Impact of the chemical form of different fluorine sources on the formation of AlF molecules in a C2H2/N2O flame

  • The formation of diatomic AlF molecules was studied in a C2H2/N2O flame by means of a high-resolution continuum source flame absorption spectrometer using different fluorine containing compounds HF, H2SiF6, HBF4 and CF3COOH as fluorine sources. The fragmentation of these fluorine sources, as well the resulting impact on the AlF molecule formation, was derived from flame height distribution studies of the atomic and molecular species Al, AlO, Si, SiO, SiF, B and BF as a function of the fluorine concentration, the molar Al : F ratio and the burner gas composition. As a consequence, the used fluorine sources HF, H2SiF6, HBF4 and CF3COOH have been divided into two major groups. The first group of fluorine sources, covering HF, H2SiF6 and HBF4, decomposes during the drying of the aerosol under the formation of AlF3, which is the dominating species for the transport of aluminium into the flame. Its decomposition into AlF results in a high sensitivity of AlF molecular absorption at low flame observation heights. The second group of fluorineThe formation of diatomic AlF molecules was studied in a C2H2/N2O flame by means of a high-resolution continuum source flame absorption spectrometer using different fluorine containing compounds HF, H2SiF6, HBF4 and CF3COOH as fluorine sources. The fragmentation of these fluorine sources, as well the resulting impact on the AlF molecule formation, was derived from flame height distribution studies of the atomic and molecular species Al, AlO, Si, SiO, SiF, B and BF as a function of the fluorine concentration, the molar Al : F ratio and the burner gas composition. As a consequence, the used fluorine sources HF, H2SiF6, HBF4 and CF3COOH have been divided into two major groups. The first group of fluorine sources, covering HF, H2SiF6 and HBF4, decomposes during the drying of the aerosol under the formation of AlF3, which is the dominating species for the transport of aluminium into the flame. Its decomposition into AlF results in a high sensitivity of AlF molecular absorption at low flame observation heights. The second group of fluorine sources is exemplarily given by CF3COOH. In the upper parts of the flame the cleavage of the very stable C–F bond proceeds incompletely so that the sensitivity of the AlF molecular absorption is considerably lower than that for the other fluorine sources. In consequence, the AlF molecules are formed by the reaction between the fluorine atoms and the aluminium atoms, which are transported into the flame without the aid of fluorine, presumably via oxidic and/or carbidic species. The present investigations show that the sensitivity of the AlF molecular absorption and the pathway of AlF formation depend on the chemical form of the fluorine in the studied samples.show moreshow less

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Metadaten
Author: Jörg AckerORCiDGND, Stefan Bücker, Volker Hoffmann
URL:http://pubs.rsc.org/en/Content/ArticleLanding/2016/JA/C5JA00470E#!divAbstract
DOI:https://doi.org/10.1039/C5JA00470E
ISSN:0267-9477
ISSN:1364-5544
Title of the source (English):Journal of Analytical Atomic Spectrometry
Document Type:Scientific journal article peer-reviewed
Language:English
Year of publication:2016
Tag:C2H2/N2O flame; aluminum monofluoride; diatomic molecule; flame molecular absorption spectrometry; hexafluorosilicic acid; species fragmentation; tetrafluoro boric acid; trifluoro acetic acid
Volume/Year:31
First Page:902
Last Page:911
Faculty/Chair:Fakultät 2 Umwelt und Naturwissenschaften / FG Physikalische Chemie
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