M.Sc Thesis

M.Sc StudentGreenberg Reuven
SubjectNano-Composites for Tribological Applications
DepartmentDepartment of Mechanical Engineering
Supervisors PROFESSOR EMERITUS Izhak Etsion
DR. Gregory Halperin


            In 1992, the Department of Materials and Interfaces, Weizmann Institute, reported the formation of stable structures of layered semiconductor tungsten disulphide (WS2). Using the paradigm of carbon fullerenes, these closed structures were named inorganic fullerene-like structures (IF). Typical WS2 particles have diameters from a few tens to some hundreds of nanometers. Because of their size, the IF are also called nanoparticles. The IF are multi-walled (about 15 layers) hollow nanoparticles, seamless, quasispherical and chemically stable. All these features lead to the assumption that applying the IF in the field of tribology may be suitable. Furthermore, the unique spherical form of the IF lead to the assumption that the nanoparticles may act as tiny ball bearings in a sliding contact leading to lower friction and wear.

            The goals of the present research were to determine the operating conditions under which the IF have maximal effect on the reduction of friction and wear, and to reveal the physical mechanisms involved in friction using the IF as additive to lubrication oils.     For this end, an experimental method based on constructing the Stribeck curve of the system, was consolidated.

            The positive effect of the IF resulted in about 48 % friction reduction and was recorded in mixed lubrication mode only. A hypothesis regarding the mechanism of lubrication with the IF was formulated based on the formation of a transfer film in the contact.