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Physicists obtain molecular 'fingerprints' using plasmons

Posted By Graphene Council, Friday, June 26, 2020
Scientists from the Center for Photonics and 2D Materials of the Moscow Institute of Physics and Technology (MIPT), the University of Oviedo, Donostia International Physics Center, and CIC nanoGUNE have proposed a new way to study the properties of individual organic molecules and nanolayers of molecules. The approach, described in Nanophotonics, relies on V-shaped graphene-metal film structures.

Nondestructive analysis of molecules via infrared spectroscopy is vital in many situations in organic and inorganic chemistry: for controlling gas concentrations, detecting polymer degradation, measuring alcohol content in the blood, etc. However, this simple method is not applicable to small numbers of molecules in a nanovolume. In their recent study, researchers from Russia and Spain propose a way to address this.

A key notion underlying the new technique is that of a plasmon. Broadly defined, it refers to an electron oscillation coupled to an electromagnetic wave. Propagating together, the two can be viewed as a quasiparticle.

The study considered plasmons in a wedge-shaped structure several dozen nanometers in size. One side of the wedge is a one-atom-thick layer of carbon atoms, known as graphene. It accommodates plasmons propagating along the sheet, with oscillating charges in the form of Dirac electrons or holes. The other side of the V-shaped structure is a gold or other electrically conductive metal film that runs nearly parallel to the graphene sheet. The space in between is filled with a tapering layer of dielectric material -- for example, boron nitride -- that is 2 nanometers thick at its narrowest (fig. 1).

Such a setup enables plasmon localization, or focusing. This refers to a process that converts regular plasmons into shorter-wavelength ones, called acoustic. As a plasmon propagates along graphene, its field is forced into progressively smaller spaces in the tapering wedge. As a result, the wavelength becomes many times smaller and the field amplitude in the region between the metal and graphene gets amplified. In that manner, a regular plasmon gradually transforms into an acoustic one.

"It was previously known that polaritons and wave modes undergo such compression in tapering waveguides. We set out to examine this process specifically for graphene, but then went on to consider the possible applications of the graphene-metal system in terms of producing molecular spectra," said paper co-author Kirill Voronin from the MIPT Laboratory of Nanooptics and Plasmonics.

The team tested its idea on a molecule known as CBP, which is used in pharmaceutics and organic light emitting diodes. It is characterized by a prominent absorption peak at a wavelength of 6.9 micrometers. The study looked at the response of a layer of molecules, which was placed in the thin part of the wedge, between the metal and graphene. The molecular layer was as thin as 2 nanometers, or three orders of magnitude smaller than the wavelength of the laser exciting plasmons. Measuring such a low absorption of the molecules would be impossible using conventional spectroscopy.

In the setup proposed by the physicists, however, the field is localized in a much tighter space, enabling the team to focus on the sample so well as to register a response from several molecules or even a single large molecule such as DNA.

There are different ways to excite plasmons in graphene. The most efficient technique relies on a scattering-type scanning near-field microscope. Its needle is positioned close to graphene and irradiated with a focused light beam. Since the needle point is very small, it can excite waves with a very large wave vector -- and a small wavelength. Plasmons excited away from the tapered end of the wedge travel along graphene toward the molecules that are to be analyzed. After interacting with the molecules, the plasmons are reflected at the tapered end of the wedge and then scattered by the same needle that initially excited them, which thus doubles as a detector.

"We calculated the reflection coefficient, that is, the ratio of the reflected plasmon intensity to the intensity of the original laser radiation. The reflection coefficient clearly depends on frequency, and the maximum frequency coincides with the absorption peak of the molecules. It becomes apparent that the absorption is very weak -- about several percent -- in the case of regular graphene plasmons. When it comes to acoustic plasmons, the reflection coefficient is tens of percent lower. This means that the radiation is strongly absorbed in the small layer of molecules," adds the paper's co-author and MIPT visiting professor Alexey Nikitin, a researcher at Donostia International Physics Center, Spain.

After certain improvements to the technological processes involved, the scheme proposed by the Russian and Spanish researchers can be used as the basis for creating actual devices. According to the team, they would mainly be useful for investigating the properties of poorly studied organic compounds and for detecting known ones.

