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