Claudia Fasel

Mrs. Claudia Fasel

orcid

Research Focus & Metrics

Academic Career Length

18Years (2009-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 March 2022 in Carbon
Verified
Journal Article
Closed access
XLXingmin Liu
Xingmin Liu
MLMinghang Li
Minghang Li
HLHeqiang Liu
Heqiang Liu
WDWenyan Duan
Wenyan Duan
CFClaudia Fasel
Claudia Fasel
AWAnke Weidenkaff
Anke Weidenkaff

15 March 2009 in Journal of Applied Physics
Verified
Journal Article
Closed access
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SHS. Hesse
S. Hesse
JZJörg Zimmermann
Jörg Zimmermann
HSHeinz von Seggern
Heinz von Seggern
XMX. Meng
X. Meng
CFClaudia Fasel
Claudia Fasel
RRRalf Riedel
Ralf Riedel
The present paper relates to a method for synthesizing the photostimulable storage phosphor BaFBr:Eu2+ that features high stimulation characteristics for use in image plates. All previous synthesis routes consist of a multistep process whereas the presented route is a one-step synthesis. Starting compounds are BaCO3 , NH4F , and NH4Br , as well as EuF3 where the ammonium compounds are highly volatile at temperatures below 300°C . Their reaction products initiate the decomposition of BaCO3 and form BaFBr. The incorporation of F-centers and europium ions occurs at temperature exceeding 550°C . The individual reaction steps are monitored by simultaneous thermal analysis (thermogravimetry/differential thermal analysis) and the gaseous reaction products are detected by in situ mass spectroscopy. Intermediate and final products are characterized by x-ray diffraction techniques to determine the involved phases. Photoluminescence spectra reveal the typical emission peak of Eu2+ accompanied by a redshifted emission band at 470nm , which was assigned to oxygen incorporated into the BaFBr lattice. The synthesized powders exhibit small grain sizes well suited for the use in image plates.

6 September 2022 in Polymers
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Journal Article
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JKJohannes Klitsch
Johannes Klitsch
RPRudolf Pfaendner
Rudolf Pfaendner
CFClaudia Fasel
Claudia Fasel
FSFrank Schönberger
Frank Schönberger
In this study, the flame retardant effect of the Zn salt of 10-hydroxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (Zn-DOPOx), melamine polyphosphate (MPP) and their mixture was investigated towards the mode of action in glass fiber-reinforced polyamide 66 (PA 66 GF). The flammability was evaluated using UL 94 V and cone calorimetry. Influence on char formation was analyzed by SEM. Thermal decomposition of Zn-DOPOx and MPP was studied by TGA and ATR-FTIR. The release of gaseous PA 66 decomposition products was investigated using TGA-DTA-FTIR. Combining Zn-DOPOx and MPP leads to an improvement in flame retardancy, most pronounced for equal parts of weight. Mode of action changes significantly for Zn-DOPOx:MPP (1:1) compared to the sole components and a strong interaction between Zn-DOPOx and MPP is revealed, resulting in a more open char structure. Fuel dilution as well as less exothermic decomposition are essential for the mode of action of the combination. Through low HRR values and high CO/CO2 ratio during cone calorimetry measurements, a significant increase in gas phase activity was proven. Therefore, it is concluded that Zn-DOPOx:MPP (1:1) leads to a significant increase in flame retardancy through a combination of mode of actions in the gas and condensed phase resulting from the change in thermal stability.

1 September 2009 in Journal of Nanoscience and Nanotechnology
Verified
Journal Article
Closed access
IAImteyaz Ahmad
Imteyaz Ahmad
Subramshu Shekar BhattacharyaSubramshu Shekar Bhattacharya
Subramshu Shekar Bhattacharya
CFClaudia Fasel
Claudia Fasel
HHHorst Hahn
Horst Hahn
Of the three crystallographic allotropes of nanocrystalline titania (rutile, anatase and brookite), anatase exhibits the greatest potential for a variety of applications, especially in the area of catalysis and sensors. However, with rutile being thermodynamically the most stable phase, anatase tends to transform into rutile on heating to temperatures in the range of 500 °C to 700 °C. Efforts made to stabilize the anatase phase at higher temperatures by doping with metal oxides suffer from the problems of having a large amorphous content on synthesis as well as the formation of secondary impurity phases on doping. Recent studies have suggested that the as-synthesised phase composition, crystallite size, initial surface area and processing conditions greatly influence the anatase to rutile transformation temperature. In this study nanocrystalline titania was synthesised in the anatase form by a chemical vapour synthesis (CVS) method using titanium tetra iso-propoxide (TTIP) as a precursor under varying flow rates of oxygen and helium. The anatase to rutile transformation was studied using high temperature X-ray diffraction (HTXRD) and simultaneous thermogravimetric analysis (STA), followed by transmission electron microscopy (TEM). It was demonstrated that the anatase–rutile transformation temperatures were dependent on the oxygen to helium flow rate ratio during CVS and the results are presented and discussed.