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Rust usually indicates neglect; it undermines the structures and tools we rely on every day, from cars to bridges and buildings. But if carefully controlled, the same process that creates rust – metal oxidation – could offer scientists ways to advance state-of-the-art battery or drug delivery technologies. To achieve such control, scientists must first understand exactly how the oxidation process works. With the help of supercomputers and synchrotrons, researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory and Temple University are illustrating the process on a finer scale than ever before. In a paper published today in Science, Argonne and Temple University researchers describe the behavior of metal nanoparticles by watching them in real time as they oxidized. By using a combination of X-ray scattering and computational simulation, the researchers were able to observe and model the changes in nanoparticle geometry as they occurred. This knowledge adds to our understanding of fundamental everyday reactions like corrosion, and builds a foundation for developing new techniques to image, manipulate and control such reactions at the atomic scale. “During oxidation of metals, there is a directional flow of material across a solid/gas or solid/liquid interface which can sometimes lead to the formation of holes in the atomic lattice. This process is known as the Kirkendall effect. If well understood, it can be used to design exotic materials at the nanoscale,” said computational scientist Subramanian Sankaranarayanan, one of the principal investigators of the study and a researcher at Argonne’s Center for Nanoscale Materials. In their study, researchers sought to understand the Kirkendall effect in small particles of iron during oxidation at the nanoscale level, specifically in the 10-nanometer range. At this scale, roughly 10,000 times thinner than a sheet of paper, iron nanoparticles exposed to an oxygen environment exhibit a unique property – they form exotic structures, such as hollowed-out nanoparticles or nanoshells, which already have been used as electrodes in battery applications and as vehicles for drug delivery in medicine. The shape, structure and distribution of the holes in these nanoshells depend on how oxidation progresses in time. “What we’ve done, through experimental and theoretical approaches, is build an understanding of the process itself — how these holes form and coalesce,” said co-author Badri Narayanan, an Argonne staff scientist who was a postdoctoral appointee at the time of study. “Without understanding these processes as they naturally occur, you can never hope to control them to produce new materials with exceptional functionality.” The Argonne study was the first time-resolved analysis to use two X-ray scattering techniques to monitor structural evolution during nanoparticle oxidation in 3-D. Small-angle X-ray scattering at the Advanced Photon Source helped characterize the void structures, while wide-angle X-ray scattering provided information on the crystalline structure of the nanoparticles; the combination of the two enabled researchers to experimentally investigate both the metal lattice and pore structure. With these experimental techniques, researchers could see how voids formed at a relatively high spatial resolution, but not one that reached the level of individual atoms. For this insight, researchers turned to the supercomputing resources at the Argonne Leadership Computing Facility. Computer simulations complemented the experimental observations and enabled the researchers to simulate the oxidation of iron nanoparticles atom-by-atom – meaning researchers could visualize the formation and breakage of bonds and track the movement of individual atoms. X-ray experiments and multimillion-atom reactive simulations were performed on exactly the same particle size to facilitate direct comparison of the evolving structure. “We needed the immense computing power of the Argonne Leadership Computing Facility’s 10-petaflop supercomputer, Mira, to perform these large-scale reactive simulations,” said Narayanan. “The simulations provided more detailed insight into the transformation of nanoparticles into nanoshells and the atomic-scale processes that govern their evolution.” The ability to integrate synthesis and experimental methods (X-ray imaging and nanoparticle synthesis and transmission electron microscopy performed at the Center for Nanoscale Materials) with computer modeling and simulation to build new knowledge is among the most valuable aspects of the study, the authors said. “A full 3-D evolution of morphologies of nanoparticles under real reaction conditions with sub-nanometer to atomistic resolution had not been realized until this study,” said Sankaranarayanan. “This truly exemplifies how the sum can be greater than the parts – how theory and imaging together give us information that is better than what can be obtained when these methods are used independently.” The study, titled “Quantitative 3D Evolution of Colloidal Nanoparticle Oxidation in Solution,” is published in Science. Other authors of this study include Yugang Sun, Xiaobing Zuo, Sheng Peng and Ganesh Kamath. The research was supported by Temple University. The work was completed using resources at the Advanced Photon Source, the Center for Nanoscale Materials and the Argonne Leadership Computing Facility, as well as the National Energy Research Scientific Computing Center at Lawrence Berkeley National Laboratory – all DOE Office of Science User Facilities. Computing time at the Argonne Leadership Computing Facility was awarded through the Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program and the ASCR Leadership Computing Challenge.


