Browsing by Author "Chang, Yu-Hsu"

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Formation of porous carbon materials with in situ generated NaF nanotemplate
(2006-06-22)
Huang, Chih-Hao
;
Chang, Yu-Hsu
;
Wang, Hsiao-Wan
;
Cheng, Soofin
;
Lee, Chi-Young
Porous carbon materials with pore sizes from 3 to 200 nm were synthesized by reacting hexafluorobenzene with Na liquid at 623 K. NaF crystals, a byproduct formed in the reaction, acted as nanotemplate to assist the pore formation. By employing hexafluorobenzene to react with Na incorporated within the channels ( diameter 200 nm) of anodized aluminum oxide ( AAO) membranes at 323- 623 K, the carbon material can be fabricated into aligned porous nanotube arrays ( ca. 250 nm in diameter, ca. 20 nm in wall thickness, ca. 0.06 mm in length, and ca. 3-90 nm in pore diameter). These materials were characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray energy dispersive spectroscopy, electron diffraction, thermal gravimetric analysis, and nitrogen physical adsorption experiments.
Gold nanospirals
(2015-01-01)
Chang, Yu-Hsu
;
Wu, Yu-Chuan
;
Hsu, Ya-Ting
;
Huang, Shih-Hao
;
Huang, Yi-Chin
This study used a galvanic displacement reaction for aluminum-gold oxidation-reduction and added surfactants to act as capping agents to control the morphology and size of gold growth. Three surfactants, namely cetyltrimethylammonium bromide, polyvinylpyrrolidone, and poly(ethylene glycol)(12) tridecyl ether, were added to HAuCl4 (aq.) to create novel gold nanospirals (AuNSs) 200-500 nm in diameter and tens of mu m in length. Transmission electron microscopy analysis showed that the AuNSs were face-centered cubic in structure and that growths on the {111} facet were growth twins with mirror symmetry. Used as the base material for surface-enhanced Raman scattering, the structure of the trunk and dendrimers of the AuNSs create numerous hot spots, exhibiting a superior surface enhancement effect.
Nanocarbon materials and process for producing the same
(2003-07-10)
Chang, Yu-Hsu
;
Chiu, Hsin-Tien
;
Lee, Chi-Young
;
Peng, Chih-Wei
;
Yen, Ming-Yu
In a process for producing nanocarbon materials, a metal reducing agent and a carbon source are subjected to a chemical reduction reaction under an atmosphere which will not interfere with the reaction and at a temperature preferably lower than 1000° C., such that a nanocarbon material having a graphite-like structure is formed therefrom. Optionally, an additive, e.g. a fullerene compound, or a porous substrate such as zeolite powder, may be used during the production of the nanocarbon material.
Phase segregation assisted morphology sculpting: Growth of graphite and silicon crystals via vapor-solid reactions
(2007-03-22)
Huang, Chih-Hao
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Chang, Yu-Hsu
;
Lin, Huang-Kai
;
Peng, Chih-Wei
;
Chung, Wen-Sheng
Crystalline graphite and Si showing fertile morphologies are prepared via vapor-solid reaction growth (VSRG). By reacting CaC2 with vapors of CxCly (CxCly: CCl4, C2Cl4, C4Cl6, and C5Cl6), porous, fibrous, and planar graphite were obtained at 973-1023, 1073-1123, and 1123-1223 K, respectively. Employing SiCl4 to react with MxSiy (MxSiy: Mg2Si and CaSi2) generated many Si structures. These include clustered-particle and porous, wirelike, corallike, and planar or platelike at 1023, 1073, 1123, and 1223 K, respectively. The reaction products, the network solids (graphite and Si) and the ionic solids MCl2, phase-segregated into self-templating molds and casts and develop cooperatively into various three-dimensional structures. Final morphology of the network solids depends not only on the reaction temperature but their molar volume ratio to the MCl2 salt products.
Rectangular copper nanotubes
(2015-01-01)
Chang, Yu-Hsu
;
Hsu, Ya-Ting
;
Tsai, Yu-Heng
;
Lai, Yi-Ru
;
Huang, Ting-Kai
One-dimensional Cu nanomaterials with a new morphology, rectangular copper nanotubes (copper NTs), were synthesized on a large-scale using a cetyltrimethylammonium chloride-assisted galvanic replacement reaction on rough Al substrates. In an acidic environment, Cu(II) is reduced on sharp-topped Al substrates and copper NTs 150-300 nm in diameter and 2-10 mm in length were formed through fine-tuning the reaction temperature and chemical stoichiometry. Field-emission measurement results show that the copper NTs emitting electrons at turn-on fields of 8.76 V mu m(-1) was observed with a field enhancement factor of 85. The superior catalytic property of copper NTs in the degradation of a methylene blue aqueous solution in the presence of H2O2 was also presented in this article.