Apr. 29, 2013 ? An ultimate goal in the field of carbon nanotube research is to synthesise single-walled carbon nanotubes (SWNTs) with controlled chiralities. Twenty years after the discovery of SWNTs, scientists from Aalto University in Finland, A.M. Prokhorov General Physics Institute RAS in Russia and the Center for Electron Nanoscopy of Technical University of Denmark (DTU) have managed to control chirality in carbon nanotubes during their chemical vapor deposition synthesis.
Carbon nanotube structure is defined by a pair of integers known as chiral indices (n,m), in other words, chirality.
"Chirality defines the optical and electronic properties of carbon nanotubes, so controlling it is a key to exploiting their practical applications," says Professor Esko I. Kauppinen, the leader of the Nanomaterials Group in Aalto University School of Science.
Over the years, substantial progress has been made to develop various structure-controlled synthesis methods. However, precise control over the chiral structure of SWNTs has been largely hindered by a lack of practical means to direct the formation of the metal nanoparticle catalysts and their catalytic dynamics during tube growth.
"We achieved an epitaxial formation of Co nanoparticles by reducing a well-developed solid solution in CO," reveals Maoshuai He, a postdoctoral researcher at Aalto University School of Chemical Technology.
"For the first time, the new catalyst was employed for selective growth of SWNTs," adds senior staff scientist Hua Jiang from Aalto University School of Science.
By introducing the new catalysts into a conventional CVD reactor, the research team demonstrated preferential growth of semiconducting SWNTs (?90%) with an exceptionally high population of (6,5) tubes (53%) at 500 ?C. Furthermore, they also showed a shift of the chiral preference from (6,5) tubes at 500 ?C to (7, 6) and (9, 4) nanotubes at 400 ?C.
"These findings open new perspectives both for structural control of SWNTs and for elucidating their growth mechanisms, thus are important for the fundamental understanding of science behind nanotube growth," comments Professor Juha Lehtonen from Aalto University.
This work is financially supported by the CNB-E project in Aalto University through the Multidisciplinary Institute of Digitalization and Energy (MIDE) program and the Aalto Energy Efficiency program project (MOPPI). This work made use of facilities at Nanomicroscopy Center of Aalto University in Finland and at the Center for Electron Nanoscopy at the Technical University in Denmark sponsored by the A.P. M?ller and Chastine Mc-Kinney M?ller Foundation.
Share this story on Facebook, Twitter, and Google:
Other social bookmarking and sharing tools:
Story Source:
The above story is reprinted from materials provided by Aalto University.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Journal Reference:
- Maoshuai He, Hua Jiang, Bilu Liu, Pavel V. Fedotov, Alexander I. Chernov, Elena D. Obraztsova, Filippo Cavalca, Jakob B. Wagner, Thomas W. Hansen, Ilya V. Anoshkin, Ekaterina A. Obraztsova, Alexey V. Belkin, Emma Sairanen, Albert G. Nasibulin, Juha Lehtonen, Esko I. Kauppinen. Chiral-Selective Growth of Single-Walled Carbon Nanotubes on Lattice-Mismatched Epitaxial Cobalt Nanoparticles. Scientific Reports, 2013; 3 DOI: 10.1038/srep01460
Note: If no author is given, the source is cited instead.
Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.
best in show bret michaels bret michaels pekingese tcu football westminster bonnaroo 2012 lineup
Less than 20 percent of children survived cancer in the 1960?s. Fortunately, the five-year survival rate for childhood cancer is now approaching 80 percent. (1) 
During appointments with our patients, we do our best to educate adolescents and young adults about the importance of learning their own medical histories and speaking up when they have a concern about how they are feeling. This can be difficult, as adolescents may be inclined to deny symptoms like pain, depression or certain worries in front of their parents, and ?neglect? to share information unless the right questions are asked. Well-meaning parents, on the other hand, are so used to being the primary historian and making decisions for their child, that it?s a learning process for them, too. 
ry Lee Gannon ? 
A Singapore clean-tech company called Gcorelab has just received $482,000 (S$589,000) in funding for a new technology that promises to control the thermal issues that have plagued lithium-ion batteries. Battery packs that use lithium-ion cells such as those found in laptops and, in larger deployments like electric cars, can suffer from cells failing. When the cells do and overheat, they can cause a chain reaction with neighboring cells, in a process known as thermal runway propagation, and this can lead to explosions. Gcorelab has patented its cooling technology. It relies on cooling plates, and the team claims that its “oblique fin technology” can achieve 50 to 80 percent better results compared with liquid cooling, while using the same amount of energy. Battery temperatures are managed by transferring heat away from components, and sensors help to regulate the cooling process, said Gcorelab co-founder, Ray Kung. It also works in cold climates, with heaters and coolers jumping in to keep things optimal, he added. (Batteries are finicky things; arctic temperatures can make them blow up, too.) “Currently, battery thermal management is transitioning from air cooling to liquid cooling systems. While affordable and easy to implement, air cooling is vastly inferior in terms of heat transfer performance compared to liquid cooling,” said Kung. So while the industry transitions to liquid cooling methods, Gcorelab is hoping its technology will provide a more affordable alternative to the latter. If successful, the company’s technology could spell revolution for the battery industry and reliant industries, because of the cooling needed to prevent overheating and explosions. Plenty of lithium-ion batteries have exploded over the years, from iPhones to electric toothbrushes. Bad enough to have something burst into flames while you’re brushing your teeth, but you can see why the airline and automotive industries are a lot antsier about safety standards regarding this. Boeing’s brand new Dreamliner 787 planes recently suffered battery overheating faults, and regulators ordered all 50 planes to be grounded?the first US fleet grounding to happen in 34 years. The grounding has reportedly cost Boeing an estimated $600 million, excluding other costs like compensation to airlines which have had business disrupted. Tesla’s CEO, Elon Musk, has commented on Boeing’s battery woes. Musk’s diagnosis of Boeing’s design fault is that the 787 batteries have large cells placed close to each other. In order to minimize the cascading effects of thermal runway, Tesla cars use smaller battery cells![[ Back to EurekAlert! ]](http://www.eurekalert.org/images/back2e.gif){kind=small}
Public release date: 21-Apr-2013
Share ]