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Flexible, transparent monolayer graphene device for power generation and storage

Posted By Graphene Council, The Graphene Council, Wednesday, May 15, 2019
Updated: Tuesday, May 14, 2019
Researchers at Daegu Gyeongbuk Institute of Science and Technology developed single-layer graphene based multifunctional transparent devices that are expected to be used as electronics and skin-attachable devices with power generation and self-charging capability (ACS Applied Materials & Interfaces, "Single-Layer Graphene-Based Transparent and Flexible Multifunctional Electronics for Self-Charging Power and Touch-Sensing Systems").

Senior Researcher Changsoon Choi's team actively used single-layered graphene film as electrodes in order to develop transparent devices. Due to its excellent electrical conductivity and light and thin characteristics, single-layered graphene film is perfect for electronics that require batteries.

By using high-molecule nano-mat that contains semisolid electrolyte, the research team succeeded in increasing transparency (maximum of 77.4%) to see landscape and letters clearly.

Furthermore, the research team designed structure for electronic devices to be self-charging and storing by inserting energy storage panel inside the upper layer of power devices and energy conversion panel inside the lower panel. They even succeeded in manufacturing electronics with touch-sensing systems by adding a touch sensor right below the energy storage panel of the upper layer.

Senior Researcher Changsoon Choi in the Smart Textile Research Group, the co-author of this paper, said that "We decided to start this research because we were amazed by transparent smartphones appearing in movies. While there are still long ways to go for commercialization due to high production costs, we will do our best to advance this technology further as we made this success in the transparent energy storage field that has not had any visible research performances."

Tags:  Batteries  Changsoon Choi  Daegu Gyeongbuk Institute of Science and Technolog  Graphene  nanomaterials 

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New Technique Produces Longer-lasting Lithium Batteries

Posted By Graphene Council, The 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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Graphene and the Nuclear Decommissioning Authority in the UK

Posted By Graphene Council, The Graphene Council, Friday, April 5, 2019
Updated: Friday, April 5, 2019

Emerging technologies such as graphene are being investigated by the Nuclear Decommissioning Authority (NDA) in the UK for their potential to improve decommissioning of nuclear sites.

The Challenge

To identify how graphene, an emerging technology, could improve delivery of NDA’s mission.

The Solution

Review the properties of graphene including the latest developments and areas for potential deployment.

Technology Review : Graphene – a form of carbon consisting of a single layer of carbon atoms arranged in a hexagonal lattice with unique chemical and physical properties.

Expected Benefits: Raising awareness of new emerging technology across the NDA Group and supply chain.

The NDA published a report on its findings and research over the period of 2016 - 2018: "Graphene and its use in nuclear decommissioning", produced in collaboration with NSG Environmental, the University of Manchester and the National Physical Laboratory

Highlights:

Graphene’s chemical and physical properties are unique:

- one of the thinnest but also strongest materials

- conducts heat better than all other materials

- conducts electricity

- is optically transparent but so dense that it is impermeable to gases

Developments in graphene-based technology have been rapid in a number of areas, including advanced electronics, water filtration and high-strength materials. NDA identified graphene as an emerging technology that could be useful to improve delivery of its mission.

NDA carried out a technology review to compare the properties and potential uses of graphene against the challenges facing the UK in decommissioning its earliest nuclear sites. The opportunities identified included:

  • Advanced materials: Graphene-doped materials could help to immobilise nuclear wastes.
  • Composites incorporating graphene could be used in the construction of stronger buildings or containers for storing nuclear materials.
  • Cleaning up liquid wastes: Graphene-based materials could absorb or filter radioactive elements, helping to clean up spills or existing radioactive wastes.
  • Sensors: Graphene in sensors could improve the detection of radiation or monitor for the signs of corrosion in containers.
  • Batteries: Graphene could produce smaller, longer-lasting batteries that would enable robots to operate for longer in contaminated facilities.

NDA also assessed the potential limitations in graphene’s use to provide a balanced assessment.

The issues identified included:
- cost
- scale-up
- environmental concerns
- lack of standardization
- knowledge regarding radiation tolerance

The report was shared with technical experts across the NDA group, published online and summarised in the Nuclear Institute’s journal: Nuclear Futures. As the technology moves on from early-stage research, NDA and its businesses are continuing to monitor developments, such as the recently opened Graphene Engineering and Innovation Centre (GEIC), with the aim of supporting graphene-based technologies and accelerating their uptake within the nuclear decommissioning sector.

NDA is progressing further projects investigating the potential of other emerging technologies. Engagement continues with academia and industry to identify innovations that could improve delivery of the mission.

Tags:  Andre Geim  Batteries  Graphene  Graphite  Konstantin Novoselov  Sensors  University of Manchester 

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Expanding the Use of Silicon in Batteries, By Preventing Electrodes From Expanding

Posted By Graphene Council, The Graphene Council, Tuesday, March 26, 2019
The latest lithium-ion batteries on the market are likely to extend the charge-to-charge life of phones and electric cars by as much as 40 percent. This leap forward, which comes after more than a decade of incremental improvements, is happening because developers replaced the battery’s graphite anode with one made from silicon. Research from Drexel University and Trinity College in Ireland now suggests that an even greater improvement could be in line if the silicon is fortified with a special type of material called MXene.

This adjustment could extend the life of Li-ion batteries as much as five times, the group recently reported in Nature Communications. It’s possible because of the two-dimensional MXene material’s ability to prevent the silicon anode from expanding to its breaking point during charging — a problem that’s prevented its use for some time.

