Friday, January 25, 2013

Carbon nanotube composite material could replace carbon fiber

The ribbon-like material being wound onto a spool, while being sprayed with polymer and st...
The ribbon-like material being wound onto a spool, while being sprayed with polymer and stretched

When people need a material that’s strong yet lightweight, they usually look to carbon fiber. In the near future, however, they may instead choose to go with composite materials made from stretched carbon nanotubes. These materials could theoretically offer the same strength as carbon fiber at one-tenth the weight, or the same weight at ten times the strength. Researchers from North Carolina State University have recently succeeded in creating such a composite.
According to the university, scientists have spent decades trying to achieve the four goals that must be met in order to create CNT (carbon nanotube) composites – the nanotubes must be long in order to effectively carry loads; they must be aligned in rows; there must be a high ratio of CNTs to the polymer or resin used to hold them together; and, in order for the material to bear weight evenly, the nanotubes must be as straight as possible.
NC State’s Dr. Yuntian Zhu, a professor of materials science and engineering, is reportedly the first person to come up with a method of meeting all of these requirements.
The process begins by growing an array of long, skinny carbon nanotubes out of a flat substrate. Because the nanotubes aren’t rigid, they tend to flop over and lean against one another. The CNTs at one end of the array are then pulled sideways, causing all the other nanotubes to topple over in the same direction. As a result, they end up all being aligned.
The aligned array is then wound onto a rotating spool, simultaneously being stretched and being sprayed with a polymer solution that keeps the nanotubes bound together. This respectively results in a straightening of the nanotubes, and a high CNT-to-polymer ratio.
The finished product is a ribbon-like material, several bonded layers of which could supposedly be used to build anything from bicycle frames to aircraft. Because of the CNT-stretching process, that material has 90 percent more tensile strength and is 100 percent stiffer than it would be otherwise. Additionally, its thermal conductivity is almost tripled, while its electrical conductivity is boosted by 50 percent.
A paper on the research conducted by Zhu's team was recently published in the journal Materials Research Letters.
Source: North Carolina State University

Thursday, January 24, 2013

GeS “nanoflowers” could blossom in next-gen solar cells

The GeS 'nanoflowers' have petals only 20-30 nanometers thick, and provide a large surface...
The GeS 'nanoflowers' have petals only 20-30 nanometers thick, and provide a large surface area in a small amount of space

Researchers have already turned to the humble sunflower for inspiration to design more efficient Concentrating Solar Power (CSP) plant layouts, and now a team from North Carolina State University has developed a “nanoflower” structure out of germanium sulfide (GeS) that shows great promise for use in energy-storage devices and more efficient solar cells. The secret is the material's ultrathin petals that provide a large surface area in only a small amount of space.
The researchers created the flower-like structures by first heating GeS powder in a furnace until it began to vaporize. The vapor is then blown into a cooler region of the furnace, where the GeS settles into a layered sheet measuring just 20 to 30 nanometers thick and up to 100 micrometers long. A flower-like structure similar to a carnation or marigold is formed as additional layers are added causing the sheets branch out from one another.
GeS is a semiconductor material that is attractive for use in solar cells because it is inexpensive and non-toxic, while its atomic structure makes it good at absorbing solar energy and converting it into useable power. But solar cells aren’t the only potential applications for the nanoflower technology.
“This could significantly increase the capacity of lithium-ion batteries, for instance, since the thinner structure with larger surface area can hold more lithium ions,” says Dr. Linyou Cao, an assistant professor of materials science and engineering at NC State and co-author of a paper on the research. “By the same token, this GeS flower structure could lead to increased capacity for supercapacitors, which are also used for energy storage.”
The team’s paper is published in the journal ACS Nano.
Source: North Carolina State University

Wednesday, January 23, 2013

New tech converts regular paper into powerful medical diagnostic tool

Researchers at the University of Washington have found a way to turn scraps of common offi... 
Researchers at the University of Washington have found a way to turn scraps of common office paper into a powerful diagnostic too


