• Title/Summary/Keyword: Transition metals

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Microstructures and Repeated Usage-Properties of de-$NO_{x}$ Transition Metals/ZSM-5 Catalyst Made by Mechanical Alloying Method (기계적합금화법을 이용하여 제조된 $NO_{x}$ 제거용 천이금속/ZSM-5촉매의 미세구조 및 반복사용특성)

  • 조규봉;안인섭;남태현
    • Journal of Powder Materials
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    • v.5 no.4
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    • pp.273-278
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    • 1998
  • $De-NO_x$ transition metals(Cu, Co)/ZSM-5 catalyst was made by mechanical alloying method, and their microstructures and repeated usage-properties were investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The conversions ability of NO in the catalyst was measured. A part of ZSM-5 in CO/ZSM-5 composite powders was amorphous and the amorphous phase became less stable with increasing Co content. Conversion ability of NO in 10Cu/ZSM-5 powders decreased from 89% to 12% and that in 10Co/ZSM-5 decreased from 22% to 17% by 7 times conversion tests.

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Stability and Electronic Properties of the Adsorption of Molecular Hydrogen on Metal-containing Single-walled Carbon Nanotubes

  • Michael, Mananghaya
    • Journal of the Korean Chemical Society
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    • v.59 no.5
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    • pp.429-433
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    • 2015
  • The binding ability and hydrogen storage capacity of nitrogen doped carbon nanotube with divacancy (4NDCNxNT) that is decorated with transition metals was investigated based on density functional theory calculations. Results indicate that scandium shows an ideal reversible hydrogen binding capability with promising system-weight efficiency compared with other transition metals when functionalized with 4ND-CNxNT. The (Sc/4ND)10-CNxNT can store up to 50H2 molecules, corresponding to a maximum gravimetric density of 5.8 wt%. Detailed structural stability and electronic properties were reported as hydrogen molecules were absorbed. It takes about 0.16 eV/H2 to add one H2 molecule, which assures reversible storage of H2 molecules under ambient conditions.

Controlled synthesis of mesoporous codoped titania nanoparticles and their photocatalytic activity

  • Mathis, John E.;Kidder, Michelle K.;Li, Yunchao;Zhang, Jinshui;Paranthaman, M.P.
    • Advances in nano research
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    • v.4 no.3
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    • pp.157-165
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    • 2016
  • The photocatalytic (PC) activity of anatase titania nanoparticles can be improved through codoping with transition metals and nitrogen. In addition, the PC activity can also be improved by creating monodisperse, mesoporous nanoparticles of titania. The question naturally arose as to whether combining these two characteristics would result in further improvement in the PC activity or not. Herein, we describe the synthesis and photocatalytic characteristics of codoped, monodisperse anatase titania. The transition metals tested in the polydisperse and the monodisperse forms were Mn, Co, Ni, and Cu. In each case, it was found that the monodisperse version had a higher PC activity compared to the corresponding polydisperse version.

An experimental study on methanol decomposition catalysts for long distance-heat transportation (장거리 열수송을 위한 메탄올 분해 촉매에 대한 실험적 연구)

  • 문승현;박성룡;윤형기;윤기준
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.3
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    • pp.334-342
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    • 1998
  • In this experimental study, methanol was chosen as a system material for a long -distance heat transportation. Not only transition metals but also noble metals were investigated as an active component, and several metal oxides, such as ${\gamma}$-$Al_2$,$O_3$, $SiO_2$, etc. as a support. In general, transition metal catalysts absorbed more heat than noble metal catalysts. The amount of heat absorption and CO selectivity depends on temperature and methanol partial pressure, and 25$0^{\circ}C$ Ni/$SiO_2$ catalyst showed the best result for methanol decomposition reaction.

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Synergistic Effect on the Photocatalytic Degradation of 2-Chlorophenol Using $TiO_2$Thin Films Doped with Some Transition Metals in Water

  • Jeong, O Jin
    • Bulletin of the Korean Chemical Society
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    • v.22 no.11
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    • pp.1183-1191
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    • 2001
  • The metallorganic chemical vapor deposition (MOCVD) method has been used to prepare TiO2 thin films for the degradation of hazardous organic compounds, such as 2-chlorophenol (2-CP). The effect of supporting materials and metal doping on the photocatalytic activity of TiO2 thin films also has been studied. TiO2 thin films were coated onto various supporting materials, including stainless steel cloth(SS), quartz glass tube (QGT), and silica gel (SG). Transition metals, such as Pd(II), Pt(IV), Nd(III) and Fe(III), were doped onto TiO2 thin film. The results indicate that Nd(Ⅲ) doping improves the photodegradation of 2-CP. Among all supporting materials studied, SS(37 ${\mu}m)$ appears to be the best support. An optimal amount of doping material at 1.0 percent (w/w) of TiO2-substrate thin film gives the best photodegration of 2-CP.

