• Polymer(Korea)
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• v.33 no.6
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• pp.596-601
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• 2009

We prepared nanoparticles containing insoluble aceclofenac by the method of solid dispersions using spray dryer to improve solubility of aceclofenac. We used PVP-K30 as a water soluble carrier for the solid dispersion and poloxamer as a surfactant. Characterization of aceclofenac solid dispersion was performed by SEM, DSC, XRD and FT-IR. The results of SEM, DSC and XRD demonstrated that aceclofenac is amorphous in solid dispersion. The formation of salt by hydrogen bond between aceclofenac and PVP K-30 was confirmed by FT-IR. The dissolution rate measured in intestinal juice showed the method of solid dispersion improved aceclofenac solubility as compared with a conventional drug($Airtal^{(R)}$). In conclusion, the method of solid dispersion using spray dryer would improve solubility of aceclofenac in oral administration.

• Journal of Hydrogen and New Energy
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• v.28 no.4
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• pp.419-425
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• 2017

In this study, an efficient dye-sensitive solar cells (DSSC) was developed after post-treatment of ZnO on $TiO_2$ photoelectrode. The $TiO_2$ electrode with ZnO post treatment was prepared with Titanium isoporopoxide in Zinc Nitrate Hexahydrate aqueous solution by incineration for 30 min at $450^{\circ}C$. The ZnO-post treated $TiO_2$ electrode showed strong dispersion force between particles in relation to the control $TiO_2$, referring high specific surface area and dye-adsorption rate. Proper addition of ZnO enhanced electron mobility and reduced internal resistance and electron recombination. Light conversion efficiency of DSSCs containing the ZnO-posttreated $TiO_2$ electrode increased 35.4% when compared to the DSSCs using $TiO_2$ electrode. It is similar to the DSSCs with $TiCl_4$ post treatment $TiO_2$ electrode. Increasing of light conversion efficiency was due to high specific surface area and dispersion force, and low dye-adsorption rate and electron recombination. Taken together, ZnO may be used as posttreatment of photoelectrode and replaced $TiCl_4$ that has high toxicity and causticity.

• Analytical Science and Technology
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• v.19 no.5
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• pp.394-399
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• 2006

The polishing performance and the relationships of electrochemistry depending upon oxidizers and additives in the tungsten CMP slurry used in semiconductor industry were investigated. Hydrogen peroxide, ferric nitrate and potassium iodate were used as oxidizers and they showed different oxidation reactions on tungsten film depending on the kind of oxidizers and pH of slurry. The differences influenced the polishing performance. Etching reaction was predominated in the hydrogen peroxide. However, passivation reaction was prevailed in ferric nitrate and potassium iodate. TMAH and KOH raised the potential energy and removal rate of tungsten, and improved a dispersion characteristic of slurry by increasing absolute value of zeta potential. Addition of 100 ppm of poly(acrylic acid) of M.W. 250,000 improved dispersion ability.

• Journal of Hydrogen and New Energy
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• v.25 no.3
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• pp.227-233
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• 2014

Simulated waste-derived synthesis gas has been tested for hydrogen production through water-gas shift (WGS) reaction over supported Cu catalysts prepared by co-precipitation method. $CeO_2$, $ZrO_2$, MgO, and $Al_2O_3$ were employed as supports for WGS reaction in this study. $Cu-CeO_2$ catalyst exhibited excellent catalytic activity as well as 100% $CO_2$ selectivity for WGS in severe conditions ($GHSV=40,206h^{-1}$ and CO concentration = 38.0%). In addition, $Cu-CeO_2$ catalyst showed stable CO conversion for 20h without detectable catalyst deactivation. The high activity and stability of $Cu-CeO_2$ catalyst are correlated to its easier reducibility, high oxygen mobility/storage capacity of $CeO_2$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.228-233
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• 2010

Mn-doped $Zn_2SiO_4$ phosphor particles having submicrometer sizes were synthesized by a solid-state reaction method using methyl hydrogen polysiloxane-treated ZnO, fumed $SiO_2$ and various Mn sources. The crystallization and photoluminescent properties of the phosphor particles were investigated by X-ray diffraction(XRD), scanning electron microscope(SEM), and by their photoluminescence(PL) spectra. Due to the effect of the dispersion and coherence of the methyl hydrogen polysiloxane-treated ZnO, the Mn-doped $Zn_2SiO_4$ particles were successfully obtained by a solid state method at $1000^{\circ}C$, and the maximum PL intensity of the prepared particles under vacuum ultra violet(VUV) excitation occurred at a Mn concentration of 0.02mol and a sintering temperature of $1000^{\circ}C$.

