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  • richardmitnick 3:42 pm on May 16, 2016 Permalink | Reply
    Tags: , Material Sciences, Novel 'liquid wire' material inspired by spiders' capture silk,   

    From phys.org: “Scientists create novel ‘liquid wire’ material inspired by spiders’ capture silk” 

    physdotorg
    phys.org

    May 16, 2016

    1
    Hybrid material inspired from spiders. Credit: University of Oxford

    Why doesn’t a spider’s web sag in the wind or catapult flies back out like a trampoline? The answer, according to new research by an international team of scientists, lies in the physics behind a ‘hybrid’ material produced by spiders for their webs.

    Pulling on a sticky thread in a garden spider’s orb web and letting it snap back reveals that the thread never sags but always stays taut—even when stretched to many times its original length. This is because any loose thread is immediately spooled inside the tiny droplets of watery glue that coat and surround the core gossamer fibres of the web’s capture spiral.

    This phenomenon is described* in the journal PNAS by scientists from the University of Oxford, UK and the Université Pierre et Marie Curie, Paris, France.

    The researchers studied the details of this ‘liquid wire’ technique in spiders’ webs and used it to create composite fibres in the laboratory which, just like the spider’s capture silk, extend like a solid and compress like a liquid. These novel insights may lead to new bio-inspired technology.

    Professor Fritz Vollrath of the Oxford Silk Group in the Department of Zoology at Oxford University said: ‘The thousands of tiny droplets of glue that cover the capture spiral of the spider’s orb web do much more than make the silk sticky and catch the fly. Surprisingly, each drop packs enough punch in its watery skins to reel in loose bits of thread. And this winching behaviour is used to excellent effect to keep the threads tight at all times, as we can all observe and test in the webs in our gardens.’


    Access mp4 video here .

    The novel properties observed and analysed by the scientists rely on a subtle balance between fibre elasticity and droplet surface tension. Importantly, the team was also able to recreate this technique in the laboratory using oil droplets on a plastic filament. And this artificial system behaved just like the spider’s natural winch silk, with spools of filament reeling and unreeling inside the oil droplets as the thread extended and contracted.

    Dr Hervé Elettro, the first author and a doctoral researcher at Institut Jean Le Rond D’Alembert, Université Pierre et Marie Curie, Paris, said: ‘Spider silk has been known to be an extraordinary material for around 40 years, but it continues to amaze us. While the web is simply a high-tech trap from the spider’s point of view, its properties have a huge amount to offer the worlds of materials, engineering and medicine.

    ‘Our bio-inspired hybrid threads could be manufactured from virtually any components. These new insights could lead to a wide range of applications, such as microfabrication of complex structures, reversible micro-motors, or self-tensioned stretchable systems.’

    *Science paper: In-drop capillary spooling of spider capture thread inspires hybrid fibers with mixed solid–liquid mechanical properties, PNAS

    See the full article here .

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    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 7:20 pm on May 9, 2016 Permalink | Reply
    Tags: , Argonne Lab, Material Sciences, Molecular engineering,   

    From U Chicago: “Molecular engineers discuss future of computing, healthcare and energy storage” 

    U Chicago bloc

    University of Chicago

    May 9, 2016
    Greg Borzo

    1
    From left: Profs. Melody Swartz, Supratik Guha, David Awschalom and Paul Nealey discuss molecular engineering research being conducted at the University of Chicago and Argonne National Laboratory. Prof. Matthew Tirrell, director of IME and deputy laboratory director for science at Argonne, moderates the panel.

    Imagine unbreakable encryption, room-temperature superconductors, inexpensive molecular sensors, a cure for cancer. These are the challenges molecular engineers are taking on.

    These and other promising technologies were explored during “Future Science: Small Scale, Big Impact,” a presentation by scientists and engineers from the University of Chicago’s Institute for Molecular Engineering. The program, part of the UChicago Discovery Series, showcased research being conducted at the University and Argonne National Laboratory.

    Argonne Lab
    Argonne Lab Campus

    “We’re creating not only the first engineering program at the University of Chicago, but really the first of its kind in the world,” said moderator Matthew Tirrell, director of IME and deputy laboratory director for science at Argonne. “Engineering is about taking science into society and doing useful things for society,” he said.

    Trekkie technologies

    The program featured four speakers. David Awschalom, IME’s deputy director and an expert on spintronics and quantum information engineering, spoke about how some of the technology dreamed up long ago in Star Trek episodes, have actually become reality. The show’s universal translators and personal access data devices are today’s translation apps and tablet computers. Transporters, though, are still a work in progress, but quantum engineering is now enabling teleportation, a related technology operating at the level of single particles. Awschalom’s group is harnessing the way electrons spin to make highly sensitive sensors, build a framework for quantum simulators to design and test pharmaceuticals, develop tamper-proof encryption, bring medical imaging to the molecular level, and other cutting edge devices.

    “We’re building technologies with single atoms, and when you do that, the laws of quantum physics determine their behavior,” said Awschalom, the Liew Family Professor of Molecular Engineering. Quantum probes have extraordinary sensitivity and “may ultimately reveal the exact structure of molecules to determine their structural-functional relationships.

    “Students here are even taking quantum probes and placing them inside living cells,” he added. These probes “act as beacons, looking at the electromagnetic and thermal properties of the cells and sending that information out to the observer.

    “Quantum engineering is becoming a reality, and it will enable the discovery and design of new materials for practical applications,” Awschalom concluded. “What’s exciting is that we don’t know what ’s ahead in the future.”

    Nanoparticle vaccines that kill cancer

    Melody Schwartz, the William B. Ogden Professor of Molecular Engineering, noted that while engineers often take basic science and translate it into new technologies, engineers often do the reverse: use technology to understand basic science. For example, she and her collaborators are developing nanoparticle vaccines that can influence immune responses to tumors. These vaccines are designed to have surface molecules that look like a virus or bacteria, and Schwartz is researching whether these vaccines can activate immune system T-cells to kill tumors.

