ISSN:
1551-2916
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Maschinenbau
,
Physik
Notizen:
The stresses of laminate structures obtained by joining single layers of pure alumina (A), pure yttria-stabilized tetragonal zirconia, 3Y-TZP (Z), and an intimate mixture of alumina and zirconia (AZ) have been determined by fluorescence (in alumina) and Raman (in zirconia) piezospectroscopy. Three symmetrical stacking sequences were examined, namely, A/Z/A, A/AZ/A, and AZ/Z/AZ, with the aim of designing structures where the higher coefficient of thermal expansion (CTE) of zirconia could be used to induce compressive stress in the external layers (and ensuing tensile stress in the central layer). Two experimental sessions, 6 years apart, were conducted on the same samples, also taking care to record the spectra from the same locations; during the time elapsed between the two sessions, the samples were kept at room temperature and humidity. The stress values in alumina obtained during the more recent session were markedly different from those observed in the first session. Monoclinic zirconia (m-zirconia) was absent in all samples in the first session, whereas up to 25 vol% zirconia could be observed during the second session. m-Zirconia could only be observed in AZ layers and not in Z layers, irrespective of the position in the stacking sequence. It was concluded that 3Y-TZP underwent spontaneous tetragonal-to-monoclinic (t–m) transformation, that is, “aging,” when mixed with alumina at the grain-size level. Aging occurred only where pristine t-zirconia was subject to tensile stresses larger than ∼400 MPa.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1551-2916.2004.00247.x
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