Browsing by Author "Yen, Ming-Yu"

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Cone-stacked carbon nanofibers with cone angle increasing along the longitudinal axis
(2007-02-01)
Lin, Cheng-Te
;
Chen, Wen-Chao
;
Yen, Ming-Yu
;
Wang, Lung-Shen
;
Lee, Chi-Young
Using porous anodic aluminum oxide as template and petroleum pitch as precursor, a massive amount of uniform carbon nanofibers was obtained after thermal treatment. The diameter and length were 300 nm and 60 pm, respectively. The difference between these and the classic herringbone structure is that the angle between the graphenes and the fiber axis increases regularly along the axis instead of being fixed. TEM observations show that the nanofiber consists of stacked conical graphenes with cone angles that steadily increase from 60 degrees to 180 degrees along the fiber axis. This structure is the first to be produced without using catalytic CVD, and has not been reported using template procedures. The large deformation of the graphene planes at the tip of the nanofiber may produce interesting electronic applications. (c) 2006 Elsevier Ltd. All rights reserved.
Growth of Cu nanobelt and Ag belt-like materials by surfactant-assisted galvanic reductions
(2007-05-08)
Huang, Ting-Kai
;
Cheng, Tzu-Hou
;
Yen, Ming-Yu
;
Hsiao, Wei-Han
;
Wang, Lung-Shen
We demonstrate the syntheses of single crystalline Cu nanobelt and Ag belt-like materials via CTAC-assisted (CTAC, cetyltrimethylammonium chloride) galvanic reductions. The single crystalline face-centered cubic phase Cu nanobelt was prepared by reacting CuCl2(aq) with Al(s) in an aqueous solution of CTAC and HNO3. The Cu nanobelt exhibited a high-quality ribbon-like nanostructure with a thickness less than 15 nm, a width of 30-150 nm, and a length up to 10 mu m. The belt-like Ag, with a thickness less than 10 nm, a width of 30-100 nm, a length up to 5 mu m, and a novel single crystalline 4H structure, was prepared by reacting AgNO3(aq) and Cu(s) in an aqueous solution of CTAC.
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.
Thermal conductivity and structure of non-covalent functionalized graphene/epoxy composites
(2011-12-01)
Teng, Chih-Chun
;
Ma, Chen-Chi M.
;
Lu, Chu-Hua
;
Yang, Shin-Yi
;
Lee, Shie-Heng
Non-covalent functionalization was used to functionalize graphene nanosheets (GNSs) through pi-pi stacking of pyrene molecules with a functional segmented polymer chain, which results in a remarkable improvement in the thermal conductivity of GNS-filled polymer composites. The functional segmented poly(glycidyl methacrylate) containing localized pyrene groups (Py-PGMA) was prepared by atom transfer radical polymerization, and Py-PGMA was characterized by nuclear magnetic resonance spectroscopy. Raman spectra, X-ray photoelectron spectroscopy and thermogravimetric analysis reveal the characteristics of Py-PGMA-GNS. Differential scanning calorimetry indicated that the functional groups on Py-PGMA-GNSs can generate covalent bonds with the epoxy matrix, and further form a cross-linked structure in Py-PGMA-GNS/epoxy composites. The Py-PGMA on the GNS surface not only plays an important role to facilitate a homogeneous dispersion in the polymer matrix but also improves the GNS-polymer interaction, which results in a high contact area. Consequently, the thermal conductivity of integrated Py-PGMA-GNS/epoxy composites exhibited a remarkable improvement and is much higher than epoxy reinforced by multi-walled carbon nanotubes or GNSs. The thermal conductivity of 4 phr Py-PGMA-GNS/epoxy has about 20% (higher than that of pristine GNS/epoxy) and 267% (higher than pristine MWCNT/epoxy). (C) 2011 Elsevier Ltd. All rights reserved.