MIT researchers discover astonishing behavior of water confined in carbon nanotubes.
It’s a well-known fact that water, at sea level, starts to boil at a temperature of 212 degrees Fahrenheit, or 100 degrees Celsius. And scientists have long observed that when water is confined in very small spaces, its boiling and freezing points can change a bit, usually dropping by around 10 C or so.
But now, a team at MIT has found a completely unexpected set of changes: Inside the tiniest of spaces — in carbon nanotubes whose inner dimensions are not much bigger than a few water molecules — water can freeze solid even at high temperatures that would normally set it boiling.
“All bets are off when you get really small,” Strano says. “It’s really an unexplored space.”
The discovery illustrates how even very familiar materials can drastically change their behavior when trapped inside structures measured in nanometers, or billionths of a meter. And the finding might lead to new applications — such as, essentially, ice-filled wires — that take advantage of the unique electrical and thermal properties of ice while remaining stable at room temperature.
The results are being reported today in the journal Nature Nanotechnology, in a paper by Michael Strano, the Carbon P. Dubbs Professor in Chemical Engineering at MIT; postdoc Kumar Agrawal; and three others.
“If you confine a fluid to a nanocavity, you can actually distort its phase behavior,” Strano says, referring to how and when the substance changes between solid, liquid, and gas phases. Such effects were expected, but the enormous magnitude of the change, and its direction (raising rather than lowering the freezing point), were a complete surprise: In one of the team’s tests, the water solidified at a temperature of 105 C or more. (The exact temperature is hard to determine, but 105 C was considered the minimum value in this test; the actual temperature could have been as high as 151 C.)
“The effect is much greater than anyone had anticipated,” Strano says.
It turns out that the way water’s behavior changes inside the tiny carbon nanotubes — structures the shape of a soda straw, made entirely of carbon atoms but only a few nanometers in diameter — depends crucially on the exact diameter of the tubes. “These are really the smallest pipes you could think of,” Strano says. In the experiments, the nanotubes were left open at both ends, with reservoirs of water at each opening.
Even the difference between nanotubes 1.05 nanometers and 1.06 nanometers across made a difference of tens of degrees in the apparent freezing point, the researchers found. Such extreme differences were completely unexpected. “All bets are off when you get really small,” Strano says. “It’s really an unexplored space.”
In earlier efforts to understand how water and other fluids would behave when confined to such small spaces, “there were some simulations that showed really contradictory results,” he says. Part of the reason for that is many teams weren’t able to measure the exact sizes of their carbon nanotubes so precisely, not realizing that such small differences could produce such different outcomes.
In fact, it’s surprising that water even enters into these tiny tubes in the first place, Strano says: Carbon nanotubes are thought to be hydrophobic, or water-repelling, so water molecules should have a hard time getting inside. The fact that they do gain entry remains a bit of a mystery, he says.
Strano and his team used highly sensitive imaging systems, using a technique called vibrational spectroscopy, that could track the movement of water inside the nanotubes, thus making its behavior subject to detailed measurement for the first time.
The team can detect not only the presence of water in the tube, but also its phase, he says: “We can tell if it’s vapor or liquid, and we can tell if it’s in a stiff phase.” While the water definitely goes into a solid phase, the team avoids calling it “ice” because that term implies a certain kind of crystalline structure, which they haven’t yet been able to show conclusively exists in these confined spaces. “It’s not necessarily ice, but it’s an ice-like phase,” Strano says.
Because this solid water doesn’t melt until well above the normal boiling point of water, it should remain perfectly stable indefinitely under room-temperature conditions. That makes it potentially a useful material for a variety of possible applications, he says. For example, it should be possible to make “ice wires” that would be among the best carriers known for protons, because water conducts protons at least 10 times more readily than typical conductive materials. “This gives us very stable water wires, at room temperature,” he says.
The Latest on: Water wires
via Google News
The Latest on: Water wires
- WIRES wildlife rehabilitation hindered by burnt bushon February 25, 2020 at 10:07 am
She said WIRES volunteers were often faced with an ethical dilemma between rescuing an animal ... she said to "make sure what you are doing will assist". "One of the water stations put up recently had ...
- Fairbanks Energy Services Designs New, Highly Efficient Heating System for RSCC Wire & Cableon February 25, 2020 at 8:46 am
140,000+ square feet of RSCC Wire & Cable’s manufacturing space was serviced by a steam generator with heat exchanger that served a hot water loop and 13 air handlers (AHUs). The boiler and AHUs were ...
- Perfect Water Technologies, Inc. Introduces Model Paid FMLAon February 25, 2020 at 8:35 am
PHOENIX--(BUSINESS WIRE)--#HomeMaster--Perfect Water Technologies, a leading manufacturer of innovative residential water filtration solutions has implemented a new, additional paid time off benefit ...
- Water Coolers Market 2019-2023 | Increasing Demand from the Residential Sector to Boost Growth | Technavioon February 24, 2020 at 4:00 pm
LONDON--(BUSINESS WIRE)--Technavio has been monitoring the water coolers market and it is poised to grow by USD 582.53 mn during 2019-2023, progressing at a CAGR of 7% during the forecast period. The ...
- Automated Water System at House Using Arduino Uno and C# Desktop Application to Reduce Water Wastage and Energy Losson February 24, 2020 at 2:09 pm
In this system, the identification of water level is done by setting parallel wires into the tank. Generally, ground water is impure and this kind of water is perfect for conducting electricity ...
- Illinois American Water’s Pontiac District Awarded a Partnership in Conservation Award for Environmental Stewardshipon February 24, 2020 at 12:22 pm
PONTIAC, Ill.--(Business Wire)--Illinois American Water’s Pontiac District was recently awarded a Partnership in Conservation Award from the Livingston County Soil and Water Conservation District ...
- Missouri American Water to Invest $15 Million in Water Main Replacements in Webster Groves Through 2023on February 24, 2020 at 12:06 pm
ST. LOUIS COUNTY, Mo.--(Business Wire)--Missouri American Water is working to keep its safe, clean, affordable, and reliable water flowing in Webster Groves with an investment of $15 million in water ...
- Evoqua Water Technologies Appoints Lisa Glatch to Its Board of Directorson February 21, 2020 at 4:00 am
PITTSBURGH--(BUSINESS WIRE)--Evoqua Water Technologies (NYSE: AQUA), an industry leader in mission-critical water treatment solutions, today announced the appointment of Lisa Glatch to its Board of ...
- New Study Projects Severe Water Shortages in the Colorado River Basinon February 20, 2020 at 11:47 am
Your inbox. Every weekend. Please subscribe me to the following mailing lists Clean Economy Wire Today's Climate ICN Articles Weekly Newsletter I agree to InsideClimate News' Terms of Service and ...
via Bing News