Mixed Applied Fields to Control Freeze Casting Microstructure and Properties

There is an ongoing need for tailored, porous materials for a variety of applications including biomedical materials, energy materials, semiconductors, and high-strength low-weight composites, to name a few. One promising advanced manufacturing technique to produce these tailored, porous materials is freeze casting, which is also known as ice templating. Upon freezing, the growing ice crystals template a low-viscosity colloidal slurry. In particular, the reliance of freeze casting on the solidification of low-viscosity, often water-based, colloidal slurries allow for applied energized fields to easily impact the process. This allows for the potential for the application of energized fields to apply user-defined microstructures and associated physical properties on the resultant porous materials generated by the process. This award supports fundamental research to investigate currently used energized field sources, specifically electrical, magnetic, and ultrasound, in combination with freeze casting. In particular, as these energized fields each will interact with the colloidal slurry based on different physics, both their direct impacts and interactions will be characterized. Once completed, this knowledge base will provide a foundation for the use of energized fields to create tailored materials both in freeze casting and within other advanced manufacturing processes that employ colloidal slurries, such as tape casting, injection molding, and deposition modeling. This award will also provide education and research opportunities for women in STEM and undergraduate researchers from backgrounds that are traditionally underrepresented in STEM. This grant will conduct basic research into understanding the operating space of an advanced manufacturing process that includes all current forms of external energized fields, such as electrical, magnetic, and ultrasound, applied simultaneously to the freeze-casting process, which is referred to as Mixed-Energized Field (MEF) Freeze Casting. The application of these energized fields and their interactions will be explored experimentally through a factorial study and characterized by microstructural and physical property measurements. In addition, a constitutive theory of the MEF Freeze Casting process will be developed based on the physics of each component of the process that allows for prediction of the final structure and properties of the tailored, porous materials fabricated with the MEF Freeze Casting process. This new constitutive theory will be used to identify the energized-field parameters that will produce the most favorable properties in the final tailored, porous materials, e.g., highest compressive strength, greatest alignment of the microstructure, and fabricate these tailored, porous. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.