• Proceedings of the Korean Magnestics Society Conference
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• 2004.12a
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• pp.127-128
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• 2004

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.109-116
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• 2001

In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk in sliding are investigated. Also wear mechanism to form the oxide layer and the characteristics of the oxide layer formation are investigated. AIS152100 steel ball is used for the substrate of coated ball specimens. Two types of coated ball specimens were prepared by depositing TiN coating with 1 and 4um in coating thickness. AISI1045 steel is used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of the two materials, the tests were performed both in ambient for forming oxide layer on the contact parts and in nitride environment to avoid oxidation. And to study the effects of surface roughness of counter-body, TiN coating thickness and contact load of sliding test on the characteristics of oxide layer formation on counter-body, various tests were carried out. From the results, the friction characteristics between the two materials was predominated by iron oxide layer that formed on wear track on counter-body and this layer caused the high friction. And the formation rate of the oxide layer on wear track increased as the real contact area between the two materials increased as the contact load increased, the TiN coating thickness decreased and the surface of counter-body smoothened.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.319-323
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• 1988

For finding the effects of As on $TiSi_2$ formation, sputter deposited Ti film on Si substrates implanted with various doses of As have been rapid thermal annealed in Ar atmosphere at temperatures of 600-900$^{\circ}C$ for 20 sec. The sheet resistance of Ti-Silicides was examined with 4-point probe, the thickness with ${\alpha}$-step, and the As dopant behavior in Si substrates with ASR. The thickness of Ti-Silicides decreased with increasing As doping, but Ti-Silicides sheet resistance increased with increasing it. However, the critical concentration effect reported by Park et al. was not observed. We observed that the thickness of native oxide increase with increasing As doping. Thus, we concluded that native oxide act as a "barrier" for the Si diffusion.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.387-393
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• 1998

The formation of titanium diboride ($TiB_2$ ) via the reduction of $TiO_2$ with boric oxide and carbon was studied in a partially reducing atmosphere of argon mixed with 4 vol.%H2. The effect of reaction time, temperature, partial pressure of nitrogen and $TiO_2/B_2_O3$ stoichiometric ratio on the reducibility of oxides has been studied. The phases formed were analysed by using X-ray rowder diffraction and scanning sosctron microscopic techniques. In this paper, we also investigated the presence of $CaC_2$ as a reducing agent on the reducibility of oxide mixtures and on the Ti-B-C-Ca-O phase equilibria. The morphology of $TiB_2$ formed in the presence of $CaC_2$ is compared with the microstructure of $TiB_2$ formed as a consequence of carbothermic reduction. The observed variation in $TiB_2$ crystals formed is also explained.

• Korean Journal of Materials Research
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• v.17 no.1
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• pp.6-10
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• 2007

In the present study, we investigated the formation of self-organized nanostructure oxide layers on CP Ti and Ti-10Ta-10Nb alloy in an electrolyte of 1M phosphoric acid and 1.5 wt% Hydrofluoric acid. The morphology of oxide film on substrate was observed using scanning electron microscopy and transmission electron microscopy The surface roughness of titanium oxide film was analyzed by atomic force microscopy and the crystalline of specimen was investigated using X-ray diffractometer. The results of this study showed that well-aligned titanium oxide nanotubes are formed with diameter of approx. 100nm and length of approx. 500nm with CP Ti. However, it is clear that TiTaNb alloy highly irregular structure with various diameters. Transmission electron microscope investigations show that the specimens were confirmed as amorphous. Such titanium oxide nanotubes are expected a well-adhered bioacitive surface layer on titanium substrate for orthopedics and dental implants.

• Korean Journal of Materials Research
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• v.33 no.2
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• pp.77-86
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• 2023

High-temperature oxidation of a Ni-based superalloy was analyzed with samples taken from gas turbine blades, where the samples were heat-treated and thermally exposed. The effect of Cr/Ti/Al elements in the alloy on high temperature oxidation was investigated using an optical microscope, SEM/EDS, and TEM. A high-Cr/high-Ti oxide layer was formed on the blade surface under the heat-treated state considered to be the initial stage of high-temperature oxidation. In addition, a PFZ (γ' precipitate free zone) accompanied by Cr carbide of Cr₂₃C₆ and high Cr-Co phase as a kind of TCP precipitation was formed under the surface layer. Pits of several ㎛ depth containing high-Al content oxide was observed at the boundary between the oxide layer and PFZ. However, high temperature oxidation formed on the thermally exposed blade surface consisted of the following steps: ① Ti-oxide formation in the center of the oxide layer, ② Cr-oxide formation surrounding the inner oxide layer, and ③ Al-oxide formation in the pits directly under the Cr oxide layer. It is estimated that the Cr content of Ni-based superalloys improves the oxidation resistance of the alloy by forming dense oxide layer, but produced the σ or µ phase of TCP precipitation with the high-Cr component resulting in material brittleness.

