Radio Frequency Heating of Carbon-based Nanomaterial Films

Abstract

Electromagnetic (EM) energy-induced heating of carbon-based materials has opened up novel routes in material synthesis and processing applications. Three dimensional (3D) printed parts with strengths similar to bulk polymers are now possible due to rapid locally-induced radio frequency (RF) heating and welding of 3D printed interfaces. Automotive and aerospace assembly lines can be improved and sped up due to RF-induced curing to green strength of adhesives loaded with carbon nanomaterials. The flexibility in RF applicator designs to induce heating in a non-contact manner has also extended applications to synthesis of industrially-important ceramics such as silicon carbide. The applicable areas are wide-ranging and continue to increase; however, the fundamental understanding of the phenomenon is still limited and needs to be explored to further develop and improve the efficiency of the new processes. It is known that electrical conductivity is required for RF heating of carbon-based materials. However, it is not well understood how RF heating rates vary with conductivity and if the pattern is generalizable for all types of RF susceptor-loaded structures. The goal of this work is to contribute to the fundamental understanding of the RF heating phenomenon and also extend its applications to other relevant areas. In this work, we first show that the RF heating of semiconducting single-walled carbon nanotubes is significantly higher than that of the metallic single-walled carbon nanotubes primarily due to differences in electrical conductivity. Next, we confirm using experiments and simulation that the RF heating is non-monotonically related with the electrical conductivity; the trend is similar at high frequencies and is universal for a range of carbon-based nanomaterials and their composites. We also demonstrate that RF heating response of carbon-based nanomaterials can be used to detect faults in printed carbon nanotube circuits which allows for rapid screening of nanomaterial-based electronics. Lastly, we show techniques to generate thermal patterns using direct current (DC) and alternating current (AC)-based heating of carbon