UCLA researchers create exceptionally strong and lightweight new metal

Magnesium infused with dense silicon carbide nanoparticles could be used for airplanes, cars, mobile electronics and more

A team led by researchers from the UCLA Henry Samueli School of Engineering and Applied Science has created a super-strong yet light structural metal with extremely high specific strength and modulus, or stiffness-to-weight ratio. The new metal is composed of magnesium infused with a dense and even dispersal of ceramic silicon carbide nanoparticles. It could be used to make lighter airplanes, spacecraft, and cars, helping to improve fuel efficiency, as well as in mobile electronics and biomedical devices.

To create the super-strong but lightweight metal, the team found a new way to disperse and stabilize nanoparticles in molten metals. They also developed a scalable manufacturing method that could pave the way for more high-performance lightweight metals. The research waspublished today in Nature. 

“It’s been proposed that nanoparticles could really enhance the strength of metals without damaging their plasticity, especially light metals like magnesium, but no groups have been able to disperse ceramic nanoparticles in molten metals until now,” said Xiaochun Li, the principal investigator on the research and Raytheon Chair in Manufacturing Engineering at UCLA. “With an infusion of physics and materials processing, our method paves a new way to enhance the performance of many different kinds of metals by evenly infusing dense nanoparticles to enhance the performance of metals to meet energy and sustainability challenges in today’s society.”

Structural metals are load-bearing metals; they are used in buildings and vehicles. Magnesium, at just two-thirds the density of aluminum, is the lightest structural metal. Silicon carbide is an ultra-hard ceramic commonly used in industrial cutting blades. The researchers’ technique of infusing a large number of silicon carbide particles smaller than 100 nanometers into magnesium added significant strength, stiffness, plasticity and durability under high temperatures.

The researchers’ new silicon carbide-infused magnesium demonstrated record levels of specific strength — how much weight a material can withstand before breaking — and specific modulus — the material’s stiffness-to-weight ratio. It also showed superior stability at high temperatures.

Ceramic particles have long been considered as a potential way to make metals stronger. However, with microscale ceramic particles, the infusion process results in a loss of plasticity.

Nanoscale particles, by contrast, can enhance strength while maintaining or even improving metals’ plasticity. But nanoscale ceramic particles tend to clump together rather than dispersing evenly, due to the tendency of small particles to attract one other.

To counteract this issue, researchers dispersed the particles into a molten magnesium zinc alloy. The newly discovered nanoparticle dispersion relies on the kinetic energy in the particles’ movement. This stabilizes the particles’ dispersion and prevents clumping.

To further enhance the new metal’s strength, the researchers used a technique called high-pressure torsion to compress it.

“The results we obtained so far are just scratching the surface of the hidden treasure for a new class of metals with revolutionary properties and functionalities,” Li said.

The new metal (more accurately called a metal nanocomposite) is about 14 percent silicon carbide nanoparticles and 86 percent magnesium. The researchers noted that magnesium is an abundant resource and that scaling up its use would not cause environmental damage.

The paper’s lead author is Lian-Yi Chen, who conducted the research as a postdoctoral scholar in Li’s Scifacturing Laboratory at UCLA. Chen is now an assistant professor of mechanical and aerospace engineering at Missouri University of Science and Technology.

The paper’s other authors from UCLA include Jia-Quan Xu, a graduate student in materials science and engineering; Marta Pozuelo, an assistant development engineer; and Jenn-Ming Yang, professor of materials science and engineering.

The other authors on the paper are Hongseok Choi, of Clemson University; Xiaolong Ma, of North Carolina State University; Sanjit Bhowmick of Hysitron, Inc. of Minneapolis; and Suveen Mathaudhu of UC Riverside.

UCLA

Autonomous Atom Assembly of Nanostructures using a Scanning Tunneling Microscope

Automated assembly of individual cobalt atoms on an atomically
flat copper surface into simple geometric shapes, a square, a triangle,
and a circle. From left to right, each figure shows the configuration
after each atom move. Image size 15 nm × 15 nm. Center: Perfect
assembly of the NIST logo after four steps of automated assembly.
Image size 40 nm × 17 nm. All images are shown in colored 3D top view
with light shadowing with a height range of ≈100 pm.

NIST researchers have demonstrated the autonomous computer-controlled assembly of atoms into perfect nanostructures using a low temperature scanning tunneling microscope. The results, published in an invited article in the Review of Scientific Instruments, show the construction without human intervention of quantum confined two-dimensional nanostructures using single atoms or single molecules on a copper surface.

A major goal of nanotechnology is to develop so-called “bottom up” technologies to arrange matter at will by placing atoms exactly where one wants them in order to build nanostructures with specific properties or function. The researchers, led by Robert Celotta and Joseph Stroscio from the CNST, have demonstrated the first steps towards achieving that capability using the atom manipulation mode of a scanning tunneling microscope (STM) in combination with autonomous motion algorithms.

