Please check if alumina or ceramic has formed any phase with your material by reaction or diffusion. For any transition oxide or rare earth oxide containing compositions, alumina or ceramic crucibles do react with material to be heated.

We generally suggest to  first try HCl (≥25 wt%). If it is ineffective then it may be worth to try HCl + HNO3 (1:1 v/v; ≥25 wt%), with the safety concerns that apply to aqua regia. We will request to carry out all these experiments under fumehood.  After cleaning rinsed with Distilled water. Dry the crucible at 110 Degree for 10 h and heat first empty run slowly up to 1000 Degree.

If the marking is due to organic part of Carbon simply heat your boat/crucibles in air atmosphere slowly up to 1200 Degree Centigrade. Ramp rate 2 Degree and Dwell Time at 900 Degree for 10 minute will be good enough to remove solid carbon deposited in your components.

Please check if alumina or ceramic has formed any phase with your material by reaction or diffusion. For any transition oxide or rare earth oxide containing compositions, alumina or ceramic crucibles do react with material to be heated.

We generally suggest to  first try HCl (≥25 wt%). If it is ineffective then it may be worth to try HCl + HNO3 (1:1 v/v; ≥25 wt%), with the safety concerns that apply to aqua regia. We will request to carry out all these experiments under fumehood.  After cleaning rinsed with Distilled water. Dry the crucible at 110 Degree for 10 h and heat first empty run slowly up to 1000 Degree.

If the marking is due to organic part of Carbon simply heat your boat/crucibles in air atmosphere slowly up to 1200 Degree Centigrade. Ramp rate 2 Degree and Dwell Time at 900 Degree for 10 minute will be good enough to remove solid carbon deposited in your components.

Dear Roy: Thank You for your suggestion. Can we make this in muffle furnace at mentioned degree will it work out..

I think it should work. Please let me know after your experiment.

Tina, It will work....