Functional glass-ceramic foams from \u2018inorganic gel casting\u2019 and sintering of glass/slag mixtures

The here described investigation was essentially aimed at exploring the chemical stabilization and reutilization of iron-rich slag from copper metallurgy, by the manufacturing of glass-ceramic foams. The foams were developed according to a new method, recently reported for pure recycled soda-lime glass. Mixtures of soda-lime glass/slag powders (with slag content ranging from 10 to 30\u202fwt%), suspended in alkaline aqueous solution, underwent progressive low temperature (80\u202f\ub0C) hardening, owing to the formation of hydrated calcium silicate compounds (CSH). Before complete setting, an extensive foaming could be achieved by vigorous mechanical stirring, with the help of a surfactant. After foaming, glass/slag mixtures could be sintered at 800\u20131000\u202f\ub0C; the mutual interaction caused an extensive crystallization, with precipitation of CaFe silicates and iron oxides (hematite and magnetite), promoting the mechanical properties (up to 4.4\u202fMPa, with a porosity of about 80%). Leaching test confirmed the stabilization of pollutants, from the slag, in the final ceramics. Owing to the separation of iron oxides, particularly magnetite, the newly obtained foams exhibited a ferrimagnetic behavior, that could be exploited in electromagnetic shielding applications