Agency: Department of Energy | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 149.78K | Year: 2014
Over the past fifteen years, the demand for improved battery performance has increasingly focused on the development of battery chemistries based on lithium, due to their advantages over alternate battery chemistries. Among various alternative anodes, one thrust has been the use of materials that form alloys with lithium, providing up to a 10 fold improvement in the energy densities of current anode materials made from graphitic materials. Silicon-coated nanocarbons are among the best performing composite material, providing increases in energy and power densities. The technical performance of silicon-coated carbon nanofibers and nanotubes has been confirmed and well-established by numerous research groups and is potentially transformative for applications dependent on electrochemical energy storage; however, a barrier to utilization of this innovative solution is the high cost of fabrication, and the consequent lack of availability of the material for the battery manufacturing community. The goal of the proposed Phase I SBIR effort is to advance the manufacturing technology for novel, high- performance anodes based on silicon-coated carbon nanofiber, by creating a framework for production and utilization of low-cost silicon-coated carbon nanofibers for the battery industry. The outcomes sought through this developmental effort are increased throughput, energy savings, and consequent cost reductions; coupled with methods of quality control for the silicon-coated carbon nanofiber composite anode material. These two accomplishments will provide the sustainable competitive advantages needed to enable production of the improved anode material at a price reduction from ~ $300/lb to $20/lb or below, competitive to the cost but substantially higher in performance than current anode materials. It is proposed to utilize a fluidized bed reactor for production of silicon-coated carbon nanofiber, to enable both high volume, low-cost production and real-time characterization of the coatings. Commercial Applications and Other Benefits: The proposed manufacturing technology will increase the throughput, reduce the cost and improve the quality of silicon-coated carbon nanofiber composite anode materials. The automotive battery market is identified as a high value, near-term market for this anode technology. In addition to the automotive markets, there is significant interest in the silicon-coated carbon nanofiber technology from military and aerospace organizations. These and other high-volume markets such as consumer electronics warrant continued development of this low-risk, high-reward material. The advancements and solutions that are proposed herein are marked improvements in manufacturing technology for advanced lithium ion anodes that will provide stimulus for domestic production of high capacity lithium ion batteries and battery materials, providing the US with a competitive advantage in manufacturing of the next generation of energy storage devices based on lithium chemistry.
News Article | September 7, 2016
Applied scientists led by Caltech's Kerry Vahala have discovered a new type of optical soliton wave that travels in the wake of other soliton waves, hitching a ride on and feeding off of the energy of the other wave. Solitons are localized waves that act like particles: as they travel across space, they hold their shape and form rather than dispersing as other waves do. They were first discovered in 1834 when Scottish engineer John Scott Russell noted an unusual wave that formed after the sudden stop of a barge in the Union Canal that runs between Falkirk and Edinburgh. Russell tracked the resulting wave for one or two miles, and noted that it preserved its shape as it traveled, until he ultimately lost sight of it. He dubbed his discovery a "wave of translation." By the end of the century, the phenomenon had been described mathematically, ultimately giving birth to the concept of the soliton wave. Under normal conditions, waves tend to dissipate as they travel through space. Toss a stone into a pond, and the ripples will slowly die down as they spread out away from the point of impact. Solitons, on the other hand, do not. In addition to water waves, solitons can occur as light waves. Vahala's team studies light solitons by having them recirculate indefinitely in micrometer-scale circular circuits called optical microcavities. Solitons have applications in the creation of highly accurate optical clocks, and can be used in microwave oscillators that are used for navigation and radar systems, among other things. But despite decades of study, a soliton has never been observed behaving in a dependent -- almost parasitic--manner. "This new soliton rides along with another soliton -- essentially, in the other soliton's wake. It also syphons