Nbc-Ni Cermets samples are sintered in a vacuum sintering furnace at @1450 degrees. The Samples were placed in the Alumina Piece as shown in the attached pictures. after sintering the color of the alumina piece changes to blue as shown in the picture. what can be the reason behind it? Thanks
Dear Abdul,
Bluish appearance of oxide ceramics stem from lack of oxygen. The free electron of the metal gives the blue color. Look for the term color centers.
Good luck.
BTW you can reoxidize the material in oxygen or air atmosphere at lower temperature, e.g. 1200 C.
Ori Yeheskel Thanks a lot for your response. so it means when we used alumina-based crucible in the high vacuum environment there is a possibility of a blue color appearance. Does it affect the properties of the sample which is in the crucible?
It might affect the material as there are "free" ions of Al or of the metallic impurities in the crucible matrix. What is the material you are working on?
Ori Yeheskel I am working in NbC-Ni and NbC-Ferrous alloy cermets with the addition of secondary carbide i.e TiC, VC, Mo2C.
Dear Abdul,
I never worked with these materials but they are high melting point-based, so I believe the influence will be minor. I recommend you'll measure Al content prior to and after the heat treatment of your samples.
Good luck.
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