Stanford University researchers have discovered a new way to ‘decorate’ nanowires with coatings of metal oxide and noble metal nanoparticles that greatly improve surface area. Credit: Stanford Nanocharacterization Lab.

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High-strength silk protein scaffolds for bone repair

(PNAS) Biomaterials for bone tissue regeneration represent a major focus of orthopedic research. However, only a handful of polymeric biomaterials are utilized today because of their failure to address critical issues like compressive strength for load-bearing bone grafts. In this study development of a high compressive strength (~13 MPa hydrated state) polymeric bone composite materials is reported, based on silk protein-protein interfacial bonding. Micron-sized silk fibers (10-600 µm) obtained utilizing alkali hydrolysis were used as reinforcement in a compact fiber composite with tunable compressive strength, surface roughness, and porosity based on the fiber length included. A combination of surface roughness, porosity, and scaffold stiffness favored human bone marrow-derived mesenchymal stem cell differentiation toward bone-like tissue in vitro based on biochemical and gene expression for bone markers. Further, minimal in vivo immunomodulatory responses suggested compatibility of the fabricated silk-fiber-reinforced composite matrices for bone engineering applications.

Prominent electrochromism through vacancy-order melting in a complex oxide

(Nature Communications) Electrochromes are materials that have the ability to reversibly change from one colour state to another with the application of an electric field. Electrochromic colouration efficiency is typically large in organic materials that are not very stable chemically. Here we show that inorganic Bi_0.9Ca_0.1FeO_3-0.05 thin films exhibit a prominent electrochromic effect arising from an intrinsic mechanism due to the melting of oxygen-vacancy ordering and the associated redistribution of carriers. We use a combination of optical characterization techniques in conjunction with high-resolution transmission electron microscopy and first-principles theory. The absorption change and colouration efficiency at the band edge (blue-cyan region) are 4.8×106 m^-1 and 190 cm² C^-1, respectively, which are the highest reported values for inorganic electrochromes, even exceeding values of some organic materials.

Light touch keeps a grip on delicate nanoparticles

(NIST Tech Beat) Using a refined technique for trapping and manipulating nanoparticles, researchers at the National Institute of Standards and Technology have extended the trapped particles’ useful life more than tenfold.* This new approach, which one researcher likens to “attracting moths,” promises to give experimenters the trapping time they need to build nanoscale structures and may open the way to working with nanoparticles inside biological cells without damaging the cells with intense laser light. NIST researchers’ new approach uses a control and feedback system that nudges the nanoparticle only when needed, lowering the average intensity of the beam and increasing the lifetime of the nanoparticle while reducing its tendency to wander.

New method increases the surface area of nanowires by “decorating” them with sinuous chains of metal oxide or noble metal nanoparticles

Though science has known for some time that ornamentation can greatly increase the surface area and alter the surface chemistry of nanowires, engineers at Stanford University have found a more effective method of decorating them that is simpler and faster than previous techniques. The development, say the researchers, might someday lead to better lithium-ion batteries, more efficient thin-film solar cells and improved catalysts that yield new synthetic fuels. The key to the Stanford team’s discovery was a flame. Engineers had long known that nanoparticles could be adhered to nanowires to increase surface area, but the methods for creating them were not very effective in forming the much-desired porous nanoparticle chain structures. Those other methods proved too slow and resulted in a too-dense, thick layer of nanoparticles coating the wires, doing little to increase the surface area. They dipped the nanowires in a solvent-based gel of metal and salt, then air-dried them before applying the flame. In the process, the solvent burns in a few seconds, allowing the all-important nanoparticles to crystalize into branch-like structures fanning out from the nanowires.

Materials Genome and the energy efficient soldier: University of Utah-led group gets $15 million from Army to help design new materials

US soldiers are increasingly weighed down by batteries to power weapons, detection devices and communications equipment. So the Army Research Laboratory has awarded a University of Utah-led consortium almost $15 million to use computer simulations to help design materials for lighter-weight, energy efficient devices and batteries. The consortium includes Boston University, Rensselaer Polytechnic Institute, Pennsylvania State University, Harvard University, Brown University, the University of California, Davis, and the Polytechnic University of Turin, Italy. The Utah-led consortium calls itself Alliance for Computationally-guided Design of Energy Efficient Electronic Materials. The Army says its grant to Utah is for Multiscale Multidisciplinary Modeling of Electronic Materials. “Designing new, transformational materials for our soldiers is the aim of our Enterprise for Multiscale Research of Materials,” says John M. Miller, director of the U.S. Army Research Laboratory. He says a strong foundation for that enterprise will be provided both by the University of Utah-led project, and by a related project led by Johns Hopkins University to understand how materials behave when subjected to high-velocity impacts - work aimed at developing new, lightweight materials to protect U.S. soldiers and vehicles. Miller says funding the research “also shows the Army’s commitment to the national Materials Genome Initiative.” President Barack Obama announced the initiative in June 2011 as a way to speed development and use of new materials.

