• 한국수소및신에너지학회논문집
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• 제25권3호
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• pp.305-310
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• 2014

This study examined the morphological changes in lithium surface immersed in 1mol $dm^{-3}$ (M) $LiPF_6 $ dissolved in propylene carbonate (PC) containing different 1,2-dimethoxyethane (DME) concentrations as a co-solvent. A passivation film was formed on the surface of lithium metal by electrolyte decomposition. The passivation film formation reactions were significantly affected by the amount of co-solvent, DME, in electrolyte solution. A stable film was obtained from the 1 M $LiPF_6 $ / PC:DME (67:33) solution in which lithium electrode showed good electrochemical performances. Atomic force microscope (AFM) and electrochemical impedance spectroscopy (EIS) results revealed that there were no direct correlations between changes in the surface morphology of lithium metal and the resistance behavior of its passivation film.

• 접착 및 계면
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• 제4권4호
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• pp.1-6
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• 2003

대기압 플라즈마를 이용하여 폴리프로필렌 필름의 표면을 처리한 후 각각 극성 용매(water)와 비극성 용매(diiodomethane)를 사용한 접촉각 측정기로 필름 표면의 접촉각을 측정하였다. 측정된 접촉각을 이용해 표면 자유에너지 변화를 계산한 후 대기압 플라즈마 처리 전후의 폴리프로필렌 필름의 접촉각과 표면 자유에너지 상태를 비교, 분석하였다. 또한 대기압 플라즈마의 처리 조건을 바꿔가며 폴리프로필렌 필름 표면을 처리함으로써 접촉각과 표면 자유에너지가 각각의 처리 조건에 따라 어떠한 영향을 받는지 연구하였다. 대기압 플라즈마 처리 조건에 따라 접촉각 및 표면 자유에너지는 최적값을 보여주거나 일정한 값에 도달하는 경향을 보여 주었다.

• 한국군사과학기술학회지
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• 제11권3호
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• pp.154-160
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• 2008

We investigated molecular polarity by using theoretical means and comparing empirical solvent polarity. Our approach employed electrostatic potentials at the molecular surface calculated by density functional methods. A number of molecular descriptors related to molecular polarities were computed from molecular surface electrostatic potentials. Among computed molecular descriptors, the most positive electrostatic potential provided the best correlation with the empirical solvent polarities. A regression equation was developed in order to predict molecular polarities of molecules whose experimental solvent polarities were unknown. The new regression equations were utilized in estimating solvent polarities of cubane derivatives which are considered important precusors of high-energy density meterials.

• Korean Chemical Engineering Research
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• 제56권1호
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• pp.14-23
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• 2018

The effect of dodecylbenzene sulfonic acid (DBSA) with different addition amount of DBSA ($M_{DBSA}$), temperatures and solvent-to-oil ratio (SOR, v/v) on asphaltene aggregation in a solvent deasphalting system was investigated. Increasing the $M_{DBSA}$ at SOR 10 and $55^{\circ}C$ caused the asphaltene removal ratio (ARR) to increase first, then maximize at 1 wt% of $M_{DBSA}$ and then decrease continuously. Based on the SARA (saturate, aromatic, resin, asphaltene) composition, the adsorption amount of DBSA on the asphaltene surface and the self-aggregation of the DBSA, the reason for the change in ARR with $M_{DBSA}$ was found due to the adsorption mechanism. In addition, the asphaltene-resin-DBSA colloidal size confirmed the change of adsorption behavior between the asphaltene and DBSA. Based on the results of this study, a hypothetical adsorption mechanism of DBSA on asphaltene aggregation in the solvent deasphalting system was conceived of and proposed.

• 분석과학
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• 제21권2호
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• pp.117-122
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• 2008

표면오염도 측정용 검출소재로 주로 이용되고 있는 알파와 베타선의 동시 측정용 이중섬광체 검출소재를 개발하였다. 본 연구에서는 기존의 열용융 공정이 아닌, 고분자 소재를 용매로 녹여서 검출소재를 제조하는 용매법을 이용함으로써 제조공정을 단순화하였다. 베타선 측정용 플라스틱 섬광체는 유기섬광체, 고분자, 그리고 용매가 혼합된 용액을 도말한 후에 고형화하여 제조하였다. ZnS(Ag) 섬광체는 플라스틱 섬광체 위에 ZnS(Ag), 접착소재, 그리고 용매가 혼합된 용액을 스크린 프린팅 방법으로 도포하여 제조하였다. 제조한 이중섬광체의 알파선과 베타선에 대한 방사능 검출 성능을 평가한 결과 우수한 검출 성능을 확인하였으며, 표염오염도 측정용 소재로 적용이 가능함을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제13권6호
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• pp.613-620
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• 1992

The solvent-dependent photophysical properties of 2-biphenylcarboxylic acid (2BPCA) and 4-biphenylcarboxylic acid(4BPCA), which have a pre-twisted conformation in the ground state, have been investigated. The fluorescence spectra of 4BPCA show vibrational structure with a non-mirror image to the absorption spectra in nonpolar solvent while those of 2BPCA show no structure even in nonpolar solvents. As the solvent polarity increases, the fluorescence spectra become diffuse and broad with a strong red shift resulting in the large Stokes shift. The large fluorescence Stokes shift of BPCA's in polar solvent is also partially due to an intramolecular charge transfer (ICT) interaction in the excited state, as demonstrated by the large dipole moment in the excited state (7.6-10.6 D). The fluorescence decay behaviors of BPCA's (decay-times and their pre-exponential factors) also depend on solvent polarity in agreement with the solvent-dependent properties of the steady-state fluorecence. The data have been discussed in terms of change in the excited-state potential energy surface with respect to change of the dihedral angle of biphenyl moiety.