A group of researchers at the University of Washington has found a way to isolate and identify medically interesting molecules using little more than scraps of office paper, a Ziplock bag and a cheap diluted solvent. If properly developed, the system – which requires minimal costs and know-how to build and operate – could be made to administer a wide range of medical tests nearly free of charge.
Healthcare can come at a steep price: according to the American College of Physicians, the costs of unnecessary medical testing in the U.S. alone have soared to upwards of US$200 billion per annum – the grand total being much higher. With such a wide margin for improvement, a lot of research is going into putting a dent in this figure in an effort that could not only reduce expenses at home, but also do a great deal toward raising the standard of medical care in developing (or simply cash-strapped) countries.
One way to tackle the problem is to use cheap but effective materials, such as specially treated paper. Today, most paper-based diagnostics are made from nitrocellulose, a sticky membrane that can detect proteins, DNA or antibodies in the immune system and is used, among many other things, in home pregnancy tests.
Researchers at the University of Washington have worked out a way to replace nitrocellulose with much cheaper scraps of paper – the kind you would find in a typical office setting. When properly treated, the paper can detect a wide range of chemically interesting molecules (even more than nitrocellulose can) and could serve as a virtually zero-cost framework to build devices like home pregnancy tests that work for malaria, diabetes and other diseases.
The image illustrates the process by which the researchers produced and tested their new p...
The team filled a Ziplock bag with a 10 percent solution of divinyl sulfone – a cheap industrial solvent that is commonly used as an adhesive – and added a stack of paper. They then shook the mix for a couple of hours, extracted the paper from the bag, and let it out to dry.
When treated this way, the paper acquires a very interesting property: it normally feels smooth to the touch, but becomes sticky in the presence of chemicals that are of medical interest – proteins, antibodies and DNA, just like nitrocellulose, but also sugars and the small-molecule drugs used to treat most medical conditions.
To test their concept, the researchers printed an invisible pattern of galactose onto a treated scrap of paper. They then exposed the paper to fluorescent ricin, a poison that sticks to galactose, and detected that the poison was present in the exact same pattern in which the galactose had just been printed. This showed that the paper had indeed become sticky in the presence of a galactose, retaining it in place.
"We wanted to make the system as independent of the end applications as possible, something to not just ask a single question but many personal health questions,” assistant professor Daniel Ratner, the main author of the study, commented. “‘Is there protein in the urine? Is this person diabetic? Do they have malaria or influenza?'"
After producing this simple but effective framework, the researchers are hoping that other groups will build on their work to develop actual diagnostic tests in the near future.
A paper detailing the study was published in the journal Langmuir.
Source: University of Washington

Tuesday, January 22, 2013

Heat-conducting composite pipes could make desalination less costly

Fraunhofer's polymer-copper desalination pipes


Fraunhofer's polymer-copper desalination pipes

In a typical desalination plant, pipes made from titanium or other expensive types of metal are an integral part of the process. Now, however, scientists have created a new type of piping material that is much cheaper to produce – potentially making desalination possible in countries that previously couldn’t afford it.
Ordinarily, hot water or gas is pumped through pipes composed of titanium or a high-alloy steel. That piping conducts heat from the water or gas, which is transferred to its outer surface, causing it to become hot. When seawater is then sprayed onto the outside of that hot pipe, its pure water content evaporates and is collected, while its salt content forms into a sludge on the pipe.
In an effort to come up with a less costly heat-conductive piping material, researchers from Germany’s Fraunhofer Institute for Manufacturing Technology and Advanced Materials combined a polymer with copper microfibers – the mix is as much as 50 percent copper, by volume. The resulting composite can reportedly still be processed like regular plastic, yet it conducts heat like metal.
Pipes made from the material are now being tested in a desalination plant, where gas heated to 70ºC (158ºF) is continuously being pumped through them. The scientists plan on assessing the material’s thermal conductivity along with its corrosion resistance, then tweaking the mixture as needed.
Source: Fraunhofer

Monday, January 21, 2013

A graphene coating can make copper nearly 100 times more resistant to corrosion (Image: Sh... 


A graphene coating can make copper nearly 100 times more resistant to corrosion
Following on from news out of the University at Buffalo earlier this year that a graphene varnish could significantly slow the corrosion of steel, researchers from Monash and Rice Universities have used a graphene coating to improve copper’s resistance to corrosion by nearly 100 times. The researchers say such a dramatic extension of the metal’s useful life could result in significant cost savings for a wide range of industries.
Metals are often treated with polymer coatings to help prevent corrosion, but their protective capabilities can be easily compromised by scratches. Although graphene is only one-atom thick and is invisible, not changing the appearance or feel of the metal, it is exceptionally strong and much harder to damage. This gives the material enormous potential for protecting metals even in harsh environments.
A graphene coating is applied to copper using chemical vapor disposition (Image: Derek Lob...
Using chemical vapor disposition, the researchers applied the graphene coating to copper at temperatures between 800 and 900 degrees Celsius (1,472 and 1,652° F). They then tested it in saline water and witnessed resistance to corrosion almost 100 times that of untreated copper.
“We have obtained one of the best improvements that have been reported so far,” said study co-author Dr Mainak Majumder. “Other people are maybe five or six times better, so it’s a pretty big jump.”
The researchers are now expanding their research to see if the technique produces similar results with other metals. They are also looking for ways to apply the coating at lower temperatures in an effort to simplify production and enhance the technique’s market potential.
The team's paper appears in the journal Carbon.
Source: Monash University