The team, which includes Stephen Balakirsky (previously in EL and now at Georgia Tech), Aaron Fein (PML), Frank Hess (previously in the CNST), and Gregory Rutter (previously in the CNST and now at Intel), used autonomous algorithms to manipulate single atoms and molecules, much like the algorithms for “hands-free” car driving. The system works by first scanning the locations of available atoms on the surface. It then specifies the desired coordinates of atoms of a nanostructure, and autonomously calculates and directs the trajectories for the STM probe tip to move all the atoms to their desired locations.  

The team was able to demonstrate that it could autonomously construct cobalt atoms into nanostructures that confine the quantum properties of the copper’s surface electrons.  It then used the STM to measure those properties. In addition to demonstrating the construction of nanostructures made out of atoms, they demonstrated that it was possible to construct nanoscale lattices made of carbon monoxide molecules and to tailor-make interacting quantum dots formed from vacancies in the carbon monoxide lattices.

The researchers believe that an approach based on autonomous construction of atoms and molecules using this technique could be the foundation for an easily accessed toolkit for producing tailored quantum states with applications in quantum information processing and nanophotonics.

http://www.nist.gov/cnst/automated_atom_assembly.cfm

Nano-paper filter can remove viruses

The illustration shows the nanofibers in white and the virus in green. Photograph: Björn Syse

Researchers at the Division of Nanotechnology and Functional Materials, Uppsala University have developed a paper filter, which can remove virus particles with an efficiency matching that of the best industrial virus filters. The paper filter consists of 100 percent high purity cellulose nanofibers, directly derived from nature.

The research was carried out in collaboration with virologists from the Swedish University of Agricultural Sciences/Swedish National Veterinary Institute and is published in the Advanced Healthcare Materials journal.

Virus particles are very peculiar objects- tiny (about thousand times thinner than a human hair) yet mighty. Viruses can only replicate in living cells but once the cells become infected the viruses can turn out to be extremely pathogenic. Viruses can actively cause diseases on their own or even transform healthy cells to malignant tumors.

‘Viral contamination of biotechnological products is a serious challenge for production of therapeutic proteins and vaccines. Because of the small size, virus removal is a non-trivial task, and, therefore, inexpensive and robust virus removal filters are highly demanded’, says Albert Mihranyan, Associate Professor at the Division of Nanotechnology and Functional Materials, Uppsala University, who heads the study.

Cellulose is one of the most common materials to produce various types of filters because it is inexpensive, disposable, inert and non-toxic. It is also mechanically strong, hydrophyllic, stable in a wide range of pH, and can withstand sterilization e.g. by autoclaving. Normal filter paper, used for chemistry, has too large pores to remove viruses.

The undergraduate student Linus Wågberg, Professor Maria Strømme, and Associate Professor Albert Mihranyan at the Division of Nanotechnology and Functional Materials, Uppsala University, in collaboration with virologists Dr. Giorgi Metreveli, Eva Emmoth, and Professor Sándor Belák from the Swedish University of Agricultural Sciences (SLU)/Swedish National Veterinary Institute (SVA), report a design of a paper filter which is capable of removing virus particles with the efficiency matching that of the best industrial virus filters. The reported paper filter, which is manufactured according to the traditional paper making processes, consists of 100 percent high purity cellulose nanofibers directly derived from nature.

The discovery is a result of a decade long research on the properties of high surface area nanocellulose materials, which eventually enabled the scientists to tailor the pore size distribution of their paper precisely in the range desirable for virus filtration.

Previously described virus removal paper filters relied heavily on interception of viruses via electrostatic interactions, which are sensitive to pH and salt concentrations, whereas the virus removal filters made from synthetic polymers and which rely on size-exclusion are produced through tedious multistep phase-inversion processing involving hazardous solvents and rigorous pore annealing processing.

Incidentally, it was the Swedish chemist J.J. Berzelius (1779-1848), one of the most famous alumni of Uppsala University, who was the first one to use the pure wet-laid-all-rag paper for separation of precipitates in chemical analysis. In a way, the virus removal nano-paper filter developed by the Uppsala scientists is the modern day analogue of the widely popular Swedish Filter Paper developed by Berzelius nearly two centuries ago.

Source: http://www.uu.se/en/media/news/article/?id=3317&area=2,10,16&typ=artikel&na=&lang=en#sthash.rKkmbmdN.dpuf

A new possibility for all-optical switching

York physicists pave the way for more energy efficient technology

An international team of scientists led by physicists from the University of York has paved the way for a new class of magnetic materials and devices with improved performance and power efficiency.

Magnetic materials are currently used to store almost all digital information. However, with information processing and storage now making up a significant fraction of the world’s energy consumption, continuing improvements in energy efficiency will require new technologies and materials.

