Functionally graded multi-material freeze-cast structures with continuous microchannels

We present the processing of functionally graded multi-material freeze-cast structures, i.e. structures with varying material properties but continuous and homogeneous microchannels. We demonstrate this for stepwise, continuous, highly viscous and gelation freezing to achieve freeze-cast structures of graded La0.66Ca0.24Sr0.09Mn1.05O3 (LCSM9) and La0.67Ca0.27Sr0.06Mn1.05O3 (LCSM6) ceramics.

The two phases are successfully distinguished from one another by the addition of 10 wt% Ce0.9Gd0.1O2 (CGO) to the LCSM6 phase. The relative Ce-content facilitates tracking of the LCSM6 phase using energy-dispersive X-ray (EDS) elemental analysis. Coupled with scanning electron microscopy, we show well-defined interfaces with continuous microchannels between the two LCSM phases in both green and sintered samples.

By implementing constant freezing rates of −1.5 K/min a consistent freezing front velocity of ∼13 μm/s is maintained, and we found that a structural continuity can be maintained across the LCSM9–LCSM6/CGO interface, however, with varying pore morphology depending on the various freezing procedures.