JEC names Innovation Award winners
JEC has named the companies who have won a composites Innovation Award. The winners will receive an award at JEC Asia, taking place in Seoul, South Korea, on 2 November, 2017.
The winners are:
- Railway: The Korea Railroad Research Institute (South Korea) for railway sleepers using cementitious composites
- Transportation: Omni Willig Carbon GmbH (Germany) for a carbon mini tank for highly-corrosive materials
- Automotive: Daimler AG (Germany) for a multifunctional carbon SMC spare wheel pan
- Racing car: Epotech Composite Corporation (Taiwan) for a lightweight body structure design Aeronautics: Composite Technology Centre/CTC GmbH for a hybrid SMC technology for aircraft applications
- Wind energy: Arkema (France) for an infusion thermoplastic resin for wind turbine blade manufacturing
- Sports and Leisure: Chomarat (France) for thin-ply carbon NCF with visual stitching applied to an windsurf board
- Construction: Logelis (France) for a composite sandwich panel for modular construction
- Marine: Talon Technology Pty Ltd (Australia) for a carbon fiber/Kevlar hinge system
- Raw materials: OCSiAl (Luxembourg) for a single-wall nanotube-based industrial predispersed concentrate
- NDT and monitoring: R-TECH Services Ltd (UK) for an acoustic emission system for the assessment of hydrogen tanks for fuel cell vehicles
- Process: Textile For Life Co Ltd (South Korea) for an Industry 4.0 robotic braiding factory.
This story is reprinted from material from JEC, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Metaltech to become part of the Wallwork Group
Coating company Metaltech Ltd says it is is to join the Wallwork Group, which specializes in the thermal processing and coating of metals for the aerospace, automotive, medical device and precision engineering sectors.
Metaltech was founded in 1981 and now has 22 staff serving clients in the UK and internationally.
The deal will ensure the future of the business and employees as well as giving Metaltech the wider product portfolio of the Wallwork Group to offer our clients,’ said Dr Graeme Forster, managing director of Metaltech. ‘The fact that the Wallwork Group are committed to continue processing in the North East was instrumental to the deal.’
Wallwork has plans to invest in the Metaltech site and also base some of its transport operation there.
This story is reprinted from material from Metaltech, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
EPMA launches new edition of AM booklet
EPMA and the EuroAM Sectoral Group have launched the second edition of its Introduction to Additive Manufacturing Technology booklet. This new edition, which was launched at the Euro PM2017 Congress in Milan, Italy, expands on the original version by providing updated and improved case studies from a range of different industries, as well as updating some of the technical content from the first edition.
The first edition was originally launched in 2013 by the EuroAM.
The new 56-page edition includes content from over 90 contributors and now has over 50 case studies and contains three new chapters covering HIP post processing, non destructive testing for AM parts and powder handling and safety areas of focus
'This is a great booklet for potential users of the additive manufacturing (AM) process, as it provides a neutral view of the main AM processes available to date,' said Andrew Almond, EPMA's marketing manager.
To download a PDF copy of the new edition, please go here.
This story is reprinted from material from the EPMA, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Ultracold atoms in a laser lattice reveal secrets of superconductivity
Using atoms cooled to just billionths of a degree above absolute zero, a team led by researchers at Princeton University has discovered an intriguing magnetic behavior that could help explain how high-temperature superconductivity works.
The researchers found that applying a strong magnetic field to ultracold atoms caused them to line up in an alternating pattern and lean away from each other. This behavior, which researchers call ‘canted antiferromagnetism’, is consistent with predictions from a decades-old model used to understand how superconductivity arises in certain materials. The results are published in a paper in Science.
"No one has observed this type of behavior in this system before," said Waseem Bakr, assistant professor of physics at Princeton University. "We used lasers to create artificial crystals and then explored what is happening in microscopic detail, which is something you just cannot do in an everyday material."
The experiment, conducted on a table-top in Princeton's Jadwin Hall, provides a way to investigate a model describing how quantum behaviors give rise to superconductivity, a state where current can flow without resistance, which is prized for electricity transmission and making powerful electromagnets. While the basis of conventional superconductivity is understood, researchers are still exploring the theory of high-temperature superconductivity in copper-based materials called cuprates.
Due to the complexity of cuprates, it is difficult for researchers to study them directly to find out what properties are responsible for their ability to conduct current without resistance. Instead, by building a synthetic crystal using lasers and ultracold atoms, the researchers can ask questions that are otherwise impossible to address.
Bakr and his team cooled lithium atoms to just a few ten-billionths of a degree above absolute zero, a temperature where the atoms follow the laws of quantum physics. The researchers then used lasers to create a grid to trap the ultracold atoms in place. This grid, known as an optical lattice, can be thought of as a virtual egg-tray created entirely from laser light, in which atoms can hop from one well to the next.
