Pereira, Colombia
Pereira, Colombia

Time filter

Source Type

News Article | January 26, 2016
Site: www.cemag.us

A thin coating of graphene nanoribbons in epoxy developed at Rice University has proven effective at melting ice on a helicopter blade. The coating by the Rice lab of chemist James Tour may be an effective real-time de-icer for aircraft, wind turbines, transmission lines, and other surfaces exposed to winter weather, according to a new paper in the American Chemical Society journal ACS Applied Materials and Interfaces. In tests, the lab melted centimeter-thick ice from a static helicopter rotor blade in a minus-4-degree Fahrenheit environment. When a small voltage was applied, the coating delivered electrothermal heat — called Joule heating — to the surface, which melted the ice. The nanoribbons produced commercially by unzipping nanotubes, a process also invented at Rice, are highly conductive. Rather than trying to produce large sheets of expensive graphene, the lab determined years ago that nanoribbons in composites would interconnect and conduct electricity across the material with much lower loadings than traditionally needed. Previous experiments showed how the nanoribbons in films could be used to de-ice radar domes and even glass, since the films can be transparent to the eye. “Applying this composite to wings could save time and money at airports where the glycol-based chemicals now used to de-ice aircraft are also an environmental concern,” Tour says. In Rice’s lab tests, nanoribbons were no more than 5 percent of the composite. The researchers led by Rice graduate student Abdul-Rahman Raji spread a thin coat of the composite on a segment of rotor blade supplied by a helicopter manufacturer; they then replaced the thermally conductive nickel abrasion sleeve used as a leading edge on rotor blades. They were able to heat the composite to more than 200 degrees Fahrenheit. For wings or blades in motion, the thin layer of water that forms first between the heated composite and the surface should be enough to loosen ice and allow it to fall off without having to melt completely, Tour says. The lab reported that the composite remained robust in temperatures up to nearly 600 degrees Fahrenheit. As a bonus, Tour says, the coating may also help protect aircraft from lightning strikes and provide an extra layer of electromagnetic shielding. Co-authors of the paper are Rice undergraduates Tanvi Varadhachary and Kewang Nan, graduate student Tuo Wang, postdoctoral researchers Jian Lin and Yongsung Ji, alumni Yu Zhu of the University of Akron and Bostjan Genorio of the University of Ljubljana, Slovenia, and research scientist Carter Kittrell. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering. The Air Force Office of Scientific Research and Carson Helicopter supported the research.


News Article | February 15, 2017
Site: www.eurekalert.org

A chunk of conductive graphene foam reinforced by carbon nanotubes can support more than 3,000 times its own weight and easily bounce back to its original height, according to Rice University scientists. Better yet, it can be made in just about any shape and size, they reported, demonstrating a screw-shaped piece of the highly conductive foam. The Rice lab of chemist James Tour tested its new "rebar graphene" as a highly porous, conductive electrode in lithium ion capacitors and found it to be mechanically and chemically stable. The research appears in the American Chemical Society journal ACS Applied Materials and Interfaces. Carbon in the form of atom-thin graphene is among the strongest materials known and is highly conductive; multiwalled carbon nanotubes are widely used as conductive reinforcements in metals, polymers and carbon matrix composites. The Tour lab had already used nanotubes to reinforce two-dimensional sheets of graphene. Extending the concept to macroscale materials made sense, Tour said. "We developed graphene foam, but it wasn't tough enough for the kind of applications we had in mind, so using carbon nanotubes to reinforce it was a natural next step," Tour said. The three-dimensional structures were created from a powdered nickel catalyst, surfactant-wrapped multiwall nanotubes and sugar as a carbon source. The materials were mixed and the water evaporated; the resulting pellets were pressed into a steel die and then heated in a chemical vapor deposition furnace, which turned the available carbon into graphene. After further processing to remove remnants of nickel, the result was an all-carbon foam in the shape of the die, in this case a screw. Tour said the method will be easy to scale up. Electron microscope images of the foam showed partially unzipped outer layers of the nanotubes had bonded to the graphene, which accounted for its strength and resilience. Graphene foam produced without the rebar could support only about 150 times its own weight while retaining the ability to rapidly return to its full height. But rebar graphene irreversibly deformed by about 25 percent when loaded with more than 8,500 times its weight. Junwei Sha, a visiting graduate student at Rice and a graduate student at Tianjin University, China, is lead author of the paper. Co-authors from Rice are postdoctoral researchers Rodrigo Salvatierra, Pei Dong and Yongsung Ji; graduate students Yilun Li, Tuo Wang, Chenhao Zhang and Jibo Zhang; former postdoctoral researcher Seoung-Ki Lee; Pulickel Ajayan, chair of the Department of Materials Science and NanoEngineering, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of chemistry; and Jun Lou, a professor of materials science and nanoengineering. Naiqin Zhao, a professor at Tianjin University and a researcher at the Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, is also a co-author. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice. The Air Force Office of Scientific Research and its Multidisciplinary University Research Initiative supported the research. This news release can be found online at http://news. A piece of rebar graphene stands up to a good soaking in a test at Rice University. (Credit: Tour Group/Rice University) Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for happiest students and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl. .


