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Haydale Awarded Funding to Develop Non-Metallic Gas Tanks for Spacecraft Propulsion Systems

Posted By Graphene Council, The Graphene Council, Wednesday, September 11, 2019
Updated: Thursday, September 5, 2019

Haydale has been awarded a technology de-risking project by the European Space Agency (ESA), to develop non-metallic gas tanks for spacecraft propulsion systems. This activity is alongside ISP International Space Propulsion Ltd through the ESA ARTES Competitiveness & Growth, in conjunction with UK Space Agency.

The recent market growth of small spacecraft constellations has created a challenge within the existing space propulsion supply chain for low-cost reliable components, which meet the rapid delivery schedule and support the on-going reduction of orbital debris. With the constellation market set to increase rapidly, the development of components that meet these criteria is critical. Haydale’s non-metallic system offers a low-cost alternative with reduced lead time that can be offered in a wider range of configurations to exactly suit the end user requirement.



This award follows on from the successful outcome of the GSTP project in 2018 performed with ESA and the UK Space Agency (UKSA) entitled “Assessments to Prepare and De-Risk Technology Developments - Tank using Advanced Composites.” This latest project will see Haydale develop findings from the GSTP project, performing comprehensive tests to determine the best material and process for developing non-metallic gas tanks.

Upon careful consideration and selection of both material and process, Haydale will formulate and model a largely de-risked tank, prior to the manufacture of development models for full testing. This will result in the qualification for specific Spacecraft Propulsion Systems. 

The role of this equipment is to store pressurised gas in a location onboard the spacecraft platform, in a manner that is intrinsically safe, and offers reliable provision of stored media, as and when required by the system. Within this equipment, the product will offer; leak-free storage and delivery on demand of all propellant and pressurised gases stored within, under specified environmental conditions and expected transient load cases; high pressure storage capabilities, with required levels of safety and reliability; highly reliable connections to the feed system and mechanical mounting; 

Prominent producers of Satellite technology have been identified and are engaged in developing the specification and tank design for eventual manufacture and deployment.

Keith Broadbent, CEO, Haydale, said: “This funding will allow Haydale to develop existing knowledge in the space industry and we look forward to developing the technology alongside our partners. We are pleased to have gained the support of the Airbus DS Tank Product Group who are interested in the development of competitive non-conventional pressure vessel products, and can provide clear design drivers thanks to their invaluable expertise. With the UK space market growing, Haydale is delighted to be part of this progression.”

Tags:  Aerospace  Airbus  Graphene  Haydale  Keith Broadbent 

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World’s smallest accelerometer points to new era in wearables, gaming

Posted By Graphene Council, The Graphene Council, Wednesday, September 11, 2019
Updated: Friday, September 6, 2019
In what could be a breakthrough for body sensor and navigation technologies, researchers at KTH have developed the smallest accelerometer yet reported, using the highly conductive nanomaterial, graphene.

Each passing day, nanotechnology and the potential for graphene material make new progress. The latest step forward is a tiny accelerometer made with graphene by an international research team involving KTH Royal Institute of Technology, RWTH Aachen University and Research Institute AMO GmbH, Aachen.

Among the conceivable applications are monitoring systems for cardiovascular diseases and ultra-sensitive wearable and portable motion-capture technologies.

For decades microelectromechanical systems (MEMS) have been the basis for new innovations in, for example, medical technology. Now these systems are starting to move to the next level – nano-electromechanical systems, or NEMS.

Xuge Fan, a researcher in the Department for Micro and Nanosystems at KTH, says that the unique material properties of graphene have enabled them to build these ultra-small accelerometers.

“Based on the surveys and comparisons we have made, we can say that this is the smallest reported electromechanical accelerometer in the world,” Fan says. The researchers reported their work in Nature Electronics.

The measure by which any conductor is judged is how easily, and speedily, electrons can move through it. On this point, together with its extraordinary mechanical strength, graphene is one of the most promising materials for a breathtaking array of applications in nano-electromechanical systems.

