• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.50-52
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• 2022

Brownish rings (BRs) with white interiors are formed during the manufacture of silicon ingots in quartz glass crucibles. These BRs inhibit the yield of silicon ingots. However, the composition and mechanism of the formation of these BRs remain unclear thus far. Therefore, in this study, we analyzed the color and shape of these BRs. Raman analysis revealed that the brown and white colors appear owing to oxygen deficiency rather than crystallization from excess oxygen supply as previously assumed. Moreover, the dark shade of the brown areas depends on the degree of oxygen deficiency and the asymmetrical width of the brown areas is attributed to the direction of the molten silicon flow, which is influenced by the rotation and heat of the ingot crucible.

• Korean Journal of Microbiology
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• v.35 no.4
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• pp.283-288
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• 1999

The effect of dissolved oxygen(DO) concentration on the growth of Pseudomonas aeruginosa and it's mutant M-10 was studied the growth kinetics and the possibility of waste treatment for reducing the amount of excess sludge. Different DO concentrations on the growth of wild type Pseudomonas aeruginosa affected to cellular yields, decreasing with increasing DO concentrations. Under these conditions, the maximum 14 folds decrease of cellular yield was achieved at 90 ppm DO levels by screened, being able to reduce their cellular yields under low DO concentration. The optimum mutation conditions were obtained by the treatment of NTG mutagen at 30${\circ}C$ for 1 hr. The growth characteristics of the selected mutant M-10 showed the same as the wild type growth kinetics. However, cellular yields are significantly decreased to 55% compared with those of wild type under DO concentrations increased. We, therefore, expect the application of the mutants to waste treatment for reducing excess sludge.

• Journal of the Korean Chemical Society
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• v.18 no.2
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• pp.117-125
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• 1974

The catalytic reaction between carbon monoxide and oxygen was investigated in the presence of catalysts which were specially treated by applying an annealing method at different monoxide and oxygen and at reaction temperatures in the region of partial pressures of carbon $40^{\circ}C$ to $95^{\circ}C$. The oxidation rate is highest on NiO annealed at low temperature in vacuum. The data has been correlated with the first order kinetics, and the activation energies from the Arrhenius equation are found to be 4Kcal/mole in the region of the experimental temperatures. The excess oxygen in NiO obtained from the decomposition of $NiCO_3$does not cause activation at $95^{\circ}C$. But NiO catalysts annealed again in vacuum display activation even at $40^{\circ}C$. The quantity of the excess oxygen in NiO surfaces seems to be the controlling factor in determining the rates of oxidation of carbon monoxide.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.39-41
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• 2012

The influence of coal blending methods such as out-furnace (external or pre-mixed) blending and in-furnace (initially non-mixed) blending with different excess oxygen (highest, medium, and lowest stoichiometric conditions) on unburned carbon and NOx emissions of blend combustion in an entrained flow reactor (EFR) has been analyzed, using experimental and numerical approaches for binary coals used by Korean power plants. The results confirm that under the medium condition, contrasting processes such as reactive and un-reactive effects occur with SBRs in the out-furnace blending method. The in-furnace blending method results in an improvement in the efficiency of unburned carbon fractions and a further reduction in the NOx emission. Under the highest condition, the unburned carbon fraction in both the out-furnace and the in-furnace blending methods corresponds with the tendency under the medium condition with contrasting processes of lower magnitude, whereas the NOx emission in the highest condition increases slightly. Under the lowest conditions, the unburned carbon fraction in the out-furnace blending method gradually decreases as SBR decreases, without a competition effect. The reduction of NOx emission under the lowest conditions is more effective than those under other conditions for the two blending methods because of a homogeneous and heterogeneous NOx reduction mechanism.

• 연구논문집
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• s.29
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• pp.5-15
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• 1999

Present study deals with performance analysis of an inert gas generator (IGG) which is to be used as an effective mean to suppress the fire. The IGG uses a turbo jet cycle gas turbine engine to generate inert gas for fire extinguishing. It is generally known that a lesser degree of oxygen content in the product of combustion will increase the effectiveness of fire suppressing. An inert gas generator system with water injection will bring advantages of suffocating and cooling effects which are considered as vital factors for fire extinguishing. As the inert gas is injected to the burning site, it lowers the oxygen content of the air surrounding the flame as well as reduces the temperature around the fire as the vapour in the inert gas evaporates during the time of spreading. Some important aspects of influencing parameters, such as, air excess coefficient. $\alpha$, compressor pressure ratio, $ pi_c$, air temperature before combustion chamber, $T_2$, gas temperature after combustion chamber, $T_3$, mass flow rate of water injection, $M_w$, etc., on the performance of IGG system are investigated. Calculations of total amount of water needed to reduce the turbine exit temperature to pre-set nozzle exit temperature employing a heat exchanger were made to compare the economics of the system. A heat exchanger with two step cooling by water and steam is considered to be better than water cooling only. Computer programs were developed to perform the cycle analysis of the IGG system and heat exchanger considered in the present study.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.249-254
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• 2020

