• Macromolecular Research
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• v.17 no.3
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• pp.187-191
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• 2009

Platinum (Pt) nanoparticles were prepared by the liquid-phase reduction of tetraammineplatinum (II) chloride $([Pt(NH_3)_4]Cl_2)$ using Nafion as a stabilizer under various conditions of the Nation phase. This method is novel in its use of electrostatic interactions between the Pt complex ions and sulfonic groups in the hydrated Nation molecules. The synthesized Pt nanoparticles of the recast film system had a cubic shape. In the case of the Nation solution system, the Pt nanoparticles mainly had a spherical shape. The shapes and sizes of the Pt nanoparticles were strongly influenced by the Nation phase.

• Membrane and Water Treatment
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• v.11 no.4
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• pp.237-245
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• 2020

The effects of the mixed two solvents, Dimethylacetamide (DMAc) and Dimethylformamide (DMF), and Polyethylene glycol (PEG) and Polyvinylpyrrolidone (PVP) as additives on performance of Polyvinylidene fluoride (PVDF) membranes were studied. Initially, PEG200 was used as a primary additive at fixed percentage of 5% wt. PVP was then blended with PEG200 in different concentrations. PVDF and DMAc were used as polymer and solvent in the casting solutions, respectively. To control the diffusion rate of PVP in the presence of PEG200 and PVP blend, mixtures of DMAc and DMF were used as the mixed solvent in the casting solutions. Asymmetric PVDF membranes were prepared via phase inversion process in a water bath and the effects of two additives and two solvents on the membrane morphology, pure water flux (PWF), hydrophilicity and rejection (R) were investigated. Attenuated Total Reflection Fourier Transform Infrared Spectra (ATR-FTIR) analysis was used to show the residual PVP on the surface of the membranes. Atomic Force Microscopy (AFM) was utilized to determine roughness of membrane surface. The use of mixed solvents in the casting solution resulted in reduction of PVP diffusion rate and increment of PEG diffusion rate. Eventually, PWF and R values reduced, while porosity and hydrophilicity increased.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2283-2289
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• 2018

$TiO_2$ microspheres were successfully synthesised by simple solution phase method by using various amount of titanium butoxide as precursor. The prepared $TiO_2$ were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance absorption spectra (UV-DRS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XRD analysis revealed that the as-synthesized $TiO_2$ microsphere poses an anatase phase. The photocatalytic degradation experiments were carried out with three different dyes, such as methylene blue, brilliant black, reactive red-120 for four hours under UV light irradiation. The results show that $TiO_2$ morphology had great influence on photocatalytic degradation of organic dyes. The experimental results of dye mineralization indicated the concentration was reduced by a high portion of up to 99% within 4 hours. On the basis of various characterization of the photocatalysts, the reactions involved to explain the photocatalytic activity enhancement due to the concentration of titanium butoxide and morphology include a better separation of photogenerated charge carriers and improved oxygen reduction inducing a higher extent of degradation of aromatics.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.594-599
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• 2011

$SrAl_2O_4:Eu$ green phosphor was prepared by spray pyrolysis and its luminescence properties were controlled by replacing the Al sites with boron and using organic modifier or drying control chemical additive. It was clear that the substitution of B into the Al sites was helpful to obtain pure monoclinic $SrAl_2O_4$ phase and greatly enhance the emission intensity. In terms of the emission intensity, the optimal content of boron was about 1 at% with respect to the aluminum element. The luminescence intensity of $Sr_{0.9}Al_{1.98}B_{0.02}O_4:Eu_{0.1}$ phosphor could be improved by the use of 0.2 M organic additives in the spray solution. Futhermore, using 0.5 M dimethylformamide(DMF) as a drying control chemical with organic additives made it possible to improve about 172% the emission intensity of $Sr_{0.9}Al_{1.98}B_{0.02}O_4:Eu_{0.1}$ phosphor. According to XRD analysis, the organic additive and DMF used enhanced the crystallinity without any change in the crystal phase. When used only the organic additive without DMF, the surface area of the prepared $Sr_{0.9}Al_{1.98}B_{0.02}O_4:Eu_{0.1}$ phosphor became enlarged. The use of DMF with the organic additive resulted in significant reduction in the surface area. It was concluded that the increase of the crystallinity as well as the reduction of surface area mainly contribute to the improvement in the luminescence intensity of $Sr_{0.9}Al_{1.98}B_{0.02}O_4:Eu_{0.1}$ phosphor prepared using DMF and organic additives.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.9
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• pp.582-588
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• 2014

3 mol% Co-added $Ni(OH)_2$ fine powders, which showed ${\beta}$-phase, as positive electrode materials have been fabricated using $NiSO_4{\cdot}6H_2O$ aqueous solution by ultrasonic spray-chemical precipitation and subsequent hydrothermal method, and sheet-like Ni nanopowder was fabricated by mechano-chemical reduction method. The addition effects of the sheet-like Ni nanopowder on the electrochemical properties of the positive electrode in Ni-Zn Redox flow battery were investigated. Impedance spectroscopy revealed that the addition of the sheet-like Ni nanopowder resulted in decrease in the electrical resistivity; 10 wt.% addition reduced the electrical properties by a fifth. Cyclic voltammetry showed the addition of the sheet-like Ni nanopowder resulted in decrease in the potential difference of oxidation and reduction; this means the increase in the reversability for electrode reduction. Charge/discharge measurement confirmed that the addition of the sheet-like Ni nanopowder resulted in the increase in the discharge efficiency.

