Study of graphene nanolubricant using thermogravimetric analysis

Thermal degradation of graphene based mineral oil lubricants was studied using thermogravimetric analysis (TGA). As-synthesized graphene sheets of 8, 12, and 60 nm thick and engine oil formulations 20W50 SN/CF and 20W50 SJ/CF were used for synthesizing various test samples. UV-Vis spectrophotometry, zeta potential, field emission scanning electron microscopy, and energy-dispersive x-ray spectroscopy were used to characterize the graphene sheets and the nanolubricants. TGA revealed that the onset temperature of oxidation for the SN/CF oil could be delayed by 13–17 °C in the presence of graphene. Moreover the rate of oxidation when the weight loss of oil in the presence of graphene reaches 40–20% could be delayed by more than 30 °C. Resistance to oil degradation depends strongly on the graphene nanoparticle size and concentration. TGA kinetics studies show that the base oils have higher activation energy (Ea) and the addition of graphene significantly reducesEa.