• Journal of Powder Materials
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• v.26 no.1
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• pp.1-5
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• 2019

In this study, porous Mo-5 wt% Cu with unidirectionally aligned pores is prepared by freeze drying of camphene slurry with $MoO_3-CuO$ powders. Unidirectional freezing of camphene slurry with dispersion stability is conducted at $-25^{\circ}C$, and pores in the frozen specimens are generated by sublimation of the camphene crystals. The green bodies are hydrogen-reduced at $750^{\circ}C$ and sintered at $1000^{\circ}C$ for 1 h. X-ray diffraction analysis reveals that $MoO_3-CuO$ composite powders are completely converted to a Mo-and-Cu phase without any reaction phases by hydrogen reduction. The sintered bodies with the Mo-Cu phase show large and aligned parallel pores to the camphene growth direction as well as small pores in the internal walls of large pores. The pore size and porosity decrease with increasing composite powder content from 5 to 10 vol%. The change of pore characteristics is explained by the degree of powder rearrangement in slurry and the accumulation behavior of powders in the interdendritic spaces of solidified camphene.

• Bulletin of the Korean Chemical Society
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• v.26 no.4
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• pp.563-568
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• 2005

The Pt/C and Pd/C catalysts were prepared from conventional chloride precursors by adsorption or precipitation-deposition methods. Their activities for hydrogenation reactions of cyclohexene and acetophenone were compared with those of commercial catalysts. The Pt/C and Pd/C catalysts obtained from the adsorption procedure reveal higher hydrogenation activity than commercial catalysts and the catalysts prepared by the precipitation-deposition method. Their improved performances are attributed to the decreased metal crystallite sizes of Pt or Pd formed on the active carbon support upon the adsorption of the precursors probably due to the same negative charges of the chloride precursor and the carbon support. Under the preparation conditions studied, the reduction of the supported catalysts using borohydrides in liquid phase is superior to a gas phase reduction by using hydrogen in the viewpoint of particle size, hydrogenation activity and convenience.

• Korean Journal of Materials Research
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• v.12 no.8
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• pp.656-660
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• 2002

It was investigated that $Al_2$$O_3$/Cu nanocomposite powder could be optimally prepared by dispersion and reduction of Cu oxide, and suitably consolidated by employing pulse electric current sintering (PECS) process. $\alpha$-$Al_2$$O_3$ and CuO powders were used as elemental powders. In order to obtain $Al_2$O$_3$ embedded by finely and homogeneously dispersed CuO particles, the elemental powders were high energy ball milled at the rotating speed of 900 rpm, with the milling time varying up to 10 h. The milled powders were heat treated at $350^{\circ}C$ in H$_2$ atmosphere for 30 min to reduce CuO into Cu. The reduced powders were subsequently sintered by employing PECS process. The composites sintered at $1250^{\circ}C$ for 5 min showed the relative density of above 98%. The fracture toughness of the $Al_2$$O_3$/Cu nanocomposite was as high as 4.9MPa.$m^{1}$2//, being 1.3 times the value of pure $Al_2$$O_3$ sintered under the same condition.

• Polymer(Korea)
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• v.28 no.6
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• pp.487-493
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• 2004

The distribution of particles, in the mixture of poly(ethyl acrylate-co-t-butyl acrylate) (PEB) emulsion polymer and silica nanoparticles, was determined mainly depending on the pH of the mixture. The weak interfacial interaction was responsible for the severe coagulation of silica particles and the irregular dispersion for these nanocomposites. Methacryloxypropyltrimethoxysilane (MPS) was used to modify both the polymer and the silica. The nanocomposites which were prepared with these modified components had finer dispersion of silica nanoparticles and core-shell morphology due to the strong interfacial interaction. The strong hydrogen bonds were identified for these nanocomposites with FT-IR. The nanocomposites having strong interfacial interaction showed the increased glass transition temperature, the decreased ΔC$_{p}$ , and the increased decomposition temperature of the polymer chains. polymer chains.

• Archives of Metallurgy and Materials
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• v.66 no.3
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• pp.799-802
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• 2021

The nano-sized Y₂O₃ dispersed W composite powder is prepared by ultrasonic spray pyrolysis of a tungsten precursor using ammonium metatungstate hydrate and a polymer addition solution method using Y-nitrate. XRD analysis for calcined powder showed the formation of WO₂ phase by partial oxidation of W powder during calcination in air. The TEM and phase analysis for further hydrogen reduction of calcined powder mixture exhibited that the W powder with a uniform distribution of Y₂O₃ nanoparticles can be successfully produced. These results indicate that the wet chemical method combined with spray pyrolysis and polymer solution is a promising way to synthesis the W-based composites with homogeneous dispersion of fine oxide particles.