The Experts below are selected from a list of 36255 Experts worldwide ranked by ideXlab platform
Hongming Zhou - One of the best experts on this subject based on the ideXlab platform.
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a kinetic study of the leaching of a low grade Niobium tantalum ore by concentrated koh solution
2005Co-Authors: Hongming Zhou, Shili Zheng, Yi ZhangAbstract:A kinetic study of the leaching of a low-grade Niobium-tantalum ore by concentrated KOH solution under atmospheric pressure has been investigated. The effects of reaction temperature, KOH concentration, agitation speed, particle size and alkalito-ore mass ratio on the dissolution rate of Niobium were examined. It was found that the dissolution rate of Niobium is significantly influenced by the temperature, particle size and concentration of KOH solution. The experimental data were well interpreted with a shrinking core model under diffusion control through the product layer. By using the Arrhenius expression, the apparent activation energy for the dissolution of Niobium was evaluated. Finally, on the basis of the shrinking core model, the following rate equation was established:
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leaching of a low grade Niobium tantalum ore by highly concentrated caustic potash solution
2005Co-Authors: Hongming Zhou, Shili Zheng, Yi ZhangAbstract:The recovery of Niobium and tantalum from a low-grade Niobium-tantalum ore by using highly concentrated caustic potash as an alternative to hydrofluoric acid has been investigated. Experiments on the leaching behavior of Niobium and tantalum, as well as other associated impurities, such as titanium, iron, manganese, silicon, and aluminum were carried out. The effect of various parameters including leaching temperature, KOH concentration, leaching time, alkali-to-ore mass ratio and particle size on the agitation leaching was examined. When finely ground ore (-61 mu m) reacted with KOH solution (84 wt.%) in a mass ratio of alkali-to-ore of 7:1 at 300 degrees C for 60 min, almost complete extraction of both Niobium and tantalum was achieved while the extraction of titanium was 85% and the extraction of other impurities in the ore was less than 35%. (c) 2005 Elsevier B.V. All rights reserved.
Yi Zhang - One of the best experts on this subject based on the ideXlab platform.
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a kinetic study of the leaching of a low grade Niobium tantalum ore by concentrated koh solution
2005Co-Authors: Hongming Zhou, Shili Zheng, Yi ZhangAbstract:A kinetic study of the leaching of a low-grade Niobium-tantalum ore by concentrated KOH solution under atmospheric pressure has been investigated. The effects of reaction temperature, KOH concentration, agitation speed, particle size and alkalito-ore mass ratio on the dissolution rate of Niobium were examined. It was found that the dissolution rate of Niobium is significantly influenced by the temperature, particle size and concentration of KOH solution. The experimental data were well interpreted with a shrinking core model under diffusion control through the product layer. By using the Arrhenius expression, the apparent activation energy for the dissolution of Niobium was evaluated. Finally, on the basis of the shrinking core model, the following rate equation was established:
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leaching of a low grade Niobium tantalum ore by highly concentrated caustic potash solution
2005Co-Authors: Hongming Zhou, Shili Zheng, Yi ZhangAbstract:The recovery of Niobium and tantalum from a low-grade Niobium-tantalum ore by using highly concentrated caustic potash as an alternative to hydrofluoric acid has been investigated. Experiments on the leaching behavior of Niobium and tantalum, as well as other associated impurities, such as titanium, iron, manganese, silicon, and aluminum were carried out. The effect of various parameters including leaching temperature, KOH concentration, leaching time, alkali-to-ore mass ratio and particle size on the agitation leaching was examined. When finely ground ore (-61 mu m) reacted with KOH solution (84 wt.%) in a mass ratio of alkali-to-ore of 7:1 at 300 degrees C for 60 min, almost complete extraction of both Niobium and tantalum was achieved while the extraction of titanium was 85% and the extraction of other impurities in the ore was less than 35%. (c) 2005 Elsevier B.V. All rights reserved.
Ivi Smid - One of the best experts on this subject based on the ideXlab platform.
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development of Niobium powder injection molding part ii debinding and sintering
2007Co-Authors: Gaurav Aggarwal, Seong Jin Park, Ivi Smid, Randall M GermanAbstract:Abstract This article is a continuation of feedstock preparation and powder injection molding (PIM) of pure Niobium. Part II discusses debinding and sintering of injection molded Niobium. PIM of pure Niobium powder was analyzed for efficiency of the process. After solvent and thermal debinding, sintering of injection molded material was conducted up to 2000 °C in vacuum as well as inert-gas low-oxygen partial pressure atmosphere. This paper investigates the effect of sintering time, temperature and atmosphere on the processing of pure Niobium. Under all sintering conditions the oxygen content is reduced from ∼19,000 in the as-received powder to as low as 300 ppm, at e.g. 2000 °C for 2 h in a low-vacuum atmosphere. The carbon content increased from the as-received 70 to 200–300 ppm, depending on the sintering conditions. However, this amount of carbon is not considered detrimental for structural application. Master decomposition and sintering curves are introduced for pure Niobium to study the optimum debinding and sintering conditions. Further, sintering parameters (atmosphere, peak temperature and hold time) are optimized for achieving maximum densities with minimal impurities.
