Effect of composition and heat treatment on the phase evolution and mechanical properties of tough miserite-based glass ceramics

摘要

Glass specimens with the Stoichiometric formula of miserite after the optimization of composition to obtain the maximum amount of miserite phase were melted and cast in the bulk form and converted into miserite glass ceramics. The optimum nucleation and crystallization conditions, as determined by differential thermal analysis (DTA), were 1 h/610 °C and 3 h/806 °C+3-5 h/1015 °C, respectively. The crystalline products and resulting microstructures were studied by X-ray diffraction (XRD), and scanning electron microscopy (SEM). It was shown that xonotlite crystals nucleated from the phase separated F-Ca rich glass droplets, rapidly grown as spherulites and gradually disappeared and replaced by miserite crystals at higher temperatures. Themost promising specimens comprising interwoven, rod-shaped miserite crystals, showed the bend strength and fracture toughness values of 315±14 MPa and 3.70±0.15MPa·m~(1/2), respectively. These specimens also exhibited the favorable signs of bioactivity.