• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.593-596
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• 2017

Sodium titanate nanosheets were prepared by a hydrothermal synthesis method under basic conditions. Ruthenium was introduced on the surface of sodium titanate nanosheets through an UV irradiation in the aqueous $RuCl_3$ solution. The crystal phase and morphology of synthesized samples were analyzed by X-ray diffraction, transmission electron microscopy and energy dispersive spectroscopy. In addition, the content of Ru was evaluated by inductively coupled plasma. It was proposed that a monomeric form of ruthenium was incorporated on the surface of sodium titanate. Ruthenium incorporated sodium titanates were applied to alcohol oxidation using molecular oxygen as an oxidant. The sample with 7% ruthenium showed a catalytic activity with a turnover frequency value of $2.1h^{-1}$ in oxidizing benzyl alcohol to benzaldehyde without any other byproducts at $105^{\circ}C$ and 1 atmosphere.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.264-265
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• 2014

This Paper reports the photocatalytic activity of $g-C_3N_4/NaTaO_3$ hybrid composite photocatalysts synthesized by ball-mill method. The $g-C_3N_4$ and $NaTaO_3$ were individually prepared by Solid state reaction and microwave hydrothermal process, respectively. The $g-C_3N_4/NaTaO_3$ composite showed the enhanced photocatalytic activity for degradation of rhodamine B dye (Rh. B) under simulated solar light irradiation. The results revealed that the band-gap energy absorption edge of hybrid composite samples was shifted to a longer wavelength as compared to $NaTaO_3$ and the 50 wt% $g-C_3N_4/NaTaO_3$ hybrid composite exhibited the highest percentage (99.6 %) of degradation of Rh. B and the highest reaction rate constant ($0.013min^{-1}$) in 4 h which could be attributed to the enhanced absorption of the hybrid composite photocatalyst in the UV-Vis region. Hence, these results suggest that the $g-C_3N_4/NaTaO_3$ hybrid composite exhibits enhanced photocatalytic activity for the degradation of rhodamine B under simulated solar light irradiation in comparison to the commercial $NaTaO_3$.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.182-185
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• 2012

N-doped $TiO_2$nanotubes have been newly prepared by two stage sol-gel and strong-alkali hydrothermal process using $TiCl_4$ and hydrazine/ammonia aqueous solution as raw materials. These nanotubes revealed a well developed anatase crystalline phase and perfect nanotube morphology with the diameter around 10nm and the wall thickness below 3 nm. Also, they showed a superior visible light activity and yellowish color due to the light absorption redshifted by ~35 nm and ~25 nm compared to undoped $TiO_2$ nanotubes and anatase nanoparticles, respectively.

• Korean Chemical Engineering Research
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• v.48 no.6
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• pp.684-689
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• 2010

We synthesized a variety of SAPO catalysts with various structure directing agents by the hydrothermal method and applied them to the D-xylose dehydration. Single or mixtures of organic amines, viz. tetraethylammonium hydroxide(TEAOH), dipropylamine(DPA), diethylamine(DEA), morpholine and diethanolamine(DEtA) were used as structure directing agents. The $N_2$-isotherm, $NH_3$-temperature programmed desorption(TPD) and temperature programmed oxidation(TPO) were conducted to characterize SAPO catalysts. Among tested SAPO catalysts, the SAPO-34 synthesized with morpholine showed the highest furfural yield. The external surface area as well as the surface concentration of acid sites appeared to affect the catalytic activity for the dehydration of xylose into furfural.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.21-28
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• 2020

The stem extract from Pyrus serotina var has natural antioxidant ability, but the extraction method does not result in a soluble compound in cosmetic formulations. This study investigated the cosmetic efficacy of the Pyrus serotina var stem extract and its epidermis permeation ability when combined with polymer micelles and a cell penetrating peptide. The total concentration of polyphenol compounds was determined to be 103.1644 ± 1.38 mg/g in the ethanol extract and 78.97 ± 1.45 mg/g in the hydrothermal extract. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging effects were 55.94 ± 0.22% in the ethanol extract at 1,000 mg/L. Superoxide dismutase (SOD) activity rates were 104.05 ± 3.28% in the ethanol extract at 62.5 mg/L. The elastase inhibition rate was 67.21 ± 2.72% in the ethanol extract at 1,000 mg/L. An antimicrobial effect was observed in the Propionibacterium acnes strain. In the epidermal permeability experiment, it was confirmed that formulation of the polymer micelle containing the Pyrus serotina var stem extract and cell penetrating peptide (R6, hexa-D-arginine) showed small particle size and much better skin permeability. The cumulative amount of total Pyrus serotina var stem extract that penetrated to the skin over time increased over 24 hours in three formulations. The three formulations showed 51.61 ㎍/㎠ (Formulation 0), 75.97 ㎍/㎠ (Formulation 1) and 95.23 ㎍/㎠ (Formulation 2) skin penetration, respectively. Therefore, it was confirmed that the ethanol extracts of Pyrus serotina var stem showed good cosmetic efficacy and excellent epidermis permeation ability when combined with a polymer micelle and cell penetrating peptide. Thus, this extract has the potential to be used as a safe and natural cosmetic material in the future.

