• Journal of Pharmaceutical Investigation
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• 제35권2호
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• pp.95-99
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• 2005

Mucoadhesive microspheres were prepared by interpolymer complexation of chitosan with poly(acrylic acid) (PAA) and solvent evaporation method to increase gastric residence time. The chitosan-PAA complex formation was confirmed by differential scanning calorimetry and swelling study. The DSC thermogram of chitosan-PAA microspheres showed two exothermic peaks for the decomposition of chitosan and PAA. The swelling ratio of the chitosan-PAA microspheres was dependent on the pH of the medium. The swelling ratio was higher at pH 2.0 than at neutral pH. The results indicated that the microspheres were formed by electrostatic interaction between the carboxyl groups of PAA and the amine groups of chitosan. The effect of various process parameters on the formation and morphology of microspheres was investigated. The best microspheres were obtained when 1.5% of the high molecular weight chitosan and 0.3% of PAA were used as an internal phase. The optimum internal phase volume was 7%. The com oil was used as the external phase of emulsion, and span 80 was used as the surfactant. The prepared microspheres had spherical shape.

• 한국자기공명학회논문지
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• 제6권1호
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• pp.78-83
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• 2002

A new fluoroquinolone (DW-116) with a broad antibacterial spectrum was synthesized by introducing functional fluoropyridyl and methylpyrazine groups on N1, C7 position of quinolone moiety, respectively. $^{1}$H and $^{13}$ C NMR signal assignments and structure were completely elucidated by 2D-NMR methods. Physicochemical properties of products were also investigated. DW-116 is decomposed at 306.9$^{\circ}C$ and the decomposition starts at around 285$^{\circ}C$. The free base form is melt at 280.7$^{\circ}C$ and started to be decomposed immediately. DW-116 has two kinds of polymorphism which is important in drug action but these two plate and rod types have the same solubility in water. However the solubility is quite different in less or polar solvent. The plate type is more soluble in less polar solvent except in dichloromethane.

• Carbon letters
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• 제8권1호
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• pp.6-11
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• 2007

Carbon/$TiO_2$ composites were prepared by $CCl_4$ solvent mixing method with different mixing ratios. Since the carbon layers derived from pitch on the $TiO_2$ particles were porous, the Carbon/$TiO_2$ composite series showed a good adsorptivity and photo decomposition activity. The BET surface area for the carbon layer in the sample increases to increasing with pitch contents. The SEM results present to the characterization of porous texture on the Carbon/$TiO_2$ composite and pitch distributions on the surfaces for all the materials used. From XRD data, a weak and broad carbon peak of graphene with pristine anatase peaks were observed in the X-ray diffraction patterns for the Carbon/$TiO_2$. The EDX spectra show the presence of C, O and S with strong Ti peaks. Most of these samples are richer in carbon and major Ti metal than any other elements. Finally, the excellent photocatalytic activity of Carbon/$TiO_2$ with slope relationship between relative concentration (C/$C_0$) of MB and t could be attributed to the homogeneous coated pitch on the external surface by $CCl_4$ solvent method.

• 멤브레인
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• 제12권2호
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• pp.97-106
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• 2002

Polysulfone (PSf/NMP/alcohol 용액과 chlorinated poly(vinyl chloride) (CPVC)/THF/Alcohol 용액에 대한 광산란 패턴을 SALS (Small angle light scattering)와 FE-SEM (field emission scanning electron microscope)을 이용하여 조사하였다. PSf 용액에서는 시간에 따라 q값의 최대 산란 강도를 보이는 광산란 거동을 나타내어 스피노달 (SD) 상분리 거동을 나타내는 반면, CPVC 용액에서는 q값이 증가함에 따라 광산란 강도가 줄어드는 핵성장 (NG) 거동을 나타냈다. 각 고분자 용액에서 상분리 중반과 후반부에서 비용매 첨가제로 사용된 알코올의 탄소수가 증가할수록 농도분극의 증가율은 줄어들었다. 또한, SD에서의 초반부의 시간에 따른 산란 강도는 비용매 첨가제의 종류에 무관하게 Cahn의 건형 이론에 잘 부합되었다. 또한, SALS 장치로 얻어진 기공크기와 전자현미경으로 얻어진 영역 크기는 상호간에 비교되었다. 20PSf/70NMP/10n-butano1 (w/w%) 용액에 대한 산란 패턴은 초기 상분리 거동에서부터 후기 거동까지 매우 선명하게 관측되었고, 초반, 중반, 그리고 후반부에 대한 SD에 대한 이론적 결과와 잘 일치하였다. 최고의 산란강도를 나타낸 각도의 크기는 n-butanol>n-propanol>methanol>no alcohol 순으로 관찰되었으며, 이 순서로 최종 형성된 막 단면의 기공 크기가 감소되는 것으로 조사되었다.

• 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.

• 한국전기전자재료학회논문지
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• 제17권5호
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• pp.486-491
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• 2004

Dimensionally stable anode(DSA) can be used for the hydro-metallurgy of non-ferrous metals like as Zn, and the electrolysis of sea water. MnO$_2$ electrode satisfies the requirements of DSA, and has a good cycle life and a low overpotential for oxygen evolution. MnO$_2$ electrodes based on Ti matrix were prepared by using thermal decomposition method and also MnO$_2$ was coated on Ti and Pb matrix with DMF and PVDF compositions. The MnO$_2$ electrodes prepared by thermal decomposition method had very weak adhesive strength onto Ti matrix and MnO$_2$ layer was removed out so that electrochemical properties for MnO$_2$ were not investigated. The viscosity of solvent used as a binder of MnO$_2$ Powder increased with the increasing PVDF contents. The thickness of the MnO$_2$ layer on Pb matrix in DSA, which was prepared with 5 times dipping at the solution mixed with PVDF : DMF = 1 : 9, was 150${\mu}{\textrm}{m}$. When the ratio of PVDF to MnO$_2$ was lower than 1 : 6, the Pb electrode didn't show any reaction irrespective of the concentrations of DMF. However, When the ratio of PVDF to MnO$_2$ was higher than 1: 6, the Pb electrode showed constant current reactions and homogeneous cyclic voltammetry even though at a high cycle. The reason for the high current and homogeneous cyclic voltammetry is the good catalytic reactions of MnO$_2$ powder in electrode.

