M K Basu

Ageing of zirconia-toughened alumina ceramics under different hydrothermal conditions

Abstract Changes in the crystalline phases of ZrO2 in different zirconia-toughened alumina (ZTA) compositions were studied at lower temperature (150–250 °C) by exposing them in a stream of humid air for a period of 24 h. Fresh samples of these compositions were also aged in an autoclave with superheated water for 2.5 h in the same temperature range, and the degree of phase transformation was compared with data from the previous samples to establish the effect of pressure on this phenomenon. It was observed for all the ZTA compositions that phase transformation increased monotonically with ageing time, temperature and pressure, although for the compositions with a lower percentage (15 vol%) of zirconia (3 mol% Y2O3), ageing in an autoclave was more detrimental particularly at lower temperature. As the ageing temperature increased in the composition with 15 vol% ZrO2 (3 mol% Y2O3), the influence of ageing duration on phase transformation of ZrO2 increased and the effect for 24 h of exposure time was found to be even more catastrophic than that of autoclave pressure at 250 °C. On the other hand, for the ZTA compositions containing more than 15 vol% zirconia (3 mol% Y2O3), the damaging effect of ageing in the autoclave was greater and this difference increased with increase in temperature.

Effect of grinding and subsequent annealing on the properties of transformation-toughened alumina ceramics

The extent of phase transformation due to grinding as well as the recovery of transformable phase upon annealing is discussed in the light of X-ray diffraction analysis and variation in mechanical properties.

Development of alumina ceramic head for hemi-hip joint prosthesis and its short term clinical report

In recent years polycrystalline alumina ceramics have been widely used as bioceramic implants in various orthopaedic applications in western countries. Alumina ceramics have been proved to be more biocompatible, resistant to corrosion and abrasion over conventional metals and, therefore, higher durability of the implants is envisaged. The present paper deals with the development of ceramic heads for hemi-hip prosthesis implants which have been implanted to 18 different human patients. Physical and mechanical characteristics and biocompatibility of these ceramic heads have been examined in short term clinical studies. The study revealed no abnormal clinical effect on the patients after 2 years of implantation.