    “Cancer immunotherapy holds enormous promise,” she said. “One way to potentially facilitate cancer immunotherapy is to combine molecular engineering and nanotechnology with information about how the lymphatic system works.”

    Using protein engineering and nanoscale materials, this research is based on the fact the lymphatic system plays a central role in helping the immune system regulate immunity and make decisions about whether particular cells should be tolerated or killed.

    “The lymphatic system is a gold mine of information about tumors … such as the specific details of which proteins are being expressed and secreted,” she said. Targeting a lymph node that holds a metastatic tumor could manipulate the lymphatic system into using the information the system holds about that tumor to stimulate the immune system to fight the cancer. So far, Schwartz’s nanoparticle vaccines have been effective in mice when delivered to a lymph node to which cancer has metastasized. They have not been definitive when delivered to a lymph node on the other side of the body from where the cancer originated. Taken together, these results support the theory that the lymphatic system holds valuable information about a tumor, at least in mice.

    “Perhaps, instead of cutting out the lymph node of a patient (with cancer), we should target it and use (the information it holds),” Schwartz said.

    Cheaper sensors for agriculture and water utilization

    “Cyber physical systems that feature powerful yet inexpensive sensors made of nanoparticles will become ubiquitous,” said Supratik Guha, professor of molecular engineering and director of Argonne’s nanoscience and technology division. These systems will provide vast amounts of real-time data that will be used to measure and control pollution, electrical power consumption, water utilization, agricultural practices and other vital functions.

    “Nanotechnology has been around for about 25 years, but its ‘calling card’ will be what it does for sensors,” Guha said. “Nanoparticles are ideal for sensors because their properties are determined by the environment they’re in. They interact in different ways with light, magnetic fields, pressure” and other factors.

    Once these sensors become more powerful and less expensive, researchers will be able to “screw them in and out of cyber physical systems like light bulbs,” Guha said. “Once that happens, it could change the world.”

    For example, agriculture accounts for 70 percent of fresh water consumption. While working at IBM, Guha participated in an experiment at a vineyard that delivered water based on need rather than randomly. Using satellite data, each section was monitored for greenery—and then watered accordingly. “Over two harvests, yields and water efficiency went up by 10 to 20 percent,” Guha said.

    If agriculture could employ sensors to measure not only soil moisture but also dissolved nitrates, wind speed, plant disease, solar irradiance and other factors, tremendous savings could be realized, he concluded.

    “Magic materials” that can transform semi-conductor manufacturing

    When traditional photo lithographic techniques for manufacturing integrated circuits

    approached a limit to place an ever-increasing number of transistors on a single computer chip, other techniques, such as self-aligned double patterning, filled the gap, said Paul Nealey, the Brady W. Dougan professor of molecular engineering and senior scientist at Argonne.

    Nealey pioneered a relatively new technique called directed self-assembly, which involves making a chemical pattern on a chip and then depositing what he calls “magic materials” that respond to the chemical pattern and assemble themselves into the desired shape and structure.

    “These magic materials are not all that exotic,” Nealey said. They are co-polymers—two kinds of polymer chains connected at one end by a covalent bond. One of the materials is polystyrene (used to make plastic cups) and the other is PMMA (used to make Plexiglas). “These materials form structures at the molecular-length scale, which would be very difficult to achieve with traditional lithography.”

    Directed self-assembly is being commercialized in the context of semi-conductor manufacturing and applied to other areas, he added. For example, it is being used to make ion-conducting materials for membranes in fuel cells and batteries.

    Free and open to the public, the UChicago Discovery Series is designed to share the transformative research being conducted at the University. Attending this program were members of the Maroon Kids, a group organized by IME alumni and friends to promote interest in science and engineering topics among children in grades 6-12.

    One member asked, “How much do your fields interact with each other, and does solving a problem in one help solve a problem in another?”

    “Yes,” Schwartz answered. “New solutions will come from people who are interacting from completely different fields because they’re not stuck in one way of thinking about a solution. They’re coming at a problem from a fresh perspective and have multiple different perspectives.

    See the full article here .

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  • richardmitnick 10:33 am on April 5, 2016 Permalink | Reply
    Tags: , Material Sciences,   

    From Science Alert: “Scientists have just discovered a new state of matter – This is Big” 

    ScienceAlert

    Science Alert

    5 APR 2016
    FIONA MACDONALD

    1
    Genevieve Martin/Oak Ridge National Laboratory

    Researchers have just discovered evidence of a mysterious new state of matter in a real material. The state is known as ‘quantum spin liquid’ and it causes electrons – one of the fundamental, indivisible building blocks of matter – to break down into smaller quasiparticles.

    Scientists had first predicted the existence of this state of matter in certain magnetic materials 40 years ago, but despite multiple hints of its existence, they’ve never been able to detect evidence of it in nature. So it’s pretty exciting that they’ve now caught a glimpse of quantum spin liquid, and the bizarre fermions that accompany it, in a two-dimensional, graphene-like material.

    “This is a new quantum state of matter, which has been predicted but hasn’t been seen before,” said one of the researchers, Johannes Knolle, from the University of Cambridge in the UK.

    They were able to spot evidence of quantum spin liquid in the material by observing one of its most intriguing properties – electron fractionalisation – and the resulting Majorana fermions, which occur when electrons in a quantum spin state split apart. These Majorana fermions are exciting because they could be used as building blocks of quantum computers.

    To be clear, the electrons aren’t actually splitting down into smaller physical particles – which of course would be an even bigger deal (that would mean brand new particles!). What’s happening instead is the new state of matter is breaking electrons down into quasiparticles. These aren’t actually real particles, but are concepts used by physicists to explain and calculate the strange behaviour of particles.

