Other materials stories that may be of interestPublished on April 2nd, 2013 | By: Eileen De Guire
The Strategic Materials Advisory Council has cautioned the Department of Defense to avoid the risky mitigation strategy of stockpiling strategic and critical materials from China. The DOD recently completed its biannual “Strategic and Critical Materials 2013 Report on Stockpile Requirements,” which recommended stockpiling $120.43 million of heavy rare earth elements—materials produced only in China. “The root cause of these material shortages is our ongoing dependence on Chinese suppliers,” says Council Executive Director Jeff Green. “While it is encouraging that DoD acknowledges these risks, we urge DOD to move from theoretical studies to the only appropriate and permanent solution: the creation and nurturing of a US-based rare earth supply chain.” The rare earth stockpile recommendation represents over one-third of a $319.74 million stockpiling plan to mitigate a $1.2 billion shortfall of 23 strategic and critical materials. This encouraging recommendation contrasts dramatically with previous DOD assessments that asserted domestic sources could meet all military requirements by 2013, except for yttrium, and that substitution would be a viable approach to risk mitigation for heavy rare earths.
A new chemotherapy drug in the form of nanoparticles is less toxic to young women’s fertility but extra tough on cancer, say researchers. “Our overall goal is to create smart drugs that kill the cancer but don’t cause sterility in young women,” says Teresa Woodruff, a co-principal investigator of the study and chief of fertility preservation at Northwestern University. The chemotherapy drug, arsenic trioxide, is packed into a very tiny Trojan horse called a nanobin. The nanobin consists of nano-size crystalline arsenic particles densely packed and encapsulated in a fat bubble. The fat bubble, a liposome, disguises the deadly cargo-half a million drug molecules. The fat bubble is the perfect size to stealthily slip through holes in the leaky blood vessels that rapidly grow to feed tumors. The local environment of the tumor is often slightly acid and it’s this acid that causes the nanobin to release its drug cargo and deliver a highly effective dose of arsenic where it is needed. The scientists show this approach to packaging and delivering the active drug has the desired effect on the tumor cells but prevents damage to ovarian tissue, follicles, or eggs. Arsenic trioxide was approved a few years ago for treating some types of blood cancers such as leukemia in humans, but the researchers think the arsenic trioxide nanobins can be used against breast cancer and other solid tumors.
At the Hannover trade fair, Fraunhofer researchers are now presenting a new manufacturing process with which these thermoelectric generators can be cost-effectively produced in the form of large-area flexible components from non-toxic synthetic materials. The scientists‘ vision is described by Aljoscha Roch of the Fraunhofer Institute for Material and Beam Technology IWS in Dresden: “Thermoelectric generators (TEG) currently have an efficiency of around eight percent. That sounds very small. But if we succeed in producing TEG cost-effectively, on a large scale and from flexible materials we can install them extensively on the insides of the concave cooling tower wall. In this way, through the enormous amount of energy produced in the huge plants—around 1500 liters of water evaporate per minute—we could generate large quantities of electricity.” The scientists have succeeded in producing TEGs by means of a printing process. The miniaturized generators can not only be produced cost-effectively, on large surfaces and in a flexibly manageable manner, but an additional major advantage is that the materials used are environmentally-friendly. “TEG are today largely produced by hand from toxic components which contain lead for example. We are now using modern 3D printing technology and harmless polymers (plastics) that are electrically conductive,” explains Roch. The IWS researchers are demonstrating the printed TEG for the first time in a cooling tower model at the Hannover trade fair.
Researchers have developed a “hyperbolic metamaterial waveguide” that halts and ultimately absorbs each frequency of light, at slightly different places in a vertical direction, to catch a “rainbow” of wavelengths. The technology is essentially an advanced microchip made of ultrathin films of metal and semiconductors and/or insulators. “Right now, researchers are developing compact light absorbers based on optically thick semiconductors or carbon nanotubes. However, it is still challenging to realize the perfect absorber in ultrathin films with tunable absorption band,” says Qiaoqiang Gan, an assistant professor of electrical engineering at University at Buffalo. Gan previously helped pioneer a way to slow light without cryogenic gases. He and other researchers at Lehigh University made nanoscale-sized grooves in metallic surfaces at different depths, a process that altered the optical properties of the metal. While the grooves worked, they had limitations. For example, the energy of the incident light cannot be transferred onto the metal surface efficiently, which hampered its use for practical applications. As reported in the journal Scientific Reports, the waveguide solves that problem because it is a large area of patterned film that can collect the incident light efficiently. Researchers say the technology could lead to advancements in an array of fields, such as preventing crosstalk in electronics or energy-harvesting devices.
