Zhang Chenhui

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

Preparation and Characteristics of Nanoscale Diamond-Like Carbon Films for Resistive Memory Applications

We propose diamond-like carbon (DLC) as the resistance change material for nonvolatile memory applications. Nanoscale DLC films are prepared by filtered cathodic vacuum arc technique and integrated to W/DLC/W structure devices. The deposited DLC film has a thickness of about 20 nm and high sp3 fraction content. Reversible bistable resistive switching from a high resistance state to a low resistance state, and vice versa, is observed under appropriate unipolar stimulation pulses. High resistance switching ratio (larger than a thousand times) and low level of switching power (about 11 μW) are demonstrated. We propose that the mechanism of the repetitive resistive switching is the growth and breakage of conductive sp2-like filaments in the predominantly sp3-type insulating carbon upon applications of voltage pulses, which is consistent with the experimental results.

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.

Lubricating properties of polyalkylene glycol and organic phosphate ester mixed aqueous solutions

Till now, water based lubricants, especially aqueous solutions, have not been employed in the elastohydrodynamic lubrication (EHL) due to their poor film forming capability or low wear resistance. In this paper, we proposed a method to develop water based lubricant: employing polyalkylene glycol solution as base stock to improve EHL film forming capability and using organic phosphate ester (DPZ) as anti-wear additive to improve wear resistance property. The lubricating properties of the mixed solutions, including load carrying capability, wear resistance property, friction reduction property, EHL film forming behavior, were investigated. The experimental results indicate that the mixed solution presents excellent lubricating properties, which make it a promising candidate in developing water based lubricants.

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.

Research on the Preparation, Characterization and Tribological Properties of Ultra-Thin Self-Assembled Monolayers on the Magnetic Head Surface

To improve the tribological properties of the magnetic head and increase its anti-contaminantion abilities, self-assembly of silane with hydroxyl group on the substrate was adopted to prepare a SAM(self-assembled monolayer) of 1H,1H,2H,2H-perfluorodecanetr- ichorosilanes (FDTS) on the magnetic head. TOF-SIMS (Time-of-flight secondary ion mass spectrometer), XPS (X-ray photoelectron spectroscopy), AFM (atomic force microscopy), and contact angle measurement were used to characterize the FDTS SAM. A component centered at Binding Energy of 287.627eV appearing in the C1s XPS spectra of FDTS SAM, suggests that the FDTS SAM deposited on the magetic head surface with the C-O-Si bond. The experimental results show that an ultra-thin smooth FDTS SAM, with a thickness of 2.3 nm, Ra value of 0.123nm and a water contact angle of 130.7°, can be prepared on the magnetic head surface by controlling reaction time. Having good durability property, the FDTS SAMs made the stiction of the magnetic head less than 1g after the 20000 Contact Start Stop (CSS) test, and leads to considerably improved tribological properties of the magnetic head surface.