Browsing by Author "Chen, Hsien-Wei"

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Complicated phase behavior and ionic conductivities of PVP-co-PMMA-based polymer electrolytes
(2007-02-23)
Chiu, Chun-Yi
;
Yen, Ying-Jie
;
Kuo, Shlao-Wei
;
Chen, Hsien-Wei
;
Chang, Feng-Chih
We have used DSC, FTIR spectroscopy, and ac impedance techniques to investigate the interactions that occur within complexes of poly(vinylpyrrolidone-co-methyl methacrylate) (PVP-co-PMMA) and lithium perchlorate (LiClO(4)) as well as these systems' phase behavior and ionic conductivities. The presence of MMA moieties in the PVP-co-PMMA random copolymer has an inert diluent effect that reduces the degree of self-association of the PVP molecules and causes a negative deviation in the glass transition temperature (T,). In the binary LiClO(4)/PVP blends, the presence of a small amount of LiClO(4) reduces the strong dipole-dipole interactions within PVP and leads to a lower T(g). Further addition of LiClO(4) increases T(g) as a result of ion-dipole interactions between LiClO(4) and PVP. In LiClO(4)/PVP-co-PMMA blend systems, for which the three individual systems-the PVP-co-PMMA copolymer and the LiClO(4)/PVP and LiClO(4)/PMMA blends-are miscible at all compositional ratios, a phase-separated loop exists at certain compositions due to a complicated series of interactions among the LiClO(4), PVP and PMMA units. The PMMA-rich component in the PVP-co-PMMA copolymer tends to be excluded, and this phenomenon results in phase separation. At a LiClO(4) content of 20 wt% salt, the maximum ionic conductivity occurred for a LiClO(4)/VP57 blend (i.e., 57 mol% VP units in the PVP-co-PMMA copolymer). (c) 2007 Elsevier Ltd. All rights reserved.
Mechanical and tribological properties evaluation of cathodic arc deposited CrN/ZrN multilayer coatings
(2011-12-25)
Huang, Sung-Hsiu
;
Chen, Siao-Fan
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Kuo, Yu-Chu
;
Wang, Chaur-Jeng
;
Lee, Jyh-Wei
Five nanostructured CrN/ZrN multilayer coatings were deposited periodically by cathodic arc evaporation. The bilayer periods of the CrN/ZrN multilayer coatings were controlled in the range of 5 to 30 nm. The structures and bilayer period of the multilayer coatings were characterized by an X-ray diffractometer. The microstructures of thin films were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. Nanoindentation, scratch tests, Daimler-Benz Rockwell-C (HRC-DB) adhesion tests, microhardness and pin-on-disk wear tests were used to evaluate the hardness, adhesion, indentation toughness and tribological properties of thin films, respectively. It was found that the hardness and tribological properties were strongly influenced by the bilayer period of the CrN/ZrN multilayer coatings. An optimal combination of mechanical properties and excellent tribological behavior was found for a coating with a critical bilayer period of 30 nm. (C) 2011 Elsevier B.V. All rights reserved.
The effect of Cr/Zr chemical composition ratios on the mechanical properties of CrN/ZrN multilayered coatings deposited by cathodic arc deposition system
(2013-09-01)
Chen, Siao-Fan
;
Kuo, Yu-Chu
;
Wang, Chaur-Jeng
;
Huang, Sung-Hsiu
;
Lee, Jyh-Wei
CrN/ZrN multilayer coatings with various Cr/Zr chemical compositions ratio were fabricated by a cathode arc deposition system. The Cr/Zr atomic ratios of the CrN/ZrN multilayer coatings were controlled, ranging from I to 2.5. The chemical composition of CrN/ZrN multilayer thin films was determined by a field emission electron probe microanalyzer (FE-EPMA). The phase composition of multilayer coatings was analyzed by a glancing angle X-ray diffractometer. Microstructures of the thin films were examined by field emission scanning electron microscopy (FE-SEM). Nanoindentation, the Daimler Benz Rockwell-C (HRC-DB) adhesion, microhardness, pin-on-disc wear tests and scratch tests were used to evaluate the hardness, adhesion, toughness and tribological properties of the thin films, respectively. It was found that the hardness and tribological properties were strongly influenced by the Cr/Zr chemical composition ratios of the CrN/ZrN multilayer coatings. Optimal mechanical properties and the maximum hardness of 28 GPa were achieved for the coating when the Cr/Zr atomic ratio was 2.1. (C) 2012 Elsevier B.V. All rights reserved.