Columbite
Mostrando 1-6 de 6 artigos, teses e dissertações.
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1. Uncommon Nb-tantalate from the Cachoeira mine, Araçuaí pegmatite district (Minas Gerais)
Abstract Important spodumene-rich pegmatites have been mined by CBL (Companhia Brasileira de Lítio, Brazilian Lithium Co.) at the Cachoeira mine (northeastern Minas Gerais state) since the 1990's. In this deposit, black platy crystals resembling columbitetantalite are also found; they were analyzed by electronic microprobe as part of the first author's mast
Rem: Rev. Esc. Minas. Publicado em: 2015-12
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2. Metais raros associados ao granito desemborque : estudo mineralogical and chemical study using MEV-EDS / Rare metals associated to desemborque granite : mineralogical and chemical study using MEV-EDS
The Desemborque Granite, a body almost of circular shape, placed in the southernmost part of São Paulo State, has an area of ca. 50 km2. and it is represented by a sienogranite biotite. Its peraluminous features with significant contents of K2O and Na2O, together with low CaO contents, high Fe/Mg ratios, elevated values of SiO2 and trace elements as Zr, Nb
Publicado em: 2007
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3. Obtenção de pós de tântalo metálico a partir da redução aluminotérmica com ignição a plasma
Metallic tantalum has a high commercial value due to intrinsic properties like excellent ductility, corrosion resistance, high melt and boiling points and good electrical and thermal conductivities. Nowadays, it is mostly used in the manufacture of capacitors, due to excellent dielectric properties of its oxides. In the nature, tantalum occurs in the form of
Publicado em: 2007
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4. Estratégias de síntese para obtenção de niobato e perovskitas a base de chumbo.
This work reports the study on the synthesis of the solid solution 65Pb(Mg1 3 Nb2 3 )O335PbT iO3 (65PMN35PT) using combination of dierent synthesis methods, such as columbite, partial oxalate and oxidant peroxo methods. Nanosized and highly reactive magnesium niobate (MgNb2O6 or MN) powders were successfully synthesized by a new wet-chemical method by means
Publicado em: 2006
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5. Effect of the Addition of Potassium or Lithium on the Columbite Precursor Microstructure
Pechini method has been used to synthesize MN powders with stoichiometric control. By this method, K and Li-doped MN in the range from 0.1 to 5.0 mol% of dopants have been obtained at relatively lower temperatures than it is possible with the conventional mixture of oxides. The results from BET analysis indicated that the doped powders have lower surface are
Materials Research. Publicado em: 2002-10
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6. Crystal chemistry and structure of the orthorhombic (Fe,Mn)(Ta,Nb)2O6 family of compounds
In this paper we review the crystal chemistry and structure data from the literature and our results reported in the last decade for natural and synthetic samples of the tantalite-columbite series. Order-disorder transitions and oxidation reactions on the ixiolite-columbite-wodginite system are reported for one Brazilian sample. It is shown that reports on t
Brazilian Journal of Physics. Publicado em: 2001-12