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Thermionic Energy Converters on the Rise Thanks to Graphene

Posted By Dexter Johnson, IEEE Spectrum, Tuesday, January 10, 2017

 

Schematic sketch of the TEC prototype.

At the height of the Cold War, thermionic energy converters (TECs) were often used as the energy source for both NASA and the Soviet space program satellites. However, the combination of decreased space funding since the end of the Cold War and some of the engineering challenges associated with TECs has left the development of the technology largely stagnant until quite recently.

Over the past ten years there has been a bit of renaissance in TECs due to developments in modern wafer-scale fabrication techniques, device physics and material science, as well as an increasing attention to clean and renewable energy globally. This has led to TECs again receiving a considerable amount of interest both in the academia and industry, including two startups: Spark Thermionics and Modern ElectronWhile these companies and general trends are signs of TECs resurfacing as an alternative energy source, there remain some pretty significant engineering hurdles that still need to be overcome.

Now a team of researchers at Stanford University has taken a huge step in solving a couple of the key problems with TEC technology: improving the efficiency and stability of the anodes.The result could be the TECs taken on a far larger role in alternative energy solutions.

In research published in the journal Nano Energy, the Stanford researchers have employed graphene as the anode material and in so doing have boosted the efficiency of the device by a factor of 6.7 compared with a traditional tungsten anode.

The researchers successfully demonstrated an electronic conversion efficiency in the graphene-based anode of 9.8%. Electronic conversion efficiency is the efficiency at which  an electron converts thermal energy to electrical energy. In other words, it is the efficiency of moving one electron from the cathode to the anode by heat.

“One of the major challenges for wider adoption of TECs is high anode work function, which directly reduces the output voltage as well as the net efficiency,” explained Hongyuan Yuan, a PhD candidate at Stanford and lead author of the research, in an e-mail interview with The Graphene Council. “The theoretical maximum efficiency for a TEC with a 2 electron volt (eV) work function anode is 3% at a cathode temperature of 1500 K, compared to an astonishing 10-fold increment of 32% with a 1 eV work function anode.”

The work function of a material is the energy difference between its vacuum level and Fermi level. Before the discovery of graphene, the world-record low work function for a conductor was around 1.1 eV to 1.2 eV, which is achieved by lowering the vacuum level through the deposition of a monolayer of cesium oxide on the surface.

In 2015, Stanford researchers discovered that the work function of graphene can be reduced by not only lowering its vacuum level, but also raising its Fermi level by electrostatic gating through a back gate at the same time. “In this ‘combo’ approach, we discovered that the work function of graphene reached a new world-low record of 1.0 eV in 2015,” added Yuan.

The second major challenge to the success of TEC has been the high space charge barrier between TEC’s cathode and anode, which directly reduces the output current and thus the net efficiency. In order to reduce the space charge barrier, TEC requires a very small vacuum gap to separate the cathode and anode, usually around 10 mm. If the gap is much larger than 10 mm, all the benefit that an ultra-low work function anode could bring would be diminished.

“In our most recent work, we successfully addressed the above mentioned two challenges, and demonstrated that the previously discovered ultra-low work function graphene can indeed be applied to TEC with a significant amount of efficiency enhancement. Compared to a traditionally used tungsten anode, the net efficiency is increased by a factor of 6.7,” said Yuan.

While applications for TECs remain limited at the moment, with improvement in efficiency and device stability, Yuan believes that TECs are expected to see an enormous market both in the centralized power plants, i.e. in a tandem cycle, as well as in the distributed systems, e.g. automobiles with internal combusting engines and domestic houses with water heaters.

The current demonstration of the TEC device has been performed in an ultra-high vacuum chamber, with many pumps constantly pumping down the pressure. “In reality, we need to fabricate such a TEC device and seal it in a vacuum ‘chip’ using the state-of-the-art nano/micro fabrication techniques,” added Yuan. “Only by making the device small and reliably stable would it be economically feasible in the sustainable energy industry.

Yuan added: “We envision such a TEC device in the future, which is sealed in a small and thin cell (TEC cell). To generate electricity, all you need to do is to attach one side of the cell to a heat source. You may attach a couple of the TEC cells to the water heater at your home to charge your phone. Or attach many TEC cells to a fossil-fuel power station to improve its overall efficiency.”

Tags:  alternative energy  anodes  cathodes  thermionic energy converters  water heaters 

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CealTech AS - Endless Possibilities

Posted By Dexter Johnson, IEEE Spectrum, Thursday, January 5, 2017

Established in 2012, Norway-based CealTech AS is already staking claim to being the largest volume producer of graphene in the world. This past year, 2016, was a big year in the company’s development with a number of landmark events occurring, perhaps most notably bringing online a new production unit with capacity of 10,000m3 of single layer graphene

If graphene is going to find use in a more applications, companies like CealTech will undoubtedly play a key role in making that happen by providing high-quality graphene at a competitive price. The company is also moving up the value chain with plans of bringing online this year a large-scale battery production unit that will use graphene on the electrodes

As the newest member of The Graphene Council’s corporate members we took the opportunity to discuss with them how they see graphene and its applications evolving and how they are positioning themselves in this changing landscape. To do this we spoke with the company’s CEO, Runar Tunem.

Q: Your website makes the claim of having the largest volume production of graphene globally. Can you say what forms of graphene you are producing, i.e. graphene platelets, and how do your volumes breakdown according to those different forms and how they supply your various markets?

