• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.227-228
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• 2006

Powder injection molding (PIM) is a suitable technology for the fabrication of complex shape titanium and its alloys, and has a great potential in many applications. This paper dealt with the injection molding of hydride dehydrogenization (HDH) titanium powder, spheroidized HDH titanium powder and gas atomized titanium powder. Rheological and thermalgravimetric behaviors were compared between the feedstocks of the three powders, and a tentative application of Ti PIM to eye frame temple and bridge was briefed.

• Journal of Korean Ophthalmic Optics Society
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• 제14권4호
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• pp.33-37
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• 2009

Purpose: To examine the coloring condition of titanium spectacle frames with various colors by using anodization method. Methods: We made an anodization coater. Platinum plate with $3{\times}3cm^2$ was used for a cathode and titanium spectacle frame specimens was mounted on an anode in an electrolyte. An electric source device were designed to supply steady state current. The color of the coated spectacle frame specimens were measured by a spectrophotometer equipped with an integrating sphere. We use CIE $L^*a^*b$ color system as chromaticity coordinates. Results: The thickness of $TiO_2$ of titanium spectacle frame specimens was varied as controlling current flow time for electrodes. The specimens with various kinds of color as a walnut, a yellow brown, a navy blue, a blue, a light blue, a mung bean, a yellowish green, a light purple, a purple, a flower pink, a bluish green, an emerald, and a green color etc. were obtained. The values of CIE $L^*a^*b^*$ for these specimens were measured and analyzed to be changed clockwise in chromaticity coordinates as the thickness of $TiO_2$ increases. Conclusions: We identified the coloring mechanism by anodization method in titanium spectacle frame specimens.

• Journal of the Korea Concrete Institute
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• 제27권4호
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• pp.363-375
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• 2015

This research investigated the effects of diameter and material of energy frame on the impact velocity or strain rate of Strain Energy Frame Impact Machine (SEFIM). The impact speed of SEFIM have been clearly affected by changing the diameter and material of the energy frame. The reduced diameter of the energy frame clearly increased the impact velocity owing to the higher strain at the moment of coupler breakage. And, titanium alloy energy frame produced the fastest speed of impact among three materials including steel, aluminum and titanium alloys because titanium alloy has faster wave velocity than steel. But, aluminium energy frame was broken during impact tests. In addition, the tensile stress versus strain response of high performance fiber reinforced cementitious composites at higher and wider strain rates between 10 and 72 /sec was successfully obtained by using four different energy frames.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.143-148
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• 2013

Novel titanium containing solid core mesoporous shell silica has been synthesized by using octadecyltrichloro silane and triethylamine. The synthesized material was characterized by various physicochemical techniques. The mesoporous character of the material has been revealed from PXRD studies. The presence of octadecyltrichloro silane and triethylamine in the sample has been confirmed from EDAX studies. TG/DTA analysis reveals the thermal characteristics of the synthesized material. The presence of titanium in the frame work and its coordination state has been studies by UV-vis DR studies and XPS analysis. Chemical environment of Si in the framework of the material has been studied by $^{29}SiMASNMR$ studies. The surface area of the material is found to be around $550\;m^2g^{-1}$ and pore radius is of nano range from BET analysis. The spherical morphology and particle size of the core as well as shell has been found to be 300 nm and 50 nm respectively from TEM analysis. The catalytic application of this material towards the synthesis of caprolactam from cyclohexanone in presence of hydrogen peroxide through ammoxidation reaction has been investigated. The optimum conditions for the reaction have been established. The plausible mechanism for the formation of core silica and conversion of cyclohexanone has been proposed.

• Transactions of Materials Processing
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• 제28권1호
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• pp.15-20
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• 2019

The superplastic forming/diffusion bonding process has been developed to fabricate a core frame structure with joint nodes out of tubes, for the development of a titanium high performance bicycle. The hydroforming process has been applied for bulging of a tube in the superplastic condition before, and during the diffusion bonding process. In this experiment, a commercial Ti-3Al-2.5V tube was selected as raw material for the study. The forming experiment has been performed using a servo-hydraulic press with a capacity of 200 ton. Next, nitrogen gas was used to acquire necessary pressure for the bulging and bonding of the tubes to fabricate the joint nodes. The pertinent processing temperature was $870^{\circ}C$ for the superplastic hydroforming/diffusion bonding (SHF/DB) process, using the Ti-3Al-2.5V tube. The bonding quality and the progress of bulging and diffusion bonding have been observed by the investigation of the joining interfaces at the cross section of the joint structure. The control of the nitrogen pressure throughout the SHF/DB process, was an important factor to avoid any significant defects in the joint structure. The whole progress stage of the diffusion bonding could be observed at a joint interface. A core structure with 5 joint nodes to manufacture a titanium bicycle could be obtained in a SHF/DB process.

