December 5, 2012
In collaboration with the National Institute of Advanced Industrial Science and Technology (hereinafter “AIST”), we have successfully applied a wet-spinning method(note 1) to produce polymer-free, high-density carbon nano tube (hereinafter “CNT”) fibers with the world’s highest electrical conductivity.
In collaboration with AIST, we analyzed the conditions for preparation of CNT dispersion liquids and types of congealed liquid. We found that CNT fibers could be produced under certain conditions even with the use of organic solvent that does not contain polymers as congealed liquid. With the absence of polymer components, an insulating body, the CNT fibers have a high electrical conductivity nearly 20 times greater than that of the conventional wet-spinning method using polymers as congealed liquid.
At the present, CNT fibers fall short of regular copper wires in terms of electric conductivity, but CNTs are stronger and lighter than metals. By maximizing their characteristics, we will continue to generate improvements in pursuit of development of next-generation electrical wires that match the conductivity of copper wires.
Background of development
Electrical wires are an essential product of our social infrastructure. They are increasingly used and are becoming more important in wire harnesses installed in vehicles, since manufacturers are shifting to electrical operation for more and more components. At the same time, the recent measures to counteract global warming and the demand for realization of a low-carbon society are presenting a growing need to trim the weight of electrical wires. Copper alloys and aluminum alloys are already replacing copper as wire conductors.
CNTs are stronger and lighter carbon materials and have greater conductivity than metals. We continue our research on providing electrical wire-like properties to CNTs while focusing on developments for the shift to aluminum alloys. In this way we stay committed to facilitation of efficient use of vehicle space in the future and improvement of fuel efficiency.
Description of the developed product
The developed product involves proper conditions for CNT dispersion and uses organic solvent as congealed liquid. We have successfully used a wet-spinning method to produce polymer-free, high-density CNT fibers with the world’s highest electrical conductivity.By not containing polymer components, an insulating body, the CNT fibers have a high electrical conductivity nearly 20 times greater than that with the conventional wet-spinning method using polymers as congealed liquid. At the present, CNT fibers fall short of regular copper wires in terms of electrical conductivity, but CNTs are stronger and lighter than metals. By maximizing these characteristics, we will continue to add improvements in pursuit of development of next-generation electric wires that match the conductivity of copper wires.
Data on developed product
- Electrical conductivity: 2,800 S/cm(note 2) (about 100 S/cm in the conventional wet-spinning method)
- Length: nearly 80 cm (according to our original pulling process)
This description was presented at an academic meeting held in Boston, MA, USA (2012 MRS Fall Meeting & Exhibit: November 25-30).
(note 1) Wet-spinning method
This method gives fiber-like properties to CNT dispersion liquid, the basic ingredient, by discharging it from the nozzle in congealed liquid (solvent) to solidify it.
(note 2) S/cm
S/cm represents the electrical conductivity per centimeter of a conductor’s length. The larger the numerical value, the greater the conductivity it represents. S stands for siemens and is defined as the reciprocal of an ohm (Ω), a unit of electrical resistance.