Self-assembly of colloidal particles at the fluid-fluid interface can be utilized for several applications including stabilizing emulsions and foams.Emulsions are heterogeneous mixtures consisting of two (or more) immiscible liquids wherein one of the liquids is dispersed in the other as droplets. Similar to surfactants, solid particles can also act as efficient emulsifiers and the emulsion so formed are popularly known as Pickering emulsions, wherein their formation, microstructure, as well as processability are tuned by controlling the physico-chemical properties of the particles. There is a growing interest in the development of processable Pickering emulsions and current research mainly focus on the field of fabrication techniques, stabilisers and their requirements, rheological properties, and porous materials derived from them.These emulsions provide excellent templates for the fabrication of materials with different morphologies, such as solid/porous spheres, hollow capsules, and other functional porous materials. These material designs have numerous functional applications in energy storage, encapsulation, separation, thermal insulation etc. In the present work, we propose a simple and modular approach to realize processable Pickering emulsions from mixtures of commercially available oppositely charged fumed oxide particles. The ability of weakly charged hetero-aggregates to adsorb to the oil-water interface favours the formation of highly stable emulsions.Control over the microstructure and rheology of the Pickering emulsion is demonstrated by tuning parameters such as composition, pH, and the total concentration of particles. The Pickering emulsions formed under optimal conditions are found to be gel-like and excellent templates for the fabrication of porous ceramics. Further, a porous ceramic structure is obtained by drying and sintering of the emulsion template. The phase evolution, microstructure, and porosity of the resulting ceramic are characterizedusing various techniques.
Key Words: Pickering emulsion, hetero-aggregation, porous materials