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Park, Hyun-Uk,Park, Ah-Hyeon,Shi, Wenjuan,Park, Gu-Gon,Kwon, Young-Uk Elsevier 2019 Ultrasonics sonochemistry Vol.58 No.-
<P><B>Abstract</B></P> <P>In this work, we introduce composition-tunable core-shell-like PdM@Pt (M = Mn and Fe) nanoparticles (NPs) on carbon support (PdM@Pt/C) synthesized by one-pot sonochemical reactions using high-intensity ultrasonic probe (150 W, 20 kHz, with 13 mm solid probe) and investigate their electrocatalytic performance for oxygen reduction reaction (ORR). The core-shell-like structure of the NPs are evidenced by the elemental distribution maps obtained by energy dispersive X-ray spectroscopy equipped on scanning transmission electron microscopy. Based on the characterization data, PdM@Pt NPs were synthesized with variable elemental compositions (Pd<SUB>49</SUB>Fe<SUB>21</SUB>@Pt<SUB>30</SUB>, Pd<SUB>17</SUB>Fe<SUB>31</SUB>@Pt<SUB>52</SUB>, Pd<SUB>46</SUB>Mn<SUB>6</SUB>@Pt<SUB>48</SUB> and Pd<SUB>15</SUB>Mn<SUB>5</SUB>@Pt<SUB>80</SUB>). All PdM@Pt samples are composed of large (~10 nm) and small (~3 nm) NPs, the large ones appear to be aggregates of the smaller ones, and the proportion of the larger NPs increases with the Pd content, which can be explained with the known mechanisms of sonochemical reactions of related systems. Electrochemical analyses on samples show that the ORR mass activity of PdM@Pt/C is 3-fold (normalized by Pt) and 1.7-fold (normalized by platinum group metal (PGM)) higher than those of Pt/C (commercial). All PdM@Pt/C sample show superior durability with the electrochemical surface area (ECSA) change of −4.4–+12.0% and half-wave potential change (ΔE<SUB>1/2</SUB>) of 8–14 mV after 10 k cycles accelerated stress test (AST) to Pt/C with ECSA change of −25.6% and ΔE<SUB>1/2</SUB> of 19 mV.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We have synthesized PdM@Pt/C (M = Mn and Fe) samples by one-pot sonochemical reaction. </LI> <LI> PdM@Pt/C samples consist of large (~10 nm) and small (~3 nm) NPs with different proportion in each sample. </LI> <LI> Particle size distribution of samples is mainly controlled along with Pd content. </LI> <LI> The effect of particle size and composition of samples affect electrocatalytic performance for ORR. </LI> <LI> All PdM@Pt/C samples showed enhanced ORR activity and durability than Pt/C. </LI> </UL> </P>
Distribution Characteristics of Dioxins in Marine Sediment from Busan Port in Korea
Tae-Uk Jeong,Dong-Cheol Seo,Seung-Ryul Jeong,Bok-Joo Song,Jeong-Gu Cho,Pyung-Jong Yoo,Gi-Gon Kim,Ju-Sik Cho,Jong-Soo Heo 한국토양비료학회 2012 한국토양비료학회지 Vol.45 No.1
Eight marine sediments from Busan port in Korea were annually analyzed to examine the concentration distribution of dioxins from 2006 to 2010. Yearly mean concentration of dioxins ranged from 186.3 to 383.3 pg g<SUP>-1</SUP> in real values and 5.087 to 8.541 pg-TEQ (Toxicity equivalency) based on dry weight of samples. The dioxin concentration at the site near fishing market was the highest concentration among all sampling sites. Also the dioxin concentration at the sites with various pollutant sources such as large ships, sewage influx and thermal power station as well as fishing market was higher than that of the sites without specific pollutant sources. Another main factor that affects the dioxin concentration is topography characteristics of the bay. The bay has relatively high dioxin concentration because of the lack of the pollutant diffusion. This study demonstrated that the dioxin concentration in the site with pollutant sources and the lack of the pollutant diffusion was relatively high as compared with the other sites. As a result of contribution ratio of dioxin congeners, OCDD (Octachlorodibenzodioxin) in all sites was major contributor in real value, in contrast, dioxin congeners in TEQ values were dominated by 2,3,4,7,8-PeCDF.
Hyun-Uk Park,Eunjik Lee,Jeongyun Jang,Min Ho Seo,Gu-Gon Park 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
In this work, we propose a method to easily control the size of the core-shell nanoparticles (NPs) by controlling the pressure of the inert gas during the heat treatment process. As synthesized Fe@Pt/C catalysts were conducted heat treatment with varied pressure control (1, 40, 80 bar) under inert atmosphere. The average size of the metal NPs was distributed in the range of about 3 to 5 nm, and the particle size was clearly reduced in inverse proportion to the pressure. By scanning transmission electron microscopy (STEM) analysis, we also confirmed that the catalysts show clear M core-Pt shell structure. We also confirmed that the NPs retained the core-shell structure even after heat treatment at all pressure conditions and were successfully applied to the oxygen reduction reaction (ORR) electrocatalysts, confirming that the mass activity was higher than commercial Pt/C (HiSPEC4000) catalyst. Theoretical calculations show the correlation between the size of metal NPs and external pressure. Herein, we introduce a novel particle size control method and our unique synthetic approach can be a promising way to obtain intermetallic structure NPs with controlled particle size.
Jae-Uk Lee,Jeong-Eun Lim,Ji-Soo Yuk,Sam-Haeng Yi,Myung-Gyu Lee,Joo-Seok Park,Young-Gon Kim,Sung-Gap Lee 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.6
BaTiO3/La0.7Sr0.3MnOs/BaTiO3 multilayer films are fabricated using the chemical solution deposition and spin-coatingmethod. The upper BT film exhibits an average grain size of approximately 42 nm, indicating a uniform and dense microstructure. The single-coated film has an average thickness ranging from 40 to 45 nm. A phase transition temperature of approximately4 °C is observed in all films. The BT/LSMO/BT multilayer film, coated with LSMO four times, demonstrates amaximum dielectric constant of 2008 at 20 °C. The BT/LSMO/BT multilayer film, coated with LSMO two times, shows a ΔTof 0.59 K at 24 °C. The remnant polarization, coercive field, and ΔT/ΔE of the BT/LSMO/BT multilayer film, coated withLSMO four times, are 19.8 μC/cm2, 42 kV/cm, and 4.56 mKcm/kV, respectively.