Institute of Materials Science

Agía Paraskeví, Greece

Institute of Materials Science

Agía Paraskeví, Greece
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News Article | July 17, 2017
Site: phys.org

"Stabilizing nanocrystals at elevated temperatures is a common challenge," says Peiman Shahbeigi-Roodposhti, a postdoctoral research scholar with UConn's Institute of Materials Science and the study's lead author. "In certain alloys, we found that high levels of oxygen can lead to a significant reduction in their efficiency." Using a special milling process in an enclosed glove box filled with argon gas, UConn scientists, working in collaboration with researchers from North Carolina State University, were able to synthesize nano-sized crystals of Iron-Chromium and Iron-Chromium-Hafnium with oxygen levels as low as 0.01 percent. These nearly oxygen-free alloy powders appeared to be much more stable than their commercial counterparts with higher oxygen content at elevated temperatures and under high levels of stress. "In this study, for the first time, optimum oxygen-free nanomaterials were developed," says Sina Shahbazmohamadi, an assistant professor of biomedical engineering at UConn and a co-author on the paper. "Various characterization techniques, including advanced aberration corrected transmission electron microscopy, revealed a significant improvement in grain size stability at elevated temperatures." Grain size stability is important for scientists seeking to develop the next generation of advanced materials. Like fine links in an intricately woven mesh, grains are the small solids from which metals are made. Studies have shown that smaller grains are better when it comes to making stronger and tougher metals that are less prone to cracking, better conductors of electricity, and more durable at high temperatures and under extreme stress. Recent advances in technology have allowed materials scientists to develop grains at the scale of just 10 nanometers, which is tens of thousands of times smaller than the thickness of a sheet of paper or the width of a human hair. Such nanocrystals can only be viewed under extremely powerful microscopes. But the process isn't perfect. When some nanograins are created in bulk for applications such as semiconductors, the stability of their size can fluctuate under higher temperatures and stress. It was during the investigation of this instability that Shahbeigi-Roodposhti and the UConn research team learned the role oxygen played in weakening the nanocrystals' stability at high temperatures. "This is only a first step, but this line of investigation could ultimately lead to developing faster jet engines, more capacity in semiconductors, and more sensitivity in biosensors," Shahbeigi-Roodposhti says. Moving forward, the UConn researchers intend to test their theory on other alloys to see whether the presence or absence of oxygen impacts their performance at elevated temperatures. The study, "Effect of oxygen content on thermal stability of grain size for nanocrystalline Fe10Cr and Fe14Cr4Hf alloy powders," which was supported by funding from the U.S. Department of Energy, currently appears online in the Journal of Alloys and Compounds. Explore further: New model should expedite development of temperature-stable nano-alloys More information: Peiman Shahbeigi Roodposhti et al, Effect of oxygen content on thermal stability of grain size for nanocrystalline Fe10Cr and Fe14Cr4Hf alloy powders, Journal of Alloys and Compounds (2017). DOI: 10.1016/j.jallcom.2017.05.261


