• 한국대기환경학회지
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• 제20권5호
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• pp.647-654
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• 2004

This study examines the local oxidation chemistry of reduced sulfur compounds (RSC) in the urban air. The chemical conversion of RSC (such as DMS, $CS_2,\;H_2S,\;DMDS,\;and\;CH_3SH)\;to\;SO_2$ was modeled using a photochemical box model. For our model prediction of the RSC oxidation, measurements were carried out from an urban monitoring station in Seoul (37.6$^{\circ}$N, 127.0$^{\circ}$E), Korea for three separate time periods (Sep. 17~18; Oct 23; and Oct. 27~28, 2003). The results of our measurements indicated that DMS and $H_2S$ were the dominant RSC with their concentrations of 370${\pm}$140 and 110${\pm}$60 pptv, respectively. The conversion of DMDS to $SO_2$ can occur efficiently in comparison to other RSC, but it is not abundant enough to affect their cycles. The overall results of our study indicate that the photochemical conversion of the RSC can contribute ≶ 20% of the observed $SO_2$.

• Environmental Engineering Research
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• 제16권2호
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• pp.97-102
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• 2011

This study investigates the treatment of pigment wastewater using a sequential batch reactor (SBR) followed by dissolved ozone flotation-pressurized ozone oxidation treatement (DOF-$PO_2$). The process efficiency has been evaluated at the lab scale on the basis of water quality parameters. In addition, the effect of pure oxygen and air was investigated on the removal of COD, BOD, and TN in the SBR process. It was observed that under comparable conditions the removal efficiencies of these water quality parameters using pure oxygen and air were similar. The effect of the recycle rate was also investigated for its impact on the water quality parameters using different ozone dissolving pressures in a DOF process in order to optimise conditions. The results conclude that the use of an SBR and ozone contact by DOF-$PO_2$ is a highly effective treatment for pigment wastewater and aids in the achievement of effluent discharge criteria.

• 한국자동차공학회논문집
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• 제7권7호
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• pp.15-23
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• 1999

In recent years, environmental damage to urban area becomes serious problem due to the exhaust emissions by increasing the number of vehicle . Especially, diesel particulate matters(DPM) are hazardous air pollutant s to human health and environment. The reduction technologies of exhaust emissions from diesel engines are improvement of engine combustion, fuel quality and development of diesel exhaust aftertreatment. In this study, a diesel oxidation catalyst(DOC) that is one of diesel exhaust aftertreatments was made for performance evaluation . It was tested for NA and turbocharged engine by D-13 mode that currently be used for regulation driving test mode in Korea Scanning mobility particle sizer (SMPS) was used for the analysis of the particle size distribution with and w/o DOC. As the results , for NA and tubochartged engine, CO, THC, DPM was respectively reduced 85.7, 40.7,3.3% and 79.1, 53.1, 11.6% by DOC. Test results of particle size distribution was showed that particle number is 107 ~108per ㎤ , 2 $\times$105 ~5$\times$105$\mu\textrm{g}$/㎥ for weight concentration and 100~200nm for particle mean size in diesel engine and there is no effect to reduce the particle concentration by the DOC.

• 한국재료학회지
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• 제15권6호
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• pp.375-381
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• 2005

High temperature oxidation behavior of thermal barrier coating (TBC) system (IN738 substrate + NiCoCrAlY or NiAl bond coat with or without Pt + yttria stabilized zirconia) prepared by air plasma spray (APS) process has been studied in order to understand the effect of Pt addition to bond coat on the stability of TBC system. Specimens were oxidized in thermal cycling and isothermal oxidation test at $1100^{\circ}C$. The Pt addition in TBC system with NiCoCrAlY bond coat showed a longer life time compared to that without addition of Pt. Pt addition to TBC system is believed to help the formation of more stable thermally grown oxide, $Al_2O_3$, at the TBC/bond coat interface, leading to a longer lifetime of TBC system.

• 분석과학
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• 제14권6호
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• pp.516-521
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• 2001

본 연구는 우리나라 생활폐기물 대형소각시설(200톤/일 이상)에서 발생되는 바닥재중유해금속류의 용출저감을 위해 수행된 것이며, 주요 유해물질로는 납(Pb)과 구리(Cu)를 택하였다. 납의 용출저감을 위해서 공기접촉 산화처리방법을 사용한 결과, 납이 거의 검출되지 않을 정도의 저감효과를 나타내었으며 구리의 용추저감을 위한 방안에서는 물 세척법이 저감효과가 있는 것으로 나타났다. 또한, pH 변화에 따른 금속의 용출농도를 분석한 결과, 용출저감을 위한 안정적인 pH 범위는 7~12가 되어야함을 알 수 있었다.

• Asian Journal of Atmospheric Environment
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• 제11권4호
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• pp.217-234
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• 2017

Indoor air pollutants can cause severe health problems, specifically in terms of toxicological impacts on human. Every day, a complex mixture of many air pollutants is emitted from various sources and subject to atmospheric processes that can create varied classes of pollutants such as carboxylic acids, aldehydes, ketones, peroxyacetyl nitrate, and hydrocarbons. To adhere to indoor air quality standards, a number of techniques such as photocatalytic oxidation of various volatile organic compounds (VOCs) have been employed. Among these techniques, titania ($TiO_2$) based photocatalytic reactions have proven to be the best benchmark standard approach in the field of environmental applications. Over the last 45 years, $TiO_2$-based photocatalytic reactions have been explored for the degradation of various pollutants. This review discusses the indoor air quality profile, types of indoor pollutants, available indoor air cleaning approaches, and performance of $TiO_2$-based catalysts. Finally, we have presented the perspectives on the progress of $TiO_2$ induced photocatalysis for the purification of indoor air.

