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Scientists Realize High Performance Broadband Graphene Saturable Absorber

Posted By Graphene Council, The Graphene Council, Sunday, October 6, 2019
The unique mechanical, chemical, electronic and photonic features of graphene are attracting much attention, especially its unusual nonlinear optical (NLO) properties, making it a progressive solution to ultrafast saturable absorption and optical limiting. However, small NLO coefficient in natural materials restricts its applications due to high-intensity thresholds. Embedding NLO materials in a photonic crystal (PC) can yield lower NLO thresholds than bulk materials, making it an exciting NLO device again.

Recently, a study led by Prof. WANG Jun from Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences proposed a simple and accessible technology for PC manufacturing and presented a PC1 designed for infrared and visible λ pairs, which is suitable for the two harmonics of a standard laser source. The result was published in Optics Letters.

Their study was based on the polymer dispersion of graphene flakes. To prepare the crystal, graphene was first suspended using the liquid phase exfoliation method. Then the 1D PCs consisting 12 alternating layers of poly(9-vinylcarbazole) (PVK) and of graphene-based poly(vinyl-alcohol) (PVA) nanocomposite was spin coated on a glass substrate.

In order to compare the NLO response of graphene in PC with partially resonant and non-resonant cases, PC2 crystal and a pure PVA-G film were fabricated. In PC1 structure, two bandgaps near 515 nm and 1030 nm were observed. For PC2, the second bandgap fell on 1425 nm, which deprived the possible advantage at 1030 nm.

NLO properties of the three samples were studied using an open-aperture Z-scan setup with 340 fs pulses at the main and second harmonics of a fiber laser. More pronounced saturable behavior with significant enhancement of the nonlinear absorption coefficient and the imaginary part of the third-order nonlinear susceptibility was obtained in the PC structures as compared to the bulk PVA-G film.

Their experiment also showed a remarkable decrease of saturable absorption threshold and saturation intensities of graphene embedded in the PC in comparison with the bulk PVA-G. The saturable absorption enhancement factor reached 7 in the visible and 8 in the infrared, which could be explained by the combination of light field enhancement and absorptive and scattering losses inside the structures.

This work provides a desirable solution for an advanced all-optical laser mode-locking device. This work was supported by the Chinese National Natural Science Foundation, the Strategic Priority Research Program of CAS, the Key Research Program of Frontier Science of CAS, and the Program of Shanghai Academic Research Leader.

Tags:  Graphene  Jun Wang  optoelectronics  Shanghai Institute of Optics and Fine Mechanics 

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Thomas Skordas: "Graphene is on the way to changing our lives"

Posted By Graphene Council, The Graphene Council, Wednesday, October 2, 2019
Thomas Skordas, Director for Digital Excellence and Science Infrastructure, takes a look at the latest developments in graphene research on the occasion of Graphene Week 2019 – Europe's leading graphene conference, which brings together the latest innovations, leading-edge technology and research on graphene and other layered materials.

Graphene Week was a chance to hear about recent scientific discoveries and technological advances in graphene, one of the key technology areas in Europe today. The great strength of the Graphene Flagship is that it provides a nurturing environment for top scientists, researchers and industry to discover new uses for this fascinating material, which consists of a single layer of carbon atoms.

This year alone, the Flagship has scored some significant achievements. For example, it has used graphene to increase the lifetime of Perovskite solar cells, the most efficient way of converting sunlight to energy in existence, when facing conditions such as heat and moisture. Once they are commercially viable, they could be a game changer for the clean energy transition. Flagship researchers have also built silicon-graphene coin cell batteries, of which a high proportion of the components can be recycled. This patented technology forms the basis of the spin-off Bedimensional, which received a private investment of €18 million in 2018, and test production is expected to start in the coming months.

Graphene has the potential to change our lives, and we are witnessing more and more graphene product launches and spin-offs. The Flagship also regularly presents new demonstrators at events, such as the mobile phone-related technology shown at Mobile World Congress: this video shows what they presented. We are also looking forward to the publication in the next few weeks of a 400-page open-access book, the work of 70 co-authors, with information on how to produce graphene and up to 5000 other layered materials. It will be a “bible” for students and industrial manufacturers interested in the fabrication processes of these materials. We have come a long way: merely fifteen years ago, graphene was isolated for the first time ever, in pioneering experiments using pieces of Scotch tape, but today the methods for synthesising thousands of similar materials are available to anyone in the world.

