Sintered silicophosphate glass ceramics from MBM ash and recycled soda-lime-silica glass

Mixtures of meat and bone meal (MBM) ash and soda-lime-silica (SLS) glass scrap were successfully melted, together with small additions of secondary materials, to form two calcium silico-phosphate glasses. Both glasses were successfully converted into glass-ceramics by sintering fine powders (<37 μm) at 700°C - 1070°C for 0.5 - 2h, after very rapid heating (40°C/min). The MBM-SLS mixture with added CaO and CaF2 led to fluorapatite-wollastonite glass-ceramics, which retained significant porosity even after sintering at 1070°C, since the remarkable crystallization hindered viscous flow. This feature was exploited for the preparation of open-celled macro-cellular glass-ceramic foams by thermal treatment of fine glass powders mixed with PE sacrificial templates. The MBM-SLS mixture with added CaO and Na2O led to dense combeite glass-ceramics exhibiting excellent mechanical properties (bending strength far exceeding 100 MPa), and sintered at particularly low temperatures (800°C) for 1h. Since the crystal phases developed in these glass-ceramics are well known for their biocompatibility, MBM ash and scrap SLS glass could find applications in the field of biomaterials or other applications requiring low-cost, high-strength glass-ceramics.