Role of OH Termination in Mitigating Friction of Diamond-like Carbon under High Load: A Joint Simulation and Experimental Study

Abstract

Diamond-like carbon (DLC) has recently attracted much attention as a promising solid-state lubricant because it exhibits low friction, low abrasion, and high wear resistance. Although we previously reported the reason why H-terminated DLC exhibits low friction based on a tight-binding quantum chemical molecular dynamics (TB-QCMD) simulation, experimentally, the low-friction state of H-terminated DLC is not stable, limiting its application. In the present work, our TB-QCMD simulations suggest that H/OHterminated DLC could give low friction even under high loads, whereas H-terminated DLC could not. By using gas-phase friction experiments, we confirm that OH termination can indeed provide much more stable lubricity than H termination, validating the predictions from simulations. We conclude that H/OH-terminated DLC is a new low-friction material with high load capacity and high stable lubricity that may be suitable for practical use in industrial applications.

An All-Atom Force Field for Dry and Water-Lubricated Carbon Tribological Interfaces

“…81 Finally, the ranking and magnitude of the shear stresses in Figure 14 indicates that at local contact pressures of about 1 GPa or lower, a 100% H surface termination is more suitable than a mixed OH/H termination to achieve superlubricity in dry a-C contacts. This agrees with the results of tightbinding MD simulations reported in ref 19…”

“…Several studies have investigated in detail the mechanisms underlying the BL properties of carbon coatings. The list of studies includes experimental works combining tribometry and surface analyses, , purely computational studies with reactive interatomic potentials , or quantum-mechanical (QM) methods, , and combinations of experiments and simulations. ,– A result that emerges from all these studies is that the reduction of friction and wear relies on a stable chemical passivation of the a-C surfaces and depends on their topography and a-C’s mechanical properties. Surface passivation prevents the formation of strong chemical bonds across the sliding interface, thus lowering the resistance to sliding.…”

Effect of the Graphitization Mechanism on the Friction and Wear Behavior of DLC Films Based on Molecular Dynamics Simulations

“…Since the industrial revolution, a large part of the energy generated by increasing industrial activities has been consumed by friction within the mechanical system . Effectively reducing the energy consumed by friction has profound significance for sustainable development. , Diamond-like carbon (DLC) films have excellent physical and chemical properties, low-friction coefficients, and high wear resistance, which have already been widely used in industry fields. − However, the related friction and wear mechanisms are still controversial at present, especially the effect of the graphitization mechanism on the low-friction behavior of the DLC film, and there are diametrically opposed views. Therefore, it is very meaningful to further study how the graphitization mechanism controls the influence of friction and the wear behavior of the DLC film.…”

Probing Friction Properties of Hydrogen-Free DLC Films in a Nitrogen Environment Based on ReaxFF Molecular Dynamics

“…Due to its excellent optical, tribological, mechanical, and biological qualities, it has drawn much scientific attention. − DLC films are widely used on the surfaces of various engineering parts because of their high hardness and wear resistance, and because they have an extremely low coefficient of friction. − However, due to the test conditions and environmental conditions, the DLC film will have chemical or physical reactions with different components in the atmosphere. Therefore, the frictional properties of DLC films are highly dependent on the experimental environment. , Undoubtedly, the predominant gas in the atmosphere is nitrogen, with a content of up to 78%, about 3.7 times that of oxygen. As a result, it is important to understand the friction mechanism of DLC in nitrogen environment.…”

“…Therefore, the frictional properties of DLC films are highly dependent on the experimental environment. 9,10 Undoubtedly, the predominant gas in the atmosphere is nitrogen, with a content of up to 78%, about 3.7 times that of oxygen. As a result, it is important to understand the friction mechanism of DLC in nitrogen environment.…”