MIT’s (Massachusetts Institute of Technology) Department of Aeronautics and Astronautics reported that sodium-containing compounds found in common household ingredients such as baking soda and table salt are able to catalyze the growth of carbon nanotubes (CNTs) at much lower temperatures than traditional catalysts require.
Researchers at MIT say that sodium may make it possible for carbon nanotubes to be grown on a host of lower-temperature materials, such as polymers, which normally melt under the high temperatures needed for traditional CNT growth.
CNTs are grown on various materials coated in a catalyst through chemical vapor deposition (CVD). The furnace is heated at up to 800 degrees Celsius for the process. The MIT team was experimenting with ways to grow CNTs on various surfaces by coating them with different solutions of traditional iron-containing compounds. Brian Wardle, Professor of Aeronautics and Astronautics, said, “The tubes looked a little funny, and the team carefully peeled the onion back, as it were, and it turns out a small quantity of sodium, which we suspected was inactive, was actually causing all the growth.”
The team tested a range of sodium-containing compounds, including commercial-grade sodium in baking soda, table salt, and detergent pellets. They upgraded to purified versions of those compounds, dissolved them in water, and immersed a carbon fiber in each compound’s solution, coating the entire surface in sodium. They placed the material in a furnace and carried out the CVD process to grow CNTs. The sodium catalysts were able to form CNTs at only about 480 degrees Celsius, and after 15 to 30 minutes in the furnace, the sodium simply vaporized away, leaving behind hollow carbon nanotubes.
Richard Li, the study’s lead author and a graduate student in MIT’s Department of Aeronautics and Astronautics, plans to fine tune the timing, temperature and environmental conditions of the CVD process to improve the quality of CNTs so the walls of the tubes are aligned in perfectly hexagonal patterns, providing them with their characteristic strength.
Mr. Li said, “There are so many variables you can still play with, and sodium can still compete pretty well with traditional catalysts. We anticipate with sodium, it is possible to get high-quality tubes in the future. And we have pretty high confidence that, even if you were to use regular Arm and Hammer baking soda, it should work.”
This research was supported, in part, by Airbus, Boeing, Embraer, Lockheed Martin, Saab AB, ANSYS, Saertex, and TohoTenax through MIT’s Nano-Engineered Composite aerospace STructures (NECST) Consortium.