• 제어로봇시스템학회논문지
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• 제13권7호
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• pp.616-623
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• 2007

A dual micro gas sensor array was fabricated using nano sized $SnO_2$ thin films which had good sensitivities to CO and combustible gases, or $H_2S$ gas for air quality sensors in automobile. The already existed air quality sensor detects oxidizing gases and reducing gases, the air quality sensor(AQS), located near the fresh air inlet detected the harmful gases, the fresh air inlet door/ventilation flap was closed to reduce the amount of pollution entering the vehicle cabin through HVAC(heating, ventilating, and air conditioning) system. In this study, to make $SnO_2$ thin film AQS sensor, thin tin metal layer between 1000 and $2000{\AA}$ thick was oxidized between 600 and $800^{\circ}C$ by thermal oxidation. The gas sensing layers such as $SnO_2$, $SnO_2$(pt) and $SnO_2$(+CuO) were patterned by metal shadow mask for simple fabrication process on the silicon substrate. The micro gas sensors with $SnO_2$(+Pt) and $SnO_2$(CuO) showed good selectivity to CO gas among reducing gases and good sensitivity to $H_2S$ that is main component of bad odor, separately.

• 한국대기환경학회지
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• 제20권3호
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• pp.411-419
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• 2004

Titania particles are widely used as a photocatalyst to treat various contaminants in air and water. Titania particles were formed by vapor-phase oxidation of titanium tetraisopropoxide (TTIP) in a tube furnace between 773 and 1,273 K. The effect of process variables such as furnace temperature, flow rate of carrier air, and flow rate of sheath air on powder size and phase characteristics was investigated using a scanning mobility particle sizer (SMPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The size distribution of synthesized titania particles was characterized with mode diameter and peak concentration. The mode diameter ranging from 20 to 80 nm decreased with increasing flow rates of sheath air and carrier air, and increased with increasing furnace temperature. The peak concentration increased with increasing flow rates of sheath air and carrier air The best synthetic condition for high production rate can be derived from the experimental data set represented by mode diameter and peak concentration. The crystal structure of synthesized titania particles was found to be anatase phase, ensuring high photocatalytic potential.

• Journal of Korean Society for Atmospheric Environment
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• 제16권E호
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• pp.39-46
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• 2000

Volatile Organic Compounds (VOCs) are considered as the precursors of atmospheric ozone and photochemical smog formation. In particular, chemical plants have produced a lot of VOCs and thus they have been forced to reduce or remove air emissions from the on-site chemical facilities. For the effective removal of VOCs produced in the chemical plants, the authors employed a titanium oxide(TiO$_2$) mediated photo-catalytic oxidation method. The initiation methods employed in this study to produce oxygen radicals for th photo-catalytic oxidation of the VOCs were Ultra-Violet(UV), Non-Thermal Plasma(NTS), and a combination of Uv and NTP. This study focused on a comparison of the removal efficiencies of VOCs as a function of the initiation method such as NTP and/or UV techniques. Removal efficiency change of VOCs as was investigated as a function of the wavelength of the UV lamp(254, 302, and 365 nm) and the degree of TiO$_2$ coating (10 and 30%). In this study, it was identified that removal efficiencies if the VOCs under the normal air environment were much better than those under the nitrogen gas environment containing small amount of oxygen. Removal efficiency by NTP technique was much better than the UV or the combination of UV and NTP techniques. In a comparison if UV wavelengths employed, it was found that shorter wavelength showed better removal efficiency, compared with longer ones. When the removal efficiencies of VOCs were compared in terms of the degree of TiO$_2$ coating, the higher TiO$_2$coating showed better removal efficiency that the lower TiO$_2$ coating

• Applied Microscopy
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• 제47권3호
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• pp.131-147
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• 2017

In this work further optical and electrical investigations of pure and Zr doped $Mn_3O_4$ (from 0 up to 20 at.%) thin films as a function of frequency. First, the refractive index, the extinction coefficient and the dielectric constants in terms of Zr content are reached from transmittance and reflectance data. The dispersion of the refractive index is discussed by means of Cauchy model and Wemple and DiDomenico single oscillator models. By exploiting these results, it was possible to estimate the plasma pulse ${\omega}_p$, the relaxation time ${\tau}$ and the dielectric constant ${\varepsilon}_{\infty}$. Second, we have performed original ac and dc conductivity studies inspired from Jonscher model and Arrhenius law. These studies helped establishing significant correlation between temperature, activation energy and Zr content. From the spectroscopy impedance analysis, we investigated the frequency relaxation phenomenon and hopping mechanisms of such thin films. Moreover, a special emphasis has been putted on the effect of the oxidation in air of hausmannite thin films to form $Mn_2O_3$ ones at $350^{\circ}C$. This intrigue phenomenon which occurred at such temperature is discussed along with this electrical study. Finally, all results have been discussed in terms of the thermal activation energies which were determined with two methods for both undoped and Zr doped $Mn_3O_4$ thin films in two temperature ranges.