Browsing by Author "Chao, Chuen-Guang"

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A facile cosolvent/chelation method for the preparation of semi-crystalline CuCl2(ethylene glycol)/poly(3-hexylthiophene) complexes displaying specific luminescence properties
(2015-01-01)
Lu, Fang-Hsien
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Mohamed, Mohamed Gamal
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Liu, Tzeng-Feng
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Chao, Chuen-Guang
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Kuo, Shiao-Wei
Semi-crystalline CuCl2(ethylene glycol)/poly(3-hexylthiophene) complexes (CE-P3HT) with specific textures and self-assembled structures can be fabricated using a facile co-solvent/chelation method. The morphologies and self-assembled structures of these CE-P3HT complexes were dependent on the concentration of CuCl2(ethylene glycol) (CuCl(2)EG) in solution. Transmission electron microscopy (TEM) revealed the CE-P3HT sample comprising EG and numerous CuCl2/P3HT dots (C-P3HT dots) that originated from the P3HT main chains interacting with CuCl2 crystals; the average size of this C-P3HT dots was ca. 20 nm. Prior to formation of the solid state of CE-P3HT structures, the CE-P3HT complex in solution displayed a novel phenomenon: a specific luminescence property with an absorption energy gap of 3.71-4.46 eV. This quantum effect resulted from the chelates formed between the Cu2+ ions and the thioether units of the conjugated P3HT polymer.
A novel high-strength, high-ductility and high-corrosion-resistance FeAlMnC low-density alloy
(2013-03-01)
Chen, Po-Chih
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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
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Department of Materials Science and Engineering
The as-quenched Fe-8.68 wt.% Al-30.5 wt.% Mn-1.85 wt.% C alloy is plasma-nitrided at 500 degrees C for 8 h. The nitrided layer obtained is 40 mu m thick and composed predominantly of AlN, with a small amount of Fe4N. The resultant surface hardness (1860 Hv), substrate hardness (550 Hv), ductility (33.6%) and corrosion resistance in 3.5% NaCl solution in the present nitrided alloy are far superior to those obtained previously in optimally nitrided high-strength alloy steels, as well as martensitic and precipitation-hardening stainless steels. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
A novel method of centrifugal processing for the synthesis of lead-bismuth eutectic alloy nanospheres and nanowires
(2007-03-01)
Kuo, Chin-Guo
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Chao, Chuen-Guang
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材料科學與工程學系
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Department of Materials Science and Engineering
In the present study, lead-bismuth (Pb-Bi) eutectic alloy nanospheres and nanowires were fabricated using a process based on centrifugal force. When various centrifugal forces were applied, nanospheres and nanowires were formed on/inside the highly ordered anodic aluminum oxide (AAO) templates. The X-ray diffraction spectrum showed that nanoscale wires were composed of Pb(7)Bi(3) and Bi phases. The scanning electron microscopy (SEM) images proved the formation of nanospheres and nanowires on/inside the alumna channel templates. During centrifugation, the repulsive force between the nanochannel and the alloy melt was calculated from the surface tension on the ultra-fine tube. The force applied to the melt of Pb-Bi inside the AAO was controlled by the centrifugal force.
A quenching method for the preparation of metal oxide-polythiophene composites having fiber structures
(2014-01-01)
Lu, Fang-Hsien
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Mohamed, Mohamed-Gamal
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Liu, Tzeng-Feng
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Chao, Chuen-Guang
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Dai, Lizong
In this study we developed a simple quenching method to fabricate metal oxide (CuO, ZnO, TiO2, Fe(OH) 3)polythiophene (PT) composites. By varying the metal oxide, PT, and rate of crystallization, we could control the fiber morphology in these composites. Four-probe-station analyses revealed that the conductivities of these metal oxide-PT composites ranged from 10(-5) to 10(-3) S cm(-1), higher than that of any species of metal oxide alone (from 10(-10) to 10(-7) S cm(-1)), because the fiber morphology behaved as an exceptional transmission factor for electrons. Moreover, these metal oxide-PT composites exhibited the characteristics of colloids, as well as high viscosity, suggesting that they could also be applied as coatings on silicon and glass substrates, and could provide the opportunity to form useful materials for large-scale gas sensors due to good flexibility and porosity. UV-vis spectroscopic analyses revealed variations in the energy level (>3.37 eV for ZnO) and confirmed the mechanism of the morphology change of the composite.