    And the quantum spin liquid state is definitely making electrons act weirdly – in a typical magnetic material, electrons behave like tiny bar magnets. So when the material is cooled to a low enough temperature, these magnet-like electrons order themselves over long ranges, so that all the north magnetic poles point in the same direction.

    But in a material containing a quantum spin liquid state, even if a magnetic material is cooled to absolute zero, the electrons don’t align, but instead form an entangled soup caused by quantum fluctuations.

    “Until recently, we didn’t even know what the experimental fingerprints of a quantum spin liquid would look like,” said one of the researchers, Dmitry Kovrizhin. “One thing we’ve done in previous work is to ask, if I were performing experiments on a possible quantum spin liquid, what would I observe?”

    To figure out what was going on, the researchers worked alongside a team from Oak Ridge National Laboratory in Tennessee and used neutron scattering techniques to look for evidence of electron fractionalisation in alpha-ruthenium chloride – a material that’s structurally similar to graphene.

    ORNL
    ORNL

    This also allowed them to measure the signatures of Majorana fermions for the first time by illuminating the material with neutrons, and then observing the pattern of ripples that the neutrons produced when scattered from the sample.

    These patterns were exactly what they’d expect to see based on the main theoretical model of quantum spin liquid, confirming for the first time that they’d seen evidence of it happening in a material.

    “This is a new addition to a short list of known quantum states of matter,” said Knolle.

    “It’s an important step for our understanding of quantum matter,” added Kovrizhin. “It’s fun to have another new quantum state that we’ve never seen before – it presents us with new possibilities to try new things.”

    Some of those new things involve quantum computers – which would be exponentially faster than regular computers – so even though all of this sounds pretty theoretical, they could actually have some really exciting potential applications.

    The results have been published in Nature Materials.

    Proximate Kitaev quantum spin liquid behaviour in a honeycomb magnet

    The science team:
    A. Banerjee, C. A. Bridges, J.-Q. Yan, A. A. Aczel, L. Li, M. B. Stone, G. E. Granroth, M. D. Lumsden, Y. Yiu, J. Knolle, S. Bhattacharjee, D. L. Kovrizhin, R. Moessner, D. A. Tennant, D. G. Mandrus & S. E. Nagler

    Affiliations:

    Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
    A. Banerjee, A. A. Aczel, M. B. Stone, G. E. Granroth, M. D. Lumsden & S. E. Nagler
    Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
    C. A. Bridges
    Material Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
    J.-Q. Yan & D. G. Mandrus
    Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
    J.-Q. Yan & D. G. Mandrus
    Department of Physics, University of Tennessee, Knoxville, Tennessee 37996, USA
    L. Li & Y. Yiu
    Neutron Data Analysis & Visualization Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
    G. E. Granroth
    Department of Physics, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
    J. Knolle & D. L. Kovrizhin
    Max Planck Institute for the Physics of Complex Systems, D-01187 Dresden, Germany
    S. Bhattacharjee & R. Moessner
    International Center for Theoretical Sciences, TIFR, Bangalore 560012, India
    S. Bhattacharjee
    Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
    D. A. Tennant
    Bredesen Center, University of Tennessee, Knoxville, Tennessee 37966, USA
    S. E. Nagler

    Contributions

    S.E.N., A.B. and D.G.M. conceived the project and the experiment. C.A.B., A.B., L.L., J.-Q.Y., Y.Y. and D.G.M. made the sample. J.-Q.Y., L.L., A.B. and C.A.B. performed the bulk measurements, A.B., A.A.A., M.B.S., G.E.G., M.D.L. and S.E.N. performed INS measurements, A.B., S.E.N., C.A.B., M.D.L., M.B.S. and D.A.T. analysed the data. Further modelling and interpreting of the neutron scattering data was carried out by A.B., M.D.L., S.E.N., J.K., S.B., D.L.K. and R.M., where A.B., M.D.L., S.B. and S.E.N. performed SWT simulations, and J.K., S.B., D.L.K. and R.M. carried out QSL theory calculations. A.B. and S.E.N. prepared the first draft, and all authors contributed to writing the manuscript.

    See the full article here .

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  • richardmitnick 3:05 pm on February 2, 2016 Permalink | Reply
    Tags: "Shock/shear” platform, , , Material Sciences,   

    From LLNL: “NIF experiments shed light on turbulent mix” 


    Lawrence Livermore National Laboratory

    NIF Bloc
    LLNL NIF
    NIF

    LLNL NIF target on the National Ignition Facility (NIF) target positioner
    Cryogenics operator John Cagle mounts a target on the National Ignition Facility (NIF) target positioner for an experiment. An area backlighter disc is seen on-edge on the right of the assembly. The front of the target is covered with a gold shield with a diagnostic slit.

    Scientists from Los Alamos National Laboratory (LANL) are leading an experimental campaign on the National Ignition Facility (NIF) designed to further understand turbulent mix models used in both high energy density (HED) and inertial confinement fusion (ICF) experiments. NIF is the only facility with the energy and shot-to-shot reproducibility needed for the experiments.

    During shots using what’s known as the “shock/shear” platform, NIF fires 300 kilojoules of laser energy at each end of a target comprised of two half-hohlraums to produce shock waves from opposite ends of a foam-filled shock tube. These waves turn the foam into plasma and allow the shocks to travel and create a counter-propagating shear mixing effect across a metal foil.

    The target has evolved over time — different experiments have used titanium, copper, aluminum and roughened aluminum, and more materials are to come — but they all have one thing in common: each experiment enhances understanding of turbulent mix models in the HED regime. These models, developed and calibrated by LANL using hydrodynamic test data from the 1980s through the present, are now being examined through the lens of the shock/shear HED experiments to see how the data matches up to more extreme conditions.

    “We have created a system that reproduces instability features similar to those of traditional hydro experiments that have not previously been seen in HED experiments,” said LANL scientist Kirk Flippo, the lead experimental investigator. “This kind of experiment is rapidly evolving our understanding and we’ve discovered a lot of behaviors that we didn’t expect.”