Tags:  2D materials  boron nitride  Graphene  Kirill Voronin  Moscow Institute of Physics and Technology  Photonics  University of Oviedo 

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New study unveils ultrathin boron nitride films for next-generation electronics

Posted By Graphene Council, Friday, June 26, 2020
An international team of researchers, affiliated with UNIST has unveiled a novel material that could enable major leaps in the miniaturization of electronic devices. Published in the prestigious journal Nature, this study represent a significant achievement for future electronics.

This breakthrough comes from a research, conducted by Professor Hyeon Suk Shin (School of Natual Sciences, UNIST) and Principal Researcher Dr. Hyeon-Jin Shin from Samsung Advanced Institute of Technology (SAIT), in collaboration with Graphene Flagship researchers from University of Cambridge (UK) and Catalan Institute of Nanoscience and Nanotechnology (ICN2, Spain).

In this study, the team successfully demonstrated the synthesis of thin film of amorphous boron nitride (a-BN) with extremely low dielectric constant as well as high breakdown voltage and superior metal barrier properties. The research team noted that this newly fabricated material has great potential as interconnect insulators in the next-generation of electronic circuits.

In the ongoing process of miniaturization of logic and memory devices in electronic circuits, minimizing the dimensions of interconencts - metal wires that link the different device components on the chip - is crucial to guarantee improved performance and faster response of the device. Extensive research efforts have been devoted to decreasing the resistance of scaled interconnects because integration of dielectrics using complementary metal oxide semiconductor (CMOS) compatible processes has proven to be exceptionally challenging. According to the research team, the required interconnect isolation materials should not only possess low relative dielectric constants (referred to as k-values), but should also be thermally, chemically, and mechanically stable.

There has been an ongoing quest to obtain materials with ultra-low-k (relative permittivity around or below 2) avoiding the artificial addition of pores in the thin film in the semiconductor industry for at least the past 20 years. Several attempts had been made to develop materials with desired characteristics, yet those materials have failed to be successfully integrated in interconnects due to poor mechanical properties or poor chemical stability upon integration, causing reliability failures.

In this study, the joint research has succeeded in demonstrating a Back-End-ofthe-Line (BEOL) compatible approach to grow amorphous boron nitride (a-BN) with extremely low-k dielectrics. In particular, they synthesized approximately 3 nm thin a-BN on a Si substrate, using low temperature remote inductively coupled plasma-chemical vapour deposition (ICP-CVD). The resulting material showed an extremely low dielectric constant in the range of 1.78, which is 30% lower than the dielectric constant of currently available insulators.

In this study, the joint research has succeeded in demonstrating a Back-End-ofthe-Line (BEOL) compatible approach to grow amorphous boron nitride (a-BN) with extremely low-k dielectrics. In particular, they synthesized approximately 3 nm thin a-BN on a Si substrate, using low temperature remote inductively coupled plasma-chemical vapour deposition (ICP-CVD). The resulting material showed an extremely low dielectric constant in the range of 1.78, which is 30% lower than the dielectric constant of currently available insulators.

"We found that temperature was the most important parameter with ideal a-BN film deposition occurring at 400° C," says Seokmo Hong in the Doctoral program of Natural Sciences, the first author of the study. "This material with ultra-low-k also manifests a high breakdown voltage and likely superior metal barrier properties, making the film very attractive for practical electronic applications."

Angle-dependent near-edge X-ray absorption fine structure (NEXAFS) measured in partial electron-yield (PEY) mode at Pohang Light Source-II 4D beam line was also used to investigate the chemical and electronic structures of a-BN. Their findings indicated that the irregular, random atomic arrangement causes the dielectric constant value to drop.

The new material also manifests excellent mechanical properties of high strength. Moreover, when researchers tested the diffusion barrier properties of a-BN in very harsh conditions, they found it can prevent metal atom migration from the interconnects into the insulator. This result will help resolves a long-standing issue of interconnects in CMOS integrated circuit fabrication, enabling further miniaturaization of electronic devices.

"Development of electrically, mechanically and thermally robust low-k materials (k < 2) has long been technically challenging," says Dr. Hyeon-Jin Shin from Samsung Advanced Institute of Technology (SAIT). "Our research is also a great example that shows companies and academic institutions working together to create greater synergy."

