Monday, November 2, 2009

Breakthrough in industrial-scale nanotube processing

The liquid-crystaline phase of carbon nanotubes dissolved in chlorosulfonic acid.

(Rice University) Rice University scientists today unveiled a method for the industrial-scale manufacturing of pure carbon-nanotube fibers, a breakthrough that could lead to revolutionary advances in materials science, power distribution and nanoelectronics. The method builds upon tried-and-true processes the chemical industry has used for decades to produce polymer fibers. Findings from Rice's methodical, nine-year program are detailed in this week's Nature Nanotechnology.

"Plastics is a $300 billion U.S. industry because of the massive throughput that's possible with fluid processing," said Rice's Matteo Pasquali, a paper co-author and professor in chemical and biomolecular engineering and in chemistry. "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 train-car load. Processing nanotubes as fluids opens up all of the fluid-processing technology that has been developed for polymers."

The report was co-authored by an 18-member team of scientists from Rice's Richard E. Smalley Institute for Nanoscale Science and Technology, the University of Pennsylvania and the Technion-Israel Institute of Technology. Co-authors include Smalley Institute namesake Rick Smalley, the late Nobel laureate chemist who developed the first high-throughput method for producing high-quality carbon nanotubes, as well as Virginia Davis, a former doctoral student of Pasquali's and Smalley's who is now a professor at Auburn University, and Micah Green, a former postdoctoral researcher of Pasquali's who is now a professor at Texas Tech University.

The new process builds upon the 2003 Rice discovery of a way to dissolve large amounts of pure nanotubes in strong acidic solvents like sulfuric acid. The research team subsequently found that nanotubes in these solutions aligned themselves, like spaghetti in a package, to form liquid crystals that could be spun into monofilament fibers about the size of a human hair.

"That 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," said Wade Adams, director of the Smalley Institute and co-author of the new paper. "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." …

Breakthrough in industrial-scale nanotube processing

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