“We can scale down components because of the material’s atomic-scale thickness, and it has great electrical and mechanical properties,” Fan says. “We created a piezoresistive NEMS accelerometer that is dramatically smaller than any MEMS accelerometers available today, but retains the sensitivity these systems require.”

The future for such small accelerometers is promising, says Fan, who compares advances in nanotechnology to the evolution of smaller and smaller computers.

“This could eventually benefit mobile phones for navigation, mobile games and pedometers, as well as monitoring systems for heart disease and motion-capture wearables that can monitor even the slightest movements of the human body,” he says.

Other potential uses for these NEMS transducers include ultra-miniaturized NEMS sensors and actuators such as resonators, gyroscopes and microphones. In addition, these NEMS transducers can be used as a system to characterize the mechanical and electromechanical properties of graphene, Fan says.

Max Lemme, professor at RWTH, is excited about the results: "Our collaboration with KTH over the years has already shown the potential of graphene membranes for pressure and Hall sensors and microphones. Now we have added accelerometers to the mix. This makes me hopeful to see the material on the market in some years. For this, we are working on industry-compatible manufacturing and integration techniques."

Tags:  AMO GmbH  Electronics  Graphene  KTH Royal Institute of Technology  Max Lemme  RWTH Aachen University  Sensors  Xuge Fan 

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Grolltex Graphene Closes Oversubscribed Private Placement Financing Round

Posted By Graphene Council, The Graphene Council, Wednesday, September 11, 2019
Updated: Tuesday, September 10, 2019

Grolltex (named for ‘graphene-rolling-technologies’) is the largest commercial producer of single layer, ‘electronics grade’ graphene and graphene sensing materials in the U.S. They have announced that it has closed a non-brokered, oversubscribed private placement financing, in the form of a convertible note, with local area private investors. 

The gross proceeds of the private placement will be used for general working capital purposes and for increasing the capacity and quality testing capabilities of the company’s production facility in San Diego, California.


The company is focused on delivering inexpensive and enabling solutions to advanced nano-device and graphene sensor makers by fabricating the highest quality single layer graphene attainable, via chemical vapor deposition (or ‘CVD’).

The company is now capable of producing monolayer graphene sensors on large area plastic sheets at a cost of pennies per unit, in a high throughput and sustainable way.  Further, Grolltex is helping customers that currently produce their graphene sensors on silicon wafers, to transition that production capacity to making their sensors on large area sheets of biodegradable plastic instead, at a >100X cost savings. 

Monolayer graphene films are today seen as the most promising futuristic sensing materials for their combination of surface to volume ratio (the film is only one atom thick) and conductivity (the most conductive substance known at room temperature). Markets that are commercializing advanced sensors made of graphene include DNA sensing and editing, new drug discovery and wearable bio-monitors for glucose sensing and autonomous blood pressure monitoring via patches or watch-like wearable bracelet devices.

No securities were issued and no cash was paid as bonuses, finders’ fees, compensation or commissions in connection with the private placement.

Tags:  Biosensor  CVD  Graphene  Groltex  Sensors 

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MIT engineers build advanced microprocessor out of carbon nanotubes

Posted By Graphene Council, The Graphene Council, Tuesday, September 3, 2019

After years of tackling numerous design and manufacturing challenges, MIT researchers have built a modern microprocessor from carbon nanotube transistors, which are widely seen as a faster, greener alternative to their traditional silicon counterparts.

The microprocessor, described today in the journal Nature, can be built using traditional silicon-chip fabrication processes, representing a major step toward making carbon nanotube microprocessors more practical.

Silicon transistors — critical microprocessor components that switch between 1 and 0 bits to carry out computations — have carried the computer industry for decades. As predicted by Moore’s Law, industry has been able to shrink down and cram more transistors onto chips every couple of years to help carry out increasingly complex computations. But experts now foresee a time when silicon transistors will stop shrinking, and become increasingly inefficient.

Making carbon nanotube field-effect transistors (CNFET) has become a major goal for building next-generation computers. Research indicates CNFETs have properties that promise around 10 times the energy efficiency and far greater speeds compared to silicon. But when fabricated at scale, the transistors often come with many defects that affect performance, so they remain impractical.