• 한국분말재료학회지
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• 제30권2호
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• pp.101-106
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• 2023

Liquid metal extraction (LME), a pyrometallurgical recycling method, is popular owing to its negligible environmental impact. LME mainly targets rare-earth permanent magnets having several rare-earth elements. Mg is used as a solvent metal for LME because of its selective and eminent reactivity with rare-earth elements in magnets. Several studies concerning the formation of Dy-Fe intermetallic compounds and their effects on LME using Mg exist. However, methods for reducing these compounds are unavailable. Fe reacts more strongly with B than with Dy; B addition can be a reducing method for Dy-Fe intermetallic compounds owing to the formation of Fe₂B, which takes Fe from Dy-Fe intermetallic compounds. The FeB alloy is an adequate additive for the decomposition of Fe₂B. To accomplish the former process, Mg must convey B to a permanent magnet during the decomposition of the FeB alloy. Here, the effect of Mg on the transfer of B from FeB to permanent magnet is observed through microstructural and phase analyses. Through microstructural and phase analysis, it is confirmed that FeB is converted to Fe₂B upon B transfer, owing to Mg. Finally, the transfer effect of Mg is confirmed, and the possibility of reducing Dy-Fe intermetallic compounds during LME is suggested.

• 공업화학
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• 제31권3호
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• pp.317-322
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• 2020

수산화암모늄나이트레이트(HAN; NH₃OHNO₃)는 낮은 용융점과 증기압의 특성을 가지고 있고, 상대적으로 높은 산소균형을 이루고 있는 이온성 화합물이다. 본 연구에서는 높은 함량의 액상추진제를 제조하기 위한 산화제로 활용하기 위하여 이중용매를 적용하여 고체입자상으로 얻었다. 감압 하에서 액상의 HAN으로부터 수분을 증발시킨 후, 반용매로서 아세톤과 에탄올을 적용하여 추출한 입자상의 HAN에는 13.8 wt%의 수분이 포함되어 있었다. 아세톤을 단독으로 적용하였을 때, 합성수율은 질량기준으로 최대 88%이었고, TGA로 측정된 최대 함량은 86.2%, 분해온도는 160~205℃ 범위로 나타났다.

• 공업화학
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• 제1권1호
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• pp.73-82
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• 1990

로진과 말레산무수물로부터 rosin-maleic anhydride adduct (RMA)를 합성하고 이를 방향족디이소시아네이트와 반응시켜서 폴리아미드이미드를 합성하였다. 반응촉매로는 Sodium methoxide ($CH_3ONa$)를 사용하였고 반응용제로는 N-메틸-2-피롤리돈 (이하 NMP)을 사용하였다. NMP는 방향족디이소시아네이트와 부반응을 하기 때문에 중합체의 수율과 점성도가 낮았다. 부반응을 줄이기 위하여 NMP에 방향족용제인 크실렌, 아세토페논, 벤조니트릴 및 니트로벤젠을 공용제로 혼합, 사용하였다. 극성이 비교적 작은 공용제의 혼합시 공용제 혼합비율이 60%인 경우 약 70%정도, 극성이 비교적 큰 공용제의 혼합계에서는 혼합비율이 40%인 경우 90% 이상의 수율로서 높은 수율을 얻을 수 있었다. 중합체는 무정형이거나 약간의 결정성을 갖는 구조였으며 고극성용제에서만 용해하였다. 중합체의 점성도는 0.12-0.26dl/g의 범위였다. 열분석 결과 중합체의 초기분해온도는 $330^{\circ}C$ 이상으로서 양호한 열안정성을 나타내었다.

• 자원리싸이클링
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• 제20권6호
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• pp.50-55
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• 2011

태양전지(Photovoltaic, PV) 모듈의 층간 접착제로 사용된 EVA(Ethylene Vinyl Acetate)를 초음파 조사(irradiation)를 이용하여, 선택적으로 분해함으로써 모듈 내 실리콘웨이퍼(Si-wafer)로 제조된 셀(cell)을 분리, 회수하는 연구를 진행하였다. 본 실험에 사용한 초음파 발생장치는 bath-type의 초음파 세척기 (Output: 130 W, Frequency: 40 kHz)로, PV모듈과의 거리는 2 cm로 고정하고 유기용매 종류, 농도, 온도를 조절하면서 EVA 분해 및 셀의 분리 최적 조건을 도출하였다. $55^{\circ}C$, 5M인 조건에서는 용매 종류에 상관없이 160 min 이내에 EVA층의 완전 분해는 가능하였으나, 분해과정 중 발현되는 팽창현상(swelling)에 의해 셀의 일부분이 파손된 상태로 회수되었다. 반면에 $65^{\circ}C$, 5M조건에서는 셀의 파손이 억제된 상태로 회수 가능하였으며, 이는 온도 상승에 의해 EVA 성분의 분해속도가 상승되고, 이로 인해 EVA층의 팽창현상이 발현되기 전에 분해가 일어난 결과라고 판단된다.