Cellular ceramic foam derived from potassium-based geopolymer composite: Thermal, mechanical and structural properties

Porous geopolymers have drawn widespread attention owing to the flexibility of the production processes and the diversity of their structural properties. This paper first investigates and describes the key parameters for the fabrication of ceramic foam based on a geopolymer mixture by impregnation using the replica technique. The influence of geopolymer mixture viscosity on total porosity, pore size and mechanical strength of leucite ceramic foams is evaluated. The accelerated solidification step at 70 °C was investigated using time-dependent viscoelastic parameters such as tan δ, G' and G". For the fabrication of highly porous ceramics based on the geopolymer mixture, the optimum viscosity ranges between 9 and 15 Pa.s at 100 s−1. Differential thermal analysis (DTA) and X-ray diffraction (XRD) indicated the crystallization of the main leucite phase at 1073.5 °C, during the thermal exposure up to 1300 °C. It has been revealed that ceramic foam with an open porosity of 76 to 79 vol% can be fabricated using a replica technique. Scanning electron microscopy (SEM) and X-ray micro-computed tomography (micro-CT) have confirmed interconnected macroporosity with an open pore size up to 2 mm. This study introduces a novel group of materials combining geopolymer chemistry and traditional production of ceramic foams.