Invigorating the idea of computers based on fluids instead of silicon, researchers at the National Institute of Standards and Technology (NIST) have shown how computational logic operations could be performed in a liquid medium by simulating the trapping of ions (charged atoms) in graphene (a sheet of carbon atoms) floating in saline solution. The scheme might also be used in applications such as water filtration, energy storage or sensor technology.
The idea of using a liquid medium for computing has been around for decades, and various approaches have been proposed. Among its potential advantages, this approach would require very little material and its soft components could conform to custom shapes in, for example, the human body.
NIST’s ion-based transistor and logic operations are simpler in concept than earlier proposals. The new simulations show that a special film immersed in liquid can act like a solid silicon-based semiconductor. For example, the material can act like a transistor, the switch that carries out digital logic operations in a computer. The film can be switched on and off by tuning voltage levels like those induced by salt concentrations in biological systems.
Typically research has focused on the effects induced by different materials in graphene. Convinced that this is only half the story, Dr Zeila Zanolli turned the tables to look at the proximity effects of graphene on magnetic semiconducting substrates. Using first principles calculations she observes a switching of internal spin alignment from antiferromagnetic to ferromagnetic. Persisting close to room temperature, her findings could find applications in magnetic memories or spin filters.
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In a refreshing change of perspective, theoretical physicist Dr Zeila Zanolli has looked at the proximity effects of graphene on a magnetic semiconducting substrate, finding it to affect the substrate’s magnetism down to several layers below the surface. Her paper was published on 5 October in Physical Review B. She was also one of three recipients of the first MaX Prize for frontier research in computational materials science.
The first boards for gliding over snow existed as early as 1900, but it was not until 1963 that American surfers brought the feeling of surfing to the snow and developed the original snowboard—the so-called snurfer. A few years later, the snowboard drew the interest of the winter sports industry, and since 1998, snowboarding has been recognized as an Olympic sport.
Chemnitz University of Technology researchers have presented an innovation from the 2020/2021 winter sports season: Together with silbaerg GmbH, a spin-off from the Institute of Lightweight Structures at Chemnitz University of Technology, they have developed a lightweight snowboard that can also be manufactured far more sustainably than comparable boards. This is made possible by a new type of textile fiber, a semi-finished product made of carbon fibers. By using the dry fiber placement process, fiber waste in snowboard production can be reduced by around 60%. “This not only saves costs, but thanks to the board’s sustainable production, its carbon footprint is also significantly reduced,” says Prof. Dr. Holger Cebulla, head of the Chair of Textile Technologies.
When two sheets of the carbon nanomaterial graphene are stacked together at a particular angle with respect to each other, it gives rise to some fascinating physics. For instance, when this so-called “magic-angle graphene” is cooled to near absolute zero, it suddenly becomes a superconductor, meaning it conducts electricity with zero resistance.
Now, a research team from Brown University has found a surprising new phenomenon that can arise in magic-angle graphene. In research published in the journal Science, the team showed that by inducing a phenomenon known as spin-orbit coupling, magic-angle graphene becomes a powerful ferromagnet.
“Magnetism and superconductivity are usually at opposite ends of the spectrum in condensed matter physics, and it’s rare for them to appear in the same material platform,” said Jia Li, an assistant professor of physics at Brown and senior author of the research. “Yet we’ve shown that we can create magnetism in a system that originally hosts superconductivity. This gives us a new way to study the interplay between superconductivity and magnetism, and provides exciting new possibilities for quantum science research.”
A new form of 3-D-printed material made by combining commonly-used plastics with carbon nanotubes is tougher and lighter than similar forms of aluminium, scientists say.
The material could lead to the development of safer, lighter and more durable structures for use in the aerospace, automotive, renewables and marine industries.
In a new paper published in the journal Materials & Design, a team led by University of Glasgow engineers describe how they have developed a new plate-lattice cellular metamaterial capable of impressive resistance to impacts.
Metamaterials are a class of artificially-created cellular solids, designed and engineered to manifest properties which do not occur in the natural world.
In 2018, the physics world was set ablaze with the discovery that when an ultrathin layer of carbon, called graphene, is stacked and twisted to a “magic angle,” that new double layered structure converts into a superconductor, allowing electricity to flow without resistance or energy waste. Now, in a literal twist, Harvard scientists have expanded on that superconducting system by adding a third layer and rotating it, opening the door for continued advancements in graphene-based superconductivity.