• Tribology and Lubricants
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• v.18 no.4
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• pp.260-266
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• 2002

In this study, the effects of oxide layer farmed on the wear tracks of TiN coated silicon wafer on friction and wear characteristics were investigated. Silicon wafer was used for the substrate of coated disk specimens, which were prepared by depositing TiN coating with 1 ${\mu}{\textrm}{m}$ in coating thickness. AISI 52100 steel ball was used fur the counterpart. The tests were performed both in air for forming oxide layer on the wear track and in nitrogen to avoid oxidation. This paper reports characterization of the oxide layer effects on friction and wear characteristics using X-ray diffraction(XRD), Auger electron spectroscopy(AES), scanning electron microscopy (SEM) and multi-mode atomic force microscope(AFM).

• Korean Journal of Materials Research
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• v.12 no.5
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• pp.353-358
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• 2002

The microstructure and growth behaviors of anodic oxide layers on titanium were investigated. $TiO_2$ oxide films were prepared by anodizing at constant voltages of 180 and 200V in sulfuric acid electrolyte. The anodic $TiO_2$ layer formed at 200V showed a cell structure with more irregular pore shapes around the interface between the anodic oxide layer and the substrate titanium compared with that formed at 180V. Irregular shape of pores at the initial stage of anodization seemed to be attributed to spark discharge phenomena which heavily occurred during increasing voltages. The thickness of the anodic oxide film increased linearly at a rate of $1.9{\times}10^{ -1}\mu\textrm{m}$/min. The oxide layers formed at 180 and 200V were composed mainly of anatase structure, and the anodizing process could be suggested as one of fabrication methods of photocatalytic $TiO_2$.

• Korean Journal of Metals and Materials
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• v.46 no.6
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• pp.370-376
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• 2008

The formation of anodic oxide film of titanium (Ti) was studied at a variety of electrolyte concentrations and current density to clarify their effects on morphology, microstructure and composition of Ti oxide layer. For the analysis of the Ti oxide films, a scanning electron microscopy (SEM), X-ray diffractometer (XRD), and X-ray photoelectron spectroscopy (XPS) were used. The results showed that the concentration of phosphoric acid played a crucial role in the crystalline structure of the Ti oxide layer while the current density gave a critical effect on the thickness and diameter of its pore. In particular, the crystalline anatase phase with a thickness larger than $2{\mu}m$, which is quite desirable for a dental implant application, could be readily prepared at the phosphoric acid concentration of 0.5 M and current density higher than $2.0A/dm^2$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.31.2-31.2
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• 2011

We have investigated frequency dependant conductivity (or permittivity) of low dimensional oxide structures represented by [($Sr_{0.75}$, $La_{0.25}$)$TiO_3$]$_1$/1$[SrTiO_3]_n$ superlattices. The low dimensional oxide superlattice was made by cumulative stacking of one unit cell thick La doped $SrTiO_3$ and $SrTiO_3$ with variable thickness from 1 to 6 unit cell, i,e, [($Sr_{0.75}$, $La_{0.25}$)$TiO_3$]$_1$/$[SrTiO_3]_n$ (n=1, 2, 3, 4, 5, 6). We found two kinds of relaxation when n is 3 and 4, while, inductance component was observed at n=1. This behavior can be explained by electron modulation in ($Sr_{0.75}$, $La_{0.25}$)$TiO_3/SrTiO_3$ superlattices. When n is 1, electrons by La doping well extend to un-doped layer. Therefore, the transport of superlattices follows bulk-like behavior. On the other hand, as n increased, the doped electrons became two types of carrier: one localized and the other extended. These results in two kinds of transport phase. At further increase of n, most of doped electrons are localized at the doped layer. This result shows that dimensionality of the oxide structure significantly affect the transport of oxide nanostructures.