Papers by Keyword: Transition Metal

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Authors: W.V.M. Machado, João F. Justo, Lucy V.C. Assali
Abstract: The electronic and structural properties of isolated 3d-transition metal impurities in 3C, 4H, and 2H silicon carbide have been investigated bytotal energy ab initio methods. The stability, spin states and transition energies of substitutional (Si sub-lattice) Cr, Mn, and Fe impurities in several charge states were computed. Our results are discussed in the context of available experimental data.
531
Authors: Wen Qin Wang, Xiao Long Tang, Hong Hong Yi, Jing Li Hu
Abstract: Cu-Mn/Al2O3, Cu-Mn/TiO2 and Cu-Mn/SBA-15 were prepared by incipient wetness impregnation. The activity of those catalysts for selective catalytic oxidation (SCO) of ammonia to nitrogen at low temperature (100°C~250°C) is not so satisfying. 5%Cu-5%Zr/TiO2 has the highest NH3 conversion and highest NO, NO2 yield. 5%Cu-5%Mn/Al2O3 is a promising NH3 selective catalytic oxidation catalyst, but still needs further study. SBA-15 is a bad support for Cu-Mn. Al2O3-based catalysts and TiO2-based catalysts were also prepared by incipient wetness impregnation to sure the synergistic effect between transition metal. The results find the activity on Cu-Mn/Al2O3 is better than Cu-Mn/TiO2, but NH3 conversion on Cu-Zr/TiO2 is rather well with high yield of NO. The role of supports and transition metals play in catalyst are discussed by a series of experiments. Key ward: SCO, NH3, transition metal, γ-Al2O3, TiO2, SBA-15
239
Authors: I.I. Parfenova, E.I. Yuryeva, Sergey A. Reshanov, V.P. Rastegaev, A.L. Ivanovskii
515
Authors: Guo Xian Yu, Ji Bing Li, Xiao Long Zhou, Cheng Lie Li, Li Fang Chen, Jin An Wang
Abstract: Transition metal-modified carbon-based adsorbents were prepared by impregnating activated carbon with solutions of copper, cobalt or nickel chloride or nitrate. The mixtures were dried and then calcined under nitrogen stream. The surface metal species were analyzed by XRD technique and the surface oxygen-containing groups were characterized by FTIR. Their adsorption capacities for dibenzothiophene (DBT) were measured by using DBT-containing n-octane solution as model oil. Experimental results show that the metal species on the carbon surface could be controlled by the calcination process under nitrogen atmosphere. Both the transition metal precursors and kinds of metal species on the carbon surface have significant effects on DBT adsorption capacity.
141
Authors: Shao Hua Liao, Fang Yang, Fang Fang Li, Jing Yang, Min Wu
Abstract: Electron paramagnetic resonance (EPR) spectrometer was widely applied to physics, chemistry and biomedicine. This research provided possible electron and valence information of environmental samples interaction through high sensitivity. The EPR signals of transition metals and organic radicals were distinguished well. Three kinds of carbon nanotubes (CNTs) (MW50, MW30 and MWG) had strong EPR signals. Addition of transition metals may be a suitable way to decrease environmentally persistent free radicals (EPFRs). The potential risks of EPFRs in BC and the reactive free electron in transition metals must be addressed to ensure their safe and scientific absorption application.
589
Authors: G. Pasold, N. Achtziger, Joachim Grillenberger, W. Witthuhn
471
Authors: You Xie, Jian Min Zhang
Abstract: The modified analytical embedded atom method is applied to calculate the phonon dispersion of body-centered cubic 3d transition metals Cr and Fe along five symmetry directions [q 0 0], [1 q q], [q q q], [q q 0] and [1/2 1/2 q]. Our results of phonon dispersion curves are in good agreement with the available experimental data. For the two transition metals Cr and Fe, along the same direction, a similar phonon dispersion curve is obtained in spite of the phonon frequency decreases for Cr and Fe due to the atom mass increases. There are no experimental results for comparison along the directions [1 q q] and [1/2 1/2 q], further experimental measurement are needed.
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