News Article | November 28, 2016
Site: www.eurekalert.org

A peacock's bright teal and brilliant blue feathers are not the result of pigments but rather nanoscale networks that reflect specific wavelengths of light. This so-called structural coloration has long interested researchers and engineers because of its durability and potential for application in solar arrays, biomimetic tissues and adaptive camouflage. But today's techniques to integrate structural color into materials are time-consuming and costly. Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), in collaboration with King Abdullah University of Science and Technology, have developed a new, more robust and cost effective system to build large-scale metamaterials with structural color. The research is described in the journal Nature Light: Science and Applications. A peacock's feather or butterfly's wing rely on photonic crystals or highly ordered arrays of nanofibers to produce colors. Reproducing those structures in a lab requires precision and expensive fabrication. SEAS researchers were inspired by a very different kind of feather. Contingas are one of the most flamboyant bird families on the planet. In a sea of Amazon green, their feathers pop with electric blues, bright oranges and vibrant purples. Unlike a peacock's ordered array of nanostructures, contingas get their vibrant hues from a disordered and porous nanonetwork of keratin that looks like a sponge or piece of coral. When light strikes the feather, the porous keratin pattern causes red and yellow wavelengths to cancel each other out, while blue wavelengths of light amplify one another. "Usually, we associate the idea of disorder with the notion that something is uncontrollable," said Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS and senior of author of the paper. "Here disorder can be put to our advantage and used as a design parameter to create a new class of metamaterials with a wide range of funcitionalities and applications." Inspired by the cotinga feather, the researchers used a simple etching process to create a complex but random porous nanonetwork in a metallic alloy. The structure was then coated with an ultra-thin transparent alumina layer. You may be thinking, what kinds of colors can a metallic alloy produce other than gray? As it turns out, lots. Ever since 19th century English scientist Michael Faraday, scientists have known that metals contain a plethora of colors but light doesn't penetrate deep enough to reveal them. A gold particle, for example, depending on its size and shape, can be red, pink or even blue. The porous nanostructure creates localized hotspots of different colors in the alloy. The color that is reflected by the localized states depends on the thickness of the transparent coating. With no alumina overlayer the material looks dark . With a coating 33-nanometers thick, the material reflects blue light. At 45 nanometers, the material turns red and with a coating 53 nanometers thick, the material is yellow. By changing the thickness of the coating, the researchers could create a gradient of colors. "This situation is equivalent to a material with an extremely large number of microscopic and colorful sources of light," said Andrea Fratalocchi, corresponding author of the paper and Professor of Electrical Engineering; Applied Mathematics and Computational Science at the King Abdullah University of Science and Technology. "The presence of a thin layer of oxide can control the intensity of these sources, collectively switching them on and off according to the thickness of the oxide layer. This research shows of how disordered materials can be turned into an extremely powerful technology, which can enable large scale applications that would be impossible with conventional media." The metasurface is extremely lightweight and scratch-proof and could be used in large-scale commercial applications such as lightweight coatings for the automotive sector, biomimetic tissues and camouflage. "This is a completely new way to control optical responses in metamaterials," said Henning Galinski, co-first author of the paper and former postdoctoral fellow in the Capasso group. "We now have a way to engineer metamaterials in very small regions, which previously were too small for conventional lithography. This system paves the way for large-scale and extremely robust metamaterials that interact with light in really interesting ways." This research is supported by the Airforce Office of Scientific Research.


