• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2003년도 춘계학술발표회 초록집
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• pp.42-42
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• 2003

• Journal of Welding and Joining
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• 제31권2호
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• pp.16-20
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• 2013

Titanium and its alloys have been widely using in the various field of industry application due to high corrosion resistant properties and mechanical properties. Titanium is highly reactive in the high temperature state and the formation of titanium oxide and porosities in the nuggets of fusion welding will results in the degradation of the mechanical properties. For this reason the studies of friction stir welding for titanium have been investigated recently. The FSW zones of titanium were classified by the weld nugget (WN), the linear transition boundary (TB) and the heat affected zone (HAZ). The WN along with titanium parent was characterized by the presence of twins and dislocations. The average grain size and hardness of WN has been changed according to heat input. The grain refinement resulted from the FSW increased the hardness in the stir zone. Sound dissimilar joints between SUS 304 and CP-Ti were achieved using an advancing speed of 50 mm/min and rotation speeds in the range of 700-1100 rpm. Aluminum 1060 and titanium alloy Ti-6Al-4V plates were lap joined by friction stir welding, hence the ultimate tensile shear strength of joint reached 100% of Al 1060. Mg alloy and Ti were successfully butt joined by inserting a probe into the Mg alloy plate with slightly offsetting. But Ti-Al intermetallic compound layers formed at the interface of these joints.

• 자원리싸이클링
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• 제11권5호
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• pp.24-29
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• 2002

철강압연공장에서 산세공정중 발생하는 산화철의 색상을 개선하기 위하여 배소로 조업과 색상혼합공정을 연구하였다. 배소로 조업에서는 조업온도, 폐산장입량, 폐산분사 노즐수에 대하여 검토하였으며, 색상혼합공정에서는 산화티탄, 실리카, 괴타이트를 색상혼합재로 검토하였다. 배소로 조업에서는 조업온도를 낮게 할수록 산화철의 명도가 개선되었으며, 색상혼합공정에서는 괴타이트 첨가 경우에 제일 많이 산화철의 적색 및 명도가 개선되었다.

• 한국분말재료학회지
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• 제16권5호
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• pp.310-315
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• 2009

Ultra-fine TiC/Co composite powder was synthesized by the carbothermal reduction process without wet chemical processing. The starting powder was prepared by milling of titanium dioxide and cobalt oxalate powders followed by subsequent calcination to have a target composition of TiC-15 wt.%Co. The prepared oxide powder was mixed again with carbon black, and this mixture was then heat-treated under flowing argon atmosphere. The changes in the phase, mass and particle size of the mixture during heat treatment were investigated using XRD, TG-DTA and SEM. The synthesized oxide powder after heat treatment at 700$^{\circ}C$ has a mixed phase of TiO$_2$ and CoTiO$_3$ phases. This composite oxide powder was carbothermally reduced to TiC/Co composite powder by the solid carbon. The synthesized TiC/Co composite powder at 1300$^{\circ}C$ for 9 hours has particle size of under about 0.4 $\mu$m.

• 대한기계학회논문집B
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• 제29권9호
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• pp.1065-1073
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• 2005

The thermal conductivity of water- and ethylene glycol-based nanofluids containing alumina $(Al_2O_3)$, zinc oxide (ZnO) and titanium dioxide $(TiO_2)$ nanoparticles is measured by varying the particle diameter and volume fraction. The transient hot-wire method using an anodized tantalum wire for electrical insulation is employed for the measurement. The experimental results show that nanofluids have substantially higher thermal conductivities than those of the base fluid and the ratio of thermal conductivity enhancement increases linearly with the volume fraction. It has been found that the ratio of thermal conductivity enhancement increases with decreasing particle size but no empirical or theoretical correlation can explain the particle-size dependence of the thermal conductivity. This work provides, for the first time to our knowledge, a set of consistent experimental data over a wide range of nanofluid conditions and can therefore serve as a basis for developing theoretical models to predict thermal conduction phenomena in nanofluids.

• Tribology and Lubricants
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• 제18권2호
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• pp.167-172
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• 2002

The wear behaviors of ultrahigh molecular weight polyethylene pins against titanium alloy and stainless steel disks moving in two different kinematic motion were investigated by conducting repeat pass rotational sliding and linear reciprocal sliding wear tests. Linear reciprocal motion wore more the polyethylene pin than did repeat pass rotational motion for both disk materials. It means that the repeated directional change of contact stresses generates more wear debris in polyethylene. For the linear reciprocal sliding tests, titanium alloy disks were damaged with some scratches after one million cycles but no surface damage was observed on the polyethylene pins. On the other hand, fur the repeat pass rotational sliding tests, all titanium alloy disks were severely abraded on the entire region of sliding track. This phenomenon can be interpreted by that stress fatigue under repeated sliding contact initiated titanium oxide layer wear particles from disk surface, and these hard particles were embedded into polyethylene pin and then they severely abraded the disk surface. From these results it can be concluded that the kinematic motion in pin-on-disk wear tests play a crucial role on the wear behaviors of UHMWPE pins against titanium alloy and stainless steef discs.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.306-306
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• 2007

