Browsing by Author "Cheng, Yu"

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Combination of microspheres and sol-gel electrophoresis for the formation of large-area ordered macroporous SiO2
(2017-12-01)
Liao, Chen-Hong
;
Hung, Pei-Sung
;
Cheng, Yu
;
Wu, Pu-Wei
;
材料科學與工程學系
A simple and effective fabrication scheme involving sequential electrophoretic depositions of polystyrene (PS) microspheres (500 nm and 1 mu m in diameter) and SiO2 sols (similar to 5 nm in diameter) to produce large-area ordered macroporous SiO2 inverse opals (2 x 2 cm(2)) on ITO substrates is demonstrated. The zeta potentials for PS microsphere suspension and SiO2 sols are measured to determine an optimized processing window in which both samples carry negative surface charges and sol-gel transformation can be properly implemented. Our approach entails the electrophoresis of PS microspheres to render a colloidal crystal with negligible defects. Afterward, SiO2 sols are infiltrated to the interstitial voids among the closely-packed PS microspheres via another electrophoresis process, followed by an oxidation treatment to remove the PS colloidal template and complete the densification of SiO2 gels. The resulting SiO2 inverse opals reveal impressive surface uniformity and structural integrity. Fourier transform infrared spectroscopy confirms the complete removal of PS microspheres, leaving an intact SiO2 skeleton, whereas X-ray diffraction pattern indicates its amorphous nature.
Mechanical properties of three-dimensional ordered macroporous Ni foam
(2018-03-15)
Liao, Chen-Hong
;
Hung, Pei-Sung
;
Cheng, Yu
;
Chang, Shou-Yi
;
Wua, Pu-Wei
We employ a sequential electrophoresis and electrodeposition approach to fabricate a large-area ordered macroporous Ni foam in 5 x 5 cm(2) via a template route. Images from scanning electron microscope exhibit hierarchical structures with hexagonally-arranged pores and interconnected pore channels. For as-prepared and annealed ordered macroporous Ni foams, the loading-depth profiles from nano indentation show typical elastic and plastic deformation. Upon annealing, moderate growth in grain size is observed, resulting in lower hardness and Young's modulus. In contrast, for disordered macroporous Ni foam and solid Ni film, nano indentation results reveal larger hardness and undetermined Young's modulus. The ordered macroporous foam reveals hardness that is 22% of that of solid Ni film, a value close to its theoretic packing density of 24%. (C) 2017 Elsevier B.V. All rights reserved.