Production of alumina ceramics with graded porosity processed by slip casting and freeze casting

Abstract

The objective was to study the processing of alumina ceramic materials with graded porosity produced by freeze casting and slip casting with aluminum hydroxide as a porogenic agent. After processing of the samples, porosity was studied by scanning electron microscopy, apparent porosity by the Archimedes’ principle, and size and average pore size by mercury porosimetry. The mechanical strength of the samples was studied through compression testing. The characterization allowed confirmation of the relation between the samples processed individually and their respective layer in materials with graded porosity. The samples also showed good interfacial interaction between the layers of the graded materials. The porosities obtained by both methods were distinct due to different morphologies; by slip casting, the pores showed smaller sizes with few interconnections and by freeze casting, pores were interlayered with elongated and interconnected morphology. Porosity and compressive strength values were different for each technique. The graded sample processed by freeze casting showed higher porosity and compressive strength when compared to the sample processed by slip casting. Both techniques showed to be efficient for the production of graded porosity material.

Keywords:
slip casting; alumina; aluminum hydroxide; functionally graded materials