Other materials stories that may be of interestPublished on May 21st, 2013 | By: Eileen De Guire
Topological insulators (TIs) are an exciting new type of material that on their surface carry electric current, but within their bulk, act as insulators. Since the discovery of TIs about a decade ago, their unique characteristics (which point to potential applications in quantum computing) have been explored theoretically, and in the last five years, experimentally. But where in theory, the bulk of TIs carry no current, in the laboratory, impurities and disorder in real materials mean that the bulk is, in fact, conductive. This has proven an obstacle to experimentation with TIs: findings from prior experiments designed to test the surface conductivity of TIs unavoidably included contributions from the surplus of electrons in the bulk. Now an interdisciplinary research team at the University of Illinois at Urbana-Champaign, in collaboration with researchers at Brookhaven National Laboratory’s Condensed Matter Physics and Materials Science Department, has measured superconductive surface states in TIs where the bulk charge carriers were successfully depleted. To deplete the electrons in the bulk, the team used three strategies: the TI material was doped with antimony, then it was doped at the surface with a chemical with strong electron affinity, and finally an electrostatic gate was used to apply voltage that lowered the energy of the entire system.
The University of Dayton Research Institute will benefit from the first round of applied research and development project awards the National Additive Manufacturing Innovation Institute announced in a few weeks ago. Rapid Prototype + Manufacturing LLC of Avon Lake, Ohio, was awarded $1 million for “Maturation of Fused Deposition Modeling Component Manufacturing,” and will contract with UD’s Research Institute for $575,000 for technology support and education. Other partners in the program, designed to resolve issues that have inhibited the transition to manufacturing of Fused Deposition Modeling, a popular thermoplastic-based additive process, include Stratasys of Eden Prairie, Minn., as well as aerospace companies Boeing, GE Aviation, Lockheed Martin and Northrop Grumman. “This program allows us to pool resources and leverage highly developed composites industry design practices to mature FDM manufacturing for aerospace and defense applications,” says Brian Rice, head of the Research Institute’s Multi-Scale Composites and Polymers Division. “UDRI’s role will be to analyze material properties and define how to design and certify parts manufactured for aerospace applications.” In July 2012, UDRI received $3 million from the Ohio Third Frontier to work with Stratasys, RP+M and additional partners to develop aircraft-engine components through additive manufacturing —also known as 3D printing—for several aerospace manufacturers.
Eliminating the defects at the interface separating two crystals, or grains, has been shown by nanotechnology experts to be a powerful strategy for making materials stronger, more easily molded, and less electrically resistant-or a host of other qualities sought by designers and manufacturers. Since 2004, when a seminal paper came out in Science, materials scientists have been excited about one special of arrangement of atoms in metals and other materials called a “coherent twin boundary” or CTB. Based on theory and experiment, these coherent twin boundaries are often described as “perfect,” appearing like a perfectly flat, one-atom-thick plane in computer models and electron microscope images. But new research now shows that coherent twin boundaries are not so perfect after all. A team of scientists at the University of Vermont’s College of Engineering and Mathematical Sciences and the Lawrence Livermore National Laboratory and elsewhere report that coherent twin boundaries found in copper “are inherently defective.” With a high-resolution electron microscope, using a more powerful technique than has ever been used to examine these boundaries, they found tiny kink-like steps and curvatures in what had previously been observed as perfect. Even more surprising, these kinks and other defects appear to be the cause of the coherent twin boundary’s strength and other desirable qualities. “Everything we have learned on these materials in the past 10 years will have to be revisited with this new information,” says UVM engineer Frederic Sansoz.
The DOE’s Fuel Cell Technologies Office has issued a request for information seeking feedback from interested stakeholders regarding the use of rotating disk electrode (RDE) experiments and best practices for experimental conditions for characterization of the activity and durability of proton exchange membrane fuel cell oxygen reduction reaction (ORR) electrocatalysts. A review of recent literature shows that the determination of the ORR activity has numerous intricacies that have not been systemically cataloged, resulting in values for the activity of Pt/C that vary significantly. Next steps will be to establish standard procedures and measurement parameters for the RDE technique so that novel catalysts can be benchmarked for ORR activity versus an accepted Pt/C baseline for polymer electrolyte fuel cell applications. DOE is specifically interested in information on best practices/protocols to enable consistency in procedures and less variability in results from different laboratories.
In a process comparable to squeezing an elephant through a pinhole, researchers at Missouri University of Science and Technology have designed a way to engineer atoms capable of funneling light through ultra-small channels. Their research is the latest in a series of recent findings related to how light and matter interact at the atomic scale, and it is the first to demonstrate that the material—a specially designed “meta-atom” of gold and silicon oxide—can transmit light through a wide bandwidth and at a speed approaching infinity. The meta-atoms’ broadband capability could lead to advances in optical devices, which currently rely on a single frequency to transmit light, the researchers say. “These meta-atoms can be integrated as building blocks for unconventional optical components with exotic electromagnetic properties over a wide frequency range,” write Jie Gao and Xiaodong Yang, assistant professors of mechanical engineering at Missouri S&T, and Lei Sun, a visiting scholar at the university. The researchers created mathematical models of the meta-atom, a material 100 nanometers wide and 25 nanometers tall that combined gold and silicon oxide in stairstep fashion. In their simulations, the researchers stacked 10 of the meta-atoms, then shot light through them at various frequencies. They found that when light encountered the material in a range between 540 terahertz and 590 terahertz, it “stretched” into a nearly straight line and achieved an “effective permittivity” known as epsilon-near-zero. Effective permittivity refers to the ratio of light’s speed through air to its speed as it passes through a material. As light passes through the engineered meta-atoms described by Gao and Yang, however, its effective permittivity reaches a near-zero ratio. In other words, through the medium of these specially designed materials, light actually travels faster than the speed of light. It travels “infinitely fast” through this medium, Yang says.
Acting Secretary of Energy Daniel Poneman announced that DOE is awarding 88 grants to small businesses in 28 states to develop clean energy technologies with a strong potential for commercialization and job creation. These awards, totaling over $16 million in investments, will help small businesses with promising ideas that could improve manufacturing processes, boost the efficiency of buildings, reduce reliance on foreign oil, and generate electricity from renewable sources. Companies competing for these grants were encouraged to propose outside-the-box innovations to meet ambitious cost and performance targets. The small businesses receiving the awards are located in 28 states: Alabama, Arizona, Arkansas, California, Colorado, Delaware, Florida, Georgia, Illinois, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Missouri, Montana, Nevada, New Hampshire, New Jersey, New Mexico, New York, Ohio, Pennsylvania, Tennessee, Texas, Utah, Virginia, and Washington. Companies competing for these grants were encouraged to propose outside-the-box innovations to meet ambitious cost and performance targets. The selections are for Phase I and Fast Track (combined Phase I and II) work. That means that the new projects will go toward exploring the feasibility of innovative concepts that could be developed into prototype technologies. Seventy-nine awards will go to SBIR projects, and another nine will go to STTR projects.
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