Tags:  Batteries  Digital Excellence and Science Infrastructure  Graphene  Graphene Flagship  Thomas Skordas 

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Graphmatech’s Latest Invention Brings Metal Additive Manufacturing to the Next Level

Posted By Graphene Council, The Graphene Council, Thursday, September 26, 2019
Additive manufacturing (AM) or “3D-printing” is a manufacturing technology which allows the formation of complex geometries under computer control. Flowability of metal powder is among the challenges in metals AM industry. Graphmatech, a Swedish graphene materials technology scaleup company focuses on solving industrial challenges with graphene technology, have breaking news to share. Graphmatech scientists recently achieved remarkable improvement in the flowability of metal powders. This is another milestone in the success story of Graphmatech AB (founded 2017) that began with the patented technology and material Aros Graphene®. Strategic collaborations with Swedish, Swiss and German key industries, lead to that Graphmatech was appointed the “Nanotech company of the year in the Nordics” in 2018.

The latest story, on 3D printing enhancements, is best told by Dr. Mamoun Taher, the CEO, and co-founder of Graphmatech:

”Being a CEO of the fast-growing Graphmatech has never stopped me from being at the lab doing innovative and outside of the box experiments. One late afternoon, I went to the lab with an intention to investigate the influence of a graphene-based material on the magnetic properties of metal powders. Unexpected behavior of metal powder was observed after treatment with the graphene-based additive. The dreams about the observations woke me up very early the next morning and made me drive to Uppsala University to microscopically investigate the results from last night.

The results were immediately discussed with our collaborator at Uppsala University, Prof. Ulf Jansson, a Chair Professor, Inorganic Chemistry program leader and the leader for Additive Manufacturing Program at Uppsala University in Sweden.”

”When I saw the samples and results I immediately told Dr. Taher that this has the potential to solve a major challenge in metal powder industry and mainly for metal additive manufacturing. And this then turned out to be right! The newly found multifunctionality of the graphene-based additive allows the simultaneous addressing of different challenges in metal powder industry, and we are eager to continue our research” Says Prof. Ulf Jansson.

Further research and development have been carried out between Graphmatech and the group of Prof. Jansson to optimize and develop an eco-friendly, cost-efficient and scaleable process for treating metal powder with graphene-based materials for additive manufacturing and powder metallurgy.

Graphmatech was founded by material scientist Dr. Mamoun Taher and the serial entrepreneur Björn Lindh. The major investors of the company are ABB Technology Venture, InnoEnergy and the well-known business angel Jane Walerud.

Tags:  3D Printing  Björn Lindh  Graphene  Graphmatech  InnoEnergy  Jane Walerud  Mamoun Taher  Ulf Jansson  Uppsala University 

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Graphene is wonderful – The Graphene Flagship project presents innovations in Brussels

Posted By Graphene Council, The Graphene Council, Thursday, September 26, 2019
European Commission funded research project, the Graphene Flagship, will demonstrate a selection of the project’s most exciting innovations at the Science is Wonderful exhibition in Brussels, Belgium, on 25 and 26 September 2019. The free exhibition, held at Tour & Taxis, a redeveloped industrial space in Brussels, is part of the European Research and Innovation Days and aims to bring a world of science and technology to the general public.

Demonstrations from the Graphene Flagship include technology that has been developed for human health and wellbeing. For example, a graphene-based brain implant that could be used to provide information on the onset of seizures. The new technology, which has been developed by Graphene Flagship partners the Microelectronic Institute of Barcelona (IMB-CNM, CSIC), the Catalan Institute of Nanoscience and Nanotechnology (ICN2) and ICFO, demonstrates a major step in understanding the functions of the human brain.

The exhibition will also showcase examples of graphene dispersions and graphite electrodes manufactured by Graphene Flagship partner Talga. As a high-tech materials company and a leader in bulk graphene and graphite supply, Talga will demonstrate how graphene can easily be exfoliated from graphite, illustrating the journey from material exfoliation, right through to commercialisation.

Other demonstrations at Science is Wonderful include a newly developed virtual reality (VR) system which can be used to construct, manipulate and build graphene and other layered material structures. Developed by Graphene Flagship partner the Technical University of Denmark (DTU), the VR system demonstrates clearly how graphene can be modified and manipulated, with the ability to edit molecules and perform calculations on their electronic properties in real-time.

