Using Nanosuspensions to Explore the Capability of the Quartz Crystal Microbalance as a Tribotronic Sensor and for Linking Nano- and Macro-scale Friction

In this work the active control of friction was explored using various methodologies employing quartz crystal microbalance (QCM) as the primary technique. QCM was used to examine the friction of both dry and lubricated contacts in boundary and hydrodynamic lubrication regimes. The hydrodynamic lubrication regime was explored applying fields perpendicular to a QCM immersed in nanoparticle and molecular suspensions. These studies established that QCM is capable of monitoring how friction can be tuned at a solid-liquid interface in a lubricant with charged constituents in suspension. In particular, an electric field was perpendicularly applied across two Pt QCMs submerged in nanoparticle (NP) suspensions, where the NPs studied were 30 nm diameter TiO2 , 5 nm diameter TiO2 , and 30 nm diameterAl2O3 . It was found that the fields observably pushed the NPs towards or away from the QCM surface and had a measurable effect on the friction of the system. Additionally, the electrochemical properties of these systems were examined using two- and three-probe cyclic voltammetry. It was observed that the 30 nm TiO2 suspension showed electrochemical properties consistent with reversible electrophoretic deposition.