Fraunhofer Institute for Ceramic Technologies and Systems demonstrates power without the cord

Because of the limited lifespan, battery power is not a feasible option for many applications in the fields of medicine or test engineering, such as implants or probes. Investigators in Germany have now developed a process that supplies these systems with power and without the power cord. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS succeeded in wirelessly transmitting power from a portable transmitter module to a mobile generator module - the receiver. “The cylindrical shaped transfer module is so small and compact that it can be attached to a belt,” says Holger Lausch, scientist at IKTS. The transmitter provides an electric current of over 100 milliwatts and has a range of about 50 centimeters. As a result, the receiver can be placed almost anywhere in the body. “With our portable device, we can remotely supply power to implants, medication dosing systems and other medical applications without touching them - such as ingestible endoscopic capsules that migrate through the gastrointestinal tract and transmit images of the body‘s inside to the outside,” says Lausch. The generator module can be traced any time - regardless of power transfer - with respect to its position and location. So if the generator is located inside a video endoscopy capsule, the images produced can be assigned to specifi c intestinal regions. If it is placed inside a dosing capsule, then the active ingredient in the medication can be released in a targeted manner.

Atomic-scale visualization of electrons confirms theory of iron-based superconductors

Research at Cornell University has for the first time confirmed key theoretical predictions about how iron-based high-temperature superconductors behave. J.C. Séamus Davis, the James Gilbert White Distinguished Professor in the Physical Sciences at Cornell and director of the Center for Emergent Superconductivity at Brookhaven National Laboratory, and colleagues report in the May 4 online edition of the journal Science that they have identified gaps in the energy levels of electrons in an iron-based superconductor that were predicted by leading theories in this new field. The gaps represent electrons that have paired up with twins from adjacent atoms to form so-called “Cooper pairs” that move through the conductor without interference. The research also confirms a prediction that the energy binding the Cooper pairs varies with the direction they take when leaving an atom. Studying crystals of a compound of lithium, iron and arsenic, LiFeAs for short, that becomes a superconductor at 15K (Kelvins, or Celsius degrees above absolute zero), the Cornell researchers found three of the five possible electron bands. “There are two more pairing gaps that we should have been able to detect, and we don’t know yet why not,” Davis said. But finding these three along with the directionality is enough to strongly support the theory, he said, and the measurements give the theorists numbers to plug in to refine and extend their predictions.

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(Note: the most recent Ceramic Tech Today email—May 15, 2012—accidentally contained an older link that directs readers to this page. For readers who want to go to P. Carlo Ratto’s most recent “News from the glass and refractory worlds, please click here.)

• According to reports, Asahi Glass is considering expanding a factory it has just started building in Brazil, in order to double the facility’s planned output of automotive glass.

• Martin Marietta Magnesia Specialties LLC announced recently it would add a sixth kiln at its dolomitic lime production facility in Woodville.

• A silicon metal smelter will be setup in Abu Dhabi’s newest industrial zone KIZAD, which will supply high grade silicon to aluminium smelters in the region. The plant operated by Al Braik Investments is estimated to cost around Dh638 million.

• Montreal-based Rio Tinto Alcan hopes to seal the sale of four alumina plants by the end of September; at the end of March, Rio Tinto had received a binding offer from private equity group HIG for its three specialty alumina plants in France and one in Germany and would respond to the offer after consulting unions.

• Kerneos, a world leader in calcium aluminates, is pleased to announce that it has acquired a 54% stake in the capital of the Greek company Elmin, the leading European exporter of monohydrate bauxite.

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Examples of 3D wollastonite-based scaffold from preceramic polymers with reactive fillers. This sample from is from fused deposition, after ceramization. Credit: E. Bernardo et. al.; Adv. Eng. Mater.

