Structural incorporation of titanium and/or aluminum in layered silicate magadiite through direct syntheses

Abstract

Synthesized inorganic layered magadiite containing structurally incorporated titanium and aluminum was obtained through hydrothermal procedures. The effects associated with reaction time and amount of metal used in the crystallization process yielded mostly pure and crystalline samples with 1.0% of aluminum after 36 h at 423 K. Amounts up to 4.0 and 2.0% for aluminum and titanium were successfully incorporated in the magadiite structure without co-crystallization of other phases. A higher amount of metal source or longer crystallization times led to formation of crystobalite and trydimite phases, detected by X-ray diffraction (XRD) and scanning electron microscopies. Metal incorporation slightly improved the thermal resistance of the precursor layered magadiite. Replacement of both atoms in the silicon network was examined by spectroscopy analysis. The changes in tetrahedral-oxygen-tetrahedral structural shape vibrations caused the appearance of the Ti–O–Si band at 960 cm−1. Nuclear magnetic resonance in the solid state demonstrated tandem octahedral and tetrahedral aluminum sites. Another structural feature related to titanium incorporation was observed through diffuse reflectance with UV–Vis and X-ray photoelectron spectroscopies, which distinguish crystalline and amorphous TiO2 and titanium incorporated into the silica network. Metal quantification by energy dispersive spectroscopy and X-ray fluorescence (XRF) was also followed with multivariate analysis, including principal component analysis (PCA) and partial least squares (PLS). The PCA methodology procedure clearly gives information to separate sample groups, in agreement with XRD results, which becomes a valuable feature obtained for the first time for these kinds of materials.