Sunday, January 20, 2013

Black silicon could boost efficiency of traditional solar cells

Dark silicon could improve efficiency in traditional solar cells by harvesting energy in t... 
Dark silicon could improve efficiency in traditional solar cells by harvesting energy in the infrared spectrum


Researchers at the Fraunhofer Institute for Telecommunications have developed a system that allows solar cells to effectively harvest energy from the infrared spectrum, tapping into a source of energy that in the past has mostly been out of reach. The new technology, which promises to work well with commercially available solar cells, has the potential of becoming a standard in the solar panels of tomorrow.
When photons hit the surface of a solar cell, the energy they carry can be absorbed by a semiconductor. If the energy absorbed is higher than a set threshold – which is known as the energy gap, and depends on the semiconductor used – electrons are freed from the semiconductor and can be used to generate an electric current.
The electromagnetic spectrum (Image: Shutterstock)
The energy carried by a photon is proportional to its frequency. In silicon solar cells, photons in the infrared often don't carry enough energy to produce electricity, and IR light simply passes through the cell, unused. Red photons are carrying just enough energy to knock an electron loose and photons in the blue spectrum or beyond (UV light) are carrying too much energy – so part of it is used to free a single electron, but the rest is wasted as heat. The inability to fully extract the energy carried by a photon is the main reason why solar cells are so inefficient.
Over the past few years, researchers have produced solar cells that can absorb infrared and ultraviolet light more effectively. Now, researchers at Fraunhofer Institute have come up with a straightforward way to capture more energy from the infrared spectrum, developing something that could very well become standard technology in the solar cell of the near future.
The research is based on absorbing infrared light using what's known as black silicon. This material is made by using precision lasers to "zap" sulfur atoms into the silicon lattice in well-defined patterns.
The sulfur lowers the energy gap, and therefore allows much lower-energy photons to free electrons from the semiconductor. In theory, this should boost the solar cell's efficiency; unfortunately, though, the smaller energy gap also makes it easier for electrons to "travel" in the opposite direction, causing electricity to be lost once again.
The researchers at Fraunhofer set out to address this issue and came up with a conceptually simple yet ingenious solution. They chose to change the patterns of laser pulses that drive sulfur atoms into the silicon lattice, altering their conformation to maximize the number of electrons that can climb "up" the energy gap and become conductive, while minimizing the number of electrons that can go back "down" it.
Prototypes of the cells have shown that the mechanism can double the efficiency of black silicon, but the researchers are still looking to identify the configuration of sulfur atoms that can result in the best performance.
The next step will be to embed the cells with already existing commercial technology, and the good news is that the two are very much compatible, and seem to complement each other. By simply removing the back cover of a traditional solar cell and incorporating a layer of black silicon, the team has found that they can increase efficiency of such panels by about one percent.
The researchers are now planning to market a laser system that manufacturers can use to produce the black silicon themselves and include it in their products as standard.
Source: Fraunhofer HHI

Saturday, January 19, 2013

Scientists invent transparent soil to reveal the secret life of plants

Lettuce grown in transparent soil developed by researchers at the James Hutton Institute a...


Lettuce grown in transparent soil developed by researchers at the James Hutton Institute and the University of Abertay Dundee in Scotland

Most people’s image of plants is actually upside down. For most of our photosynthetic friends, the majority of the plant is underground in the form of an intricate system of roots. The bit that sticks up is almost an afterthought. That’s a problem for scientists trying to study plants because growing them in media that allow you to see the roots, such as hydroponics, doesn't mimic real soil very well. Now, a team of researchers at the James Hutton Institute and the University of Abertay Dundee in Scotland has developed an artificial transparent soil that allows scientists to make detailed studies of root structures and subterranean soil ecology on a microscopic level.
Developed by a team led by Lionel Dupuy, a theoretical biologist in the Ecological Sciences group at the James Hutton Institute, the transparent soil is the result of two years of research. It doesn't look much like conventional soil. In fact, it’s a bit like those high-tech ant farms where instead of sand, the ants burrow through a jelly that also provides them with food and water. However, mechanically, it does mimic real soil. It supports root structures, holds suspended minerals, can be colonized by microorganisms and even exchanges gases like soil.
It’s made from granules of Nafion, which is a lot easier than calling it a sulfonated tetrafluoroethylene based fluoropolymer-copolymer. Used in batteries, fuel cells and a wide range of applications, Nafion is naturally transparent, but in order to make it translucent enough for for botanical purposes it needs a special water-based formula. Forming the polymer into pellets allows it to mimic soil particle properties, such as forming channels, retaining water and nutrients and sustaining plant growth. Fluorescent dyes can also be added to it to aid studies.
Researchers say that the transparent soil could be used to study root systems, help breed crops with more efficient roots that need less fertilizers, and study the ecology of plants and microorganisms. Currently, the team is working on controlling the properties of the transparent soil and bringing down its cost.
The team's research is published in the journal PLOS One.
Source: James Hutton Institute

