Porous ceramics via 3D printing and emulsion templating

Coupling foaming or emulsion templating techniques with additive manufacturing is a very efficient and innovative method for the elaboration of tailored materials with a hierarchical porosity. During this work, new formulations have been developed driven by a low toxicity to health and the environment approach, based on the combination of an emulsion with a vegetable oil, with no surfactant, and a suspension of halloysite. This mineral, with a nanotubular morphology, is known for its ability to stabilize Pickering emulsions. The emulsion template being directly transformed into porosity after thermal treatments was characterized at each step. At first, different formulations of emulsions without solid phase were studied in terms of stability, and droplets size and their dispersion. In a second step, the emulsions were enriched with the mineral phase. Robocasting process, also known as Direct Ink Writing (DIW), imposes both plasticity and consistency to the formulated pastes for optimal processing, which could be adjusted through both oil and solid fractions. The porosity of the printed ceramic structures was then evaluated after the elimination of the template and at different sintering temperatures. This approach allows to achieve complex geometries with high porosity, between 60 % and 70 % of the volume depending on the heat treatment, and a very good preservation of the shape of the printed objects and the pores created by the emulsion template. • Stable emulsions enriched in clay particles are 3d-printed via robocasting technique. • The emulsions' continuous phase is a partially dispersed suspension of halloysite. • Emulsion template and thus final porosity have been tuned by modifying formulation. • High porosity and spherical pore shape could be maintained after thermal treatments. • Natural and less environmentally toxic materials like clay and vegetable oil are used.