Papers by Author: Y.J. Lee

Abstract: SMC composites consist of chopped glass fiber as a reinforcements, polyester and mineral fillers. Among them, filler is one of the important factors for improving mechanical and thermal properties of composites, but it has not drawn much attention for SMC composites. In this study, the size effect of calcium carbonate as mineral filler on mechanical properties of SMC composites was discussed using five different sizes of commercial calcium carbonates without chopped fiber reinforcement, to focus on the size effect itself. The SMC process was modified to be suitable for a laboratory scale composed of three steps. The mean sizes of the calcium carbonates were 3 – 20 μm, and the specific surface areas were calculated to be 1 – 5 m²/g by BET. Small size of calcium carbonate having high surface area up to 4 m²/g showed high thermal resistance, and showed higher strength comparing to the large fillers because it affected to form a dense packed microstructure.

Abstract: Uniform nanosized β-SiC powders have been prepared in a flow reactor by thermal pyrolysis using organometallic precursors with different C/Si mole ratios such as methyltrichlorosilane and triphenylsilane. The temperature was varied from 1200°C to 1400°C. In order to examine the pyrolysis residue after the reaction, the sample was collected and analyzed with XRD, Raman and TEM. The X-ray diffraction result of the pyrolysis residue shows that the diffraction peaks around 35°, 60°, and 73° correspond to the beta SiC phase. All the diffraction peaks were quite broad, which indicated that the SiC powder was in the early stage of crystallization at this heat treatment temperature.