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Materialteknologi

InnleggSkrevet: 09 Sep 2010, 15:08
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North Carolina State University, September 8, 2010: A North Carolina State University researcher and colleagues have figured out a way to make an aluminum alloy just as strong as steel. That’s important, says Dr. Yuntian Zhu, professor of materials science and the NC State researcher involved in the project, because the search for ever lighter – yet stronger – materials is crucial to devising everything from more fuel-efficient cars to safer airplanes. In a paper published in the journal Nature Communications, Zhu and his colleagues describe the new nanoscale architecture within aluminum alloys that have unprecedented strength but also reasonable plasticity to stretch and not break under stress. The technique of creating these nanostructures can be used on many different types of metals. Zhu says the aluminum alloys have unique structural elements that, when combined to form a hierarchical structure at several nanoscale levels, make them super-strong and ductile. Now, Zhu plans on working on strengthening magnesium, a metal that is even lighter than aluminum. He’s collaborating with the Department of Defense on a project to make magnesium alloys strong enough to be used as body armor for soldiers - Study Shows Nano-Architectured Aluminum Has Steely Strength

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InnleggSkrevet: 13 Sep 2010, 19:04
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Massachusetts Institute of Technology, September 13, 2010: New antenna made of carbon nanotubes could make photovoltaic cells more efficient by concentrating solar energy. Using carbon nanotubes, MIT chemical engineers have found a way to concentrate solar energy 100 times more than a regular photovoltaic cell. “Instead of having your whole roof be a photovoltaic cell, you could have little spots that were tiny photovoltaic cells, with antennas that would drive photons into them,” says Michael Strano, the Charles and Hilda Roddey Associate Professor of Chemical Engineering and leader of the research team. Strano and his students describe their new carbon nanotube antenna, or “solar funnel,” in the Sept. 12 online edition of the journal Nature Materials. Lead authors of the paper are postdoctoral associate Jae-Hee Han and graduate student Geraldine Paulus. Their new antennas might also be useful for any other application that requires light to be concentrated, such as night-vision goggles or telescopes - Solar funnel

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This filament containing about 30 million carbon nanotubes absorbs energy
from the sun as photons and then re-emits photons of lower energy, creating
the fluorescence seen here. The red regions indicate highest energy intensity,
and green and blue are lower intensity.
Image: Geraldine Paulus

Re: Materialteknologi

InnleggSkrevet: 19 Sep 2010, 17:09
nico
Mer om sterke lettmetaller

http://news.sciencemag.org/sciencenow/2 ... m-as-.html

Metal Smasher Makes Aluminum as Strong as Steel

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Strong as steel. Atom probe tomography suggests that packing zinc and magnesium atoms together in groups of various sizes (small spots) can greatly improve the strength of aluminum alloy.



Snuffing out a cigarette butt with a 10-ton boot would be excessive, but using the equivalent on certain metals can yield amazing results. By smashing an aluminum alloy between two anvils, researchers have created a metal that's as strong as steel but much lighter. If the process can be commercialized, it could yield better components for aircraft and automobiles, as well as metal armor light enough for soldiers to wear in battle.

Aluminum's main advantage is its lightness. But the second-most-abundant metal in Earth's crust is also a weakling: It breaks apart under loads that heavier metals such as steel shoulder easily. For decades, scientists have been looking for a way to manufacture the aluminum equivalent of titanium, a lightweight metal that's stronger than steel, but without titanium's high cost.

In the new study, an international team of materials scientists turned to an emerging metal-processing technique called high-pressure torsion (HPT). Basically, HPT involves clamping a thin disk of metal to a cylindrical anvil and pressing it against another anvil with a force of about 60,000 kilograms per square centimeter, all while turning one anvil slowly. The researchers also kept the processed samples at room temperature for over a month, in a common metallurgical process called natural aging. The deformation under the enormous pressure plus the aging alters the basic structure of metals at the nanoscale—or distances measured in billionths of a meter.

And indeed, when the team subjected an alloy of aluminum called aluminum 7075 (which contains small percentages of magnesium and zinc) to the process, the metal attained a strength of 1 gigapascal, the researchers report in the current issue of Nature Communications. That's equal to some of the strongest steels and more than three times higher than conventional aluminum. A meter-square plate of the processed alloy could withstand the weight of a fully loaded aircraft carrier.

