22 Apr 2017
It’s time for an update on graphene, that super material of the future! Scientists have come up with some new ways of making it that are easier and cheaper than ever before.
“Fascination with this material stems from its remarkable physical properties and the potential applications these properties offer for the future. Although scientists knew one atom thick, two-dimensional crystal graphene existed, no-one had worked out how to extract it from graphite.”
Charge Your Cell Phone In 5 Seconds
Supercapacitors: They’ll enable you to charge your cell phone in 5 seconds, or an electric car in about a minute. They’re cheap, biodegradable, never wear out and as Trace’ll tell you, could be powering your life sooner than you’d think.
Still More …
Scientists cook up material 200 times stronger than steel out of soybean oil
“Many production techniques involve the use of intense heat in a vacuum, and expensive ingredients like high-purity metals and explosive compressed gases. Now a team of Australian scientists has detailed how they turned cheap everyday ingredients into graphene under normal air conditions. They said the research, published today in the journal Nature Communications, may open up a new avenue for the low-cost synthesis of the highly sought-after material.” Click on the Link below to read more:
“By 2025 the UN expects that 14% of the world’s population will encounter water scarcity.”
Graphene-oxide membranes have attracted considerable attention as promising candidates for new filtration technologies. Now the much sought-after development of making membranes capable of sieving common salts has been achieved.
New research demonstrates the real-world potential of providing clean drinking water for millions of people who struggle to access adequate clean water sources.
The new findings from a group of scientists at The University of Manchester were published today in the journal Nature Nanotechnology. Previously graphene-oxide membranes have shown exciting potential for gas separation and water filtration.
Graphene-oxide membranes developed at the National Graphene Institute have already demonstrated the potential of filtering out small nanoparticles, organic molecules, and even large salts. Until now, however, they couldn’t be used for sieving common salts used in desalination technologies, which require even smaller sieves.
Previous research at The University of Manchester found that if immersed in water, graphene-oxide membranes become slightly swollen and smaller salts flow through the membrane along with water, but larger ions or molecules are blocked.
The Manchester-based group have now further developed these graphene membranes and found a strategy to avoid the swelling of the membrane when exposed to water. The pore size in the membrane can be precisely controlled which can sieve common salts out of salty water and make it safe to drink.
As the effects of climate change continue to reduce modern city’s water supplies, wealthy modern countries are also investing in desalination technologies. Following the severe floods in California major wealthy cities are also looking increasingly to alternative water solutions.
When the common salts are dissolved in water, they always form a ‘shell’ of water molecules around the salts molecules. This allows the tiny capillaries of the graphene-oxide membranes to block the salt from flowing along with the water. Water molecules are able to pass through the membrane barrier and flow anomalously fast which is ideal for application of these membranes for desalination.
Professor Rahul Nair, at The University of Manchester said: “Realisation of scalable membranes with uniform pore size down to atomic scale is a significant step forward and will open new possibilities for improving the efficiency of desalination technology.
“This is the first clear-cut experiment in this regime. We also demonstrate that there are realistic possibilities to scale up the described approach and mass produce graphene-based membranes with required sieve sizes.”
Mr. Jijo Abraham and Dr. Vasu Siddeswara Kalangi were the joint-lead authors on the research paper: “The developed membranes are not only useful for desalination, but the atomic scale tunability of the pore size also opens new opportunity to fabricate membranes with on-demand filtration capable of filtering out ions according to their sizes.” said Mr. Abraham.
By 2025 the UN expects that 14% of the world’s population will encounter water scarcity. This technology has the potential to revolutionize water filtration across the world, in particular in countries which cannot afford large scale desalination plants.
It is hoped that graphene-oxide membrane systems can be built on smaller scales making this technology accessible to countries which do not have the financial infrastructure to fund large plants without compromising the yield of fresh water produced.
More information: Tunable sieving of ions using graphene oxide membranes, Nature Nanotechnology, nature.com/articles/doi:10.1038/nnano.2017.21
29 Jan 2017
A team of researchers at MIT has designed one of the strongest lightweight materials known, by compressing and fusing flakes of graphene, a two-dimensional form of carbon. The new material, a sponge-like configuration with a density of just 5 percent, can have a strength 10 times that of steel.
