Stronger than steel, novel metals are as moldable as plastic

Imagine a material that's stronger than steel, but just as versatile as plastic, able to take on a seemingly endless variety of forms. For decades, materials scientists have been trying to come up with just such an ideal substance, one that could be molded into complex shapes with the same ease and low expense as plastic but without sacrificing the strength and durability of metal.

Now 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. The alloys are made up of different metals, including zirconium, nickel, titanium and copper.

The team blow molded the alloys at low temperatures and low pressures, where the bulk metallic glass softens dramatically and flows as easily as plastic but without crystallizing like regular metal. It's the low temperatures and low pressures that allowed the team to shape the BMGs with unprecedented ease, versatility and precision, Schroers said. In order to carefully control and maintain the ideal temperature for blow molding, the team shaped the BMGs in a vacuum or in fluid.

"The trick is to avoid friction typically present in other forming techniques," Schroers said. "Blow molding completely eliminates friction, allowing us to create any number of complicated shapes, down to the nanoscale."

Schroers and his team are already using their new processing technique to fabricate miniature resonators for microelectromechanical systems (MEMS)-tiny mechanical devices powered by electricity-as well as gyroscopes and other resonator applications.

In addition, by blow molding the BMGs, the team was able to combine three separate steps in traditional metal processing (shaping, joining and finishing) into one, allowing them to carry out previously cumbersome, time- and energy-intensive processing in less than a minute.

"This could enable a whole new paradigm for shaping metals," Schroers said. "The superior properties of BMGs relative to plastics and typical metals, combined with the ease, economy and precision of blow molding, have the potential to impact society just as much as the development of synthetic plastics and their associated processing methods have in the last century."

Other authors of the paper include Thomas M. Hodges and Golden Kumar (Yale University); Hari Raman and A.J. Barnes (SuperformUSA); and Quoc Pham and Theodore A. Waniuk (Liquidmetal Technologies).

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Yale University.

Journal Reference:

Jan Schroers, Thomas M. Hodges, Golden Kumar, Hari Raman, Anthony J. Barnes, Quoc Pham, Theodore A. Waniuk. Thermoplastic blow molding of metals. Materials Today, 2011; 14 (1-2): 14 DOI: 10.1016/S1369-7021(11)70018-9

New kind of optical fiber developed: Made with a core of zinc selenide

A team of scientists led by John Badding, a professor of chemistry at Penn State University, has developed the very first optical fiber made with a core of zinc selenide -- a light-yellow compound that can be used as a semiconductor. The new class of optical fiber, which allows for a more effective and liberal manipulation of light, promises to open the door to more versatile laser-radar technology. Such technology could be applied to the development of improved surgical and medical lasers, better countermeasure lasers used by the military, and superior environment-sensing lasers such as those used to measure pollutants and to detect the dissemination of bioterrorist chemical agents.

The team's research will be published in the journal Advanced Materials.

"It has become almost a cliche to say that optical fibers are the cornerstone of the modern information age," said Badding. "These long, thin fibers, which are three times as thick as a human hair, can transmit over a terabyte -- the equivalent of 250 DVDs -- of information per second. Still, there always are ways to improve on existing technology." Badding explained that optical-fiber technology always has been limited by the use of a glass core. "Glass has a haphazard arrangement of atoms," Badding said. "In contrast, a crystalline substance like zinc selenide is highly ordered. That order allows light to be transported over longer wavelengths, specifically those in the mid-infrared."

Unlike silica glass, which traditionally is used in optical fibers, zinc selenide is a compound semiconductor. "We've known for a long time that zinc selenide is a useful compound, capable of manipulating light in ways that silica can't," Badding said. "The trick was to get this compound into a fiber structure, something that had never been done before." Using an innovative high-pressure chemical-deposition technique developed by Justin Sparks, a graduate student in the Department of Chemistry, Badding and his team deposited zinc selenide waveguiding cores inside of silica glass capillaries to form the new class of optical fibers. "The high-pressure deposition is unique in allowing formation of such long, thin, zinc selenide fiber cores in a very confined space," Badding said.

The scientists found that the optical fibers made of zinc selenide could be useful in two ways. First, they observed that the new fibers were more efficient at converting light from one color to another. "When traditional optical fibers are used for signs, displays, and art, it's not always possible to get the colors you want," Badding explained. "Zinc selenide, using a process called nonlinear frequency conversion, is more capable of changing colors."