Silicon anodes are projected to replace graphite anodes in Li-ion batteries with a huge impact on the amount of energy stored,” said Yury Gogotsi, PhD, Distinguished University and Bach Professor in Drexel’s College of Engineering and director of the A.J. Drexel Nanomaterials Institute in the Department of Materials Science and Engineering, who was a co-author of the research. “We’ve discovered adding MXene materials to the silicon anodes can stabilize them enough to actually be used in batteries.”

In batteries, charge is held in electrodes — the cathode and anode — and delivered to our devices as ions travel from anode to cathode. The ions return to the anode when the battery is recharged. Battery life has steadily been increased by finding ways to improve the electrodes’ ability to send and receive more ions. Substituting silicon for graphite as the primary material in the Li-ion anode would improve its capacity for taking in ions because each silicon atom can accept up to four lithium ions, while in graphite anodes, six carbon atoms take in just one lithium. But as it charges, silicon also expands — as much as 300 percent — which can cause it to break and the battery to malfunction.

Most solutions to this problem have involved adding carbon materials and polymer binders to create a framework to contain the silicon. The process for doing it, according to Gogotsi, is complex and carbon contributes little to charge storage by the battery.

By contrast, the Drexel and Trinity group’s method mixes silicon powder into a MXene solution to create a hybrid silicon-MXene anode. MXene nanosheets distribute randomly and form a continuous network while wrapping around the silicon particles, thus acting as conductive additive and binder at the same time. It’s the MXene framework that also imposes order on ions as they arrive and prevents the anode from expanding.

“MXenes are the key to helping silicon reach its potential in batteries,” Gogotsi said. “Because MXenes are two-dimensional materials, there is more room for the ions in the anode and they can move more quickly into it — thus improving both capacity and conductivity of the electrode. They also have excellent mechanical strength, so silicon-MXene anodes are also quite durable up to 450 microns thickness.”

MXenes, which were first discovered at Drexel in 2011, are made by chemically etching a layered ceramic material called a MAX phase, to remove a set of chemically-related layers, leaving a stack of two-dimensional flakes. Researchers have produced more than 30 types of MXene to date, each with a slightly different set of properties. The group selected two of them to make the silicon-MXene anodes tested for the paper: titanium carbide and titanium carbonitride. They also tested battery anodes made from graphene-wrapped silicon nanoparticles.

All three anode samples showed higher lithium-ion capacity than current graphite or silicon-carbon anodes used in Li-ion batteries and superior conductivity — on the order of 100 to 1,000 times higher than conventional silicon anodes, when MXene is added.

“The continuous network of MXene nanosheets not only provides sufficient electrical conductivity and free space for accommodating the volume change but also well resolves the mechanical instability of Si,” they write.  “Therefore, the combination of viscous MXene ink and high-capacity Si demonstrated here offers a powerful technique to construct advanced nanostructures with exceptional performance.”

Chuanfang Zhang, PhD, a post-doctoral researcher at Trinity and lead author of the study, also notes that the production of the MXene anodes, by slurry-casting, is easily scalable for mass production of anodes of any size, which means they could make their way into batteries that power just about any of our devices.

“Considering that more than 30 MXenes are already reported, with more predicted to exist, there is certainly much room for further improving the electrochemical performance of battery electrodes by utilizing other materials from the large MXene family,” he said.

Tags:  Batteries  Battery  Chuanfang Zhang  Drexel University  Graphene  Li-ion batteries  Trinity College in Ireland  Yury Gogotsi 

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THE SECRET LIFE OF BATTERIES

Posted By Graphene Council, The Graphene Council, Friday, February 22, 2019
Updated: Friday, February 22, 2019

Koffi Pierre Yao, a new assistant professor of mechanical engineering at the University of Delaware, is uncovering novel insights about what happens inside the batteries that power our smartphones, laptops, and electric vehicles. He plans to use this knowledge to develop faster-charging batteries that make electric vehicles the go-to automobiles for drivers.

Several of today’s electric vehicles, such as the Tesla Model 3 and Nissan Leaf, run on lithium-ion batteries. But it takes inconveniently too long to recharge those vehicles when you can fill up your gas tank in the time it takes to pick up gas-station coffee. In a lithium-ion battery, positively charged lithium ions move through the electrode to deliver energy.

Scientists all over the world do time-consuming research on lithium-ion batteries in an attempt to optimize these power units. “Usually people will make an electrode, test it, make another one, test it, and so on, and it’s kind of a serial process,” said Yao.

Instead, Yao uses physical probes to look inside batteries while they work and develop a direct physical understanding of how lithium ions flow within batteries. When a battery is charging, the lithium flows unevenly in a way that’s difficult to measure. Yao started working on this while he was a postdoctoral associate at Argonne National Laboratory (ANL), a position he held from 2016 until 2018, when he joined UD’s faculty.

In a new paper published in Energy & Environmental Science, a journal published by the Royal Society of Chemistry, Yao describes how he and his colleagues at ANL used X-rays to get a micron-scale movie of how lithium distributes within the electrode while lithium-ion batteries are running.

“We put an industrial-grade battery under an X-ray beam and mapped the distribution of the lithium within the electrodes,” he said.



Yao and his colleagues knew that the lithium did not distribute homogeneously. Imagine a group of people running through a small doorway. It takes time for people to spread out into the interior of the room; therefore, there will be crowding at the entry point. That’s similar to how lithium moves through the electrode. Still, Yao and his colleagues were surprised at the extent to which lithium scattered inhomogeneously.

The goal is to use this knowledge to reduce testing time and speed up the research and development (R&D) process for these batteries.

In another new paper published in Advanced Energy Materials, Yao describes how he and his colleagues used X-rays to quantify the activity in a silicon-graphite electrode. Cell phone batteries typically contain graphite, but silicon offers some potential benefits over graphite.

