Local and Extended-Order Evolution of Synthetic Talc during Hydrothermal Synthesis: Extended X-ray Absorption Fine Structure, X-ray Diffraction, and Fourier Transform Infrared Spectroscopy Studies

DUMAS, ANGELA; MIZRAHI, MARTÍN; MARTIN, FRANÇOIS; REQUEJO, FELIX G.

CRYSTAL GROWTH & DESIGN

AMER CHEMICAL SOC

Año: 2015 vol. 15 p. 5451 - 5463

1528-7483

Synthetic talc is a new filler of industrial interest due to its submicron size, its chemical and mineral purity, and its hydrophilic character. To develop this filler on a preindustrial scale, this work aimed to understand the mechanisms of transformation from the amorphous talc precursor to crystalline synthetic talc. X-ray diffraction, Fourier transform infrared spectroscopy, and extended X-ray absorption fine structure at Ni-K edge techniques were used to study a Ni-talc series composed of a talc precursor sample and talc samples synthesized at 100, 200, and 300 °C for 1 or 6 h. As soon as the Ni-talc precursor precipitated, a tetrahedral-octahedral-tetrahedral-type structure appeared that was characterized by 2-3 Ni-octahedra distanced 3.07 Å from each other and by 3-4 Si tetrahedra distributed on the top and bottom of the octahedral "sheet" and distanced 3.29 Å from Ni. Simultaneously following the synthesis temperature, the octahedral sheet grew, and the tetrahedral sheet expanded; the distances Ni-Ni and Ni-Si also gradually shortened. The intracrystalline distribution of the octahedral sheet was also studied. At 300 °C, a random distribution was obtained. Cluster distribution was not observed at low temperature, which we hypothesize is a function of crystallite size.