Kyong Sop Han

Synthesis and Characterization of Nanosized ZnxMn1-xFe2O4 Powders by Glycothermal Process

Nanosized ZnxMn1-xFe2O4 powders were prepared in ethylene glycol solution under mild temperature and pressure conditions by precipitation from metal nitrates. The average size and distribution of the synthesized ZnxMn1-xFe2O4 powders were 10- 20 ㎚ and narrow, respectively. The magnetic property of the synthesized ZnxMn1- xFe2O4 powder was of superparamagnetic character at room temperature.

Synthesis and Formation Mechanism of Mn-Doped Zn2SiO4 Brown Pigment

A willemite brown inorganic pigment was synthesized by subsyituting MnO for ZnO. The composition of MnxZn2-xSiO4 (X=0.1, 0.3, 0.5, 0.7 and 0.9mole) was synthesized at 1200~1300°C by solid state method. The characteristics of synthesized pigment were analyzed by X-ray diffraction, FT-IR spectroscopy, Raman spectroscopy and SEM. The UV- vis spectroscopy and CIE L*a*b* measurement were employed to analyzed color. Willemite single crystal phase was synthesized with compositions of Mn0.3Zn1.5SiO2 and Mn0.5Zn1.5 SiO2 from 1300°C/3h. The synthesized pigment of Mn0.5Zn1.5 SiO2 at1300°C/3h was applicated to lime barium glaze and lime zinc glaze and the CIE L*a*b* values were 30.32, 7.17, 3.14 and 32.04, 8.18, 3.49, respectively.

Fabrication and Microstructure of ZnO-TiO2 Composite Membranes by a Reverse Micelle and Sol-Gel Processing

ZnO-TiO2 nanoparticles were synthesized by a reverse micelle and sol-gel process. The average particle size of the colloid was below 30 nm and well dispersed in the solution. ZnOTiO2 composite membranes were fabricated by using the dip-coating method on a porous alumina support. ZnO-TiO2 composite membranes showed a crack-free microstructure and narrow particle size distribution even after the heat treatment up to 600°C. The average particle size of the membrane was 30-40nm, and the pore size of ZnO-TiO2 composite membrane was below 10 nm.

The Effect of Phenol Resin Types and Mixing Ratios on the Synthesis of High-Purity β-SiC Powder by the Sol-Gel Method

In this study, we carried out a sol-gel processing to synthesize two types of phenol resin and TEOS sol with fluoric acid as the catalysts, and fabricated the β-SiC powder by carbothermal reduction of the obtained precursor gels. The gels were observed to be cross linked between TEOS and phenol resins by FT-IR and TG-DTA. After pyrolyzed at 1000oC in Ar to obtain the precursor, to confirm the phase transition and morphologies by XRD, and SEM were measured. Finally, the light green colored SiC powder was obtained after carbothermal reduction process up to 1800oC. The residual condensed SiO(v) phase and free carbons as a role of impurities for final products using the solid type phenol resin was observed in the surface of powder by BSE.

Synthesis of Perovskite Brown Pigments

This study aims to synthesize Cr doped Perovskite brown pigments. The pigment were synthesized by doping Cr2O3(0.01 ~ 0.05mole) for TiO2(0.993 ~ 0.963 mole) at 1150 ~ 1350°C. The samples were characterized by X-ray diffraction (XRD), Raman Spectrometer, Scanning Electron Microscope(SEM) and the UV/Vis spectroscopy. The optimum composition was CaCr0.03Ti0.978O3and heating condition was 1300°C for 3h of soaking time. The doped Cr ion for Perovskite was observed to be Cr(Ⅲ) and Cr(Ⅳ). The brown color was mixed with violet doped by Cr4+(3A2 → 3T2) and Blueish-Green doped by Cr3+(4A2g → 4F1g). The results of SEM analysis showed the Perovskite structure and the particle size was approximately 2µm. The color in Frit 6060 glaze adding 10wt% pigment was Redish Brown, and CIE Lab parameters were L*= 41.53, a*=13.27 and b*=9.94 .

Synthesis of Co-Doped Tialite Ceramic Pigments and Coloring in Glazes

Synthesis of gray ceramic pigment was carried out by doping cobalt on Tialite crystal structure. Tialite was synthesized by using Al2O3 and TiO2, and was doped with Co3O4 as a chromophore material. To prevent the thermal decomposition during cooling procedure Fe2O3 was added by 0.05mole as a stabilizer. Samples were fired at 1400~1500°C for 2hours and cooled naturally. Crystal structure, solubility limit and color of synthesized pigment were analyzed by XRD, Raman spectroscopy, UV and UV-vis. Yield percentage of Tialite was 96.15% with using Fe2O3 as a stabilizer. It was found that solubility limit of Co2+ in Tialite crystal was 0.03 mole% through analysis of XRD and Raman. By adding pigment with 0.03 mole% of Co2+ to lime-barium glaze, stabilized Dark Gray color glaze having 46.12, -1.26, 0.53 as CIE-L*a*b* was synthesized.

Synthesis and Characterization of Ag-Pd Nanoparticles by a Reverse Micelle Process

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.

Synthesis and Microstructure of TiO2-SiO2 Nanoparticles by a Reverse Micelle and Sol-Gel Processing

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.

Synthesis and Characterization of Nanosized ITO Powders by Glycothermal Processing

Nanosized ITO(indium tin oxide) powders were prepared in ethylene glycol solution under mild temperature and pressure conditions by precipitation from metal nitrates with aqueous potassium hydroxide. The average size and distribution of the synthesized ITO powders were about 20 ㎚ and broad, respectively. The phase of synthesized particles was crystalline reacted at 230 0C for 6 h.. The optical properties of the synthesized ITO powders were transparent.

Fabrication and Microstructure of Pt/SiO2 Composite Membranes by a Reverse Micelle and Sol-Gel

Pt/SiO 2 composite membranes were synthesized by sol-gel process. The average particle size of the mixed sol was below 30 nm and well dispersed in the solution. TEM results show the microstructure of Pt/SiO 2 composite membranes was homogeneous. Average pore size of the Al 2 O 3 support was about 0.125 μm and the pore size distribution was narrow. The average pore size of the Pt/SiO 2 composite membranes has smaller than that of SiO 2 composite membrane. It was observed that the Pt/SiO 2 composite membranes showed a crack-free microstructure and narrow particle size distribution even after heat treatment up to 500°C.