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News Article | December 16, 2016
Site: phys.org

Now, scientists from the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, California State University-Northridge, Soochow University, Peking University, and Shanghai Institute of Applied Physics have developed catalysts that can undergo 50,000 voltage cycles with a negligible decay in their catalytic activity and no apparent changes in their structure or elemental composition. As described in a paper published online in the December 16 issue of Science, the catalysts are "nanoplates" that contain an atomically ordered Pt and lead (Pb) core surrounded by a thick uniform shell of four Pt layers. To date, the most successful catalysts for boosting the activity of the oxygen reduction reaction (ORR)—a very slow reaction that significantly limits fuel cell efficiency—have been of the Pt-based core-shell structure. However, these catalysts typically have a thin and incomplete shell (owing to their difficult synthesis), which over time allows the acid from the fuel cell environment to leach into the core and react with the other metals inside, resulting in poor long-term stability and a short catalyst lifetime. "The goal is to make the ORR as fast as possible with catalysts that have the least amount of platinum and the most stable operation over time," said corresponding author Dong Su, a scientist at Brookhaven Lab's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility, who led the electron microscopy work to characterize the nanoplates. "Our PtPb/Pt catalysts show high ORR activity and stability—two parameters that are key to enabling a hydrogen economy—placing them among the most efficient and stable bimetallic catalysts reported for ORR." In previous studies, scientists have shown that ORR activity can be optimally enhanced in core-shell catalysts by compressing the Pt atoms on one specific lattice surface plane called Pt(111). This compressive strain is induced by adding metals smaller in size than Pt, such as nickel, to the shell's core, and has the effect of weakening the binding of oxygen to the Pt surface, where the catalytic reaction takes place. "The ideal ORR catalyst needs to help break bonds (between oxygen molecules) and form bonds (between oxygen and hydrogen), so oxygen can't be too strongly or too weakly bound to the platinum surface," explained Su. "Scientists have focused their research on the compressively strained Pt(111) surfaces, in which Pt atoms are squeezed across the surface, because the oxygen binding energy is optimized. In general, scientists thought that tensile strain on the same surface plane would result in overly strong binding of oxygen and thus hinder the ORR reaction." But Su and his collaborators showed that introducing a large tensile strain along one direction of a different surface plane, Pt(110), could also improve ORR catalytic activity. They added Pb (which is larger than Pt) to the core of the Pt shell, causing the Pt atoms to stretch across the surface. After the research group led by Xiaoqing Huang, corresponding author from Soochow University, synthesized the nanoplates, Su characterized their structure and elemental composition at the CFN. Using electron diffraction patterns and images from high-resolution scanning transmission electron microscopy (STEM), both of which reveal the relative positions of atoms, he confirmed the core-shell structure and the composition and sequence of the atoms. To verify that the core contained Pt and Pb and that the shell contained Pt, he measured the change in energy of the electrons after they interacted with the nanoplates—a technique called electron energy-loss spectroscopy. With this information, the team distinguished how the nanoplates formed with the individual Pt and Pb atoms. To their surprise, the surface planes were not Pt(111) but Pt(110), and these Pt(110) planes were under biaxial strain—compressive strain in one direction and tensile strain in the other—originating from the PtPb core. In durability tests simulating fuel cell voltage cycling, Su's collaborators found that after 50,000 cycles there was almost no change in the amount of generated electrical current. In other words, the nanoplates had minimal decay in catalytic activity. After this many cycles, most catalysts exhibit some activity loss, with some losing more than half of their original activity. Microscopy and synchrotron characterization techniques revealed that the structure and elemental composition of the nanoplates did not change following durability testing. "The electron microscopy work at CFN was critical in explaining why our nanoplates showed such high catalytic activity and stability," said Huang. Compared to commercial Pt-on-carbon (Pt/C) catalysts, the team's PtPb/Pt nanoplates have one of the highest ORR activities to date, taking the amount of Pt used into account, and excellent durability. The team's nanoplates also showed high electrocatalytic activity and stability in oxidation reactions of methanol and ethanol. "We believe the relatively thick and complete Pt layers play an important role in protecting the core," said Su. To understand how the high ORR activity originates in the nanoplates, the scientists calculated the binding energy between oxygen atoms and Pt atoms on the surface. Their calculations confirmed the tensile strain on the Pt(110) surface was responsible for the enhanced ORR activity. "This work opens up a new way to introduce large tensile strain on the stable Pt(110) plane to achieve very high activity for oxygen reduction catalysis. We believe that our approach will inspire efforts to design new nanostructured catalysts with large tensile strain for more efficient catalysis," said corresponding author Shaojun Guo of Peking University. Eventually, the laboratory-level electrocatalysts will need to be tested in a larger fuel cell system, where real-world variables—such as pollutants that could impact surface reactivity—can be introduced. Explore further: For platinum catalysts, tiny squeeze gives big boost in performance


