For the first time, researchers at Penn State University and Rice University have created solid, spongy blocks of carbon nanotubes that have an astounding ability to clean up oil spills in water.
Separating oil from seawater is just one of a range of potential applications for the new material formed using carbon and a dash of boron.
The international team, which includes Mauricio Terrones, a professor of physics and of materials science and engineering at Penn State; Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering at Rice University; and other scientists from the United States, Spain, Belgium and Japan, has published the results of its research in Nature's online journal Scientific Reports.
Terrones explained that carbon nanotubes are tiny tubes with diameters ranging from 1-50 nanometers -- much narrower than the width of a human hair. They are also 100 times stronger than steel and about one sixth the weight. "Our goal was to find a way to make three-dimensional networks of these carbon nanotubes that would form a macroscale fabric -- a spongy block of nanotubes that would be big and thick enough to be used to clean up oil spills and to perform other tasks," Terrones said. "We realised that the trick was adding boron -- which is a chemical element that is next to carbon on the periodic table -- because boron helps to trigger the interconnections of the material. To add the boron, we used very high temperatures and we then 'knitted' the substance into the nanotube fabric."
Ajayan explained that the boron puts kinks and elbows into the nanotubes and promotes the formation of covalent bonds, which give the sponges their robust qualities.
"The boron helps to tangle the sponges into a complex network," Ajayan said. "In the past, people have made nanotube solids via post-growth processing but without proper covalent connections. The advantage with our method is that the material is created directly and comes out as a cross-linked porous network."