Jinjun Lu

Characterization of nanocrystalline diamond films implanted with nitrogen ions

Abstract Nanocrystalline diamond films, prepared by a microwave plasma-enhanced CVD, were implanted using 110-keV nitrogen ions under fluence ranging from 1016–1017 ions cm−2. AFM, XRD, XPS and Raman spectroscopy were used to analyze the changes in surface structure and chemical state of the films before and after implantation. Results show that high-fluence nitrogen ions implanted in the nanocrystalline diamond film cause a decline in diamond crystallinity and a swelling of the crystal lattice; the cubic-shaped diamond grains in the film transform into similar roundish-shaped grains due to the sputtering effect of implanted nitrogen ions. Nitrogen-ion implantation changes the surface chemical state of the nanocrystalline diamond film. After high-fluence implantation, the surface of the film is completely covered by a layer of oxygen-containing groups. This phenomenon plays an importance role in the reduction of the adhesive friction between an Al2O3 ball and the nanocrystalline diamond film.

Thermal properties and tribological characteristics of CeF3 compact

Abstract By studying the oxidation behavior of CeF 3 in air, a CeF 3 compact was prepared on a substrate and the structure is characterized in the paper. Effects of temperature, load and velocity on the sliding friction behavior of the compact were studied on a pin-on-disk tribometer. Findings indicated that the CeF 3 compact provided low friction in sliding against Hastelloy C between 400°C and 700°C at high velocity and low load. Analysis results suggested that preferential orientation of plane (002) and the oxidation of CeF 3 are the two factors that affect the friction-reducing property of CeF 3 . Furthermore, the transfer film provided by CeF 3 compact provided Hastelloy C with minimized wear rate over the evaluated temperatures. All these suggested that CeF 3 can be used as solid lubricant for use from 400°C to 700°C.

Effect of silver on the sliding friction and wear behavior of CeF3 compact at elevated temperatures

Abstract A CeF3 compact with 10% silver in volume on the substrate of Hastelloy C was prepared in the paper. Effects of abrasive paper on the composition and surface roughness of the compact were studied. The effect of silver on the sliding friction and wear behavior of CeF3 compact at temperatures to 700°C in air was investigated. By adding 10% silver in volume in CeF3 compact, the sliding friction behavior of the compact could be greatly improved. The friction coefficients were quite low below 300°C. At 400°C, the friction coefficient was higher than that of without silver addition. At 700°C, silver and CeF3 had a synergetic effect on reducing friction, were the friction coefficient was as low as 0.11. The use of silver can prevent the compact from severe damage by forming a thin solid film on the worn surface.

Tribological behavior and phase transformation of single-crystal silicon in air

The tribological behaviors and phase transformations of single-crystal silicon against Si3N4 with different sliding velocities and durations under low contact stress at room temperature were investigated. SEM and Raman analysis indicate that phase transformation was involved and characterized by plastically deformed area which consists of Si-III, Si-XII, and a-Si, especially in the early stage at the low sliding velocity. The plastically deformed layer was wiped off at high-velocity or long sliding duration. TEM analysis indicated that the wear debris consists of amorphous silicon.

Physical and chemical effects of CeF3 compact in sliding against Hastelloy C in temperature to 700°C

Abstract The dependence of friction coefficient vs. temperature of Hastelloy C/CeF 3 compact was studied in the paper. The wear debris was studied by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Findings indicated that CeF 3 had physical and chemical effects in sliding at evaluated temperatures. The physical effects were known as preferential orientation, degree of crystallization and plastic deformation. The preferential orientation of plane (002) had a positive effect on friction reduction. The friction coefficients were low as the degrees of crystallization were high. The chemical effect was known as oxidation. The difference between static and sliding conditions was that the starting temperature of the former was higher than that of the latter. The cause was the temperature difference between the sliding surface and environment caused by frictional action. The oxidation of CeF 3 compact had a negative effect on its lubricity below 700°C since CeO 2 showed poor lubricity within the range of these temperatures. At 700°C, CeO 2 exhibited good friction-reducing, transferring and film-forming properties, which means the oxidation above 700°C may have a beneficial effect on friction reduction.

