Effects of SiO2 Contaminant on Thermo-Mechanical/Chemical Properties and Lubricity of PFPE Lubricants

Abstract

Using the molecular dynamics (MD) simulations with ReaxFF potential, two different types of PFPE lubricants (Ztetraol and ZTMD) are prepared on a-C film, and SiO2 particles are adsorbed onto the lubricants at room temperature. From the simulation results, it is observed that the adsorbed SiO2 particles increase the stiffness of PFPE lubricants leading to less airshear displacement. Since Ztetraol has higher mobility with lower viscosity than ZTMD, the adsorbed SiO2 particles penetrate deeper into the Ztetraol lubricants. Accordingly, the effect of SiO2 on the airshear displacement is more obvious to Ztetraol than ZTMD. In addition, the adsorbed SiO2 particles increase the friction force and the amount of lubricant pick-up during the sliding contact with a nanosized a-C tip.

Mechano-Chemical Properties and Tribological Performance of Thin Perfluoropolyether (PFPE) Lubricant Film under Environmental Contaminants

“…Ztetraol and Ztetraol multidentate (ZTMD) were prepared using Materials Studio and Avogadro [39]. Based on previous studies [21,40,41], the chemical structures for Ztetraol and ZTMD were chosen, as shown in Figure 1. Both PFPE lubricants were optimized by using the NWChem computational chemistry package [42] with the B3LYP functional approximation [43], Mulliken population for electronic charge distribution [44], and the STO-3G minimal basis set due to its computational cost [45,46].…”

“…Previous experimental studies showed that hydroxyl endgroups (-OH) in the Fomblin Z-dol lubricant interact with water molecules, which degrades the lubricant properties, producing unstable HDI behaviors at elevated temperatures and humidity conditions [14][15][16][17][18][19][20]. Also, from molecular dynamics (MD), it can be observed that the adsorption of silicon dioxide (SiO 2 ) nanoparticles into PFPE lubricant can increase the HDI friction force and the lubricant pick-up [21].…”

A review of advances in tribology in 2020–2021

“…Based on the material characterization results of contaminated head surfaces in actual hard disk drives (HDD), Rahman et al [978] used reactive MD simulations with ReaxFF potential to study the effect of SiO 2 particles as contaminants on the friction behavior and lubrication performance of PFPE lubricants (Fig. 83(a)).…”

“…Fig 83. Reactive molecular dynamics simulations of tribochemistry at sliding interface[978,981,984,985]. Reproduced with permission from Ref [978],.…”

“…Reactive molecular dynamics simulations of tribochemistry at sliding interface[978,981,984,985]. Reproduced with permission from Ref [978],. © The author(s), 2021; Reproduced with permission from Ref [981],.…”