A study of weldability and fracture modes in electron beam weldments of AZ series magnesium alloys
(2006-11-05)
Chi, Chao-Ting
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Chao, Chuen-Guang
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Liu, Tzeng-Feng
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Wang, Che-Chung
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材料科學與工程學系
Given the growing need for environmental protection and lightweight construction, electron beam welding (EBW) is becoming the most important welding technology because it can compensate for the poor formability of magnesium alloys. This paper examines interactions between the properties of three AZ series magnesium alloys and welding conditions. The EBW process can yield four kinds of defect in a weld: cavities, the heat-affected zone (HAZ), undercuts, and root concavities. These defects obviously induce stress concentrations in the weld, and may seriously damage its strength. Additionally, the distribution of precipitates (gamma phase, Mg17Al12) in the fusion zone (FZ) changes from a relatively small number of scattered particles to a dense population of dendrites as the Al content of the magnesium alloy increases. Under excessive tensile stress, alloy weldments break in one of two fracture modes: an irregular FZ fracture, or a regular HAZ fracture. AZ31B usually exhibits the former mode and AZ91D the latter, while AZ61A exhibits each mode half the time. The overall weldability, which depends on the random distribution of these precipitates and defects, is found to be greatest for the AZ61A alloy. The best process window, on the other hand, is found for the AZ91D alloy. Finally, we obtain optimum parameters for the EBW process and empirical formulae for the weldment strength as a function of these parameters. These results are closely related to each other. (c) 2006 Elsevier B.V. All rights reserved.
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.
Aluminum element effect for electron beam welding of similar and dissimilar magnesium-aluminum-zinc alloys
(2007-05-01)
Chi, Chao-Ting
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Chao, Chuen-Guang
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Liu, Tzeng-Feng
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Lee, Chuan-Hua
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材料科學與工程學系
Defects causing stress concentration from electron beam welding are related to the Al content of the Mg-AI-Zn weldment and its effect will be most conspicuous for the welding of dissimilar metals. Precipitates which are gamma phase (Mg-17(Al,Zn)(12)) also influence the formative mechanism of pores, the heat-affected zone and the fracture mode of the weld. More noteworthy is that the Al content of 6.0 wt.% is a very important delimitation for these mechanisms. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Characterization on electron beam welds and parameters for AZ31B-F extrusive plates
(2007-02-02)
Chi, Chao-Ting
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Chao, Chuen-Guang
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材料科學與工程學系
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Department of Materials Science and Engineering
Recent years have seen a renewal of interest in magnesium alloys because of the extensive applications in the industry of 3C, aerospace and traffic. However, applications of magnesium alloys are still restricted by their poor formability. This can be improved by dividing the shape-complicated work piece into several easily-made parts and then combining into one. There are various kinds of defects in the weld under the interaction of AZ31B properties and welding conditions. These defects will produce obvious stress concentration and serious material damage. In this study, a home-made 11 mm-thick AZ31B extrusive plate was used. By operating and comparing the changeable parameters of electron beam welding (EBW), the condition was optimized as 100 mA, 50 kV, 60.6 mm/s and focus position at bottom. Seventy-eight percent and 91% of the base material strength were obtained by stress and non-stress concentration weldments, respectively. Meanwhile, the harmful influence of SC and grain coarsening reached at least 13% and 9%, respectively. With other worse parameters, the strength of AZ31B weldments were reduced by undercut, root concavity, cavities and heat-affected zone (HAZ). (c) 2006 Elsevier B.V. All rights reserved.