• Journal of the Korean Ceramic Society
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• v.26 no.6
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• pp.771-782
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• 1989

Synthesis of $\beta$-Sialon powder was attempted with carbothermal reduction of porous glass. The porous glass was prepared by heat and hydrothermal treatments of 9.32 Li2O.46.5B2O3.37.2SiO2.6.98Al2O3 glass. Carbon pyrolyzed from propane gas was deposited on the porous glass, thereafter activated carbon was added as reducing agents. The synthesized $\beta$-Sialon powder was pressureless sintered at 175$0^{\circ}C$ for 1hr in N2 atmosphere. The characterization of the $\beta$-Sialon powder was performed with XRD, BET, SEM and particle size analysis. The sinterability and mechanical properties of the sintered bodies were investigated in terms of bulk density, M.O.R., fracture toughness, morphology of microstructure and etc. The reduction effect of deposited carbon was better than that of activated carbon mechanically added. The formation of SiC was precominant over that of Si2ON2 and $\beta$-Sialon owing to low partial pressure of N2 inside the pore, wehreas on the surface of porous glass the formation of Si2ON2 and $\beta$-Sialon were predominant. Thereafter, SiC reduced unreacted glass to be $\beta$-Sialon. Single phase of $\beta$-Sialon(Z=1.92) was obtained from PGA porous glass having the largest pore radius by the simultaneous reduction and nitridation method at 145$0^{\circ}C$ for 5hrs. The bulk density, M.O.R., and KIC of the sitered body are 3.17g/cc, 434.4MPa and 4.1MPa.m1/2, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.117-120
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• 2006

$TiOCl_2$를 중화시키고 과산화수소와 반응시켜 Ti peroxo 전구체를 수열합성법을 이용하여 autoclave 반응기 내에서 가열하여 $TiO_2$ 졸을 제조하였다. Autoclave 반응기 내에 압력을 가하면 브룩카이트상 $TiO_2$졸이 형성됨을 확인하였고, 중화과정에서 NaCl을 첨가하여 Ti 수산화물 격자 내에 Na 이온을 포획되어 브룩카이트상이 나타남을 알 수 있었다. Na 이온의 첨가량에 따라 브룩카이트 결정상 함량이 달라져 광촉매 활성도 달라짐을 브룩카이트상 $TiO_2$가 코팅된 박막의 기상벤젠 광분해 실험을 통해 확인하였고 미세구조, 결정성, 광흡수도률 측정하여 특성평가를 실시하였다.

• Nuclear Engineering and Technology
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• v.15 no.1
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• pp.23-32
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• 1983

In the previous studies on Rb-Sr geochronology, Gyeonggi Massif was known as the oldest rock in Korea Peninsula but the detailed sequence of geochronology was not studied yet. In the present study, some of whole rock isochrons considered here can be geochronologically grouped as follows: The ages of leucocratic gneisses at Yangpyeong, and augen and banded gneisses at Anyang show 2200 to 2300 m.y. which may represent the time of the Massif formation or an igneous intrusion. The age of the granite gneiss distributed in Yangpyeong area shows about 1400 m.y., which apparently represents the intrusion time of the gneiss. The age of the extremely altered metamorphic rock shows about 500 m.y., which may represent the time of a Caledonian orogenic event probably with hydrothermal activities. The other episodic ages of 800 to 900 m.y. which was widely observed through the Massif, may represent the ages of Precambrian igneous activities or regional metamorphism in the Massif. It seems to be reasonable that the ages of 120 to 270 m.y. show the times of Mesozoic and Late Palaeozoic Plutonisms in the Massif.

• Korean Journal of Materials Research
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• v.20 no.8
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• pp.418-422
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• 2010

As a starting material, BCP (biphasic calcium phosphate) nano powder was synthesized by a hydrothermal microwave-assisted process. A highly porous BCP scaffold was fabricated by the sponge replica method using 60 ppi (pore per inch) of polyurethane sponge. The BCP scaffold had interconnected pores ranging from $100\;{\mu}m$ to $1000\;{\mu}m$, which were similar to natural cancellous bone. To realize the antibacterial property, a microwave-assisted nano Ag spot coating process was used. The morphology and distribution of nano Ag particles were different depending on the coating conditions, such as concentration of the $AgNO_3$ solution, microwave irradiation times, etc. With an increased microwave irradiation time, the amount of coated nano Ag particles increased. The surface of the BCP scaffold was totally covered with nano Ag particles homogeneously at 20 seconds of microwave irradiation time when 0.6 g of $AgNO_3$ was used. With an increased amount of $AgNO_3$ and irradiation time, the size of the coated particles increased. Antibacterial activities of the solution extracted from the Ag-coated BCP scaffold were examined against gram-negative (Escherichia coli) and gram-positive bacteria (Staphylococcus aureus). When 0.6 g of $AgNO_3$ was used for coating the Ag-coated scaffold, it showed higher antibacterial activities than that of the Ag-coated scaffold using 0.8 g of $AgNO_3$.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.691-696
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• 2011

CTAB or CTAB-Nafion catalyst were successfully supported on siliceous hollow tubular MCM-41 which synthesized by hydrothermal method using CTAB as a single template or CTAB and Nafion-Na as mixed templates. The properties of two kinds of catalysts were characterized with XRD, SEM and adsorption and desorption isotherms of nitrogen and pore diameter distribution, respectively. Then they were applied to catalyze brominating reaction of 1,7-heptanediol, moreover the rate of brominating reaction with different catalysts was compared. The results showed that catalytic activities of CTAB/MCM-41 and CTAB-Nafion/MCM-41 are better than CTAB, and that of CTAB-Nafion/MCM-41 is the best because of its phase-transfer and strong acidity function. The two kinds of catalysts can be separated from the reactive products and recycled.