Processing and Mechanical Behavior of Al2O3/ZrO2 Nanocomposites

Key role of processing to avoid low temperature ageing in alumina zirconia composites for orthopaedic application

“…Numerous studies have shown that ZTA composites exhibit high mechanical properties: fracture toughness ranging from 5.5 to 10.5 MPa m 1/2 is reported in the literature. [9][10][11][12][13][14] However, very few studies have focused on their resistance to ageing. Some studies [15][16][17] claim that no decrease in bending strength is observed after ageing experiments on alumina-zirconia composites, compared to the detrimental effect observed on the strength of aged Y-TZP.…”

Densification and mechanical properties of fine-grained Al2O3–ZrO2 composites consolidated by spark plasma sintering

“…The total ionic conductivity of the ZrO 2 sample sintered by HP was also 1.5-2.2 times lower than the one measured on the sample sintered by SPS [19,20]. Because dislocations are sources/sinks of vacancies, then it is understandable that a higher dislocation density will promote ionic conductivity and accelerate the grain boundary or lattice diffusion [16][17][18][19]. When the contents of ZrO 2 are higher, the diffusion of atoms/vacancies along the interface between the Al 2 O 3 grain and ZrO 2 particle should increase, so the densification rate would have a little increase.…”

“…Full-density fine-grained alumina ceramics could obtain under a pressure of 100 MPa within 3 min and 1200 • C. In comparison, the rate of densification Al 2 O 3 -ZrO 2 composites fabricated by the SPS is delayed with the addition of ZrO 2 . With regard to nanocomposite Al 2 O 3 /ZrO 2 , due to the adoption of fine Al 2 O 3 powder and nano ZrO 2 powder, which is prone to locate in the interstices of the densified Al 2 O 3 matrix, lattice diffusion and/or grain boundary diffusion which are major densification mechanisms in the high-temperature regime [16]. When ZrO 2 particles are located at grain boundaries in the intermediate and final stages of sintering, the grain boundary diffusion path becomes longer, and the diffusion of atoms/vacancies along the interface between the Al 2 O 3 grain and ZrO 2 particle should decrease.…”

Mechanisms of Microstructure Control in Conventional Sintering

“…Figure 10 shows the linear shrinkage rate as function of temperature for alumina-5%vol zirconia at 15 o C/min constant heating rate and 1500 o C. The presence of zirconia particles increases the maximum densification rate temperature; for alumina this temperature is 1350 o C (figure 1) and for alumina-zirconia the temperature is increased for 1440 o C. The temperature at the beginning of shrinkage process is also altered from 1030 to 1210 o C with the addition of zirconia particles. Zirconia inclusions hinder the movement of grain boundary, reducing the densification rate and grain growth (Hori et al, 1985;Liu et al, 1998;Stearns & Harmer, 1996). In the figure 11 (a) and (b), that shows the micrographs of samples of alumina-zirconia and alumina, respectively, sintered at 1500 o C for 2h, the influence of zirconia on microstructure evolution is noted through observing the grain growth behavior.…”