News Article | July 17, 2017
Site: www.eurekalert.org

Researchers at the University of Connecticut have found that reducing oxygen in some nanocrystalline materials may improve their strength and durability at elevated temperatures, a promising enhancement that could lead to better biosensors, faster jet engines, and greater capacity semiconductors. "Stabilizing nanocrystals at elevated temperatures is a common challenge," says Peiman Shahbeigi-Roodposhti, a postdoctoral research scholar with UConn's Institute of Materials Science and the study's lead author. "In certain alloys, we found that high levels of oxygen can lead to a significant reduction in their efficiency." Using a special milling process in an enclosed glove box filled with argon gas, UConn scientists, working in collaboration with researchers from North Carolina State University, were able to synthesize nano-sized crystals of Iron-Chromium and Iron-Chromium-Hafnium with oxygen levels as low as 0.01 percent. These nearly oxygen-free alloy powders appeared to be much more stable than their commercial counterparts with higher oxygen content at elevated temperatures and under high levels of stress. "In this study, for the first time, optimum oxygen-free nanomaterials were developed," says Sina Shahbazmohamadi, an assistant professor of biomedical engineering at UConn and a co-author on the paper. "Various characterization techniques, including advanced aberration corrected transmission electron microscopy, revealed a significant improvement in grain size stability at elevated temperatures." Grain size stability is important for scientists seeking to develop the next generation of advanced materials. Like fine links in an intricately woven mesh, grains are the small solids from which metals are made. Studies have shown that smaller grains are better when it comes to making stronger and tougher metals that are less prone to cracking, better conductors of electricity, and more durable at high temperatures and under extreme stress. Recent advances in technology have allowed materials scientists to develop grains at the scale of just 10 nanometers, which is tens of thousands of times smaller than the thickness of a sheet of paper or the width of a human hair. Such nanocrystals can only be viewed under extremely powerful microscopes. But the process isn't perfect. When some nanograins are created in bulk for applications such as semiconductors, the stability of their size can fluctuate under higher temperatures and stress. It was during the investigation of this instability that Shahbeigi-Roodposhti and the UConn research team learned the role oxygen played in weakening the nanocrystals' stability at high temperatures. "This is only a first step, but this line of investigation could ultimately lead to developing faster jet engines, more capacity in semiconductors, and more sensitivity in biosensors," Shahbeigi-Roodposhti says. Moving forward, the UConn researchers intend to test their theory on other alloys to see whether the presence or absence of oxygen impacts their performance at elevated temperatures. The study, "Effect of oxygen content on thermal stability of grain size for nanocrystalline Fe10Cr and Fe14Cr4Hf alloy powders," which was supported by funding from the U.S. Department of Energy, currently appears online in the Journal of Alloys and Compounds. Also serving as co-authors on the paper were Mostafa Saber, an assistant professor at Portland State University; and Professors Ronald Scattergood and Carl Koch from North Carolina State University. DOE funding supporting the research was acquired by Scattergood's lab.


News Article | August 1, 2017
Site: www.materialstoday.com

Researchers at the University of Connecticut have found that reducing oxygen in some nanocrystalline materials may improve their strength and durability at elevated temperatures. This is a promising enhancement, reported in a paper in the Journal of Alloys and Compounds, that could lead to better biosensors, faster jet engines and greater capacity semiconductors. "Stabilizing nanocrystals at elevated temperatures is a common challenge," says Peiman Shahbeigi-Roodposhti, a postdoctoral research scholar with UConn's Institute of Materials Science and the paper's lead author. "In certain alloys, we found that high levels of oxygen can lead to a significant reduction in their efficiency." Using a special milling process in an enclosed glove box filled with argon gas, UConn scientists, working in collaboration with researchers from North Carolina State University, were able to synthesize nano-sized crystals of iron chromium and iron chromium hafnium with oxygen levels as low as 0.01%. These nearly oxygen-free alloy powders appeared to be much more stable at elevated temperatures and under high levels of stress than their commercial counterparts with higher oxygen contents. "In this study, for the first time, optimum oxygen-free nanomaterials were developed," explains Sina Shahbazmohamadi, an assistant professor of biomedical engineering at UConn and a co-author on the paper. "Various characterization techniques, including advanced aberration corrected transmission electron microscopy, revealed a significant improvement in grain size stability at elevated temperatures." Grain size stability is important for scientists seeking to develop the next generation of advanced materials. Like fine links in an intricately woven mesh, grains are the small solids from which metals are made. Studies have shown that smaller grains are better when it comes to making stronger and tougher metals that are less prone to cracking, better at conducting electricity, and more durable at high temperatures and under extreme stress. Recent advances in technology have allowed materials scientists to develop grains at the scale of just 10nm. Such nanocrystals can only be viewed under extremely powerful microscopes. But the process isn't perfect. When some nanograins are created in bulk for applications such as semiconductors, the stability of their size can fluctuate under higher temperatures and stress. It was while investigating this instability that Shahbeigi-Roodposhti and the UConn research team learned the role oxygen played in weakening the nanocrystals' stability at high temperatures. "This is only a first step, but this line of investigation could ultimately lead to developing faster jet engines, more capacity in semiconductors and more sensitivity in biosensors," Shahbeigi-Roodposhti says. Moving forward, the UConn researchers intend to test their theory on other alloys to see whether the presence or absence of oxygen impacts their performance at elevated temperatures. This story is adapted from material from the University of Connecticut, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.


