• Advances in materials Research
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• v.1 no.3
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• pp.191-204
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• 2012

In this paper, we report on the obtention of nanocrystalline $SrMoO_4$ synthesized through modified combustion process. These powders were characterized by X-ray diffraction, Fourier Transform Raman and Infrared Spectroscopy. These studies reveal that the scheelite-type $SrMoO_4$ crystallizes in tetragonal structure with I41/${\alpha}$ (N#88) space group. Transmission electron microscopy image shows that the nanocrystalline $SrMoO_4$ powders have average size of 18 nm. The optical band gap determined from the UV-V is absorption spectra for the as prepared sample is 3.7 eV. These powders showed a strong green photoluminescence emission. The samples are sintered at a relatively low temperature of $850^{\circ}C$. The morphology of the sintered pellet is studied with scanning electron microscopy. The dielectric constant and loss factor values obtained at 5 MHz for a well sintered $SrMoO_4$ pellet has been found to be 9.50 and $7.5{\times}10^{-3}$ respectively. Thus nano $SrMoO_4$ is a potential candidate for low temperature co-fired ceramics and luminescent applications.

• Journal of Powder Materials
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• v.12 no.4 s.51
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• pp.249-254
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• 2005

Titanium dioxide was prepared by Polymer Complex Solution Method(PCSM) according to the mole ratio of Titanium (IV) isopropoxide(TTIP)/solvent and polymer(Poly Ethylene Glycol). Polymer electrolytes were usually made by dispersing preproduced ceramic nanoparticles in a polymer matrix. Using this method, pure and nano-sized $TiO_2$ powder was synthesized through a simple procedure and polymer entrapment route. At the optimum amount of the polymer, the titanium ions are dispersed in solution and a homogeneous polymeric network is formed. The maximum intensity of anatase phase of $TiO_2$ was achieved by calcining at $500^{\circ}C$ for 2h. The synthesized $TiO_2$ powders were nano-sized and the average size was about 50nm. Anatase/Rutile ratio of the synthesized $TiO_2$ was 70%/30%.

• Journal of Powder Materials
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• v.8 no.2
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• pp.98-103
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• 2001

Metallic tin powder with diameter less than 50 nm was synthesized by inert gas condensation method and subsequently oxidized to tin oxide ($SnO_2$) along the two heat-treatment routes. The $SnO_2$ powder of single phase with a tetragonal structure was obtained by the heat-treatment route with intermediate annealing step-wise oxidation, whereas the $SnO_2$ powder with mixture of orthorhombic and tetragonal phases was obtained by the heat-treatment route without intermediate annealing (direct oxidation). $SnO_2$ gas sensors fabricated from the nano-phase $SnO_2$ powders were investigated by structural observations as well as measurement of electrical resistance. The $SnO_2$ gas sensors fabricated from the mixed-phase powder exhibited much lower sensitivity against $H_2$ gas than those fabricated from the powder of tetragonal phase. Reduced sensitivity of gas sensors with the new orthorhombic phase was attributed to detrimental effects of phase boundaries between orthorhombic and tetragonal phases and many twin boundaries on the charge mobility.

• Journal of Powder Materials
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• v.12 no.4 s.51
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• pp.291-295
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• 2005

CdSe hollow sphere with average size of about 30-50 nm was synthesized from the mixed solution of cadmium chloride $(CdCl_2)$, sodium selenosulfate $(Na_2SeSO_3)$ and ethylenediamine(EDA, $H_2NCH_2CH_2NH_2$) at room temperature. The molar ratio of EDA to $Cd^{2+}$ showed the most significant effect on the morphology of CdSe hollow sphere. This paper will present and discuss the possible formation mechanism of CdSe hollow sphere based on the observation of morphological changes.

• Journal of Pharmaceutical Investigation
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• v.39 no.6
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• pp.417-422
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• 2009

Budesonide belongs to Class II in the Biopharmaceutics Classification System (BCS) for its high permeability and poor aqueous solubility. The purpose of this study was to improve the solubility and dissolution rate of budesonide using an o/w microemulsion system in order to develop a nasal formulation. Based on the results of the solubility study and pseudo ternary phase diagrams, microemulsions of about 80 nm in mean diameter were formulated using isopropyl myristate and Labrasol$^{(R)}$ as an oil phase and a surfactant, respectively. Solubility of budesonide in the microemulsions increased up to 6.50 mg/mL, which is high enough for a nasal formulation. In vitro release profiles of budesonide significantly increased from the microemulsions compared to that of the budesonide powder. These results suggest that the microemulsions of budesonide could further be developed into a clinically useful nasal formulation.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.2
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• pp.152-162
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• 2013

