Seong-Ho Yoon

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Nitrogen-doped graphene sheets were prepared through a hydrothermal reduction of colloidal dispersions of graphite oxide in the presence of hydrazine and ammonia at pH of 10. The effect of hydrothermal temperature on the structure, morphology, and surface chemistry of as-prepared graphene sheets were investigated though XRD, N(2) adsorption, solid-state(More)
The pore structures of commercial pitch and PAN-based activated carbon fibers (ACFs) were investigated. The pore size and pore size distribution of pitch-based ACFs were measured by nitrogen adsorption isotherms and 129Xe NMR spectroscopy and compared with each other. Scanning tunneling microscopy showed that the ACFs were composed of spherical microdomain(More)
Graphene sheets were prepared via chemical reduction of graphite oxides and then graphitized at 2800 °C. The structure changes from pristine graphite to graphitized graphene sheets were monitored using X-ray diffraction and Raman spectroscopy. It was found that the graphitized graphene sheets exhibited relatively low degree of graphitization and high level(More)
The graphene discs with well-defined shape are successfully fabricated using a simple oxidation and exfoliation process of high-crystalline carbon nanofibers (CNFs). To control the shapes of graphene discs, two different types of CNFs (platelet and herringbone-type) are used as starting materials. The CNFs are formed by the perpendicular stacking of(More)
PtRu alloy nanoparticles (24 +/- 1 wt %, Ru/Pt atomic ratios = 0.91-0.97) supported on carbon nanofibers (CNFs) were prepared within a few minutes by using a microwave-polyol method. Three types of CNFs with very different surface structures, such as platelet, herringbone, and tubular ones, were used as new carbon supports. The dependence of particles sizes(More)
Wiskott-Aldrich syndrome (WAS) and X-linked thrombocytopenia (XLT) are caused by a mutation in the WAS gene on Xp11.22. We report two patients with IVS6+5G>A of WAS in a Korean family. The proband presented with classic WAS, whereas his maternal cousin had symptoms limited to XLT. Their mothers were proved to be carriers. The IVS6+5G>A mutation was reported(More)
Reported is the capacitive behavior of homogeneous and well-defined surfaces of pristine carbon nanofibers (CNFs) and surface-modified CNFs. The capacitances of the well-defined CNFs were measured with cyclic voltammetry to correlate the surface structure with capacitance. Among the studied pristine CNFs, the edge surfaces of platelet CNFs (PCNF) and(More)
The electrocatalytic activity of nitrogen-doped carbon nanofibers (N-CNFs), which are synthesized directly from vaporized acetonitrile over nickel-iron based catalysts, for oxygen reduction reaction (ORR), was investigated. The nitrogen content and specific surface area of N-CNFs can be controlled through the synthesis temperature (300-680 degrees C). The(More)
A platinum nanoparticle-reduced graphene oxide (Pt-RGO) nanohybrid for proton exchange membrane fuel cell (PEMFC) application was successfully prepared. The Pt nanoparticles (Pt NPs) were deposited onto chemically converted graphene nanosheets via ethylene glycol (EG) reduction. According to the powder X-ray diffraction (XRD) pattern and transmission(More)