Characterization on electron beam welds and parameters for AZ31B-F extrusive plates
(2006-02-02)
Chi, Chao-Ting
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Chao, Chuen-Guang
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Recent years have seen a renewal of interest in magnesium alloys because of the extensive applications in the industry of 3C, aerospace and traffic. However, applications of magnesium alloys are still restricted by their poor formability. This can be improved by dividing the shape-complicated work piece into several easily-made parts and then combining into one. There are various kinds of defects in the weld under the interaction of AZ31B properties and welding conditions. These defects will produce obvious stress concentration and serious material damage. In this study, a home-made 11 mm-thick AZ31B extrusive plate was used. By operating and comparing the changeable parameters of electron beam welding (EBW), the condition was optimized as 100 mA, 50 kV, 60.6 mm/s and focus position at bottom. Seventy-eight percent and 91% of the base material strength were obtained by stress and non-stress concentration weldments, respectively. Meanwhile, the harmful influence of SC and grain coarsening reached at least 13% and 9%, respectively. With other worse parameters, the strength of AZ31B weldments were reduced by undercut, root concavity, cavities and heat-affected zone (HAZ). (c) 2006 Elsevier B.V. All rights reserved.
Conducting Ag/oligothiophene complex pastes through a simple quenching/chelation method
(2014-08-14)
Lu, Fang-Hsien
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Chang, Feng-Chih
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Mohamed, Mohamed-Gamal
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Liu, Tzeng-Feng
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Chao, Chuen-Guang
This paper describes a simple and environmentally friendly approach-a facile, one-pot, quenching/ chelation method-for the fabrication of a silver paste in the form of Ag/oligothiophene complex composites. These Ag/oligothiophene complex composites possess excellent conductivities of 1.8 x 10(4) S cm(-1) in the bulk state and 6.08 x 10(2) S cm(-1) in the form of thin films. We have used X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) to characterize the microstructures of these novel Ag/oligothiophene complex composites.
Conducting Ag/oligothiophene complex pastes through a simple quenching/chelation method
(2014-08-14)
Lu, Fang-Hsien
;
Chang, Feng-Chih
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Mohamed, Mohamed-Gamal
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Liu, Tzeng-Feng
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Chao, Chuen-Guang
This paper describes a simple and environmentally friendly approach-a facile, one-pot, quenching/ chelation method-for the fabrication of a silver paste in the form of Ag/oligothiophene complex composites. These Ag/oligothiophene complex composites possess excellent conductivities of 1.8 x 10(4) S cm(-1) in the bulk state and 6.08 x 10(2) S cm(-1) in the form of thin films. We have used X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) to characterize the microstructures of these novel Ag/oligothiophene complex composites.
Control ability of spin coating planarization of resist film and optimal control of developers
(2006-08-01)
Kuo, Yang-Kuao
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Chao, Chuen-Guang
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材料科學與工程學系
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Department of Materials Science and Engineering
The issue of how to transfer a pattern onto a wafer during photolithography is very important. Normally, the resist is treated as a pattern-transferring medium. Such a medium should have a very smooth surface to reduce the focus error. In this experiment, spin coating is used. The velocity of the center differs from that of the outer edges of a rotating disk, so a perfectly smooth surface cannot be obtained. Therefore, resist temperature, cooling temperature, heating temperature, cup temperature, cup humidity and exhaust pressure were controlled to eliminate this imperfection to yield an acceptable error. A lower cooling temperature yields a thicker center, such that the surface of the wafer protrudes at the center. A lower cooling temperature also corresponds to a thicker center, with the same effect. The cup temperature was set to the cooling temperature so that thickness distribution would be the same as. A higher heating temperature yields a thinner wafer. Higher humidity yields a thinner wafer. (c) 2005 Elsevier Ltd. All rights reserved.
Deformation mechanisms in ultrahigh-strength and high-ductility nanostructured FeMnAlC alloy
(2014-02-15)
Lin, Chih-Lung
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Chao, Chuen-Guang
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Juang, Jenh-Yih
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Yang, Jenn-Ming
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Liu, Tzeng-Feng
The deformation mechanisms of a bulk nanostructured Fe-30Mn-9.5Al-2.0C (in wt.%) alloy were investigated. After aging at 450 degrees C for 9-12 h, the alloy exhibits an exceptional strength-ductility combination (e. g. yield strength similar to 1406 MPa with elongation similar to 32%). The aged alloy exhibits a novel microstructure with isolated austenite nano-channels bounded by an extremely high volume fraction of directional nano-sized (Fe,Mn)(3)AlC carbides (kappa'-carbides). The plastic deformation was found to be dominated by bursting dislocation nucleation within the isolated austenite nano-channels. (C) 2013 Elsevier B. V. All rights reserved.
