Papers by Author: Tae Whan Hong

Abstract: Recently, touch screen is one of the most popular pieces of electrical and electronic equipment in our society, such as laptops, cellular phones, and digital cameras. Indium tin oxide (ITO) is mainly used to make transparent conductive coatings for touch and flat screen. Therefore, there is an increasing demand accordingly. Although accounted for 1% of the touch screen, indium is rare metals. Consequently, it is important to Recycling ITO for National Strategies about Resource Conservation, and reduce Environmental burden. The case which disuses ITO like landfill or incineration, it cloud be harmful to the human health in the long-term. This study intended to identify the environmental aspects with the ITO recycling. The potential environmental impacts were evaluated by using Material Life Cycle assessment method (MLCA). As the result of this study, MLCA would provide more information for environmental issues of ITO. So that it is possible to improve the environmental issues by the monitoring that could be useful and effective for ITO. The study includes two scenarios, the basic scenario is recycling of ITO (10, 20 and 30%) and the other scenario is landfill of ITO.

Abstract: Nowadays, rapidly growing mobile machines such as tablet PC and smart phone equipped with touch screen panel using a sturdy material for products surface protection. Therefore, surge of chemical strengthening glass was increased. Through large areas of chemical strengthening glass, the surface scratch will cause a major failure. Most of these failures will be discarded because it is difficult to reuse. Thus, discarded chemical strengthening glass is expected to increase as with the demand. Accordingly, the importance of environmental pollution, waste landfill has been proposed. Recently, touch screen of chemical strengthened glass all-in-one type was commercialized. Therefore reuse is possible, due to surface of discarded chemical strengthening glass is washed and wipe off the electrode. In this study, we carried out the MLCA(Material Life Cycle Assessment; MLCA) on a chemical strengthening glass by landfill scenario, reuse scenario and identified the key issues.

Abstract: Hydrogen energy had recognized clean systems and high energy carrier. Mg and Mg-based materials have been lightweight and low cost materials which had been 7.6wt.% hydrogen capacity. However, Mg and Mg-alloys were currently hinder by its high absorption/desorption temperature, and very slow reaction kinetics. Therefore, one of the most methods to improve kinetics focused on addition transition metal oxide. Addition to transition metal oxide in MgH_x powder produce MgH_x-metal oxide composition by mechanical alloy and it analyze XRD, EDS, TG/DSC, SEM, and PCI. This report considers kinetics by transition metal oxide rate and hydrogen pressure. In this research, we can see behavior of hydriding/dehydriding profiles by addition catalyst (transition metal oxide). MgH_x-5wt.%Fe₂O₃ composite was measured most high hydrogen capacity and fast kinetics.

Abstract: The most promising methods for high purity hydrogen production are membranes separation such as polymer, metal, ceramic and composites. It is well known that Pd and Pd-alloys membranes have excellent properties for hydrogen separation. However, it has hydrogen embrittlement and high cost for practical applications. Therefore, most scientists have studied new materials instead of Pd and Pd-alloys. On the other hand, ceramic materials are great in resistance to acids and chemically stable under high operating temperature. Recent research in cermet materials for membrane applications interests to permeability and selectivity of hydrogen. High purity hydrogen can be produced through simple process by membrane. Recently, research in ceramic composites for membrane applications attract to hydrogen separation. Porous ceramic membrane process which has high permeability and hydrogen flux is chemically and thermally stable. Therefore, they are attractive for applications in hydrogen production process. However, porous ceramic membrane had low selectivity, hard to produce high purity hydrogen. Many studies were carried out Pd and Pd alloys coating, they were fabricated dense cermet membrane. In this work, ACZ ceramic membrane was fabricated disk type membrane by cold isostatic press (CIP) and then coated Pd and Pd-alloys.. It was characterized by XRD, SEM, EDX and BET. Also, we estimated the hydrogen permeability by Sievert's type hydrogen permeation membrane equipment.

Abstract: The Al₂O₃-CuO-ZnO (ACZ) was synthesized from sol-gel process with aluminum isopropoxide, copper (II) nitrate hemi pentahydrate, Zn (II) nitrate hexahydrate and primary distilled water. The ACZ synthesized powders were analyzed by TG/DTA, XRD, BET and FE-SEM. The ACZ-Co composites membrane was prepared by hot press sintering (HPS). Hydrogen permeability was characterized by Sievert's type hydrogen permeation membrane equipment. The hydrogen permeation rate was measured 0.0496 mol m^-2 s^-1 at room temperature under 2 bar of H2 atmosphere.

