Improved structural and mechanical performance of iron oxide scaffolds freeze cast under oscillating magnetic fields

Abstract

Manufacturing processes yielding stronger, yet lighter structures are sought for in many industries and scientific applications. Freeze casting is a fabrication process that offers a way to achieve these strong, lightweight structures, but only in a single direction (the direction of the templating-ice growth). Applying a uniform magnetic field to these structures allows for increased strength in an additional direction, thus allowing for them to be applied in a variety of complex loading environments. Using a Helmholtz coil, it is possible to apply weak, uniform fields in any direction, magnitude, or frequency. Previous research using Helmholtz coils has shown that an applied field can increase strength through microstructural alignment, but the limited field strength reduces the applicability of these materials. To mitigate this, an oscillating field (i.e., a stronger magnetic field in a single direction with a weaker alternating field in an orthogonal direction) of various magnitudes of oscillation during the fabrication of freeze-cast materials was applied using Helmholtz coils. These oscillating magnetic fields led to an increase of strength of up to 2.5x compared to materials fabricated with either no applied field or a non-oscillating applied field due to increased alignment and thickness of the lamellar walls. This demonstrates that increased material response can be induced through the application of an oscillating field without increasing the maximum magnetic field strength.