Synthesis and structural characterization of MoS2 nanospheres and nanosheets using solvothermal method

This paper reports the solvothermal synthesis of MoS2 nanospheres and nanosheets. The nanospheres were obtained using ammonium polysulfide as a sulfur source and have a mean diameter of about 100 nm. The nanosheets were assembled from a few lamellar layers and were obtained using thiourea as a sulfur source. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used in order to characterize the prepared powders. Conglomerate size and stability of the synthesized samples in hexane were studied with zeta potential. The four-ball method was used to assess the lubricating effect when these materials were used as additives in engine oil dispersions. The topography of the wear scar was analyzed using SEM, EDX, and 3D surface profilometry. The tribological properties of base engine oil containing the nanomaterials penetrated more easily into the interface space, and it formed a tribo-film at contact interface. The tribological performance showed that the synthesized nanosheets had superior anti-wear and friction-reducing properties as a lubrication additive compared with nanospheres, and the wear scar of balls lubricated with nanospheres revealed larger width compared to nanosheets. From the results, it is observed that nanosheets dispensed in oil have better tribological performance compared to nanospheres oil in terms of capability to reduce wear.