    This enhanced understanding and refined data is vital for ICF. According to Flippo, it has become increasingly clear that ICF capsules experience some kind of mix as they are imploding.

    “Some of the outstanding issues in ICF are how does the capsule mix, how does this play into the degradation of the yield and how does it affect ignition,” he said. “It’s important for us to make sure that when we run a code to model an ICF implosion, we get all of the details correct. These experiments will help us quantify precisely how much of an effect this type of shear mixing has.”

    Shock/shear experiments initially were fielded on the OMEGA Laser at the University of Rochester’s Laboratory for Laser Energetics, but due to the limited volume that could be driven, the experiments experienced boundary effects. The LANL project manager, scientist John Kline, believed the platform was mature enough to be deployed on NIF and pushed hard for its implementation. Kline knew that by scaling the experiments up to NIF energies, the researchers would be able to take advantage of larger volumes to eliminate the edge effects and do the experiments they wanted to do.

    “We cannot do experiments in this way anywhere but at NIF,” Flippo said. “In the regimes that we are in at NIF, the experiment behaves much more like a traditional hydro experiment and scales like a hydro experiment would scale.”

    Data from the NIF experiments already has been used by the campaign’s principal investigator, LANL scientist Forrest Doss, to refine the way the model is implemented in the code — producing a direct, immediate impact. But the work isn’t complete just yet.

    “Now that this platform is available, and has been shown to produce really nice data, we can start modifying it by changing the shock velocities, changing the materials or foams and using different shocks,” Flippo said. “This platform has infinite variation and infinite complexity.”

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  • richardmitnick 10:33 am on January 20, 2016 Permalink | Reply
    Tags: , Material Sciences, , Switchable material   

    From MIT: “Switchable material could enable new memory chips” 


    MIT News

    January 20, 2016
    David L. Chandler | MIT News Office

    Temp 1
    This diagram shows how an electrical voltage can be used to modify the oxygen concentration, and therefore the phase and structure, of strontium cobaltites. Pumping oxygen in and out transforms the material from the brownmillerite form (left) to the perovskite form (right).
    Courtesy of the researchers

    Small voltage can flip thin film between two crystal states — one metallic, one semiconducting.

    Two MIT researchers have developed a thin-film material whose phase and electrical properties can be switched between metallic and semiconducting simply by applying a small voltage. The material then stays in its new configuration until switched back by another voltage. The discovery could pave the way for a new kind of “nonvolatile” computer memory chip that retains information when the power is switched off, and for energy conversion and catalytic applications.

    The findings, reported in the journal Nano Letters in a paper by MIT materials science graduate student Qiyang Lu and associate professor Bilge Yildiz, involve a thin-film material called a strontium cobaltite, or SrCoOx.

    Usually, Yildiz says, the structural phase of a material is controlled by its composition, temperature, and pressure. “Here for the first time,” she says, “we demonstrate that electrical bias can induce a phase transition in the material. And in fact we achieved this by changing the oxygen content in SrCoOx.”

    “It has two different structures that depend on how many oxygen atoms per unit cell it contains, and these two structures have quite different properties,” Lu explains.

    One of these configurations of the molecular structure is called perovskite, and the other is called brownmillerite. When more oxygen is present, it forms the tightly-enclosed, cage-like crystal structure of perovskite, whereas a lower concentration of oxygen produces the more open structure of brownmillerite.

    The two forms have very different chemical, electrical, magnetic, and physical properties, and Lu and Yildiz found that the material can be flipped between the two forms with the application of a very tiny amount of voltage — just 30 millivolts (0.03 volts). And, once changed, the new configuration remains stable until it is flipped back by a second application of voltage.

    Strontium cobaltites are just one example of a class of materials known as transition metal oxides, which is considered promising for a variety of applications including electrodes in fuel cells, membranes that allow oxygen to pass through for gas separation, and electronic devices such as memristors — a form of nonvolatile, ultrafast, and energy-efficient memory device. The ability to trigger such a phase change through the use of just a tiny voltage could open up many uses for these materials, the researchers say.

    Previous work with strontium cobaltites relied on changes in the oxygen concentration in the surrounding gas atmosphere to control which of the two forms the material would take, but that is inherently a much slower and more difficult process to control, Lu says. “So our idea was, don’t change the atmosphere, just apply a voltage.”

    “Voltage modifies the effective oxygen pressure that the material faces,” Yildiz adds. To make that possible, the researchers deposited a very thin film of the material (the brownmillerite phase) onto a substrate, for which they used yttrium-stabilized zirconia.

    In that setup, applying a voltage drives oxygen atoms into the material. Applying the opposite voltage has the reverse effect. To observe and demonstrate that the material did indeed go through this phase transition when the voltage was applied, the team used a technique called in-situ X-ray diffraction at MIT’s Center for Materials Science and Engineering.

    The basic principle of switching this material between the two phases by altering the gas pressure and temperature in the environment was developed within the last year by scientists at Oak Ridge National Laboratory. “While interesting, this is not a practical means for controlling device properties in use,” says Yildiz. With their current work, the MIT researchers have enabled the control of the phase and electrical properties of this class of materials in a practical way, by applying an electrical charge.

    In addition to memory devices, the material could ultimately find applications in fuel cells and electrodes for lithium ion batteries, Lu says.

    “Our work has fundamental contributions by introducing electrical bias as a way to control the phase of an active material, and by laying the basic scientific groundwork for such novel energy and information processing devices,” Yildiz adds.

    In ongoing research, the team is working to better understand the electronic properties of the material in its different structures, and to extend this approach to other oxides of interest for memory and energy applications, in collaboration with MIT professor Harry Tuller.

    José Santiso, the nanomaterials growth division leader at the Catalan Institute of Nanoscience and Nanotechnology in Barcelona, Spain, who was not involved in this research, calls it “a very significant contribution” to the study of this interesting class of materials, and says “it paves the way for the application of these materials both in solid state electrochemical devices for the efficient conversion of energy or oxygen storage, as well as in possible applications in a new kind of memory devices.”

