• 한국세라믹학회지
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• 제43권2호
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• pp.114-120
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• 2006

Nano-size Au particle doped $TiO_2$ films were prepared with $Ti(OC_3H_7^i)_4$, polyvinylpyrrolidone(PVP), $HAuCl_4$ and $C_3H_7OH$ etc. by sol-gel method. $TiO_2$ gel films were obtained by the dip-coating method on the $SiO_2$ glass substrates, and then heat-treated at $700^{\circ}C$ for 10 min. The thickness of $TiO_2$ films were $0.7\~1.8\;{\mu}m$. It was found that the thickness of films prepared from PVP containing solution was about $2\~8$ times higher values than that of thin films without PVP. The size of Au particles doped in the films were about $350\~750\;nm$. Nano-size Au particle dispersed $TiO_2$ films showed high absorption peak at visible region 450nm, which made them good candidates for non-linear optical materials and photo-catalytic materials. The contact angle of $TiO_2$ film for water was $12.5^{\circ}$, and therefore it is clear that $TiO_2$ films have very high hydrophilic properties and the self-cleaning effects.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.174-177
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• 1991

Fluorine-doped $SnO_2\;(SnO_2:F)$ films were prepared in ordinary atmosphere on borosilicate glass substrates using pyrosol deposition method starting from the solutions composed of $SnCl_4-5H_2O-NH_4F-CH_3OH-H_2O-HCl$ in an attempt to develop transparent conductors for use in amorphous silicon (a-Si) solar cello. The deposition rate of films increased with the increase in the content of $H_2O$, whereas it decreased with increasing the content of $CH_3OH$. When air was used as the carrier gas, the lowest electrical resistivity was obtained from a solution having $CH_3OH/H_2O$ mol ratio of about $2{\sim}3$ in the solution. The use of $N_2$ of the same flow rate as the carrier gab resulted always in the high resistive films, but the resistivity of the films decreased continuously with the increase in the content of $H_2O$. The surface morphology and preferred orientation of films were also affected by the solvent composition and the content of HCl in the solution. The room-temperature resistance of the films were fairly stable after heat-treatments up to $600^{\circ}C$.

• 한국지하수토양환경학회지:지하수토양환경
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• 제22권3호
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• pp.10-17
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• 2017

In this study, the evolution and origin of major dissolved constituents of crystalline bedrock groundwater in a coastal area were evaluated using multivariate statistical and groundwater quality analyses. The groundwater types mostly belonged to the $Na(Ca)-HCO_3$ and $Ca-HCO_3$ types, indicating the effect of cation exchange. Stable isotopes of water showed two areas divided by first and secondary evaporative effects, indicating a pattern of rapid hydrological cycling. Saturation indices of minerals showed undersaturation states. Thus, the degree of evolution of groundwater is suggested as in the low to intermediate stage, based on field and laboratory analytical conditions. According to the principal component analysis (PCA) results, the chemical components of EC, $Ca^{2+}$, $Mg^{2+}$, $K^+$, $HCO_3{^-}$, $SO{_4}^{2-}$ (PCA 1), $F^-$ (PCA 3), $SiO_2$ (PCA 4), and $Fe^{2+}$ (PCA 5) are derived from various water-rock interactions. However, $NO_3{^-}$, $Na^+$, and $Cl^-$ (PCA 2) represented the chemical characteristics of both anthropogenic sources and natural sea spray.

• Journal of Forest and Environmental Science
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• 제22권1호
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• pp.13-17
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• 2006

오동나무잎, 열매, 내수피, 외수피 그리고 목질부를 채취하여 건조시킨 후 분말로 제조하여 각 시료 약 5.0 kg을 아세톤-물(7:3. v/v) 혼합용액으로 추출하고 유기용매를 제거한 후 헥산, 메틸렌클로라이드, 에틸아세테이트 및 물 등 네 개의 분획으로 분리하였다. 오동나무 각 부위별 추출물 수율은 내수피(11.35%)가 가장 높았고 잎(7.87%), 열매(6.94%), 외수피(4.24%)의 순 이었으며 목질부가 4.10%로 가장 낮게 나타났다. 오동나무 각 부위별 조추출물, 고형분과 분획물을 가지고 DPPH radical 소거법을 이용하여 기초적인 항산화 실험을 실시하였다. 기준물질로는 천연 항산화제인 ${\alpha}$-tocopherol과 합성항산화제인 BHT를 사용하여 항산화효능을 비교하였다. 그 중에서는 모든 EtOAc용성 분획이 기준물질 보다 더 우수한 항산화 활성을 나타내었다.

