Comparison of Microwave and Conventionally Sintered Yttria Doped Zirconia Ceramics and Hydroxyapatite-Zirconia Nanocomposites


Comparisons of microwave and conventional sintering of zirconia and hydroxyapatite (HA) -zirconia bodies were investigated in order to understand how microwave energy may affect the physical and mechanical properties of the materials for use in biomedical applications. Powder compacts of commercial nano-sized ZrO2, with 2 to 5 mol% Y2O3, and mixtures of laboratory synthesised nano-sized HA with 0-10 wt% zirconia were microwave and conventionally sintered at temperatures up to 1450°C for the zirconia and 1200°C for the composites with the same heating profile and a 1h hold time. Microwave sintering improves physical and mechanical properties of Y2O3-doped ZrO2 ceramics compared with conventional sintering. Compositions containing 2 mol% Y2O 3 exhibit the greatest improvement due to retention of tetragonal ZrO2, with higher relative density, 22% increase in Young's modulus and a 165% increase in biaxial flexural strength compared with conventional sintering. Significant grain growth occurred in microwave sintered samples which is thought to be related to enhanced diffusional effects during microwave sintering. HA-ZrO2 composites exhibited densities of only 80% with corresponding open porosities. Nanosized ZrO2 prevents the densification of the HA matrix by effectively pinning grain boundaries and this effect is more pronounced in microwave sintered ceramics. Nanocomposites microwave sintered at 1200°C showed similar strengths to those produced by conventional sintering but with higher volume fraction open porosity. Increased open porosity is considered to be useful for biomedical applications to promote osteo-integration.


Chemical and Biochemical Engineering

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Article - Conference proceedings

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Publication Date

01 Jan 2011