Xue Fan

Graphene sheets embedded carbon film prepared by electron irradiation in electron cyclotron resonance plasma

We used a low energy electron irradiation technique to prepare graphene sheets embedded carbon (GSEC) film based on electron cyclotron resonance plasma. The particular π electronic structure of the GSEC film similar to bilayer graphene was verified by Raman spectra 2D band analyzing. The phase transition from amorphous carbon to GSEC was initiated when electron irradiation energy reached 40 eV, and the growth mechanism of GSEC was interpreted as inelastic scattering of low energy electrons. This finding indicates that the GSEC film obtained by low energy electron irradiation can be excepted for widely applications with outstanding electric properties.

Contact Mechanisms of Transfer Layered Surface During Sliding Wear of Amorphous Carbon Film

The contact mechanisms of a transfer layered surface during sliding wear of a Si3N4 ball against the amorphous carbon film were investigated. In this study, amorphous carbon films were deposited by electron cyclotron resonance plasma sputtering technique. The dependence of friction coefficient and wear life of the films on transfer layer was tested with pin-on-disk tribometer. Wear tracks and the transfer layered surfaces at different friction coefficient stages were observed with scanning electron microscope and measured with energy dispersive spectrometer In order to clarify the contact mechanisms of a transfer layered surface, three contact models of initial high friction coefficient stage without transfer layer (state I), transfer layer forming stage with friction coefficient decreasing (state II), and transfer layered surface stable sliding stage with low friction coefficient (state III) were proposed, and the contact stresses (normal stress, shear stress, von Mises stress) of the three contact states were calculated by using finite element analysis. The results demonstrated that a transfer layer formed at the contact interface and gradually decreased the maximum contact stresses, which contributed to the long wear life of amorphous carbon films. [DOI: 10.1115/1.4004999]

Experimental study on load capacity of nanoparticles-laden gas film in thrust bearing

Purpose – The purpose of this paper is to study the load capacity of nanoparticles-laden gas film (NLGF) in thrust bearing. Design/methodology/approach – SiO2 nanoparticles were added into gas to form an NLGF. The nanoparticles volume fraction in the film was controlled by a vibrator. The film thickness and the film pressure were measured by a micro cantilever displacement sensor and a membrane pressure sensor, respectively. The total load that makes the film thickness keeping constant was quantified, and then, the film load capacity was obtained. Findings – The investigation shows that nanoparticles can enlarge the film load capacity remarkably; even a little amount of nanoparticles (0.01 per cent) could lead to a sharp rise. With the increase of nanoparticles volume fraction, load capacity increases. However, the increment of load capacity decreases gradually. In addition, the film pressure variation proves the enhancement effect of nanoparticles on the film load capacity. Research limitations/implicati...

Lubrication Performance of Nanoparticles-Laden Gas Film in Thrust Bearing Under Noncontact and Contact Conditions

The nanoparticles-laden gas film (NLGF), which is formed by adding nanoparticles into the gas film, has a potential to increase the load capacity of the gas film and to protect the surfaces of the bearing from severe contact damage. In order to explore the lubrication performance of NLGF, the load capacity in the noncontact state and the friction coefficient in the contact state were studied experimentally by a novel NLGF thrust bearing apparatus. The effects of nanoparticles concentration on the load capacity and the friction coefficient were investigated, respectively. The lubrication performance of NLGF in a 200 start-stop cyclic test was evaluated. The contact surfaces were analyzed by the surface profilometer, scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS). The results showed that NLGF had the enhancement of the load capacity in the noncontact state and possessed the properties of friction reduction and surface protection in the contact state. An optimal nanoparticles concentration of 60 g/m(3) was found, making NLGF have a relative high load capacity in the noncontact state and the lowest friction coefficient in the contact state. With the optimal concentration, the friction coefficient with NLGF kept a low value during the 200 start-stop cyclic test. Then the friction reduction mechanism of NLGF was discussed, and it was inferred that the surface of the disk was covered with a protective film formed by nanoparticles, leading to a lower shear force. This study opens new perspectives of adding nanoparticles into gas bearings to improve the lubrication performance.

Nanoparticles-Laden Gas Film in Aerostatic Thrust Bearing

Nanoparticles-laden gas film (NLGF) was formed by adding SiO2 nanoparticles with volume fraction in the range of 0.014‐0.330% and size of 30nm into the air gas film in a thrust bearing. An effective viscosity of the gas-solid two phase lubrication media was introduced. The pressure distribution in NLGF and the load capacity of the thrust bearing were calculated by using the gassolid two phase flow model with the effective viscosity under the film thicknesses range of 15‐60lm condition. The results showed that the NLGF can increase the load capacity when the film thickness is larger than 30lm. The mechanism of the enhancement effect of load capacity was attributed to the increase of the effective viscosity of the NLGF from the pure air film, and the novel lubrication media of the NLGF can be expected for the bearing industry application. [DOI: 10.1115/1.4026503]