Duplex zirconia

Lee S.J., Kriven,W.M. A suhmicron-scale duplex zirconia and alumina composites hy polymer complexation processing. Ceramic engineering and science proceedings, 1999, v.20, N.3, p. 69-76. 

FIGURE 5.7 Optical micrographs of the reaction products between Ni and Al. (a) Duplex phases of nickel aluminides formed after a treatment of 1000°C for 1 hour in vacuum (b) a cracked nickel aluminide layer formed after being treated at 640°C for 1 hour in vacuum and (c) a cross-section of a nickel and zirconia joint which was joined together through a nickel aluminide layer at a temperature of 680°C in vacuum. N nickel, R nickel aluminide, A aluminium, and C zirconia. (Reprinted from Mei, J. and Xiao, R, Joining metals to zirconia for high temperature applications, Scripta Materialia 40 (1999) 587-594, with permission from Elsevier Science.)... 

It has been known for some time that considerable improvement of the mechanical properties of alumina in terms of flexural strength, fracture toughness, yield strength and elastic modulus can be achieved by adding particles of stabilised zir-conia as a structural reinforcement (see Chapter 4.1.2). Such ceramics are known as ZTA (zirconia-toughened alumina), duplex ceramics or dispersion ceramics. 

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

Figure 14.20 Microcrack process zone around a crack in an alumina-zirconia duplex ceramic, where the stress-induced phase transformation of zirconia particles induces microcracking. From Ref. [21],...

Duplex Ceramics. Spherical pressure zones 10-50pm diameter are homogenously dispersed in a ceramic matrix, to toughen it and to enhance its thermal shock resistance. The zones contain a high proportion of unstabilized zirconia. Spontaneous or stress-induced tetragonal/monoclinic transformation of the zirconia produces compressive stresses in the zones, and radial compressive and tensile hoop stresses in the nearby matrix. (H.E. Lutz and N. Claussen, J. Ear. Ceram. Soc. 7 (1991) 209)... 

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