Superlubricity in centimetres-long double-walled carbon nanotubes under ambient conditions

Abstract

Friction and wear are two main causes of mechanical energy dissipation and component failure, especially in micro/nanomechanical systems with large surface-to-volume ratios. In the past decade there has been an increasing level of research interest regarding superlubricity, a phenomenon, also called structural superlubricity, in which friction almost vanishes between two incommensurate solid surfaces. However, all experimental structural superlubricity has been obtained on the microscale or nanoscale, and predominantly under high vacuum. Here, we show that superlubricity can be realized in centimetres-long double-walled carbon nanotubes (DWCNTs) under ambient conditions. Centimetres-long inner shells can be pulled out continuously from such nanotubes, with an intershell friction lower than 1 nN that is independent of nanotube length. The shear strength of the DWCNTs is only several pascals, four orders of magnitude lower than the lowest reported value in CNTs and graphite. The perfect structure of the ultralong DWCNTs used in our experiments is essential for macroscale superlubricity.

Friction of low-dimensional nanomaterial systems

“…They found that the force acting between the core and the outer casing is modulated by the presence of stable defects and generally exhibits ultralow friction (below the . The intershell friction (4# and 5#) was lower than 3 nN when the overlap length was about 5,000 μm or smaller [38]. measurement limit of 1.4 × 10 −15 N/atom) and total dissipation per cycle lower than 0.4 meV/atom.…”

“…In a commensurate pair of tubes, the fluctuation of interlayer slidingresistance force increases with tube length, but in an incommensurate pair this force can remain unchanged [37]. Recent experiments conducted by Zhang et al [38] show that, under ambient conditions, superlubricity can occur in centimeter-long DWCNTs with perfect structures. Here, intershell friction was measured while the inner shells were pulled out from centimeter-long DWCNTs.…”

A Review of Double-Walled and Triple-Walled Carbon Nanotube Synthesis and Applications

“…Again, CNT growth has been identified as a major drawback in helping to control the species being grown, as well as the density and specific number of walls at the resulting carbon nanotube [157]. Double-walled carbon nanotubes have also been identified as materials with interesting electronic transport properties (such as chirality dependence and inner/outer tube selectivity) and superconductivity [158][159][160][161][162]. Fujisawa et al [158], as shown in Figure 9b, investigated the transport properties in films containing pea pod-derived DWNTs and CVD DWNTs.…”

Critical Length Limiting Superlow Friction

“…4(b), we compare the theoretical predictions of Eq. We tested our theory by estimating the critical length for DWCNTs [11]. Here, for clarity we considered the incommensurability of the chain and substrate structures corresponding to the golden ratio, for which the difference between two periods is relatively large.…”