Content and Distribution of Transition Metals and Rare Earth Elements in Magnetically and Mechanically Separated Brown Coal Ash

  • Malikov, Sh.R.;Pikul, V.P.;Mukhamedshina, N.M.;Sandalov, V.N.;Kudiratov, S.;Ibragimova, E.M.
    • Journal of Magnetics
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    • v.18 no.3
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    • pp.365-369
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    • 2013
  • Coal ash is known to contain a noticeable amount of valuable elements, including transition metals and lanthanides. Therefore it is quite actual problem to extract them for metallurgy and other applications. This paper presents the results of high gradient magnetic and mechanical separation, microscopy, element analyses and optical spectroscopy of brown coal ash taken from the combustion camera and chimney-stalk of Angren thermal power station. The separated magnetic fraction was 3.4 wt.%, where the content of Fe in ferrospheres increased to 58 wt.%. The highest contents of Fe and rare earth elements were found in the fine fractions of $50-100{\mu}m$. Optical absorption spectroscopy of water solutions of the magnetic fractions revealed $Fe^{2+}$ and $Fe^{3+}$ ions in the ratio of ~1:1. The separated coal ash could be used for cleaning of technological liquid waste by means of the high gradient magnetic field.

Separation of the Heavy Metals by macrocycles- mediated Emulsion Liquid Membrane Systems (거대고리 화합물을 매질로한 에멀존 액체막게에 의한 중금속이온의 분리)

  • 정오진
    • Journal of Environmental Science International
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    • v.2 no.1
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    • pp.61-72
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    • 1993
  • Result of this study indicate that two criteria must be met in order to have effective macrocycle-mediated transport in these emulsionsystem. First, one must effective extraction of the post transition metals, $Cd^{2+}$. $Pb^{2+}$ and $Hg^{2+}$ , into toluene membrane. The effectiveness of this extraction is greatest if log K values for the metal-macrocycle interaction is large. Second, the ratio of the log K values for the metal ion-receiving phase to the metal ion-macrocycle interaction must be large enough to ensure quantitative stripping of the metal ion at the toluene phase interface. Control of the first step can be obtained by appropriate selection of macrocycle donor atom, substituents, and cavity radius. The second step can be controlled by selecting the proper complexing agent for inclusion in the receiving phase. The order of the transport, when using the several $A^-$ species such as $SCN^-$, $1^-$, $Br^-$ and $Cl^-$ is the order of the changing degree of solvation for $A^-$ and the transport of the metals is also affected by the control of concentration for receiving species because of solubility-differences. In this study, we can seperate each single metal ion from the mixture of $Cd^{2+}$, $Pb^{2+}$, and $Hg^{2+}$ ions by using the toluene membranes controlled by optimized conditions. Transport of the single metal is also very good, and alkaline and alkaline earth metals as interferences ions did not affect the seperation of the metals in this macrocycle-liquid membrances but transition metal ions were partially affected as interferences for the post transition metal ions.

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Growth of highly purified carbon nanotubes by thermal chemical vapor deposition (열화학기상증착법에 의한 고순도 탄소나노튜브의 성장)

  • Lee, Tae-Jae;Lee, Cheol-Jin;Kim, Dae-Won;Park, Jung-Hoon;Son, Kwon-Hee;Lyu, Seung-Chul;Song, Hong-Ki;Kim, Seong-Jeen
    • Proceedings of the KIEE Conference
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    • 1999.07d
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    • pp.1839-1842
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    • 1999
  • We have synthesized carbon nanotubes by thermal chemical vapor deposition of $C_2H_2$ on transition metal-coated silicon substrates. Carbon nanotubes are uniformly synthesized on a large area of the plain Si substrates, different from Previously reported porous Si substrates. It is observed that surface modification of transition metals deposited on substrates by either etching with dipping in a HF solution and/or $NH_3$ pretreatment is a crucial step for the nanotube growth prior to the reaction of $C_2H_2$ gas. We will demonstrate that the diameters of carbon naotubes can be controlled by applying the different transition metals.

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