Home > Press > Water-Repellent Nanotextures Found to Have Excellent Anti-Fogging Abilities: Cone-shaped nanotextures could prevent fog condensation on surfaces in humid environments, including for power generation and transportation applications Abstract: Some insect bodies have evolved the abilities to repel water and oil, adhere to different surfaces, and eliminate light reflections. Scientists have been studying the physical mechanisms underlying these remarkable properties found in nature and mimicking them to design materials for use in everyday life. Several years ago, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory developed a nanoscale surface-texturing method for imparting complete water repellency to materials-a property inspired by insect exoskeletons that have tiny hairs designed to repel water by trapping air. Their method leverages the ability of materials called block copolymers (chains of two distinct molecules linked together) to self-assemble into ordered patterns with dimensions measuring only tens of nanometers in size. The scientists used these self-assembled patterns to create nanoscale textures in a variety of inorganic materials, including silicon, glass, and some plastics. Initially, they studied how changing the shape of the textures from cylindrical to conical impacted materials' ability to repel water. Cone-shaped nanotextures proved much better at forcing water droplets to roll off, carrying dirt particles away and leaving surfaces completely dry. Now, working with colleagues in France-from ESPCI Paris Tech, École Polytechnique, and the Thales Group-they have further shown that the optimized nanotextures have excellent anti-fogging abilities, as described in a paper published online in the Feb. 27 issue of Nature Materials. Led by David Quéré of ESPCI and École Polytechnique, the research provides a fundamental understanding that may inform new designs for condensing coils of steam turbine power generators, car and aircraft windshields, and other materials prone to fogging. "Many textured materials can repel water, with millimeter-size water drops bouncing off their surfaces, but many of these surfaces fail when exposed to foggy or humid conditions," said Charles Black, director of Brookhaven Lab's Center for Functional Nanomaterials [ https://www.bnl.gov/cfn/ ] (CFN), the DOE Office of Science User Facility where Black and former physicist Antonio Checco of Brookhaven's Condensed Matter Physics and Materials Science Department and former CFN postdoctoral research associate Atikur Rahman fabricated the nanotextures. Fog forms when warm, moist air hits a cooler surface (such as a window or windshield) and forms water droplets-a process called condensation. When water droplets are similar in size to the structural features of a textured hydrophobic ("water hating") surface, they can get inside and grow within the texture, instead of remaining on top. Once the texture fills up, water landing on the material gets stuck, resulting in the appearance of fog. Scientists have previously observed that the wings of cicadas, which are covered by nanosized cone-shaped textures, have the ability to repel fog by causing water droplets to spontaneously jump off their surface-a phenomenon caused by the efficient conversion of surface energy to kinetic energy when two droplets combine. Motivated by this example from nature, the team investigated how reducing texture size and changing texture shape impacts the anti-fogging ability of a model surface. To simulate fogging conditions, the scientists heated water and measured the adhesion force as warm water droplets cooled upon contacting the nanotextured surfaces. These measurements revealed that droplet adhesion was significantly affected by the type of surface nanotexture, with warm drops strongly sticking to those with large textures and hardly sticking at all to surfaces with the smallest ones. "Textures with the smallest feature sizes and the appropriate shape-in this case, conical-resist fogging because condensing water droplets are too big to penetrate the texture. The droplets remain on top, essentially floating on the cushion of air trapped beneath," said Black. The scientists next used an optical microscope connected to a high-resolution video camera to view droplet condensation on different textures during dew formation, when atmospheric moisture condenses faster than it evaporates. While all textures are initially covered by large numbers of microdroplets, over time textures with a cylindrical shape become covered in water, while the ones with a conical shape spontaneously dry themselves. Conical-shaped textures resist dew formation because the water droplets are so lightly adhered to the surface that when two drops join together, they gain enough energy to spontaneously jump off the surface, similar to the mechanism observed in cicada wings. "This work represents the excellent, multiplicative power of DOE user facilities. In this case, CFN's initial collaboration with a user from one of Brookhaven's departments led to a new international connection with different users, who carried the study of hydrophobic surfaces in new directions," said Black. This research was supported by the DOE Office of Science, the French Ministry of Defense procurement agency, and the Thales Group. About Brookhaven National Laboratory Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The 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. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article | February 16, 2017
Site: www.nanotech-now.com

Abstract: Francis (Frank) Alexander, a physicist with extensive management and leadership experience in computational science research, has been named Deputy Director of the Computational Science Initiative at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, effective February 1. Alexander comes to Brookhaven Lab from DOE's Los Alamos National Laboratory, where he was the acting division leader of the Computer, Computational, and Statistical Sciences (CCS) Division. During his more than 20 years at Los Alamos, he held several leadership roles, including as leader of the CCS Division's Information Sciences Group and leader of the Information Science and Technology Institute. Alexander first joined Los Alamos in 1991 as a postdoctoral researcher at the Center for Nonlinear Studies. He returned to Los Alamos in 1998 after doing postdoctoral work at the Institute for Scientific Computing Research at DOE's Lawrence Livermore National Laboratory and serving as a research assistant professor at Boston University's Center for Computational Science. "I was drawn to Brookhaven by the exciting opportunity to strengthen the ties between computational science and the significant experimental facilities-the Relativistic Heavy Ion Collider, the National Synchrotron Light Source II, and the Center for Functional Nanomaterials [all DOE Office of Science User Facilities]," said Alexander. "The challenge of getting the most out of high-throughput and data-rich science experiments is extremely exciting to me. I very much look forward to working with the talented individuals at Brookhaven on a variety of projects, and am grateful for the opportunity to be part of such a respected institution." In his new role as deputy director, Alexander will work with CSI Director Kerstin Kleese van Dam to expand CSI's research portfolio and realize its potential in data-driven discovery. He will serve as the primary liaison