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Electrochemical behavior of Co-Cr and Ni-Cr dental cast alloys

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中国有色金属学会会刊：英文版 2009年第4期19卷 785-790页

作者： Viswanathan S. SAJI han-cheol choe Department of Dental Materials College of DentistryChosun University

The cast structures influencing the electrochemical corrosion behavior of Co-Cr and Ni-Cr dental alloys were studied using potentiodynamic polarization and AC impedance in 0.9% (mass fraction) NaCl solution at (37±1) ℃. The phase and microstructure of the alloys that were fabricated using two different casting methods viz. centrifugal casting and high frequency induction casting, were examined using X-ray diffraction analysis, scanning electron microscopy and energy dispersive spectroscopy. The roles of alloying elements and the passive film homogeneity on the corrosion resistance of Co-Cr-Mo and Ni-Cr-Mo dental cast alloys were reviewed. The results of electrochemical study show that the dependence of corrosion resistance on the microstructure associated with the casting methods is marginal. The Co-Cr alloy exhibits more desirable corrosion resistance properties than the Ni-Cr alloy. There is severe preferential dissolution of Ni-rich, Cr and Mo depleted zones in the Ni-Cr alloy.

关键词：镍铬合金合金铸造电化学行为牙科电化学腐蚀行为 X射线衍射分析 NaCl溶液钴

Mechanical properties and corrosion resistance of low rigidity quaternary titanium alloy for biomedical applications

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中国有色金属学会会刊：英文版 2009年第4期19卷 862-865页

作者： han-cheol choe Viswanat han S.SAJI Yeong-Mu KO Department of Dental Materials College of DentistryChosun University

Electrochemical corrosion of Ti-35Nb-5Ta-7Zr alloy fabricated by arc melting and heat treatment process was studied in 0.9% NaCl at(37±1) ℃.Phase and microstructure of the fabricated alloy were investigated using X-ray diffractometer and scanning electron microscope.Mechanical properties such as yield strength and elastic modulus of the alloy were determined by tensile test.Potentiodynamic polarization technique and impedance spectroscopy were employed to study the corrosion behavior.The results of the study were compared with those obtained for Ti-6Al-4V commercial alloy.The result of the study supports feasibility of Ti-35Nb-5Ta-7Zr alloy for implant applications.

关键词：生物医学应用钛合金力学性能耐腐蚀性扫描电子显微镜四元刚性 X射线衍射仪

Effects of TiN film coating on electrochemical behaviors of nanotube formed Ti-xHf alloys

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中国有色金属学会会刊：英文版 2009年第4期19卷 857-861页

作者： Kang LEE Won-Gi KIM Joo-Young CHO Sang-Won EUN han-cheol choe Department of Dental Materials & Research Center of Nano-Interface Activation for Biomaterials College of DentistryChosun University Department of Applied Advanced Materials Korea Polytechnic Ⅴ Colleges

Ti-xHf(x=10%,20%,30% and 40%,mass fraction) alloys were prepared by arc melting,and the microstructure was controlled for 24 h at 1 000 ℃ in argon atmosphere.The formation of nanotube was conducted by anodizing on Ti-Hf alloys in 1.0 mol/L H3PO4 electrolytes with small amounts of NaF at room temperature.And then TiN coatings were coated by DC-sputtering on the anodized surface.Microstructures and nanotube morphology of the alloys were examined by field emission scanning electron microscopy(FE-SEM) and X-ray diffractometry(XRD).The corrosion properties of the specimens were examined through potentiodynamic test(potential range from -1 500 to 2 000 mV) in 0.9 % NaCl solution by potentiostat.The microstructure shows the acicular phase and α' phase with Hf content.The amorphous oxide surface is transformed to crystalline anatase phase.TiN coated nanotube surface has a good corrosion resistance.

