Slow‐Crack‐Growth Behavior of Zirconia‐Toughened Alumina Ceramics Processed by Different Methods

Abstract

A study of slow-crack propagation in zirconia-toughened alumina (ZTA) ceramics is presented. Different ZTA composites, using either unstabilized or yttria-stabilized zirconia, have been tested. The materials were prepared in the range 0 -15 vol% ZrO 2 , using two processing methods: powder mixing and a modified colloidal route. Crack propagation tests have been conducted for crack velocities from 10 ؊12 to 10 ؊2 m/s by means of a double-torsion method. The influence of the processing conditions and compositions on the microstructures and the effect of these microstructures on the slow-crackgrowth behavior have been studied. The option that these composites may offer in terms of the lifetime of ceramic joint prostheses is discussed.

Slow Crack Growth Behavior of Zirconia‐Toughened Alumina and Alumina Using the Dynamic Fatigue Indentation Technique

“…Tables 2 and 3 summarize values of the SCG parameter n obtained for alumina and ZTA by different methods. The values of the SCG parameter n reported here for alumina (36 for 99.5% alumina and 65 for the 99.9% alumina) fall within the wide range of values reported for alumina: 30–75 11,13–15,26–28,30,31 . As discussed further, it is likely that the difference in behavior between these two aluminas is a result of the difference in purity between them.…”

“…From the results, it is clear that the addition of zirconia and β‐alumina platelets to alumina results in a composite, which has a greater resistance to stress corrosion (higher n ), in addition to increased strength and toughness. This is especially interesting because ZrO 2 is reported to have a lower resistance to SCG than Al 2 O 3 26,57 . Because the source of the Al 2 O 3 used to process the alumina matrix composite in the present study is also a high‐purity (>99.9%) Al 2 O 3 , it might be expected that the addition of a phase with lower resistance to SCG would not raise the resistance.…”

“…Furthermore, the presence of ZrO 2 and β‐alumina at the crack tip vicinity would be expected to modify the local residual stress field due to thermal anisotropies similar to the anisotropy‐induced effect in alumina. Because ZrO 2 and β‐alumina by themselves are not expected to exhibit higher SCG resistance than the high‐purity alumina, 26,58 it is suggested that their presence modifies the local stress field around the crack tip, either by the thermally induced stresses or by crack tip shielding, thereby effectively increasing the threshold value of K 0 and also changing the relationship between crack velocity and crack driving force. Residual strains in ZTA have been previously observed and are reported to influence the SCG behavior 53 .…”

Alúminas porosas: El método de bio-réplica para la síntesis de alúminas estables de alta superficie específica

“…Su aplicación en catálisis está ampliamente extendida, debido a la superficie específica y a las propiedades ácidas que presenta (17), usándose como catalizador activo, por ejemplo en las reacciones tipo Claus para transformar el sulfuro de hidrógeno en azufre (18,19), pero especialmente como soporte de catalizadores (20,21), empleado en diferentes procesos industriales, como en la hidrodesulfuración del petróleo (22), en la síntesis de óxido de etileno (23), o en la oxidación de metano (24), entre otros muchos ejemplos recopilados por Fierro (17a). Asimismo, debido a su inercia química y su alta resistencia mecánica (25)(26)(27), la alúmina también ha sido utilizada en implantes y prótesis debido a su comprobada biocompatibilidad (28)(29)(30)(31), resultando ser su estructura porosa un factor clave en muchas de las investigaciones relacionadas con el aumento de la capacidad de osteointegración de la alúmina (32)(33)(34)(35)(36).…”

Rheological Characterization and Coagulation Casting of Al2O3–Nano Zirconia Suspensions

“…Alumina-based composites containing dispersions of zirconia generally display superior strength, toughness and wear resistance compared to monolithic alumina and consequently there has been considerable interest in them, [1][2][3] with a wide range of different processing routes being used for their preparation. 1,[4][5][6] Applications include cutting tool tips and abrasion wheels amongst others; the latter can outperform monolithic alumina wheels by up to a factor of 8.…”