Zirconia Reaction Sintering Mode
Zirconia ceramics can be used in various fields due to their unique properties, but there are problems such as high preparation cost and difficulty in preparing large-sized special-shaped components. Drawing on the experience of preparing reactive sintered alumina ceramics, the Al and AIN powders were fully mixed, then formed by cold isostatic pressing and reacted in a zirconium gas atmosphere.
The newly generated Al particles after zirconization of the Al powder are nanoparticles, and the “old” Al particles are combined during the sintering process to obtain reaction-bonded aluminum anchor (RBA) ceramics.
Since Al zirconium is accompanied by a quantitative volume expansion, it can partially offset the shrinkage during sintering. The systematic study of Al/AIN system shows that Al powder content, Al powder particle size and china density are important process parameters for RBA. The volume fraction of Al should not be too high, and the particle size of Al directly affects the zirconization behavior and sintering process of the green body. The zirconium reaction rate of RBAN is controlled by nitrogen diffusion, which conforms to the parabolic law.
The zirconization mechanism of RBAN is controlled by different processes in different temperature ranges: at lower temperatures, the zirconization process is dominated by the zirconization of small Al particles, which is controlled by the diffusion of nitrogen through the broken zirconium film; At higher temperature, the zirconization in the early stage is controlled by the diffusion of Nz along the zirconium film of the large Al particles, and the film layer of the large Al particles is ruptured in the later stage, and the zirconization reaction is accelerated.
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