The team used this set-up to look at the interactions between single atoms, which can behave in a manner analogous to tiny magnets due to a quantum property called spin. The spin of each atom can orient either up or down. If two atoms land on the same site, they experience a strong repulsive interaction and spread out so that there is only one atom in each well. Atoms in neighboring wells of the egg-tray tend to have their spins aligned opposite to each other.
This effect, called antiferromagnetism, happens at very low temperatures due to the quantum nature of the cold system. When the two types of spin populations are roughly equal, the spins can rotate in any direction as long as neighboring spins remain anti-aligned.
When the researchers applied a strong magnetic field to the atoms, they saw something curious. Using a high-resolution microscope able to image individual atoms on the lattice sites, the Princeton team studied how changes in the strength of the field affected the magnetic correlations of the atoms. In the presence of a large field, the researchers found that neighboring spins remained anti-aligned but oriented themselves in a plane at a right angle to the field. Taking a closer look, they saw that the oppositely-aligned atoms canted slightly in the direction of the field, so that the magnets were still opposite facing but were not precisely aligned in the flat plane.
Spin correlations were observed last year in experiments at Harvard University, the Massachusetts Institute of Technology and Ludwig Maximilian University in Munich, Germany. But the Princeton study is the first to apply a strong field to the atoms and observe a canted antiferromagnet.
These observations were predicted by the Fermi-Hubbard model, created to explain how cuprates could be superconducting at relatively high temperatures. The Fermi-Hubbard model was developed by Philip Anderson, professor of physics, emeritus, at Princeton, who won a Nobel Prize in Physics in 1977 for his work on theoretical investigations of the electronic structure of magnetic and disordered systems.
"Understanding the Fermi-Hubbard model better could help researchers design similar materials with improved properties that can carry current without resistance," Bakr said.
The study also looked at what would happen if some of the atoms in the egg-tray were removed, introducing holes in the grid. The researchers found that when the magnetic field was applied, the response agreed with measurements performed on cuprates. "This is more evidence that the proposed Fermi-Hubbard model is probably the correct model to describe what we see in the materials," Bakr said.
This story is adapted from material from Princeton University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.
A sprinkling of sulphur can improve charge transport in quantum dots
Quantum dots are nanometer-sized semiconductor particles with potential applications in solar cells and electronics. Scientists at the University of Groningen in the Netherlands, together with colleagues at ETH Zürich in Switzerland, have now discovered a way to improve how charge is transported in lead-sulphur quantum dots, potentially leading to more efficient quantum dot solar cells. They report their results in a paper in Science Advances.
Quantum dots are clusters of some 1000 atoms that act as one large 'super-atom'. The dots, which are synthesized as colloids –suspended in a liquid like a sort of paint – can be organized into thin films with simple solution-based processing techniques. These thin films can turn light into electricity.
However, scientists have also discovered that the electronic properties of quantum dots create a bottleneck. “Especially the conduction of holes, the positive counterpart to negatively-charged electrons,” explains Daniel Balazs, a PhD student in the Photophysics and Optoelectronics group of Maria Loi at the University of Groningen Zernike Institute for Advanced Materials.
Loi's group works with lead-sulphide quantum dots. When a beam of light produces an electron-hole pair in these dots, the electron and hole do not move with the same efficiency through the assembly of dots. This means they can easily recombine, reducing the efficiency of the light-to-energy conversion. Balazs therefore set out to improve the poor hole conductance in the quantum dots, and to find a toolkit to make this class of materials tunable and multifunctional.
“The root of the problem is the lead-sulphur stoichiometry,” he says. In quantum dots, nearly half the atoms are on the surface of the super-atom. In the lead-sulphur system, lead atoms preferentially fill the outer part of the quantum dot, producing a ratio of lead to sulphur of 3:1 rather than 1:1. This excess of lead makes the quantum dot a better conductor of electrons than holes.
In bulk material, transport is generally improved by 'doping' the material: adding small amounts of impurities. However, attempts to add extra sulphur to the quantum dots have so far failed. But now Balazs and Loi have found a way to do this, and thus increase hole mobility without affecting electron mobility.
Many groups have tried combining the addition of sulphur with other production steps. However, this has caused many problems, such as disrupting the assembly of the dots into the thin film. Instead, Balazs first produced ordered thin films of quantum dots and then added activated sulphur. This meant the sulphur atoms could be added to the surface of the quantum dots without affecting the other properties of the film.
“A careful analysis of the chemical and physical processes during the assembly of quantum dot thin films and the addition of extra sulphur were what was needed to get this result,” says Balazs. “That's why our group, with the cooperation of our chemistry colleagues from Zürich, was successful in the end.”
