Open-Cell, Low-Density Ceramics Fabricated from Reticulated Polymer Substrates

Processing procedures and resulting mechanical properties of open-cell, low-density (relative density < 0.1) ceramic macrostructures were investigated. These macrostructures were fabricated by slurry coating reticulated polymer substrates. Cracks in the struts powder coating, which were produced during the pyrolysis of the substrate, remained after powder densification at high temperatures and were the major cause of suboptimum properties. Additionally, lack of slurry drainage during the coating process could fill cells with powder which would differentially shrink during densification, leaving large regions within the macrostructure void of cell struts. This problem became increasingly produced with decreasing cell size. Mechanical properties were measured for a commercial transformation-toughened Al{sub 2}O{sub 3}/ZrO{sub 2} open-celled material fabricated using reticulated polymer substrates with cell sizes of 12, 26, and 39 pores/cm. Approximately half of the specimens were treated by the manufacturer in an attempt to heal the partially cracked struts. The relative density of all materials ranged from 7 to 12% of theoretical. Mechanical properties appeared to be independent of cell size. The elastic modulus, which ranged from 1 to 5 GPa, increased with density and was higher for the healed materials.