• Journal of the Korean Society for Heat Treatment
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• v.32 no.3
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• pp.124-130
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• 2019

Friction stir welding is one of the interesting welding methods for titanium and its alloy which proceeds with plastic flow due to thermo-mechanical stirring and friction heat. Solid-state welding can solve severe problems such as high-temperature oxidation, interstitial oxygen diffusion and grain coarsening by liquid-state welding. Dynamic recrystallization and grain refinement can vary significantly with the plunging load and rotational speed of tool during friction stir welding, and suitable process conditions must be optimized to obtain microstructure and better mechanical characteristics. Suitable FSW conditions were 1000 kg of plunging load and 200 rpm of rotational speed and it showed YS 270 MPa, UTS 332.1 MPa, and El 17.3%, which were very similar to those of wrought titanium sheet.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.9
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• pp.729-734
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• 2000

Recently, Very Large Scale Integrated (VLSI) circuit & deep-submicron bulk Complementary Metal Oxide Semiconductor(CMOS) devices require gate electrode materials such as metal-silicide, Titanium-silicide for gate oxides. Many previous authors have researched the improvement sub-micron gate oxide quality. However, few have reported on the electrical quality and reliability on the ultra thin gate oxide. In this paper, at first, I recommand a novel shallow trench isolation structure to suppress the corner metal-oxide semiconductor field-effect transistor(MOSFET) inherent to shallow trench isolation for sub 0.1${\mu}{\textrm}{m}$ gate oxide. Different from using normal LOCOS technology deep-submicron CMOS devices using novel Shallow Trench Isolation(STI) technology have a unique"inverse narrow-channel effects"-when the channel width of the devices is scaled down, their threshold voltage is shrunk instead of increased as for the contribution of the channel edge current to the total channel current as the channel width is reduced. Secondly, Titanium silicide process clarified that fluorine contamination caused by the gate sidewall etching inhibits the silicidation reaction and accelerates agglomeration. To overcome these problems, a novel Two-step Deposited silicide(TDS) process has been developed. The key point of this process is the deposition and subsequent removal of titanium before silicidation. Based on the research, It is found that novel STI structure by the SEM, in addition to thermally stable silicide process was achieved. We also obtained the decrease threshold voltage value of the channel edge. resulting in the better improvement of the narrow channel effect. low sheet resistance and stress, and high threshold voltage. Besides, sheet resistance and stress value, rms(root mean square) by AFM were observed. On the electrical characteristics, low leakage current and trap density at the Si/SiO$_2$were confirmed by the high threshold voltage sub 0.1${\mu}{\textrm}{m}$ gate oxide.

• Journal of Welding and Joining
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• v.28 no.4
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• pp.73-80
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• 2010

In this work, the effect of welding variables on weldability of gas tungsten arc(GTA) welding was investigated with experimental analysis for a commercial pure(CP) titanium (Grade.1). The GTA welding tests on sheet samples with 0.5mm in thick were carried out at different process variables such as arc length, welding speed and electrode shape. In order to search an optimum arc length with full penetration, bead- on-plate welding before butt-welding were performed with different arc length conditions. From the bead- on-plate welding results, the optimum condition considering arc stability and electrode loss was obtained in the arc length of 0.8mm. Butt-welding tests based on the arc length of 0.8mm were carried out to achieve the optimum conditions of welding speed and electrode shape. Optimum conditions of welding speed and electrode shape were suggested as 10 mm/s and truncated electrode shape, respectively. It was successfully validated by the microstructural observation, tensile tests, micro-hardness tests and formability tests.

• Korean Journal of Metals and Materials
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• v.46 no.11
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• pp.747-754
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• 2008

Recently, the requirement for the ultra thin copper foil increases with smaller and miniaturized electronic components. Therefore, it is important to examine the surface state of substrate depending on the processing parameter during the anodic oxidation. This study investigated the effect of the various electrolyte concentrations on anodizing of titanium anode prior to copper electrodeposition. Different surface morphology of anodized titanium was obtained at different electrolytic concentration 0.5 M to 3.0 M. In addition, the effect that the surfaces and the electrical characteristics on the electrodeposited copper layer was observed. In this study, surface anodized in the group containing 0.5M $H_2SO_4$ shows more uniform copper crystals with low surface roughness. the surface roughness and sheet resistance for 0.5M $H_2SO_4$ group were $1.353{\mu}m$ and $0.104m{\Omega}/sq$, respectively.

• Polymer(Korea)
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• v.38 no.1
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• pp.103-107
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• 2014

Poly(acrylonitrile-butadiene-styrene) (ABS) composite sheets containing titanium dioxide ($TiO_2$), barium sulfate ($BaSO_4$), calcium carbonate ($CaCO_3$) were prepared by using a co-rotating twin screw extruder, and the reflectance and flexural modulus of the composite sheets were measured. The fillers were well dispersed in ABS matrix. The reflectance of composite sheet was increased with increasing $TiO_2$ and $BaSO_4$ content. Sheet having $TiO_2$ 20 wt% composition, with 5~20 wt% $BaSO_4$ resulted in more than 95% of reflectance. The flexural modulus of composite sheet was increased from 1864 MPa for $ABS/TiO_2/BaSO_4$ 85/10/5 (w/w/w) to 3134 MPa for $ABS/TiO_2/BaSO_4$ 55/20/25 (w/w/w).

