential applications.
, for example, "ice wire" may be used as the best known proton carrier because water-conductive protons are more than 10 times faster than many typical conductive materials.
"We got a very stable waterline at room temperature," he said, and the team also included MIT graduate students Steven Shimizu and Lee Drahushuk, as well as undergraduate Daniel Kilcoyne.
work is supported by the U.S. Army Research Laboratory, the MIT Soldier Nanotechnology Research Institute, supported by the U.S. Army Research Office, and the Shell MIT Energy Initiative Energy Research Foundation.
source: DeepTech DeepTech.