Pickering emulsions are emulsions stabilized by colloidal particles homogeneously distributed at the liquid-liquid interface, leading to a high stability against coalescence and a high state of dispersion. This work is part of the IDEMAP project (“Impression 3D D’Emulsions céramiques. Application à l’élaboration de MAtériaux Poreux architecturés”), which aims at shaping ceramic materials with a multi-scale porosity. The originality of the project is to develop hybrid formulations of Pickering emulsion-suspension that are suitable for the microextrusion process, in order to benefit from a versatile and efficient shaping for new applications in the field of porous ceramics. In these systems, the dispersed phase serves as a "template" for the porosity and is removed after the heat treatment [1]. Another specificity of the project lies in the use of phyllosilicates, in particular halloysite. This phase has amphiphilic properties but also a tubular anisotropic morphology [2,3], which makes it a good candidate for producing emulsions. One of the challenges of the project is also to favour the use of additives and materials that are environmentally friendly.

To introduce a high content of mineral phase and promote the printability of the mixtures, the first stage of the process consists of the elaboration of an oil-in-water emulsion, without any solid phase. The study focuses on the effect of additives (surfactant, binder, plasticizer) on the properties of the emulsions, in particular their stability, the size and size distribution of the droplets, and their rheological properties, as well as the impact of the preparation parameters (mode of introduction of the constituents of the emulsion, mode of mixing, stirring speed, etc.). The halloysite is added in a second step. The adsorption of mineral particles at the interface of the dispersed phase droplets is studied, in order to highlight the hybrid aspect of these formulations (suspension-emulsion) and their compatibility with the targeted shaping process of microextrusion.
 
[1] C. Minas et al., « 3D Printing of Emulsions and Foams into Hierarchical Porous Ceramics », Advanced Materials, 28 (2016), 45
 [2] D. Kpogbemabou et al., Colloids Surfaces A: Physicochemical and Engineering Aspects, 463 (2014), 85
[3] M. Ouadaker et al., Colloids and Surfaces A: Physicochemical and Engineering Aspects, 585 (2020), 124156