Sintered and glazed glass-ceramics from natural and waste raw materials

Monolithic sintered glass-ceramics and porous glass-ceramic components were produced from natural raw materials together with industrial waste. The waste, including fly ash from thermal power plants and metallurgical slags, either was mixed with natural raw materials (e.g., clay and silica sand) and vitrified or was directly sintered, after dry pressing at 40 MPa. Fine powders of waste-derived glasses were also converted into sinter-crystallized glass-ceramics, after dry pressing at 40 MPa and subjection of the pressed powders to controlled heating cycles, producing dense components with bending strength as high as ~80 MPa. The two types of waste-derived materials, namely, ceramic tiles from direct sintering and sinter-crystallized glass-ceramics, were combined to obtain double-layered glass-ceramics. These featured a dense wear-resistant coating on a porous substrate and possessed mechanical properties that make them suitable, for example, as structural lightweight panels in building facades.