Chemistry 2 - Course #84.122 SECTIONS 202, 223, and 227

    NEAT SCIENCE

3/2/2011 5:46:15 PM
Stronger Than Steel, Novel Metals Are Moldable as Plastic

Now a team led by Jan Schroers, a materials scientist at Yale University, has shown that some recently developed bulk metallic glasses (BMGs)-metal alloys that have randomly arranged atoms as opposed to the orderly, crystalline structure found in ordinary metals-can be blow molded like plastics into complex shapes that can't be achieved using regular metal, yet without sacrificing the strength or durability that metal affords. Their findings are described online in the current issue of the journal Materials Today.

"These alloys look like ordinary metal but can be blow molded just as cheaply and as easily as plastic," Schroers said. So far the team has created a number of complex shapes-including seamless metallic bottles, watch cases, miniature resonators and biomedical implants-that can be molded in less than a minute and are twice as strong as typical steel.

The materials cost about the same as high-end steel, Schroers said, but can be processed as cheaply as plastic. The alloys are made up of different metals, including zirconium, nickel, titanium and copper.

The team blow molded the alloys at low temperatures and low pressures, where the bulk metallic glass softens dramatically and flows as easily as plastic but without crystallizing like regular metal. It's the low temperatures and low pressures that allowed the team to shape the BMGs with unprecedented ease, versatility and precision, Schroers said. In order to carefully control and maintain the ideal temperature for blow molding, the team shaped the BMGs in a vacuum or in fluid.

"The trick is to avoid friction typically present in other forming techniques," Schroers said. "Blow molding completely eliminates friction, allowing us to create any number of complicated shapes, down to the nanoscale."

Schroers and his team are already using their new processing technique to fabricate miniature resonators for microelectromechanical systems (MEMS)-tiny mechanical devices powered by electricity-as well as gyroscopes and other resonator applications.

In addition, by blow molding the BMGs, the team was able to combine three separate steps in traditional metal processing (shaping, joining and finishing) into one, allowing them to carry out previously cumbersome, time- and energy-intensive processing in less than a minute.

"This could enable a whole new paradigm for shaping metals," Schroers said. "The superior properties of BMGs relative to plastics and typical metals, combined with the ease, economy and precision of blow molding, have the potential to impact society just as much as the development of synthetic plastics and their associated processing methods have in the last century."

Other authors of the paper include Thomas M. Hodges and Golden Kumar (Yale University); Hari Raman and A.J. Barnes (SuperformUSA); and Quoc Pham and Theodore A. Waniuk (Liquidmetal Technologies).

3/2/2011 5:50:43 PM
Professor uses nanotechnology to prolong machine and engine life

“The technology should be useful in a wide range of machineries other than automobile engines,” says Dr. Liu, a professor in the Department of Chemistry and an expert in polymer synthesis. “If implemented industrially, this nanotechnology should help prolong machine life and improve energy efficiency.”

Dr Liu’s team prepared miniscule polymer particles that were only tens of nanometers in size. These particles were then dispersed in automobile engine base oils. When tested under metal surface contact conditions that simulated conditions found in automobile engines, these tiny particles were discovered to have an unprecedented friction reduction capability.

Even at a low concentration, the nanoparticles performed much better than the friction additive that is currently used by many industries. They were able to reduce friction by 55 per cent more than the currently achievable rate.

Dr. Liu’s discovery has earned the Society of Tribologists and Lubrication Engineers’ Captain Alfred E. Hunt Memorial Award. This prestigious award is given annually to the STLE member who authors the best paper dealing with the field of lubrication or an allied field.

This is the first research that Dr. Liu has done in the field of friction reduction and lubrication.

Dec. 20, 2010

Carbon nanotubes could be ideal optical antennae

By Anne Ju

Just as walkie-talkies transmit and receive radio waves, carbon nanotubes can transmit and receive light at the nanoscale, Cornell researchers have discovered.

Carbon nanotubes, cylindrical rolled-up sheets of carbon atoms, might one day make ideal optical scattering wires -- tiny, mostly invisible antennae with the ability to control, absorb and emit certain colors of light at the nanoscale, according to research led by Jiwoong Park, Cornell assistant professor of chemistry and chemical biology. The study, which includes co-author Garnet Chan, also in chemistry, is published online Dec. 19 in the journal Nature Nanotechnology. The paper's first author is Daniel Y. Joh, a former student in Park's lab.