News Article | April 21, 2017
Site: www.treehugger.com

The Deepwater Horizon oil spill, the worst in U.S. history, taught us a a lot of lessons. We learned that deep water oil drilling required far more fail-safes than were being used and we also realized that deep water oil spills are far more complex than previous surface spills and leaks. Huge plumes of oil below the surface were hard or impossible to collect, especially since most of the oil clean up techniques we had focused on retrieval at the surface. In the years since Deepwater Horizon, there have been numerous technologies invented that would make clean up of another large oil spill more effective. Now, researchers at Argonne National Laboratory have invented a material that may be the best and most revolutionary oil spill solution yet. The scientists have invented a new foam material that acts like a sponge and absorbs oil from the water while repelling water. That's not the unique part. The sponge can be reused and is able to collect oil from the entire water column, not just the surface. We've seen previous sponge materials that can pull the oil from the surface of the water, but this sponge is truly groundbreaking because of ability to pull oil from the depths of water as well. The material called the Oleo Sponge can be wrung out and the collected oil can be recovered. The sponge can then be re-submerged to collect more oil. “The Oleo Sponge offers a set of possibilities that, as far as we know, are unprecedented,” said co-inventor Seth Darling, a scientist with Argonne’s Center for Nanoscale Materials and a fellow of the University of Chicago’s Institute for Molecular Engineering. The sponge is made from a normal polyurethane foam but it's oil grabbing properties come from the application of oil-loving molecules to the surface. The material is primed with a thin layer of metal oxide on the surface which act as a grippy surface for the molecules. The oil-loving molecules cling to the sponge on one end and then pull in oil on the other. In tests, the scientists filled a giant tank with seawater and diesel and crude oil and the Oleo sponge successfully absorbed the oils from both the surface and below. It was also able to be reused again and again without a decline in performance. “The technique offers enormous flexibility, and can be adapted to other types of cleanup besides oil in seawater. You could attach a different molecule to grab any specific substance you need,” said Argonne chemist Jeff Elam. One potential application beyond just major oil spill clean up is to use the material for regular cleaning of ports and harbors where diesel and oil accumulate over time from heavy ship activity. The team is currently looking to commercialize the material. You can watch this amazing sponge in action below.


News Article | January 15, 2016
Site: www.nanotech-now.com

Abstract: While lithium-ion batteries have transformed our everyday lives, researchers are currently trying to find new chemistries that could offer even better energy possibilities. One of these chemistries, lithium-air, could promise greater energy density but has certain drawbacks as well. Now, thanks to research at the U.S. Department of Energy's (DOE) Argonne National Laboratory, one of those drawbacks may have been overcome. All previous work on lithium-air batteries showed the same phenomenon: the formation of lithium peroxide (Li2O2), a solid precipitate that clogged the pores of the electrode. In a recent experiment, however, Argonne battery scientists Jun Lu, Larry Curtiss and Khalil Amine, along with American and Korean collaborators, were able to produce stable crystallized lithium superoxide ((LiO2) instead of lithium peroxide during battery discharging. Unlike lithium peroxide, lithium superoxide can easily dissociate into lithium and oxygen, leading to high efficiency and good cycle life. "This discovery really opens a pathway for the potential development of a new kind of battery," Curtiss said. "Although a lot more research is needed, the cycle life of the battery is what we were looking for." The major advantage of a battery based on lithium superoxide, Curtiss and Amine explained, is that it allows, at least in theory, for the creation of a lithium-air battery that consists of what chemists call a "closed system." Open systems require the consistent intake of extra oxygen from the environment, while closed systems do not - making them safer and more efficient. "The stabilization of the superoxide phase could lead to developing a new closed battery system based on lithium superoxide, which has the potential of offering truly five times the energy density of lithium ion," Amine said. Curtiss and Lu attributed the growth of the lithium superoxide to the spacing of iridium atoms in the electrode used in the experiment. "It looks like iridium will serve as a good template for the growth of superoxide," Curtiss said. "However, this is just an intermediate step," Lu added. "We have to learn how to design catalysts to understand exactly what's involved in lithium-air batteries." ### The researchers confirmed the lack of lithium peroxide by using X-ray diffraction provided by the Advanced Photon Source, a DOE Office of Science User Facility located at Argonne. They also received allocations of time on the Mira supercomputer at the Argonne Leadership Computing Facility, which is also a DOE Office of Science User Facility. The researchers also performed some of the work at Argonne's Center for Nanoscale Materials, which is also a DOE Office of Science User Facility. A study based on the research appeared in the January 11 issue of Nature. The work was funded by the DOE's Office of Energy Efficiency and Renewable Energy and Office of Science. About Argonne National Laboratory Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science. The U.S. Department of Energy's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website. 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 | November 18, 2016
Site: www.eurekalert.org

