prezintă un nou tip de material metalic extrem de puternic, dar ductil;
contribuie astfel la proiectarea viitoare a componentelor metalice cu foi mai subțiri, ajutând astfel la economisirea resurselor
În majoritatea cazurilor, ei au observat că materialul compozit rezultat poate fi întins într-o măsură mai mare și cu o forță mai mare înainte de a se rupe. Într-adevăr, adăugarea a doar o zecime dintr-un procent de grafen a fost tot ce a fost necesar pentru a face cauciucul cu 50% mai puternic.”În acest caz, am făcut un compozit de cauciuc, care este moale și elastic, dar fragil, cu grafen și materialul rezultat este atât mai puternic și mai stretchier”.
| Posted: May 20, 2016 | |
Graphene makes rubber more rubbery(Nanowerk News) In an article published in Carbon („Graphene and water-based elastomers thin-film composites by dip-moulding”), Dr Aravind Vijayaraghavan and Dr Maria Iliut from Manchester have shown that adding a very small amount of graphene, the world’s thinnest and strongest material, to rubber films can increase both their strength and the elasticity by up to 50%. Thin rubber films are ubiquitous in daily life, used in everything from gloves to condoms. |
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| Graphene rubber rings. | |
| In their experiments, the scientists tested two kinds of rubbery materials – natural rubber, comprised of a material called polyisoprene, and a man-made rubber called polyurethane. To these, they added graphene of different kinds, amounts and size. | |
| In most cases, it they observed that the resulting composite material could be stretched to a greater degree and with greater force before it broke. Indeed, adding just one tenth of one percent of graphene was all it took to make the rubber 50% stronger. | |
| Dr Vijayaraghavan, who leads the Nano-functional Materials Group, explains “A composite is a material which contains two parts, a matrix which is soft and light and a filler which is strong. Taken together, you get something which is both light and strong. This is the principle behind carbon fibre composites used in sports cars, or Kevlar composites used in body armour. | |
| “In this case, we have made a composite of rubber, which is soft and stretchy but fragile, with graphene and the resulting material is both stronger and stretchier.” | |
| Dr Maria Iliut, a research associate in Dr Vijayaraghavan’s group, describes how this material is produced: “We use a form of graphene called graphene oxide, which unlike graphene is stable as a dispersion in water. The rubber materials are also in a form that is stable in water, allowing us to combine them before forming thin films with a process called dip moulding.” | |
| “The important thing here is that because these films are so thin, we need a strengthening filler which is also very thin. Fortunately, graphene is both the thinnest and strongest material we know of.” | |
| The project emerged from a call by the Bill & Melinda Gates Foundation, to develop a more desirable condom. According to Dr Vijayaraghavan, this composite material has tremendous implications in daily life. | |
| He adds “Our thinking was that if we could make the rubber used in condoms stronger and stretchier, then you could use that to make even thinner condoms which would feel better without breaking. | |
| “Similar arguments can be made for using this material to make better gloves, sportswear, medical devices and so on. We are seeing considerable industrial interest in this area and we hope more companies will want to get involved in the commercial opportunities this research could create.” |
| Source: The University of Manchester |
pentru prima dată, două tipuri de compozite de lemn foarte anizotropice, foarte transparente, sunt demonstrate prin utilizarea avantajelor macrostructurilor din lemn original
Wellbores forate pentru a extrage petrol și gaz pot fi armate în mod dramatic cu o cantitate mică de nanofibre modificate de grafină adăugate la un polimer și cu microunde, potrivit cercetătorilor Universității Rice
au combinat nanoribonii cu un polimer termosetat pe bază de ulei destinat să facă fântâni mai stabile și să reducă costurile de producție. Atunci când se vindecă cu microunde cu putere redusă care ies din ansamblul burghiu, compozitul va conecta fracturile microscopice care permit fluidului de foraj să treacă și să destabilizeze pereții.