A: CealTech produces graphene in powder form. Our graphene is produced by a patented plasma-enhanced chemical vapor deposition (PE-CVD) technology based on DA Boyd, W-H Lin, C-C Hsu, ML Teague, C-C Chen, Y-Y Lo, W-Y Chan, W-B Su, TC Cheng, C-S Chang, et al. Single-step deposition of high-mobility graphene at reduced temperatures. Nature Communications, 6, 2015.

The patent pending FORZA™ production unit makes it possible to produce different types of graphene depending on application. More recently, Dr. David Boyd was able to optimize the process for mass production and the quality of the graphene flakes has been found to be very good. Another advantage of the production unit is that flakes can be directly functionalized according to the intended application, e.g. nitrogen and or oxygen functional groups, without any chemical modification. 

Q: In your company’s estimates what is the global production of graphene in all its forms and what percentage of the production does your company represent?

A: Regarding the volumes of graphene, a 28 tons global production was reported in 2010, which is projected to grow to about 575-600 tons by this year. Our estimate lies within the same range for fine- and for ultra-fine graphite. It is important to differentiate between graphite products from graphene’s, as both materials have different properties.

We do expect that the market for pure graphene will grow by leaps and bounds in the coming decade. This will be possible thanks to the advances in manufacturing processes which will address the main challenge of producing large quantities of graphene, in various formats, and at an affordable price, with effective yields and a purity sufficient so as not to impair graphene’s desired chemical properties. In that respect, we believe that CealTech’s technology will be a major enabler, and will contribute to taking graphene to the next level, as we soon start our commercial production of graphene – currently planned from March 2017. CealTech’s expected yearly production volume of pure graphene (from March 2017) is 10,000m3, and this volume will be adjusted (i.e. ramped-up) to accommodate the market needs.

Q: What were the market drivers in demand that spurred your company to make such a large increase in production capacity this year?

A: Over the last couple of years, CealTech has conducted a comprehensive research program aimed at assessing if the use of fine and ultra-fine graphite helped to enhance the properties of a wide range of engineering materials. Examples of the materials investigated by the program are rubber, paints, lacquers, carbon fibers, glass fiber, etc. 

During the research program, it became apparent that neither the fine nor the ultra-fine graphite available on today’s market are suitable to attaining such a goal. In comparison, when using the pure graphene produced by our patented PE-CVD technique, we achieved great results by significantly improving the properties of the different materials studied by the program. This learning process was one of the catalysts for CealTech to set sight at becoming the world’s largest manufacturer of PE-CVD graphene. 

Q:  Going forward what market segments do you see requiring the most volume of graphene? And, what are the markets that will likely exhibit the largest profit margins for graphene producers?

A: The application segments are currently dominated by electronics industry. Due to its high strength and conduction property, graphene is (to be) widely used in this industry. Apart from touch screens for tablets and mobile phones, it can also be used to make circuitry of laptops and personal computers, making them run faster. Also, due to its low thickness, it can be used as a semiconductor. Its chips are faster than the existing silicon chips. The electronics industry is driven by growing demand from the Asia Pacific region and a manufacturing rebound in the U.S. brought on by the economic slowdown of 2007 to 2009. In addition, growing markets for smartphones, tablets, high-definition TVs are further expected to boost the global electronics industry.

Composites accounted for the second largest share (36%) of graphene applications in 2016, dispersed among the automotive, plastics, coatings, construction, metals and engineering materials, aerospace, medical implants and energy markets. These composites can enhance the strength and conductivity of bulk materials. The composites and coatings have also found applications in sports, including lawn tennis and Formula 1 racing.

Looking ahead, Energy Storage and Supercapacitors are expected to emerge as a key area for PE-CVD graphene, followed by composites and graphene coatings. Graphene inks are said to be constantly improving (while their prices seem to be dropping), which might promote, among others, applications like sensor electrodes and smart packaging. Reports project that energy storage will account for around 40%, and composites, 25%, of the market by 2026, and that nearly $100 million worth of graphene will be sold into the energy storage sector in 2026.

Currently, graphene commercialization follows primarily a supplementation/substitution strategy. While products marketed as ‘graphene’ may be on the market in 2016, many, if not all, are still likely (to be) constructed principally from more traditional materials and incorporate a limited quantity of graphite. Accordingly, the profit margins are or will be, to some extent, dictated by the type of graphite used (i.e. quality), and/or the cost of the material that graphene is attempting to substitute. For example, on the low end of the graphene market is bulk material used as a filler to provide strength and conductivity in future day-to-day composite products.

The market for carbon fiber composites was $16,479.4 million in 2013, and was expected to grow at a rate of 12.8% annually from 2014 to 2019 with bulk carbon costs on the order of half-a-dollar per gram. Graphene could replace these products if sold at lower costs. Profit margins on the bulk material are likely to be minimal but significant profits will be made through large volumes. On the other end of the spectrum, the highest quality graphene will be used in applications that are being developed that require graphene, or where the use of high-quality graphene significantly improves the product specifications and performance; hence justifying a premium price. This material will probably command the highest margins –assuming a market structure similar to cell phones.  Lithium-ion electrodes are an example where graphite is used as an additive to boost the performance of the electrodes and alleviating a key shortcoming: limited cycle life. In this case, profit margins can be proportional to the degree of improvement enabled by graphene, and as such, could be significantly high.