Loi's team is now able to add different amounts of sulphur, allowing them to tune the electric properties of the super-atom assemblies. “We now know that we can improve the efficiency of quantum dot solar cells above the current record of 11%,” says Balazs. “The next step is to show that this method can also make other types of functional devices such as thermoelectric devices.”
This study also underlines the unique properties of quantum dots: they act as one atom with specific electric properties. “And now we can assemble them and can engineer their electrical properties as we wish. That is something which is impossible with bulk materials and it opens new perspectives for electronic and optoelectronic devices.”
This story is adapted from material from the University of Groningen, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.
Novel conductive coating keeps fingers nice and toasty
Commuters, skiers, crossing guards and others who endure frozen fingers in cold weather can look forward to future relief, thanks to a new technique for creating electrically heated cloth developed by materials scientist Trisha Andrew and colleagues at the University of Massachusetts Amherst. As a demonstration, they have made gloves that keep fingers as warm as the palm of the hand.
In a new paper in Applied Materials & Interfaces, the scientists describe how they used a vapor deposition method for nano-coating fabric to create sewable, weavable, electrically-heated material. The three-layered glove – with one layer coated with the conducting polymer poly(3,4-ethylenedioxytiophene), also known as PEDOT – are powered by a button battery weighing just 1.8 grams, which can still keep fingers toasty for up to eight hours.
"Lightweight, breathable and body-conformable electrical heaters have the potential to change traditional approaches to personal thermal management, medical heat therapy, joint pain relief and athletic rehabilitation," say the scientists.
"We took a pair of cotton gloves and coated the fingers to allow a small amount of current to pass through, so they heat up. It's regular old-fashioned cotton cloth. We chose to make a pair of gloves because the fingers require a high curvature that allows us to show that our material is really flexible," explains Andrew. "The glove is powered by a small coin battery and they run on nano-amps of current, not enough to pass current through your skin or to hurt you. Our coating works even when it's completely dunked in water, it will not shock you, and our layered construction means the conductive cloth does not come into contact with your skin.
"We hope to have this reach consumers as a real product in the next few years. Maybe it will be two years to a prototype, and five years to the consumer. I think this is the most consumer-ready device we have. It's ready to take to the next phase."
Until recently, textile scientists didn’t use vapor deposition because of technical difficulties and the high cost of scaling up from the laboratory, but manufacturers have now found that the technology can be scaled up while remaining cost-effective. Using the vapor deposition method described in their paper, Andrew and her colleagues also coated threads of a thick cotton yarn commonly used for sweaters. It performed well, say the scientists, and offers another avenue for creating heated clothing.
"One thing that motivated us to make this product is that we could get the flexibility, the nice soft feel, while at the same time it's heated but not making you sweaty," says Andrew. "A common thing we hear from commuters is that in the winter, they would love to have warmer fingers." In laboratory tests, four fingers of the test glove warmed to the same temperature as the palm, and "the wearer could feel the heat transferred from the fabric heaters to her fingers a few seconds after the voltage was applied."
Andrew and chemistry postdoctoral researcher Lushuai Zhang, together with chemical engineering graduate student Morgan Baima, conducted several tests to assure that their gloves could stand up to hours of use, laundering, rips, repairs and overnight charging. "If you are skiing and rip your glove, you can repair it just by sewing it back together with plain thread," Andrew says.
"Right now we use an off-the-shelf battery that lasts for eight hours, but you would need a rechargeable to make these more practical," she adds.
Andrew and her colleagues arranged for biocompatibility testing at an independent lab, where mouse connective tissue cells were exposed to PEDOT-coated samples. This showed that their PEDOT-coated materials are safe for contact with human skin and don’t cause any adverse reactions.
They also addressed questions of heat, moisture and skin contact stability, to prevent the wearer from experiencing any electric shock from a wet conducting element. "Chemically, what we use to surround the conductive cloth looks like polystyrene, the stuff used to make packing peanuts. It completely surrounds the conducting material so the electrical conductor is never exposed," says Andrew.
Experimenting with different variables in the vapor nano-coating process, they found that adjusting the temperature and chamber pressure were important in achieving optimal surface coverage of the cloth. In a test of the fabric's ability to resist cracking, creasing or other changes when heated, they generated a temperature of 28°C (82.4°F) with connection to a 4.5V battery and 45°C (113°F) with connection to a 6V battery for an hour. They found "no dramatic morphology changes", indicating that the PEDOT-coated cotton textile was rugged and stable enough to maintain its performance when used as a heating element.
This story is adapted from material from the University of Massachusetts Amherst, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.
