Grafenul forjat în forme tridimensionale(Graphene forged into three-dimensional shapes)

Noul grafen 3D este stabil și are proprietăți electronice și optice care diferă de grafenul 2D normal. Grafenul optic forjat poate ajuta la fabricarea de arhitecturi 3D pentru dispozitive bazate pe grafen.

Posted: Sep 26, 2017

Graphene forged into three-dimensional shapes

(Nanowerk News) Researchers from Finland and Taiwan have discovered how graphene, a single-atom-thin layer of carbon, can be forged into three-dimensional objects by using laser light. A striking illustration was provided when the researchers fabricated a pyramid with a height of 60 nm, which is about 200 times larger than the thickness of a graphene sheet. The pyramid was so small that it would easily fit on a single strand of hair (Nano Letters, „Optical Forging of Graphene into Three-Dimensional Shapes”).
forging a graphene sheet into controlled 3D shapes
Jst as a blacksmith uses a hammer to forge a metal sheet into 3D shapes, a pulsed laser beam can forge a graphene sheet into controlled 3D shapes in the nanoscale. The forging mechanism is based on laser-induced local expansion of graphene, as confirmed by computer simulations using thin sheet elasticity theory. (Image: Academy of Finland)
Graphene is a close relative to graphite, which consists of millions of layers of graphene and can be found in common pencil tips. After graphene was first isolated in 2004, researchers have learned to routinely produce and handle it. Graphene can be used to make electronic and optoelectronic devices, such as transistors, photodetectors and sensors. In future, we will probably see an increasing number of products containing graphene.
“We call this technique optical forging, since the process resembles forging metals into 3D shapes with a hammer. In our case, a laser beam is the hammer that forges graphene into 3D shapes,” explains Professor Mika Pettersson, who led the experimental team at the Nanoscience Center of the University of Jyväskylä, Finland. “The beauty of the technique is that it’s fast and easy to use; it doesn’t require any additional chemicals or processing. Despite the simplicity of the technique, we were very surprised initially when we observed that the laser beam induced such substantial changes on graphene. It took a while to understand what was happening.”
“At first, we were flabbergasted. The experimental data simply made no sense,” says Dr Pekka Koskinen, who was responsible for the theory. “But gradually, by close interplay between experiments and computer simulations, the actuality of 3D shapes and their formation mechanism started to become clear.”
“When we first examined the irradiated graphene, we were expecting to find traces of chemical species incorporated into the graphene, but we couldn’t find any. After some more careful inspections, we concluded that it must be purely structural defects, rather than chemical doping, that are responsible for such dramatic changes on graphene,” explains Associate Professor Wei Yen Woon from Taiwan, who led the experimental group that carried out X-ray photoelectron spectroscopy at the synchrotron facility.
The novel 3D graphene is stable and it has electronic and optical properties that differ from normal 2D graphene. Optically forged graphene can help in fabricating 3D architectures for graphene-based devices.
Source: Suomen Akatemia

Catedralele Europei primesc o nouă viață datorită nanoparticulelor(Europe’s cathedrals get new life thanks to nanoparticles)

un material nou fabricat din nanoparticule inovatoare. Scopul este de a consolida structura interioară a pietrelor. Se aplică în principal pe marmură.Materialul dezvoltat de echipa de cercetare europeană ( proiectul Nano-Cathedral include carbonatul de calciu, care este un amestec de oxid de calciu, apă și dioxid de carbon.

