LI Ximing CHEN Jiayong Institute of Chemical Metallurgy
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Academia Sinica
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Beijing
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ChinaR.KAMMEL Institut Für Metallurgie
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Technische Universitt Berlin
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Germany Research Assistant
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Institute of Chemical Metallurgy
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Academia Sinica
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Beijing 100080
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China
金属学报(英文版)
The influence of mechanical activation on the leaching behaviour of scheelite was studied by means of fine grinding in an attritor and subsequently HCl leaching in presence of PO_4~(3-). Results showed that after fine grinding in the attritor,the reaction rate of scheelite with HCl-Na_3PO_4 solution was remarkably increased,the extraction of W increased from about 8 to 99%.The IR spectra and X-ray diffraction analysis indicated that in addition to an enlargement of surface area the fine grinding action had made also changes of fine struc- ture and reactivity of solid surface,hence the leaching process of scheelite can be carried out under mild leaching conditions.
关键词:
scheelite
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null
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null
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null
K. MUller
金属学报(英文版)
Hot working steels have been used as die materials for hot extrusion of aluminium.Due to tribological interaction at elevated temperature between the die bearing and thesurface of extruded aluminium profiles, not only the surface quality of the extrudedproduct, but also the lifetime of the dies decreases. Deposition of TiBN hard films onthe die bearing could improve the die performance. Treatment should be done in aduplex process process combining a plasma nitriding pretreatment (PN) and a plasmaassisted chemical vapour deposition (PACVD) of TiBN. In this study the influence ofthe process conditions on the properties of the duplex coatings was investigated. Therelationship between structure and mechanical property was researched. For testingthese TiBN hardfilms under elevated temperature conditions and for comparison withother possible coatings special extrusion dies with different coated bearings were used.The extrusion trials were performed on the 8MN-extrusion press at the research anddevelopment center for extrusion, Technical University of Berlin.
关键词:
hard film
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null
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null
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Physica B-Condensed Matter
Ab initio calculations of the electronic structure were performed for the silver palladium oxide, Ag2PdO2 by the full potential mixed linearized augmented plane wave and augmented plane wave plus local orbitals method (mixed LAPW/APW + lo) within the density functional theory and using the generalized gradient approximation (GGA96, Phys. Rev. Lett. 77 (1996) 3865) for the exchange-correlation potential. The lattice parameters were calculated from the ground-state total energy versus volume curve, and are in good agreement with the available experimental results. Our calculations of band structure predicted that the compound Ag2PdO2 has indirect band gap, and the Pd 4d states strongly hybridize with the O 2p states all over the valence bands and conduction bands. The valence bands are composed mainly of Ag, Pd 4d states and 0 2p states, while the conduction bands consist mainly of the Pd 4d states and 0 2p states. In addition, focusing on the calculation precision of the band gap, three different kinds of basis sets ("pure" LAPW, APW + lo and mixed LAPW/APW + lo) and three versions of exchange-correlation potential (GGA96, Phys. Rev. Lett. 77 (1996) 3865; LIDA, Phys. Rev. B 45 (1992) 13244; GGA91, Phys. Rev. B 46 (1992) 6671; Ziesche and Eschrig (Eds.), Electronic Structure of Solids '91, Akademie Verlag, Berlin, 199 1, p. 11) were chosen to calculate the band structure, the results show that the three basis sets lead to almost the same band gap values. (C) 2003 Elsevier B.V. All rights reserved.
关键词:
silver palladium oxide;ab initio calculation;mixed LAPW/APW plus lo;method;band structure;band gap;generalized gradient approximation;plane-wave method;crystal-structure;band-structure;phase-diagram;system;copper;energy;solids