The work is described in a new paper in Science and can one day help lead toward superconductors that operate at higher or even close to room temperature. These superconductors are considered the holy grail of condensed matter physics since they would allow for tremendous technological revolutions in many areas including electricity transmission, transportation, and quantum computing. Most superconductors today, including the double layered graphene structure, work only at ultracold temperatures.
“Superconductivity in twisted graphene provides physicists with an experimentally controllable and theoretically accessible model system where they can play with the system’s properties to decode the secrets of high temperaturesuperconductivity,” said one of the paper’s co-lead authors Andrew Zimmerman, a postdoctoral researcher in working in the lab of Harvard physicist Philip Kim.
A new type of battery developed by researchers at MIT could be made partly from carbon dioxide captured from power plants. Rather than attempting to convert carbon dioxide to specialized chemicals using metal catalysts, which is currently highly challenging, this battery could continuously convert carbon dioxide into a solid mineral carbonate as it discharges.
The battery is made from lithium metal, carbon, and an electrolyte that the researchers designed. While still based on early-stage research and far from commercial deployment, the new battery formulation could open up new avenues for tailoring electrochemical carbon dioxide conversion reactions, which may ultimately help reduce the emission of the greenhouse gas to the atmosphere.
Currently, power plants equipped with carbon capture systems generally use up to 30 percent of the electricity they generate just to power the capture, release, and storage of carbon dioxide. Anything that can reduce the cost of that capture process, or that can result in an end product that has value, could significantly change the economics of such systems, the researchers say.
Betar Gallant, Assistant Professor of Mechanical Engineering at MIT, said, ‘Carbon dioxide is not very reactive. Trying to find new reaction pathways is important.’Ideally, the gas would undergo reactions that produce something worthwhile, such as a useful chemical or a fuel. However, efforts at electrochemical conversion, usually conducted in water, remain hindered by high energy inputs and poor selectivity of the chemicals produced.
The team looked into whether carbon-dioxide-capture chemistry could be put to use to make carbon-dioxide-loaded electrolytes — one of the three essential parts of a battery — where the captured gas could then be used during the discharge of the battery to provide a power output.
The team developed a new approach that could potentially be used right in the power plant waste stream to make material for one of the main components of a battery. By incorporating the gas in a liquid state, however, Gallant and her co-workers found a way to achieve electrochemical carbon dioxide conversion using only a carbon electrode. The key is to preactivate the carbon dioxide by incorporating it into an amine solution.
‘What we’ve shown for the first time is that this technique activates the carbon dioxide for more facile electrochemistry,’ Gallant says. ‘These two chemistries — aqueous amines and nonaqueous battery electrolytes — are not normally used together, but we found that their combination imparts new and interesting behaviors that can increase the discharge voltage and allow for sustained conversion of carbon dioxide.’
The battery is made from lithium metal, carbon, and an electrolyte that the researchers designed. While still based on early-stage research and far from commercial deployment, the new battery formulation could open up new avenues for tailoring electrochemical carbon dioxide conversion reactions, which may ultimately help reduce the emission of the greenhouse gas to the atmosphere.
The direct band gap of AlN-based materials makes them suitable for fabricating DUV optoelectronic devices, which have a wide range of application prospects in the fields of curing, water and air disinfection, medicine and biochemistry. Therefore, achieving a high-quality epitaxy of AlN films is of particular importance to ensure the excellent performance of DUV photoelectric devices.
Currently, due to the lack of cost-effective homogenous substrates, the optimal choice to grow AlN films is usually to perform heteroepitaxial growth on sapphire. Unfortunately, the inherent mismatches between AlN and sapphire substrate inevitably introduce a variety of crystalline defects into the AlN epilayer. In particular, the large residual strain in the AlN film leads to the nonuniformity of the Al distribution in the upper AlGaN layer accompanied by wafer bending, which severely limits the device performance. Therefore, a feasible strategy is required to make a qualitative leap to realize high-quality growth of heteroepitaxial AlN films and to meet the application requirements of DUV optoelectronic devices.
Even today, clean water is a privilege for many people across the world. According to the World Health Organization (WHO), at least 1.8 billion people consume water contaminated with feces, and by 2040, a large portion of the world will endure water stress because of insufficient resources of drinking water. Meanwhile, the United Nations Children’s Fund (UNICEF), around 1,800 children die every day from diarrhea because of unsafe water supply, which causes diseases like cholera.
It has become imperative then that we develop efficient and cost-efficient ways to decontaminate water. And that is exactly what a team of scientists led by László Forró at EPFL have accomplished, with a new water purification filter that combines titanium dioxide (TiO2) nanowires and carbon nanotubes powered by nothing but sunlight.
