Surface functionalization of alumina powders with a responsive surfactant
(BCS) leads to particles that react to a chemical switch. These ‘responsive’ building blocks
are capable of assembling into macroscopic and complex ceramic structures. The aggregation
follows a bottom up approach and can be easily controlled. The directed assembly of
concentrated suspensions leads to highly dense (~99%) ceramic components with average
4-point bending strength of ~200 MPa. On the other hand, the emulsification of suspensions
with concentrations from 7 to 43 vol% and 50 vol% decane results in emulsions with
different properties (stability, droplet size and distribution). The oil droplets provide a soft
template confining the alumina particles in the continuous phase and at the oil/water interfaces.
Aggregation of these emulsions followed by drying and sintering leads to
macroporous (pore sizes ranging from 30 to 4 µm) alumina structures with complex shapes
and a wide range of microstructures, from closed cell structures to highly interconnected foams with total porosities up to 83%. Alumina scaffolds with ~55 % porosity can reach
crushing strength values above 300 MPa in compression and ~50 MPa in 4-point bending.