News Article | July 6, 2017
Site: www.cemag.us

One afternoon, Carnegie Mellon University Materials Science and Engineering (MSE)'s Mohammad Islam walked into colleague Paul Salvador's office and asked what the biggest problem was in photocatalysis that he'd like to be able to solve. Salvador's answer: He'd like to determine how the oxidation and reduction reactions in photocatalysis could be separated into distinct channels in order to increase performance. A photocatalyst, which uses energy from light to accelerate a reaction, typically facilitates two reactions: an oxidation reaction and a reduction reaction. They are used in generating hydrogen, in remediating environmental biofouling, and potentially for killing drug-resistant bacteria. "We're making open carbon nanotubes," responded Islam, research professor of MSE, "so how about we put the photocatalyst on the outside and the co-catalyst on the inside of each nanotube?" Salvador, professor of MSE, said he thought that was an elegant solution—but was it possible? Thus was formed a team including Islam, Salvador, and MSE Professor and Department Head Greg Rohrer, with Ph.D. student Hang-Ah Park, master's student Siyuan Liu, and former postdoc Youngseok Oh (currently a senior scientist at the Korea Institute of Materials Science). Recently, the team published a paper on their new approach to optimizing photocatalysts. Like many Carnegie Mellon research projects, the project started with a problem that could only be solved through collaboration. The challenge: photocatalysts need to be cheap, efficient, and environmentally friendly. Though current photocatalysts may be inexpensive, they either have high toxicity or don't perform well. In a photocatalyst, both the oxidation reaction and the reduction reaction need to be optimized, as does the space between these reactions. Typically, a photocatalyst that is good at performing one type of reaction (such as oxidation) has a co-catalyst added to it that is good at performing the opposite reaction (reduction). Though this helps with optimization, the reactions are not entirely separated, and therefore, products such as hydrogen and oxygen are generated in the same space. "Imagine that you have a micrometer-sized sphere known to be good at oxidation, and you add onto it small co-catalyst hemispheres known to be good at reduction (typically 10 nanometers)," says Rohrer. "Even though the reactions are technically separated, they are still occurring in close proximity, which decreases the photocatalyst's performance. So, we put them in completely different channels." What makes their work novel is not the complete separation of the channels, which is well known in standard photoelectrochemical cells (PECs), but that they brought a PEC down to the nanoscale, developed massively parallel arrays of those nanoscale PECs, and maintained complete separation. "It's a very simple idea," says Salvador. "Many of us have done lab experiments in high school or college using traditional PECs, which separate products into two large beakers. We have taken that huge PEC from chemistry lab and brought it down to the nanoscale, and then we fabricated thousands of them that operate in parallel. In that process, we found some interesting new fundamental materials behavior, including high activity in visible light, and saw a phenomenal performance that has many applications." A big application of photocatalysts is in remediating environmental biofouling, or removing organisms like barnacles and algae from surfaces such as pipes. Another application is in killing drug-resistant bacteria. Many hospitals, for example, use paints loaded with titania and irradiated with UV light to disinfect walls or other surfaces. But with the new photocatalytic method, they can use visible light, which is much safer. Finally, during hydrogen generation their photocatalysts suppress the mixing of product gases, an important advancement. "The question now is, why is it doing a lot better?" says Islam. "Why did it become photoactive in the visible light when I am doing this with carbon nanotubes and titanium? What are the parameters that we can tweak to make it better? That's the direction we're going."


