Preparation characterization and tribological behavior of lube oil with nanoparticles additives / Waleed Alghani

Waleed , Alghani (2020) Preparation characterization and tribological behavior of lube oil with nanoparticles additives / Waleed Alghani. PhD thesis, Universiti Malaya.

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Abstract

There are many companies worldwide that would like to improve and upgrade the lube oil and enhance its performance. There is a big concern for the enhancement of lube oil by using nanotechnology and more precisely with using nanomaterial additives. Much work has made to explore and develop new sorts of lubricating oil nano-additives to diminish wear and friction in tribological configurations and to enhance surface morphology. It has noted that the use of dual nano-additives should examine the lubricating capacity and durability of lubricant. (TiO2 Anatase + Graphene) and (ZnO + Graphene) nanoparticles have selected to formulate nano-additives that can add to API Group II base oil (PBO-GII). Nanoparticles have characterized by employing a transmission electron microscope (TEM) to examine the morphology of these three nanostructures. Sonication treatment and dispersion stability investigation carried out for the mixtures. A range of concentrations (0.0 wt%, 0.2 wt%, 0.4 wt%, and 0.6 wt% mg/ml) of two groups of dual nanoparticles which include (TiO2 (A) + Graphene) and (ZnO + Graphene) were blended with PBO-GII individually to recognize the lowest friction and wear losses that took place throughout the sliding motion. Oil formulations tested by using a four-ball machine to find out the coefficient of friction (COF), wear scar diameter (WSD), and specific wear rate (SWR) for each sample. Additionally, balls scars have characterized by using field emission-scanning electron microscopy (FE-SEM), energy-dispersive x-ray spectroscopy (EDX/EDS), elements mapping, Raman spectroscopy, and surface roughness measurements for distinguishing the morphology structure, presence of tribofilm, surface finish, friction, and wear effect on all employed balls. It is also noteworthy a 3-dimensional optical (contact-free) surface texture analysis apparatus used to study the scarred region on each ball surface. For the (TiO2 (A) + Graphene) group/samples, the average reduction in COF, WSD, and SWR for an hour was 38.83%, 36.78%, and 15.78% respectively, for (0.4 wt% TiO2 (A) + 0.2 wt% Graphene) nanolubricant compared to PBO-GΙΙ. The formation of the tribofilm and the deposition of nanoparticles on contacted areas protected the surfaces of balls from acute friction and adhesion wear. For the (ZnO + Graphene) group/samples, the average reduction in COF, WSD, and SWR was 43.81%, 36.78%, and 39.47% respectively for (0.4 wt% ZnO + 0.2 wt% Graphene) nanolubricant compared to PBO-GΙΙ. The superb lubrication performance was due to the tribofilm of the nanoparticle mixture deposition on the mating metal surfaces during sliding motion. The driving force for nano-sized particles (TiO2 (A) + Graphene) and (ZnO + Graphene) in pure base oil entering the sliding surfaces throughout three mechanisms micro rolling bearing technique, depositing film technique, and mending technique. These phenomena confirmed the significance of uniform nanoparticles dispersion for improved wear protection. The tribological analyses and the surface characterization tools TEM, FE-SEM, EDX/EDS, elements mapping, Raman spectra, and surface roughness measurements have clearly explained the nanoparticles' role and lubrication mechanisms. This research proved the essential role of blending two mixtures of nanoparticles to enhance the tribological performance and surface morphology via the surface activity of the additives.

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