The unique structure
and physical properties of graphene and anatase
TiO2 make them suitable for use as additives for engine
lubricants. This study describes the use of dielectric barrier discharge
plasma-assisted ball milling to synthesize a multilayer graphene-reinforced
TiO2 composite nanolubricant additive (MGTC). A variety
of physical and chemical tests were performed to characterize the
resulting experimental materials, including X-ray diffraction (XRD),
Fourier transform infrared (FT-IR), Raman, X-ray photoelectron spectroscopy
(XPS), and scanning electron microscopy (SEM). Four-ball friction
and wear testing machines were used to study the tribological properties
and extreme pressure anti-wear properties of a base oil containing
0.1, 0.5, 1.0, and 1.5 wt % of the modified TiO2. Raman
spectroscopy, XPS, SEM, and energy-dispersive spectrometry (EDS) analyses
were used to examine and analyze the microstructure of the friction
pairs. As a result of the plasma-assisted ball milling process, expanded
graphite was successfully separated into multilayer graphene nanosheets,
and spherical TiO2 was successfully bonded to the nanosheets
of the multilayer graphene. The 1.0 wt % composite oil was found to
provide good friction reduction and wear resistance. It had a film
thickness of 27.5 nm, which was 167% thicker than base oil. Due to
its excellent dispersion stability, the MGTC nanocomposite exhibited
excellent lubrication performance, which was attributed to the formation
of carbon protective films, titanium dioxide deposition films, transfer
films, and the occurrence of nano ball effects on the surface of friction
pairs.
Poor lubrication performance of low-sulfur fuel leads to increased wear of diesel engine components. In order to improve the lubrication properties of low-sulfur fuel, we successfully prepared graphene lubricant additives by dielectric barrier discharge plasma-assisted ball milling. The tribological properties of graphene lubricant additives in two types of 0# diesel oils with different sulfur content were evaluated by high-frequency reciprocating rig (HFRR). The results indicated that the expanded graphite was exfoliated and refined into graphene sheets with nine layers by the synergistic effect of the heat explosive effect of the discharge plasma, the impact of mechanical milling function, and the cavitation effect of 0# diesel oil. The organic functional groups of 0# diesel oil were successfully grafted on the surface of graphene sheets. The addition of 0.03 wt % graphene resulted in 20% reduction in the friction coefficient (COF) and 28% reduction in wear scar diameter (WSD) compared to pure 0# diesel oil with a sulfur content of 310 mg/kg. The addition of 0.03 wt % graphene resulted in 24% reduction in the friction coefficient (COF) and 30% reduction in wear scar diameter (WSD) compared to pure 0# diesel oil with a sulfur content of 1.1 mg/kg. The formation of graphene tribofilm on rubbing surfaces improved the lubrication properties of low-sulfur fuel.
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