Q: Do you foresee a business model in which your company will become more involved in downstream production of graphene-enabled products, i.e. moving from producing graphene to producing graphene-enabled products?

A: Further to producing and supplying large volume, high quality PE-CVD Graphene, CealTech is committed to developing and commercializing Graphene-enabled products and solutions for major industries, such as but no limited to: defense, automotive, space & aerospace, energy storage, electronics and sensors, medicine, maritime, and oil & gas. In that respect, our business portfolio is set to encompass everything from Raw Material (i.e. the graphene itself), Manufactured Materials (i.e. graphene doped with oxygen, nitrogen organic and inorganic molecules, etc.), to Component Parts and Finished Products (i.e. battery electrodes, conductive inks, paints and coatings, etc.). On the latter, we are proud to say that we are well on track with the development of a new, revolutionary battery technology. The test results so far are very promising (to be published online soon), and the aim is for an in-house annual production capacity of 20 millions square meters of CealTech’s PE-CVD graphene-based electrodes.

Furthermore, we are working with several leading companies, both nationally in Norway and internationally, to implement our PE-CVD graphene in various industrial products. You will have to stay tuned for more information…

Q: In the mid-2000s, some large chemical companies, like Bayer, drastically increased carbon nanotube production (multi-walled carbon nanotubes) with the idea that the resulting lowered costs of the material would help drive demand. The demand never picked up enough to soak up the increased capacity. What sort of precautions are graphene producers taking to avoid this same kind of pitfall?

A: To answer this, one must try to understand the likely reasons for this ‘pitfall’.

Firstly, one can cite the intrinsic problems of Carbon Nanotubes themselves. In an ideal perfect world, the carbon atoms that form nanotubes should be arranged in a hexagonal network. In this way, each carbon atom is bonded to three other carbon atoms making a sp2 bond, but that is when the nanotubes are perfect and they are of a uniform diameter. However, in reality, there are defects in the nanotubes that cause sp3 bonding to occur. Defects can be observed in the gradual widening or narrowing along the length of nanotubes. Also, nanotubes are not flat, and therefore cannot accurately be modeled with sp2 bond characters. Subsequently, CNTs suffer from lack of control of physical and chemical properties, difficulties in scalability, as well as the high cost of production and purification thus limiting the range of their applications.

In contrast, our produced Graphene with its Sp2 bonding means that the carbon has a ONE double bond. For a carbon with 1 double bond and 2 single bonds, the orbitals will become 33% "s" and 66.7% "p" making our graphene "sp2." That means that our graphene does not suffer from the same issues as nanotubes as all of our graphene sheets are identical, and therefore its properties are easily reproduced.

Secondly, it is reasonable to say that while some observers believed that the price cut of the MWNT would result in the applications being developed, it was soon recognized that this was a case of putting the cart before the horse, or “technology push” ahead of the preferable “market pull.” In contrast, we see a more downstream-focused approach for the graphene, with the aim of fostering concrete commercial benefits across key industries. As such, significant investments have been made in recent years to hasten the pace at which we start to see more practical applications of graphene and new technologies. For example, the European Union has invested $1.3 billion in ‘The Graphene Flagship’, a consortium of academic and commercial researchers, tasked with taking graphene from the realm of academic laboratories into European society in the space of 10 years, thus generating economic growth, new jobs and new opportunities. Similar efforts are taken by governments across the world (such as USA, China, UK, Japan, South Korea, Singapore, Malaysia, etc.) to build awareness about the vast potential of graphene and to facilitate partnerships and collaborations across the various stakeholders in the ecosystem (e.g., between industry and academia, and/or between upstream and downstream producers). For example, the UK Government has provided £235 million ($353 million) to fund a graphene research center. Tech companies are investing in developing their understanding of the material. Samsung, for example, has already applied for hundreds of graphene-related patents. Furthermore, we see that Graphene producers are also on the ‘offensive’, continuously innovating and developing new technologies aligned to targeted market needs and requirements.    

For CealTech’s part, we know that our technology expertise and business strategy address both points above. First, our unique PE-CVD Graphene will be of high quality, produced at large scale, in a reproducible manner, and soon to be commercially available. Accordingly, CealTech is strongly committed to having a resilient and flexible supply chain to ensure fast turnaround times and close customer relationships for its graphene production. Second, we acknowledge the risk of being only in the business of producing a nanomaterial that serves just to make some other product. Therefore, and as mentioned above, we are also focused on developing graphene-enabled products for various industrial applications. We are collaborating with other leading companies to contribute to bringing graphene-enhanced products to the market.

Q: What do you see being some of the graphene-enabled products that are most likely to grow significantly over the next five years and how will that shape graphene production?

A: As stated above, it is expected that graphene continues to be used mainly as a supplementary material in the short term (and through to 2020 at least), until the manufacturing process for graphene is mature enough for it to be used as a key material in products. Barriers to widespread industry uptake mirror carbon nanotubes: functionalization and dispersion; mass manufacturing at an acceptable cost; need for application partnerships; and health and safety issues. So the adoption of graphene and developments of graphene-enabled products depend on how soon these challenges are addressed.

