Leilei Li

The improved tribological performance of the lubricating oils addresses durability challenges in mechanical systems. Herein, the physicochemical and tribological properties of 1-hexadecanol (16O) and 1-hexadecanethiol (16S) as oil additives for lubricating steel tribosystems were studied under various concentrations. The tribological behavior of lubricated steel surfaces was evaluated using an SRV-IV tribometer. In addition, a simulation was conducted that highlights the mechanism of additive adsorption on metal surfaces based on density functional theory (DFT). The tribological findings demonstrated that the 16O and 16S additives reduced the friction coefficient by 50–52% and wear volume by 79.9–82.6% compared with PAO10 oil. Notably, the 16O additive offers more consistent and concentration-independent friction reduction, while the 16S additive provides higher anti-wear protection at 0.5 wt% concentration due to the formation of a robust Fe-S tribofilm, which results from its stable physical adsorption mechanism based on simulation results. Briefly, this comparative analysis highlights the importance of optimizing additive concentration based on the specific balance of friction and wear requirements in mechanical applications.

Lubricant additives play a crucial role in improving the tribological performance of lubricating oils to reduce frictional energy losses and improve the durability and reliability of mechanical systems. In this study, soft metallic-based core–shell Ag@Cu microparticles were synthesized via an in-situ galvanic displacement method and incorporated into EHC-50 base oil with various concentrations. The tribological performance evaluations indicated that 0.3 wt% Ag@Cu significantly enhanced friction-reducing and anti-wear properties, achieving a stable friction coefficient of 0.12, a 45% reduction, and a wear volume reduction of 75% compared to the pristine oil. Additionally, the surface characterization techniques (SEM/EDS, XPS, XRD, and TOF-SIMS) were employed to explore the wear patterns and related lubrication mechanisms. The results indicated that the synergistic interaction between the micro-bearing effect, physical mending, and tribochemical reactions facilitated the formation of a robust tribofilm composed of metallic Ag, ternary CuFe₃O₂, and sulfides, which achieved higher lubrication performance. Ultimately, this research provides novel metallic micro-additives, offering a facile approach to formulating wear-resistant lubricants with significant potential for saving energy for mechanical tribosystems in industrial applications.

ZrB₂-SiC-Zr₂Al₄C₅ multi-phase ceramics with uniform structure and high density were successfully prepared through the introduction of in situ synthesized Zr₂Al₄C₅ into ZrB₂-SiC ceramic via SPS at 1800 °C. A systematic analysis and discussion of the experimental results and proposed mechanisms were carried out to demonstrate the composition-dependent sintering properties, mechanical properties and oxidation behavior. The results showed that the in situ synthesized Zr₂Al₄C₅ could be evenly distributed in the ZrB₂-SiC ceramic matrix and inhibited the growth of ZrB₂ grains, which played a positive role in the sintering densification of the composite ceramics. With increasing Zr₂Al₄C₅ content, the Vickers hardness and Young’s modulus of composite ceramics gradually decreased. The fracture toughness showed a trend that first increased and then decreased, and was increased by about 30% compared with ZrB₂-SiC ceramics. The major phases resulting from the oxidation of samples were ZrO₂, ZrSiO₄, aluminosilicate and SiO₂ glass. With increasing Zr₂Al₄C₅ content, the oxidative weight showed a trend that first increased then decreased; the composite ceramic with 30 vol.% Zr₂Al₄C₅ showed the smallest oxidative weight gain. We believe that the presence of Zr₂Al₄C₅ results in the formation of Al₂O₃ during the oxidation process, subsequently resulting in a lowering of the viscosity of the glassy silica scale, which in turn intensifies the oxidation of the composite ceramics. This would also increase oxygen permeation through the scale, adversely affecting the oxidation resistance of the composites with high Zr₂Al₄C₅ content.