Film thickness decreased with escalating the concentration of CuO. Thus, the dark regions represent the deposition of CuO nanoparticles on the contact surfaces. This deposition can compensate for the mass loss around the speak to surfaces by the “mending effect”. This mechanism of CuO nanoparticles was reported in earlier study, exactly where CuO nanoparticles had been C2 Ceramide Description utilized as an additive in synthesis oil [25]. Inside the tests lubricated with ZnO, the colour in the center of interferometric pictures was identified to be very related to that with the test with pure IL. It suggests that ZnO combined with the IL did not considerably influence the tribofilms’ properties formed by the IL. Nonetheless, as the concentration of zinc oxide nanoparticles increased, colored locations appeared around the put on surface in the ball that were distinct in the colour of tribofilms formed by the IL. The improve in the tribofilms’ thickness inside the test of IL 0.5 wt ZnO was shown by the darker colors within the interferometric pictures.Figure 7. Cont.Supplies 2021, 14,9 ofFigure 7. Series of interference photos for different concentrations of nanoparticles after increasing rubbing time: (a) IL, (b) IL 0.2 wt CuO, (c) IL 0.five wt CuO, (d) IL 0.two wt ZnO, and (e) IL 0.five wt ZnO.three.three. Surface Evaluation Chemical components on disc surfaces after the wear test were analyzed by SEM/EDX at 3 areas, which includes unwear surfaces, scratches, and defects. Prior to any test of surface analysis, the specimens were cleaned with ethanol in an VBIT-4 Data Sheet ultrasonic bath. Figure 8 shows an SEM image and EDX analysis results in the unwear surface. Even though the unwear surface was not abraded by the speak to in between the ball and disc, the look with the fluorine component from the [N1888] [NTf2] showed that chemical reactions may possibly occur among the [NTf2] anion and the metal surfaces upon heating. The chemical element fluorine may possibly influence the corrosion method around the metal surfaces depending on its concentration [36].Materials 2021, 14,10 ofFigure 8. (a) SEM image and (b) EDX evaluation from the unwear surface on the disc.SEM/EDX surface evaluation in the rubbed surfaces on discs in the tests lubricated with the IL and various concentrations of CuO and ZnO nano-oxides are shown in Figure 9. The chemical composition of worm surfaces on the disc was analyzed at two distinct points, defects, and scratches. The survey spectra along with the weight percentages of chemical compositions on the defects are represented by the figures on the appropriate side on the corresponding SEM images. The distribution of chemical components around the scratch line for all tested lubricants is summarized in Table four.Figure 9. Cont.Components 2021, 14,11 ofFigure 9. SEM micrographs of worn surface (left) and EDX analysis of defects (correct) for the tests lubricated with the IL and various concentrations of nanoparticles: (a) IL, (b) IL 0.2 wt CuO, (c) IL 0.five wt CuO, (d) IL 0.2 wt ZnO, and (e) IL 0.5 wt ZnO.Each of the oxide nanoparticles exhibited different lubrication mechanisms once they were added to the [N1888] [NTf2]. The presence of copper in the EDX final results, shown in Figure 9b,c and Table 4, indicates that the CuO nano-oxide reacted with all the IL and deposited around the surfaces in get in touch with. An example of a chemical reaction of CuO having a water-free [NTf2] anion-based IL was represented in the work [37]. The authors pointed out that CuO could successfully be dissolved within the water-free IL upon heating to 175 C for 24 h. Since the wear test condit.
