• Korean Journal of Metals and Materials
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• v.47 no.2
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• pp.91-98
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• 2009

The titania nanotubular layer for photocatalytic application was synthesized by anodization process in HF solution and the photocatalytic efficiencies of nanotubular film were evaluated by the decomposition rate of aniline blue. In order to facilitate the photocatalytic reaction, the electron acceptors such as potassium bromate, hydrogen peroxide and ammonium persulfate were added to aniline blue solution and the effects of electron acceptors on the dye degradation efficiency were evaluated. The results showed that the photocatalytic efficiency has markedly improved by adding the electron acceptors.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.138-138
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• 2015

In this study, highly ordered nanotubular surface of Ti-25Ta-xHf alloys for dental applications was researched. Ti-25Ta-xHf alloys were contained from 0% to 15% Hf content. Formation of nanotubular structure was achieved by an electrochemical method in 1M $H_3PO_4$ electrolytes containing 0.8%wt. % NaF.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.108-108
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• 2015

In order to investigate on hydroxyapatite precipitation phenomena on nanotubular Ti-29Nb-xHf ternary alloys, Ti-29Nb-xHf alloys contained (0% to 15%) Hf were manufactured using arc melting furnace. Formation of nanotubular structure was achieved by an electrochemical method in 1M $H_3PO_4$ electrolytes containing 0.8%wt. % NaF. Electrochemical deposition was carried out using cyclic and voltammetry(CV) method at $85^{\circ}C$ in $5mM\;Ca(NO_3)_2+3mM\;NH_4H_2PO_4$. HA coating on nanotube formed Ti-29Nb-xHf ternary alloys showed a good wettability.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.1
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• pp.16-21
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• 2011

Purpose: The purpose of this study was to investigate the bioactivity of precalcified nanotubular $TiO_2$ layer on Ti-6Al-7Nb alloy. Materials and methods: Anodic oxidation was carried out at a potential of 20 V and current density of 20 mA/$cm^2$ for 1 hour. The glycerol solution containing 1 wt% $NH_4F$ and 20 wt% deionized water was used as an electrolyte. Precalcification treatment was obtained by soaking in $Na_2HPO_4$ solution at $80^{\circ}C$ for 30 minutes followed by soaking in saturated $Ca(OH)_2$ solution at $100^{\circ}C$ for 30 minutes, followed by heat treatment at $500^{\circ}C$ for 2 hours. To evaluate the activity of precalcified nanotubular $TiO_2$ layer, specimens were immersed in a simulated body fluid with pH 7.4 at $36.5^{\circ}C$ for 10 days. Results: 1. Nanotubular $TiO_2$ layer showed the highly ordered dense structure by interposing small diameter nanotubes between large ones, the shape of nanotubes was enlarged as going down. 2. The mean length of nanotubes was $517.0{\pm}23.2\;nm$ innm glycerol solution containing 1 wt% $NH_4F$ and 20 wt% $H_2O$ at 20 V for 1 hour. 3. The bioactivity of Ti-6Al-7Nb alloy was improved with formation of nanotubular $TiO_2$ layer and precalcification treatment in $80^{\circ}C$ 0.5 M $Na_2HPO_4$ and saturated $100^{\circ}C$ $Ca(OH)_2$ solution. Conclusion: Bioactivity of precalcified nanotubular $TiO_2$ layer on Ti-6Al-7Nb alloy was improved.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.81-82
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• 2013

In this study, precipitation behaviors of hydroxyapatite on highly ordered nanotubular Ti-35Ta-xNb alloy surface were researched. Ta and Nb additions to Ti increased corrosion resistance. The surface characteristics of anodized alloy depended on the nanotube formed voltage and alloy element. The HA precipitation morphology was influenced by nanorubular structure of alloys.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.194-194
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• 2013

