Other materials stories that may be of interestPublished on February 19th, 2013 | By: Eileen De Guire
Lots of interesting things going on around the US and the world:
A new type of nanoscale engine has been proposed that would use quantum dots to generate electricity from waste heat, potentially making microcircuits more efficient. The engines would be microscopic in size, and have no moving parts. Each would only produce a tiny amount of power—a millionth or less of what a light bulb uses. But by combining millions of the engines in a layered structure, researchers at the University of Rochester say a device that was a square inch in area could produce about a watt of power for every one degree difference in temperature. They say the path the electrons have to take across both quantum dots can be adjusted to have an uphill slope. To make it up this (electrical) hill, electrons need energy. They take the energy from the middle of the region, which is kept hot, and use this energy to come out the other side, higher up the hill. This removes heat from where it is being generated and converts it into electrical power with a high efficiency. To do this, the system makes use of a quantum mechanical effect called resonant tunneling, which means the quantum dots act as perfect energy filters. When the system is in the resonant tunneling mode, electrons can only pass through the quantum dots when they have a specific energy that can be adjusted. All other electrons that do not have this energy are blocked.
A team of researchers from Russia, Spain, Belgium, the UK and the DOE’s Argonne National Laboratory announced findings last week that may represent a breakthrough in applications of superconductivity. The team discovered a way to efficiently stabilize tiny magnetic vortices that interfere with superconductivity-a problem that has plagued scientists trying to engineer real-world applications for decades. The discovery could remove one of the most significant roadblocks to advances in superconductor technology. When magnetic fields reach a certain strength, they cause a superconductor to lose its superconductivity. But there is a type of superconductor-known as “Type II”-which is better at surviving in relatively high magnetic fields. In these superconductors, magnetic fields create tiny whirlpools or “vortices.” Superconducting current continues to travel around these vortices to a point, but eventually, as the magnetic field strengthens, the vortices begin to move about and interfere with the material’s superconductivity, introducing resistance. Scientists have spent a lot of time and effort over the past few decades trying to immobilize these vortices, but until now, the results have been mixed. The team, however, discovered a surprise. They began with very thin superconducting wires that could accommodate only one row of vortices. When researchers applied a high magnetic field, the vortices crowded together in long clusters and stopped moving. Increasing the magnetic field restored the material’s superconductivity, instead of destroying it. Next, the team carved superconducting film into an array of holes so that only a few vortices could squeeze between the holes, where they stayed, unable to interfere with current.
A new form of clean coal technology reached an important milestone recently, with the successful operation of a research-scale combustion system at Ohio State University. The technology is now ready for testing at a larger scale. For 203 continuous hours, the Ohio State combustion unit produced heat from coal while capturing 99 percent of the carbon dioxide produced in the reaction. The key to the technology is the use of tiny metal beads to carry oxygen to the fuel to spur the chemical reaction. The fuel is coal that’s been ground into a powder, and mixed with metal beads made of iron oxide composites. The coal and iron oxide are heated to high temperatures, where the materials react with each other. Carbon from the coal binds with the oxygen from the iron oxide and creates carbon dioxide, which rises into a chamber where it is captured. Hot iron and coal ash are left behind. Because the iron beads are so much bigger than the coal ash, they are easily separated out of the ash, and delivered to a chamber where the heat energy would normally be harnessed for electricity. The coal ash is removed from the system. The carbon dioxide is separated and can be recycled or sequestered for storage. The iron beads are exposed to air inside the reactor, so that they become re-oxidized be used again. The beads can be re-used almost indefinitely, or recycled.
Silicon, the material of high-tech devices from computer chips to solar cells, requires a surface coating before use in these applications. The coating “passivates” the material, tying up loose atomic bonds to prevent oxidation that would ruin its electrical properties. But this passivation process consumes a lot of heat and energy, making it costly and limiting the kinds of materials that can be added to the devices. Now a team of MIT researchers has found a way to passivate silicon at room temperature, which could be a significant boon to solar-cell production and other silicon-based technologies. Typically, silicon surfaces are passivated with a coating of silicon nitride, which requires heating a device to 400°C. By contrast, the team’s process team uses organic vapors decomposed over wires heated to 300°C, but the silicon itself never goes above 20°C.
Workers began installing thousands of energy-efficient glass panels at the base of 1 World Trade Center Friday. The panels will adorn the podium wall and are designed to maximize sunlight while keeping the inside cool. LED lights will be housed within the panels, which officials say will give the base a look that is both visually pleasing and environmentally friendly. More than 4,000 glass panels will be used to cover the buildings base.
A new material that generates electricity from body heat could lead to clothing that can keep a mobile phone charged. The material developed by scientists in South Korea is an organic thermoelectric generator (TEG) that produces an electric charge from the temperature difference between the body and the environment and can be formulated as a flexible, cuttable film. The researchers from Yonsei University led by Eunkyoung Kim, synthesised a polymer based on an electrically conductive material known as PEDOT (poly(3,4-ethylenedioxythiophene)), which has been investigated for use protecting the cathodes and anodes in fuel cells from fouling. Kim’s team combined a method to polymerise the material directly from solution with a reduction/oxidation reaction. This produced a material that has a power factor—a measure of how much electricity can be produced related to the temperature difference-of 1270µM/m/K2, four times higher than any previous organic TEG. The material is flexible enough to be incorporated into clothing and the team now hope to use the material to produce a wearable item that can harvest electricity from human body heat.
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