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: Deleg Sangaa, Baatartsogt Khongorzul, Enkhnaran Uyanga, Narmandakh Jargalan, Namsrai Tsogbadrakh, Hideyuki Hirazawa
Abstract: In recent time, interest to ferrite magnetic nanomaterials has considerably grown mainly due to their much promising medical and biological applications. The spinel ferrite powder samples having high heat generation ability in AC magnetic field was studied for application to hyperthermia treatment of cancer tumor. These properties of ferrites are strongly depending on their chemical composition, ion distribution, spin orientation and method of preparation in general and crystal structure in particular nature of the material. In this study, several samples of ferrite magnetic structures were investigated by neutron diffraction. The explanation of the mechanism to occurs the heat generation ability in the magnetic materials and the electronic and magnetic states of ferrite-spinel – type structures were theoretically defined by the first-principles calculations within the framework of DFT.
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: Roberto de Oliveira Magnago, Carlos Eduardo de Lima Abreu, Ronaldo Reis Silva, Manuel Fellipe Rodrigues Pais Alves, Caio Marcelo Felbinger Azevedo Cossu, Claudinei dos Santos
Abstract: In this work three dental ceramics were characterized according to ISO 6872: yttria-stabilized zirconia (ZrO2-Y2O3), lithium disilicate (Li2Si2O5) and the spinel-zirconia composite (MgAl2O4-ZrO2). The zirconia ceramic and the zirconia-spinel composite were sintered at 1600°C-2h, while the lithium disilicate was thermally treated at 820°C-20min. These materials were characterized by relative density, X-ray diffraction, scanning electron microscopy, hardness, fracture toughness, chemical solubility and cytotoxicity. The XRD results showed for the stabilized zirconia only the tetragonal phase of ZrO2, and to the composite only the phase MgAl2O4, Li2Si2O5 was the only phase to lithium disilicate. Relative density results showed that the zirconia and the lithium disilicate showed high densification (> 99.5%) and the composite had a relative density of 75% (10% composite doped with ZrO2) and 90% (50% doped with ZrO2). Hardness and toughness showed 450HV and 3.2MPa.m1/2 to ZrO2-MgAl2O4 composites, 525HV and 1.8MPam1/2 to lithium disilicate and 1280HV and 8.0MPa.m1/2 to zirconia. The materials evaluated showed chemical solubility <30μg/cm2 and the results of cytotoxicity tests indicated cell viability of the samples near 100% for all the materials, showing good chemical stability and potential for dental applications.
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