Papers by Author: Gyo Woo Lee

Abstract: TiO2 nanoparticles were synthesized with using N2-diluted and O2-enriched coflow hydrogen diffusion flames. We investigated the effects of the flame temperature on the crystalline phases and particle characteristics of the TiO2 nanoparticles that were formed. For the higher temperature conditions, the maximum centerline temperatures that were measured were greater than approximately 1,600K, and TiO2 nanoparticles, which had spherical shapes with diameters of approximately 60nm, were synthesized. For the lower temperature conditions, the maximum centerline temperatures that were measured were less than approximately 1,600K, and the diameters of the nanoparticles that were formed had unclear boundaries that ranged from 35 to 50nm. From the XRD analyses, it was believed that the crystalline structures of the nanoparticles that were formed were divided into two types. For the higher temperature cases, the fractions of the TiO2 nanoparticles that were synthesized, which had anatase-phase crystalline structures, increased with the increase of the flame temperatures. On the contrary, for the lower temperature cases, the fraction of anatase-phase nanoparticles increased with the decrease of the flame temperatures.

Abstract: Even though activated carbon fibers (ACF) have been attractive due to high specific surface area and uniform micropore structure, there are only a few reports about the photocatalyst immobilization on ACF or their photodegradation behavior for removal of organic pollutants. In this study, ACF were selected as adsorptive support for photocatalyst immobilization. As photocatalysts, TiO2 nanoparticles were synthesized by using a N2-diluted and oxygen-enriched co-flow hydrogen diffusion flame. The visible flame length of 150mm was obtained by direct photographs. Flame temperature was measured by rapid insertion measurement technique with a R-type (Pt/Pt-13%Rd) thermocouple which was in wire shape (127μm diameter). TiO2 particles were sampled by using a high temperature particle sampler and then were coated on ACF filters. The sampling was carried out at 70mm and 110mm above the burner. The structure of TiO2 particles was analyzed by XRD. TiO2 coated ACF filters were characterized by FESEM-EDX and BET analyses. TiO2 particles on ACF filters were found to be agglomerated particles and the size of primary particles was approximately 50nm. The structure of TiO2 particle was anatase-phase crystalline structure. The specific surface area of TiO2 coated ACF filter was enhanced to be 1700~1860m2/g, depending on the sampling location, and the pores were micropores, regardless of the sampling location.