Papers by Author: Dong Sik Bae

Abstract: Ga doped SiO2 nanosized particles have been synthesized using a reverse micelle technique combined with metal alkoxide hydrolysis and condensation. The size of the particles and the thickness of the coating can be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethyl orthosilicate(TEOS) within the micro-emulsion. The average size of synthesized Ga doped SiO2 nanoparticles were about in the size range of 10-15 nm and Ga particles 2-5 nm. The effects of synthesis parameters, such as the molar ratio of water to TEOS, and the molar ratio of water to surfactant, are discussed.

Abstract: Gd2O3 doped CeO2 nanopowders were prepared under high temperature and pressure conditions by precipitation from metal nitrates with aqueous ammonium hydroxide. Spherical shape Gd2O3 doped CeO2 nanopowders were obtained By a reaction at the temperature range of 200°C – 230°C for 6 h. The average size and size distribution of the synthesized particles were below 10 nm and narrow, respectively. The XRD diffraction pattern shows that the synthesized powders were crystalline. This study has shown that the synthesis of Gd2O3 doped CeO2 nanopowders is possible under glycothermal conditions in ethylene glycol solution. The effects of synthesis parameters, such as the solvent ratio of starting solution, pH of starting solution, reaction temperature and time, are discussed.

Abstract: Al2O3-SiO2 nanoparticles have been synthesized by a sol-gel processing. Size and composition of the synthesized particles can be controlled by manipulating the relative rates of the hydrolysis and condensation reaction of precursor. The average size of synthesized Al2O3-SiO2 nanoparticles was about in the size range of 50~100nm. The effects of synthesis parameters, such as the molar ratio of water to precursor, the molar ratio of water to surfactant and stirring rate, are discussed.

Abstract: CoFe2O4 nanoparticles were prepared in ethylene glycol solution under mild temperature and pressure conditions by precipitation from metal nitrates. The average size of the synthesized CoFe2O4 nanoparticles was in the range of 5 to 10
, and they were narrowly distributed in the crystalline phase. Their magnetic property was of superparamagnetic character at room temperature. The effect of synthesis parameters is discussed such as the pH of starting solutions and reaction temperature.

Abstract: Preparation of Ag-Pd nanoparticles by the reduction of AgNO3 and PdCl2 with hydrazine in Igepal CO-520/cyclohexane reverse micelle solutions was studied. An analysis by transmission electron microscope and electron diffraction spectrum revealed that the resultant particles are silver-palladium. The average size of the synthesized nanoparticles slightly changed with increases in the molar ratio of water to Igepal CO 520. The average size of the synthesized nanoparticles was below 5
and they were broadly distributed.

Abstract: Pentacene channel for organic thin film transistor was deposited on the SiOC film by thermal evaporation. The growth of pentacene is related with the Diels-Alder reaction and the nucleophilic reaction by the thermal induction. The surface is an important factor to control the recursive Diels-Alder reaction for growing of pentacene on SiOC film. The terminal C=C double bond of pentacene molecule was broken easily as a result of attack of the nucleophilic reagents on the surface of SiOC film. The nucleophilic reaction can be accelerated by increasing temperature on surface, and it making pentacene to grow hardly on the SiOC film with a flow rate ratio of O2/(BTMSM+O2)=0.5 due to its inorganic property. The nucleophlic reaction mechanism is SN2 (bimolecular nucleophilic substitution) type.

Abstract: Zinc titanate nanoparticles were prepared under high temperature and pressure conditions by precipitation from metal precursors with aqueous ammonium hydroxide. Zinc titanates powders were obtained in the temperature range of 180
-230
for 4 h. The phase of synthesized particle with calcined at 800
for 2h. ZnTiO3, Zn2TiO4, Zn2Ti3O8, TiO2, ZnO. The average particle size and distribution of the synthesized zinc titanate nanoparticles were below 100 nm and narrow, respectively.

Abstract: Ba(MgxNb1-x)O3 nanoparticles were prepared under high temperature and pressure conditions by precipitation from metal nitrates with aqueous potassium hydroxide. Ba(MgxNb1-x)O3 nanoparticles were obtained in the temperature range of 170

185
for 4 h. TEM and X-ray diffraction patterns showed that the synthesized particles were crystalline. The average size and size distribution of the synthesized particles were around 100 nm and broad, respectively.

Abstract: TiO2-SiO2 nanoparticles have been synthesized using a reverse micelle technique combined with metal alkoxide hydrolysis and condensation. The size of the particles can be controlled by manipulating the relative rates of the hydrolysis and condensation reaction of tetraethyl orthosilicate (TEOS) and titanium isopropoxide (TIP) within the micro-emulsion. The average size of synthesized TiO2-SiO2 nanoparticles was about in the size range of 20-100 nm. The effects of synthesis parameters, such as the molar ratio of water to precursor and the molar ratio of water to surfactant, are discussed.

Abstract: ZnO-SiO2 nanoparticles were synthesized using a reverse micelle technique combined with metal alkoxide hydrolysis and condensation. The size of the particles was controlled by manipulating the relative rates of the hydrolysis and condensation reaction of tetraethyl orthosilicate (TEOS) within the micro-emulsion. The average size of synthesized ZnO-SiO2 nanoparticles was in the range of 20-40 nm. The effects of synthesis parameters such as the molar ratio of water to precursor and the molar ratio of water to surfactant are discussed.