Influence of morphology on the radiative properties of geopolymer foams: A theoretical and experimental analysis

There has been growing interest in geopolymer foams, particularly with regard to the possibility of imparting macroporous properties with a honeycomb structure. These characteristics are relevant to the problems posed by solar applications. As the photo-conversion process is intimately linked to radiation transfer, it is necessary to understand and describe the correlations between the structural and radiative properties of foams. This study focused on the detailed analysis of the radiative properties of macroporous cellular geopolymer foams with different characteristics in terms of porosity and pore size distribution. Transmittance and reflectance measurements were carried out using a dedicated optical bench. The Two-Flux approximation model was used to describe the radiative transfers taking place in the material. Specific absorption and scattering coefficients were accurately represented in the UV and visible ranges. The importance of the structure of macroporous cellular foams on radiative properties has been discussed. Our results also show that it is possible to play on structural characteristics (porosity, pore size) to obtain distinct radiative properties. This makes it possible to select the most appropriate foam for optimum radiation utilization in a given photoreactor configuration.