Abstract
We report a study of the response of a Quartz Crystal Microbalance (QCM) to rubbing contacts in air, water and aqueous suspensions of 40nm TiO2 nanoparticles. Measurements were performed with a contact comprised of 3 close-packed 304SS ball bearings situated symmetrically about the center of a 304SS QCM electrode with 2nm rms roughness. Two continuum methods were employed to infer macroscale friction coefficients μ employing QCM nanotribological data recorded in the Cattaneo-Mindlin (CM) slip regime at vibrational amplitudes that varied between 1nm and 17nm. The “slope” Method 1 involved sweeps of the QCM amplitude of vibration as ball bearings were held in continuous contact with the oscillating electrode. The “contact” Method 2 obtained μ by analyzing the shifts in frequency and bandwidth that occur at a fixed uo to solve for μ. when ball bearings were brought in and out of contact with the QCM’s electrode. The results for dry and water lubricated contacts compared favorably with macroscale friction coefficients reported in the literature. The model failed to adequately describe contacts lubricated with the NP suspension, but its continuum nature did not appear to be the dominant factor underlying failure. The failure was more likely attributable to either a lack of a CM slip regime when NP were present at the interface and/or the fact that the amplitude of vibration was close in size to the individual NP contacting regions, in violation of a key underlying assumption of the model.
Highlights
We report a study of the response of a Quartz Crystal Microbalance (QCM) to rubbing contacts in air, water and aqueous suspensions of 40 nm TiO2 nanoparticles
We report here a study of the response of QCMs with 304 Stainless Steel (304SS) sensing electrodes to rubbing contact with 304SS ball bearings, employing a continuum model to analyze the response in air, water and an aqueous TiO2 suspensions
The apparatus was comprised of a Ball Bearing (BB) configuration with three 304SS bearings arranged in a close packed triangular array centered on the QCM upper electrode
Summary
Quartz Crystal Microbalance (QCM) studies of tribological contacts (Rodahl and Kasemo, 1996; Laschitsch and Johannsmann, 1999; Brizmer et al, 2007; Johannsmann, 2007; Dawson et al, 2009; Krim, 2012; M’boungui et al, 2014; Borovsky et al, 2017) at both the macro and nanoscale are of increasing importance in a wide range of nano-technological and energy-related applications (Braiman et al, 2003; Kim and Kim, 2009; Zhang and Li, 2010; Krim, 2012; Hsu et al, 2014) Literature reports in this area have, to date, focused primarily on either macroscale or nanoscale contacts, and a remaining challenge in the field of tribology is to establish linkage between studies performed at wide-ranging length and time scales. The models must eventually break down as nanoscale length scales are approached, where systems become less uniform in nature and/or as contact regions become more poorly defined (Figure 1)
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