“We’re interested in silicon because it can increase the capacity of the electrode by a factor of 10 compared to graphite,” he said. However, silicon is less stable than graphite and degrades faster, so a blend of the two may prove to be a viable solution. “Some of the lithium goes into the graphite, and some goes into the silicon,” he said.

Yao and his colleagues sought to discover exactly where the lithium ions traveled within this blended electrode.

“It’s something people haven’t previously been able to do in the literature,” Yao said. “We provide a clear picture of which of silicon and graphite plays host to lithium at any point in time. Now we can go forward and manipulate this pattern to stabilize the cycling.” This knowledge can help Yao in his quest to design novel particles to make faster-charging and higher energy batteries.

At UD, Yao plans to expand upon his research on batteries with his colleagues at the Center for Fuel Cells and Batteries and more. Yao received his master’s and doctoral degrees in mechanical engineering from the Massachusetts Institute of Technology (MIT) and his bachelor’s degree in mechanical engineering at UD. As an undergraduate at UD, he was mentored by Ajay Prasad, Engineering Alumni Distinguished Professor and Chair of Engineering, who introduced him to electric cars and electrochemistry, and the science behind them.

Tags:  Batteries  Graphene  Koffi Pierre Yao  Li-ion Batteries  Lithium  University of Delaware 

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Further gains from Talga high energy battery anode product

Posted By Graphene Council, The Graphene Council, Tuesday, February 19, 2019
Updated: Tuesday, February 19, 2019

Australian advanced materials technology company, Talga Resources is pleased to announce further test results from its high energy graphene silicon lithium ion ("Li-ion") battery anode product Talnode™-Si.



Following initial test results (Oct 2018) further optimisation of Talnode-Si, with up to 15% silicon loading, has been underway at Talga's battery material facility in the Maxwell Centre of Cambridge University, UK. Highlights of new half cell cycling test results include:

• ~70% higher reversible capacity (~600mAh/g) than commercial graphite (~350mAh/g)*

• Coulombic efficiency of 99.5% - 99.9% with first cycle efficiency ~ 91%

• Up to 94% reversible capacity (after >130 cycles in a range of silicon loadings)

Talga Managing Director, Mr Mark Thompson: "The rapid development of our natural graphite anode products for Li-ion batteries have been extraordinary and the continued positive market response to products under development, Talnode-Si and Talnode-X, as well as our flagship product, Talnode-C, support plans for scaling up of Talnode products as part of our vertically integrated business strategy."

Moving Forward

Talnode-Si consists of a mixture of silicon and graphene particles engineered by Talga to be suitable for existing Li-ion battery manufacturing equipment as a high performance, cost-effective and scalable replacement for standard graphite anode materials. Commercial samples are being prepared, under confidentiality and material transfer agreements, with delivery commencing end of February 2019. Recipients include some of the world's largest electronics companies.

Development continues under the Safevolt project, a part of the £246 million UK-funded Faraday program, with Talga partners Johnson Matthey, Cambridge University and TWI. Based on the encouraging test results to date the Company has opted to progress to full cell testing and optimisation of Talnode-Si. Progress on the other Faraday projects, "Scale-up" and "Sodium" is continuing according to plan and updates will be provided as the programs proceed through their individual project stages.

Tags:  batteries  Graphene  Li-ion batteries  Mark Thompson  Talga Resources 

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Nanotech Energy, the UCLA Energy Incubator and Holder of First Patent for Graphene Announces Profound Achievement in Production of High Quality Graphene Based Materials

Posted By Graphene Council, The Graphene Council, Tuesday, January 29, 2019
Updated: Tuesday, January 29, 2019
Nanotech Energy, a leading supplier of graphene, graphene oxide and graphene super batteries, announced today that it has cleared a monumental hurdle in the production of high-quality graphene-based materials. The first patent for Graphene, now exclusively licensed to Nanotech Energy, was filed in 2002 by Dr. Richard Kaner, Nanotech co-founder and UCLA professor of Chemistry and of Materials Science and Engineering.

Through its proprietary technology, Nanotech Energy is now able to produce graphene with an unsurpassed surface area of over 2,500 meters squared per gram, almost the theoretical limit. A second version of graphene with a surface area of 2,000 to 2,200 meters squared per gram, measured by methylene blue adsorption is available for purchase based on downstream application, while the other version of over 2,500 meters squared per gram is being used only for Nanotech’s downstream products.

Graphene is a single layer of carbon with a theoretical surface area limit of slightly over 2,600 meters squared per gram. The surface area determines how many electrons can be stored and, in turn, how much energy can be stored in batteries and supercapacitors. Without the large surface area, graphene loses most of its superlatives and behaves just like graphite.

Jack Kavanaugh, Nanotech founder and CEO said, ”Nanotech Energy has created a remarkable technology that reaches the boundaries of superior energy density, power density, cycle life and, most importantly, safety. It’s an exciting time for the company and the industry.”

Dr. Maher El-Kady added “it’s widely accepted that the properties of graphene vary depending on the number of layers. The high surface area of our graphene has potential to dramatically transform the graphene industry. We already produce super-batteries, supercapacitors, conductive inks and conductive epoxies with unprecedented performance and have responsibly extended our leads in each of those arenas by making them all safer.”

Dr. Kaner further added, “After tests have demonstrated that almost all graphene sold today is really thin layer graphite and not graphene, this is a major step forward to be able to scale real graphene with a surface area (over 2500 m 2 /g) that approaches the theoretical limit.”

Tags:  Batteries  Graphene  graphene oxide  Nanotech Energy 

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UVA researchers devise method for converting retired Li-ion anodes to graphene and GO

Posted By Terrance Barkan, Saturday, December 29, 2018

Researchers at the University of Virginia (UVA) have devised a process for converting retired Li-ion battery anodes to graphene and graphene oxide (GO). A paper on the work is published in the ACS journal Nano Letters.