As to which graphene-enabled products are expected to grow the most over the next five years, it is best to refer to interview by the Graphene Council with Prof. Jari Kinaret in his interview – we quote: “The early applications are more likely to use exfoliated graphene flakes than large sheets of graphene. Functional and structural nanocomposites fall in this category – wind power plant blades are one specific example. Other low-hanging fruits are applications where graphene and related materials offer advantages as new or greatly improved functionalities. Here advanced batteries or supercapacitors in anything from portable electric appliances to cars is a promising direction. Also flexible electronics – screens, sensors, smart textiles etc. – are coming strongly. Applications that require large, defect free graphene sheets are likely to take longer time to develop; many solid state electronic applications fall in this category.” We are in perfect agreement with this statement as CealTech and the industry alike, are currently focusing on such products as coatings, batteries, structural composites, functional inks, etc.

Tags:  batteries  CealTech  energy storage  PE-CVD 

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CEALTECH

Posted By Terrance Barkan, Tuesday, December 20, 2016
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IDTechEx USA 2016 Highlights Graphene Developments

Posted By Terrance Barkan, Friday, December 2, 2016

The Graphene Council participated at the IDTechEx conference in Santa Clara, California on 16-17 November 2016. The event brought together more than 3,000 attendees to learn about the latest developments in graphene, 3D printing, electric vehicles, flexible electronics and related technologies. 

What was very noticeable during this event was the clearly increasing interest from large industrial companies in the application of graphene in their current and future products. Companies like Ford Motors, GE, Dupont, Siemens, Lockheed Martin and many others. 

The range of applications runs from super hydrophobic coatings to heat management systems using graphene in combination with other materials. 

It was also a great opportunity for graphene producers like Applied Graphene Materials, Perpetuus and Graphenea, graphene material specialist firm Haydale and high quality graphite supplier First Graphite from Australia to exhibit their knowledge, products and capabilities.

We have a winner!

The Graphene Council held a drawing for visitors to our stand and we are very pleased to announce that Dr. Alison Schultz, advanced scientist for Owens Corning, was selected as the winner!

Alison attended the University of Rhode Island for her undergraduate studies where she earned a B.S. in Chemistry and Spanish. She then pursued a graduate career with Prof. Timothy E. Long at Virginia Tech, ultimately receiving her Ph.D. in Polymer Chemistry. Her research dissertation concentrated on ion-containing macromolecules for the production of thermally stable compositions with tunable physical and mechanical properties, targeting technologies ranging from electro-active membranes to high performance adhesives.

Alison is now working as an advanced scientist for Owens Corning within the Front End of Innovation (FEI) group. She is interested in exploring and leveraging new graphene technologies to improve electrical, mechanical, and barrier properties for a variety of composites. A major aspect of this endeavor involves understanding graphene's dispersion with various solvents and polymeric resins. To accomplish this goal, she is actively seeking new collaborative opportunities with graphene companies.

Alison can be reached at: Alison.Schultz@owenscorning.com

IDTechEx Europe 10-11 May 2017 in Berlin

The Graphene Council will participate at the next major graphene commercialization conference to be held in Berlin on 10-11 May 2017. We are preparing special presentations and important announcements regarding graphene standards, the establishment of a health and safety task force, a certification program for graphene producers and more. Stay tuned!

If you would like more information about how to participate as an exhibitor in a dedicated "Graphene Pavilion" or to simply attend as a participant at favorable discount rates, contact me directly at: tbarkan@thegraphenecouncil.org

We expect 2017 to be a year of increased public announcements of commercial applications of graphene as well as significant increases in industry scale production volumes. 

The Graphene Council's mission is to serve the global graphene community and help to accelerate the commercialization of this unique and multifunctional material. 

 

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2D materials - Graphene and hBN (hexagonal boron nitride) enhances methanol fuel cell performance

Posted By Terrance Barkan, Tuesday, November 29, 2016

This is an authorized reprint of a recent publication in Advanced Energy Materials journal (Impact Factor: 16) (http://dx.doi.org/10.1002/aenm.201601216), by Stuart M. Holmes (Reader) and Prabhuraj - (PhD student - http://www.prabhuraj.co.uk/) from the School of Chemical Engineering and Analytical Science, University of Manchester in collaboration with the School of Physics, reporting the usage of 2D materials in operating direct methanol fuel cells, showing zero resistance to protons enhancing cell performance, thereby opening the bottle neck for commercialization of fuel cells. 

The content published is the sole responsibility of the authors. 

Fuel cells are an interesting energy technology for the near future, as they aid in production of sustainable energy using hydrocarbons as fuels, such as methanol, ethanol, acetone etc by a simple oxidation-reduction reaction mechanism.

Among different liquid fuels, methanol is attractive as it has a higher energy density (compared to lithium ion batteries and hydrogen) and other features such as ease in handling, availability etc. Hence methanol fuel cells find their potential use in laptop chargers, military applications or other scenarios where the access to electricity is difficult.

However the wider spectrum of commercial potential for methanol systems is greatly hindered by methanol cross over occurring in the membrane area of fuel cells. This is defined as the passage of methanol from anode to the cathode through the membrane, hence creating short circuit and greatly affecting the fuel cell performance.

This is mitigated by using barrier layer, in addition to the membrane used. 

Figure 1: Schematic illustration of methanol fuel cell and structure of graphene

So far many materials have been used as a barrier layer in methanol fuel cells, where the proton conductivity is balanced with the methanol cross over. Proton conductivity is one of the dominant factors, where slight reduction in proton conductivity can influence the fuel cell performance to a large extent. All the materials reported in the literature to date have seen a reduction in proton conductivity though methanol cross over is reduced. 

