Welding Model for a Carbon Nanotube Bundle with Staggered Electrodes: Implications for Conductivity with Joule Heating

Carbon nanotubes (CNTs) have excellent electrical properties. However, it is challenging to demonstrate these properties in actual electrochemical measurements fully. Previous research has improved the electrical properties of CNTs through welding experiments. But the mechanism of the conductivity enhancement is still unclear. The welding process lacks adequate mechanistic studies and theoretical models. This article presents a theoretical model of a CNT circuit with staggered electrodes, which considers the effect of twist angle on a CNT bundle. A welding model of the CNT bundle circuit is also developed based on the structural changes of CNTs after welding and characterized by the resistance ratio of the CNT circuit pre- and post-welding. The welding model is analyzed to explore how the quantity, diameter, and length of CNTs in the bundle affect the welding effect. An electrical measurement system for CNTs was established to validate the welding model using a nanomanipulation system compatible with a scanning electron microscope. Then, a constant voltage and long-duration electric welding experiment was performed, which showed that the conductivity was enhanced about 1.5–4 times after welding. The results also demonstrated that longer and fewer CNTs in the bundle could improve the electrical conductivity by the welding process more significantly. These findings were consistent with the trend of the welding model. This article establishes a welding theoretical model of the CNT bundle with staggered electrodes, which effectively accounts for the electrical conductivity enhancement during CNT welding and will help more fully express excellent performance in carbon-based nanoelectronic devices, nanoelectromechanical systems, and electrocatalysts in its manufacturing stage.