to national security agencies, as well as develop strategic partnerships with other national laboratories, universities, and research institutions. His current research interest is the intersection of machine learning and physics (and other domain sciences). "We are incredibly happy that Frank decided to join our CSI team," said Kleese van Dam. "With his background in high-performance computing, data science, and computational and statistical physics, he is the ideal fit for Brookhaven." Throughout his career, Alexander has worked in a variety of areas, including nonequilibrium physics and computational physics. More recently, he has focused on the optimal design of experiments as part of the joint DOE/National Cancer Institute collaboration on cancer research, as well as on uncertainty quantification and error analysis for the prediction of complex systems' behavior. Alexander has served on many committees and advisory panels, including those related to DOE's Laboratory Directed Research and Development [http://science.energy.gov/lp/laboratory-directed-research-and-development/] program. Currently, he is on DOE's Computational Research Leadership Council and the editorial board of Computing in Science & Engineering Magazine. Alexander received his PhD in physics in 1991 from Rutgers University and a BS in mathematics and physics in 1987 from The Ohio State University. About Brookhaven National Laboratory Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The 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 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 | September 27, 2016
Site: www.cemag.us

A team of scientists studying solar cells made from cadmium telluride, a promising alternative to silicon, has discovered that microscopic "fault lines" within and between crystals of the material act as conductive pathways that ease the flow of electric current. This research—conducted at the University of Connecticut and the U.S. Department of Energy's Brookhaven National Laboratory, and described in the journal Nature Energy—may help explain how a common processing technique turns cadmium telluride into an excellent material for transforming sunlight into electricity, and suggests a strategy for engineering more efficient solar devices that surpass the performance of silicon. "If you look at semiconductors like silicon, defects in the crystals are usually bad," said co-author Eric Stach, a physicist at Brookhaven Lab's Center for Functional Nanomaterials (CFN). As Stach explained, misplaced atoms or slight shifts in their alignment often act as traps for the particles that carry electric current—negatively charged electrons or the positively charged "holes" left behind when electrons are knocked loose by photons of sunlight, making them more mobile. The idea behind solar cells is to separate the positive and negative charges and run them through a circuit so the current can be used to power houses, satellites, or even cities. Defects interrupt this flow of charges and keep the solar cell from being as efficient as it could be. But in the case of cadmium telluride, the scientists found that boundaries between individual crystals and "planar defects"—fault-like misalignments in the arrangement of atoms—create pathways for conductivity, not traps. Members of Bryan Huey's group at the Institute of Materials Science at the University of Connecticut were the first to notice the surprising connection. In an effort to understand the effects of a chloride solution treatment that greatly enhances cadmium telluride's conductive properties, Justin Luria and Yasemin Kutes studied solar cells before and after treatment. But they did so in a unique way. Several groups around the world had looked at the surfaces of such solar cells before, often with a tool known as a conducting atomic force microscope. The microscope has a fine probe many times sharper than the head of a pin that scans across the material's surface to track the topographic features—the hills and valleys of the surface structure—while simultaneously measuring location-specific conductivity. Scientists use this technique to explore how the surface features relate to solar cell performance at the nanoscale. But no one had devised a way to make measurements beneath the surface, the most important part of the solar cell. This is where the UConn team made an important breakthrough. They used an approach developed and perfected by Kutes and Luria over the last two years to acquire hundreds of sequential images, each time intentionally removing a nanoscale layer of the material, so they could scan through the entire thickness of the sample. They then used these layer-by-layer images to build up a three-dimensional, high-resolution 'tomographic' map of the solar cell—somewhat like a computed tomography (CT) brain scan. "Everyone using these microscopes basically takes pictures of the 'ground,' and interprets what is beneath," Huey said. "It may look like there's a cave, or a rock shelf, or a building foundation down there. But we can only really know once we carefully dig, like archeologists, keeping track of exactly what we find every step of the way—though, of course, at a much, much smaller scale." The resulting CT-AFM maps uniquely revealed current flowing most freely along the crystal boundaries and fault-like defects in the cadmium telluride solar cells. The samples that had been treated with the chloride solution had more defects overall, a higher density of these defects, and what appeared to be a high degree of connectivity among them, while the untreated samples had few defects, no evidence of connectivity, and much lower conductivity. Huey's team suspected that the defects were so-called planar defects, usually caused by shifts in atomic alignments or stacking arrangements within the crystals. But the CTAFM system is not designed to reveal such atomic-scale structural details. To get that information, the UConn team turned to Stach, head of the electron microscopy group at the CFN, a DOE Office of Science User Facility. "Having previously shared ideas with Eric, it was a natural extension of our discovery to work with his group," Huey said. Said Stach, "This is the exact type of problem the CFN is set up to handle, providing expertise and equipment that university researchers may not have to help drive science from hypothesis to discovery." CFN staff physicist Lihua Zhang used a transmission electron microscope (TEM) and UConn's results as a guide to meticulously study how atomic scale features of chloride-treated cadmium telluride related to the conductivity maps. The TEM images revealed the atomic structure of the defects, confirming that they were due to specific changes in the stacking sequence of atoms in the material. The images also showed