Effect of dispersant on preparation of colloidal magnetite nanocrystals
(2006-07-01)
Shauo, Chang-Neng
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Chao, Chuen-Guang
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材料科學與工程學系
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Department of Materials Science and Engineering
Nanometer scale magnetite particles were prepared in a very low concentration dispersing system with a dispersant. The average size of the particles prepared under optimum conditions was determined by transmission electron microscopy to be approximately 1.8 nm. The magnetic properties were investigated using a superconducting quantum interference device (SQUID) magnetometer. The dried samples exhibited approximately super-paramagnetic behavior. Rhelogical property measurement shows that the colloidal magnetite both with and without polyurethane reveals shear thinning. The surface morphology of the films of the magnetite nanoparticles on the glass, as shown by atomic force microscopy (AFM) images, produces well-formed surface structure's that are evenly spaced by the magnetite nanoparticles. It also shows that this is an effective method of surface modification for nanometer scale magnetite.
Effect of ECAE on Microstructures and Mechanical Properties of Solution Heat Treated Mg-5(mass%) Sn Alloy
(2013-08-01)
Tsai, Hao-Jan
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Kuo, Chin-Guo
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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 microstructures and mechanical properties of the Mg-5(mass%) Sn alloy subjected to a solution heat treatment (SHT) were investigated by using equal channel angular extrusion (ECAE). The average grain size was significantly refined from 147 mu m (as-cast) to 16 mu m by ECAE four passes. Further, the fine Mg2Sn particles were uniformly distributed in the matrix by dynamic precipitation after ECAE four passes. The yield strength (YS), ultimate tensile strength (UTS) and elongations also showed notable improvements at room temperature and high temperatures (100 and 200 degrees C) on account of the ECAE process. Further, the tensile strength and elongations were better than those of the ECAE without SHT alloy. Those results show that SHT is a useful way to enhance the effect of ECAE on the mechanical properties of Mg-5 (mass%) Sn alloy.
Effect of Microstructure Factors on Stress Corrosion Behavior of Mg-xSn Alloys (x=2, 5, 8 mass%)
(2016)
Chang, Pei-Shan
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Chen, Chun-Hung
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Chao, Chuen-Guang
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交大名義發表
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材料科學與工程學系
The effect of microstructure on the stress corrosion behavior of Mg-Sn alloys was investigated using a bent-beam method. The effects of an Mg2Sn phase and Sn in the matrix on stress corrosion were investigated. Mg2Sn phase mainly formed at the grain boundary. The volume fraction of the Mg2Sn phase increased with increasing Sn content, and the morphology of Mg2Sn changed from spherical to a semi-continuous network. The average volume fractions of Mg2Sn phase increased from 0.07 +/- 0.02% to 5.06 +/- 0.92% as the Sn content was increased from 2 to 8 mass%. An increase in the amount of Mg2Sn phase increased the pit density, whereas dissolution of the Mg2Sn phase into the matrix resulted in decreased pit density. An intergranular cracking mode was observed. The solution heat treatment dissolved the Mg2Sn phase and eliminated the micro-galvanic corrosion due to Mg2Sn, thereby delaying crack initiation also enhancing stress corrosion resistance. Mg-8% Sn sample through solution heat treatment showed the best stress corrosion resistance.
Effect of phosphate surface pretreatment on corrosion resistance and adhesion of PI coating on Mg-5 wt.% Sn alloy
(2015-06-18)
Lee, Hsiao-Chien
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Huang, Yi-Chia
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Liu, Tzeng-Feng
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Whang, Wha-Tzong
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Chao, Chuen-Guang
In this study, phosphate surface pretreatment (PSPT) and poly[pyromellitic dianhydride-co-4,4MODIFIER LETTER PRIME-oxydianiline] polyimide (PMDA-ODA PI) coating were used to provide corrosion protection for Mg-5 wt.% Sn alloy. PSPT enhanced the adhesion of PI coating by mechanical interlocking and chemical anchoring. Surface roughness was increased and provided stronger mechanical interlocking. Phosphates were formed on the alloy surface to act as anchor groups. Energy dispersive X-rayspectrometer and X-ray photoelectron spectroscopy results indicated that bonds formed between anchor groups and PI coating. The bonds provided chemical anchoring and enhanced the adhesion of PI coating. The increase of corrosion resistance of PI coating on Mg-5 wt.% Sn alloy (E-corr = -0.86V/SCE, [GRAPHICS] mu A cm(-2) and corrosion rate far less than [GRAPHICS] showed the bonds were stable enough to stand the attack of electrolyte and inhibit the electrochemical reaction at the interface.