The MIT researchers have invented new techniques to dramatically limit defects and enable full functional control in fabricating CNFETs, using processes in traditional silicon chip foundries. They demonstrated a 16-bit microprocessor with more than 14,000 CNFETs that performs the same tasks as commercial microprocessors. The Nature paper describes the microprocessor design and includes more than 70 pages detailing the manufacturing methodology.

The microprocessor is based on the RISC-V open-source chip architecture that has a set of instructions that a microprocessor can execute. The researchers’ microprocessor was able to execute the full set of instructions accurately. It also executed a modified version of the classic “Hello, World!” program, printing out, “Hello, World! I am RV16XNano, made from CNTs.”

“This is by far the most advanced chip made from any emerging nanotechnology that is promising for high-performance and energy-efficient computing,” says co-author Max M. Shulaker, the Emanuel E Landsman Career Development Assistant Professor of Electrical Engineering and Computer Science (EECS) and a member of the Microsystems Technology Laboratories. “There are limits to silicon. If we want to continue to have gains in computing, carbon nanotubes represent one of the most promising ways to overcome those limits. [The paper] completely re-invents how we build chips with carbon nanotubes.”

Joining Shulaker on the paper are: first author and postdoc Gage Hills, graduate students Christian Lau, Andrew Wright, Mindy D. Bishop, Tathagata Srimani, Pritpal Kanhaiya, Rebecca Ho, and Aya Amer, all of EECS; Arvind, the Johnson Professor of Computer Science and Engineering and a researcher in the Computer Science and Artificial Intelligence Laboratory; Anantha Chandrakasan, the dean of the School of Engineering and the Vannevar Bush Professor of Electrical Engineering and Computer Science; and Samuel Fuller, Yosi Stein, and Denis Murphy, all of Analog Devices.

Fighting the “bane” of CNFETs

The microprocessor builds on a previous iteration designed by Shulaker and other researchers six years ago that had only 178 CNFETs and ran on a single bit of data. Since then, Shulaker and his MIT colleagues have tackled three specific challenges in producing the devices: material defects, manufacturing defects, and functional issues. Hills did the bulk of the microprocessor design, while Lau handled most of the manufacturing.

For years, the defects intrinsic to carbon nanotubes have been a “bane of the field,” Shulaker says. Ideally, CNFETs need semiconducting properties to switch their conductivity on an off, corresponding to the bits 1 and 0. But unavoidably, a small portion of carbon nanotubes will be metallic, and will slow or stop the transistor from switching. To be robust to those failures, advanced circuits will need carbon nanotubes at around 99.999999 percent purity, which is virtually impossible to produce today.  

The researchers came up with a technique called DREAM (an acronym for “designing resiliency against metallic CNTs”), which positions metallic CNFETs in a way that they won’t disrupt computing. In doing so, they relaxed that stringent purity requirement by around four orders of magnitude — or 10,000 times — meaning they only need carbon nanotubes at about 99.99 percent purity, which is currently possible.

Designing circuits basically requires a library of different logic gates attached to transistors that can be combined to, say, create adders and multipliers — like combining letters in the alphabet to create words. The researchers realized that the metallic carbon nanotubes impacted different pairings of these gates differently. A single metallic carbon nanotube in gate A, for instance, may break the connection between A and B. But several metallic carbon nanotubes in gates B may not impact any of its connections.

In chip design, there are many ways to implement code onto a circuit. The researchers ran simulations to find all the different gate combinations that would be robust and wouldn’t be robust to any metallic carbon nanotubes. They then customized a chip-design program to automatically learn the combinations least likely to be affected by metallic carbon nanotubes. When designing a new chip, the program will only utilize the robust combinations and ignore the vulnerable combinations.

“The ‘DREAM’ pun is very much intended, because it’s the dream solution,” Shulaker says. “This allows us to buy carbon nanotubes off the shelf, drop them onto a wafer, and just build our circuit like normal, without doing anything else special.”

Exfoliating and tuning

CNFET fabrication starts with depositing carbon nanotubes in a solution onto a wafer with predesigned transistor architectures. However, some carbon nanotubes inevitably stick randomly together to form big bundles — like strands of spaghetti formed into little balls — that form big particle contamination on the chip.  

