• Journal of Pharmaceutical Investigation
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• v.35 no.2
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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.

• Journal of the Korean Magnetic Resonance Society
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• v.6 no.1
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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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• v.8 no.1
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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.

• Membrane Journal
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• v.12 no.2
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• pp.97-106
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• 2002

Small angle light scattering (SALS) and field emission scanning electron microscope (FE-SEM) have been used to investigate the light scattering patterns with time evolved during water vapor quenching (relative humidity of 53 (${\pm}3)%$ at $26^{\circ}C$ of polysulfone (PSf)/NMP/Alcohol and chlorinated poly(vinyl chloride) (CPVC)/THF/Alcohol, respective1y. Time dependence of the position of the light scattering maximum was observed at PSf dope solutions, confirming spinodal decomposition (SD), while CPVC dope solutions showed a decreased scattered light intensity with an increased q-value, indicating nucleation & growth (NG). For the each system, domain growth rate in the intermediate and late stage of phase separation decreased with increasing the number of carbon of alcohol used as additive (non-solvent). Also, in the early stage for SD, the scattering intensity with time was in accordance with Cahn's linear theory of spinodal decomposition, regardless of types of non-solvent additive. Also, the size scales obtained by SALS were mutually compared to domain sizes gained by FE-SEM measurement. These observations of scattering pattern were much clearly observed for the 20PSf/70NMP/10n-butanol (w/w%) and agreed with the theoretical predictions for scattering patterns of each stage like the early, the intermediate, and the late stage of SD type phase separation. As the scattering maximum was observed at the larger angles (larger q) in the order of n-butanol > n-propanol > methanol > no alcohol, the pore size of final morphology decreased.

• Korean Journal of Materials Research
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• v.26 no.12
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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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.5
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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.

• Journal of Powder Materials
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• v.30 no.2
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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.

• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.317-322
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• 2020

Hydroxylammonium nitrate (HAN; NH₃OHNO₃) is an ionic energy material having a low melting temperature and vapor pressure with a high oxygen balance. To utilize it as an oxidizer for a high content liquid mono-propellant, a dual solvent was used to obtain HAN in a solid particulate form. The dehydrated crystal from an aqueous HAN was washed with dual organic solvents including acetone and ethanol, finally resulting in the moisture content of 13.8 wt%. When acetone was applied as a single solvent, the maximum synthesis yield of 88%, the HAN content evaluated by TGA of 86.2%, and the decomposition temperature ranged 160℃ to 205℃ were achieved.

• Applied Chemistry for Engineering
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• v.1 no.1
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• pp.73-82
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• 1990

Rosin-maleic anhydride adduct (RMA) was synthesized from rosin and maleic anhydride. The polyamideimides were obtained by reacting the adduct with two aromatic diisocyanates using sodium methoxide as catalyst. The yield and the inherent viscosity of polymers obtained by the reaction in NMP solvent were low because of the possible reaction of NMP solvent with diisocyanate monomer. The polymers were synthesized in solvent mixture of NMP and cosolvents such as xylene, acetophenone, benzonitrile, and nitrobenzene in order to minimize the side reaction of NMP with diisocyanates. The yield of polymer obtained by the reaction in NMP-nonpolar cosolvent mixtures was about 70% and that obtained by the reaction in NMP-polar cosolvent mixtures was over 90%, respectively. The polymers were either amorphous or poorly cystalline, and soluble only in highly polar solvents. The inherent viscosity of polymers ranges from 0.12-0.26dl/g. The results of thermal analysis showed that the polymer had good thermal stability with initial decomposition temperature over $330^{\circ}C$.

• Resources Recycling
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• v.20 no.6
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• pp.50-55
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• 2011

Using ultrasonic irradiation, the separation and recovery of PV cell, made of silicon wafer, from PV module was carried out through selective decomposition of EVA used as an interlaminated binder. The ultrasonic cleaner of bath-type (Output: 130 W, Frequency: 40 kHz) was used as an ultrasonic apparatus in this research. With the fixed distance of 2 cm, from ultrasonic generator to PV cell, the experiment of EVA decomposition was performed in various organic solvents such as Toluene, Trichloroethylene, O-dichlorobenzene, Benzene. And also their concentrations and temperature was changed to survey the optimum conditions. However EVA can be decomposed perfectly at $55^{\circ}C$ within 160 min in 5 M of all kinds of solvent, PV cell may be recovered with being damaged or broken severely. This damage may be resulted from the swelling of EVA in the process of decomposition. Whereas, at the condition of 5 M at $65^{\circ}C$, PV cell can be recovered with the state of minor damage or crack. This implies that the decomposition rate of EVA increases with an increase of temperature, thereby EVA can be decomposed before the swelling of EVA layer. Conclusively, it is possible for PV cell to be recovered within 40 min, at $65^{\circ}C$ in 5 M, with less damage.