Effect of Temperature and Extrusion Pass on the Consolidation of Magnesium Powders Using Equal Channel Angular Extrusion
(2013-05-01)
Lee, Hsiao-Chien
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Chao, Chuen-Guang
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Liu, Tzeng-Feng
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Lin, Che-Yi
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Wang, Hsiao-Chung
The microstructure and characteristics of bulk magnesium consolidated from Mg powder by equal channel angular extrusion (ECAE) were investigated. Cu cans filled with Mg powder, of about 74 mu m in diameter, were ECAE processed for one, two and four passes via the Bc route at 473, 523 and 573 K. The microstructure of ECAE-processed samples was observed by OM and SEM. The density of each sample was determined using Archimedes' principle. Microhardness and compression tests were conducted to investigate the mechanical properties of each ECAE-processed sample. The best consolidated condition between powders was achieved after four passes of ECAE at 573 K. Density at 98.4% of the ideal density of bulk Mg was achieved, microhardness was about 49 Hv, and compressive yield stress was about 100 MPa.
Effects of equal channel angular extrusion on the microstructure and high-temperature mechanical properties of ZA85 magnesium alloy
(2012-07-01)
Lin, Che-Yi
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Tsai, Hao-Jan
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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
This study examined the microstructure and high-temperature tensile properties of the Mg-8wt.%Zn-5 wt.%Al (ZA85) alloy that was subjected to equal channel angular extrusion (ECAE) with various passes at 180-250 degrees C. The original grain size and precipitate size of the as-cast specimen were 150 and 100 mu m, respectively. The average grain size was reduced to 4 mu m by dynamic recrystallization and the precipitate size was reduced to 1 mu m after six ECAE passes at 180 degrees C. However, the average grain size of the ECAE-processed specimens at 250 degrees C increased from 14 mu m after two passes to 20 mu m after four passes owing to the grain growth effect. In tensile tests at 200 degrees C, the ultimate tensile strength (UTS) and yield strength (YS) of the specimens processed with six ECAE passes at 180 degrees C improved to 249 MPa and 162 MPa, respectively, compared with 105 MPa (UTS) and 74 MPa (YS) for the as-cast specimens. Furthermore, elongation increased from 5.1% to 28.5%. This significant improvement in the high-temperature tensile properties of the ZA85 alloy was attributed to the refined grains and the well-distributed fine Mg-32(Al, Zn)(49) (tau-phase) precipitates. (C) 2012 Elsevier B.V. All rights reserved.
Effects of Rhenium on Microstructure and Phase Stability of MAR-M247 Ni-Base Fine-Grain Superalloy
(2010-04-01)
Liao, Jian-Hong
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Bor, Hui-Yun
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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 effects of Re additions on the microstructure and phase stability of the cast fine-grain Mar-M247 superalloy were investigated in this study. The results showed that the grain sizes of the alloys with 0, 3, and 4.5 mass% Re content were 90, 60, and 50 mu m, respectively. The primary gamma' phase became finer and more cuboidal as Re content increased. The addition of 3 mass% Re caused strip-like MC carbides within the grain to degenerate into discontinuous M(23)C(6) carbides and initiated the formation of a deleterious topological closed-packed (TCP) phase within the grain interior. The addition of 4.5 mass% Re promoted phase instabilities that led to the precipitation of large amounts of needle-like P phase in the grain interior, attributable to Re and W segregation. This study found that 3 mass% Re was a critical addition to maintain optimal microstructure and phase stability, and improved the ultimate tensile strength and the yield strength at room temperature and 760 degrees C. However, the addition of 4.5 mass% Re obviously resulted in a decrease in tensile properties at room temperature and 760 degrees C. [doi:10.2320/matertrans.M2009331]