Kinky nanotubes

While in Mexico, Hashim gradually tweaked the chemical vapor deposition (CVD) process, varying the boron quantity, the temperature and the flow rate. “Suddenly he found a material that looked completely different from a standard nanotube sample,” Terrones says. “It looked like a sponge with a fascinating texture.” It takes just 30 minutes to grow chunks as long as 4 inches and weighing 2 to 3 grams.

Hashim, however, had to shelve the research when Ajayan, his advisor, left RPI for Rice. When Hashim rejoined him as a graduate student in 2010, the massive Deepwater Horizon petroleum leak prompted them to redirect the research from batteries to environmental remediation. The work was supported by NSF, the Air Force Office of Scientific Research, the Army Research Laboratory and the Department of Energy’s Office of Science through ORNL’s Center for Nanophase Materials Science and the LCF. Other participating institutions include Spain’s Universidade de Vigo and Instituto de Microelectrónica de Madrid, the University of Illinois at Urbana-Champaign, the Air Force Research Laboratory and Arizona State University.

It should be relatively easy for manufacturers to modify bulk nanotube production processes to scale up nanosponge fabrication, Terrones says. Ultimately, how inexpensive the sponges become could be a function of the uses for them – and many are possible. They conduct electricity, so Sumpter sees applications in electronics and energy storage. Terrones says the material’s low density could make it a good scaffold for bone tissue growth. Impregnate the sponge with polymers and it could become a robust and light material for use in cars and planes. Hashim speculates the material even could be used to remove the salt from seawater.

For now, Hashim is continuing to explore ways to exploit nanotubes’ one-dimensional properties by engineering them into porous, three-dimensional solids. He’s focusing on enhancing the covalent bonding that makes them possible – and on finishing his doctoral studies. But, working with Ajayan and Rice, he’s also seeking ways to commercialize the discovery.