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Liu J.,Guizhou Normal University | Li Q.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing
Journal of Rare Earths | Year: 2013

The structure and hydriding/dehydriding behaviors of La2Mg 17-10 wt.%Ni composite prepared by mechanical milling were investigated. Compared with the un-milled sample, the as-milled alloys were ready to be activated and the kinetics of hydrogen absorption was relatively fast even at environmental temperature. The composite milled for 10 h absorbed 3.16 wt.% hydrogen within 100 s at 290 K. The kinetic mechanisms of hydriding/dehydriding reactions were analyzed by using a new model. The results showed that hydrogenation processes for all composites were controlled by hydrogen diffusion and the minimum activation energy was 15.3 kJ/mol H 2 for the composite milled for 10 h. Mechanical milling changed the dehydriding reaction rate-controlling step from surface penetration to diffusion and reduced the activation energy from 204.6 to 87.4 kJ/mol H2. The optimum milled duration was 5 h for desorption in our trials. © 2013 The Chinese Society of Rare Earths.


Zou X.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Lu X.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Li C.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Zhou Z.,University of Oxford
Electrochimica Acta | Year: 2010

The titanium silicide intermetallics have been directly prepared from the mixture of titanium oxide (TiO2) and silicon oxide (SiO2) powder by using the solid-oxygen-ion-conducting membrane (SOM) electrolysis process. The electrochemical process was carried out in a molten flux CaCl2 at 950 °C with a potential of 3.5-4.0 V. The effects of the stoichiometry of the initial mixture on the electrolysis characteristics and the final product compositions were investigated. It has been found that the molar ratio of TiO2:SiO2 dominates the composition of final products. A single-phase silicide Ti5Si3 intermetallic was obtained when the TiO2:SiO2 molar ratio is 5:3; the TiSi was identified as the dominant phase with a minor amount of TiSi2 at TiO2:SiO2 molar ratio 1:1; three silicide phases, Ti5Si4, Ti5Si3 and TiSi, were found coexisting in the final product produced from TiO2-SiO2 mixture of molar ratio 5:4; the product of electrolysis consisted of the compound Ti5Si3 and the pure metal Ti as TiO2:SiO2 molar ratio equals to 3:1; and two silicide phases, TiSi and TiSi2, are formed as TiO2:SiO2 molar ratio equals to 1:2. The preliminary experimental results suggest that the electro-deoxidization process is fast and the current efficiency reached 75%. © 2010 Elsevier Ltd.


Zhang Y.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Liu J.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Ding W.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Lu X.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing
Fuel | Year: 2011

Perovskite-type oxygen-permeable membrane reactors of BaCo 0.7Fe0.2Nb0.1O3-δ packed with Ni-based catalyst had high oxygen permeability and could be used for syngas production by partial oxidation of methane in coke oven gas (COG). The BCFNO membrane itself had a poor catalytic activity to partial oxidation of CH4 in COG. After the catalyst was packed on the membrane surface, 92% of methane conversion, 90% of H2 selectivity, 104% of CO selectivity and as high as 15 ml/cm2/min of oxygen permeation flux were obtained at 1148 K. During continuously operating for 550 h at 1148 K, no degradation of performance of the BCFNO membrane reactor was observed under the condition of hydrogen-rich COG. The possible reaction pathways were proposed to be an oxidation-reforming process. The oxidation of H2 in COG with the surface oxygen on the permeation side improves the oxygen flux through the membrane, and H2O reacts with CH4 by reforming reactions to form H2 and CO. © 2010 Elsevier Ltd. All rights reserved.


Li-Hui Z.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Qing-Wei H.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing
Ceramics International | Year: 2011

It is of great importance to control the morphology of α-Al 2O3 plate-like powders since α-Al2O 3 platelets with different shapes are needed in various applications. This paper was focused on how to control the morphology of α-Al 2O3 platelets by molten salt synthesis. Results show that the morphology of α-Al2O3 platelets is affected by the heating temperature, heating time, the molten salts species, the weight ratio of salt to powders, additives and the addition of nano-sized seeds. Especially, it is very effective to control the morphology of α-Al 2O3 platelets by adjusting the addition of additives such as Na3PO4·12H2O and TiOSO4. α-Al2O3 flakes with irregular shape are obtained by the addition of Na3PO4·12H2O, while thick α-Al2O3 particles with hexagonal shape are obtained by the addition of TiOSO4. The combination addition of Na3PO4·12H2O and TiOSO4 makes it possible to obtain thin α-Al2O3 platelets with discal shape. A small amount of nano-sized seeds addition also has a strong effect on the size of α-Al2O3 platelets. However, if the seeds are added too much, the overlapping and abnormal crystal growth of α-Al2O3 platelets occur, and the size distribution becomes nonuniform. The effect mechanism of additives and seeds on the morphology of α-Al2O3 platelets was also discussed in this paper. © 2010 Elsevier Ltd and Techna Group S.r.l.


Wu Y.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Shen T.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Lu X.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing
Chemical Physics Letters | Year: 2013

A structural evolution during solidification and melting processes of nanoparticle Fe9577 was investigated from MD simulations. A perfect lamellar structure, consisting alternately of fcc and hcp layers, was obtained from solidification process. A structural heredity of early embryo is proposed to explain the structural preference of solidification. Defects were found inside the solid core and play the same role as surface premelting on melting. hcp was found more stable than fcc in high temperature. The difference between melting and solidification points can be deduced coming fully from the overcoming of thermodynamic energy barrier, instead of kinetic delay of structural relaxation. © 2013 Elsevier B.V. All rights reserved.