Posted: Sep 26, 2017

Europe’s cathedrals get new life thanks to nanoparticles

(Nanowerk News) Just a few meters from Pisa’s famous Leaning Tower, restorers are defying scorching temperatures to bring back shine to the city’s Cathedral.
Ordinary restoration techniques like laser are being used on much of the stonework that dates back to the 11th century. But a brand new technique is also being used: a new material made of innovative nanoparticles. The aim is to consolidate the inner structure of the stones. It’s being applied mainly on marble.
Pisa cathedral
Pisa cathedral
“Marble has very low porosity, which means we have to use nanoparticles in order to go deep inside the stone, to ensure that the treatment is both efficient while still allowing the stone to breathe,” explains Roberto Cela, civil engineer at Opera Della Primaziale Pisana.
The material developed by the European research team (Nano-Cathedral project includes calcium carbonate, which is a mix of calcium oxide, water and carbon dioxide.
The nanoparticles penetrate the stone cementing its decaying structure.
“It is important that these particles have the same chemical nature as the stones that are being treated, so that the physical and mechanical processes that occur over time don’t lead to the break-up of the stones,” says Dario Paolucci, chemist at the University of Pisa.
Vienna’s St Stephen’s is another of the five cathedrals where the new restoration materials are being tested.
The first challenge for researchers is to determine the mechanical characteristics of the cathedral’s stones. Since there are few original samples to work on, they had to figure out a way of “ageing” samples of stones of similar nature to those originally used.
“We tried different things: we tried freeze storage, we tried salts and acids, and we decided to go for thermal ageing,” explains Matea Ban, material scientist at the University of Technology in Vienna. “So what happens is that we heat the stone at certain temperatures. Minerals inside then expand in certain directions, and when they expand they build up stresses to neighbouring minerals and then they crack, and we need those cracks in order to consolidate them.”
Consolidating materials were then applied on a variety of limestones, sandstones and marble – a selection of the different types of stones that were used to build cathedrals around Europe.
What researchers are looking for are very specific properties.
“First of all, the consolidating material has to be well absorbed by the stone,” says petrologist Johannes Weber of the University of Applied Arts in Vienna. “Then, as it evaporates, it has to settle properly within the stone structure. It should not shrink too much. All materials shrink when drying, including consolidating materials. They should adhere to the particles of the stone but shouldn’t completely obstruct its pores.”
Further tests are underway in cathedrals across Europe in the hope of better protecting our invaluable cultural heritage.
Source: European Commission

Cercetătorii dezvoltă un generator solar termoelectric purtător(Researchers develop wearable solar thermoelectric generator)

a introdus un nou sistem avansat de recoltare a energiei, capabil să genereze electricitate pur și simplu atașat la haine, ferestre și pereți exteriori o clădire ( Nano Energy , „Generator termoelectric purtător solar, condus de o diferență de temperatură fără precedent” ).
Acest nou dispozitiv se bazează pe o diferență de temperatură între părțile calde și cele reci. Diferența de temperatură poate fi mărită cu până la 20,9 ° C, care este mult mai mare decât diferențele de temperatură tipice de 1,5 până la 4,1 ° C ale generatoarelor termoelectrice purtate de căldură. Echipa de cercetare se așteaptă ca generatorul lor termoelectric purtător solar să propună o modalitate promițătoare de a îmbunătăți în continuare eficiența prin creșterea diferenței de temperatură.

Posted: Sep 26, 2017

Researchers develop wearable solar thermoelectric generator

(Nanowerk News) A recent study, led by Professor Kyoung Jin Choi in the School of Materials Science and Engineering at UNIST has introduced a new advanced energy harvesting system, capable of generating electricity by simply being attached to clothes, windows, and outer walls of a building (Nano Energy, „Wearable solar thermoelectric generator driven by unprecedentedly high temperature difference”).
This new device is based on a temperature difference between the hot and cold sides. The temperature difference can be increased as high as 20.9°C, which is much higher than the typical temperature differences of 1.5 to 4.1°C of wearable thermoelectric generators driven by body heat. The research team expects that their wearable solar thermoelectric generator proposes a promising way to further improve the efficiency by raising the temperature difference.
thermoelectric ink printed in lines and shapes
This is a photograph of the TE ink printed in various shapes with curves and straight lines. (Image: UNIST)
Energy harvesting is a diverse field encompassing many technologies, which involve a process that captures small amounts of energy that would otherwise be lost as heat, light, sound, vibration, or movement. A thermoelectric generator (TEGs) refers to a device that converts waste heat energy, such as solar energy, geothermal energy, and body heat into additional electrical power.
There has been a great increase in the study of wearable thermoelectric (TE) generators using the temperature difference between the body heat and surrounding environment. However, one of the main drawbacks of wearable TEG techniques driven by body heat was that such temperature difference is only 1-4 °C and this has hindered further commercialization.
The research team solved this low temperature difference faced by conventional wearable TEGs by introducing a local solar absorber on a PI substrate. The solar absorber is a five-period Ti/MgF2 superlattice, in which the structure and thickness of each layer was designed for optimal absorption of sunlight. This has increased the temperature difference as high as 20.9°C, which is the highest value of all wearable TEGs reported to date.
„Through this study, we have secured a temperature difference with the ten-fold increase from the conventional wearable solar thermoelectric generators,” says Yeon Soo Jung in the Graduate School of Materials Science and Engineering at UNIST. „Since the output of a TE generator is proportional to the square root of the temperature difference, one can significantly increase the output with the help of this technology.”
In this study, Professor Choi and his team designed a noble wearable solar thermoelectric generator (W-STEG) by integrating flexible BiTe-based TE legs and sub-micron thick solar absorbers on a polymide (PI) substrate. The TE legs were prepared by dispenser printing with an ink consisting of mechanically alloyed BiTe-based powders and an Sb2Te3-based sintering additive dispersed in glycerol. They report that a W-STEG comprising 10 pairs of p-n legs has an open-circuit voltage of 55.15 mV and an output power of 4.44 µW when exposed to sunlight.
„Our new werable STEG is expected to be useful in various applications, such as in self-powered wearable electronic devices,” says Professor Choi. „It will also serve as a catalyst to further improve the future wearable electronic technology market.”
Source: Ulsan National Institute of Science and Technology