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development of Niobium powder injection molding part i feedstock and injection molding
2006Co-Authors: Gaurav Aggarwal, Seong Jin Park, Ivi SmidAbstract:Abstract It has been only during the past four decades that Niobium has been consumed on an industrial scale. Pure Niobium and Niobium base alloys constitute less than 2% of the global Niobium market. Niobium being a refractory metal doesn’t have a powder cost penalty as in ferrous materials, since refractory parts are formed from powders. This article details a systematical approach to develop feedstock for powder injection molding of Niobium. It has been proven that powder injection molding is a viable forming technique for pure Niobium. Further, rheological properties have been combined to determine optimal and critical solids loading. Based on simulation, injection temperatures and pressures were determined for optimal filling time. For the first time, a processing window has been identified based on the rheological behavior and simulation of Niobium feedstock.
Gaurav Aggarwal - One of the best experts on this subject based on the ideXlab platform.
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development of Niobium powder injection molding part ii debinding and sintering
2007Co-Authors: Gaurav Aggarwal, Seong Jin Park, Ivi Smid, Randall M GermanAbstract:Abstract This article is a continuation of feedstock preparation and powder injection molding (PIM) of pure Niobium. Part II discusses debinding and sintering of injection molded Niobium. PIM of pure Niobium powder was analyzed for efficiency of the process. After solvent and thermal debinding, sintering of injection molded material was conducted up to 2000 °C in vacuum as well as inert-gas low-oxygen partial pressure atmosphere. This paper investigates the effect of sintering time, temperature and atmosphere on the processing of pure Niobium. Under all sintering conditions the oxygen content is reduced from ∼19,000 in the as-received powder to as low as 300 ppm, at e.g. 2000 °C for 2 h in a low-vacuum atmosphere. The carbon content increased from the as-received 70 to 200–300 ppm, depending on the sintering conditions. However, this amount of carbon is not considered detrimental for structural application. Master decomposition and sintering curves are introduced for pure Niobium to study the optimum debinding and sintering conditions. Further, sintering parameters (atmosphere, peak temperature and hold time) are optimized for achieving maximum densities with minimal impurities.
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development of Niobium powder injection molding part i feedstock and injection molding
2006Co-Authors: Gaurav Aggarwal, Seong Jin Park, Ivi SmidAbstract:Abstract It has been only during the past four decades that Niobium has been consumed on an industrial scale. Pure Niobium and Niobium base alloys constitute less than 2% of the global Niobium market. Niobium being a refractory metal doesn’t have a powder cost penalty as in ferrous materials, since refractory parts are formed from powders. This article details a systematical approach to develop feedstock for powder injection molding of Niobium. It has been proven that powder injection molding is a viable forming technique for pure Niobium. Further, rheological properties have been combined to determine optimal and critical solids loading. Based on simulation, injection temperatures and pressures were determined for optimal filling time. For the first time, a processing window has been identified based on the rheological behavior and simulation of Niobium feedstock.
Chu Yong Cheng - One of the best experts on this subject based on the ideXlab platform.
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solvent extraction technology for the separation and purification of Niobium and tantalum a review
2011Co-Authors: Zhaowu Zhu, Chu Yong ChengAbstract:Abstract In this paper, solvent extraction technology for the separation and purification of Niobium and tantalum has been extensively reviewed. Although a variety of solvents have been investigated for Niobium and tantalum solvent extraction, only four have been commercially used in the production of Niobium and tantalum from their raw materials. These are methyl iso-butyl ketone (MIBK), tri-butyl phosphate (TBP), cyclohexanone (CHN) and 2-Octanol (2-OCL). In industrial operations, the separation and purification of Niobium and tantalum by solvent extraction are all performed in the presence of fluoride to enable the formation of fluoro-complexes which can combine with the organic molecules. MIBK is the most commonly used extractant due to its low density, low viscosity and other properties, which makes it possible to obtain high purity products. Tertiary amines such as Alamine® 336 (mainly tri-octylamine) are promising extractants for purifying Niobium and tantalum from very low HF concentrations or in oxalic acid solutions where HF is not present. Further investigation is required to indentify aqueous complex systems and solvent extraction systems to enable the purification of Niobium and tantalum without the use of fluorides.
