Abstract
The tribological performances of fullerenol and nanodiamonds (NDs) as additives in water-based lubricants for amorphous carbon (a-C) coatings are investigated to avoid disadvantage factors, such as chemical reactions and deformation of particles. The effects of size and additive amount on tribological properties of nanoparticles are studied by rigid nanoparticles within the dot size range. The results show that owing to its small particle size (1–2 nm), fullerenol cannot prevent direct contact of the friction pair at low concentration conditions. Only when the quantity of fullerenol increased to support the asperity contact loads in sufficient concentration did nano-bearings perform well in anti-friction and anti-wear effects. Unlike fullerenol, nanodiamond particles with a diameter of about 5–10 nm show friction-reducing effect based on the nano-bearing effects at ultra-low concentration (0.01 wt.%), whereas particles at higher concentration block the rolling movement, hence increasing the coefficient of friction (COF) and wear. As a result of the effect of difference in size, fullerenol provides a better overall lubrication, but it is hard to reach a friction coefficient as low as NDs even under the optimal conditions.
Highlights
Received: 20 November 2021With the increasing of the energy resources consumption and industrial pollution, the issues of energy and environmental protection increasingly become the focus of research in many fields including tribology
The results showed that carbon dots (CDs) exhibited remarkable friction and wear reduction effects when the content of CDs was only 0.1 wt.% [18]
The results suggest that the amorphous carbon (a-C) coating preserved the amorphous structure during friction
Summary
With the increasing of the energy resources consumption and industrial pollution, the issues of energy and environmental protection increasingly become the focus of research in many fields including tribology. Many eco-friendly lubricants and environmentally friendly additives have been researched and developed to replace conventional oil and grease lubricants for alleviating energy crisis and solving environmental problems. As the most environmentally friendly, abundant, and renewable resource on earth, water has its own unique advantages in energy saving and environmental protection. Water is a medium with very low viscosity, showing inadequate lubricity and having a corrosive effect on many metals. These defects strictly limit the further application of water-based lubricants in the industry [1]. For the past decades, a growing number of studies have been focused on the promotion of water-based lubrication and corrosion resistance, suggesting that the tribological properties of friction pairs as well as the additive effect can strongly affect the tribological performances of water-based lubrication [2,3,4,5]
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