| Posted: May 13, 2016 | |
Microwaved nanoribbons may bolster oil and gas wells(Nanowerk News) Wellbores drilled to extract oil and gas can be dramatically reinforced with a small amount of modified graphene nanoribbons added to a polymer and microwaved, according to Rice University researchers. |
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| The Rice labs of chemist James Tour and civil and environmental engineer Rouzbeh Shahsavari combined the nanoribbons with an oil-based thermoset polymer intended to make wells more stable and cut production costs. When cured in place with low-power microwaves emanating from the drill assembly, the composite would plug the microscopic fractures that allow drilling fluid to seep through and destabilize the walls. | |
| Results of their study appeared in the American Chemical Society journal ACS Applied Materials and Interfaces („Microwave Heating of Functionalized Graphene Nanoribbons in Thermoset Polymers for Wellbore Reinforcement”). | |
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| Rice University researchers have developed a method to treat composite materials of graphene nanoribbons and thermoset polymers with microwaves in a way that could dramatically reinforce wellbores for oil and gas production. (Image: Nam Dong Kim/Rice University) (click on image to enlarge) | |
| The researchers said that in the past, drillers have tried to plug fractures with mica, calcium carbonate, gilsonite and asphalt to little avail because the particles are too large and the method is not efficient enough to stabilize the wellbore. | |
| In lab tests, a polymer-nanoribbon mixture was placed on a sandstone block, similar to the rock that is encountered in many wells. The team found that rapidly heating the graphene nanoribbons to more than 200 degrees Celsius with a 30-watt microwave was enough to cause crosslinking in the polymer that had infiltrated the sandstone, Tour said. The microwave energy needed is just a fraction of that typically used by a kitchen appliance, he said. | |
| „This is a far more practical and cost-effective way to increase the stability of a well over a long period,” Tour said. | |
| In the lab, the nanoribbons were functionalized – or modified – with polypropylene oxide to aid their dispersal in the polymer. Mechanical tests on composite-reinforced sandstone showed the process increased its average strength from 5.8 to 13.3 megapascals, a 130 percent boost in this measurement of internal pressure, Shahsavari said. Similarly, the toughness of the composite increased by a factor of six. | |
| „That indicates the composite can absorb about six times more energy before failure,” he said. „Mechanical testing at smaller scales via nanoindentation exhibited even more local enhancement, mainly due to the strong interaction between nanoribbons and the polymer. This, combined with the filling effect of the nanoribbon-polymer into the pore spaces of the sandstone, led to the observed enhancements.” | |
| The researchers suggested a low-power microwave attachment on the drill head would allow for in-well curing of the nanoribbon-polymer solution. |
| Source: Rice University |
metodă eficientă de răcire a electronicii prin utilizarea nanoflacilor grafeni funcționali
| Posted: Apr 29, 2016 | |
Cooling graphene-based film close to pilot-scale production(Nanowerk News) Heat dissipation in electronics and optoelectronics is a severe bottleneck in the further development of systems in these fields. To come to grips with this serious issue, researchers at Chalmers University of Technology have developed an efficient way of cooling electronics by using functionalized graphene nanoflakes. The results will be published in the renowned journal Nature Communications(„Functionalization mediates heat transport in graphene nanoflakes”). |
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| Functionalization mediates heat transport of graphene nanoflakes. (Image: Johan Liu, credit: Philip Krantz, Krantz Nanoart) | |
| „Essentially, we have found a golden key with which to achieve efficient heat transport in electronics and other power devices by using graphene nanoflake-based film. This can open up potential uses of this kind of film in broad areas, and we are getting closer to pilot-scale production based on this discovery,” says Johan Liu, Professor of Electronics Production at Chalmers University of Technology in Sweden. | |
| The researchers studied the heat transfer enhancement of the film with different functionalized amino-based and azide-based silane molecules, and found that the heat transfer efficiency of the film can be improved by over 76 percent by introducing functionalization molecules, compared to a reference system without the functional layer. This is mainly because the contact resistance was drastically reduced by introducing the functionalization molecules. | |
| Meanwhile, molecular dynamic simulations and ab initio calculations reveal that the functional layer constrains the cross-plane scattering of low-frequency phonons, which in turn enhances in-plane heat-conduction of the bonded film by recovering the long flexural phonon lifetime. The results suggested potential thermal management solutions for electronic devices. | |
| In the research, scientists studied a number of molecules that were immobilized at the interfaces and at the edge of graphene nanoflake-based sheets forming covalent bonds. They also probed interface thermal resistance by using a photo-thermal reflectance measurement technique to demonstrate an improved thermal coupling due to functionalization. | |
| „This is the first time that such systematic research has been done. The present work is much more extensive than previously published results from several involved partners, and it covers more functionalization molecules and also more extensive direct evidence of the thermal contact resistance measurement,” says Johan Liu. |
| Source: Chalmers University of Technology |
Read more: Cooling graphene-based film close to pilot-scale production
Ele pot fi depozitate direct pe materiale ca straturi subtiri facut sunt de 50 de ori mai subtire decat un fir de păr uman, astfel încât nu este nevoie să producă siliciu«napolitana»celule și să le interconecta separat“, a adăugat el. „Ei, de asemenea, să răspundă mai bine decât siliciu la lungimi de unda albastru de lumină, și pot fi stivuite ca un film subțire pe partea de sus a celulelor de siliciu pentru a îmbunătăți performanța generală În cele din urmă.“
Prin posibilitatea de a depozita celule solare CZTS pe diverse suprafețe, echipa Hao cred că acest lucru le pune ferm pe drumul de a face celule fotovoltaice thin-film facut poate fi rigid sau flexibil și durabil și suficient de ieftine pentru a fi integrate pe scară largă în clădiri pentru a genera energie electrică de greve lumina soarelui au structuri, cum ar fi: geamuri, fațade, țigle și ferestre.