The High-Pressure Collaborative Access Team (HPCAT), a group linked to the Advanced Photon Source (APS) facility at the Argonne National Lab, held a workshop Oct. 10-12, 2012, to review the successes of HPCAT over the past 10 years, as well as opportunities for addressing key grand challenges in future of extreme conditions science. During the past decade, HPCAT has taken advantage of the nation’s most brilliant high-energy synchrotron source and developed a multitude of integrated synchrotron radiation techniques optimized for high-pressure research. These X-ray probes, integrated with hydrostatic or uniaxial compression, static or dynamic loading, resistive or laser heating, and cryogenic cooling, have enabled users’ investigations of structural, vibrational, electronic, and magnetic properties at high pressure and high/low temperature that were not possible a decade ago. The workshop consisted of over 120 people from the US and abroad. Emerging from the workshop and its discussions is a clear signal of the outstanding opportunities for the future of extreme conditions science at the APS in the years to come. The report is approximately 120 pages (pdf)
New experiments set the record of the superconducting transition temperatures for a new family of iron-based selenide superconductors. These materials were recently found to superconduct below 30 K, but their transition temperatures decline until approaching absolute zero temperature with the application of pressure. Now Carnegie scientists Xiao-Jia Chen, Lin Wang, and Ho-Kwang Mao, in collaboration with scientists from from the National Institute of Standards and Technology, the Chinese Academy of Science, and Zhejiang University, have uncovered reemerging superconductivity above 48 K in iron selenides upon further compression. The disappearance of superconductivity in the low-pressure cycle and the re-emergence of superconductivity with higher transition temperatures in the high-pressure cycle reflect detailed structural variances within the basic unit cell itself. The two superconducting domes were likely the result of different charge carriers. Finding the reentrance of superconductivity at 48 K in the new iron family of superconductors points to the possibility of achieving similar higher transition temperatures at ambient pressure through some structural modifications
New research carried out at MIT and elsewhere has demonstrated for the first time that when inserted into a pool of liquid, nanowires – wires that are only hundreds of nanometers across – naturally draw the liquid upward in a thin film that coats the surface of the wire. The finding could have applications in microfluidic devices, biomedical research and inkjet printers. Although this upward pull is always present with wires at this tiny scale, the effect can be further enhanced in various ways: Adding an electric voltage on the wire increases the force, as does a slight change in the profile of the wire so that it tapers toward one end. The researchers used nanowires made of different materials—silicon, zinc oxide and tin oxide, as well as two-dimensional graphene—to demonstrate that this process applies to many different materials. The results are published in the journal Nature Nanotechnology by a team of researchers led by Ju Li, an MIT professor of nuclear science and engineering and materials science and engineering, along with researchers at Sandia National Laboratories in New Mexico, the University of Pennsylvania, the University of Pittsburgh, and Zhejiang University in China. Several brief videos of the nanowires in action have been posted on YouTube by Li’s research group.
Even graphene, the Superman of materials, has its kryptonite: Defects in polycrystalline graphene will sap its strength. The unexpected weakness is in the form of a seven-atom ring that inevitably occurs at the junctions of grain boundaries in graphene, where the regular array of hexagonal units is interrupted, report researchers. At these points, under tension, polycrystalline graphene has about half the strength of pristine samples of the material. New research shows defects in polycrystalline forms of graphene will sap its strength. The new calculations could be important to materials scientists using graphene in applications where its intrinsic strength is a key feature, like composite materials and stretchable or flexible electronics. The team calculated that the particular seven-atom rings found at junctions of three islands are the weakest points, where cracks are most likely to form. These are the end points of grain boundaries between the islands and are ongoing trouble spots.
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