A promising development is all-optical thermally induced magnetic switching (TIMS), which uses ultrafast laser pulses to change the magnetic state of the material, equivalent to writing a single bit of data. In all-optical switching there is no need to use magnetic fields to write the data and so a significant reduction in power consumption can be made. Moreover, the deposited laser energy per written bit is much smaller.

Until now, only rare-earth-transition-metal alloys called ferrimagnets have been shown to exhibit all-optical switching. However, these materials are both difficult to produce at the nanoscale necessary for technological devices and expensive due to their use of rare-earth metals such as Gadolinium (Gd) and Terbium (Tb).

Now new research, led by York’s Department of Physics and involving scientists from Helmholtz-Zentrum Berlin (HZB), Germany and Radboud University Nijmegen, the Netherlands offers a new possibility for all-optical switching.

The research, published in Applied Physics Letters, demonstrates the use of a synthetic ferrimagnet - a sandwich of two ferromagnetic materials and a non-magnetic spacer layer. The spacer layer engineers the coupling between the two ferromagnets so that they align opposite to one another. When subjected to an ultrafast laser pulse this structure spontaneously switches its magnetic state representing writing a single bit of data.

Corresponding author Dr Richard Evans, from York’s Department of Physics, said: “Energy efficiency is one of the most important goals for technological devices due to their expanding use with an increasing world population and resultant demand for energy.

“The synthetic ferrimagnet structure overcomes the intrinsic problems of rare-earth-transition-metal alloys and paves the way for a new class of magnetic materials and devices with improved performance and power efficiency. The results are a significant step towards realising a device based on thermally induced switching as it shows that structures on the nanometre length scale can be used.”

Co-author Professor Theo Rasing, Head of the Department Spectroscopy of Solids and Interfaces at Radboud University Nijmegen, said: “Since our original discovery of all-optical-switching of magnetic domains in these ferrimagnetic alloys more than five years ago, the fruitful collaboration between our experimental efforts, the possibilities provided by the unique instrumentation of the Helmholtz-Zentrum  and the theoretical insight provided by the York team, has led to this truly European success.”

Source: http://www.york.ac.uk/news-and-events/news/2014/research/ferrimagnets/

Better nanoswitches by integrating double and triple strand DNA

The road from simple nanomaterials and nanodevices to atomically precise manufacturing will involve integrating these simple components into ever more complex and capable systems. 

The early stages of such integration will also advance current and near-future nanotechnology across multiple application areas, as will be explored in the the Integration Conference, February 7-9, 2014, in Palo Alto, California. A hat tip to Nanotechnology Now for news of this advance from researchers in Rome, Santa Barbara, and Montreal that integrates two basic interactions that have been exploited in DNA nanotechnology—Watson–Crick base pairing and triplex-forming Hoogsteen interactions—to form more sensitive and accurate nanoswitches. From a Université de Montréal press release “DNA clamp to grab cancer before it develops“


As part of an international research project, a team of researchers has developed a DNA clamp that can detect mutations at the DNA level with greater efficiency than methods currently in use. Their work could facilitate rapid screening of those diseases that have a genetic basis, such as cancer, and provide new tools for more advanced nanotechnology. The results of this research is published this month in the journal ACS Nano [abstract].

Toward a new generation of screening tests

An increasing number of genetic mutations have been identified as risk factors for the development of cancer and many other diseases. Several research groups have attempted to develop rapid and inexpensive screening methods for detecting these mutations. “The results of our study have considerable implications in the area of diagnostics and therapeutics,” says Professor Francesco Ricci, “because the DNA clamp can be adapted to provide a fluorescent signal in the presence of DNA sequences having mutations with high risk for certain types cancer. The advantage of our fluorescence clamp, compared to other detection methods, is that it allows distinguishing between mutant and non-mutant DNA with much greater efficiency. This information is critical because it tells patients which cancer(s) they are at risk for or have.”

“Nature is a constant source of inspiration in the development of technologies,” says Professor Alexis Vallée-Bélisle. “For example, in addition to revolutionizing our understanding of how life works, the discovery of the DNA double helix by Watson, Crick and Franklin in 1953 also inspired the development of many diagnostic tests that use the strong affinity between two complementary DNA strands to detect mutations.”

“However, it is also known that DNA can adopt many other architectures, including triple helices, which are obtained in DNA sequences rich in purine (A, G) and pyrimidine (T, C) bases,” says the researcher Andrea Idili, first author of the study. “Inspired by these natural triple helices, we developed a DNA-based clamp to form a triple helix whose specificity is ten times greater than a double helix allows.”

“Beyond the obvious applications in the diagnosis of genetic diseases, I believe this work will pave the way for new applications related in the area of DNA-based nanostructures and nanomachines,” notes Professor Kevin Plaxco, University of California, Santa Barbara. “Such nanomachines could ultimately have a major impact on many aspects of healthcare in the future.”