The VR system gives students and other citizens an unforgettable, low-barrier to entry for the complex machinery of atomic-scale materials and technology. However, it can also provide even experienced researchers with a unique sandbox for scientific problem solving, quantitative analysis, idea generation and discovery.

“The Graphene Flagship’s presence at Science is Wonderful will bolster its efforts to promote the use of graphene in commercial products,” explained Jari Kinaret, director of the Graphene Flagship. “During the first five years of our ambitious Graphene Flagship project, we managed to bring together academic researchers and industrial business leaders to create and commercialise technologies that are already improving European society — the demonstrations at Science is Wonderful will showcase some beautiful examples.”

Tags:  CSIC  Graphene  Graphene Flagship  Healthcare  ICFO  ICN2  Jari Kinaret  Technical University of Denmark 

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XG Sciences Adds Engine Oil Additives to Growing List of Commercial Applications Leveraging its Graphene-Based Products

Posted By Graphene Council, The Graphene Council, Tuesday, September 24, 2019
XG Sciences announced today commercial adoption of its products for use in engine oil. HELLA, an innovative family-owned company serving the automotive and industrial markets with revenue of €7 Billion in the fiscal year 2018/2019, completed a successful launch of a new line of engine oil additives incorporating XG Sciences’ graphene nanoplatelets to improve performance.

The engine oil additive product was marketed in Korea where the first 25,000 units sold out within 100 days. Based on this success, HELLA extended distribution to China and Japan and may extend use of graphene nanoplatelets to other lubrication-related products. HELLA’s graphene-enhanced lubricant is specially formulated to reduce wear and friction in internal combustion engines delivering a range of benefits including extended engine life, reduced engine vibration, improved power output, 50% reduction in engine wear, improved fuel economy and enhanced ride comfort.

First isolated and characterized in 2004, graphene is a single layer of carbon atoms. Among many noted properties, monolayer graphene is harder than diamonds, lighter than steel but significantly stronger, and conducts electricity better than copper. Graphene nanoplatelets are particles consisting of multiple layers of graphene with unique capabilities for energy storage, thermal conductivity, electrical conductivity, barrier properties, lubricity and the ability to impart physical property improvements when incorporated into plastics, metals or other matrices.

“XG Sciences is excited to accelerate the performance of HELLA’s engine oil additive through use of our graphene nanoplatelets. HELLA’s adoption provides another example of the potential for this revolutionary material and further demonstrates the power of our graphene nanoplatelets,” said Bamidele Ali, Chief Commercial Officer, XG Sciences.

Tags:  Automotive  Bamidele Ali  Graphene  HELLA  XG Sciences 

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First Graphene to develop graphene-based energy storage materials for supercapacitors

Posted By Graphene Council, The Graphene Council, Tuesday, September 24, 2019
First Graphene has signed an exclusive worldwide licensing agreement with the University of Manchester to develop graphene-hybrid materials for use in supercapacitors. The licencing agreement is for patented technology for the manufacture of metal oxide decorated graphene materials, using a proprietary electrochemical process.

The graphene-hybrid materials will have the potential to create a new generation of supercapacitors, for use in applications ranging from electric vehicles to elevators and cranes. Supercapacitors offer high power-density energy storage, with the possibility of multiple charge/discharge cycles and short charging times. The market for supercapacitor devices is forecast to grow at 20% per year to approximately USD 2.1 billion by 2022. Growth may, however, be limited by the availability of suitable
materials.

Supercapacitors typically use microporous carbon nanomaterials, which have a gravimetric capacitance between 50 and 150 Farads/g. Research carried out by the University of Manchester shows that high capacitance materials incorporating graphene are capable of reaching up to 500 Farads/g. This will significantly increase the operational performance of supercapacitors in a wide range of applications, as well as increasing the available supply of materials.

Published research1 by Prof. Robert Dryfe and Prof. Ian Kinloch of The University of Manchester reveals how high capacity, microporous materials can be manufactured by the electrochemical processing of graphite raw materials. These use transition metal ions to create metal oxide decorated graphene materials, which have an extremely high gravimetric capacitance, to 500 Farads/g.