energy off of the other soliton so that it is self-sustaining. It can eventually grow larger than its host," says Vahala, Ted and Ginger Jenkins Professor of Information Science and Technology and Applied Physics and executive officer for applied physics and materials science in the Division of Engineering and Applied Science. Vahala likens these newly discovered solitons to pilot fish, carnivorous tropical fish that swim next to a shark so they can pick up scraps from the shark's meals. And by swimming in the shark's wake, the pilot fish reduce the drag of water on their own body, so they can travel with less effort. Vahala is the corresponding author of a paper in the journal Nature Physics announcing and describing the new type of soliton, dubbed the "Stokes soliton." (The name "Stokes" was chosen for technical reasons having to do with how the soliton syphons energy from the host.) The new soliton was first observed by Caltech graduate students Qi-Fan Yang and Xu Yi. Because of the soliton's ability to closely match the position and shape of the original soliton, Yang's and Yi's initial reaction to the wave was to suspect that laboratory instrumentation was malfunctioning. "We confirmed that the signal was not an artifact of the instrumentation by observing the signal on two spectrometers. We then knew it was real and had to figure out why a new soliton would spontaneously appear like this," Yang says. The microcavities that Vahala and his team use include a laser input that provides the solitons with energy. This energy cannot be directly absorbed by the Stokes soliton -- the "pilot fish." Instead, the energy is consumed by the "shark" soliton. But then, Vahala and his team found, the energy is pulled away by the pilot fish soliton, which grows in size while the other soliton shrinks. "Once we understood the environment required to sustain the new soliton, it actually became possible to design the microcavities to guarantee their formation and even their properties like wavelength -- effectively, color," Yi says. Yi and Yang collaborated with graduate student Ki Youl Yang on the research.
News Article | September 12, 2016
A new service developed at Binghamton University, State University of New York could improve performance of mobile devices that save data to the cloud. Storage and computing power is limited on mobile devices, making it necessity to store data in the cloud. However, with the myriad of apps from a myriad of developers that use the cloud, the user experience isn't always smooth. Battery life can be taxed due to extended synchronization times and clogged networks when multiple apps are trying to access the cloud all at the same time. "We may be using many different apps developed by different developers that make use of cloud storage services, whereas on PCs we tend to use apps offered by the official providers. This app and developer diversity can cause problems due to a developer's inexperience and/or carelessness," said Yifin Zhang, assistant professor of computer science at Binghamton University's Thomas J. Watson School of Engineering and Applied Science. Zhang and a team of Binghamton University researchers designed and developed StoArranger, a service to intercept, coordinate and optimize requests made by mobile apps and cloud storage services. StoArranger works as a "middleware system," so there is no change to how apps or an iPhone or Android-device run, just improved performance of both the device and the network overall. Essentially, StoArranger takes cloud storage requests--either to upload a file or to open a file for editing--and orders them in the best way to save power, get things completed as quickly as possible and minimize the amount of data used to complete the tasks. Even though the work could affect millions of mobile devices and users-- e.g. Microsoft's cloud computing and storage system Azure had 10 trillion objects stored on its servers as of January 2015--it is only a promising first step in the development of StoArranger, which isn't commercially available. Further research is scheduled for evaluation experiments, and a full paper will be submitted later this year. "We are planning on developing an app for public use," Zhang said. "We are trying to solve problems without changing operating systems or the existing apps, which makes our solution practical and scalable to existing smartphone users." Zhang presented the paper with Binghamton PhD candidates Yongshu Bai and Xin Zhang, both co-authors of the paper, at the proceedings of the seventh ACM SIGOPS Asia-Pacific Workshop on Systems (APSys '16) in Hong Kong in August. "The programming committee thought the work presented is a good demonstration of the negative effects of the way that current cloud storage providers chose to deploy their services," said Zhang. "The solution we proposed could be a practical way to solve the problem."