“The next step is to test the clamp on human samples, and if it is successful, it will begin the process of commercialization,” concludes Professor Vallée-Bélisle.

This research presents a clear case in which work aimed at better DNA sequence probes for diagnosis and therapy has yielded an improved device that the authors expect to also lead to, in the final words of their abstract, “better control over the building of nanostructures and nanomachines.”

—James Lewis, PhD

Source: http://www.foresight.org/nanodot/?p=6005

A new wrinkle in the control of waves

Flexible materials could provide ways to manipulate sound and light.

In the top pair of images, sound waves (blue and yellow bands) passing through a flat layered material are only minimally affected. In the lower images, when sound goes through a wrinkled layered material, certain frequencies of sound are blocked and filtered out by the material. 

IMAGE: FELICE FRANKEL

Flexible, layered materials textured with nanoscale wrinkles could provide a new way of controlling the wavelengths and distribution of waves, whether of sound or light. The new method, developed by researchers at MIT, could eventually find applications from nondestructive testing of materials to sound suppression, and could also provide new insights into soft biological systems and possibly lead to new diagnostic tools.

The findings are described in a paper published this week in the journal Physical Review Letters, written by MIT postdoc Stephan Rudykh and Mary Boyce, a former professor of mechanical engineering at MIT who is now dean of the Fu Foundation School of Engineering and Applied Science at Columbia University.

While materials’ properties are known to affect the propagation of light and sound, in most cases these properties are fixed when the material is made or grown, and are difficult to alter later. But in these layered materials, changing the properties — for example, to “tune” a material to filter out specific colors of light — can be as simple as stretching the flexible material.

“These effects are highly tunable, reversible, and controllable,” Rudykh says. “For example, we could change the color of the material, or potentially make it optically or acoustically invisible.”

The materials can be made through a layer-by-layer deposition process, refined by researchers at MIT and elsewhere, that can be controlled with high precision. The process allows the thickness of each layer to be determined to within a fraction of a wavelength of light. The material is then compressed, creating within it a series of precise wrinkles whose spacing can cause scattering of selected frequencies of waves (of either sound or light).

Surprisingly, Rudykh says, these effects work even in materials where the alternating layers have almost identical densities. “We can use polymers with very similar densities and still get the effect,” he says. “How waves propagate through a material, or not, depends on the microstructure, and we can control it,” he says.

By designing that microstructure to produce a desired set of effects, then altering those properties by deforming the material, “we can actually control these effects through external stimuli,” Rudykh says. “You can design a material that will wrinkle to a different wavelength and amplitude. If you know you want to control a particular range of frequencies, you can design it that way.”

The research, which is based on computer modeling, could also provide insights into the properties of natural biological materials, Rudykh says. “Understanding how the waves propagate through biological tissues could be useful for diagnostic techniques,” he says.

For example, current diagnostic techniques for certain cancers involve painful and invasive procedures. In principle, ultrasound could provide the same information noninvasively, but today’s ultrasound systems lack sufficient resolution. The new work with wrinkled materials could lead to more precise control of these ultrasound waves, and thus to systems with better resolution, Rudykh says.

The system could also be used for sound cloaking — an advanced form of noise cancellation in which outside sounds could be completely blocked from a certain volume of space rather than just a single spot, as in current noise-canceling headphones.

“The microstructure we start with is very simple,” Rudykh says, and is based on well-established, layer-by-layer manufacturing. “From this layered material, we can extend to more complicated microstructures, and get effects you could never get” from conventional materials. Ultimately, such systems could be used to control a variety of effects in the propagation of light, sound, and even heat.

George Fytas, professor of materials science and head of the polymer group at the University of Crete, Greece, says this is a "very novel idea, because it induces a directional phonic gap not existing in the layered structure." He adds that this finding "shows how well-established theoretical tools can predict new materials behavior, which is challenging for experimentalists."

The technology is being patented, and the researchers are already in discussions with companies about possible commercialization, Rudykh says.

The research was supported by the U.S. Army Research Office through the MIT Institute for Soldier Nanotechnologies.

Source: http://web.mit.edu/newsoffice/2014/a-new-wrinkle-in-the-control-of-waves-0124.html

Nano-inspired packaging plastic protects as well as aluminium foil

The encapsulated nanoparticles layer (center and right) consists of nanoparticles encapsulated by an organic species (left) via a self-assembly method in which the nanoparticles concentration is very high—up to 70 to 80% by weight. Image: A*STAR

Tera-Barrier Films invents alternative stretchable plastic for prolonging shelf-life of pharmaceuticals, food and electronics

Tera-Barrier Films (TBF) Pte Ltd, a spin-off company from A*STAR’s Institute of Materials Research and Engineering’s (IMRE), has invented a new plastic film using a revolutionary nano-inspired process that makes the material thinner but as effective as aluminium foil in keeping air and moisture at bay. The stretchable plastic could be an alternative for prolonging shelf-life of pharmaceuticals, food and electronics, bridging the gap of aluminium foil and transparent oxide films.