• 대한기계학회논문집B
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• 제20권5호
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• pp.1671-1678
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• 1996

In external chemical vapor deposition processes including VAD and OVD the distribution of flame-synthesized silica particles is determined by heat and mass transfer limitations to particle formation. Combustion gas flow velocities are such that the particle diffusion time scale is longer than that of gas flow convection in the zone of particle formation. The consequence of these effects is that the particles formed tend to remain along straight smooth flow stream lines. Silica particles are formed due to oxidation and hydrolysis. In the hydrolysis, the particles are formed in diffuse bands and particle formation thus requires the diffusion of SiCl$\_$4/ toward CH$\_$4//O$\_$2/ combustion zone to react with H$\_$2/O diffusing away from these same zones on the torch face. The conversion kinetics of hydrolysis is fast compared to diffusion and the rate of conversion is thus diffusion-limited. In the language of combustion, the hydrolysis occurs as a Burke-Schumann process. In selected conditions, reaction zone shape and temperature distributions predicted by the Burke-Schumann analysis are introduced and compared with experimental data available. The calculated centerline temperatures inside the reaction zone agree well with the data, but the calculated values outside the reaction zone are a little higher than the data since the analysis does not consider diffusion in the axial direction and mixing of the combustion products with ambient air. The temperatures along the radial direction agree with the data near the centerline, but gradually diverge from the data as the distance is away from the centerline. This is caused by the convection in the radial direction, which is not considered in the analysis. Spatial distribution of silica particles are affected by convection and diffusion, resulting in a Gaussian form in the radial direction.

• 한국의류산업학회지
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• 제17권6호
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• pp.1004-1012
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• 2015

The purpose of this study is to investigate the loess dyeability of soybean fabric using loess as colorants. Recent days, various textile products such as inner wears, sheets and interior goods are manufactured using materials dyed with loess emphasizing its improved metabolism, anti-bacterial, deodorizing properties, and far infrared ray emissions. Soybean fabric was dyed with loess solution according to concentration of loess, dyeing temperature and dyeing time. To improve washing fastness, soybean fabric and dyed soybean fabric with loess were mordanted by mordanting agents such as sodium chloride(NaCl), Acetic acid(CH₃COOH) and Aluminium Potassium Sulfate(AlK(SO₄)₂·12H₂O). Dyeability and color characteristics of dyed soybean fabric were obtained by CCM observation. Particle size distribution of loess, the dyeability(K/S) of soybean fabric, morphology and washing durability of loess dyed soybean fabric were investigated. The results obtained were as follows; Mean average diameter of loess was 1.08µm. The main components of loess used in this study were silicon dioxide(SiO₂), aluminium oxide(Al₂O₃), and iron oxide(Fe₂O₃). The content of these three component was above 75 weight %. The dyeability of soybean fabric was increased gradually with increasing concentration of loess. The optimum dyeing temperature and dyeing time were 90℃ and 60minutes expectively. The fastness to washing according to concentration of loess and mordanting method indicated good grade result as more than 4 degree in all conditions.

• Carbon letters
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• 제11권4호
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• pp.293-297
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• 2010

To investigate new potential application of a clay material for C/C composites, illite added C/C composites were prepared with various illite contents. The improvement of filler effect by illite size reduction was also investigated using wet ballmilling by evaluating illite/phenolic resin infiltration using bulk density and porosity measurements, chemical structural changes of the composites using XRD, and thermal oxidation stability in air of the composites using TGA. The size reduction of illite resulted in narrower particle size distribution and improved illite infiltration into carbon preform. And the resultant C/C composites prepared with illite had even more improved thermal oxidation stability in air, showing more increased IDTs up to $100^{\circ}C$, compared to those of the C/C composites with pristine illite, due to the SiC formation through carbothermal reduction between illite and carbon materials. The illite induced delay in oxidation of the illite-C/C composites was also observed and the delayed oxidation behavior was attributed to the layered structure of illite, which improved illite/phenol resin infiltration. Therefore, the potential use of illite as filler to improve oxidation stability of C/C composite can be promising. And the size reduction of illite can improve its effect on the desired properties of illite-C/C composites even more.

