Technology Org » Nanotechnology news - 21. 11. 2013

New milestone could help magnets end era of computer transistors

 

New work by researchers at UC Berkeley could soon transform the building blocks of modern electronics by making nanomagnetic switches a viable replacement for the conventional transistors found in all computers. As current passes through a strip of tantalum, electrons with opposite spins separate. Researchers used the resulting polarization to create a nanomagnetic switch that could one day replace computer transistors. (Image by Debanjan Bhowmik, UC Berkeley) Semiconductor-based transistors, the on-off switches that direct the flow of electricity and form a computer’s nervous system, have been consuming greater chunks of power at increasingly hotter temperatures as processing speeds grow. For more than a decade, researchers have been pursuing magnets as an alternative to transistors because they require far less energy needs when switching. However, until now, the power needed to generate the magnetic field to orient the magnets so they can easily clock on and off has negated much of the energy savings that would have been gained by moving away from transistors. UC Berkeley researchers overcame this limitation by exploiting the special properties of the rare, heavy metal tantalum. In a paper published online Sunday, Nov. 17, in the journal Nature Nanotechnology, the researchers describe how they created a so-called

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Graphene: Minor rotation of ‘chicken wire’ has major consequences

 

Since the discovery of graphene, a great future has been predicted for the material, which is strong and highly conductive. The just one atom layer thick carbon can lead to new electronics. Examples include printable and flexible electronics, touch screens and OLEDs. For this, interaction with other materials is necessary, however. PhD student Menno Bokdam from the University of Twente MESA+ Institute for Nanotechnology examined what happens at the interface with other materials and thus brings graphene electronics a step closer. He will defend his PhD thesis on 15 November. Graphene was given the status of ‘miracle material’ and Andre Geim and Konstantin Novoselov received the Nobel Prize for Physics for it in 2010. The carbon is extremely thin, has a chicken wire structure and can conduct electrons very well. But how does it behave in contact with another material with a similar structure, such as boron nitride? What happens if the boron nitride layer is inserted between a layer of copper and a layer of graphene? Insight into the interfaces is very important if you want to design electronics. ‘Gap’ or not? Bokdam has performed detailed electron structure theory calculations of graphene on boron nitride. This material is also

The post Graphene: Minor rotation of ‘chicken wire’ has major consequences has been published on Technology Org.

New technique controls dimensions of gold nanorods while manufactur...

 

NC State University researchers found they could control the dimensions of the nanorods by varying how quickly they added ascorbic acid. Credit: Joseph Tracy, North Carolina State University North Carolina State University researchers have a developed a technique for efficiently producing nanoscale gold rods in large quantities while simultaneously controlling the dimensions of the nanorods and their optical properties. The optical properties of gold nanorods make them desirable for use in biomedical applications ranging from imaging technologies to cancer treatment. “This technique should facilitate the economical manufacture of large volumes of gold nanorods,” says Dr. Joseph Tracy, an associate professor of materials science and engineering at NC State and senior author of a paper on the work. “And that should be good news for both the science community and the biomedical research and development community.” The NC State team started with an existing technique, in which gold nanorods are formed by mixing two chemical solutions together. However, that technique only converts 30 percent of the gold into nanorods – the rest remains dissolved in solution. To convert the remaining 70 percent of the gold into nanorods, the researchers added a continuous stream of ascorbic acid (better known as vitamin C) to the solution, while

The post New technique controls dimensions of gold nanorods while manufactur... has been published on Technology Org.

Researchers develop technique to convert thermoelectric material in...