Friday, January 18, 2013

Vestas increases capacity of massive V164 wind turbine

Vestas has upped the capacity of ts V164 wind turbine to 8 MW


Vestas has upped the capacity of ts V164 wind turbine to 8 MW

Danish wind turbine specialist Vestas was already looking to claim the title of the world’s largest offshore wind turbine with its proposed V164 that boasts a diameter of 164 m (538 ft). The company claims the V164 was developed with the potential of increasing its turbine size and now it has done just that, upping the capacity from seven to eight megawatts. So not only is the V164 set to boast the largest swept area of any single wind turbine, it will also claim the title for the world’s largest capacity wind turbine.
The current titleholder for the largest swept area goes to the G10X prototype installed by Gamesa in Spain, with a rotor diameter of 128 m (420 ft) and a capacity of 4.5 MW. Meanwhile, with a rated capacity of 7.58 MW and rotor diameter of 126 m (413 ft), the Enercon E-126 has held the title for the world’s largest capacity wind turbine since its introduction in 2007.
“As we progressed in the technology development it was clear that an 8 MW version of the turbine will offer lower cost of energy and at the same time keep the reliability and structural integrity of the turbine unchanged,” says Anders Vedel, Vestas Executive Vice President and CTO.
Vestas has increased the turbine size of its V164 wind turbine by one megawatt
The company is currently constructing a purpose-built test bench that is due to enter service in January 2013 and will allow the company to conduct in-house testing of the turbine’s complete drivetrain. The first V164-8.0 MW turbine isn’t due to be installed in Oesterid, Denmark until 2014, so with a number of other companies working on 10 MW and higher wind turbines, it remains to be seen whether Vestas’ effort will actually be able to claim the records. But at the moment the company definitely seems well placed to do so.
Source: Vestas

Friday, January 11, 2013

Solid when wet and liquid when dry – Cornell's new DNA hydrogel seems confused

DNA hydrogel letters collapse, flow, and reform into their original shape


DNA hydrogel letters collapse, flow, and reform into their original shape

Every now and again, Cornell University Professor Dan Luo gets a surprise. His research team has discovered a new variety of hydrogel – like Jello, except made with DNA instead of gelatin. When full of water, it is a soft, elastic solid. But when the water is removed, the hydrogel collapses, losing its shape. The resulting material pours like a liquid, and conforms to the shape of its container. The most interesting part, however, is that the liquid hydrogel remembers its shape. Add water and you get back the original Jello-like shape. Terminator T-1000, anyone?
DNA has a wide range of potential applications based solely on its properties as an unusual polymer. These include controlled delivery of pharmaceuticals, 3D tissue scaffolding and engineering, and a range of other biomedical applications. Among these DNA-based materials are self-assembling hydrogels, in which standard cross-linked DNA polymers form large, loose polymer networks that can adsorb huge amounts of water. As they do so, their mechanical properties change dramatically.
Micron-sized spheres of DNA polymer form the basis of the DNA hydrogels
Micron-sized spheres of DNA polymer form the basis of the DNA hydrogels
The polymer networks that make up the DNA hydrogels form spontaneously under certain conditions, and in the process take the shape of micron-sized spheres which bond weakly to each other. It is this bonding that allows a hydrogel to be formed in a particular shape – if the tiny polymer spheres did not bond together in some manner, the "wet" (hydrated) form of the hydrogel would be a thick soup rather than, say, the letters DNA.
When most of the water surrounding the DNA hydrogel letters is removed, they collapse into a pool of what to all intents seems to be a fluid. The collapsed material flows, pours, fills molds of other shapes, and appears to have lost all trace of the original shape. Despite this, when water is reintroduced, some memory of the bonding between the spheres remains – enough to completely reproduce the original shape of the DNA letters.
This is a new behavior, and the ultimate mechanism that preserves shape information is not yet known, nor is the strength of the mechanism. For example, will stirring the collapsed hydrogels destroy the shape memory? Prof. Luo's group is still investigating such questions.
As a simple example of a potential application, one might imagine an injectable stent. Such a stent would be produced with the desired shape in the presence of large amounts of environmental water, then collapsed into a pseudo-liquid to be injected into the proper place in the body, whereupon it would reproduce the original shape. While it is too early to guess what other applications may appear, there are very few unusual mechanical properties which remain laboratory curiosities for long.
Source: Cornell Chronicle

Thursday, January 10, 2013

Shoal's robot fish could be the first line of defense against water pollution

The Shoal Consortium's robo-fish could provide round the clock protection against harmful ...
The Shoal Consortium's robo-fish could provide round the clock protection against harmful pollutants by patrolling in teams.