In its two-dimensional form, graphene is thought to be the strongest of all known materials. But researchers until now have had a hard time translating that two-dimensional strength into useful three-dimensional materials.
The new findings show that the crucial aspect of the new 3-D forms has more to do with their unusual geometrical configuration than with the material itself, which suggests that similar strong, lightweight materials could be made from a variety of materials by creating similar geometric features.
The findings are being reported today in the journal Science Advances, in a paper by Markus Buehler, the head of MIT’s Department of Civil and Environmental Engineering (CEE) and the McAfee Professor of Engineering; Zhao Qin, a CEE research scientist; Gang Seob Jung, a graduate student; and Min Jeong Kang MEng ’16, a recent graduate.
Other groups had suggested the possibility of such lightweight structures, but lab experiments so far had failed to match predictions, with some results exhibiting several orders of magnitude less strength than expected. The MIT team decided to solve the mystery by analyzing the material’s behavior down to the level of individual atoms within the structure. They were able to produce a mathematical framework that very closely matches experimental observations.
Two-dimensional materials—basically flat sheets that are just one atom in thickness but can be indefinitely large in the other dimensions—have exceptional strength as well as unique electrical properties. But because of their extraordinary thinness, “they are not very useful for making 3-D materials that could be used in vehicles, buildings, or devices,” Buehler says. “What we’ve done is to realize the wish of translating these 2-D materials into three-dimensional structures.”
The team was able to compress small flakes of graphene using a combination of heat and pressure. This process produced a strong, stable structure whose form resembles that of some corals and microscopic creatures called diatoms. These shapes, which have an enormous surface area in proportion to their volume, proved to be remarkably strong. “Once we created these 3-D structures, we wanted to see what’s the limit—what’s the strongest possible material we can produce,” says Qin. To do that, they created a variety of 3-D models and then subjected them to various tests. In computational simulations, which mimic the loading conditions in the tensile and compression tests performed in a tensile loading machine, “one of our samples has 5 percent the density of steel, but 10 times the strength,” Qin says.
Buehler says that what happens to their 3-D graphene material, which is composed of curved surfaces under deformation, resembles what would happen with sheets of paper. Paper has little strength along its length and width, and can be easily crumpled up. But when made into certain shapes, for example rolled into a tube, suddenly the strength along the length of the tube is much greater and can support substantial weight. Similarly, the geometric arrangement of the graphene flakes after treatment naturally forms a very strong configuration.
The new configurations have been made in the lab using a high-resolution, multimaterial 3-D printer. They were mechanically tested for their tensile and compressive properties, and their mechanical response under loading was simulated using the team’s theoretical models. The results from the experiments and simulations matched accurately.
The new, more accurate results, based on atomistic computational modeling by the MIT team, ruled out a possibility proposed previously by other teams: that it might be possible to make 3-D graphene structures so lightweight that they would actually be lighter than air, and could be used as a durable replacement for helium in balloons. The current work shows, however, that at such low densities, the material would not have sufficient strength and would collapse from the surrounding air pressure.
But many other possible applications of the material could eventually be feasible, the researchers say, for uses that require a combination of extreme strength and light weight. “You could either use the real graphene material or use the geometry we discovered with other materials, like polymers or metals,” Buehler says, to gain similar advantages of strength combined with advantages in cost, processing methods, or other material properties (such as transparency or electrical conductivity).
“You can replace the material itself with anything,” Buehler says. “The geometry is the dominant factor. It’s something that has the potential to transfer to many things.”
The unusual geometric shapes that graphene naturally forms under heat and pressure look something like a Nerf ball—round, but full of holes. These shapes, known as gyroids, are so complex that “actually making them using conventional manufacturing methods is probably impossible,” Buehler says. The team used 3-D-printed models of the structure, enlarged to thousands of times their natural size, for testing purposes.
