Browsing by Author "Lee, Hsiao-Chien"

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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
;
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
;
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.
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
;
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.
Numerical Method for the Design of Healing Chamber in Additive-Manufactured Dental Implants
(2017-01-01)
Lee, Hsiao-Chien
;
Tsai, Pei-I
;
Huang, Chih-Chieh
;
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.