Abstract: Poly(ether ketone)s (PEK) containing 25-75 mol % valeric acid were prepared with bisphenol A, 4,4-dichlorobenzophenone and 4,4-Bis(4-hydroxylphenyl)valeric acid using potassium carbonate in DMAc (dimethyl acetami de) at 165 °C. Copolymers containing carboxylacid group were reduced to hydroxy group by BH3 solution 1M in THF and NaBH4 co-catalyst. Sulfonated poly(ether ketone)s (S-PEK) were obtained by reaction of 1,3-propanesultone and the reduced copolymer (PEK-OH) with sodium methoxide. A series of copolymers were studied by 1H-NMR spectroscopy, differential scanning calorimeter (DSC), and thermo gravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. The S-PEK membranes exhibited proton conductivities from 1.31  10-3 to 3.52  10-3 S/cm, water swell from 12.70 to 35.50 %, IEC from 0.45 to 0.75 meq/g and methanol diffusion coefficients from 3.65  10-7 to 5.10  10-7 cm2/S at 25 °C.

Abstract: The hydrogen permeation properties of the Pd-coated Ni37.5Nb27.5Zr25Co5Ta5 amorphous membranes have been investigated at 673 and 723K for 720 hours (1 month). Values of the hydrogen permeability during these long term tests were found to be reduced of about 50 and 30 % at 673 and 723K, respectively. The reduction in the hydrogen permeability could be correlated to the change in the composition of the coating as well as at the interface between Pd coating and Ni-based amorphous membrane.

Abstract: Nowadays, the most promising methods for high purity hydrogen production are membranes separation such as polymer, metal, ceramic and composites. It is well known that Pd and Pd-alloys membranes have excellent properties for hydrogen separation. However, it has hydrogen embrittlement and high cost for practical applications. Therefore, most scientists have studied new materials instead of Pd and Pd-alloys. On the other hand, TiN powders are great in resistance to acids and chemically stable under high operating temperature. In order to get specimens for hydrogen permeation, the TiN powders synthesized were consolidated together with pure Co powders by hot press sintering. During the consolidation of powders at HPS, heating rate was 10K/min and the pressure was 10MPa. It was characterized by XRD, SEM, and BET. Also, we estimated the hydrogen permeability by Sievert's type hydrogen permeation membrane equipment.

Abstract: Hydrogen has attracted clean energy media as a high-quality and renewable energy source in recent years. On the one hand, a ceramic catalyst and/or catalyst support such as Al2O3 has often been a preferred choice due to their specific properties such as thermal stability and high surface area. Al2O3-CuO-ZnO was synthesized by using the sol-gel process with aluminum isopropoxide and primary distilled water as the precursor and solvent. In this synthesized process, metal oxides caused to precursors such as copper and zinc nitrate were added. To prepare membranes, cobalt metal powder was used to increase the strength and durability. The Al2O3-CuO-ZnO/Co composite membranes were produced using hot press sintering for consolidation of powders following reactively mechanical alloying process. The characterizations of membrane were measured XRD, FE-SEM and EDS. Hydrogen permeation evaluations were examined at a room temperature to 773 K under increasing pressure. Hydrogen permeation rate was obtained with 0.18 mol m-2 s-1 at 773 K result from complex diffusion mechanism such as Sievert’s type, Knudsen diffusion and/or molecular sieving.

Abstract: The purpose of this work was hydrogen permeation of ceramic or metal/ceramic membrane using γ-Al2O3 by synthesizing. The γ-Al2O3 was synthesized by using the sol-gel process with aluminum isopropoxide and primary distilled water as the precursor and solvent. The γ-Al2O3-based membranes were prepared using HPS. The phase transformation, thermal evolution, surface are and morphology of γ-Al2O3 and γ-Al2O3-based membranes were characterized by XRD, TG-DTA, BET and FE-SEM. The hydrogen permeation of γ-Al2O3-based membranes was examined at room temperature comparing with other paper using nickel composited membrane on alumina ceramic support.