Sea Cheon Oh

A Study on the Synthesis of SiC Powder from the Silicon Sludge of the Photovoltaic Industry

β-SiC powder was synthesized directly from silicon sludge with carbon black. Large amount of silicon sludge is generated from Solar Cell industry. In an environmental and economic point of view, recycling silicon sludge is important. In this study, two kinds of silicon sludge were characterized using XRD, SEM/EDS and FT-IR. SiC powder was synthesized by the reaction of ball-milled silicon powder for 3h in vacuum at different temperatures (1350 and 1600). Physical properties of the heat treated SiC have been characterized using a SEM, XRD, Particle size analyzer and FT-IR Spectroscopy.

Size Effect of CaCO3 Filler on the Mechanical Properties of SMC Composites

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.

Effect of Temperature and Carbon Contents on the Synthesis of β-SiC from Silicon Sludge by Direct Carbonization Method

β-SiC powder was synthesized using silicon sludge from photovoltaic silicon-wafer production by varying heat treatment temperature and carbon contents. The synthesized β-SiC powder and silicon sludge was analyzed by XRD, SEM, FT-IR and Particle size analysis. It is known that the conversion of SiC from the mixture of Silicon and Carbon is mainly affected by the mole ratio of C/Si and heat treatment temperature. In this study, the influence of reaction temperature and carbon contents on the synthesis of β-SiC from silicon sludge was examined.

Additive Effects on Sintering of Si/SiC Mixtures

The effects of clay, aluminum hydroxide, and carbon powder on the sintering of a Si/SiC mixture from photovoltaic silicon-wafer production were investigated. Sintering temperature was fixed at and the sintered bodies were characterized by SEM and XRD to analyze the microstructure and to measure the apparent porosity, absorptivity, and apparent density. The XRD peak intensity of SiC in the sintered body was increased by adding 5% carbon to the Si/SiC mixture. From this result, it is confirmed that Si in the Si/SiC mixture had reacted with the added carbon. Addition of aluminum hydroxide decreased the cristobalite phase and increased the stable mullite phase. The measurement of the physical properties indicates that adding carbon to the Si/SiC mixture enables us to obtain a dense sintered body that has high apparent density and low absorptivity. The sintered body produced from the Si/SiC mixture with aluminum hydroxide and carbon powder as sintering additives can be applied to diesel particulate filters or to heat storage materials, etc., since it possesses high thermal conductivity, and anticorrosion and antioxidation properties.

The Behavior of Automobile Shredder Residue Chips in a Precalciner for Cement Manufacturing Process

This paper presents a numerical simulation of Automobile Shredder Residue (ASR) chips motion and combustion in a cement works precalciner. The work was done using the commercial computational fluid dynamic (CFD) code FLUENT. The aim of this work is to develop an understanding of the processes within the percalciner to aid in the prediction of ASR chip aerodynamic and combustion behaviors for its use as an alternative fuel. The effects of the mutual interactions between ASR chips were simulated by discrete phase modeling approach, while ASR combustion was simulated by the finite rate devolatilization models. A useful approach to simulate the characteristics of turbulent gas-particle flow, heat transfer and ASR combustion process in a precalciner has been demonstrated.

Recovery of Silicon and Silicon Carbide Powder from Waste Silicon Wafer Sludge

In an environmental and economic point of view, recycling of silicon wafer sludge is important. The aim of this work is to investigate the recycling method of silicon wafer sludge. Therefore, drying rate of silicon wafer sludge has been studied for separation of liquid and solid from sludge. Silicon and silicon carbide powder obtained from silicon wafer sludge were analyzed by SEM, XFR, XRD and particle size analyzer. The recovered oil was also characterized using GC-MS. From this work, it can be seen that the falling drying rate of silicon wafer sludge is linear equation. Various metal components have been found in recovered solid powder caused by wire sawing processing.

Characterization of Silicon Kerf and the Effect of Grinding on the Synthesis of SiC Powder

Characterization of silicon kerf from photovoltaic silicon-wafer production was carried out. Also, SiC powder was synthesized using high purity silicon kerf by varying grinding conditions. With increase of grinding time, surface of the silicon was oxidized to form silicon oxide. Also, it was observed that the unreacted silicon oxide and free silicon amount in the SiC powder increases with an increasing grinding times, even though silicon particle size of the starting material is decreased.

Effect of Silicon Particle Size on Synthesis and Crystallinity of β-Silicon Carbide Particles

β-SiC particles were synthesized using silicon powder and carbon black at 1300°C. The effect of grinding the silicon powder raw material into smaller particles on the synthesis and crystallinity of the SiC particles was investigated. The size of the silicon particles decreased and the surface of the silicon particles increasingly oxidized into silicon oxide with increasing grinding time, thus decreasing the yield of SiC because of the higher SiO2 content in the ground silicon powder, since SiO2 transforms into SiC at a higher temperature than does silicon. Although the sizes of the silicon particles in the raw materials were different, all the synthesized SiC crystallites showed similar size. Transmission electron microscopy-energy dispersive X-ray spectroscopy analysis showed that although most of the synthesized SiC particles were smaller than 100 nm, the primary SiC particles had aggregated, and some unreacted silicon was observed inside the large aggregated SiC particles.

Decomposition Characteristics of Wood Using Supercritical Methanol for Biodiesel Production

In this work, the decomposition characteristics of wood using supercritical methanol have been studied. The kinetic analysis was carried out for three heating rates of 5.2, 11.6 and 16.3 oC/min. And the liquid products analysis has been performed for reaction temperatures of 300-320 oC and reaction times of 0-120 min, respectively. The activation energies of wood decomposition in supercritical methanol were 45.2-48.8 kJ/mol, depending on the heating rates. And the reaction orders were 0.25 for all heating rates. And the liquid product has been analyzed by GC-MS. From this work, the yields of liquid product increased as increasing of reaction temperature and reaction time. And it was also found that the components of liquid products were mainly acetic acid, latic acid, pentanol and phenol.