Papers by Author: Whan Gi Kim

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Authors: Kyeong Il Kim, Sang Hern Kim, Whan Gi Kim, Soon Chul Ur, Tae Whan Hong
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.
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Authors: Whan Gi Kim, Soon Chul Ur, Y.G. Lee, Young Jig Kim, Tae Whan Hong
Abstract: In order to fabricate high efficiency, light-weight hydrogen storage materials in an economical way, we have been made to propose a new mechanical alloying process by high-pressure hydrogen induced planetary ball milling(HIMA) using Mg and Ni chips. Microstructural evaluations of the Mg-Ni-H systems synthesized were investigated by scanning electron microscopy and the transmission electron microscopy. X-ray diffraction analysis was also made to characterize the lattice constant, crystallite size and misfit strain. The hydrogenation properties of the particles synthesized were evaluated by automatic PCI (pressure-composition-isotherm). Adopting 66:1 BCR (ball to chips mass ratio) for HIMA process, fully hydrogenated alloys were obtained after 96 hrs of milling, resulting in total hydrogen content of 2.25 mass%.
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Authors: Jung Il Lee, Kyeong Il Kim, Sung Woong Yoo, Young Geun Lee, Whan Gi Kim, Mie Won Jung, Tae Whan Hong
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 MgHx powder produce MgHx-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). MgHx-5wt.%Fe2O3 composite was measured most high hydrogen capacity and fast kinetics.
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Authors: Tae Whan Hong, Dong Hun Lee, Hae Suck Park, Dong Hwan Suh, Whan Gi Kim
Abstract: Branched sulfonated poly(ether ketone sulfone) copolymer was prepared from1,1,1- tris(4-hydroxyphenyl) ethane, 4,4-difluorophenylsulfone, 3,3'-disodiumsulfonylbenzophenone (40 mol% of bisphenol A) and bisphenol A by polycondensation with the elimination of water in toluene and NMP at 160) in the presence of anhydrous potassium carbonate. Composite membranes were successfully cast from the control of organic polymer with SiO2 4-10 wt% of polymer in DMSO. The films were converted from the salt to acid forms with dilute hydrochloric acid. Organicinorganic composite membranes for operation in polymer electrolyte membrane fuel cells (PEMFCs) were characterized and cell-tested. The physico-chemical properties of all membranes were investigated their thermal properties, water uptake, DSC and thermogravimetric analyzer (TGA). Branched copolymer and nano composite membranes exhibit proton conductivities from 1.7x10-3 to 8.3x10-3 S/cm2, water uptake from 22 to 26%, IEC from 1.28 to 1.46 meq/g and methanol diffusion coefficients from 1.2x10-7 to 1.7x10-7 cm2/S.
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Authors: Dong Wan Seo, Young Don Lim, Soon Ho Lee, Md. Monirul Islam, Hyun Mi Jin, Keun Ho Lee, Ho Hyoun Jang, Whan Gi Kim
Abstract: Organic-inorganic Nano composite membranes were prepared by Sulfonated amine-poly(ether sulfone)s (S-APES)s and SiO2. S-APESs were prepared by nitration, reduction and sulfonation of poly(ether sulfone) (ultrason®-S6010). Poly(ether sulfone) was reacted with ammonium nitrate and trifluoroacetic anhydride to produce the nitrated poly(ether sulfone), and was followed by reduction using tin(Ⅱ)chloride and sodium iodide as reducing agents to give the amino-poly(ether sulfone). The S-APES was obtained by reaction of 1,3-propanesultone and the amino-poly(ether sulfone) (NH2-PES) with sodium methoxide. The different degrees of nitration and reduction of poly(ether sulfone) were successfully synthesized by an optimized process. Organic-inorganic nano composite membranes were obtained by mixing S-APES (45 %) with hydrophilic SiO2 (20 nm, 4-10 %) obtained by sol-gel process. Different contents of SiO2 of the S-APES were studied by FT-IR, 1H-NMR spectroscopy, differential scanning calorimetry (DSC), and thermo gravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. The ion exchange capacity (IEC), a measure of proton conductivity, was evaluated. The nano composite membranes exhibit conductivities (25 °C) from 3.51 x 10-3 to 4.10 x 10-3 S/cm, water swell from 57.25 to 60.50 %, IEC from 0.68 to 0.73 meq/g, and methanol diffusion coefficients from 2.81 x 10-7 to 3.33 x 10-7 cm2/S at 25 °C.
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Authors: Hae Suck Park, Dong Hwan Suh, Dong Hun Lee, Whan Gi Kim
Abstract: Novel bisphenol-based wholly aromatic poly(ether ketone)/poly(ether sulfone) copolymers containing pendant sulfonate groups were prepared by direct aromatic nucleophilic substitution polycondensation of 4,4-difluoro-3,3’-disodiumsulfonylbenzophenone (40mol% of bisphenol), difluorophenylsulfone and bisphenol A. Organic-inorganic composite membranes were obtained by mixing organic polymers with hydrophilic SiO2 (ca. 20nm) obtained by sol-gel process. The physic-chemical properties of these composite membranes were studied by thermogravimetry analysis(TGA), differential scanning calorimetry (DSC) and transform infrared(FTIR) spectroscopy. Scanning electron microscopy (SEM) and atomic Force microscopy (AFM) were used to observe the surface of membrances. The proton conductivity as a function of temperature decreased as SiO2 content increased, but water uptake increased. The membranes were shown all requisite properties; IEC (1.5meq./g), thermal stablity (Tg= 185°C), and low affinity towards methanol (1.5x10-7 - 4.3x10-7 cm2/S).
