MATERIALS ENGINEERING

Need to store electricity more efficiently? Put it behind bars.

That's essentially the finding of a team of Rice University researchers who have created hybrid carbon nanotube metal oxide arrays as electrode material that may improve the performance of lithium-ion batteries.

With battery technology high on the list of priorities in a world demanding electric cars and gadgets that last longer between charges, such innovations are key to the future. Electrochemical capacitors and fuel cells would also benefit, the researchers said.

The team from Pulickel Ajayan's research group published a paper this week describing the proof-of-concept research in which nanotubes are grown to look – and act – like the coaxial conducting lines used in cables. The coax tubes consist of a manganese oxide shell and a highly conductive nanotube core.

"It's a nice bit of nanoscale engineering," said Ajayan, Rice's Benjamin M. and Mary Greenwood Anderson Professor in Mechanical Engineering and Materials Science.

"We've put in two materials – the nanotube, which is highly electrically conducting and can also absorb lithium, and the manganese oxide, which has very high capacity but poor electrical conductivity," said Arava Leela Mohana Reddy, a Rice postdoc researcher. "But when you combine them, you get something interesting."

That would be the ability to hold a lot of juice and transmit it efficiently. The researchers expect the number of charge/discharge cycles such batteries can handle will be greatly enhanced, even with a larger capacity.

"Although the combination of these materials has been studied as a composite electrode by several research groups, it's the coaxial cable design of these materials that offers improved performance as electrodes for lithium batteries," said Ajayan.

"At this point, we're trying to engineer and modify the structures to get the best performance," said Manikoth Shaijumon, also a Rice postdoc. The microscopic nanotubes, only a few nanometers across, can be bundled into any number of configurations. Future batteries may be thin and flexible. "And the whole idea can be transferred to a large scale as well. It is very manufacturable," Shaijumon said.

The hybrid nanocables grown in a Rice-developed process could also eliminate the need for binders, materials used in current batteries that hold the elements together but hinder their conductivity.

The paper was written by Reddy, Shaijumon, doctoral student Sanketh Gowda and Ajayan. It appears in the online version of the American Chemical Society's Nano Letters.

The project is supported by funding from the Hartley Family Foundation.

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Journal reference:

1. Reddy et al. Coaxial MnO2/ Carbon Nanotube Array Electrodes for High-Performance Lithium Batteries. Nano Letters, 2009; 090202085144070 DOI: 10.1021/nl803081j

Scientists in Arizona and New Jersey are reporting that aerogels, a super-lightweight solid sometimes called “frozen smoke,” may serve as the ultimate sponge for capturing oil from wastewater and effectively soaking up environmental oil spills.

In the new study, Robert Pfeffer and colleagues point out that the environmental challenges of oil contamination go beyond widely publicized maritime oil spills like the Exxon Valdez incident.

Experts estimate that each year people dump more than 200 million gallons of used oil into sewers, streams, and backyards, resulting in polluted wastewater that is difficult to treat. Although there are many different sorbent materials for removing used oil, such as activated carbon, they are often costly and inefficient. Hydrophobic silica aerogels are highly porous and absorbent material, and seemed like an excellent oil sponge.

The scientists packed a batch of tiny aerogel beads into a vertical column and exposed them to flowing water containing soybean oil to simulate the filtration process at a wastewater treatment plant. They showed that the aerogel beads absorbed up to 7 times their weight and removed oil from the wastewater at high efficiency, better than many conventional sorbent materials.

FEB 16,2009
MIT researchers who study the structure of protein-based materials with the aim of learning the key to their lightweight and robust strength have discovered that the particular arrangement of proteins that produces the sturdiest product is not the arrangement with the most built-in redundancy or the most complicated pattern.

Instead, the optimal arrangement of proteins in the rope-like structures they studied is a repeated pattern of two stacks of four bundled alpha-helical proteins.

This composition of two repeated hierarchies (stacks and bundles) provides great strength—the ability to withstand mechanical pressure without giving way—and great robustness—the ability to perform mechanically, even if flawed. Because the alpha-helical protein serves as the building block of many common materials, understanding the properties of those materials has been the subject of intense scientific inquiry since the protein's discovery in the 1940s.