    The work was supported by the National Science Foundation.

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  • richardmitnick 11:17 am on January 8, 2016 Permalink | Reply
    Tags: , Material Sciences, , Perovskites, Silicon and solar materials   

    From MIT Tech Review: “Promising New Solar Material Boosts Performance of Silicon” 

    MIT Technology Review
    M.I.T Technology Review

    January 7, 2016
    Mike Orcutt

    Silicon probably won’t be replaced as the dominant solar material anytime soon, but it might not be too long before it gets a partner from a promising class of materials called perovskites.

    A group led by Henry Snaith, a physicist at the University of Oxford and leading perovskite researcher, has demonstrated what it says is a viable pathway to a device that combines a conventional silicon cell with a perovskite cell to boost the efficiency of that silicon cell by several percentage points.

    Perovskites, which have captured the interest of solar researchers and energy policy experts because of their rapidly improving performance and low cost, are distinguished by a chemical structure that gives rise to unique electronic properties that make them attractive for solar technology (see “Could a New Solar Material Outperform Silicon?”). Snaith and his colleagues say the new composition they’ve developed overcomes a fundamental obstacle to designing a highly efficient device that combines the light-absorbing characteristics of silicon with those of a perovskite material.

    The researchers say the result suggests it should be possible to make a silicon-perovskite “tandem” device that is more than 25 percent efficient, higher than the performance of today’s commercially available silicon cells, which are about 17 to 20 percent efficient. The measurements they took were in a laboratory environment, but the approach could eventually be used to achieve significantly higher efficiencies than the best silicon panels on the market today.

    High-performance tandem devices made of semiconductors other than perovskite have already achieved efficiencies in the lab of over 40 percent, but they are extremely expensive because they require very technically complex manufacturing processes. Making perovskite solar cells is much simpler and cheaper, and the process could be integrated into existing silicon panel manufacturing lines by adding a few steps. Many experts believe the most realistic near-term commercial application of perovskites will be a tandem device with silicon.

    Several groups have demonstrated working tandem devices made of a silicon cell and a perovskite cell, but the efficiencies have been limited because the range of the solar spectrum the perovskite absorbed did not fully complement the range that silicon absorbs. Attempts to tweak the range of light the perovskite absorbs led to instabilities within the material’s structure that compromised performance. Snaith and his colleagues came up with a method, which relies on substituting certain ions in the material with cesium ions, to achieve the desired photovoltaic properties while maintaining the material’s structural stability.

    The researchers have only demonstrated the new composition at a small scale, and a lot of work would be needed before we might see it in commercially available panels. But a company Snaith cofounded, Oxford PV, is also focused on developing silicon-perovskite tandem devices.

    Chris Case, chief technology officer of Oxford PV, says results like this reflect how quickly researchers are addressing the inherent challenges to making reliable, high-performing tandem cells. Case won’t reveal the specifics of his company’s technology, but says Oxford PV is close to demonstrating full-size devices that are 23 percent efficient and could hit 25 percent shortly thereafter. Case says it’s not unrealistic to think 28 or even 30 percent efficiency is possible within just a few years.

    Perovskite-based technologies still face challenges due to the material’s sensitivity to moisture and air, and questions remain about whether perovskite cells can be made durable enough to survive the long lifetimes required of power systems. Still, Case says Oxford PV is on track to deliver a commercial product—aimed at silicon panel manufacturers who want to “upgrade” the efficiency of their products—in 2017.

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  • richardmitnick 6:24 pm on December 23, 2015 Permalink | Reply
    Tags: , Material Sciences,   

    From UCLA: “UCLA researchers create exceptionally strong and lightweight new metal” 

    UCLA bloc

    UCLA

    December 23, 2015
    Matthew Chin

    Temp 1
    At left, a deformed sample of pure metal; at right, the strong new metal made of magnesium with silicon carbide nanoparticles. Each central micropillar is about 4 micrometers across.

    A team led by researchers from the UCLA Henry Samueli School of Engineering and Applied Science has created a super-strong yet light structural metal with extremely high specific strength and modulus, or stiffness-to-weight ratio. The new metal is composed of magnesium infused with a dense and even dispersal of ceramic silicon carbide nanoparticles. It could be used to make lighter airplanes, spacecraft, and cars, helping to improve fuel efficiency, as well as in mobile electronics and biomedical devices.

    To create the super-strong but lightweight metal, the team found a new way to disperse and stabilize nanoparticles in molten metals. They also developed a scalable manufacturing method that could pave the way for more high-performance lightweight metals. The research was published today in Nature.

    “It’s been proposed that nanoparticles could really enhance the strength of metals without damaging their plasticity, especially light metals like magnesium, but no groups have been able to disperse ceramic nanoparticles in molten metals until now,” said Xiaochun Li, the principal investigator on the research and Raytheon Chair in Manufacturing Engineering at UCLA. “With an infusion of physics and materials processing, our method paves a new way to enhance the performance of many different kinds of metals by evenly infusing dense nanoparticles to enhance the performance of metals to meet energy and sustainability challenges in today’s society.”

    1
    Xiaochun Li

    Structural metals are load-bearing metals; they are used in buildings and vehicles. Magnesium, at just two-thirds the density of aluminum, is the lightest structural metal. Silicon carbide is an ultra-hard ceramic commonly used in industrial cutting blades. The researchers’ technique of infusing a large number of silicon carbide particles smaller than 100 nanometers into magnesium added significant strength, stiffness, plasticity and durability under high temperatures.

    The researchers’ new silicon carbide-infused magnesium demonstrated record levels of specific strength — how much weight a material can withstand before breaking — and specific modulus — the material’s stiffness-to-weight ratio. It also showed superior stability at high temperatures.