| Posted: Apr 28, 2016 | |
At last: Non-toxic and cheap thin-film solar cells for zero-energy buildings(Nanowerk News) ‘Zero-energy’ buildings – which generate as much power as they consume – are now much closer after a team at Australia’s University of New South Wales achieved the world’s highest efficiency using flexible solar cells that are non-toxic and cheap to make. |
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| Until now, the promise of ‘zero-energy’ buildings been held back by two hurdles: the cost of the thin-film solar cells (used in façades, roofs and windows), and the fact they’re made from scarce, and highly toxic, materials. | |
| That’s about to change: the UNSW team, led by Dr Xiaojing Hao of the Australian Centre for Advanced Photovoltaics at the UNSW School of Photovoltaic and Renewable Energy Engineering, have achieved the world’s highest efficiency rating for a full-sized thin-film solar cell using a competing thin-film technology, known as CZTS. | |
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| The new high-efficiency, low-toxicity solar cells developed by UNSW’s Australian Centre for Advanced Photovoltaics. (Image: Robert Largent/UNSW) | |
| NREL, the USA’s National Renewable Energy Laboratory, confirmed this world leading 7.6% efficiency in a 1cm2 area CZTS cell this month. | |
| Unlike its thin-film competitors, CZTS cells are made from abundant materials: copper, zinc, tin and sulphur. | |
| And CZTS has none of the toxicity problems of its two thin-film rivals, known as CdTe (cadmium-telluride) and CIGS (copper-indium-gallium-selenide). Cadmium and selenium are toxic at even tiny doses, while tellurium and indium are extremely rare. | |
| „This is the first step on CZTS’s road to beyond 20% efficiency, and marks a milestone in its journey from the lab to commercial product,” said Hao, named one of UNSW’s 20 rising stars last year. „There is still a lot of work needed to catch up with CdTe and CIGS, in both efficiency and cell size, but we are well on the way.” | |
| „In addition to its elements being more commonplace and environmentally benign, we’re interested in these higher bandgap CZTS cells for two reasons,” said Professor Martin Green, a mentor of Dr Hao and a global pioneer of photovoltaic research stretching back 40 years. | |
| „They can be deposited directly onto materials as thin layers that are 50 times thinner than a human hair, so there’s no need to manufacture silicon ‘wafer’ cells and interconnect them separately,” he added. „They also respond better than silicon to blue wavelengths of light, and can be stacked as a thin-film on top of silicon cells to ultimately improve the overall performance.” | |
| By being able to deposit CZTS solar cells on various surfaces, Hao’s team believe this puts them firmly on the road to making thin-film photovoltaic cells that can be rigid or flexible, and durable and cheap enough to be widely integrated into buildings to generate electricity from the sunlight that strikes structures such as glazing, façades, roof tiles and windows. | |
| However, because CZTS is cheaper – and easier to bring from lab to commercialisation than other thin-film solar cells, given already available commercialised manufacturing method – applications are likely even sooner. UNSW is collaborating with a number of large companies keen to develop applications well before it reaches 20% efficiency – probably, Hao says, within the next few years. | |
| „I’m quietly confident we can overcome the technical challenges to further boosting the efficiency of CZTS cells, because there are a lot of tricks we’ve learned over the past 30 years in boosting CdTe and CIGS and even silicon cells, but which haven’t been applied to CZTS,” said Hao. | |
| Currently, thin-film photovoltaic cells like CdTe are used mainly in large solar power farms, as the cadmium toxicity makes them unsuitable for residential systems, while CIGS cells is more commonly used in Japan on rooftops. | |
| First Solar, a US$5 billion behemoth that specialises in large-scale photovoltaic systems, relies entirely on CdTe; while CIGS is the preferred technology of China’s Hanergy, the world’s largest thin-film solar power company. | |
| Thin-film technologies such as CdTe and CIGS are also attractive because they are physically flexible, which increases the number of potential applications, such as curved surfaces, roofing membranes, or transparent and translucent structures like windows and skylights. | |
| But their toxicity has made the construction industry – mindful of its history with asbestos – wary of using them. Scarcity of the elements also renders them unattractive, as price spikes are likely as demand rises. Despite this, the global market for so-called Building-Integrated Photovoltaics (BIPV) is already valued at US$1.6 billion. | |
| Hao believes CZTS’s cheapness, benign environmental profile and abundant elements may be the trigger that finally brings architects and builders onboard to using thin-film solar panels more widely in buildings. | |
| Until now, most architects have used conventional solar panels made from crystalline silicon. While these are even cheaper than CZTS cells, they don’t offer the same flexibility for curved surfaces and other awkward geometries needed to easily integrate into building designs. |
| Source: University of New South Wales |
Read more: At last: Non-toxic and cheap thin-film solar cells for zero-energy buildings
DARPA caută idei inovatoare pentru valorificarea noilor materiale și metode de fabricare.Materialele avansate încorporează din ce în ce mai multe proprietăți contraintuitive, cum ar fi rezistența excesivă și super-ușurință, în timp ce producția de aditivi și alte tehnologii noi îmbunătățesc enorm capacitatea de a modela aceste materiale noi în forme care anterior ar fi fost extrem de costisitoare sau chiar imposibil de creat
au creat un material complet nou, în care pot coexista proprietăți complet contradictorii.
