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In this process, MgO and Nb 2 O 5 are reacted at 1000 °C to form an intermediate columbite (MgNb 2 O 6) phase, which is then reacted with PbO at 800 °C to form PMN powder. This process still yielded about 5% pyrochlore phase. Swartz et al. [1] later prepared pyrochlore-free PMN powder by using excess MgO.
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used in capacitors as platinum substitute. Columbite, tantalite, columbite-tantalite (Coltan), pyrochlore, and euxenite constitute the major primary sources for niobium and tantalum and are located in Canada, Brazil, Nigeria, Zaire and Russia [5, 6]. These interesting elements are chemically similar and are associated with each other in nature.
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This late magmatic phase is partly characterized by a process that liberates Nb, Ta, Sn, and W, subsequently crystallizing cassiterite, columbite tantalite, and other Nb-enriched phases. As new magma ceased to be emplaced and the laccolith cooled, the volatile-rich vapor phase quenched to form the accessory, late-stage phases.
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Moreover, production of single-phase columbite MgNb 2 O 6 is not straightforward, due to the corundum-like Mg 4 Nb 2 O 9 phase being formed alongside the columbite phase. 7, 11 More recently, limited attempts have been made to rationalise experimental results in terms of the starting materials and processing steps involved, in …
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The martensitic-type phase transition pathways between any two among rutile, columbite-type, and baddeleyite-type phase of TiO 2 are studied with linear interpolation and G-SSNEB methods within first-principles calculations. Our theoretical simulations reveal that the reverse transition from the rutile to the columbite-type phase …
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Commercial and innovative pyrometallurgical (direct reduction), hydrometallurgical (pure leaching) and pyro-hydrometallurgical (NH 4 HF 2 or alkali …
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TaF 6-and NbF 6-remain stable in organic phase and suitable for the solvent extraction method to separate Ta and Nb. Aqueous solutions of TaF 7-and NbOF 6-can also be ... To reduce operating temperature and complications involved during processing of columbite-tantalite ore, hydrometallurgical methods gained popularity to recover both Ta …
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Perovskite structures in the PZ–PNN system with formula (1−x)PbZrO3–xPb(Ni1/3Nb2/3)O3 with x = 0.0–0.5 are synthesized via the columbite precursor technique. The formation of the perovskite phase in … Expand
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The thermoelasticity and stability of diaspore (α-AlOOH, Al1.002Fe0.003OOH) were investigated in this study by in situ synchronous X-ray diffraction (XRD) and Raman spectroscopy methods at high pressure and high temperature conditions. The results indicate that diaspore is stable within the pressure and temperature (P-T) region …
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mineral phase Sergio Sanchez-Segado 1, Tamara Monti2, Juliano Katrib 2, Kingman2, Chris ... Towards sustainable processing of columbite group minerals: elucidating the relation between ...
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The XRD results revealed that LiNaSO 4 was the major phase after heating a 5 h milled mixture of spodumene-Na 2 SO 4 in both metallic and zirconia media at 1000 °C. ... In situ modification of MCM-41 using niobium and tantalum mixed oxide from columbite processing for methylene blue adsorption: Characterization, kinetic, isotherm, ...
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43 ZnNb 2 O 6 was made as the single columbite phase at 11001C/2 h, and was 498% dense at 11501C/2 h, with a mean grain size of 3.5 mm. 43 NiNb 2 O 6 required a higher sintering temperature than ...
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Leaching of columbite-tantalite ore to convert Ta and Nb oxides into intermediate compounds is a twofold process, which includes purification (solvent …
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The pyrometallurgical methods of the recovery of various critical metals have been established. Certain pyrometallurgical approaches for niobium (Nb) and tantalum (Ta) extraction have been studied and investigated by several researchers. For instance, the conventional reduction of Nb mineral or Nb2O5 to Nb metal has been conducted over the …
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The TiO2-II formation by HPT processing leads to photocurrent generation under visible light, while the visible-light photocurrent is enhanced further after the recovery of oxygen vacancies by thermal annealing. ... which limits its activity to the UV light region. In this study, a high-pressure TiO2-II (columbite) phase, which has already been ...