"Our results demonstrate that the amorphous counterpart of two-dimensional hexagonal BN possesses the ideal low-k dielectric characteristics for high-performance electronics," says Professor Shin. "If they are commercialized, it will be a great help in overcoming the crisis looming over the semiconductor industry."

Tags:  boron nitride  Electronics  Graphene  hexagonal boron nitride  Hyeon Suk Shin  Hyeon-Jin Shin  Samsung Advanced Institute of Technology  UNIST 

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Thomas Swan granted additional process patents broadening their ownership of the high shear, liquid exfoliation space in graphene production

Posted By Graphene Council, Wednesday, May 13, 2020
Thomas Swan & Co. Ltd., one of the UK’s leading independent chemical manufacturers, has built on the previously announced portfolio of patents for the separation of atomically thin 2-dimensional materials, including graphene and Boron Nitride, by today announcing that it has now been granted a further portfolio of three patents GB2550985, GB2555097 and GB2545060 for the production of these atomically thin 2-dimensional materials, using high shear liquid phase exfoliation by high volume homogeniser technology.

Thomas Swan’s patents in this area are part of a growing portfolio of international rights in the evolving graphene (and other 2D materials) processing arena. As the challenge to deliver more high-performance composite materials increases, adopting graphene as an additive often demands processing of critically fine laminar particle grades demonstrating superior features and enhanced levels of performance. The Graphene Nanoplatelets (GNP) delivered in various forms using this high-shear processing technique adopting homogenisation technology is a stronghold for the Durham based manufacturing company.

This use of homogenisation in the production of graphene though high shear liquid phase exfoliation builds upon its exclusive licensing of patented, original, core exfoliation technology developed with Trinity College Dublin, and puts Thomas Swan in the unique position in owning this production space. 

Michael Edwards, Commercial Director – Advanced Materials at Thomas Swan said, “Our patented process capabilities for 2D materials, but specifically graphene nanoplatelets [GNP], is now strongly protected. Our GNPs can be used as additives in many diverse applications, into the commercial adoption of bulk graphene. The process patents deliver a modular, scalable production capability in our ISO-standard manufacturing operation. We are in the ideal position to support the market demand and we will continue to work with our partners in this field to further develop our unique production position.”

Tags:  2D materials  Boron Nitride  Graphene  Graphene Nanoplatelets  Michael Edwards  Thomas Swan 

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New study reveals unexpected softness of bilayer graphene

Posted By Graphene Council, Saturday, May 2, 2020
In the study, published in the journal Physical Review B, the researchers showed that bilayer graphene, consisting of two layers of graphene, was noticeably softer than both two-dimensional (2D) graphene and three-dimensional (3D) graphite along the stacking direction.

This surprising result differs from previous research which showed that 2D graphene, a flat single layer of carbon atoms arranged in a honeycomb structure had many of the same mechanical properties as 3D graphite, which is a naturally occurring form of carbon made up from a very weak stack of many layers of graphene.

Measuring stiffness
Graphene is a 2D material, but has 3D properties such as its stiffness in the ‘out-of-plane’ direction, perpendicular to the plane of the graphene sheets.

The behaviour of π electrons within multilayer graphene determine its out-of-plane stiffness. In this study, the researchers found that when bilayer graphene is compressed out-of-plane, some π electrons are ‘squeezed’ through the graphene planes, which are impenetrable to small molecules such as water. This response makes the material softer and much easier to compress.   

Dr Yiwei Sun, lead author of the study from Queen Mary University of London, said: “Our previous study showed that 2D graphene and 3D graphite have many of the same mechanical properties, so we were surprised to see that bilayer graphene is much softer than both of these materials. We think that the softness of bilayer graphene results from the ‘squeezing’ of pi-electronic orbitals through the graphene layers. For example, if the bread on a burger is replaced by a bagel it is even easier to compress because the contents can be squeezed out of the bagel hole.”

Realising potential
Often hailed as a 'wonder material', graphene has the highest known thermal and electrical conductivity and is stronger than steel, as well as being light, flexible and transparent. 

It was discovered in 2004 by peeling off graphene flakes from bulk graphite (used in pencil leads and lubricants) using sticky tape.