The researchers used the Rayleigh scattering of light -- the same phenomenon that creates the blue sky -- from carbon nanotubes grown in the lab. They found that while the propagation of light scattering is mostly classical and macroscopic, the color and intensity of the scattered radiation is determined by intrinsic quantum properties. In other words, the nanotubes' simple carbon-carbon bonded molecular structure determined how they scattered light, independent of their shape, which differs from the properties of today's metallic nanoscale optical structures.

"Even if you chop it down to a small scale, nothing will change, because the scattering is fundamentally molecular," Park explained.

They found that the nanotubes' light transmission behaved as a scaled-down version of radio-frequency antennae found in walkie-talkies, except that they interact with light instead of radio waves. The principles that govern the interactions between light and the carbon nanotube are the same as between the radio antenna and the radio signal, they found.

To perform their experiments, the researchers used a methodology developed in their lab that completely eliminates the problematic background signal, by coating the surface of a substrate with a refractive index-matching medium to make the substrate "disappear" optically, not physically. This technique, which allowed them to see the different light spectra produced by the nanotubes, is detailed in another study published in Nano Letters.

The technique also allows quick, easy characterization of a large number of nanotubes, which could lead to ways of growing more uniform batches of nanotubes.

The paper's principal authors are former student Daniel Y. Joh; graduate student Lihong Herman; and Jesse Kinder, a postdoctoral research associate in Chan's lab. Park is a member of the Kavli Institute at Cornell for Nanoscale Science. Both the Nature Nanotechnology and Nano Letters work were supported by the Air Force Office of Scientific Research and the National Science Foundation through the Center for Nanoscale Systems, Cornell Center for Materials Research, Center for Molecular Interfacing and an NSF CAREER grant.

http://www.news.cornell.edu/stories/Dec10/ParkNanotubes.html

Platinum-coated nanoparticles could power fuel cell cars

Fuel cells may power the cars of the future, but it's not enough to just make them work -- they have to be affordable. Cornell researchers have developed a novel way to synthesize a fuel cell electrocatalytic material without breaking the bank.

The research, published online Nov. 24 in the Journal of the American Chemical Society, describes a simple method for making nanoparticles that drive the electrocatalytic reactions inside room-temperature fuel cells.

An illustration of the synthesis procedure of the core-shell nanoparticles and subsequent deposition of platinum.

Fuel cells convert chemical energy directly into electrical energy. They consist of an anode, which oxidizes the fuel (such as hydrogen), and a cathode, which reduces oxygen to water. A polymer membrane separates the electrodes. Fuel cell-powered cars in production today use pure platinum to catalyze the oxygen reduction reaction in the cathode side. While platinum is the most efficient catalyst available today for the oxygen reduction reaction, its activity is limited, and it is rare and expensive.

The Cornell researchers' nanoparticles offer an alternative to pure platinum at a fraction of the cost. They are made of a palladium and cobalt core and coated with a one-atom-thick layer of platinum. Palladium, though not as good a catalyst, has similar properties as platinum (it is in the same group on the Periodic Table of Elements; it has the same crystal structure; and it is similar in atomic size), but it costs one-third less and is 50 times more abundant on Earth.

Researchers led by Héctor D. Abruña, the E.M. Chamot Profesor of Chemistry and Chemical Biology, made the nanoparticles on a carbon substrate and made the palladium-cobalt core self-assemble -- cutting down on manufacturing costs. First author Deli Wang, a postdoctoral associate in Abruña's lab, designed the experiments and synthesized the nanoparticles.

Atomic resolution images of the palladium-cobalt nanoparticle, before platinum deposition.

David Muller, professor of applied and engineering physics and co-director of the Kavli Institute at Cornell for Nanoscale Science, led the efforts geared at imaging the particles down to atomic resolution to demonstrate their chemical composition and distribution, and to prove the efficacy of the catalytic conversions.

"The crystal structure of the substrate, composition and spatial distribution of the nanoparticles play important roles in determining how well the platinum performs," said Huolin Xin, a graduate student in Muller's lab.

