Compartido por Tweetcaster
lunes, 3 de febrero de 2014
viernes, 20 de septiembre de 2013
A major milestone in the quest to find more efficient ways of generating electricity from waste heat, and to reduce carbon emissions, has real potential in a vast range of applications - from reducing the energy consumption of cars by converting exhaust heat into electrical power, to cooling hot spots on computer chips and solid state refrigerators, even powering deep-space missions.
This important research, which was led by the University of London's Royal Holloway, and included STFC's Scientific Computing department, is reported in Nature Materials. This approach will pave the way for the design of a new, environmentally-friendly generation of thermoelectric materials, that is more effective than any currently in existence – and which can convert heat into electricity which can also be used for cooling.
As part of the project, the team conducted a series of experiments on thermoelectric sodium cobaltate at STFC's ISIS pulsed neutron and muon source at its Rutherford Appleton Laboratory, as well as at the European Synchrotron Radiation Facility (ESRFC) and the Institut Laue-Langevin in Grenoble, UK access to both of which is funded by STFC.
Advanced computer calculations, which were central to the interpretation of the experiments, were performed by STFC's Scientific Computing Department. Dr Keith Refson, Computational Scientist at STFC, said:
View the full press release.
Notes to Editors
This research paper has been published in Nature Materials - "Suppression of thermal conductivity by rattling modes in thermoelectric sodium cobaltate" - D. J. Voneshen, et al, paper reference: doi:10.1038/nmat3739.
The Science and Technology Facilities Council is keeping the UK at the forefront of international science and tackling some of the most significant challenges facing society such as meeting our future energy needs, monitoring and understanding climate change, and global security.
The Council has a broad science portfolio and works with the academic and industrial communities to share its expertise in materials science, space and ground-based astronomy technologies, laser science, microelectronics, wafer scale manufacturing, particle and nuclear physics, alternative energy production, radio communications and radar.
STFC operates or hosts world class experimental facilities including in the UK the ISIS pulsed neutron source, the Central Laser Facility, and LOFAR, and is also the majority shareholder in Diamond Light Source Ltd.
It enables UK researchers to access leading international science facilities by funding membership of international bodies including European Laboratory for Particle Physics (CERN), the Institut Laue Langevin (ILL), European Synchrotron Radiation Facility (ESRF) and the European Southern Observatory (ESO). STFC is one of seven publicly-funded research councils.
It is an independent, non-departmental public body of the Department for Business, Innovation and Skills (BIS).
Follow us on Twitter at @STFC_Matters.
jueves, 19 de septiembre de 2013
Researchers at North Carolina State University have created a new compound that can be integrated into silicon chips and is a dilute magnetic semiconductor – meaning that it could be used to make "spintronic" devices, which rely on magnetic force to operate, rather than electrical currents.
The researchers synthesized the new compound, strontium tin oxide (Sr3SnO), as an epitaxial thin film on a silicon chip. Epitaxial means the material is a single crystal. Because Sr3SnO is a dilute magnetic semiconductor, it could be used to create transistors that operate at room temperature based on magnetic fields, rather than electrical current.
"We're talking about cool transistors for use in spintronics," says Dr. Jay Narayan, John C. Fan Distinguished Professor of Materials Science and Engineering at NC State and senior author of a paper describing the work. "Spintronics" refers to technologies used in solid-state devices that take advantage of the inherent "spin" in electrons and their related magnetic momentum.
"There are other materials that are dilute magnetic semiconductors, but researchers have struggled to integrate those materials on a silicon substrate, which is essential for their use in multifunctional, smart devices," Narayan says. "We were able to synthesize this material as a single crystal on a silicon chip."
"This moves us closer to developing spin-based devices, or spintronics," says Dr. Justin Schwartz, co-author of the paper, Kobe Steel Distinguished Professor and Department Head of the Materials Science and Engineering Department at NC State. "And learning that this material has magnetic semiconductor properties was a happy surprise."
The researchers had set out to create a material that would be a topological insulator. In topological insulators the bulk of the material serves as an electrical insulator, but the surface can act as a highly conductive material – and these properties are not easily affected or destroyed by defects in the material. In effect, that means that a topological insulator material can be a conductor and its own insulator at the same time.
Two materials are known to be topological insulators – bismuth telluride and bismuth selenide. But theorists predicted that other materials may also have topological insulator properties. Sr3SnO is one of those theoretical materials, which is why the researchers synthesized it. However, while early tests are promising, the researchers are still testing the Sr3SnO to confirm whether it has all the characteristics of a topological insulator.