They say diamonds are forever, but diamonds in fact are a metastable form of carbon that will slowly but eventually transform into graphite, another form of carbon. Being able to design and synthesize other long-lived, thermodynamically metastable materials could be a potential gold mine for materials designers, but until now, scientists lacked a rational understanding of them. Now researchers at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have published a new study that, for the first time, explicitly quantifies the thermodynamic scale of metastability for almost 30,000 known materials. This paves the way for designing and making promising next-generation materials for use in everything from semiconductors to pharmaceuticals to steels. "There's a great amount of possibility in the space of metastable materials, but when experimentalists go to the lab to make them, the process is very heuristic--it's trial and error," said Berkeley Lab researcher Wenhao Sun. "What we've done in this research is to understand the metastable phases that have been made, so that we can better understand which metastable phases can be made." The research was published last week in the journal Science Advances in a paper titled, "The Thermodynamic Scale of Inorganic Crystalline Metastability." Sun, a postdoctoral fellow working with Gerbrand Ceder in Berkeley Lab's Materials Sciences Division, was the lead author, and Ceder was the corresponding author. The study involved large-scale data mining of the Materials Project, which is a Google-like database of materials that uses supercomputers to calculate properties based on first-principles quantum-mechanical frameworks. The Materials Project, directed by Berkeley Lab researcher Kristin Persson, who was also a co-author of the new paper, has calculated properties of more than 67,000 known and predicted materials with the goal of accelerating materials discovery and innovation. "Materials design and development is truly a slow process but is now being greatly accelerated by the fact that we can compute properties of compounds before they are made," Ceder said. "Although we still don't fully understand which materials can be made and how, mapping the underlying thermodynamics is an important first step." Metastable materials, or materials that transform to another state over a long period of time, are ubiquitous in both nature and technology and often have superior properties. Chocolate, for example, is metastable, with a lower melting point and better texture than stable chocolate. There are also metastable steels that have both toughness and strength, properties not normally found simultaneously in most stable steels. Scientists would love to develop new materials with certain properties for various applications--an ultra-strong yet lightweight metal for vehicles, for example--but to make any new material with desired properties, materials scientists must understand how synthesizing the material influences its structure, and then how the structure in turn affects its properties and performance. This, Sun explains, is the fundamental paradigm of materials science. "The Materials Project has helped us link a material's structure to its properties," Ceder said. "What we've done here is the first quantitative step in understanding synthesis-structure relationships." Sun offers an analogy to food: "If the Materials Project were a cookbook, it'd be like a database of ingredients and delicious dishes but no recipes. Designing recipes is difficult because scientists have a poor understanding of why metastable phases appear during 'cooking.' There are some applications where a metastable material is better, and others where the stable phases are better. This study sets a foundation to investigate how to use computers to predict recipes." Previously, scientists had thermodynamic numbers for less than 1,000 metastable compounds. "It's very hard to survey metastability over known materials because there's not much data out there in terms of calorimetry, which is measuring thermodynamic numbers," Sun said. What's more, metastable materials come in many forms, spanning metal alloys and minerals to ceramics, salts, and more, making a comprehensive survey difficult. "What we've done is large-scale data mining on nearly 30,000 observed materials to explicitly measure the thermodynamic scale of metastability, as a function of a wide variety of parameters, like chemistry and composition, which inorganic chemists and materials scientists can use to build intuition," Sun said. Based on their observations, the researchers went a step further, to propose a new principle they term "remnant metastability" to explain which metastable materials can be synthesized and which cannot. "We're essentially proposing search criteria¬?we're identifying which crystalline materials can be made, and possibly under what conditions they can be made," Sun said. "We hope this can be a more refined way to think about which crystal structure nature chooses when a material forms." The other co-authors of the paper are: Anubhav Jain of Berkeley Lab, Stephen Dacek and William Richards of MIT, Shyue Ping Ong and Anthony Gamst of UC San Diego, and Geoffroy Hautier of the Université Catholique de Louvain in Belgium. The research was supported by the Materials Project and was a collaboration with the DOE's Office of Science as part of its Center for Next Generation of Materials by Design, a DOE Energy Frontier Research Center. The researchers also used computing resources at the Center for Nanoscale Materials (CNM) at Argonne National Laboratory and well as resources at the Center for Functional Nanomaterials (CFN) at Brookhaven National Laboratory. CNM and CFN are DOE Office of Science User Facilities. Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit http://www. . DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.


