Oak Ridge Today

ORNL-led team demonstrates desalination with graphene membrane

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Nature Nanotech Pores

Researchers created nanopores in graphene (red, and enlarged in the circle to highlight its honeycomb structure) that are stabilized with silicon atoms (yellow) and showed their porous membrane could desalinate seawater. Orange represents a non-graphene residual polymer. (Source: Oak Ridge National Laboratory, U.S. Department of Energy)

 

By Dawn Levy

Less than 1 percent of Earth’s water is drinkable. Removing salt and other minerals from our biggest available source of water—seawater—may help satisfy a growing global population thirsty for fresh water for drinking, farming, transportation, heating, cooling, and industry. But desalination is an energy-intensive process, which concerns those wanting to expand its application.

Now, a team of experimentalists led by the U.S. Department of Energy’s Oak Ridge National Laboratory has demonstrated an energy-efficient desalination technology that uses a porous membrane made of strong, slim graphene—a carbon honeycomb one atom thick. The results are published in the March 23 advance online issue of Nature Nanotechnology.

“Our work is a proof of principle that demonstrates how you can desalinate saltwater using free-standing, porous graphene,” said Shannon Mark Mahurin of ORNL’s Chemical Sciences Division, who co-led the study with Ivan Vlassiouk in ORNL’s Energy and Transportation Science Division.

“It’s a huge advance,” said Vlassiouk, pointing out a wealth of water travels through the porous graphene membrane. “The flux through the current graphene membranes was at least an order of magnitude higher than (that through) state-of-the-art reverse osmosis polymeric membranes.” [Read more…]

Science: ORNL researchers tune friction in ionic solids at the nanoscale

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Friction Release

Researchers used electricity and water to control friction levels on ionic surfaces at the nanoscale. As water forms around the nanoscale electrode, it allows for further penetration into the sample surface, thereby increasing or decreasing friction. (Image courtesy ORNL)

Friction impacts motion, hence the need to control friction forces. Currently, this is accomplished by mechanistic means or lubrication, but experiments conducted by researchers at the U.S. Department of Energy’s Oak Ridge National Laboratory have uncovered a way of controlling friction on ionic surfaces at the nanoscale using electrical stimulation and ambient water vapor.

The research, which demonstrates a new physical effect, was undertaken at the Center for Nanophase Materials Sciences, a DOE Office of Science User Facility at ORNL, and is published in the journal Scientific Reports.

“Our finding can have a significant technological impact on applications for both macroscopic and nanoscale devices,” said lead author Evgheni Strelcov. “Decreasing or increasing nanoscale friction at will and thus controlling mechanical energy losses and wear of a microelectromechanical system’s parts has enormous implications for applied energy research and opens a new vista for fundamental science studies.” [Read more…]

Novel ORNL technique enables air-stable water droplet networks

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Water Droplet

Researchers at Oak Ridge National Laboratory have developed a method to create air-stable water droplet networks that are valuable for applications in biological sensing and membrane research. (Image credit: Kyle Kuykendall)

 

A simple new technique to form interlocking beads of water in ambient conditions could prove valuable for applications in biological sensing, membrane research, and harvesting water from fog.

Researchers at the U.S. Department of Energy’s Oak Ridge National Laboratory have developed a method to create air-stable water droplet networks known as droplet interface bilayers. These interconnected water droplets have many roles in biological research because their interfaces simulate cell membranes. Cumbersome fabrication methods, however, have limited their use.

“The way they’ve been made since their inception is that two water droplets are formed in an oil bath then brought together while they’re submerged in oil,” said ORNL’s Pat Collier, who led the team’s study published in the Proceedings of the National Academy of Sciences. “Otherwise they would just pop like soap bubbles.”

Instead of injecting water droplets into an oil bath, the ORNL research team experimented with placing the droplets on a superhydrophobic surface infused with a coating of oil. The droplets aligned side by side without merging. [Read more…]

‘Double-duty’ electrolyte enables new chemistry for longer-lived batteries

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ORNL Battery Chemistry

When ORNL researchers incorporated a solid lithium thiophosphate electrolyte into a lithium-carbon fluoride battery, the device generated a 26 percent higher capacity than what would be its theoretical maximum if each component acted independently. (Image courtesy ORNL)

 

Researchers at Oak Ridge National Laboratory have developed a new and unconventional battery chemistry aimed at producing batteries that last longer than previously thought possible.