News Article | July 7, 2017
Site: phys.org

A photocatalyst, which uses energy from light to accelerate a reaction, typically facilitates two reactions: an oxidation reaction and a reduction reaction. They are used in generating hydrogen, in remediating environmental biofouling, and potentially for killing drug-resistant bacteria. "We're making open carbon nanotubes," responded Islam, research professor of MSE, "so how about we put the photocatalyst on the outside and the co-catalyst on the inside of each nanotube?" Salvador, professor of MSE, said he thought that was an elegant solution—but was it possible? Thus was formed a team including Islam, Salvador, and MSE Professor and Department Head Greg Rohrer, with Ph.D. student Hang-Ah Park, master's student Siyuan Liu, and former postdoc Youngseok Oh (currently a senior scientist at the Korea Institute of Materials Science). Recently, the team published a paper on their new approach to optimizing photocatalysts. Like many Carnegie Mellon research projects, the project started with a problem that could only be solved through collaboration. The challenge: photocatalysts need to be cheap, efficient, and environmentally friendly. Though current photocatalysts may be inexpensive, they either have high toxicity or don't perform well. In a photocatalyst, both the oxidation reaction and the reduction reaction need to be optimized, as does the space between these reactions. Typically, a photocatalyst that is good at performing one type of reaction (such as oxidation) has a co-catalyst added to it that is good at performing the opposite reaction (reduction). Though this helps with optimization, the reactions are not entirely separated, and therefore, products such as hydrogen and oxygen are generated in the same space. "Imagine that you have a micrometer-sized sphere known to be good at oxidation, and you add onto it small co-catalyst hemispheres known to be good at reduction (typically 10 nanometers)," says Rohrer. "Even though the reactions are technically separated, they are still occurring in close proximity, which decreases the photocatalyst's performance. So, we put them in completely different channels." What makes their work novel is not the complete separation of the channels, which is well known in standard photoelectrochemical cells (PECs), but that they brought a PEC down to the nanoscale, developed massively parallel arrays of those nanoscale PECs, and maintained complete separation. "It's a very simple idea," says Salvador. "Many of us have done lab experiments in high school or college using traditional PECs, which separate products into two large beakers. We have taken that huge PEC from chemistry lab and brought it down to the nanoscale, and then we fabricated thousands of them that operate in parallel. In that process, we found some interesting new fundamental materials behavior, including high activity in visible light, and saw a phenomenal performance that has many applications." A big application of photocatalysts is in remediating environmental biofouling, or removing organisms like barnacles and algae from surfaces such as pipes. Another application is in killing drug-resistant bacteria. Many hospitals, for example, use paints loaded with titania and irradiated with UV light to disinfect walls or other surfaces. But with the new photocatalytic method, they can use visible light, which is much safer. Finally, during hydrogen generation their photocatalysts suppress the mixing of product gases, an important advancement. "The question now is, why is it doing a lot better?" says Islam. "Why did it become photoactive in the visible light when I am doing this with carbon nanotubes and titanium? What are the parameters that we can tweak to make it better? That's the direction we're going." Explore further: Nanomaterials with potential for environmentally friendly hydrogen production More information: Hang-Ah Park et al, Nano-Photoelectrochemical Cell Arrays with Spatially Isolated Oxidation and Reduction Channels, ACS Nano (2017). DOI: 10.1021/acsnano.6b08387


