Showing papers by "Xianting Zeng published in 2006"

Oxidation and wear behaviors of Ti-based thin films

Abstract: The degradation of Ti-based coatings is known to be due to the formation of titanium oxide (TiO 2 ) at their surfaces. In this study, wear and thermal oxidation behaviors of various magnetron sputtered Ti-based thin films were studied after static oxidation and sliding wear. The oxidized surfaces after the static oxidation and the wear debris generated from pin-on-disc wear tests with alumina ball were characterized to identify the compounds, particularly titanium oxides, to gain a better understanding of the tribochemical reactions. The coatings that were examined include TiN, TiCN (N rich), TiCN (C rich), TiAlN, AlTiN, TiSiN, and TiCNO thin films. These coatings were characterized using Raman spectroscopy, scanning electron microscopy, and X-Ray diffractometer. The results show that TiSiN and AlTiN have the highest oxidation resistance, comparing with other coatings. As for the analyses of wear debris, all of the Ti-based coatings are worn by the mechanism of forming TiO 2 , except AlTiN. AlTiN is worn by ploughing wear.

Synthesis and Characterization of Transparent Hydrophobic Sol-Gel Hard Coatings

Abstract: It is challenging to make a transparent hydrophobic hard coating when soft hydrophobic additives are added into the coating system. Material non-homogeneity due to phase separation, non-durable hydrophobicity and deteriorated transparency are the main issues. In this paper, we describe a chemical formulation, which contains a pre-linked hydrophobic cluster and a silica hard matrix with silica hard fillers so that the hydrophobic property and hardness can be tuned separately and optimized. The transparency of the coating is found to be related to the effective modification of the reactive titanium tetraisopropoxide (TIP) precursor by ethyl acetoacetate (EacAc) and the right ratio between TIP and polydimethylsiloxane (PDMS) (≤0.5). The water contact angle is increased to a maximum of 133° when 50 Vol% of PDMS is added into the silica matrix. The hardness of coating is proportional to silica filler content and curing temperature, and inversely proportional to PDMS Vol%. 30 Vol% silica filler in silica matrix and curing temperature at 300°C result in the best hardness in this study. Hardness at 50 Vol% PDMS dropped to 0.2 GPa from 0.85 GPa of pure silica coating. The Vol% of PDMS and silica filler will be further optimized in our next stage experiments.

Characterization of organic photovoltaic devices with indium-tin-oxide anode treated by plasma in various gases

Abstract: Indium-tin-oxide (ITO) anode treated by different gas plasma or UV ozone has been used for photovoltaic (PV) cells with structure of ITO/copper phthalocyanine (CuPc)/C60/bathocuproine/Al. Both surface energy and work function of the ITO substrates were affected by these treatments. However, the main performance parameters of PV cells, including short circuit current, open circuit voltage, power conversion efficiency, and fill factor, were almost unaffected. On the other hand, series and shunt resistances of the PV cells derived from numerical fitting of I-V curves were not significantly changed with different treatments. Therefore, no significant impact of substrate treatment on hole collection was concluded, although hole injection under forward bias showed strong dependence on treatment methods. It indicates that hole transfer from CuPc layer to ITO is not the bottleneck in the CuPc/C60 based organic solar cells.

Effect of oxygen incorporation on structural and properties of Ti–Si–N nanocomposite coatings deposited by reactive unbalanced magnetron sputtering

Abstract: Ti–Si–N–O nanocomposite coatings with different contents of oxygen were deposited by a combined dc/rf reactive unbalanced magnetron sputtering process in an Ar+N2+O2 mixture atmosphere. The composition, structure, mechanical, and tribological properties of the as-deposited coatings were analyzed by energy dispersive analysis of x-rays, x-ray diffraction (XRD), nanoindentation, and pin-on-disk tribometer experiments, respectively. It was found that in the range of lower oxygen content with atomic ratio of O∕N⩽0.72, the tribological properties of the Ti–Si–N–O coatings are evidently improved, in comparison with the coating without oxygen incorporation. At O∕N=0.72, the friction coefficient and wear rate of the as-deposited coatings are reduced to 20% and 45%, respectively. Meanwhile, however, their hardness was not reduced, but, on the contrary, slightly increased. With increasing oxygen content further to O∕N⩾0.72, coating hardness decreased significantly. The friction coefficient of the as-deposited coati...