Zirconia toughened alumina with

What exactly takes place here is not yet completely clear. For the transformation of the zirconium crystal in their free state a temperature of appr. 1200 °Cis needed. It will be clear that this temperature will not be reached in the situation of figure 14.8. Apparently we are not only dealing with a transfer of energy here. To end this item, one more technical term ZTA (Zirconia Toughened Alumina), which is aluminium oxide which has been made tougher by adding zirconium. 

Fig. 15. Scanning electron microscope photomicrograph of multilayer TiB2/Al203 with zirconia toughened alumina (Adapted from DeAngelis and Weiss, 1990).

Figure 4.2 Reinforcement mechanism of a ZTA (zirconia-toughened alumina) duplex ceramics with agglomerated Y-PSZ particles.

Alumina-based composites These comprise especially zirconia-toughened alumina (ZTA), and alumina-based nanocomposites with non-oxide second phases such as SiCorTiC. However, thelattertwo, in particular, are b ond the scopeofthis chapter. 

Fig. 2.22 Effect of ceria addition on fracture toughness and modulus of elasticity of ZTA (zirconia toughened alumina) [35]. With kind permission of Eisevier...

Zirconia-toughened alumina (ZTA) ceramics with high transformation toughening ability can be obtained if a high portion of tetragonal phase with the possibility to transform under applied stress is retained at room temperature. This requires that the... 

Figure 14. SCG behavior of zirconia toughened alumina nano composites, with different compositions (from 35).

There are three t5q)es of ceramics that are cUiucally relevant to contemporary total hip replacement, including alumina, zirconia, and zirconia-toughened alumina composites. A fourth ceramic biomaterial, oxidized zirconium, is a ceramic-metal composite with a surface layer of zirconia. A fifth biomaterial, silicon nitride, is in advanced stages of commerciahzation for hip arthroplasty. 

FIGURE 6.19 Comparison of a ceramic revision femoral head fabricated from zirconia-toughened alumina (ZTA) with primary ceramic heads. The revision head has a metal sleeve to regenerate die trunnion of a femoral stem, which may become damaged in vivo. 

Golf putters have been constructed with ceramic heads. Some drivers contain ceramic inserts and some golf cleats are also made of ceramics. The ceramics used for all these are transformation-toughened zirconia or alumina. Some bowling balls contain a ceramic core. Some race cars are equipped with ceramic valves and composite ceramic brakes. 

Zirconium oxide is fused with alurnina in electric-arc furnaces to make alumina—zirconia abrasive grains for use in grinding wheels, coated-abrasive disks, and belts (104) (see Abrasives). The addition of zirconia improves the shock resistance of brittle alurnina and toughens the abrasive. Most of the baddeleyite imported is used for this appHcation, as is zirconia produced by burning zirconium carbide nitride. 

As mentioned previously, the main body of research on whisker-reinforced composites was concerned with alumina, mullite, and silicon nitride matrix materials. None the less, selected work examined zirconia, cordierite, and spinel as matrix materials.16-18 The high temperature strength behavior reported for these composites is summarized in Table 2.5. As shown, the zirconia matrix composites exhibited decreases in room temperature strength with the addition of SiC whiskers. However, the retained strength at 1000°C, was significantly improved for the whisker composites over the monolithic. Claussen and co-workers attributed this behavior to loss of transformation toughening at elevated temperatures for the zirconia monolith, whereas the whisker-reinforcement contribution did not decrease at the higher temperature.17,18... 

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