News Article | November 8, 2016
Site: www.chromatographytechniques.com

This Veterans Day we remember that nearly 75 years ago dozens of American academic, commercial, nonprofit, and governmental institutions – including FDA – joined together in a race to provide a promising but complex and unstable medicine to troops fighting in World War II — penicillin. Knowing that infection is the major killer in wars, not battle injuries, their goal was to help turn a British discovery into a crucial wartime medical contribution and what would become an indispensable therapeutic agent long after that conflict ended. Many people are familiar with the story of Alexander Fleming’s 1928 discovery of a   mold that had contaminated — and surprisingly destroyed — his cultures of pathogenic organisms. Though Fleming and several others in the next decade studied the mold filtrate, known as penicillin, it was Howard Florey and his colleagues at Oxford who uncovered the drug’s chemotherapeutic potential. Their work began with studies in mice in May 1940 and transitioned to a handful of clinical cases nine months later. However, the drug was difficult to purify. Also, it presented an immense challenge to produce in sufficient quantities for study, and with Britain under siege firms there were too involved in other aspects of the war effort to offer much assistance. So Florey and a colleague came to the U. S. in the summer of 1941 for help. Among the first sites they visited was the Department of Agriculture’s Northern Regional Research Laboratory (NRRL) in Illinois, which had extensive experience in fermentation work, and from there they contacted several drug and chemical companies to drum up support.  Americans quickly combined forces to tackle the challenge. The federal Office of Scientific Research and Development (OSRD), the federal entity that organized and facilitated investigations to support the war effort, arranged to act as a clearing-house for the latest research on chemical and other studies of penicillin, exchanging data with dozens of organizations in the U.S. and Britain. NRRL developed several production modifications that increased the yield of penicillin by 100 fold. FDA’s first experience with the potential wonder drug was around September 1942, when the NRRL Director approached FDA about testing the antibacterial effectiveness of a small quantity of penicillin. A year later, enough of the drug had been produced to confirm in 200 patients what the early results at Oxford had suggested, and penicillin was ready to enter the war. First, however, OSRD asked that FDA certify every lot produced by the half-dozen or so manufacturers, a task the agency also performed for insulin under statutory authority that began in 1941. Six FDA technicians certified samples for potency, absence of fever-producing contaminants, toxicity, sterility, and optimum moisture, which can affect the drug’s stability. So scarce was penicillin that companies always reconditioned the occasional rejected lot rather than destroying it. By the end of the war, some of the participating firms had increased purity of the drug from the Oxford group’s one percent to about 85 percent. Penicillin was not only more potent, it was also more abundant, its production having increased by a factor of 500 from 1943 to 1945. In fact, by 1945 the output of penicillin, formerly under severe restriction outside of military and scientific use, was now available for most civilian needs as well. In a few years the cost of producing penicillin had decreased so much that the glass used to store ampules of the drug cost more than the drug itself. FDA’s wartime work was codified in the Penicillin Amendment of 1945, which mandated FDA’s certification of penicillin and, through subsequent laws, most other antibiotics — a responsibility that continued for nearly four decades, when the need for government testing no longer existed based on industry’s record of production. But it all started with an international effort to provide a lifesaving drug to the armed forces, bringing together all sorts of scientific and medical institutions, including FDA. Like so many others participating in this collaboration on a scale unseen up to that point, FDA played a small but critical role to support our troops at this time of global crisis.