clearly that these planar defects connected different grains in the crystal, leading to high-conductivity pathways for the movement of electrons and holes. "When we looked at the regions with good conductivity, the planar defects linked from one crystal grain to another, forming continuous pathways of conductance through the entire thickness of the material," said Zhang. "So the regions that had the best conductivity were the ones that had a high degree of connectivity among these defects." The authors say it's possible that the chloride treatment helps to create the connectivity, not just more defects, but that more research is needed to definitively determine the most significant effects of the chloride solution treatment. In any case, Stach says that combining the CTAFM technique and electron microscopy, yields a "clear winner" in the search for more efficient, cost-competitive alternatives to silicon solar cells, which have nearly reached their limit for efficiency. "There is already a billion-dollar-a-year industry making cadmium telluride solar cells, and lots of work exploring other alternatives to silicon. But all of these alternatives, because of their crystal structure, have a higher tendency to form defects," he said. "This work gives us a systematic method we can use to understand if the defects are good or bad in terms of conductivity. It can also be used to explore the effects of different processing methods or chemicals to control how defects form. In the case of cadmium telluride, we may want to find ways to make more of these defects, or look for other materials in which defects improve performance." This research was supported by the DOE Office of Energy Efficiency and Renewable Energy (EERE)—including its SunShot Initiative—and the DOE Office of Science. The cadmium telluride samples were provided by Andrew Moore of Colorado State University.


Some insect bodies have evolved the abilities to repel water and oil, adhere to different surfaces, and eliminate light reflections. Scientists have been studying the physical mechanisms underlying these remarkable properties found in nature and mimicking them to design materials for use in everyday life. Several years ago, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory developed a nanoscale surface-texturing method for imparting complete water repellency to materials--a property inspired by insect exoskeletons that have tiny hairs designed to repel water by trapping air. Their method leverages the ability of materials called block copolymers (chains of two distinct molecules linked together) to self-assemble into ordered patterns with dimensions measuring only tens of nanometers in size. The scientists used these self-assembled patterns to create nanoscale textures in a variety of inorganic materials, including silicon, glass, and some plastics. Initially, they studied how changing the shape of the textures from cylindrical to conical impacted materials' ability to repel water. Cone-shaped nanotextures proved much better at forcing water droplets to roll off, carrying dirt particles away and leaving surfaces completely dry. Now, working with colleagues in France--from ESPCI Paris Tech, École Polytechnique, and the Thales Group--they have further shown that the optimized nanotextures have excellent anti-fogging abilities, as described in a paper published online in the Feb. 27 issue of Nature Materials. Led by David Quéré of ESPCI and École Polytechnique, the research provides a fundamental understanding that may inform new designs for condensing coils of steam turbine power generators, car and aircraft windshields, and other materials prone to fogging. "Many textured materials can repel water, with millimeter-size water drops bouncing off their surfaces, but many of these surfaces fail when exposed to foggy or humid conditions," said Charles Black, director of Brookhaven Lab's Center for Functional Nanomaterials (CFN), the DOE Office of Science User Facility where Black and former physicist Antonio Checco of Brookhaven's Condensed Matter Physics and Materials Science Department and former CFN postdoctoral research associate Atikur Rahman fabricated the nanotextures. Fog forms when warm, moist air hits a cooler surface (such as a window or windshield) and forms water droplets--a process called condensation. When water droplets are similar in size to the structural features of a textured hydrophobic ("water hating") surface, they can get inside and grow within the texture, instead of remaining on top. Once the texture fills up, water landing on the material gets stuck, resulting in the appearance of fog. Scientists have previously observed that the wings of cicadas, which are covered by nanosized cone-shaped textures, have the ability to repel fog by causing water droplets to spontaneously jump off their surface--a phenomenon caused by the efficient conversion of surface energy to kinetic energy when two droplets combine. Motivated by this example from nature, the team investigated how reducing texture size and changing texture shape impacts the anti-fogging ability of a model surface. To simulate fogging conditions, the scientists heated water and measured the adhesion force as warm water droplets cooled upon contacting the nanotextured surfaces. These measurements revealed that droplet adhesion was significantly affected by the type of surface nanotexture, with warm drops strongly sticking to those with large textures and hardly sticking at all to surfaces with the smallest ones. "Textures with the smallest feature sizes and the appropriate shape--in this case, conical--resist fogging because condensing water droplets are too big to penetrate the texture. The droplets remain on top, essentially floating on the cushion of air trapped beneath," said Black. The scientists next used an optical microscope connected to a high-resolution video camera to view droplet condensation on different textures during dew formation, when atmospheric moisture condenses faster than it evaporates. While all textures are initially covered by large numbers of microdroplets, over time textures with a cylindrical shape become covered in water, while the ones with a conical shape spontaneously dry themselves. Conical-shaped textures resist dew formation because the water droplets are so lightly adhered to the surface that when two drops join together, they gain enough energy to spontaneously jump off the surface, similar to the mechanism observed in cicada wings. "This work represents the excellent, multiplicative power of DOE user facilities. In this case, CFN's initial collaboration with a user from one of Brookhaven's departments led to a new international connection with different users, who carried the study of hydrophobic surfaces in new directions," said Black.