For actual synthesis, the researchers say, one possibility is to use the polymer or metal particles as templates, coat them with graphene by chemical vapor deposit before heat and pressure treatments, and then chemically or physically remove the polymer or metal phases to leave 3-D graphene in the gyroid form. For this, the computational model given in the current study provides a guideline to evaluate the mechanical quality of the synthesis output.
The same geometry could even be applied to large-scale structural materials, they suggest. For example, concrete for a structure such a bridge might be made with this porous geometry, providing comparable strength with a fraction of the weight. This approach would have the additional benefit of providing good insulation because of the large amount of enclosed airspace within it.
Because the shape is riddled with very tiny pore spaces, the material might also find application in some filtration systems, for either water or chemical processing. The mathematical descriptions derived by this group could facilitate the development of a variety of applications, the researchers say.
More information: “The mechanics and design of a lightweight three-dimensional graphene assembly,” Science Advances, DOI: 10.1126/sciadv.1601536 , advances.sciencemag.org/content/3/1/e1601536
Researchers create perfect nanoscrolls from graphene’s imperfect form.
Water filters of the future may be made from billions of tiny, graphene-based nanoscrolls. Each scroll, made by rolling up a single, atom-thick layer of graphene, could be tailored to trap specific molecules and pollutants in its tightly wound folds. Billions of these scrolls, stacked layer by layer, may produce a lightweight, durable, and highly selective water purification membrane.
But there’s a catch: Graphene does not come cheap. The material’s exceptional mechanical and chemical properties are due to its very regular, hexagonal structure, which resembles microscopic chicken wire. Scientists take great pains in keeping graphene in its pure, unblemished form, using processes that are expensive and time-consuming, and that severely limit graphene’s practical uses.
Seeking an alternative, a team from MIT and Harvard University is looking to graphene oxide — graphene’s much cheaper, imperfect form. Graphene oxide is graphene that is also covered with oxygen and hydrogen groups. The material is essentially what graphene becomes if it’s left to sit out in open air. The team fabricated nanoscrolls made from graphene oxide flakes and was able to control the dimensions of each nanoscroll, using both low- and high-frequency ultrasonic techniques. The scrolls have mechanical properties that are similar to graphene, and they can be made at a fraction of the cost, the researchers say.
“If you really want to make an engineering structure, at this point it’s not practical to use graphene,” says Itai Stein, a graduate student in MIT’s Department of Mechanical Engineering. “Graphene oxide is two to four orders of magnitude cheaper, and with our technique, we can tune the dimensions of these architectures and open a window to industry.”
Stein says graphene oxide nanoscrolls could also be used as ultralight chemical sensors, drug delivery vehicles, and hydrogen storage platforms, in addition to water filters. Stein and Carlo Amadei, a graduate student at Harvard University, have published their results in the journalNanoscale.
Getting away from crumpled graphene
The team’s paper originally grew out of an MIT class, 2.675 (Micro/Nano Engineering), taught by Rohit Karnik, associate professor of mechanical engineering. As part of their final project, Stein and Amadei teamed up to design nanoscrolls from graphene oxide. Amadei, as a member of Professor Chad Vecitis’ lab at Harvard University, had been working with graphene oxide for water purification applications, while Stein was experimenting with carbon nanotubes and other nanoscale architectures, as part of a group led by Brian Wardle, professor of aeronautics and astronautics at MIT.
The researchers’ graphene nano scroll research originated in this MIT classes 2.674 and 2.675 (Micro/Nano Engineering Laboratory).
Video: Department of Mechanical Engineering
“Our initial idea was to make nanoscrolls for molecular adsorption,” Amadei says. “Compared to carbon nanotubes, which are closed structures, nanoscrolls are open spirals, so you have all this surface area available to manipulate.”
“And you can tune the separation of a nanoscroll’s layers, and do all sorts of neat things with graphene oxide that you can’t really do with nanotubes and graphene itself,” Stein adds.
When they looked at what had been done previously in this field, the students found that scientists had successfully produced nanoscrolls from graphene, though with very complicated processes to keep the material pure. A few groups had tried doing the same with graphene oxide, but their attempts were literally deflated.
“What was out there in the literature was more like crumpled graphene,” Stein says. “You can’t really see the conical nature. It’s not really clear what was made.”