It is known that Andre Geim and his co-workers (Nature, A.K. Geim et.al 2014), discovered proton transfer through single layer graphene and other 2D materials. Also graphene is known for its dense lattice packing structure, inhibiting the passage of methanol and other hydrocarbon based molecules across the membrane. However the actual application of these 2D materials in fuel cell systems has not yet been realized.

In this Advanced Energy Materials paper, the researchers have used single layer graphene and hBN, formed by chemical vapour deposition method, as a barrier layer in the membrane of methanol fuel cells. They have reported that this thinnest barrier layer ever used before shows negligible resistance to protons, at the same time reducing cross over, enhancing the cell performance by 50%. This is of significant interest, as this would lead to usage of 2D materials in fuel cells.

Based on the results of the research obtained, researchers have been granted EPSRC (Engineering and Physical Sciences Research council grant “Adventurers in Energy grant”) to pursue further research in this field. They have shown that as the surface coverage of the 2D material on the system improved, the performance improved.  This would lead to the usage of fuel cells, operating with high concentrated methanol fuels, as the current fuel cells suffer from cross over phenomena, with increased concentration. 

Moreover, this would pave the way for a membrane-less fuel cell system operating with higher efficiency. This technology could further be extended to other fuel cells types namely hydrogen fuel cells. Hydrogen fuel cells suffer from the usage of high cost humidifier, where the membrane needs to be humidified for improved proton conductivity. Whereas graphene, as reported in earlier studies, showed improved proton conductivity with temperature, without the need for humidifier systems. The future prospect could be realized in such a way that the fuel cells will make significant contribution to the future energy demand. 


Tags:  Fuel Cells  Graphene  hBN  Hexagonal boron nitride  Methane 

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What is the Best Form of Carbon Nanomaterial for Your Sporting Goods?

Posted By Dexter Johnson, IEEE Spectrum, Wednesday, November 16, 2016

Ever since nanomaterials made their first tentative steps into commercial markets, the early targets were in sporting goods. There is a pretty good catalogue of the different nanomaterials and the various sporting good products that they have been used for in a paper published in the Center for Knowledge Management of Nanoscience and Technology’s (CKMNT) from which an excerpt is provided here

The CKMNT report was compiled over three years ago and what is conspicuously absent from its list of nanomaterials for sporting goods is graphene. Carbon nanotubes are there as well as carbon nanofibers for bicycle frames—an application I had a brief foray into seven years ago when I tried to discern whether there was any appreciable benefit to using carbon nanofibers than just run-of-the-mill fillers in the composite.  But graphene just a few years back didn’t apparently make a blip on the radar.

That has all changed, of course, with graphene finding high-profile applications in tennis racquets and skis, both of which are produced by Head. However, I was more intrigued by the recent application of graphene in cycling since I am an avid cyclist myself.

The application that has gotten a lot of press is the adoption of graphene by venerable Italian cycling tire manufacturer Vittoria when it launched graphene-enabled tire dubbed G+ or Graphene Plus. You can see a promotional video below, but the main advantages of the graphene-enabled tires are supposed to be lighter weight, greater strength and durability. Of course, every tire is supposed to provide good grip and low rolling resistance and this new series of tires claims to tick those boxes as well.

My question was whether graphene could really offer much benefit over conventional reinforcing fillers like carbon black, or were we just looking at a bit of marketing and extra price per tire. So, I asked an industry expert in using graphene with different compounds, who asked to remain anonymous, if much benefit could be derived from using graphene in an application like this.

Vittoria has made it known that they are using a graphene platelet material for their tires. My source explained rubber compounding has so many variables that the kind of graphene platelet they are using would depend on the elastomer system, other parts of the filler system, protection system, process aids, curing package.

He added that as important as the specifications of the graphene are how they are processing the material is equally as important. Conventional reinforcing fillers such as carbon black are usually compounded into the raw rubber in mixers prior to vulcanization. Graphene, he explained, could be added into the product through a similar approach. However there are other routes to introducing graphene into the rubber matrix, which he was not at liberty to discuss.

The aims of modifying tire rubber formulations have traditionally been aimed at improving the so-called "tire triangle" of properties. This triad includes: Low rolling resistance, Abrasion resistance and Wet-traction control.

While graphene has been thought to improve these above properties, my source concedes that no matter what reinforcing fillers are used it is usually very difficult to obtain improvement to all three properties of the tire triangle simultaneously, there is usually a trade-off in performance between these properties. 

My source also points out that carbon nanotubes have long been expected to deliver the same type of improvements as graphene to tire performance but have never managed to gain a market foothold.

In the UK-based Cycling Weekly, the question of graphene in tires was given a lengthy discussion in which they interviewed one of Vittoria’s competitors, Continental.

“In the past we did some trials with graphene in the casing and tread of our tyres,” said Christian Wurmbäck, head of product development bicycle tires at Continental in the interview with Cycling Weekly. “However, although the directionality of the compound brought some benefits to the casing, the development of our Carbon Black compounds [which are said to use carbon nano particles] is at a higher level, so there was no need to jump back on graphene.”

It would seem the jury is still out on how much of a difference can make on improving your bicycle tires. I may just have to go and do a test, if I can get someone to send me a couple for testing purposes.

