Competing Effects of Radio Frequency Fields on Carbon Nanotube/Resin Systems: Alignment versus Heating

• Published in: Macromolecular materials and engineering 2023-11, Vol.308 (11), p.n/a
• Main Authors: Sarmah, Anubhav, Mee, Raymond D., Arole, Kailash, Chi, David, Harkin, Ethan M., Dasari, Smita Shivraj, Wright, Aniela J. K., Tran, Thang Q., Rout, Ankush, Green, Micah J.
• Format: Article
• Language: English
• Subjects: aligned nanocomposites; Alignment; Carbon; Carbon nanotubes; direct ink writing; Electric fields; Electrical conductivity; Electrical resistivity; Joule heating; Nanocomposites; Nanotubes; Ohmic dissipation; Radio frequency; Radio frequency heating; radio‐frequency fields; Resins; Resistance heating; Shear forces; Tensile strength
• ISSN: 1438-7492; 1439-2054
• DOI: 10.1002/mame.202300174

This work shows that radio‐frequency (RF) fields can simultaneously align carbon nanotubes (CNTs) dispersed in a resin and induce Joule heating to cure the resin. The timescales of alignment and curing using RF heating are numerically computed and compared at different field strengths in order to determine a temperature where alignment happens before the matrix crosslinks. Composites are experimentally fabricated at the desired target temperature and are optically analyzed and quantified; the CNT network is successfully aligned in the direction of the applied electric field. This methodology can be used to create composites where the local alignment can be varied across the sample. Composites fabricated using RF fields have higher electrical conductivity in the direction of the aligned CNTs than an oven‐cured, randomly aligned sample. Also, RF‐cured nanocomposites exhibit higher tensile strength and modulus in the direction of alignment compared to an oven‐cured sample. Finally, it is further demonstrated how this methodology can be coupled with a direct ink writing additive manufacturing process to induce alignment in any desired direction, even orthogonal to the shear forces in the extrusion direction. Radio‐frequency fields induce two competing effects in carbon nanotube (CNT)‐filled resins: alignment of CNTs due to electric field‐induced torque, and Joule heating which results in curing. This work addresses the potential to use these competing effects to rapidly heat and cure the CNT‐filled resin to fabricate nanocomposites with aligned CNT networks.