The work was supported by the Energy Materials Center at Cornell, a Department of Energy-supported Energy Frontiers Research Center. Researchers also used equipment at the Cornell Center for Materials Research.

http://nanotechwire.com/news.asp?nid=11242

12/22/2010 4:08:51 PM
Ever-sharp urchin teeth may yield tools that never need honing

To survive in a tumultuous environment, sea urchins literally eat through stone, using their teeth to carve out nooks where the spiny creatures hide from predators and protect themselves from the crashing surf on the rocky shores and tide pools where they live.

The rock-boring behavior is astonishing, scientists agree, but what is truly remarkable is that, despite constant grinding and scraping on stone, urchin teeth never, ever get dull. The secret of their ever-sharp qualities has puzzled scientists for decades, but now a new report by scientists from the University of Wisconsin-Madison and their colleagues has peeled back the toothy mystery.

Writing today (Dec. 22, 2010) in the journal Advanced Functional Materials, a team led by UW-Madison professor of physics Pupa Gilbert describes the self-sharpening mechanism used by the California purple sea urchin to keep a razor-sharp edge on its choppers.

The urchin's self-sharpening trick, notes Gilbert, is something that could be mimicked by humans to make tools that never need honing.

"The sea urchin tooth is complicated in its design. It is one of the very few structures in nature that self-sharpen," says Gilbert, explaining that the sea urchin tooth, which is always growing, is a biomineral mosaic composed of calcite crystals with two forms — plates and fibers — arranged crosswise and cemented together with super-hard calcite nanocement. Between the crystals are layers of organic materials that are not as sturdy as the calcite crystals.

"The organic layers are the weak links in the chain," Gilbert explains. "There are breaking points at predetermined locations built into the teeth. It is a concept similar to perforated paper in the sense that the material breaks at these predetermined weak spots."

The crystalline nature of sea urchin dentition is, on the surface, different from other crystals found in nature. It lacks the obvious facets characteristic of familiar crystals, but at the very deepest levels the properties of crystals are evident in the orderly arrangement of the atoms that make up the biomineral mosaic teeth of the sea urchin.

To delve into the fundamental nature of the crystals that form sea urchin teeth, Gilbert and her colleagues used a variety of techniques from the materials scientist's toolbox. These include microscopy methods that depend on X-rays to illuminate how nanocrystals are arranged in teeth to make the sea urchins capable of grinding rock. Gilbert and her colleagues used these techniques to deduce how the crystals are organized and melded into a tough and durable biomineral.

Knowing the secret of the ever-sharp sea urchin tooth, says Gilbert, could one day have practical applications for human toolmakers. "Now that we know how it works, the knowledge could be used to develop methods to fabricate tools that could actually sharpen themselves with use," notes Gilbert. "The mechanism used by the urchin is the key. By shaping the object appropriately and using the same strategy the urchin employs, a tool with a self-sharpening edge could, in theory, be created."

The new research was supported by grants from the U.S. Department of Energy and the National Science Foundation. In addition to Gilbert, researchers from the University of California, Berkeley; Argonne National Laboratory; the Weizmann Institute of Science; and the Lawrence Berkeley National Laboratory contributed to the report.

http://www.news.wisc.edu/18804

12/9/2010 11:33:02 AM
Better batteries from the bottom up

Rice University researchers have moved a step closer to creating robust, three-dimensional microbatteries that would charge faster and hold other advantages over conventional lithium-ion batteries. They could power new generations of remote sensors, display screens, smart cards, flexible electronics and biomedical devices.

The batteries employ vertical arrays of nickel-tin nanowires perfectly encased in PMMA, a widely used polymer best known as Plexiglas. The Rice laboratory of Pulickel Ajayan found a way to reliably coat single nanowires with a smooth layer of a PMMA-based gel electrolyte that insulates the wires from the counter electrode while allowing ions to pass through.

The work was reported this week in the online edition of the journal Nano Letters.

"In a battery, you have two electrodes separated by a thick barrier," said Ajayan, professor in mechanical engineering and materials science and of chemistry. "The challenge is to bring everything into close proximity so this electrochemistry becomes much more efficient."

Ajayan and his team feel they've done that by growing forests of coated nanowires -- millions of them on a fingernail-sized chip -- for scalable microdevices with greater surface area than conventional thin-film batteries. "You can't simply scale the thickness of a thin-film battery, because the lithium ion kinetics would become sluggish," Ajayan said.

"We wanted to figure out how the proposed 3-D designs of batteries can be built from the nanoscale up," said Sanketh Gowda, a graduate student in Ajayan's lab. "By increasing the height of the nanowires, we can increase the amount of energy stored while keeping the lithium ion diffusion distance constant."

