Dispersion toughened ceramics

T. N. Tiegs, etal., Dispersion-Toughened Composites, in Ceram. Tech, for Adv. Heat Eng. Proj. Semiann. Prog. Rep. for April through Sept. 1988, ORNL/TM-11116, Oak Ridge National Laboratory, Oak Ridge, TN, 1989, pp. 92-97. 

Zirconia-toughened ceramics (ZTCs). These consist of tetragonal or monoclinic zirconia particles finely dispersed in other ceramic matrices such as alumina, mullite, and spinel. 

In PSZ, the toughening is due to the transformation of the precipitates, which can take lenticular shapes. A common PSZ is Mg-PSZ, while the TZP s in use are Y-TZP and Ce-TZP. Also note that in TZP, transformation occurs within the grains (Fig. 8.68b), whereas in ZTA it occurs in the dispersed zirconia particles (Fig. 8.68c). Often the abbreviation DZC (i.e., dispersed zirconia ceramics) is applied to the stress-activated transformation in t-Zr02 particles dispersed in a ceramic matrix. In Fig. 8.68c, the ZTA is a commercially developed DZC system. The main objective of the fabrication of a transformation-toughened ceramic is the retention of t-Zr02, which transforms into m-Zr02 at or close to RT under the influence of an applied stress having a shear component. Control of the composition and thermal treatment are also important parameters in the fabrication of... 

Tho objectives of the program "Dispersion-Toughened Silicon Nitride" carried out within the scope of the Ceramic Technology for Advanced Heat Engines (CTAHE) program are to develop an advanced toughened silicon nitride composite and a process for near net shape part fabrication. The work on this program was Initiated In 1985. 

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. 

Begand, S., Oberbach, T., and Gliem, W. (2006) Mechanical properties of hip joint heads made of the dispersion ceramic - alumina toughened zirconia. Key Eng. Mater., 309-311, 1257-1260, 1261-1264. 

One important field of application for dispersion-reinforced glass matrix composites is as biomaterials for implants and in orthopaedics. Bioactive sihcate and phosphate glasses and glass-ceramics are toughened by incorporating biocompatible second phases, for example titanium, silver or stainless steel particles or chopped fibres [20,24,54,76,77]. 

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