Inorganic/Inorganic Composites Through Emulsion Templating

Inorganic/inorganic composites are found in multiple applications crucial for the energy transition, from nuclear reactors to energy storage devices. Their microstructures dictate their properties from mass transport to fracture resistance. Consequently, there has been a multitude of processes developed to control them, from powder mixing and the use of short or long fibers, to tape casting for laminates up to recent 3D printing. Here, emulsions and slip casting are combined into a simpler, broadly available, inexpensive processing platform that allows for in situ control of composite microstructure while also enabling complex 3D shaping. This study shows that slip casting of emulsions triggers a two-step solvent removal, opening the possibility for the conformal coating of pores. This process is showcased by producing strong and lightweight alumina scaffolds reinforced by a conformal zirconia coating. In addition, by manipulating magnetically responsive droplets, their distribution can be controlled, allowing for the formation of inorganic fibers inside an inorganic matrix in situ during slip casting. Using this approach, alumina has been reinforced with aligned metallic iron fibers to prepare composites with a work of fracture an order of magnitude higher than the pure ceramics.