Fracture Toughness of Al₂O₃ with an Unstabilized ZrO₂Dispersed Phase

Abstract

Keramische Werkstoffe konnen durch Einlagerungen verstarkt bzw. zaher gemacht werden (1)(2)(3)(4)(5)

Crack growth resistance of alumina, zirconia and zirconia toughened alumina ceramics for joint prostheses

“…The obtained results support definitively this theoretical prediction. This is of course only true if strong chemical bonding occurs between alumina and zirconia particles and if no microcracks are present after processing, which is the case of 10 vol% zirconia composites [20]. It has been shown that this zirconia content corresponds to a maximum toughening [20].…”

“…7). Thus, it is possible to obtain nano-sized particles in the range from the critical size for spontaneous transformation after sintering, D c ; (above which there is no reinforcement) to the critical size for transformation during crack growth, D 0 c ; (below which there is no crack induced transformation, thus no reinforcement) [20,[31][32][33]. Fig.…”

“…Additionally, in the case of a zirconia matrix, the problem related with hydrothermal stability will still remain due to the need of yttria to stabilise zirconia [19]. On the other hand, with an alumina matrix this addition can be avoided since the alumina matrix acts constraining the zirconia particles, retaining the tetragonal zirconia in a metastable state, toughening the ceramic host material [19,20]. Moreover, the hardness of composites with an alumina matrix will be greater, because alumina is harder than zirconia [7].…”

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

“…The incorporation of zirconia (ZrO 2 ) inclusions into oxide ceramics, especially into alumina matrixes, to deliberately toughen them was undertaken shortly thereafter. 2 The mechanisms by which zirconia acts to toughen the composites are complementary: [3][4][5][6][7] they include transformation toughening, microcracking, and deflection. ZTA composites with high transformation toughening can be obtained if a high portion of tetragonal phase with the ability to transform under applied stress is retained at room temperature.…”

Recuperação da fase tetragonal em cerâmicas dentárias à base de ZrO2(Y2O3) submetidas à transformação martensítica precoce

“…Objetivando obter tenacidade máxima, a fração volumétrica de inclusões de zircônia deve estar em um nível ótimo, de acordo com Claussen (39) . Segundo o mesmo autor, a tenacidade atinge um valor máximo, e a partir daí, as microtrincas geradas pelas partículas de zircônia irão interagir umas com as outras resultando um decréscimo da resistência.…”