Finally, the ‘ultimate’ carbon nanotube development

By Barry Copping

Nanotube strength enhancement will emulate Kevlar technologyAn industrial-scale production process for manufacturing pure carbon nanotube fibres could lead to “revolutionary” advances in materials science, power distribution and nanoelectronics, according to a joint research team from three establishments – Houston-based Rice University and the University of Pennsylvania in the USA, and the Technion-Israel Institute of Technology.

Rice University scientists claim to have found the “ultimate” solvent for all kinds of carbon nanotubes (CNTs), bringing the creation of a highly electrically conductive quantum nanowire closer.

The researchers regard working with long nanotubes (made by a process analogous to polymerisation) as key to attaining exceptional physical attributes in fibres, because both their mechanical and electrical properties depend on the length of the constituent nanotubes. Using longer nanotubes should enhance fibre properties by one to two orders of magnitude, say the team, and similarly enhanced properties should also be expected in thin films of carbon nanotubes being investigated for flexible electronics applications.

Professor Matteo Pasquali, a team member and author of a research paper in the ACS Nano journal commented: “Plastics is a $300 billion US industry because of the massive throughput that’s possible with fluid processing. The reason grocery stores use plastic bags instead of paper and the reason polyester shirts are cheaper than cotton is that polymers can be melted or dissolved and processed as fluids by the [railway wagon] load. Processing nanotubes as fluids opens up all of the fluid processing technology that has been developed for polymers.”

Co-author Wade Adams added: “[Our] research established an industrially relevant process for nanotubes that was analogous to the methods used to create Kevlar from rodlike polymers, except for the acid not being a true solvent.

“The current research shows that we have a true solvent for nanotubes– chlorosulfonic acid – which is what we set out to find when we started this project nine years ago.”

Kevlar, the para-aramid polymer synthetic fibre used in bulletproof vests, is about five to ten times stronger than the strongest nanotube fibres today, but in principle the Rice scientists expect to make their fibres about 100 times stronger.