Stacking the graphene flakes one on top of the other provides more possibilities as the material’s extraordinary properties are determined by interactions between its stacked layers. Its unique characteristics can also be fine-tuned for various applications by stacking other 2D materials, such as boron nitride and molybdenum disulphide, to graphene.

This study provides insight into the complex interactions between graphene bilayers and enables quantification of its properties, which is critical for exploring future applications of the material in devices such as vertical transistors and pressure sensors.

Tags:  2D materials  boron nitride  Graphene  Queen Mary University of London  transistor  Yiwei Sun 

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What a pair! Coupled quantum dots may offer a new way to store quantum information

Posted By Graphene Council, Friday, January 31, 2020
Researchers at the National Institute of Standards and Technology (NIST) and their colleagues have for the first time created and imaged a novel pair of quantum dots -- tiny islands of confined electric charge that act like interacting artificial atoms. Such "coupled" quantum dots could serve as a robust quantum bit, or qubit, the fundamental unit of information for a quantum computer. Moreover, the patterns of electric charge in the island can't be fully explained by current models of quantum physics, offering an opportunity to investigate rich new physical phenomena in materials.

Unlike a classical computer, which relies on binary bits that have just one of two fixed values -- "1" or "0" -- to store memory, a quantum computer would store and process information in qubits, which can simultaneously take on a multitude of values. Therefore, they could perform much larger, more complex operations than classical bits and have the potential to revolutionize computing.

Electrons orbit the center of a single quantum dot similar to the way they orbit atoms. The charged particles can only occupy specific permitted energy levels. At each energy level, an electron can occupy a range of possible positions in the dot, tracing out an orbit whose shape is determined by the rules of quantum theory. A pair of coupled quantum dots can share an electron between them, forming a qubit.

To fabricate the quantum dots, the NIST-led team, which included researchers from the University of Maryland NanoCenter and the National Institute for Materials Science in Japan, used the ultrasharp tip of a scanning tunneling microscope (STM) as if it were a stylus of an Etch A Sketch. Hovering the tip above an ultracold sheet of graphene (a single layer of carbon atoms arranged in a honeycomb pattern), the researchers briefly increased the voltage of the tip.

The electric field generated by the voltage pulse penetrated through the graphene into an underlying layer of boron nitride, where it stripped electrons from atomic impurities in the layer and created a pileup of electric charge. The pileup corralled freely floating electrons in the graphene, confining them to a tiny energy well.

But when the team applied a magnetic field of 4 to 8 tesla (about 400 to 800 times the strength of a small bar magnet), it dramatically altered the shape and distribution of the orbits that the electrons could occupy. Rather than a single well, the electrons now resided within two sets of concentric, closely spaced rings within the original well separated by a small empty shell. The two sets of rings for the electrons now behaved as if they were weakly coupled quantum dots.

This is the first time that researchers have probed the interior of a coupled quantum dot system so deeply, imaging the distribution of electrons with atomic resolution (see illustration), noted NIST co-author Daniel Walkup. To take high-resolution images and spectra of the system, the team took advantage of a special relationship between the size of a quantum dot and the spacing of the energy levels occupied by the orbiting electrons: The smaller the dot, the greater the spacing, and the easier it is to distinguish between adjacent energy levels.

In a previous quantum dot study using graphene, the team applied a smaller magnetic field and found a structure of rings, resembling a wedding cake, centered on a single quantum dot, which is the origin of the concentric quantum dot rings. By using the STM tip to construct dots about half the diameter (100 nanometers) of dots that they had previously studied, the researchers succeeded in revealing the full structure of the coupled system.

The team, which included Walkup, Fereshte Ghahari, Christopher Gutiérrez and Joseph Stroscio at NIST and the Maryland NanoCenter, describes its findings today in Physical Review B.

The way in which the electrons are shared between the two coupled dots can't be explained by accepted models of quantum dot physics, said Walkup. This puzzle may be important to solve if coupled quantum dots are eventually to be used as qubits in quantum computing, Stroscio noted.