Working with scientists at two other Department of Energy (DOE) labs—Brookhaven National Laboratory and SLAC National Accelerator Laboratory—a team led by Berkeley Lab battery scientist Marca Doeff was surprised to find that using a simple technique called spray pyrolysis can help to overcome one of the biggest problems associated with NMC cathodes—surface reactivity, which leads to material degradation. "We made some regular material using this technique, and lo and behold, it performed better than expected," said Doeff, who has been studying NMC cathodes for about seven years. "We were at a loss to explain this, and none of our conventional material characterization techniques told us what was going on, so we went to SLAC and Brookhaven to use more advanced imaging techniques and found that there was less nickel on the particle surfaces, which is what led to the improvement. High nickel content is associated with greater surface reactivity." Their results were published online in the premier issue of the journal Nature Energy in an article titled, "Metal segregation in hierarchically structured cathode materials for high-energy lithium batteries." The facilities used were the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC and the Center for Functional Nanomaterials (CFN) at Brookhaven, both DOE Office of Science User Facilities. These results are potentially significant because they pave the way for making lithium-ion batteries that are cheaper and have higher energy density. "We still want to increase the nickel content even further, and this gives us a possible avenue for doing that," Doeff said. "The nickel is the main electro-active component, plus it's less expensive than cobalt. The more nickel you have, the more practical capacity you may have at voltages that are practical to use. We want more nickel, but at the same time, there's the problem with surface reactivity." The cathode is the positive electrode in a battery, and development of an improved cathode material is considered essential to achieving a stable high-voltage cell, the subject of intense research. Spray pyrolysis is a commercially available technique used for making thin films and powders but has not been widely used to make materials for battery production. The surface reactivity is a particular problem for high-voltage cycling, which is necessary to achieve higher capacities needed for high-energy devices. The phenomenon has been studied and various strategies have been tried to ameliorate the issue over the years, including using partial titanium substitution for cobalt, which counteracts the reactivity of the surfaces to some extent. At SSRL researchers Dennis Nordlund and Yijin Liu used x-ray transmission microscopy and spectroscopy to examine the material in the tens of nanometers to 10-30 micron range. At CFN researcher Huolin Xin used a technique called electron energy loss spectroscopy (EELS) with a scanning transmission electron microscope (STEM), which was able to zoom in on details down to the nanoscale. At these two scales, Doeff and her Berkeley Lab colleagues—Feng Lin, Yuyi Li, Matthew Quan, and Lei Cheng—working with the scientists at SSRL and CFN made some important findings about the material. Lin, a former Berkeley Lab postdoctoral researcher working with Doeff and first author on the paper, said: "Our previous studies revealed that engineering the surface of cathode particles could be the key to stabilizing battery performance. After some deep effort to understand the stability challenges of NMC cathodes, we are now getting one step closer to improving NMC cathodes by tuning surface metal distribution." The research results point the way to further refinements. "This research suggests a path forward to getting these materials to cycle with higher capacities—that is to design materials that are graded, with less nickel on the surface," Doeff said. "I think our next step will be to try to make these materials with a larger compositional gradient and combine some other things to make them work together, such as titanium substitution, so we can utilize more capacity and thereby increase the energy density in a lithium ion battery." Spray pyrolysis is an inexpensive, common technique for making materials. "The reason we like it is that it offers a lot of control over the morphology. You get beautiful spherical morphology which is very good for battery materials," Doeff said. "We're not the first ones who have come up with idea of decreasing nickel on the surface. But we were able to do it in one step using a very simple procedure." Explore further: Argonne battery technology confirmed by US Patent Office


News Article | March 2, 2017
Site: www.eurekalert.org

