• BMB Reports
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• 제34권1호
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• pp.39-42
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• 2001

Previous studies indicate that B. subtilis protoporphyrinogen oxidase is poorly inhibited by diphenyl ether herbicides. To better understand the basis of this insensitivity, the enzyme was overexpressed as a soluble protein in E. coli, purified and characterized. The mechanism of oxidation of B. subtilis protoporphyrinogen IX was studied and the enzyme kinetic parameters were determined for protoporpyrinogen IX; $K_m$, and $k_{cat}$ were $6.3\;{\mu}M$ and $0.028\;h-^1$, respectively. The enzyme required flavin adenine dinucleotide as a cofactor and its activity was enhanced by 1 mM n-octylglucopyranoside. The nonenzymatic oxidation rate was dependent on the concentration of protoporphyrinogen IX, suggesting that the reaction involves a pre-equilibrium step followed by a rate-limiting step.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.48-51
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• 1995

We have developed the three dimensional mesh generator for three dimensional process simulation using the FEM(Finite Element Method). Tetrahedron element construct the presented three dimensional mesh, which is suitable for the simulation of three dimensional behavior of the LOCOS. The simulation of thermal oxidation is one of the problem in scale downed semiconductor processes. As three dimensional simulators use the huge size of the memory, we use the efficient method that generates the new nodes inside the growing oxide and removes the nodes nearby the SiO2/Si interface in silicon. The resented three dimensional mesh generator was designed to be used in various process simulations, for instance thermal oxidation, silicidation, nitridation, ion implantation, diffusion, and so on.

• Nuclear Engineering and Technology
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• 제41권8호
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• pp.1073-1078
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• 2009

A kinetic model for the oxidation of a $UO_2$ pellet to $U_3O_8$ powder has been suggested by considering the mass transfer and the diffusion of oxygen molecules. The kinetic parameters were estimated by a fitting of the experimental data. The activation energies for the chemical reaction and the product layer diffusion were calculated from the kinetic model. The oxidation conversion of a $UO_2$ pellet was simulated at various operating conditions. The suggested model explains the oxidation behavior of $UO_2$ well.

• 대한전자공학회논문지
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• 제25권7호
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• pp.767-773
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• 1988

We have proposed a new simple and easy method for the observation of OSF growth and shrinkage. This method is to observe the behavior of OSF in thedamaged region during oxidation as well as annealing process after introducing mechanical damage on the silicon surface by pressure-controllable indentor. The effect of SiO2 layer on the shrinkage of pregrown OSF generated by the proposed method has been investigated using the samples with or without SiO2 layer. From the experimental data, we suggest a model for the shrinkage of OSF, which is based on the recombinaiton mechanism between silicon interstitial and vacancy at the Si-SiO2 interface.

• 한국표면공학회지
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• 제35권5호
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• pp.312-318
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• 2002

A study on the change of mechanical properties and oxidation behavior of Zircaloy-4 fuel cladding after exposing at 90$0^{\circ}C$ and $1000^{\circ}C$ for various periods of exposure time under the steam atmosphere was carried out. The growth of the $ZrO_2$ layer combined with an oxygen-rich-phase layer into the Zircaloy tube material can be described by an expression, E = 1.1√Dt + $2 $\times$ 10^{-4}$ . The tensile strength of Zircaloy tubes increased for a short period of exposure time and decreased rapidly with further exposure while the hoop strength was not decreased greatly. In the meantime, the axial and circumferential elongations of oxidized Zircaloy tubes were decreased drastically with increasing exposure time as a result of embrittlement phenomena.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.330-331
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• 2005

It was found possible to evaluate the temperature at which major scale failure takes place during cooling by installing a most modem acoustic emission(AE) analytical system. Ultra low carbon steel and low carbon steels containing a few minor alloying elements were oxidized in air at 900, 1050 and $1200^{\circ}C$ for 20 min, and then cooled in vacuum at 30, 70 and $110^{\circ}C/min$. The significance of the present research is the evaluation of the spallation temperature and thus the calculation of apparent thermal stress for scale spallation using the difference between oxidation temperature and spallation temperature. They were assessed as 0.22 to 0.68, 0.45 to 1.80, and 0.65 to 1.95 GPa for oxidation at 900, 1050 and $1200^{\circ}C$, respectively.

• Corrosion Science and Technology
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• 제5권6호
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• pp.213-217
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• 2006

Titania coatings were prepared on commercially pure Ti by plasma electrolytic oxidation (PEO) method with various electrolytes and process condition. Coatings were formed under galvanostatic condition with several current density values, and the change of applied voltage with process time was recorded. The microstructure of the titania coatings was observed using XRD, SEM, TEM, and the time-voltage diagrams were analyzed in terms of microstructure evolution.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2013년도 춘계학술대회 논문집
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• pp.109-110
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• 2013

Medium carbon steel was aluminized by hot dipping into molten Al or Al-1%Si baths. After hot-dipping in these baths, a thin Al-rich topcoat and a thick alloy layer rich in $Al_5Fe_2$ formed on the surface. A small a mount of FeAl and $Al_3Fe$ was incorporated in the alloy layer. Silicon from the Al-1%Si bath was uniformly distributed throughout the entire coating. The hot dipping increased the microhardness of the steel by about 8 times. Heating at $700-1000^{\circ}C$ however decreased the microhardness through interdiffusion between the coating and the substrate. The oxidation at $700-1000^{\circ}C$ in air formed a thin protective ${\alpha}-Al_2O_3$ layer, which provided good oxidation resistance. Silicon was oxidized to amorphous silica, exhibiting a glassy oxide surface.

• Corrosion Science and Technology
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• 제8권6호
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• pp.227-231
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• 2009

Mg and Mg alloys have been used for lots of applications, including automobile industry, aerospace, mobile phone and computer parts owing to low density. However, Mg and Mg alloys have a restricted application because of poor corrosion properties. Thus, improved surface treatments are required to produce protective films that protect the substrate from corrosive environments. Environmental friendly Plasma Electrolytic Oxidation (PEO) has been widely investigated on magnesium alloys. PEO process combines electrochemical oxidation with plasma treatment in the aqueous solution. In this study, AZ91 Mg alloys were treated by PEO process in controlling the current with PC condition and treated time, concentration of NaF, NaOH, and $Na_2SiO_3$. The surface morphology and phase composition were analyzed using SEM, EDS and XRD. The potentiodynamic polarization tests were carried out for the analysis of corrosion properties of specimen. Additionally, salt spray tests were carried out to examine and compare the corrosion properties of the PEO treated Mg alloys.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2729-2734
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• 2009

We report here the surface behavior of zirconium oxide deposited on Si(100) substrate depending on the different substrate temperatures. The zirconium oxide thin films were successfully deposited on the Si(100) surfaces applying radio-frequency (RF) magnetron sputtering process. The obtained zirconium oxide films were characterized by X-ray photoelectron spectroscopy (XPS) for study about the chemical environment of the elements, X-ray diffraction (XRD) for check the crystallinity of the films, spectroscopic ellipsometry (SE) technique for measuring the thickness of the films, and the morphology of the films were investigated by atomic force microscope (AFM). We found that the oxidation states of zirconium were changed from zirconium suboxides ($ZrO_{x,y}$, x,y < 2) (x; higher and y; lower oxidation state of zirconium) to zirconia ($ZrO_2$), and the surface was smoothed as the substrate temperature increased.