    Ceramic particles have long been considered as a potential way to make metals stronger. However, with microscale ceramic particles, the infusion process results in a loss of plasticity.

    Nanoscale particles, by contrast, can enhance strength while maintaining or even improving metals’ plasticity. But nanoscale ceramic particles tend to clump together rather than dispersing evenly, due to the tendency of small particles to attract one other.

    To counteract this issue, researchers dispersed the particles into a molten magnesium zinc alloy. The newly discovered nanoparticle dispersion relies on the kinetic energy in the particles’ movement. This stabilizes the particles’ dispersion and prevents clumping.

    To further enhance the new metal’s strength, the researchers used a technique called high-pressure torsion to compress it.

    “The results we obtained so far are just scratching the surface of the hidden treasure for a new class of metals with revolutionary properties and functionalities,” Li said.

    The new metal (more accurately called a metal nanocomposite) is about 14 percent silicon carbide nanoparticles and 86 percent magnesium. The researchers noted that magnesium is an abundant resource and that scaling up its use would not cause environmental damage.

    The paper’s lead author is Lian-Yi Chen, who conducted the research as a postdoctoral scholar in Li’s Scifacturing Laboratory at UCLA. Chen is now an assistant professor of mechanical and aerospace engineering at Missouri University of Science and Technology.

    The paper’s other authors from UCLA include Jia-Quan Xu, a graduate student in materials science and engineering; Marta Pozuelo, an assistant development engineer; and Jenn-Ming Yang, professor of materials science and engineering.

    The other authors on the paper are Hongseok Choi, of Clemson University; Xiaolong Ma, of North Carolina State University; Sanjit Bhowmick of Hysitron, Inc. of Minneapolis; and Suveen Mathaudhu of UC Riverside.

    The research was funded in part by the National Institute of Standards and Technology.

    See the full article here .

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    UC LA Campus

    For nearly 100 years, UCLA has been a pioneer, persevering through impossibility, turning the futile into the attainable.

    We doubt the critics, reject the status quo and see opportunity in dissatisfaction. Our campus, faculty and students are driven by optimism. It is not naïve; it is essential. And it has fueled every accomplishment, allowing us to redefine what’s possible, time after time.

    This can-do perspective has brought us 12 Nobel Prizes, 12 Rhodes Scholarships, more NCAA titles than any university and more Olympic medals than most nations. Our faculty and alumni helped create the Internet and pioneered reverse osmosis. And more than 100 companies have been created based on technology developed at UCLA.

     
  • richardmitnick 4:11 pm on September 10, 2015 Permalink | Reply
    Tags: , , , Material Sciences, SLAC UED   

    From SLAC: “SLAC’s Ultrafast ‘Electron Camera’ Visualizes Ripples in 2-D Material” 


    SLAC Lab

    September 10, 2015

    1
    Researchers have used SLAC’s experiment for ultrafast electron diffraction (UED), one of the world’s fastest “electron cameras,” to take snapshots of a three-atom-thick layer of a promising material as it wrinkles in response to a laser pulse. Understanding these dynamic ripples could provide crucial clues for the development of next-generation solar cells, electronics and catalysts. (SLAC National Accelerator Laboratory)

    2
    Illustrations (each showing a top and two side views) of a single layer of molybdenum disulfide (atoms shown as spheres). Top left: In a hypothetical world without motions, the “ideal” monolayer would be flat. Top right: In reality, the monolayer is wrinkled as shown in this room-temperature simulation. Bottom: If a laser pulse heats the monolayer up, it sends ripples through the layer. These wrinkles, which researchers have now observed for the first time, have large amplitudes and develop on ultrafast timescales. (SLAC National Accelerator Laboratory)

    SLAC Electron Camera UED
    SLAC’s electron Camera

    SLAC electron camera schematic
    SLAC’s electron Camera schematic

    New research led by scientists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University shows how individual atoms move in trillionths of a second to form wrinkles on a three-atom-thick material. Revealed by a brand new “electron camera,” one of the world’s speediest, this unprecedented level of detail could guide researchers in the development of efficient solar cells, fast and flexible electronics and high-performance chemical catalysts.

    The breakthrough, accepted for publication Aug. 31 in Nano Letters, could take materials science to a whole new level. It was made possible with SLAC’s instrument for ultrafast electron diffraction (UED), which uses energetic electrons to take snapshots of atoms and molecules on timescales as fast as 100 quadrillionths of a second.

    “This is the first published scientific result with our new instrument,” said scientist Xijie Wang, SLAC’s UED team lead. “It showcases the method’s outstanding combination of atomic resolution, speed and sensitivity.”

    SLAC Director Chi-Chang Kao said, “Together with complementary data from SLAC’s X-ray laser Linac Coherent Light Source, UED creates unprecedented opportunities for ultrafast science in a broad range of disciplines, from materials science to chemistry to the biosciences.” LCLS is a DOE Office of Science User Facility.

    SLAC LCLS Inside
    LCLS


    download mp4 here.

    Extraordinary Material Properties in Two Dimensions

    Monolayers, or 2-D materials, contain just a single layer of molecules. In this form they can take on new and exciting properties such as superior mechanical strength and an extraordinary ability to conduct electricity and heat. But how do these monolayers acquire their unique characteristics? Until now, researchers only had a limited view of the underlying mechanisms.

    “The functionality of 2-D materials critically depends on how their atoms move,” said SLAC and Stanford researcher Aaron Lindenberg, who led the research team. “However, no one has ever been able to study these motions on the atomic level and in real time before. Our results are an important step toward engineering next-generation devices from single-layer materials.” The research team looked at molybdenum disulfide, or MoS2, which is widely used as a lubricant but takes on a number of interesting behaviors when in single-layer form – more than 150,000 times thinner than a human hair.

    For example, the monolayer form is normally an insulator, but when stretched, it can become electrically conductive. This switching behavior could be used in thin, flexible electronics and to encode information in data storage devices. Thin films of MoS2 are also under study as possible catalysts that facilitate chemical reactions. In addition, they capture light very efficiently and could be used in future solar cells.