Pan Y.-B.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Wu Y.-F.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Li Q.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing
International Journal of Hydrogen Energy | Year: 2011

Chou model was used to analyze the influences of LaNi5 content, preparation method, temperature and initial hydrogen pressure on the hydriding kinetics of Mg-LaNi5 composites. Higher LaNi5 content could improve hydriding kinetics of Mg but not change hydrogen diffusion as the rate-controlling step, which was validated by characteristic reaction time tc. The rate-controlling step was hydrogen diffusion in the hydriding reaction of Mg-30 wt.% LaNi5 prepared by microwave sintering (MS) and hydriding combustion synthesis (HCS), and surface penetration was the rate-controlling step of sample prepared by mechanical milling (MM). Rising temperature and initial hydrogen pressure could accelerate the absorption rate. The rate-controlling step of Mg-30 wt.% LaNi5 remained hydrogen diffusion at temperatures ranging from 302 to 573 K, while that of Mg-50 wt.% LaNi5 changed from surface penetration to hydrogen diffusion with increasing initial hydrogen pressure ranging from 0.2 to 1.5 MPa. Apparent activation energies of absorption for Mg-30 wt.% LaNi5 prepared by MS and MM were respectively 25.2 and 28.0 kJ/mol H2 calculated by Chou model. Kinetic curves fitted and predicted by Chou model using temperature and hydrogen pressure were well exhibited. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Bao Z.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Ding W.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Li Q.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing
International Journal of Hydrogen Energy | Year: 2012

Catalysts with different Fe/Cu molar ratios were prepared by co-precipitation method and evaluated under hydrogen-rich atmosphere (H 2 = 72.2 vol%). The effect of Fe/Cu ratio on the activity of Fe-Al-Cu catalysts for water gas shift reaction (WGSR) was investigated. The samples were characterized by X-ray diffraction (XRD), Temperature programmed reduction (TPR) and Brunauer-Emmett-Teller (BET) techniques. The results suggested that the optimal Fe/Cu ratio of Fe-Al-Cu catalyst was 1:1 and its highest CO conversion efficiency is 97.8% at 300 °C, excessive Cu resulted in poor catalytic activity. Fe-Al-Cu catalysts possessed a good activity at 250-550 °C and their CO conversions reached 87.3% and 84.6% at 250 °C and 550 °C, respectively, which is ascribed to the fact that copper not only acts as an active role for water gas shift reaction at 250 °C but also conducts as an electronic promoter in solid solution at higher temperature. Furthermore, magnetite had catalytic effect at higher temperature. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Shen T.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Wu Y.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Lu X.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing
Journal of Molecular Modeling | Year: 2013

In the current study, we provide a structural evolution process of isolated Fe nanoparticle with 5601 atoms during solidification. Five-fold twinned structure has been found in the final configuration of the nanoparticle. Furthermore, detailed formation process has been visualized and carefully discussed. During the formation of five-fold twinned structure, two main stages have been identified, including i) liquid-solid phase transition at solidification point, in which the main part of the five-fold twinned structure formed, and ii) structural relaxation, in which twinning boundaries and five-fold axis were transformed to eliminate the dislocation between two adjacent five-fold twins. © 2012 Springer-Verlag.


Xuan W.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Ren Z.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Li C.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing
Journal of Alloys and Compounds | Year: 2015

The effect of a high magnetic field on the dendrite morphology of superalloy DZ417G during directional solidification at a low solidification velocity has been investigated experimentally. It was found that the magnetic field induces columnar to equiaxed transition (CET) and makes the primary dendrite arm spacing decrease. In addition, the magnetic field causes deformation of the solid-liquid interface shape and the macrosegregation in the mushy zone. Based on these results, it was found that both of the thermoelectric magnetic convection (TEMC) and the thermoelectric magnetic force (TEMF) cause CET, the change of solid-liquid interface shape and the formation of macrosegregation. This is in good agreement with predicted values of the TEMC and TEMF, respectively. The primary dendrite arm spacing was changed by the interdendritic TEMC in the magnetic field. © 2014 Elsevier B.V. All rights reserved.


Yang Z.P.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Li Q.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Zhao X.J.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing
Journal of Alloys and Compounds | Year: 2013

A novel magnetic annealing assisted route was applied to improve the electrochemical properties of La0.67Mg0.33Ni 3.0. The effects of magnetic annealing parameters, including annealing temperature, annealing time and magnetic induction density, on electrochemical performance of La0.67Mg0.33Ni 3.0 hydride electrode alloys was investigated using L9 orthogonal array based on Taguchi method. Based on the analysis of signal to noise ratio and the variance, the optimum magnetic annealing parameters for La 0.67Mg0.33Ni3.0 hydride electrode alloy are determined to be 1 T, 1123 K, and 2 h. A confirmation test was conducted subsequently, and the results were found to be within the confidence interval. The discharge capacity, the cyclic stability and the electrochemical kinetics of the alloy electrode were noticeably improved by magnetic annealing. © 2012 Elsevier B.V. All rights reserved.

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