Preparation of porous glass-ceramics under different hydrothermal hot pressing conditions

Porous glass-ceramics were prepared by conventional firing from compacts prepared by hydrothermal hot pressing of a used glass powder. The effect of hydrothermal hot pressing parameters on the expansion of waste glass powder was investigated by varying the parameters from the standard conditions, at 200 °C for 2 h at a constant uniaxial pressure of 20 MPa. A new glass phase was formed in the glass compacts during hydrothermal hot pressing, and water was incorporated into the new phase. The preparation of porous glass ceramic was made by decomposition of the new phase in the compacts, during a conventional heating. A minimum apparent density of 0.40 g/cm3 was obtained on specimens prepared with low water content (5 wt.%) and medium particle size (39–45 μm).