Browsing all articles in Publications

X-ray sources based on carbon nanotube cold cathodes

Author Rémi Longtin    Category Publications     Tags ,

Scientists at the Swiss Federal Laboratories for Materials Science and Technology in Zurich, Switzerland, have built a functional X-ray tube using carbon nanotubes as electron sources. Carbon nanotube electron field-emission is well known effect and has been studied since the mid 1990s. Since then, several X-ray sources have been described in the scientific and technical literature.

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Benign joining of ultrafine grained aluminum alloys

Researchers at Empa in Zurich Switzerland have successfully joined nanostructured aerospace grade aluminum alloys with a minimal loss in mechanical properties using nanotechnology. The authors outline in a communication to Advanced Materials how it is possible to braze and solder benignly ultrafine grain aluminum. Nanostructured reactive foils were used as local heat sources. These foils rapidly release thermal energy directly at the interface between two materials leading to a metallurgical joint. The heat affected zone and the duration of heating are substantially limited, which in turn minimizes damage to the bulk. This is a first in the literature and is extremely relevant to several industries that have been struggling with the problem of joining temperature-sensitive materials while avoiding grain growth. This oven-less joining demonstration increases the attractiveness of nanostructured aluminum alloys as lightweight replacements material for conventional alloys.

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The geographic distribution of nanoscience and nanotechnology literature

Author Rémi Longtin    Category News, Publications     Tags ,

An essay in the journal Small (2011, 7, No. 20, 2836-C2839) discusses the growing footprint of nanoscience and nanotechnology on the global scientific landscape. The authors used query terms such as nano*, graphene* and polymer* in Web of Science by Thomson Reuters to generate search results from several key journals in the field such as ACS Nano and Nano Letters. The search results were subsequently analyzed in terms of scope, geographic distribution and footprint on the scientific literature. The essay’s main points are outlined below.

The percentage of the records returned by the search terms for each year dramatically increased from 20 % in 1991 to 80 % in 2010. Also, the term nano* was not sufficient to capture the full activity in these fields and tended to underestimate the literature, especially that of the 1990s. In terms of subject category, the increase in nanoscale studies has been of several-fold for the top 5 Web of Science categories, namely Physics, Materials Science, Chemistry (physical), Chemistry (multidisciplinary) and Nanoscience and Nanotechnology. The latter had the greatest increase from 18 to 70 % from 1997 to 2009.

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Designing diamond circuits for extreme environments

There is a new way to design computer chips and electronic circuitry for extreme environments: make them out of diamond. A team of electrical engineers at Vanderbilt University has developed all the basic components needed to create microelectronic devices out of thin films of nanodiamond. They have created diamond versions of transistors and, most recently, logical gates, which are a key element in computers.

“Diamond-based devices have the potential to operate at higher speeds and require less power than silicon-based devices,” Research Professor of Electrical Engineering Jimmy Davidson said. “Diamond is the most inert material known, so our devices are largely immune to radiation damage and can operate at much higher temperatures than those made from silicon.” Their design of a logical gate is described in the journal Electronics Letters.

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RezQu: a scalable quantum computer

RezQu quantum chipRezQu is a family of devices and architecture for a scalable quantum computer based on superconducting phase qubits. RezQu is being developed by a team at the University of California, Santa Barbara led by John Martinis and Andrew Cleland. The team described their work at the American Physical Society meeting held on March 2011.

The 6cm-by-6cm chip holds nine quantum devices, among them four “quantum bits” that do the calculations. The team said further scaling up to 10 qubits should be possible this year. The team’s key innovation was to find a way to completely disconnect – or “decouple” – interactions between the elements of their quantum circuit. The delicate quantum states that they create must be manipulated, moved, and stored without destroying them. “It’s a problem I’ve been thinking about for three or four years now, how to turn off the interactions,” told John Martinis. “Now we’ve solved it, and that’s great – but there’s many other things we have to do.”

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Integration of carbon nanotubes on CMOS wafers

CNT on CMOSCarbon nanotubes (CNT) – like other nanostructured materials – have high sensitivity to a large number of different gases and vapours which are important in areas as diverse as process monitoring in industry, environmental monitoring, agriculture, personal safety, medicine, or security screening. Gas sensors often operate by detecting the subtle changes that deposited gas molecules make in the way electricity moves through a surface layer. One advantage that carbon nanotubes offer for gas sensors, compared to metal oxide materials, is their fast response time and the fact that they react with gases at lower temperatures, sometimes even as low as room temperature.

In one promising application, researchers demonstrated the detection of specific odorous molecules with high resolution using a functionalized carbon nanotube based sensor. While the possibilities for CNT-based gas sensors are huge, the problem lies with the fabrication technologies, more specifically with a lack of technology for batch fabrication.