Nanopore filtru poate fi un meci pentru fracking de apă(Nanopore filter may be a match for fracking water)

Un nou filtru superhidrofil sa dovedit a fi capabil sa indeparteze mai mult de 90% din hidrocarburi, precum si toate bacteriile si particulele din apa contaminata produsa prin operatiuni de fracturare hidraulica (fracking) la sisturi de petrol si gaze,

Posted: Sep 25, 2017

Nanopore filter may be a match for fracking water

(Nanowerk News) A new superhydrophilic filter has proven able to remove greater than 90 per cent of hydrocarbons, as well as all bacteria and particulates from contaminated water produced by hydraulic fracturing (fracking) operations at shale oil and gas wells, according to researchers at the Energy Safety Research Institute at Swansea University in collaboration with researchers at Rice University.
The work by Prof Andrew R Barron and his colleagues turns a ceramic membrane with microscale pores into a superhydrophilic filter that „essentially eliminates” the common problem of fouling.
The researchers determined one pass through the membrane should clean contaminated water enough for reuse at a well, significantly cutting the amount that has to be stored or transported.
The work is reported in Nature’s open-access Scientific Reports („Superhydrophilic Functionalization of Microfiltration Ceramic Membranes Enables Separation of Hydrocarbons from Frac and Produced Water”).
The filters keep emulsified hydrocarbons from passing through the material’s ionically charged pores, which are about one-fifth of a micron wide, small enough that other contaminants cannot pass through. The charge attracts a thin layer of water that adheres to the entire surface of the filter to repel globules of oil and other hydrocarbons and keep it from clogging.
A hydraulically fractured well uses more than 5 million gallons of water on average, of which only 10 to 15 per cent is recovered during the flow back stage, Barron said.
„This makes it very important to be able to re-use this water”
Not every type of filter reliably removes every type of contaminant, he said.
Solubilized hydrocarbon molecules slip right through micro filters designed to remove bacteria. Natural organic matter, like sugars from guar gum used to make fracking fluids more viscous, require ultra- or nanofiltration, but those foul easily, especially from hydrocarbons that emulsify into globules. A multistage filter that could remove all the contaminants isn’t practical due to cost and the energy it would consume.
Frac water and produced waters represent a significant challenge on a technical level. If you use a membrane with pores small enough to separate they foul, and this renders the membrane useless. In our case, the superhydrophilic treatment results in an increased flux (flow) of water through the membrane as well as inhibiting any hydrophobic material – such as oil – from passing through. The difference in solubility of the contaminants thus works to allow for separation of molecules that should in theory pass through the membrane.
Barron and his colleagues used cysteic acid to modify the surface of an alumina-based ceramic membrane, making it superhydrophilic, or extremely attracted to water. The superhydrophilic surface has a contact angle of 5 degrees.
The acid covered not only the surface but also the inside of the pores, and that kept particulates from sticking to them and fouling the filter.
In tests with fracking flow back or produced water that contained guar gum, the alumna membrane showed a slow initial decrease in flux – a measure of the flow of mass through a material – but it stabilized for the duration of lab tests. Untreated membranes showed a dramatic decrease within 18 hours.
The researchers theorized the initial decrease in flow through the ceramics was due to purging of air from the pores, after which the superhydrophilic pores trapped the thin layer of water that prevented fouling.
„This membrane doesn’t foul, so it lasts,” Barron said. „It requires lower operating pressures, so you need a smaller pump that consumes less electricity. And that’s all better for the environment.”
„Fracking has proved highly controversial in the UK in part as a result of the pollution generated from produced waters”, co-author Darren Oatley-Radcliffe, an associate professor, at Swansea University, said, „However, with this new super-hydrophilic membrane we can clean up this waste produced water to a very high standard and recycle all of the materials, significantly improving the environmental performance of the fracking process.”
Source: Swansea University