Tags:  boron nitride  Daniel Walkup  Graphene  National Institute of Standards and Technology  quantum dots 

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New Technique Produces Longer-lasting Lithium Batteries

Posted By Graphene Council, Monday, April 29, 2019
Updated: Friday, April 26, 2019
The grand challenge to improve energy storage and increase battery life, while ensuring safe operation, is becoming evermore critical as we become increasingly reliant on this energy source for everything from portable devices to electric vehicles. A Columbia Engineering team led by Yuan Yang, assistant professor of materials science and engineering, announced that they have developed a new method for safely prolonging battery life by inserting a nano-coating of boron nitride (BN) to stabilize solid electrolytes in lithium metal batteries. Their findings are outlined in a new study published by Joule.

While conventional lithium ion (Li-ion) batteries are currently widely used in daily life, they have low energy density, resulting in shorter battery life, and, because of the highly flammable liquid electrolyte inside them, they can short out and even catch fire. Energy density could be improved by using lithium metal to replace the graphite anode used in Li-ion batteries: lithium metal’s theoretical capacity for the amount of charge it can deliver is almost 10 times higher than that of graphite. But during lithium plating, dendrites often form and, if they penetrate the membrane separator in the middle of the battery, they can create short-circuits, raising concerns about battery safety.

“We decided to focus on solid, ceramic electrolytes. They show great promise in improving both safety and energy density, as compared with conventional, flammable electrolytes in Li-ion batteries,” says Yang. “We are particularly interested in rechargeable solid-state lithium batteries because they are promising candidates for next-generation energy storage.”

Most solid electrolytes are ceramic, and therefore non-flammable, eliminating safety concerns. In addition, solid ceramic electrolytes have a high mechanical strength that can actually suppress lithium dendrite growth, making lithium metal a coating option for battery anodes. However, most solid electrolytes are unstable against Li—they can be easily corroded by lithium metal and cannot be used in batteries.

“Lithium metal is indispensable for enhancing energy density and so it’s critical that we be able to use it as the anode for solid electrolytes,” says Qian Cheng, the paper’s lead author and a postdoctoral research scientist in the department of applied physics and applied mathematics who works in Yang's group. “To adapt these unstable solid electrolytes for real-life applications, we needed to develop a chemically and mechanically stable interface to protect these solid electrolytes against the lithium anode. It is essential that the interface not only be highly electronically insulating, but also ionically conducting in order to transport lithium ions. Plus, this interface has to be super-thin to avoid lowering the energy density of batteries.”

To address these challenges, the team worked with colleagues at Brookhaven National Lab and the City University of New York. They deposited 5~10 nm boron nitride (BN) nano-film as a protective layer to isolate the electrical contact between lithium metal and the ionic conductor (the solid electrolyte), along with a trace quantity of polymer or liquid electrolyte to infiltrate the electrode/electrolyte interface. They selected BN as a protective layer because it is chemically and mechanically stable with lithium metal, providing a high degree of electronic insulation. They designed the BN layer to have intrinsic defects, through which lithium ions can pass through, allowing it to serve as an excellent separator. In addition, BN can be readily prepared by chemical vapor deposition to form large-scale (~dm level), atomically thin scale (~nm level), and continuous films.

“While earlier studies used polymeric protection layers as thick as 200 µm, our BN protective film, at only 5~10 nm thick, is record-thin—at the limit of such protection layers—without lowering the energy density of batteries,” Cheng says. “It’s the perfect material to function as a barrier that prevents the invasion of lithium metal to solid electrolyte. Like a bullet-proof vest, we’ve developed a lithium-metal-proof ‘vest’ for unstable solid electrolytes and, with that innovation, achieved long-cycling lifetime lithium metal batteries.”

The researchers are now extending their method to a broad range of unstable solid electrolytes and further optimizing the interface. They expect to fabricate solid-state batteries with high performance and long-cycle lifetimes.

Tags:  Batteries  Boron Nitride  Columbia Engineering  Graphene  Li-Ion batteries  Qian Cheng  Yuan Yang 

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Both Graphene and Financial Expertise Leads to Unique Graphene Player

Posted By Dexter Johnson, The Graphene Council, Tuesday, September 18, 2018

About four years ago, Alan Dalton, a professor at the University of Sussex in the UK, made some news in graphene circles when, in collaboration with colleagues at Trinity College Dublin, he demonstrated that rubber bands when combined with graphene could serve as effective health monitors.  A couple of years later, Dalton continued to make news by using graphene to link together silver nanowires to create a material that could potentially replace indium tin oxide (ITO) as a transparent conductor in touch-screen displays. The following year in 2017, Dalton, serving as chief scientific officer, joined with an experienced group of individuals, led by CEO John Lee, who had a long career in energy and cleantech equity markets, to form Advanced Material Development (AMD).

