• Journal of Korean Society of Water and Wastewater
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• v.27 no.5
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• pp.571-579
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• 2013

The aggregation behaviors of silver nanoparticles (AgNPs) and titanium dioxide ($TiO_2$) nanoparticles were investigated. Time-resolved dynamic light scattering (DLS) was used to study the initial aggregation of AgNPs and $TiO_2$ over a range of mono (NaCl) and divalent ($CaCl_2$) electrolyte concentrations. The effects of pH, initial concentration of NPs and natural organic matters (NOM) on the aggregation of NPs were also investigated. The aggregation of both nanoparticles showed classical Derjaguin-Landau-Verwey-Overbeek (DLVO) type behavior. Divalent electrolyte was more efficient in destabilize the AgNPs and $TiO_2$ than monovalent electrolyte. The effect of pH on the aggregation of AgNPs was not significant. But the aggregation rate of $TiO_2$ was much higher with increasing pH. Higher NPs concentration leads to faster aggregation. Natural organic matter (NOM) was found to substantially hinder the aggregation of both AgNPs and $TiO_2$. This study found that the aggregation behavior of AgNPs and $TiO_2$ are closely associated with environmental factors such as ionic strength, pH, initial concentration of NPs and NOM.

• Economic and Environmental Geology
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• v.24 no.1
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• pp.1-8
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• 1991

North ore deposits of the Dunjeon gold mine is disseminated-stockworks deposits emplaced in Ordovician Dongjeom quartzite. Six types of fluid inclusions are recongnized in the stage I quartz. Among them polyphase inclusions(type-IV-A, B) are predominent in the lower part of stage I quartz crystals whereas liquid and gas inclusions(type I, II) are abundant in the upper part of the same quartz crystals. Liquid $CO_2$-bearing inclusions(type III-A, B)occur as pseudosecondary inclusions. Solid phases in polyphase inclusions are identified by using scanning electron microscopy combined with energy dispersive x-ray spectroscopy. The solid phases are as follows; halite, sylvite, hydrophyllite, quartz, muscovite, calcite, ankerite, K-Mg-Fe-Al-Si mineral, Ca-Fe-Si mineral, Mg-Al-Si mineral, two kinds of Fe-mineral and Cu-Fe mineral. Results of freezing and heating experiments of fluid inclusions and identification of daughter minerals in polyphase inclusions in the stage I quartz reveal that ore fluids were high saline system NaCl-KCl-$CaCl_2$-$H_2O$ in the earier stage and then evolved to rather simple system NaCl-$H_2O$ in the later stage, and temporally fluid mixing occured with system $CO_2$-$H_2O$. Homogenization temperatures and salinity of fluid inclusions in the stage I range from 290 to $454^{\circ}C$ and from 0.2 to 54.2 wt. % equivalent to NaCl.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.48-48
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• 2007

P-type transparent conducting $CuGaO_2$ thin films have been prepared by DC/RF sputtering using Quartz(0001) and sapphire(0001) substrates. The target was fabricated by heating a stoichiometric mixture of CuO and $Ga_2O_3$ at 1373K for 12h under $N_2$ atmosphere. The film were deposited under mixture gas of Ar and $O_2(Ar:O_2=4:1)$ during 10~30min. and the as-deposited films were annealed at 1123K and $N_2$ atmosphere. Room temperature conductivity and the activation energy of the sintered body in the temperature range of 223K ~ 423K were 0 004S/cm, 1.9eV, respectively. XRD revealed that all of the as-deposited films were amorphous. Heating of the films deposited on Quartz substrates above 1123K resulted in crystallization with a second phase of $CuSiO_3$, which was assumed owing to reaction with Quartz substrate. The single phase of $CuGaO_2$ was obtained at the film deposited on the sapphire substrates. The transmittance after annealing of DC- and RF-sputtered films were 55~75% at 550nm. From the transmittance and reflectance measurement. the direct band gap of the DC/RF-sputtered films were 3.63eV and 3.57eV. and there was little difference between DC and RF sputtered films.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.545-551
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• 2007

HCl concentration, reaction temperature, and $Ti^{4+}$ concentration are the decisive factors in determining the structure of precipitates in the process of synthesis of $TiO_2$ particles from aqueous $TiCl_4$ solution by precipitation and the volumetric proportion of brookite phase in $TiO_2$ particles can be controlled by these factors. Pure brookite-type $TiO_2$ nanoparticles were synthesized by heating the aqueous $TiCl_4$ solution with no more than 1.0 M of $Ti^{4+}$, in which the concentration of HCl was kept in the range of about 2.53~6.41 M during reaction, at the temperature below $70^{\circ}C$ for 20 h. Also, Pure brookite was finally transformed to a rutile phase via an anatase phase through heat-treatment.