« BMW using Hexcel CFRP in 7 Series B-pillar | Main | Zhejiang VIE Science and Technology leads US$10M Series B for wireless charging company Evatran » Researchers from Argonne National Laboratory, with colleagues in the US and Korea, have demonstrated a lithium-oxygen battery based on lithium superoxide (LiO ). The work, reported in the journal Nature, could open the way to very high-energy-density batteries based on LiO as well as to other possible uses of the compound, such as oxygen storage. Lithium-air batteries form lithium peroxide (Li O )—a solid precipitate that clogs the pores of the electrode and degrades cell performance—as part of the charge−discharge reaction process. This remains a core challenge that needs to be overcome for the viable commercialization of Li-air technology. However, a number of studies of Li–air batteries have found evidence of LiO being formed as one component of the discharge product along with lithium peroxide (Li O ). Unlike lithium peroxide, lithium superoxide can easily dissociate into lithium and oxygen, leading to high efficiency and good cycle life. In addition, theoretical calculations have indicated that some forms of LiO may have a long lifetime. Here we show that crystalline LiO can be stabilized in a Li–O battery by using a suitable graphene-based cathode. Various characterization techniques reveal no evidence for the presence of Li O . A novel templating growth mechanism involving the use of iridium nanoparticles on the cathode surface may be responsible for the growth of crystalline LiO . Our results demonstrate that the LiO formed in the Li–O battery is stable enough for the battery to be repeatedly charged and discharged with a very low charge potential (about 3.2 volts). The major advantage of a battery based on lithium superoxide, Argonne battery scientists Larry Curtiss and Khalil Amine explained, is that it allows, at least in theory, for the creation of a lithium-air battery that consists of a closed system. Open systems require the consistent intake of extra oxygen from the environment, while closed systems do not—making them safer and more efficient. The researchers attributed the growth of the lithium superoxide to the spacing of iridium atoms in the electrode used in the experiment. The researchers confirmed the lack of lithium peroxide by using X-ray diffraction provided by the Advanced Photon Source, a DOE Office of Science User Facility located at Argonne. They also received allocations of time on the Mira supercomputer at the Argonne Leadership Computing Facility, which is also a DOE Office of Science User Facility. The researchers also performed some of the work at Argonne’s Center for Nanoscale Materials, which is also a DOE Office of Science User Facility. The work was funded by the DOE’s Office of Energy Efficiency and Renewable Energy and Office of Science.


News Article | November 21, 2016
Site: www.cemag.us

They say diamonds are forever, but diamonds in fact are a metastable form of carbon that will slowly but eventually transform into graphite, another form of carbon. Being able to design and synthesize other long-lived, thermodynamically metastable materials could be a potential gold mine for materials designers, but until now, scientists lacked a rational understanding of them. Now researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have published a new study that, for the first time, explicitly quantifies the thermodynamic scale of metastability for almost 30,000 known materials. This paves the way for designing and making promising next-generation materials for use in everything from semiconductors to pharmaceuticals to steels. “There’s a great amount of possibility in the space of metastable materials, but when experimentalists go to the lab to make them, the process is very heuristic — it’s trial and error,” says Berkeley Lab researcher Wenhao Sun. “What we’ve done in this research is to understand the metastable phases that have been made, so that we can better understand which metastable phases can be made.” The research was published recently in the journal Science Advances in a paper titled, “The Thermodynamic Scale of Inorganic Crystalline Metastability.” Sun, a postdoctoral fellow working with Gerbrand Ceder in Berkeley Lab’s Materials Sciences Division, was the lead author, and Ceder was the corresponding author. The study involved large-scale data mining of the Materials Project, which is a Google-like database of materials that uses supercomputers to calculate properties based on first-principles quantum-mechanical frameworks. The Materials Project, directed by Berkeley Lab researcher Kristin Persson, who was also a co-author of the new paper, has calculated properties of more than 67,000 known and predicted materials with the goal of accelerating materials discovery and innovation. “Materials design and development is truly a slow process but is now being greatly accelerated by the fact that we can compute properties of compounds before they are made,” Ceder says. “Although we still don’t fully understand which materials can be made and how, mapping the underlying thermodynamics is an important first step.” Metastable materials, or materials that transform to another state over a long period of time, are ubiquitous in both nature and technology and often have superior properties. Chocolate, for example, is metastable, with a lower melting point and better texture than stable chocolate. There are also metastable steels that have both toughness and strength, properties not normally found simultaneously in most stable steels. Scientists would love to develop new materials with certain properties for various applications — an ultra-strong yet lightweight metal for vehicles, for example — but to make any new material with desired properties, materials scientists must understand how synthesizing the material influences its structure, and then how the structure in turn affects its properties and performance. This, Sun explains, is the fundamental paradigm of materials science. “The Materials Project has helped us link a material’s structure to its properties,” Ceder says. “What we’ve done here is the first quantitative step in understanding synthesis-structure relationships.” Sun offers an analogy to food: “If the Materials Project were a cookbook, it’d be like a database of ingredients and delicious dishes but no recipes. Designing recipes is difficult because scientists have a poor understanding of why metastable phases appear during ‘cooking.’ There are some applications where a metastable material is better, and others where the stable phases are better. This study sets a foundation to investigate how to use computers to predict recipes.” Previously, scientists had thermodynamic numbers for less than 1,000 metastable compounds. “It’s very hard to survey metastability over known materials because there’s not much data out there in terms of calorimetry, which is measuring thermodynamic numbers,” Sun says. What’s more, metastable materials come in many forms, spanning metal alloys and minerals to ceramics, salts, and more, making a comprehensive survey difficult. “What we’ve done is large-scale data mining on nearly 30,000 observed materials to explicitly measure the thermodynamic scale of metastability, as a function of a wide variety of parameters, like chemistry and composition, which inorganic chemists and materials scientists can use to build intuition,” Sun says. Based on their observations, the researchers went a step further, to propose a new principle they term “remnant metastability” to explain which metastable materials can be synthesized and which cannot. “We’re essentially proposing search criteria — we’re identifying which crystalline materials can be made, and possibly under what conditions they can be made,” Sun says. “We hope this can be a more refined way to think about which crystal structure nature chooses when a material forms.” The other co-authors of the paper are: Anubhav Jain of Berkeley Lab, Stephen Dacek and William Richards of MIT, Shyue Ping Ong and Anthony Gamst of UC San Diego, and Geoffroy Hautier of the Université Catholique de Louvain in Belgium. The research was supported by the Materials Project and was a collaboration with the DOE’s Office of Science as part of its Center for Next Generation of Materials by Design, a DOE Energy Frontier Research Center. The researchers also used computing resources at the Center for Nanoscale Materials (CNM) at Argonne National Laboratory and well as resources at the Center for Functional Nanomaterials (CFN) at Brookhaven National Laboratory. CNM and CFN are DOE Office of Science User Facilities.


