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Conducting Ag/oligothiophene complex pastes through a simple quenching/chelation method
(2014-08-14)
Lu, Fang-Hsien
;
Chang, Feng-Chih
;
Mohamed, Mohamed-Gamal
;
Liu, Tzeng-Feng
;
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.
Microstructure and Wear Property of As-cast Mg-2-wt.%-Sn Alloys after Different Heat Treatment Processes
(2019-01-01)
Chen, Jung-Hsuan
;
Wang, Yi-Fung
;
Chao, Chuen-Guang
;
Liu, Tzeng-Feng
;
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.
Stress Corrosion Behavior of Mg-2 mass% Sn Alloy by Equal-Channel Angular Extrusion
(2017-01-01)
Chang, Pei-Shan
;
Chao, Chuen-Guang
;
Liu, Tzeng-Feng
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this work, the stress corrosion behavior of Mg-2 mass% Sn alloy in simulated body fluid solution was systematically investigated to determine its performance in a physiological environment. The effect of equal-channel angular extrusion (ECAE) on stress corrosion behavior of Mg-2 mass% Sn alloy was investigated using three-point bending test. ECAE process changed both grain size and Mg2Sn second phase distribution. The average grain size under homogenization annealing condition (about 123.61 mu m) was significantly reduced to 34.32 mu m after four ECAE passes. Mg2Sn phase formed more uniformly both in the grains and along the grain boundaries with ECAE process. The average volume fraction of Mg2Sn phase increased with increasing passes. The microstructure became more homogeneous with further ECAE passes. In bent-beam stress corrosion test, the average crack depths of samples underwent ECAE process were significantly lower than that of sample under homogenization annealing condition. This showed that the ECAE process could reduce crack propagation rate. The enhancement of stress corrosion resistance is attributable to uniform second phase distribution and grain refinement via ECAE process.
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
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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.
Mechanical behavior and electrochemical stability of gas-nitrided FeMnAlC alloy in simulated body fluid
(2018-04-01)
Hsueh, Shun-Jen
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Huang, Jhen-Yi
;
Chao, Chuen-Guang
;
Juang, Jenh-Yih
;
Liu, Tzeng-Feng
The mechanical performance and electrochemical stability in simulated body fluid (SBF) of a lightweight Fe-30Mn-10Al-1C (in wt.%) alloy after gas nitridation were investigated. The gas nitriding process was performed at 550 degrees C for 5 h under pure NH3 atmosphere. The nitrided layer was similar to 45 mu-thick and consisted predominantly of fine AlN. The surface microhardness, ultimate tensile strength, yield strength, and elongation of the present gas-nitrided alloy are 1814 Hv, 1078 MPa, 1024 MPa, and 77%, respectively. The corrosion tests in SBF showed that the gas-nitrided alloy exhibited a corrosion current density (I-corr) of 5.0 x 10(-9) A/cm(2), a pitting corrosion current density (I-pit) of 5.1 x 10(-7) A/cm(2), and a passivation region with Delta E (equivalent to E-p - E-corr) approximate to + 1804 mV, respectively, which are substantially better than those obtained in the plasma-nitrided and hydroxyapatite-coated 316L stainless steel. The results demonstrated that the present gas-nitrided alloy having an excellent combination of strength, ductility and corrosion resistance is a promising candidate to replace 316L stainless steel for medical implants. (C) 2018 Elsevier B.V. All rights reserved.
Effect of Microstructure Factors on Stress Corrosion Behavior of Mg-xSn Alloys (x=2, 5, 8 mass%)
(2016)
Chang, Pei-Shan
;
Chen, Chun-Hung
;
Chao, Chuen-Guang
;
交大名義發表
;
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.
