I have two different phases in my composite which are Alumina and Zirconia. The shrinkage rate Vs temperature graph shows two peaks at different temperature. I am not sure if two different max shrinkage rates will cause a problem during sintering and densification process. Also what would be the best temperature to start applying force in SPS considering two different shrinkage rates.
However, 2 (but conjugated!) questions: (a) how have you prepared the sintering composition and (b) what is the particle size distribution in your composition ingredients...
If using SPS, try both, these are fast runs. Try lower temperature first.
Hi Sami,
two maxima in the first derivative is nothing special, it happens quite frequently in multiphase materials, we have observed and quantitatively described this for alumina zirconia and alumina-YAG. In these composites the activation energy of densification rises significantly in the final stage of sintering. this means by pressureless sintering you cannot densify the materials unless you have a certain minimum temperature.
By brute force (HIP, HP or SPS) under applied load densification can be carried out by significantly lower temperature. You should however keep in mind that full density is only one criterion for good alumina zirconia compsotes, if the material is ultrafine grained the zirconia will not transform and will consequently be very brittle. You have to check the microstructure and phase composition and correlate them to mechanical properties.
The sintering stuff is in the following paper Pola Palmero and made a few years ago.
doi:10.1016/j.ceramint.2011.06.011
best regards
Frank
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