To cleanse that contamination, the researchers created RINSE (for “removal of incubated nanotubes through selective exfoliation”). The wafer gets pretreated with an agent that promotes carbon nanotube adhesion. Then, the wafer is coated with a certain polymer and dipped in a special solvent. That washes away the polymer, which only carries away the big bundles, while the single carbon nanotubes remain stuck to the wafer. The technique leads to about a 250-times reduction in particle density on the chip compared to similar methods.

Lastly, the researchers tackled common functional issues with CNFETs. Binary computing requires two types of transistors: “N” types, which turn on with a 1 bit and off with a 0 bit, and “P” types, which do the opposite. Traditionally, making the two types out of carbon nanotubes has been challenging, often yielding transistors that vary in performance. For this solution, the researchers developed a technique called MIXED (for “metal interface engineering crossed with electrostatic doping”), which precisely tunes transistors for function and optimization.

In this technique, they attach certain metals to each transistor — platinum or titanium — which allows them to fix that transistor as P or N. Then, they coat the CNFETs in an oxide compound through atomic-layer deposition, which allows them to tune the transistors’ characteristics for specific applications. Servers, for instance, often require transistors that act very fast but use up energy and power. Wearables and medical implants, on the other hand, may use slower, low-power transistors.  

The main goal is to get the chips out into the real world. To that end, the researchers have now started implementing their manufacturing techniques into a silicon chip foundry through a program by Defense Advanced Research Projects Agency, which supported the research. Although no one can say when chips made entirely from carbon nanotubes will hit the shelves, Shulaker says it could be fewer than five years. “We think it’s no longer a question of if, but when,” he says.

Tags:  Analog Devices  Carbon Nanotubes  Graphene  Max M. Shulaker  MIT  transistor 

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First Graphene announce PureGRAPH Incorporated into Steel Blue Safety Boots

Posted By Graphene Council, The Graphene Council, Wednesday, August 28, 2019
First Graphene is pleased to advise that in conjunction with Steel Blue have manufactured prototype sets of safety boots incorporating PureGRAPH®10.

The boots were made last week at Steel Blue’s Malaga WA factory and incorporated PureGRAPH® into the safety capped boot TPU soles and polyurethane foam innersole.

Full boots and the sole samples will be exposed to extensive laboratory tests which are expected to exceed current industry standards for safety footwear. Following laboratory testing it is anticipated extensive field trials, will be conducted, lasting approximately six months.

The incorporation of PureGRAPH® into a thermoplastic polyurethane (TPU) is a major advance for FGR. Previously, the successful dispersion of graphene into a TPU masterbatch has been a major graphene industry issue. Extensive research by FGR has resulted in a manufacturing method which has overcome what was previously seen as a real issue.

While existing TPU’s already possess high abrasion resistance and tensile strength it is anticipated the incorporation of PureGRAPH® will improve mechanical properties while providing additional benefits in thermal heat transfer, chemical resistance and reduced permeability. 

FGR will be conducting extensive laboratory tests on the PureGRAPH® infused TPU and polyurethane foam inner sole in Australia and Manchester. Steel Blue safety boot properties are being enhanced by PureGRAPH® in the Metatarsal Guard (Steel Blue’s Met-Guard), which is specially designed to protect the metatarsal area of the foot that extends from the toes. This is a popular choice for mining workers, factory hands and drillers, who often need the extra protection the Met-Guard affords. 

The incorporation of PureGRAPH® in the Met-Guard will improve both flexibility and strength of the product.

“The development work with Steel Blue provides yet another example of FGR working on real industrial applications” said Craig McGuckin, Managing Director First Graphene Ltd. “Like FGR, Steel Blue is an Australian company and the world leader in its field of safety boots systems. These developments continue to enhance that reputation.”

Garry Johnson, Chief Executive Officer of Steel Blue said “Steel Blue is committed to developing innovative solutions for our customers. We’re excited by these recent developments with FGR and look forward to delivering these solutions to our market.’’

