În munca care are ca scop protejarea soldaților de amenințările biologice și chimice, o echipă de cercetători ai Lawrence Livermore National Laboratory a creat un material care este foarte respirabil, dar protector de agenți biologici
Inginerii aerospațiali MIT au găsit o modalitate de a lega straturile compozite, producând un material care este substanțial mai puternic și mai rezistent la deteriorare decât alte compozite avansate
Acest material este prima componentă cheie a uniformelor futuriste inteligente, care vor răspunde și vor proteja împotriva pericolelor chimice de mediu
materiale comestibile pentru fabricarea acoperirilor superhidrofobe într-un proces simplu, ieftin, scalabil, într-un singur pas.Acoperirile superhidrofobe nu sunt noi, dar în mod obișnuit sunt fabricate cu fluorocarburi
Materialul este silicena, cea mai subțire formă posibilă de siliciu, compusă dintr-un strat bidimensional de cristale de siliciu.
Electronii se deplasează ultra-rapid în siliciu, reducând energia necesară pentru acționarea dispozitivelor electronice și deschizând calea pentru electronice și mai mici, flexibile, transparente și cu consum redus de energie.
| Posted: Aug 01, 2016 | |
Peeling off the silicene layers for new electronics(Nanowerk News) Much like an overcooked dinner, the next so-called wonder material for next-generation electronics has been ‘stuck to the pan’ until researchers at the UOW’s Institute for Superconducting and Electronic Materials (ISEM) came up with a breakthrough solution. |
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| The material is silicene, the thinnest possible form of silicon, comprised of a two-dimensional layer of silicon crystals. | |
| Electrons move ultrafast in silicene, reducing the energy required to drive electronic devices and paving the way for even smaller, flexible, transparent and low-energy-cost electronics. | |
| Until now, silicene has been ‘grown’ on a metal surface, but researchers had no proven way of freeing it from the substrate to create a freestanding material that could then be incorporated into electronic devices and components. | |
| ISEM Research Fellow Dr Yi Du and his team have used oxygen to separate a single-atom thick layer of silicon from its surface, overcoming the key hurdle preventing the production of a material with potential to supercharge electronics. | |
| “We know silicene crystals prefer to firmly attach on the metallic substrate and because they are too thin to be peeled off by any mechanical tools, it’s impossible to remove them from the substrate,” Dr Du said. | |
| Researchers have experimented with the idea of using ‘chemical scissors’ to break the bond between silicene and the substrate and the breakthrough for Dr Du and his team came through using oxygen molecules as chemical scissors to cut the silicene from its substrate. | |
| The work, supported by the Australian Research Council (ARC), involves several special techniques that can be done only at ISEM with the help of its powerful tools, including a scanning tunneling microscope, which creates an ultra-high vacuum environment about a hundred times higher than the vacuum level experienced in orbit at the International Space Station. | |
| “Because the vacuum levels are so high, we can inject the oxygen molecules into the chamber and they become a ‘molecular flux’ that follows a straight pathway,” Dr Du said. | |
| “This allows us to direct these molecules precisely into the silicene layers, acting like scissors to separate the silicene.” | |
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| Injecting oxygen molecules precisely into the silicene layers creates ‘scissors’ that separate the silicene from the metal surface. | |
| The result is a layer of freestanding silicene – with an appearance much like a honeycomb lattice – that could be transferred to an insulating substrate to make advanced transistors. | |
| The theory for two-dimensional silicene was introduced in 1994 but it wasn’t until 2012 that scientists, including a team at UOW, successfully fabricated silicene in the lab. | |
| Silicene is emerging player in the super-materials category, alongside graphene, which is a single-atom thick layer of carbon. | |
| Graphene has been shown to be the fastest conductor of electricity yet found, faster than commonly used silicon. Graphene can’t be switched between on and off states of conductivity. | |
| This makes it unsuitable for applications such as transistors. Because silicon and carbon sit side-by-side on the periodic table, scientists were inspired to investigate if silicon’s atomic properties could be similarly revolutionary but more easily exploited because of its compatibility with existing silicon-based electronics. | |
| “This work solves the long-lasting problem of isolating this super material for further device development. It challenges the entire scientific literature on silicene since its discovery,” Dr Du said. | |
| “These findings are relevant for the future design and application of silicene-based nano-electronic and spintronic devices.” | |
| The research was published recently in the journal Science Advances („Quasi-freestanding epitaxial silicene on Ag(111) by oxygen intercalation”) and ACS Central Science („Observation of van Hove Singularities in Twisted Silicene Multilayers”) and is the result of collaboration between Australian and Chinese researchers including Professor Jijun Zhao, from the Dalian University of Technology and Dr Jiaou Wang at the Beijing Synchrotron Radiation Facility (Chinese Academy of Sciences). |
| Source: University of Wollongong |
Read more: Peeling off the silicene layers for new electronics
Multe studii au prezis proprietățile nanofibrelor de grafen cu marginile zigzag”, a declarat Guangyu Zhang, autor principal al studiului. „Dar în experimente este foarte greu să faci acest material.”