In a paper published in the Jan. 27 online issue of Nanotechnology, Markus Buehler and Theodor Ackbarow describe a model of the protein’s performance, based on molecular dynamics simulations. With their model they tested the strength and robustness of four different combinations of eight alpha-helical proteins: a single stack of eight proteins, two stacks of four bundled proteins, four stacks of two bundled proteins, and double stacks of two bundled proteins. Their molecular models replicate realistic molecular behavior, including hydrogen bond formation in the coiled spring-like alpha-helical proteins.

“The traditional way of designing materials is to consider properties at the macro level, but a more efficient way of materials’ design is to play with the structural makeup at the nanoscale,” said Buehler, the Esther and Harold E. Assistant Professor in the Department of Civil and Environmental Engineering. “This provides a new paradigm in engineering that enables us to design a new class of materials.”

More and more frequently, natural protein materials are being used as inspiration for the design of synthetic materials that are based on nanowires and carbon nanotubes, which can be made to be much stronger than biological materials. Buehler and Ackbarow's work demonstrates that by rearranging the same number of nanoscale elements into hierarchies, the performance of a material can be radically changed. This could eliminate the need to invent new materials for different applications.

In a follow-up study, Buehler and CEE graduate students Zhao Qin and Steve Cranford ran similar tests using more than 16,000 elements instead of eight. They found that 98 percent of the randomly arranged rope-like structures did not meet the optimal performance level of the self-assembled natural molecules, which made up the other 2 percent of the structures. The most successful of those again utilized the bundles of four alpha-helical proteins.

That analysis shows that random arrangements of elements typically lead to inferior performance, and may explain why many engineered materials are not yet capable of combining disparate properties such as robustness and strength.

“Only a few specific nanostructured arrangements provide the basis for optimal material performance, and this must be incorporated in the material design process,” said Buehler.

This work is funded by the Army Research Office, a National Science Foundation CAREER Award, and the Air Force Office of Scientific Research. Ackbarow, a graduate student at the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany, was supported in this work by the German National Academic Foundation, the Hamburg Foundation for research studies abroad and the Dr. Juergen Ulderup Foundation.

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FEB 4,2009
UV light-enhanced tooth bleaching is not only a con, but is dangerous to your eyes and skin, says a Royal Society of Chemistry journal.

The light treatment gives absolutely no benefit over bleaching without UV, and damages skin and eyes up to four times as much as sunbathing, reports a study in Photochemical & Photobiological Sciences.

Those looking to match Tom Cruise’s glittering pearly-whites would be better off ignoring claims of better bleaching with UV light treatment.

The treatment is at least as damaging to skin and eyes as sunbathing in Hyde Park for a midsummer’s afternoon – one lamp actually gave four times that level of radiation exposure.

And as with sunbathing, fair-skinned or light-sensitive people are at even greater risk, said lead author Ellen Bruzell of the Nordic Institute of Dental Materials.

Bruzell also found that bleaching damaged teeth. She saw more exposed grooves on the enamel surface of bleached teeth than on unbleached teeth. These grooves make the teeth more vulnerable to mechanical stress.

Tooth bleaching is one of the most popular cosmetic dental treatments available. It uses a bleaching agent – usually hydrogen peroxide – to remove stains such as those from red wine, tea and coffee, and smoking.

UV light is claimed to further activate the oxidation process, improving bleaching efficiency. The authors of this Photochemical & Photobiological Sciences article say there is very little substantive evidence to support this claim, and their new study finds no benefit to using UV light.

Courtesy: www.sciencedaily.com

FEB 23,2009
“One of the most important problems in materials science solved,” reports Professor Peter Oppeneer of Uppsala University. Together with three colleagues, he has managed to explain the hitherto unsolved riddle in materials science known as ‘the hidden order' - how a new phase arises and why.

This is a discovery that can be of great importance to our understanding of how new material properties occur, how they can be controlled and exploited in the future.

For a long time researchers have attempted to develop the superconducting materials of the future that will be able to conduct energy without energy losses, something of great importance to future energy production. But one piece of the puzzle has been missing. There are several materials that evince a clear phase shift in all thermodynamic properties when the temperature falls below a certain transitional temperature, but no one has been able to explain the new collective order in the material. Until now, it has been called the hidden order.

"The hidden order was discovered 24 years ago, and for all these years scientists have tried to find an explanation, but so far no one has succeeded. This has made the question one of the hottest quests in materials science. And now that we can explain how the hidden order in materials occurs, in a manner that has never been seen before, we have solved one of the most important problems of our day in this scientific field," says Professor Peter Oppeneer.

