**4. Superlubricity mechanisms**

weak peak at 2*θ* = 22.4°, according with other studies [46], can be attributed to fullerene-like or onion-like nanoparticles (considering HRTEM and Raman results). And after friction testing, the peak at 2*θ* = 22.4° become prominent, accompanying with a new band at 2*θ* = 15° which arise from fullerene-like or onion-like nanoparticles, which leads low friction and small wear

central wear tracks (WK) have a higher odd (pentagonal and heptagonal) carbon ring fraction than that of the originally

**Figure 7.** Hardness and elastic recovery of the as-prepared films with different pulse duty cycles. Inset show the growth rate of the as-prepared films with different pulse duty cycles. (Reproduced from Ref. [42] with permission from the

. All the

**Figure 8.** Friction coefficient and odd ring fraction of the FL-C:H films as a function of the gas flow rate of H2

deposited surfaces (OS). (Reproduced from Ref. [45] with permission from the Royal Society of Chemistry).

in open wear.

Royal Society of Chemistry).

102 Fullerenes and Relative Materials - Properties and Applications

Benefit from unique bulk structures of FL-C:H films, some of well shelled graphene assemble nanoparticles are discovered on the friction interface. Thus, one can speculate that the main reason to the superlubricity is based on the bulk of fullerene-like structure which provides the

**Acknowledgements**

51661135022).

**References**

2009.199

**Author details**

This work is supported by CAS "Light of West China" Program, Youth Innovation Promotion Association CAS (Grant no. 2017459), China Scholarship Council (File no. 201604910183) and the National Natural Science Foundation of China (Grant nos. 51205383, 51611530704 and

Super-Lubricious, Fullerene-like, Hydrogenated Carbon Films

http://dx.doi.org/10.5772/intechopen.70412

105

1 R&D Center of Lubricating and Protecting Materials, Lanzhou Institute of Chemical

2 Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese

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[2] Li J, Luo J. Advancements in superlubricity. Science China Technological Sciences.

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[4] Erdemir A. Design criteria for superlubricity in carbon films and related microstructures. Tribology International. 2004;**37**(7):577-583. DOI: 10.1016/j.triboint.2003.12.007 [5] Wang C, Yang S, Wang Q, Wang Z, Zhang J. Super-low friction and super-elastic hydrogenated carbon films originated from a unique fullerene-like nanostructure.

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[7] Lantz MA, Wiesmann D, Gotsmann B. Dynamic superlubricity and the elimination of wear on the nanoscale. Nature Nanotechnology. 2009;**4**:586-591. DOI: 10.1038/nnano.

Nanotechnology. 2008;**29**(22):225709. DOI: 10.1088/0957-4484/19/22/225709

Bin Zhang1,2,3\*, Kaixiong Gao1,2, Yuanlie Yu1,2 and Junyan Zhang1,2

Physics, Chinese Academy of Science, Lanzhou, Gansu, P.R. China

3 Lawrence Berkeley National Laboratory, Berkeley, CA, USA

2013;**56**(12):2877-2887. DOI: 10.1007/s11431-013-5387-y

\*Address all correspondence to: bzhang@licp.cas.cn

Academy of Science, Lanzhou, Gansu, P.R. China

DOI: 10.1103/PhysRevB.41.11837

1122. DOI: 10.1126/science.1262024

427-432. DOI: 10.1016/0257-8972(94)90197-X

**Figure 10.** A incommensurate and rolling contact for the superlubricity of FL-C:H films. (Reproduced from Ref. [26] with permission from the Royal Society of Chemistry).

raw materials to grow of onion-like nanoparticles at certain conditions. One of issues worth exploring is that the onion-like nanoparticles only can see below 30% humidity. Theoretical model of the graphene to fullerene transformation confirmed that the formation of defects at the edge of graphene is the crucial step. Usually, water molecules exhibit higher activation energies that those of the non-polar adsorbates (O<sup>2</sup> , N<sup>2</sup> and Ar) via stronger hydrogen bonds. Thus, at lower humidity, unsaturated dangling bonds of graphene have a high reaction activity and the hybridization are easy to occur on the edge of graphene itself, but at higher humidity, dangling bonds are saturated by water molecules, hindering the hybridization of graphene fragment, which limits the nucleation and growth of onion-like nanoparticles. In addition, these particles have a chemically inert surface, which reduces the couple of dual interface via offering incommensurate and rolling contact (**Figure 10**).
