Rice University in the United States has produced a carbon nanotube fiber, which is stronger than the existing aromatic polyamide synthetic fiber Kevlar, and also improves the conductivity. Matteo Pasquali, an engineer at Rice University's Laboratory of Chemistry and Biomolecules, said that the strongest and most conductive fiber has been developed so far, and it is made of long carbon nanotubes through a wet spinning process.
In this new study, the researchers pointed out that carbon nanotube fibers made by wet spinning can bring breakthroughs in medical and material applications. In carbon nanotube fibers, there is a trend that has continued for nearly two decades, that is, the strength and conductivity of such fibers will double every three years.
Although this trend cannot imitate Moore's Law (when the price remains the same, the number of components that can be accommodated on an integrated circuit will double about every 18-24 months, and the performance will also double), but the researchers Innovative methods of manufacturing carbon nanotube fibers have been developed. The thread-like fibers manufactured in the laboratory, with tens of millions of nanotubes in cross-section, are being studied whether they can be used as a stent for repairing a damaged heart, an electronic interface to the brain, cochlear implants, and flexible antennas. And for automotive and aerospace applications.
In addition, the research is also part of the "Carbon Hub" project, which was initiated by Rice University in 2019 and supported by Shell, Prysmian and Mitsubishi. The goal is to create a zero-emissions future.
The researcher said: "Because of its superior performance, carbon nanotube fibers have always been very popular. Research institutions such as Rice University have been committed to researching such fibers for 20 years. Now, we need to work hard to improve production efficiency so that this material can be realized. Zero carbon dioxide emissions, while producing clean hydrogen."
The tensile strength of the flexible fiber developed by Rice University is 4.2 GPa, while the tensile strength of Kevlar fiber is only 3.6 GPa. This kind of fiber needs to be made of long nanotubes with high crystallinity, that is, it needs to be made of carbon atom rings with almost no defects and regular arrangement. The researchers said that adding an acid solution during the production process can also reduce impurities that interfere with fiber strength, and can improve the metallic properties of nanotubes through residual doping.
"The length to aspect ratio of the nanotube is the decisive feature that determines the performance of the fiber. Nanotubes with a surface area of 12 microns can achieve better Van der Waals forces (intermolecular forces). In addition, by controlling the metal in the catalyst The amount of impurities (amorphous carbon impurities) can also be optimized for solution treatment to improve fiber performance."
The researchers said that the conductivity of the fiber has been increased to 10.9 million Siemens/meter, which is the first time that carbon nanotube fiber has exceeded the 10 million Siemens mark, bringing it to a new order of magnitude. In terms of weight, the conductivity of this fiber is about 8% of copper, and researchers are working to make it surpass platinum wire. In addition, in addition to pitch graphite fiber, the thermal conductivity of this fiber is better than any metal and synthetic fiber.
The goal of the laboratory is to increase the efficiency of producing high-quality fibers while reducing costs to achieve mass production. In the process of producing Kevlar fibers, it is very common to use solution solutions, so factories can use familiar processes without large-scale equipment modification to produce such fibers.