Lu Xinchun

Superlubricity of a Mixed Aqueous Solution

A super-low friction coefficient of 0.0028 is measured under a pressure of 300 MPa when the friction pair (the silicon nitride ball sliding on the silicate glass) is lubricated by the mixed aqueous solution of glycerol and boric acid. The morphorlogies of the hydroxylated glass plate are observed by an atomic force microscope (AFM) in deionized water, glycerol, boric acid and their mixed aqueous solution. Bonding peaks of the retained liquids adhered on the surface of the sliding track are detected by an infrared spectrum apparatus and a Raman spectrum apparatus. The mechanism of the superlubricity of the glycerol and boric acid mixed aqueous solution is discussed. It is deduced that the formation of the lubricant film has enough strength to support higher loads, the hydration effect offering the super lower shear resistance. Key words: superlubricity, water based lubricant, ultra-low friction

Tribological properties of La2O3 and CeO2 doped CoCrW coatings deposited by supersonic plasma spraying

A novel supersonic plasma spraying was used to prepare rare earth oxides doped CoCrW coatings. X-ray diffractometer, contact surface profiler, hardness tester, micro-friction and-wear tester and environmental scanning electron microscope equipped with energy dispersive X-ray spectroscopy were employed to investigate the phase structure, surface morphology, microhardness, friction and wear properties of the sprayed coatings. The results show that rare earth oxide doped coatings have high microhardness and excellent tribological properties. Furthermore, the friction and wear mechanisms of sprayed coatings are also discussed.

Preparation and tribological properties of DLC/Ti film by pulsed laser arc deposition ∗

This paper reports that DLC (diamond like carbon)/Ti and DLC films were prepared by using pulsed laser arc deposition. R-ray diffraction, Auger electron spectroscopy, Raman spectroscopy, atomic force microscopy, nanoindenter, spectroscopic ellipsometer, surface profiler and micro-tribometer were employed to study the structure and tribological properties of DLC/Ti and DLC films. The results show that DLC/Ti film, with I(D)/I(G) 0.28 and corresponding to 76% sp3 content calculated by Raman spectroscopy, uniform chemical composition along depth direction, 98 at% content of carbon, hardness 8.2 GPa and Youngs modulus 110.5 GPa, compressive stress 6.579 GPa, thickness 46 nm, coefficient of friction 0.08, and critical load 95mN, exhibits excellent mechanical and tribological properties.

Tribological properties of diamond-like carbon films deposited by pulsed laser arc deposition

A novel method, pulsed laser arc deposition combining the advantages of pulsed laser deposition and cathode vacuum arc techniques, was used to deposit the diamond-like carbon (DLC) nanofilms with different thicknesses. Spectroscopic ellipsometer, Auger electron spectroscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, scanning electron microscopy and multi-functional friction and wear tester were employed to investigate the physical and tribological properties of the deposited films. The results show that the deposited films are amorphous and the sp2, sp3 and C-O bonds at the top surface of the films are identified. The Raman peak intensity and surface roughness increase with increasing film thickness. Friction coefficients are about 0.1, 0.15, 0.18, when the film thicknesses are in the range of 17-21 nm, 30-57 nm, 67-123 nm, respectively. This is attributed to the united effects of substrate and surface roughness. The wear mechanism of DLC films is mainly abrasive wear when film thickness is in the range of 17-41 nm, while it transforms to abrasive and adhesive wear, when the film thickness lies between 72 and 123 nm.

Effect of pH on Material Removal Rate of Cu in Abrasive-Free Polishing

The effect of pH on the material removal rate (MRR) of Cu in an organic phosphonic acid system abrasive-free slurry was investigated by thermodynamics, X-ray photoelectron spectroscopy analysis, and electrochemical measurements. The pH range can be divided into three chemical regions according to the evolution of the polishing MRR, which relies on the effect of pH on the chelating effect of the chelating ligand, diethylene triamine penta methylene phosphonic acid. The higher the pH is, the more efficient the chelating ligand is. In the alkaline pH region, because of the enhanced chelating effect and precipitation of the chelate complex on the surface, both the MRR and friction coefficient during polishing process increase significantly, and the corrosion current acquired from the potentiodynamic polarization measurement decreases.

Chemical Mechanical Polishing of Copper in Organic Phosphonic Acid System Slurry

Chemical mechanical polishing behavior of copper in organic phosphonic acid system shiny with ammonium persulfate as oxidizer was studied, including the effect of different organic phosphonic acids, concentration of oxidizer and also pH value of slurry. Results showed that there is an optimized concentration value for each kinds of organic phosphonic acid to get maximum material removal rate. With the increasing of pH value, material removal rate also increases, especially when conies into alkaline scope. Shiny with 10mM Dietliylene Triamine Penta Methylene Phosphonic Acid and 3% ammonium persulfate gives the best polishing performance with a too high material removal rate as about 2000 nm/min. With appropriate additives, the material removal rate can be restricted in an acceptable value as below 800 nm/min, and the surface profile is also improved.

Film Characteristics of Grease in Point Contact under Micro-Swaying Motion

Transient thin-film lubrication of the grease occurs in many machine elements including bearings, gears and cams. It also occurs in rolling-element bearings at the start or stop of motion. Thus the lubricant supply and film formation are important in ensuring the successful operation of a bearing.