Control over the mechanical properties of surface-magnetized alumina magnetically freeze-cast scaffolds

Magnetic freeze-casting with a mix of particles and particles of increased aspect ratio (platelets) in surface-magnetized alumina scaffolds gives rise to the Hall effect, which increases the ability to tune scaffold mechanical properties in an unexpected way. Even after surface magnetization, alumina particles are only weakly magnetically susceptible, which has greatly limited their ability to be controlled via Helmholtz coils in magnetic freeze-casting due to their low-strength magnetic fields. The magnetic susceptibility of alumina can be increased by increasing the aspect ratio of alumina particles used. It was found that when a low-strength magnetic field was applied via Helmholtz coils perpendicular to the ice-growth direction to alumina scaffolds at a 1:1 weight ratio of platelets to particles (mixed scaffolds) during freeze-casting, the ultimate compressive strength perpendicular to the applied field and ice-growth direction increased in a statistically significant manner. Lowered viscosity in mixed slurries allowed for more particle movement which resulted in greater Hall voltages than in slurries with a uniform type of particle (either particles or platelets). Using this method, mechanical properties of porous alumina scaffolds can be controlled and tailored to best suit a given application. Given the wide scope of applications of alumina, this method has the potential to be highly impactful for uses ranging from aerospace to dental implants and medical devices.