Browsing by Author "Chen, Jung-Hsuan"

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A study on fabrication, morphological and optical properties of lead sulfide nanocrystals
(2008-02-01)
Chen, Jung-Hsuan
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Lo, Shen-Chuan
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Chao, Chuen-Guang
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Liu, Tzeng-Feng
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材料科學與工程學系
To investigate the properties of lead sulfide (PbS) nanocrystals, we have prepared PbS nanocrystals on/in the porous alumina membrane with a pore diameter 20 nm. Utilizing the reaction of Pb wires and the hydrogen sulfide (H2S) gas, PbS nanocrystals produced and grew as the reaction time increased. The composition identification of the nanocrystals was performed by the XPS and EDS analyses. More structure characteristics of the PbS nanocrystals obtained from the TEM analysis. As indicated in the PL spectra, an orange-red emission band appeared and the emission intensities were obviously related to the defects in the nanocrytals. A significant quantum confinement effect made the energy gap of PbS nanocrystals produce a blue shift from 0.41 eV to 1.89 eV. Furthermore, the growth mechanism of the PbS nanocrystals was also discussed.
Growth and characteristics of lead sulfide nanocrystals produced by the porous alumina membrane
(2007-11-15)
Chen, Jung-Hsuan
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Chao, Chuen-Guang
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Ou, Jong-Chyan
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Liu, Tzeng-Feng
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材料科學與工程學系
Lead sulfide (PbS) nanocrystals were formed by using Pb nanowires reacted with hydrogen sulfide (H2S) gas. The structure and composition of the as-prepared nanocrystals were confirmed by scanning electron microscopy, X-ray diffraction, transmission electron microscope and energy dispersive X-ray spectroscopy. According to the differential scanning calorimeter analysis, the PbS nanocrystals in a cubic structure owned excellent thermal stability. Furthermore, the optical properties including photoluminescence (PL) and Raman scatting spectrum were also measured. The PL emission measurement of the PbS nanocrystal showed that there was an orange-red emission peak located around 655 nm. A significant quantum confinement effect made the energy gap of PbS produce a blue shift from 0.41 eV to 1.9 eV. (C) 2007 Elsevier B.V. All rights reserved.
Highly graphitized laterally interconnected SWCNT network synthesis via a sandwich-grown method
(2011-04-13)
Teng, I-Ju
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Chen, Kai-Ling
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Hsu, Hui-Lin
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Jian, Sheng-Rui
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Wang, Li-Chun
We present a sandwich-grown method for growing laterally interconnected single-walled carbon nanotube (SWCNT) networks with a high degree of graphitization by microwave plasma chemical vapour deposition (MPCVD). An Al(2)O(3)-supported Fe catalyst precursor layer deposited on an oxidized Si substrate with an upper Si cover is first pretreated in pure hydrogen, and then exposed to a gas mixture of methane/hydrogen for growth process at a lower growth temperature and a faster rate. The effects of various parameters, such as catalyst film thickness, gas flow rate, working pressure, growth time and plasma power, on the morphologies and structural characteristics of the SWCNT networks are investigated, and therefore provide the essential conditions for direct growth of laterally interconnected SWCNT networks. Analytical results demonstrate that the SWCNT-based lateral architecture comprises a mixture of graphene-sheet-wrapped catalyst particles and laterally interconnected nanotubes, isolated or branched or assembled into bundles. The results also show that the formation of the laterally interconnected SWCNT networks is related to the sandwich-like stack approach and the addition of an Al(2)O(3) layer in the MPCVD process. The successful growth of lateral SWCNT networks provides new experimental information for simply and efficiently preparing lateral SWCNTs on unpatterned substrates, and opens a pathway to create network-structured nanotube-based devices.
METHOD FOR FABRICATING NANOSCALE THERMOELECTRIC DEVICE
(2011-03-10)
CHAO, Chuen-Guang
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Chen, Jung-Hsuan
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Yang, Ta-Wei
The present invention discloses a method for fabricating a nanoscale thermoelectric device, which comprises steps: providing at least one template having a group of nanoscale pores; forming a substrate on the bottom of the template; injecting a molten semiconductor material into the nanoscale pores to form a group of semiconductor nanoscale wires; removing the substrate to obtain a semiconductor nanoscale wire array; and using metallic conductors to cascade at least two semiconductor nanoscale wire arrays to form a thermoelectric device having a higher thermoelectric conversion efficiency.
