Other materials stories that may be of interestPublished on May 15th, 2012 | By: Peter Wray
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A team led by Johns Hopkins engineers has discovered some previously unknown properties of a common memory material, paving the way for development of new forms of memory drives, movie discs and computer systems that retain data more quickly, last longer and allow far more capacity than current data storage media. The work was reported in the online edition of PNAS. The research focused on an inexpensive phase-change memory alloy composed of germanium, antimony and tellurium, called GST, for short. Although this phase-change material has been used for at least two decades, the precise mechanics of this switch from one state to another have remained something of a mystery because it happens so quickly-in nanoseconds-when the material is heated. To solve this mystery, Ming Xu and his team used another method to trigger the change more gradually. The researchers used two diamond tips to compress the material. They employed a process called X-ray diffraction and a computer simulation to document what was happening to the material at the atomic level. The researchers found that they could “tune” the electrical resistivity of the material during the time between its change from amorphous to crystalline form.
If you stacked alternating sheets of a material that conducts heat and another that insulates it, the heat would be conducted more freely sideways than in the top-to-bottom direction. Electrical engineers are familiar with this principle: It’s the same one that makes resistors, one of the most common electrical components, conduct more when wired in parallel than when wired in series. The breakthrough of the new research is to tailor composite materials so that their thermal conduction is not just side to side or top to bottom, but in a direction that changes throughout. “Heat current, like electric current, should be viewed as a medium that can be manipulated, controlled, and processed,” says study author Yuki Sato, a physicist at Harvard University. In principle, a thermal computer could be used for the same tasks as a normal computer, such as word processing or surfing the Internet, says Jiping Huang, a physicist at Fudan University in Shanghai, China. But a thermal computer would benefit from being energy saving, because it could run off waste heat in the environment—even heat produced by a human body.
The SunShot Grand Challenge: Summit and Technology Forum will feature key solar industry influencers at the event, which will take place June 13-14, 2012, in Denver, Colorado. Plenary speakers will include Energy Secretary Steven Chu; plasmonics pioneer Harry Atwater; SunPower founder Richard Swanson; BrightSource Energy CEO John Woolard. Additional speakers will be announced in the coming weeks.The forum is the first event in a series of DOE’s Grand Challenges. This event focuses on SunShot Initiative goals of achieving grid-parity solar energy within the decade. Through the Grand Challenge series, the Energy Department is launching a broad-based effort to address the scientific, technological, and market barriers to achieving breakthroughs in national energy challenges.
Drawing on powerful computational tools and a state-of-the-art scanning transmission electron microscope, a team of University of Wisconsin-Madison and Iowa State University materials science and engineering researchers has discovered a new nanometer-scale atomic structure in solid metallic materials known as metallic glasses. This understanding ultimately could help manufacturers fine-tune such properties of metallic glasses as ductility, the ability to change shape under force without breaking, and formability, the ability to form a glass without crystalizing. In studies of a zirconium-copper-aluminum metallic glass, lead researcher Paul Voyles’ team found there are clusters of squares and hexagons-in addition to clusters of pentagons, some of which form chains-all located within the space of just a few nanometers. “One or two nanometers is a group of about 50 atoms-and it’s how those 50 atoms are arranged with respect to one another that’s the new and interesting part,” he says.
Strange new materials experimentally identified just a few years ago are now driving research in condensed-matter physics around the world. First theorized and then discovered by researchers at the DOE’s Lawrence Berkeley National Laboratory and their colleagues in other institutions, these “strong 3D topological insulators”—TIs for short-are seemingly mundane semiconductors with startling properties. For starters, picture a good insulator on the inside that’s a good conductor on its surface—something like a copper-coated bowling ball. A topological insulator’s surface is not an ordinary metal, however. The direction and spin of the surface electrons are locked together and change in concert. And perhaps the most surprising prediction is that the surface electrons cannot be scattered by defects or other perturbations and thus meet little or no resistance as they travel. In the jargon, the surface states remain “topologically protected”-they can’t scatter without breaking the rules of quantum mechanics. The TI in question is bismuth selenide, Bi2Se3, on whose surface electrons can flow at room temperature, making it an attractive candidate for practical applications like spintronics devices, plus farther-out ones like quantum computers. Much of the research on electron-phonon coupling in Bi2Se3 was conducted at beamline 12.0.1
(GigaOm) China likes to do things on a grand scale, which allows it to serve its vast population and brag about its technical advancements. The country is now building a 800-kilovolt transmission line that will ferry wind and solar power over 2,210 kilometers (1,373 miles) and when completed in 2014 could claim a world record for its capacity of 8 GW, according to the Chinese government-run China Daily. This isn’t the first project to use ultrahigh voltage direct current lines at 800 kV, which are state of the art. Both Siemens and ABB, two powerline equipment makers, previously announced projects selling their 800 kV equipment to China Southern Power Grid and State Grid Corporation of China, respectively. State Grid will also build the project touted by People’s Daily on Monday. The project will run power lines from the Hami prefecture in the Xinjiang province in the west to Zhengzhou city in Henan province in central China. The equipment will rise up along regions of big solar power development, such as the Gansu and Ningxia provinces. The project will cost 23.39 billion yuan ($3.7 billion), People’s Daily reports
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