The new plastic by TBF has one of the lowest moisture vapour transmission rates (mvtr), preventing air and moisture from penetrating the layer. The plastic has an air and moisture barrier that is about 10 times better than the transparent oxide barriers which are currently being used to package food and medicines owing to its uniquely encapsulated nanoparticle layer. The film has been validated by a number of companies and potential commercialisation partners.

TBF’s 700nm encapsulated nanoparticle barrier films - which are thinner than a strand of human hair - have high transparency and are also stretchable, features not possible with aluminium-based packaging material. Inorganic barrier thin films are highly transparent but have lower barrier property and are not stretchable. TBF’s films will allow see-through packing and a longer shelf-life for a wide range of products from high-end electronics to perishable goods. Stretchability is another attractive feature in facilitating simple packaging processes.

Aluminium as a metal has very high oxygen and moisture barrier properties, but aluminium-based packaging comes at a higher processing cost, is opaque, non-stretchable, and interferes with electronics, making the integration of components like RFID devices difficult. TBF’s new stretchable thin films are cost effective and transparent, with barrier properties comparable to that of aluminium foil.

“TBF’s strategy is to bridge the gap between aluminium foil and transparent oxide films by creating new packaging structures for the niche applications in the food, medical, pharmaceuticals and electronics markets,” said Mr Senthil Ramadas, Director & Chief Technology Officer of TBF. “The secret behind TBF’s film lies in our patented encapsulated nanoparticle layer that consists of nanoparticles in polymer shells”.

Conventional multilayer barrier plastics have successive layers of barrier plastic films to enhance the impermeability to air and moisture but they have not achieved higher barrier properties. TBF’s film uses minimal layers as its encapsulated nanoparticles increase the packing density of nanoparticles, which in turn makes it extremely difficult for water and oxygen molecules to pass through the film. The encapsulated nanoparticles also actively adsorb and react with water and oxygen molecules to trap them, thus further lowering the amount of moisture and air passing through the film.

“The innovation creates a whole new generation of packaging materials that add new and superior functions for use in high value products such as medicine”, says Professor Andy Hor, Executive Director of A*STAR’s IMRE from where the unique barrier film technology was initially developed, incubated and spun-off. “We are glad to see our scientist-entrepreneurs advancing an IMRE-born technology and are looking forward to seeing it make an impact in the market”.

“The University of Tokyo confirmed TBF’s barrier film performance at 10-6g/m2/day”, said Mr. Nakazawa, Managing Director, KISCO (Asia) Pte. Ltd. “There has been very favourable response from our potential customers in a spectrum of industries wishing to benefit by incorporating TBF’s superior barrier films into their products, these applications range from food and medical packaging to high end PV, lighting and display sectors where TBF’s barrier films excel.”

TBF was recently recognised by leading Global Growth consulting firm, Frost & Sullivan as the ‘2013 Global Next Generation Technology Company of the Year in the field of Barrier Films’ due to its novel approach of developing innovative technology for its patented barrier material and barrier stack technology that enhances the performance and reliability of barrier films. TBF has pioneered a unique and innovative technology for developing barrier films, by using nanoparticles to plug the defects in the barrier oxide layer, thereby enhancing barrier effectiveness and at the same time, reducing the number of barrier layers needed.

TBF’s reduced number of barrier layers and lower material costs, as compared to conventional barrier film technologies, brings in tremendous cost efficiencies into TBF’s manufacturing process. With TBF’s unique technology and low cost, access to newer applications like Quantum dot color filters, Vacuum Insulated Panels (VIPs), Food & Medical Packaging has been made possible in addition to the conventional application areas like OLED displays or lighting and flexible Solar cells. This opens up a wide spectrum of opportunities for the barrier films market and TBF’s barrier films are well positioned to address the needs from these new and emerging applications.

Source: http://www.a-star.edu.sg/Media/News/Press-Releases/articleType/ArticleView/articleId/1980.aspx

Alzheimer-substance may be the nanomaterial of tomorrow

It causes brain diseases like Alzheimer’s, Parkinson’s and Creutzfeldt-Jakob’s disease. It is also hard and rigid as steel. Now research at Chalmers University of Technology shows that the amyloid protein carries unique characteristics that may lead to the development of new composite materials for nano processors and data storage of tomorrow and even make objects invisible.

Piotr Hanczyc, PhD student at the department of Chemical and Biological Engineering, shows in an article in Nature Photonics, that the amyloid, a very dense aggregate of protein that causes brain diseases like Alzheimer's and Parkinson's, carries unique characteristics. Unlike well-functioning protein the amyloid reacts upon multi photon laser irradiation. This laser may in the future possibly be used for detection of amyloids inside a human brain. This discovery is in itself a breakthrough.