Four physicists from Uppsala University, led by Peter Oppeneer and in collaboration with John Mydosh from the University of Cologne, who discovered the hidden order 24 years ago, show through large-scale calculations how the hidden order occurs. Extremely small magnetic fluctuations prompt changes in the macroscopic properties of the material, so an entirely new phase arises, with different properties.

"Never before have we seen the so-called ‘magnetic spin excitations' produce a phase transition and the formation of a new phase. In ordinary material this excitation cannot change the phase and properties of the material because it is too weak. But now we have shown that this is in fact possible," says Peter Oppeneer.

What explains in detail all of the physical phenomena in the hidden order is a computer-based theory. Among other applications, it can be used to better understand high-temperature superconducting materials and will thus be important in the development of new superconducting materials and future energy production.

Courtesy: www.sciencedaily.com

New plastics may soon replace metals in auto bodies. Designers are beginning to discover a whole new world of possibilities offered by materials that can be bent into futuristic shapes.

DETROIT--Imaginations are let loose on car designs of the future. Now, young, creative minds are pushing automotive design to its limits, using every shape, color and size in their creations.

Designers and engineers who take their dreams and turn them into reality create these new cars of the future.

Chris Piscitelli's zest for cars started when he was just a kid. "My father is an old car enthusiast, so I grew up around it." Piscitelli is a design student at the College for Creative Studies in Detroit. As he got older, he learned his love of cars could be linked with his artistic talent.

"I have a passion for cars and design, so it was just natural for me to get into automotive design," Piscitelli says.

Now, Chris is part of a future generation of car designers learning to put new materials to use in exciting, futuristic ways. "We're supposed to stress the use of a lot of the new plastics and things that you do with plastics that you couldn't necessarily do with say, you know, steel," Piscitelli tells Ivanhoe.

Plastic is easy to mold so using materials engineering, Chris used the advantages of plastic by heating it so the long, spaghetti-like molecules slide over each other to form new shapes, giving us durable, cost-effective, lightweight plastics with sleek curves.

Jim Kolb, vice president of American Plastics Council in Troy says, "The limitations that some metals have in forming parts -- are overcome with the use of plastics."

Plastic concepts have caught the eye of car companies who see the future of car design in students like Piscitelli. "We're able to push the limit with the project, and so to make something that was, you know, kind of futuristic and, you know, out there, but also could be seen on the road," Piscitelli says. His concept car may not be road-ready right now, but it's a nice sneak peak at what the future holds.

Car manufacturers are working to make affordable plastic cars available to consumers.

New steel technologies are offering better looks, performance and protection for cars. To make new steel alloys, metallurgical engineers are mixing different kinds of metals like nickel, with iron to make a lighter, stronger, more-flexible automobile.

PITTSBURGH--High gas prices are forcing consumers to fork over fistfuls of cash at the pump. In fact, AAA says prices are now a dollar more than this time last year. Now, a new car technology might offer some relief when filling up your car at the pump.

Rising gas prices are hitting Andy Carson where it hurts -- his wallet. "I think gas prices are going to have a tremendous effect on my decision on what car I'm going to buy," Carson says. Fuel economy is playing a big part in his decision. Now, new high-tech materials for cars may produce a car to fit his budget.

Richard Fruehan, a metallurgical engineer from Carnegie Mellon University in Pittsburgh, says, "These very new steels have unique properties. This will enable us to use these steels in automobiles and reduce the weight of the automobiles and get the resulting fuel economy."

New steel technologies offer better looks, performance and protection for cars. Fruehan says, "The result will be a car that lasts longer, a car that gets better fuel economy and a car that is safe for the passenger." To make new steel materials, metallurgical engineers mix different kinds of metals, like nickel with iron to make a lighter, stronger, more-flexible product. "These steels are more coatable to resist corrosion, so the steels that we're pitting in are much better," Fruehan says.

Improved materials for cars could be the answer to gas mileage sticker-shock and give Andy Carson an upgrade. "I get good gas mileage now, but I think I can do a lot better," he says. But for now, he's paying the price at the pump and hopes for relief down the road.

If you think the United States prices are high, in Europe, they pay $7 a gallon. So experts say now is the time to tackle the problem.

Coutesy: www.sciencedaily.com