The paper, "Epitaxial integration of dilute magnetic semiconductor Sr3SnO with Si (001)," was published online Sept. 9 in Applied Physics Letters. Lead author of the paper is Y. F. Lee, a Ph.D. student at NC State. Co-authors include F. Wu and R. Kumar, both Ph.D. students at NC State, and Dr. Frank Hunte, an assistant professor at NC State. The work was supported, in part, by the National Science Foundation.
Note to Editors: The study abstract follows.
"Epitaxial integration of dilute magnetic semiconductor Sr3SnO with Si (001)"
Authors: Y.F. Lee, F. Wu, R. Kumar, F. Hunte, J. Schwartz, and J. Narayan, North Carolina State University
Published: online Sept. 9, Applied Physics Letters
Abstract: Epitaxial thin films heterostructures of topological insulator candidate Sr3SnO (SSO) are grown on a cubic yttria-stabilized zirconia (c-YSZ)/Si (001) platform by pulsed laser deposition. X-ray and electron diffraction patterns confirm the epitaxial nature of the layers with cube-on-cube orientation relationship: (001)SSOk(001)c-YSZk(001)Si. The temperature dependent electrical resistivity shows semiconductor behavior with a transport mechanism following the variable-range-hopping model. The SSO films show room-temperature ferromagnetism with a high saturation magnetization, and a finite non-zero coercivity persisting up to room temperature. These results indicate that SSO is a potential dilute magnetic semiconductor, presumably obtained by controlled introduction of intrinsic defects.
New research from NBI shows that cement made with waste ash from sugar production is stronger than ordinary...
martes, 10 de septiembre de 2013
Posted by A'ndrea Elyse Messer-Penn State on September 10, 2013
Researchers have combined several approaches to test natural materials from squid, mussels, and marine snails that may lead to a wide range of biologically inspired products.
The researchers combined three approaches—protein studies, materials science, and RNA sequencing—that would allow them to quickly characterize the materials and translate their molecular designs into useable, unique materials.
"Biological methods of synthesizing materials are not new," says Melik C. Demirel, professor of engineering science and mechanics at Penn State. "What is new is the application of these principles to produce unique materials."
Demirel and colleagues looked at proteins because they are the building blocks of biological materials and also often control sequencing, growth, and self-assembly. RNA produced from the DNA in the cells is the template for biological proteins. Materials science practices allow researchers to characterize all aspects of how a material functions.
"One problem with finding suitable biomimetic materials is that most of the genomes of model organisms have not yet been sequenced," says Demirel. "Also, the proteins that characterize these materials are notoriously difficult to solubilize and characterize."
The researchers examined three model systems: egg case membranes of a tropical marine snail, a mussel foot, and jumbo squid sucker ring teeth.
Snail, mussel, squid
The egg case membranes of a tropical marine snail are intriguing because they have unusual shock-absorbing qualities and elasticity. The analysis shows that the material has a coiled structure with cross-linking that absorbs energy.
Analysis of a mussel foot showed that a species-to-species variation exists in mussels, including unusual variation in the protein. These variations suggest that protein engineering could produce a range of self-healing properties.
The final model used jumbo squid sucker ring teeth (SRT), grappling-hook-like structures used for predatory attacks. Analysis of the squid teeth showed nanotubular structure and strong polymers. While there was some similarity to silk and oyster shell matrix proteins, the protein was novel and the researchers named it Suckerin-39. Further analysis showed that Suckerin-39′s structure allowed it to be reprocessed into a variety of shapes.
"While some biological materials have interesting properties, they cannot be reshaped or remolded because they do not soften upon heating," says Demirel. "The SRT is an elastomer, which is moldable, it is a thermoplastic and can be reshaped."
The materials properties of SRT do not change after heating and reshaping.
"We now know that nature can do all kinds of things including nanotubes, cross-linked structures, and shock-absorbing coils," says Demirel. "Now that we know the secrets, we need to find ways to mimic the structures and do it inexpensively."
This may mean having bacteria produce the required proteins or some other biomimetic approach.
"Integrating these ecofriendly materials into devices for wetting, friction, and transport is relatively straightforward and will constitute an important part of our future research," says Demirel.