An 80 nm thick zinc aluminate thin film was deposited on a glass substrate via radio-frequency (rf) magnetron sputtering and heat treated to analyze changes in the wetting angles due to a surface modification. The thin films were modified from hydrophilic to hydrophobic by a simple thermal treatment. The surface modification from a heat treatment increased the wetting angles up to 111°, which was explained by the relationship with the excess surface area. The wetting angles of the annealed thin films decreased with increasing exposure time under ambient conditions, which was attributed to the oxygen vacancies in the films that were introduced during deposition. The annealed thin films were treated by ionized oxygen via oxygen plasma. After the oxygen plasma treatment, the decreased wetting angles were maintained at ~95° for 11 days.

• Journal of the Korean Chemical Society
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• v.13 no.4
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• pp.241-247
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• 1969

The catalytic reaction between carbon monoxide and oxygen was investigated with the various nickel oxide catalysts at different partial pressures of carbon monoxide and oxygen and at reaction temperatures in the region of 120$^{circ}$to 250$^{circ}C$. The reaction has the highest rate with the nickel oxide catalyst which is sintered at low temperature. A reaction mechanism to explain the data is derived. From the Arrhenius equation, the activation energies in the region of experimental temperatures are found to be from 5.49 to 9.15 kcal/mole. The concentration of excess oxygen in the nickel oxide seems to vary according to the sintering temperatures and periods and is the controlling factor in determining the type of kinetics followed by the catalytic reaction.

• Journal of the Korean Ceramic Society
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• v.37 no.8
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• pp.787-791
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• 2000

Samples with the nominal composition, Bi2-xGexSr2CaCu2O8＋$\delta$ (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared by the solid-state reaction method. We have studied the effect of substitution Ge for Bi and investigated the superconducting properties by changing oxygen content with Ge substitution. It was found that temperature difference, ΔK, between TCon and TCzero was considerably smaller in the samples prepared by the intermediate pressing method than that in the samples by the solid-state reaction method. We found the solubility limit of Ge to the 80 K single phase was around x=0.3. Within the solubility limit, lattice constant c decreased with the increase of x. In the region of the 80K single phase, the onset critical temperature TCon increased and excess oxygen content decreased with increase of x.

• Korean Journal of Materials Research
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• v.22 no.8
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• pp.385-389
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• 2012

Significant improvements in the switching voltage distribution are required for the development of unipolar resistive memory devices using $MnO_x$ thin films. The $V_{set}$ of the as-grown $MnO_x$ film ranged from 1 to 6.2 V, whereas the $V_{set}$ of the oxygen-annealed film ranged from 2.3 to 3 V. An excess of oxygen in an $MnO_x$ film leads to an increase in $Mn^{4+}$ content at the $MnO_x$ film surface with a subsequent change in the $Mn^{4+}/Mn^{3+}$ ratio at the surface. This was attributed to the change in $Mn^{4+}/Mn^{3+}$ ratios at the $MnO_x$ surface and to grain growth. Oxygen annealing is a possible solution for improving the switching voltage distribution of $MnO_x$ thin films. In addition, crystalline $MnO_x$ can help stabilize the $V_{set}$ and $V_{reset}$ distribution in memory switching in a Ti/$MnO_x$/Pt structure. The improved uniformity was attributed not only to the change of the crystallinity but also to the redox reaction at the interface between Ti and $MnO_x$.

• Journal of the Korean Ceramic Society
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• v.34 no.7
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• pp.722-730
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• 1997

The nonstoichiometry (x) of UO2+x and (Er0.06U0.94)O2+x has been in-situ measure against oxygen activity (Po2) at elevated temperatures by a coulometric titration method. From the dependence of the oxygen excess (x) of UO2+x on Po2 at 1000℃, it has been concluded that (2Vo2Oia2Oib)〃〃and (2Vo2Oia2Oib)' clusters are prevailing at low oxygen partial pressure [log(Po2/atm) -10.6] and at high oxygen partial pressure [log(Po2/atm) -10.6], respectively. The nonstoichiometry is found to be reduced with the addition of Er, which is ascribed to the fact that the fixed-valent Er3+ reduces the oxidation capacities of UO2+x. The enthalpy of oxygen incorporation in (Er0.06li0.94)O2+x has been evaluated from the mean valences of U-ion as -180±70 kJ/mole.