Abstract
In this study, the tribological behaviours of graphene nanoparticles as lubricant additive in vegetable oil were investigated as a function of nanoparticle concentration. Graphene nanoparticles were added at 25 ppm, 50 ppm and 100 ppm as additive into vegetable oil as lubricant through hydrodynamic and acoustic cavitation as homogenising mechanism. The tribological properties of each homogenised solution were tested using a four-ball machine according to ASTM D4172. Wear scar diameter and friction coefficient were the determining parameters in this study. The results showed that 50 ppm is the optimum concentration that recorded the lowest wear scar diameter and friction coefficient as compared to control sample.
Highlights
Over the past decades, numerous studies have been carried out on the effect of different nanoparticles in lubricant
3.1 Suspension Stability Figure 4(a) shows that graphene powders floated temporary in vegetable oil (VO) after mixing through acoustic and hydrodynamic cavitation
The results showed that 25 ppm and 50 ppm graphene can reduce friction coefficient and wear scar diameter as compared to pure VO
Summary
Numerous studies have been carried out on the effect of different nanoparticles in lubricant. The five major groups of nanoparticles added to lubricant are metal,[1,2] metal oxide[3,4] metal composite,[5,6] boron-based[7,8] and carbon-based nanoparticles.[9,10,11,12,13] In general, the majority of the studies accepted that nanoparticle plays a role in improving tribological properties by forming a tribofilm that is deposited between the contact surfaces.[14,15] Among all lubricant additives, graphene was chosen as lubricant additive in this study because of its excellent chemical and physical properties such as ultrathin structure, high thermal stability, ultra-smooth surface and ultimate mechanical strength.[16]. Usage of vegetable oil is recommended because it is renewable, biodegradable and nontoxic in nature. It possesses the properties required for lubrication, including excellent lubricity, high flash point and viscosity index.[17] VO was selected as lubricant in this study
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