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59. The dissolution behavior of Nb2O5, Ta2O5 and their mixture in highly concentrated KOH solution

Author

Zhou, Hong-ming, Yi, Dan-qing, Zhang, Yi, and Zheng, Shi-li

Subjects
*LEACHING, *NIOBIUM oxide, *TANTALUM oxide, *CHEMICAL engineering
Abstract

Abstract: The dissolution behavior of Nb2O5, Ta2O5 and their mixture in highly concentrated KOH solution (>50% wt.) has been investigated. A 43 orthogonal design was used to study the effects of four leaching parameters, reaction temperature, KOH/Nb2O5, mole ratio, agitation speed and reaction time on the dissolution yield of Nb(V). It was found that the effect of reaction temperature on the dissolution yield of Nb(V) was much greater than that of the other three factors. The results of factorial experiments showed that a high KOH concentration was benefit to the formation of soluble potassium hexaniobate, but high temperature was benefit to the formation of insoluble potassium niobate, and almost all Ta2O5 was converted into insoluble potassium tantalate. The insoluble potassium niobate and potassium tantalate were analyzed by XRD, which were proved to be KNbO3 and KTaO3, respectively. The dissolution behavior of the mixture of Nb2O5 and Ta2O5 was similar with that of Nb2O5. [Copyright &y& Elsevier]

Published
2005
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60. Formation of Fe86Zr5.5Nb5.5B3 Nanocrystalline Bulk Alloy under High Pressure

Author

Lu, Bin, Yi, Dan Qing, Yan, Biao, Yin, Jun Lin, Liu, Yan, Liu, Hui Qun, Wu, Biao Li, and Chen, Xiao Li

Abstract

Mechanical alloying(MA) technique and single-roller melt spinning technique were used to prepare Fe86Zr5.5Nb5.5B3 nanocrystalline and amorphous powders, bulk alloys were prepared by cryogenically high-pressure quick sintering. The results showed that: (1) after MA process for 15 hours, the grain size of α-Fe phase was ≤10nm; (2) melt spinning powders were fragmented by ball milling, but remained amorphous state. The crystallization temperature of this amorphous powder was about 500℃. Apparent activation energy of the amorphous crystallization was E=294.1KJ/mol; (3) under the quick sintering conditions of P=5.5GPa/t=3min/Pw≥1050W, single phaseα-Fe nanocrystalline(8～15nm) bulk alloys with relative density≥98.7% can be obtained.

Published
2005
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