The research team of Nikhil Gupta, a New York Univ. (NYU) School of Engineering associate professor in the Dept. of Mechanical and Aerospace Engineering, working with the Toledo, Ohio, company Deep Springs Technology and the U.S. Army Research Laboratory, published their findings in Materials Science and Engineering: A .

Conventional metal foams have gas-filled pores within the metal, which reduce weight but pose some drawbacks, such as difficulty in controlling the size and shape of the pores during manufacturing.

By contrast, metal matrix syntactic foams incorporate porosity in their foam-like structure by means of hollow particles. In recent years there has been an upsurge in the use of these materials, mainly because of their compressive strength. However, bending strength was a limitation for many potential applications, notably automotive structures.

Metallic foams previously have been sandwiched between two stiff sheets, which provide increased flexural strength while the foam core allows the material to withstand large deformation and absorb energy. But Gupta and his colleagues are the first to develop a metal matrix syntactic foam core sandwich composite.

The discovery of a previously unknown type of metal deformation-sinuous flow-and a method to suppress it could lead to more efficient machining and other manufacturing advances by reducing the force and energy required to process metals. 

Researchers at Purdue Univ. discovered sinuous flow deformation and were surprised to find a potentially simple way to control it, said Srinivasan Chandrasekar, a professor of industrial engineering, who is working with W. Dale Compton, the Lillian M. Gilbreth Distinguished Professor Emeritus of Industrial Engineering, postdoctoral research associate Ho Yeung and graduate student Koushik Viswanathan.

The team discovered the phenomenon by using high-speed microphotography and analysis to study what happens while cutting ductile metals. They found that the metal is deformed into folds while it is being cut-contrary to long-held assumptions that metals are sheared uniformly-and also that sinuous flow can be controlled by suppressing this folding behavior.

"When the metal is sheared during a cutting process it forms these finely spaced folds, which we were able to see for the first time only because of direct observation in real time," Yeung said.

Findings showed the cutting force can be reduced 50% simply by painting metal with a standard marking ink. Because this painted layer was found to suppress sinuous flow, the implications are that not only can energy consumption be reduced by 50% but also that machining can be achieved faster and more efficiently and with improved surface quality, Chandrasekar said.

The findings are detailed in a research paper appearing in Proceedings of the National Academy of Sciences.

"The fact that the metal can be cut easily with less pressure on the tool has significant implications," Compton said. "Machining efficiency is typically limited by force, so it is possible to machine at a much faster rate with the same power."

Lithium-ion batteries remain the technology-of-choice for today's crop of electric cars, but challengers are revving up to try to upset the current order. An article in Chemical & Engineering News (C&EN) takes a look at two of the top contenders vying to erode lithium-ion's dominance.

Alex Scott, a senior editor at C&EN, reports on two developments from companies in England that seem poised to compete in the electric car battery market within the next two to four years. One is a sodium-ion version, produced by a start-up called Faradion. The other is a battery powered by lithium-sulfur technology and is being developed by Oxis Energy. Both companies assert their advances will be able to compete with lithium-ion in performance, safety and costs.

Some industry watchers, however, remain unconvinced by the claims, given that a slew of other battery-makers made similar promises and then failed to deliver. Soon enough, the fates of Faradion and Oxis could also be determined. Faradion has set a goal to match the energy density of lithium-ion batteries by 2017. And although they're still dealing with battery cycle issues, Oxis' lithium-sulfur technology has already attracted the attention of the military.

Scientists have long worked to understand how crystals grow into complex shapes. Crystals are important in materials from skeletons and shells to soils and semiconductor materials, but much is unknown about how they form.

Now, an international group of researchers has shown how nature uses a variety of pathways to grow crystals that go beyond the classical, one-atom-at-a-time route.

The findings, published in Science, have implications for decades-old questions in science and technology such as how animals and plants grow minerals into shapes that have no relation to their original crystal symmetry. Or why some contaminants are so difficult to remove from stream sediments and groundwater.