While the work of Dalton along with a focus on graphene remains part of the company’s genetic makeup, it has established itself first and foremost as a company set up to support scientific research in materials science conducted at British Universities.

Using a unique process, AMD already has a commercially available product it has dubbed “nHance” that includes graphene, molybdenum disulfide and boron nitride in dispersions for use in a range of bespoke emulsions and applications. The patent-pending emulsions have been developed with the University of Sussex.

In addition to having a commercial product in hand, AMD also has secured £750,000 ($985,000) in funding in April to support its commercialization aims and has now commenced R&D funding.

As a corporate partner to the Graphene Council, we got an opportunity to conduct a Q&A with John Lee, the CEO of AMD and below is that interview.

Q: Could you give a little bit more background on the nature of AMD’s business? It seems to at least initially to be a company based on the research of Alan Dalton at the University of Sussex. But it seems that you are also open to any technologies in the area of graphene and 2D materials that might be licensable. Could you explain a bit more about how AMD has set itself up and what its business models and strategies are?

Advanced Material Development Ltd (AMD) is a UK-based, privately funded business recently formed to support scientific research in British universities. The first collaboration, with leading academic Professor Alan Dalton from the University of Sussex Material Physics Group will fund several distinct research streams within the field of 2D materials. AMD is already engaged in a number of key partnerships with other commercial enterprises to further work in areas such as composites, coatings, printed electronics and wearable sensors. In addition, AMD is also producing nano-dispersion inks and emulsions under the brand name “nHance” for its own internal R&D efforts and also for commercial sale.

Q: Some of the work of Alan Dalton that got the most publicity was the simple process he developed for infusing graphene into elastic bands so that they become extremely sensitive strain sensors. Is that a line of research your company is looking to commercialize? If so, what sort of landmarks have you reached in the development of this technology? If not, what went behind the decision not to follow that line of research into commercial applications?

Although AMD supplies materials into this and other ongoing projects, it is not a programme we are funding at this point. IP in this area is already well established, allocated, and outside of our core focus. Our website outlines the areas that we are keen to support.

Q: At the moment, you have likely narrowed down the technologies you are pursuing commercially. Could you say what those technologies currently are and why you chose to pursue those over some others?

One of the main areas of focus for AMD is producing nano-dispersion inks and emulsions. These support our own R&D work and also provide a foundation for bespoke materials formulations being developed for partners. This is a key reason why we choose to keep our R&D efforts within the University - to retain a critical high-end capability. Our other efforts in coatings, flexible electronics, composites and medtech sensors all sit nicely on this platform technology.

Q: In the broader market of graphene, what applications area do you see holding the most commercial potential and what is your company doing to be a part of those applications? If you are not, why have you chosen to not get involved, i.e. already too many competitors, etc.?

There are plenty of key verticals that have obvious areas of application for these materials. The graphene “fatigue” described by some early adopters comes from the frustration associated with a cure-all mentality. The hard to come-by knowledge and critical component that the team is focused on is the ability to disperse these materials into other matrices to provide a worthwhile benefit. We have chosen to support the areas of R&D where the University team can demonstrate a path to commercial interest, notably electronics in the consumer supply chain, material composites and medtech sensors where we consider there to be a realistic pathway to a commercial endgame within two years.

Q: Where do you see AMD in the value chain of graphene, i.e. a manufacturer of devices based on graphene or a company that enables other companies to make devices based on graphene?

The answer really is both. Although AMD cannot claim to be a manufacturer of devices and hence is not fully vertically integrated, it is already a materials manufacturer and is funding research with an end-game goal of prototype applications that we can then market to heavyweight commercial partners, a number of which, we are already doing early development work for or are in discussions to do so.