Stein and Amadei first used a common technique called the Hummers’ method to separate graphite flakes into individual layers of graphene oxide. They then placed the graphene oxide flakes in solution and stimulated the flakes to curl into scrolls, using two similar approaches: a low-frequency tip-sonicator, and a high-frequency custom reactor.
The tip-sonicator is a probe made of piezoelectric material that shakes at a low, 20Hz frequency when voltage is applied. When placed in a solution, the tip-sonicator produces sound waves that stir up the surroundings, creating bubbles in the solution.
Similarly, the group’s reactor contains a piezoelectric component that is connected to a circuit. As voltage is applied, the reactor shakes — at a higher, 390 Hz frequency compared with the tip-sonicator — creating bubbles in the solution within the reactor.
Stein and Amadei applied both techniques to solutions of graphene oxide flakes and observed similar effects: The bubbles that were created in solution eventually collapsed, releasing energy that caused the flakes to spontaneously curl into scrolls. The researchers found they could tune the dimensions of the scrolls by varying the treatment duration and the frequency of the ultrasonic waves. Higher frequencies and shorter treatments did not lead to significant damage of the graphene oxide flakes and produced larger scrolls, while low frequencies and longer treatment times tended to cleave flakes apart and create smaller scrolls.
While the group’s initial experiments turned a relatively low number of flakes — about 10 percent — into scrolls, Stein says both techniques may be optimized to produce higher yields. If they can be scaled up, he says the techniques can be compatible with existing industrial processes, particularly for water purification.
“If you can make this in large scales and it’s cheap, you could make huge bulk samples of filters and throw them out in the water to remove all sorts of contaminants,” Stein says.
This work was supported, in part, by the Department of Defense through the National Defense Science and Engineering Graduate (NDSEG) fellowship program.
Genesis Nanotechnology, Inc. ~ “Great Things from Small Things”
Ciphers and invisible ink – many of us experimented with these when we were children. A team of Chinese scientists has now developed a clever, high-tech version of “invisible ink”. As reported in the journal Angewandte Chemie, the ink is based on carbon nitride quantum dots. Information written with this ink is not visible under ambient or UV light; however, it can be seen with a fluorescence microplate reader. The writing can be further encrypted or decrypted by quenching or recovering the fluorescence with different reagents.
Fluorescing security inks are primarily used to ensure the authenticity of products or documents, such as certificates, stock certificates, transport documents, currency notes, or identity cards. Counterfeits may cost affected companies lost profits, and the poor quality of the false products may damage their reputations. In the case of sensitive products like pharmaceuticals and parts for airplanes and cars, human lives and health may be endangered. Counterfeiters have discovered how to imitate UV tags but it is significantly harder to copy security inks that are invisible under UV light.
Researchers working with Xinchen Wang and Liangqia Guo at Fuzhou University have now introduced an inexpensive “invisible” ink that increases the security of encoded data while also making it possible to encrypt and decrypt secure information.
The new ink is based on water-soluble quantum dots, nanoscopic “heaps” of a semiconducting material. Quantum dots have special optoelectronic properties that can be controlled by changing the size of the dots.
The scientists used quantum dots made from graphitic carbon nitride. This material consists of ring systems made of carbon and nitrogen atoms linked into two-dimensional molecular layers. The structure is similar to that of graphite (or graphene), one of the forms of pure carbon, but also has semiconductor properties.
Information written with this new ink is invisible under ambient and UV light because it is almost transparent in the visible light range and emits fluorescence with a peak in the UV range. The writing only becomes visible under a microplate reader like those used in biological fluorescence tests. In addition, the writing can be further encrypted and decrypted: treatment with oxalic acid renders it invisible to the microplate reader. Treatment with sodium bicarbonate reverses this process, making the writing visible to the reader once more.
