Papers by Keyword: Spinel

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Authors: Shi Ling Guo, Zi Yang Yu, Yi Liang Chen, Xin Xing Chen
Abstract: Zeolite NaKL was in-situ crystallized under static condition with kaolin microspheres calcined at 980 °C as silicon and aluminium sources. Influences of hydrothermal synthesis conditions such as the mole ratio of n(K2O)/n(Na2O), n(OH-)/n(SiO2) and crystallizaion time on crystallization of zeolite L were studied in detail. The crystal phase and morphology of the as-prepared zeolite samples were characterized by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The results showed that the as-synthesized samples owned characteristic peaks of zeolite L with high crystallinity and were covered uniformly by regular crystal of zeolite L on its kaolin microsphere surface , which maintained complete ball shape as before. The optimum conditions to get zeolite NaKL with high crystallinity by this method were found to be the mole ratio of n(K2O)/n(Na2O) =7:3 and n(OH-)/n(SiO2) =0.50 in the reaction mixture, an aging of the reactants at room temperature for 30 h and crystallization temperature 120 °C for 24 h.
Authors: Gui Yang Liu, Jun Ming Guo, Li Li Zhang, Bao Sen Wang, Ying He
Abstract: In this paper, spinel LiMn2O4 was prepared by the solution combustion synthesis using acetate or nitrate salts as raw materials and acetic acid as fuel. The composition and phase structure are determined by X-ray diffraction (XRD) and the electrochemical performance is tested by using a coin type half-battery versus Li+/Li. The results indicate that the products prepared from acetate salts have higher purities, higher crystallinities and better electrochemical performances than these of the products prepared from nitrate salts. And for the products prepared from acetate salts, the performance becomes worse with increasing acetic acid ratios. Contrarily, for the products prepared from nitrate salts, the performance becomes little better with increasing acetic acid ratios.
Authors: Gui Yang Liu, Jun Ming Guo, Li Li Zhang, Bao Sen Wang, Ying He
Abstract: To improve the cyclability of spinel LiMn2O4, Al3+ doped LiAlxMn2−xO4 (x=0, 0.01, 0.05 and 0.10) materials are prepared using a solution combustion synthesis method using acetic salts as raw materials and acetic acid as fuel. Their phase structures are characterized by X-ray diffraction (XRD). Electrochemical performances of the materials are investigated by galvanostatic charge/discharge methods. XRD results reveal that the purity of the samples increases with increasing Al3+ content. Electrochemical experiments demonstrate that the charge/discharge cyclability of the LiAlxMn2-xO4 increases with increasing Al3+ content. Compared with the pristine LiMn2O4, the Al-doped LiAlxMn1−xO4 show the obviously improved cyclability, especially for the sample LiAl0.1Mn1.9O4.
Authors: Xuemin Pan, Heino Sieber, Stephan Senz, D. Hesse, J. Heydenreich
Authors: Christos G. Aneziris, Steffen Dudczig
Abstract: In terms of this work formulations of carbon bonded castables based on new binder approaches and nanoadditions will be demonstrated. The new binder system allows the manufacturing of water based magnesia carbon castables with the same properties and chemistry of pressed magnesia carbon bricks. This binder can be also applied in oxide castables offering them high refractoriness and workability during processing. According to the workability nano-additions improve significantly the spreading diameter of carbon castables and as a result their flowability.
Authors: Gilberto Artioli, A. Pavese, Didier Lévy, U. Russo, A. Hoser
Authors: T.-L. Tsai, Joerg Töpfer, S. Aggarwal, E. Chen, Rüdiger Dieckmann
Authors: Łukasz Zych, Anna Wajler, Radosław Lach
Abstract: Magnesium-aluminium spinel (MgAl2O4) in the form of transparent ceramics is applied in shields of infrared detectors or emitters, high-temperature widows and elements of military aircrafts and vehicles. Apart from high transparency for specific wave lengths, such materials should have good mechanical properties, especially hardness. It is the reason for production of the fine-grained materials. It seems that they can be produced from submicron powders consolidated by one of colloidal techniques. The work presents preliminary results of investigations on colloidal consolidation of two fine spinel powders with different particle size by pressure filtration and slip casting. The aim of the studies was consolidation of the fine powders leading to green samples with narrow pore size distribution. The samples were then sintered in isothermal conditions. Microstructure, Vickers hardness and transmission in infrared spectrum of the dense materials were examined.
Authors: P.M. Pimentel, M.F. Ginani, Antonio Eduardo Martinelli, D.M.A. Melo, A.M. Garrido Pedrosa, M.A.F. Melo
Abstract: Transition-metal spinels are efficient catalysts in a number of heterogeneous processes, such as CO oxidation, catalytic combustion of hydrocarbons and oxychlorination of methane. The properties of catalytic materials are highly dependent on the synthesis route. Spinels are often produced at high temperatures by the calcination of precursors such as powder mixtures, slurries or resins. Combustion synthesis is a cost-efficient method used to produce homogeneous and fine particles with high reproducibility. Cu0.8Ni0.2Cr2O4 spinel was obtained by the combustion of metallic nitrates using urea as fuel. The resulting powders were calcinated at different temperatures and characterized by thermogravimetric and particle size analyses, X ray diffraction, and scanning electron microscopy. The effect of urea on the control of the process and particle morphology was investigated. The results revealed the formation of porous powders with increasing crystallinity as the calcination temperature increased. Crystallization of spinel started at 700 oC.
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