Glass - Back to the Future!

Presenting Author:
Acacio Rincón

article posted 04 April 2016

Acacio Rincón graduated from the Complutense University of Madrid in Chemistry, speciality in Materials Science, and obtained a Master Degree in Applied Chemistry from the Autónoma University of Madrid. During his Master´s thesis, he worked in the colloidal processing of ceramic oxides containing carbon nanodispersoids under the supervision of professor Rorigo Moreno.
Nowadays he is involved as a PhD researcher in the CoACH project (Advanced glasses, Composites And Ceramics for High growth Industries), a European Training Network (ETN) studding the development of low cost waste-derived sintered glass and glass-ceramics for energy saving and recovery at the University of Padova under the supervision of professor Enrico Benardo.

Production of glass foams by a novel gel casting technique

Acacio Rincón*, Enrico Bernardo
Dipartimento di Ingegneria Industriale. Università degli Studi di Padova Via Marzolo 9, 35131 Padova, Italy

A new technique for the production of glass foams was developed, based on gel casting. The new process is less expensive and more environmentally friendly than the current procedures, based on glass powders mixed with foaming agents, which decompose and release gases at temperature well exceeding the glass softening point. This technique has been studied in different glasses coming from waste, as soda-lime cullet and an alumino-boro-silicate glass (glass from the recycling of pharmaceutical vials). The alkali activation of soda-lime waste glass allows the obtainment of well-dispersed concentrated suspensions, undergoing gelation by treatment at low temperature (75 °C), owing to the formation of calcium-rich silicate hydrates. An extensive direct foaming was achieved by mechanical stirring of partially gelified suspensions, comprising also a surfactant. The suspensions were carefully studied in terms rheological behaviour, so that the final microstructure (total amount of porosity, cell size) can be directly correlated with the degree of gelification. A sintering treatment, at only 700 °C, was finally applied to stabilize the structures, particularly for limiting the leaching of alkaline ions. The “tobermoritic gel” (i.e. determined by the formation of calcium hydrates) provided by soda-lime glass, after alkali activation, was replaced by a truly “geopolymeric gel” from the alkali activation of a CaO-free alumino-boro-silicate glass, demonstrating the versatility of this technique in achieving glass foams.