Anterior, cercetatorii au incercat sa faca nanofibri de grafen prin plasarea foilor de grafen intr-un strat de silice si folosind hidrogenul atomic pentru a etchiza benzi cu marginile zig-zag, un proces cunoscut sub numele de gravura anizotropica. Aceste margini sunt esențiale pentru a modula proprietățile nanoribbonului.
Dar această metodă a funcționat doar bine pentru a face panglici care aveau două sau mai multe straturi de grafen. Neregulile din silicele create de vârfurile și văile electronice scrâșnesc suprafața sa, astfel încât să se creeze margini precise de zigzag pe monostraturile de grafen, a fost o provocar
| Posted: Aug 01, 2016 | |
Swapping substrates improves edges of graphene nanoribbons(Nanowerk News) It is now feasible to make a prized material for spintronic devices and semiconductors – monolayer graphene nanoribbons with zigzag edges. |
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| Miniscule ribbons of graphene are highly sought-after building blocks for semiconductor devices because of their predicted electronic properties. But making these nanostructures has remained a challenge. Now, a team of researchers from China and Japan have devised a new method to make the structures in the lab. Their findings appear in the current issue of Applied Physics Letters („Patterning monolayer graphene with zigzag edges on hexagonal boron nitride by anisotropic etching”). | |
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| Graphene etched with an underlying silica substrate produces uneven edges (left) but forms precise edges when placed on boron nitride (right). (Image: Guangyu Zhang) | |
| „Many studies have predicted the properties of graphene nanoribbons with zigzag edges,” said Guangyu Zhang, senior author on the study. „But in experiments it’s very hard to actually make this material.” | |
| Previously, researchers have tried to make graphene nanoribbons by placing sheets of graphene over a layer of silica and using atomic hydrogen to etch strips with zigzag edges, a process known as anisotropic etching. These edges are crucial to modulate the nanoribbon’s properties. | |
| But this method only worked well to make ribbons that had two or more graphene layers. Irregularities in silica created by electronic peaks and valleys roughen its surface, so creating precise zigzag edges on graphene monolayers was a challenge. Zhang and his colleagues from the Chinese Academy of Sciences, Beijing Key Laboratory for Nanomaterials and Nanodevices, and the Collaborative Innovation Center of Quantum Matter teamed up with Japanese collaborators from the National Institute for Materials Science to solve the problem. | |
| They replaced the underlying silica with boron nitride, a crystalline material that’s chemically sluggish and has a smooth surface devoid of electronic bumps and pits. By using this substrate and the anisotropic etching technique, the group successfully made graphene nanoribbons that were only one-layer thick, and had well-defined zigzag edges. | |
| „This is the first time we have ever seen that graphene on a boron nitride surface can be fabricated in such a controllable way,” Zhang explained. | |
| The zigzag-edged nanoribbons showed high electron mobility in the range of 2000 cm2/Vs even at widths of less than 10nm – the highest value ever reported for these structures – and created clean, narrow energy band gaps, which makes them promising materials for spintronic and nano-electronic devices. | |
| „When you decrease the width of the nanoribbons, the mobility decreases drastically because of edge defects,” said Zhang. „Using standard lithography fabrication techniques, studies have seen mobility of 100 cm2/Vs or even lower, but our material still exceeds 2000 cm2/Vs even at the sub-10 nanometer scale, demonstrating that these nanoribbons are of very high quality.” | |
| In future studies, extending this method to other kinds of substrates could enable the quick large scale processing of monolayers of graphene to make high-quality nanoribbons with zigzag edges. |
| Source: American Institute of Physics |
Read more: Swapping substrates improves edges of graphene nanoribbons
