Meso- and Macroporous Ceramics by Phase Separation and Reactive Sintering Methods

Controlled pore glasses are formed through selective etching of one phase of a spinodally decomposed borosilicate glass, an old technique that is the basis of the porous Vycor synthesis technique developed in the 1920s. This technique is receiving renewed attention as these glasses find new applications as substrates for biosensing, bioreactors, precise filtration, and chromatography. Analogous techniques are being applied to crystalline ceramics, such as directed cooling of ZrO2/MgO and MgAl2O4/Al2O3 eutectics to drive phase separation with the subsequent dissolution of one phase. Pyrolytic reactive sintering is a combination of the phase separation method and the reactive sintering method to obtain a 3D porous structure network. For example, dolomite (CaMg[CO3]2) and ZrO2 yield a uniformly porous CaZrO3/MgO composite that utilizes evolved CO2 as a “pore-forming agent.” This article gives an overview of recent developments on meso- and macroporous ceramics based on phase separation and reactive sintering technologies.