Schematic illustration of the proposed smart fabrication of graphene and graphene oxide from end-of-life batteries. Zhang et al.

… accompanying the booming expansion of the Li-ion battery market, a tremendous amount of batteries retire every year and most of them are disposed of in landfills, which not only causes severe waste of precious sources but also induces hazardous soil contamination due to the plastic components and toxic electrolytes. So far, only 1% of end-of-life Li-ion batteries have been recycled. Apparently, it is an urgent necessity to develop effective battery recycling techniques. 

… A rational strategy to simultaneously solve the environmental issues from waste batteries and graphite mining is to fabricate graphene directly from end-of-life battery anodes.

 

… Here, graphite powders from end-of-life Li-ion battery anodes were used to fabricate graphene.

—Zhang et al.

Graphite powders collected from end-of-life Li-ion batteries exhibited irregular expansion because of the lithium-ion intercalation and deintercalation in the anode graphite during battery charge/discharge. 

Such lattice expansion of graphite can be considered as a prefabrication of graphene because it weakened the van der Waals bonds and facilitated the exfoliation. 

—Zhang et al.

 

This “prefabrication” process facilitates both chemical and physical exfoliations of the graphite. Comparing with the graphene oxide derived from pristine, untreated graphite, the graphene oxide from anode graphite exhibited excellent homogeneity and electrochemical properties. 

The lithiation aided pre-expansion enabled 4 times enhancement of graphene productivity by shear mixing, the researchers found. 

The graphene fabrication was seamlessly inserted into the currently used battery recycling streamline in which acid treatment was found to further swell the graphite lattice, pushing up the graphene productivity to 83.7% (10 times higher than that of pristine graphite powders).

Tags:  Batteries  Graphene  graphene oxide  Li-ion  Li-ion batteries  UVA 

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2D Fluidics Pty Ltd created to launch the Vortex Fluidic Device (VFD)

Posted By Terrance Barkan, Friday, June 22, 2018

 

Advanced materials company, First Graphene Limited (“FGR” or “the Company”) (ASX: FGR) is pleased to announce the launch of its 50%-owned associate company, 2D Fluidics Pty Ltd, in collaboration with Flinders University’s newly named Flinders Institute for NanoScale Science and Technology

 

The initial objective of 2D Fluidics will be the commercialisation of the Vortex Fluidic Device (VFD), invented by the Flinders Institute for NanoScale Science and Technology’s Professor Colin Raston. The VFD enables new approaches to producing a wide range of materials such as graphene and sliced carbon nanotubes, with the bonus of not needing to use harsh or toxic chemicals in the manufacturing process (which is required for conventional graphene and shortened carbon nanotube production). 

 

This clean processing breakthrough will also greatly reduce the cost and improve the efficiency of manufacturing these new high quality super-strength carbon materials. The key intellectual property used by 2D Fluidics comprises two patents around the production of carbon nanomaterials, assigned by Flinders University. 

 

2D Fluidics will use the VFD to prepare these materials for commercial sales, which will be used in the plastics industry for applications requiring new composite materials, and by the electronics industry for circuits, supercapacitors and batteries, and for research laboratories around the world.

 

2D Fluidics will also manufacture the VFD, which is expected to become an in-demand state-of-the-art research and teaching tool for thousands of universities worldwide, and should be a strong revenue source for the new company. 

 

Managing Director, Craig McGuckin said “First Graphene is very pleased to be partnering Professor Raston and his team in 2D Fluidics, which promises to open an exciting growth path in the world of advanced materials production. Access to this remarkably versatile invention will complement FGRs position as the leading graphene company at the forefront of the graphene revolution.” 

 

Professor Colin Raston AO FAA, Professor of Clean Technology, Flinders Institute for NanoScale Science and Technology, Flinders University said “The VFD is a game changer for many applications across the sciences, engineering and medicine, and the commercialisation of the device will have a big impact in the research and teaching arena,” Nano-carbon materials can replace metals in many products, as a new paradigm in manufacturing, and the commercial availability of such materials by 2D Fluidics will make a big impact. It also has exciting possibilities in industry for low cost production where the processing is under continuous flow, which addresses scaling up - often a bottleneck issue in translating processes into industry.

Tags:  2D Fluidics  batteries  Carbon Nanotubes  circuits  Composites  electronics  First Graphene  Graphene  Plastics  research laboratories  supercapacitors  Vortex Fluidic Device (VFD) 

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Perfect Right Limited (Oovao Powers)—Insights from Hong Kong-based Graphene Producer

Posted By Dexter Johnson, IEEE Spectrum, Friday, June 23, 2017

 

The Graphene Council’s industrial partners span from North America to Europe and all the way to Australia. But our latest industrial partner hails from Hong Kong and as such represents the Council’s first Asian corporate partner.

It is sometimes difficult to learn how Asia-based graphene producers see the graphene marketplace and how they see themselves fitting into the overall scheme of things. So our interview with Mr. Ho, Chairman of Perfect Right Limited, a subsidiary of Oovao Powers Holdings Limited, provided us with a unique opportunity to learn about an Asia-based graphene producer that moved beyond marketing materials.

What we can learn from those marketing materials is that Perfect Right Ltd. developed its low-cost process for producing high-quality graphene this year. What you will learn in this interview is what that process is, how they are functionalizing their graphene and how and when they intend to move up the graphene value chain.

The details contained in this interview will provide us with key insights on how this company sees its place in the marketplace now and well into the future.

Q: Can you please tell us what kind of process you have developed for producing a high-quality graphene in bulk quantities, i.e. chemical vapor deposition, liquid-phase exfoliation, plasma, etc.?