Explore further: Luminescent ink from eggs
More information: Zhiping Song et al. Invisible Security Ink Based on Water-Soluble Graphitic Carbon Nitride Quantum Dots, Angewandte Chemie International Edition (2016). DOI: 10.1002/anie.201510945
Journal reference: Angewandte Chemie Angewandte Chemie International Edition
Provided by: Angewandte Chemie
Fuel cell electric vehicles have a long way to go before they can compete with their battery EV cousins, and energy storage is a key sticking point when the fuel is hydrogen. Hydrogen is light, plentiful, and fabulously energy dense, but energy storage in a personal mobility unit racing down a crowded highway is a different kind of chicken. Safety, cost, and performance are critical sticking points, and a research team at Lawrence Berkeley Laboratory is on to a solution for at least one of those.
Energy Storage Challenges For Hydrogen Fuel Cell EVs
The US Energy Department’s 2015 annual report provides a birds-eye view of the array of energy storage solutions that are emerging for hydrogen fuel cells, including advancements in hydrogen tank technology as well as solids-based storage.
Despite the progress, according to the Energy Department, challenges still remain for stationary and portable fuel cells in terms of raising the energy storage density, and there are “significant challenges” for fuel cell EVs. The problem is this:
Hydrogen has the highest energy per mass of any fuel; however, its low ambient temperature density results in a low energy per unit volume, therefore requiring the development of advanced storage methods that have potential for higher energy density.
The Energy Department has set a goal of 2020 for achieving verifiable hydrogen storage systems for light duty fuel cell EVs that meet the driving public’s thirst for range, comfort, refueling convenience, and performance. Here are the targets:
1.8 kWh/kg system (5.5 wt.% hydrogen)
1.3 kWh/L system (0.040 kg hydrogen/L)
$10/kWh ($333/kg stored hydrogen capacity)
However, the Energy Department is already looking beyond the current state of on-road technology to meet its 2020 goal. According to the agency, the 300-mile range is being met by using compressed gas, high pressure energy storage technology, and the problem is that competing technology on the market today — primarily gasmobiles and hybrids — already exceeds that range.
To compete for consumers on the open market, the agency is pursuing a near-term goal of improving compressed gas storage, primarily by deploying fiber reinforced composites that enable 700 bar pressure.
The long term goal consists of two pathways. One is to improve “cold” compressed gas energy storage technology, and the other is to go a different route altogether and store hydrogen within materials such as sorbents, chemical hydrogen storage materials, and metal hydrides.
The Berkeley Lab Energy Storage Solution
Where were we? Oh right, Berkeley Lab. Berkeley Lab has been tackling the metal hydride pathway.
Metal hydrides are compounds that consist of a transition metal bonded to hydrogen. They are believed to be the most “technologically relevant” class of materials for storing hydrogen, partly due to the broad range of applications.
That’s the theory. The problem is that when it comes to real world performance, metal hydrides are highly sensitive to contamination and they degrade somewhat rapidly unless properly shielded.
The Berkeley Lab energy storage solution consists of a graphene “filter” encasing nanocrystals of magnesium. With the addition of the graphene layer, the magnesium crystals act as a sort of sponge for absorbing hydrogen, providing both safety and compactness without causing performance issues:
The graphene shields the nanocrystals from oxygen and moisture and contaminants, while tiny, natural holes allow the smaller hydrogen molecules to pass through. This filtering process overcomes common problems degrading the performance of metal hydrides for hydrogen storage.
Berkeley Lab has provided this photo to show off how stable the crystals are when exposed to air (for scale, the bottle cap is about the size of a thumbnail):
At one atom thick (yes, one atom), graphene is known to be an incredibly finicky material to work with. It is extremely difficult to synthesize it without defects, but that’s not a problem for this energy storage solution. The defects are actually desirable in this case. The tiny gaps enable molecules of hydrogen gas to wriggle through, but oxygen, water, and other contaminants are too large to penetrate the shield.
The new energy formula also solves another key challenge for metal hydrides. They tend to take in and dispense hydrogen at a relatively slow pace, but the Berkeley Lab solution has sped up the intake-outflow cycle significantly. That effect is attributed to the nanoscale size of the graphene-shielded crystals, which provide a greater surface area.
Energy Department Gets The Last Word?
