2024 AIChE Annual Meeting
(416g) Intershell Locking of Double-Walled Carbon Nanotubes Resulting from Enhanced Intershell Friction at High Shear Rates
Friction is a pervasive phenomenon in various mechanical processes, especially in systems involving high-speed motion where friction has a great impact on energy dissipation and mechanical transmissions. Meanwhile, friction in some nanomaterials exhibits velocity-dependent phenomena that are different from macroscopic friction, suggesting that friction has a significant impact on nanoscale systems involving highspeed motion. However, the measurement of nanoscale-friction at high sliding velocities has remained elusive due to the limitations in temporal and spatial resolution associated with nanomanipulation techniques in electron microscopes. Here, we developed a non-contact photocatalytic cut-off method specifically tailored for the outer shells of double-walled carbon nanotubes (DWCNTs), and captured the motion of the outer shells as they slide along the inner shells subsequent to fracture under an optical microscope. The result indicates that the intershell friction is independent of the overlap length but linearly related to the sliding velocity. At velocity of 977 mm/s or shear rate of 109 s-1, the intershell friction reaches 195 nN——comparable in scale to tensile stress. Moreover, the linear increase of shear stress with shear rate presents a quasi-Newtonian fluids sliding behavior, wherein the shear viscosity exhibits a decrease from 2 mPa∙s to 0.06 mPa∙s and then maintains a relatively constant value at high shear rates. Such enhanced intershell friction leads to locking of the inner and outer tubes when the DWCNTs undergo high-speed fracture, thus improving the resistance of DWCNTs to high-speed impacts.