Formation of Laminar Structure Under Unlubricated Friction of Cu–SiO2 Composite

A laminar-structured tribolayer on the worn surface of Cu–SiO2 composite in sliding against 1045 steel is observed by etching the longitudinal sections. In morphology, the tribolayer consists of many subunits with different lengths and heights. The subunits are curved or parallel to the contact surface at different depths from bulk to the worn surface. In microstructure, the tribolayer is unconsolidated after etching, and fine Cu grains, as well as few fractured SiO2 particles, are observed. The main formation mechanism of the laminar-structured tribolayer is grain boundary sliding. Shear localization with large plastic strain is a prerequisite for the formation of laminar structure. The generation and accumulation of frictional heating promote the plastic deformation and decrease the activation energy for grain boundary sliding. The etching effect is contributed to the presentation of the laminar structure.

Effect of ion mixing by C+ implantation on friction and adhesion of amorphous carbon film on SiO2

Abstract Amorphous carbon films on the SiO 2 substrates have been implanted with C ions with energy of 110 KeV and fluences ranging from 1×10 16 to 1×10 17 C cm −2 . The effect of ion mixing on the friction behavior of amorphous carbon film and changes in chemical composition and structure were investigated. The results show that the anti-wear life and adhesion of amorphous carbon films on SiO 2 substrate were significantly increased by C ions implantation, especially when the fluence reached 1×10 17 C cm −2 . The Si–C chemical bonding across the interface plays the key role in the increase of adhesion strength and the anti-wear life of amorphous carbon film. The friction and wear mechanism of the amorphous carbon film under dry friction was also discussed.

Effect of C+ implantation on the structure and tribological properties of three metal/SiO2 systems

In this paper, Ti, Al and Ag films were deposited on SiO2 (100) using vacuum evaporation method and were modified by 100 keV C+ implantation using a dose of 1×1017 ions/cm2. The variations in structure, chemistry and tribological properties were studied. It was found that C+ implantation had beneficial effect on both the tribological behavior and rupture load of the metal/SiO2 systems due to the enhancement in mechanical properties and interfacial adhesion between the films and substrates. Atomic force microscopy images showed the microstructure of nano-grains of the Ti film before and after C+ implantation. X-Ray diffraction and X-ray photoelectron spectrometer results revealed that TiC existed at the near-surface, and Ti-C solid solution existed in the film and the interfacial layer.

The effect of nitrogen ion implantation on wear behaviour of single-crystal SiO2

The effect of nitrogen ion implantation on the wear behaviour and the change of structure of single-crystal SiO2 was investigated by SEM, TEM and XPS. The results show that the tribological properties of single-crystal SiO2 under dry friction conditions change with the nitrogen ion implantation. At low implanted doses, the hardness and critical peeling load for single-crystal SiO2 varies inconspicuously and the tribological properties are also not improved. However, the wear resistance is greatly improved at doses of 5 × 1016 and 1 × 1017 N cm-2 . When the dose reaches 5 × 1017 N cm-2 , the tribological properties of single-crystal SiO2 decrease again. The possible friction and wear mechanisms for single-crystal SiO2 were discussed.

Friction and Wear of Al2O3-Based Composites with Dispersed and Agglomerated Nanoparticles

In recent years, Al2O3-based nanocomposite which is composed of micro-size Al2O3 matrix and a second phase nanoparticles (e.g. SiC, Ni) as the reinforcement phase have received considerable attention and come a long way mainly because of their good mechanical property and resistance to abrasive wear and erosive wear. Up to now, practice on tribologcial design and testing of high temperature self-lubricating Al2O3-based nanocomposites is an exciting field to be explored. In this chapter, the principle for fabrication of Al2O3-based nanocomposite for better mechanical property than that of monolithic Al2O3 ceramic is briefly introduced on basis of literature review. In other words, the microstructure, and mechanical property of Al2O3-SiC, Al2O3-Ni nanocomposites are briefly introduced and discussed. This chapter focuses on the design and tribological property of high temperature self-lubricating Al2O3-based nanocomposites. As the first step, the tribological consideration of Al2O3-SiC nanocomposite is discussed according to Todd’s work which gives useful information on the pullouts of grains during grinding and polishing. In addition, a concept for designing high temperature self-lubricating Al2O3-based nanocomposite with dispersed and agglomerated ceramic nanoparticles is proposed and discussed using Al2O3-TiCN composite as an example. Al2O3-5 wt % TiCN and Al2O3-10 wt % TiCN composites had high hardness and good tribological property at room temperature in air. Al2O3-TiCN composites containing 10 and 20 wt % TiCN nanoparticles in sliding against Ni-Cr alloy are self-lubricating at 500 °C.