We’ve been having a lively debate about fuel cell electric EVs over here at CleanTechnica, so let’s hear from the Berkeley Lab team:
A potential advantage for hydrogen-fuel-cell vehicles, in addition to their reduced environmental impact over standard-fuel vehicles, is the high specific energy of hydrogen, which means that hydrogen fuel cells can potentially take up less weight than other battery systems and fuel sources while yielding more electrical energy.
However, the team also makes it clear that:
More R&D is needed to realize higher-capacity hydrogen storage for long-range vehicle applications that exceed the performance of existing electric-vehicle batteries…
Among other issues, the next step for a sustainable fuel cell EV future is to develop sustainable and renewable sources for hydrogen fuel. Currently the main source of hydrogen is natural gas, which puts fuel cell EVs in the same boat as battery EVs that draw electricity from a coal or natural gas-fired grid.
Kingston, Ontario’s Grafoid Inc. has signed a Memorandum of Understanding (MOU) for the establishment of a strategic joint venture partnership with China’s largest producer and exporter of tungsten products, Xiamen Tungsten Co. Ltd., which will see Xiamen take up to a 20% equity stake in privately held Grafoid, pending the completion of due diligence which is set to conclude on May 22, 2016.
Xiamen’s equity position in Grafoid was negotiated through its parent company, Ottawa’s Focus Graphite Inc. (TSX VENTURE:FMS) (OTCQX:FCSMF) (FRANKFURT:FKC), through the purchase of up to 7 million Grafoid common shares currently held by Focus Graphite.
“In addition to providing Grafoid with a strategic partner, Grafoid’s MOU with Xiamen, has benefits for Focus Graphite. When finalized, it will provide additional funding to allow us to advance our overall mine and transformation plant financing, and potentially open the China market to Focus Graphite for additional offtake partners and the sale of value added graphite products,” said Focus Graphite CEO and Director Gary Economo.
“Specifically, this injection of funding could enable Focus Graphite to advance our Lac Knife detailed engineering and finalize the environmental permitting process” said Economo. “And, it enables us to move to the next stage in assembling our mine CAPEX financing.”
Last September, Grafoid and Focus Graphite finalized two offtake agreements for obtaining graphite concentrate from a mining project at Lac Knife in Quebec for the next 10 years, one of the priorities of the Quebec government’s Plan Nord initiative.
Focus Graphite, with 7.9 million shares, is currently Grafoid’s largest stakeholder.
The MOU will also see the establishment of Xiamen’s business office at the Grafoid Global Technology Center in Kingston, providing Xiamen with a North American base for future business expansion, as well as the establishment of a Grafoid business office in China.
Grafoid’s path to commercialization lies in its patented product, a high-quality graphene trading under the name Mesograf.
Other terms of the MOU include the desire of Xiamen to introduce a clean energy technology platform and associated technologies to the Chinese market, and the opportunity for Grafoid to bring its suite of Mesograf and Amphioxide graphene based products to China.
With the Lac Knife project moving forward, Grafoid is well positioned to supply global markets with with high purity, value-added, cost-competitive graphite products while supporting the next generation battery development platform of Grafoid, Focus Graphite, Stria Lithium Inc., and Braille Battery Inc.
With annual revenue surpassing 10.143B CNY ($1.55B US), Xiamen, a publicly traded company listed on the Shanghai Exchange (SHA:600549), is a major player in that country’s smelting, processing and exporting of tungsten and other non-ferrous metal products, the operation of rare earth business interests, and the supply of battery materials.
Grafoid currently has 17 joint partnership ventures with industrial and academic partners, including Japan’s Mitsui & Co., Hydro Quebec, Rutgers University, the University of Waterloo, and Phos Solar Systems in Greece.
Last February, Grafoid received an $8.1 million investment from the SD Tech Fund of Sustainable Development Technology Canada (SDTC) to help automate the production of Mesograf and end-product development.
Earlier this month, Professor Aiping Yu of the University of Waterloo’s Chemical Engineering department received a $450,000 Strategic Partnership Grant through the Natural Sciences and Engineering Research Council of Canada (NSERC) to help Grafoid develop an advanced graphene fiber based wearable supercapacitor
11 Mar 2016
A new type of graphene-based filter could be the key to managing the global water crisis, a study has revealed. The new graphene filter, which has been developed by Monash University and the University of Kentucky, allows water and other liquids to be filtered nine times faster than the current leading commercial filter.