INVESTIGATING MICROSTRUCTURES AND HIGH TEMPERATURE SUPERPLASTICITY BEHAVIOR OF MG-5(MASS%) SN ALLOY BY USING EQUAL CHANNEL ANGULAR EXTRUSION
(2016-06)
Tsai, Hao-Jan
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Kuo, Chin-Guo
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Chao, Chuen-Guang
;
Liu, Tzeng-Feng
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材料科學與工程學系
In this study, we investigated the microstructures and high temperature plasticity behaviour of an Mg-5(mass%) Sn alloy after equal channel angular extrusion (ECAE). These results show that the grain boundary of the as-cast Mg-5(mass%) Sn alloy contained continuous eutectic alpha-Mg + Mg2Sn precipitates. After an ECAE process, the average grain size decreased from 147 mu m to about 10 mu m and the continuous eutectic alpha-Mg + Mg2Sn particles were broken down, and those particles distributed uniformly. The maximum elongation was 550 % at high temperature 350 degrees C with strain rate of 1 x 10(-3) s(-1).
Numerical Method for the Design of Healing Chamber in Additive-Manufactured Dental Implants
(2017)
Lee, Hsiao-Chien
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Tsai, Pei-I
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Huang, Chih-Chieh
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Chen, San-Yuan
;
Chao, Chuen-Guang
The inclusion of a healing chamber in dental implants has been shown to promote biological healing. In this paper, a novel numerical approach to the design of the healing chamber for additive-manufactured dental implants is proposed. This study developed an algorithm for the modeling of bone growth and employed finite element method in ANSYS to facilitate the design of healing chambers with a highly complex configuration. The model was then applied to the design of dental implants for insertion into the posterior maxillary bones. Two types of ITI (R) solid cylindrical screwed implant with extra rectangular-shaped healing chamber as an initial design are adopted, with which to evaluate the proposed system. This resulted in several configurations for the healing chamber, which were then evaluated based on the corresponding volume fraction of healthy surrounding bone. The best of these implants resulted in a healing chamber surrounded by around 9.2% more healthy bone than that obtained from the original design. The optimal design increased the contact area between the bone and implant by around 52.9%, which is expected to have a significant effect on osseointegration. The proposed approach is highly efficient which typically completes the optimization of each implant within 3-5 days on an ordinary personal computer. It is also sufficiently general to permit extension to various loading conditions.
Excellent enhancement of corrosion properties of Fe-9Al-30Mn-1.8C alloy in 3.5% NaCl and 10% HCl aqueous solutions using gas nitriding treatment
(2015-06-05)
Chen, Yung-Chang
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Lin, Chih-Lung
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Chao, Chuen-Guang
;
Liu, Tzeng-Feng
;
材料科學與工程學系
The as-quenched Fe-9.0Al-30Mn-1.8C (in wt.%) alloy gas nitrided at 550 degrees C for 4 h show excellent corrosion resistance investigated in 3.5% NaCl and 10% HCl solutions. Owing to the high corrosion resistance components, the gas-nitrided layer consists mainly of AlN with a slight amount of Fe3N and Fe4N identified by grazing incidence X-ray diffraction technique. Therefore, the pitting potential and corrosion potential of the nitrided sample are + 1860 mV and + 30 mV, respectively. Surprisingly, it is worthy to be pointed out that the nitrided and then tensile-tested alloy reveals very shallow in fracture depth and the excellent lattice coherence is shown between the nitrided layer and the substrate. Moreover, due to the extremely high nitrogen concentration (about 17-18 wt.%) at stretched surface, the corrosion resistance of present gas-nitrided and then tensile-tested alloy is superior to those optimally gas-nitrided or plasma-nitrided high-strength alloy steels, as well as martensitic stainless steels. The nitrided and then stretched alloy still retains a satisfactory corrosion resistance (E-pit = + 890 mV; E-corr = + 10 mV). Furthermore, only nanoscale-size pits were observed on the corroded surface after being immersed in 10% HCl for 24 h. (C) 2015 Elsevier B.V. All rights reserved.
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
;
Huang, Yi-Chia
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Liu, Tzeng-Feng
;
Whang, Wha-Tzong
;
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.

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