Tags:  Craig McGuckin  First Graphene  Garry Johnson  Graphene  PureGRAPH®  Ross Fitzgerald  Steel Blue 

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Using 3-D Printed Mother-of-Pearl to Create Tough New Smart Materials

Posted By Graphene Council, The Graphene Council, Monday, August 12, 2019

The silvery shine of mother-of-pearl has long been prized for jewelry and decorative arts. But the interior of mollusk shells, also known as nacre, is more than just a pretty face. It is actually one of the most robust materials in the natural world. You can drive over nacre with a truck, and while the mollusk shell might crack under the weight, the shiny interior will stay intact.



Professor in the Daniel J. Epstein Department of Industrial and Systems Engineering and the Center for Advanced Manufacturing, Yong Chen and his team have created a new 3-D-printed replica of this natural super-material, which will have important new applications in responsive smart materials and safety devices, such as helmets and armor for sports or military, as well as smart wearable technology, biomedical devices and more.

The work, which was recently published in Science Advances, also represents the first time that electrical fields were used in 3-D printing to form the material, meaning the finished product has strong electrical conductivity. This makes it ideal for smart products.

Chen and postdoctoral researcher Yang Yang worked on the paper with co-authors Qiming Wang, Assistant Professor in the Sonny Astani Department of Civil and Environmental Engineering, Qifa Zhou, Professor of Ophthalmology and Biomedical Engineering and others.

Chen said that in nature, the main purpose of a material like nacre is to protect a delicate, soft-bodied creature inside the shell.

“Nacre is strong because it stacks microscale and nanoscale components together in a brick-like structure and uses soft material to bind them together.”

Chen said the result was a very lightweight, robust material that was also far more responsive to pressure and loading compared with more rigid materials like ceramic and glass.

“Even very strong glass can be easy to crack when you drop it. Microcracks on the surface of these materials can quickly propagate all the way through it, whereas nacre combines soft and hard material in an intelligent way,” Chen said.

He said that when microcracks form in nacre, the soft material binding the nacre together works to deflect the force of impact and prevent cracks from propagating into more serious damage.

“The main motivation for this research was to see whether we could 3-D print any shape at a microscale, using the architecture of nacre combining both hard and soft materials, to achieve a much tougher structure.”

Replicating nacre with graphene and polymer
To do this, the team used a novel method to build synthetic nacre at a microscale using graphene powder as a building block. The researchers ran an electrical charge of around 1,000 volts through the graphene.

“Originally we had this randomly distributed graphene,” Chen said. “When you add it to the electrical field, these random grains of graphene are aligned parallel to each other.”

“Then we cure the material and finalize the layer. We then stack layer after layer on top so that it is similar in microstructure to nacre,” Chen said.

“We create a composite with polymer, which serves as the soft material inside and between the graphene.”

Chen said that previously nacre-like materials were formed using different approaches, such as magnetic fields to align the particles. After fabrication, the research team conducted material testing that showed the electrically-aligned product was lightweight with strong engineering properties.

He said that while naturally-formed nacre doesn’t conduct electricity, the 3-D printed bioinspired version can. As such, if it were used to fabricate protective material such as helmets or armor, the synthetic nacre can act as a sensor that alerts the wearer of any structural weaknesses before it fails.

The team tested the material by creating a small scale model of a smart helmet. The helmet functioned as a sensor connected to a LED light. When enough pressure was put on the helmet, the LED would be activated, indicating the material was under stress.

“Using the electrical-aligned approach leads to better alignment of the particles. It also means we can work with particles that react to an electrical field. When you use a magnetic field, then you can only work with a particle that reacts to that.”

Chen said that for the next stage of the research, the team would be investigating the new material’s capacity for thermal conductivity, in addition to its mechanical strength and ability to conduct electricity.

Tags:  3D Printing  Graphene  polymers  Qifa Zhou  USC Viterbi School of Engineering  Yong Chen 

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3D printable 2D materials based inks show promise to improve energy storage devices

Posted By Graphene Council, The Graphene Council, Sunday, August 11, 2019
Updated: Sunday, August 4, 2019
For the first time, a team of researchers, from the School of Materials and the National Graphene Institute at The the University of Manchester have formulated inks using the 2D material MXene, to produce 3D printed interdigitated electrodes.