 

Pooja Puneet, Ph.D., the lead author on the article published in Scientific Reports and Prof. Jian He discuss their custom-made resistivity and Seebeck measurement system which is located in Prof. Terry Tritt’s complex advanced material laboratory. Credit: Clemson University A team of Clemson University physicists consisting of nanomaterial scientists Apparao Rao and Ramakrishna Podila and thermoelectricians Terry Tritt, Jian He and Pooja Puneet worked synergistically through the newly established Clemson Nanomaterials Center to develop a novel technique of tailoring thermoelectric properties of n-type bismuth telluride for high thermoelectric performance. Their findings were published in journal Scientific Reports. The current US energy economy and environment are increasingly threatened by fast-dwindling domestic reserves of fossil fuel coupled with severe environmental impact of fossil fuel combustion. Highly-efficient thermoelectric devices are expected to provide clean energy technology-needs of the hour for US energy sustainability. This research is a step towards optimizing the device performance since it outlines a methodology to overcome a challenge that has “frustrated” thermoelectric researchers to date. Thermoelectric (TE) devices convert waste heat into electricity through a unique material’s property called the Seebeck effect. Basically, the Seebeck effect results in a voltage across the two ends of a TE material, akin to the voltage present across the two

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Holistic cell design leads to high-performance, long cycle-life lit...

 

Battery could find use in mobile applications, and eventually, electric vehicles with 300-mile range Researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have demonstrated in the laboratory a lithium-sulfur (Li/S) battery that has more than twice the specific energy of lithium-ion batteries, and that lasts for more than 1,500 cycles of charge-discharge with minimal decay of the battery’s capacity. This is longest cycle life reported so far for any lithium-sulfur battery. A schematic of a lithium-sulfur battery with SEM photo of silicon-graphene oxide material. Click to enlarge. Long-term cycling test results of the Li/S cell with CTAB-modified S-GO composite cathodes. This result represents the longest cycle life (exceeding 1500 cycles) with an extremely low decay rate (0.039% per cycle) demonstrated so far for a Li/S cell. Demand for high-performance batteries for electric and hybrid electric vehicles capable of matching the range and power of the combustion engine encourages scientists to develop new battery chemistries that could deliver more power and energy than lithium-ion batteries, currently the best performing battery chemistry in the marketplace. For electric vehicles to have a 300-mile range, the battery should provide a cell-level specific energy of 350 to 400 Watt-hours/kilogram (Wh/kg).

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Overcoming Brittleness: New Insights into Bulk Metallic Glass

 

From the production of tougher, more durable smart phones and other electronic devices, to a wider variety of longer lasting biomedical implants, bulk metallic glasses are poised to be  mainstay materials for the 21stCentury. Featuring a non-crystalline amorphous structure, bulk metallic glasses can be as strong or even stronger than steel, as malleable as plastics,  conduct electricity and resist corrosion. These materials would seem to have it all save for one problem: they are often brittle, with a poor and uneven resistance to fatigue that makes their reliability questionable. The creation of multicomponent bulk-metallic glass composites is addressing this issue but the problem remains for monolithic metallic glasses, which are major components of bulk metallic composites. In palladium-based bulk metallic glass, the extensive formation and proliferation of shear bands along fan-shaped slip lines results in significant crack-tip blunting   A new study by a collaboration of Berkeley Lab and Caltech researchers may point the way to improving the fatigue resistance of monolithic bulk glasses. The collaboration found that a bulk metallic glass based on palladium displayed a fatigue strength as good as the best composite bulk metallic glasses and comparable to regular polycrystalline structural alloys, such as steel, aluminum and

The post Overcoming Brittleness: New Insights into Bulk Metallic Glass has been published on Technology Org.

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Refined materials provide booster shot for solar energy conversion

 

If you want to get the most out of the sun, you have to improve the performance of the materials used.   This is one of several projects receiving support from the College of Engineering SRI program. Project group members include (l to r) Lane Martin, Elif Ertekin, Ed Seebauer, Sungki Lee and Brent Apgar (seated). An interdisciplinary team of Engineering at Illinois researchers has set its sights on improving the materials that make solar energy conversion/photocatalysis possible. Together, they have developed a new form of high-performance solar photocatalyst based on the combination of the TiO2 (titanium dioxide) and other “metallic” oxides that greatly enhance the visible light absorption and promote more efficient utilization of the solar spectrum for energy applications.   “This is a fundamentally new way of approaching these matters,” explained Lane Martin, who is an assistant professor in the Department of Materials Science and Engineering at Illinois. “Our research group incorporatesaspects of condensed matter physics, semiconductor device engineering, and photochemistry to make new performance possible. From these materials we can imagine carbon-neutral energy production of clean-burning fuels, waste water purification and remediation, and much more. “As a follow-up to our prior work, we expanded our discovery of new strongly absorbing energy

The post Refined materials provide booster shot for solar energy conversion has been published on Technology Org.

