We are melting silicon granules into furnace (Ar) and reading the temperature on the top of the bed with a pyrometer. The melting temperature readings are always higher than theory during hetaing, while upon cooling, with power off, the solidification temperature is perfectly matching.
Is there any reflectivity issue I am missing?
Dear Alberto,
I thing the deviation could be due to:
- emissivity or
- reflections of the heating source (as reflectivity changes with wavelength, the reflectivity for optical spectrum is not necessarily comparable to the reflectivity for IR spectrum; this is especially important if using IR-cameras or pyrometers with different wavelengths); if the heat source of your oven is on the same side of the specimen as your pyrometer you could measure reflected radiation of the heat source or anything else having a different/elevated temperature than your specimen (when I am doing IR troubleshouting I assume the specimen's surface as a mirror and in 90% this leads me to the source of error).
I would assume that you are on the right track and it is a reflectivity issue. Using a matt (ceramic) tube to shield the radiation path from your specimen (2 mm offset the surface) to the pyrometer, would be my suggestion to ensure nearly no reflection influence. Additionally it would be helpful to precisely determine the emissivity of the silicone at melting temperature under defined conditions.
Regards,
Eike
Official melting point of silicon is 1415 C. But we have to note the latent heat of crystallization. I think the overheating for melting of the small granules or powder in argon ambient may achieve 100 C as a minimum.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science