In a study published in the Journal of the American Chemical Society, ORNL researchers challenged a long-held assumption that a battery’s three main components—the positive cathode, negative anode, and ion-conducting electrolyte—can play only one role in the device.

The electrolyte in the team’s new battery design has dual functions: It serves not only as an ion conductor but also as a cathode supplement. This cooperative chemistry, enabled by the use of an ORNL-developed solid electrolyte, delivers an extra boost to the battery’s capacity, and extends the lifespan of the device.

“This bi-functional electrolyte revolutionizes the concept of conventional batteries and opens a new avenue for the design of batteries with unprecedented energy density,” said ORNL’s Chengdu Liang. [Read more…]

‘Atomic switcheroo’ explains origins of thin-film solar cell mystery

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Current Maps

Cross-sectional electron beam-induced current maps show the difference in cadmium telluride solar cells before (pictured above) and after (below) cadmium chloride treatment. The increased brightness after treatment indicates higher current collection at the grain boundaries. (Submitted photo)

Treating cadmium-telluride (CdTe) solar cell materials with cadmium-chloride improves their efficiency, but researchers have not fully understood why. Now, an atomic-scale examination of the thin-film solar cells led by Oak Ridge National Laboratory has answered this decades-long debate about the materials’ photovoltaic efficiency increase after treatment.

A research team from ORNL, the University of Toledo, and the U.S. Department of Energy’s National Renewable Energy Laboratory used electron microscopy and computational simulations to explore the physical origins of the unexplained treatment process. The results are published in Physical Review Letters, or PRL.

Thin-film CdTe solar cells are considered a potential rival to silicon-based photovoltaic systems because of their theoretically low cost per power output and ease of fabrication. Their comparatively low historical efficiency in converting sunlight into energy, however, has limited the technology’s widespread use, especially for home systems. [Read more…]

Christen leads ORNL’s Center for Nanophase Materials Sciences

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Hans M. Christen

Hans M. Christen

Hans M. Christen of Oak Ridge National Laboratory has been named director of ORNL’s Center for Nanophase Materials Sciences, one of the five DOE Nanoscale Science Research Centers.

Christen joined ORNL in 2000 and led the Thin Films and Nanostructures group from 2006 to 2013. In 2013, he became associate director within the Materials Science and Technology Division and has managed the DOE Materials Sciences and Engineering Program since 2011.

His research has focused on the effects of epitaxial strain, spatial confinement, and interfacial mechanisms on the properties of complex-oxide thin films, in particular ferromagnetic, ferroelectric, and multiferroic perovskites. He has authored more than 150 scientific publications and several patents, is a fellow of the American Physical Society, and has served on a number of National Science Foundation and DOE review panels. [Read more…]

ORNL finding goes beyond surface of oxide films

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Oxide Figure

This figure shows the spectroscopic measurement (current as a function of voltage) and this as a function of temperature. (Reproduced by permission of The Royal Society of Chemistry)

Better batteries, catalysts, electronic information storage and processing devices are among potential benefits of an unexpected discovery made by Oak Ridge National Laboratory scientists using samples isolated from the atmosphere.

Researchers at the U.S. Department of Energy lab learned that key surface properties of complex oxide films are unaffected by reduced levels of oxygen during fabrication—an unanticipated finding with possible implications for the design of functional complex oxides used in a variety of consumer products, said Zheng Gai, a member of DOE’s Center for Nanoscale Materials Sciences at ORNL.

The findings are detailed in a paper published in Nanoscale. [Read more…]

New all-solid sulfur-based battery outperforms lithium-ion technology

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ORNL Lithium-Sulfur Battery

A new all-solid lithium-sulfur battery developed by an Oak Ridge National Laboratory team led by Chengdu Liang has the potential to reduce cost, increase performance, and improve safety compared with existing designs. (Submitted photo)

Scientists at Oak Ridge National Laboratory have designed and tested an all-solid lithium-sulfur battery with approximately four times the energy density of conventional lithium-ion technologies that power today’s electronics.

The ORNL battery design, which uses abundant low-cost elemental sulfur, also addresses flammability concerns experienced by other chemistries.

“Our approach is a complete change from the current battery concept of two electrodes joined by a liquid electrolyte, which has been used over the last 150 to 200 years,” said Chengdu Liang, lead author on the ORNL study published this week in Angewandte Chemie International Edition. [Read more…]