Sintered Iron-Rich Glass-Ceramics and Foams Obtained in Air and Argon

The subsequent synthesis of sintered self-glazed glass-ceramics and/or glass-ceramic foams using metallurgical slag is the topic under discussion. The observed intensive sample expansion can be considered as an autocatalytic process related to the oxygen release due to thermal reduction of Fe2O3 and MnO2 present in the slag. The sintering of the samples is studied by optical dilatometry and the foaming process by hot-stage microscopy, while the structure of the final materials is revealed by 3-D computed tomography and SEM. The phase composition of the glass-ceramic foams is analyzed by XRD. The species are characterized by moderate crystallinity, 80–85 vol.% porosity and fire resistance above 1000°C. The innovative point of this study is the synthesis in argon of sintered glass-ceramic materials where reduction is inhibited, together with a double-stage foam formation in air and argon, leading to lower working temperatures and better material characteristics

Augite-anorthite glass-ceramics from residues of basalt quarry and ceramic wastes

Dark brown glasses were prepared from residues of basalt quarries and wastes of ceramic factories. Addition of CaF2, Cr2O3 and their mixture CaF2-Cr2O3 were used as nucleation catalysts. Generally, structures with augite and anorthite as major phases and small amount of magnetite and olivine phases were developed through the crystallization process. In the samples heat treated at 900 °C the dominant phase is augite, whereas the content of anorthite usually overcomes the augite at higher temperature (1100 °C). Fine to medium homogenous microstructures were detected in the prepared glass-ceramic samples. The coefficient of thermal expansion and microhardness measurements of the glass-ceramic samples were from 6.16×10-6 to 8.96×10-6 °C-1 (in the 20–500 °C) and 5.58 to 7.16 GP, respectively