The main problem with the production of preceramic polymers is the formation of cracks and pores upon heat treatment. It is associated with the gas release and shrinkage occurring during the polymer-to-ceramic conversion. For the most part, this problem can be solved using so-called ‘active fillers’. These are metallic or metal-silicide particles capable of reacting chemically with the decomposition products or the pyrolysis gas in the furnace during the conversion. Nevertheless, it is still diffficult to sinter silicate ceramics from mixtures of oxides.

Lately, experiments have shown that wollastonite (CaSiO₃) ceramics, a well known biomaterial, can be obtained from silicones containing calcium oxide precursors like micropowders or nanoparticles.

In this field, a group of scientists from the University of Padova in Italy conducted a study in cooperation with ACerS Fellow Paolo Colombo, who is affiliated both with the Italian school and Pennsylvania State University, In recent work they present an innovative processing method employing preceramic polymers containing micro- and nanometer-sized particles of calcium carbonate, which act as reactive fillers. With the aim of obtaining wollastonite ceramics, they employed a solid and a liquid silicone in their study. Extrusion experiments were conducted on both thick pastes (cold extrusion) and melts (hot extrusion). The researchers also added hydroxyapatite powders to modify the biological response of the material.

In the study, silica from the decomposition of the silicone resins reliably reacts at low temperature with the calcium oxide (CaO) deriving from the fillers and yielding wollastonite ceramics. This approach enables the fabrication of 3D scaffolds for bone tissue engineering via fused deposition or via conventional hot extrusion. The results provide evidence of the flexibility of the approach employing silicones containing fillers.

The scientists from Italy and the US obtained further improvements by implementing several processing advancements, such as enhancing the mixing of components before extrusion. However, the enhancement of mixing and fused deposition will constitute the focus of their future efforts.

Their work is reported on in a paper in Advanced Engineering Materials (doi:10.1002/adem.201100241).

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The first macroscopic, commercially usable BNNTs, spun into a 3-centimeter-long, 1-milimeter-diameter piece of yarn. Credit: Michael Smith.

Once again, we are reminded that not all scientifically interesting nanotubes are of the carbon variety. Researchers from a number of US and international institutions have released a new study that suggests that placing boron nitride nanotubes on the surface of cancer cells may be able to significantly improve one of the treatment options for soft-tissue cancers, such as those in the pancreas, liver, lung, brain and prostate.

The treatment is called Irreversible Electroporation and it is a relatively new and minimally invasive treatment for difficult-to-treat cancers in soft tissues that uses short pulses of high amplitude static electric fields to attack the cell walls of tumors. ”Irreversible Electroporation is a way of putting holes in the wall of a tumor cell,” says Michael W. Smith in a story on the Jefferson Lab website. Smith, now the chief scientist at BNNT LLC, was formerly a staff scientist at NASA’s Langley Research Center. ”The cell will literally go, ‘Oh, something’s terribly wrong,’ and kill itself. That’s called apoptosis,” he explains.

According to the Jefferson Lab story, Smith read about research being conducted at the Institute of Life Sciences, Scuola Superiore Sant’Anna in Pisa with BNNTs in a journal, and “he offered the researchers a sample of the very high-quality Jefferson Lab/NASA Langley/National Institute of Aerospace BNNTs. These BNNTs are highly crystalline and have a small diameter. Structurally, they also contain few walls with minimal defects, and are very long and highly flexible.”

Using the new BNNTs with in vitro samples, the Italian researchers found the IRE treatment method combined with BNNTs killed twice as many cancer cells (88 percent) on the tumor surface than without (40 percent).

“They were able to get, in a petri dish, more than double the effectiveness. So, this technique works twice as well with our nanotubes on the cells than without them” says Smith. Smith’s company acquired on March 22 the intellectual property rights for making the material available for scientific and commercial research, development and products.

The collaborators are now attempting to scale up the BNNT production process and improve their purity. They caution that their IRE/BNNT work is still very preliminary and say their next step will be studies in mice.

The BNNTs given to the Italian group were made, according to the Jefferson Lab story, using a pressurized vapor/condenser, where a laser aimed at at a boron target first creates boron gas. Then the gas is exposed to a condensor metal wire, which causes liquid boron droplets to form. These droplets combine with the nitrogen to self-assemble into BNNTs.

The work is featured in a paper in Technology in Cancer Research and Treatment.

