Vìsnik Odesʹkogo Nacìonalʹnogo Unìversitetu: Hìmìâ (May 2017)

STUDY OF DISPERSE SYSTEMS OF CeO2 AND CeF3 IN STIFFENED MELTS NaNO3-KNO3 BY METHODS OF SPECTROSCOPY OF DIFFUSE REFLECTANCE AND BY THE CHEMICAL ANALYSIS

  • I. V. Stoyanova,
  • N. А. Chivireva,
  • V. P. Antonovich,
  • G. V. Nechyporenko,
  • L. F. Koshkina,
  • V. F. Zinchenko

DOI
https://doi.org/10.18524/2304-0947.2017.2(62).102208
Journal volume & issue
Vol. 22, no. 2(62)
pp. 22 – 31

Abstract

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Processes of dispersion and solubility of CeO2 and CeF3 in the melts of systems NaNO3-KNO3 which are widely used as medium for synthesis of various oxide materials are investigated. The basis of the mechanism of the specified processes is made by the acid-basic and oxidationreduction reactions between initial substances and saline melt. For identification and definition of oxidation degree of Cerium in interaction products are applied spectroscopy of diffuse reflectance in an UV range of a spectrum and the substantial chemical analysis with use as a reagent of a solution of phosphoric acid. For reduction of influence of own absorption of ions NO3– as the sample of comparison it is used stiffened melt of NaNO3-KNO3. Definition of content of Ce(III) is carried out basing on decrease of intensity of coloring of KMnO4. Content of Ce(IV) is established photometrically on intensity of absorption of a phosphate complex (at high content of Ce(IV)) and on decrease of coloring of methanyl yellow (at low content). The data of spectroscopy of diffuse reflectance specifies in prevalence of Ce(IV) with small admixture of Ce(III) in case of system CeO2-(NaNO3-KNO3) and Ce(III) with admixture of Ce(IV) in case of system CeF3-(NaNO3-KNO3). Because of influence of H3PO4 on oxidation degree of cerium in last system, definition of Ce(III) and Ce(IV) by chemical analysis was not carried out. As for system with CeO2, contents of Ce(IV) by method of the chemical analysis are established at level 8-16%масс., and they are higher at system heat treatment on air in comparison with heat treatment in an inert (He) medium. Some inconsistency in the results received by a method of spectroscopy of diffuse reflectance and the chemical analysis, which reason while up to the end is not established, is observed. The role of the superficial phenomena on border solid state – saline melt - gas in processes of dispersion of CeO2 and CeF3 is shown.

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