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Honda-Led Research Team Devises Method to Control Growth of Nanotubes with Metallic Conductivity

Carbon nanotubes are preferentially grown by controlling the shape and size of the catalyst. Tubes growing on red and pink exhibit metallic properties, while semiconducting tubes are on blue. The height of the nanotubes indicates the probability of each specific tube in the experiment. Source: Honda RI. Click to enlarge.

A team of researchers from Honda Research Institute USA, Inc., in conjunction with researchers at Purdue University and the University of Louisville, has developed a method for controllably growing carbon nanotubes with metallic conductivity. With further optimization, the researchers say, “direct control over nanotube structure during growth may well be feasible.” A paper on their work appears in the 2 Oct issue of the journal Science.

Carbon nanotubes are grown on the surface of metal nanoparticles, and take the form of rolled graphene sheets. The nanotube bonding configuration is known as its chirality. The chirality determines the conductivity of the nanotube—i.e., either metallic or semiconducting. Nanotubes exhibiting metallic conductivity 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.

The ability either to separate or to synthesize either all semiconducting or all metallic tubes would open new possibilities for fully exploiting carbon nanotubes in a wide range of miniaturization and energy efficiency applications, 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.

Though some methods exist to bias the population of one type of nanotube during synthesis, there is only a limited understanding of exactly what determines chirality during synthesis. There have been important achievements in separating single-walled carbon nanotubes (SWNTs) according to their conductivity and in enriching the distribution of nanotubes with a specific conductivity. Meanwhile, there have been a few reports regarding direct control over nanotube structure during growth. The fact that SWNTs with narrow chiral distributions have been successfully grown indicates that there may be a specific mechanism that controls chirality. The concept of amplifying existing SWNT distributions by seeding growth from another nanotube with well-defined chirality has been proposed; however, evidence for the maintenance of chirality has not yet been reported. The preferential growth of nearly 90 to 96% of semiconducting SWNTs by plasma-enhanced chemical vapor deposition has been reported, but the mechanism that leads to this selectivity remains unclear.

—Harutyunyan et al.

The Honda-led team grew SWNTs from Fe nanocatalysts deposited onto a SiO2/Si support and in situ annealed in a He or Ar ambient that contained various ratios of H2 and H2O. They used methane as the carbon source at 860 °C. By varying the noble gas ambient during thermal annealing of the catalyst, and in combination with oxidative and reductive species, they altered the fraction of SWNTs with metallic conductivity from one-third of the population to a maximum of 91%. 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%.

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.

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.

—Dr. Avetik Harutyunyan, principal scientist from Honda Research Institute USA, and the leader of the project

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.


  • Avetik R. Harutyunyan, Gugang Chen, Tereza M. Paronyan, Elena M. Pigos, Oleg A. Kuznetsov, Kapila Hewaparakrama, Seung Min Kim, Dmitri Zakharov, Eric A. Stach, Gamini U. Sumanaseker (2009) Preferential Growth of Single-Walled Carbon Nanotubes with Metallic Conductivity. Science Vol. 326. no. 5949, pp. 116 - 120 doi: 10.1126/science.1177599



A very well written description of the technology .
It sounds like significant progress toward super materials.


"Nanotubes exhibiting metallic conductivity 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."

It can scale up economically - WOW..


Look at the names of scientists (at bottom) - almost all foreigners, Indians, Russians, Chinese ...

In ten years many of them will be going to universities in China, if they are smart to attract them, first to introduce studies for higher degrees in English, to remove the language barrier.


If we paid our scientists and engineers the salaries of sports stars, movie stars, and Wall Street crooks maybe we would atract the best and brightest young Americans into the physical sciences.

Carlos Fandango

You are just about right on that point Mannstein.

Up until about 100 years ago musicians, mimics and clowns had a certain place in society roughly equivalent to their usefullness. Close to the bottom of the pile in most cases.

Unfortunately with the advent of TV and mass advertisment, the image rights of a famous individual can command reward far in excess of their merit and capability. Dunno how we can fix that.

Bankers, capitalists, lawyers and salesmen are a different story. They provide little value to society and skim off an outstanding chunk of the productivity.

Bring on the 21st century revolution.


Oh it's not just rewards these famous people command; if you're really famous you can get a free pass to commit crime. Witness Roman Polansk.


They are useful: they entertain millions of people. Most importantly, people are ready to pay quite a lot to see them playing or acting or whatever they do.

That's why they are paid a lot.

If the general public was ready to pay a lot to save the environnement, scientists would be paid a lot more. And some are: people working at Microsoft are paid a lot because the public pays for Windows.

That's another reason to put something like a carbon tax or a cap-and-trade system: it gives more value to green scientists and may lure young people into becoming the next generation of scientists.


At the local University, the business and nursing schools are overloaded and the science and math wing is a ghost town. Students know that science and math are tough and business will just exploit them and bring in foreigners on green cards. Why bust your behind and just be abused.


Well said Simodul.

People developing green technologies could be paid much more if pollution was taxed. This may not be for tomorrow because we prefer paying for something else (like $200 to go to the circus or a ball game) and we do not want to pay more taxes.

Taxes are not very popular and could be replaced with users' fees like; an extra $1/lb or $2/lb for registration fees for vehicles over 2000 lbs; an extra $0.10/mile for all highway usage; an extra $50/year for driver licenses, an extra $1/hour fee for parking smaller cars and double for larger cars, etc etc.

One way way or another, we will all pay for the transition.


This, and other similar breakthroughs into basic technologies, may eventually lead to much better batteries and ultra-caps for future post 2020 high performance BEVs.

Good work Honda, Purdue and Louiseville Universities.

Henry Gibson

One possible problem with the US is that there are few scientists in public offices. Scientists must deal with the truth. Hydrogen and Oxygen form water and give off energy. To get hydrogen out of water takes a lot of energy. One atom plus two atoms makes two atoms.

Carbon nanotubes will not make a radical difference in the need for energy for people directly and industry indirectly.

Honda has developed a very good machine to save energy and CO2 in homes and small buildings, but its use and introduction to the world was not well engineered. It is a combined heat and power unit. It is a far cheaper way to reduce CO2 than solar cells. But it costs too much to rapidly spread in the US eventhough there are 50,000 units in Japan. The unit cannot even be bought in most of the US. It also cannot be bought alone, it has to be bought with a new, very, expensive home heating system if it can be bought at all.

Honda killed FuelMaker after it bought it. It was too high priced for people. ..HG..

The biggest change that this technology will bring is the stationary space elevator. The cost of transporting goods to space will drop to around 2 dollars a pound to geosynchronous orbit. Material availability from space will change the cost of all platinum group metals to next to nothing, all those on the gold standard will suffer. Cheap clean renewable energy will be available from the Sun from solar powersats at less cost than we pay today for fossil fuels. No one will burn fossil fuels anymore so your carbon tax wishes will be moot.

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