The fracture toughness of glass ceramics produced from the fly ash of the Seyitömer power plant of Turkey has been investigated using an indentation fracture technique. In this process, fly ash was melted and cast as a glass. The glass materials produced were heat treated at 1073 K, 1123 K and 1173 K for 30-240 minutes in order to obtain glass-ceramics. X-ray diffraction analysis (XRD) showed that the phases formed in the glass ceramics were diopsite and augite. Atomic force microscope (AFM) images were used for the examination of the surface structure of the glass ceramics. The fracture toughness of the glass ceramics ranged from 1.80 ± 0.15MPa.m1/2 to 2.92 ± 0.65MPa.m1/2 depending on the treatment temperature and time. The higher the crystallization temperature and the longer the treatment time, the higher the fracture toughness became.

Keywords: Fly ash, Glass-ceramics, Fracture toughness, Hardness.