Freeze casting process for the generation of graded porosity in Al2O3 ceramics

Abstract

Alumina ceramic materials with graded functional porosity were prepared by the freeze casting method and characterized. The effects of processing route parameters on the pore formation were studied. Pore characteristics were investigated concerning morphology and distribution in the ceramic matrix. The mercury intrusion method was used to evaluate the porosity. Mechanical properties, as well as the fracture mode, were investigated by the uniaxial compression test. Scanning electron microscopy was used to analyze and correlate the created interface between the layers with the mechanical response. The results suggested that the porosity obtained in all samples was similar, even with varying parameters (different suspension solidification configurations). When evaluating the mechanical behavior, these distinct parameters showed drastic differences in compressive strength and failure mode. This was due to the formation of interfaces between the layers of different porosities, according to the solidification configuration. The interfaces modified the fracture mode, changing from a longitudinal-directed to an interface-directed fracture. The pore microstructure and morphology indicated highly connected pore channels.

Lithography-Based Additive Manufacturing of Porosity Graded Alumina

“…Porous ceramics have always been attractive materials in applications where low density, high thermal shock resistance, or high thermal insulation is demanded [ 1 , 2 ]. In recent years, alumina ceramics exhibiting gradient in porosity, i.e., porosity graded alumina ceramics (PGACs), with a controlled amount of both open/closed or macro/micro pores is of high interest for several applications such as thick barrier coating, cores for precision casting, biocompatible implants, membranes/filters, and fabrication of functionally graded metals through infiltration [3][4][5][6] . For instance, the osteointegration in bioceramic implants can be improved increasing the contact area between bone and implant by introducing open pores [7] .…”