View More View Less
  • 1 Materials Processing Division, Bhabha Atomic Research Centre, Mumbai 400085, India
  • | 2 Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076, India
Restricted access

Abstract

The kinetics of thermal decomposition of ammonium yttrium fluoride intermediates, (NH4)3Y2F9 and NH4Y2F7 were studied by a non-isothermal thermogravimetric (TG) technique at different heating rates. Kinetic parameters were determined from the TG curves by using two model-free methods, i.e. Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS). The activation energy (E) for the decomposition of (NH4)3Y2F9 was dependent on the fraction converted, α; its value was 152 kJ/mol (for α = 0.1–0.3) and 232 kJ/mol (for α = 0.4–0.8) from both models; and the pre-exponential factor (ln(A)) was 43 (for α = 0.1–0.3) and 59 (for α = 0.4–0.8). For the decomposition of NH4Y2F7, the activation energy (E) was independent of the fraction converted, α, and its value was 123 kJ/mol; the pre-exponential factor (ln(A)) was 31. The decomposition of (NH4)3Y2F9 proceeds by one-dimensional diffusion (for α = 0.1–0.3), followed by two-dimensional diffusion (for α = 0.4–0.8). The decomposition of NH4Y2F7 occurs by random nucleation and growth.

  • 1.

    Spedding, FH, Daane, AH. 1961 The rare earths Wiley New York.

  • 2.

    Gupta, CK, Krishnamurthy, N. 2004 Extractive metallurgy of rare earths CRC Press .

  • 3.

    Batsanova, LR. 1971. Rare-earth fluorides. Russ Chem Rev. 40 6 465484 .

  • 4.

    Rothenberg, G, Royz, M, Arrad, O, Sasson, Y. 1999. In situ generation and synthetic applications of anhydrous hydrogen fluoride in a solid-liquid biphasic system. J Chem Soc Perkin Trans. 1:14911494 .

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5.

    Rakov, EG, Mel'nichenko, EI. 1984. The properties and reactions of ammonium fluorides. Russ Chem Rev. 53 9 851869 .

  • 6.

    Patwe, SJ, Wani, BN, Rao, URK, Venkateswarlu, KS. 1989. Synthesis and thermal study of tris (ammonium) hexafluoro metallates (III) of some rare earths. Canad J Chem. 67:18151818 .

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7.

    Kalinnikov, VT, Makarov, DV, Tikhomirova, EL, Elizarova, IR, Kuznetsov, VYa. 2002. Hydrofluoride synthesis of fluorides of some rare-earth elements. Russ J Inorg Chem. 75 11 17601764.

    • Search Google Scholar
    • Export Citation
  • 8.

    Mukherjee A , Sahoo DK, Kumar S, Awasthi A (2008) DTA studies on preparation of YF3 by ammonium bifluoride route. In: Proceedings of 16th national symposium of Indian thermal analysis, pp 151153.

    • Search Google Scholar
    • Export Citation
  • 9.

    Flynn, JH, Wall, LA. 1966. A quick, direct method for the determination of activation energy from thermogravimetric data. Polym Lett. 4:323328 .

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10.

    Ozawa, T. 1965. A new method of determining thermogravimetric data. Bull Chem Soc Jpn. 38:18811886 .

  • 11.

    Kissinger, HE. 1957. Reaction kinetics in differential thermal analysis. Anal Chem. 29:17021706 .

  • 12.

    Akahira, T, Sunose, T. 1971. Res. Rep Chiba Inst Technol. 16:2231.

  • 13.

    Ortega, A. 1996. Some successes and failures of the methods based on several experiments. Thermochim Acta. 284:379387 .

  • 14.

    Doyle, CD. 1961. Kinetic analysis of thermogravimetric data. J Appl Polym Sci. 5:285292 .

  • 15.

    Reading, M, Dollimore, D, Whitehead, R. 1991. The measurement of meaningful kinetic parameters for solid state decomposition reactions. J Therm Anal. 37:21652188 .

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16.

    Boonchom, B, Danvirutai, C, Thongkam, M. 2010. Non-isothermal decomposition kinetics of synthetic serrabrancaite (MnPO4·H2O) precursor in N2 atmosphere. J Therm Anal Cal. 99 1 357362 .

    • Crossref
    • Search Google Scholar
    • Export Citation