• Journal of the Korean Society for Precision Engineering
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• v.9 no.4
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• pp.90-99
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• 1992

In resent year Laser Speckle and its development have enabled surface deformation of engineering components and materials to be interferometrically examined. Laser Speckle- Pettern Interferometry Method is a very useful method for measuring In-plane components of displacement. In measuring thermal expansion coefficient, the various problems generated were established, and the measuring limitation examined. Metarial INCONEL 601 was used in experiments. Specimen was heated to the high temperature(100$0^{\circ}C$) by diong current to the direct two specimen. Then, those problems appear to the influence of back-ground radiation by the heated specimen, the influence by air turbulence, the oxidation of specimen. The color monitor and interference filter prevented the back-ground radiation by rad heat. The oxidation occuring in specimen itself was not generated by the being acid-proof excellence of material INCONEL 601. Yet, in this experiments, the serious problems are the oxidation of specimen and influence by air turbulence. By more reserching these problems forward, it is helpful that the thermal expansion coefficient of many materials is directly measured under high temperature.

• Journal of Powder Materials
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• v.25 no.1
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• pp.48-53
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• 2018

One-dimensional rutile $TiO_2$ is an important inorganic compound with applicability in sensors, solar cells, and Li-based batteries. However, conventional synthesis methods for $TiO_2$ nanowires are complicated and entail risks of environmental contamination. In this work, we report the growth of $TiO_2$ nanowires on a Ti alloy powder (Ti-6wt%Al-4wt%V, Ti64) using simple thermal oxidation under a limited supply of $O_2$. The optimum condition for $TiO_2$ nanowire synthesis is studied for variables including temperature, time, and pressure. $TiO_2$ nanowires of ${\sim}5{\mu}m$ in length and 100 nm in thickness are richly synthesized under the optimum condition with single-crystalline rutile phases. The formation of $TiO_2$ nanowires is greatly influenced by synthesis temperature and pressure. The synthesized $TiO_2$ nanowires are characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM).

• Korean Journal of Metals and Materials
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• v.48 no.6
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• pp.514-522
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• 2010

Graphite epoxy composite material (GECM) shows high specific strength and its application in the aerospace industry is gradually increasing. However, its application would induce galvanic corrosion between GECM and metallic materials. This work focused on the effects of anodizing and thermal oxidation on galvanic corrosion in a 3.5% NaCl solution between GECM and aluminium and titanium. In the case of anodized aluminium, galvanic corrosion resistance to the GECM was greatly improved by the anodizing treatment regardless of area ratio. In the case of anodized titanium, the anodizing by a formation voltage of 50V increased corrosion resistance of titanium in galvanic tests. Thermal oxidation of titanium also improved corrosion resistance of Ti to GECM.

• Korean Chemical Engineering Research
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• v.45 no.2
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• pp.183-189
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• 2007

We have investigated the oxidation of gas phase elemental mercury using dielectric barrier discharge (DBD). In the DBD process, active species such as $O_3$, OH, O and $HO_2$ are generated by collisions between electrons and gas molecules. Search active species convert elemental mercury into mercury oxide which is deposited into the wall of DBD reactor because of its low vapor pressure. The oxidation efficiency of elemental mercury has been decreased from 60 to 30% by increasing the initial concentration of the elemental mercury from 72 to $655{\mu}g/Nm^3$. The gas retention time at the DBD reactor has showed the little effect on the oxidation efficiency. The more oxygen concentration has induced the more oxidation of elemental mercury, whereas there has been no appreciable oxidation within pure $N_2$ discharge. It has indicated that oxygen atom and ozone, generated in air condition determine the oxidation of elemental mercury.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.10
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• pp.106-112
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• 1990

The progress of oxidation of a porous silicon layer(PSL) was studied by examining the temperature dependence of the oxidation and the infrared absorption spectra. Thick OPSL(oxidized porous silicon layer). which has the same properties as thermal $SiO_{2}$ of bulk silicon, is formed in a short time by two steps wet oxidation of PSL at $700^{\circ}C$, 1 hr and $1100^{\circ}C$, 1 hr. Etching rate, breakdown strength of the OPSL are strongly dependent on the oxidation temperature, oxidation atmosphere. And its breakdown field was ${1\MV/cm^-2}$ MV/cm The oxide film stress was determined through curvature measurement using a dial gauge. During oxidation at temperature above $1000^{\circ}C$ in dry $O_{2}$, stress on the order of ${10^9}\dyne/{cm^2}{-10^10}\dyne/{cm^2}$ are generated in the OPSL.

• 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.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.2
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• pp.47-49
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• 2004

Gate protection $SiN_x$ as an alternative to a conventional re-oxidation process in Dynamic Random Access Memory devices is investigated. This process can not only protect the gate electrode tungsten against oxidation, but also save the thermal budget due to the re-oxidation. The protection $SiN_x$ process is applied to the poly-Si gate, and its device performance is measured and compared with the re-oxidation processed poly-Si gate. The results on the gate dielectric integrity show that etch damage-curing capability of protection $SiN_x$ is comparable to the re-oxidation process. In addition, the hot carrier immunity of the $SiN_x$ deposited gate is superior to that of re-oxidation processed gate.

• Transactions on Electrical and Electronic Materials
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• v.5 no.6
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• pp.215-218
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• 2004

This paper presents a three-dimensional numerical simulation for thermal oxidation process. A new elasto-viscoplastic model for robust numerical oxidation simulation is proposed. The three-dimensional effects of oxidation process such as mask lifting effect and corner effects are analyzed. In nano-scale process, the oxidant diffusion is punched through to the other side of the mask. The mask is lifted so the thickness of oxide region is greatly enhanced. The compressive pressure during the oxidation is largest in the mask corner of the island structure. This is because the masked area near the corner is surrounded by an area larger than the others in the island structure. This stress induces the retardation of the oxide growth, especially at the masked corner in the island structure.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.392-397
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• 2009

Gravity pressure vessels find their use in the wet oxidation of sewage sludge, which can be defined as the oxidation of organic and inorganic substances in an aqueous solution or suspension by means of oxygen or air at elevated pressures and temperatures. Numerical analyses were carried out for investigating the flow characteristics and wet air oxidation in the reaction vessel with various conditions such as supply oxidation and the supply positions of oxidation, etc. Wet air oxidation is promoted in the vicinity of bottom in the reactor with increase of oxygen supply. Also, it is the best condition to the oxidation supply position of 150 m and oxidation flow of 0.06 kg/s in the GPV reactor as the remnant of sludge and creation of organic acids.

• Korean Journal of Materials Research
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• v.6 no.1
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• pp.57-66
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• 1996

MoSi2 heating elements were fabricated by sintering of MoSi2 powders which were synthesized through SHS(Self-propagating high-temperature synthesis). Their high-temperature oxidation behavior in air through SHS(Self-propagating high-temperature synthesis). Their high-temperature oxidation behavior on air at 1000-1600$^{\circ}C$ was investigated through a high-temperature X-ray diffractomer and isothermal heating in a muffle furnace. The thermal expansion of MoSi2 and SiO2 was studied by measuring their lattice parameters on heating. The linear expansion coeffcient of MoSi2 along c-axis was about 1.5 times larger than that along a-axis showing a strong thermal anisotropy. Few $\mu\textrm{m}$-thick Mo5Si3 layer was found beneath SiO2 layer suggesting that The major reaction products would be SiO2 and Mo5Si3. The Si-rich bentonite resulted in the faster growth of MoSi2 grains probably by enhancing the mass transport when they are melted during high-temperature oxidation.