News Article
Site: www.asminternational.org

Jolting a super-stretchy, self-healing material with an electrical field causes it to twitch or pulse in a muscle-like fashion. The polymer can also stretch to 100 times its original length, and even repair itself if punctured. Cheng-Hui Li, working in the Stanford University, Calif, lab of chemical engineering professor Zhenan Bao, wanted to test the stretchiness of a rubberlike type of plastic known as an elastomer that he had just synthesized. Such materials can normally be stretched two or three times their original length and spring back to original size. One common stress test involves stretching an elastomer beyond this point until it snaps. But Li, a visiting scholar from China, hit a snag: The clamping machine typically used to measure elasticity could only stretch about 45 in. To find the breaking point of their 1-in. sample, Li and another lab member had to hold opposing ends in their hands, standing further and further apart, eventually stretching a 1-in. polymer film to more than 100 in. Bao was stunned. "I said, ‘How can that be possible? Are you sure?'" she recalls. Artificial muscles currently have applications in some consumer technology and robotics, but they have shortcomings compared to a real bicep, Bao says. Small holes or defects in the materials currently used to make artificial muscle can rob them of their resilience. Nor are they able to self-repair if punctured or scratched. But this new material, in addition to being extraordinarily stretchy, has remarkable self-healing characteristics. Damaged polymers typically require a solvent or heat treatment to restore their properties, but the new material showed a remarkable ability to heal itself at room temperature, even if the damaged pieces are aged for days. Indeed, researchers found that it could self-repair at temperatures as low as negative 4°F (-20°C), or about as cold as a commercial walk-in freezer. The team attributes the extreme stretching and self-healing ability of their new material to some critical improvements to a type of chemical bonding process known as crosslinking. This process, which involves connecting linear chains of linked molecules in a sort of fishnet pattern, has previously yielded a tenfold stretch in polymers. First they designed special organic molecules to attach to the short polymer strands in their crosslink to create a series of structure called ligands. These ligands joined together to form longer polymer chains—spring-like coils with inherent stretchiness. Then they added to the material metal ions, which have a chemical affinity for the ligands. When this combined material is strained, the knots loosen and allow the ligands to separate. But when relaxed, the affinity between the metal ions and the ligands pulls the fishnet taut. The result is a strong, stretchable and self-repairing elastomer. "Basically the polymers become linked together like a big net through the metal ions and the ligands," Bao explains. "Each metal ion binds to at least two ligands, so if one ligand breaks away on one side, the metal ion may still be connected to a ligand on the other side. And when the stress is released, the ion can readily reconnect with another ligand if it is close enough." The team found that they could tune the polymer to be stretchier or heal faster by varying the amount or type of metal ion included. The version that exceeded the measuring machine's limits, for example, was created by decreasing the ratio of iron atoms to the polymers and organic molecules in the material. Researchers also showed that this new polymer with the metal additives would twitch in response to an electric field. They have to do more work to increase the degree to which the material expands and contracts and control it more precisely. But this observation opens the door to promising applications. In addition to its long-term potential for use as artificial muscle, this research dovetails with Bao's efforts to create artificial skin that might be used to restore some sensory capabilities to people with prosthetic limbs. In previous studies her team has created flexible but fragile polymers, studded with pressure sensors to detect the difference between a handshake and a butterfly landing. This new, durable material could form part of the physical structure of a fully developed artificial skin. "Artificial skin is not just made of one material," says Franziska Lissel, a postdoctoral fellow in Bao's lab and member of the research team. "We want to create a very complex system." Even before artificial muscle and artificial skin become practical, this work in the development of strong, flexible, electronically active polymers could spawn a new generation of wearable electronics, or medical implants that would last a long time without being repaired or replaced. The Air Force Office of Scientific Research, Samsung Electronics, and the Major State Basic Research Development Program of China supported the work at Stanford. Other members of the research team are from University of California, Riverside and University of Colorado, Boulder.


