Interações físico-químicas em nanotribologia: elucidação de mecanismos e controle do atrito em escala nanométrica

Abstract

The study of friction, wear, lubrication, and adhesion at the nanoscale forms nanotribology, an interdisciplinary area dedicated to understanding and promoting advances in the most diverse applications in which these phenomena are present. Friction is a collective event, formed by independent mechanisms that result in the final property observed. With the experimental and theoretical advances of the last decades, it was possible to separate the different contributions. Understanding each one in depth promotes the change and even the active control of this property, inherent in any interface of materials in contact and relative sliding. Several contributions can be better understood by the physical chemistry of interactions, and, in this context, the present work aims to investigate and relate such characteristics to nanotribological phenomena. Initially, a physicochemical model based on the polarizability of the materials that form the interface is proposed and satisfactorily describes, when compared with experimental data, the elastic regime of nanofriction for amorphous and crystalline systems. In materials in which the polarizability of the atoms does not vary significantly, the formation of chemical bonds at the interface was investigated as responsible for the friction variation in experimental and simulation work. This observation allowed the proposal of an indirect isotopic effect for surfaces passivated with hydrogen and deuterium atoms, joining previously divergent results in the bibliography, and the experimental confirmation of the slip-dependent friction for silicon films passivated with hydrogen, recently suggested by simulation. Finally, it was proposed the active control of friction in nanoparticle systems, where the light was the agent responsible for reversibly changing surface properties, leading to the change of interface interactions. Thus, physicochemical properties were used to understand nanotribology and proposed as a tool for active control of its phenomena. [resumo fornecido pelo autor]