• Journal of Powder Materials
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• v.22 no.4
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• pp.271-277
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• 2015

As wrought stainless steel, sintered stainless steel (STS) has excellent high-temperature anti-corrosion even at high temperature of $800^{\circ}C$ and exhibit corrosion resistance in air. The oxidation behavior and oxidation mechanism of the sintered 316L stainless was reported at the high temperature in our previous study. In this study, the effects of additives on high-temperature corrosion resistances were investigated above $800^{\circ}C$ at the various oxides ($SiO_2$, $Al_2O_3$, MgO and $Y_2O_3$) added STS respectively as an oxidation inhibitor. The morphology of the oxide layers were observed by SEM and the oxides phase and composition were confirmed by XRD and EDX. As a result, the weight of STS 316L sintered body increased sharply at $1000^{\circ}C$ and the relative density of specimen decreased as metallic oxide addition increased. Compared with STS 316L sintered parts, weight change ratio corresponding to different oxidation time at $900^{\circ}C$ and $1000^{\circ}C$, decreased gradually with the addition of metallic oxide. The best corrosion resistance properties of STS could be improved in case of using $Y_2O_3$. The oxidation rate was diminished dramatically by suppression the peeling on oxide layers at $Y_2O_3$ added sintered stainless steel.

• Korean Journal of Metals and Materials
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• v.48 no.5
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• pp.394-400
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• 2010

The effects of oxidation behavior on the hot ductility of plain carbon steels were investigated at various temperatures in order to simulate the continuous casting process more precisely, in which the process undergoes in air atmosphere rather than Ar atmosphere. The high temperature oxidation behavior and scale morphology of the carbon steels exposed to the air and Ar atmosphere at various temperatures were also investigated in order to assess the mechanism of the RA value decreasing in an air atmosphere. The RA values obtained from the air atmosphere were marked below 45% by the test temperature, except for over 1000${^{\circ}C}$, with the RA values remaining in low values in both the low and high temperature region, at which the RA values generally recovered in the Ar atmosphere. The surface roughness of the specimen was developed by external and internal oxidation when the specimen was deformed in an air atmosphere at high temperature, with the result being the stress concentrated at the roughness of the specimen surface, resulting in low RA values. The hot ductility in the air atmosphere was found to be likely controlled by the oxidation rate instead of the microstructures corresponding to test temperatures.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.288-288
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• 2012

The oxidation characteristics of tungsten line pattern during the carbon-based mask layer removal process using oxygen plasmas and the reduction characteristics of the WOx layer formed on the tungsten line surface using hydrogen plasmas have been investigated for sub-50 nm patterning processes. The surface oxidation of tungsten line during the mask layer removal process could be minimized by using a low temperature ($300^{\circ}K$) plasma processing instead of a high temperature plasma processing for the removal of the carbon-based material. Using this technique, the thickness of WOx on the tungsten line could be decreased to 25% of WOx formed by the high temperature processing. The WOx layer could be also completely removed at the low temperature of $300^{\circ}K$ using a hydrogen plasma by supplying bias power to the tungsten substrate to provide an activation energy for the reduction. When this oxidation and reduction technique was applied to actual 40 nm-CD device processing, the complete removal of WOx formed on the sidewall of tungsten line could be observed.

• Journal of Environmental Science International
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• v.26 no.11
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• pp.1201-1208
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• 2017

Oxidative degradation of chlorinated ethenes was carried out using heat-activated persulfate. The activation rate of persulfate was dependent on the temperature and the activation reaction rate could be explained based on the Arrhenius equation. The activation energy of persulfate was 19.3 kcal/mol under the assumption that the reaction between the sulfate radical and tricholoroethene (TCE) is very fast. Activation could be achieved at a moderate temperature, so that the adverse effects due to high temperature in the soil environment were mitigated. The reaction rate of TCE was directly proportional to the concentration of persulfate, indicating that the remediation rate can be controlled by the concentration of the injected persulfate. The solution was acidized after the oxidation, and this was dependent on the oxidation temperature. The consumption rate of persulfate was high in the presence of the target organic, but the self-decomposition rate became very low as the target was completely removed.

• Journal of Energy Engineering
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• v.5 no.2
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• pp.193-197
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• 1996

A study was conducted on the oxidation behavior of U-0.75 wt% Ti chips (Depleted Uranium, DU chips) using an XRD and a thermogravimetric analyzer in the temperature range from 250 to 500$^{\circ}C$ in air. At the temperature lower than 400$^{\circ}C$, DU chips were converted to UO$_2$, U$_3$O$\_$7/, and U$_3$O$\_$8/ whereas at the temperature higher than 400$^{\circ}C$, DU chips were completely converted to U$_3$O$\_$8/, the most stable form of uranium oxide. The activation energy for the oxidation of DU chips is found, 44.9 kJ/mol and the oxidation rate in terms of weight gain (%) can be expressed as; dW/dt8.4${\times}$10$^2$e(equation omitted) wt%/min (250$\leq$T($^{\circ}C$) $\leq$ 500) where W=weight gain (%), t=time and T=temperature.

