Whan Gi Kim

Sulfonated Polystyrene Ionomers Containing 4-Aminobenzoic Acid Studied by a Small-Angle X-Ray Scattering Technique

In a recent study by the same authors using a DMTA (Dynamic Mechanical Thermal Analyzer), it was found that the 4-aminobenzoic acid (ABA) molecules acted as either a neutralizing agent, or a plasticizer, or a filler, depending on the order of mixing of poly(styrene-co-styrenesulfonic acid) (PSSA), ABA, and NaOH. Subsequent to that study, we here pursued the same topic, i.e., the effect of the addition of CsOH (instead of NaOH) and ABA on the morphology of PSSA, but this time, by using a small-angle X-ray scattering (SAXS) technique. In line with the previous results, the present study with the SAXS technique verified that the order of mixing has a significant effect on the morphology of ionomers. In addition, with the SAXS data and the density values of the ionomers, we attempted to calculate both the number of sulfonate ionic groups per multiplet and the size of the multiplet of the ionomer.

Synthesis and Photopolymerization of Vinyl Ether and Epoxy-Functionalized Silicones

The reactive precursors, vinyl ethers, and epoxy-silicones, were synthesized. The vinyl ether monomers were prepared from primary alcohol and ethyl vinyl ether with mercury (II) acetate. The epoxy-functionalized silicones have been achieved by the controlled, rhodium-catalyzed, chemoselective hydrosilation of vinyl ether with siloxanes or silane. It was shown that the hydrosilation proceeds exclusively at the vinyl ether group of alkenyl vinyl ether without participation at the alkenyl group. The photoinduced cationic polymerization of these monomers was studied and found to be all highly reactive.

Synthesis and Characterization of Grafted Silicone Polycarbonates

Grafted silicone polycarbonates were synthesized from precursors, which are allyl polycarbonates (Allyl-PCs), and siloxanes by hydrosilylation reaction using Karstedts catalyst. Allyl-PCs were synthesized using polycarbonate oligomer and 3,3′-diallyl bisphenol A (DABA) through an interfacial polymerization process. FT-IR, 1H-NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC) were studied in order to understand the characterization of the synthesized compounds. Atomic force microscopy (AFM) was used to observe the surface morphology of the polymer films. The contact angle measurement of the sessile water drop onto the polymer films was also performed. The silicone polycarbonates (Si-PC) and their active precursors (Allyl-PC) were different in thermal properties to that of the bisphenol A polycarbonate (BPA-PC). Grafted silicone polymers exhibited lower wettability than those of their precursors and BPA-PC.

Synthesis and Thermoelectric Properties of Half-Heusler Zr-Ni-Sn Alloy Processed by Mechanically Alloying and Hot Pressing

Recent search for novel thermoelectric materials has revealed a new class of compounds with half-Heusler structure as good candidates for higher performance thermoelectric conversion [1-2], since the structure was first found [3]. The unit cell of the half-Heusler with a space group F4¯ 3m consists of 4 interpenetrating cubic lattices. The crystallographic sites (0,0,0) and (1/4, 1/4, 1/4) are occupied by two different transition metals, the (1/2, 1/2, 1/2) site is occupied by Sn, Sb, or Bi, and the site (3/4, 3/4, 3/4) is empty [4,5]. Candidates with this structure for the investigation would be categorized into the combination of (Ti/Zr/Hf)(Co/Ni/Pt)(Sb/Sn/Bi) [4-6].

Evaluations of Microstructure and Hydrogenation Properties on Mg2NiHx Hydrogen Absorbing Alloys by Hydrogen Induced Mechanical Alloying

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%.

Nano Composite Membranes of Sulfonated Amine-Poly(ether sulfone)s and SiO2 for Fuel Cell Application

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.

Synthesis and Electronic Transport Properties of Sn-Doped CoSb3

Sn-doped CoSb3 skutterudites were prepared by encapsulated induction melting and their electronic transport properties were examined. The Sn dopant generated excess charge carriers, which increased in concentration with increasing Sn doping content. However, the carrier mobility decreased with increasing doping content, indicating a decrease in the hole mean free path by impurity scattering. The Seebeck coefficient decreased and the electrical resistivity decreased slightly with increasing the carrier concentration due to the reduced carrier mobility by impurity scattering. The lattice thermal conductivity was dominant in the Sn-doped CoSb3 skutterudites.

Synthesis and Characterization of Poly(ether ketone) Containing Side Sulfonic Acid Group for Proton Exchange Membrane Fuel Cell

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.

Synthesis and properties of polycarbonate-co-poly(siloxane-urethane-siloxane) block copolymers

AbstractPolycarbonate-co-poly(siloxane-urethane-siloxane) block copolymers (SiUrPC) were synthesized from siloxane-urethane monomer and polycarbonate (PC) oligomer, and their properties were compared with those of linear Bisphenol A PC (BPA-PC) and siloxane PC (SiPC). The synthesized polymers were characterized by 1H NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC). The contact angle of the sessile water drop onto the polymer films was also measured. The thermal and mechanical properties of SiUrPC differed from those of BPA-PC and SiPC. SiUrPC exhibited superior flow properties and lower wettability than BPA-PC.

Fabrications and Evaluations of Hydrogen Capacities on MgHX-Transition Metal Oxide(TMO) Composites by Mechanical Alloying

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.