Ali Miserez, an assistant professor at Nanyang Technological University in Singapore, led the project, which was funded in part by the Office of Naval Research and the National Institutes of Heath. The results of the work appear in a recent issue of Nature Biotechnology.
Source: Penn State
lunes, 9 de septiembre de 2013
UNIVERSITY PARK, Pa. -- A wide range of biologically inspired materials may now be possible by combining protein studies, materials science and RNA sequencing, according to an international team of researchers.
"Biological methods of synthesizing materials are not new," said Melik C. Demirel, professor of engineering science and mechanics, Penn State. "What is new is the application of these principles to produce unique materials."
The researchers looked at proteins because they are the building blocks of biological materials and also often control sequencing, growth and self-assembly. RNA produced from the DNA in the cells is the template for biological proteins. Materials science practices allow researchers to characterize all aspects of how a material functions. Combining these three approaches allows rapid characterization of natural materials and the translation of their molecular designs into useable, unique materials.
"One problem with finding suitable biomimetic materials is that most of the genomes of model organisms have not yet been sequenced," said Demirel who is also a member of the Materials Research Institute and Huck Institutes of Life Sciences, Penn State. "Also, the proteins that characterize these materials are notoriously difficult to solubilize and characterize."
The team, lead by Ali Miserez, assistant professor, School of Materials Science and Engineering, Nanyang Technological University, Singapore, looked at mollusk-derived tissues that had a wide range of high-performance properties including self-healing elastomeric membranes and protein-based polymers. They combined a variety of approaches including protein sequencing, amino acid composition and a complete RNA reference database for mass spectrometry analysis. They present their results in a recent issue of Nature Biotechnology.
The researchers looked at three model systems. The protein containing egg case membranes of a tropical marine snail are intriguing because they have unusual shock-absorbing qualities and elasticity. Investigation using the variety of methods showed this material has a coiled structure with crosslinking that absorbs energy. This information can be applied to biomimetic engineering of robust yet permeable coiled, protein-based membranes with precisely tailored mechanical properties.
The array of techniques applied to analysis of a mussel foot showed that a species-to-species variation exists in mussel, including unusual variation in the protein. These variations suggest that protein engineering could produce a range of self-healing properties.
The final model used jumbo squid sucker ring teeth (SRT), grappling-hook-like structures used for predatory attacks. Analysis of the squid teeth showed nanotubular structure and strong polymers. While there was some similarity to silk and oyster shell matrix proteins, the protein was novel and the researchers named it Suckerin-39. Further analysis showed that Suckerin-39's structure allowed it to be reprocessed into a variety of shapes.
"While some biological materials have interesting properties, they cannot be reshaped or remolded because they do not soften upon heating," said Demirel. "The SRT is an elastomer, which is moldable, it is a thermoplastic and can be reshaped."
The materials properties of SRT do not change after heating and reshaping.
"We now know that nature can do all kinds of things including nanotubes, cross-linked structures and shock-absorbing coils," said Demirel. "Now that we know the secrets, we need to find ways to mimic the structures and do it inexpensively."
This may mean having bacteria produce the required proteins or some other biomimetic approach.
"Integrating these eco-friendly materials into devices for wetting, friction and transport is relatively straightforward and will constitute an important part of our future research," said Demirel.
Also working on this project from Penn State was Abdon Pena-Francesch, graduate student in engineering science and mechanics.
Those at other institutions include Paul A. Guerette; Shawn Hoon; Sharouz Amini; Gavin Tay; and Dawei Ding, all of Nanyang Technological University, Singapore. Yiqi Seow; Fong Tian Wong, Vincent H.B. Ho; Kong Kiat Whye, all of Biomedical Sciences Institute, Singapore. Manfred Raida, Experimental Therapeutics Centre, Singapore; Admir Masic, Max-Planck Institute of Colloids and Interfaces, Potsdam, Germany.
The Office of Naval Research and NIH partially funded this research.
viernes, 30 de agosto de 2013
Earthquake researchers test out a super-elastic material known as nitinol, with promising results
August 27, 2013
Bridges are a main component of the transportation infrastructure as we know it today. There are no less than 575,000 highway bridges nationwide, and more than $5 billion are allocated yearly from the federal budget for bridge repairs.
Over the past couple of decades, increasing seismic activity around the world has been identified as an impending threat to the strength and well-being of our bridges. Earthquakes have caused bridge collapses in the U.S., Japan, Taiwan, China, Chile, Turkey, and elsewhere. Therefore, we need to find ways to minimize seismic effects on bridges, both by improving existing bridges and refining specifications and construction materials for future bridges.