Gurit wins automotive contract
Gurit has received a contract for the production and supply of carbon fiber-based exterior car body panels from an Italian automotive OEM.
The total value of the new five-year contract is at around CHF 8.5 million, with series production for the project scheduled to start in 2019. The parts will be manufactured with Gurit’s press technology at the company’s site in Hungary.
The newly won contract increases Gurit’s order intake for exterior car body panels in 2017 to a total value of CHF 29 million, the company says.
This story is reprinted from material from Gurit, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
NTPT licenses composite tubes software
AnalySwift, LLC, which provides modeling software for composites and other advanced materials, says that North Thin Ply Technologies (NTPT) has licensed its VABS software for simulation of composite golf club shafts and other tubes for use in aerospace, industrial and sports applications.
NTPT has licensed the VABS beam modeling software initially for simulation of the company’s line of composite golf club shafts, TPT Golf, as well as other tubes, including those used for sport and industrial applications. Other potential applications include automotive drive shafts, aircraft struts, landing gear, and windsurf masts.
‘VABS provides a uniquely rigorous solution as a general-purpose cross-sectional analysis tool for quickly computing beam sectional properties and recovering 3D fields of slender composite structures,’ said Allan Wood, president and CEO of AnalySwift. ‘This includes not only composite tubes, but also composite helicopter and wind turbine rotor blades, as well as other slender composite parts, such as fishing rods, landing gear, propellers and high-aspect ratio wings.’
This story is reprinted from material from NTPT, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Alcoa to review aluminium powder plant
Alcoa Corporation, which makes bauxite, alumina and aluminum products, has terminated the electricity contract tied to Alcoa’s Rockdale mine in Texas, USA. The smelter at Rockdale has been fully curtailed since the end of 2008.
Alcoa says that the cost of power under the contract exceeded the related revenue.
As a result of the early termination, Alcoa has initiated a strategic review of the remaining buildings and equipment associated with the smelter, casthouse and the aluminum powder plant. A decision on those assets is expected by the end of 2017, the company said.
‘Reaching a resolution on the Rockdale power contract aligns with two of our strategic priorities – to reduce complexity and to drive returns,’ said William Oplinger, executive vice president and chief financial officer. ‘It eliminates a complex, long-term contract tied to the Rockdale location, and positions Alcoa for improved profitability and higher returns.’
This story is reprinted from material from Alcoa, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
GE Additive and GKN form AM collaboration
GE Additive, Concept Laser and Arcam AB have signed a Memorandum of Understanding (MoU) with GKN to collaborate on additive manufacturing (AM). The companies will provide 3D printing machines and services to GKN, allowing them to be a GE Additive ‘production partner’. GKN also becomes a non-exclusive preferred AM powder supplier to GE Additive and its affiliated companies.
GKN will also work with GE Additive on part development projects on powder bed machines to enable new market opportunities, while GE Additive’s engineering consulting team will help GKN industrialize AM machines.
‘GE Additive and GKN both understand the transformative power that additive manufacturing will have in the aerospace and automotive industries,’ said vice president and general manager of GE Additive, Mohammad Ehteshami.
‘We look forward to working with GE Additive on this revolutionary technology,’ said Jos Sclater, Head of Strategy at GKN. ‘GKN has a strong history of producing and certifying AM parts and powder, and by working together, GKN and GE can accelerate future developments in additive manufacturing and meet the growing demand we’re seeing across a range of industries.’
This story is reprinted from material from GKN, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Hole transport breakthrough produces stable perovskite solar cells
Perovskite solar cells (PSCs) can offer high light-conversion efficiencies with low manufacturing costs. But to be commercially viable, perovskite films must also be durable and not degrade under sunlight over time.
Scientists at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland have now found a way to improve the operational stability of PSCs. They have developed versions that retain more than 95% of their initial 20% conversion efficiency under full sunlight illumination at 60°C for more than 1000 hours. The breakthrough, which marks the highest stability ever achieved for PSCs, is published in a paper in Science.
In conventional silicon solar cells, efficiencies have plateaued at around 25%, while problems with their high cost of manufacturing, heavy weight and rigidity have remained largely unresolved. In contrast, despite being a much more recent technology, PSCs have already achieved more than 22% efficiency.
Given the vast chemical versatility and low processing costs of perovskite materials, PSCs hold the promise for creating cheap, lightweight and highly efficient solar cells. But until now, only highly expensive, organic hole-transporting materials (HTMs), which selectively transport positive charges in a solar cell, have been able to achieve power-conversion efficiencies of over 20%. And by virtue of their ingredients, these hole-transporting materials adversely affect the long-term operational stability of the PSC.