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Process flow of preparing the vertically aligned single-walled CNTs-DSCs. Pre-etched VASWCNTs on silicon substrate (Process 1) were flipped on top of the FTO-glass, and then a force was loaded onside the silicon top. Credit: Feng Hao et al.; Nature Scientific Reports.

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NIST mini-sensor measures magnetic activity in human brain

A miniature atom-based magnetic sensor developed by the National Institute of Standards and Technology has passed an important research milestone by successfully measuring human brain activity. Experiments reported this week verify the sensor’s potential for biomedical applications such as studying mental processes and advancing the understanding of neurological diseases. NIST and German scientists used the NIST sensor to measure alpha waves in the brain associated with a person opening and closing their eyes as well as signals resulting from stimulation of the hand. The measurements were verified by comparing them with signals recorded by a SQUID (superconducting quantum interference device). The chip-scale NIST sensor is about the size of a sugar cube and operates at room temperature, so it might enable lightweight and flexible MEG helmets. It also would be less expensive to mass produce than typical atomic magnetometers, which are larger and more difficult to fabricate and assemble. The mini-sensor consists of a container of about 100 billion rubidium atoms in a gas, a low-power infrared laser and fiber optics for detecting the light signals that register magnetic field strength-the atoms absorb more light as the magnetic field increases. The sensor has been improved since it was used to measure human heart activity in 2010. NIST scientists redesigned the heaters that vaporize the atoms and switched to a different type of optical fiber to enhance signal clarity.

House panel tops Senate mark for NSF

(Science) A House of Representatives spending panel wants to nearly match the president’s budget request for the National Science Foundation. A proposed $299 million increase in the agency’s 2013 budget would represent a 4.1% boost, to $7.332 billion. That’s even higher than the $240 million boost approved yesterday by the equivalent spending panel in the Senate, although it falls short of the $340 million sought by President Barack Obama. The House figure is expected to be voted on tomorrow morning by the commerce, justice, and science appropriations subcommittee chaired by Rep. Frank Wolf (R-VA). The House mark would provide a $253 million increase for NSF’s six research directorates, just short of the $294 million boost that Obama requested, and a $46 million hike to NSF’s education directorate, which meets the president’s request. The major research facilities account would also receive the administration’s request of $196 million.

First atomic-scale real-time movies of platinum nanocrystal growth in liquids

They won’t be coming soon to a multiplex near you, but movies showing the growth of platinum nanocrystals at the atomic-scale in real-time have blockbuster potential. A team of scientists with the Lawrence Berkeley National Laboratory and the University of California, Berkeley has developed a technique for encapsulating liquids of nanocrystals between layers of graphene so that chemical reactions in the liquids can be imaged with an electron microscope. With this technique, movies can be made that provide unprecedented direct observations of physical, chemical and biological phenomena that take place in liquids on the nanometer scale.

Low-cost solar cells from nanotube ‘forests’

By replacing platinum with carbon nanotubes, researchers hope to make efficient solar cells at a fraction of the current cost for silicon-based solar cells. Single-wall nanotube arrays, grown in a process invented at Rice University, are both much more electroactive and potentially cheaper than platinum, a common catalyst in dye-sensitized solar cells, says Jun Lou, a materials scientist at Rice. When combined with newly developed sulfide electrolytes synthesized at Tsinghua University, the work paves the way for a low-cost, efficient alternative to silicon-based cells. Lou and co-lead investigator Hong Lin, a professor of materials science and engineering at Tsinghua, detailed their work in the open-access Nature journal Scientific Reports. DSCs are easier to manufacture than silicon-based solid-state photovoltaic cells but not as efficient, explains Lou.

Materials under stress: A cracking twist

(NPG Asia Materials) Materials are prone to crack under stress - this can either cause materials failure or, when deliberately induced, offer a useful manufacturing step. In both situations, knowing how to control and predict how materials crack will help in their design and synthesis. Yet exerting control is difficult - for example, we have all seen pottery cracked along random directions. Yong Zhao and co-workers have now prepared core-shell fibres that undergo helical cracking at specific positions. A tough glass fibre was dip-coated with a brittle metal oxide film featuring regular spindle knots. On calcination, the thermal expansion undergone by the tough core does not match that of the brittle shell, creating longitudinal and circumferential stresses. The stress lines in turn cause the knots to crack into helical coils, whose shapes depend on the initial formation process. These findings represent a step forward along the way of controllable fracture.

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