To find out why the alloy had gotten so much stronger, the team examined samples using a technique called atom probe tomography. Resembling a combination of an electron microscope and a CT scanner, the method showed that HPT had deformed the lattice of atoms in the alloy into an unprecedented arrangement. Instead of the normal structure found in the conventional metal, HPT had created what the researchers call a hierarchical nanostructure: the size of the aluminum grains was reduced, and the zinc and magnesium atoms clustered together in groups of various sizes, depending on whether they were located inside the aluminum grains or on the edges (see photo).

Exactly how this arrangement creates stronger aluminum is unclear, says co-author Simon Ringer, director of the Electron Microscope Unit at the University of Sydney in Australia. He says the atoms at the edges of the grains seem to be bonded tightly to atoms at adjoining grain edges. Whatever the physics, he says, the hierarchical structures are "very potent for strengthening."

Ringer adds that even though the experiments produced only laboratory quantities of the superstrength alloy, the process could quickly be adapted to produce small components that require high strength but low weight, such as biomedical implants. Co-author and materials scientist Yuntian Zhu of North Carolina State University in Raleigh says there is strong incentive to scale up the process because the alloy could be useful for "many lightweight, energy-efficient applications such as aerospace, transportation, and body armor."

The experiments "have achieved remarkable strength" in a conventional commercial aluminum alloy, says materials scientist Terence Langdon of the University of Southern California in Los Angeles. The research team has also demonstrated "the exceptional capabilities provided through processing by high-pressure torsion," a technique that Langdon and others have been working with for several years.

Materials scientist Yuri Estrin of Monash University in Melbourne, Australia, calls the results exciting and agrees that the hierarchical nanostructures "appear to be crucial to the spectacular enhancement of [the alloy's] strength."

Re: Materialteknologi

InnleggSkrevet: 30 Sep 2010, 03:25
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Nanowerk, September 29, 2010: A revolutionary new spherical nanostructure, fully derived from very simple organic elements, yet strong as steel, has been developed and characterized at the laboratories of Ehud Gazit of Tel Aviv University and Itay Rousso of the Weizmann Institute of Science. Hard and strong as steel, this new nanostructure is an ideal element for the reinforcement of composite materials used in the space, aviation and transportation industries; biologically compatible yet extremely rigid and durable, it is an excellent candidate for replacing metallic implants; tough, light and impenetrable, it is an exceptional option for manufacturing bullet-proof vests; - to name just a few high-potential uses - Nanotechnology Team Reports the Strongest Organic Nano-Material Ever Developed

Re: Materialteknologi

InnleggSkrevet: 04 Nov 2010, 22:42
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University of St Andrews, November 4, 2010: An Invisible Man with perfect vision sounds like a superhero from a comic, but may be close to reality thanks to scientists at the University of St Andrews. The St Andrews’ research team, led by EPSRC Career Acceleration Fellow Dr Andrea Di Falco, have developed an elaborate technique which frees the meta-atoms from the hard surface (‘substrate’) they are constructed on - Scientists create 'invisible' material

Re: Materialteknologi

InnleggSkrevet: 03 Des 2010, 05:00
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NASA, December 2, 2010: Black is black, right? Not so, according to a team of NASA engineers now developing a blacker-than pitch material that will help scientists gather hard-to-obtain scientific measurements or observe currently unseen astronomical objects, like Earth-sized planets in orbit around other stars. The nanotech-based material now being developed by a team of 10 technologists at the NASA Goddard Space Flight Center in Greenbelt, Md., is a thin coating of multi-walled carbon nanotubes — tiny hollow tubes made of pure carbon - Blacker Than Black


Re: Materialteknologi

InnleggSkrevet: 06 Des 2010, 19:25
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Science, December 3, 2010: Viscoelasticity describes the ability of a material to possess both elasticity and viscosity. Viscoelastic materials, such as rubbers, possess a limited operational temperature range (for example, for silicone rubber it is –55° to 300°C), above which the material breaks down and below which the material undergoes a glass transition and hardens. We created a viscoelastic material composed from a random network of long interconnected carbon nanotubes that exhibited an operational temperature range from –196° to 1000°C. The storage and loss moduli, frequency stability, reversible deformation level, and fatigue resistance were invariant from –140° to 600°C. We interpret that the thermal stability stems from energy dissipation through the zipping and unzipping of carbon nanotubes at contacts - Carbon Nanotubes with Temperature-Invariant Viscoelasticity from –196° to 1000°C


Re: Materialteknologi

InnleggSkrevet: 16 Des 2010, 03:13
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Nature, December 15, 2010: Until now, physicists have been unable to fabricate a cloak that could hide macroscopic items at visible wavelengths. Two independent groups have now achieved this feat, by building transparent 'carpet cloaks', made from calcite crystals, that lie over the object to be hidden - Invisibility rug hides 'large' objects

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A calcite carpet-cloak can shield a steel wedge a few cm long.