Home > Press > Graphene foam gets big and tough: Rice University's nanotube-reinforced material can be shaped, is highly conductive Abstract: A chunk of conductive graphene foam reinforced by carbon nanotubes can support more than 3,000 times its own weight and easily bounce back to its original height, according to Rice University scientists. Better yet, it can be made in just about any shape and size, they reported, demonstrating a screw-shaped piece of the highly conductive foam. The Rice lab of chemist James Tour tested its new "rebar graphene" as a highly porous, conductive electrode in lithium ion capacitors and found it to be mechanically and chemically stable. The research appears in the American Chemical Society journal ACS Applied Materials and Interfaces. Carbon in the form of atom-thin graphene is among the strongest materials known and is highly conductive; multiwalled carbon nanotubes are widely used as conductive reinforcements in metals, polymers and carbon matrix composites. The Tour lab had already used nanotubes to reinforce two-dimensional sheets of graphene. Extending the concept to macroscale materials made sense, Tour said. "We developed graphene foam, but it wasn't tough enough for the kind of applications we had in mind, so using carbon nanotubes to reinforce it was a natural next step," Tour said. The three-dimensional structures were created from a powdered nickel catalyst, surfactant-wrapped multiwall nanotubes and sugar as a carbon source. The materials were mixed and the water evaporated; the resulting pellets were pressed into a steel die and then heated in a chemical vapor deposition furnace, which turned the available carbon into graphene. After further processing to remove remnants of nickel, the result was an all-carbon foam in the shape of the die, in this case a screw. Tour said the method will be easy to scale up. Electron microscope images of the foam showed partially unzipped outer layers of the nanotubes had bonded to the graphene, which accounted for its strength and resilience. Graphene foam produced without the rebar could support only about 150 times its own weight while retaining the ability to rapidly return to its full height. But rebar graphene irreversibly deformed by about 25 percent when loaded with more than 8,500 times its weight. Junwei Sha, a visiting graduate student at Rice and a graduate student at Tianjin University, China, is lead author of the paper. Co-authors from Rice are postdoctoral researchers Rodrigo Salvatierra, Pei Dong and Yongsung Ji; graduate students Yilun Li, Tuo Wang, Chenhao Zhang and Jibo Zhang; former postdoctoral researcher Seoung-Ki Lee; Pulickel Ajayan, chair of the Department of Materials Science and NanoEngineering, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of chemistry; and Jun Lou, a professor of materials science and nanoengineering. Naiqin Zhao, a professor at Tianjin University and a researcher at the Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, is also a co-author. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice. The Air Force Office of Scientific Research and its Multidisciplinary University Research Initiative supported the research. About Rice University Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation’s top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice’s undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for happiest students and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger’s Personal Finance. To read “What they’re saying about Rice,” go to http://tinyurl.com/RiceUniversityoverview . Follow Rice News and Media Relations via Twitter @RiceUNews For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article | February 23, 2017
Site: www.cemag.us