News Article | September 28, 2017
Site: www.materialstoday.com

Glass, while it possesses an unmatched combination of transparency, mechanical, thermal, and chemical resistance, along with thermal and electrical insulating properties, is notoriously difficult to shape into complex structures. Now, however, researchers Bastian E. Rapp and colleagues from Karlsruhe Institute of Technology have created a composite comprising silica nanopowder in a polymeric matrix that promises easy printing of a wide variety of complex, freestanding glass structures [Kotz et al., Nature (2017), doi: 10.1038/nature22061]. The crucial starting material is the nanocomposite — a liquid prepolymer in which silica glass nanoparticles 40 nm in diameter are suspended. The prepolymer can be formed into any structure using 3D printing and cured to fix its shape. The mixture is then heated to remove the polymeric binder before finally converting the silica nanoparticles into glass through a high-temperature treatment known as sintering. “We have made high-quality fused silica glass, one of the oldest materials used by the human race, accessible to modern 3D-printing methods,” says Rapp. “Our approach is the very first method that allows structuring of fused silica glass at resolutions sufficient for optical applications.” The silica glass is nonporous, as optically transparent as commercial glass made by conventional methods, and smooth. In fact, with surface roughness of only a few nanometers, the fused silica glass structures have the clarity and reflectivity necessary for optical devices like lenses and filters. Moreover, colored glasses can be easily created by adding metal salts to the initial mixture: chromium nitrate salts (Cr(NO ) ) for green, vanadium chloride (VCl ) for blue, or gold chloride (AuCl ) for red. The new process gets around the previous size and resolution limits on the formation of glass structures, producing complex architectures such as honeycombs, pretzels, and even a microscale model of castle gate, without any need of harsh chemicals (Fig. 1). “3D printing is currently restricted mostly to polymers,” points out Rapp. “So, the novelty in our approach is in the design of the nanocomposite, which is processable using standard desktop 3D printers.” The nanocomposite precursor mixture is highly stable and can be stored for weeks in a refrigerator before being used in a regular, bench-top 3D printer. The glass structures produced by the team are also, as would be expected of any fused silica glass, resistant to swelling, defects or changes in optical properties when exposed to hazardous chemicals like acids, alkalis, or alcohols. “[Our approach] opens up applications [of fused silica glass] ranging from high-performance optics to chemistry-on-achip applications, from making decorative glass objects to potentially whole facade elements,” says Rapp. Lithography-based additive manufacturing is well known for its outstanding capabilities in terms of feature resolution and surface quality of printed parts but there has been a lack of available materials for demanding academic and industrial applications, points out Jürgen Stampfl of the Institute of Materials Science and Technology at TU Wien. “Now Kotz et al. have added quartz glass to the spectrum of 3D-printable photopolymerizable materials,” he comments. “Of high importance is the excellent transparency of the material, which is crucial for targeted use in microfluidics or chemical process engineering.” The researchers are now looking at the scalability of their approach — how well the process could work for manufacturing larger meter-scale objects. The team is spinning out a company to commercialize the technology and tackle the manufacturing challenges, says Rapp. This article was originally published in Nano Today (2017), doi: 10.1016/j.nantod.2017.06.003


News Article | September 28, 2017
Site: www.gizmag.com

When olive oil is produced commercially, olives are crushed and mixed with water in mills. The oil is then separated out and saved, while the leftover water and solid residue are discarded – and that can be problematic. Help may be on the way, however, as scientists have devised a process of converting olive mill wastewater into biofuel, fertilizer and clean water. As things currently stand, there's no good way of disposing of the wastewater. Dumping it in waterways pollutes them, while pumping it directly onto farm land damages the soil and reduces crop yields. That's why a team led by Mejdi Jeguirim of France's Mulhouse Institute of Materials Science has taken a different approach. The scientists started by mixing the wastewater with cypress sawdust, which is another waste product that's common in the Mediterranean, where 97 percent of the world's olive oil is produced. That mixture was rapidly dried, and the water was collected as it evaporated – that water was clean, and could be used to irrigate crops. The remaining dried material was then subjected to pyrolysis, which is a process wherein organic material is exposed to high temperatures in the absence of oxygen. This caused it to decompose into combustible gas and charcoal pellets. That gas was collected and condensed into bio-oil, which could ultimately be used as a heat source for the drying and pyrolysis processes. The charcoal, meanwhile – which contains high amounts of nutrients such as potassium, phosphorus and nitrogen – was gathered and used as a crop fertilizer. In field tests, it was found that the pellets "significantly improved plant growth." A paper on the research was recently published in the journal ACS Sustainable Chemistry & Engineering.