关键词：氮化钛涂层合金制备纳米管电化学行为薄膜包衣 0.9%NaCl溶液扫描电子显微镜微观结构

Surface characteristics of HA coated Ti-Hf binary alloys after nanotube formation

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中国有色金属学会会刊：英文版 2009年第4期19卷 852-856页

作者： Yong-Hoon JEONG Won-Gi KIM Geun-Hyeong PARK han-cheol choe Yeong-Mu KO Department of Dental Materials & Research Center of Nano-Interface Activation for Biomaterials College of DentistryChosun University Research Center for Oral Disease Regulation of the Aged College of DentistryChosun University

Ti-Hf binary alloys contained 10%,20%,30% and 40%(mass fraction)Hf were manufactured in the vacuum furnace system.And then,specimens were homogenized for 24 h at 1 000 ℃ in argon atmosphere.The formation of oxide nanotubes was conducted by anodic oxidation on the Ti-Hf alloy in 1 mol/L H3PO4 electrolytes containing small amounts of NaF at room temperature.The hydroxyapatite(HA) coating made of tooth ash prepared by electron-beam physical vapor deposition(EB-PVD) method.The corrosion behaviors of the specimens were examined through potentiodynamic test in 0.9% NaCl solution by potentiostat.The microstructures of the alloys were examined by field emission scanning electron microscopy(FE-SEM) and x-ray diffractometer(XRD).It was observed that the lamellar structure translated to needle-like structure with Hf contents.Nanotube formed and HA coated Ti-xHf alloys had a good corrosion resistance.

关键词：二元合金 HA涂层纳米管表面特性管形 0.9%NaCl溶液物理气相沉积铪

Electrochemical behavior of dental implant system before and after clinical use

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中国有色金属学会会刊：英文版 2009年第4期19卷 846-851页

作者： Chae-Heon CHUNG Hee-Jung KIM Yong-Tae JEONG Mee-Kyoung SON Yong-Hoon JEONG han-cheol choe Department of Prosthodontics College of DentistryChosun University Department of Dental Materials & Research Center of Nano-Interface Activation for Biomaterials College of DentistryChosun University

Electrochemical behavior of dental implant system before and after clinical use(in vivo and in vitro) was researched by using abutment and titanium fixture.To simulate an oral environment,the samples of clinically used and non-used implant systems as a working electrode were exposed to artificial saliva at(36.5±1) ℃.Electrochemical tests were carried out using a potentiostat.After electrochemical test,the corrosion morphology of each sample was investigated by FE-SEM and EDS.The corrosion potential and pitting potential of clinically used implant system are lower than those of non-used implant system,and clinically used implant system exhibits a lower range of passivation,indicating a less degree of inherent resistance against chloride ion.The polarization resistance decreases in the case of clinically used implant system,whereas,Rp for clinically non-used implant system increases compared with clinically used implant system.

关键词：电化学行为种植制度临床应用使用制度临床使用电化学测试夹具系统腐蚀形态

Photoelectrochemical Behavior of HA Film on the Nanotubular Surface after Laser Texturing on the Ti-35Nb-xZr Alloy for Dental Implant Use

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Photoelectrochemical Behavior of HA Film on the Nanotubular ...

Effects of HA/Ti Coating on the Corrosion of Nanostructured Ti-35Ta-xZr Alloys for Dental Implants

第18届国际真空大会

作者： Yong-Hoon Jeong han-cheol choe Department of Dental Materials ＆ Research Center of Nano-Interface Activation for Biomaterials School of DentistryChosun University

The increasing lifetime of population in developed countries wakes up the request of materials for bones, orthopaedic and dental implant that has inspired new research of new Ti alloys for biomaterial field. In this sense, the Ti-35Nb-xZr alloys have the low modulus of elasticity, non-allergic and non-toxicity which can be good for biomaterials. The surface treatment to improve adherent between bone and Ti surface is necessary for osseointegration. The femtosecond laser techniques can easily achieve micro roughness and the anodizing methods can give bioactive nanotubular surface for dental implant. Also, hydroxyapatite （HAp, Ca10（PO4）6（OH）2） has been widely used for coating materials on dental and orthopedic implants, due to their close similarly of chemical composition with natural bone tissue. The photoelectrochemistry is proven to be reliable and sensitive for giving information on structure and electronic properties of surface film to bone tissue.

关键词： Photoelectrochemistry Ti-35Nb-xZr alloy Femto second laser Hydroxyapatite EB-PVD

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Effects of HA/Ti Coating on the Corrosion of Nanostructured ...