News Article | December 7, 2016
Site: www.eurekalert.org

Machine learning, a field focused on training computers to recognize patterns in data and make new predictions, is helping doctors more accurately diagnose diseases and stock analysts forecast the rise and fall of financial markets. And now materials scientists have pioneered another important application for machine learning -- helping to accelerate the discovery and development of new materials. Researchers at the Center for Nanoscale Materials and the Advanced Photon Source, both U.S. Department of Energy (DOE) Office of Science User Facilities at DOE's Argonne National Laboratory, announced the use of machine learning tools to accurately predict the physical, chemical and mechanical properties of nanomaterials. In a study published in The Journal of Physical Chemistry Letters, a team of researchers led by Argonne computational scientist Subramanian Sankaranarayanan described their use of machine learning tools to create the first atomic-level model that accurately predicts the thermal properties of stanene, a two-dimensional (2-D) material made up of a one-atom-thick sheet of tin. The study reveals for the first time an approach to materials modeling that applies machine learning and is more accurate at predicting material properties compared to past models. "Predictive modeling is particularly important for newly discovered materials, to learn what they're good for, how they respond to different stimuli and also how to effectively grow the material for commercial applications -- all before you invest in costly manufacturing," said Argonne postdoctoral researcher Mathew Cherukara, one of the lead authors of the study. Traditionally, atomic-scale materials models have taken years to develop, and researchers have had to rely largely on their own intuition to identify the parameters on which a model would be built. But by using a machine learning approach, Cherukara and fellow researchers were able to reduce the need for human input while shortening the time to craft an accurate model down to a few months. "We input data obtained from experimental or expensive theory-based calculations, and then ask the machine, 'Can you give me a model that describes all of these properties?'" said Badri Narayanan, an Argonne postdoctoral researcher and another lead author of the study. "We can also ask questions like, 'Can we optimize the structure, induce defects or tailor the material to get specific desired properties?'" Unlike most past models, the machine learning model can capture bond formation and breaking events accurately; this not only yields more reliable predictions of material properties (e.g. thermal conductivity), but also enables researchers to capture chemical reactions accurately and better understand how specific materials can be synthesized. Another advantage of building models using machine learning is the process is not material-dependent, meaning researchers can look at many different classes of materials and apply machine learning to various other elements and their combinations. The computational model Cherukara, Narayanan and their colleagues have developed describes stanene, a structure made of tin that has caught the eye of researchers in recent years. Interest in stanene mirrors a growing interest in 2-D materials evolving from the 2004 discovery of graphene, a single-layer arrangement of carbon with attractive electronic, thermal and mechanical properties. While stanene remains far from commercialization, researchers find it promising for applications in thermal management (the regulation of heat) across some nanoscale devices. The study, "Ab Initio-Based Bond Order Potential to Investigate Low Thermal Conductivity of Stanene Nanostructures," appeared in the The Journal of Physics Chemistry Letters. This work was supported by Argonne's Laboratory Directed Research and Development (LDRD) program and tapped the high-performance computing clusters of Argonne's Laboratory Computing Resource Center. It also used the Extreme Science and Engineering Discovery Environment, a project supported by the National Science Foundation, as well as resources at the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility. Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science. The U.S. Department of Energy's Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit the Office of Science website.