A five foot long (1.5 meter) robo-fish prototype that monitors oxygen levels and salinity is currently being tested in waters north of Spain as part of the EU-funded Shoal Consortium project. If the project proves successful, teams of autonomous robot fish could be patrolling ports, harbors, and estuaries for telltale signs of pollutants in the next few years.
With current monitoring techniques relying on the collection of samples, usually by divers, that then need to be transported to a lab for testing, many harbors limit their pollution monitoring efforts to about once a month. So if harmful chemicals are detected, the culprit may be long gone.
"The idea is that we want to have real-time monitoring of pollution," says Luke Speller, a senior scientist at the BMT Group, a member of the consortium. "So that if someone is dumping chemicals or something is leaking, we can get to it straight away, find out what is causing the problem and put a stop to it."
In addition to its oxygen and salinity monitoring capabilities, the current prototype has an interchangeable sensor unit which can detect a variety of harmful chemicals and heavy metals like copper and lead. The robots can communicate with one another to locate the source of the problem, and regularly report back to a monitoring station.
"Traditional robots use propellers or thrusters for propulsion. What we're trying to do is use the fin of a fish to propel ourselves through the water," explains Ian Dukes, from the University of Essex, another member of the consortium. "The fin does lend itself for a really useful tool in shallow waters, especially where there is a lot of debris. We can work in environments that are very weedy, and would usually snag up propellers."
The Shoal Consortium's robo-fish could provide round the clock protection against harmful ...
Biomimetic robot fish aren't new – researchers at MIT developed the RoboTuna back in 1993 – and this year alone has added the BIOSwimmer and this example from NYU-Poly to the mix. Others are attempting to replicate the swimming motion of rays, jellyfish, and octopi, but these and other robots are stymied by limited battery life, which prevents them from becoming truly practical.
The Shoal Consortium's prototypes, which cost US$32,000 each, operate for just eight hours before needing to be charged. However, there's no doubt that if this problem can be overcome (with, perhaps, some sort of underwater charging station) the robo-fish will find homes in coastal waters around the world.
Source: Shoal Consortium via BBC news

Wednesday, January 09, 2013

New study distils the eco footprint of biofuels

A new study by Swiss research group Empa found that some biofuels, especially the ones mad... 
A new study by Swiss research group Empa found that some biofuels, especially the ones made from crops cultivated on deforested land, produce more GHG emissions than petrol



The controversial debate over the sustainability of biofuels has been reignited by new research from Swiss-based research institute Empa. While the study maintains that biofuels can be sustainable depending on certain conditions and the technology involved, the findings suggest that only a few are more environmentally friendly than gasoline.

The study entitled Harmonisation and extension of the bioenergy inventories and assessment was carried out by the Swiss Federal Laboratories for Materials Science and Technology (Empa) in conjunction with the Institute Agroscope Reckenholz-Tänikon (ART), and the Paul Scherrer Institute (PSI). It is an update on a first of its kind report compiled in 2007, made more relevant for the present with new energy plants, manufacturing processes and updated assessment methods. Yet, the researchers arrived at a similar conclusion.
Although biofuels can have a smaller carbon footprint compared with fossil fuels, they produce other types of environmental pollution, including soil acidity and excessive levels of fertilizers finding their way into lakes and rivers.
More alarmingly, biofuels from deforested areas have a bigger greenhouse gas (GHG) footprint than fossil fuels. This is also true of indirect land usage – if existing agricultural land is used for the first time for a biofuel crop, new areas will have to be cleared to make up for displaced food and animal feed crops.
Empa overview of the environmental impacts of various biofuels relative to petrol
Empa overview of the environmental impacts of various biofuels relative to petrol
“Most biofuels therefore just deflect the environmental impact: fewer greenhouse gases, thus more growth-related pollution for land used for agriculture,” says Empa researcher Rainer Zah.
Biogas made from residues and waste materials performs particularly well in terms of reducing emissions, having up to half the environmental impact of gasoline. Meanwhile, ethanol-based fuels tend to be greener than those biofuels with an oil base. Nevertheless, any environmental advantage or disadvantage is dependent on how the fuel is manufactured and the technology involved.
Besides the methodological updates, the new report also fixed some "weaknesses" of the previous report, where the researchers underestimated how much changes to natural areas, such as the deforestation of the rainforest, impacted on GHG balance.
On a positive note, biofuel crops can increase the carbon content of the soil. As examples, the report cites the cultivation of oil palms on unused grazing land in Colombia or jathopha plantations in India and eastern Africa, where deserted land has been transformed into arable areas. However, the report's authors warn that all these benefits depend on the type of agriculture being practiced and the land’s previous use, with each biofuel type needing to be analyzed individually.
The report also includes some general advice on what to do to avoid the most adverse ecological results from biofuel production. Clearing forests and bush areas is an obvious no-no. In the case of agricultural land, indirect change of land is also bad practice. Finally, second generation biofuels, based on residues such as straw, garden and timber waste can be environmentally sound if they are not being diverted from other uses and if their extraction does not compromise soil fertility and biodiversity.
The report can be downloaded via the link below.
Source: EMPA

