• Title, Summary, Keyword: highly dispersed

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Enhanced room-temperature HCHO decomposition activity of highly-dispersed Pt/Al2O3 hierarchical microspheres with exposed {110} facets

  • Zhua, Xiaofeng;Yu, Jiaguo;Jiang, Chuanjia;Cheng, Bei
    • Journal of Industrial and Engineering Chemistry
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    • v.45
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    • pp.197-205
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    • 2017
  • Formaldehyde (HCHO) catalytic decomposition at room temperature is an important method for HCHO removal in indoor environment. Herein, flower-like ${\gamma}-Al_2O_3$ microspheres with high specific surface area, special textural structure, and abundant surface defects were prepared through a one-pot hydrothermal method by using aluminum foil as Al source. And it was used as oxide support to prepare highly-dispersed Pt catalyst ($Pt/Al_2O_3$). Compared with Pt supported on commercial ${\gamma}-Al_2O_3$, the as-prepared $Pt/Al_2O_3$ showed enhanced catalytic activity for HCHO decomposition at room temperature. This work provides new insights into designing and fabricating highly-dispersed Pt catalysts for efficient indoor air purification.

Copper Oxide-Modified Polymeric Composite Elecrodes for Amperometric Detection of Carbohydrates in LCEC Analysis

  • 정혜경;박종만
    • Bulletin of the Korean Chemical Society
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    • v.18 no.9
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    • pp.952-957
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    • 1997
  • Modified polymeric composite electrodes having highly dispersed CuO particles through the electrode matrix were prepared for LCEC or flow injection analysis of carbohydrates. The composite electrodes were prepared by incorporating carbon black and highly dispersed copper oxide particles in polystyrene matrix cross-linked with divinylbenzene. The analytical characteristics of the electrodes for LCEC and flow injection analysis of carbohydrates were evaluated. Improved performance in LCEC and flow injection analysis of carbohydrates is demonstrated in terms of sensitivity, reproducibility, stability and surface renewability. It was possible to get improved performance of the electrodes as well as adaptability of the electrodes for practical applications by employing highly dispersed catalyst particles through the electrode matrix and robust polymeric electrode matrix.

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Isolation and Culture Characteristics of a Bacterial Symbiont from Entomopathogenic Nematode Steinernema galseri (Steinernema glaseri 곤충병원선충으로부터 공생박테리아의 분리 및 배양특성)

  • 박선호;유연수
    • KSBB Journal
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    • v.14 no.2
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    • pp.198-204
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    • 1999
  • Asymbiotic bacterium with highly effective toxins was isolated from entomopathogenic nematode Steinernema glaseri which has been widely used against various soil-inhabiting pests. The symbiont of S. glaseri was identified as Xenorhabdus nematophilus sp. by using several biochemical and physiological tests. When this strain was released into the hemolymph of insect larva, it produced highly toxic substances and killed the larva within 2 days. Two colony forms that differed n some biochemical characteristics were observed when cultures in vitro. Phase l colonies were mucid and difficult to be dispersed in liquid. Phase II was not mucoid and was easily dispersed in liquid. It did not adsorb neutral red or bromothymol blue. Rod-shaped cell size was highly variable between two phases, ranging 2-10 ${\mu}{\textrm}{m}$. It was also found that only infective-stage nematodes can carry only primary-phase Xenorhabdus in their intestine.

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[ $H_2$ ] uptake of the Li dispersed nickel oxide nanotubes (리튬이 첨가된 니켈 산화물 나노튜브의 수소저장)

  • Lee, Jin-Bae;Lee, Soon-Chang;Lee, Sang-Moon;Lee, Young-Seak;Kim, Hae-Jin
    • Transactions of the Korean hydrogen and new energy society
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    • v.17 no.1
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    • pp.39-46
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    • 2006
  • Highly ordered Li dispersed nickel oxide nanotubes were prepared with anodic aluminum oxide (AAO) template for hydrogen storage. Electron microscope results showed that uniform length and diameter of nickel oxide nanotubes were obtained. The wall thickness and outer diameter of nickel oxide nanotubes are about 40 - 50 nm and 200 - 400 nm, respectively. It was observed that the diameter of nickel oxide nanotubes is bigger than the pore diameter of AAO template. Li dispersed nickel oxide were consisted of nanoflakes and had structures of nanotubes and nanorods. For increasing the hydrogen adsorption and desorption capacity, the Li dispersed nickel oxide nanotubes were fluorinated. The fluorinated Li dispersed nickel oxide nanotubes showed 1.65 wt% of the hydrogen adsorption capacities at 77 K under 47 atm.

Characterization of Enhanced CO Oxidation Activity by Alumina Supported Platinum Catalyst

  • Jo, Myung-Chan
    • Journal of Environmental Science International
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    • v.18 no.10
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    • pp.1071-1077
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    • 2009
  • A novel pretreatment technique was applied to the conventional Pt/alumina catalyst to prepare for the highly efficient catalyst for the preferential oxidation of carbon monoxide in hydrogen-rich condition. Their performance was investigated by selective CO oxidation reaction. CO conversion with the oxygen-treated Pt/Alumina catalyst increased remarkably especially at the low temperature below $100^{\circ}C$. This result is promising for the normal operation of the proton exchange membrane fuel cell (PEMFC) without CO poisoning of the anode catalyst. XRD analysis results showed that metallic Pt peaks were not observed for the oxygen-treated catalyst. This implies that well dispersed small Pt particles exist on the catalyst. This result was continued by high resolution transmission electron microscopy (HRTEM) analysis. Consequently, it can be concluded that highly dispersed Pt nanoparticles could be prepared by the novel pretreatment technique and thus, CO conversion could be increased considerably especially at the low temperatures below $100^{\circ}C$.