According to the World Economic Forum’s Global Risks Report, lack of access to safe, clean water is the biggest risk to society over the coming decade. Yet some of these risks could be mitigated by the development of this filter, which is so strong and stable that it can be used for extended periods in the harshest corrosive environments, and with less maintenance than other filters on the market.
The research team was led by Associate Professor Mainak Majumder from Monash University. Associate Professor Majumder said the key to making their filter was developing a viscous form of graphene oxide that could be spread very thinly with a blade.
“This technique creates a uniform arrangement in the graphene, and that evenness gives our filter special properties,” Associate Prof Majumder said.
This technique allows the filters to be produced much faster and in larger sizes, which is critical for developing commercial applications. The graphene-based filter could be used to filter chemicals, viruses, or bacteria from a range of liquids. It could be used to purify water, dairy products or wine, or in the production of pharmaceuticals.
This is the first time that a graphene filter has been able to be produced on an industrial scale – a problem that has plagued the scientific community for years.
Research team member and PhD candidate, Abozar Akbari, said scientists had known for years that graphene filters had impressive qualities, but in the past they had been difficult and expensive to produce.
“It’s been a race to see who could develop this technology first, because until now graphene-based filters could only be used on a small scale in the lab,” Mr Akbari said.
Graphene is a lattice of carbon atoms so thin it’s considered to be two-dimensional. It has been hailed as a “wonder-material” because of its incredible performance characteristics and range of potential applications.
The team’s new filter can filter out anything bigger than one nanometre, which is about 100,000 times smaller than the width of a human hair.
The research has gathered interest from a number of companies in the United States and the Asia Pacific, the largest and fastest-growing markets for nano-filtration technologies.
The team’s research was supported by industry partner Ionic Industries, as well as a number of Australian Research Council grants.
Ionic Industries’ CEO, Mark Muzzin, said the next step was to get the patented graphene-based filter on the market.
“We are currently developing ways to test how the filter fares against particular contaminants that are of interest to our customers” Mr Muzzin said.
Co-author of the research and Director of the Center for Membrane Science, Professor Dibakar Bhattacharyya, from the University of Kentucky, said: “The ability to control the thickness of the filter and attain a sharper cut-off in separation, and the use of only water as the casting solvent, is a commercial breakthrough.”
Explore further: Graphene’s love affair with water
More information: Abozar Akbari et al. Large-area graphene-based nanofiltration membranes by shear alignment of discotic nematic liquid crystals of graphene oxide, Nature Communications (2016). DOI: 10.1038/ncomms10891
23 Feb 2016
Yat Li (left) and Tianyu Liu worked with researchers at Lawrence Livermore National Laboratory to develop supercapacitors using 3D-printed graphene aerogel electrodes. Credit: T. Stephens
Scientists at UC Santa Cruz and Lawrence Livermore National Laboratory (LLNL) have reported the first example of ultrafast 3D-printed graphene supercapacitor electrodes that outperform comparable electrodes made via traditional methods. Their results open the door to novel, unconstrained designs of highly efficient energy storage systems for smartphones, wearables, implantable devices, electric cars and wireless sensors.
Using a 3D-printing process called direct-ink writing and a graphene-oxide composite ink, the team was able to print micro-architected electrodes and build supercapacitors with excellent performance characteristics. The results were published online January 20 in the journal Nano Letters and will be featured on the cover of the March issue of the journal.
“Supercapacitor devices using our 3D-printed graphene electrodes with thicknesses on the order of millimeters exhibit outstanding capacitance retention and power densities,” said corresponding author Yat Li, associate professor of chemistry at UC Santa Cruz. “This performance greatly exceeds the performance of conventional devices with thick electrodes, and it equals or exceeds the performance of reported devices made with electrodes 10 to 100 times thinner.”
