Evolution of ZDDP-derived reaction layer morphology with rubbing time

Tribological Anti-Wear and Extreme-Pressure Performance of Multifunctional Metal and Nonmetal Doped C-based Nanodots

Carbon nanodots (CDs) are extensively explored due to their little toxicity, excellent water solubility, and biocompatibility. Particularly, fluorescent CDs have received ever-increasing attention. Nevertheless, up to now, only a few findings have been dedicated to measuring the tribological properties of doped CDs, especially Ga doped CDs (Ga@CDs and nitrogen doped CDs (N@CDs)), and to compare their tribological properties with CDs. Here, we describe a strategy for the low-cost one-pot synthesis of CDs for tribological study. The presented research for the first time describes tribological properties and indicates a possible application of the multifunctional CDs (N@CDs, Ga@CDs, and CDs) as highly specific materials for various tests of engine oils and hydraulic oils. Further, it is stated that the doping of the CDs with various elements can tailor demanding tribological performances like anti-wear and extreme-pressure performances.

Lignin from Hardwood and Softwood Biomass as a Lubricating Additive to Ethylene Glycol

Ethylene glycol (EG)-based lubricant was prepared with dissolved organosolv lignin from birch wood (BL) and softwood (SL) biomass. The effects of different lignin types on the rheological, thermal, and tribological properties of the lignin/EG lubricants were comprehensively investigated by various characterization techniques. Dissolving organosolv lignin in EG results in outstanding lubricating properties. Specifically, the wear volume of the disc by EG-44BL is only 8.9% of that lubricated by pure EG. The enhanced anti-wear property of the EG/lignin system could be attributed to the formation of a robust lubrication film and the strong adhesion of the lubricant on the contacting metal surface due to the presence of a dense hydrogen bonding (H-bonding) network. The lubricating performance of EG-BL outperforms EG-SL, which could be attributed to the denser H-bonding sites in BL and its broader molecular weight distribution. The disc wear loss of EG-44BL is only 45.7% of that lubricated by EG-44SL. Overall, H-bonding is the major contributor to the different tribological properties of BL and SL in EG-based lubricants.

Grafting heteroelement-rich groups on graphene oxide: Tuning polarity and molecular interaction with bio-ionic liquid for enhanced lubrication

Two different heteroelement-rich molecules have been successfully grafted on graphene oxide (GO) sheets which were then used as lubricant additives in bio-ionic liquid. The grafting was processed with reactions between GO sheets and synthesized heteroelement-rich molecules (Imidazol-1-yl phosphonic dichloride and 1H-1,2,4-triazol-1-yl phosphonic dichloride, respectively). The modified GO (m-GO) was added into [Choline][Proline] ([CH][P]) bio-ionic liquid, and has been demonstrated effective additive in promoting lubrication. Different characterization techniques have been utilized to study the reaction between GO and the two modifiers. The effect of molecular structure of the modifiers on the rheological and tribological properties of m-GO/[CH][P] lubricants was systematically investigated. Both theoretical calculation and experimental results demonstrated that the introduced heteroelement-rich groups are beneficial to increase the robustness of lubrication film by intensified hydrogen bonding and enhance the lubricant/friction surface adhesion by increased polarity of the m-GO. As a result, the interfacial lubrication could be significantly improved by these newly developed m-GO/[CH][P] lubricants.