Second, as Badding and his team expected, they found that the new class of fiber provided more versatility not just in the visible spectrum, but also in the infrared -- electromagnetic radiation with wavelengths longer than those of visible light. Existing optical-fiber technology is inefficient at transmitting infrared light. However, the zinc selenide optical fibers that Badding's team developed are able to transmit the longer wavelengths of infrared light. "Exploiting these wavelengths is exciting because it represents a step toward making fibers that can serve as infrared lasers," Badding explained. "For example, the military currently uses laser-radar technology that can handle the near-infrared, or 2 to 2.5-micron range. A device capable of handling the mid-infrared, or over 5-micron range would be more accurate. The fibers we created can transmit wavelengths of up to 15 microns."

Badding also explained that the detection of pollutants and environmental toxins could be yet another application of better laser-radar technology capable of interacting with light of longer wavelengths. "Different molecules absorb light of different wavelengths; for example, water absorbs, or stops, light at the wavelengths of 2.6 microns," Badding said. "But the molecules of certain pollutants or other toxic substances may absorb light of much longer wavelengths. If we can transport light over longer wavelengths through the atmosphere, we can see what substances are out there much more clearly." In addition, Badding mentioned that zinc selenide optical fibers also may open new avenues of research that could improve laser-assisted surgical techniques, such as corrective eye surgery.

In addition to Badding and Sparks, other researchers who contributed to this study include Rongrui He of Penn State's Department of Chemistry and the Materials Research Institute; Mahesh Krishnamurthi and Venkatraman Gopalan of Penn State's Department of Materials Science and Engineering and the Materials Research Institute; and Pier J.A. Sazio, Anna C. Peacock, and Noel Healy of the Optoelectronics Research Centre at the University of Southampton. Support for this research was provided by the Engineering and Physical Sciences Research Council, the National Science Foundation, and the Penn State University Materials Research Science and Engineering Center.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Penn State, Eberly College of Science. The original article was written by Katrina Voss.

Journal Reference:

Justin R. Sparks, Rongrui He, Noel Healy, Mahesh Krishnamurthi, Anna C. Peacock, Pier J. A. Sazio, Venkatraman Gopalan, John V. Badding. Zinc Selenide Optical Fibers. Advanced Materials, 2011; DOI: 10.1002/adma.201003214

Engineering atomic interfaces for new electronics

Most people cross borders such as doorways or state lines without thinking much about it. Yet not all borders are places of limbo intended only for crossing. Some borders, like those between two materials that are brought together, are dynamic places where special things can happen.

For an electron moving from one material toward the other, this space is where it can join other electrons, which together can create current, magnetism or even light.

A multi-institutional team has made fundamental discoveries at the border regions, called interfaces, between oxide materials. Led by University of Wisconsin-Madison materials science and engineering professor Chang-Beom Eom, the team has discovered how to manipulate electrons oxide interfaces by inserting a single layer of atoms. The researchers also have discovered unusual electron behaviors at these engineered interfaces.

Their work, which is sponsored by the National Science Foundation, will be published Feb. 18 in the journal Science and could allow researchers to further study and develop interfaces with a wide array of properties.

Eom's team blends theorists and experimentalists, including UW-Madison physics professor Mark Rzchowski and collaborators at the University of Nebraska-Lincoln, University of Michigan, Argonne National Laboratory and Brookhaven National Laboratory.

The researchers used two pieces of precisely grown strontium titanate, which is a type of oxide, or compound with oxygen as a fundamental element. Between the pieces, the researchers inserted a one-atom-thick layer of one of five rare-earth elements, which are important components in the electronics industry.

The team found that the rare-earth element layer creates an electron gas that has some interesting characteristics. The gas actually behaves more like an electron "liquid," since the electrons move more in tandem, or in correlation, than a gas normally does.

"If you take two materials, each has different characteristics, and if you put them together, at their interface you may find something unexpected," Eom says.

This research is the first demonstration of strong correlation among electrons at an oxide interface. The electron layer displayed distinct characteristics depending on the particular rare-earth element the team used. Materials with larger ionic radii, such as lanthanum, neodymium and praseodymium, are conducting, whereas materials with smaller radii, including samarium and yttrium, are insulating.

The insulating elements form an electron gas that can be compared to a thick liquid, somewhat like honey. The higher viscosity (basically, thickness) means the electrons can't move around as freely, making them more insulating. Conversely, the conducting elements form a gas that is a "liquid" more like gasoline; the viscosity is lower, so the electrons can move more freely and are better conductors.