    Because of this strong interaction with light, researchers also think they may be able to manipulate the material’s properties with light pulses.

    “To engineer future devices, control them with light and create new properties through systematic modifications, we first need to understand the structural transformations of monolayers on the atomic level,” said Stanford researcher Ehren Mannebach, the study’s lead author.

    3
    Visualization of laser-induced motions of atoms (black and yellow spheres) in a molybdenum disulfide monolayer: The laser pulse creates wrinkles with large amplitudes – more than 15 percent of the layer’s thickness – that develop in a trillionth of a second. (K.-A. Duerloo/Stanford)

    Electron Camera Reveals Ultrafast Motions

    Previous analyses showed that single layers of molybdenum disulfide have a wrinkled surface. However, these studies only provided a static picture. The new study reveals for the first time how surface ripples form and evolve in response to laser light.

    Researchers at SLAC placed their monolayer samples, which were prepared by Linyou Cao’s group at North Carolina State University, into a beam of very energetic electrons. The electrons, which come bundled in ultrashort pulses, scatter off the sample’s atoms and produce a signal on a detector that scientists use to determine where atoms are located in the monolayer. This technique is called ultrafast electron diffraction.

    The team then used ultrashort laser pulses to excite motions in the material, which cause the scattering pattern to change over time.

    “Combined with theoretical calculations, these data show how the light pulses generate wrinkles that have large amplitudes – more than 15 percent of the layer’s thickness – and develop extremely quickly, in about a trillionth of a second. This is the first time someone has visualized these ultrafast atomic motions,” Lindenberg said.

    Once scientists better understand monolayers of different materials, they could begin putting them together and engineer mixed materials with completely new optical, mechanical, electronic and chemical properties.

    The research was supported by DOE’s Office of Science, the SLAC UED/UEM program development fund, the German National Academy of Sciences, and the U.S. National Science Foundation.

    4

    To study ultrafast atomic motions in a single layer of molybdenum disulfide, researchers followed a pump-probe approach: They excited motions with a laser pulse (pump pulse, red) and probed the laser-induced structural changes with a subsequent electron pulse (probe pulse, blue). The electrons of the probe pulse scatter off the monolayer’s atoms (blue and yellow spheres) and form a scattering pattern on the detector – a signal the team used to determine the monolayer structure. By recording patterns at different time delays between the pump and probe pulses, the scientists were able to determine how the atomic structure of the molybdenum disulfide film changed over time. (SLAC National Accelerator Laboratory)

    Citation: E. M. Mannebach et al., Nano Letters, 31 August 2015 (10.1021/acs.nanolett.5b02805)

    Press Office Contact: Andrew Gordon, agordon@slac.stanford.edu, (650) 926-2282

    See the full article here .

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    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
    i1

     
  • richardmitnick 4:01 pm on September 9, 2015 Permalink | Reply
    Tags: , , Material Sciences, ,   

    From MIT: “How to spawn an ‘exceptional ring'” 


    MIT News

    September 9, 2015
    David L. Chandler

    1
    A schematic drawing of how a ring of exceptional points (shown in white) can be spawned from a Dirac point (a dot), and thus change the dispersion from the normal, widely known conical shape into an exotic lantern-like shape. Courtesy of the researchers

    2
    A schematic picture showing the conical dispersion of a Dirac cone being deformed into a new hour-glass-like shape due to radiation. Courtesy of the researchers

    The Dirac cone, named after British physicist Paul Dirac, started as a concept in particle and high-energy physics and has recently became important in research in condensed matter physics and material science. It has since been found to describe aspects of graphene, a two dimensional form of carbon, suggesting the possibility of applications across various fields.

    4
    Graphene is an atomic-scale honeycomb lattice made of carbon atoms.

    Now physicists at MIT have found another unusual phenomenon produced by the Dirac cone: It can spawn a phenomenon described as a “ring of exceptional points.” This connects two fields of research in physics and may have applications in building powerful lasers, precise optical sensors, and other devices.

    The results are published this week in the journal Nature by MIT postdoc Bo Zhen, Yale University postdoc Chia Wei Hsu, MIT physics professors Marin Soljačić and John Joannopoulos, and five others.

    This work represents “the first experimental demonstration of a ring of exceptional points,” Zhen says, and is the first study that relates research in exceptional points with the physical concepts of parity-time symmetry and Dirac cones.

    Individual exceptional points are a peculiar phenomenon unique to an unusual class of physical systems that can lead to counterintuitive phenomena. For example, around these points, opaque materials may seem more transparent, and light may be transmitted only in one direction. However, the practical usefulness of these properties is limited by absorption loss introduced in the materials.

    The MIT team used a nanoengineered material called a photonic crystal to produce the exceptional ring. This new ring of exceptional points is different from those studied by other groups, making it potentially more practical, the researchers say.

    “Instead of absorption loss, we adopt a different loss mechanism — radiation loss — which does not affect the device performance,” Zhen says. “In fact, radiation loss is useful and is necessary in devices like lasers.”

    This phenomenon could enable creation of new kinds of optical systems with novel features, the MIT team says.

    “One important possible application of this work is in creating a more powerful laser system than existing technologies allow,” Soljačić says. To build a more powerful laser requires a bigger lasing area, but that introduces more unwanted “modes” for light, which compete for power, limiting the final output.

    “Photonic crystal surface-emitting lasers are a very promising candidate for the next generation of high-quality, high-power compact laser systems,” Soljačić says, “and we estimate we can improve the output power limit of such lasers by a factor of at least 10.”

    “Our system could also be used for high-precision detectors for biological or chemical materials, because of its extreme sensitivity,” Hsu says. This improved sensitivity is due to another exotic property of the exceptional points: Their response to perturbations is not linear to the perturbation strength.