Scientists are therefore actively investigating cheap and stable hole transporters with high efficiencies to allow the large-scale deployment of perovskite solar cells. Among various inorganic HTMs, cuprous thiocyanate (CuSCN) stands out as a stable, efficient and cheap candidate ($0.5/g versus $500/g for a commonly used organic HTM known as spiro-OMeTAD). But previous attempts at using CuSCN as a hole transporter in perovskite solar cells have had limited success. This is due to problems associated with depositing a high-quality CuSCN layer on top of a perovskite film and the chemical instability of the CuSCN layer when integrated into a PSC.
Now, researchers in Michael Grätzel's lab at EPFL, led by postdocs Neha Arora and Ibrahim Dar, have introduced two new concepts that overcome the major shortcomings of CuSCN-based PSCs. First, they developed a simple dynamic solution-based method for depositing highly conformal, 60nm-thick CuSCN layers to produce PSCs with stabilized power-conversion efficiencies exceeding 20%. This is comparable to the efficiencies of the best performing, state-of-the-art spiro-OMeTAD-based PSCs.
Second, the scientists introduced a thin spacer layer of reduced graphene oxide between layers of CuSCN and gold. This innovation allowed the PSCs to achieve excellent operational stability: they retained over 95% of their initial efficiency while operating at maximum power for 1000 hours under full-sun illumination at 60°C, surpassing the stability of organic HTM-based PSCs. It also shows that the instability of previous CuSCN-based PSCs originated from the degradation of the CuSCN/gold contact during operation.
"This is a major breakthrough in perovskite solar-cell research and will pave the way for large-scale commercial deployment of this very promising new photovoltaic technology," says Grätzel.
"It will benefit the numerous scientists in the field that have been intensively searching for a material that could replace the currently used, prohibitively expensive organic hole-transporters," adds Dar.
This story is adapted from material from EPFL, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.
‘Jiggle and wiggle’ simulations explain metal strength
Researchers at Lawrence Livermore National Laboratory (LLNL) have dived down to the atomic scale to resolve every ‘jiggle and wiggle’ of atomic motion that underlies metal strength.
In a first-of-its-kind series of computer simulations focused on the metal tantalum, the researchers predicted that on reaching certain critical conditions of straining, the plasticity (the ability to change shape under load) of tantalum meets its limits. One limit is reached when crystal defects known as dislocations are no longer able to relieve mechanical loads. This activates another mechanism – twinning, or the sudden reorientation of the crystal lattice – which takes over as the dominant mode of dynamic response. This research is reported in a paper in Nature.
The strength and plasticity properties of a metal are defined by dislocations, line defects in the metal’s crystal lattice whose motion causes material slippage along crystal planes. The theory of crystal dislocation was first advanced in the 1930s; much research since then has focused on dislocation interactions and their role in metal hardening, in which continued deformation increases the metal's strength (much like a blacksmith pounding on steel with a hammer). These simulations strongly suggest that the metal cannot be strengthened forever.
"We predict that the crystal can reach an ultimate state in which it flows indefinitely after reaching its maximal strength," said Vasily Bulatov, LLNL lead author of the paper. "Ancient blacksmiths knew this intuitively because the main trick they used to strengthen their metal parts was to repeatedly hammer them from different sides, just like we do in our metal kneading simulation."
Due to severe limits on accessible length and time scales, it was long thought impossible or even unthinkable to use direct atomistic simulations to predict metal strength. Taking full advantage of LLNL's world-leading high-performance computing facilities through a grant from LLNL’s Computing Grand Challenge program, the researchers demonstrated that not only are such simulations possible, but they can deliver a wealth of important observations on the fundamental mechanisms of dynamic response. This includes the quantitative parameters needed to define strength models important to the Stockpile Stewardship Program, which ensures the safety, security and reliability of nuclear weapons without testing.
"We can see the crystal lattice in all details and how it changes through all stages in our metal strength simulations," Bulatov said. "A trained eye can spot defects and even characterize them to an extent just by looking at the lattice. But one's eye is easily overwhelmed by the emerging complexity of metal microstructure, which prompted us to develop precise methods to reveal crystal defects that, after we apply our techniques, leave only the defects while completely wiping out the remaining defect-less (perfect) crystal lattice. "
The researchers developed the first fully dynamic atomistic simulations of the plastic strength response of single crystal tantalum subjected to high-rate deformation. Unlike computational approaches to strength prediction, atomistic molecular dynamics simulations rely purely on an interatomic interaction potential to resolve every ‘jiggle and wiggle’ of atomic motion and reproduce material dynamics in full atomistic detail.
This story is adapted from material from Lawrence Livermore National Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.
Hexcel and Vestas expand supply agreement
Hexcel has expanded its existing supply agreement with Vestas Wind Systems A/S to provide composite materials for wind blades.