Prior to this research, scientists knew extra electrons could reside at interfaces, but they didn't realize the complexity of how the electrons then behaved together at those interfaces.

The discovery of liquid-like behavior in the electron layer could open up an entire field of interfacial engineering for other scientists to explore, as well as new applications that take advantage of electron interactions. Since Eom and his colleagues developed an understanding of the basic physics behind these behaviors, their work could be expanded to create not only conductive or insulating interfaces, but also magnetic or optical ones.

Though scientists previously have looked at semiconductor interfaces, Eom's team is the first to specifically address those that use oxide interfaces to control conducting states with a single atomic layer. Oxides make up a class of materials including millions of compounds, and each has its own unique set of properties. The ability to manipulate various oxide interfaces could give rise to new generations of materials, electronics and other devices.

"This advancement could make a broad impact in fields even beyond physics, materials or chemistry," Eom says. "People can use the idea that an interface made from a single atomic layer of different ions can be used to create all kinds of properties."

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by University of Wisconsin-Madison, via EurekAlert!, a service of AAAS.

Journal Reference:

H. W. Jang, D. A. Felker, C. W. Bark, Y. Wang, M. K. Niranjan, C. T. Nelson, Y. Zhang, D. Su, C. M. Folkman, S. H. Baek, S. Lee, K. Janicka, Y. Zhu, X. Q. Pan, D. D. Fong, E. Y. Tsymbal, M. S. Rzchowski, C. B. Eom. Metallic and Insulating Oxide Interfaces Controlled by Electronic Correlations. Science, 2011; 331 (6019): 886 DOI: 10.1126/science.1198781

Hair dyeing poised for first major transformation in 150 years

Technological progress may be fast-paced in many fields, but one mundane area has been almost left in the doldrums for the last 150 years: The basic technology for permanently coloring hair. That's the conclusion of an analysis of almost 500 articles and patents on the chemistry of permanent hair dyeing, which foresees much more innovation in the years ahead, including longer lasting, more-natural-looking dyes and gene therapy to reverse the gray.

The article appears in ACS's journal Chemical Reviews.

Robert Christie and Olivier Morel note that hair dye already is a multibillion dollar international industry, poised for even greater expansion in the future due to the graying of a global population yearning to cling to appearances of youth. Most permanent hair coloring technology, however, is based on a 150-year-old approach that uses p-phenylenediamine (PPD), a chemical that produces darker, browner shades when exposed to air. Concern over the safety of PPD and other hair dye ingredients, and demand for more convenient hair dyeing methods, has fostered an upswing in research on new dyes and alternative hair coloring technologies.

The scientists describe progress toward those goals. Future hair coloring techniques include nano-sized colorants, for instance. Composed of pigments 1/5,000th the width of a human hair, they will penetrate the hair and remain trapped inside for longer-lasting hair coloration. Scientists also are developing substances that stimulate the genes to produce the melanin pigment that colors hair. These substances promise to produce a wider range of more natural-looking colors, from blond to dark brown and black, with less likelihood of raising concerns about toxicity and better prospects for more natural results. Other new technologies may stop graying of the hair or prevent its formation altogether, the scientists say.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by American Chemical Society.

Journal Reference:

Olivier J. X. Morel, Robert M. Christie. Current Trends in the Chemistry of Permanent Hair Dyeing. Chemical Reviews, 2011; : 110125093129032 DOI: 10.1021/cr1000145

Engineering atomic interfaces for new electronics

Most people cross borders such as doorways or state lines without thinking much about it. Yet not all borders are places of limbo intended only for crossing. Some borders, like those between two materials that are brought together, are dynamic places where special things can happen.

For an electron moving from one material toward the other, this space is where it can join other electrons, which together can create current, magnetism or even light.

A multi-institutional team has made fundamental discoveries at the border regions, called interfaces, between oxide materials. Led by University of Wisconsin-Madison materials science and engineering professor Chang-Beom Eom, the team has discovered how to manipulate electrons oxide interfaces by inserting a single layer of atoms. The researchers also have discovered unusual electron behaviors at these engineered interfaces.

Their work, which is sponsored by the National Science Foundation, will be published Feb. 18 in the journal Science and could allow researchers to further study and develop interfaces with a wide array of properties.

Eom's team blends theorists and experimentalists, including UW-Madison physics professor Mark Rzchowski and collaborators at the University of Nebraska-Lincoln, University of Michigan, Argonne National Laboratory and Brookhaven National Laboratory.

