Tribological property of MoS2-Cr3O4 nanocomposite films prepared by PVD and liquid phase synthesis

Superhydrophobic MoS2 Nanosheet–Cu2O Nanoparticle Antiwear Coatings

“…As shown in Figure , we integrated the sputtering technology and liquid-phase synthesis; the MoS 2 nanosheets were formed on the carbon steel by RF-sputtered technology and presented a typical porous lamellar-like cross-sectional morphology. During deposition, the dangling bonds with high activity are formed by the missing S atoms. ,, Then, the sputtered MoS 2 coating was further modified by liquid-phase synthesis. During the reaction, the color of the solution turns from light blue to dark blue and finally to yellow.…”

“…When the composite coatings were exposed to air for almost 1 year (Figure c), the friction coefficients of the MoS 2 and MoS 2 –Cu 2 O composite coatings were 0.02–0.05 and 0.015–0.025 and their wear lives were ∼2 × 10 5 and ∼8 × 10 5 r, respectively. Molybdenum oxide with high hardness leads to an increase in the load-bearing capacity of the coating, and then the life is slightly increased . However, molybdenum oxide with poor property caused a large fluctuation in the friction coefficient.…”

“…This is attributed to the fact that MoS 2 has affinity for the nucleated vapor, and during friction, a lot of nucleated vapor in the groove can accelerate oxidation and then shorten the wear life of MoS 2. Meanwhile, the Cu 2 O layer can be destroyed and the MoS 2 in the Cu 2 O layer may react with a large amount of nucleated vapor, thereby decreasing the antiwear life of the MoS 2 –Cu 2 O coating.…”

“…The humidity resistance and lubrication mechanisms for the MoS 2 and MoS 2 nanosheet–Cu 2 O nanoparticle coatings are displayed in Figure . Due to the loose texture (schematic structure in Figure b) and affinity for vapor and water, the sputtered MoS 2 coatings easily react with moisture and oxygen in the air to reduce their surface energy. ,, Therefore, when the sputtered MoS 2 coating was exposed to a humid environment, the vapor and water may accelerate oxidation. On the contrary, after treatment, the Cu 2 O clusters and layers (Figures f and c) were constructed into coatings that can protect the MoS 2 against water and parts of vapor.…”

“…The surface of the MoS 2 coating is smooth, while a few nanoparticles of different sizes were detected on the wear scars for MoS 2 nanosheet–Cu 2 O nanoparticle coatings. Hence, although the film is very rough, Cu 2 O nanospheres can disperse and roll at the friction interface and play a role of “nanobearing” during friction, and then reduce the friction coefficient . Meanwhile, when the Cu 2 O branches were formed in MoS 2 -2% (Figure d), Cu 2 O branch showed a negative effect on “nanobearing effects” because of its shape.…”