The scientists first show that the TiO2nanowires by themselves can efficiently purify water in the presence of sunlight. But interweaving the nanowires with carbon nanotubes forms a composite material that adds an extra layer of decontamination by pasteurizing the water – killing off human pathogens such as bacteria and large viruses.
A team of researchers at MIT has designed one of the strongest lightweight materials known, by compressing and fusing flakes of graphene, a two-dimensional form of carbon. The new material, a sponge-like configuration with a density of just 5 percent, can have a strength 10 times that of steel.
In its two-dimensional form, graphene is thought to be the strongest of all known materials. But researchers until now have had a hard time translating that two-dimensional strength into useful three-dimensional materials.
The new findings show that the crucial aspect of the new 3-D forms has more to do with their unusual geometrical configuration than with the material itself, which suggests that similar strong, lightweight materials could be made from a variety of materials by creating similar geometric features.
The findings are being reported today in the journal Science Advances, in a paper by Markus Buehler, the head of MIT’s Department of Civil and Environmental Engineering (CEE) and the McAfee Professor of Engineering; Zhao Qin, a CEE research scientist; Gang Seob Jung, a graduate student; and Min Jeong Kang MEng ‘16, a recent graduate.
Porphyrins, the same molecules that convey oxygen in hemoglobin and absorb light during photosynthesis, can be joined to the material of the future, graphene, to give it new properties. This was recently shown by a team of scientists at the Technical University of Munich, in which a Spanish researcher also participated. The resulting hybrid structures could be used in the field of molecular electronics and in developing new sensors.
At the moment, it is difficult to find a material that attracts as much attention from scientists and engineers as graphene, which is made up of a layer of carbon atoms arrange in a hexagonal structure. It is flexible, extremely thin and clear, while being highly resistant and a conductor of electricity – ideal requirements for a number of uses, especially in the field of electronics.
However, using graphene to capture solar energy or as a gas sensor requires specific properties which it lacks, although it can acquire them by addition or functionalisation with certain molecules.
A team of researchers from the Technical University of Munich (TUM), led by Professor Wilhelm Auwärter, has succeeded in bonding an important biochemical group to the graphene sheet: porphyrins, protein rings which are part of chlorophyll, essential for photosynthesis in plants, and hemoglobin, which is responsible for conveying oxygen in animals’ blood.
A skin-like polymeric material is using carbon nanotubes (CNTs) to bring a sense of touch to robotic and prosthetic devices. Developed by researchers at Stanford University and Xerox Palo Alto Research Center, the flexible, polymeric skin or ‘digital tactile system’ (DiTact) incorporates CNT pressure sensors and flexible organic printed circuits to mimic human response [Tee et al., Science 350 (2015) 313].
‘‘We wanted to make a sensor skin that communicates in the same way as the body,’’ explains research student Alex Chortos, one of the lead authors of the work. ‘‘The goal is to make skin for prosthetics that can feel touch in a natural way and communicate that information to the person wearing the prosthetic device.’’
In the body, receptors in the skin relay sensing information directly to the brain in a series of voltage pulses rather like Morse code. Artificial devices employ tactile sensing to improve the control of neuroprosthetics and relieve phantom limb pain. But, to date, prosthetic skin devices have had to use a computer or microprocessor to turn the output from sensors into a signal compatible with neurons.
The new approach, by contrast, combines these operations in a single system of piezoresistive pressure sensors embedded in a flexible circuit layer. The sensors are made from a CNT composite dispersed in a flexible polyurethane plastic and molded into pyramidal structures. The pyramidal shape is crucial because it allows the pressure range of the sensor to be tuned to that of skin.
1. The American Edward Goodrich Acheson heated a mixture of clay – aluminium silicate, and powdered coke (carbon) in an iron bowl with a carbon arc, and found shiny hexagonal crystals attached to the carbon electrode. Acheson eventually patented this method for producing powdered silicon carbide (SiC), a compound of silicon and carbon in 1893.
2. The mineral form of silicon carbide is called moissanite and gets its name from Dr Ferdinand Henry Moissan, who first discovered it in the Canyon Diablo Crater in Arizona in 1904.
3. Silicon carbide crystals can be strongly birefringent, meaning the crystals exhibit different refractive indices down different axes.
4. SiC powder production involves the Acheson resistance furnace, produced by the Lely Process. This method creates large single crystals by sublimating silicon carbide powder to form a high-temperature species called silicon dicarbide (SiC2) and disilicon carbide (Si2C).
