Formation mechanism of Al₂O₃/MoS₂ nanocomposite coating by plasma electrolytic oxidation (PEO)

In this study, an Al₂O₃/MoS₂ nanocomposite coating was created on an aluminum 1050 substrate using the plasma electrolytic oxidation method. The zeta potential measurements showed that small MoS₂ particles have negative potential and move toward the anode electrode. The nanoparticles of MoS₂ were found to have a zeta potential of −25 mV, which prevents suspension in the solution. Thus, to produce an Al₂O₃/MoS₂ nanocomposite, one has to use the microparticles of MoS₂. The X-ray diffraction analyses showed that the produced coatings contained α-Al₂O₃, γ-Al₂O₃, and MoS₂, and that the size of MoS2 particles can be reduced to 30 nm. It was observed that prolonged suspension in the electrolyte results in an enhanced formation of an Al₂O₃/MoS₂ nanocomposite. Using the results, it was hypothesized that the mechanism of the formation of the Al2O3/MoS2 nanocomposite coating on the aluminum 1050 substrate is based on electrical energy discharge.