Feasibility of wear reduction for soft nanostructured thin film through enhanced elastic recoverability and contact stress relief

This work shows that a soft,thin film comprising randomly aligned carbon nanotubes(CNTs)can reduce surface wear more effectively than a homogeneous thin film because of enhanced elastic recoverability and contact stress relief originating from its mesh structure.To investigate the wear characteristics of the mesh structure compared to those of the homogeneous thin film,multi-walled CNTs(MWCNTs)and diamond-like carbon(DLC)thin films were prepared to conduct nanoscale tribological experiments using the atomic force microscopy(AFM).The MWCNT thin film showed unmeasurably low wear compared with the DLC thin film under a certain range of normal load.To demonstrate the wear reduction mechanism of the MWCNT thin film,its indentation and frictional behaviors were assessed.The indentation behavior of the MWCNT thin film revealed repetitive elastic deformation with a wide strain range and a significantly lower elastic modulus than that of the DLC thin film.The permanent deformation of the MWCNT thin film was observed through frictional experiments under relatively high normal load conditions.These results are expected to provide insights into the design of highly wear-resistant surfaces using nanostructures.

Study on frictional behavior of carbon nanotube thin films with respect to surface condition

In this work, tribological characteristics of thin films composed of entangled carbon nanotubes(CNTs) were investigated. The surface roughness of CNT thin films fabricated via a dip‐coating process was controlled by squeezing during the process with an applied normal force ranging from 0 to 5 kgf. Raman spectra and scanning electron microscopy(SEM) images of the thin films were obtained to estimate the influence of the squeezing process on the crystallinity of the CNTs. The analysis revealed that squeezing could reduce surface roughness, while preserving the crystallinity of the CNTs. Moreover, the surface energy of the cover glass used to press the CNT thin film was found to be the critical factor controlling surface roughness. A micro‐tribometer and macro‐tribometer were used to assess the tribological characteristics of the CNT thin film. The results of the tribotest exhibited a correlation between the friction coefficient and surface roughness. Dramatic changes in friction coefficient could be observed in the micro‐tribotest, while changes in friction coefficient in the macro‐tribotest were not significant.