Surface Phenomena of TiN/HA Coating on the Nanotubular Structured Beta Ti-29Nb-5Zr Alloy for Biomaterials

第18届国际真空大会

作者： Won-Gi Kim han-cheol choe Department of Dental Materials ＆ Research Center of Nano-Interface Activation for Biomaterials School of DentistryChosun University

β-Titanium alloys are highly attractive metallic materials for biomedical applications due to their high specific strength, high corrosion resistance and excellent biocompatibility, including low elastic modulus. The mechanical properties of Ti alloys can be tailor adjusted through compositional variation, thermomechanical processing and microstructural control. The Ta present in these alloys, a known β stabilizer reduces the modulus of the alloy. Further, the presence of β phase in the microstructure enhances the ability of the alloy to harden on subsequent aging. The addition of Zr results in high level of blood compatibility when used in cardiovascular implants and leads to better corrosion resistance due to the formation of stable oxide layer.

关键词： Ti alloy Nanostructure HA/Ti coating RF magnetron sputtering

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Surface Phenomena of TiN/HA Coating on the Nanotubular Struc...

Restimate:Recovery Estimation Tool for Resilience Planning

第18届国际真空大会

作者： Eun-Ju Kim han-cheol choe Yeong-Mu Ko Department of Dental Materials & Research Center of Nano-Interface Activation for Biomaterials School of DentistryChosun University Research Center for Oral Disease Regulation of the Aged School of DentistryChosun University

Titanium and its alloys are increasingly used in technological applications due to their excellent mechanical properties, high corrosion resistance and good biocompatibility. However, above alloys are also found to release toxic ions （e.g. V and Al） into the body, leading to undesirable long-term effects. In this regard, the β type titanium alloys composed of non-toxic elements, such as Nb, Zr, and Ta with lower moduli of elasticity and greater strength have been developed recently. From the surface treatment of Ti alloy for biomaterial fields, titanium oxide layer has been used to form the nanotubular structure for improving the biocompatibility of implants. The advantage of using TiO2 nanotubular structure is that it can be grown directly on the Ti and Ti alloys surfaces, by electrochemical methods such as anodic oxidation. Hydroxyapatite （HA, Ca10（PO4）6（OH）2） with characteristic features of a biomaterial, a crystallographic similarity with natural bone minerals, can be derived from both synthetic and natural origins and titanium nitride （TiN） has high hardness, low coefficient of friction, high corrosion resistance and good chemical stability for biomedical application. In this point, TiN/HA Multi-layered coating method can achieve a good adhesion property between nanotubular surface and human bone.

关键词： Ti-29Nb-5Zr Nanotubular structure Titanium nitride Hydroxyapatite Magnetron sputter

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Journal of Safety Science and Resilience 2024年第1期5卷 47-63页

作者： Scott Miles Megan Ly Nick Terry Youngjun choe Department of Human Centered Design&Engineering Campus Box 352315University of WashingtonSeattleWA 98195United States of America Department of Industrial&Systems Engineering Box 352650University of WashingtonSeattleWA 98195United States of America

The U.S.National Institute of Standards and Technology(NIST)published the Community Resilience Planning Guide in 2016.The NIST Guide advocates for a participatory process for developing a performance measurement framework for the jurisdiction’s resilience against a scenario hazard.The framework centers around tables of expected and desired recovery times for selected community assets,such as electricity,water,and natural gas infrastructures.The NIST Guide does not provide a method for estimating the expected recovery times.However,building high-fidelity computer models for such estimations requires substantial resources that even larger ju-risdictions cannot cost-justify.The most promising approach to recovery time estimation is to systematically use data elicited from people to tap into the wisdom of the(knowledgeable)crowd.This paper describes a novel research-through-design project to enable the computer-supported elicitation of recovery time series data.This work is the first in the literature to examine people’s ability to estimate recovery curves and how design in-fluences such estimations.Its main contribution to resilience planning is three-fold:development of a new elicitation tool called Restimate,understanding its potential user base,and providing insights into how it can facilitate resilience planning.Restimate is the first tool to enable evidence-based expert elicitation in any community with limited resources for resilience planning.Beyond resilience planning,those who facilitate high-stakes planning activities under large uncertainties(e.g.,mission-critical system design and planning)will benefit from a similar research-through-design process.

关键词： expert elicitation disaster natural hazard infrastructure community resilience restoration user-centered design computer-supported cooperative work