UPTON, NY -- Some insect bodies have evolved the abilities to repel water and oil, adhere to different surfaces, and eliminate light reflections. Scientists have been studying the physical mechanisms underlying these remarkable properties found in nature and mimicking them to design materials for use in everyday life. Several years ago, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory developed a nanoscale surface-texturing method for imparting complete water repellency to materials--a property inspired by insect exoskeletons that have tiny hairs designed to repel water by trapping air. Their method leverages the ability of materials called block copolymers (chains of two distinct molecules linked together) to self-assemble into ordered patterns with dimensions measuring only tens of nanometers in size. The scientists used these self-assembled patterns to create nanoscale textures in a variety of inorganic materials, including silicon, glass, and some plastics. Initially, they studied how changing the shape of the textures from cylindrical to conical impacted materials' ability to repel water. Cone-shaped nanotextures proved much better at forcing water droplets to roll off, carrying dirt particles away and leaving surfaces completely dry. Now, working with colleagues in France--from ESPCI Paris Tech, École Polytechnique, and the Thales Group--they have further shown that the optimized nanotextures have excellent anti-fogging abilities, as described in a paper published online in the Feb. 27 issue of Nature Materials. Led by David Quéré of ESPCI and École Polytechnique, the research provides a fundamental understanding that may inform new designs for condensing coils of steam turbine power generators, car and aircraft windshields, and other materials prone to fogging. "Many textured materials can repel water, with millimeter-size water drops bouncing off their surfaces, but many of these surfaces fail when exposed to foggy or humid conditions," said Charles Black, director of Brookhaven Lab's Center for Functional Nanomaterials (CFN), the DOE Office of Science User Facility where Black and former physicist Antonio Checco of Brookhaven's Condensed Matter Physics and Materials Science Department and former CFN postdoctoral research associate Atikur Rahman fabricated the nanotextures. Fog forms when warm, moist air hits a cooler surface (such as a window or windshield) and forms water droplets--a process called condensation. When water droplets are similar in size to the structural features of a textured hydrophobic ("water hating") surface, they can get inside and grow within the texture, instead of remaining on top. Once the texture fills up, water landing on the material gets stuck, resulting in the appearance of fog. Scientists have previously observed that the wings of cicadas, which are covered by nanosized cone-shaped textures, have the ability to repel fog by causing water droplets to spontaneously jump off their surface--a phenomenon caused by the efficient conversion of surface energy to kinetic energy when two droplets combine. Motivated by this example from nature, the team investigated how reducing texture size and changing texture shape impacts the anti-fogging ability of a model surface. To simulate fogging conditions, the scientists heated water and measured the adhesion force as warm water droplets cooled upon contacting the nanotextured surfaces. These measurements revealed that droplet adhesion was significantly affected by the type of surface nanotexture, with warm drops strongly sticking to those with large textures and hardly sticking at all to surfaces with the smallest ones. "Textures with the smallest feature sizes and the appropriate shape--in this case, conical--resist fogging because condensing water droplets are too big to penetrate the texture. The droplets remain on top, essentially floating on the cushion of air trapped beneath," said Black. The scientists next used an optical microscope connected to a high-resolution video camera to view droplet condensation on different textures during dew formation, when atmospheric moisture condenses faster than it evaporates. While all textures are initially covered by large numbers of microdroplets, over time textures with a cylindrical shape become covered in water, while the ones with a conical shape spontaneously dry themselves. Conical-shaped textures resist dew formation because the water droplets are so lightly adhered to the surface that when two drops join together, they gain enough energy to spontaneously jump off the surface, similar to the mechanism observed in cicada wings. "This work represents the excellent, multiplicative power of DOE user facilities. In this case, CFN's initial collaboration with a user from one of Brookhaven's departments led to a new international connection with different users, who carried the study of hydrophobic surfaces in new directions," said Black. This research was supported by the DOE Office of Science, the French Ministry of Defense procurement agency, and the Thales Group. Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The 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.