The physico-chemical characteristics and nanostructure of the aerosol samples from a coal-fired power plant, a charcoal kiln and diesel vehicles were investigated with focusing on black carbon (BC). Aerosols from the coal-fired power plant were mostly comprised of mineral ash spheres which are heterogeneously mixed. The main components of the aerosols from coal-fired power plant were calcium compounds, iron oxide, alumino-silicate without BC. The typical combustion-generated BC which shows the shape of bunch of grapes with 20~50 nm particles which were detected in aerosol particles from diesel vehicles. The nanostructure of each BC particle shows the shape of concentric circles which is comprised of closely-packed graphene layers. Aerosols from charcoal kiln were likely condensed organic carbon generated from the low-temperature combustion process.

• Journal of the Korean Applied Science and Technology
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• v.19 no.4
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• pp.339-348
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• 2002

Self-diffusion coefficients of colloidal ass9Ciation structures in the aqueous solutions of anionic ammonium dodecyl sulfate (ADS) and cationic octadecyltrimethylammonium chloride (OTAC) surfactants were measured by pulsed-gradient spin echo NMR. The results were interpreted on the basis of the ADS/OTAC/water phase diagram. Crossing the phase boundaries, significant changes in self diffusion coefficients were observed and well correlated to the phase diagram. For the micelles their apparent radii were obtained from Stokes-Einstein equation. Their values were 15 for the ADS micelles and 54 ${{\AA}}$ for the OTAC micelles, respectively. For vesicles which were formed spontaneously at different relative amounts of the surfactants and total surfactant concentrations, the radius was measured as 50 to 200 nm. This result is in fair agreement with those by TEM and light scattering.

• Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.361-363
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• 2012

We investigated ultraviolet (UV) absorption materials from Russian seaweeds. First, the UV absorptivities of five seaweeds Gloiopeltis fucatas, Mazzaella sp., Mastocarpus pacificus, Laminaria cichorioides, Saccharina japonica were evaluated by a UV spectrometer. Of these seaweeds, Gloiopeltis fucatas and Mazzaella sp. showed high levels of UV absorption. Column chromatography of active 50% aqueous ethanol extracts from Gloiopeltis fucatas and Mazzaella sp. resulted in the purification of two known compounds. Spectroscopic techniques identified their structures as shinorine and palythine. These materials exhibited UV absorptive capabilities at wavelengths of 333 and 320 nm, respectively. These results suggest that Gloiopeltis fucatas and Mazzaella sp. may be useful as natural cosmeceutical sources.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.6
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• pp.675-687
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• 2012

Applying an external electric field across air filter media is one of methods to improve the filtration performance. Metal wire meshes have been commonly used as electrodes situated on both sides of a thick filter pad. For a thin filter medium a short circuit, known as the biggest drawback for applying an external electric field to air filter, can occur at the closest point between electrodes. In this study several types of insulated meshes were prepared by coating #50 meshes with a dielectric material, Nylon 66, and the filtration property of air filter was evaluated at the presence of external electric field using those insulated meshes as electrodes and compared with that of filters using bared meshes. The collection efficiency of tested filter was increased from 78% to 95% for singly charged 100 nm particles by application of external electric field. As a result, there was no significant difference in collection efficiency between filters with insulated and bared electrodes. Similar results could be also seen from the tests using polydisperse particles. Finally, through this study, we found that the insulation of mesh electrodes doesn't affect the filtration performance of fibrous air filter under external electric field.

• Environmental Engineering Research
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• v.12 no.2
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• pp.72-80
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• 2007

Experiments were conducted to identify the emissions from the car air freshener and to identify the formation of ultra-fine particles and secondary gaseous compounds during the ozone-initiated oxidations with emitted VOCs. The identified primary constituents emitted from the car air freshener in this study were $\alpha$-pinene, $\beta$-pinene, $\rho$-cymene and limonene. Formation of ultra-fine particles (4.4-160 nm) was observed when ozone was injected into the chamber containing emitted monoterpenes from the air freshener. Particle number concentrations, particle mass concentrations, and surface concentrations were measured in time dependent experiments to describe the particle formation and growth within the chamber. The irritating secondary gaseous products formed during the ozone-initiated reactions include formaldehyde, acetaldehyde, acrolein, acetone, and propionaldehyde. Ozone concentration (50 and 100 ppb) and temperature (30 and $40^{\circ}C$) significantly affect the formation of particles and gaseous products during the ozone-initiated reactions. The results obtained in this study provided an insight on the potential exposure of particles and irritating secondary products formed during the ozone-initiated reaction to passengers in confined spaces.