Under the terms of the multi-year agreement, Hexcel will supply Vestas with prepreg systems manufactured at Hexcel plants in Neumarkt, Austria, Colorado, USA, and Tianjin, China)
Hexcel has developed a new prepreg system to meet the requirements for large thick structures such as wind blades. This product reportedly allows for more energy savings in the curing process due to a low temperature cure cycle. It also enables shorter cycle times for higher throughput. Hexcel was also instrumental in developing the first prepreg materials for composite wind blades, the company says.
This story is reprinted from material from Hexcel, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Nanoparticle-polymer octopus creates ‘bijels’ to order
A new two-dimensional (2D) film, made of polymers and nanoparticles and developed by researchers at the US Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab), can direct two different non-mixing liquids into a variety of exotic architectures. This finding could lead to soft robotics, liquid circuitry, shape-shifting fluids, and a host of new materials made from soft, rather than solid, substances.
The study, reported in a paper in Nature Nanotechnology, presents the newest entry in a class of substances known as bicontinuous jammed emulsion gels, or bijels, which hold promise as a malleable liquid that can support catalytic reactions, electrical conductivity and energy conversion.
Bijels are typically made of immiscible, or non-mixing, liquids. Anyone who shakes their bottle of vinaigrette before pouring the dressing on their salad are familiar with such liquids. As soon as the shaking stops, the liquids start to separate again, with the lower density liquid – often oil – rising to the top.
Trapping, or jamming, particles where these immiscible liquids meet can prevent the liquids from completely separating, stabilizing the substance into a bijel. What makes bijels remarkable is that, rather than just making the spherical droplets that we normally see when we try to mix oil and water, the particles at the interface shape the liquids into complex networks of interconnected fluid channels.
Bijels are notoriously difficult to make, however, requiring exact temperatures at precisely timed stages. In addition, the liquid channels are normally more than 5µm across, making them too large to be useful in energy conversion and catalysis.
"Bijels have long been of interest as next-generation materials for energy applications and chemical synthesis," said study lead author Caili Huang. "The problem has been making enough of them, and with features of the right size. In this work, we crack that problem."
Huang started the work as a graduate student with Thomas Russell, the study's principal investigator, at Berkeley Lab's Materials Sciences Division, and he continued the project as a postdoctoral researcher at DOE's Oak Ridge National Laboratory (ORNL).
The method described in this new study simplifies the bijel process by first using specially-coated particles about 10–20nm in diameter. The smaller-sized particles line the liquid interfaces much more quickly than the ones used in traditional bijels, forming the smaller channels that are highly valued for applications.
"We've basically taken liquids like oil and water and given them a structure, and it's a structure that can be changed," said Russell, a visiting faculty scientist at Berkeley Lab. "If the nanoparticles are responsive to electrical, magnetic or mechanical stimuli, the bijels can become reconfigurable and re-shaped on demand by an external field."
The researchers were able to prepare new bijels from a variety of common organic, water-insoluble solvents, such as toluene, containing dissolved polymers, and deionized water, which contained the nanoparticles. To ensure thorough mixing of the liquids, they subjected the emulsion to a vortex spinning at 3200 revolutions per minute.
"This extreme shaking creates a whole bunch of new places where these particles and polymers can meet each other," explained study co-author Joe Forth, a postdoctoral fellow at Berkeley Lab's Materials Sciences Division. "You're synthesizing a lot of this material, which is in effect a thin, 2D coating of the liquid surfaces in the system."
The liquids remained a bijel even after one week, a sign of the system's stability.
Russell, who is also a professor of polymer science and engineering at the University of Massachusetts-Amherst, added that these shape-shifting characteristics would be valuable in microreactors, microfluidic devices and soft actuators.
Nanoparticles had not been seriously considered in bijels before because their small size made them hard to trap at the liquid interface. To resolve that problem, the researchers coated nano-sized particles with carboxylic acids and put them in water. They then took polymers with an added amine group – a derivative of ammonia – and dissolved them in the toluene.
This configuration took advantage of the amine group's affinity for water, a characteristic that is comparable to surfactants like soap. The researchers’ nanoparticle ‘supersoap’ was designed so that the nanoparticles joined with the polymers, forming an octopus-like shape with a polar head and nonpolar legs that get jammed at the interface, the researchers said.
"Bijels are really a new material, and also excitingly weird in that they are kinetically arrested in these unusual configurations," said study co-author Brett Helms, a staff scientist at Berkeley Lab's Molecular Foundry. "The discovery that you can make these bijels with simple ingredients is a surprise. We all have access to oils and water and nanocrystals, allowing broad tunability in bijel properties. This platform also allows us to experiment with new ways to control their shape and function since they are both responsive and reconfigurable."