Study on the Partial Hydrogenation of Butadiene over Highly Dispersed Supported Gold Catalysts (고분산 담지 금 촉매에 의한 Butadiene의 부분 수소화에 관한 연구)

  • Ahn, Ho-Geun;Hiroo, Niiyama
    • Applied Chemistry for Engineering
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    • v.10 no.7
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    • pp.1003-1007
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    • 1999
  • The activity and products distribution for the hydrogenation of butadiene and pentadiene over the gold and cobalt catalysts prepared by coprecipitation and impregnation method was investigated with using a flow reactor under atmospheric pressure. The reaction characteristics of the highly dispersed gold particles and its role were studied. The activity of the gold catalyst by coprecipitation was much higher than that by impregnation. The selectivity of butene on all gold particles was always 100% even in the absence of butadiene in the stream, but butadiene on cobalt supported catalyst was easily hydrogenated to butane. It was therefore considered that the active sites at circumferences of the gold particles possessed an unique property which took a proper affinity to hydrogen. In the hydrogenation of butadiene and pentadiene, the percentages of 1-butene and 2-pentene were 60%~70% and about 62%, respectively. The results could be simply explained by a statistical concepts of hydrogen addition.

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Ultra-Drawing of Gel Films of Ultra High Molecular Weight Polyethylene/Low Molecular Weight Polymer Blends Containing $BaTiO_3$ Nanoparticles

  • Park Ho-Sik;Lee Jong-Hoon;Seo Soo-Jung;Lee Young-Kwan;Oh Yong-Soo;Jung Hyun-Chul;Nam Jae-Do
    • Macromolecular research
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    • v.14 no.4
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    • pp.430-437
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    • 2006
  • The ultra-drawing process of an ultra high molecular weight polyethylene (UHMWPE) gel film was examined by incorporating linear low-density polyethylene (LLDPE) and $BaTiO_3$ nanoparticles. The effects of LLDPE and the draw ratios on the morphological development and mechanical properties of the nanocomposite membrane systems were investigated. By incorporating $BaTiO_3$ nanoparticles in the UHMWPE/LLDPE blend systems, the ultra-drawing process provided a highly extended, fibril structure of UHMWPE chains to form highly porous, composite membranes with well-dispersed nanoparticles. The ultra-drawing process of UHMWPE/LLDPE dry-gel films desirably dispersed the highly loaded $BaTiO_3$ nanoparticles in the porous membrane, which could be used to form multi-layered structures for electronic applications in various embedded, printed circuit board (PCB) systems.

Rheology of Decamethylceclopentasiloxane (cyclomethicone) W/O Emulsion System

  • Choi, Min-Hyung;Jeong, So-Ra;Nam, Sang-In;Shim, Sang-Eun;Chang, Yoon-Ho
    • Macromolecular research
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    • v.17 no.12
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    • pp.943-949
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    • 2009
  • A highly dispersed W/O emulsion of silicone oil (cyclomethicone)/water system was prepared with a nonionic surfactant. The surface and interfacial tension between the oil and water were characterized in terms of the droplet size distribution and viscosity change of the emulsion. When the dispersed phase concentration was relatively high, the viscosity of the emulsion was rapidly increased and the droplet size of the emulsion was decreased. The rheological behavior of the emulsion system showed non-Newtonian and shear thinning phenomena depending upon the content of the dispersed phase. The droplet size of the emulsion was decreased with increasing surfactant content and water concentration. The relative viscosity of the emulsion was better predicted with the Choi-Schowalter model than with the Taylor model. The value of the complex modulus increased with increasing surfactant concentration. The linear viscoelastic region was expanded with a dispersed phase concentration. According to the change in the viscosity, the behavior was classified into three distinct regions: [I] linear viscoelastic, [II] partially viscoelastic, and [III] viscous. The creep/recovery behaviors in each region were characterized.

Effect of V2O5 Modification in V2O5/TiO2-ZrO2 Catalysts on Their Surface Properties and Catalytic Activities for Acid Catalysis

  • Sohn, Jong-Rack;Lee, Cheul-Kyu
    • Bulletin of the Korean Chemical Society
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    • v.28 no.12
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    • pp.2459-2465
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    • 2007
  • V2O5/TiO2-ZrO2 catalyst modified with V2O5 was prepared by adding Ti(OH)4-Zr(OH)4 powder into an aqueous solution of ammonium metavanadate followed by drying and calcining at high temperatures. The characterization of prepared catalysts was performed using XRD, DSC, solid-state 51V NMR, and FTIR. In the case of calcination temperature of 500 oC, for the catalysts containing low loading V2O5 below 25 wt % vanadium oxide was in a highly dispersed state, while for catalysts containing high loading V2O5 equal to or above 25 wt % vanadium oxide was well crystallized due to the V2O5 loading exceeding the formation of monolayer on the surface of TiO2-ZrO2. The strong acid sites were formed through the bonding between dispersed V2O5 and TiO2-ZrO2. The larger the dispersed V2O5 amount, the higher both the acidity and catalytic activities for acid catalysis.