• The Journal of Korean Academy of Prosthodontics
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• 제44권5호
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• pp.654-664
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• 2006

Statement of problem: There has been a eat interest in the use of titanium for fixed and removable prostheses in recent because of its excellent biocompatibility. However, the melting temperature and chemical reactivity of titanium necessities casting system different from those used in conventional casting. The current titanium casting systems are based on an electric-arc design for melting the metal in an argon atmosphere and its exclusive investment. Despite the new development in Ti casting system, inadequate mold filling and internal porosity are frequently observed casting defects. Purpose : The purposes of this study were to compare the castibility and reaction layer of the casting titanium under the two casting machines and their investment condition. Material and method: coping and machine-milled titanium coping according to the casting methods and the marginal configurations. The total 28 specimens were used, and these are divided into 4 groups according to 2 casting machines and 2 investments. The castings were analyzed using x-ray microanalysis and microhardness testing. The reaction layer between margin of titanium casting and the investments was observed and analyzed with scanning electron microscope. Result: 1. Castabiliy of casting titanium specimen was best in the group of centrifugal casting machine and Selevest $CB^{\circledR}$ and good that of Selevest CB and pressure differential casting machine, Rematitan plus and centrifugal casting machine, Rematitan plus and pressure differential casting machine in order. 2. There was no significanct correlation in titanium castability in respect of casting machine. However ANOVA indicated that Selevest $CB^{\circledR}$ groups had significantly better castability than Rematitan $plus^{\circledR}$ groups.(p<0.05) 3. There was a significant microhardness difference between centrifugal casting machine groups and pressure differential groups.(p<0.05) Titanium castings in centifugal groups had significantly harder than those in pressure differential groups. 4. The addition of zirconia decreased interfacial reactivity. Conclusion: above result revealed that of the castability of titanium casting specimens had little correlation in casting machines and was better in magnesia-based investment contained ZrO2 groups. However in order to practice casting titanium in clininic, its castability should be improved, also there should be more research on factor of castability so that long-span prothesis and removable partial denture metla frame may be casted completly.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제12권3호
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• pp.1058-1062
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• 2011

After the design and production of cold rolling to make titanium-alloyed(Gr.9) eyerim, the function of the roller was evaluated. The surface roughness values of the roller of Ra was $0.05{\sim}0.156{\mu}m$ and of Rz was $0.23{\sim}067{\mu}m$. The values showed a satisfactory result compared with the surface roughness values Ra was $0.04{\mu}m$ and Rz was $0.3{\mu}m$ which was measured after barrel polishing for the titanium eyeglasses frame PVD (Physical Vapor Deposition) gilding. As a result of cold rolling of Ti-3Al-2.5V (Half Titanium), the degree of hardness increased to 221Hv, 247Hv(1st), 270Hv(2nd), etc. Therefore, it was found that proper heat treatment and multi-stand rolling process are necessary.

• Composites Research
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• 제28권3호
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• pp.89-93
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• 2015

This study analyzes the transplanting parts used as the graft of artificial knee joint. The low elastic titanium alloy is applied to clear up the stress shield effect. The simulation analysis is carried about the stress distribution of the transplanting parts. The correlation with frame is inferred and investigated through the equivalent stress distribution of titanium alloy due to elastic modulus. The stress of the transplanting parts decreases as the elastic modulus decreases at the first time. It decreases greatly near the stress of 46 GPa and increases again. Because the stress happened at the transplanting parts decreases, more stress is applied on the frame. This phenomenon is the stress shield effect. The result of this study can be thought to be necessary to develop the safe design of composite material.

• Journal of Korean Ophthalmic Optics Society
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• 제20권1호
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• pp.9-14
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• 2015

Purpose: In this paper, the changes in eyeglasses frames were investigated when the frames were exposed to artificial sweat. Methods: The changes in surface, hardness, and tensile strength of eyeglasses frames made of nickel silver, Monel, and titanium were tested after the exposure to the artificial sweat of pH 6.5, 6.0, and 5.0, during 1, 3, and 6 week(s), for each. Results: Corrosion pattern of eyeglasses frames made of nickel silver, Monel, and titanium was induced by artificial sweat, and the patterns were different from another frame materials. In proportion to the pH of artificial sweat and exposure time to artificial sweat, hardness of all frames made of three different material decreased, however, tensile strength of the three frames was not changed. Conclusions: The necessity of routine management for eyeglasses frames can be suggested since the changes in surface corrosion and hardness of eyeglasses frames induced by sweat were shown.

• Transactions of the Korean Society of Automotive Engineers
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• 제13권3호
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• pp.117-122
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• 2005

Titanium alloy has widely been used as material for glasses frame parts because it has high specific strength. It is also light and harmless to human body. However, we have little design data about the mechanical properties such as the creep behaviors of the alloy. Therefore, in this study, creep tests under four constant stress conditions have been conducted with four different temperature conditions. A series of creep tests had been performed to get the basic design data and life prediction of titanium products and we have gotten the following results. First, the stress exponents decrease as the test temperatures increased. Secondly, the creep activation energy gradually decrease as the stresses became bigger. Thirdly, the constant of Larson-Miller parameter on this alloy was estimated as about 2.5. Finally, the fractographs at the creep rupture showed the ductile fracture due to the intergranullar rupture and some dimples.