• Environmental Engineering Research
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• 제23권3호
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• pp.309-315
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• 2018

Chlortetracycline (CTC) is one of the most important compounds in antibiotic production, and its distribution has been widely investigated due to health and ecological concerns. This study presents systematic approach to optimize the high-performance liquid chromatography-tandem mass spectrometry for analyzing CTC in a multiple reaction monitoring mode ($479{\rightarrow}462m/z$). One-factor-at-a-time (OFAT) test with response surface analysis (RSA) was used as optimization strategy. In OFAT tests, the fragmentor voltage, collision energy, and ratio of acetonitrile in the mobile phase were selected as major factors for RSA. The experimental conditions were determined using a composite in cube design (CCD) to maximize the peak area. As a result, the partial cubic model precisely predicted the peak area response with high statistical significance. In the model, the (solvent composition) and (collision $energy^2$) terms were statistically significant at the 0.1 ${\alpha}$-level, while the two-way interactions of the independent variables were negligible. By analyzing the model equation, the optimum conditions were derived as 114.9 V, 15.7 eV, and 70.9% for the fragmentor voltage, collision energy, and solvent composition, respectively. The RSA, coupled with the CCD, offered a comprehensive understanding of the peak area that responds to changes in experimental conditions.

• 공업화학
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• 제10권6호
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• pp.822-827
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• 1999

본 연구에서는 에너지 밀도가 큰 초고용량 캐패시터를 제작하기 위한 기초 연구로서 활성탄소섬유의 물성과 유기 전해질의 특성이 초고용량 캐패시터의 전기화학적 특성에 미치는 영향을 조사하였다. 유기성 전해질의 경우는 이온의 크기가 수용성 전해질 보다 훨씬 크기 때문에 탄소전극의 세공크기에 많은 영향을 받으며, 용량을 발현할 수 있는 유효세공의 크기가 커야 한다는 것을 알 수 있었다. 혼합용매를 이용한 전해액의 조성은 큰 비축전용량과 빠른 충전속도, 그리고 낮은 ESR 및 방전전류의 세기에 대한 높은 비축전용량 유지성 등의 우수한 충방전 특성을 나타내는 것을 알 수 있었고, 전해질의 높은 이온전도도가 용량발현 및 자가방전 특성에 큰기여를 하고 있으며, 전해질 이온의 크기는 충전속도에 많은 영향을 미치는 것을 알 수 있었다.

• 한국재료학회지
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• 제26권12호
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• pp.733-740
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• 2016

$Al_2O_3$ nanosol dispersed under ethanol or N-Methyl-2-pyrrolidone(NMP) was studied and optimized with various dispersion factors and by utilizing the silane modification method. The two kinds of $Al_2O_3$ powders used were prepared by thermal decomposition method from aluminum ammonium sulfate$(AlNH_4(SO_4)_2)$ while controlling the calcination temperature. $Al_2O_3$ sol was prepared under ethanol solvent by using a batch-type bead mill. The dispersion properties of the $Al_2O_3$ sol have a close relationship to the dispersion factors such as the pH, the amount of acid additive(nitric acid, acetic acid), the milling time, and the size and combination of zirconia beads. Especially, $Al_2O_3$ sol added 4 wt% acetic acid was found to maintain the dispersion stability while its solid concentration increased to 15 wt%, this stability maintenance was the result of the electrostatic and steric repulsion of acetic acid molecules adsorbed on the surface of the $Al_2O_3$ particles. In order to observe the dispersion property of $Al_2O_3$ sol under NMP solvent, $Al_2O_3$ sol dispersed under ethanol solvent was modified and solvent-exchanged with N-Phenyl-(3-aminopropyl)trimethoxy silane(APTMS) through a binary solvent system. Characterization of the $Al_2O_3$ powder and the nanosol was observed by XRD, SEM, ICP, FT-IR, TGA, Particles size analysis, etc.

• Macromolecular Research
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• 제13권5호
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• pp.409-417
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• 2005

The surface of rutile titania nanoparticles was chemically modified by reacting with alkoxy silane. The surface and rheological properties in silicone oil having a wide range of viscosity were investigated. Total surface free energy($\gamma_S$) of the titania particles decreased from 53.12 to 26.94 mJ/$m^2$ as the silane used for surface treatment was increased from 0 to 5.0 wt$\%$. The surface free energy of neat silane was 25.5 mJ/$m^2$, which is quite close to that oftitania particles treated with 5.0 wt$\%$ silane. Due to the hydrophobic nature oftreated-titania, the contact angle was accordingly higher for polar solvent in the order of water>ethylene glycol> formamide>$\alpha$-bromonaphthalene. In sum of rheological behavior, as the applied shear stress or viscosity of the silicone oil increased, the titania particles tend to form layers and agglomerated clusters, showing shear-thinning and shear-thickening behaviors, sequentially. A good dispersion of discrete titania particles obeying a Newtonian flow behavior was achieved at a surface energy or low concentration of silane-treated titania particles in hydrophobic silicone oil.