Setting up the production process of diatomite-based ceramic foams

The design of the production process of diatomite-based ceramic foams, starting from different percentages of metakaolin, diatomite, and sodium silicate solution as reactive ingredients and vegetable surfactant and silicon powder as blowing agents, has been set up. The foams were obtained using the double effect of different foaming approaches: mechanical stirring and chemical foaming. Six systems were prepared fixing the amount of diatomite (100%) and adding in the starting mixture of different percentages (0.05, 0.1, 0.25, 0.5, 0.75, and 1 wt%) of silicon metal. Once the optimal percentage of silicon metal (0.05%) is chosen thanks to XRD analysis, other three systems were prepared only changing the amount of diatomite (50, 70, and 100 wt%) in starting formulation. The foam obtained with 100% of diatomite results to be the optimized final formulation, as it shows a hierarchical porosity with a high homogeneity of the matrix at the same time. The results highlighted that the best performances in terms of lightness, high porosity as well as homogenous microstructure were obtained using, with respect to the total amount, 6 wt% of mechanical stirred vegetable surfactant together with 0.05 wt% of Si as physical and chemical blowing agents, respectively.