No abstract

No abstract

This study provides experimentally determined values for the actual micro-Raman spectroscopy sampling depth in zirconia ceramics (ZrO2) via line scans on a wedge-shaped sample. Common instrumental settings with metallurgical objective lenses in dry air, argon-ion, and helium-neon laser radiation of approximately 10 mW were chosen. Under those conditions effective sampling depths, defined as the depth at which 99% of the information is recorded, range from 20 to more than 50 microm, depending on the numerical aperture of the lens and the laser wavelength. These results elucidate the pitfalls of the investigation of surface phenomena in zirconia ceramics such as low-temperature degradation or mechanically induced phase transformations by Raman spectroscopy.

No abstract

No abstract

This work follows a study on hydrothermal aged 3Y-TZP bioceramics, which showed that the surface X-ray diffraction data from moisture exposed samples give distorted results, reflecting a simple linear growth of a partially transformed layer from the surface into the interior. There is no indication for a leveling off or retardation of this growth at elevated temperatures (134°C) and here we present evidence that this is probably true at body temperatures as well. However, the rate constants at body temperature for the studied material are low and indicate a long lifetime. It should be noted that this statement is specific and other materials with minor changes to chemistry or microstructure may behave much better or much worse under those conditions. Furthermore slow crack growth and crack interactions are not yet investigated and may necessitate a minimum of low-temperature degradation susceptibility to ensure reliable long-time use.

No abstract

No abstract