Tags:  bicycles  graphene  graphene platelets  sporting goods 

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Graphene used as toxic free MRI biomarker

Posted By Terrance Barkan, Saturday, November 12, 2016

This image from a high-resolution transmission electron microscope shows one of Rice University’s graphene-based MRI contrast agents, nanoparticles measuring about 10-nanometers in diameter that are so thin that they are difficult to distinguish. Credit: C.S. Tiwari/Rice University

Graphene, the atomically thin sheets of carbon that materials scientists are hoping to use for everything from nanoelectronics and aircraft de-icers to batteries and bone implants, may also find use as contrast agents for magnetic resonance imaging (MRI), according to new research from Rice University.

"They have a lot of advantages compared with conventionally available contrast agents," Rice researcher Sruthi Radhakrishnan said of the graphene-based quantum dots she has studied for the past two years. "Virtually all of the widely used contrast agents contain toxic metals, but our material has no metal. It's just carbon, hydrogen, oxygen and fluorine, and in all of our tests so far it has shown no signs of toxicity."

The initial findings for Rice's nanoparticles—disks of graphene that are decorated with fluorine atoms and simply organic molecules that make them magnetic—are described in a new paper in the journal Particle and Particle Systems Characterization.

Pulickel Ajayan, the Rice materials scientist who is directing the work, said the fluorinated graphene oxide quantum dots could be particularly useful as MRI contrast agents because they could be targeted to specific kinds of tissues.

"There are tried-and-true methods for attaching biomarkers to carbon nanoparticles, so one could easily envision using these quantum dots to develop tissue-specific contrast agents," Ajayan said. "For example, this method could be used to selectively target specific types of cancer or brain lesions caused by Alzheimer's disease. That kind of specificity isn't available with today's contrast agents."

Rice University graduate student Sruthi Radhakrishnan spent two years developing a process to make graphene-based quantum dots that could be used as MRI contrast agents. Credit: Jeff Fitlow/Rice University

MRI scanners make images of the body's internal structures using strong magnetic fields and radio waves. As diagnostic tests, MRIs often provide greater detail than X-rays without the harmful radiation, and as a result, MRI usage has risen sharply over the past decade. More than 30 million MRIs are performed annually in the U.S.


Radhakrishnan said her work began in 2014 after Ajayan's research team found that adding fluorine to either graphite or graphene caused the materials to show up well on MRI scans.
All materials are influenced by magnetic fields, including animal tissues. In MRI scanners, a powerful magnetic field causes individual atoms throughout the body to become magnetically aligned. A pulse of radio energy is used to disrupt this alignment, and the machine measures how long it takes for the atoms in different parts of the body to become realigned. Based on these measures, the scanner can build up a detailed image of the body's internal structures.

MRI contrast agents shorten the amount of time it takes for tissues to realign and significantly improve the resolution of MRI scans. Almost all commercially available contrast agents are made from toxic metals like gadolinium, iron or manganese.


"We worked with a team from MD Anderson Cancer Center to assess the cytocompatibility of fluorinated graphene oxide quantum dots," Radhakrishnan said. "We used a test that measures the metabolic activity of cell cultures and detects toxicity as a drop in metabolic activity. We incubated quantum dots in kidney cell cultures for up to three days and found no significant cell death in the cultures, even at the highest concentrations."

Unlike most currently used MRI contrast agents, Rice University’s fluorinated graphene oxide quantum dots contain no toxic metals and could potentially be targeted to specific kinds of tissues. Credit: Jeff Fitlow/Rice University

The fluorinated graphene oxide quantum dots Radhakrishnan studies can be made in less than a day, but she spent two years perfecting the recipe for them. She begins with micron-sized sheets of graphene that have been fluorinated and oxidized. When these are added to a solvent and stirred for several hours, they break into smaller pieces. Making the material smaller is not difficult, but the process for making small particles with the appropriate magnetic properties is exacting.

Radhakrishnan said there was no "eureka moment" in which she suddenly achieved the right results by stumbling on the best formula. Rather, the project was marked by incremental improvements through dozens of minor alterations.

"It required a lot of optimization," she said. "The recipe matters a lot."

Radhakrishnan said she plans to continue studying the material and hopes to eventually have a hand in proving that it is safe and effective for clinical MRI tests.
"I would like to see it applied commercially in clinical ways because it has a lot of advantages compared with conventionally available agents," she said.

 

Source: Phys.org

Tags:  contrast agents  GNP  magnetic resonance imaging  MD Anderson Cancer Center  MRI  Pulickel Ajayan  Rice University  Sruthi Radhakrishnan 

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New Properties Open Up New Applications for Graphene

Posted By Terrance Barkan, Friday, November 11, 2016

From properties as a superconductor to unexpected membrane separation abilities, graphene continues to surprise

 

When graphene is discovered to have new and sometimes unexpected properties, it quickly adds on potential new applications that it could be used for. 

 

This year we have seen that it actually does become a superconductor, opening up potential as material used in quantum computers. We have also seen graphene surprise even the Nobel Laureate who discovered it by it serving as a membrane for filtering out nuclear waste at nuclear power plants.

 

Graphene’s Potential as a Superconductor Just Got a Clearer

 


 

Illustration: Takashi Takahashi/Tohoku University

 

Graphene’s property as a conductor is unrivalled. The ballistic transport of graphene—the speed at which electrons pass through a material at room temperature—is so fast that it has surpassed what scientists believed were its theoretical limits. It is at the point now where electrons seem to be behaving like photons in graphene. Whenever this amazing property of graphene as a conductor is mentioned, people wonder if it might make for a good superconductor.

