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

Abstract 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 (CaSiO 3 ), larnite (Ca 2 SiO 4 ), merwinite (Ca 3 MgSi 2 O 8 ), and calcium magnesium silicate (Ca 5 MgSi 3 O 12 ) were formed. It was found that bredigite was not produced directly and that the formation of merwinite, enstatite and Ca 5 MgSi 3 O 12 was unavoidable during the synthesis of bredigite.