• Korean Journal of Metals and Materials
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• v.49 no.8
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• pp.596-600
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• 2011

Thermal degradation behavior of a $WO_3-TiO_2$ monolithic catalyst was investigated in terms of structural, morphological, and physico-chemical analyses. The catalyst with 4 wt.% $WO_3$ contents were prepared by a wet-impregnation method, and a durability test of the catalysts were performed in a temperature range between $400^{\circ}C$ and $800^{\circ}C$ for 3 h. An increase of thermal stress decreased the specific surface area, which was caused by grain growth and agglomeration of the catalyst particles. The phase transition from anatase to rutile occurred at around $800^{\circ}C$ and a decrease in the Brønsted acid sites was confirmed by structural analysis and physico-chemical analysis. A change in Brønsted acidity can affect to the catalytic efficiency; therefore, the thermal degradation behavior of the $WO_3-TiO_2$ catalyst could be explained by the transition to a stable rutile phase of $TiO_2$ and the decrease of specific surface area in the SCR catalyst.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.5
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• pp.228-236
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• 2009

In this study, we investigated morphological characteristics of $SF_6$ clathrate hydrate crystals to understand its formation and growth mechanism. $SF_6$ clathrate hydrate crystals were formed in high-pressure reaction cell charged with pure water and $SF_6$ gas at constant pressure and temperature. Two-phase ($SF_6$ gas/aqueous solution) and three-phase ($SF_6$ gas/aqueous solution/$SF_6$ liquid) conditions were investigated, In both conditions, dendritic shape hydrate crystals were grown as like fibriform crystals along upward growth direction at the gas/aqueous solution interface. In the case of the reaction process of three-phase condition, when the $SF_6$ gas bubbles which were generated in $SF_6$ liquid phase due to the reduction of reaction cell pressure stuck to the gas/aqueous interfaces, the hydrate phase were appeared at the surface of the bubbles. This paper presents the detail growth characteristics of $SF_6$ hydrate crystals including crystal nucleation, migration, growth and interference.

• Journal of the Korean Chemical Society
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• v.36 no.3
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• pp.412-418
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• 1992

The electrochemical behaviors and analytical application of copper-1,5,9,13-tetrathiacyclohexadecane[16-ane-$S_4$] complex in acetonitrile(AN) solution have been investigated by the use of DC polarography and differential pulse polarography. Thus the formation constant of copper complex was $10^{3.51}$. Copper (Ⅱ) ion was found to form complex of 1-to-1 composition with [16-ane-$S_4$]. In addition, reduction step was irreversible and the reduction current was diffusion controlled. And the effect of concentration of the salting-out reagent and chelating agent and pH of aqueous phase on the determination of copper (Ⅱ) was investigated and diverse ion effect was discussed. By salting-out extraction technique, we can be determined until the concentration of copper (Ⅱ) of 60 ppb.

• Membrane and Water Treatment
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• v.9 no.2
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• pp.69-77
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• 2018

The use of membrane as an innovative technology for water treatment process has now widely been accepted and adopted to replace the conventional water treatment process in increasing fresh water production for various domestic and industrial purposes. In this study, ultrafiltration (UF) membranes with different formulation were fabricated via phase inversion method. The membranes were fabricated by varying the polymer concentration (16 wt%, 18 wt%, 20 wt%, and 21 wt%). A series of tests, such as field emission scanning electron microscope (FESEM), pore size and porosity, contact angle, and zeta potential were performed to characterize the membranes. The membrane performance in terms of permeation flux and rejection were evaluated using a laboratory bench-scale test unit with mine water, lake water and tube well as model feed solution. Long hour filtration study of the membranes provides the information on its fouling property. Few pore blocking mechanism models were proposed to examine the behaviour of flux reduction and to estimate the fouling parameters based on different degree of fouling. 21 wt% PVDF membrane with smaller membrane pore size showed an excellent performance for surface water treatment in which the treated water complied with NWQS class II standard.

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.587-592
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• 2017

Uniform and optimum sized silver nanoplates were synthesized through the liquid phase reduction method by using silver nitrate solution as a starting chemical, dimethylformmide (DMF) as a reducing solvent, and polyvinylpyrrolidone (PVP) as reducing and surfactant agents. Synthesized and also film samples were characterized by using SEM, TEM, UV-Vis-NIR spectroscopy, particle size analyzer (PSA), and XRD. Triangle nanoplates with the size of 100~200 nm were found from the sample synthesized at $70^{\circ}C$ for 72 h using silver nitrate, DMF and 26 wt% PVP. The sample could reflect near-infrared light because it showed the maximum absorbing peak at about 1,000 nm. When the content or particle size of silver nanoplates increased in coating solutions, the transmittance decreased and the reflectance increased in film samples.