Re: Materialteknologi

InnleggSkrevet: 21 Des 2010, 05:22
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Lawrence Berkeley National Laboratory, December 20, 2010: For years, scientists have been searching for an example of Möbius symmetry in natural materials without any success. Now a team of scientists has discovered Möbius symmetry in metamaterials - Strange New Twist: Berkeley Researchers Discover Möbius Symmetry in Metamaterials

Re: Materialteknologi

InnleggSkrevet: 06 Jan 2011, 05:30
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University of Illinois, January 5, 2011: Led by mechanical science and engineering professor Nicholas Fang, Illinois researchers have demonstrated an acoustic cloak, a technology that renders underwater objects invisible to sonar and other ultrasound waves. While materials that can wrap sound around an object rather than reflecting or absorbing it have been theoretically possible for a few years, realization of the concept has been a challenge. The cloak is made of metamaterial, a class of artificial materials that have enhanced properties as a result of their carefully engineered structure - Newly developed cloak hides underwater objects from sonar

Re: Materialteknologi

InnleggSkrevet: 10 Jan 2011, 23:03
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Lawrence Berkeley National Laboratory, January 10, 2011: Glass stronger and tougher than steel? A new type of damage-tolerant metallic glass, demonstrating a strength and toughness beyond that of any known material, has been developed and tested by a collaboration of researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the California Institute of Technology. What’s more, even better versions of this new glass may be on the way. “These results mark the first use of a new strategy for metallic glass fabrication and we believe we can use it to make glass that will be even stronger and more tough,” says Robert Ritchie, a materials scientist who led the Berkeley contribution to the research - New Glass Tops Steel in Strength and Toughness

Re: Materialteknologi

InnleggSkrevet: 01 Mar 2011, 22:35
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Yale University, February 28, 2011: A team led by Jan Schroers, a materials scientist at Yale University, has shown that some recently developed bulk metallic glasses (BMGs)-metal alloys that have randomly arranged atoms as opposed to the orderly, crystalline structure found in ordinary metals-can be blow molded like plastics into complex shapes that can't be achieved using regular metal, yet without sacrificing the strength or durability that metal affords. Their findings are described online in the current issue of the journal Materials Today. "These alloys look like ordinary metal but can be blow molded just as cheaply and as easily as plastic," Schroers said. So far the team has created a number of complex shapes-including seamless metallic bottles, watch cases, miniature resonators and biomedical implants-that can be molded in less than a minute and are twice as strong as typical steel. The materials cost about the same as high-end steel, Schroers said, but can be processed as cheaply as plastic - Stronger Than Steel, Novel Metals Are Moldable as Plastic

Re: Materialteknologi

InnleggSkrevet: 16 Mar 2011, 12:27
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General Electric, March 15, 2011: Scientists in GE’s Global Research Center have demonstrated an advanced thermal material system that could pave the way to faster computing and higher performing electronic systems. [...] During testing at the Air Force Research laboratories, GE’s research team successfully demonstrated a prototype substrate that was measured to have at least twice the thermal conductivity as copper at only one–fourth of its weight. In addition, the prototype successfully operated in a condition that was more than 10 times normal gravity - GE Scientists Demonstrate Breakthrough Thermal Material System to Enable Faster Computing


Re: Materialteknologi

InnleggSkrevet: 20 Apr 2011, 21:10
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University of Technology Sydney, April 20, 2011: UTS Scientists have reported remarkable results in developing a composite material based on graphite that is a thin as paper and ten times stronger than steel. [...] Compared to steel, the prepared GP is six times lighter, five to six times lower density, two times harder with 10 times higher tensile strength and 13 times higher bending rigidity - A breakthrough on paper that's stronger than steel

Re: Materialteknologi

InnleggSkrevet: 24 Apr 2011, 10:46
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Nature, April 20, 2011: Polymers with the ability to repair themselves after sustaining damage could extend the lifetimes of materials used in many applications. Most approaches to healable materials require heating the damaged area. Here we present metallosupramolecular polymers that can be mended through exposure to light. They consist of telechelic, rubbery, low-molecular-mass polymers with ligand end groups that are non-covalently linked through metal-ion binding. On exposure to ultraviolet light, the metal–ligand motifs are electronically excited and the absorbed energy is converted into heat. This causes temporary disengagement of the metal–ligand motifs and a concomitant reversible decrease in the polymers’ molecular mass and viscosity, thereby allowing quick and efficient defect healing - Optically healable supramolecular polymers