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A study has been carried out on Ta and Nb recovery by a liquid-liquid extraction process using 4-methylacetophenone (4-MAcPh) as the organic phase.
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Furthermore, MgNb2O6 is in wide use as a precursor to synthesize single phase PMN (Pb(Mg1/3Nb2/3)O3) in the "columbite" process, and NiNb2O6 is being increasingly investigated as a catalyst ...
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Among the several processing methods used to fabricate PMN-PT ceramics to form pure pervoskite phase, the Columbite precursor method has been widely used due to higher yield of perovskite phase content . The Columbite precursor method can synthesize raw material corresponding to B-site in perovskite structure in ABO 3, prior to …
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This study presents a fluoride-free, rapid, and energy-efficient process for niobium and tantalum extraction from columbite using microwave-assisted alkali …
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3.2 Phase and structure. The XRD patterns of Zn(Ti 1−x Zr x)Ta 2 O 8 ceramics sintered at their optimum temperature are shown in Fig. 2.Through indexing the patterns, the ceramics adopted the tetragonal cell of the triutile-type structure (JCPDS: #32–0702, P42/m n m (#136)) when x = 0.However, when x = 0.4–0.6, all patterns were …
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The increased demand of metals such as tantalum (Ta) and niobium (Nb) reflect the on-going development in modern science, engineering and technology. The extraction of these two metals from columbite-tantalite ore is based on generic extractive metallurgy. However, the upstream purification of ore and downstream extraction of Ta …
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used in capacitors as platinum substitute. Columbite, tantalite, columbite-tantalite (Coltan), pyrochlore, and euxenite constitute the major primary sources for niobium and tantalum and are located in Canada, Brazil, Nigeria, Zaire and Russia [5, 6]. These interesting elements are chemically similar and are associated with each other in nature.
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In 1990 the production of 1 ton of niobium and tantalum oxides generated an average of 14 tons of solid waste of which 500 kg were radioactive 6.The reduction of solid and …
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for columbite-type phase; and a =4.66˚A, b =4.96˚A, c =4.91˚A, β =99.4 for baddeyite-type phase) [10], which indicate that our calculations are reasonable and reliable. The crystallographic correspondence between ru-tile and columbite-type phase is [100] α [100] rut and (001) α (011) rut [8], and that between columbite-type and ...
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Figure 2: Hydrometallurgical Processing of Niobium and Tantalum. Columbite and tantalite, either naturally occurring or synthetically produced as concentrates from …
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Niobium and tantalum primary minerals are naturally occurring complex oxide ores, majorly of low grade deposits with chemical content of mainly Nb 2 /Ta 2 O 5 and oxides of Fe, Mn, Sn, Ti and other metal oxides. Over the decades, researchers have extensively and consistently investigated the extraction and recovery of Nb and Ta from …
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Methylctylammonium chloride has been recently studied in the extraction of Nb and Ta from a HF-free leachate of columbite processing, and demonstrated potential to uptake almost complete ...
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There is a growing interest in the columbites as microwave dielectric ceramics, due to their lower processing temperatures, less complicated processing due …
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@article{SanchezSegado2017TowardsSP, title={Towards sustainable processing of columbite group minerals: elucidating the relation between dielectric properties and physico-chemical transformations in the mineral phase}, author={Sergio Sanchez-Segado and Tamara Monti and Juliano Katrib and W. Kingman and …
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The microstructure of the specimens manufactured using the columbite method is shown in Fig. 1.The average grain size was 11.5 µm. The XRD patterns of Pb(Ni,Nb)O 3-Pb(Zr,Ti)O 3-Pb(Mg,W)O 3 prepared by the columbite method are shown in Fig. 2.A perovskite phase including a second phase, appeared in the specimen.
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