Tuesday, January 08, 2013

Liquid laundry additive turns clothes into air purifiers

Clothing treated with the CatClo laundry additive can remove nitrogen oxides from the air


Clothing treated with the CatClo laundry additive can remove nitrogen oxides from the air

A laundry additive created by researchers from the University of Sheffield and the London College of Fashion turns clothing into a photocatalytic material that can help remove nitrogen oxides (NOx) from the air. One of the most prominent air pollutants, nitrogen oxides are emitted from the exhausts of ICE-powered vehicles and aggravate asthma and other respiratory diseases. The researchers claim one person getting around town in clothing treated with the additive for a day would be able to remove roughly the same amount of nitrogen oxides produced by the average family car each day.
Dubbed “CatClo,” (short for Catalytic Clothing), the liquid laundry additive contains pollution-eating titanium dioxide (TiO2) nanoparticles that, in daylight, oxidize the nitrogen oxides in the fabric when they come into contact with them in the air. The treated nitrogen oxides, which are odorless, colorless and pose no pollution hazard, are then either dissipated harmlessly in the wearer’s sweat of removed in the next wash.
The researchers say the additive itself is also completely harmless and unnoticeable to the wearer. Additionally, because the TiO2 nanoparticles grip to fabrics very tightly, items of clothing only need to be washed in the additive once.
Because the additive is photocatalytic, meaning that the chemical reaction requires light to take place, the clothing best performs its air-purifying magic when worn out in daylight. The researchers claim CatClo treated clothing can remove around 5 grams of nitrogen oxides from the air in the course of a day, which is roughly equivalent to the amount of nitrogen oxides emitted from the exhaust of an average family car each day.
The additive was used to create Wendy, the 14-meter (46 ft) high air-purifying sculpture covered in nylon fabric sprayed with CatClo that was on display at New York’s Museum of Modern Art (MoMA) earlier this year. The researchers say that over a 10-week period, Wendy soaked up nitrogen oxides equivalent to the amount produced by around 260 cars.
“If thousands of people in a typical town used the additive, the result would be a significant improvement in local air quality”, says Professor Ryan OBE of the University of Sheffield. “This additive creates the potential for community action to deliver a real environmental benefit that could actually help to cut disease and save lives. In Sheffield, for instance, if everyone washed their clothes in the additive, there would be no pollution problem caused by nitrogen oxides at all.”
The researchers say that as well as the benefits to general air quality, individuals with respiratory conditions could also improve the quality of the air they breathe by wearing clothes treated with CatClo.
The additive is said to function particularly well on denim, which is why a “Field of Jeans” display highlighting the benefits of the technology will be featured as part of the Manchester Science Festival that runs from October 27 to November 4.
The research team is currently working with a manufacturer to bring CatClo to market, with Professor Ryan estimating that using the additive in a final rinse of a full washing load would potentially cost as little as 10 pence (approx. US$0.16).
Source: University of Sheffield

Monday, January 07, 2013

Scientists create ultra-thin, cheap, flexible, transparent graphene semiconductors

A rendering of the gallium/arsenic nanowires on the graphene substrate

A rendering of the gallium/arsenic nanowires on the graphene substrate

Ordinarily, electronics are made with silicon semiconductors that are rigid, opaque, and about half a millimeter thick. Thanks to research being carried out at the Norwegian University of Science and Technology, however, that may be about to change. Led by Dr. Helge Weman and Prof. Bjørn-Ove Fimland, a team there has developed a method of making semiconductors out of graphene. At a thickness of just one micrometer, they are flexible and transparent. Also, because they require so little raw material, they should be considerably cheaper to manufacture than their silicon counterparts.
Graphene, for anyone who still doesn’t know, is a material made up of a one-atom thick sheet of hexagonally-linked carbon atoms. It is very electrically-conductive, inexpensive to produce, and is simultaneously the thinnest material in existence yet also one of the strongest.
To create the semiconductors, the Norwegian team starts by “bombing” a graphene substrate with gallium atoms, within a vacuum chamber. Those atoms stick to the graphene, and clump together with one another to form gallium droplets. On the underside of each droplet, where it meets the graphene, the gallium atoms naturally arrange themselves to match the hexagonal pattern of the graphene.
Next, arsenic molecules are also introduced to the graphene sheet, as the gallium atoms continue to rain down. Both arsenic molecules and gallium atoms are absorbed into the existing gallium droplets. Once inside a droplet, the arsenic travels to the bottom, where it combines with the gallium atoms. They form into a crystalline structure, on the bottom of the droplet.
As the process repeats itself, with countless other arsenic molecules entering the droplet and reacting with the gallium atoms on the bottom, the crystals accumulate to grow into a nanowire, with the droplet perched at the top. After just a few minutes, the hybrid finished product is ready – a graphene substrate covered with an array of one-micrometer-tall gallium/arsenic nanowires, evenly distributed in a hexagonal layout.
“A material comprising a pliable base that is also transparent opens up a world of opportunities, one we have barely touched the surface of,” said Dr. Weman. “This may bring about a revolution in the production of solar cells and LED components. Windows in traditional houses could double as solar panels or a TV screen. Mobile phone screens could be wrapped around the wrist like a watch. In short, the potential is tremendous.”
A spin-off company, CrayoNano, has been established to further develop the technology. Animation of the process can be seen in the video below.
Source: The Research Council of Norway