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Authors: Young Gi Jeong, Hye Seok Park, Dong Wan Seo, Seung Woo Choi, Whan Gi Kim
Abstract: The Sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) / poly(2,6-diphenyl-1,4-phenylene oxide) (S-PPO) was prepared by oxidative coupling polymerization with 2,6-dimethyl phenol, 2,6-diphenyl phenol, CuCl(І) and pyridine, and followed sulfonation with chlorosulfonic acid. Copolymer was consisted of 2,6-diphenyl phenol 30 mol% and 2,6-dimethyl phenol 70 mol%. Organic-inorganic nano composite membranes were prepared with copolymer and a series of SiO2 nanoparticles (20 nm, 4, 7 and 10 wt%). The composite membranes were cast from dimethylsulfoxide solution. The membranes were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. S-PPO copolymer and nano composite membranes exhibited proton conductivities from 0.79×10-3 to 0.98×10-3 S/cm, water uptake from 21.70 to 24.77 %, IEC from 0.720 to 0.955 meq/g and methanol diffusion coefficients from 2.97×10-7 to 3.70×10-7 cm2/S.
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Authors: Young Don Lim, Dong Wan Seo, Soon Ho Lee, Md. Monirul Islam, Hyun Mi Jin, Ho Hyoun Jang, Insuk Jeong, Whan Gi Kim
Abstract: Poly(ether sulfone)s (PES) containing 25-75 mol % valeric acid were prepared with bisphenol A, bis(4-chlorophenyl)sulfone and 4,4-Bis(4-hydroxylphenyl)valeric acid using potassium carbonate in DMAc (dimethylacetamide) at 160 °C. Copolymers containing carboxylacid group were reduced to hydroxy group by BH3 solution 1M in THF and NaBH4 co-catalyst. Sulfonated poly(ether sulfone)s (S-PES) were obtained by reaction of 1,3-propanesultone and the reduced copolymer (PES-OH) with potassium t-butoxide. Composite membranes were prepared with copolymers and SiO2 nanoparticles(20 nm, 4-10 wt%). The composite membranes were cast from DMSO.A series of composite membranes were studied by 1H-NMR spectroscopy, differential scanning calorimetry (DSC), and thermo gravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol.
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Authors: Young Don Lim, Dong Wan Seo, Soon Ho Lee, Md. Awlad Hossain, Hyun Chul Lee, In Seok Jung, Whan Gi Kim
Abstract: Sulfonated poly (ethersulfone) s (S-PDHTPEs) were prepared from 4,4-(2,2-diphenylethenylidene) bisphenol (DHTPE), 4,4-sulfonyldiphenol, 4-fluorophenylsulfone using potassium carbonate, and followed sulfonation reaction with conc. sulfuric acid. DHTPE is a conjugated structure, which enables to form planar conformation between aromatic rings, and selectively sufonated on phenyl rings of polymer side chain. Composite membranes were prepared with copolymers and SiO2 nanoparticles (20 nm, 4~10%wt). The composite membranes were cast from DMSO. A series of composite membranes structures and characteristic were evaluated by the 1H-NMR spectroscopy, and thermal stabilities. The membranes were performed by ion exchange capacity (IEC), water uptake and proton conductivity as a function of degree of sulfonation.
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Authors: Dong Hoon Lee, Hye Suk Park, Dong Wan Seo, Whan Gi Kim
Abstract: Novel bisphenol-based wholly aromatic sulfonated poly(ether sulfone-ketone) copolymer and organic-inorganic composite membranes were prepared for operation 80°C in polymer electrolyte membrane fuel cell (PEMFCs). The copolymer were synthesized by direct aromatic nucleophilic substitution polycondensation of 4,4-difluorobenzophenone, 2,2’-disodiumsulfonyl- 4,4’-fluorophenylsulfone (40mole% of bisphenol A) and bisphenol A. Polymerization proceeded quantitatively to high molecular weight in N-methyl-2-pyrrolidinone at 180°C. Organic-inorganic composite membranes were obtained by mixing organic polymers with hydrophilic SiO2 obtained by sol-gel process. The polymer and a series of composite membranes were studied by FT-IR, 1HNMR, differential scanning calorimetry (DSC) and thermal stability. The proton conductivity as a function of temperature decreased as SiO2 content increased, but methanol permeability decreased. The nano composite membranes were found to poses all requisite properties; Ion exchange capacity (1.2meq./g), glass transition temperatures (164-183), and low affinity towards methanol (4.63-1.08x10-7 cm2/S).
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