Absorbția solară în bandă largă a fost realizată anterior utilizând rezonatoare metal-izolator-metal (sau MIM), care constau dintr-un izolator sandwich între un fund gros și un strat superior subțire, fiecare realizat din metale precum cromul și aurul. Componentele metalice utilizate în rezonanții MIM au puncte de topire relativ scăzute – temperaturi care sunt reduse în continuare atunci când materialele sunt în straturi foarte subțiri, ca în rezonatoare, datorită unui fenomen numit depresie la punctul de topire, în care punctul de topire al unui material Scade în jos ca dimensiunile de scădere a materialului. Metalele din rezonanții standard MIM se topesc la aproximativ 500 de grade Celsius, împiedicând utilizarea lor în celulele solare.
Sunt rezistente la căldură, inclusiv șoc termic, și prezintă proprietăți fizice și chimice stabile la temperaturi ridiccate
| Posted: Aug 01, 2016 | |
New high-temperature device captures a broader solar wavelength spectrum(Nanowerk News) The photovoltaic (PV) cells in traditional solar cells convert sunlight efficiently within a narrow range of wavelengths determined by the material used in the PV cells. This limits their efficiency, as long wavelengths of sunlight are not converted at all and the energy of short wavelength light is largely wasted. Scientists have sought to increase the efficiency of photovoltaics by creating „multi-junction” solar cells, made from several different semiconductor materials that absorb at varying wavelengths of light. The problem is, such multi-junction cells are expensive to make. |
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| Broadband solar absorption previously has been achieved using metal-insulator-metal (or MIM) resonators, which consist of an insulator sandwiched between a thick bottom and a thin top layer, each made of metals like chromium and gold. The metal components used in MIM resonators have relatively low melting points–temperatures that are reduced further when the materials are in very thin layers, as in the resonators, because of a phenomenon called melting point depression, in which the melting point of a material scales down as the dimensions of the material decrease. The metals in standard MIM resonators melt at around 500 degrees Celsius, hindering their usefulness in solar cells. | |
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| The schematic energy flow of standard and solar thermophotovoltaic (STPV) systems. In standard solar cells, a PV cell is directly illuminated by the sun. Whereas in STPV systems (b), an absorber placed between the sun and PV cell is heated by absorbing the broad solar spectrum. A thermal emitter connected to the absorber converts the heat into narrowband thermal radiation that illuminates the PV cell. The inset represents the schematic of the multilayer broadband absorber device. (Image: Manohar Chirumamilla) | |
| Now a group of researchers in Denmark have discovered an alternative method to capture a broad spectrum of sunlight using a heat-resistant device made of tungsten and alumina layers that can be fabricated using inexpensive and widely available film-deposition techniques. The researchers describe their work and the new material in a paper published this week in the journal Optical Materials Express („Multilayer tungsten-alumina-based broadband light absorbers for high-temperature applications”). | |
| „They are resistant to heat, including thermal shock, and exhibit stable physical and chemical properties at high temperatures,” explained Manohar Chirumamilla of Aalborg University in Denmark, the first author of the new paper. This allows the absorbers to maintain their structural properties at very high temperatures. | |
| In experiments, the new absorbers were shown to operate at a temperature of 800 degrees Celsius and to absorb light of wavelengths ranging from 300 to 1750 nanometers, that is, from ultraviolet (UV) to near-infrared wavelengths. | |
| „MIM resonators absorbing in the spectral region from UV to near-infrared can be directly employed in different applications, such as solar TPV [thermophotovoltaic] /TPV systems and solar thermal systems,” Chirumamilla said. „Other potential applications include in so-called tower power plants, where concentrated solar light generates steam to drive a generator.” | |