The nanoparticles were made of silica, but the researchers noted that in previous studies they used graphene and carbon nanotubes to form nanoparticle surfactants. "The key is that the nanoparticles can be made of many materials," said Russell. "The most important thing is what's on the surface."
This story is adapted from material from Lawrence Berkeley National Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.
Johns Manville plant certified for food
Johns Manville (JM) reports that its plant in Slovakia has received Good Manufacturing Practice certification for its continuous filament glass fiber (CFGF) used in contact with food in engineered thermoplastic applications, according to EU regulation 10/2011.
The certification was granted by the certification body TÜV SÜD Slovakia. This certification is the first to be granted to a European CFGF manufacturer.
JM has developed a range of CFGF grades for various engineered thermoplastics intended to come into contact with food, including ThermoFlow 674 chopped strands designed for PA and high-heat polymer reinforcements, ThermoFlow 636 and StarRov 490 for PP and ThermoFlow 601 for PBT/PET.
This story is reprinted from material from Johns Manville, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Surface tension helps to produce large, pure perovskite crystals
In the race to replace silicon in low-cost solar cells, semiconductors known as metal halide perovskites are favored because they can be solution-processed into thin films with excellent photovoltaic efficiency. A collaboration between researchers at King Abdullah University of Science & Technology (KAUST) in Saudi Arabia and Oxford University in the UK has now uncovered a strategy for using surface tension to grow perovskites into centimeter-scale, highly pure crystals. The researchers describe this strategy in a paper in ACS Energy Letters.
In their natural state, perovskites have difficultly transporting solar-generated electricity because they crystallize with randomly-oriented grains. Osman Bakr from KAUST's Solar Center and co-workers are working on ways to dramatically speed up the flow of these charge carriers using inverse temperature crystallization (ITC). This technique uses special organic liquids and thermal energy to force perovskites to solidify into structures resembling single crystals – the optimal arrangement for device purposes.
While ITC produces high-quality perovskites far faster than conventional chemical methods, the curious mechanisms that initiate crystallization in hot organic liquids are poorly understood. Ayan Zhumekenov, a PhD student in Bakr's group, recalls spotting a key piece of evidence during efforts to adapt ITC for large-scale manufacturing. "At some point, we realized that when crystals appeared, it was usually at the solution's surface," he says. "And this was particularly true when we used concentrated solutions."
The KAUST team partnered with Oxford theoreticians to identify how interfaces influence perovskite growth in ITC. They propose that metal halides and solvent molecules initially cling together in tight complexes that begin to stretch and weaken at higher temperatures. With sufficient thermal energy, the complex breaks and perovskites begin to crystallize.
Interestingly, however, the researchers found that complexes located at the solution surface can experience additional forces due to surface tension – the strong cohesive forces that allow certain insects to stride over lakes and ponds. The extra pull provided by the surface makes it much easier to separate the solvent-perovskite complexes and nucleate crystals that float on top of the liquid.
Exploiting this knowledge helped the team to produce centimeter-sized, ultrathin single crystals and then to prototype a photodetector with characteristics comparable to state-of-the-art devices. Although the single crystals are currently fragile and difficult to handle due to their microscale thicknesses, Zhumekenov explains that this method could help to direct perovskite growth on specific substrates.
"Taking into account the roles of interfaces and surface tension could have a fundamental impact," he says, "we can get large-area growth, and it's not limited to specific metal cations – you could have a library of materials with perovskite structures."
This story is adapted from material from KAUST, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.
Precise positioning gives precise control over optical properties
Control is a constant challenge for materials scientists, who are always seeking the perfect material – and the perfect way of treating it – to induce exactly the right electronic or optical activity for a given application.
One key challenge to modulating activity in a semiconductor is controlling its band gap. When a material is excited with energy – say a light pulse – the wider its band gap, the shorter the wavelength of light it emits. The narrower the band gap, the longer the wavelength.
As electronics and the devices that incorporate them – smartphones, laptops and the like – have become smaller and smaller, the semiconductor transistors that power them have shrunk to the point of being not much larger than an atom. They can't get much smaller. To overcome this limitation, researchers are seeking ways to harness the unique characteristics of nanoscale atomic cluster arrays – known as quantum dot superlattices – for building next generation electronics such as large-scale quantum information systems. In the quantum realm, precision is even more important.
New research conducted at the University of California, Santa Barbara's Department of Electrical and Computer Engineering reveals a major advance in precision superlattice materials. The findings by Kaustav Banerjee, his PhD students Xuejun Xie, Jiahao Kang and Wei Cao, postdoctoral fellow Jae Hwan Chu and their collaborators at Rice University are described in a paper in Scientific Reports.