- But you can also create these aggregates in an artificial way in a laboratory and in combination with other materials create unique characteristics, Piotr Hanczyc says.

The amyloid aggregates are as hard and rigid as steel. The difference is that steel is much heavier and has defined material properties whereas amyloids can be tuned for desired purpose. By attaching a material’s molecules to the dense amyloid its characteristics change. This has been known for more than ten years and is already used by scientists.

- What hasn’t been known is that the amyloids react to multi-photon irradiation and this opens up new possibilities to also change the nature of the material attached to the amyloids, Piotr Hanczyc says.

The amyloids are shaped like discs densely piled upon each other.  When a material gets merged with these discs its molecules end up so densely and regularly that they can communicate and exchange information. This means totally new possibilities to change a material’s characteristics. 

Multi-photon tests on materials tied to amyloids are yet to be performed, but Piotr sees an opportunity for cooperation with Chalmers material science researchers interested for example in solar cell technology. 

And though it may still be science fiction, he also considers that one day scientists may use the material properties of amyloid fibrils in the research of invisible metamaterials.

- An object’s ability to reflect light could be altered so that what’s behind it gets reflected instead of the object itself, in principle changing the index of light refraction, kind of like when light hits the surface of water, Piotr Hanczyc says. 

Source: http://www.chalmers.se/en/departments/chem/news/Pages/Alzheimer-substance-may-be-the-nanomaterial-of-tomorrow.aspx

Less is more with adding graphene to nanofibers

Figuring that if some is good, more must be better, researchers have been trying to pack more graphene, a supermaterial, into structural composites. Collaborative research led by University of Nebraska-Lincoln materials engineers discovered that, in this case, less is more.

The team, led by Yuris Dzenis, McBroom professor of mechanical and materials engineering and a member of UNL's Nebraska Center for Materials and Nanoscience, learned that using a small amount of graphene oxide as a template improves carbon nanomaterials which, in turn, promises to improve composite materials. Composites are used in everything from airplanes to bicycles and golf clubs.

Graphene is a one-atom thick layer of carbon with a crystalline structure that makes it exceptionally strong and an excellent heat and electrical conductor. It was the subject of research that earned the 2010 Nobel Prize in Physics.

UNL engineers collaborated with researchers from Northwestern University and Materials and Electrochemical Research Corp. of Tucson, Ariz., on this study. The UNL team developed a process to incorporate graphene oxide nanoparticles as a template to guide the formation and orientation of continuous carbon nanofibers, which should improve the fiber's properties. That process involves crumpling the graphene, like crumpling a sheet of paper, in a way that improves graphene as a templating and orientation agent. Only small amounts of crumpled graphene nanoparticles are needed. A group led by chemist SonBinh Nguyen of Northwestern synthesized the graphene oxide.

"Many people are trying to put as much graphene as possible into fibers," Dzenis said, adding that it is difficult to do. "But we did the unconventional thing: We used very small quantities followed by carbonization."

The resulting carbon nanofiber structure has an orientation similar to fibers with demonstrated enhanced strength and other properties, Dzenis said. He and his colleagues are now testing their graphene-based nanofibers for these enhanced properties as well as improving the technique.

The method is promising, he said. It could lower the cost of making composites significantly because it requires only small quantities of expensive nanoparticles and uses an inexpensive nanofiber manufacturing process, which was developed at UNL.

"All of this has potential for high-performance but, at the same time, low-cost carbon nanofibers," Dzenis said.

The team reported its findings in the Dec. 10 issue of Advanced Functional Materials. Co-authors are UNL mechanical and materials engineering colleagues Dimitry Papkov and Alexander Goponenko; facilities specialist Xing-Zhong Li of the Nebraska Center for Materials and Nanoscience; Owen C. Compton, Zhi An and SonBinh T. Nguyen of Northwestern; and Alexander Moravsky of Materials and Electrochemical Research Corp.

This research was funded by grants from the U.S. Army Research Office Multidisciplinary University Research Initiative, Air Force Office of Scientific Research and the National Science Foundation.

Source: http://newsroom.unl.edu/releases/2013/12/11/UNL-led+team+finds+less+is+more+with+adding+graphene+to+nanofibers

Project aims to mass-produce 'nanopetals' for sensors, batteries

These color-enhanced scanning electron microscope images
show nanosheets resembling tiny rose petals.
The nanosheets are key components of a new type
of biosensor that can detect minute concentrations
of glucose in saliva, tears and urine. The technology
might eventually help to eliminate or reduce
the frequency of using pinpricks for diabetes testing.
(Purdue University photo/Jeff Goecker)

Researchers at Purdue University are developing a method to mass-produce a new type of nanomaterial for advanced sensors and batteries, with an eye toward manufacturing in the Midwest.

Research findings indicate the material shows promise as a sensor for detecting glucose in the saliva or tears and for "supercapacitors" that could make possible fast-charging, high-performance batteries.