5. Semiconducting silicon carbide first found application as a detector in early radios at the beginning of the 20thCentury.
To find out more about the history of silicon carbide, read Anna Ploszajski’s Material of the Month feature in our January issue.
They are not to eat, but this insect-inspired ordered monolayer of hollow carbon spheres may be a new, green and extremely lightweight antireflective coating that almost perfectly absorbs microwave radiation
Antireflective coatings are used to cut surface glare in everything from eyeglasses and camera lenses to solar cells, TV screens and LED devices. Now researchers from Research Institute for Nuclear Problems of Belarusian State University in Belarus and Institut Jean Lamour-Université de Lorraine in France have developed a novel, low-cost, ultra-lightweight material that could be used as an effective anti-reflective surface for microwave radiation based on the eyes of moths.
The eyes of moths are covered with a periodic, hexagonal pattern of tiny bumps smaller than the wavelength of the incident light. They act as a continuous refractive index gradient, allowing the moths to see at night and avoid nocturnal predators, like the bat. The physiology also makes the moth eye one of the most effective antireflective coatings in nature. It has already successfully been mimicked by scientists for developing high-performance antireflective coatings for visible lights – albeit coatings that are often expensive to fabricate and difficult to customize.
The new material cuts down reflections from microwaves rather than from visible light – invisible energy from a different part of the energy spectrum. Blocking microwave reflection is an important application for precise microwave measurements, and the coating may be used as a radar absorbing material in stealth technology, a technique that makes make an airplane invisible to radar, or police traffic radar that uses microwaves to measure car speed.
A novel technique that nudges single atoms to switch places within an atomically thin material could bring scientists another step closer to realizing theoretical physicist Richard Feynman’s vision of building tiny machines from the atom up.
A significant push to develop materials that harness the quantum nature of atoms is driving the need for methods to build atomically precise electronics and sensors. Fabricating nanoscale devices atom by atom requires delicacy and precision, which has been demonstrated by a microscopy team at the Department of Energy’s Oak Ridge National Laboratory.
They used a scanning transmission electron microscope, or STEM, at the lab’s Center for Nanophase Materials Sciences to introduce silicon atoms into a single-atom-thick sheet of graphene. As the electron beam scans across the material, its energy slightly disrupts the graphene’s molecular structure and creates room for a nearby silicon atom to swap places with a carbon atom.
“We observed an electron beam-assisted chemical reaction induced at a single atom and chemical bond level, and each step has been captured by the microscope, which is rare,” said ORNL’s Ondrej Dyck, co-author of a study published in the journal Small that details the STEM demonstration.
Using non-conventional methods, Christina Birkel and her colleagues in the Department of Chemistry of the TU Darmstadt produce metallic ceramics and new materials for the energy supply of the future.
The microwave oven in the laboratory of Christina Birkel, junior research group leader at the TU Darmstadt, is not only larger and significantly more expensive than the usual household device, but also more powerful and fire and explosion-proof. Birkel had the turntable and its plastic support removed. “That would have melted anyway,” she says. The chemist uses the oven for the synthesis of substances that experts call MAX phases. M stands for a transition metal, for example for titanium or vanadium, A for a main group element – usually aluminium – and X for carbon, and more rarely also nitrogen. Thus far, approximately 70 members of this family are known.
“Around the turn of the millennium, research efforts in the field of MAX phases have increased significantly,” explains Birkel. No wonder, because the materials are scratch-resistant, high-temperature stable and in many cases oxidation-resistant like a ceramic, but they also conduct electricity and sometimes have extraordinary magnetic proper ties. They are therefore also referred to as metallic ceramics. Similarly to clay minerals, MAX phases have a lamellar structure of alternating A and M-X-M layers.
Professor of Chemistry Craig Teague and his students have discovered that the by-products of soft drinks could help reduce global warming.
A Cornell College team of researchers worked with other experts at the Oak Ridge National Laboratory in Tennessee on the idea starting in 2016, and their final conclusions were published in the journal article “Microporous and hollow carbon spheres derived from soft drinks: Promising CO2separation materials” in April of 2019. Their new research shows that the by-products of some soft drinks actually remove carbon dioxide, a gas known to warm the planet, from gas streams.
“In this research, we are looking at turning one waste material into something of value,” Teague said. “We looked at waste soft drinks–asking could we possibly find a way to make that waste useful by doing a simple process in the lab and taking the carbon out? That carbon, by the way we synthesized it, has tiny pores, which are able to capture carbon dioxide.”