News Article | September 19, 2016
Site: www.cemag.us

Graphene is the stuff of the future. For years, researchers and technologists have been predicting the utility of the one-atom-thick sheets of pure carbon in everything from advanced touch screens and semiconductors to long-lasting batteries and next-generation solar cells. But graphene’s unique intrinsic properties — supreme electrical and thermal conductivities and remarkable electron mobility, to name just a few — can only be fully realized if it is grown free from defects that disrupt the honeycomb pattern of the bound carbon atoms. A team led by Materials Scientist Anirudha Sumant with the U.S. Department of Energy’s (DOE) Argonne National Laboratory’s Center for Nanoscale Materials (CNM) and Materials Science Division, along with collaborators at the University of California-Riverside, has developed a method to grow graphene that contains relatively few impurities and costs less to make, in a shorter time and at lower temperatures compared to the processes widely used to make graphene today. Theoretical work led by Argonne nanoscientist Subramanian Sankaranarayanan at the CNM helped researchers understand the molecular-level processes underlying the graphene growth. The new technology taps ultrananocrystalline diamond (UNCD), a synthetic type of diamond that Argonne researchers have pioneered through years of research. UNCD serves as a physical substrate, or surface on which the graphene grows, and the source for the carbon atoms that make up a rapidly produced graphene sheet. “When I first looked at the [scanning electron micrograph] and saw this nice uniform, very complete layer, it was amazing,” says Diana Berman, the first author of the study and former postdoctoral research associate who worked with Sumant and is now an Assistant Professor at the University of North Texas. “I’d been dealing with all these different techniques of growing graphene, and you never see such a uniform, smooth surface.” Current graphene fabrication protocols introduce impurities during the etching process itself, which involves adding acid and extra polymers, and when they are transferred to a different substrate for use in electronics. “The impurities introduced during this etching and the transferring step negatively affect the electronic properties of the graphene,” Sumant says. “So you do not get the intrinsic properties of the graphene when you actually do this transfer.” The team found that the single-layer, single-domain graphene can be grown over micron-size holes laterally, making them completely free-standing (that is, detached from the underlying substrate). This makes it possible to exploit the intrinsic properties of graphene by fabricating devices directly over free-standing graphene. The new process is also much more cost-effective than conventional methods based on using silicon carbide as a substrate. Sumant says that the 3- to 4-inch silicon carbide wafers used in these types of growth methods cost about $1,200, while UNCD films on silicon wafers cost less than $500 to make. The diamond method also takes less than a minute to grow a sheet of graphene, where the conventional method takes on the order of hours. The high quality of graphene was confirmed by the UC Riverside co-authors Zhong Yan and Alexander Balandin by fabricating top-gate field-effect transistors from this material and measuring its electron mobility and charge carrier concentration. “It is well known that certain metals, such as nickel and iron, dissolve diamond at elevated temperatures, and the same process has been used for many years to polish diamond,” says Sumant. He and his team used this property to employ nickel in converting the top layer of diamond into amorphous carbon, but it was not clear how these freed carbon atoms converted instantly into high-quality graphene. After Sumant’s and Berman’s initial breakthrough of growing graphene directly on UNCD, Sankaranarayanan and his postdocs Badri Narayanan and Sanket Deshmukh, computational material scientists at the CNM used resources at the Argonne Leadership Computing Facility (ALCF) to help the team better understand the mechanism of the growth process underlying this interesting phenomenon using reactive molecular dynamic simulations. Computer simulations developed by Narayanan, Deshmukh and Sankaranarayanan showed that certain crystallographic orientation of nickel-111 highly favor nucleation, and subsequent rapid growth of graphene; this was then confirmed experimentally. These large-scale simulations also showed how graphene forms. The nickel atoms diffuse into the diamond and destroy its crystalline order, while carbon atoms from this amorphous solid move to the nickel surface and rapidly form honeycomb-like structures, resulting in mostly defect-free graphene. The nickel then percolated through the fine crystalline grains of the UNCD, sinking out of the way and removing the need for acid to dissolve away excess metal atoms from the top surface. “It is like meeting a good Samaritan at an unknown place who helps you, does his job and leaves quietly without a trace,” says Sumant. “The proven predictive power of our simulations places us in a position of advantage to enable rapid discovery of new catalytic alloys that mediate growth of high-quality graphene on dielectrics and move away on their own when the growth is completed,” adds Narayanan. In addition to the utility in making minimally defective, application-ready graphene for things like low-frequency vibration sensors, radio frequency transistors and better electrodes for water purification, Berman and Sumant say that the Argonne team has already secured three patents arising from their new graphene growth method. The researchers have already struck a collaboration with Swedish Institute of Space Physics involving the European Space Agency for their Jupiter Icy Moons Explorer (JUICE) program to develop graphene-coated probes that may help exploratory vehicles sense the properties of plasma surrounding the moons of Jupiter. Closer to home, the team has also crafted diamond and graphene needles for researchers at North Carolina University to use in biosensing applications. The Argonne researchers are now fine-tuning the process — tweaking the temperature used to catalyze the reaction and adjusting the thickness of the diamond substrate and the composition of the metal film that facilitates the graphene growth — to both optimize the reaction and to better study the physics at the graphene-diamond interface. “We’re trying to tune this more carefully to have a better understanding of which conditions lead to what quality of graphene we’re seeing,” Berman says. Other Argonne authors involved in the study were Alexander Zinovev and Daniel Rosenmann. The paper, “Metal-induced rapid transformation of diamond into single and multilayer graphene on wafer scale,” is published in Nature Communications. The study used resources of the CNM and the ALCF as well as the National Energy Research Scientific Computing Center at Lawrence Berkeley National Laboratory, all DOE Office of Science User Facilities. Additional support was provided by the U.S. Department of Energy’s Office of Science.