Abstract: Splitting water into its hydrogen and oxygen parts may sound like science fiction, but it's the end goal of chemists and chemical engineers like Christopher Murray of the University of Pennsylvania and Matteo Cargnello of Stanford University. They work in a field called photocatalysis, which, at its most basic, uses light to speed up chemical reactions. They've come a step closer to such a feat by tailoring the structure of a material called titania, one of the best-known photocatalysts, to hasten hydrogen production from biomass-derived compounds. Through a five-year collaboration with Drexel University, the University of Trieste in Italy, the University of Cadiz in Spain and the Leibniz Institute for Catalysis in Germany, the researchers determined that lengthening nanorods to 50 nanometers, a size 1,000 times smaller than the diameter of a hair, increased the hydrogen production rate of a rare form of titania called brookite, only accessible at the nanoscale. Using this unique crystal structure and controlling the nanorod dimensions offer new avenues for engineering the material's activity, and, because the process is theoretically simple to replicate, even at a large scale, it could have real implications for the future of clean energy and sustainable hydrogen production. The researchers published their results in the journal Proceedings of the National Academy of Sciences. "These insights are one more piece in an important puzzle as we work to harness the phenomena exhibited by Earth's materials," said Murray, a Penn Integrates Knowledge Professor and the Richard Perry University Professor of Chemistry and Materials Science and Engineering. One such material comes from the sun. "One idea behind photocatalysis is, what if we could make hydrogen using sunlight from abundant compounds? We wouldn't have to produce it from fossil fuels, which has global warming effects," said Cargnello, a former Penn postdoc who is now a Stanford assistant professor of chemical engineering. "If we could get that hydrogen from a renewable source, then the entire process would be totally sustainable" said Paolo Fornasiero, a University of Trieste professor of chemical and pharmaceutical sciences who collaborated with the Murray team on hydrogen measurements. On its face, the process sounds straightforward: Titania absorbs sunlight, which initiates a chemical reaction that generates hydrogen. But the vehicles responsible for this response, called electrons and holes, tend to jump the gun, reacting with each other almost immediately due to their opposite charges. They also execute different functions, with the negatively charged electrons carrying out reductions, and the positively charged holes performing oxidations. "What you want is that electron to reduce the water to hydrogen and that hole to oxidize the water to oxygen, such that the combination of these two half-reactions produces hydrogen gas on one side and oxygen gas on the other," Cargnello said. To attempt to stop the electrons and holes from reacting too soon, the research team put space between them using nanorods sized precisely from 15 to 50 nanometers, eventually determining that the longest rod resulted in the best activity. Though the experiment parameters didn't allow them to build beyond 50 nanometers, the scientists had essentially forced the electrons and holes to react with water rather than each other. Cargnello said what they've learned can be a playbook for others in the field. "If you want to have more efficient photocatalysts," he said, "make elongated structures to create these highways for electrons to escape from holes and react much faster with the molecules." This team isn't the first to attempt such an experiment with titania, according to Murray, who has appointments in the School of Arts & Sciences and the School of Engineering and Applied Science. "Titania is Earth-abundant and non-toxic, highly desirable as a material for solar-energy conversion," he said. "Many researchers are working to improve the efficiency with which it uses the solar spectrum." Murray's team opted to use solution-phase chemistry, a bottom-up approach, instead of a process many others employ called fabrication, which is top-down. "With fabricated structures, you take a big chunk and cut it down into smaller and smaller features," Cargnello said. "There is a limit to how small these structures can be, however, and the production is not scalable. In the Murray lab, we added one atom to another to make the nanorods, with precise control at the nanoscale and potential scalability." Jason Baxter's team at Drexel explored the photo-dynamics of these systems. Though the chemical process gets much more exact, it hasn't yet lead Murray's team to that dream of splitting pure water. To date, the scientists have employed biomass-derived compounds such as alcohols, breaking them down into hydrogen and carbon dioxide. That this generates CO2 may be counter to the clean-energy ideal, but Cargnello has an answer to this concern: Plants will absorb and turn the otherwise-discarded CO2 into additional biomass. "This would give us a close to carbon-neutral cycle," he said. Right now, that's precisely what's happening. "The nanorods take the light and the biomass-derived compound and transform them into hydrogen and CO2." Hydrogen has shown great promise as an emission-free alternative fuel when not made from natural gas. One challenge to wide acceptance, though, is the low cost and convenience of fossil fuels. That could change with the discovery of more efficient materials capable of producing hydrogen from sunlight and abundant compounds at higher rates. Then "we may be more competitive with hydrogen production from fossil fuels," Cargnello said. "Our work is one step in that direction." ### Funding for the U.S. research came primarily from the National Science Foundation, with additional support from the Department of Energy, the Department of Defense and Stanford University's School of Engineering and SUNCAT Center. Support for the European collaborators came from the Ministero dell'Istruzione, Università e Ricerca and the University of Trieste. 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.
