Faculty of Physics - University of Bucharest

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FACULTY OF PHYSICS

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2024-11-22 2:21

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Conference: Bucharest University Faculty of Physics 2010 Meeting

Section: Optics, Spectroscopy, Plasma and Lasers

Title:

Spectroscopic characterization of some layered materials of LDH-type. Thermal analysis support

Authors:

N. Gheorghe, F. Iova, L. Frunza, P. Ganea, F. Neatu, V.I. Parvulescu

Affiliation:

National Institute of Materials Physics, Magurele, Dept. Optics and Spectroscopy, Faculty of Physics, University of Bucharest, Dept. Chemical Technology and Catalysis, Faculty of Chemistry, University of Bucharest

E-mail

nicoleta.gheorghe@infim.ro

Keywords:

layered double hydroxides, thermal analysis, water content

Abstract:

In a previous work layered oxide materials positively charged, with the structure of layered double hydroxides (LDHs) and containing in the interlayer space anions (for electroneutrality) and water molecules were studied by spectroscopic methods. In this contribution the support given by the thermal analysis method to the investigation of the interlayer species is presented. Layered oxide materials have the general formula [M1−x2+Mx3+(OH)2]x+(Az−)x/z•mH2O, where M2+and M3+ are metal cations. In our case M2+ = Zn2+, Mg2+; M3+ = Al3+, Ga3+, Az− represents the anions to balance the positive charge of the layer (here, nitrate NO3- and/or carbonate CO32-). The samples were prepared in laboratory and were further noted Mg3Al, Mg3Ga, Zn2Al and Zn2Ga. They were characterized by powder X-ray diffraction, FTIR and nitrogen adsorption. Thermal analysis measurements were performed with a Diamond TG-DTA apparatus from Perkin Elmer. The samples were investigated in the temperature range of 30-800oC, under dry air flow, at a heating rate of 10 degree/min. The thermal processes observed in the TG-DTG-DTA curves were assigned by comparison with the behaviour of similar samples in the literature. Water amount was quantified and the equivalent thickness of the layer was estimated, by considering that water is uniformly spread onto the sample surface. The found values were used in assessing the FTIR and dielectric spectroscopic behaviour.