Microstructure and properties of zirconia-alumina composites fabricated via powder injection molding

This study aimed to fabricate zirconia-alumina composites via powder injection molding and investigate the effects of alumina addition on microstructure as well as physical properties of the composites. Zirconia-alumina composites were prepared using polyethylene glycol (PEG) and polyvinyl butyral (PVB) as binders. The powder loading was fixed at 38 vol%, and PEG: PVB binder weight ratio was fixed at 80:20. Alumina content within ceramic component was varied at 0, 10, 20, 30, 40 and 50 vol% to observe the effect of alumina on the composite structures and properties. The injection molding was done at 190 degrees C followed by water debinding of PEG at 40 degrees C. Thermal debinding of PVB at 450 degrees C. was performed prior to sintering at 1450 degrees C. From the density measurement via Archimedes' method, the relative density of sintered samples was found to be highest at 10 vol% alumina and gradually lower at higher alumina content. The condition with highest density yielded the highest flexural modulus and flexural strength. XRD indicated that tetragonal zirconia phase coexisted with alumina when alumina was added. Above 20 vol% alumina, monoclinic zirconia was also detected. The increased porosity in samples with high alumina content, as confirmed in SEM morphological observation, correlated with lower flexural strength and lower flexural modulus. The results illustrated the feasibility of powder injection molding in the production of zirconia-alumina composites and the optimum condition in this study was 10 vol% alumina.