Synthetic Kilogram Carbon Dots for Superior Friction Reduction and Antiwear Additives

Abstract

Because of the high synthesis cost, strong chemical inertness, complex process, and easy to endanger environment of traditional carbon-based nanolubricant additives, the development of its application in lubrication is limited. Therefore, a new type of lubricant additive with low cost, high yield, high performance, and environmental protection is urgently needed. Herein, a kilogram-scale carbon dots (CDs) lubricant additive was prepared by a simple and green one-step reaction of aldol condensation, which showed excellent lubricating properties in water and sunflower oil. The tribological properties of the CDs lubricant additive at different concentrations, loads, and speeds were systematically studied. The results show that the average friction coefficient of water is significantly reduced by 75% by a CDs lubricant additive. In particular, CDs not only exhibited excellent service life and lubrication stability during friction but also kept the friction coefficient change rate of sunflower seed oil close to 0 within 500 min. According to the tribological evaluation and wear surface analysis, the lubrication mechanism of CDs was attributed to their own morphological characteristics and abundant oxygen-containing functional groups on the surface. In the friction process, the charge adsorption effect, the adsorption protective film, and the hydrogen bonding layer are generated, which play an essential role in obvious antiwear and friction reduction. Therefore, this work provides a reference for the preparation of high-performance and high-yield lubricant additives.

Nitrogen-Doped Carbon Dot as a Lubricant Additive in Polar and Non-polar Oils for Superior Tribological Properties via Condensation Reaction

“…The kinematic viscosity was equal to the ratio of dynamic viscosity and density, so the dynamic viscosity of the two dispersions was η 1 = 6.15 × 10 –2 Pa·s (SFO 1 wt %) and η 2 = 20.21 × 10 –2 Pa·s (PAO10 0.12 wt %). Also, u = 62.8 mm/s, fixed sphere radius ( R ) = 2 mm, applied loads W 1 = 3 N and W 2 = 1 N, k approximately 1, and E ′ = 233 GPa …”

“…The preparation of CD lubricating additives has been reported in our previous work. 24 In short, acetaldehyde (CH 3 CHO) and sodium hydroxide (NaOH) directly undergo aldol condensation reaction to prepare CD lubricating additives.…”

“…In our previous work, CD lubricating additives were prepared and their tribological properties in sunflower oil (SFO) were comprehensively analyzed in terms of concentration, load, and rotational speed . The average friction coefficient of SFO can be reduced by about 50% when CDs were dispersed in SFO at an optimal concentration of 0.05 wt %.…”

Synthesis of Eco-Friendly Carbon Dots as Self-Repairing Additives of Polyalphaolefin by Means of a Green Solvation Effect

“…Among the diverse inorganic nanoadditives, the CDs are lately becoming the most attractive additives owing to their regular morphology, small but uniform particle size, high chemical stability, and strong film-building ability. − As most CDs have been synthesized by the bottom-up method, abundant target groups could be facilely grafted on the surfaces of CDs during the synthesis processes. Based on this merit, the long-term dispersion stability of CDs in polar and partially polar base oils has been perfectly resolved. − However, the research studies on CDs as additives of nonpolar base oil of PAO were far from enough since the synthesis and extraction of CDs modified by totally nonpolar groups were especially difficult . To avoid the abovementioned tedious and even polluting chemical modification process, the amphiphilic CDs were conveniently dispersed into PAO as additives by using Span-80 as dispersant .…”

Artificial Intelligence-Based Rapid Design of Grease with Chemically Functionalized Graphene and Carbon Nanotubes as Lubrication Additives

“…Grease can stick better than lubricating oils through their excellent adhesion on frictional interfaces where gravity and centrifugal force cause serious loss. , Recently, the continuous development of productivity has required a higher grease performance. It has been confirmed that the addition of lubricant additives may enhance their tribological properties. − The dispersibility of nanoadditives is the most critical factor to influence their performance in lubricants, and chemical functionalization is the most common method to improve its dispersibility. − Ismail et al performed a reaction at 80 °C for 24 h and successfully grafted the straight alkyl chain onto graphene oxide to enhance its hydrophobicity and tribological properties in lubricants. In addition, the functionalized additive has excellent lipophilic properties and improves the solubility of the additive in the oil .…”