Carbon nanotubes have long been regarded as a futuristic dream material, but the dream is giving way to an exciting reality that is bringing big changes to everything from semiconductors to car parts.
It is easy to understand the appeal of the material, which was discovered a little over 20 years ago by Sumio Iijima, a researcher at Japanese electronics company NEC. It is only half the weight of aluminum but 20 times stronger than steel. And its excellent electrical and thermal conductivity make the material ideal for semiconductors.
One company at the forefront of the carbon nanotube movement is Toray Industries of Japan. It is developing a semiconductor designed for use in such advanced products as bendable displays and sensors implanted in the body that can monitor blood-sugar levels. Carbon nanotubes play a crucial role in the device.
Bring the superlatives
The material is composed of carbon atoms linked in a chicken-wire-like mesh to form tiny cylinders with a diameter of just 0.4 nanometers to 50 nanometers (0.4 to 50 billionths of a meter). Toray says semiconductors using the material will be able to transmit electronic signals 10 times faster than ordinary silicon chips and can be made thinner. The company also claims carbon nanotube-based displays will offer sharper, smoother moving images and consume less electricity than conventional displays.
For the semiconductor it is working on, Toray is using single-wall nanotubes for the primary material. Because this type of nanotube typically has the properties of both a semiconductor and a metal, using it as a semiconductor material presents many difficulties.
However, working with the National Institute of Advanced Industrial Science and Technology (AIST), Toray has developed a technology for extracting only semiconductor-type nanotubes from clusters of the single-wall variety. This has enabled them to increase the purity of semiconductor-type nanotubes to more than 95%, a “level sufficient for enabling the practical use of the material,” said Yuichiro Iguchi, head of Toray’s Electronic & Imaging Materials Research Laboratories.
Toray has also devised a way to make a semiconductor that involves spraying carbon nanotubes on a substrate. Because the method involves fewer steps than usual, production costs are only about a tenth those for silicon chips. The company aims to commercialize semiconductors produced using the spray-on method by around 2016.
Another Japanese company finding new uses for the material is Nitta, a major industrial belt maker. It has increased the impact resistance of carbon fiber-reinforced plastic, which is used in autoparts, by adding a tiny amount of carbon nanotubes in the production process. The resultant material is also likely to prevent the accumulation of static electricity, which Nitta says can cause problems.
The company aims to mass-produce the improved plastic, which can be produced using existing facilities, as soon as possible.
Wired for success
Meanwhile, Japan’s Furukawa Electric is trying to use carbon nanotubes in wire harnesses that connect electronic devices in automobiles. The company has developed a composite material by mixing carbon nanotubes with aluminum. Furukawa says the material will be able to make wire harnesses up to 40% lighter than the traditional copper variety. Demand would likely be strong among carmakers, which are constantly seeking ways to shave the weight of their vehicles to improve their mileage.
Research on technologies for producing carbon nanotubes is also making progress. Zeon, a major Japanese maker of synthetic rubber, has created a method for mass-producing carbon nanotubes that have high electrical conductivity and few impurities. The technology, based on a process invented by Kenji Hata of AIST, uses water to activate a catalyst needed to make high-purity carbon nanotubes, thereby raising production efficiency.
With the technology, “it will become possible to develop completely new materials, such as rubber that conducts electricity,” said Kohei Arakawa, a senior engineer at Zeon.
Zeon will build a new production facility at its Tokuyama plant in Shunan, Yamaguchi Prefecture, to start mass-producing highly pure, highly conductive carbon nanotubes in the latter half of 2015. As a start, the company intends to sell the material to Nippon Chemi-Con, which wants to use it for parts for electric double-layer capacitors, a type of storage battery.
In it together
The public sector is supporting private-sector efforts to advance carbon-nanotube technology. Zeon, for example, received financial and other help from the government-affiliated New Energy and Industrial Technology Development Organization for its work on the production technology. Also, the Saitama prefectural government has a subsidy program.
Carbon nanotubes are attracting attention in other countries, as well. China’s Tsinghua University and Taiwan’s Hon Hai Precision Industry, also known as Foxconn, have jointly developed and commercialized a smartphone touch panel using the material.
Huawei Technologies, a Chinese communications equipment maker, is moving ahead of Japanese rivals in the practical use of carbon nanotubes in the smartphone field. Although Japan has an advantage in cutting-edge technologies, industry insiders there are worried about the speed with which China and Taiwan are catching up.
“Carbon nanotubes are suited for use as a memory material for high-capacity servers,” said Ken Takeuchi, a professor at Chuo University who is working with Harvard University-based startup Nantero to develop a high-speed memory chip using carbon nanotubes.
In theory, with carbon nanotube memory chips, data can be rewritten 100 billion times, 10 million times more than possible with flash memories.
“Success in the competition for developing next-generation semiconductors will hinge on the use of carbon nanotubes,” predicted Takeuchi, who has experience developing flash memories at a Japanese manufacturer.
This article was published in Nikkei Asian Review’s website. Image courtesy of NEDO