Papers by Author: Soo Chang Choi

Abstract: M-CNTs (Multiwall Carbon Nano Tubes) can be used as an electrode, transferring electrons and heat very easily. This property helps transfer electrons created in TiO2 layer of DSSC (Dye-sensitized Solar Cell). CNTs layer with TiO2 utilized for the photocatalyst is expected to contribute to improve the efficiency of the solar cell. The Photocatalyst of TiO2 thin film was manufactured from titanium isopropoxide, ethanol, and HCl by a sol-gel process. To determine the property of TiO2 thin film with CNT, we performed to mix acid dispersed CNT in TiO2 Sol-gel and make coating membranes using sol-gel with different densities of CNT. It was found that the crystal structure changed from the anatase phase to the rutile phase having higher efficiency by XRD measure after treatment of high temperature sintering. To demonstrate the property of each sample, the transmittance of the TiO2 thin film was measured by a spectrometer and dispersion of CNT of the thin film was measured by SEM. In conclusion, the capacitance as the parameter which can affect performance of DSSC was investigated.

Abstract: Recently, ultra-precision machining of components and dies for information and communication industries, such as fresnel mirrors, diffraction lens, and die for super high intensity reflective sheet is one of the major target. To machine three-dimensional micro patterns, such as super high-intensity reflective sheets, ultra-precision and mirror surface fabrication processes are required. It has been reported, however, that continuous cutting, such as turning or shaping, is more suitable to ultra-precision machining. Many researchers have studied the manufacturing process of reflective sheet dies to obtain high form accuracy and surface quality. In this paper, ultra-precision shaping system was developed to fabricate micro patterns mechanically. In order to estimate performance of the shaping system, micro V-shaped grooves and tetrahedron pattern arrays for a super high intensity reflective sheet was applied. Also, a new measuring technology to inspect form and machining errors of a machined tetrahedron patterns was proposed. The results show that shaping system has a positioning accuracy of x, y, z axis with 100, 10, 10nm resolution, respectively. Micro V-shaped grooves could be machined at various depths and micro tetrahedron patterns with a good quality were obtained as well.