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The subatomic roots of ferromagnetism

The discovery of the link between electricity and magnetism less than two centuries ago had a profound impact on our world where electronic devices and electrical power are ubiquitous. But while engineers have harnessed electromagnetic forces on a global scale, physicists still struggle to describe the dance between electrons that creates magnetic fields.

Two theoretical physicists from Rice University are reporting initial success in that area in a paper published in the Proceedings of the National Academy of Science. Their new conceptual model, which was created to learn more about the quantum quirks of high-temperature superconductors and other high-tech materials, has also proven useful in describing the origins of ferromagnetism — the everyday “magnetism” of compass needles and refrigerator magnets.

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Grain-sized nanotechnology electronic noses are on the horizon

electronic noseImagine a device the size of a grain of sand which is capable of analyzing the environment around it, recognize its chemical composition, and report it to a monitoring system. This is the concept of nanotechnology-based electronic noses (e-nose) – miniature electronic devices which mimic the olfactory systems of mammals and insects.

An international team of researchers has made a further step towards this vision and demonstrated a novel analytical sensor which mimics our olfaction system. The difference between this and similar prior e-noses is that the active element of this new device is an individual wedge-like nanowire (nanobelt) made of tin dioxide. The required diversity of the sensing elements is encoded in the nanobelt morphology via longitudinal width variations of the nanobelt realized during its growth and via functionalization of some of the segments with palladium catalyst. “Our approach demonstrates the potential of combining bottom-up nanowire fabrication protocols with state-of-the art microfabrication methods to design prospective simple sensing arrays which, in principle, might be scaled down to the size of few micrometers and thus become the smallest analytical instrument,” tells Andrei Kolmakov, an associate professor in the physics department at Southern Illinois University at Carbondale.

Kolmakov and a team of researchers from Karlsruhe Institute of Technology, Rensselaer Polytechnic Institute, Sincrotrone Trieste, and first author Victor V. Sysoev from Saratov State Technical University, have published their findings in ACS Nano. In what probably is the simplest and yet fully functioning e-nose, the device is made of an individual single-crystal metal oxide quasi-1D nanobelt. The nanobelt was indexed with a number of platinum electrodes in a way that each segment of the nanobelt between two electrodes defines an individual sensing elemental receptor of the array.

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Nanoconfined chemistry for hydrogen storage

The main obstacle to building a ‘hydrogen economy’ – this much touted vision of a society where the main energy carrier is hydrogen – is the lack of efficient hydrogen storage. The research conducted in the hydrogen storage scientific community is aimed towards mobile applications. Hydrogen is a gas at ambient conditions and takes up a lot of space. For stationary storage facilities, for which available space is not an issue, hydrogen gas can be kept in large tanks at moderate pressures using already known technology. However, in order to utilize hydrogen for mobile applications i.e. to produce and be able to sell hydrogen fuelled cars on a large scale, it must be stored in a compact, safe, cheap and efficient way.

In 2009, the U.S Department of Energy (DOE) proposed on-board hydrogen storage system performance targets that have become widely accepted. So far, researchers haven’t been able to successfully demonstrate a material that is capable of simultaneously meeting all of the requirements and criteria set out by the DOE.

A European research team has now reported on a new concept for hydrogen storage using nanoconfined reversible chemical reactions. They demonstrate that nanoconfined hydride has a significant hydrogen storage potential. Research at the Nano Energy-Materials research group at Interdisciplinary Nanoscience Center (iNANO) at Aarhus University in Denmark, led by Flemming Besenbacher and Torben R. Jensen, focuses on the utilization of nanoporous materials as scaffolds for preparation and confinement of nanosized metal hydrides. This bottom-up approach limits the particle size of the hydride to the average pore size of the scaffold material, which allows for the direct production of smaller particles than obtainable mechanically. Furthermore, particle growth and agglomeration may be hindered by the compartmentalization of the nanoparticles within the scaffold material. Nanoconfinement may also mediate improved re-hydrogenation properties of complex metal hydrides.

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Replacing Silicon with Graphene on Nanocircuitry

graphene nanocircuitryScientists have made a breakthrough toward creating nanocircuitry on graphene, widely regarded as the most promising candidate to replace silicon as the building block of transistors. They have devised a simple and quick one-step process based on thermochemical nanolithography (TCNL) for creating nanowires, tuning the electronic properties of reduced graphene oxide on the nanoscale and thereby allowing it to switch from being an insulating material to a conducting material.

The technique works with multiple forms of graphene and is poised to become an important finding for the development of graphene electronics. The research is published in the Science journal. Scientists who work with nanocircuits are enthusiastic about graphene because electrons meet with less resistance when they travel along graphene compared to silicon and because today’s silicon transistors are nearly as small as allowed by the laws of physics. Graphene also has the edge due to its thickness – it’s a carbon sheet that is a single atom thick. While graphene nanoelectronics could be faster and consume less power than silicon, no one knew how to produce graphene nanostructures on such a reproducible or scalable method. That is until now.

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