LLNL engineer Cheng Zhu and UCSC graduate student Tianyu Liu are lead authors of the paper. “This breaks through the limitations of what 2D manufacturing can do,” Zhu said. “We can fabricate a large range of 3D architectures. In a phone, for instance, you would only need to leave a small area for energy storage. The geometry can be very complex.”
Supercapacitors also can charge incredibly fast, Zhu said, in theory requiring just a few minutes or seconds to reach full capacity. In the future, the researchers believe newly designed 3D-printed supercapacitors will be used to create unique electronics that are currently difficult or even impossible to make using other synthetic methods, including fully customized smartphones and paper-based or foldable devices, while at the same time achieving unprecedented levels of performance.
According to Li, several key breakthroughs made these novel devices possible, starting with the development of a printable graphene-based ink. Modification of the 3D printing scheme to be compatible with aerogel processing made it possible to maintain the important mechanical and electrical properties of single graphene sheets in the 3D-printed structures. Finally, the use of 3D printing to intelligently engineer periodic macropores into the graphene electrode significantly enhances mass transport, allowing the device to support much faster charge/discharge rates without degrading its capacity.
“This work provides an example of how 3D-printed materials such as graphene aerogels can significantly expand the design space for fabricating high-performance and fully integrable energy storage devices optimized for a broad range of applications,” Li said.
The advantages of graphene-based inks include their ultrahigh surface area, lightweight properties, elasticity, and superior electrical conductivity. The graphene composite aerogel supercapacitors are also extremely stable, the researchers reported, capable of nearly fully retaining their energy capacity after 10,000 consecutive charging and discharging cycles.
“Graphene is a really incredible material because it is essentially a single atomic layer that can be created from graphite. Because of its structure and crystalline arrangement, it has really phenomenal capabilities,” said LLNL materials engineer Eric Duoss.
Over the next year, the researchers intend to expand the technology by developing new 3D designs, using different inks, and improving the performance of existing materials.
Explore further: Energy storage of the future
More information: Cheng Zhu et al. Supercapacitors Based on Three-Dimensional Hierarchical Graphene Aerogels with Periodic Macropores, Nano Letters (2016). DOI: 10.1021/acs.nanolett.5b04965
Graphene is a single-atomic carbon sheet with a hexagonal honeycomb network. Electrons in graphene take a special electronic state called Dirac-cone where they behave as if they have no mass. This allows them to flow at very high speed, giving graphene a very high level of electrical conductivity.
This is significant because electrons with no mass flowing with no resistance in graphene could lead to the realization of an ultimately high-speed nano electronic device.
The collaborative team of Tohoku University and the University of Tokyo has developed a method to grow high-quality graphene on a silicon carbide (SiC) crystal by controlling the number of graphene sheets. The team fabricated bilayer graphene with this method and then inserted calcium (Ca) atoms between the two graphene layers like a sandwich.
They measured the electrical conductivity with the micro four-point probe method and found that the electrical resistivity rapidly drops at around 4 K (-269 °C), indicative of an emergence of superconductivity.
The team also found that neither genuine bilayer graphene nor lithium-intercalated bilayer graphene shows superconductivity, indicating that the superconductivity is driven by the electron transfer from Ca atoms to graphene sheets.
The success in fabricating superconducting graphene is expected to greatly impact both the basic and applied researches of graphene.
It is currently not clear what phenomenon takes place when the Dirac electrons with no mass become superconductive with no resistance. But based on the latest study results, further experimental and theoretical investigations would help to unravel the properties of superconducting graphene.
The superconducting transition temperature (Tc) observed in this study on Ca-intercalated bilayer graphene is still low (4 K). This prompts further studies into ways to increase Tc, for example, by replacing Ca with other metals and alloys, or changing the number of graphene sheets.
From the application point of view, the latest results pave the way for the further development of ultrahigh-speed superconducting nano devices such as a quantum computing device, which utilizes superconducting graphene in its integrated circuit.
- Satoru Ichinokura, Katsuaki Sugawara, Akari Takayama, Takashi Takahashi, Shuji Hasegawa. Superconducting Calcium-Intercalated Bilayer Graphene. ACS Nano, 2016; DOI: 10.1021/acsnano.5b07848