Q. As a company trying to bring emerging technologies to market, what do you see as the greatest challenges you face, i.e. customers resistant to change, lack of standards in graphene, etc.?

It’s been said that the greatest fear of many start-up companies is the threat of its ideas being stolen. The truth is that taking a product, however good and trying to convince someone already overwhelmed with new ideas and getting them to listen is a huge challenge. But the main problem I see at the moment is that many companies are a little burned by engaging with the graphene dream without having had the right degree of support to see the proper benefits – the lack of standards until now has been a major bugbear in this outcome and so these are vital. However, whatever the standard, no size fits all and the varying material requirements for different applications, like nature, are unlikely to conform to the categories we try to define.

Q. Over the next 5-10 years, how do you see the graphene market developing, i.e. fewer graphene producers and more downstream device producers?

I would agree with this outlook – ultimately graphene and other 2D materials will commoditize as production scales and applications become more accepted, but this will need the development of end-markets to facilitate such growth. I believe the real secret is the integration of the right formulation into devices that solve real world challenges.

Tags:  boron nitride  finance  Medical devices  touch screen displays 

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Boron nitride-graphene hybrid for next-gen energy storage

Posted By Terrance Barkan, Tuesday, October 25, 2016

Layers of graphene separated by nanotube pillars of boron nitride may be a suitable material to store hydrogen fuel in cars, according to Rice University scientists.

The Department of Energy has set benchmarks for storage materials that would make  a practical fuel for light-duty vehicles. The Rice lab of materials scientist Rouzbeh Shahsavari determined in a new computational study that pillared boron nitride and graphene could be a candidate.

The study by Shahsavari and Farzaneh Shayeganfar appears in the American Chemical Society journal Langmuir.

Shahsavari's lab had already determined through computer models how tough and resilient pillared graphene structures would be, and later worked boron nitride nanotubes into the mix to model a unique three-dimensional architecture. (Samples of  seamlessly bonded to graphene have been made.)

Just as pillars in a building make space between floors for people, pillars in boron nitride graphene make space for hydrogen atoms. The challenge is to make them enter and stay in sufficient numbers and exit upon demand.

In their latest molecular dynamics simulations, the researchers found that either pillared graphene or pillared boron nitride graphene would offer abundant surface area (about 2,547 square meters per gram) with good recyclable properties under ambient conditions. Their models showed adding oxygen or lithium to the materials would make them even better at binding hydrogen.

They focused the simulations on four variants: pillared structures of boron nitride or pillared boron nitride graphene doped with either oxygen or lithium. At room temperature and in ambient pressure, oxygen-doped boron nitride graphene proved the best, holding 11.6 percent of its weight in hydrogen (its gravimetric capacity) and about 60 grams per liter (its volumetric capacity); it easily beat competing technologies like porous boron nitride, metal oxide frameworks and carbon nanotubes.

At a chilly -321 degrees Fahrenheit, the material held 14.77 percent of its weight in hydrogen.

The Department of Energy's current target for economic storage media is the ability to store more than 5.5 percent of its weight and 40 grams per liter in hydrogen under moderate conditions. The ultimate targets are 7.5 weight percent and 70 grams per liter.

Shahsavari said  adsorbed to the undoped pillared boron nitride graphene, thanks to weak van der Waals forces. When the material was doped with oxygen, the atoms bonded strongly with the hybrid and created a better surface for incoming hydrogen, which Shahsavari said would likely be delivered under pressure and would exit when pressure is released.

"Adding oxygen to the substrate gives us good bonding because of the nature of the charges and their interactions," he said. "Oxygen and hydrogen are known to have good chemical affinity."

He said the polarized nature of the  where it bonds with the graphene and the electron mobility of the graphene itself make the material highly tunable for applications.

"What we're looking for is the sweet spot," Shahsavari said, describing the ideal conditions as a balance between the material's surface area and weight, as well as the operating temperatures and pressures. "This is only practical through computational modeling, because we can test a lot of variations very quickly. It would take experimentalists months to do what takes us only days."

He said the structures should be robust enough to easily surpass the Department of Energy requirement that a hydrogen fuel tank be able to withstand 1,500 charge-discharge cycles.


Tags:  Boron Nitride  Boron nitride-graphene hybrid  Department of Energy  Energy Storage 

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