As published in Advanced Materials, these inks have been used to 3D print electrodes that can be used in energy storages devices such as supercapacitors.

MXene, a ‘clay-like’ two-dimensional material composed of early transition metals (such as titanium) and carbon atoms, was first developed by Drexel University. However, unlike most clays, MXene shows high electrical conductivity upon drying and is hydrophilic, allowing them to be easily dispersed in aqueous suspensions and inks.

Graphene was the world’s first two-dimensional material, more conductive than copper, many more times stronger than steel, flexible, transparent and one million times thinner than the diameter of a human hair.

Since its isolation, graphene has opened the doors for the exploration of other two-dimensional materials, each with a range of different properties. However, in order to make use of these unique properties, 2D materials need to be efficiently integrated into devices and structures. The manufacturing approach and materials formulations are essential to realise this.

Dr Suelen Barg who led the team said: “We demonstrate that large MXene flakes spanning a few atoms thick, and water can be independently used to formulate inks with very specific viscoelastic behaviour for printing. These inks can be directly 3D printed into freestanding architectures over 20 layers tall. Due to the excellent electrical conductivity of MXene, we can employ our inks to directly 3D print current collector-free supercapacitors. The unique rheological properties combined with the sustainability of the approach open many opportunities to explore, especially in energy storage and applications requiring the functional properties of 2D MXene in customized 3D architectures.”

Wenji and Jae, PhD students at the Nano3D Lab at the University, said: “Additive manufacturing offers one possible method of building customised, multi-materials energy devices, demonstrating the capability to capture MXene’s potential for usage in energy applications. We hope this research will open avenues to fully unlock the potential of MXene for use in this field.”

The unique rheological properties combined with the sustainability of the approach open many opportunities to explore, especially in energy storage and applications requiring the functional properties of 2D MXene in customized 3D architectures. Dr Suelen Barg, School of Materials

The performance and application of these devices increasingly rely on the development and scalable manufacturing of innovative materials in order to enhance their performance.

Supercapacitors are devices that are able to produce massive amounts of power while using much less energy than conventional devices. There has been much work carried out on the use of 2D materials in these types of devices due to their excellent conductivity as well as having the potential to reduce the weight of the device.

Potential uses for these devices are for the automotive industry, such as in electric cars as well as for mobile phones and other electronics.

Tags:  2D materials  3D Printing  Drexel University  Graphene  Suelen Barg  Supercapacito  University of Manchester 

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A novel graphene-matrix-assisted stabilization method will help unique 2D materials become a part of quantum computers

Posted By Graphene Council, The Graphene Council, Sunday, August 11, 2019
Updated: Monday, August 5, 2019
The family of 2D materials was recently joined by a new class, the monolayers of oxides and carbides of transition metals, which have been the subject of extensive theoretical and experimental research. These new materials are of great interest to scientists due to their unusual rectangular atomic structure and chemical and physical properties. 

Scientists are particularly interested in a unique 2D rectangular copper oxide cell, which does not exist in crystalline (3D) form, as opposed to most 2D materials, whether well known or discovered recently, which have a lattice similar to that of their crystalline (3D) counterparts. The main hindrance for practical use of monolayers is their low stability.

A group of scientists from MISiS, the Institute of Biochemical Physics of RAS (IBCP), Skoltech, and the National Institute for Materials Science in Japan (NIMS) discovered 2D copper oxide materials with an unusual crystal structure inside a two-layer graphene matrix using experimental methods.

“Finding that a rectangular-lattice copper-oxide monolayer can be stable under given conditions is as important as showing how the binding of copper oxide and a graphene nanopore and formation of a common boundary can lead to the creation of a small, stable 2D copper oxide cluster with a rectangular lattice. In contrast to the monolayer, the small copper oxide cluster’s stability is driven to a large extent by the edge effects (boundaries) that lead to its distortion and, subsequently, destruction of the flat 2D structure. Moreover, we demonstrated that binding bilayered graphene with pure copper, which never exists in the form of a flat cluster, makes the 2D metal layer more stable,” says Skoltech Senior Research Scientist Alexander Kvashnin.