"Researchers across all disciplines have made observations of skeletons and laboratory-grown crystals that cannot be explained by traditional theories," said Patricia Dove, a University Distinguished Professor at Virginia Tech and the C.P. Miles Professor of Science in the College of Science. "We show how these crystals can be built up into complex structures by attaching particles-as nanocrystals, clusters, or droplets-that become organized into complex shapes. Many scientists have contributed to identifying these particles and pathways to becoming a crystal-our challenge was to put together a framework to understand them."

The results emerged from discussions among 15 scientists working in the fields of geochemistry, physics, biology, and the earth and materials sciences, including at the U.S. Dept. of Energy (DOE)'s Pacific Northwest National Laboratory. At home, these researchers conduct lab experiments, investigate animal skeletons, study soils and streams, or use computer simulations to visualize how particles can form and attach.

Research from North Carolina State University shows that lightweight composite metal foams are effective at blocking X-rays, gamma rays and neutron radiation, and are capable of absorbing the energy of high impact collisions. The finding means the metal foams hold promise for use in nuclear safety, space exploration and medical technology applications.

"This work means there's an opportunity to use composite metal foam to develop safer systems for transporting nuclear waste, more efficient designs for spacecraft and nuclear structures, and new shielding for use in CT scanners," says Afsaneh Rabiei, a professor of mechanical and aerospace engineering at NC State and corresponding author of a paper on the work.

Rabiei first developed the strong, lightweight metal foam for use in transportation and military applications. But she wanted to determine whether the foam could be used for nuclear or space exploration applications - could it provide structural support, protect against high impacts and provide shielding against various forms of radiation?

To that end, she and her colleagues conducted multiple tests to see how effective it was at blocking X-rays, gamma rays and neutron radiation. She then compared the material's performance to the performance of bulk materials that are currently used in shielding applications. The comparison was made using samples of the same "areal" density - meaning that each sample had the same weight, but varied in volume.

The most effective composite metal foam against all three forms of radiation is called "high-Z steel-steel" and was made up largely of stainless steel, but incorporated a small amount of tungsten. However, the structure of the high-Z foam was modified so that the composite foam that included tungsten was not denser than metal foam made entirely of stainless steel.

The researchers tested shielding performance against several kinds of gamma ray radiation. Different source materials produce gamma rays with different energies. For example, cesium and cobalt emit higher-energy gamma rays, while barium and americium emit lower-energy gamma rays.

The researchers found that the high-Z foam was comparable to bulk materials at blocking high-energy gamma rays, but was much better than bulk materials - even bulk steel - at blocking low-energy gamma rays.

Similarly, the high-Z foam outperformed other materials at blocking neutron radiation.

But thermoelectric modules require semiconductor pairs to transport holes and electrons separately. Finding a suitable polymer for electron transport, or one which can be doped in order to make it suitable, is a challenge.

Researchers from the USA have now fabricated a purely n-type polymer semiconductor composite for electron transport. They combine a pyromellitic diimide polymer which has pentafluorophenyl end caps with an in situ-crystallized inorganic component, SnCl2, chosen for its well-known reduction ability. This solid additive increases the electron-carrying capacity and the voltage that can be obtained from the temperature difference. The mechanism is a combination of electron donation to the polymer and surface electroni c effects.

They compare their polymer with current commercial polymer systems, and find that their voltage per unit temperature breaks the current record for n-type polymers.

Advanced Science is a new journal from the team behind Advanced Materials, Advanced Functional Materials, and Small. The journal is fully Open Access and is free to read now at www.advancedscience.com.

Now researchers at Massachusetts Institute of Technology (MIT) and Brookhaven National Laboratory have explained how electrical charge carriers move in these compounds, potentially opening up further research on such applications. A paper presenting the new findings is published in Advanced Materials.

Conjugated polymers fall somewhere between crystalline and amorphous materials-and that's caused some of the difficulty in explaining how they work, says Asli Ugur, an MIT postdoc and lead author of the paper. Crystals have a perfectly regular arrangement of atoms and molecules, while amorphous materials have a completely random arrangement. But conjugate polymers have some of both characteristics: regions of orderly arrangement, mixed randomly with regions of complete disorder.

"Some models have tried to explain how these materials behave, but there's been no direct evidence," Ugur says, for which model matches the reality. "Here, we've shown that the effect of crystallite size"-the sizes of the ordered domains within the material-plays a crucial role.