The researchers used two pieces of precisely grown strontium titanate, which is a type of oxide, or compound with oxygen as a fundamental element. Between the pieces, the researchers inserted a one-atom-thick layer of one of five rare-earth elements, which are important components in the electronics industry.

The team found that the rare-earth element layer creates an electron gas that has some interesting characteristics. The gas actually behaves more like an electron "liquid," since the electrons move more in tandem, or in correlation, than a gas normally does.

"If you take two materials, each has different characteristics, and if you put them together, at their interface you may find something unexpected," Eom says.

This research is the first demonstration of strong correlation among electrons at an oxide interface. The electron layer displayed distinct characteristics depending on the particular rare-earth element the team used. Materials with larger ionic radii, such as lanthanum, neodymium and praseodymium, are conducting, whereas materials with smaller radii, including samarium and yttrium, are insulating.

The insulating elements form an electron gas that can be compared to a thick liquid, somewhat like honey. The higher viscosity (basically, thickness) means the electrons can't move around as freely, making them more insulating. Conversely, the conducting elements form a gas that is a "liquid" more like gasoline; the viscosity is lower, so the electrons can move more freely and are better conductors.

Prior to this research, scientists knew extra electrons could reside at interfaces, but they didn't realize the complexity of how the electrons then behaved together at those interfaces.

The discovery of liquid-like behavior in the electron layer could open up an entire field of interfacial engineering for other scientists to explore, as well as new applications that take advantage of electron interactions. Since Eom and his colleagues developed an understanding of the basic physics behind these behaviors, their work could be expanded to create not only conductive or insulating interfaces, but also magnetic or optical ones.

Though scientists previously have looked at semiconductor interfaces, Eom's team is the first to specifically address those that use oxide interfaces to control conducting states with a single atomic layer. Oxides make up a class of materials including millions of compounds, and each has its own unique set of properties. The ability to manipulate various oxide interfaces could give rise to new generations of materials, electronics and other devices.

"This advancement could make a broad impact in fields even beyond physics, materials or chemistry," Eom says. "People can use the idea that an interface made from a single atomic layer of different ions can be used to create all kinds of properties."

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by University of Wisconsin-Madison, via EurekAlert!, a service of AAAS.

Journal Reference:

H. W. Jang, D. A. Felker, C. W. Bark, Y. Wang, M. K. Niranjan, C. T. Nelson, Y. Zhang, D. Su, C. M. Folkman, S. H. Baek, S. Lee, K. Janicka, Y. Zhu, X. Q. Pan, D. D. Fong, E. Y. Tsymbal, M. S. Rzchowski, C. B. Eom. Metallic and Insulating Oxide Interfaces Controlled by Electronic Correlations. Science, 2011; 331 (6019): 886 DOI: 10.1126/science.1198781

Reseasrcher investigates new material grown from sugar

Ordinary table sugar could be a key ingredient to developing much lighter, faster, cheaper, denser and more robust computer electronics for use on U.S. military aircraft.

Though admittedly far in the future, recent results from a program led by chemist and Rice University professor, Dr. James Tour demonstrate yet another example of the cutting-edge basic research funded by the Air Force Research Laboratory's Office of Scientific Research.

Tour and his colleagues at Rice have developed a relatively easy and controllable method for making pristine sheets of graphene --- the one-atom-thick form of carbon --- from regular table sugar and other solid carbon sources.

"Dr. Tour is exploring a chemical approach to producing high quality carbon based nanostructures such as nanotubes and graphenes with well defined properties," said AFOSR program manager, Dr. Charles Lee.

In their method, a small amount of sugar is placed on a tiny sheet of copper foil. The sugar is then subjected to flowing hydrogen and argon gas under heat and low pressure. After 10 minutes, the sugar is reduced to a pure carbon film, or a single layer of graphene. Adjusting the gas flow allowed the researchers to control the thickness of the film.

The use of solid carbon sources like sugar has allowed Tour to stay away from the more cumbersome chemical vapor deposition method and the high temperatures associated with it. His one-step, low-temperature process makes graphene considerably easier to manufacture.

"In a traditional CVD point of view, it was straightforward to optimize the pristine graphene's quality through adjusting the growth conditions and the metal catalysts with continuous gas sources (CH4 or C2H2)," explained Tour. "With this technique using different kinds of solid carbon sources, more benefits such as graphene doping and thickness control could be realized."

