October 5, 2009 -- Microscopic carbon nanotubes 100,000 times thinner than a human hair may have the potential to transport electricity faster and over greater distances with minimal loss of energy, according to new research published in the October 2nd edition of Science magazine. The research was led by Honda Research Institute USA, Inc., in conjunction with researchers at Purdue University and the University of Louisville.
The findings open new possibilities for miniaturization and energy efficiency, including much more powerful and compact computers, electrodes for supercapacitors, electrical cables, batteries, solar cells, fuel cells, artificial muscles, composite material for automobiles and planes, energy storage materials and electronics for hybrid vehicles.
Microscopic carbon nanotubes are grown on the surface of metal nanoparticles, taking the cylindrical form of rolled honeycomb sheets with carbon atoms in their tips. When these tiny carbon nanotubes exhibit metallic conductivity they possess extraordinary strength compared to steel, higher electrical properties than copper, are as efficient in conducting heat as a diamond and are as light as cotton. "Our goal is not only the creation of new and better technologies and products, but to fulfill Honda's commitment to environment sustainability," says Dr. Hideaki Tsuru, project director from Honda Research Institute USA.
Past research efforts to control the structural formation of carbon nanotubes with metallic conductivity through conventional methodology resulted in a success rate of approximately 25 - 50 percent. Honda, which has worked in the field of carbon nanotube synthesis for almost a decade, reports that it has achieved a success rate of 91 percent metallic conductivity for grown carbon nanotubes.
"This is the first report that shows we can control fairly systematically whether carbon nanotubes achieve a metallic state. Further research is in progress with the ultimate goal to take complete control over grown nanotube configurations to support their real world application," says Dr. Avetik Harutyunyan, principal scientist from Honda Research Institute USA, and the leader of the project.
"Our finding shows that the nanotube configuration which defines its conductivity depends not only on the size of the metal nanocatalyst used to nucleate the tube as was previously believed, but importantly also is based on its shape and crystallographic structure, and we learned to control it," continues Dr. Harutyunyan, whose team of Honda scientists included Dr. Gugang Chen and Dr. Elena Pigos.
"We are excited about our teamwork and collaborations with researchers at Purdue and Louisville, who helped achieve this advance," he adds.
Researchers at Purdue, led by Professor Eric Stach, used a transmission electron microscope to observe nanotube formation, revealing that changes in the gaseous environment can vary the shape of the metal catalyst nanoparticles from very sharp faceted to completely round. Researchers at Louisville, led by Professor Gamini Sumanasekera, produced the nanotubes in larger volumes and made careful measurements to determine whether the nanotubes achieve a metallic state.
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