That's because the trickiest part of conduction in such materials is what happens when charge carriers-in this case ions, or electrically charged atoms-reach the edge of one type of domain and have to "hop" into the next.

In bulk materials, those ions can go in any direction. But in this polymer, which can be very thin, there are fewer neighboring crystalline domains to which an ion can hop. With fewer options, conduction is more efficient, Ugur says, adding that, "As you get thinner, the conditions [for conduction] improve, even though the material didn't change."

The discovery of a fiber-reinforced, concrete-like rock formed in the depths of a dormant supervolcano in Italy could help explain the unusual ground swelling that led to the evacuation of an Italian port city in recent years, and may inspire the creation of durable building materials in the future, Stanford Univ. scientists say.

The "natural concrete" at the Campi Flegrei volcano near Naples is similar to Roman concrete, a legendary compound invented by the Romans and used to construct the Pantheon, the Coliseum and ancient shipping ports throughout the Mediterranean.

"This implies the existence of a natural process in the subsurface of Campi Flegrei that is similar to the one that is used to produce concrete," said Tiziana Vanorio, an experimental geophysicist at the Stanford School of Earth, Energy & Environmental Sciences.

Campi Flegrei lies at the center of a large depression, or caldera, that is pockmarked by craters formed during past eruptions, the last of which occurred nearly 500 years ago. Nestled within this caldera is the colorful port city of Pozzuoli, which was founded in 600 B.C. by the Greeks.

Beginning in 1982, the ground beneath Pozzuoli began rising at an alarming rate. Within a two-year span, the uplift exceeded 6 feet-an amount unprecedented anywhere in the world. "The rising sea bottom rendered the Bay of Pozzuoli too shallow for large craft," Vanorio said.

Teymouri, Kwamen and Blümich from RWTH Aachen University have studied the degradation of factory-grade LDPE (low-density polyethylene) pellets when exposed to air at different temperatures with a desktop NMR machine that uses a compact, permanent magnet and is maintenance-free. This user-friendly device delivers NMR relaxation data, which report the concentration and mobility of the crystalline, interfacial and amorphous domains of the semi-crystalline polymer and their changes with progressive aging.

According to the researchers, sample preparation and measurement are simple and fast, and their NMR observations are in agreement with more demanding DSC, FTIR, and SEC measurements.  During the aging process, crystallization and chemical degradation progress at different rates. While at temperature below 90° C crystallization dominates, oxidative degradation takes over after 28 days when aging at 100° C. LDPE degrades chemically by crosslinking and chains scission, whereby chain scission dominates at long aging times.

However, in addition to time and temperature, the molecular weight distribution plays a role in the aging process. In nearly all factory-grade polymer materials a considerable fraction of oligomers and low-molecular weight polymers is contained as wax. Their NMR data reveal that the wax content can accelerate the aging process and increase the crystallinity during thermal aging.

WEST LAFAYETTE, Ind. - New research is revealing details about how the exoskeleton of a certain type of deep-sea shrimp allows the animal to survive scalding hot waters in hydrothermal vents thousands of feet under water.

"A biological species surviving in that kind of extreme environment is a big deal," said Vikas Tomar, an associate professor in Purdue University's School of Aeronautics and Astronautics. "And shrimp are a great test case for evolution because you can find different species all over the world living at various depths and with a range of adaptation requirements."

Tomar and doctoral students Tao Qu, Devendra Verma, Yang Zhang and Chandra Prakash compared the exoskeletons of the deep-sea shrimp Rimicaris exoculata and the shallow-dwelling shrimp Pandalus platyceros. The deep-sea species lives 2,000 meters below the ocean surface in volcanic hydrothermal vents where temperatures can exceed 400 degrees Celsius, whereas the other species lives just below the ocean surface.

"We want to understand how evolution affects material behavior in the exoskeletons of these two shrimp species that thrive in far different conditions," Tomar said.

Insights into the complex molecular behavior of the materials could have implications for the design of new synthetic armor capable of withstanding environmental extremes.

New findings were detailed in a research paper published online July 2 and will appear in a future print issue of the journal Acta Biomaterialia. Two other recent papers by the same researchers focused on laboratory experiments into the shrimp exoskeletons.  