Beetles wear a body armor that should weigh them down — think medieval knights and turtles. In fact, those hard shells protecting delicate wings are surprisingly light, allowing even flight. Better understanding the structure and properties of beetle exoskeletons could help scientists engineer lighter, stronger materials. Such materials could, for example, reduce gas-guzzling drag in vehicles and airplanes and reduce the weight of armor, lightening the load for the 21st-century knight. But revealing exoskeleton architecture at the nanoscale has proven difficult. Nebraska's Ruiguo Yang, assistant professor of mechanical and materials engineering, and his colleagues found a way to analyze the fibrous nanostructure. Their findings were featured recently on the cover of Advanced Functional Materials. The lightweight exoskeleton is composed of chitin fibers just around 20 nanometers in diameter (a human hair measures approximately 75,000 nanometers in diameter) and packed and piled into layers that twist in a spiral, like a spiral staircase. The small diameter and helical twisting, known as Bouligand, make the structure difficult to analyze. Yang and his team developed a method of slicing down the spiral to reveal a surface of cross-sections of fibers at different orientations. From that viewpoint, the researchers were able to analyze the fibers' mechanical properties with the aid of an atomic force microscope. This type of microscope applies a tiny force to a test sample, deforms the sample and monitors the sample’s response. Combining the experimental procedure and theoretical analysis, the researchers were able to reveal the nanoscale architecture of the exoskeleton and the material properties of the nanofibers. They made their discoveries in the common figeater beetle, Cotinis mutabilis, a metallic green native of the western United States. But the technique can be used on other beetles and hard-shelled creatures and might also extend to artificial materials with fibrous structures, Yang says. Comparing beetles with differing demands on their exoskeletons, such as defending against predators or environmental damage, could lead to evolutionary insights as well as a better understanding of the relationship between structural features and their properties. Yang’s co-authors are Alireza Zaheri and Horacio Espinosa of Northwestern University; Wei Gao of the University of Texas at San Antonio; and Cheryl Hayashi of the University of California, Riverside. The Air Force Office of Scientific Research’s Multidisciplinary University Research Initiative funded this research.


News Article | February 22, 2017
Site: www.eurekalert.org

Beetles wear a body armor that should weigh them down -- think medieval knights and turtles. In fact, those hard shells protecting delicate wings are surprisingly light, allowing even flight. Better understanding the structure and properties of beetle exoskeletons could help scientists engineer lighter, stronger materials. Such materials could, for example, reduce gas-guzzling drag in vehicles and airplanes and reduce the weight of armor, lightening the load for the 21st-century knight. But revealing exoskeleton architecture at the nanoscale has proven difficult. Nebraska's Ruiguo Yang, assistant professor of mechanical and materials engineering, and his colleagues found a way to analyze the fibrous nanostructure. Their findings were featured recently on the cover of Advanced Functional Materials. The lightweight exoskeleton is composed of chitin fibers just around 20 nanometers in diameter (a human hair measures approximately 75,000 nanometers in diameter) and packed and piled into layers that twist in a spiral, like a spiral staircase. The small diameter and helical twisting, known as Bouligand, make the structure difficult to analyze. Yang and his team developed a method of slicing down the spiral to reveal a surface of cross-sections of fibers at different orientations. From that viewpoint, the researchers were able to analyze the fibers' mechanical properties with the aid of an atomic force microscope. This type of microscope applies a tiny force to a test sample, deforms the sample and monitors the sample's response. Combining the experimental procedure and theoretical analysis, the researchers were able to reveal the nanoscale architecture of the exoskeleton and the material properties of the nanofibers. They made their discoveries in the common figeater beetle, Cotinis mutabilis, a metallic green native of the western United States. But the technique can be used on other beetles and hard-shelled creatures and might also extend to artificial materials with fibrous structures, Yang said. Comparing beetles with differing demands on their exoskeletons, such as defending against predators or environmental damage, could lead to evolutionary insights as well as a better understanding of the relationship between structural features and their properties. Yang's co-authors are Alireza Zaheri and Horacio Espinosa of Northwestern University; Wei Gao of the University of Texas at San Antonio; and Cheryl Hayashi of the University of California, Riverside. The Air Force Office of Scientific Research's Multidisciplinary University Research Initiative funded this research.