According to Tour, doped graphene opens more possibilities for both Air Force and commercial electronics applications. Pristine graphene has no bandgap, but doped graphene allows for manipulation of electronic and optical properties, important factors for making switching and logic devices.

"These materials can be used in advanced electronics, photonics as well as structural applications for the Air Force," explained Lee.

While the Air Force is focusing primarily on potential electronics applications, many other commercial and medical uses could be possible, including transparent touch screen devices, special biocompatible films for surgery of traumatic brain injuries, faster transistors in personal computers or thin materials for solar energy harvesting.

Provided by Air Force Office of Scientific Research

 

Why chemotherapy causes more infertility in women than in men

For a long time a relationship between infertility and chemotherapeutic agents has been assumed. Now, the mechanism has been elucidated. Mainly women are affected because the quality control in the oocytes is different from male germ cells. As biosicentists from Goethe-University have found out, tetramer and dimer structures in the p53 protein family play a key role.

Chemotherapeutic agents, used in cancer treatment, destroy not only cancer cells but also healthy cells, thus affecting germ cells as well. Consequently, after surviving cancer many female patients are confronted with the diagnosis: infertility. For a long time a relationship between infertility and chemotherapeutic agents has been assumed, but until now, the exact mechanism was not known.

Scientists from the research group of Prof. Volker Dötsch (Institute of Biophysical Chemistry, Goethe University Frankfurt) in cooperation with international partners have now started to unveil the mechanism of cancer treatment related infertility. Their results are published in the internationally renowned journal Cell. Mainly women suffer from infertility because the quality control in the oocytes is different from male germ cells. Male germ cells are produced throughout the whole life span but the number of female germ cells is restricted and already fixed before birth. If the oocytes are damaged during cancer treatment, they are destroyed by the female quality control mechanism.

Essential for this process is the protein p63 which shows striking similarity to another important protein of the same family: p53. p53 is also named "guardian of the genome" because of its regulatory function in cell division and cell death of damaged cells and, therefore, plays a key role in the suppression of genetic anomalies which could lead to cancer. In more than half of all human tumors p53 is altered and no longer functional.

For a long time the exact regulation of p53 and p63 and the similarities and differences between these two proteins have been the object of many international research projects. In the currently accepted model the concentration of p53 in healthy cells is relatively low. If genetic anomalies occur in a cell which could cause the transition to a cancer cell, the concentration of p53 increases and four p53 proteins form a tetramer. In this tetrameric state the tumor suppressor is active and initiates either repair of the damaged DNA or programmed cell death. Surprisingly, despite the fact that p53 and p63 show high similarity, the mechanism by which the activity of p63 is controlled in oocytes seemed to be different.

The research group of Prof. Volker Dötsch could show now that the two mechanisms that regulate the activity of p53 and of p63 are closely related, but distinct. The level of p63 in normal oocytes is high and the protein is kept in a closed dimeric and inactive state. If DNA double-strand breaks occur, for example caused by radioactive radiation, p63 becomes phosphorylated. As a result of this phosphorylation, the structure of the p63 dimer changes to an open state allowing the attachment of a second phosphorylated dimer. The resulting active p63 tetramer is similar to the active p53 tetramer and leads to the death of the damaged oocyte. Many of the chemotherapeutic agents cause DNA double-strand breaks which activate p63, finally leading to the cell death of the oocytes.

The related proteins of model organisms such as Caenorhabditis elegans (nematode) are also investigated by the Dötsch group. Because of the short life span of this worm its p63 related protein does not act as a tumor suppressor but controls the genetic stability of the germ cells. The quality control of germ cells, thus, seems to be the original function of the p53 protein family and leads to the conclusion that p63 is the ancestor of the entire p53 family.

Interestingly, p63 shows an additional function: it is essential for the maintenance of stem cells in epithelial layers like skin. Because of the close similarity of stem and germ cells, this second function shows the evolutionary process of the p53 protein family from p63-like proteins, that in simple organisms are responsible for the genetic stability of germ cells, via controlling the maintenance of stem cells in organisms with renewal tissues, finally to p53-like tumor repressors in somatic cells. This demonstrates the outstanding importance of the p53 protein family for the development and health of human beings.

More information: Deutsch et al., DNA Damage in Oocytes Induces a Switch of the Quality Control Factor TAp63a from Dimer to Tetramer, Cell (2011), doi:10.1016/j.cell.2011.01.013

Provided by Goethe University Frankfurt