"Amplified" nanotubes for efficient, loss-free grid
fine-tuning the temperature and environment in which amplification could occur.
“My group, with Smalley and Tour’s group, demonstrated you could do this — but in the first demonstration, we got only one tube to grow out of hundreds or thousands,” Barron said. Subsequent experiments raised the yield, but tube growth was minimal. In other attempts, the catalyst would literally eat — — or “etch” — the nanotubes, he said.
The release notes that refining the process has taken years, but the payoff is clear because up to 90 percent of the nanotubes in a batch can now be amplified to significant lengths, Barron said. The latest experiments focused on single-walled carbon nanotubes of various chiralities, but the researchers feel the results would be as great, and probably even better, with a batch of pristine armchairs.
The key was finding the right balance of temperatures, pressures, reaction times and catalyst ratios to promote growth and retard etching, Barron said.
“What we’re getting to is that sweet spot where most of the nanotubes grow and none of them etch,” Barron said.
Wade Adams, director of Rice’s Richard E. Smalley Institute for Nanoscale Science and Technology and principal investigator on the AQW project, compared the technique to making sourdough bread. “You make a little batch of pure metallics and then amplify that tremendously to make a large amount. This is an important increment in developing the science to make AQW.
Adams noted eight Rice professors and dozens of their students are working on aspects of AQW. “We know how to spin nanotubes into fibers, and their properties are improving rapidly too,” he said. “All this now has to come together in a grand program to turn quantum wires into a product that will carry vast amounts of electricity around the world.”
Barron and his team are continuing to fine-tune their process and hope that by summer’s end they can begin amplifying armchair nanotubes with the goal of making large quantities of pure metallics. “We’re always learning more about the mechanisms by which nanotubes grow,” said Orbaek, who sees the end game as the development of a single furnace to grow nanotubes from scratch, cap them with new catalyst, amplify them and put out a steady stream of fiber for cables.
“What we’ve done is a baby step,” he said. “But it verifies that, in the big picture, armchair quantum wire is technically feasible.”
Orbaek said he is thrilled to play a role in achieving amplification, which Smalley recognized as necessary to his dream of an efficient energy grid that would catalyze solutions to many of the world’s problems.
“I’d love to meet him now to say, ‘Hey, man, you were right,’” he said.
The Robert A. Welch Foundation and the Air Force Office of Scientific Research funded the research. The Air Force Research Laboratory is primary funding agency for the AQW project.