The surface was transformed to porous titanium oxide by the anodization of pure titanium. Titanium was anodized in non-aqueous and aqueous electrolytes at different potentials between 5 V and 150 V. Various electrolytes were compose of ethylene glycerol, $H_2SO_4,\;NH_4F\;and\;H_2O$. We obtained titania nanotube arrays on the micro pore of titanium. Micro pores and nano tubes were obtained by anodization at high potentials and low potentials, respectively. Morphologies of nanotubes and micro pore were characterized by FE-SEM. The unique surface structure is very attractive to electrical and medical applications such as gas sensor, biosensor, dental implant and stent.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.67-71
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• 2000

The wear behaviors of ultrahigh molecular weight polyethylene pins against titanium alloy and stainless steel disks moving in two different kinematic motion were investigated by conducting repeat pass rotational sliding and linear reciprocal sliding wear tests. Linear reciprocal motion wore more the polyethylene pin than did repeat pass rotational motion for both disk materials. It means that the repeated directional change of contact stresses generates more wear debris in polyethylene. For the linear reciprocal sliding tests, titanium alloy disks were damaged with some scratches after one million cycles but no surface damage was observed on the polyethylene pins. On the other hand, for the repeat pass rotational sliding tests, all titanium alloy disks were severely abraded on the entire region of sliding track. This phenomenon can be interpreted by that stress fatigue under repeated sliding contact initiated titanium oxide layer wear particles from disk surface, and these hard particles were embedded into polyethylene pin and then they severely abraded the disk surface. From these results it can be concluded that the kinematic motion in pin-on-disk wear tests play a crucial role on the wear behaviors of UHMWPE pins against titanium alloy and stainless steel disks.

• 한국산학기술학회논문지
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• 제14권2호
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• pp.846-849
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• 2013

$TiO_2$ 박막을 저온 열처리 졸-겔 법으로 합성하였다. 박막의 기판은 면적이 $100mm^2$인 붕규산염 유리를 사용하여 시료를 $300^{\circ}C$부터 $1100^{\circ}C$까지 열처리하였고, 이때 제조된 박막의 두께는 약 $1.5{\mu}m$정도였다. $300^{\circ}C$에서 2시간 동안 열처리한 $TiO_2$ 박막은 아나타제 상을 나타내었고 열처리 온도가 증가함에 따라 비정질 상태에서 아나타제상과 루타일 상이 공존하면서 각 상의 분율이 변화하였다. SEM 분석에 의하면 박막의 입자 크기는 $0.1{\sim}0.54{\mu}m$이었으며 Uv-visible 반사특성에 있어서 390nm부근에서 광흡수가 되는 것을 알 수 있었다. 따라서 낮은 열처리 온도에서 생성된 $TiO_2$ 박막은 주로 아나타제 상을 가지며 광촉매 특성을 2.4배 증가시키는 것으로 나타났다.

• 대한치과보철학회지
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• 제46권3호
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• pp.227-237
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• 2008

STATEMENT OF PROBLEM: Zirconium oxide can be a substitute to titanium as implant materials to solve the esthetic problems of dark color in the gingival portion of implant restorations. PURPOSE: This study was performed to define attachment and growth behavior of osteoblast- like cells cultured on grooved surfaces of zirconium oxide and evaluate the genetic effect of zirconium oxide surfaces using the reverse transcriptase-polymerase chain reaction (RT-PCR). MATERIAL AND METHODS: MC3T3-E1 cells were cultured on (1) commercially pure titanium discs with smooth surface (T group), (2) yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) with machined surface (ZS group), and (3) Y-TZP with $100{\mu}m$ grooves (ZG group). Cell proliferation activity was evaluated through MTT assay and cell morphology was examined by SEM. The mRNA expression of Runx2, alkaline phosphatase, osteocalcin, TGF-${\beta}1$, IGF-1, G3PDH in E1 cells were evaluated by RT-PCR. RESULTS: From the MTT assay, after 48 hours of adhesion of MC3T3-E1 cells, the mean optical density value of T group and ZG group significantly increased compared to the ZS group. SEM images of osteoblast-like cells showed that significantly more cells were observed to attach to the grooves and appeared to follow the direction of the grooves. After 24 hours of cell adhesion, more spreading and flattening of cells with active filopodia formation occurred. Results of RT-PCR suggest that T group, ZS group, and ZG group showed comparable osteoblast-specific gene expression after 24 hours of cell incubation. CONCLUSION: Surface topography and material of implants can play an important role in expression of osteoblast phenotype markers. Zirconia ceramic showed comparable biological responses of osteoblast-like cells with titanium during a short-time cell culture period. Also, grooves influence cell spreading and guide the cells to be aligned within surface grooves.