News Article | September 19, 2016
Site: www.rdmag.com

Graphene is the stuff of the future. For years, researchers and technologists have been predicting the utility of the one-atom-thick sheets of pure carbon in everything from advanced touch screens and semiconductors to long-lasting batteries and next-generation solar cells. But graphene's unique intrinsic properties – supreme electrical and thermal conductivities and remarkable electron mobility, to name just a few – can only be fully realized if it is grown free from defects that disrupt the honeycomb pattern of the bound carbon atoms. A team led by Materials Scientist Anirudha Sumant with the U.S. Department of Energy's (DOE) Argonne National Laboratory's Center for Nanoscale Materials (CNM) and Materials Science Division, along with collaborators at the University of California-Riverside, has developed a method to grow graphene that contains relatively few impurities and costs less to make, in a shorter time and at lower temperatures compared to the processes widely used to make graphene today. Theoretical work led by Argonne nanoscientist Subramanian Sankaranarayanan at the CNM helped researchers understand the molecular-level processes underlying the graphene growth. "I'd been dealing with all these different techniques of growing graphene, and you never see such a uniform, smooth surface." The new technology taps ultrananocrystalline diamond (UNCD), a synthetic type of diamond that Argonne researchers have pioneered through years of research. UNCD serves as a physical substrate, or surface on which the graphene grows, and the source for the carbon atoms that make up a rapidly produced graphene sheet. "When I first looked at the [scanning electron micrograph] and saw this nice uniform, very complete layer, it was amazing," said Diana Berman, the first author of the study and former postdoctoral research associate who worked with Sumant and is now an Assistant Professor at the University of North Texas. "I'd been dealing with all these different techniques of growing graphene, and you never see such a uniform, smooth surface." Current graphene fabrication protocols introduce impurities during the etching process itself, which involves adding acid and extra polymers, and when they are transferred to a different substrate for use in electronics. "The impurities introduced during this etching and the transferring step negatively affect the electronic properties of the graphene," Sumant said. "So you do not get the intrinsic properties of the graphene when you actually do this transfer." The team found that the single-layer, single-domain graphene can be grown over micron-size holes laterally, making them completely free-standing (that is, detached from the underlying substrate). This makes it possible to exploit the intrinsic properties of graphene by fabricating devices directly over free-standing graphene. The new process is also much more cost-effective than conventional methods based on using silicon carbide as a substrate. Sumant says that the 3- to 4-inch silicon carbide wafers used in these types of growth methods cost about $1,200, while UNCD films on silicon wafers cost less than $500 to make. The diamond method also takes less than a minute to grow a sheet of graphene, where the conventional method takes on the order of hours. The high quality of graphene was confirmed by the UC Riverside co-authors Zhong Yan and Alexander Balandin by fabricating top-gate field-effect transistors from this material and measuring its electron mobility and charge carrier concentration. "It is well known that certain metals, such as nickel and iron, dissolve diamond at elevated temperatures, and the same process has been used for many years to polish diamond," said Sumant. He and his team used this property to employ nickel in converting the top layer of diamond into amorphous carbon, but it was not clear how these freed carbon atoms converted instantly into high-quality graphene. After Sumant's and Berman's initial breakthrough of growing graphene directly on UNCD, Sankaranarayanan and his postdocs Badri Narayanan and Sanket Deshmukh, computational material scientists at the CNM used resources at the Argonne Leadership Computing Facility (ALCF) to help the team better understand the mechanism of the growth process underlying this interesting phenomenon using reactive molecular dynamic simulations. Computer simulations developed by Narayanan, Deshmukh and Sankaranarayanan showed that certain crystallographic orientation of nickel-111 highly favor nucleation, and subsequent rapid growth of graphene; this was then confirmed experimentally. These large-scale simulations also showed how graphene forms. The nickel atoms diffuse into the diamond and destroy its crystalline order, while carbon atoms from this amorphous solid move to the nickel surface and rapidly form honeycomb-like structures, resulting in mostly defect-free graphene. The nickel then percolated through the fine crystalline grains of the UNCD, sinking out of the way and removing the need for acid to dissolve away excess metal atoms from the top surface. "It is like meeting a good Samaritan at an unknown place who helps you, does his job and leaves quietly without a trace," said Sumant. "The proven predictive power of our simulations places us in a position of advantage to enable rapid discovery of new catalytic alloys that mediate growth of high-quality graphene on dielectrics and move away on their own when the growth is completed," added Narayanan. In addition to the utility in making minimally defective, application-ready graphene for things like low-frequency vibration sensors, radio frequency transistors and better electrodes for water purification, Berman and Sumant say that the Argonne team has already secured three patents arising from their new graphene growth method. The researchers have already struck a collaboration with Swedish Institute of Space Physics involving the European Space Agency for their Jupiter Icy Moons Explorer (JUICE) program to develop graphene-coated probes that may help exploratory vehicles sense the properties of plasma surrounding the moons of Jupiter. Closer to home, the team has also crafted diamond and graphene needles for researchers at North Carolina University to use in biosensing applications. The Argonne researchers are now fine-tuning the process – tweaking the temperature used to catalyze the reaction and adjusting the thickness of the diamond substrate and the composition of the metal film that facilitates the graphene growth – to both optimize the reaction and to better study the physics at the graphene-diamond interface. "We're trying to tune this more carefully to have a better understanding of which conditions lead to what quality of graphene we're seeing," Berman said. Other Argonne authors involved in the study were Alexander Zinovev and Daniel Rosenmann. The paper, "Metal-induced rapid transformation of diamond into single and multilayer graphene on wafer scale," is published inNature Communications.