In their research, the team uses a focused electron beam to fabricate a large-scale quantum dot superlattice in which each quantum dot has a specific pre-determined size and is positioned at a precise location on an atomically thin sheet of the two-dimensional (2D) semiconductor molybdenum disulphide (MoS2). When the focused electron beam interacts with the MoS2 monolayer, it turns that area, which is on the order of a nanometer in diameter, from semiconducting to metallic. The quantum dots can be placed less than 4nm apart, so that they become an artificial crystal – essentially a new 2D material where the band gap can be specified to order, from 1.8 to 1.4 electron volts (eV).
This is the first time scientists have created a large-area 2D superlattice – nanoscale atomic clusters in an ordered grid – on an atomically thin material on which both the size and location of the quantum dots are precisely controlled. "We can, therefore, change the overall properties of the 2D crystal," said Banerjee.
Each quantum dot acts as a quantum well, where electron-hole activity occurs, and all of the dots in the grid are close enough to each other to ensure interactions. The researchers can vary the spacing and size of the dots to vary the band gap, which determines the wavelength of light it emits.
"Using this technique, we can engineer the band gap to match the application," Banerjee said. Quantum dot superlattices have been widely investigated for creating materials with tunable band gaps, but all were made using ‘bottom-up’ methods in which atoms naturally and spontaneously combine to form a macro-object. But these methods make it inherently difficult to design the lattice structure as desired and, thus, to achieve optimal performance.
As an example, depending on conditions, combining carbon atoms yields only two results in the bulk (or 3D) form: graphite or diamond. These cannot be 'tuned' and so cannot make anything in between. But when atoms can be precisely positioned, the material can be designed with desired characteristics.
"Our approach overcomes the problems of randomness and proximity, enabling control of the band gap and all the other characteristics you might want the material to have – with a high level of precision," Xie said. "This is a new way to make materials, and it will have many uses, particularly in quantum computing and communication applications. The dots on the superlattice are so close to each other that the electrons are coupled, an important requirement for quantum computing."
The quantum dot is theoretically an artificial ‘atom’. The developed technique makes such design and ‘tuning’ possible by permitting top-down control of the size and the position of the artificial atoms at large scale.
To demonstrate the level of control achieved, the authors produced an image of ‘UCSB’ spelled out in a grid of quantum dots. By using different doses from the electron beam, they were able to cause different areas of the university's initials to light up at different wavelengths.
"When you change the dose of the electron beam, you can change the size of the quantum dot in the local region, and once you do that, you can control the band gap of the 2D material," Banerjee explained. "If you say you want a band gap of 1.6eV, I can give it to you. If you want 1.5eV, I can do that, too, starting with the same material."
This demonstration of tunable direct band gap could usher a new generation of light-emitting devices for photonics applications.
This story is adapted from material from the University of California, Santa Barbara, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.
Lanxess to research new urethanes
Lanxess’ Urethane Systems business unit has joined forces with the University of Massachusetts to help develop new urethane materials.
Lanxess will join Flammability Cluster (Cluster F) and Mechanical Properties & Additive Manufacturing Cluster (Cluster M) at the Center for UMass/Industry Research on Polymers (CUMIRP). The collaboration will begin in October 2017.
‘This team-oriented approach fosters cross-industry collaboration as well as gives us access to top experts in polymer science as consultants,’ said Dr Polina Ware, head of global research and development at Lanxess Urethane Systems. ‘As members of Cluster M and F, we expect to gain potential cost savings and business growth though new product innovation.’
A key figure in the academic collaboration will be scientist Alan Lesser who is a world expert in deformation and fracture of polymers and composites. According to Lanxess. His research focuses on strength, durability, and micromechanics of polymer blends and composites, nano and molecular composites, constructive modeling of polymers in complex stress states as well as unique processing methods and multi-functional additives.
This story is reprinted from material from Lanxess, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
GKN forms new AM brand
Global aerospace and automotive engineering Group GKN has formed a new brand for its additive manufacturing (AM) activity.
GKN Additive will act as the focal point for all AM activity in the future, the company says.
GKN has made components arts using AM for aerospace and automotive. It is also a powder producer through its Powder Metallurgy division.
‘The benefits of AM are significant, both for our customers and the world around us in terms of greener, more efficient production,’ said Jos Sclater, head of strategy at GKN. ‘There is also a tangible feeling that manufacturing is suddenly a very exciting place to be for the brightest and best engineering talent. […]Thanks to our specialist powder business, Hoeganaes, and based on our 250 years of manufacturing and engineering experience, GKN is outstandingly placed to continue to lead in all four areas.’
This story is reprinted from material from GKN, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.