News Article | September 19, 2017
Site: www.prweb.com

Jack Crane, director of growth and innovation services of CONNSTEP, will receive the 2017 Leadership Award at the American Manufacturing Hall of Fame Induction Ceremony on October 5, 2017. The event, sponsored by BlumShapiro, the largest regional business advisory firm based in New England with offices in Connecticut, Massachusetts and Rhode Island, takes place at the Trumbull Marriott, 180 Hawley Lane, Trumbull, CT, from 5:30 p.m. to 9:00 p.m. “Jack has been a giant in our state’s manufacturing industry for years,” said Janet A. Prisloe, CPA, a partner at BlumShapiro. “His wealth of manufacturing experience is multi-faceted and includes leadership positions in both business and the community. The American Manufacturing Hall of Fame has certainly selected an inspiring person for its 2017 Leadership Award.” BlumShapiro is a founding sponsor of the American Manufacturing Hall of Fame Induction Ceremony. At CONNSTEP, Crane provides manufacturers with guidance and mentoring in strategic planning, marketing, new product development, and linking strategy deployment with Lean activities. He also assists manufacturers with materials problems related to fabrication and function and connects companies with UCONN’s Institute of Materials Science. Additionally, Crane helps to match inventors and start-ups seeking manufacturing assistance. Crane’s manufacturing experience includes research and development, product development and commercialization, as well as materials processing and fabrication. He also facilitated the Connecticut Metal Finishers Training Network, helping to create a 10-week basic course for metal finishers. Crane developed the CERT program supported by CONNSTEP, NIST, and DECD to improve growth of technology-based business in Connecticut. Crane earned a Bachelor of Science in metallurgical engineering at Purdue University and a master’s degree in metallurgical engineering at Yale University. He has authored or co-authored more than 50 papers on new products, synthesis, and fabrication of materials, and he is also the holder or co-holder of more than 30 patents related to alloys, processes, and products. Crane is a Fellow of the American Society of Materials. The American Manufacturing Hall of Fame Leadership Award is given annually to one or more members of the community who have, over time, consistently displayed commitment to workforce and economic development through volunteer activities and board membership; provided leadership within their own companies; advocated for manufacturers at the local, state and federal levels; served as a role model for those considering a career in manufacturing; and constantly strives for continuous improvement to products, services and processes. In addition to Crane, the 2017 business inductees of the American Manufacturing Hall of Fame at Housatonic Community College are: Better Packages, Inc.; R.C. Bigelow, Inc.; MacDermid Performance Solutions; Stanley Black & Decker; and Ulbrich Stainless Steels & Special Metals, Inc. BlumShapiro is the Founding and Diamond Sponsor of the annual American Manufacturing Hall of Fame Induction Ceremony. For more information about the attending or supporting the American Manufacturing Hall of Fame Induction Ceremony, contact Emily Hyde at emchabot@gmail.com or 203-249-9859. BlumShapiro is the largest regional business advisory firm based in New England, with offices in Connecticut, Massachusetts and Rhode Island. The firm, with over 450 professionals and staff, offers a diversity of services which includes auditing, accounting, tax and business advisory services. In addition, BlumShapiro provides a variety of specialized consulting services such as succession and estate planning, business technology services, employee benefit plan audits and litigation support and valuation. The firm serves a wide range of privately held companies, government and non-profit organizations and provides non-audit services for publicly traded companies.