Prof. Dryfe has secured funding from the UK EPSRC (Engineering and Physical Sciences Council) for further optimisation of metal oxide/graphene materials. Following successful completion of this study, FGR is planning to build a pilot-scale production unit at its laboratories within the Graphene Engineering and Innovation Centre (GEIC). It is anticipated that this will be the first step in volume production in the UK, to enable the introduction of these materials to supercapacitor device manufacturers.

Andy Goodwin, Chief Technology Officer of First Graphene Ltd says: “This investment is a direct result of our presence at the Graphene Engineering and Innovation Centre. It emphasises the importance of effective external relationships with university research partners. The programme is also aligned with the UK government’s industrial strategy grand challenges and we’ll be pursuing further support for the development of our business within the UK.”

James Baker, Chief Executive of Graphene@Manchester, added: “We are really pleased with this further development of our partnership with First Graphene. The University’s Graphene Engineering Innovation Centre is playing a key role in supporting the acceleration of graphene products and applications through the development of a critical supply chain of material supply and in the development of applications for industry. This latest announcement marks a significant step in our Graphene City developments, which looks to create a unique innovation ecosystem here in the Manchester city-region, the home of graphene.”

Tags:  Andy Goodwin  Energy Storage  First Graphene  Graphene  Graphene Engineering and Innovation Centre  Ian Kinloch  James Baker  nanomaterials  Robert Dryfe  supercapacitors  University of Manchester 

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Clarification of a new synthesis mechanism of semiconductor atomic sheet

Posted By Graphene Council, The Graphene Council, Tuesday, September 24, 2019
In Japan Science and Technology Agency's Strategic Basic Research Programs, Associate Professor Toshiaki Kato and Professor Toshiro Kaneko of the Department of Electronic Engineering, Graduate School of Engineering, Tohoku University succeeded in clarifying a new synthesis mechanism regarding transition metal dichalcogenides (TMD)1), which are semiconductor atomic sheets having thickness in atomic order.

Because it is difficult to directly observe the aspect of the growing process of TMD in a special environment, the initial growth process remained unclear, and it has been desirable to elucidate a detailed mechanism of synthesis to obtain high-quality TMD.

An in-situ observing synthesis method2) has been developed by our research group to examine the growth aspect of TMD as a real-time optical image in a special high temperature atmosphere of about 800°C in the presence of corrosive gases. In addition, a synthesis substrate, which is a mechanism to control diffusion during the crystal growth of a precursor3), has been developed in advance; further, it has been clarified that the growing precursor diffuses a distance about 100 times larger than in conventional semiconductor materials. 

It was also demonstrated that nucleation occurs due to the involvement of the precursor in a droplet state. Furthermore, by utilizing this method, a large-scale integration of more than 35,000 monolayer single crystal atomic sheets has been achieved on a substrate in a practical scale (Figure 1).

Utilizing the results of the present research, the large-scale integration of atomic-order thick4) semiconductor atomic sheets can be fabricated and is expected to be put into practical use in the field of next-generation flexible electronics.

Tags:  Electronics  Graphene  Semiconductor  Tohoku University  Toshiaki Kato  Toshiro Kaneko 

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Nanochains could increase battery capacity, cut charging time

Posted By Graphene Council, The Graphene Council, Tuesday, September 24, 2019
How long the battery of your phone or computer lasts depends on how many lithium ions can be stored in the battery's negative electrode material. If the battery runs out of these ions, it can't generate an electrical current to run a device and ultimately fails.

Materials with a higher lithium ion storage capacity are either too heavy or the wrong shape to replace graphite, the electrode material currently used in today's batteries.

Purdue University scientists and engineers have introduced a potential way that these materials could be restructured into a new electrode design that would allow them to increase a battery's lifespan, make it more stable and shorten its charging time.

The study, appearing as the cover of the September issue of Applied Nano Materials, created a net-like structure, called a "nanochain," of antimony, a metalloid known to enhance lithium ion charge capacity in batteries.

The researchers compared the nanochain electrodes to graphite electrodes, finding that when coin cell batteries with the nanochain electrode were only charged for 30 minutes, they achieved double the lithium-ion capacity for 100 charge-discharge cycles.

Some types of commercial batteries already use carbon-metal composites similar to antimony metal negative electrodes, but the material tends to expand up to three times as it takes in lithium ions, causing it to become a safety hazard as the battery charges.

"You want to accommodate that type of expansion in your smartphone batteries. That way you're not carrying around something unsafe," said Vilas Pol, a Purdue associate professor of chemical engineering.