News Article | October 26, 2016
Site: www.eurekalert.org

When it comes to making chemical bonds, some elements go together like peanut butter and jelly; but for others, it's more like oil and water. Scientists can combat this elemental antipathy using extreme pressures. And now in ACS Central Science, researchers report that they have used pressure equivalent to that within the core of Mars to forge the first-ever iron-bismuth bond, which could help them make brand-new magnetic and superconducting materials. For most reactions, the first step is to mix the "ingredients" evenly, which is unbelievably difficult to do with iron and bismuth. Even at nearly 3,000 degrees Fahrenheit -- a temperature hot enough to melt both metals -- only 0.16 percent of the bismuth will dissolve into the molten iron. Danna Freedman and colleagues proposed using very high pressure to make the two elements more amenable to bonding. At pressures around 30 GPa, the researchers observed evidence of a new substance: FeBi2. They found they could lower the pressure to 3GPa and still maintain the material, although back at earth's atmospheric pressure (nearly 30,000 times lower) the compound returns to its constituent parts. Freedman notes that her group is currently working on approaches to scale up the synthesis to allow them to further investigate whether this unique compound is superconductive and magnetic, as they predict it could be and find ways to make it stable. The authors acknowledge funding from the Defense Advanced Research Projects Agency, The Air Force Office of Scientific Research, the National Science Foundation and the Department of Energy. The paper will be freely available on October 26, 2016, at this link: http://pubs. A video on this research is available at http://mrsec. . It is the video titled "Why do rare earth magnets need to be replaced?" The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With nearly 157,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio. To automatically receive news releases from the American Chemical Society, contact newsroom@acs.org.


News Article | March 10, 2016
Site: www.cemag.us

Light and electrons interact in a complex dance within fiber optic devices. A new study by University of Illinois engineers found that in the transistor laser, a device for next-generation high-speed computing, the light and electrons spur one another on to faster switching speeds than any devices available. Milton Feng, the Nick Holonyak Jr. Emeritus Chair in electrical and computer engineering, found the speed-stimulating effects with graduate students Junyi Qiu and Curtis Wang and Holonyak, the Bardeen Emeritus Chair in electrical and computer engineering and physics. The team published its results in the Journal of Applied Physics. As big data become bigger and cloud computing becomes more commonplace, the infrastructure for transferring the ever-increasing amounts of data needs to speed up, Feng says. Traditional technologies used for fiber optic cables and high-speed data transmission, such as diode lasers, are reaching the upper end of their switching speeds, Feng says. “You can compute all you want in a data center. However, you need to take that data in and out of the system for the user to use,” Feng says. “You need to transfer the information for it to be useful, and that goes through these fiber optic interconnects. But there is a fundamental switching limitation of the diode laser used. This technology, the transistor laser, is the next-generation technology, and could be a hundred times faster.” Diode lasers have two ports: an electrical input and a light output. By contrast, the transistor laser has three ports: an electrical input, and both electrical and light outputs. The three-port design allows the researchers to harness the intricate physics between electrons and light. For example, the fastest way for current to switch in a semiconductor material is for the electrons to jump between bands in the material in a process called tunneling. Light photons help shuttle the electrons across, a process called photon-assisted tunneling, making the device much faster. In the latest study, Feng’s group found that not only does photon-assisted tunneling occur in the transistor laser, but that it in turn stimulates the photon absorption process within the laser cavity, making the optical switching in the device even faster and allowing for ultra-high-speed signal modulation. “The collector can absorb the photon from the laser for very quick tunneling, so that becomes a direct-voltage-modulation scheme, much faster than using current modulation,” Feng says. “We also proved that the stimulated photon-assisted tunneling process is much faster than regular photon-assisted tunneling. Previous engineers could not find this because they did not have the transistor laser. With just a diode laser, you cannot discover this. “This is not only proving the scientific point, but it’s very useful for high-speed device modulation. We can directly modulate the laser into the femtosecond range. That allows a tremendous amount of energy-efficient data transfer,” Feng says. The researchers plan to continue to develop the transistor laser and explore its unique physics while also forming industry partnerships to commercialize the technology for energy-efficient big data transfer. The Air Force Office of Scientific Research supported this work. Feng also is associated with the Micro and Nano Technology Laboratory and the Coordinated Science Laboratory at the U. of I.

Loading Office of Scientific Research collaborators
Loading Office of Scientific Research collaborators