| „This is the first step in utilizing the energy of the sun in a more efficient way than with current solar cells,” he added. „Using an emitter in contact with our absorber, the generated heat can then be used to illuminate a solar cell–which can then function more efficiently when it is placed directly in the sun.” |
| Source: The Optical Society |
Read more: New high-temperature device captures a broader solar wavelength spectrum
Am avut deja mult interes din partea companiilor dintr-o gamă diversă de sectoare. De la asistența medicală, unde nanoparticulele pot fi utilizate în acoperiri pe dispozitive medicale, la țesături îmbunătățite, unde nanomaterialele pot adăuga rezistență și flexibilitate la textile și în electronică tipărită, deoarece putem imprima materiale precum cuprul
| Posted: Aug 01, 2016 | |
Introducing the world’s biggest nanomaterial production plant(Nanowerk News) The European SHYMAN project aims to establish continuous hydrothermal synthesis as the most flexible and sustainable process to create nanomaterials at industrial scale. After demonstrating this potential in the lab, the project has now announced the opening of its first facility in Nottingham. |
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| ‘This new facility opens up a significant amount of new opportunities for us,’ says Professor Ed Lester, Technical Coordinator of Promethean Particles. This spin-out of the University of Nottingham is in charge of operating the new plant, which is expected to produce over 1 000 tonnes of nanomaterials every year. The production cost is lower than that of other facilities and the chosen production method – continuous hydrothermal synthesis – is expected to impact even markets for which sale prices had so far been an obstacle. | |
| ‘We have already had a lot of interest from companies in a diverse range of sectors. From healthcare, where nano-particles can be used in coatings on medical devices, to enhanced fabrics, where nano-materials can add strength and flexibility to textiles, and in printed electronics, as we are able to print materials such as copper,’ Prof. Lester continues. Solvay, Fiat, PPG and Repsol are among the major companies already set to benefit from the plant’s products. | |
| To reach these impressive levels of production, the plant notably relies on high pressure triplex plunger pumps manufactured by Cat Pumps. These pumps have helped the 18-strong consortium to overcome engineering issues related to the mixing of the heated fluid and the aqueous metal salt flow, by creating the continuous pressure and fluid flow necessary to achieve continuous production. | |
| Another enabling technology is the Nozzle Reactor, a customised design that uses buoyancy-induced eddies to produce an ‘ideal’ mixing scenario in a pipe-in-pip concentric configuration in which the internal pipe has an open-ended nozzle. This technology allows Promethean Particles to dramatically improve reproducibility and reliability whilst controlling particles properties such as size, composition and shape. | |
| Betting on hydrothermal synthesis | |
| Started in 2012, SHYMAN built upon the observation that hydrothermal synthesis had numerous advantages compared to alternatives: it doesn’t resort to noxious chemicals, uses relatively simple chemistry relying on cheap precursors, allows straightforward downstream processing, can avoid agglomeration and allows for narrow and well-controlled size and shape distribution. | |
| The optimisation of hydrothermal synthesis has been a key objective of the University of Nottingham for the past 14 years, and SHYMAN is the pinnacle: the project began with the development of bench scale reactors, followed by a 30-times-larger pilot scale reactor. The reactor at the heart of the new production plant is 80 times larger than the latter and features four Cat Pumps Model 3801 high pressure triplex plunger pumps. | |
| ‘These are very exciting times for Promethean Particles,’ said Dr Susan Huxtable, Director of Intellectual Property and Commercialisation at the University of Nottingham. ‘The new facility opens up a myriad of opportunities for them to sell their services into new markets right across the world. It is a great example of how many of the technologies developed by academics here at the University of Nottingham have the potential to benefit both industry and society.’ |
| Source: Cordis | |
Read more: Introducing the world’s biggest nanomaterial production plant
