Oak Ridge Today

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 devises recipe to fine-tune silica rod diameters

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By controlling the temperature of silica rods as they grow, researchers at Oak Ridge National Laboratory could be setting the stage for advances in anti-reflective solar cells, computer monitors, TV screens, eye glasses, and more.

The goal of fabricating fixed-size one-dimensional silica structures and being able to precisely control the diameter during growth has long eluded scientists. Now, Panos Datskos and Jaswinder Sharma have demonstrated what they describe as the addressable local control of diameter of each segment of the silica rod.

“In nature, many intricate structures develop and grow in response to their environments,” said Sharma, a Wigner Fellow and corresponding author of the Angewandte Chemie International Edition paper that outlines the process. “For example, in addition to genotype, shell shape is also controlled by the local environment in many oysters and scallops.” [Read more…]

ORNL-grown oxygen ‘sponge’ presents path to better catalysts, energy materials

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ORNL Oxygen Sponge

This schematic depicts a new ORNL-developed material that can easily absorb or shed oxygen atoms. (Photo courtesy ORNL)

Scientists at Oak Ridge National Laboratory have developed a new oxygen “sponge” that can easily absorb or shed oxygen atoms at low temperatures. Materials with these novel characteristics would be useful in devices such as rechargeable batteries, sensors, gas converters, and fuel cells.

Materials containing atoms that can switch back and forth between multiple oxidation states are technologically important but very rare in nature, said ORNL’s Ho Nyung Lee, who led the international research team that published its findings in Nature Materials. [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…]

ORNL develops lignin-based thermoplastic conversion process

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Turning lignin, a plant’s structural “glue” and a byproduct of the paper and pulp industry, into something considerably more valuable is driving a research effort headed by Amit Naskar of Oak Ridge National Laboratory.

In a cover article published in Green Chemistry, the research team describes a process that ultimately transforms the lignin byproduct into a thermoplastic—a polymer that becomes pliable above a specific temperature. Researchers accomplished this by reconstructing larger lignin molecules either through a chemical reaction with formaldehyde or by washing with methanol. Through these simple chemical processes, they created a crosslinked rubber-like material that can also be processed like plastics.

[Read more…]

ORNL study confirms magnetic properties of silicon nano-ribbons

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Nano-ribbons of silicon configured so the atoms resemble chicken wire could hold the key to ultrahigh density data storage and information processing systems of the future.

This was a key finding of a team of scientists led by Paul Snijders of the U.S. Department of Energy’s Oak Ridge National Laboratory.

The researchers used scanning tunneling microscopy and spectroscopy to validate first principle calculations—or models—that for years had predicted this outcome. The discovery, detailed in New Journal of Physics, validates this theory and could move scientists closer to their long-term goal of cost-effectively creating magnetism in non-magnetic materials.

“While scientists have spent a lot of time studying silicon because it is the workhorse for current information technologies, for the first time we were able to clearly establish that the edges of nano-ribbons feature magnetic silicon atoms,” said Snijders, a member of the Materials Science and Technology Division.

The surprise is that while bulk silicon is non-magnetic, the edges of nano-ribbons of this material are magnetic.

Snijders and colleagues at ORNL, Argonne National Laboratory, the University of Wisconsin and Naval Research Laboratory showed that the electron spins are ordered anti-ferromagnetically, which means they point up and down alternatingly. Configured this way, the up and down spin-polarized atoms serve as effective substitutes for conventional zeros and ones common to electron, or charge, current.

“By exploiting the electron spins arising from intrinsic broken bonds at gold-stabilized silicon surfaces, we were able to replace conventional electronically charged zeros and ones with spins pointing up and down,” Snijders said.

This discovery provides a new avenue to study low-dimensional magnetism, the researchers noted. Most importantly, such stepped silicon-gold surfaces provide an atomically precise template for single-spin devices at the ultimate limit of high-density data storage and processing.

“In the quest for smaller and less expensive magnets, electro-motors, electronics and storage devices, creating magnetism in otherwise non-magnetic materials could have far-reaching implications,” Snijders said.

The paper is available online at http://iopscience.iop.org/1367-2630/14/10/103004. This research was funded by DOE’s Office of Science, the National Science Foundation, and the Office of Naval Research.

This work was supported by the Center for Nanophase Materials Sciences at ORNL. CNMS is one of the five DOE Nanoscale Science Research Centers supported by the DOE Office of Science, premier national user facilities for interdisciplinary research at the nanoscale.

Together, the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge, and Sandia and Los Alamos national laboratories. For more information about the DOE NSRCs, visit http://science.energy.gov/bes/suf/user-facilities/nanoscale-science-research-centers/.