Microstructure and properties of LZSA glass-ceramic foams

Commercial polyurethane foams with a monomodal pore size distribution were used to produce LZSA glass-ceramic foams by the polymeric sponge method. A suspension containing LZSA glass powder, bentonite and sodium silicate was prepared in isopropanol to impregnate the polymeric foams by dip coating. The sintering conditions were varied in the range of 700–850 °C for 30–180 min. The cellular microstructure of glass-ceramic foams was characterized by scanning electron microscopy (SEM) and micro-computer X-ray tomography (μCT). Optimum physical, mechanical and fluidynamic properties of the LZSA glass-ceramic foams were obtained at 750 °C for 60 min. Main crystalline phases detected were β-spodumene and zirconium silicate. The compressive strength of the foams (0.1–10 MPa) is strongly dependent on their overall porosity and their behaviour could be explained using the Gibson-Ashby model. The Darcyan permeability of LZSA foams was found to be in the range of 0.1–4 × 10−9 m2, which is in the order of magnitude of cellular supports for aerosol filters, and, therefore, suitable for several other technological applications.