Graphene Nanoribbons With Nanopores for Fast DNA Sequencing

 

The instructions for building all of the body’s proteins are contained in a person’s DNA, a string of chemicals that, if unwound and strung end to end, would form a sentence 3 billion letters long. Each person’s sentence is unique, so learning how to read gene sequences as quickly and inexpensively as possible could pave the way to countless personalized medical applications. Researchers at the University of Pennsylvania have now made an advance towards realizing a new sequencing technique based on threading that string through a tiny hole and using a nearby sensor to read each letter as it passes through. Their DNA sensor is based on graphene, an atomically thin lattice of carbon. Earlier versions of the technique only made use of graphene’s unbeatable thinness, but the Penn team’s research shows how the Nobel Prize-winning material’s unique electrical properties may be employed to make faster and more sensitive sequencing devices. Critically, the team’s latest study shows how to drill these nanopores without ruining graphene’s electrical sensitivity, a risk posed by simply looking at the material through an electron microscope. The team includes Marija Drndić, professor of physics in the School of Arts and Sciences, and members in her laboratory, including

The post Graphene Nanoribbons With Nanopores for Fast DNA Sequencing has been published on Technology Org.

New Technique Controls Dimensions of Gold Nanorods while Manufactur...

 

North Carolina State University researchers have a developed a technique for efficiently producing nanoscale gold rods in large quantities while simultaneously controlling the dimensions of the nanorods and their optical properties. The optical properties of gold nanorods make them desirable for use in biomedical applications ranging from imaging technologies to cancer treatment. “This technique should facilitate the economical manufacture of large volumes of gold nanorods,” says Dr. Joseph Tracy, an associate professor of materials science and engineering at NC State and senior author of a paper on the work. “And that should be good news for both the science community and the biomedical research and development community.” The NC State team started with an existing technique, in which gold nanorods are formed by mixing two chemical solutions together. However, that technique only converts 30 percent of the gold into nanorods – the rest remains dissolved in solution. To convert the remaining 70 percent of the gold into nanorods, the researchers added a continuous stream of ascorbic acid (better known as vitamin C) to the solution, while constantly stirring the mixture. The ascorbic acid essentially pulls the gold out of the solution and deposits it on the existing nanorods. But the

The post New Technique Controls Dimensions of Gold Nanorods while Manufactur... has been published on Technology Org.

Magnetic nanoparticles could aid heat dissipation

 

Cooling systems generally rely on water pumped through pipes to remove unwanted heat. Now, researchers at MIT and in Australia have found a way of enhancing heat transfer in such systems by using magnetic fields, a method that could prevent hotspots that can lead to system failures. The system could also be applied to cooling everything from electronic devices to advanced fusion reactors, they say. The system, which relies on a slurry of tiny particles of magnetite, a form of iron oxide, is described in the International Journal of Heat and Mass Transfer, in a paper co-authored by MIT researchers Jacopo Buongiorno and Lin-Wen Hu, and four others. Hu, associate director of MIT’s Nuclear Reactor Laboratory, says the new results are the culmination of several years of research on nanofluids — nanoparticles dissolved in water. The new work involved experiments where the magnetite nanofluid flowed through tubes and was manipulated by magnets placed on the outside of the tubes. The magnets, Hu says, “attract the particles closer to the heated surface” of the tube, greatly enhancing the transfer of heat from the fluid, through the walls of the tube, and into the outside air. Without the magnets in place, the fluid behaves just

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