Chemical Heat Treatment of Zirconia Ceramics

Chemical Heat Treatment of Zirconia Ceramics

Zirconia ceramics, like metals, can also be modified by surface infiltration of other elements to achieve the desired properties and structure. Carburization or nitriding of the surface layer of zirconia ceramic and its composite ceramic materials can increase the content of metastable tetragonal zirconia at room temperature, thereby affecting its toughening effect

Zirconia ceramics have obvious phase transformation toughening effect. The important condition for its toughening is that the high-temperature tetragonal phase (T phase) of zirconia is retained at room temperature instead of being transformed into room temperature stable monoclinic phase (M phase). Under the induction of stress, the T-M phase transformation of stress occurs, leading to volume expansion, producing an effect similar to that of Martensite transformation in iron carbon alloys. Melting Mg2+, Y3+plasma solids into the crystal lattice of zirconia ceramics can stabilize the tetragonal phase, and using chemical heat treatment provides a new way to stabilize T-phase zirconia ceramics.

The zirconia toughened alumina ceramic was buried in Sic powder at 1300 ° C for 15 hours, and the tetragonal phase in zyo2 increased from 8% to 92%. With the increase of temperature and insulation time, the stabilization effect on zirconia ceramic became more obvious.

After embedding zirconia ceramic toughened mullite into graphite+BaCO3 powder and charcoal BaCO3 powder, and holding at 1200 degrees for 6 hours, the tetragonal phase content in both ceramics was significantly increased, especially the effect of graphite as a solid carburizing agent. This indicates that highly activated carbon can diffuse into zirconia ceramics at high temperatures, preventing the transformation of tetragonal phase into monoclinic phase during cooling. Nitriding into ceramics also achieved a similar effect: with the increase of nitrogen partial pressure and heat treatment temperature, the tetragonal phase content in ZTM ceramics showed an increasing trend.

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