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Functional glass-ceramic foams from ‘inorganic gel casting’ and sintering of glass/slag mixtures

Rincón, Acacio, Desideri, Daniele, Bernardo, Enrico
Journal of cleaner production 2018 v.187 pp. 250-256
aqueous solutions, calcium silicate, ceramics, copper, crystallization, foaming, foams, gels, glass, hematite, leaching, magnetite, mechanical properties, mixing, pollutants, porosity, powders, slags, temperature
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 wt%), suspended in alkaline aqueous solution, underwent progressive low temperature (80 °C) 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 800–1000 °C; 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 MPa, 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.