State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China.
Phys Chem Chem Phys. 2018 Sep 12;20(35):22445-22454. doi: 10.1039/c8cp00859k.
The friction behaviors of highly sp3-hybridized carbon films, including ultra-nanocrystalline diamond and diamond-like carbon materials, strongly depend on the atmosphere. However, the roles of the corresponding molecules in the interfacial bonding characteristics remain a subject of debate. By means of density functional theory calculations, this study aims to fill a knowledge gap about the correlation between the evolving contact quality induced by the adsorption of molecules, and the friction behavior of highly sp3-bonded carbons. The results prove that gas-solid adsorption is responsible for the diversity in friction coefficients of ultra-nanocrystalline diamond and diamond-like carbons in different atmospheres. This study emphasizes the role of terminal states in friction coefficients, and demonstrates that electron lubrication is another available strategy for hydrogenated diamond-like carbons to achieve ultra-low friction. This conclusion is validated by the ultra-low friction coefficient (∼0.009) of hydrogenated diamond-like carbons in a dry nitrogen atmosphere. These findings provide atomic scale descriptions of the surface passivation mechanisms for ultra-nanocrystalline diamond and diamond-like carbons, which contribute to our understanding of their macro-scale friction behaviors.
高度 sp3 杂化碳膜（包括超纳米晶金刚石和类金刚石碳材料）的摩擦行为强烈依赖于气氛。然而，相应分子在界面键合特性中的作用仍存在争议。本研究通过密度泛函理论计算，旨在填补关于分子吸附引起的接触质量演变与高度 sp3 键合碳的摩擦行为之间相关性的知识空白。结果证明，气固吸附是导致超纳米晶金刚石和类金刚石碳在不同气氛中摩擦系数多样性的原因。本研究强调了末端状态在摩擦系数中的作用，并表明电子润滑是氢化类金刚石碳实现超低摩擦的另一种可行策略。这一结论得到了在干燥氮气气氛中氢化类金刚石碳超低摩擦系数（约 0.009）的验证。这些发现为超纳米晶金刚石和类金刚石碳的表面钝化机制提供了原子尺度的描述，有助于我们理解它们的宏观摩擦行为。