Through applying chemical compounds -- a reducing agent and a nucleating agent -- Purdue scientists connected the tiny antimony particles into a nanochain shape that would accommodate the required expansion. The particular reducing agent the team used, ammonia-borane, is responsible for creating the empty spaces -- the pores inside the nanochain -- that accommodate expansion and suppress electrode failure.

The team applied ammonia-borane to several different compounds of antimony, finding that only antimony-chloride produced the nanochain structure.

"Our procedure to make the nanoparticles consistently provides the chain structures," said P. V. Ramachandran, a professor of organic chemistry at Purdue.

The nanochain also keeps lithium ion capacity stable for at least 100 charging-discharging cycles. "There's essentially no change from cycle 1 to cycle 100, so we have no reason to think that cycle 102 won't be the same," Pol said.

Henry Hamann, a chemistry graduate student at Purdue, synthesized the antimony nanochain structure and Jassiel Rodriguez, a Purdue chemical engineering postdoctoral candidate, tested the electrochemical battery performance.

The electrode design has the potential to be scalable for larger batteries, the researchers say. The team plans to test the design in pouch cell batteries next.

Tags:  batteries  Battery  Graphene  Henry Hamann  Jassiel Rodriguez  Li-ion  nanomaterials  P. V. Ramachandran  Purdue University  Vilas Pol 

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AGM at the Western Coatings Show 2019

Posted By Graphene Council, The Graphene Council, Wednesday, September 18, 2019
Applied Graphene Materials are exhibiting at Western Coatings Show in Las Vegas, on 20-23 October 2019.

At the show AGM will be promoting their Genable® range which delivers outstanding enhancements to anti-corrosion and barrier performance, while providing opportunities to further optimise other coating characteristics. AGM will soon be promoting a new addition to the Genable® range.

Andy Gent will be giving a presentation titled: Corrosion: Meeting Tomorrows Performance Needs with Graphene Nano-Platelets.

John Willhite and Adrian Potts will also be at stand 332 to answer any questions you may have. You can contact them on +44 (0)1642 438214, or, by e-mail at info@appliedgraphenematerials.com.

Tags:  Adrian Potts  Andy Gent  Applied Graphene Materials  coatings  Graphene  John Willhite 

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Conductivity at the edges of graphene bilayers

Posted By Graphene Council, The Graphene Council, Wednesday, September 18, 2019
The conductivity of dual layers of graphene greatly depends on the states of carbon atoms at their edges; a property which could have important implications for information transmissions on quantum scales.

Made from 2D sheets of carbon atoms arranged in honeycomb lattices, graphene displays a wide array of properties regarding the conduction of heat and electricity.

When two layers of graphene are stacked on top of each other to form a 'bilayer', these properties can become even more interesting. At the edges of these bilayers, for example, atoms can sometimes exist in an exotic state of matter referred to as the 'quantum spin Hall' (QSH) state, depending on the nature of the interaction between their spins and their motions, referred to as their 'spin-orbit coupling' (SOC). While the QSH state is allowed for 'intrinsic' SOC, it is destroyed by 'Rashba' SOC. In an article recently published in EPJ B, Priyanka Sinha and Saurabh Basu from the Indian Institute of Technology Guwahati showed that these two types of SOC are responsible for variations in the ways in which graphene bilayers conduct electricity.

For nanoribbons of bilayer graphene, whose edge atoms are arranged in zigzag patterns, the authors showed that the bands of electron energies which are allowed and forbidden are significantly different to those found in monolayer graphene. For intrinsic SOC, the QSH state even caused atoms in the zigzag to have a gap between these bands, which disappeared in odd atoms. However, this asymmetry disappeared for Rashba SOC, which changed the relationship between the energy required to add an electron to the bilayer, and its conductivity.

This conduction sensitivity to the states of edge atoms shows that graphene bilayers could be particularly useful for spintronics applications. This field studies how quantum spins can be used to efficiently transmit information, which is of particular interest to researchers in fields like quantum computing. Sinha and Basu also found that the characteristic SOC behaviours they uncovered persisted with or without voltage across the bilayers, which dispelled theories that this aspect could prevent the QSH state from forming. Their work furthers our knowledge of graphene bilayers, potentially opening up new areas of research into their intriguing properties.

Tags:  2D  Graphene  Indian Institute of Technology Guwahati  Priyanka Sinha  Saurabh Basu 

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