The researchers, led by Gowda and postdoctoral researcher Arava Leela Mohana Reddy, worked for more than a year to refine the process.

"To be fair, the 3-D concept has been around for a while," Reddy said. "The breakthrough here is the ability to put a conformal coat of PMMA on a nanowire over long distances. Even a small break in the coating would destroy it." He said the same approach is being tested on nanowire systems with higher capacities.

The process builds upon the lab's previous research to build coaxial nanowire cables that was reported in Nano Letters last year. In the new work, the researchers grew 10-micron-long nanowires via electrodeposition in the pores of an anodized alumina template. They then widened the pores with a simple chemical etching technique and drop-coated PMMA onto the array to give the nanowires an even casing from top to bottom. A chemical wash removed the template.

They have built one-centimeter square microbatteries that hold more energy and that charge faster than planar batteries of the same electrode length. "By going to 3-D, we're able to deliver more energy in the same footprint," Gowda said.

They feel the PMMA coating will increase the number of times a battery can be charged by stabilizing conditions between the nanowires and liquid electrolyte, which tend to break down over time.

The team is also studying how cycling affects nanowires that, like silicon electrodes, expand and contract as lithium ions come and go. Electron microscope images of nanowires taken after many charge/discharge cycles showed no breaks in the PMMA casing -- not even pinholes. This led the researchers to believe the coating withstands the volume expansion in the electrode, which could increase the batteries' lifespans.

Co-authors are Rice graduate student Xiaobo Zhan; former Rice postdoctoral researcher Manikoth Shaijumon, now an assistant professor at the Indian Institute of Science Education and Research, Thiruvananthapuram, India; and former Rice research scientist Lijie Ci, now a senior research and development manager at Samsung Cheil Industries.

The Hartley Family Foundation and Rice University funded the research.

Read the abstract at http://pubs.acs.org/doi/abs/10.1021/nl102919m

nanotechwire.com      1/21/2011 5:09:06 PM
Butterfly wings behind anti-counterfeiting technology

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The Secret of Bright Butterfly Wings: LED Technology

By Ker Than, LiveScience Staff Writer

posted: 17 November 2005 02:01 pm ET

Optical image showing magnified colored wing scales of Papilio nireus. credit: Peter Vukusic/University of Exeter

Optical image showing magnified colored wing scales of Papilio nireus. credit: Peter Vukusic/University of Exeter

Peter Vukusic with butterflies that use photonic nanostructures. credit: Peter Vukusic/University of Exeter

Image of colored banding on the dorsal wing surfaces of Papilio hornimani. credit: Peter Vukusic/University of Exeter

Science was way behind nature in developing LED light technology, a new study finds.

The beautifully colored wings of African swallowtail butterflies manipulate light using engineering tricks similar to those found in digital displays. The butterflies have black wings with bright patches of green and blue, which they use to communicate across long distances. Microscopic scales covering the wings absorb ultraviolet light and then re-emit it.

The re-emitted light interacts with fluorescent pigments found on the butterflies’ wings to produce the vibrant green-blue color.

Like LEDs

Researchers investigating how the scales work found that they have many similarities to digital devices known as light emitting diodes, also known as LEDs, which are found in everything from computer and television screens to traffic lights.

The first LEDs invented in the late 1960s weren’t very bright. They produced a lot of light but most of it tended to either become trapped inside the device or to spread sideways and become diluted.

In the early 1990s, engineers came up with ways to get around these problems. They outfitted LEDs with tiny mirrors that could reflect and channel the light and made microscopic holes in them to help the light escape.

Behind the butterflies

While studying the wings of swallowtail butterflies, researchers discovered that there were a lot of similarities between the scale coverings and LEDs.

The scales that cover the butterflies’ wings contain tiny structures called “photonic crystals,” which act very much like the microholes found in LEDs.

“[The scales] prevent the fluorescent light from being trapped inside the scales and from being emitted sideways,” said Pete Vukusic of Exeter University, a researcher in the study.

The scales on the wing also have a specialized mirror underneath them, which act very much like the tiny mirrors found in LEDs.

The mirror reflects all the scattered fluorescent light it receives upward, giving the butterflies control over the direction in which in the light is emitted.

The study was reported in the Nov. 18 issue of the journal Science.