Sunday, January 06, 2013

Flexible, high-strength polymer aerogels deliver "super-insulation" properties

Flexible sheets of NASA's new polymer aerogel. A sheet this thick would provide thermal insulation equal to about an inch (25 mm) of foam insulation
Often called "frozen smoke", aerogels are among the amazing materials of our time, with fifteen Guinness Book of World Records entries to their name. However, despite their list of extreme properties, traditional aerogels are brittle, crumbling and fracturing easily enough to keep them out of many practical applications. A new class of mechanically robust polymer aerogels discovered at NASA's Glenn Research Center in Ohio may soon enable engineering applications such as super-insulated clothing, unique filters, refrigerators with thinner walls, and super-insulation for buildings.
First synthesized in 1931, aerogels were the result of a bet between two chemists. Knowing that jellies are mostly pectin gelled with water, they challenged each other to remove the water without shrinking the jelly. Now aerogels are among the least dense solids, possess compressive specific strength similar to aerospace grade graphite composite, and provide the smallest thermal conductivity for any solid. With this array of amazing properties, why don't we see more aerogel applications?
Mary Ann B. Meador, Ph.D., a chemist at NASA Glenn, explains that despite these amazing properties, traditional aerogels made from silica (silicon dioxide, or beach sand) are brittle, and break and crumble easily. Not so when newer polymer aerogels are considered. Meador and her team have developed a particularly encouraging form of polymer aerogel, which is strong, flexible, and robust against folding, creasing, crushing, and being stepped upon. Their new class of polymer aerogels won a 2012 R&D100 award.
“The new aerogels are up to 500 times stronger than their silica counterparts,” says Meador. “A thick piece actually can support the weight of a car. And they can be produced in a thin form, a film so flexible that a wide variety of commercial and industrial uses are possible.”
So just how did Meador and her colleagues approach the problem of synthesizing robust, flexible aerogels? Early attempts to produce stronger and more durable aerogels focused on taking a silica aerogel, and depositing a thin layer of a polymer on the surface of the aerogel structures. This can be done using chemical vapor deposition, for example, but the process is quite slow. (Such coating can also be accomplished by putting a silica aerogel in a small container with a pool of super glue, just as exposure to superglue vapors can reveal fingerprints by coating their grease.) In addition, most of the polymers that could be deposited in this manner have rather low melting temperatures, whereas many of the potential applications require some degree of thermal tolerance.
A new idea was called for. As the only role of the silica aerogel was to give shape to the conformal polymer coating, why not see if a polymer aerogel can be directly formed? Polyimides such as Kapton generally show resistance to temperatures of 400 C (750 F) or higher, are structurally very strong, and have high glass transition temperatures, so were an obvious candidate for such applications.
Unfortunately, standard methods for forming aerogels ran into serious problems. When polyimides in a dilute solution were gelled and then subjected to supercritical drying, the gels shrank by up to 40%, leading to unacceptably dense materials. A number of variations have been tried, primarily based on altering the properties of the polyimides with a range of additives, but these were unsatisfactory in various ways.
The NASA group tried a cross-linking approach, where linear polyamides were reacted with a bridging compound to form a three-dimensional covalent polymer. Such polymers are far more stiff than linear polymers, rather like an I-beam compared to a solid round rod of the same weight. They formed the gel at room temperature, and were able to achieve virtually total coupling between the various three-dimensional polymers. When this gel was subjected to supercritical drying, they were able to form polymer aerogels with densities as small as 0.14 g/cc and having 90% porosity – far from a record, but light enough to provide useful properties such as very low thermal conductivity.
Scanning electron micrograph of the nano-sized cell structure of NASA's new polymer aeroge...
The above micrograph of the nanocellular structure of the aerogel shows pores averaging about ten nanometers in size. A quarter-inch (6 mm) sheet of this aerogel would provide as much insulation as three inches of fiberglass.
The new class of polymer aerogels also have superior mechanical properties. For example silica aerogels of a similar density have a resistance to comperession and tensile limit more than 100 times smaller than the new polymer aerogels.
A Smart car parked on top of a thick piece of NASA's new polymer aerogel (Photo: NASA)
A Smart car parked on top of a thick piece of NASA's new polymer aerogel (Photo: NASA)
Silica aerogels would crush to powder if placed under a car tire. As seen above, the same is not true of the new polymer aerogels, even if the car is only a Smart car. Overall, the mechanical properties are rather like those of a synthetic rubber, save that the aerogel has the same properties (and far smaller thermal conductivity) with only about 10 percent of the weight.
Applications in clothing as well as insulation of pipes, buildings, water heaters, and the like are enabled by these materials. Tents and sleeping bags can also benefit from the combination of light weight and thermal insulation. NASA is even considering the new polymer aerogels for use as inflatable heat shields. The practicality of many such applications will depend on the cost of polymer aerogel in commercial quantities. In any case, these types of products now have another dimension of design flexibility.
Source: NASA Glenn Research Center