In order to investigate nanotube morphology change of Ti-6Al-4V alloys by heat treatments, the Ti-6Al-4V alloys were used in this study. In non-treated Ti-6Al-4V alloy case, nanotubes only exhibited at ${\alpha}$ phase region with dissolved V-oxide area of ${\beta}$ phase. However, in Ti-6Al-4V alloy at $800^{\circ}C$ WQ case, nanotubes exhibited at both ${\alpha}$ and ${\beta}$ phase region. Electrochemical corrosion studies showed that the nanotubular alloy at $800^{\circ}C$WQ possesses slightly higher corrosion resistance than non-treated nanotubular alloy.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.1
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• pp.33-38
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• 2015

In this study, flat-type photocatalytic reaction system is applied to reduce toxic hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) in aqueous solution under UV irradiation. To overcome the limitation of conventional photocatalysis, a novel approach toward photocatalytic system for reduction of hexavalent chromium including nanotubular $TiO_2$ (NTT) on two kinds of titanium substrates (foil and mesh) were established. In addition, modified Ti substrates were prepared by bending treatment to increase reaction efficiency of Cr(VI) in the flat-type photocatalytic reactor. For the fabrication of NTT on Ti substrates, Ti foil and mesh was anodized with mixed electrolytes ($NH_4F-H_2O-C_2H_6O_2$) and then annealed in ambient oxygen. The prepared NTT arrays were uniformly grown on two Ti substrates and surface property measurements were performed through SEM and XRD. Hydraulic retention time(HRT) and substrate type were significantly affected the Cr(VI) reduction. Hence, the photocatalytic Cr(VI) reduction was observed to be highest up to 95% at bended(modified) Ti mesh and lowest HRT. Especially, Ti mesh was more effective as NTT substrate in this research.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.164-170
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• 2012

Nanotubular structure formation on the Ti-6Al-4V and Ti-Ta alloy surfaces by electrochemical methods has been studied using the anodizing method. A nanotube layer was formed on Ti alloys in 1.0 M $H_3PO_4$ electrolyte with small additions of $F^-$ ions. The nanotube nucleation and growth of the ${\alpha}$-phase and ${\beta}$-phase appeared differently, and showed different morphology for Cp-Ti, Ti-6Al-4V and Ti-Ta alloys. In the ${\alpha}$-phase of Cp-Ti and martensite ${\alpha}^{\prime}$ and in the ${\alpha}^{{\prime}{\prime}}$ and ${\beta}$-phase of the Ti-Ta alloy, the nanotube showed a clearly highly ordered $TiO_2$ layer. In the case of the Ti-Ta alloy, the pore size of the nanotube was smaller than that of the Cp-Ti due to the ${\beta}$-stabilizing Ta element. In the case of the Ti-6Al-4V alloy, the ${\alpha}$-phase showed a stable porous structure; the ${\beta}$-phase was dissolved entirely. The nanotube with two-size scale and high order showed itself on Ti-Ta alloys with increasing Ta content.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.111-111
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• 2013

골이식 부위에서 연조직의 붕괴를 막아주면서 골이식재를 위한 안정적인 공간을 확보하기 위해서 타이타늄 메쉬가 적용된다. 본 연구에서 생체 불활성의 특성을 보이는 타이타늄 차폐막에 양극산화와 석회화 순환처리에 의해서 생체활성을 부여한 결과, 골형성을 촉진하는 결과를 보여주었다.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.121-127
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• 2015

Nanotubular $TiO_2$ prepared by electrochemical anodization has been significantly used for various applications due to high aspect ratio structures showing a high chemical stability. Morphological properties of nanotubular titanium oxide are easily tailored by adjusting types and compositions of electrolyte, pH value, applied voltage, temperature and anodization time. Since their catalytic properties can be enhanced by doping foreign elements into $TiO_2$, metal as well as non-metal elements are doped into $TiO_2$ nanotubes using different methods. For example, single anodization, thermal annealing, precipitation, and electrochemical deposition have been applied to simplify the doping process. In this review, anodization of Ti to produce $TiO_2$ and doping methods will be discussed in detail.