Carbon nanotube above a photonic crystal waveguide with electrodes. The structure converts electric signals into light. Credit: WWU Worldwide growing data volumes make conventional electronic processing reach its limits. Future information technology is therefore expected to use light as a medium for quick data transmission also within computer chips. Researchers under the direction of KIT have now demonstrated that carbon nanotubes are suited for use as on-chip light source for tomorrow's information technology, when nanostructured waveguides are applied to obtain the desired light properties. The scientists now present their results in Nature Photonics. On the large scale, data transmission by light has long become a matter of routine: Glass fiber cables as light waveguides transmit telephone and internet signals, for instance. For using the advantages of light, i.e. speed and energy efficiency, also on the small scale of computer chips, researchers of KIT have made an important step from fundamental research towards application. By the integration of smallest carbon nanotubes into a nanostructured waveguide, they have developed a compact miniaturized switching element that converts electric signals into clearly defined optical signals. "The nanostructures act like a photonic crystal and allow for customizing the properties of light from the carbon nanotube," Felix Pyatkov and Valentin Fütterling, the first authors of the study of KIT's Institute of Nanotechnology, explain. "In this way, we can generate narrow-band light in the desired color on the chip." Processing of the waveguide precisely defines the wavelength at which the light is transmitted. By engravings using electron beam lithography, the waveguides of several micrometers in length are provided with finest cavities of a few nanometers in size. They determine the waveguide's optical properties. The resulting photonic crystals reflect the light in certain colors, a phenomenon observed in nature on apparently colorful butterfly wings. As novel light sources, carbon nanotubes of about 1 micrometer in length and 1 nanometer in diameter are positioned on metal contacts in transverse direction to the waveguide. At KIT, a process was developed, by means of which the nanotubes can be integrated specifically into highly complex structures. The researchers applied the method of dielectrophoresis for deposition of carbon nanotubes from the solution and their arrangement vertically to the waveguide. This way of separating particles using inhomogeneous electric fields was originally used in biology and is highly suited to deposit nanoscaled objects on carrier materials. The carbon nanotubes integrated into the waveguide act as a small light source. When electric voltage is applied, they produce photons. The compact electricity/light signal converter presented now meets the requirements of the next generation of computers that combine electronic components with nanophotonic waveguides. The signal converter bundles the light about as strongly as a laser and responds to variable signals with high speed. Already now, the optoelectronic components developed by the researchers can be used to produce light signals in the gigahertz frequency range from electric signals. Among the leading researchers involved in the project were Ralph Krupke, who conducts research at the KIT Institute of Nanotechnology and at the Institute of Materials Science of TU Darmstadt, Wolfram H.P. Pernice, who moved from the KIT to the University of Münster one year ago, and Manfred M. Kappes, Institute of Physical Chemistry and Institute of Nanotechnology of KIT. The project was funded by the Science and Technology of Nanosystems (STN) programme of the Helmholtz Association. It is aimed at studying nanosystems of unique functionality and the potential of materials of a few nanometers in structural size. The Volkswagen Foundation financed a Ph.D. student position for the research project. In addition, the project was supported by the Karlsruhe Nano Micro Facility (KNMF) platform. Explore further: World-record micrometer-sized converter of electrical into optical signals More information: Felix Pyatkov et al. Cavity-enhanced light emission from electrically driven carbon nanotubes, Nature Photonics (2016). DOI: 10.1038/NPHOTON.2016.70


Pradhan S.K.,Institute of Materials Science
Journal of Materials Science: Materials in Electronics | Year: 2013

Monophasic rhombohedral structure of BiFeO3 electroceramic is successfully synthesized by conventional solid state reaction route followed by slow step sintering schedule. Effect of sintering temperature is found to greatly influence its structural, dielectric, ferroelectric, capacitance and leakage behavior of bulk ceramic. From XRD analysis it is seen that at lower sintering temperature (750 C) bulk BiFeO3 sample showed rhombohedral structure (R3c) along with few impurity phases, which become suppressed at higher sintering temperature and facilitates the compactness of grains and formation of dense microstructure. The leakage current and capacitive characteristic of the sample was improved significantly with increase in sintering temperature of BiFeO3 (850 C). At higher sintering temperature, ferroelectric behavior of the sample is found to change its shape from semi elliptical lossy P-E features to a typical ferroelectric loop with improvement of its remnant as well as saturation polarization value. Raman spectra over the frequency range of 100-700 cm-1 have been systematically investigated. Besides the changes of the peak position and the line width of all modes, the prominent frequency shift, the line broadening and variation of the intensity were observed with increase in sintering temperature. © 2013 Springer Science+Business Media New York.

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