We synthesize graphene with an arc-discharge method.  The electric arc oven for synthesis of graphene mainly comprises two electrodes in the atmosphere of air.  The cathode and anode are both pure graphite rods. As the rods are brought close together, discharge occurs resulting in the formation of plasma.  

Q: How have you improved on one of these processes to make it produce a higher quality of graphene at bulk quantities?

We have enhanced and patented our new production method, including the modification of production equipment, which produces high quality graphene that retains graphene’s desired properties, using a low current to create the arc discharge, effectively lowering the cost of production significantly.  Our solution is also scalable, and we are able to ramp up production of our high quality graphene in accordance with market demand.  We already have full production lines running at our factory, and we plan to expand our production capability as demand for our high quality graphene ramps up.  We are continuing to fine tune various parameters in the production process, resulting in a continuous improvement in the quality of the graphene being produced in both purity and domain size, as evidenced by independent lab test results. Our production process is cost effective and completely environmentally-friendly.

For what applications have you functionalized your graphene? I see that many applications of graphene have been identified on your website, but for what specific applications are you functionalizing your graphene?

We are focused on the functionalizing graphene in the areas of energy storage, supercapacitor, coatings, and focused on utilizing the conductive properties of graphene in various applications.  We are currently working with organizations in academia and industry, developing promising applications in the areas mentioned above, and aim to have commercial applications which are ready for market within the next 12 to 18 months.

What is your business model, i.e. are you producing master batches of functionalized graphene for various device manufacturers or are you producing these functionalized graphene materials for your own device manufacturing? If so, what are those devices or technologies?

We currently have our scalable production lines producing high quality graphene for use in the applications being researched, working in collaboration with organizations in academia and industry to bring to market consumer ready solutions which maximizes the unique properties of graphene.  Our business model is to solidify and scale our graphene production, and in lock step develop commercial applications using our high quality graphene.  We believe graphene applications has so far eluded the wider consumer market due to the lack of high quality and stable graphene supply being made available at cost effective prices.  We believe our production method is the solution, as we will be able to provide high quality graphene at prices which will make the consumer applications cost effective, leading to wider adoption of graphene in even more applications. 

What are the greatest challenges your company currently faces in the marketplace, i.e. cautious customers unsure of a new material for their processes, a stable value chain, etc.?

We believe our challenges are twofold, product differentiation and application. There are numerous graphene producers in the market; however, there seems to be a wide range in terms of quality and supplies available.  We have encountered customers who are either using low quality graphene, or graphene oxide in some cases, where they are not maximizing the potential of their products.  As for application, we believe that is an issue that faces all companies in the graphene space.  Until commercial applications of graphene enhanced products become widespread and the application of graphene in products better understood, we will continue to see a fragmented industry where end users are not able to maximize the potential of graphene in their products.

What do you see as the key to success for graphene establishing a foothold for itself in the marketplace, i.e. a ‘killer app’, standardization in graphene, etc.?

We believe standardization of graphene will go a long way towards the adoption and wide spread use of graphene.  Through our market research and interaction with academia, investment funds, and potential end users, one common theme is that there is a wide range of graphene products already in the market, but the lack of standardization makes it very hard for users to compare products, or to even secure a stable supply for their own use.  Another milestone is to have a wide spread consumer facing application where the advantages of using graphene in that product is immediately recognizable.  Graphene has been in the news for some time, however there are still no breakthroughs in the areas which graphene is known to be good for, e.g. energy storage, applications taking advantage of its conductivity, etc.

Where do you see your company in the next five years?

We see ourselves as being one of the premier suppliers of high quality graphene in the Asia region, and also an enabler of the commercialization of graphene enhanced products, through our partnerships with academia and industry players.  We aim to have graphene enhanced products on the market within the next two years, and will focus on projects where the successful commercialization of that product will help push the entire graphene industry forward.

Tags:  Asia  batteries  graphene  production 

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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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Electronics Applications for Graphene Hold Great Promise

Posted By Terrance Barkan, Monday, October 31, 2016

Applications that have really spurred a huge amount of graphene and other two-dimensional (2D) material research over the years have come from the field of electronics. The fear that complementary metal–oxide–semiconductor (CMOS) technology is quickly nearing the end of its ability to ward off Moore’s Law, in which the number of transistors in a dense integrated circuit doubles approximately every two years, has been the spur for much graphene research.

However, there has always been the big problem for graphene that it does not have an intrinsic band gap. It’s a pure conductor and not a semiconductor, like silicon, capable turning on and off the flow of electrons through it. While graphene can be functionalized in a way that it does have a band gap, research for it in the field of electronics have looked outside of digital logic where an intrinsic band gap is such an advantage. 

In the stories below, we see how graphene’s unrivaled conductivity is being exploited to take advantage of its strengths rather than trying to cover up for its weaknesses.

Graphene Comes to the Rescue of Li-ion Batteries

The role of graphene in increasing the charge capacity of the electrodes in lithium-ion (Li-ion) batteries has varied. There’s been “decorated graphene” in which nanoparticles are scattered across the surface of the graphene, and graphene nanoribbons, just to name a few of the avenues that have been pursued.

Another way in which graphene has been looked at is to better enable silicon to serve as the electrode material for Li-ion batteries. Silicon is a great material for increasing the storage capacity of electrodes in Li-ion batteries, but there’s one big problem: it cracks after just few charge/discharge cycles. The aim has been to find a way to make silicon so that it’s not so brittle and can withstand the swelling and shrinking during the charge charging and discharing of lithium atoms into the electrode material In these efforts, like those out Northwestern University, the role of graphene has been to sandwich silicon between layers graphene sheets in the anode of the battery.

