Papers by Author: Yong Wang

Abstract: In this paper, self-assembled monolayers (SAMs) of stearic acid (SA) surface treatment on pure magnesium were studied to improve bioactivity and corrosion resistance of pure Mg. Three pre-treatment methods (HCl-NaOH treatment, alkali-heat treatment and heat treatment) were used. SAMs treated samples were soaked in simulated body fluid (SBF) and untreated samples were taken as control. The pH variation of SBF solution was examined everyday. The electrochemical property of treated and untreated samples was tested to evaluate the anticorrosion performance of organic surface layer. Scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analysis were performed to observe the surface appearance and to identify the composition and phases of samples. The results showed that stearic acid SAMs had successfully been assembled on the surface of the samples, which had a good effect on corrosion resistance of materials and decreased the electric current density of SAM-sample 1% to that untreated sample; SAM inhibited the form of Mg(OH)₂ and had a good influence on bioactivities of pure magnesium.

Abstract: In this paper, continuous running test was conducted using the disk drive spindle micromotors used in automobiles DVD. The commutator and brush were made of AuAg/AgCuNiCe/Cu and AgPd/CuNiSn layered composite respectively. In order to investigate the wear behavior of the commutator, the micromotors were dissected after ran continuously for different time. The worn surface of the commutator and the brush were characterized using an SEM equipped with EDS. Also, the cross section of the commutator was analyzed. It was shown that the AuAg layer was not totally worn off until 1500 h of running test. AuAg transferred from the commutator to the brush. It was interesting that Au was found on the silver layer where the depth of wear crater surpassed the thickness of the original AuAg layer. Small particles enriched in Cu, Ni and Ce were observed on the contact surface of AgCuNiCe layer, which was thought to improve the wear resistance of the commutator. The wear mechanism was mainly slight abrasion whereas no effect of arc was found on the sliding contact area.