News Article | March 2, 2017
Site: www.cemag.us

Some insect bodies have evolved the abilities to repel water and oil, adhere to different surfaces, and eliminate light reflections. Scientists have been studying the physical mechanisms underlying these remarkable properties found in nature and mimicking them to design materials for use in everyday life. Several years ago, scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory developed a nanoscale surface-texturing method for imparting complete water repellency to materials — a property inspired by insect exoskeletons that have tiny hairs designed to repel water by trapping air. Their method leverages the ability of materials called block copolymers (chains of two distinct molecules linked together) to self-assemble into ordered patterns with dimensions measuring only tens of nanometers in size. The scientists used these self-assembled patterns to create nanoscale textures in a variety of inorganic materials, including silicon, glass, and some plastics. Initially, they studied how changing the shape of the textures from cylindrical to conical impacted materials’ ability to repel water. Cone-shaped nanotextures proved much better at forcing water droplets to roll off, carrying dirt particles away and leaving surfaces completely dry. Now, working with colleagues in France — from ESPCI Paris Tech, École Polytechnique, and the Thales Group — they have further shown that the optimized nanotextures have excellent anti-fogging abilities, as described in a paper published online in the Feb. 27 issue of Nature Materials. Led by David Quéré of ESPCI and École Polytechnique, the research provides a fundamental understanding that may inform new designs for condensing coils of steam turbine power generators, car and aircraft windshields, and other materials prone to fogging. “Many textured materials can repel water, with millimeter-size water drops bouncing off their surfaces, but many of these surfaces fail when exposed to foggy or humid conditions,” said Charles Black, director of Brookhaven Lab’s Center for Functional Nanomaterials (CFN), the DOE Office of Science User Facility where Black and former physicist Antonio Checco of Brookhaven’s Condensed Matter Physics and Materials Science Department and former CFN postdoctoral research associate Atikur Rahman fabricated the nanotextures. Fog forms when warm, moist air hits a cooler surface (such as a window or windshield) and forms water droplets — a process called condensation. When water droplets are similar in size to the structural features of a textured hydrophobic (“water hating”) surface, they can get inside and grow within the texture, instead of remaining on top. Once the texture fills up, water landing on the material gets stuck, resulting in the appearance of fog. Scientists have previously observed that the wings of cicadas, which are covered by nanosized cone-shaped textures, have the ability to repel fog by causing water droplets to spontaneously jump off their surface — a phenomenon caused by the efficient conversion of surface energy to kinetic energy when two droplets combine. Motivated by this example from nature, the team investigated how reducing texture size and changing texture shape impacts the anti-fogging ability of a model surface. To simulate fogging conditions, the scientists heated water and measured the adhesion force as warm water droplets cooled upon contacting the nanotextured surfaces. These measurements revealed that droplet adhesion was significantly affected by the type of surface nanotexture, with warm drops strongly sticking to those with large textures and hardly sticking at all to surfaces with the smallest ones. “Textures with the smallest feature sizes and the appropriate shape — in this case, conical — resist fogging because condensing water droplets are too big to penetrate the texture. The droplets remain on top, essentially floating on the cushion of air trapped beneath,” says Black. The scientists next used an optical microscope connected to a high-resolution video camera to view droplet condensation on different textures during dew formation, when atmospheric moisture condenses faster than it evaporates. While all textures are initially covered by large numbers of microdroplets, over time textures with a cylindrical shape become covered in water, while the ones with a conical shape spontaneously dry themselves. Conical-shaped textures resist dew formation because the water droplets are so lightly adhered to the surface that when two drops join together, they gain enough energy to spontaneously jump off the surface, similar to the mechanism observed in cicada wings. “This work represents the excellent, multiplicative power of DOE user facilities. In this case, CFN’s initial collaboration with a user from one of Brookhaven’s departments led to a new international connection with different users, who carried the study of hydrophobic surfaces in new directions,” says Black. This research was supported by the DOE Office of Science, the French Ministry of Defense procurement agency, and the Thales Group.


Several years ago, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory developed a nanoscale surface-texturing method for imparting complete water repellency to materials—a property inspired by insect exoskeletons that have tiny hairs designed to repel water by trapping air. Their method leverages the ability of materials called block copolymers (chains of two distinct molecules linked together) to self-assemble into ordered patterns with dimensions measuring only tens of nanometers in size. The scientists used these self-assembled patterns to create nanoscale textures in a variety of inorganic materials, including silicon, glass, and some plastics. Initially, they studied how changing the shape of the textures from cylindrical to conical impacted materials' ability to repel water. Cone-shaped nanotextures proved much better at forcing water droplets to roll off, carrying dirt particles away and leaving surfaces completely dry. Now, working with colleagues in France—from ESPCI Paris Tech, École Polytechnique, and the Thales Group—they have further shown that the optimized nanotextures have excellent anti-fogging abilities, as described in a paper published online in the Feb. 27 issue of Nature Materials. Led by David Quéré of ESPCI and École Polytechnique, the research provides a fundamental understanding that may inform new designs for condensing coils of steam turbine power generators, car and aircraft windshields, and other materials prone to fogging. "Many textured materials can repel water, with millimeter-size water drops bouncing off their surfaces, but many of these surfaces fail when exposed to foggy or humid conditions," said Charles Black, director of Brookhaven Lab's Center for Functional Nanomaterials (CFN), the DOE Office of Science User Facility where Black and former physicist Antonio Checco of Brookhaven's Condensed Matter Physics and Materials Science Department and former CFN