• Journal of Environmental Health Sciences
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• v.21 no.4
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• pp.24-31
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• 1995

Gas sensing element, $\alpha-Fe_2O_3$ was synthesized by dehydration, reduction, and oxidation of $\alpha-FeOOH$, which was synthesized with $FeSO_4\cdot 7H_2O$ and NaOH. They were produced as a bulk-type, a thick film-type. Then, their responses and mechanisms of response to the gas of carbon monoxide were studied. The qualities of gas sefising elements are decided by the structure and the relative surface area. In the process of $\alpha-FeOOH$ synthesis, the effects of reaction conditions as the equivalent ratio, on the structure and the relative surface area of gas sensing element were observed. The changes of the structure were measured with XRD, SEM,TG-DTA and BET. The resistance changes of the synthesized gas sensor in the air were measured. The response ratio were also measured for the changes of working temperature and gas concentration. As a result of analysis with XRD, it was confirmed that the the best conditions for the synthesis of $\alpha-FeOOH$ were equivalent ratio 0.65. The thick film-type element of $\gamma-Fe_2O_3$ responded more quickly than the bulk-type did. The structure and the relative surface area of the $\rho-FeOOH$ were confirmed as the important factors deciding gas response charcteristics.

• Journal of Conservation Science
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• v.28 no.3
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• pp.277-283
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• 2012

This study conducted analysis of paint samples from a streetcar No. 381 (Registration Cultural Property No. 467) to identify the characteristics of the modern paint. The samples were analyzed by Microscopic observation, infrared spectroscopy and SEM-EDS. The upper part is consist of 26 layers and the under part is 29 layers. And the layers were painted various thickness from $10{\mu}m$ to $100{\mu}m$, and confirmed that several color had been used. The putty was used for surface treatment before painting. According to the results of infrared spectroscopy, paint specimens were identified as alkyd resin. Some bands such as C-H and C=O stretcing, aromatic, C-H bending, C-O stretching were found in spectra. Inorganic analysis showed that gold color on the surface was used copper-based paint. And type of the putty was lacquer-putty that was consist of kaolin, talc and zinc white.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1487-1489
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• 2001

The tantalum oxide($Ta_2O_5$) is an important material for present thin-film capacitor application owing to its high dielectric constant and thermal stability. We report dielectric property of Si(p type)/Pt/$Ta_2O_5$/Ag based MIM structure obtained by RF sputtering and annealed in vacuum environment. We have measured and researched the characteristics of C-F, C-V and EPMA. And we describe parameter dependence on sputtered condition and annealed temperature with dielectric property.

• Proceedings of the Korean Journal of Food and Nutrition Conference
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• 2001.12a
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• pp.126-126
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• 2001

The Rhus verniciflua contains alkly(en)-catechol type allergens with a saiurated or unsaturated alkly chain of 15 or 17 carbon atoms. It has been recognized as an extremely active allergen causing skin reactions similar In poison ivy. The allergic contact dermatitis induced by the urushiol is known to be mediated be T lymphocytes whicht specifically recognize the hepten urushiol. Therefore. direct use of this plant as a medicinal purpose might imply a considerable hazard in Korea. In this study, using the established method for the detoxification from the stem bark of Rhus verniciflua, an strong antioxidant substance was isolated and characterized DPPH (diphenypricryl hydrazyl) assay measures hydrogen atom-donating activity and hence provides a measure of free radical scavenging antioxidant activity. DPPH, a purple-colored stable free radical, is reduced to yellow-colored diphenylpicryl hydrazine by antioxidants to deducing agents. Antioxidative effects of the water extract from RV were measured by DPPH assay. Twenty microliters of the extract was added to 1ml of 100mM DPPH solution in ethanol The mixture was shaken and left to stand for 10min at room temperature. The crude water extracts was purified by using HPLC method with a DEAE (anionic type), CN, ODS column. The purified compound remained stable at pH 3.0-6,0, but unstable above pH 6.5. It was stable heat at 10$0^{\circ}C$ for 4 hours, but still had about 80% of residual activity after treatment at 10$0^{\circ}C$ for 5 hours. The elemental composition of the HR-EI mass spectrum at m/z 170.02 was estimated the empirical formula as $C_{7}$ $H_{6}$ $O_{5}$. $C_{10}$ $H_4$ $O_2$N$_1$, $C_{5}$ $H_4$ $O_4$N$_3$, $C_{8}$$H_2O$$_1$N$_4$. In antimicrobial test, no inhibition was observed against Gram-positive and negative bacteria. This compound was stronger than that of commercial antioxidant by DPPH test, such as BHT, BHC at the same concentration (20$\mu$g/ml).ml).