Home > Press > Penn engineers develop first transistors made entirely of nanocrystal 'inks Abstract: The transistor is the most fundamental building block of electronics, used to build circuits capable of amplifying electrical signals or switching them between the 0s and 1s at the heart of digital computation. Transistor fabrication is a highly complex process, however, requiring high-temperature, high-vacuum equipment. Now, University of Pennsylvania engineers have shown a new approach for making these devices: sequentially depositing their components in the form of liquid nanocrystal "inks." Their new study, published in Science, opens the door for electrical components to be built into flexible or wearable applications, as the lower-temperature process is compatible with a wide array of materials and can be applied to larger areas. The researchers' nanocrystal-based field effect transistors were patterned onto flexible plastic backings using spin coating but could eventually be constructed by additive manufacturing systems, like 3-D printers. The study was lead by Cherie Kagan, the Stephen J. Angello Professor in the School of Engineering and Applied Science, and Ji-Hyuk Choi, then a member of her lab, now a senior researcher at the Korea Institute of Geoscience and Mineral Resources. Han Wang, Soong Ju Oh, Taejong Paik and Pil Sung Jo of the Kagan lab contributed to the work. They collaborated with Christopher Murray, a Penn Integrates Knowledge Professor with appointments in the School of Arts & Sciences and Penn Engineering; Murray lab members Xingchen Ye and Benjamin Diroll; and Jinwoo Sung of Korea's Yonsei University. The researchers began by taking nanocrystals, or roughly spherical nanoscale particles, with the electrical qualities necessary for a transistor and dispersing these particles in a liquid, making nanocrystal inks. Kagan's group developed a library of four of these inks: a conductor (silver), an insulator (aluminum oxide), a semiconductor (cadmium selenide) and a conductor combined with a dopant (a mixture of silver and indium). "Doping" the semiconductor layer of the transistor with impurities controls whether the device transmits a positive or negative charge. "These materials are colloids just like the ink in your inkjet printer," Kagan said, "but you can get all the characteristics that you want and expect from the analogous bulk materials, such as whether they're conductors, semiconductors or insulators. "Our question was whether you could lay them down on a surface in such a way that they work together to form functional transistors." The electrical properties of several of these nanocrystal inks had been independently verified, but they had never been combined into full devices. "This is the first work," Choi said, "showing that all the components, the metallic, insulating, and semiconducting layers of the transistors, and even the doping of the semiconductor could be made from nanocrystals." Such a process entails layering or mixing them in precise patterns. First, the conductive silver nanocrystal ink was deposited from liquid on a flexible plastic surface that was treated with a photolithographic mask, then rapidly spun to draw it out in an even layer. The mask was then removed to leave the silver ink in the shape of the transistor's gate electrode. The researchers followed that layer by spin-coating a layer of the aluminum oxide nanocrystal-based insulator, then a layer of the cadmium selenide nanocrystal-based semiconductor and finally another masked layer for the indium/silver mixture, which forms the transistor's source and drain electrodes. Upon heating at relatively low temperatures, the indium dopant diffused from those electrodes into the semiconductor component. "The trick with working with solution-based materials is making sure that, when you add the second layer, it doesn't wash off the first, and so on," Kagan said. "We had to treat the surfaces of the nanocrystals, both when they're first in solution and after they're deposited, to make sure they have the right electrical properties and that they stick together in the configuration we want." Because this entirely ink-based fabrication process works at lower temperatures than existing vacuum-based methods, the researchers were able to make several transistors on the same flexible plastic backing at the same time. "Making transistors over larger areas and at lower temperatures have been goals for an emerging class of technologies, when people think of the Internet of things, large area flexible electronics and wearable devices," Kagan said. "We haven't developed all of the necessary aspects so they could be printed yet, but because these materials are all solution-based, it demonstrates the promise of this materials class and sets the stage for additive manufacturing." ### The research was supported primarily by the National Science Foundation through its Materials Research Science and Engineering Centers Award DMR-1120901 and its Chemical, Bioengineering, Environmental and Transport Systems Award CBET-1236406; the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering Award DE-SC0002158; and the Office of Naval Research Multidisciplinary University Research Initiative Award ONR-N00014-10-1-0942. 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.