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Loops (seen above in blue) between graphene layers can be minimized using electron irradiation (bottom). (Credit: ORNL)

According to a press release, researchers at Oak Ridge National Lab have discovered how loops develop in graphene, an electrically conductive high-strength low-weight material that resembles an atomic-scale honeycomb. The nanoscale simulations are bringing scientists closer to using graphene in electronic applications.

“Graphene is a rising star in the materials world, given its potential for use in precise electronic components like transistors or other semiconductors,” says Bobby Sumpter, a staff scientist at ORNL.

Structural loops that sometimes form during a graphene cleaning process can render the material unsuitable for electronic applications.

However, when graphene was subjected to electron irradiation with a transmission electron microscope, it  prevented loop formation. The simulations showed that by injecting electrons to collect an image, the electrons were simultaneously changing the material’s structure.

“Taking a picture with a TEM is not merely taking a picture,” Sumpter says. “You might modify the picture at the same time that you’re looking at it.”

Graphene is only as good as the uniformity or cleanliness of its edges, which determine how effectively the material can transmit electrons. ORNL’s Vincent Meunier says the ability to efficiently clean graphene edges is crucial to using the material in electronics.

Recent experimental studies have shown that the Joule heating process can lead to undesirable loops that connect different graphene layers. Joule heating cleans graphene edges by running a current through the material. The team can show electron irradiation from a TEM prevents loop formation.

The multimetallic nanoparticle created by Brown University chemists
for fuel-cell reactions uses a palladium core and an iron-platinum shell.
Credit: Sun Lab/Brown University

According to a Brown University press release, researchers have created a unique core-and-shell nanoparticle that uses less platinum yet performs more efficiently and lasts longer than commercially available pure-platinum catalysts at the cathode end of some fuel-cells.

A redox reaction takes place at the fuel cell’s cathode, where up to 40 percent of a fuel cell’s efficiency is lost, so, “this is a crucial step in making fuel cells a more competitive technology with internal combustion engines and batteries,” says Shouheng Sun, professor of chemistry at Brown and coauthor of the study.

The research team, which includes ACerS member and Oak Ridge National Lab researcher Karren L. More, Brown graduate student Vismadeb Mazumder and other investigators from ORNL, created a five-nanometer-wide palladium core and encircled it with a one-nanometer shell consisting of iron platinum (FePt).

The trick, Mazumder says, was in molding a shell that would retain its shape and require the smallest amount of platinum to pull off an efficient reaction. The researchers found a way to create a shell that uses only 30 percent platinum, although they expect to make thinner shells and use even less platinum.

In laboratory tests, the palladium/iron-platinum nanoparticles generated 12-times more current than commercially available pure-platinum catalysts at the same catalyst weight. The output also remained consistent over 10,000 cycles, at least 10 times longer than commercially available platinum models that begin to deteriorate after 1,000 cycles.

“This is a very good demonstration that catalysts with a core and a shell can be made readily in half-gram quantities in the lab. They’re active, and they last,” Mazumder says. “The next step is to scale them up for commercial use, and we are confident we’ll be able to do that.”

According to Sun, it is uncertain if the concept of enhanced catalysis from core/shell nanoparticles can be applied to a wide range of reactions seen in fuel cells. “Different fuel cells work in different conditions. I know our core/shell particles are good under the PEMFC conditions, but they may not survive the high operating temperature used in SOFCs.”

The findings have been published in the Journal of the American Chemical Society.

The Department of Energy is teaming up with the Tennessee Valley Authority and Oak Ridge National Lab to make it easier than ever to charge electric vehicles.

Last week, the Electric Power Research Institute broke ground on one of Tennessee ’s first solar-assisted charging stations for electric vehicles in Knoxville. Chattanooga and Nashville are next in line.

“In this market, if anybody wants to drive an electric vehicle, Tennessee will be one of the places in the United States where they can,” says James Ellis, spokesman for TVA.

In addition to the solar charging stations, the DOE is giving away 1,000 home-based chargers. And TVA is looking to build 60 direct current fast chargers across the state.

The plug is standardized, which means it will work with the Nissan, GM Volt and all automotive manufactured vehicles for the United States.

The charging stations will be set up so that they use the sun to generate power needed to offset the effects of the charging during peak power demand periods. While vehicles are charging, the stationary batteries and smart grid controls will provide additional localized support to mitigate any impacts on the power system.

The TVA Fact Sheet (PDF) also discusses re-use of automotive lithium batteries stating, “Stationary battery storage will provide additional localized grid support to mitigate the impacts of charging multiple vehicles in one centralized location. Stationary storage will also provide future opportunities to re-use automotive batteries that are no longer ideal for vehicles. These batteries may have 60 to 70 percent life left in them and can be used to support the power grid.”

U.S. Deputy Secretary of Energy Daniel Poneman announced the selection of a team led by Oak Ridge National Lab for an award of up to $122 million over five years to establish and operate a new Nuclear Energy Modeling and Simulation Energy Innovation Hub.

The Hub will use the capabilities of the world’s most powerful computers to work on nuclear reactor design and engineering. I recently reported that 8 million processing hours will be directed to designing new and better reactors.

The Nuclear Energy Innovation Hub will allow engineers to create a simulation of a currently operating reactor that will act as a “virtual model” of that reactor. They will then use the “virtual model” to address important questions about reactor operations and safety. This will be used to address issues such as reactor power production increases and reactor life and license extensions.

The Nuclear Energy Innovation Hub will be located at ORNL in Tennessee. In addition to ORNL, the members of the team are:

• Electric Power Research Institute, Palo Alto, California
• Idaho National Lab, Idaho Falls, Idaho
• Los Alamos National Lab, Los Alamos, New Mexico
• Massachusetts Institute of Technology, Cambridge Massachusetts
• North Carolina State University, Raleigh, North Carolina
• Sandia National Lab, Albuquerque, New Mexico
• Tennessee Valley Authority, Knoxville, Tennessee
• University of Michigan, Ann Arbor, Michigan
• Westinghouse Electric Company, Pittsburgh, Pennsylvania

The Hub will be funded at up to $22 million this fiscal year. The Hub will then be funded at an estimated $25 million per year for the next four years, subject to Congressional appropriations.

The “Jaguar” - the most powerful computer in the world - will be used to design the next generation of nuclear reactors, according to an Oak Ridge National Lab press release.

The goal is to integrate existing nuclear energy and nuclear national security modeling and simulation capabilities with high-performance computing to simulate radiation in order to support the design and safety of nuclear facilities, improve reactor core designs and nuclear fuel performance and ensure the safety of nuclear materials, such as spent nuclear fuel.

John Wagner, technical integration manager for nuclear modeling at ORNL says, “We’re now simulating entire nuclear facilities, such as a nuclear power reactor facility with its auxiliary buildings and the ITER fusion reactor, with much greater accuracy than any other organization that we’re aware of.”

“Software for modeling radiation transport has been around for a long time,” he adds, “but it hadn’t been adapted to build on developments that have revolutionized computational science. There’s no special transformational technology in this software; but it’s designed specifically to take advantage of the massive computational and memory capabilities of the world’s fastest computers.”

The project has been awarded eight million processor hours on Jaguar for the purpose of developing a “uniquely detailed simulation of the power distribution inside a nuclear reactor core.” This is expected to cut years off the process of designing new and better reactors.