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2011-Sustainable Industrial Processing Summit
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| Editors: | Florian K |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2012 |
| Pages: | 630 pages |
| ISBN: | 978-0-9879917-2-0 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
Molecular And Ionic Species In Saturated Vapour Over Molten Ytterbium Bromides
Mikhail Butman1; Dmitri Sergeev1; Vladimir Motalov1; Lev Kudin1; Leszek Rycerz2; Marcelle Gaune-Escard3;1IVANOVO STATE UNIVERSITY OF CHEMISTRY AND TECHNOLO, Ivanovo, Russia; 2WROCLAW UNIVERSITY OF TECHNOLOGY, Wroclaw, Poland; 3ECOLE POLYTECHNIQUE, Marseille, France;
Type of Paper: Regular
Id Paper: 272
Topic: 6
Abstract:
The vaporisation behaviour of lanthanide halides with unstable Ln valence state is a challenging topic in high temperature materials science. Complex vapor composition is due to the decomposition (2LnX3,s => 2LnX2,s + X2,g) and disproportionation (3LnX2,s => Ln,s + 2LnX3,s) reactions, which in addition enter into competition at elevated temperatures. Our purpose was to identify the molecular and ionic species in the saturated vapour over Yb-Br systems by an upgraded technique of the Knudsen Effusion Mass Spectrometry and, being supplemented by the DSC measurements and quantum chemical calculations, to study their thermodynamic properties. In the temperature range 850 – 1300 K the following ions were registered in the mass spectra: Yb+, YbBr+, YbBr2+, YbBr3+, Br2+, Br+, Yb2Br+, Yb2Br2+, Yb2Br3+, Yb2Br4+, Yb2Br5+ (electron-impact-ionization mode) and YbBr3−, YbBr4− (thermionic emission mode). Analysis of the temperature and time dependences of ion currents, ionisation efficiency curves and ion appearance energies along with the special mathematic procedures of mass spectrum interpretation led us to establish the molecular vapour composition at different stages of vaporisation.It was found out that initial incongruent stage of vaporisation of pure YbBr2 or YbBr3 samples passed gradually to the stationary congruent stage with nearly the same vapor composition. A novel approach based on (i) measurements of equilibrium constants of the molecule/molecule and ion/molecule reactions in the Ln-Br systems of different compositions and (ii) solution of a system of thermochemical equations is proposed to derive the formation enthalpies of YbBrn (n = 1 - 3) molecules and YbBr3−, YbBr4− ions.