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.405-405
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• 2011

실리콘 질화막(SiNx : H)는 결정질 실리콘 태양전지 제작 공정에서 ARC (Anti Reflection Coating)과 표면 패시베이션의 역할로써 많이 사용되었지만, layer 자체의 quality가 좋지 않기 때문에 최근에는 SiNx/SiO2 이중 layer로 passivation layer를 형성하고 있다. SiO2 layer는 Si substrate를 소스로 하여 성장시키기 때문에 막의 질이 우수하기는 하지만, 막 성장을 위해서 Furnace를 이용해야 하기 때문에, 공정 시간과 공정 비용을 증가시키는 단점이 있다. 본 연구에서는 SiO2 layer를 Furnace가 아닌, 질산(HNO3)을 이용하여SiNx/Thin SiO2 passivation layer 제작하였다. 실험에서는 SiO2 성장을 위해서 질산 용액에 p-type wafer를 dipping하여 시간대 별, SiO2 막의 두께를 관찰하였고, passivation의 효과를 확인하기 위해 lifetime을 측정하였다. 그 결과 SiNx/SiO2 이중 passivation layer는 SiNx 단일 막으로 passivation을 하였을 때보다, lifetime이 10 us 상승했고, 셀 제작시 효율은 약 1.1%, Fill Factor는 약 4% 정도 증가한 것을 확인할 수 있었다.

• Korean Journal of Environmental Agriculture
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• v.14 no.2
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• pp.232-245
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• 1995

The garbage from the dwelling house was composted in two kinds of small composter in the laboratory, and the possibility of garbage composting was examined. The composters were general small. One (type 3) was constructed with the double layer walls and the other (type 4) was the same as the first except for being insulated. Because it was found that type 3 was not available for composting under our meteorological conditions through the winter experiment, only type 4 was tested in spring and summer. The experiment was performed for 8 weeks in each season. The seasonal variation of several components in the compost was evaluated and discussed. The results summarized below were those obtained at the end of the experiment, if the time was not specified. 1) The maximum temperature was $43^{\circ}C$ in winter, $55^{\circ}C$ in spring and $56^{\circ}C$ in summer. 2) The mass was reduced to an average of 63% and the volume reduction was an average of 78%. 3) The density was estimated as 1.5 kg/l in winter and 0.8 kg/l in spring and summer. 4) The water content was not much changed during the composting periods. It was 79.3% in winter, 75.0% in spring and 70.0% in summer. 5) After pH value increased during the first week, it decreased until the second week and increased again continuously thereafter. It reached pH 6.19 in winter, pH 7.59 in spring and pH 8.69 in summer. 6) The faster the organic matter was decomposed, the greater the ash content increased. The contents of cellulose and lignin increased, but that of hemicellulose decreased during the composting period. 7) Nitrogen contents were in the range of 3.3-6.8% and especially high in summer. After ammonium contents increased at the early stage of the composting period, they decreased. The maximum ammonium-nitrogen content was 2,404mg/kg after 8 weeks in winter, 12,400mg/kg after 3 weeks in spring and 20,718mg/kg after 3 weeks in summer. C/N-ratios decreased with the lapse of composting time, but they were not much changed. Nitrification occurred actively in summer. 8) The contents of volatile and higher fatty acids increased at the early stage of composting and reduced after that. The maximum content of total fatty acid was 9.7% after 6 weeks in winter, 14.8% after 6 weeks in spring and 15.8% after 2 weeks in summer. 9) The contents of inorganic components were not accumulated as composting proceeded. They were in the range of 0.9-4.4% $P_2O_5$, 1.6-2.4% $K_2O$, 2.2-5.4% CaO and 0.30-0.61% MgO. 10) CN and heavy metal contents did not show any tendency. They were in the range of 0.21-14.55mg/kg CN, 11-166mg/kg Zn, 5-65mg/kg Cu, 0.5-10.8mg/kg Cd, 6- 35mg/kg Pb, ND-33 mg/kg Cr and ND-302.04 g/kg Hg.