• Bulletin of the Korean Chemical Society
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• 제30권4호
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• pp.873-881
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• 2009

Bis(phenylethynyl)dimethylsilane is branched by the hydrosilation of the phenylethynyl group with dichloromethylsilane, and then the resulting chlorosilane is reacted with lithium phenylacetylide to give the $1^{st}$ generation. The same hydrosilation and alkynylation are repeated to obtain the $7^{th}$ generation. In addition peripheral Si-Cl moiety of the seven kind generation dendrimers are reacted with alcoholic moiety of 9-hydroxymethylanthracene and 2-(2-hydroxyphenyl)benzoxazole group in the presence of TMEDA. Then three kinds of carbosilane dendrimers are prepared from the $1^{st}$ to the $7^{th}$ generations, the $7^{th}$ generation of each dendrimer has 256 phenylethynyl, 256 9-anthracenylmethoxy, or 128 2-(2-phenoxy)benzoxazole groups. Each synthesized dendrimer is unequivocally characterized by $^1H\;and\;^{13}C\;NMR$, elemental analysis, MALDI-MS, GPC, and PL (photoluminescence). Characteristically PDI (Polydisperse Index) values of the dendrimers’ peak in GPC are in the range of $1.00{\sim}1.07$, which indicates that each generation of carbosilane is in unified distribution. PL spectra of phenylethynyl and 9- anthracenemethoxy group substituted dendrimers show no significant change with increasing the generation from the $1^{st}$ to the $7^{th}$. However, the PL spectra of 2-(2-phenoxy)benzoxazole group substituted dendrimers show a blue-shift trend with increasing the generation from the $1^{st}$ to the $7^{th}$.

• Journal of Microbiology and Biotechnology
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• 제12권2호
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• pp.189-195
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• 2002

Using Streptomyces sp. YU100 isolated from Korean soil, the fermentative production of phospholipase D was attempted along with its purification and characterization studies. When different carbon and nitrogen sources were supplemented in the culture medium, glucose and yeast extract were found to be the best. By varying the concentration of nutrients and calcium carbonate, the optimal culture medium was determined as 2.0% glucose, 1.5% yeast extract, 0.5% tryptone 0.3% calcium carbonate. During cultivation, the strain secreted most of the phospholipase D in the early stage of growth within 24 h. The phospholipase D produced in the culture broth exhibited hydrolytic activity as well as transphosphatidylation activity on lecithin (phosphatidylcholine). In particular, the culture broth showed 8.7 units/ml of hydrolytic activity when cultivated at $28^{\circ}C$ for 1.5 days. The phospholipase D was purified using 80% ammonium sulfate precipitation and DEAE-Sepharose CL-6B column chromatography, which produced a major band of 57 kDa on a 10% SDS-polyacrylamide gel with purity higher than 80%. The enzyme showed an optimal pH of 7 in hydrolytic reaction, and at pH 4 in a transphosphatidylation reaction. The enzyme activity increased until the reaction temperature was elevated to $60^{\circ}C$. The enzyme was relatively stable at high temperatures and neutral pH, but significantly unstable in the alkaline range. Among the detergents tested as emulsifiers of phospholipids, the highest enzyme activity was observed when 1.5% Triton X-100 was employed. However, no inhibitory effect by metal ions was detected. Under optimized reaction conditions, the purified enzyme not only completely decomposed PC to phosphatidic acid within 1 h, but also exhibited higher than 80% conversion rate of PC to PS by transphosphatidylation within 4 h.

• Food Science and Biotechnology
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• 제17권4호
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• pp.766-771
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• 2008

The proteolytic enzyme from Saccharomyces sp. B101 was purified to homogeneity by ammonium sulfate fractionation, ultrafiltration, diethyl aminoethyl (DEAE)-Sephadex A-50 ion-exchange chromatography, and Sephadex G-100 gel filtration chromatography from the culture supernatant of Saccharomyces sp. B101. The specific activity and the purification fold of the purified enzyme were 4,688.9 unit/mg and 18, respectively. The molecular weight of the purified enzyme was estimated to be 33 kDa by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The optimum pH and temperature for the enzyme activity were pH 8.5 and $30^{\circ}C$, respectively. The enzyme activity was relatively stable in the pH range of 6.5-8.5 at below $35^{\circ}C$. The salt-tolerance and stability for the enzyme activity were relatively stable even at NaCl concentrations of 10 and 15%. The activity of enzyme was inhibited by $Ag^{2+}$ and $Fe^{2+}$, and activated by $Mn^{2+}$. In addition, the enzyme activity was potently inhibited by ethylenediaminetetraacetic acid (EDTA) and phenylmethyl sulfonylfluoride (PMSF). Based on these findings we concluded that the purified enzyme was a serine protease. Km and Vmax values for hammastein milk casein were 1.02 mg/mL and 278.38 unit/mL, respectively.