The Ohio State University

ADHESION, FRICTION, AND WEAR ON NANOSCALE OF MWNT PROBES AND CNT ARRAYS*

Barbara Galasso
M.S. Thesis,
Department of Mechanical Engineering, October 2007

ABSTRACT

The nanotribological characterization of carbon nanotubes is fundamental for the exploration of new sliding applications. In this study, a comprehensive investigation of adhesion, friction and wear of a MWNT tip, SWNT and MWNT arrays has been carried out. A nonlinear response of the MWNT tip is observed when the tip is brought in and out of the contact with various surfaces. It is due to the buckling of the nanotube and its subsequent sliding on the surface. In addition to surface chemistry, it can also explain the relatively high value of coefficient of friction evaluated on different surfaces, as compared to that of Si and Si₃N₄ tips. The adhesion and friction studies carried out on SWNT and MWNT arrays using Si tips show that SWNT arrays exhibit lower values, possibly due to lower van der Waals forces as a result of lower packing density and higher flexibility. The wear tests conducted with the MWNT tip and a Si tip on a gold film, at two normal loads, show less damage of the surface when the MWNT tip is used because of the MWNT acting as a compliant spring, absorbing part of the load. Wear tests conducted with Si tip on SWNT and MWNT arrays, show that the arrays do not wear. However, the tip wear and the friction force in the SWNT array are lower, because of lower adhesion and higher flexibility of the SWNTs, which opposes less to the motion of the tip.

*Thesis in Italian