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.6
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• pp.620-627
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• 2008

STATEMENT OF PROBLEM: A biochemical approach for surface modification has offered an alternative for physicochemical and morphological methods to obtain desirable bone-implant interfaces. PURPOSE: The purpose of the present study was to investigate cell responses to poly (D,L-lactide-co-glycolide) (PLGA)/$1{\alpha}$,25-(OH)$_2D_3$ coating with reference to cellular proliferation and differentiation in vitro. MATERIAL AND METHODS: 96 titanium discs were fabricated and divided into four groups. Group 1 was anodized under 300 V as control. Group 2, 3 and 4 were anodized then coated with 3 ml PLGA/$1{\alpha}$,25-(OH)$_2D_3$ solutions. Amount of the solutions were 2 ul, 20 ul and 200ul respectively. The osteoblast-like Human Osteogenic Sarcoma (HOS) cells were seeded and cultured for 1, 3 and 7 days. MTSbased cell proliferation assay and ALPase activity test were carried out. RESULTS: PLGA nanoparticles were observed as fine, smooth and round and HOS cells attached to the anodized surfaces through strand-like and sheet-like filopodia. After 3 days of culture, the dendritic filopodia were exaggerated and sheet-like cytoplasmic projections covered the coated titanium surfaces. After 3 days of culture, all of the groups showed increased cellular proliferation and the lowest proliferation rate was measured on group 2. Higher amount of incorporated $1{\alpha}$,25-(OH)$_2D_3$ (Group 3 and 4) improved cellular proliferation but the differences were not significant statistically (P > .05). But they increased the rate of ALP activities than the control group at day 3 (P < .05). CONCLUSION: Biodegradable PLGA nanoparticles incorporated with vitamin D metabolite positively affected proliferation and differentiation of cells on the anodized titanium surface.

• Korean Journal of Materials Research
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• v.12 no.11
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• pp.865-869
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• 2002

We investigated the reaction stability of titanium, cobalt and their bilayer films with side-wall spacer materials of SiO$_2$ for the salicide process. We prepared Ti 350 $\AA$, Co 150 $\AA$, Co 150 $\AA$/Ti 100 $\AA$ and Ti 100 $\AA$/Co 150 $\AA$ films on 1000 $\AA$-thick thermally grown SiO$_2$ substrates, respectively. Then the samples were rapid thermal annealed at the temperatures of $500^{\circ}C$, $600^{\circ}C$, and $700^{\circ}C$ for 20 seconds. We characterized the sheet resistance of the metallic layers with a four-point probe, surface roughness with scanning probe microscope, residual phases with an Auger depth profilometer, phase identification with a X-ray diffractometer, and cross-sectional microstructure evolution with a transmission electron microscope, respectively. We report that Ti reacted with silicon dioxide spacers above $700^{\circ}C$, Co agglomerated at $600^{\circ}C$, and Co/Ti, Ti/Co formed CoTi compound requiring a special wet process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.5
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• pp.399-405
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• 1990

Rapid Thermal Process(RTP) has been used to precisely control and study the reaction rate for the formation of refractory titanuium silicide. Samples were prepared by sputtering deposition layer of titanium on n-type, poly-deposit silicon wafers. The process were then sujected to a matrix of rapid time-temperature profile under nitrgen, argon gas ambient to precisely control the silicide formation. Reacted films were analyzed by the sheet resistance measursrement, SEM, ASR and X-ray diffraction. Results were shown that the resistivity of the silicide films are below 20u-cm and the thickness of silicide films are about two times than that of as-deposited titanium films. Silicidation ambient was likely to happen at the same tamperature-time condition for argon and nitrogen gas.

• Journal of Welding and Joining
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• v.34 no.6
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• pp.69-74
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• 2016

Because the pure titanium has superior corrosion resistance and formability compared with different material, it is widely used as material of welded heat exchanger. When the welding of heat exchanger is carried out, certain area in which welding start and end are overlapped occurs. The humping of back bead is formed in the overlap area due to partial penetration. Thus in this study, the experiments were carried out by changing the length and wave shape of overlap area, and then the weldabiliay was evaluated through the observation of microstructure, the measurement of hardness and tensile-shear strength test in the overlap area. When overlap length was 9.8mm, humping bead was suppressed. The microstructure of overlap area coarsened and its hardness increased due to remelting. As a result of tensile-shear strength test in the overlap area according to applying the wave shape control, it was confirmed that the overlap area applied wave shape control had more excellent yield strength and ductility.

• Journal of Electrical Engineering and Technology
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• v.6 no.5
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• pp.684-687
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• 2011

In this study, we investigate the photovoltaic performance of transparent conductive indium tin oxide (ITO), titanium-doped indium oxide (ITiO), and fluorine-doped tin oxide (FTO) films. ITO and ITiO films are prepared by radio frequency magnetron sputtering on soda-lime glass substrate at $300^{\circ}C$, and the FTO film used is a commercial product. We measure the X-ray diffraction patterns, AFM micrographs, transmittance, sheet resistances after heat treatment, and transparent conductive characteristics of each film. The value of electrical resistivity and optical transmittance of the ITiO films was $4.15{\times}10^{-4}\;{\Omega}-cm$. The near-infrared ray transmittance of ITiO is the highest for wavelengths over 1,000 nm, which can increase dye sensitization compared to ITO and FTO. The photoconversion efficiency (${\eta}$) of the dye-sensitized solar cell (DSC) sample using ITiO was 5.64%, whereas it was 2.73% and 6.47% for DSC samples with ITO and FTO, respectively, both at 100 mW/$cm^2$ light intensity.