Method of manufacturing aluminum oxide film with arrayed nanometric pores
(2006-03-09)
Chao, Chuen-Guang
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Chen, Chien-Chon
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Chen, Jung-Hsuan
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Kuo, Chin-Guo
The present invention pertains to a method of manufacturing an aluminum oxide film with arrayed nanometric pores, wherein a commercial aluminum substrate is provided firstly; then the aluminum substrate is annealed and then electro-polished in order to have a mirror-like surface, and then anodized in order to form a aluminum oxide film with a plurality of nanometric pores, which are aligned in array, and then annealed in order that an oxidation reaction can happen thereon and generates oxide, which via self-diffusion, fills some of smaller pores with the pores size being uniformed; lastly a pore-widening is undertaken in order to increase the diameters of the pores. The present invention can accomplish the nanometric pores aligned in array and with an uniform pore diameter, and simultaneously have the advantages of simplified manufacturing process, easier operational control and reduced cost.
Microstructure and properties of Pb nanowires fabricated by casting
(2008-06-01)
Chen, Jung-Hsuan
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Lo, Shen-Chuan
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Chao, Chuen-Guang
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Liu, Tzeng-Feng
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材料科學與工程學系
In this study, we fabricated Pb nanowires in porous alumina membranes with different diameters by pressure casting. It can produce a large quantity of Ph nanowires with average diameters of 20, 80, 200, and 300 nm and lengths of up to 10 Pm. The diameter and length of the nanowires can be controlled by selecting templates with a desired size. The microstructure and size effects of Ph wires on the solidification process were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and thermal analysis. The nanowires with average diameters of 20 and 80 nm were single crystals, but those with average diameters of 200 and 300 nm were polycrystals. Finally, we also discussed the melting behaviors of the Pb nanowires in the porous alumina matrix.
Microstructure and Wear Property of As-cast Mg-2-wt.%-Sn Alloys after Different Heat Treatment Processes
(2019-01-01)
Chen, Jung-Hsuan
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Wang, Yi-Fung
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Chao, Chuen-Guang
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Liu, Tzeng-Feng
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材料科學與工程學系
The developments of biodegradable materials for orthopaedic implants has been progressing rapidly for decades. Biodegradable implants can eliminate the need for a second surgery and avoid the possible risks of retained metallic implants, such as corrosion or strength weakening. Magnesium (Mg) alloy is one of the potential materials for biodegradable implants because of its good biocompatibility and biodegradability. In this study, the microstructures and mechanical properties, especially the wear behavior and friction characteristics of Mg-Sn alloys, were investigated. Mg-Sn alloys fabricated by the ingot casting method were applied to different heat treatments, and then subjected to the pin-on-disc wear test. Experimental results showed that the Mg-Sn alloy processed by solution heat treatment (SHT) at 520 degrees C and quenching had the best wear resistance and lowest coefficient of friction (COF). The decrease in the amount of hard precipitate Mg2Sn and the solid-solution strengthening induced by the excess Sn atoms in the Mg matrix were the main causes of the enhancement of the wear properties of the Mg-Sn alloy upon SHT, compared with as-cast Mg-Sn alloy and the Mg-Sn alloys made by other heat treatments.
Wear Behavior and Microstructure of Mg-Sn Alloy Processed by Equal Channel Angular Extrusion
(2017-11-01)
Chen, Jung-Hsuan
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Shen, Yen-Chen
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Chao, Chuen-Guang
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Liu, Tzeng-Feng
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材料科學與工程學系
Mg-5wt.% Sn alloy is often used in portable electronic devices and automobiles. In this study, mechanical properties of Mg-5wt.% Sn alloy processed by Equal Channel Angular Extrusion (ECAE) were characterized. More precisely, its hardness and wear behavior were measured using Vickers hardness test and a pin-on-disc wear test. The microstructures of ECAE-processed Mg-Sn alloys were investigated by scanning electron microscope and X-ray diffraction. ECAE process refined the grain sizes of the Mg-Sn alloy from 117.6 m (as-cast) to 88.0 m (one pass), 49.5 m (two passes) and 24.4 m (four passes), respectively. Meanwhile, the hardness of the alloy improved significantly. The maximum wear resistance achieved in the present work was around 73.77 m/mm(3), which was obtained from the Mg-Sn alloy treated with a one-pass ECAE process with a grain size of 88.0 m. The wear resistance improvement was caused by the grain size refinement and the precipitate of the second phase, Mg2Sn against the oxidation of the processed alloy. The as-cast Mg-Sn alloy with the larger grain size, i.e., 117.6 m, underwent wear mechanisms, mainly adhesive wear and abrasive wear. In ECAE-processed Mg-Sn alloy, high internal energy occurred due to the high dislocation density and the stress field produced by the plastic deformation, which led to an increased oxidation rate of the processed alloy during sliding. Therefore, the oxidative wear and a three-body abrasive wear in which the oxide debris acted as the three-body abrasive components became the dominant factors in the wear behavior, and as a result, reduced the wear resistance in the multi-pass ECAE-processed alloy.