Partial
thermal reduction of ammonium paratungstate tetrahydrate |
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| Authors: | I M Szilágyi J Madarász F Hange G Pokol |
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| Institution: | (1) Institute of General and Analytical Chemistry, Budapest University of Technology and Economics, Budapest, Hungary, 1111, Szt. Gellért tér 4;(2) GE Hungary ZRt., GE Consumer & Industrial - Lighting, Budapest, Hungary, 1340, Váci út 77 |
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| Abstract: | Thermal decomposition of ammonium paratungstate
tetrahydrate, (NH4)10H2W12O42]·4H2O has been followed by simultaneous TG/DTA and online evolved
gas analysis (TG/DTA-MS) in flowing 10% H2/Ar directly
up to 900°C. Solid intermediate products have been structurally evaluated
by FTIR spectroscopy and powder X-ray diffraction (XRD). A previously unexplained
exothermic heat effect has been detected at 700–750°C. On the basis
of TG/DTA as well as H2O and NH3
evolution curves and XRD patterns, it has been assigned to the formation and
crystallization heat of γ-tungsten-oxide (WO2.72/W18O49)
from β-tungsten-oxide (WO2.9/W20O58)
and residual ammonium tungsten bronze. |
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| Keywords: | FTIR spectroscopy mass spectrometry simultaneous TG/DTA tungsten X-ray diffraction |
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