    Normally, Hsu says, it becomes very difficult to detect a substance when its concentration is low. When the concentration of the target substance is reduced by a million times, the overall signal also decreases by a million times, which can make it too small to detect.

    “But at an exceptional point, it’s not linear anymore,” Hsu says, “and the signal goes down by only 1,000 times, providing a much bigger response that can now be detected.”

    Demetrios Christodoulides, a professor of optics and photonics at the University of Central Florida who was not involved in this work, says, “This represents the first observation of an exceptional ring in a 2-D crystal associated with a two-dimensional band. The MIT work opens up a number of opportunities … in particular, around exceptional points where systems are known on many occasions to behave in a peculiar fashion.”

    The research team also included Yuichi Igarashi of NEC Corp. in Japan and MIT research scientist Ling Lu, postdoc Ido Kaminer, Harvard University graduate student Adi Pick, and Song-Liang Chua at DSO National Laboratory in Singapore. The work was supported, in part, by the Army Research Office through MIT’s Institute for Soldier Nanotechnologies, the National Science Foundation, and the Department of Energy.

    See the full article here .

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  • richardmitnick 10:41 am on August 26, 2015 Permalink | Reply
    Tags: , , Material Sciences, ,   

    From ars technica: “Quantum dots may be key to turning windows into photovoltaics” 

    Ars Technica
    ars technica

    Aug 26, 2015
    John Timmer

    1
    Some day, this might generate electricity. Flickr user Ricardo Wang

    While wind may be one of the most economical power sources out there, photovoltaic solar energy has a big advantage: it can go small. While wind gets cheaper as turbines grow larger, the PV hardware scales down to fit wherever we have infrastructure. In fact, simply throwing solar on our existing building stock could generate a very large amount of carbon-free electricity.

    But that also highlights solar’s weakness: we have to install it after the infrastructure is in place, and that installation adds considerably to its cost. Now, some researchers have come up with some hardware that could allow photovoltaics to be incorporated into a basic building component: windows. The solar windows would filter out a small chunk of the solar spectrum and convert roughly a third of it to electricity.

    As you’re probably aware, photovoltaic hardware has to absorb light in order to work, and a typical silicon panel appears black. So, to put any of that hardware (and its supporting wiring) into a window that doesn’t block the view is rather challenging. One option is to use materials that only capture a part of the solar spectrum, but these tend to leave the light that enters the building with a distinctive tint.

    The new hardware takes a very different approach. The entire window is filled with a diffuse cloud of quantum dots that absorb almost all of the solar spectrum. As a result, the “glass” portion of things simply dims the light passing through the window slightly. (The quantum dots are actually embedded in a transparent polymer, but that could be embedded in or coat glass.) The end result is what optics people call a neutral density filter, something often used in photography. In fact, tests with the glass show that the light it transmits meets the highest standards for indoor lighting.

    Of course, simply absorbing the light doesn’t help generate electricity. And, in fact, the quantum dots aren’t used to generate the electricity. Instead, the authors generated quantum dots made of copper, indium, and selenium, covered in a layer of zinc sulfide. (The authors note that there are no toxic metals involved here.) These dots absorb light across a broad band of spectrum, but re-emit it at a specific wavelength in the infrared. The polymer they’re embedded in acts as a waveguide to take many of the photons to the thin edge of the glass.

    And here’s where things get interesting: the wavelength of infrared the quantum dots emit happens to be very efficiently absorbed by a silicon photovoltaic device. So, if you simply place these devices along the edges of the glass, they’ll be fed a steady diet of photons.

    The authors model the device’s behavior and find that nearly half the infrared photons end up being fed the photovoltaic devices (equal amounts get converted to heat or escape the window entirely). It’s notable that the devices are small, though (about 12cm squares)—larger panes would presumably allow even more photons to escape.

    The authors tested a few of the devices, one that filtered out 20 percent of the sunlight and one that only captured 10 percent. The low-level filter sent about one percent of the incident light to the sides, while the darker one sent over three percent.

    There will be losses in the conversion to electricity as well, so this isn’t going to come close to competing with a dedicated panel on a sunny roof. Which is fine, because it’s simply not meant to. Any visit to a major city will serve as a good reminder that we’re regularly building giant walls of glass that currently reflect vast amounts of sunlight, blinding or baking (or both!) the city’s inhabitants on a sunny day. If we could cheaply harvest a bit of that instead, we’re ahead of the game.

    Nature Nanotechnology, 2015. DOI: 10.1038/NNANO.2015.178 (About DOIs).

    See the full article here.

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    Ars Technica was founded in 1998 when Founder & Editor-in-Chief Ken Fisher announced his plans for starting a publication devoted to technology that would cater to what he called “alpha geeks”: technologists and IT professionals. Ken’s vision was to build a publication with a simple editorial mission: be “technically savvy, up-to-date, and more fun” than what was currently popular in the space. In the ensuing years, with formidable contributions by a unique editorial staff, Ars Technica became a trusted source for technology news, tech policy analysis, breakdowns of the latest scientific advancements, gadget reviews, software, hardware, and nearly everything else found in between layers of silicon.

    Ars Technica innovates by listening to its core readership. Readers have come to demand devotedness to accuracy and integrity, flanked by a willingness to leave each day’s meaningless, click-bait fodder by the wayside. The result is something unique: the unparalleled marriage of breadth and depth in technology journalism. By 2001, Ars Technica was regularly producing news reports, op-eds, and the like, but the company stood out from the competition by regularly providing long thought-pieces and in-depth explainers.

    And thanks to its readership, Ars Technica also accomplished a number of industry leading moves. In 2001, Ars launched a digital subscription service when such things were non-existent for digital media. Ars was also the first IT publication to begin covering the resurgence of Apple, and the first to draw analytical and cultural ties between the world of high technology and gaming. Ars was also first to begin selling its long form content in digitally distributable forms, such as PDFs and eventually eBooks (again, starting in 2001).

     
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