 

While there has been some research that has suggested that graphene could be made into a superconductor—a material with zero resistance to the flow of electricity—we now have more conclusive proof that it is indeed the case. 

 

In joint research out of Tohoku University and the University of Tokyo in Japan, scientists there have developed a new method for getting graphene to behave as a superconductor,  and in so doing have eliminated the chance that what they were observing was the transformation of graphene into a semiconductor.

 

Takashi Takahashi, a professor at Tohoku University and leader of the research, explained that they took a number of different approaches to ensure that what they were witnessing was graphene becoming a superconductor. In research published in the journal ACS Nano,  the researchers were first extremely meticulous about how they fabricated the graphene. 

 

They started with high-quality graphene on a silicon carbide crystal, and controlled the number of graphene sheets. This gave them a well-characterized bilayer graphene, into which they stuffed calcium atoms. So precise was the process hat they could actually ascribe a chemical formula to their sample: C6CaC6. This was an important achievement because having a precise count for the number of Li or Ca atoms determines the amount of donated electrons into graphene, which controls the occurrence of superconductivity.

 

The researchers’ measurements confirmed that superconductivity did occur with the graphene. Electrical resistivity dropped rapidly at around 4 K (-269 °C), indicative of an emergence of superconductivity. The measurements further indicated that the bilayer graphene did not create the superconductivity, nor did lithium-intercalated bilayer graphene exhibit superconductivity. This meant that the drop in resistance was due to the electron transfer from the calcium atoms to the graphene sheets.

 

Now that graphene has been made to perform as a superconductor with a clear zero electrical resistivity, it becomes possible to start considering applying graphene into the making of a quantum computer that would use this superconducting graphene as the basis for an integrated circuit.

 

Unfortunately, like most superconducting materials, the temperature at which graphene reaches superconductivity is too low to be practical. Raising that temperature will be the next step in the research. 

 

Graphene Nanoribbons Increase Their Potential

 


Image: Patrick Han

 

Graphene nanoribbons (GNRs) appear to be among the best options for electronics applications because of the each with which it’s possible to engineer a band gap into them. Narrow ones are semiconductors, while wider ones act as conductors. Pretty simple.

 

With improved methods being developed for manufacturing GNRs that are both compatible with current semiconductor manufacturing methods and can be scaled up, the future would appear bright. But there’s not a lot of knowledge of what happens when you start trying to manipulate GNRs into actual electronic devices.

 

Now a team of researchers at Tohoku University's Advanced Institute of Materials Research (AIMR) in Japan is investigating what happens when you interconnect GNRs end to end using molecular assembly to form elbow structures, which are essentially interconnection points.  The researchers believe that this development provides the key to unlocking GNRs’ potential in high-performance and low-power-consumption electronics.

 

“Current molecular assemblies either produce straight GNRs (i.e., without identifiable interconnection points), or randomly interconnected GNRs,” said Dr. Patrick Han, the project leader, in press release. “These growth modes have too many intrinsic unknowns for determining whether electrons travel across graphene interconnection points smoothly,” said Han, who added that, “The key is to design a molecular assembly that produces GNRs that are systematically interconnected with clearly distinguishable interconnection points.”

 

In research published in the journal ACS Nano, the AIMR researchers demonstrated that both the electron and thermal conductivities of two interconnected GNRs should be the same as that of the ends of a single GNR.

 

“The major finding of this work is that interconnected GNRs do not show electronic disruption (e.g., electron localization that increases resistance at the interconnection points),” said Han in the press release. “The electronically smooth interconnection demonstrates that GNR properties (including tailored band gaps, or even spin-aligned zigzag edges) can be connected to other graphene structures. These results show that finding a way to connect defect-free GNRs to desired electrodes may be the key strategy toward achieving high-performance, low-power-consumption electronics.”

 

Graphene Has Special Properties for Cleaning Up Nuclear Waste

 


Image: The University of Manchester

 

The merits of graphene as a separation membrane medium have long been extolled.  The properties that distinguish graphene for these applications are its large surface area, the variability of its pore size and its adhesion properties.

 

These attractive properties have not gone unnoticed by Andre Geim, who, along with Konstantin Novoselov, won the 2010 Nobel Prize in Physics for their discovery and study of graphene. Geim has dedicated a significant amount of his research efforts since then to the use of graphene as a filtering medium in various separation technologies.

 

Now Geim and his colleagues at the University of Manchester have found that graphene filters are effective at cleaning up the nuclear waste produced at nuclear power plants.   This application could make one of the most costly and complicated aspects of nuclear power generation ten times less energy intensive and therefore much more cost effective.

 

In research published in the journal Science, Geim and his colleagues at Manchester experimented to see if the nuclei of deuterium—deuterons—could pass through the two-dimensional (2-D) materials graphene and boron nitride. The existing theories seemed to suggest that the deuterons would pass through easily. But to the surprise of the researchers, not only did the 2-D membranes sieve out the deuterons, but the separation was also accomplished with a high degree of efficiency.

 

“This is really the first membrane shown to distinguish between subatomic particles, all at room temperature,” said Marcelo Lozada-Hidalgo, a post-doctoral researcher at the University of Manchester and first author of the paper, in a press release. “Now that we showed that it is a fully scalable technology, we hope it will quickly find its way to real applications.”

 

Irina Grigorieva, another member of the research team, added: “It is a really simple set up. We hope to see applications of these filters not only in analytical and chemical tracing technologies but also in helping to clean nuclear waste from radioactive tritium.”