Compusul, despre care cercetatorii au descris intr-un studiu publicat 20 aprilie de revista Nature ( „Metalele polar prin design geometric” ), este un metal polar.
| Posted: Apr 21, 2016 | |
New material combines useful, typically incompatible properties(Nanowerk News) Mild-mannered Dr. Jekyll and malicious Mr. Hyde were opposite aspects of the same man, and their story ended in tragedy because the two couldn’t peacefully coexist. |
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| Most materials, too, are capable of being only one thing at a time, but a team of engineers and physicists at the University of Wisconsin-Madison have created an entirely new material in which completely contradictory properties can coexist. | |
| The compound, which the researchers described in a study published April 20 by the journal Nature („Polar metals by geometric design”), is a polar metal. | |
| „Polar metals should not be possible,” says Chang-Beom Eom, the professor of materials science and engineering who led the research. | |
| Undeterred by the laws of the universe, Eom and colleagues created a compound that is a scientific oxymoron. Through a new synthesis approach supported by computational modeling, the group made a crystal with multiple personalities: part polar, part metallic. | |
| Metals conduct electricity because electrons flow freely throughout them. Polar materials, by contrast, impede the free flow of electrons and work as electrical insulators. | |
| Eom’s team needed to find something that can demonstrate both insulating and conducting properties. First, they separated the polar and metallic parts of the crystal. Some electrons gave rise to the metallic nature, moving within the material to conduct electricity. Other electrons contributed to the polar properties. | |
| However, because the natural molecular structure of the material is symmetrical, even after separating the two components, the material as a whole would not act polar. Equal and opposite arrangements of electrons canceled each other out. To overcome this obstacle, the researchers synthesized the substance with slightly off-kilter atoms, which threw off the internal symmetry enough to make the material polar. | |
| „The initial calculations that the theory suggested did not show the polar nature so we experimentally tested the materials, then went back and improved the models,” says Eom. „We looped between theory and experiments, but most importantly, we actually created the material, demonstrated its polar and metallic properties, and developed an understanding of how this is happening.” | |
| Ultimately, Eom and colleagues made the polar metal by painstakingly growing thin films of material one atom at a time. Crucially, they grew the substance on top of a supporting lattice with a slightly offset molecular organization. Tightly clamping the growing film to this support skewed the internal arrangement of their material, stabilizing its internal geometry in the asymmetrical orientation necessary to maintain polarity. | |
| Synthesizing and characterizing this first-of-its-kind material required patience and precision. The researchers counted every atom deposited on the surface, as the substance slowly grew one layer at a time. They then used multiple complex optical and electronic and structural measurements to determine its properties. | |
| Their approach is an attempt to accelerate the discovery of multifunctional materials with unusual coexisting properties, paving the way to devices with the ability to perform simultaneous electrical, magnetic and optical functions. | |
| „This has been a complex effort, and theoretical and experimental contributions from all collaboration members has been essential. The project would not succeed otherwise,” says Eom. |
| Source: University of Wisconsin-Madison |
Cercetătorii au testat cămășile comerciale atletice în care nanoparticulele de argint au fost încorporate într-unul din cele patru moduri diferite;Cercetătorii spun, de asemenea, că argintul rămas va curge în timp când hainele sunt aruncate în depozitele de deșeuri
cercetatorii au demonstrat ca noul material , realizat din tuburi de carbon mici, emite fotonii doriti la temperatura camerei
