After making composite out of zirconia and alumina by SPS followed by grinding, polishing and thermal etch, my samples get bumps over surface. I'm not sure about the possible reasons. Please see attached example.
Was the sample prepared from Solution Precursor Plasma Spray or Suspension Plasma spray?
Hi Tanvir,
Thanks for your answer. What I meant by SPS is " Spark Plasma Sintering".
it could be due to trapped gasses; you can calculate the closed porosity for verification.
I assume that the "bumps" appear after the thermal etch and is most likely caused by the decomposition of an organic impurity that was in the starting materials once you expose the sample to an atmosphere with oxygen available. Might also happen if carbon gets into your powders.
In production unit, we do get this type of bump by conventional sintering process also. This is due to entrapped gas. After Cutting across the bump will clarify the same. It happens when gases can not escape during their binder burn out stage ( can be due to high heating rate, minimum dwell time, high density on top surface compared to bottom part, improper mixing or non uniform mixing of binder etc)
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