The preferability of the copper oxide rectangular lattice forming in a bigraphene nanopore was confirmed by the calculations performed using the USPEX evolutionary algorithm developed by Professor at Skoltech and MIPT, Artem Oganov. The studies of the physical properties of the stable 2D materials indicate that they are good candidates for spintronics applications.

Tags:  2D materials  Alexander Kvashnin  Artem Oganov  Graphene  MIPT  Skoltech 

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New research highlights similarities in the insulating states of twisted bilayer graphene and cuprates

Posted By Graphene Council, The Graphene Council, Sunday, August 11, 2019
Updated: Monday, August 5, 2019
In recent decades, enormous research efforts have been expended on the exploration and explanation of high-temperature (high-Tc) superconductors, a class of materials exhibiting zero resistance at particularly high temperatures.

Now a team of scientists from the United States, Germany and Japan explain in Nature ("Maximized electron interactions at the magic angle in twisted bilayer graphene") how the electronic structure in twisted bilayer graphene influences the emergence of the insulating state in these systems, which is the precursor to superconductivity in high-Tc materials.

Finding a material which superconducts at room temperature would lead to a technological revolution, alleviate the energy crisis (as nowadays most energy is lost on the way from generation to usage) and boost computing performance to an entirely new level. However, despite the progress made in understanding these systems, a full theoretical description is still elusive, leaving our search for room temperature superconductivity mainly serendipitous.

In a major scientific breakthrough in 2018, twisted bilayer graphene (TBLG) was shown to exhibit phases of matter akin to those of a certain class of high-Tc superconducting materials – the so-called high-Tc cuprates. This represents a novel inroad via a much cleaner and more controllable experimental setup.

The scientists from the Max Planck Institute for the Structure and Dynamics of Matter (MPSD), Freie Universität Berlin (both in Germany), Columbia University (USA) and the National Institute for Materials Science in Japan focused on the insulating state of TBLG.

This material is made up of two atomically thin layers of graphene, stacked at a very slight angle to each other. In this structure, the insulating state precedes the high- Tc superconducting phase. Hence, a better understanding of this phase and what leads up to it is crucial for the control of TBLG.

The scientists used scanning tunneling microscopy and spectroscopy (STM / STS) to investigate the samples. With this microscopic technique, electrically conducting surfaces can be examined atom by atom. Using the pioneering “tear and stack” method, they placed two atomically thin layers of graphene on top of one another and rotated them slightly. Then, the team directly mapped the material’s atomic-scale structural and electronic properties near the ‘magic angle’ of around 1.1°.

The findings, which have just been published in Nature, cast new light on the factors influencing the emergence of superconductivity in TBLG. The team observed that the insulating state, which precedes the superconducting state, appears at a particular level of filling the system with electrons. It enables scientists to estimate the strength and the nature of the interactions between electrons in these systems - a crucial step towards their description.

In particular, the results show that two distinct van Hove singularities (vHs) in the local density of states appear close to the magic angle which have a doping dependent separation of 40-57 meV. This demonstrates clearly for the first time that the vHs separation is significantly larger than previously thought. Furthermore, the team clearly demonstrates that the vHs splits into two peaks when the system is doped near half Moiréband filling. This doping-dependent splitting is explained by a correlation-induced gap, which means that in TBLG, electron-induced interaction plays a prominent role.

The team found that the ratio of the Coulomb interaction to the bandwidth of each individual vHs is more crucial to the magic angle than the vHs seperation. This suggests that the neighboring superconducting state is driven by a Cooper-like pairing mechanism based on electron-electron interactions. In addition, the STS results indicate some level of electronic nematicity (spontaneous breaking of the rotational symmetry of the underlying lattice), much like what is observed in cuprates near the superconducting state.

With this research, the team has taken a crucial step towards demonstrating the equivalence of the physics of high-Tc cuprates and those of TBLG materials. The insights gained via TBLG in this study will thus further the understanding of high-temperature superconductivity in cuprates and lead to a better analysis of the detailed workings of these fascinating systems.