postdoctoral research associate Atikur Rahman fabricated the nanotextures. Fog forms when warm, moist air hits a cooler surface (such as a window or windshield) and forms water droplets—a process called condensation. When water droplets are similar in size to the structural features of a textured hydrophobic ("water hating") surface, they can get inside and grow within the texture, instead of remaining on top. Once the texture fills up, water landing on the material gets stuck, resulting in the appearance of fog. Scientists have previously observed that the wings of cicadas, which are covered by nanosized cone-shaped textures, have the ability to repel fog by causing water droplets to spontaneously jump off their surface—a phenomenon caused by the efficient conversion of surface energy to kinetic energy when two droplets combine. Motivated by this example from nature, the team investigated how reducing texture size and changing texture shape impacts the anti-fogging ability of a model surface. To simulate fogging conditions, the scientists heated water and measured the adhesion force as warm water droplets cooled upon contacting the nanotextured surfaces. These measurements revealed that droplet adhesion was significantly affected by the type of surface nanotexture, with warm drops strongly sticking to those with large textures and hardly sticking at all to surfaces with the smallest ones. "Textures with the smallest feature sizes and the appropriate shape—in this case, conical—resist fogging because condensing water droplets are too big to penetrate the texture. The droplets remain on top, essentially floating on the cushion of air trapped beneath," said Black. The scientists next used an optical microscope connected to a high-resolution video camera to view droplet condensation on different textures during dew formation, when atmospheric moisture condenses faster than it evaporates. While all textures are initially covered by large numbers of microdroplets, over time textures with a cylindrical shape become covered in water, while the ones with a conical shape spontaneously dry themselves. Conical-shaped textures resist dew formation because the water droplets are so lightly adhered to the surface that when two drops join together, they gain enough energy to spontaneously jump off the surface, similar to the mechanism observed in cicada wings. "This work represents the excellent, multiplicative power of DOE user facilities. In this case, CFN's initial collaboration with a user from one of Brookhaven's departments led to a new international connection with different users, who carried the study of hydrophobic surfaces in new directions," said Black. More information: Timothée Mouterde et al, Antifogging abilities of model nanotextures, Nature Materials (2017). DOI: 10.1038/nmat4868


News Article | November 10, 2016
Site: www.eurekalert.org

BROOKLYN, New York - Researchers at the NYU Tandon School of Engineering have pioneered a method for growing an atomic scale electronic material at the highest quality ever reported. In a paper published in Applied Physics Letters, Assistant Professor of Electrical and Computer Engineering Davood Shahrjerdi and doctoral student Abdullah Alharbi detail a technique for synthesizing large sheets of high-performing monolayer tungsten disulfide, a synthetic material with a wide range of electronic and optoelectronic applications. "We developed a custom reactor for growing this material using a routine technique called chemical vapor deposition. We made some subtle and yet critical changes to improve the design of the reactor and the growth process itself, and we were thrilled to discover that we could produce the highest quality monolayer tungsten disulfide reported in the literature," said Shahrjerdi. "It's a critical step toward enabling the kind of research necessary for developing next-generation transistors, wearable electronics, and even flexible biomedical devices." The promise of two-dimensional electronic materials has tantalized researchers for more than a decade, since the first such material -- graphene -- was experimentally discovered. Also called "monolayer" materials, graphene and similar two-dimensional materials are a mere one atom in thickness, several hundred thousand times thinner than a sheet of paper. These materials boast major advantages over silicon -- namely unmatched flexibility, strength, and conductivity -- but developing practical applications for their use has been challenging. Graphene (a single layer of carbon) has been explored for electronic switches (transistors), but its lack of an energy band gap poses difficulties for semiconductor applications. "You can't turn off the graphene transistors," explained Shahrjerdi. Unlike graphene, tungsten disulfide has a sizeable energy band gap. It also displays exciting new properties: When the number of atomic layers increases, the band gap becomes tunable, and at monolayer thickness it can strongly absorb and emit light, making it ideal for applications in optoelectronics, sensing, and flexible electronics. Efforts to develop applications for monolayer materials are often plagued by imperfections in the material itself -- impurities and structural disorders that can compromise the movement of charge carriers in the semiconductor (carrier mobility). Shahrjerdi and his student succeeded in reducing the structural disorders by omitting the growth promoters and using nitrogen as a carrier gas rather than a more common choice, argon. Shahrjerdi noted that comprehensive testing of their material revealed the highest values recorded thus far for carrier mobility in monolayer tungsten disulfide. "It's a very exciting development for those of us doing research in this field," he said. The researchers received support from the National Science Foundation and the Center for Functional Nanomaterials at Brookhaven National Laboratory. The paper, Electronic Properties of Monolayer Tungsten Disulfide Grown by Chemical Vapor Deposition, is available at http://scitation. . About the NYU Tandon School of Engineering The NYU Tandon School of Engineering dates to 1854, when the New York University School of Civil Engineering and Architecture as well as the Brooklyn Collegiate and Polytechnic Institute (widely known as Brooklyn Poly) were founded. Their successor institutions merged in January 2014 to create a comprehensive school of education and research in engineering and applied sciences, rooted in a tradition of invention, and entrepreneurship and dedicated to furthering technology in service to society. In addition to its main location in Brooklyn, NYU Tandon collaborates with other schools within the country's largest private research university and is closely connected to engineering programs in NYU Abu Dhabi and NYU Shanghai. It operates business incubators in downtown Manhattan and Brooklyn and an award-winning online graduate program. For more information, visit http://engineering. .

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