However, for the material to be commercialized researchers must find a way to mass-produce it at low cost.

"It's one thing to say you've got a new wonder material, but can you prove that it can be made on a commercial scale?" said Arvind Raman, Robert V. Adams Professor of Mechanical Engineering. "In many cases we find that fundamental research needs to be done for scaling up. You want to be able to produce large quantities of the material at 50 cents per square meter."

Now, a team of Purdue researchers will aim to do just that. The project, funded with a $1.5 million grant from the National Science Foundation, focuses on creating a nanomanufacturing method that is "scalable," or capable of mass production at low cost.

The underlying technology was developed by a research group led by Timothy Fisher, the James G. Dwyer Professor in Mechanical Engineering. It consists of vertical nanostructures resembling tiny rose petals made of a material called graphene, which is a single-atom-thick film of carbon.

"Using these graphene nanopetals we have realized exceptional performance in a wide range of devices at laboratory scales," Fisher said.

The researchers hope to boost the production speed of nanopetal-coated surfaces to 10 square meters per hour, representing a dramatic increase over the laboratory-scale production rate.

Raman has expertise in roll-to-roll manufacturing, a mainstay of many industrial operations including paper and sheet-metal production. He models the mechanics of the process of creating flexible materials in sheets at high speed and under tension.

"A key factor is going to be industry partners," he said. "There are many industries that have roll-to-roll operations. So focusing on roll-to-roll as a platform for doing nanomaterials production is very strategic for the Midwest."

He also has expertise in precision measurement using an atomic force microscope. 

"You have to be able to measure the material while it is being manufactured, and this is a challenge because of the nanometer scale of the petals," he said.

The graphene nanopetals also have shown promise as a "thermal-interface" material to keep computer chips from overheating. 

"A slew of new device and material concepts based on graphene nanopetals are emerging in applications as diverse as carbon fiber composites and new thermal-interface materials," Raman said. "Commercial interest is extremely high for this recent carbon nanomaterial. "

Other key researchers in the project are Alina Alexeenko, an associate professor of aeronautics and astronautics; Alexander Wei, a professor in the Department of Chemistry; Ernesto E. Marinero, a professor of engineering practice in the schools of Chemical Engineering and Materials Engineering; and Euiwon Bae, a research professor of mechanical engineering.

The nanopetals are created in a vacuum by exposing a cloth of carbon fiber to high-energy plasma that contains hydrogen ions and other ingredients, a process known as plasma-enhanced chemical vapor deposition. Alexeenko will lead work to model the plasma reactor and to optimize its conditions for fast and environmentally friendly conversion of raw materials, such as methane and hydrogen, into carbon nanopetals. 

Wei will functionalize petals with metal nanoparticles and enzymes that recognize glucose or other target molecules for biosensing. Marinero will focus on reliability of devices made using the nanomaterial, and Bae will work to ensure proper petal size by analyzing patterns of light scattering from the material's surface.

Most of the research will be based at the Birck Nanotechnology Center in Purdue's Discovery Park.

"Scale-up production is a key challenge facing nanotechnology," said Ali Shakouri, the Mary Jo and Robert L. Kirk Director of the Birck Nanotechnology Center and a professor of electrical and computer engineering. "This NSF project is part of a broader nanomanufacturing initiative at the Birck Nanotechnology Center where we focus on roll-to-roll production of smart thin films for applications in pharmacy and food packaging."

Wei said, "The project represents the front edge of a much larger movement at Purdue to synergize core research expertise in science and engineering in a way that provides graduate students with opportunities to overcome the challenges of converting exciting research discoveries into products that can be commercialized."

Technologies developed in the project might be commercialized through collaboration with a local start-up company, Folium Nanotechnologies LLC, co-founded by Fisher and Marinero, as well as Roche Diagnostics and the Battery Innovation Center. The center was launched this year to leverage Indiana's public- and private-sector assets in advanced battery technologies to facilitate research and development, rapid prototyping and contract manufacturing for industry, academic and military customers.

"A regional workshop series on roll-to-roll nanomanufacturing will be organized to serve as a catalyst to innovation in the Midwest by bringing together interested small, medium and large enterprises together with original equipment manufacturers and university researchers," Raman said.

The new technology could be of particular interest to battery makers in Indiana.

The researchers also will make available advanced simulation tools for vacuum-based roll-to-roll processes. The tools will be available to companies through the cyberinfrastructure of the manufacturing HUB and nanoHUB, an interactive website that makes available scientific simulations, seminars, interactive courses and other specialized nanotech-related materials.

"We will educate the U.S. workforce through an innovative online class on nanomanufacturing offered as part of the nanoHUB U initative," Raman said.

The research has potential for broad impact. 