Saturday, January 05, 2013

The battery of the future might run on sugar

Researchers from the Tokyo University of Science have found pyrolyzed sucrose to be a surp... 
 Researchers from the Tokyo University of Science have found pyrolyzed sucrose to be a surprisingly effective material for the anode of sodium-ion batteries


Researchers at the Tokyo University of Science have turned to sugar as part of a continuous effort to control Japan's growing import costs associated with building lithium-ion batteries. It seems that sugar may be the missing ingredient for building rechargeable batteries that are more robust, cheaper, and capable of storing more energy.
Lithium-ion batteries are ubiquitous in portable electronics, but concerns over rapidly growing demands for lithium – a metal that is mainly found in politically sensitive regions such as Bolivia, Chile, Argentina and China – have pushed countries like Japan to try and develop viable alternatives for a cheap, high-performance rechargeable battery.
Sodium-ion batteries have been put forward as one of the possible successors to lithium-ion technology. Among their advantages, they promise to be more durable and cheaper to manufacture. However, being in an early developmental phase, their performance isn't currently quite up to par.
Associate Professor Shinichi Komaba and his team have been working on narrowing this performance gap and recently discovered that sucrose – the main constituent of sugar – can be easily made into a cheap and effective material for the anode of a sodium-ion battery.
The team heated sucrose to temperatures of up to 1,500 °C (2,700 °F) in a controlled oxygen-free atmosphere, a process known as pyrolysis. The result is a hard carbon powder that, when embedded in a sodium-ion battery, can achieve a storage capacity of 300mAh, 20% higher than conventional hard carbon.
While this is just one more step toward developing an effective sodium-ion battery, Komaba predicts that his group could achieve their final objective of a commercially competitive battery in around five years.
The video below, provided by Diginfo, is a short recap of the findings.
Sources: Diginfo, Stanford University

New low-cost material could help bolster carbon capture


A new material called NOTT-300 could help reduce emissions from coal-fired power plants, such as this one in central Utah

Researchers at the University of Nottingham have developed another weapon in the ongoing war to reduce the amount of greenhouse gases emitted from fossil fuel-burning power plants. The researchers have created a new porous material called NOTT-300 that they claim is cheaper and more efficient than existing materials at capturing polluting gases, such as carbon dioxide and sulfur dioxide, from flue gas.
While a wholesale switch from the burning of fossil fuels to greener alternatives such as solar, wind and wave power technologies would be the most environmentally friendly way to meet our ever-increasing demand for electricity, the simple fact is that the move will only be made incrementally. Carbon capture and sequestration is seen by many as one of the necessary steps on the road to a greener future, but current methods are expensive and consume large amounts of energy themselves.
The University of Nottingham researchers claim their NOTT-300 material offers a marked improvement over existing carbon capture methods that use a solvent that adsorbs CO2 and then releases water vapor to leave a concentrated stream of CO2 when heated. In comparison, NOTT-300 boasts a high uptake of CO2 and SO2 and releases the adsorbed gas chemicals through a simple reduction of pressure.
The material is also highly selective, with little or no adsorption into its pores of other gases, such as hydrogen, methane, nitrogen or oxygen. It also boasts high chemical stability to all common organic solvents and is stable in water at temperatures of up to 400° C (752° F). Additionally, as it is synthesized from cheap organic materials with water as the only solvent, it is cheap to produce.
“Our novel material has potential for applications in carbon capture technologies to reduce CO2 emissions and therefore contribute to the reduction of greenhouse gases in the atmosphere,” says Professor Martin Schröder, Dean of the Faculty of Science at The University of Nottingham. “It offers the opportunity for the development of an ‘easy on/easy off’ capture system that carries fewer economic and environmental penalties than existing technologies. It could also find application in gas separation processes where the removal of CO2 or acidic gases such as SO2 is required.”
The team’s research is published in the journal Nature Chemistry.
Source: University of Nottingham