Load-bearing increase in alumina evoked by introduction of a functional glass gradient

Alumina is the most commonly used ceramic in orthopedics due mainly to its wear resistance and chemical inertness. However, alumina has relatively low load-bearing capacity compared to other advanced ceramics, such as zirconia. We hypothesized that grading the elastic modulus at the surfaces may substantially increase the load-bearing capacity of alumina. In this study, graded structures were fabricated by infiltrating glass into dense alumina plates, resulting in a diminished modulus at the surface layers. The plates were then bonded to polycarbonate substrates and subjected to flexural loading with various loading rates spanning five orders of magnitude (dynamic fatigue) in water. Infiltrated specimens showed an increase in flexural load over homogenous controls for all loading rates, despite the graded alumina exhibiting greater load rate dependence than their homogenous counterparts. Our results indicate that controlled elastic gradients at the surface could be highly beneficial in improving the load-bearing capacity of alumina ceramics.