Silicone resins mixed with active oxide fillers and Ca-Mg Silicate glass as alternative/integrative precursors for wollastonite-diopside glass-ceramic foams

Ca-Mg silicates are receiving a growing interest in the field of bioceramics, mainly due to their bioactivity and biocompatibility. This paper investigates the influence of precursors on the sintering, phase assemblage and mechanical properties of wollastonite-diopside foams, using two alternative routes. Firstly, highly porous wollastonite-diopside ceramics were synthesized using silicone resins, embedding CaCO3 and Mg(OH)(2), as active fillers, and sodium borate, as a foaming and mineralizing filler. The resulting samples were almost identical, in terms of phase assemblage, to products from sinter-crystallization of a Ca/Mg-rich glass. However, they exhibited some cracking, attributed to crystallization-induced volume changes (shrinkage and release of gaseous products). Taking this into account, a second processing route was proposed, so that Ca/Mg-rich glass powders were incorporated in silicone-based mixtures as additional filler, aimed at providing liquid phase upon firing and allowing for stress relaxation. Crack-free samples, from glass-modified formulations, exhibited improvements in terms of morphology and crushing strength, with no significant modification of the phase assemblage. (C) 2015 Elsevier B.V. All rights reserved.