Influence of tribofilm on superlubricity of highly-hydrogenated amorphous carbon films in inert gaseous environments  

作　　者：LIU ShuWei ZHANG ChenHui OSMAN Eryilmaz CHEN XinChun MA TianBao HU YanZhong LUO JianBin ALI Erdemir 

机构地区：[1]State Key Laboratory of Tribology,Tsinghua University [2]Energy Systems Division,Argonne National Laboratory

出　　处：《Science China(Technological Sciences)》2016年第12期1795-1803,共9页中国科学（技术科学英文版）

基　　金：supported by the National Basic Research Program of China (Grant No.2011CB013404);National Natural Science Foundation of China(Grant Nos.51321092,51527901 and 51375010)

摘　　要：In this study,we mainly focus on the structural morphology and inter-atomic bonding state of tribofilms resulting from a highly-hydrogenated amorphous carbon(a-C:H) film in order to ascertain the underlying mechanisms for its superlubric behavior(i.e.,less than 0.01 friction coefficient).Specifically,we achieved superlubricity(i.e.,friction coefficients of down to 0.003) with this film in dry nitrogen and argon atmospheres especially when the tribo-pair is made of an a-C:H coated Si disk sliding against an a-C:H coated steel ball,while the a-C:H coated disk against uncoated ball does not provide superlubricity.We also found that the state of superlubricity is more stable in argon than in nitrogen and the formation of a smooth and uniformly-thick carbonaceous tribofilm appears to be one of the key factors for the realization of such superlubricity.Besides,the interfacial morphology of sliding test pairs and the atomic-scale bond structure of the carbon-based tribofilms also play an important role in the observed superlubric behavior of a-C:H films.Using Raman spectroscopy and high resolution transmission electron microscopy,we have compared the structural differences of the tribofilms produced on bare and a-C:H coated steel balls.For the a-C:H coated ball as mating material which provided superlow friction in argon,structural morphology of the tribofilm was similar or comparable to that of the original a-C:H coating;while for the bare steel ball,the sp^2-bonded C fraction in the tribofilm increased and a fingerprint-like nanocrystalline structure was detected by high resolution transmission electron microscopy(HRTEM).We also calculated the shear stresses for different tribofilms,and established a relationship between the magnitude of the shear stresses and the extent of sp^3-sp^2 phase transformation.

关 键 词：diamond-like carbon（DLC） films superlubricty tribofilm high resolution transmission electron microscopy（HRTEM） phase transformation 

分 类 号：O613.71[理学—无机化学] TB383.2[理学—化学]