Synthesis of nanometric molybdenum disulphide particles and evaluation of friction and wear properties

Nanometric molybdenum disulphide particles of about 30 nm diameter have been prepared by the hydrodesulphurisation of molybdenum trisulphide obtained from acidifying a mixed solution of Na2MoO4 and Na2S at ambient temperature using a quick homogeneous precipitation method (QHPM). Using X-ray diffraction and transmission electron microscopy (TEM), the size and crystallisation of the nano-MoS2 obtained by hydrodesulphurisation at different temperatures have been investigated. In addition, the tribological performance of nano-MoS2 has been investigated by means of a block-on-ring tribometer, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results show that base oils with nanometric MoS2 as an additive provide higher wear resistance than other oils containing commercially available common MoS2. However, the friction reduction is not obviously improved. SEM characterisation reveals a worn, smooth surface when using the nano-MoS2 additive, and XPS analysis indicates a greater amount of molybdenum oxide and iron sulphide in the antiwear thin film formed on the rubbed surface.