Now, Yi Cui from both Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory, who has been at the forefront of research to get silicon to be more flexible and durable for Li-ion batteries, has turned to graphene to solve the issue

Cui and his colleagues were able to demonstrate in research described in the journal Nature Energy, a method for to encasing each particle of silicon in a cage of graphene that enables the silicon to expand and contract without cracking. In a full-cell electrochemical test, the graphene-infused silicon anodes retained 90 percent of their charge capacity after 100 charge-discharge cycles. 

Previous attempts by Cui and many others to create nanostructured silicon has been very difficult, making mass production fairly impractical. However, based on these latest results, Cui believes that this approach is not only technologically possible, but may in fact be commercially viable.

The process involves coating the silicon particles with a layer of nickel. The nickel coating is used as the surface and the catalyst for the second step: growing the graphene. The final step of the process involves using an acid on the graphene-coated silicon particles so that the nickel is etched away.

“This new method allows us to use much larger silicon particles that are one to three microns, or millionths of a meter, in diameter, which are cheap and widely available,” Cui said in a press release. “Particles this big have never performed well in battery anodes before, so this is a very exciting new achievement, and we think it offers a practical solution.”

While a practical manufacturing approach was much needed, the technique also leads to an electrode material with very high charge capacity.

“Researchers have tried a number of other coatings for silicon anodes, but they all reduced the anode’s efficiency,” said Stanford postdoctoral researcher Kai Yan, in a press release. “The form-fitting graphene cages are the first coating that maintains high efficiency, and the reactions can be carried out at relatively low temperatures.”

Graphene Provides the Perfect Touch to Flexible Sensors

 

Photo: Someya Laboratory

Flexible sensors are the technological backbone of artificial skin technologies. The idea is that you can impart the sense of touch to a flexible sensor, making it possible to cover a prosthetic device for either a robot or replacement limb so it can feel. Creating materials that tick the boxes of flexibility, durability and sensitivity has been a challenge. Over the years, researchers have increasingly turned to nanomaterials, and graphene in particular, as a possible solution. 

Researchers at the University of Tokyo have found that nanofibers produced from a combination of carbon nanotubes and graphene overcomes some of the big problems facing flexible pressure sensors: they’re not that accurate after being bent or deformed. The researchers have suggested that the flexible sensor they have developed could provide a more accurate detection breast cancer.

In research described in the journal Nature Nanotechnology, the scientists produced their flexible sensor by employing organic transistors and a pressure sensitive nanofiber structure.

The researchers constructed the nanofiber structure using nanofibers with diameters ranging between 300 to 700 nanometers. The researchers produced the nanofibers by combining carbon nanotubes and graphene and mixing that into a flexible polymer. The nanofibers entangled with each other to form a thin, transparent structure.

In contrast to other flexible sensors in which the striving for accuracy makes the sensors too sensitive to being deformed in any way, the fibers in this new flexible sensor does not lose their accuracy in measuring pressures. These fibers achieve this because of their ability to change their relative alignment to accommodate the bending. This allows them to continue measuring pressure because it reduces the strain in individual fibers.

Tunable Graphene Plasmons Lead to Tunable Lasers

Illustration: University of Manchester

A few years ago, researchers found that the phenomenon that occurs when photons strike a metallic surface and stir up the movement of electrons on the surface to the point where the electrons form into waves—known as surface plasmons—also occurs in graphene. 

This discovery along with the ability to tune the graphene plasmons has been a big boon for the use of graphene in optoelectronic applications.  Now research out of the University of Manchester, led by Konstantin Novoselov, who along with Andre Geim were the two University of Manchester scientists who won the Nobel Prize for discovering graphene, has leveraged the ability of tuning graphene plasmons and combined it with terahertz quantum cascade lasers, making it possible to reversibly alter their emission. 

This ability to reversibly the alter the emission of quantum cascade lasers is a big deal in optoelectronic applicatiopns, such as fiber optics telecommunication technologies by offering potentially higher bandwidth capabilities.

“Current terahertz devices do not allow for tunable properties, a new device would have to be made each time requirements changed, making them unattractive on an industrial scale,” said Novoselov in a press release. “Graphene however, can allow for terahertz devices to be switched on and off, as well as altering their state.”

In research described in the journal Science, were able to manipulate the doping levels of a graphene sheet so that it generated plasmons on its surface. When this doped graphene sheet was combined with a terahertz quantum cascade laser, it became possible to tune the transmission of the laser by tuning the graphene plasmons, essentially changing the concentration of charge carriers.

Graphene Flakes Speed Up Artificial Brains

Illustration: Alexey Kotelnikov/Alamy


Researchers out of Princeton University have found that graphene flakes could be a key feature in computer chips that aim at mimicking the function of the human brain. 


In the human brain, neurons are used to transmit information by passing electrical charges through them. In artificial brains, transistors would take the place of neurons. One approach has been to construct the transistors out of lasers that would turn and off and the time intervals between the on and off states of the lasers would represent the 1s and 0s of digital logic.

One of the challenges that researchers have faced in this design is getting the time intervals between the laser pulses down to picosecond time scales, one trillionth of a second.

In research described in the journal Nature Scientific Reports, the Princeton researchers placed graphene flakes inside a semiconductor laser to act as a kind of “saturable absorber,” that absorbed photons and then was able to emit them in a quick burst. 

It turns out graphene possesses a number of properties that makes it attractive for this application. Not only can it absorb and release photons extremely quickly, but it can also work at any wavelength. What this means is that even if semiconductor lasers are emitting different colors, the graphene makes it possible for them to work together simultaneously without interfering with each other, leading to higher processing speeds.

