Speaker
Description
Transformation toughening, a stress induced martensitic phase transformation associated with volume expansion and shear is the main source of toughness and strength in zirconia structural ceramics. The commercially available portfolio of TZP (tetragonal zirconia polycrystal) materials is however very narrow and dominated by yttria and ceria stabilized zirconia materials which either lack toughness and low temperature degradation resistance or strength.
Shifting from co-precipitated starting powders to “stabilizer-coated powders” which are either made by wet chemical methods or by intensive co-milling of monoclinic zirconia and the stabilizer oxides open a new perspective to manufacture TZP materials with very favorable combinations of strength toughness and low temperature degradation resistance. Stabilizers may either be single rare earth oxides or combinations of oxides with larger and smaller trivalent cations.
By proper selection of starting powders, powder processing and sintering off-equilibrium TZP materials featuring grains with a core-shell structure can be created. The over-stabilized shell ensures good LTD resistance, the under-stabilized core ensures high transformability, transformation efficiency and toughness.
Such materials are highly attractive for the biomedical filed but also as a matrix material for e.g. electric discharge machinable composite ceramics with an electrically conductive second phase.
| Speaker Country | Germany |
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