Synthesis, characterization and formation mechanism of single-phase nanostructure bredigite powder

Single-phase nanocrystalline bredigite powder was successfully synthesized by mechanical activation of talc, calcium carbonate, and amorphous silica powder mixture followed by annealing. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and Fourier transform infrared spectroscopy (FT-IR) techniques were employed to characterize various powders. Single-phase nanostructure bredigite powder with crystallite size of about 65 nm was synthesized by 20 h of mechanical activation with subsequent annealing at 1200 C for 1 h. The bredigite formation mechanism was studied. During the formation process of nanostructure bredigite powder some intermediate compounds such as wollastonite (CaSiO3), larnite (Ca2SiO4), merwinite (Ca3MgSi2O8), and calcium magnesium silicate (Ca5MgSi3O12) were formed. It was found that bredigite was not produced directly and that the formation of merwinite, enstatite and Ca5MgSi3O12 was unavoidable during the synthesis of bredigite. (C) 2011 Elsevier B.V. All rights reserved.