The team’s work on the nature of the superconducting and insulating states seen in transport will allow researchers to benchmark theories and hopefully ultimately understand TBLG as a stepping stone towards a more complete description of the high-Tc cuprates. In the future, this may pave the way towards a more systematic approach of increasing superconducting temperatures in these and similar systems.

Tags:  Columbia University  Freie Universität Berlin  Graphene  Max Planck Institute for the Structure and Dynamic 

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Argonne-led center receives award for pivotal discovery in battery technology

Posted By Graphene Council, The Graphene Council, Monday, August 5, 2019
This year marks the tenth anniversary of the U.S. Department of Energy's (DOE's) Energy Frontier Research Centers (EFRCs). The DOE Office of Basic Energy Sciences launched forty-six such centers in 2009 to bring together teams of scientists to perform basic research beyond what is possible for individuals or small groups. To celebrate the ten-year milestone, DOE selected ten awardees to recognize their having made a major impact on scientific ideas, technologies and tools, and people. Hence, the award name is "Ten at Ten."

"This award is the consequence of the long-range vision, established at the very start of CEES in 2009, that a robust fundamental understanding of the electrode processes in lithium-ion batteries would have broad benefits." -- Paul Fenter, CEES director

One of the Ten at Ten Awards has gone to three researchers in the Center for Electrochemical Energy Science (CEES), a multi-organizational EFRC led by Argonne National Laboratory in partnership with Northwestern University, University of Illinois and Purdue University. The CEES mission is to explore the fundamental chemistry and materials underlying batteries and energy storage by means of state-of-the-art materials synthesis and characterization.

"This award is the consequence of the long-range vision, established at the very start of CEES in 2009, that a robust fundamental understanding of the electrode processes in lithium-ion batteries would have broad benefits," said Paul Fenter, CEES director and senior physicist in the Chemical Sciences and Engineering division. Such batteries could power electric vehicles and drones as well as provide energy storage for the grid.

The Ten at Ten Award recipients are two former CEES members, Harold Kung and Cary Hayner, and a current CEES member, Mark Hersam. Both Kung and Hersam are professors at Northwestern University, and Hayner is chief technical officer and co-founder of NanoGraf Corp. (formerly SiNode Systems).

"The interdisciplinary collaborative environment within CEES provides a breeding ground not only for fundamental discoveries but also for disruptive thinking that spawns new technologies," said Hersam.  "The EFRC program is a poignant example of how government investment in research ultimately fuels the innovation that underlies economic growth."

The Ten at Ten Award recognizes two new electrode technologies for next-generation lithium-ion batteries that were developed based on research that was initiated in CEES. Both technologies use "graphene," carbon layers just one atom thick, to coat the active materials within the battery electrode to create a "composite" electrode structure.  The first advance by Hayner and Kung used graphene in the battery anode, encapsulating particles of silicon. The second advance by Hersam incorporated graphene in the cathode, to encapsulate manganese-based oxides.

The resulting electrodes consist of graphene-coated active materials that have substantially improved properties, such as increased battery power, lifetime, and safety, as well as diminished likelihood of safety problems such as a violent reaction.

Another important feature of these technologies is that they enable lithium-ion batteries to function at temperatures well below the freezing point -- a capability critical for electric car owners in cold regions.

"CEES is especially proud that the award-winning research has given birth to two startups," noted Fenter. A startup company co-founded by Kung and Hayner in 2012 (NanoGraf) is commercializing the graphene-based silicon anode, while a startup company co-founded by Hersam in 2018 (Volexion) is bringing the graphene-based cathode to market.

"We owe our entire existence as a company to the research and people who are part of CEES," said NanoGraf co-founder Hayner. "The transformative discoveries made by CEES scientists has enabled us to further develop these technologies and bring them to the market to drive a cleaner, more sustainable future."

The award presentation took place on July 29 in Washington, DC. The Center for Electrochemical Energy Science is an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.

Tags:  Cary Hayner  CEES  Graphene  Harold Kung  Mark Hersam  NanoGraf  Paul Fenter 

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