A large majority of bridges are made of steel and concrete. While this combination is convenient and economical, steel-concrete bridges don't hold up as well in strong earthquakes (7.0 magnitude or higher). Conventional reinforced columns rely on the steel and concrete to dissipate energy during strong earthquakes, potentially creating permanent deformation and damage in the column and making the column unusable.
Under earthquake loading, engineers allow for damage in column hinges to dissipate energy and prevent total bridge collapse. While that practice is widely accepted, the effects of hinge damage can interfere with disaster recovery operations and have a major economic impact on the community.
With funding from the National Science Foundation (NSF) and using NSF's George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES), civil engineer M. Saiid Saiidi of the University of Nevada, Reno (UNR), and his colleagues have discovered a solution. They've identified several smart materials as alternatives to steel and concrete in bridges.
Shape memory alloys (SMAs) are unique in their ability to endure heavy strain and still return to their original state, either through heating or superelasticity. SMAs demonstrate an ability to re-center bridge columns, which minimizes the permanent tilt columns can experience after an earthquake.
Nickel titanium, or nitinol, the shape memory alloy tested in the UNR project, has a unique ability even amongst SMAs. While the majority of SMAs are only temperature-sensitive, meaning that they require a heat source to return to their original shape, Nitinol is also superelastic. This means that it can absorb the stress imposed by an earthquake and return to its original shape, which makes nitinol a particularly advantageous alternative to steel. In fact, the superelasticity of nickel titanium is between 10 to 30 times the elasticity of normal metals like steel.
Many of us know nickel titanium from our flexible prescription eyeglass frames. The material allows frames to easily return to their original shape after being bent in any direction. Nickel titanium's uses are extremely varied, with applications that range from medicine to heat engines, lifting devices and even novelty toys--and now, earthquake engineering.
To assess the performance of nickel-titanium reinforced concrete bridges, the researchers analyzed three types of bridge columns: traditional steel and concrete, nickel titanium and concrete, and nickel titanium and engineered cementitious composites (ECC), which include cement, sand, water, fiber and chemicals. First, they modeled and tested the columns in OpenSEES, an earthquake simulation program developed at the University of California, Berkeley. Finally, they assembled and tested the columns on the UNR NEES shake table.
To strengthen the concrete and prevent immediate failure in an earthquake, the researchers used the shake tables to test glass and carbon fiber-reinforced polymer composites. Both composites substantially enhanced the reinforcing properties of concrete and the columns resisted strong earthquake forces with minor damage.
The results of both the modeling and shake table tests were extremely promising. The nickel titanium/ECC bridge columns outperformed the traditional steel and concrete bridge columns on all levels, limiting the amount of damage that the bridge would sustain under strong earthquakes.
While the initial cost of a typical bridge made of nickel titanium and ECC would be about 3 percent higher than the cost of a conventional bridge, the bridge's lifetime cost would decrease. Not only would the bridge require less repair, it would also be serviceable in the event of moderate and strong earthquakes. As a result, following a strong earthquake, the bridge would remain open to emergency vehicles and other traffic.
-- Misha Raffiee, California Institute of Technology
About the author: Misha Raffiee is a sophomore undergraduate at the California Institute of Technology, but she began work with UNR on the NSF/NEES 4-Span Bridge Project following her graduation from high school at age 15. As an undergraduate research fellow, Raffiee was given the opportunity to conduct her own complementary research, a feasibility study of copper-based shape memory alloys and ECC. Copper-based SMAs, such as copper-aluminum-beryllium (CuAlBe) are predicted to be more cost-effective than other shape memory alloys, such as nickel titanium. Using computer modeling and testing in the Open System for Earthquake Engineering Simulation with the results from the nickel titanium-reinforced concrete runs, Raffiee was able to assess the performance of a unique CuAlBe and ECC column. She presented her findings at NSF's Young Researcher's Symposium at the University of Illinois, Urbana-Champaign, and later assisted in presentations of the nickel titanium-reinforced concrete column project at an NSF showcase event held at the United States Senate. Raffiee credits the experience as an NSF/NEES Undergraduate Research Fellow with helping her grow both as a researcher and as a scholar, solidifying her post-graduate aspirations.
Editor's Note: This Behind the Scenes article was first provided to LiveScience in partnership with the National Science Foundation.