In this study by S. Mukherjee et al. from the University of North Texas, large surface area metallic glass particles were used for rapid dissociation of AZO dye, demonstrating the potential use of these novel materials for treating a variety of toxic organic dyes. Aluminum-based metallic glass of composition Al82Y8Ni7Fe3 was found to completely degrade AZO dye at room temperature without any toxic by-products. The dye degradation rate and catalytic activity were characterized by UV-VIS absorption spectroscopy. In addition, by combining different spectroscopy techniques, the dye dissociation mechanism was identified to be a bi-functional surface catalysis process involving the transition metals in the alloy. Charge transfer from simultaneous ionization of the transition metals (iron and nickel) help in dissociating the unsaturated bonds of the AZO dye in an aqueous medium. The amorphous nature of the alloy renders it inert and durable during the reaction, while promoting high surface catalytic activity at the same time. This has the potential of creating a wide range of applications, including high performance catalysis, water purification, and chemical conversion.

Scientists at the University of Leeds in England have shown that gold nanotubes can serve as internal nanoprobes for high-resolution multispectral imaging, as drug delivery vehicles, and as agents for destroying cancer cells. In their study, they demonstrated biomedical utility of gold nanotubes in a mouse model of human cancer.

"High recurrence rates of tumors after surgical removal remain a formidable challenge in cancer therapy," explains Dr. Sunjie Ye, who is based in both the School of Physics and Astronomy and the Leeds Institute for Biomedical and Clinical Sciences at the University of Leeds, and who led the work. "Chemo- or radiotherapy is often given following surgery to prevent this, but these treatments cause serious side effects."

The researchers say that a new technique to control the length of nanotubes underpins the research. By controlling the length, the researchers were able to produce gold nanotubes with the right dimensions to absorb near-infrared (NIR) light-a wavelength for which human tissue is transparent.

"When the gold nanotubes travel through the body, if light of the right frequency is shone on them, they absorb the light," explains Professor Steve Evans from the School of Physics and Astronomy at the University of Leeds, who was the study's corresponding author. "This light energy is converted to heat, rather like the warmth generated by the Sun on skin. Using a pulsed laser beam, we were able to rapidly raise the temperature in the vicinity of the nanotubes so that it was high enough to destroy cancer cells."

In cell-based studies, by adjusting the brightness of the laser pulse, the researchers say they were able to control whether the gold nanotubes were in cancer-destruction mode, or ready to image tumors.

To see the gold nanotubes in the body, the researchers used an imaging technique called multispectral optoacoustic tomography (MSOT) to detect the gold nanotubes in mice, in which gold nanotubes had been injected intravenously. It is reportedly the first biomedical application of gold nanotubes within a living organism. It was also shown that gold nanotubes were excreted from the body and therefore are unlikely to cause problems in terms of toxicity, an important consideration when developing nanoparticles for clinical use.  

Understanding ice formation adds to our knowledge of how cold temperatures affect both living and non-living systems, including how living cells respond to cold and how ice forms in clouds at high altitudes. A more precise knowledge of the initial steps of freezing could eventually help improve weather forecasts and climate models, as well as inform the development of better materials for seeding clouds to increase rainfall.

The researchers looked at the process by which, as the temperature drops, water molecules begin to cling to each other to form a blob of solid ice within the surrounding liquid. These blobs tend to disappear quickly after their formation. Occasionally, a large enough blob, known as a critical nucleus, emerges and is stable enough to grow rather than to melt. The process of forming such a critical nucleus is known as nucleation.

To study nucleation, the researchers used a computerized model of water that mimics the two atoms of hydrogen and one atom of oxygen found in real water. Through the computer simulations, the researchers calculated the average amount of time it takes for the first critical nucleus to form at a temperature of about 230 K or -43 C, which is representative of conditions in high-altitude clouds.

They found that, for a cubic meter of pure water, the amount of time it takes for a critical nucleus to form is about one-millionth of a second. The study, conducted by Amir Haji-Akbari, a postdoctoral research associate, and Pablo Debenedetti, a professor of chemical and biological engineering, was published online in the Proceedings of the National Academy of Sciences.

"The main significance of this work is to show that it is possible to calculate the nucleation rate for relatively accurate models of water," said Haji-Akbari.