 

 

 

 

 

Tags:  Batteries  Decorated Graphene  Electronics  Flexible Sensors  Graphene  Graphene Nanoribbons  Lasers  Li-ion  optoelectronics  Semiconductor 

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Graphene "Sandwich" Supercapcitor

Posted By Terrance Barkan, Wednesday, October 26, 2016

Ramakrishna Podila and Apparao Rao at the Clemson Nanomaterials Center, along with graduate students Jingyi Zhu and Anthony Childress, have discovered how to increase by five-fold the energy capacity of supercapacitors without sacrificing strength or durability using specially designed layers of atom-thick carbon sheets called graphene.

For the average person who may use but never see a supercapacitor, Clemson’s work means faster charging times, longer lives, a lighter power source than batteries, reduced dependency on fossil fuels, tons less air pollution and possibly lower energy prices.


Graphene sealed in a pouch with electrolytes makes a flexible supercapacitor.

Image Credit: Ashley Jones / Clemson University

 

In Geneva, Switzerland, supercapacitors power public buses two kilometers from a 15-second charge, and interest in Clemson’s research is building.

“A national research and development enterprise in India is interested in the Clemson supercapacitors and visited the Clemson Nanomaterials Institute twice. Negotiations for manufacturing supercapacitors to power a bus are in progress,” said Rao, the Robert A. Bowen Professor of Physics in the College of Science.

Other potential applications of supercapacitors are far-reaching, from regenerative braking in hybrid and electric vehicles to providing the burst of power needed to adjust the direction of turbine blades in changing wind conditions.

Capacitors, unlike batteries, deliver a lot of power over a very short time. Batteries deliver less power, but they store much more energy. Batteries store energy through a chemical reaction: ions in lithium ion batteries move between negative and positive electrodes.

“While the chemical reactions hold much energy, the ion motion in batteries is rather slow, leading to low power,” said Podila, an assistant professor in physics and astronomy in the College of Science.

Supercapacitors overcome this by storing ions on the surface of nanomaterials electrostatically, like socks sticking to towels coming out of a dryer.

Graphene, the nanomaterial used by the Clemson team, is ultrathin, a million times thinner than a human hair. It’s stronger than steel, flexible and lightweight; a sheet the size of a football field would weigh less than a gram.

“The high-surface area of graphene provides space for ion storage (high-energy) and the ions are always on the surface ready to race (high power),” Podila said. “The problem, however, has been to effectively use the high surface area.”

Often, Podila said, ions can’t access some of the spaces in nanomaterials due to lack of connectivity. Also, the electrons within some nanomaterials may limit the total energy of a supercapacitor through an effect called “quantum capacitance”.

The Clemson team created microscopic layers of graphene with nanometer-sized pores, then sandwiched them together. The pores not only open new channels for ions to access all the spaces in graphene, but they also increase the quantum capacitance.

Creating the pores in specific configurations increased storage capacity 150 percent. Then the researchers introduced two different electrolytes whose ions were smaller than the pores; one by 20 percent, the other by 55 percent.

The effect was like spreading mayo on soft, light, porous bread; the electrolytes oozed into the pores.

“Testing showed the electrolytes with the larger ions did not increase the capacity, but the smaller ions travel through the pores into untapped parts of graphene. The result was a 500 percent increase in capacity,” Zhu said.

Furthermore, the graphene retained its electrical and material properties; the bread, soaked with mayo, didn’t fall apart.

Zhu and Childress also fashioned graphene into thin, flexible electrodes and inserted them into a flexible pouch. They filled the pouch with the electrolyte containing the smaller ions and sealed it, creating a lightweight, flexible supercapacitor that withstood more than 10,000 charge-discharge cycles without any loss in performance.

Source: Clemson

Tags:  Batteries  Clemson  Energy Storage  Graphene  Supercapacitor 

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Electronics Applications for Graphene Still Hold Center Stage

Posted By Terrance Barkan, Wednesday, September 21, 2016

While membranes for separation technologies may be an attractive application for graphene, it will continue to be offered up as an alternative in electronic applications

 

The applications that have really spurred the huge amount of graphene and other two-dimensional (2D) material research over the years have come from the field of electronics. The fear that complementary metal–oxide–semiconductor (CMOS) technology is quickly nearing the end of its ability to ward off Moore’s Law, in which the number of transistors in a dense integrated circuit doubles approximately every two years, has been the spur for much graphene research.

 

However, there has always been the big problem for graphene that it does not have an intrinsic band gap. It’s a pure conductor and not a semiconductor, like silicon, capable turning on and off the flow of electrons through it. While graphene can be functionalized in a way that it does have a band gap, research for it in the field of electronics have looked outside of digital logic where an intrinsic band gap is such an advantage. 

 

In the stories below, we see how graphene’s unrivaled conductivity is being exploited to take advantage of its strengths rather than trying to cover up for its weaknesses

 

Graphene Comes to the Rescue of Li-ion Batteries

 

 

The role of graphene in increasing the charge capacity of the electrodes in lithium-ion (Li-ion) batteries has varied. There’s been “decorated graphene” in which nanoparticles are scattered across the surface of the graphene, and graphene nanoribbons, just to name a few of the avenues that have been pursued.

 

Another way in which graphene has been looked at is to better enable silicon to serve as the electrode material for Li-ion batteries. Silicon is a great material for increasing the storage capacity of electrodes in Li-ion batteries, but there’s one big problem: it cracks after just few charge/discharge cycles. The aim has been to find a way to make silicon so that it’s not so brittle and can withstand the swelling and shrinking during the charge charging and discharing of lithium atoms into the electrode material In these efforts, like those out of Northwestern University, the role of graphene has been to sandwich silicon between layers graphene sheets in the anode of the battery.