News Article | March 3, 2017
Site: phys.org

A team of Argonne researchers led by materials scientist Anand Bhattacharya examined the relationship at interfaces between layers of nonmagnetic nickel-based nickelate material and a ferromagnetic manganese-based manganite. The samples were grown with single atomic layer precision using molecular beam epitaxy at Argonne's Center for Nanoscale Materials, a DOE Office of Science User Facility, by postdoctoral researcher and first author on the study Jason Hoffman. The researchers found that as electrons flowed out of the manganite into the neighboring nickelate, the non-magnetic nickelate suddenly became magnetic – but not in a typical way. While most magnetic materials are "collinear", meaning that the magnetic orientations of the electrons in the materials are arranged either in the same or opposite directions – that is, what we think of as "north" or "south" – this was not the case for the affected nickelate. As the electrons flowed into the nickelate, it created a magnetization with a twisting pattern as in a helix. Although it is nonmagnetic on its own, the nickelate has certain proclivities that make it a good candidate for being "willing to be swayed," Bhattacharya said. "The measure that scientists use to quantify how much a material wants to be magnetic is called 'magnetic susceptibility," Bhattacharya explained. "The nickelate has a very peculiar magnetic susceptibility, which varies from atom to atom within the material. Under the influence of the neighboring manganite, the nickelate becomes magnetic in a surprising way, causing a non-uniform helical magnetic structure to develop in the nickelate." According to Bhattacharya, magnetic noncollinearity is difficult to tailor in the laboratory. "This noncollinear twisty magnetism is shown by only a very few types of materials and is quite rare in nature," said Bhattacharya. "It's an exciting property to have in a material because you could conceivably use the different magnetic orientations to encode data in a novel kind of magnetic memory, or to nucleate new kinds of superconducting states that might be useful in a quantum computer." More information: Jason D. Hoffman et al. Oscillatory Noncollinear Magnetism Induced by Interfacial Charge Transfer in Superlattices Composed of Metallic Oxides, Physical Review X (2016). DOI: 10.1103/PhysRevX.6.041038

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