LZSA glass ceramic foams prepared by replication process

Abstract

In this study the replication process was applied to produce porous glass ceramic foams. Polyurethane (PU) sponges were impregnated by immersion in aqueous slurry of a parent glass (mean particle size around 3 μm) from the system Li₂O–ZrO₂–SiO₂–Al₂O₃ and submitted to heat treatment. From TGA and IR analyses, two main paths of thermal decomposition of PU sponges were observed at 312 and 393°C, which were associated with the decomposition products CO₂, CO, NH₃ and isocyanide. According to linear thermal shrinkage and DTA measurements, sintering starts at around 570°C and is completed below 700°C, when crystallisation takes place. The main crystalline phases identified by XRD analysis were zirconium silicate, lithium metasilicate and β-spodumene. The morphology and properties of the glass ceramic foams obtained from PU sponges were quite similar for all samples tested. From XCT measurements, a mean cell diameter of around 260 μm and mean strut thickness of 185 μm were calculated, corresponding to a porosity of 75–78%. Compressive strength values under 500 kPa and permeability coefficient in air of about 1000 Darcy were also measured for the samples tested. LZSA glass ceramic foams can be a very interesting alternative to ceramic gas filters, owing to low temperature processing, and to superior properties such as corrosion and thermal shock resistance.