• Journal of the Korean Applied Science and Technology
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• v.22 no.1
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• pp.56-61
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• 2005

Methanol was synthesized by homogeneous and catalytic reactions of partial oxidation of methane. The effect of pressure, temperature and oxygen concentration on methanol synthesis was investigated. The catalyst used was Bi-Cs-Mg-Cu-Mo mixed oxide. The partial oxidation reaction was carried out in a fixed bed reactor at 20${\sim}$46 bar and $450{\sim}480^{\circ}C$ and oxygen concentration of 5.3${\sim}$7.7mol%. The results were compared with results of homogeneous reaction performed at the same conditions. Methane conversions of the homogeneous and catalytic reactions increased with temperature. Methanol selectivity of the homogeneous reaction decreased with increasing temperature. However, the methanol selectivity of catalytic reaction increased with temperature. For both homogeneous and catalytic reactions, the methane conversions were around 5%. This may be due to the low oxygen concentration. Methanol selectivity of the catalytic reaction was higher than that of homogeneous one.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.3
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• pp.68-77
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• 1995

Characteristics of electron cyclotron resonance (ECR) plasma thermal oxide grown at low-temperature have been investigated. The effects of several process parameters such as substrate temperature, microwave power, gas flow rate, and process pressure on the growth rate of the oxide have been also investigated. It was found that the plasma density, reactive ion species, is strongly related to the growth rate of ECR plasma oxied. It was also found that the plasma density increases with microwave power while it decreases with decreasing O2 flow rate. The oxidation time dependence of the oxide thichness showed parabolic characteristics. Considering ECR plasma thermal oxidation at low-temperature, the linear as well as parabolic rate constants calculated from fitting data by using the Deal-Grove model was very large in comparison with conventional thermal oxidation. The ECR plasma oxide grown on (100) crystalline-Si wafer exhibited good electrical characteristics which are comparable to those of thermal oxide: fixed oxide charge(N$_{ff}$)= 7${\times}10^{10}cm^{-2}$, interface state density(N$_{it}$)=4${\times}10^[10}cm^{-2}eV^{-1}$, and breakdown field > 8MV/cm.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.634-639
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• 1996

In oder to improve the wear resistance as well as oxidation resistance at high temperature a AISI H13 steel was treated by a duplex process of calorizing followed by plasma nitriding. The surface properties of the duplex-treated AISI H13 steel was characterized and compared with those treated by single surface process of calorizing and plasma nitriding, in terms of microstruture, microhardness, wear resistance at $500^{\circ}C$, and the oxidation behaviours at $700^{\circ}C$, Duplex process on H13 steel had created duplex layer of approximately $190\mu\textrm{m}$ on the surface, and surface microhardness was measured to be above 1450Hv(0.1Kgf). There was considerable improvement of the high temperature wear resistance at $500^{\circ}C$ in the duplex-treated steel when both wear volume and weight change due to oxidation were considered. In addition the duplex-treated steel showed an improved high temperature oxidation resistance than the plasma nitrided steel at $700^{\circ}C$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.843-848
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• 2017

Metal exposed to high temperature/high pressure/oxidizer-rich environment may cause rapid oxidation(ignition and combustion). In this study, a DC power supply test system that controls the temperature of specimen by supplying power to the specimen was constructed and after simulating the high temperature/stagnation/oxidizer-rich environment, the metal oxidation and ignition of STS series metal materials were evaluated. As a result, we was confirmed that the deformation (discoloration) of the selected material, the change in the surface roughness and the peeling of the metal surface were observed, and that the weight and the specimen thickness were changed. The most oxidized specimen was STS 304 and the less oxidized specimen was XM-19.

• Journal of Korean Society of Water and Wastewater
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• v.9 no.4
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• pp.87-96
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• 1995

The Electron/Hole Pair is generated when the activation energy produced by ultraviolet ray illuminates to the semiconductor and OH- ion produced by water photocleavage reacts with positive Hole. As a results, OH radical acting as strong oxidant is generated and then Photocatalytic oxidation reaction occurs. The photocatalytic oxidation can oxidate the non-degradable and hazardous organic substances such as pesticides and aromatic materials easier, safer and shorter than conventional water treatment process. So in this study, many factors influencing the oxidation of chlorophenols, such as inorganic electrolytes addition, change of oxygen and nitrogen atmosphere, temperature, pH, oxygen concentration, chlorophenol concentration, were throughly examined. According to the experiments observations, it is founded that the rate of chlorophenol oxidation follows a first-order reaction and the modified Langmuir-Hinshelwood relationship. And the photocatalytic oxidation occurs only when activation energy acting as Electron/Hole generation, oxygen acting as electron acceptor to prevent Electron/Hole recombination, $TiO_2$ powder acting as photocatalyst are present. The effects of variation of dissolved oxygen concentration, temperature and inorganic electrolytes concentration on 2-chlorophenol oxidation are negligible. And the lower the organic concentration, the higher the oxidation efficiency becomes. Therefore, the photocatalytic oxidation is much effective to oxidation of hazardous substances at very low concentration. The oxidation is effective in the range of 0.1 g/L-10 g/L of $TiO_2$. Finally when the ultra-violet ray is illuminated to $TiO_2$, the surface characteristics of $TiO_2$ change and Adsorption/Desorption reaction on $TiO_2$ surface occurs.