 

Now, Yi Cui from both Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory, who has been at the forefront of research to get silicon to be more flexible and durable for Li-ion batteries, has turned to graphene to solve the issue. 

 

Cui and his colleagues were able to demonstrate in research described in the journal Nature Energy, a method for to encasing each particle of silicon in a cage of graphene that enables the silicon to expand and contract without cracking. In a full-cell electrochemical test, the graphene-infused silicon anodes retained 90 percent of their charge capacity after 100 charge-discharge cycles. 

 

Previous attempts by Cui and many others to create nanostructured silicon has been very difficult, making mass production fairly impractical. However, based on these latest results, Cui believes that this approach is not only technologically possible, but may in fact be commercially viable.

 

The process involves coating the silicon particles with a layer of nickel. The nickel coating is used as the surface and the catalyst for the second step: growing the graphene. The final step of the process involves using an acid on the graphene-coated silicon particles so that the nickel is etched away.

 

“This new method allows us to use much larger silicon particles that are one to three microns, or millionths of a meter, in diameter, which are cheap and widely available,” Cui said in a press release. “Particles this big have never performed well in battery anodes before, so this is a very exciting new achievement, and we think it offers a practical solution.”

 

While a practical manufacturing approach was much needed, the technique also leads to an electrode material with very high charge capacity.

 

“Researchers have tried a number of other coatings for silicon anodes, but they all reduced the anode’s efficiency,” said Stanford postdoctoral researcher Kai Yan, in a press release. “The form-fitting graphene cages are the first coating that maintains high efficiency, and the reactions can be carried out at relatively low temperatures.”

 

Graphene Provides the Perfect Touch to Flexible Sensors

 

Flexible sensors are the technological backbone of artificial skin technologies. The idea is that you can impart the sense of touch to a flexible sensor, making it possible to cover a prosthetic device for either a robot or replacement limb so it can feel. Creating materials that tick the boxes of flexibility, durability and sensitivity has been a challenge. Over the years, researchers have increasingly turned to nanomaterials, and graphene in particular, as a possible solution. 

 

Researchers at the University of Tokyo have found that nanofibers produced from a combination of carbon nanotubes and graphene overcomes some of the big problems facing flexible pressure sensors: they’re not that accurate after being bent or deformed. The researchers have suggested that the flexible sensor they have developed could provide a more accurate detection breast cancer.

 

In research described in the journal Nature Nanotechnology, the scientists produced their flexible sensor by employing organic transistors and a pressure sensitive nanofiber structure.

 

The researchers constructed the nanofiber structure using nanofibers with diameters ranging between 300 to 700 nanometers. The researchers produced the nanofibers by combining carbon nanotubes and graphene and mixing that into a flexible polymer. The nanofibers entangled with each other to form a thin, transparent structure.

 

In contrast to other flexible sensors in which the striving for accuracy makes the sensors too sensitive to being deformed in any way, the fibers in this new flexible sensor does not lose their accuracy in measuring pressures. These fibers achieve this because of their ability to change their relative alignment to accommodate the bending. This allows them to continue measuring pressure because it reduces the strain in individual fibers.

 

Tunable Graphene Plasmons Lead to Tunable Lasers


 

  

A few years ago, researchers found that the phenomenon that occurs when photons strike a metallic surface and stir up the movement of electrons on the surface to the point where the electrons form into waves—known as surface plasmons—also occurs in graphene

 

This discovery along with the ability to tune the graphene plasmons has been a big boon for the use of graphene in optoelectronic applications. Now research out of the University of Manchester, led by Konstantin Novoselov, who along with Andre Geim were the two University of Manchester scientists who won the Nobel Prize for discovering graphene, has leveraged the ability of tuning graphene plasmons and combined it with terahertz quantum cascade lasers, making it possible to reversibly alter their emission. 

 

This ability to reversibly the alter the emission of quantum cascade lasers is a big deal in optoelectronic applicatiopns, such as fiber optics telecommunication technologies by offering potentially higher bandwidth capabilities.

 

“Current terahertz devices do not allow for tunable properties, a new device would have to be made each time requirements changed, making them unattractive on an industrial scale,” said Novoselov in a press release. “Graphene however, can allow for terahertz devices to be switched on and off, as well as altering their state.”

 

In research described in the journal Science, were able to manipulate the doping levels of a graphene sheet so that it generated plasmons on its surface. When this doped graphene sheet was combined with a terahertz quantum cascade laser, it became possible to tune the transmission of the laser by tuning the graphene plasmons, essentially changing the concentration of charge carriers.

 

Graphene Flakes Speed Up Artificial Brains


 

 

Researchers out of Princeton University have found that graphene flakes could be a key feature in computer chips that aim at mimicking the function of the human brain. 

In the human brain, neurons are used to transmit information by passing electrical charges through them. In artificial brains, transistors would take the place of neurons. One approach has been to construct the transistors out of lasers that would turn and off and the time intervals between the on and off states of the lasers would represent the 1s and 0s of digital logic.

 

One of the challenges that researchers have faced in this design is getting the time intervals between the laser pulses down to picosecond time scales, one trillionth of a second.

 

In research described in the journal Nature Scientific Reports, the Princeton researchers placed graphene flakes inside a semiconductor laser to act as a kind of “saturable absorber,” that absorbed photons and then was able to emit them in a quick burst. 

 

It turns out graphene possesses a number of properties that makes it attractive for this application. Not only can it absorb and release photons extremely quickly, but it can also work at any wavelength. What this means is that even if semiconductor lasers are emitting different colors, the graphene makes it possible for them to work together simultaneously without interfering with each other, leading to higher processing speeds.



Tags:  Batteries  Electronics  Flexible electronics  Lasers  Li-ion  Sensors 

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