Revisiting the Thermal Decomposition of Layered gamma-Titanium Phosphate and Structural Elucidation of Its Intermediate Phases

resumo

The thermal transformations of gamma-titanium phosphate, Ti(PO4)(H2PO4)center dot 2H(2)O, have been studied by thermal analyses (thermogravimetry (TG) and differential thermal analysis (DTA)) and variable-temperature P-31 magic-angle spinning (MAS)/CPMAS and 2D P-31-P-31 spin-exchange NMR. The structure of this material has been refined from synchrotron powder X-ray diffraction data (monoclinic, P2(1), a=5.1811(2) angstrom, b=6.3479(2) angstrom, c=23.725(2) angstrom, beta = 102.57(1)degrees). Vyazovkin's model-free kinetic algorithms have been applied to determine the apparent activation energy to both dehydration and dehydroxylation of gamma-titanium phosphate. In these processes, several overlapped steps have been detected. Structural models for Ti(PO4)(H2PO4)center dot H2O and Ti(PO4)(H2P2O7)(0.5) intermediate layered phases have been proposed.

palavras-chave

INORGANIC-ION EXCHANGERS; RAY-DIFFRACTION SPECTROMETRY; ZIRCONIUM PHOSPHATE; POWDER DIFFRACTION; CRYSTAL-STRUCTURE; ALPHA-ZIRCONIUM; RIETVELD REFINEMENT; SUPERSTRUCTURE; DEHYDRATION; TRANSITIONS

categoria

Chemistry

autores

Garcia-Granda, S; Khainakov, SA; Espina, A; Garcia, JR; Castro, GR; Rocha, J; Mafra, L

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