Abstract
Alumina toughened zirconia (ATZ) and zirconia toughened alumina (ZTA) are currently the materials of choice to meet the need for tough, strong, and bioinert ceramics for medical devices. However, the mechanical properties of ZrO2/Al2O3 dispersion ceramics could be considerably increased by reducing the corresponding grain sizes and by improving the homogeneity of the phase dispersion. Here, we prepare nanoparticles with an intraparticular phase distribution of Zr(1−x)AlxO(2−x/2) and (γ-, δ-)Al2O3 by the simultaneous gas phase condensation of laser co-vaporized zirconia and alumina raw powders. During subsequent spark plasma sintering the zirconia defect structures and transition alumina phases transform to a homogeneously distributed dispersion of tetragonal ZrO2 (52.4 vol%) and α-Al2O3 (47.6 vol%). Ceramics sintered by spark plasma sintering are completely dense with average grain sizes in the range around 250 nm. Outstanding mechanical properties (flexural strength σf = 1500 MPa, fracture toughness KIc = 6.8 MPa m1/2) together with a high resistance against low temperature degradation make these materials promising candidates for next generation bioceramics in total hip replacements and for dental implants.
Highlights
Alumina toughened zirconia (ATZ) and zirconia toughened alumina (ZTA) are currently the materials of choice to meet the need for tough, strong, and bioinert ceramics for medical devices
The mechanical properties of ZrO2/ Al2O3 dispersion ceramics described in literature differ by a huge amount because they depend to a large extend on the ratio and homogeneity of the phase distribution, on the grain size and porosity, and on processing as well as sintering conditions[1,2,5,6,7,8]
In high resolution micrographs some of the particles show a core/shell structure (Fig. 1b) where the core consists of crystalline phases and the shell seems to be amorphous
Summary
Alumina toughened zirconia (ATZ) and zirconia toughened alumina (ZTA) are currently the materials of choice to meet the need for tough, strong, and bioinert ceramics for medical devices. In ZTA ceramics the spontaneous transformation of tetragonal to monoclinic ZrO2 grains in a humid environment and in the temperature range 20 °C to 300 °C, i.e. low temperature degradation (LTD), occurs more readily if the grain size is below a critical value (500 nm)[10]. Their narrow size distribution as well as their concentration and isolation, i.e. the absence of aggregates, are important for the inhibition of intergranular water diffusion which www.nature.com/scientificreports/. For this purpose ZrO2/ Al2O3 nanoparticles with an intraparticular phase dispersion instead of just mixing different portions of raw materials might be desirable
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