"Many results from this research are not just applicable to graphene nanopetal technology, but rather to a wide variety of nanomaterials manufactured in low-pressure and ambient roll-to-roll nanomanufacturing processes," he said. 

Source: http://www.purdue.edu/newsroom/releases/2013/Q4/project-aims-to-mass-produce-nanopetals-for-sensors,-batteries.html

Volvo uses nanotechnology for cars

Volvo says it has made conventional batteries a “thing of the past” with a new lightweight battery system.

The Chinese-owned Swedish brand has developed new nanotechnology-derived batteries housed within thin carbon fibre storage packets. Designed to slot within the panels of the car the battery packs use nanoparticles, which include microscopic components with molecular manipulation to improve its properties.

Volvo says the move could lower the weight of future electric cars and free up interior space.

It uses carbon fibre to “sandwich” ultra-small nano-structured batteries and supercapacitors, which capture kinetic energy and can also be refilled using a conventional plug. These in turn feed electricity to the car’s motor.

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The thin, light inner panels can then be fitted in different areas around the car, including under the bonnet, in the doors, in the boot lid and spare wheel housing and the roof turret. This means the batteries won’t eat into the car’s usable space; vehicles such as the Toyota Camry Hybrid feature a large battery bank behind the back seats which impinges on its practicality.

Volvo says that if an electric car were to replace its existing battery components with the new system it could cut its kerb weight by 15 per cent - meaning a car like the Nissan Leaf, which weighs 1795 kilograms, would be about 270 kilograms lighter, thus increasing its efficiency.

Volvo says it has developed an S80 experimental car that is using the technology in the boot lining in place of the regular 12-volt battery.

The ultimate goal is to also fit the battery packs in the doors and bonnet.

The project was funded by the European Union, and Volvo was the only car maker to be involved.

Source: http://smh.drive.com.au/motor-news/volvo-uses-nanotechnology-for-cars-20131021-2vw6j.html

Which makes a better solar collector, quantum dot or nanowire

A trio of researchers at North Dakota State University, Fargo and the University of South Dakota have turned to computer modeling to help decide which of two competing materials should get its day in the sun as the nanoscale energy-harvesting technology of future solar panels - quantum dots or nanowires.

 

Andrei Kryjevski and his colleagues, Dimitri Kilin and Svetlana Kilina, report in AIP Publishing's Journal of Renewable and Sustainable Energy that they used computational chemistry models to predict the electronic and optical properties of three types of nanoscale (billionth of a meter) silicon structures with a potential application for solar energy collection: a quantum dot, one-dimensional chains of quantum dots and a nanowire. The ability to absorb light is substantially enhanced in nanomaterials compared to those used in conventional semiconductors. Determining which form - quantum dots or nanowire -maximizes this advantage was the goal of the numerical experiment conducted by the three researchers.

 

"We used Density Functional Theory, a computational approach that allows us to predict electronic and optical properties that reflect how well the nanoparticles can absorb light, and how that effectiveness is affected by the interaction between quantum dots and the disorder in their structures," Kryjevski said. "This way, we can predict how quantum dots, quantum dot chains and nanowires will behave in real life even before they are synthesized and their working properties experimentally checked."

 

The simulations made by Kryjevski, Kilin and Kilina indicated that light absorption by silicon quantum dot chains significantly increases with increased interactions between the individual nanospheres in the chain. They also found that light absorption by quantum dot chains and nanowires depends strongly on how the structure is aligned in relation to the direction of the photons striking it. Finally, the researchers learned that the atomic structure disorder in the amorphous nanoparticles results in better light absorption at lower energies compared to crystalline-based nanomaterials.

 

"Based on our findings, we believe that putting the amorphous quantum dots in an array or merging them into a nanowire are the best assemblies for maximizing the efficiency of silicon nanomaterials to absorb light and transport charge throughout a photovoltaic system," Kryjevski said. "However, our study is only a first step in a comprehensive computational investigation of the properties of semiconductor quantum dot assemblies.The next steps are to build more realistic models, such as larger quantum dots with their surfaces covered by organic ligands and simulate the processes that occur in actual solar cells," he added.

 

Source and top image: American Institute of Physics

Top image shows: Amorphous Silicon nanowire (yellow network) facilitates harvesting of solar energy in the form of a photon (wavy line). In the process of light absorption a pair of mobile charge carriers is created (red clouds depict an electron smeared in space, while the blue clouds visualize the so-called hole which is a positively charged carrier). The energy of their directed motion is then transformed into electricity. Electron and hole charge distributions are often located in different regions of space due to multiple structural defects in amorphous silicon nanowires.

 

For more read Energy Harvesting and Storage for Electronic Devices 2012-2022 

 

And attend Energy Harvesting & Storage USA 20-21 November 2013, Santa Clara, USA 

Source: http://www.energyharvestingjournal.com/articles/which-makes-a-better-solar-collector-quantum-dot-or-nanowire-00005858.asp?sessionid=1