Tags:  Andre Geim  ballistic transport  Irina Grigorieva  Konstantin Novoselov  Marcelo Lozada-Hidalgo  University of Manchester 

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Graphene Certification Needed

Posted By Terrance Barkan, Wednesday, November 9, 2016

One of the major problems identified in our survey of the global graphene community was the lack of agreed standards for graphene materials.

In addition, there is a tremendous lack of transparency into the actual quality and characteristics of material that is being produced and sold as "graphene".

Survey respondents reported that batches of graphene were often inconsistent (even from the same producer) or were not material that could seriously be considered graphene. (More like micro-graphite). 


This is not only a problem for customers, researchers and users of purchased materials, it is a problem for legitimate graphene producers to differentiate themselves from companies that claim to be selling graphene but that are instead producing some other forms of carbon containing materials. 

The lack of an agreed global standard for graphene and closely related materials creates a vacuum and lack of trust in the marketplace for industrial scale adoption of graphene materials. This is true even though forms of graphene and reduced graphene oxide have proven to provide outstanding performance improvements in composites, inks and 3D filaments to name but a few examples. 

I would like to hear from you if you agree with this view and if you feel that the establishment of a regime to certify the quality / characteristics of commercially available graphene products is a good idea. 

Feel free to post a reply or send me a private message directly at: 
tbarkan@thegrapheneconcil.org

You can also see the original postings in our LinkedIn group at: 
http://www.linkedin.com/groups/Graphene-Council-5153830/about

Tags:  Certification  Developers  Graphene  Producers  Standards  Survey  Testing  Users 

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Graphene is leading to ultrafast wireless communication

Posted By Terrance Barkan, Wednesday, November 2, 2016


Graphene-based nanoantennas (blue and red dots) on a chip. Credit: University at Buffalo

For wireless communication, we’re all stuck on the same traffic-clogged highway — it’s a section of the electromagnetic spectrum known as radio waves.

Advancements have made the highway more efficient, but bandwidth issues persist as wireless devices proliferate and the demand for data grows. The solution may be a nearby, mostly untapped area of the electromagnetic spectrum known as the terahertz band.

“For wireless communication, the terahertz band is like an express lane. But there’s a problem: there are no entrance ramps,” says Josep Jornet, PhD, assistant professor in the Department of Electrical Engineering at the University at Buffalo School of Engineering and Applied Sciences.

Jornet is the principal investigator of a three-year, $624,497 grant from the U.S. Air Force Office of Scientific Research to help develop a wireless communication network in the terahertz band. Co-principal investigators are Jonathan Bird, PhD, professor of electrical engineering, and Erik Einarsson, PhD, assistant professor of electrical engineering, both at UB.

Their work centers on developing extremely small radios — made of graphene and semiconducting materials — that enable short-range, high-speed communication.

The technology could ultimately reduce the time it takes to complete complex tasks, such as migrating the files of one computer to another, from hours to seconds. Other potential applications include implantable body nanosensors that monitor sick or at-risk people, and nanosensors placed on aging bridges, in polluted waterways and other public locations to provide ultra-high-definition streaming.

These are examples of the so-called Internet of Nano-Things, a play on the more common Internet of Things, in which everyday objects are hooked up to the cloud via sensors, microprocessors and other technology.

“We’ll be able to create highly accurate, detailed and timely maps of what’s happening within a given system. The technology has applications in health care, agriculture, energy efficiency — basically anything you want more data on,” Jornet says.

The untapped potential of Terahertz waves

Sandwiched between radio waves (part of the electromagnetic spectrum that includes AM radio, radar and smartphones) and light waves (remote controls, fiber optic cables and more), the terahertz spectrum is seldom used by comparison.

Graphene-based radios could help overcome a problem with terahertz waves: they do not retain their power density over long distances. It’s an idea that Jornet began studying in 2009 as a graduate student at Georgia Tech under Ian Akyildiz, PhD, Ken Byers Chair Professor in Telecommunications.

Graphene is a two-dimensional sheet of carbon that, in addition to being incredibly strong, thin and light, has tantalizing electronic properties. For example, electrons move 50 to 500 times faster in graphene compared to silicon.

In previous studies, researchers showed that tiny antennas graphene strips 10-100 nanometers wide and one micrometer long, combined with semiconducting materials such as indium gallium arsenide — can transmit and receive terahertz waves at wireless speeds greater than one terabit per second.

But to make these radios viable outside the laboratory, the antennas need other electronic components, such as generators and detectors that work in the same environment. This is the work that Jornet and his colleagues are focusing on.

Jornet says thousands — perhaps millions — of these arrayed radios working together could allow terahertz waves to travel greater distances. The nanosenors could be embedded into physical objects, such as walls and street signs, as well as chips and other electronic components, to create an Internet of Nano-Things.

“The possibilities are limitless,” says Jornet.

Jornet is a member of the Signals, Communications and Networks research group at UB’s electrical engineering department, while Bird and Einarsson work in the department’s Solid State Electronics research group.

The work described above is an example of the department’s strategy to hire faculty members with complimentary expertise that drive the convergence of basic research areas while developing new technologies and educating students.

Source: Cory Nealon

Tags:  Graphene  Internet of Things  Josep Jornet  Nanosensors  Radio  U.S. Air Force Office of Scientific Research  University at Buffalo  Wireless 

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