This work presents a method for one-pot synthesis of N-doped nanometer-size carbon dots, which can be assembled with thermosensitive poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL, PCEC) hydrogel to achieve slow-release lubricity. The typical property of this green production was studied by fourier transform infrared (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). The photoluminescence of composite PCEC/CDs hydrogel and its released solutions were characterized by ultraviolet spectrum, and the rheological properties were tested by rotary rheometer. Tribological performance of the released solution from composite PCEC/CDs hydrogel was obtained to compare with PBS and pure CDs solution. The experimental results reveal that the CDs contain the chemical groups of N-H, C-OH/C-O-C and -COOH, etc. In addition, the diameter of the CDs is in the range of 6~8 nm. The phase transition behavior of PCEC/CDs hydrogel can be still kept and its viscoelasticity hydrogel is improved by approximatively 7%. Furthermore, friction coefficient of the released solution from composite PCEC/CDs hydrogel decreases by about 70% than that of PBS. Besides, the wear condition can be improved by a lubricating transfer film formed by released CDs. This novel strategy for slow-release application is valuable for drug delivery and bio-tribology.

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The hollow MoS2 nano-particles were synthesized via hydrothermal method and were used as additives to fabricate the carbon fiber fabric/phenolic composites (CF/PF) containing WS2 micro-particles by hot-press approach. Subsequently, the tribological properties of CF/PF composites were comprehensively investigated. We found that the addition of WS2 alone can achieve significant decrease in the friction coefficient of CF/PF composites, but it decreases the wear resistance due to the peeling off of WS2 micro-particles form matrix caused by stress concentration. Nevertheless, the addition of both WS2 micro-particles and MoS2 nano-particles can achieve significant improvement in the lubricating property and wear resistance of CF/PF composites, indicating that there existed a synergetic effect among carbon fibers, WS2 micro-particles, and MoS2 nano-particles to enhance the tribological properties of CF/PF composites. The doping of additives with large size range can promote the formation of transfer film on the surface of counterpart as well as enhance the mechanical properties of matrix. Furthermore, the multi-scale additives reduced the stress concentration of matrix around the CF and hence inhibited the breakage, pull-out of CF, resulting in the improvement of the tribological properties due to the high load-carrying capacity of CF.

Babbitt alloy is a widely used bearing material. In order to improve its thermal and anti-fatigue performance, the combined effect of additive La and heat treatment of tin-Babbitt were studied. The microhardness, wettability, and tribological performances of the Babbitt were first considered. The Babbitt alloy modified with La element (0.1 wt%) was prepared and then heat treatment was carried out (marked by the modified Babbitt). The friction and wear performances of the bare Babbitt, heated Babbitt, and modified Babbitt were conducted by a ball-on-disc tester under oil lubricated condition. The results showed that the microstructure of the modified Babbitt alloy was homogeneous. The cubic phase of SnSb intermetallic was refined and the SnSb cubes were also passivated. The microhardness of the modified Babbitt increased from 24.67 Hv to 37.84 Hv and wettability was improved with the addition La and heat treatment. Therefore, the anti-wear performance of the Babbitt was improved. The modified Babbitt alloy is observed to resist the instant scratching from the journal.

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