Hydrophilicity characterization of Al2O3-coated MoS2 particles by using thin layer wicking and sessile drop method

When hydrophobic particles are employed to prepare self-lubricating electroless composite coatings , they usually require surface modification to improve their wettability . The study focuses on the resultant change in wettability of the MoS 2 particles with an inorganic coating . Al 2 O 3 -coated MoS 2 particles were prepared by using a heterogeneous nucleation process. Then, particle surface morphology and structure were examined by using SEM, EDS and XRD . Contact angle measurements were conducted by using a thin layer wicking technique and a sessile drop method in order to determine the surface free energy components of the bare and the coated MoS 2 particles. Our results showed the MoS 2 particles were successfully coated with an Al 2 O 3 layer, which is an amorphous structure. The decreased water contact angle indicates an enhanced hydrophilicity for the coated particles. This decrease depends more strongly on a significant decrease of a new parameter ratio, γ + /γ − , than on a slight increase in total surface free energy. The surface energy component of the bare MoS 2 is very consistent with that of Talc, and that of the Al 2 O 3 -coated one is very similar to that of alumina , apart from the base component.