UltraHard Materials Limited
UHMís CeTZP engineering ceramic (Ceria stabilised Tetragonal Zirconia Polycrystals) possesses many of the exceptional properties of monolithic engineering ceramics. More importantly, UHM's CeTZP has a relatively high fracture toughness when compared to all the other currently-available commercial monolithic engineering ceramics (such as silicon nitride, silicon carbide, CBN and alumina). Table 1 lists the mechanical properties of UHM's CeTZP. Table 2 lists the thermal properties of CeTZP.
Table 1 - [Note: 1 MPa is approx 145 psi]
#estimated from bend strength
[Note: All our mechanical tests were carried out on UHM's CeTZP billets. A LECO test machine for our indentation macrohardness tests utilized 30 kg loads; K1c values were calculated from crack lengths derived from these indentation tests using the equation of Anstis el alia (reference 10)]
Note that the Weibull Modulus "m" of CeTZP (12 mole% Ceria) from three-point bend tests has been determined as 16.54 (references 5,12).
CeTZP vs Other Zirconia Ceramics
YttriaTZP is the zirconia ceramic of choice of most producers. However, YttriaTZP suffers from hydrothermal degradation (even at temperatures as low as 250 C*); that is, it has been shown to be prone to environmental degradation under humid conditions. Similarly, MagnesiaTZP and CalciaTZP require critical control of the annealing conditions and also these powders undergo continuous leaching of the magnesium and calcium ions in aqueous environments. In contrast CeriaTZP (with 12 mole% Ceria) is more environmentally stable and less prone to leaching and degradation of mechanical properties in aqueous environments. (references 5,12) When compared to YttriaTZP (3 mole%), YttriaTZP (6 mole%) and MagnesiaPSZ, CeriaTZP showed the best resistance against cyclic indentation fatigue under the range of indentation loads investigated (reference 7).
*see e.g. A. Feder and M. Anglada Low-temperature ageing degradation of 2.5Y-TZP heat-treated at 1650 įC, Journal of the European Ceramic Society; Volume 25, Issue 13 , August 2005, Pages 3117-3124.
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